Substrate mimicry: HIV-1 reverse transcriptase recognizes 6-modified-3′-azido-2′,3′-dideoxyguanosine-5′-triphosphates as adenosine analogs

PubMed Central

Herman, Brian D.; Schinazi, Raymond F.; Zhang, Hong-wang; Nettles, James H.; Stanton, Richard; Detorio, Mervi; Obikhod, Aleksandr; Pradère, Ugo; Coats, Steven J.; Mellors, John W.; Sluis-Cremer, Nicolas

2012-01-01

β-D-3′-Azido-2′,3′-dideoxyguanosine (3′-azido-ddG) is a potent inhibitor of HIV-1 replication with a superior resistance profile to zidovudine. Recently, we identified five novel 6-modified-3′-azido-ddG analogs that exhibit similar or superior anti-HIV-1 activity compared to 3′-azido-ddG in primary cells. To gain insight into their structure–activity–resistance relationships, we synthesized their triphosphate (TP) forms and assessed their ability to inhibit HIV-1 reverse transcriptase (RT). Steady-state and pre-steady-state kinetic experiments show that the 6-modified-3′-azido-ddGTP analogs act as adenosine rather than guanosine mimetics in DNA synthesis reactions. The order of potency of the TP analogs against wild-type RT was: 3′-azido-2,6-diaminopurine >3′-azido-6-chloropurine; 3′-azido-6-N-allylaminopurine > 2-amino-6-N,N-dimethylaminopurine; 2-amino-6-methoxypurine. Molecular modeling studies reveal unique hydrogen-bonding interactions between the nucleotide analogs and the template thymine base in the active site of RT. Surprisingly, the structure–activity relationship of the analogs differed in HIV-1 RT ATP-mediated excision assays of their monophosphate forms, suggesting that it may be possible to rationally design a modified base analog that is efficiently incorporated by RT but serves as a poor substrate for ATP-mediated excision reactions. Overall, these studies identify a promising strategy to design novel nucleoside analogs that exert profound antiviral activity against both WT and drug-resistant HIV-1. PMID:21914723

Dopamine D2 receptors photolabeled by iodo-azido-clebopride.

PubMed

Niznik, H B; Dumbrille-Ross, A; Guan, J H; Neumeyer, J L; Seeman, P

1985-04-19

Iodo-azido-clebopride, a photoaffinity compound for dopamine D2 receptors, had high affinity for canine brain striatal dopamine D2 receptors with a dissociation constant (Kd) of 14 nM. Irradiation of striatal homogenate with iodo-azido-clebopride irreversibly inactivated 50% of dopamine D2 receptors at 20 nM (as indicated by subsequent [3H]spiperone binding). Dopamine agonists and antagonists prevented this photo-inactivation with the appropriate rank-order of potency. Striatal dopamine D1, serotonin (S2), alpha 1- and beta-adrenoceptors were not significantly inactivated following irradiation with iodo-azido-clebopride. Thus, iodo-azido-clebopride is a selective photoaffinity probe for dopamine D2 receptors, the radiolabelled form of which may aid in the molecular characterization of these proteins.

Synthesis of novel 3'-azido-3'-deoxy-α-L-ribo configured nucleosides: A comparative study between chemical and chemo-enzymatic methodologies.

PubMed

Rana, Neha; Kumar, Manish; Singh, Ankita; Maity, Jyotirmoy; Shukla, Poonam; Prasad, Ashok K

2018-05-03

Syntheses of novel 3'-azido-3'-deoxy-2'-O,4'-C-methylene-α-L-ribofuranosyl nucleosides have been carried out from 3'-azido-3'-deoxy-4'-C-hydroxymethyl-β-D-xylofuranosyl nucleosides following both chemical and chemo-enzymatic methodologies. The precursor nucleoside in turn was synthesized from a common glycosyl donor 4-C-acetoxymethyl-1,2,5-tri-O-acetyl-3-azido-3-deoxy-α,β-D-xylofuranose, which was obtained by the acetolysis of 4-C-acetoxymethyl-5-O-acetyl-3-azido-3-deoxy-1,2-O-isopropylidene-α-D-xylofuranose in 96% yield. It has been observed that a chemo-enzymatic pathway for the synthesis of targeted nucleosides is much more efficient than a chemical pathway, leading to the improvement in yield for the synthesis of 3'-azido-3'-deoxy-α-L-ribofuranosyl thymine and uracil from 49 to 89% and 55 to 93%, respectively.

Fluorescent Probes of the Apoptolidins and their Utility in Cellular Localization Studies

PubMed Central

DeGuire, Sean M.; Earl, David C.; Du, Yu; Crews, Brenda A.; Jacobs, Aaron T.; Ustione, Alessandro; Daniel, Cristina; Chong, Katherine; Marnett, Lawrence J.; Piston, David W.; Bachmann, Brian O.; Sulikowski, Gary A.

2014-01-01

Apoptolidin A has been described as among the top 0.1% most cell selective cytotoxic agents to be evaluated in the NCI 60 cell line panel. The molecular structure of apoptolidin A consists of a 20-membered macrolide with mono- and disaccharide moieties located at C9 and C27, respectively. In contrast to apoptolidin A, the aglycone (apoptolidinone) shows no cytotoxicity (>10 μM) when evaluated against several tumor cell lines. Apoptolidin H, the C27 deglycosylated analog of apoptolidin A, was produced by targeted glycosyl transferase gene deletion and displayed sub-micromolar activity against H292 lung carcinoma cells. Selective esterification of the C2′ hydroxyl group of apoptolidins A and H with 5-azidopentanoic acid afforded azido functionalized derivatives of potency equal to their parent macrolide. Azido apoptolidins readily underwent strain-promoted alkyne azido cycloaddition (SPAAC) reactions to provide access to fluorescent and biotin functionalized probes. Microscopy studies demonstrate apoptolidins A and H localize in the mitochondria of H292 human lung carcinoma cells. PMID:25430909

Novel type 1 photosensitizers: viability of leukemia cells exposed to reactive intermediates generated in situ by in vitro photofragmentation

NASA Astrophysics Data System (ADS)

Rajagopalan, Raghavan; Karwa, Amol; Lusiak, Przemyslaw M.; Srivastava, Kripa; Poreddy, Amruta R.; Pandurangi, Raghootama S.; Galen, Karen P.; Neumann, William L.; Cantrell, Gary E.; Dorshow, Richard B.

2009-06-01

Photodynamic therapy of tumors involving Type 2 photosenstizers has been conspicuously successful, but the Type 1 process, in contrast, has not received much attention despite its considerable potential. Accordingly, several classes of molecules containing fragile bonds such as azido (-N=N=N), azo (-N=N-), sulfenato (-S-O-) and oxaza (-N-O-) functional groups that produce reactive intermediates such as radicals and nitrenes upon photoexcitation were prepared and tested for cell viability using U397 leukemia cell line. The azido photosensitizer was conjugated to leukemia cell binding peptide, SFFWRLS, for targeted cell viability study. The cells were incubated with the photosensitizer at various concentrations, and were illuminated for 5, 10, and 20 minutes. The results show that all the photosensitizers caused cell death compared to the controls when exposed to both the photosensitizers and light. Most importantly, selective cell death was observed with the azido peptide conjugate 6, which clearly demonstrates that these Type 1 sensitizers are useful for phototherapeutic applications.

Asymmetric homologation of boronic esters bearing azido and silyloxy substituents.

PubMed

Singh, R P; Matteson, D S

2000-10-06

In the asymmetric homologation of boronic esters with a (dihalomethyl)lithium, substituents that can bind metal cations tend to interfere. Accordingly, we undertook the introduction of weakly basic oxygen and nitrogen substituents into boronic esters in order to maximize the efficiency of multistep syntheses utilizing this chemistry. Silyloxy boronic esters cannot be made efficiently by direct substitution, but a (hydroxymethyl)boronic ester has been silylated in the usual manner. Conversion of alpha-halo boronic esters to alpha-azido boronic esters has been carried out with sodium azide and a tetrabutylammonium salt as phase-transfer catalyst in a two-phase system with water and either nitromethane or ethyl acetate. These are safer solvents than the previously used dichloromethane, which can form an explosive byproduct with azide ion. Boronic esters containing silyloxy or alkoxy and azido substituents have been shown to react efficiently with (dihalomethyl)lithiums, resulting in efficient asymmetric insertion of the halomethyl group into the carbon-boron bond.

Decreasing Distortion Energies without Strain: Diazo-Selective 1,3-Dipolar Cycloadditions.

PubMed

Gold, Brian; Aronoff, Matthew R; Raines, Ronald T

2016-07-15

The diazo group has attributes that complement those of the azido group for applications in chemical biology. Here, we use computational analyses to provide insights into the chemoselectivity of the diazo group in 1,3-dipolar cycloadditions. Dipole distortion energies are responsible for ∼80% of the overall energetic barrier for these reactions. Here, we show that diazo compounds, unlike azides, provide an opportunity to decrease that barrier substantially without introducing strain into the dipolarophile. The ensuing rate enhancement is due to the greater nucleophilic character of a diazo group compared to that of an azido group, which can accommodate decreased distortion energies without predistortion. The tuning of distortion energies with substituents in a diazo compound or dipolarophile can enhance reactivity and selectivity in a predictable manner. Notably, these advantages of diazo groups are amplified in water. Our findings provide a theoretical framework that can guide the design and application of both diazo compounds and azides in "orthogonal" contexts, especially for biological investigations.

Photoaffinity labeling of an herbicide receptor protein in chloroplast membranes

PubMed Central

Pfister, Klaus; Steinback, Katherine E.; Gardner, Gary; Arntzen, Charles J.

1981-01-01

2-Azido-4-ethylamino-6-isopropylamino-s-triazine (azido-atrazine) inhibits photosynthetic electron transport at a site identical to that affected by atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine). The latter is a well-characterized inhibitor of photosystem II reactions. Azido-atrazine was used as a photoaffinity label to identify the herbicide receptor protein; UV irradiation of chloroplast thylakoids in the presence of azido[14C]atrazine resulted in the covalent attachment of radioactive inhibitor to thylakoid membranes isolated from pea seedlings and from a triazine-susceptible biotype of the weed Amaranthus hybridus. No covalent binding of azido-atrazine was observed for thylakoid membranes isolated from a naturally occurring triazine-resistant biotype of A. hybridus. Analysis of thylakoid polypeptides from both the susceptible and resistant A. hybridus biotypes by sodium dodecyl sulfate/polyacrylamide gel electrophoresis, followed by fluorography to locate 14C label, demonstrated specific association of the azido[14C]atrazine with polypeptides of the 34- to 32-kilodalton size class in susceptible but not in resistant membranes. Images PMID:16592984

Synthesis, molecular structure and physicochemical properties of bis(3‧-azido-3‧-deoxythymidin-5‧-yl) carbonate

NASA Astrophysics Data System (ADS)

Raviolo, Mónica A.; Williams, Patricia A. M.; Etcheverry, Susana B.; Piro, Oscar E.; Castellano, Eduardo E.; Gualdesi, Maria S.; Briñón, Margarita C.

2010-04-01

3'-Azido-3'-deoxythymidine (zidovudine, AZT), a synthetic analog of natural nucleoside thymidine, has been used extensively in AIDS treatments. We report here the synthesis, X-ray crystal and molecular structure, NMR, IR and Raman spectra and the thermal behavior of a novel carbonate of AZT [(AZT-O) 2C dbnd O], prepared by the reaction of zidovudine with carbonyldiimidazole. The carbonate compound, C 21H 24N 10O 9, crystallizes in the tetragonal space group P4 12 12 with a = b = 15.284(1), c = 21.695(1) Å, and Z = 8 molecules per unit cell. It consists of two AZT moieties of closely related conformations which are bridged by a carbonyl group to adopt a folded Z-like shape.

Computational Chemistry-Based Enthalpy-of-Formation, Enthalpy-of-Vaporization, and Enthalpy-of-Sublimation Predictions for Azide-Functionalized Compounds

DTIC Science & Technology

2006-04-01

93.0g 92.8 102.8 Benzene+HN3 → Azidobenzene+H2 Azidomethylbenzene 99.5f 93.0 102.0 Methylbenzene+HN3 → Azidomethylbenzene+H2 2 -Azido- 2 - phenylpropane ...87.4d 73.5 86.4 2 - Phenylpropane +HN3 → 2 -Azido- 2 - phenylpropane +H2 Azidocyclopentane 52.8h 58.4 67.0 Cyclopentane+HN3 → Azidocyclopentane+H2...experimentally derived results for “higher homologous azides” (1-azidoadamantane, 3-azido-3-ethylpentane and 2 -azido- 2 - phenylpropane ) (Wayne et al., 1993

Synthesis and Explosion Hazards of 4-Azido-l-phenylalanine.

PubMed

Richardson, Mark B; Brown, Derek B; Vasquez, Carlos A; Ziller, Joseph W; Johnston, Kevin M; Weiss, Gregory A

2018-04-20

A reliable, scalable, cost-effective, and chromatography-free synthesis of 4-azido-l-phenylalanine beginning from l-phenylalanine is described. Investigations into the safety of the synthesis reveal that the Ullman-like Cu(I)-catalyzed azidation step does not represent a significant risk. The isolated 4-azido-l-phenylalanine product, however, exhibits previously undocumented explosive characteristics.

Fischer carbene mediated covalent grafting of a peptide nucleic acid on gold surfaces and IR optical detection of DNA hybridization with a transition metalcarbonyl label

NASA Astrophysics Data System (ADS)

Srivastava, Pratima; Ghasemi, Mahsa; Ray, Namrata; Sarkar, Amitabha; Kocabova, Jana; Lachmanova, Stepanka; Hromadova, Magdalena; Boujday, Souhir; Cauteruccio, Silvia; Thakare, Pramod; Licandro, Emanuela; Fosse, Céline; Salmain, Michèle

2016-11-01

Amine-reactive surfaces comprising N-hydroxysuccinimide ester groups as well as much more unusual Fischer alkoxymetallocarbene groups were generated on gold-coated surfaces via self-assembled monolayers of carboxy- and azido-terminated thiolates, respectively. These functions were further used to immobilize homothymine peptide nucleic acid (PNA) decamer in a covalent fashion involving the primary amine located at its N-terminus. These stepwise processes were monitored by polarization modulation reflection - absorption infrared spectroscopy (PM-RAIRS) that gave useful information on the molecular composition of the organic layers. PNA grafting and hybridization with complementary DNA strand were successfully transduced by quartz crystal microbalance (QCM) measurements. Unfortunately, attempts to transduce the hybridization optically by IR in a label-free fashion were inconclusive. Therefore we undertook to introduce an IR reporter group, namely a transition metalcarbonyl (TMC) entity at the 5‧ terminus of complementary DNA. Evidence for the formation of PNA-DNA heteroduplex was brought by the presence of ν(Ctbnd O) bands in the 2000 cm-1 region of the IR spectrum of the gold surface owing to the metalcarbonyl label.

Tracking G-protein-coupled receptor activation using genetically encoded infrared probes.

PubMed

Ye, Shixin; Zaitseva, Ekaterina; Caltabiano, Gianluigi; Schertler, Gebhard F X; Sakmar, Thomas P; Deupi, Xavier; Vogel, Reiner

2010-04-29

Rhodopsin is a prototypical heptahelical family A G-protein-coupled receptor (GPCR) responsible for dim-light vision. Light isomerizes rhodopsin's retinal chromophore and triggers concerted movements of transmembrane helices, including an outward tilting of helix 6 (H6) and a smaller movement of H5, to create a site for G-protein binding and activation. However, the precise temporal sequence and mechanism underlying these helix rearrangements is unclear. We used site-directed non-natural amino acid mutagenesis to engineer rhodopsin with p-azido-l-phenylalanine residues incorporated at selected sites, and monitored the azido vibrational signatures using infrared spectroscopy as rhodopsin proceeded along its activation pathway. Here we report significant changes in electrostatic environments of the azido probes even in the inactive photoproduct Meta I, well before the active receptor state was formed. These early changes suggest a significant rotation of H6 and movement of the cytoplasmic part of H5 away from H3. Subsequently, a large outward tilt of H6 leads to opening of the cytoplasmic surface to form the active receptor photoproduct Meta II. Thus, our results reveal early conformational changes that precede larger rigid-body helix movements, and provide a basis to interpret recent GPCR crystal structures and to understand conformational sub-states observed during the activation of other GPCRs.

Synthesis and photochemical behavior of the tetrazolo tautomer of 2-azido-4-pyrimidinone-2'-deoxyriboside.

PubMed

Gourdain, Stéphanie; Petermann, Christian; Martinez, Agathe; Harakat, Dominique; Clivio, Pascale

2011-03-18

The 2-azido analogue of 2'-deoxyuridine was prepared in three steps from 2'-deoxy-2-thiouridine. The sulfur atom of the 2-thio nucleoside was methylated and then displaced by hydrazine to furnish the corresponding 2-hydrazino derivative. After diazotization, the 2-azido compound that exists as its tetrazolo tautomer was obtained. Upon UV irradiation in aqueous solution, the title compound led to isocytosine.

Identification of the ubiquinone-binding domain in the disulfide catalyst disulfide bond protein B.

PubMed

Xie, Tong; Yu, Linda; Bader, Martin W; Bardwell, James C A; Yu, Chang-An

2002-01-18

Disulfide bond (Dsb) formation is catalyzed in the periplasm of prokaryotes by the Dsb proteins. DsbB, a key enzyme in this process, generates disulfides de novo by using the oxidizing power of quinones. To explore the mechanism of this newly described enzymatic activity, we decided to study the ubiquinone-protein interaction and identify the ubiquinone-binding domain in DsbB by cross-linking to photoactivatable quinone analogues. When purified Escherichia coli DsbB was incubated with an azidoubiquinone derivative, 3-azido-2-methyl-5-[(3)H]methoxy-6-decyl-1,4-benzoquinone ([(3)H]azido-Q), and illuminated with long wavelength UV light, the decrease in enzymatic activity correlated with the amount of 3-azido-2-methyl-5-methoxy-6-decyl-1,4-benzoquinone (azido-Q) incorporated into the protein. One azido-Q-linked peptide with a retention time of 33.5 min was obtained by high performance liquid chromatography of the V8 digest of [(3)H]azido-Q-labeled DsbB. This peptide has a partial NH(2)-terminal amino acid sequence of NH(2)-HTMLQLY corresponding to residues 91-97. This sequence occurs in the second periplasmic domain of the inner membrane protein DsbB in a loop connecting transmembrane helices 3 and 4. We propose that the quinone-binding site is within or very near to this sequence.

An ab initio molecular dynamics study of thermal decomposition of 3,6-di(azido)-1,2,4,5-tetrazine.

PubMed

Wu, Qiong; Zhu, Weihua; Xiao, Heming

2014-10-21

Ab initio molecular dynamics simulations were performed to study the thermal decomposition of isolated and crystal 3,6-di(azido)-1,2,4,5-tetrazine (DiAT). During unimolecular decomposition, the three different initiation mechanisms were observed to be N-N2 cleavage, ring opening, and isomerization, respectively. The preferential initial decomposition step is the homolysis of the N-N2 bond in the azido group. The release mechanisms of nitrogen gas are found to be very different in the early and later decomposition stages of crystal DiAT. In the early decomposition, DiAT decomposes very fast and drastically without forming any stable long-chains or heterocyclic clusters, and most of the nitrogen gases are released through rapid rupture of nitrogen-nitrogen and carbon-nitrogen bonds. But in the later decomposition stage, the release of nitrogen gas is inhibited due to low mobility, long distance from each other, and strong carbon-nitrogen bonds. To overcome the obstacles, the nitrogen gases are released through slow formation and disintegration of polycyclic networks. Our simulations suggest a new decomposition mechanism for the organic polyazido initial explosive at the atomistic level.

Three-dimensional structure of thymidine phosphorylase from E. coli in complex with 3'-azido-2'-fluoro-2',3'-dideoxyuridine

NASA Astrophysics Data System (ADS)

Timofeev, V. I.; Abramchik, Yu. A.; Fateev, I. V.; Zhukhlistova, N. E.; Murav'eva, T. I.; Kuranova, I. P.; Esipov, R. S.

2013-11-01

The three-dimensional structures of thymidine phosphorylase from E. coli containing the bound sulfate ion in the phosphate-binding site and of the complex of thymidine phosphorylase with sulfate in the phosphate-binding site and the inhibitor 3'-azido-2'-fluoro-2',3'-dideoxyuridine (N3F-ddU) in the nucleoside-binding site were determined at 1.55 and 1.50 Å resolution, respectively. The amino-acid residues involved in the ligand binding and the hydrogen-bond network in the active site occupied by a large number of bound water molecules are described. A comparison of the structure of thymidine phosphorylase in complex with N3F-ddU with the structure of pyrimidine nucleoside phosphorylase from St. Aureus in complex with the natural substrate thymidine (PDB_ID: 3H5Q) shows that the substrate and the inhibitor in the nucleoside-binding pocket have different orientations. It is suggested that the position of N3F-ddU can be influenced by the presence of the azido group, which prefers a hydrophobic environment. In both structures, the active sites of the subunits are in the open conformation.

Selective in vivo metabolic cell-labeling-mediated cancer targeting

PubMed Central

Wang, Hua; Wang, Ruibo; Cai, Kaimin; He, Hua; Liu, Yang; Yen, Jonathan; Wang, Zhiyu; Xu, Ming; Sun, Yiwen; Zhou, Xin; Yin, Qian; Tang, Li; Dobrucki, Iwona T; Dobrucki, Lawrence W; Chaney, Eric J; Boppart, Stephen A; Fan, Timothy M; Lezmi, Stéphane; Chen, Xuesi; Yin, Lichen; Cheng, Jianjun

2017-01-01

Distinguishing cancer cells from normal cells through surface receptors is vital for cancer diagnosis and targeted therapy. Metabolic glycoengineering of unnatural sugars provides a powerful tool to manually introduce chemical receptors onto the cell surface; however, cancer-selective labeling still remains a great challenge. Herein we report the design of sugars that can selectively label cancer cells both in vitro and in vivo. Specifically, we inhibit the cell-labeling activity of tetraacetyl-N-azidoacetylmannosamine (Ac4ManAz) by converting its anomeric acetyl group to a caged ether bond that can be selectively cleaved by cancer-overexpressed enzymes and thus enables the overexpression of azido groups on the surface of cancer cells. Histone deacetylase and cathepsin L-responsive acetylated azidomannosamine, one such enzymatically activatable Ac4ManAz analog developed, mediated cancer-selective labeling in vivo, which enhanced tumor accumulation of a dibenzocyclooctyne–doxorubicin conjugate via click chemistry and enabled targeted therapy against LS174T colon cancer, MDA-MB-231 triple-negative breast cancer and 4T1 metastatic breast cancer in mice. PMID:28192414

Biofunctionalization of a “Clickable” Organic Layer Photochemically Grafted on Titanium Substrates

PubMed Central

Li, Yan; Zhao, Meirong; Wang, Jun; Liu, Kai; Cai, Chengzhi

2011-01-01

We have developed a general method combining photochemical grafting and copper-catalyzed click chemistry for biofunctionalization of titanium substrates. The UV-activated grafting of an α,ω-alkenyne onto TiO2/Ti substrates provided a “clickable” thin film platform. The selective attachment of the vinyl end of the molecule to the surface was achieved by masking the alkynyl end with a trimethylgermanyl (TMG) protecting group. Subsequently, various oligo(ethylene glycol) (OEG) derivatives terminated with an azido group were attached to the TMG-alkynyl modified titanium surface via a one-pot deprotection/click reaction. The films were characterized by X-ray photoelectron spectroscopy (XPS), contact angle goniometry, ellipsometry, and atomic force microscopy (AFM). We showed that the titanium surface presenting click-immobilized OEG substantially suppressed the nonspecific attachment of protein and cells as compared to the unmodified titanium substrate. Furthermore, glycine-arginine-glycine-aspartate (GRGD), a cell adhesion peptide, was coimmobilized with OEG on the platform. We demonstrated that the resultant GRGD-presenting thin film on Ti substrates can promote the specific adhesion and spreading of AsPC-1 cells. PMID:21417429

Potassium 4-azidobenzene­sulfonate1

PubMed Central

Biesemeier, Frank; Geiseler, Gertraud; Harms, Klaus; Müller, Ulrich

2014-01-01

In, K+·SO3–p-C6H4–N3 −, the conformation angle of the azido group with respect to the benzene ring is 19.1 (3)°, so that the anion is chiral within the crystal structure. In addition, the crystal structure is also chiral (Sohncke space group). The potassium ion is coordinated by three closer O atoms from three different sulfonyl groups [K⋯O 2.6486 (17) to 2.7787 (17) Å], three more distant O atoms [K⋯O 2.959 (2) to 3.206 (2) Å] and three N atoms at 3.073 (2) to 3.268 (2) Å. The anions are packed into layers perpendicular to b, only O and N atoms being at the surface of the layers. The K+ ions are located between the layers. PMID:25249882

Glucosamine and Glucosamine-6-phosphate Derivatives: Catalytic Cofactor Analogs for the glmS Ribozyme

PubMed Central

Posakony, Jeffrey J.; Ferré-D'Amaré, Adrian R.

2013-01-01

Two analogues of glucosamine-6-phosphate (GlcN6P, 1) and five of glucosamine (GlcN, 2) were prepared for evaluation as catalytic cofactor of the glmS ribozyme, a bacterial gene-regulatory RNA that controls cell wall biosynthesis. Glucosamine and allosamine with 3-azido substitutions were prepared by SN2 reactions of the respective 1,2,4,6-protected sugars; final acidic hydrolysis afforded the fully deprotected compounds as their TFA salts. A 6-phospho-2-aminoglucolactam (31) was prepared from glucosamine in a 13-step synthesis, which included a late-stage POCl3-phosphorylation. A simple and widely applicable 2-step procedure with the triethylsilyl (TES) protecting group was developed to selectively expose the 6-OH group in N-protected glucosamine analogs, which provided another route to chemical phosphorylation. Mitsunobu chemistry afforded 6-cyano (35) and 6-azido (36) analogues of GlcN-(Cbz) and the selectivity for the 6-position was confirmed by NMR (COSY, HMBC, HMQC) experiments. Compound 36 was converted to the fully deprotected 6-azido-GlcN (37) and 2,6-diaminoglucose (38) analogs. A 2-hydroxylamino glucose (42) analogue was prepared via an oxaziridine (41). Enzymatic phosphorylation of 42 and chemical phosphorylation of its 6-OH precursor (43) were possible, but 42 and the 6-phospho product (44) were unstable under neutral or basic conditions. Chemical phosphorylation of the previously described 2-guanidinyl-glucose (46) afforded its 6-phospho analogue (49) after final deprotection. PMID:23578404

Active Cytokinins

PubMed Central

Mornet, René; Theiler, Jane B.; Leonard, Nelson J.; Schmitz, Ruth Y.; Moore, F. Hardy; Skoog, Folke

1979-01-01

Four series of azidopurines have been synthesized and tested for cytokinin activity in the tobacco callus bioassay: 2- and 8-azido-N6-benzyladenines, -N6-(Δ2-isopentenyl)adenines, and -zeatins, and N6-(2- and 4-azidobenzyl)adenines. The compounds having 2-azido substitution on the adenine ring are as active as the corresponding parent compounds, while those with 8-azido substitution are about 10 or more times as active. The 8-azidozeatin, which is the most active cytokinin observed, exhibited higher than minimal detectable activity at 1.2 × 10−5 micromolar, the lowest concentration tested. The shape of the growth curve indicates that even a concentration as low as 5 × 10−6 micromolar would probably be effective. By comparison, the lowest active concentration ever reported for zeatin has been 5 × 10−5 micromolar, representing a sensitivity rarely attained. All of the azido compounds have been submitted to photolysis in aqueous ethanol, and the photoproducts have been detected and identified by low and high resolution mass spectrometry. They are rationalized as products of abstraction and insertion reactions of the intermediate nitrenes. The potential of the major released products as cytokinins was also assessed by bioassay. 2-Azido-N6-(Δ2-isopentenyl)adenine competed with [14C]kinetin for the cytokinin-binding protein isolated from wheat germ. When the azido compound was photolysed in the presence of this protein, its attachment effectively blocked the binding of [14C]kinetin. PMID:16661017

Co(III)(salen)-catalyzed phenolic kinetic resolution of two stereocentered benzyloxy and azido epoxides: its application in the synthesis of ICI-118,551, an anti-hypertensive agent.

PubMed

Karabal, Pratibha U; Kamble, Dayanand A; Sudalai, Arumugam

2014-04-21

The salen Co(III)-catalyzed phenolic kinetic resolution of racemic anti- or syn-azido and benzyloxy epoxides provides a practical route to a range of enantioenriched anti- or syn-1-aryloxy-3-azido or benzyloxy-2-alcohols in excellent yields and ees. The synthetic potential of this protocol is illustrated with an enantioselective synthesis of ICI-118,551, a β-blocker, in a highly optically pure form (99% ee).

Glycosyl-Nucleolipids as new bioinspired amphiphiles.

PubMed

Latxague, Laurent; Patwa, Amit; Amigues, Eric; Barthélémy, Philippe

2013-09-30

Four new Glycosyl-NucleoLipid (GNL) analogs featuring either a single fluorocarbon or double hydrocarbon chains were synthesized in good yields from azido thymidine as starting material. Physicochemical studies (surface tension measurements, differential scanning calorimetry) indicate that hydroxybutanamide-based GNLs feature endothermic phase transition temperatures like the previously reported double chain glycerol-based GNLs. The second generation of GNFs featuring a free nucleobase reported here presents a better surface activity (lower glim) compared to the first generation of GNFs.

Photoaffinity-labeled Cytokinins

PubMed Central

Theiler, Jane B.; Leonard, Nelson J.; Schmitz, Ruth Y.; Skoog, Folke

1976-01-01

Two new azidopurine derivatives, 2-azido-N6-(Δ2-isopentenyl)adenine and 2-azido-N6-benzyladenine, have been synthesized as potential photoaffinity labels for probing cytokinin-binding sites. The preparation and the biological activity of these compounds are described. PMID:16659772

Photoinduced azidohydroperoxidation of myrtenyl hydroperoxide with semiconductor particles and lucigenin as PET-catalysts.

PubMed

Griesbeck, Axel G; Reckenthäler, Melissa; Uhlig, Johannes

2010-06-01

The allylic hydroperoxide 2 (myrtenyl hydroperoxide), available from singlet oxygen photooxygenation of beta-pinene (1), is converted into the azido bis-hydroperoxide 3 by an electron-transfer induced azidyl radical formation and trapping of the initial tertiary carbon radical by triplet oxygen. The azido bis-hydroperoxide 3 is reduced to the azido 1,2-diol 4 or the amino diol 5, respectively. Beside classical fluorescent PET sensitizers such as rhodamines, also nanosized semiconductor particles as well as lucigenin were applied as catalysts. The electron transfer rate of azide oxidation was determined for lucigenin by fluorescence quenching analysis.

Bis(azido) compounds of Pd and Pt with bulky phosphine ligands (dppn=1,8-bis(diphenylphosphino)naphthalene, dppf=1,1‧-bis(diphenylphosphino)ferrocene, 1-dpn=1-diphenylphosphino-naphthalene): Preparation, structures, and reactivity toward isocyanides

NASA Astrophysics Data System (ADS)

Huh, Hyun Sue; Lee, Yeon Kyoung; Lee, Soon W.

2006-05-01

Pd-bis(azido) compounds [Pd(dppn)(N 3) 2] and [Pd(dppf)(N 3) 2], which contain bulky chelating bis(phosphine) ligands (dppn=1,8-bis(diphenylphosphino)naphthalene, dppf=1,1'-bis(diphenylphosphino)ferrocene), were prepared from the corresponding chlorides and NaN 3. We also prepared the Pt-bis(azido) compound [Pt(1-dpn)(SMe 2)(N 3) 2] containing a bulky monodentate phosphine (1-dpn=1-diphenylphosphino-naphthalene). All these compounds underwent [2+3] cycloaddition with isocyanides (R-NC, R=cyclohexyl, tert-butyl, 2,6-dimethylphenyl) to convert azido ligands to five-membered, C-coordinated tetrazolate rings. In addition, we observed the [Pd(dppn)Cl 2]-mediated C-C coupling of PhC tbnd6 CH to generate the η 2-PhC tbnd6 C-C tbnd6 CPh ligand. All compounds have been structurally characterized by X-ray diffraction.

6-Azido hyacinthacine A2 gives a straightforward access to the first multivalent pyrrolizidine architectures.

PubMed

D'Adamio, Giampiero; Parmeggiani, Camilla; Goti, Andrea; Moreno-Vargas, Antonio J; Moreno-Clavijo, Elena; Robina, Inmaculada; Cardona, Francesca

2014-08-28

The synthesis of the first multivalent pyrrolizidine iminosugars is reported. The key azido intermediates 4 and 31 were prepared after suitable synthetic elaboration of the cycloadduct obtained from 1,3-dipolar cycloaddition of D-arabinose derived nitrone to dimethylacrylamide. The key step of the strategy was the stereoselective installation of an azido moiety at C-6 of the pyrrolizidine skeleton. The click reaction with different monovalent and dendrimeric alkyne scaffolds allowed the preparation of a library of new mono- and multivalent pyrrolizidine compounds that were preliminarily assayed as glycosidase inhibitors towards a panel of commercially available glycosyl hydrolases.

Syntheses, structures and magnetisms of copper(II)–azido coordination compounds with p-substituted benzoates as coligands

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Cuiyu; Yu, Nan; Bu, Huaitian

2016-01-15

Employing p-substituted benzoates with electron-withdrawing/electron-donating groups as coligands, four copper–azido compounds, [Cu{sub 1.5}(p-NO{sub 2}-benzoate)(N{sub 3}){sub 2}(H{sub 2}O)]{sub n} (1), [Cu(p-NO{sub 2}-benzoate)(N{sub 3})(H{sub 2}O)]{sub n} (2), [Cu(p-OH-benzoate)(N{sub 3})(H{sub 2}O)]{sub n}·nH{sub 2}O (3) and [Cu(p-CH{sub 3}-benzoate)(N{sub 3})]{sub n} (4), have been hydrothermally synthesized and structurally charactierized by single crystal X-ray diffraction. Structural analysis reveals that all compounds are composed of mixed EO-azido and syn–syn carboxylato-bridged Cu-N{sub 3}/COO chains. Compound 1 features the alternating triple-bridged (μ-EO-N{sub 3})(μ-COO)(μ-H{sub 2}O) and the double-bridged (EO-N{sub 3}){sub 2} modes. Both of 2 and 3 display the triple-bridged fashion (μ-EO-N{sub 3})(μ-COO)(μ-H{sub 2}O). While 4 exhibits the double-bridged modemore » (μ-EO-N{sub 3})(μ-COO). Based on hydrogen-bonding interactions, Cu–N{sub 3}/COO chains in 1–3 are further connected to form 3D supramolecular frameworks. As for compound 4, there are not hydrogen-bonding interactions when the p-CH{sub 3} substituted benzoate is employed as coligand. These compounds show intrachain ferromagnetic performance and different bulk properties. Remarkably, 1 features metamagnetism from antiferromagnetism to ferrimagnetism, while 3 reveals long-range ferromagnetic ordering between Cu(II) ions. Magneto-structural correlation has been also investigated. - Graphical abstract: With p-substituted benzoates as coligands, copper–azido compounds were isolated and structrually, magnetically characterized. Magneto-structural correlation has been investigated in detail.« less

Crystal structure of 2-azido-1 H -imidazole-4,5-dicarbonitrile

DOE PAGES

Windler, G. Kenneth; Scott, Brian L.; Tomson, Neil C.; ...

2015-08-06

We report that in the title compound, C 5HN 7, the nitrile and azido substituents are close to being coplanar with the central ring. Molecules in the crystal are linked via an N—H...N hydrogen bond to a nitrile acceptor, forming a chain extending along the c-axis direction.

A novel photoaffinity ligand for the phencyclidine site of the N-methyl-D-aspartate receptor labels a Mr 120,000 polypeptide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sonders, M.S.; Barmettler, P.; Lee, J.A.

1990-04-25

A radiolabeled photoaffinity ligand has been developed for the N-methyl-D-aspartate (NMDA)-preferring excitatory amino acid receptor complex. (3H)3-Azido-(5S, 10R)(+)-5-methyl-10,11-dihydro-5H- dibenzo(a,d)cyclohepten-5,10-imine (3H)3-azido-MK-801 demonstrated nearly identical affinity, density of binding sites, selectivity, pH sensitivity, and pharmacological profile in reversible binding assays with guinea pig brain homogenates to those displayed by its parent compound, MK-801. When employed in a photo-labeling protocol designed to optimize specific incorporation, (3H)3-azido-MK-801 labeled a single protein band which migrated in sodium dodecyl sulfate-polyacrylamide gels with Mr = 120,000. Incorporation of tritium into this band was completely inhibited when homogenates and (3H)3-azido-MK-801 were coincubated with 10 microM phencyclidine. These datamore » suggest that the phencyclidine site of the NMDA receptor complex is at least in part comprised of a Mr = 120,000 polypeptide.« less

Synthesis and characterization of a 1D chain-like Cu{sub 6} substituted sandwich-type phosphotungstate with pendant dinuclear Cu–azido complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Yan-Ying; Zhao, Jun-Wei, E-mail: zhaojunwei@henu.edu.cn; Wei, Qi

A novel Cu–azido complex modified hexa-Cu{sup II} substituted sandwich-type phosphotungstate [Cu(en){sub 2}]([Cu{sub 2}(en){sub 2}(μ-1,1-N{sub 3}){sub 2}(H{sub 2}O)]{sub 2}[Cu{sub 6}(en){sub 2}(H{sub 2}O){sub 2}(B-α-PW{sub 9}O{sub 34}){sub 2}])·6H{sub 2}O (1) (en=ethylene-diamine) has been prepared under hydrothermal conditions and structurally characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. 1 displays a beautiful 1-D chain architecture constructed from sandwich-type [Cu{sub 2}(en){sub 2}(μ-1,1-N{sub 3}){sub 2}(H{sub 2}O)]{sub 2}[Cu{sub 6}(en){sub 2}(H{sub 2}O){sub 2}(B-α-PW{sub 9}O{sub 34}){sub 2}]{sup 2−} units and [Cu(en){sub 2}]{sup 2+} linkers. To our knowledge, 1 represents the first hexa-Cu{sup II} sandwiched phosphotungstate with supporting Cu–azido complexes. - Graphical abstract: Themore » first hexa-Cu{sup II} sandwiched phosphotungstate with supporting Cu–azido complexes has been prepared and characterized. Display Omitted - Highlights: • Hexa-copper-substituted phosphotungstate. • Cu–azido complexes modified hexa-Cu{sup II} substituted sandwich-type polyoxometalate. • 1-D chain architecture built by hexa-copper-substituted polyoxotungstate units.« less

TEMPO Monolayers on Si(100) Electrodes: Electrostatic Effects by the Electrolyte and Semiconductor Space-Charge on the Electroactivity of a Persistent Radical.

PubMed

Zhang, Long; Vogel, Yan Boris; Noble, Benjamin B; Gonçales, Vinicius R; Darwish, Nadim; Brun, Anton Le; Gooding, J Justin; Wallace, Gordon G; Coote, Michelle L; Ciampi, Simone

2016-08-03

This work demonstrates the effect of electrostatic interactions on the electroactivity of a persistent organic free radical. This was achieved by chemisorption of molecules of 4-azido-2,2,6,6-tetramethyl-1-piperdinyloxy (4-azido-TEMPO) onto monolayer-modified Si(100) electrodes using a two-step chemical procedure to preserve the open-shell state and hence the electroactivity of the nitroxide radical. Kinetic and thermodynamic parameters for the surface electrochemical reaction are investigated experimentally and analyzed with the aid of electrochemical digital simulations and quantum-chemical calculations of a theoretical model of the tethered TEMPO system. Interactions between the electrolyte anions and the TEMPO grafted on highly doped, i.e., metallic, electrodes can be tuned to predictably manipulate the oxidizing power of surface nitroxide/oxoammonium redox couple, hence showing the practical importance of the electrostatics on the electrolyte side of the radical monolayer. Conversely, for monolayers prepared on the poorly doped electrodes, the electrostatic interactions between the tethered TEMPO units and the semiconductor-side, i.e., space-charge, become dominant and result in drastic kinetic changes to the electroactivity of the radical monolayer as well as electrochemical nonidealities that can be explained as an increase in the self-interaction "a" parameter that leads to the Frumkin isotherm.

Direct imaging of glycans in Arabidopsis roots via click labeling of metabolically incorporated azido-monosaccharides.

PubMed

Hoogenboom, Jorin; Berghuis, Nathalja; Cramer, Dario; Geurts, Rene; Zuilhof, Han; Wennekes, Tom

2016-10-10

Carbohydrates, also called glycans, play a crucial but not fully understood role in plant health and development. The non-template driven formation of glycans makes it impossible to image them in vivo with genetically encoded fluorescent tags and related molecular biology approaches. A solution to this problem is the use of tailor-made glycan analogs that are metabolically incorporated by the plant into its glycans. These metabolically incorporated probes can be visualized, but techniques documented so far use toxic copper-catalyzed labeling. To further expand our knowledge of plant glycobiology by direct imaging of its glycans via this method, there is need for novel click-compatible glycan analogs for plants that can be bioorthogonally labelled via copper-free techniques. Arabidopsis seedlings were incubated with azido-containing monosaccharide analogs of N-acetylglucosamine, N-acetylgalactosamine, L-fucose, and L-arabinofuranose. These azido-monosaccharides were metabolically incorporated in plant cell wall glycans of Arabidopsis seedlings. Control experiments indicated active metabolic incorporation of the azido-monosaccharide analogs into glycans rather than through non-specific absorption of the glycan analogs onto the plant cell wall. Successful copper-free labeling reactions were performed, namely an inverse-electron demand Diels-Alder cycloaddition reaction using an incorporated N-acetylglucosamine analog, and a strain-promoted azide-alkyne click reaction. All evaluated azido-monosaccharide analogs were observed to be non-toxic at the used concentrations under normal growth conditions. Our results for the metabolic incorporation and fluorescent labeling of these azido-monosaccharide analogs expand the possibilities for studying plant glycans by direct imaging. Overall we successfully evaluated five azido-monosaccharide analogs for their ability to be metabolically incorporated in Arabidopsis roots and their imaging after fluorescent labeling. This expands the molecular toolbox for direct glycan imaging in plants, from three to eight glycan analogs, which enables more extensive future studies of spatiotemporal glycan dynamics in a wide variety of plant tissues and species. We also show, for the first time in metabolic labeling and imaging of plant glycans, the potential of two copper-free click chemistry methods that are bio-orthogonal and lead to more uniform labeling. These improved labeling methods can be generalized and extended to already existing and future click chemistry-enabled monosaccharide analogs in Arabidopsis.

Bioorthogonal layer-by-layer encapsulation of pancreatic islets via hyperbranched polymers

PubMed Central

Gattás-Asfura, Kerim M.; Stabler, Cherie L.

2013-01-01

The encapsulation of viable tissues via layer-by-layer polymer assembly provides a versatile platform for cell surface engineering, with nanoscale control over capsule properties. Herein, we report the development of a hyperbranched polymer-based, ultrathin capsule architecture expressing bioorthogonal functionality and tailored physiochemical properties. Random carbodiimide-based condensation of 3,5-dicarboxyphenyl glycineamide on alginate yielded a highly branched polysaccharide with multiple, spatially restricted, and readily functionalizable terminal carboxylate moieties. Poly(ethylene glycol) (PEG) was utilized to link azido end groups to the structured alginate. Together with phosphine functionalized poly(amido amine) (PAMAM) dendrimer, nanoscale layer-by-layer coatings, covalently stabilized via Staudinger ligation, were assembled onto solid surfaces and pancreatic islets. The effects of electrostatic and/or bioorthogonal covalent interlayer interactions on the resulting coating efficiency and stability, as well as pancreatic islet viability and function, were studied. These hyperbranched polymers provide a flexible platform for the formation of covalently stabilized ultrathin coatings on viable cells and tissues. In addition, the hyperbranched nature of the polymers presents a highly functionalized surface capable of bioorthogonal conjugation of additional bioactive or labeling motifs. PMID:24063764

Enantioselective Synthesis of Chiral α-Azido and α-Aryloxy Quaternary Stereogenic Centers via the Phase-Transfer-Catalyzed α-Alkylation of α-Bromomalonates, Followed by SN2 Substitution.

PubMed

Kim, Doyoung; Ha, Min Woo; Hong, Suckchang; Park, Cheonhyoung; Kim, Byungsoo; Yang, Jewon; Park, Hyeung-Geun

2017-05-05

A new efficient synthetic method for chiral α-azido-α-alkylmalonates and α-aryloxy-α-alkylmalonates was developed. The enantioselective α-alkylation of diphenylmethyl tert-butyl α-bromomalonate under phase-transfer catalytic conditions [(S,S)-3,4,5-trifluorophenyl-NAS bromide, 50% KOH, toluene, and -40 °C) provided the corresponding α-bromo-α-alkylmalonates in high chemical yields (≤98%) and high optical yields (≤99% ee). The resulting α-alkylated products were converted to α-azido-α-alkylmalonates (≤96%, ≤97% ee) and α-aryloxy-α-alkylmalonates (≤79%, ≤93% ee) by S N 2 substitution with sodium azide and aryloxides, respectively.

The n-propyl 3-azido-2,3-dideoxy-β-D-arabino-hexopyranoside: Syntheses, crystal structure, physical properties and stability constants of their complexes with Cu(II), Ni(II) and VO(II)

NASA Astrophysics Data System (ADS)

Barabaś, Anna; Madura, Izabela D.; Marek, Paulina H.; Dąbrowska, Aleksandra M.

2017-11-01

The structure, conformation and configuration of the n-propyl 3-azido-2,3-dideoxy-β-D-arabino-hexopyranoside (BAra-nPr) were determined by 1H NMR, 13C NMR, and IR spectroscopy, as well as by optical rotation. The crystal structure was confirmed by single-crystal X-ray diffraction studies at room temperature. The compound crystallizes in P21 space group symmetry of the monoclinic system. The molecule has a 4C1 chair conformation with azide group in the equatorial position both in a solution as well as in the crystal. The spatial arrangement of azide group is compared to other previously determined azidosugars. The hydrogen bonds between the hydroxyl group of sugar molecules lead to a ribbon structure observed also for the ethyl homolog. The packing of ribbons is dependent on the alkyl substituent length and with the elongation changes from pseudohexagonal to lamellar. Acidity constants for the n-propyl 3-azido-2,3-dideoxy-β-D-arabino-hexopyranoside (BAra-nPr) in an aqueous solution were evaluated by the spectrophotometric and potentiometric titrations methods. Title compound exhibit blue absorption with the maximum wavelengths in the range of 266 nm and 306 nm. Based on these measurements we showed equilibria existing in a particular solution and a distribution of species which have formed during the titration. We also investigated interactions between Cu(II), Ni(II) and VO(II) and title compound (as ligand L) during complexometric titration. On these bases we identified that in [CuII-BAra-nPr]2+ the ratio of the ligand L to metal ion M(II) was 3:1, while in [NiII-BAra-nPr]2+ and [VOII-BAra-nPr]2+ complexes 2:1 ratios were found. The cumulative stability constants (as log β) occurring in an aqueous solution for the complexes of BAra-nPr with Cu(II), Ni(II) and VO(IV) were 14.57; 11.71 and 4.20, respectively.

Protein valves prepared by click reaction grafting of poly(N-isopropylacrylamide) to electrospun poly(vinyl chloride) fibrous membranes

NASA Astrophysics Data System (ADS)

Guo, Jian-Wei; Lin, Zhen-Yu; Chang, Chi-Jung; Lu, Chien-Hsing; Chen, Jem-Kun

2018-05-01

In this study, poly(vinyl chloride) (PVC) was electrospun into fibrous membranes and then reacted with NaN3 to generate azido-terminated PVC fibrous membranes. A propargyl-terminated poly(N-isopropylacrylamide) (PNIPAAm) was also synthesized and then grafted, through click reactions, onto the azido-terminated PVC fiber surface. Protrusion-, scale-, and joint-like structures of the PNIPAAm grafts on the PVC fibers were formed upon increasing the molecular weight of the PNIPAAm grafts. The PNIPAAm-grafted PVC fibrous mats exhibited completely wetted surfaces at 25 °C because of their high roughness. The static water contact angle of the PNIPAAm-grafted PVC fibrous mats reached 140° when the temperature was increased to 45 °C. This thermoresponsive behavior was significantly greater than that of the PNIPAAm grafted on a flat surface. Temperature-responsive membranes were constructed having a pore size of 1.38 μm and applied as protein valves to block and release an antibody (fluorescein-conjugated AffiniPure goat anti-rabbit IgG). At 25 °C, the collection efficiency remained at 94% for antibody concentrations up to 60 ng/L. As the temperature increased to 45 °C, the collection efficiency decreased abruptly, to 4%, when the antibody concentration was greater than 20 ng/L. Accordingly, this system of PNIPAAm-grafted PVC fibers functioned as a protein valve allowing the capture and concentration of proteins.

Mass Spectrometric Analysis of the Cell Surface N-Glycoproteome by Combining Metabolic Labeling and Click Chemistry

NASA Astrophysics Data System (ADS)

Smeekens, Johanna M.; Chen, Weixuan; Wu, Ronghu

2015-04-01

Cell surface N-glycoproteins play extraordinarily important roles in cell-cell communication, cell-matrix interactions, and cellular response to environmental cues. Global analysis is exceptionally challenging because many N-glycoproteins are present at low abundances and effective separation is difficult to achieve. Here, we have developed a novel strategy integrating metabolic labeling, copper-free click chemistry, and mass spectrometry (MS)-based proteomics methods to analyze cell surface N-glycoproteins comprehensively and site-specifically. A sugar analog containing an azido group, N-azidoacetylgalactosamine, was fed to cells to label glycoproteins. Glycoproteins with the functional group on the cell surface were then bound to dibenzocyclooctyne-sulfo-biotin via copper-free click chemistry under physiological conditions. After protein extraction and digestion, glycopeptides with the biotin tag were enriched by NeutrAvidin conjugated beads. Enriched glycopeptides were deglycosylated with peptide- N-glycosidase F in heavy-oxygen water, and in the process of glycan removal, asparagine was converted to aspartic acid and tagged with 18O for MS analysis. With this strategy, 144 unique N-glycopeptides containing 152 N-glycosylation sites were identified in 110 proteins in HEK293T cells. As expected, 95% of identified glycoproteins were membrane proteins, which were highly enriched. Many sites were located on important receptors, transporters, and cluster of differentiation proteins. The experimental results demonstrated that the current method is very effective for the comprehensive and site-specific identification of the cell surface N-glycoproteome and can be extensively applied to other cell surface protein studies.

A precursor to the beta-pyranosides of 3-amino-3,6-dideoxy-D-mannose (mycosamine).

PubMed

Alais, J; David, S

1992-06-04

SN2-type reaction of 3-O-(1-imidazyl)sulfonyl-1,2:5,6-di-O-isopropylidene-alpha-D-gluco furanose with benzoate gave the 3-O-benzoyl-alpha-D-allo derivative 2, which was hydrolysed to give the 5,6-diol 3. Compound 3 was converted into the 6-deoxy-6-iodo derivative 4 which was reduced with tributylstannane, and then position 5 was protected by benzyloxymethylation, to give 3-O-benzoyl-5-O-benzyloxymethyl-6-deoxy-1,2-O-isopropylidene-alpha -D- allofuranose (6). Debenzoylation of 6 gave 7, (1-imidazyl)sulfonylation gave 8, and azide displacement gave 3-azido-5-O-benzyloxymethyl-3,6-dideoxy- 1,2-O-isopropylidene-alpha-D-glucofuranose (9, 85%). Acetolysis of 9 gave 1,2,4-tri-O-acetyl-3-azido-3,6-dideoxy-alpha,beta-D-glucopyranose (10 and 11). Selective hydrolysis of AcO-1 in the mixture of 10 and 11 with hydrazine acetate (----12), followed by conversion into the pyranosyl chloride 13, treatment with N,N-dimethylformamide dimethyl acetal in the presence of tetrabutylammonium bromide, and benzylation gave 3-azido-4-O-benzyl-3,6-dideoxy-1,2-O-(1-methoxyethylidene)-alpha-D -glucopyranose (15). Treatment of 15 with dry acetic acid gave 1,2-di-O-acetyl-3-azido-4-O-benzyl-3,6-dideoxy-beta-D-glucopyranose (16, 86% yield) that was an excellent glycosyl donor in the presence of trimethylsilyl triflate, allowing the synthesis of cyclohexyl 2-O-acetyl-3-azido-4-O-benzyl-3,6-dideoxy-beta-D-glucopyranoside (17, 90%).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of Osmolytes on the Conformational Behavior of a Macromolecule in a Cytoplasm-like Crowded Environment: A Femtosecond Mid-IR Pump-Probe Spectroscopy Study.

PubMed

Kundu, Achintya; Verma, Pramod Kumar; Cho, Minhaeng

2018-02-15

Osmolytes found endogenously in almost all living beings play an important role in regulating cell volume under harsh environment. Here, to address the longstanding questions about the underlying mechanism of osmolyte effects, we use femtosecond mid-IR pump-probe spectroscopy with two different IR probes that are the OD stretching mode of HDO and the azido stretching mode of azido-derivatized poly(ethylene glycol) dimethyl ether (PEGDME). Our experimental results show that protecting osmolytes bind strongly with water molecules and dehydrate polymer surface, which results in promoting intramolecular interactions of the polymer. By contrast, urea behaves like water molecules without significantly disrupting water H-bonding network and favors extended and random-coil segments of the polymer chain by directly participating in solvation of the polymer. Our findings highlight the importance of direct interaction between urea and macromolecule, while protecting osmolytes indirectly affect the macromolecule through enhancing the water-osmolyte interaction in a crowded environment, which is the case that is often encountered in real biological systems.

Biofunctionalization on alkylated silicon substrate surfaces via "click" chemistry.

PubMed

Qin, Guoting; Santos, Catherine; Zhang, Wen; Li, Yan; Kumar, Amit; Erasquin, Uriel J; Liu, Kai; Muradov, Pavel; Trautner, Barbara Wells; Cai, Chengzhi

2010-11-24

Biofunctionalization of silicon substrates is important to the development of silicon-based biosensors and devices. Compared to conventional organosiloxane films on silicon oxide intermediate layers, organic monolayers directly bound to the nonoxidized silicon substrates via Si-C bonds enhance the sensitivity of detection and the stability against hydrolytic cleavage. Such monolayers presenting a high density of terminal alkynyl groups for bioconjugation via copper-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC, a "click" reaction) were reported. However, yields of the CuAAC reactions on these monolayer platforms were low. Also, the nonspecific adsorption of proteins on the resultant surfaces remained a major obstacle for many potential biological applications. Herein, we report a new type of "clickable" monolayers grown by selective, photoactivated surface hydrosilylation of α,ω-alkenynes, where the alkynyl terminal is protected with a trimethylgermanyl (TMG) group, on hydrogen-terminated silicon substrates. The TMG groups on the film are readily removed in aqueous solutions in the presence of Cu(I). Significantly, the degermanylation and the subsequent CuAAC reaction with various azides could be combined into a single step in good yields. Thus, oligo(ethylene glycol) (OEG) with an azido tag was attached to the TMG-alkyne surfaces, leading to OEG-terminated surfaces that reduced the nonspecific adsorption of protein (fibrinogen) by >98%. The CuAAC reaction could be performed in microarray format to generate arrays of mannose and biotin with varied densities on the protein-resistant OEG background. We also demonstrated that the monolayer platform could be functionalized with mannose for highly specific capturing of living targets (Escherichia coli expressing fimbriae) onto the silicon substrates.

An Azido-Biotin Reagent for Use in the Isolation of Protein Adducts of Lipid-derived Electrophiles by Streptavidin Catch and Photorelease*

PubMed Central

Kim, Hye-Young H.; Tallman, Keri A.; Liebler, Daniel C.; Porter, Ned A.

2009-01-01

HNE (4-hydroxynonenal), a byproduct of lipid peroxidation, reacts with nucleophilic centers on proteins. A terminal alkynyl analog of HNE (alkynyl HNE, aHNE) serves as a surrogate for HNE itself, both compounds reacting with protein amine and thiol functional groups by similar chemistry. Proteins modified with aHNE undergo reaction with a click reagent that bears azido and biotin groups separated by a photocleavable linker. Peptides and proteins modified in this way are affinity purified on streptavidin beads. Photolysis of the beads with a low intensity UV light releases bound biotinylated proteins or peptides, i.e. proteins or peptides modified by aHNE. Two strategies, (a) protein catch and photorelease and (b) peptide catch and photorelease, are employed to enrich adducted proteins or peptide mixtures highly enriched in adducts. Proteomics analysis of the streptavidin-purified peptides by LC-MS/MS permits identification of the adduction site. Identification of 30 separate peptides from human serum albumin by peptide catch and photorelease reveals 18 different aHNE adduction sites on the protein. Protein catch and photorelease shows that both HSA and ApoA1 in human plasma undergo significant modification by aHNE. PMID:19483245

Biofunctionalized silicon nitride platform for sensing applications.

PubMed

Hoi, Hiofan; Rezaie, Salva S; Gong, Lu; Sen, Payel; Zeng, Hongbo; Montemagno, Carlo; Gupta, Manisha

2018-04-15

Silicon nitride (SiN x ) based biosensors have the potential to converge on the technological achievements of semiconductor microfabrication and biotechnology. Development of biofunctionalized SiN x surface and its integration with other devices will allow us to integrate the biosensing capability with probe control, data acquisition and data processing. Here we use the hydrogen plasma generated by inductively coupled plasma-reactive ion etching (ICP-RIE) technique to produce amino-functionality on the surface of SiN x which can then be readily used for biomolecule immobilization. ICP-RIE produces high-density hydrogen ions/radicals at low energy, which produces high-density amino group on the SiN x surface within a short duration of time and with minimal surface damage. In this work, we have demonstrated selective amination of SiN x surface as compared to Si surface. The as-activated SiN x surface can be readily biofunctionalized with both protein and oligonucleotide through covalent immobilization. N-5-azido-2-nitrobenzoyloxysuccinimide, a photoactivable amino reactive bifunctional crosslinker, was used and greater than 90% surface coverage was achieved for protein immobilization. In addition, ssDNA immobilization and hybridization with its complemented strand was shown. Thus, we demonstrate a uniform, reliable, fast and economical technique for creating biofunctionalized SiN x surface that can be used for developing compact high-sensitivity biosensors. Copyright © 2017 Elsevier B.V. All rights reserved.

A 3D complex containing novel 2D Cu{sup II}-azido layers: Structure, magnetic properties and effects of 'Non-innocent' reagent

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Xue-Miao; Guo, Qian; Zhao, Jiong-Peng, E-mail: horryzhao@yahoo.com

A novel copper-azido coordination polymer, [Cu{sub 2}(N{sub 3}){sub 3}(L)]{sub n} (1, HL=pyrazine-2-carboxylic acid), has been synthesized by hydrothermal reaction with 'Non-innocent' reagent in the aqueous solution. In the reaction system, Cu{sup II} ions are avoided to reduce to Cu{sup I} ions due to the existence of Nd{sup III}. It is found that the complex is a 3D structure based on two double EO azido bridged trimmers and octahedron Cu{sup II} ions, in which the azide ligands take on EO and {mu}{sub 1,1,3} mode to form Cu{sup II}-azido 2D layers, furthermore L ligands pillar 2D layers into an infinite 3D frameworkmore » with the Schlaefli symbol of {l_brace}4;6{sup 2}{r_brace}4{l_brace}4{sup 2};6{sup 12};8{sup 10};10{sup 4}{r_brace}{l_brace}4{sup 2};6{sup 4}{r_brace}. Magnetic studies revealed that the interactions between the Cu{sup II} ions in the trimmer are ferromagnetic for the Cu-N-Cu angle nearly 98 Degree-Sign , while the interactions between the trimmer and octahedron Cu{sup II} ion are antiferromgantic and result in an antiferromagnetic state. - Graphical abstract: A 3D complex containing novel 2D Cu{sup II}-azido layers, [Cu{sub 2}(N{sub 3}){sub 3}(L)]{sub n} (HL=pyrazine-2-carboxylic acid), was synthesized by hydrothermal reaction and exhibit interesting structure and magnetic properties. Highlights: Black-Right-Pointing-Pointer 'Non-innocent' reagents plays a key role in the process of formation of this complex. Black-Right-Pointing-Pointer 2D layer is formed only by Cu{sup II} ions and azido ligands. Black-Right-Pointing-Pointer Pyrazine-2-carboxylate ligands reinforce 2D layers and pillar them into an infinite 3D framework. Black-Right-Pointing-Pointer Magnetic study indicates that alternating FM-AF coupling exists in the complex.« less

Divergent Synthesis of Solanidine and 22-epi-Solanidine.

PubMed

Hou, Ling-Li; Shi, Yong; Zhang, Zhi-Dan; Wu, Jing-Jing; Yang, Qing-Xiong; Tian, Wei-Sheng

2017-07-21

A divergent synthesis of solanidine and 22-epi-solanidine, two 25S natural steroidal alkaloids, from 25R-configured diosgenin acetate, is described. Initially, solanidine was synthesized through a series of transformations including a cascade ring-switching process of furostan-26-acid, an epimerization of C25 controlled by the conformation of six-membered lactone ring, an intramolecular Schmidt reaction, and an imine reduction/intramolecular aminolysis process. To address the epimerization issue during Schmidt reaction, an improved synthesis was developed, which also led to a synthesis of 22-epi-solanidine. In this synthesis, selective transformation of azido lactone to azido diol and amino diol was realized through a reduction relay tactic. The azido diol was transformed to solanidine via an intramolecular Schmidt reaction/N-alkylation/reduction process and to 22-epi-solanidine via an intramolecular double N-alkylation process.

Protein conformation by EPR spectroscopy using gadolinium tags clicked to genetically encoded p-azido-L-phenylalanine.

PubMed

Abdelkader, E H; Feintuch, A; Yao, X; Adams, L A; Aurelio, L; Graham, B; Goldfarb, D; Otting, G

2015-11-14

Quantitative cysteine-independent ligation of a Gd(3+) tag to genetically encoded p-azido-L-phenylalanine via Cu(I)-catalyzed click chemistry is shown to deliver an exceptionally powerful tool for Gd(3+)-Gd(3+) distance measurements by double electron-electron resonance (DEER) experiments, as the position of the Gd(3+) ion relative to the protein can be predicted with high accuracy.

Regioselective SN2 reactions for rapid syntheses of azido-inositols by one-pot sequence-specific nucleophilysis.

PubMed

Ravi, Arthi; Hassan, Syed Zahid; Vanikrishna, Ajithkumar N; Sureshan, Kana M

2017-04-04

Triflates of myo-inositol undergo facile solvolysis in DMSO and DMF yielding S N 2 products substituted with O-nucleophiles; DMF showed slower kinetics. Axial O-triflate undergoes faster substitution than equatorial O-triflate. By exploiting this difference in kinetics, solvent-tuning and sequence-controlled nucleophilysis, rapid synthesis of three azido-inositols of myo-configuration from myo-inositol itself has been achieved.

A triple-bridged azido-Cu(II) chain compound fine-tuned by mixed carboxylate/ethanol linkers displays slow-relaxation and ferromagnetic order: synthesis, crystal structure, magnetic properties and DFT calculations.

PubMed

Liu, Xiangyu; Chen, Sanping; Grancha, Thais; Pardo, Emilio; Ke, Hongshan; Yin, Bing; Wei, Qing; Xie, Gang; Gao, Shengli

2014-11-07

A new azido-Cu(II) compound, [Cu(4-fba)(N3)(C2H5OH)] (4-fba = 4-fluorobenzoic acid) (1), has been synthesized and characterized. The X-ray crystal structure analysis demonstrates that only one crystallographically independent Cu(II) ion in the asymmetric unit of 1 exhibits a stretched octahedral geometry in which two azido N atoms and two carboxylic O atoms locate in the equatorial square, while two ethanol O atoms occupy the apical positions, forming a 1D Cu(II) chain with an alternating triple-bridge of EO-azido, syn,syn-carboxylate, and μ2-ethanol. The title compound consists of ferromagnetically interacting ferromagnetic chains, which exhibit ferromagnetic order (T(c) = 7.0 K). The strong ferromagnetic coupling between adjacent Cu(II) ions within each chain is due to the countercomplementarity of the super-exchange pathways, whereas the ferromagnetic interchain interactions--responsible for the long-range magnetic ordering--are most likely due to the presence of coordinated ethanol molecules establishing hydrogen bonds with neighboring chains. DFT calculations have been performed on compound 1 to offer a qualitative theoretical explanation of the magnetic behavior.

Diazo Compounds: Versatile Tools for Chemical Biology.

PubMed

Mix, Kalie A; Aronoff, Matthew R; Raines, Ronald T

2016-12-16

Diazo groups have broad and tunable reactivity. That and other attributes endow diazo compounds with the potential to be valuable reagents for chemical biologists. The presence of diazo groups in natural products underscores their metabolic stability and anticipates their utility in a biological context. The chemoselectivity of diazo groups, even in the presence of azido groups, presents many opportunities. Already, diazo compounds have served as chemical probes and elicited novel modifications of proteins and nucleic acids. Here, we review advances that have facilitated the chemical synthesis of diazo compounds, and we highlight applications of diazo compounds in the detection and modification of biomolecules.

Convenient approaches to synthesis of furanoid sugar-aza-crown ethers from C-ribosyl azido aldehyde via a reductive amination/amidation.

PubMed

Hsieh, Yu-Chi; Chir, Jiun-Ly; Zou, Wei; Wu, Hsiu-Han; Wu, An-Tai

2009-05-26

A short and highly efficient route to the alpha-anomer of a furanoid sugar-aza-crown ether was developed by a one-pot reductive amination of an alpha-anomer C-ribosyl azido aldehyde. In addition, the beta-anomer furanoid sugar-aza-crown ether was synthesized from a linear disaccharide precursor via amidation and then followed by microwave-assisted amide reduction.

Biomarker-Based Metabolic Labeling for Redirected and Enhanced Immune Response.

PubMed

Li, Shanshan; Yu, Bingchen; Wang, Jiajia; Zheng, Yueqin; Zhang, Huajie; Walker, Margaret J; Yuan, Zhengnan; Zhu, He; Zhang, Jun; Wang, Peng George; Wang, Binghe

2018-06-01

Installation of an antibody-recruiting moiety on the surface of disease-relevant cells can lead to the selective destruction of targets by the immune system. Such an approach can be an alternative strategy to traditional chemotherapeutics in cancer therapy and possibly other diseases. Herein we describe the development of a new strategy to selectively label targets with an antibody-recruiting moiety through its covalent and stable installation, complementing existing methods of employing reversible binding. This is achieved through selective delivery of 1,3,4- O-acetyl- N-azidoacetylmannosamine (Ac 3 ManNAz) to folate receptor-overexpressing cells using an Ac 3 ManNAz-folate conjugate via a cleavable linker. As such, Ac 3 ManNAz is converted to cell surface glycan bearing an azido group, which serves as an anchor to introduce l-rhamnose (Rha), a hapten, via a click reaction with aza-dibenzocyclooctyne (DBCO)-Rha. We tested this method in several cell lines including KB, HEK-293, and MCF7 and were able to demonstrate the following: 1) Rha can be selectively installed to the folate receptor overexpressing cell surface and 2) the Rha installed on the target surface can recruit anti-rhamnose (anti-Rha) antibodies, leading to the destruction of target cells via complement-dependent cytotoxicity (CDC) and antibody-dependent cellular phagocytosis (ADCP).

Use of a small molecule as an initiator for interchain staudinger reaction: A new ATP sensing platform using product fluorescence.

PubMed

Yu, Huan; Zheng, Jing; Yang, Sheng; Asiri, Abdullah M; Alamry, Khalid A; Sun, Mingtai; Zhang, Kui; Wang, Suhua; Yang, Ronghua

2018-02-01

We demonstrated that a small molecule induced interchain Staudinger reaction can be employed for highly selective detection of adenosine triphosphate (ATP), an important energy-storage biomolecule. A designed ATP split aptamer (A1) was first functionalized with a weakly fluorescent coumarin derivative due to an azide group (azido-coumarin). The second DNA strand (A2) was covalently linked with triphenylphosphine, which could selectively and efficiently reduce azido to amino group through the Staudinger reaction. The A2 was then hybridized with a half of another designed longer DNA strand (T1). The second half of T1 was a split aptamer and selectively recognized ATP with A1 to form a sandwich structure. The specific interaction between ATP and the aptamers drew the two functionalized DNA strands (A1 and A2) together to initiate the interchain Staudinger reduction at fmol-nmol concentration level, hence produced fluorescent 7-aminocoumarin which could be used as an indicator for the presence of trace ATP. The reaction process had a concentration dependent manner with ATP in a large concentration range. Such a strategy of interchain Staudinger reaction can be extended to construct biosensors for other small functional molecules on the basis of judiciously designed aptamers. Copyright © 2017 Elsevier B.V. All rights reserved.

Size-matched alkyne-conjugated cyanine fluorophores to identify differences in protein glycosylation.

PubMed

Burnham-Marusich, Amanda R; Plechaty, Anna M; Berninsone, Patricia M

2014-09-01

Currently, there are few methods to detect differences in posttranslational modifications (PTMs) in a specific manner from complex mixtures. Thus, we developed an approach that combines the sensitivity and specificity of click chemistry with the resolution capabilities of 2D-DIGE. In "Click-DIGE", posttranslationally modified proteins are metabolically labeled with azido-substrate analogs, then size- and charge-matched alkyne-Cy3 or alkyne-Cy5 dyes are covalently attached to the azide of the PTM by click chemistry. The fluorescently-tagged protein samples are then multiplexed for 2DE analysis. Whereas standard DIGE labels all proteins, Click-DIGE focuses the analysis of protein differences to a targeted subset of posttranslationally modified proteins within a complex sample (i.e. specific labeling and analysis of azido glycoproteins within a cell lysate). Our data indicate that (i) Click-DIGE specifically labels azido proteins, (ii) the resulting Cy-protein conjugates are spectrally distinct, and (iii) the conjugates are size- and charge-matched at the level of 2DE. We demonstrate the utility of this approach by detecting multiple differentially expressed glycoproteins between a mutant cell line defective in UDP-galactose transport and the parental cell line. We anticipate that the diversity of azido substrates already available will enable Click-DIGE to be compatible with analysis of a wide range of PTMs. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of auxin-binding proteins from zucchini plasma membrane

NASA Technical Reports Server (NTRS)

Hicks, G. R.; Rice, M. S.; Lomax, T. L.

1993-01-01

We have previously identified two auxin-binding polypeptides in plasma membrane (PM) preparations from zucchini (Cucurbita pepo L.) (Hicks et al. 1989, Proc. Natl. Acad. Sci. USA 86, 4948-4952). These polypeptides have molecular weights of 40 kDa and 42 kDa and label specifically with the photoaffinity auxin analog 5-N3-7-3H-IAA (azido-IAA). Azido-IAA permits both the covalent and radioactive tagging of auxin-binding proteins and has allowed us to characterize further the 40-kDa and 42-kDa polypeptides, including the nature of their attachment to the PM, their relationship to each other, and their potential function. The azido-IAA-labeled polypeptides remain in the pelleted membrane fraction following high-salt and detergent washes, which indicates a tight and possibly integral association with the PM. Two-dimensional electrophoresis of partially purified azido-IAA-labeled protein demonstrates that, in addition to the major isoforms of the 40-kDa and 42-kDa polypeptides, which possess isoelectric points (pIs) of 8.2 and 7.2, respectively, several less abundant isoforms that display unique pIs are apparent at both molecular masses. Tryptic and chymotryptic digestion of the auxin-binding proteins indicates that the 40-kDa and 42-kDa polypeptides are closely related or are modifications of the same polypeptide. Phase extraction with the nonionic detergent Triton X-114 results in partitioning of the azido-IAA-labeled polypeptides into the aqueous (hydrophilic) phase. This apparently paradoxical behavior is also exhibited by certain integral membrane proteins that aggregate to form channels. The results of gel filtration indicate that the auxin-binding proteins do indeed aggregate strongly and that the polypeptides associate to form a dimer or multimeric complex in vivo. These characteristics are consistent with the hypothesis that the 40-kDa and 42-kDa polypeptides are subunits of a multimeric integral membrane protein which has an auxin-binding site, and which may possess transporter or channel function.

Characterization of auxin-binding proteins from zucchini plasma membrane.

PubMed

Hicks, G R; Rice, M S; Lomax, T L

1993-01-01

We have previously identified two auxin-binding polypeptides in plasma membrane (PM) preparations from zucchini (Cucurbita pepo L.) (Hicks et al. 1989, Proc. Natl. Acad. Sci. USA 86, 4948-4952). These polypeptides have molecular weights of 40 kDa and 42 kDa and label specifically with the photoaffinity auxin analog 5-N3-7-3H-IAA (azido-IAA). Azido-IAA permits both the covalent and radioactive tagging of auxin-binding proteins and has allowed us to characterize further the 40-kDa and 42-kDa polypeptides, including the nature of their attachment to the PM, their relationship to each other, and their potential function. The azido-IAA-labeled polypeptides remain in the pelleted membrane fraction following high-salt and detergent washes, which indicates a tight and possibly integral association with the PM. Two-dimensional electrophoresis of partially purified azido-IAA-labeled protein demonstrates that, in addition to the major isoforms of the 40-kDa and 42-kDa polypeptides, which possess isoelectric points (pIs) of 8.2 and 7.2, respectively, several less abundant isoforms that display unique pIs are apparent at both molecular masses. Tryptic and chymotryptic digestion of the auxin-binding proteins indicates that the 40-kDa and 42-kDa polypeptides are closely related or are modifications of the same polypeptide. Phase extraction with the nonionic detergent Triton X-114 results in partitioning of the azido-IAA-labeled polypeptides into the aqueous (hydrophilic) phase. This apparently paradoxical behavior is also exhibited by certain integral membrane proteins that aggregate to form channels. The results of gel filtration indicate that the auxin-binding proteins do indeed aggregate strongly and that the polypeptides associate to form a dimer or multimeric complex in vivo. These characteristics are consistent with the hypothesis that the 40-kDa and 42-kDa polypeptides are subunits of a multimeric integral membrane protein which has an auxin-binding site, and which may possess transporter or channel function.

Identification of Protein Targets of 4-Hydroxynonenal Using Click Chemistry for Ex Vivo Biotinylation of Azido and Alkynyl Derivatives

PubMed Central

Vila, Andrew; Tallman, Keri A.; Jacobs, Aaron T.; Liebler, Daniel C.; Porter, Ned A.; Marnett, Lawrence J.

2009-01-01

Polyunsaturated fatty acids (PUFA) are primary targets of free radical damage during oxidative stress. Diffusible electrophilic α, β-unsaturated aldehydes, such as 4-hydroxynonenal (HNE), have been shown to modify proteins that mediate cell signaling (e.g. IKK and Keap1) and alter gene expression pathways responsible for inducing antioxidant genes, heat shock proteins, and the DNA damage response. To fully understand cellular responses to HNE, it is important to determine its protein targets in an unbiased fashion. This requires a strategy for detecting and isolating HNE-modified proteins regardless of the nature of the chemical linkage between HNE and its targets. Azido or alkynyl derivatives of HNE were synthesized and demonstrated to be equivalent to HNE in their ability to induce heme oxygenase induction and induce apoptosis in colon cancer (RKO) cells. Cells exposed to the tagged HNE derivatives were lysed and exposed to reagents to effect Staudinger ligation or copper-catalyzed Huisgen 1,3 dipolar cycloaddition reaction (click chemistry) to conjugate HNE-adducted proteins with biotin for subsequent affinity purification. Both strategies yielded efficient biotinylation of tagged HNE-protein conjugates but click chemistry was found to be superior for recovery of biotinylated proteins from streptavidin-coated beads. Biotinylated proteins were detected in lysates from RKO cell incubations with azido-HNE at concentrations as low as 1 μM. These proteins were affinity purified with streptavidin beads and proteomic analysis was performed by linear ion trap mass spectrometry. Proteomic analysis revealed a dose-dependent increase in labeled proteins with increased sequence coverage at higher concentrations. Several proteins involved in stress signaling (heat shock proteins 70 and 90, and the 78-kDa glucose-regulated protein) were selectively adducted by azido- and alkynyl-HNE. The use of azido and alkynyl derivatives in conjunction with click chemistry appears to be a valuable approach for the identification of the protein targets of HNE. PMID:18232660

Ratiometric Fluorescence Azide-Alkyne Cycloaddition for Live Mammalian Cell Imaging.

PubMed

Fu, Hongxia; Li, Yanru; Sun, Lingbo; He, Pan; Duan, Xinrui

2015-11-17

Click chemistry with metabolic labeling has been widely used for selectively imaging biomacromolecules in cells. The first example of azide-alkyne cycloaddition for ratiometric fluorescent imaging of live cells is reported. The precursor of the azido fluorophore (cresyl violet) has a fluorescence emission peak at 620 nm. The electron-rich nitrogen of the azido group blue-shifts the emission peak to 566 nm. When the click reaction occurs, an emission peak appears at 620 nm due to the lower electronic density of the newly formed triazole ring, which allows us to ratiometrically record fluorescence signals. This emission shift was applied to ratiometric imaging of propargylcholine- and dibenzocyclooctyne-labeled human breast cancer cells MCF-7 under laser confocal microscopy. Two typical triazole compounds were isolated for photophysical parameter measurements. The emission spectra presented a fluorescence emission peak around 620 nm for both click products. The results further confirmed the emission wavelength change was the result of azide-alkyne cycloaddition reaction. Since nearly all biomolecules can be metabolically labeled by reported alkyne-functionalized derivatives of native metabolites, our method can be readily applied to image these biomacromolecules.

Azidoethoxyphenylalanine as a Vibrational Reporter and Click Chemistry Partner in Proteins

PubMed Central

Tookmanian, Elise M.; Phillips-Piro, Christine M.; Fenlon, Edward E.; Brewer, Scott H.

2016-01-01

An unnatural amino acid, 4-(2-azidoethoxy)-l-phenylalanine (AePhe, 1), was designed and synthesized in three steps from known compounds in 54% overall yield. The sensitivity of the IR absorption of the azide of AePhe was established by comparison of the frequency of the asymmetric stretch vibration in water and dimethyl sulfoxide. AePhe was successfully incorporated into superfolder green fluorescent protein (sfGFP) at the 133 and 149 sites using the amber codon suppression method. The IR spectra of these sfGFP constructs indicated that the azide group at the 149 site was not fully solvated despite the location in sfGFP and the three-atom linker between the azido group and the aromatic ring of AePhe. An X-ray crystal structure of sfGFP-149-AePhe was solved at 1.45 Å resolution and provides an explanation for the IR data as the flexible linker adopts a conformation which partially buries the azide on the protein surface. Both sfGFP-AePhe constructs efficiently undergo a bioorthogonal strain-promoted click cycloaddition with a dibenzocyclooctyne derivative. PMID:26608683

Structure-Activity Relationships of Orotidine-5′-Monophosphate Decarboxylase Inhibitors as Anticancer Agents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bello, A.; Konforte, D; Poduch, E

2009-01-01

A series of 6-substituted and 5-fluoro-6-substituted uridine derivatives were synthesized and evaluated for their potential as anticancer agents. The designed molecules were synthesized from either fully protected uridine or the corresponding 5-fluorouridine derivatives. The mononucleotide derivatives were used for enzyme inhibition investigations against ODCase. Anticancer activities of all the synthesized derivatives were evaluated using the nucleoside forms of the inhibitors. 5-Fluoro-UMP was a very weak inhibitor of ODCase. 6-Azido-5-fluoro and 5-fluoro-6-iodo derivatives are covalent inhibitors of ODCase, and the active site Lys145 residue covalently binds to the ligand after the elimination of the 6-substitution. Among the synthesized nucleoside derivatives, 6-azido-5-fluoro,more » 6-amino-5-fluoro, and 6-carbaldehyde-5-fluoro derivatives showed potent anticancer activities in cell-based assays against various leukemia cell lines. On the basis of the overall profile, 6-azido-5-fluoro and 6-amino-5-fluoro uridine derivatives exhibited potential for further investigations.« less

Evidence that Na+/H+ exchanger 1 is an ATP-binding protein.

PubMed

Shimada-Shimizu, Naoko; Hisamitsu, Takashi; Nakamura, Tomoe Y; Wakabayashi, Shigeo

2013-03-01

Na(+)/H(+) exchanger (NHE) 1 is a member of the solute carrier superfamily, which regulates intracellular ionic homeostasis. NHE1 is known to require cellular ATP for its activity, despite there being no requirement for energy input from ATP hydrolysis. In this study, we investigated whether NHE1 is an ATP-binding protein. We designed a baculovirus vector carrying both epitope-tagged NHE1 and its cytosolic subunit CHP1, and expressed the functional NHE1-CHP1 complex on the surface of Sf9 insect cells. Using the purified complex protein consisting of NHE1 and CHP1 from Sf9 cells, we examined a photoaffinity labeling reaction with 8-azido-ATP-biotin. UV irradiation promoted the incorporation of 8-azido-ATP into NHE1, but not into CHP1, with an apparent Kd of 29.1 µM in the presence of Mg(2+). The nonlabeled nucleotides ATP, GTP, TTP and CTP all inhibited this crosslinking. However, ATP had the strongest inhibitory effect, with an apparent inhibition constant (IC50) for ATP of 2.2 mM, close to the ATP concentration giving the half-maximal activation of NHE1 activity. Importantly, crosslinking was more strongly inhibited by ATP than by ADP, suggesting that ATP is dissociated from NHE1 upon ATP hydrolysis. Limited proteolysis with thrombin and deletion mutant analysis revealed that the 8-azido-ATP-binding site is within the C-terminal cytoplasmic domain of NHE1. Equilibrium dialysis with NHE1-derived peptides provided evidence that ATP directly binds to the proximal cytoplasmic region (Gly542-Pro598), which is critical for ATP-dependent regulation of NHE1. These findings suggest that NHE1 is an ATP-binding transporter. Thus, ATP may serve as a direct activator of NHE1. © 2013 The Authors Journal compilation © 2013 FEBS.

Pinpoint chemical modification of Asp160 in the 49 kDa subunit of bovine mitochondrial complex I via a combination of ligand-directed tosyl chemistry and click chemistry.

PubMed

Masuya, Takahiro; Murai, Masatoshi; Morisaka, Hironobu; Miyoshi, Hideto

2014-12-16

Through a ligand-directed tosyl (LDT) chemistry strategy using the synthetic acetogenin ligand AL1, we succeeded in the pinpoint alkynylation (-C≡CH) of Asp160 in the 49 kDa subunit of bovine complex I, which may be located in the inner part of the putative quinone binding cavity of the enzyme [Masuya, T., et al. (2014) Biochemistry, 53, 2307-2317]. This study provided a promising technique for diverse chemical modifications of complex I. To further improve this technique for its adaptation to intact complex I, we here synthesized the new acetogenin ligand AL2, possessing an azido (-N₃) group in place of the terminal alkyne in AL1, and attempted the pinpoint azidation of complex I in bovine heart submitochondrial particles. Careful proteomic analyses revealed that, just as in the case of AL1, azidation occurred at 49 kDa Asp160 with a reaction yield of ∼50%, verifying the high site specificity of our LDT chemistry using acetogenin ligands. This finding prompted us to speculate that a reactivity of the azido group incorporated into Asp160 (Asp160-N₃) against externally added chemicals can be employed to characterize the structural features of the quinone/inhibitor binding cavity. Consequently, we used a ring-strained cycloalkyne possessing a rhodamine fluorophore (TAMRA-DIBO), which can covalently attach to an azido group via so-called click chemistry without Cu¹⁺ catalysis, as the reaction partner of Asp160-N₃. We found that bulky TAMRA-DIBO is capable of reacting directly with Asp160-N₃ in intact complex I. Unexpectedly, the presence of an excess amount of short-chain ubiquinones as well as some strong inhibitors (e.g., quinazoline and fenpyroximate) did not interfere with the reaction between TAMRA-DIBO and Asp160-N₃; nevertheless, bullatacin, a member of the natural acetogenins, markedly interfered with this reaction. Taking the marked bulkiness of TAMRA-DIBO into consideration, it appears to be difficult to reconcile these results with the proposal that only a narrow entry point accessing to the quinone/inhibitor binding cavity exists in complex I [Baradaran, R., et al. (2013) Nature, 494, 443-448]; rather, they suggest that there may be another access path for TAMRA-DIBO to the cavity.

In situ tetrazole templated chair-like decanuclear azido-cobalt(II) SMM containing both tetra- and octa-hedral Co(II) ions.

PubMed

Zhang, Yuan-Zhu; Gao, Song; Sato, Osamu

2015-01-14

An azido-bridged chair-like decanuclear cluster: [Co(II)10(bzp)8(Metz)2(N3)18]·4MeOH·3H2O (1, bzp = 2-benzoylpyridine and HMetz = 5-methyl-1H-tetrazole) was prepared with in situ tetrazolate anions as templates in a sealed system. 1 containing both octahedral and tetrahedral Co(II) ions exhibited slow relaxation of magnetization with an effective barrier of 26 K under an applied dc field of 1 kOe.

Conversion of Azides into Diazo Compounds in Water

PubMed Central

Chou, Ho-Hsuan; Raines, Ronald T.

2013-01-01

Diazo compounds are in widespread use in synthetic organic chemistry, but have untapped potential in chemical biology. We report on the design and optimization of a phosphinoester that mediates the efficient conversion of azides into diazo compounds in phosphate buffer at neutral pH and room temperature. High yields are maintained in the presence of common nucleophilic or electrophilic functional groups, and reaction progress can be monitored by colorimetry. As azido groups are easy to install and maintain in biopolymers or their ligands, this new mode of azide reactivity could have substantial utility in chemical biology. PMID:24053717

Oxidized derivatives of Octopus vulgaris and Carcinus aestuarii hemocyanins at pH 7.5 and related models by x-ray absorption spectroscopy.

PubMed Central

Borghi, Elena; Solari, Pier Lorenzo; Beltramini, Mariano; Bubacco, Luigi; Di Muro, Paolo; Salvato, Benedetto

2002-01-01

The binuclear copper sites of the met and met-azido derivatives of Octopus vulgaris and Carcinus aestuarii hemocyanins at pH 7.5 were characterized by high-resolution x-ray absorption spectroscopy in the low energy region (XANES) and in the higher region (EXAFS). The accuracy of the analysis of the data was tested with two mononuclear and six binuclear copper(II) complexes of the poly(benzimidazole) ligand systems 2-BB, L-5,5 and L-6,6 (Casella et al., 1993, Inorg. Chem. 32:2056-2067; 1996, Inorg. Chem. 35:1101-1113). Their structural and reactivity properties are related to those of the protein's derivatives. The results obtained for those models with resolved x-ray structure (the 2-BB-aquo and azido mononuclear complexes, and the binuclear L-5,5 Cu(II)-bis(hydroxo) (Casella et al., unpublished)), extends the validity of our approach to the other poly(benzimidazole)-containing complexes and to the hemocyanin derivatives. Comparison between the protein's and the complexes' data, support a description of the met-derivatives as a five-coordinated O-bridged binuclear copper(II) center and favors, for both species, a bis(hydroxo) structure with a 3-A Cu-Cu distance. For O. vulgaris met-azido derivative a mu-1,3 bridging mode for the ligand appears the most likely. The structural situation of C. aestuarii met-azido-derivative is less clear: a mu-1,1 mode is favored, but a terminal mode cannot be excluded. PMID:12023249

Building blocks for the synthesis of glycosyl-myo-inositols involved in the insulin intracellular signalling process.

PubMed

Zapata, A; Martín-Lomas, M

1992-10-09

Glycosylation of (+/- )-1-O-benzyl-2,3:5,6-di-O-isopropylidene-myo-inositol (4) with 6-O-acetyl-4-O-allyl-2-azido-3-O-benzyl-2-deoxy-beta-D-glucopyranosyl trichloroacetimidate (6) gave the 4-O-(2-amino-2-deoxy-alpha-D-glucopyranosyl)- myo-inositol derivative (9) as a mixture of diastereoisomers which could be resolved by chromatography. Likewise alpha-glycosylation of 4 with 6-O-acetyl-2-azido-3-O-benzoyl-2-deoxy-4-O-(2,3,4,6-tetra-O-acetyl-beta- D- galactopyranosyl)-D-glucopyranosyl trichloroacetimidate (10) gave the corresponding pseudotrisaccharide derivative 16 as a mixture of diastereomers which could be resolved partially by chromatography. alpha-Glycosylation of enantiomerically pure 2,3:5,6- (18) and 2,3:4,5-di-O-isopropylidene-1-O-menthoxycarbonyl-myo-inositol (19) with 3,4,6-tri-O-acetyl-2-azido-2-deoxy-D-glucopyranosyl trichloroacetimidate (20) gave the pseudodisaccharide derivatives 21 and 22, respectively. Likewise, alpha-glycosylation of 18 with 10 afforded a pseudotrisaccharide derivative (23).

Azidoimidazolinium Salts: Safe and Efficient Diazo-transfer Reagents and Unique Azido-donors.

PubMed

Kitamura, Mitsuru

2017-07-01

2-Azido-1,3-dimethylimidazolinium chloride (ADMC) and its corresponding hexafluorophosphate (ADMP) were found to be efficient diazo-transfer reagents to various organic compounds. ADMC was prepared by the reaction of 2-chloro-1,3-dimethylimidazolinium chloride (DMC) and sodium azide. ADMP was isolated as a crystal having good thermal stability and low explosibility. ADMC and ADMP reacted with 1,3-dicarbonyl compounds under mild basic conditions to give 2-diazo-1,3-dicarbonyl compounds in high yields, which were easily isolated in virtue of the high water solubility of the by-products. ADMP showed high diazo-transfer ability to primary amines even in the absence of metal salt such as Cu(II). Using this diazotization approach, various alkyl/aryl azides were directly obtained from their corresponding primary amines in high yields. Furthermore, naphthols reacted with ADMC to give the corresponding diazonaphthoquinones in good to high yields. In addition, 2-azido-1,3-dimethylimidazolinium salts were employed as azide-transfer and migratory amidation reagents. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Thermochemical Kinetic-Based Study of Ignition Delays for 2-Azidoethanamine-Red Fuming Nitric Acid Systems: 2-Azido-N-Methylethanamine (MMAZ) Vs. 2-Azido-N,N-Dimethylethanamine (DMAZ)

DTIC Science & Technology

2014-01-01

ABSTRACT UU 18. NUMBER OF PAGES 68 19a. NAME OF RESPONSIBLE PERSON Chiung-Chu Chen a. REPORT Unclassified b. ABSTRACT Unclassified c ...Abstraction Reactions 33 Appendix C . Geometric Representations, Normal Mode Frequencies, and Moments of Inertia for Molecular Structures Involved in...from MMAZ and DMAZ by NO2 are also shown. ....................13 Figure 6. Potential energy diagram for the C •H2NHCH2CH2N3 + NO2 system: G4-based

Study on the interaction between bovine serum albumin and 4‧-azido-2‧-deoxyfluoroarabinocytidine or analogs by spectroscopy and molecular modeling

NASA Astrophysics Data System (ADS)

Wang, Ruiyong; Wang, Xiaogai; Li, Zhigang; Xie, Yuanzhe; Yang, Lingling; Shi, Jie; Chang, Junbiao

2014-11-01

The binding of 4‧-azido-2‧-deoxyfluoroarabinocytidine (FNC) or analogs (cytidine and 5‧-cytidylate monophosphate) to bovine serum albumin (BSA) was investigated by fluorescence, UV-vis absorption spectroscopy and molecular modeling. The three compounds quenched the intrinsic fluorescence of BSA and the results revealed the presence of static quenching mechanism. The positive ΔH and positive ΔS for the systems suggested that the hydrophobic forces stabilized the interaction between the compounds and protein. Results also showed that FNC was the weakest quencher.

Syntheses of the Stemona Alkaloids (±)-Stenine, (±)-Neostenine, and (±)-13-Epineostenine Using a Stereodivergent Diels-Alder/Azido-Schmidt Reaction

PubMed Central

Frankowski, Kevin J.; Golden, Jennifer E.; Zeng, Yibin; Lei, Yao; Aubé, Jeffrey

2009-01-01

A tandem Diels-Alder/azido Schmidt reaction sequence provides rapid access to the core skeleton shared by several Stemona alkaloids including stenine, neostenine, tuberstemonine, and neotubererostemonine. The discovery and evolution of inter- and intramolecular variations of this process and their applications to total syntheses of (±)–stenine and (±)–neostenine is described. The stereochemical outcome of the reaction depends on both substrate type and reaction condition, enabling the preparation of both (±)–stenine and (±)–neostenine from the same diene/dienophile combination. PMID:18396881

Azidoethoxyphenylalanine as a Vibrational Reporter and Click Chemistry Partner in Proteins.

PubMed

Tookmanian, Elise M; Phillips-Piro, Christine M; Fenlon, Edward E; Brewer, Scott H

2015-12-21

An unnatural amino acid, 4-(2-azidoethoxy)-L-phenylalanine (AePhe, 1), was designed and synthesized in three steps from known compounds in 54% overall yield. The sensitivity of the IR absorption of the azide of AePhe was established by comparison of the frequency of the azide asymmetric stretch vibration in water and dimethyl sulfoxide. AePhe was successfully incorporated into superfolder green fluorescent protein (sfGFP) at the 133 and 149 sites by using the amber codon suppression method. The IR spectra of these sfGFP constructs indicated that the azide group at the 149 site was not fully solvated despite the location in sfGFP and the three-atom linker between the azido group and the aromatic ring of AePhe. An X-ray crystal structure of sfGFP-149-AePhe was solved at 1.45 Å resolution and provides an explanation for the IR data as the flexible linker adopts a conformation which partially buries the azide on the protein surface. Both sfGFP-AePhe constructs efficiently undergo a bioorthogonal strain-promoted click cycloaddition with a dibenzocyclooctyne derivative. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ultrathin Polymer Films, Patterned Arrays, and Microwells

NASA Astrophysics Data System (ADS)

Yan, Mingdi

2002-05-01

The ability to control and tailor the surface and interface properties of materials is important in microelectronics, cell growth control, and lab-on-a-chip devices. Modification of material surfaces with ultrathin polymer films is attractive due to the availability of a variety of polymers either commercially or by synthesis. We have developed two approaches to the attachment of ultrathin polymer films on solid substrates. In the first method, a silane-functionalized perfluorophenyl azide (PFPA-silane) was synthesized and used to covalently immobilize polymer thin films on silicon wafers. Silanization of the wafer surface with the PFPA-silane introduced a monolayer of azido groups which in turn covalently attached the polymer film by way of photochemically initiated insertion reactions. The thickness of the film could be adjusted by the type and the molecular weight of the polymer. The method is versatile due to the general C-H and/or N-H insertion reactions of crosslinker; and therefore, no specific reactive functional groups on the polymers are required. Using this method, a new type of microwell array was fabricated from covalently immobilized polymer thin films on flat substrates. The arrays were characterized with AFM, XPS, and TOF-SIMS. The second method describes the attachment of polymer thin films on solid substrates via UV irradiation. The procedure consisted of spin-coating a polymer film and irradiating the film with UV light. Following solvent extraction, a thin film remained. The thickness of the film, from a few to over a hundred nanometers, was controlled by varying solution concentration and the molecular weight of the polymer.

Study on the interaction between bovine serum albumin and 4'-azido-2'-deoxyfluoroarabinocytidine or analogs by spectroscopy and molecular modeling.

PubMed

Wang, Ruiyong; Wang, Xiaogai; Li, Zhigang; Xie, Yuanzhe; Yang, Lingling; Shi, Jie; Chang, Junbiao

2014-11-11

The binding of 4'-azido-2'-deoxyfluoroarabinocytidine (FNC) or analogs (cytidine and 5'-cytidylate monophosphate) to bovine serum albumin (BSA) was investigated by fluorescence, UV-vis absorption spectroscopy and molecular modeling. The three compounds quenched the intrinsic fluorescence of BSA and the results revealed the presence of static quenching mechanism. The positive ΔH and positive ΔS for the systems suggested that the hydrophobic forces stabilized the interaction between the compounds and protein. Results also showed that FNC was the weakest quencher. Copyright © 2014 Elsevier B.V. All rights reserved.

Design, Synthesis and Biological Evaluation of Novel Peptide-Like Analogues as Selective COX-2 Inhibitors

PubMed Central

Ahmaditaba, Mohammad Ali; Houshdar Tehrani, Mohammad Hassan; Zarghi, Afshin; Shahosseini, Sorayya; Daraei, Bahram

2018-01-01

A new series of peptide-like derivatives containing different aromatic amino acids and possessing pharmacophores of COX-2 inhibitors as SO2Me or N3 attached to the para position of an end phenyl ring was synthesized for evaluation as selective cyclooxygenase-2 (COX-2) inhibitors. The synthetic reactions were based on the solid phase peptide synthesis method using Wang resin. One of the analogues, i.e., compound 2d, as the representative of these series was recognized as the most effective and the highest selective COX-2 inhibitor with IC50 value of 0.08 μM and COX-2 selectivity index of 351.2, among the other synthesized compounds. Molecular docking study was operated to determine possible binding models of compound 2d to COX-2 enzyme. The study showed that the p-azido-phenyl fragment of 2d occupied inside the secondary COX-2 binding site (Arg513, and His90). The structure-activity relationships acquired disclosed that compound 2d with 4-(azido phenyl) group as pharmacophore and histidine as amino acid gives the essential geometry to provide inhibition of the COX-2 enzyme with high selectivity. Compound 2d can be a good candidate for the development of new hits of COX-2 inhibitors.

Studies on novel 4beta-[(4-substituted)-1,2,3-triazol-1-yl] podophyllotoxins as potential anticancer agents.

PubMed

Bhat, Bilal A; Reddy, P Bhaskar; Agrawal, Satyam Kumar; Saxena, A K; Kumar, H M Sampath; Qazi, G N

2008-10-01

A series of 4beta-[(4-substituted)-1,2,3-triazol-1-yl] podophyllotoxin congeners have been designed and synthesized with significant regioselectivity by employing Cu(I) catalyzed 1,3-dipolar cycloaddition reaction of C4beta-azido podophyllotoxin and C4beta-azido-4'-O-demethyl podophyllotoxin with N-prop-2-yn-1-ylanilines. These compounds were evaluated for anticancer activity against a panel of seven human cancer cell lines. It was interesting to note that all the compounds exhibited promising activity especially against SF-295 (CNS), HCT-15 (colon) and 502713 (colon) cell lines. Compound 11e was found to be the most promising in this study.

Doubly end-on azido bridged mixed-valence cobalt trinuclear complex: Spectral study, VTM, inhibitory effect and antimycobacterial activity on human carcinoma and tuberculosis cells

NASA Astrophysics Data System (ADS)

Datta, Amitabha; Das, Kuheli; Sen, Chandana; Karan, Nirmal Kumar; Huang, Jui-Hsien; Lin, Chia-Her; Garribba, Eugenio; Sinha, Chittaranjan; Askun, Tulin; Celikboyun, Pinar; Mane, Sandeep B.

2015-09-01

Doubly end-on azido-bridged mixed-valence trinuclear cobalt complex, [Co3(L)2(N3)6(CH3OH)2] (1) is afforded by employing a potential monoanionic tetradentate-N2O2 Schiff base precursor (2-[{[2-(dimethylamino)ethyl]imino}methyl]-6-methoxyphenol; HL). Single crystal X-ray structure reveals that in 1, the adjacent CoII and CoIII ions are linked by double end-on azido bridges and thus the full molecule is generated by the site symmetry of a crystallographic twofold rotation axis. Complex 1 is subjected on different spectral analysis such as IR, UV-vis, emission and EPR spectroscopy. On variable temperature magnetic study, we observe that during cooling, the χMT values decrease smoothly until 15 K and then reaches to the value 1.56 cm3 K mol-1 at 2 K. Complex 1 inhibits the cell growth on human lung carcinoma (A549 cells), human colorectal (COLO 205 and HT-29 cells), and human heptacellular (PLC5 cells) carcinoma cells. Complex 1 exhibits anti-mycobacterial activity and considerable efficacy on Mycobacterium tuberculosis H37Rv ATCC 27294 and H37Ra ATCC 25177 strains.

Photoactivable analogs for labeling 25-hydroxyvitamin D3 serum binding protein and for 1,25-dihydroxyvitamin D3 intestinal receptor protein

NASA Technical Reports Server (NTRS)

Kutner, A.; Link, R. P.; Schnoes, H. K.; DeLuca, H. F.

1986-01-01

3-Azidobenzoates and 3-azidonitrobenzoates of 25-hydroxyvitamin D3 as well as 3-deoxy-3-azido-25-hydroxyvitamin D3 and 3-deoxy-3-azido-1,25-dihydroxyvitamin D3 were prepared as photoaffinity labels for vitamin D serum binding protein and 1,25-dihydroxyvitamin D3 intestinal receptor protein. The compounds prepared were easily activated by short- or long-wavelength uv light, as monitored by uv and ir spectrometry. The efficacy of the compounds to compete with 25-hydroxyvitamin D3 or 1,25-dihydroxyvitamin D3 for the binding site of serum binding protein and receptor, respectively, was studied to evaluate the vitamin D label with the highest affinity for the protein. The presence of an azidobenzoate or azidonitrobenzoate substituent at the C-3 position of 25-OH-D3 significantly decreased (10(4)- to 10(6)-fold) the binding activity. However, the labels containing the azido substituent attached directly to the vitamin D skeleton at the C-3 position showed a high affinity, only 20- to 150-fold lower than that of the parent compounds with their respective proteins. Therefore, 3-deoxy-3-azidovitamins present potential ligands for photolabeling of vitamin D proteins and for studying the structures of the protein active sites.

Ferromagnetic interaction in an asymmetric end-to-end azido double-bridged copper(II) dinuclear complex: a combined structure, magnetic, polarized neutron diffraction and theoretical study.

PubMed

Aronica, Christophe; Jeanneau, Erwann; El Moll, Hani; Luneau, Dominique; Gillon, Béatrice; Goujon, Antoine; Cousson, Alain; Carvajal, Maria Angels; Robert, Vincent

2007-01-01

A new end-to-end azido double-bridged copper(II) complex [Cu(2)L(2)(N(3))2] (1) was synthesized and characterized (L=1,1,1-trifluoro-7-(dimethylamino)-4-methyl-5-aza-3-hepten-2-onato). Despite the rather long Cu-Cu distance (5.105(1) A), the magnetic interaction is ferromagnetic with J= +16 cm(-1) (H=-JS(1)S(2)), a value that has been confirmed by DFT and high-level correlated ab initio calculations. The spin distribution was studied by using the results from polarized neutron diffraction. This is the first such study on an end-to-end system. The experimental spin density was found to be localized mainly on the copper(II) ions, with a small degree of delocalization on the ligand (L) and terminal azido nitrogens. There was zero delocalization on the central nitrogen, in agreement with DFT calculations. Such a picture corresponds to an important contribution of the d(x2-y2) orbital and a small population of the d(z2) orbital, in agreement with our calculations. Based on a correlated wavefunction analysis, the ferromagnetic behavior results from a dominant double spin polarization contribution and vanishingly small ionic forms.

Mononuclear thiocyanate containing nickel(II) and binuclear azido bridged nickel(II) complexes of N4-coordinate pyrazole based ligand: Syntheses, structures and magnetic properties

NASA Astrophysics Data System (ADS)

Solanki, Ankita; Monfort, Montserrat; Kumar, Sujit Baran

2013-10-01

Two mononuclear nickel(II) complexes [NiL1(NCS)2] (1) and [NiL2(NCS)2] (2) and two azido bridged binuclear nickel(II) complexes [Ni(()2()2] (3) and [Ni(()2()2] (4), where L1, L2, L1‧ and L2‧ are N,N-diethyl-N‧,N‧-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)ethane-1,2-diamine (L1), N,N-bis((1H-pyrazol-1-yl)methyl)-N‧,N‧-diethylethane-1,2-diamine (L2), N,N-diethyl-N‧-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)ethane-1,2-diamine (L1‧) and N-((1H-pyrazol-1-yl)methyl)-N‧,N‧-diethylethane-1,2-diamine (L2‧) have been synthesized and characterized by microanalyses and physico-chemical methods. Single crystal X-ray diffraction analyses revealed that complexes 1 and 2 are mononuclear NCS- containing Ni(II) complex with octahedral geometry and complexes 3 and 4 are end-on (μ-1,1) azido bridged binuclear Ni(II) complexes with distorted octahedral geometry. Variable temperature magnetic studies of the complexes 3 and 4 display ferromagnetic interaction with J values 19 and 32 cm-1, respectively.

A theoretical DFT study on the structural parameters and azide-tetrazole equilibrium in substituted azidothiazole systems.

PubMed

Abu-Eittah, Rafie H; El-Kelany, Khaled E

2012-12-01

Azido-tetrazole equilibrium is sensitive to: substitution, solvent, temperature and phase. In this work, the effects of the type and position of substitution on the thiazole ring of azidothiazoles on its structural parameters and on the azido-tetrazole equilibrium have been theoretically investigated using the density functional procedures at the B3LYP/6-311G(∗∗) level of theory. This study includes the investigation of the equilibrium geometry, the transformation of the trans-conformer to the cis one then the ring closure to the tetrazole isomer. The transition states of the two steps were located, confirmed and the structural parameters were calculated. In all the steps of calculations, geometry optimization was considered. The results obtained indicate that substitution by: -NO(2) and -CN group shifts the equilibrium to the azide side and in some cases the tetrazole isomer is not obtained. On the other hand, substitution by: -NH(2) and -OH groups shifts the equilibrium to the tetrazole side and in some cases the azide isomer is not obtained and if formed changes spontaneously to the tetrazole isomer. The decisive parameters which determine the position of the equilibrium are: charge density on atoms N3 and N8, rearrangement of bond length and bond angles during the process of cyclization and variation of dipole moment as a result of cyclization. Results of this work indicate that substitution on C5 is more efficient than substitution on C4 of the thiazole ring. Copyright © 2012 Elsevier B.V. All rights reserved.

Differential binding of ppGpp and pppGpp to E. coli RNA polymerase: photo-labeling and mass spectral studies.

PubMed

Syal, Kirtimaan; Chatterji, Dipankar

2015-12-01

(p)ppGpp, a secondary messenger, is induced under stress and shows pleiotropic response. It binds to RNA polymerase and regulates transcription in Escherichia coli. More than 25 years have passed since the first discovery was made on the direct interaction of ppGpp with E. coli RNA polymerase. Several lines of evidence suggest different modes of ppGpp binding to the enzyme. Earlier cross-linking experiments suggested that the β-subunit of RNA polymerase is the preferred site for ppGpp, whereas recent crystallographic studies pinpoint the interface of β'/ω-subunits as the site of action. With an aim to validate the binding domain and to follow whether tetra- and pentaphosphate guanosines have different location on RNA polymerase, this work was initiated. RNA polymerase was photo-labeled with 8-azido-ppGpp/8-azido-pppGpp, and the product was digested with trypsin and subjected to mass spectrometry analysis. We observed three new peptides in the trypsin digest of the RNA polymerase labeled with 8-azido-ppGpp, of which two peptides correspond to the same pocket on β'-subunit as predicted by X-ray structural analysis, whereas the third peptide was mapped on the β-subunit. In the case of 8-azido-pppGpp-labeled RNA polymerase, we have found only one cross-linked peptide from the β'-subunit. However, we were unable to identify any binding site of pppGpp on the β-subunit. Interestingly, we observed that pppGpp at high concentration competes out ppGpp bound to RNA polymerase more efficiently, whereas ppGpp cannot titrate out pppGpp. The competition between tetraphosphate guanosine and pentaphosphate guanosine for E. coli RNA polymerase was followed by gel-based assay as well as by a new method known as DRaCALA assay. © 2015 The Molecular Biology Society of Japan and Wiley Publishing Asia Pty Ltd.

A reagent for safe and efficient diazo-transfer to primary amines: 2-azido-1,3-dimethylimidazolinium hexafluorophosphate.

PubMed

Kitamura, Mitsuru; Kato, So; Yano, Masakazu; Tashiro, Norifumi; Shiratake, Yuichiro; Sando, Mitsuyoshi; Okauchi, Tatsuo

2014-07-07

Organic azides were prepared from primary amines in high yields by a metal free diazo-transfer reaction using 2-azido-1,3-dimethylimidazolinium hexafluorophosphate (ADMP), which is safe and stable crystalline. The choice of base was important in the diazo-transfer reaction. In general, 4-(N,N-dimethyl)aminopyridine (DMAP) was efficient, but a stronger base such as alkylamine or DBU was more appropriate for the reaction of nucleophilic primary amines. X-ray single crystal structural analysis and geometry optimization using density functional theory (B3LYP/6-31G**) were conducted to study the ADMP structure, and the diazo-transfer reaction mechanism was explained with the help of the results of these analyses.

Efficient and Tunable Three-Dimensional Functionalization of Fully Zwitterionic Antifouling Surface Coatings.

PubMed

Lange, Stefanie C; van Andel, Esther; Smulders, Maarten M J; Zuilhof, Han

2016-10-11

To enhance the sensitivity and selectivity of surface-based (bio)sensors, it is of crucial importance to diminish background signals that arise from the nonspecific binding of biomolecules, so-called biofouling. Zwitterionic polymer brushes have been shown to be excellent antifouling materials. However, for sensing purposes, antifouling does not suffice but needs to be combined with the possibility to efficiently modify the brush with recognition units. So far this has been achieved only at the expense of either antifouling properties or binding capacity. Herein we present a conceptually new approach by integrating both characteristics into a single tailor-made monomer: a novel sulfobetaine-based zwitterionic monomer equipped with a clickable azide moiety. Copolymerization of this monomer with a well-established standard sulfobetaine monomer results in highly antifouling surface coatings with a large yet tunable number of clickable groups present throughout the entire brush. Subsequent functionalization of the azido brushes via widely used strain-promoted alkyne azide click reactions yields fully zwitterionic 3D-functionalized coatings with a recognition unit of choice that can be tailored for any specific application. Here we show a proof of principle with biotin-functionalized brushes on Si 3 N 4 that combine excellent antifouling properties with specific avidin binding from a protein mixture. The signal-to-noise ratio is significantly improved over that of traditional chain-end modification of sulfobetaine polymer brushes, even if the azide content is lowered to 1%. This therefore offers a viable approach to the development of biosensors with greatly enhanced performance on any surface.

Electrochemical latent redox ratiometric probes for real-time tracking and quantification of endogenous hydrogen sulfide production in living cells.

PubMed

Manibalan, Kesavan; Mani, Veerappan; Chang, Pu-Chieh; Huang, Chih-Hung; Huang, Sheng-Tung; Marchlewicz, Kasper; Neethirajan, Suresh

2017-10-15

Hydrogen sulfide (H 2 S) was discovered as a third gasotransmitter in biological systems and recent years have seen a growing interest to understand its physiological and pathological functions. However, one major limiting factor is the lack of robust sensors to quantitatively track its production in real-time. We described a facile electrochemical assay based on latent redox probe approach for highly specific and sensitive quantification in living cells. Two chemical probes, Azido Benzyl ferrocene carbamate (ABFC) and N-alkyl Azido Benzyl ferrocene carbamate (NABFC) composed of azide trigger group were designed. H 2 S molecules specifically triggered the release of reporters from probes and the current response was monitored using graphene oxide film modified electrode as transducer. The detection limits are 0.32µM (ABFC) and 0.076µM (NABFC) which are comparable to those of current sensitive methods. The probes are successful in the determination of H 2 S spiked in whole human blood, fetal bovine serum, and E. coli. The continuous monitoring and quantification of endogenous H 2 S production in E. coli were successfully accomplished. This work lays first step stone towards real-time electrochemical quantification of endogenous H 2 S in living cells, thus hold great promise in the analytical aspects of H 2 S. Copyright © 2017 Elsevier B.V. All rights reserved.

Cytocompatible in situ forming chitosan/hyaluronan hydrogels via a metal-free click chemistry for soft tissue engineering.

PubMed

Fan, Ming; Ma, Ye; Mao, Jiahui; Zhang, Ziwei; Tan, Huaping

2015-07-01

Injectable hydrogels are important cell scaffolding materials for tissue engineering and regenerative medicine. Here, we report a new class of biocompatible and biodegradable polysaccharide hydrogels derived from chitosan and hyaluronan via a metal-free click chemistry, without the addition of copper catalyst. For the metal-free click reaction, chitosan and hyaluronan were modified with oxanorbornadiene (OB) and 11-azido-3,6,9-trioxaundecan-1-amine (AA), respectively. The gelation is attributed to the triazole ring formation between OB and azido groups of polysaccharide derivatives. The molecular structures were verified by FT-IR spectroscopy and elemental analysis, giving substitution degrees of 58% and 47% for chitosan-OB and hyaluronan-AA, respectively. The in vitro gelation, morphologies, equilibrium swelling, compressive modulus and degradation of the composite hydrogels were examined. The potential of the metal-free hydrogel as a cell scaffold was demonstrated by encapsulation of human adipose-derived stem cells (ASCs) within the gel matrix in vitro. Cell culture showed that this metal-free hydrogel could support survival and proliferation of ASCs. A preliminary in vivo study demonstrated the usefulness of the hydrogel as an injectable scaffold for adipose tissue engineering. These characteristics provide a potential opportunity to use the metal-free click chemistry in preparation of biocompatible hydrogels for soft tissue engineering applications. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A trial with 3'-azido-2',3'-dideoxythymidine and human interferon-α in cats naturally infected with feline leukaemia virus.

PubMed

Stuetzer, Bianca; Brunner, Konstanze; Lutz, Hans; Hartmann, Katrin

2013-08-01

Feline leukaemia virus (FeLV) infection is still one of the leading causes of infection-related deaths in domestic cats. Treatment with various drugs has been attempted, but none has resulted in cure or complete virus elimination. Human interferon-α2a (huIFN-α2a) and 3'-azido-2',3'-dideoxythymidine (AZT) have been proven to decrease antigenaemia in cats infected experimentally with FeLV. The purpose of this study was to assess the efficacy of huIFN-α2a, AZT and a combination of both drugs in cats infected naturally with FeLV in a placebo-controlled double-blinded trial. Fourty-four FeLV-infected cats in which free FeLV p27 antigen was detected in serum by enzyme-linked immunosorbent assay were included in the study. Cats were assigned to one of four treatment groups that received either high dose huIFN-α2a (10(5) IU/kg q24h; 12 cats), AZT (5 mg/kg q12h; 10 cats, both of these treatments (12 cats) or placebo (10 cats). All cats were treated for 6 weeks. Clinical variables, including stomatitis, and laboratory parameters, such as CD4(+) and CD8(+) counts and serum FeLV p 27 antigen concentration, were recorded throughout the treatment period. No significant difference among the groups was observed during the treatment period for any of the parameters. Aside from anaemia in one cat treated with AZT, no adverse effects were observed. It was not possible to demonstrate efficacy of huIFN-α2a or AZT alone or together in cats infected naturally with FeLV when given according to this regimen for 6 weeks; however, no notable side effects were detected.

Identification of the uridine 5'-diphosphoglucose (UDP-Glc) binding subunit of cellulose synthase in Acetobacter xylinum using the photoaffinity probe 5-azido-UDP-Glc

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, F.C.; Brown, R.M. Jr.; Drake, R.R. Jr.

1990-03-25

Photoaffinity labeling of purified cellulose synthase with (beta-32P)5-azidouridine 5'-diphosphoglucose (UDP-Glc) has been used to identify the UDP-Glc binding subunit of the cellulose synthase from Acetobacter xylinum strain ATCC 53582. The results showed exclusive labeling of an 83-kDa polypeptide. Photoinsertion of (beta-32P)5-azido-UDP-Glc is stimulated by the cellulose synthase activator, bis-(3'----5') cyclic diguanylic acid. Addition of increasing amounts of UDP-Glc prevents photolabeling of the 83-kDa polypeptide. The reversible and photocatalyzed binding of this photoprobe also showed saturation kinetics. These studies demonstrate that the 83-kDa polypeptide is the catalytic subunit of the cellulose synthase in A. xylinum strain ATCC 53582.

Exploring the Chemistry of Bicyclic Isoxazolidines for the Multicomponent Synthesis of Glycomimetic Building Blocks.

PubMed

Hoogenboom, Jorin; Lutz, Martin; Zuilhof, Han; Wennekes, Tom

2016-10-07

Starting from a chiral furanone, the nitrone-olefin [3 + 2] cycloaddition can be used to obtain bicyclic isoxazolidines for which we report a set of reactions to selectively modify each functional position. These synthetically versatile bicyclic isoxazolidines allowed us to obtain complex glycomimetic building blocks, like iminosugars, via multicomponent chemistry. For example, a library of 20 pipecolic acid derivatives, a recurring motif in various prescription drugs, could be obtained via a one-pot Staudinger/aza-Wittig/Ugi three-component reaction of a bicyclic isoxazolidine-derived azido-hemiacetal. Notably, specific pipecolic acids in this library were obtained via hydrolysis of an unique tricyclic imidate side product of the Ugi reaction. The azido-hemiacetal was also converted into an aza-C-glycoside iminosugar via an unprecendented one-pot Staudinger/aza-Wittig/Mannich reaction.

Synthesis of a suite of click-compatible sugar analogs for probing carbohydrate metabolism.

PubMed

Wang, Bo; McClosky, Daniel D; Anderson, Charles T; Chen, Gong

2016-10-04

Metabolic labeling based on the click chemistry between alkynyl and azido groups offers a powerful tool to study the function of carbohydrates in living systems, including plants. Herein, we describe the chemical synthesis of six alkynyl-modified sugars designed as analogs to D-glucose, D-mannose, L-rhamnose and sucrose present in plant cell walls. Among these new alkynyl probes, four of them are the 6-deoxy-alkynyl analogs of the corresponding sugars and do not possess any 6-OH groups. The other two are based on a new structural design, in which an ethynyl group is incorporated at the C-6 position of the sugar and the 6-OH group remains. The synthetic routes for both types of probes share common aldehyde intermediates, which are derived from the corresponding 6-OH precursor with other hydroxy groups protected. The overall synthesis sequence of these probes is efficient, concise, and scalable. Copyright © 2016 Elsevier Ltd. All rights reserved.

Flame retardant polyphosphazenes

NASA Technical Reports Server (NTRS)

Paciorek, K. L.; Karle, D. W.; Kratzer, R. H.

1976-01-01

Three processes for the preparation of polyphosphazenes were investigated: (1) the reaction of bisphosphines with diazides, (2) the condensation of bisdichlorophosphoranes with diamines; and (3) the treatment of bisphosphines with diamines in the presence of carbon tetrachloride followed by base dehydrohalogenation. All products obtained were of low molecular weight; the degree of polymerization did not exceed twelve repeating units. However, several compositions exhibited good thermal stability. No weight loss was observed up to 390 C when heated in air at 5 C/min. Treatment of bisphosphines with either an excess of a diazide or an excess of a diamine in the presence of carbon tetrachloride resulted in the production of difunctional phosphazenes which were respectively, azido and amino terminated. The reaction of these azido terminated extended monomers with bisphosphines did not produce high molecular weight materials. The bis-aminophosphazene prepared for the first time under this contract was successfully incorporated into a polyimide.

Specific photoaffinity labeling of two plasma membrane polypeptides with an azido auxin

NASA Technical Reports Server (NTRS)

Hicks, G. R.; Rayle, D. L.; Jones, A. M.; Lomax, T. L.

1989-01-01

Plasma membrane vesicles were isolated from zucchini (Cucurbita pepo) hypocotyl tissue by aqueous phase partitioning and assessed for homogeneity by the use of membrane-specific enzyme assays. The highly pure (ca. 95%) plasma membrane vesicles maintained a pH differential across the membrane and accumulated a tritiated azido analogue of 3-indoleacetic acid (IAA), 5-azido-[7-3H]IAA ([3H]N3IAA), in a manner similar to the accumulation of [3H]IAA. The association of the [3H]N3IAA with membrane vesicles was saturable and subject to competition by IAA and auxin analogues. Auxin-binding proteins were photoaffinity labeled by addition of [3H]N3IAA to plasma membrane vesicles prior to exposure to UV light (15 sec; 300 nm) and detected by subsequent NaDodSO4/PAGE and fluorography. When the reaction temperature was lowered to -196 degrees C, high-specific-activity labeling of a 40-kDa and a 42-kDa polypeptide was observed. Triton X-100 (0.1%) increased the specific activity of labeling and reduced the background, which suggests that the labeled polypeptides are intrinsic membrane proteins. The labeled polypeptides are of low abundance, as expected for auxin receptors. Further, the addition of IAA and auxin analogues to the photoaffinity reaction mixture resulted in reduced labeling that was qualitatively similar to their effects on the accumulation of radiolabeled IAA in membrane vesicles. Collectively, these results suggest that the radiolabeled polypeptides are auxin receptors. The covalent nature of the label should facilitate purification and further characterization of the receptors.

Specific photoaffinity labeling of two plasma membrane polypeptides with an azido auxin.

PubMed

Hicks, G R; Rayle, D L; Jones, A M; Lomax, T L

1989-07-01

Plasma membrane vesicles were isolated from zucchini (Cucurbita pepo) hypocotyl tissue by aqueous phase partitioning and assessed for homogeneity by the use of membrane-specific enzyme assays. The highly pure (ca. 95%) plasma membrane vesicles maintained a pH differential across the membrane and accumulated a tritiated azido analogue of 3-indoleacetic acid (IAA), 5-azido-[7-3H]IAA ([3H]N3IAA), in a manner similar to the accumulation of [3H]IAA. The association of the [3H]N3IAA with membrane vesicles was saturable and subject to competition by IAA and auxin analogues. Auxin-binding proteins were photoaffinity labeled by addition of [3H]N3IAA to plasma membrane vesicles prior to exposure to UV light (15 sec; 300 nm) and detected by subsequent NaDodSO4/PAGE and fluorography. When the reaction temperature was lowered to -196 degrees C, high-specific-activity labeling of a 40-kDa and a 42-kDa polypeptide was observed. Triton X-100 (0.1%) increased the specific activity of labeling and reduced the background, which suggests that the labeled polypeptides are intrinsic membrane proteins. The labeled polypeptides are of low abundance, as expected for auxin receptors. Further, the addition of IAA and auxin analogues to the photoaffinity reaction mixture resulted in reduced labeling that was qualitatively similar to their effects on the accumulation of radiolabeled IAA in membrane vesicles. Collectively, these results suggest that the radiolabeled polypeptides are auxin receptors. The covalent nature of the label should facilitate purification and further characterization of the receptors.

A substrate radical intermediate in the reaction between ribonucleotide reductase from Escherichia coli and 2'-azido-2'-deoxynucleoside diphosphates.

PubMed

Sjöberg, B M; Gräslund, A; Eckstein, F

1983-07-10

The B2 subunit of ribonucleotide reductase from Escherichia coli contains a tyrosine radical which is essential for enzyme activity. In the reaction between ribonucleotide reductase and the substrate analogue 2'-azido-2'-deoxycytidine 5'-diphosphate a new transient radical is formed. The EPR characteristics of this new radical species are consistent with a localization of the unpaired electron at the sugar moiety of the nucleotide. The radical shows hyperfine couplings to a hydrogen and a nitrogen nucleus, the latter probably being part of the azide substituent. The formation of the nucleotide radical in this suicidal reaction is concomitant with the decay of the tyrosine radical of the B2 subunit. Kinetic data argue for a first (pseudosecond) order decay of the B2 radical via generation of the nucleotide radical followed by a slower first order decay of the nucleotide radical. End products in the reaction are cytosine and radical-free protein B2. In the reaction between bacteriophage T4 ribonucleotide reductase and 2'-azido-2'-deoxycytidine 5'-diphosphate an identical nucleotide radical is formed. The present results are consistent with the hypothesis that the appearance and structure of the transient radical mimic stages in the normal reaction pathway of ribonucleotide reductase, postulated to proceed via 3'-hydrogen abstraction and cation radical formation of the substrate nucleotide (Stubbe, J., and Ackles, D. (1980) J. Biol. Chem. 255, 8027-8030). The nucleotide radical described here might be equivalent to such a cation radical intermediate.

Novel visible light activated type 1 photosensitizers

NASA Astrophysics Data System (ADS)

Rajagopalan, Raghavan; Karwa, Amolkumar; Poreddy, Amruta R.; Lusiak, Przemyslaw M.; Pandurangi, Raghoottama S.; Cantrell, Gary L.; Dorshow, Richard B.

2010-02-01

Photodynamic therapy of tumors involving Type 2 photosenstizers has been conspicuously successful, but the Type 1 process, in contrast, has not received much attention despite its considerable potential. Accordingly, several classes of molecules containing fragile bonds such as azido (-N=N=N), azo (-N=N-), and oxaza (-N-O-) functional groups that produce reactive intermediates such as radicals and nitrenes upon photoexcitation with visible light were prepared and tested for cell viability using U397 leukemia cell line. The cells were incubated with the photosensitizer at various concentrations, and were illuminated for 5, 10, and 20 minutes. The results show that all the photosensitizers caused cell death compared to the controls when exposed to both the photosensitizers and light.

An efficient preparation of isosteric phosphonate analogues of sphingolipids by opening of oxirane and cyclic sulfamidate intermediates with alpha-lithiated alkylphosphonic esters.

PubMed

Sun, Chaode; Bittman, Robert

2004-10-29

D-erythro-(2S,3R,4E)-Sphingosine-1-phosphonate (1), the isosteric phosphonate analogue of naturally occurring sphingosine 1-phosphate (1a), and D-ribo-phytosphingosine 1-phosphonate (2), the isosteric phosphonate analogue of D-ribo-phytosphingosine-1-phosphate (2a), were synthesized starting with methyl 2,3-O-isopropylidene-d-glycerate (4) and D-ribo-phytosphingosine (3), respectively. Oxirane 12 was formed in eight steps from 4, and cyclic sulfamidate 22 was formed in five steps from 3. The phosphonate group was introduced via regioselective ring-opening reactions of oxirane 12 and cyclic sulfamidate 22 with lithium dialkyl methylphosphonate, affording 13 and 23, respectively. The synthesis of 1 was completed by S(N)2 displacement of chloromesylate intermediate 14b with azide ion, followed by conversion of the resulting azido group to a NHBoc group and deprotection. The synthesis of 2 was completed by cleavage of the acetal, N-benzyl, and alkyl phosphonate ester groups.

Preparation and optical properties of indium tin oxide/epoxy nanocomposites with polyglycidyl methacrylate grafted nanoparticles.

PubMed

Tao, Peng; Viswanath, Anand; Schadler, Linda S; Benicewicz, Brian C; Siegel, Richard W

2011-09-01

Visibly highly transparent indium tin oxide (ITO)/epoxy nanocomposites were prepared by dispersing polyglycidyl methacrylate (PGMA) grafted ITO nanoparticles into a commercial epoxy resin. The oleic acid stabilized, highly crystalline, and near monodisperse ITO nanoparticles were synthesized via a nonaqueous synthetic route with multigram batch quantities. An azido-phosphate ligand was synthesized and used to exchange with oleic acid on the ITO surface. The azide terminal group allows for the grafting of epoxy resin compatible PGMA polymer chains via Cu(I) catalyzed alkyne-azide "click" chemistry. Transmission electron microscopy (TEM) observation shows that PGMA grafted ITO particles were homogeneously dispersed within the epoxy matrix. Optical properties of ITO/epoxy nanocomposites with different ITO concentrations were studied with an ultraviolet-visible-near-infrared (UV-vis-NIR) spectrometer. All the ITO/epoxy nanocomposites show more than 90% optical transparency in the visible light range and absorption of UV light from 300 to 400 nm. In the near-infrared region, ITO/epoxy nanocomposites demonstrate low transmittance and the infrared (IR) transmission cutoff wavelength of the composites shifts toward the lower wavelength with increased ITO concentration. The ITO/epoxy nanocomposites were applied onto both glass and plastic substrates as visibly transparent and UV/IR opaque optical coatings.

Tracking of Engineered Bacteria In Vivo Using Nonstandard Amino Acid Incorporation.

PubMed

Praveschotinunt, Pichet; Dorval Courchesne, Noémie-Manuelle; den Hartog, Ilona; Lu, Chaochen; Kim, Jessica J; Nguyen, Peter Q; Joshi, Neel S

2018-06-15

The rapidly growing field of microbiome research presents a need for better methods of monitoring gut microbes in vivo with high spatial and temporal resolution. We report a method of tracking microbes in vivo within the gastrointestinal tract by programming them to incorporate nonstandard amino acids (NSAA) and labeling them via click chemistry. Using established machinery constituting an orthogonal translation system (OTS), we engineered Escherichia coli to incorporate p-azido-l-phenylalanine (pAzF) in place of the UAG (amber) stop codon. We also introduced a mutant gene encoding for a cell surface protein (CsgA) that was altered to contain an in-frame UAG codon. After pAzF incorporation and extracellular display, the engineered strains could be covalently labeled via copper-free click reaction with a Cy5 dye conjugated to the dibenzocyclooctyl (DBCO) group. We confirmed the functionality of the labeling strategy in vivo using a murine model. Labeling of the engineered strain could be observed using oral administration of the dye to mice several days after colonization of the gastrointestinal tract. This work sets the foundation for the development of in vivo tracking microbial strategies that may be compatible with noninvasive imaging modalities and are capable of longitudinal spatiotemporal monitoring of specific microbial populations.

Preparation of carbon nanoparticles and carbon nitride from high nitrogen compound

DOEpatents

Huynh, My Hang V [Los Alamos, NM; Hiskey, Michael A [Los Alamos, NM

2009-09-01

The high-nitrogen compound 3,6-di(azido)-1,2,4,5-tetrazine (DiAT) was synthesized by a relatively simple method and used as a precursor for the preparation of carbon nanospheres and nanopolygons, and nitrogen-rich carbon nitrides.

Functional interaction between the two halves of the photoreceptor-specific ATP binding cassette protein ABCR (ABCA4). Evidence for a non-exchangeable ADP in the first nucleotide binding domain.

PubMed

Ahn, Jinhi; Beharry, Seelochan; Molday, Laurie L; Molday, Robert S

2003-10-10

ABCR, also known as ABCA4, is a member of the superfamily of ATP binding cassette transporters that is believed to transport retinal or retinylidene-phosphatidylethanolamine across photoreceptor disk membranes. Mutations in the ABCR gene are responsible for Stargardt macular dystrophy and related retinal dystrophies that cause severe loss in vision. ABCR consists of two tandemly arranged halves each containing a membrane spanning segment followed by a large extracellular/lumen domain, a multi-spanning membrane domain, and a nucleotide binding domain (NBD). To define the role of each NBD, we examined the nucleotide binding and ATPase activities of the N and C halves of ABCR individually and co-expressed in COS-1 cells and derived from trypsin-cleaved ABCR in disk membranes. When disk membranes or membranes from co-transfected cells were photoaffinity labeled with 8-azido-ATP and 8-azido-ADP, only the NBD2 in the C-half bound and trapped the nucleotide. Co-expressed half-molecules displayed basal and retinal-stimulated ATPase activity similar to full-length ABCR. The individually expressed N-half displayed weak 8-azido-ATP labeling and low basal ATPase activity that was not stimulated by retinal, whereas the C-half did not bind ATP and exhibited little if any ATPase activity. Purified ABCR contained one tightly bound ADP, presumably in NBD1. Our results indicate that only NBD2 of ABCR binds and hydrolyzes ATP in the presence or absence of retinal. NBD1, containing a bound ADP, associates with NBD2 to play a crucial, non-catalytic role in ABCR function.

Heat resistant polymers of oxidized styrylphosphine

NASA Technical Reports Server (NTRS)

Paciorek, K. J. L. (Inventor)

1980-01-01

A flame resistant, nontoxic polymer which may be used safely in confined locations where there is inadequate ventilation is prepared either by polymerizing compounds having the formula R-N=P(C6H5)2(C6H4)CH=CH2 where R is an organic moeity selected from the group of (C6H5)2P(O)-, (C6H5O)2P(O)-, (C6H5)2 C3N3-, or their mixtures, or by reacting a polymer with an organic azide such as diphenylphosphinylazide, diphenyl-phosphorylazide, 2-azido-4,6-diphenly-5-triazine, 2,4-diazido-6-phenyl-s-triazine, trimethylsilyoazide, triphenylsilylazine, and phenylazine. The reaction of the styrylphosphine with the organozaide results in the oxidation of the trivalent phosphorus atom to the pentavalent state in the form of an unsaturated P=N linkage known as a phosphazene group.

Synthesis of chitosan-PEO hydrogels via mesylation and regioselective Cu(I)-catalyzed cycloaddition.

PubMed

Tirino, Pasquale; Laurino, Rosaria; Maglio, Giovanni; Malinconico, Mario; d'Ayala, Giovanna Gomez; Laurienzo, Paola

2014-11-04

In this work, a well-defined hydrogel was developed by coupling chitosan with PEO through "click chemistry". Azide functionalities were introduced onto chitosan, through mesylation of C-6 hydroxyl groups, and reacted with a di-alkyne PEO by a regioselective Cu(I)-catalyzed cycloaddition. This synthetic approach allowed us to obtain a hydrogel with a controlled crosslinking degree. In fact, the extent of coupling is strictly dependent on the amount of azido groups on chitosan, which in turn can be easily modulated. The obtained hydrogel, with a crosslinking degree of around 90%, showed interesting swelling properties. With respect to chitosan hydrogels reported in literature, a considerably higher equilibrium uptake was reached (940%). The possibility to control the crosslinking degree of hydrogel and its capability to rapidly absorb high amounts of water make this material suitable for several applications, such as controlled drug release and wound healing. Copyright © 2014. Published by Elsevier Ltd.

Synthesis, spectral characterization, thermal and photoluminescence properties of Zn(II) and Cd(II)-azido/thiocyanato complexes with thiazolylazo dye and 1,2-bis(diphenylphoshino)ethane.

PubMed

Yamgar, B A; Sawant, V A; Bharate, B G; Chavan, S S

2011-01-01

A series of complexes of the type [M(L)(dppe)X2]; where M=Zn(II) or Cd(II); L=4-(2'-thiazolylazo)chlorobenzene (L1), 4-(2'-thiazolylazo)bromobenzene (L2) and 4-(2'-thiazolylazo) iodobenzene (L3); dppe=1,2-bis(diphenylphosphino)ethane; X=N3- or NCS- have been prepared and characterized on the basis of their microanalysis, molar conductance, thermal, IR, UV-vis and 1H NMR spectral studies. IR spectra show that the ligand L is coordinated to the metal atom in bidentate manner via azo nitrogen and thiazole nitrogen. An octahedral structure is proposed for all the complexes. The thermal behavior of the complexes revealed that the thiocyanato complexes are thermally more stable than the azido complexes. All the complexes exhibit blue-green emission with high quantum yield as the result of the fluorescence from the intraligand emission excited state. Copyright © 2010 Elsevier B.V. All rights reserved.

Small Molecule Targeting of a MicroRNA Associated with Hepatocellular Carcinoma.

PubMed

Childs-Disney, Jessica L; Disney, Matthew D

2016-02-19

Development of precision therapeutics is of immense interest, particularly as applied to the treatment of cancer. By analyzing the preferred cellular RNA targets of small molecules, we discovered that 5"-azido neomycin B binds the Drosha processing site in the microRNA (miR)-525 precursor. MiR-525 confers invasive properties to hepatocellular carcinoma (HCC) cells. Although HCC is one of the most common cancers, treatment options are limited, making the disease often fatal. Herein, we find that addition of 5"-azido neomycin B and its FDA-approved precursor, neomycin B, to an HCC cell line selectively inhibits production of the mature miRNA, boosts a downstream protein, and inhibits invasion. Interestingly, neomycin B is a second-line agent for hepatic encephalopathy (HE) and bacterial infections due to cirrhosis. Our results provocatively suggest that neomycin B, or second-generation derivatives, may be dual functioning molecules to treat both HE and HCC. Collectively, these studies show that rational design approaches can be tailored to disease-associated RNAs to afford potential lead therapeutics.

"Click" on Alkynylated Carbon Quantum Dots: An Efficient Surface Functionalization for Specific Biosensing and Bioimaging.

PubMed

Gao, Ming Xuan; Yang, Lin; Zheng, Yi; Yang, Xiao Xi; Zou, Hong Yan; Han, Jing; Liu, Ze Xi; Li, Yuan Fang; Huang, Cheng Zhi

2017-02-10

Surface functionalization is an essential pre requisite for wide and specific applications of nanoparticles such as photoluminescent (PL) carbon quantum dots (CQDs), but it remains a major challenge. In this report, alkynylated CQDs, prepared from carboxyl-rich CQDs through amidation with propargylamine in the presence of 1,1'-carbonyldiimidazole, were modified efficiently with azido molecular beacon DNA through a copper(I)-catalyzed alkyne-azide cycloaddition reaction (CuAAC). As a proof-of-concept, the DNA-modified CQDs are then bonded with gold nanoparticles (AuNPs, 5 nm) through a gold-sulfur bond. Owing to the emission enhancement, this complex can then be applied to the recognition of a single-base- mismatched target. The same functionalizing strategy applied to click the alkynylated CQDs with a nuclear localization sequence (NLS) peptide showed that the NLS-modified CQDs could target the nuclei specifically. These results indicate that surface functionalization of CQDs through a nonstoichiometric copper chalcogenide nanocrystal- (nsCuCNC-) catalyzed click reaction is efficient, and has significant potential in the fields of biosensing and bioimaging. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Degradable polymeric nanoparticles by aggregation of thermoresponsive polymers and ``click'' chemistry

NASA Astrophysics Data System (ADS)

Dworak, Andrzej; Lipowska, Daria; Szweda, Dawid; Suwinski, Jerzy; Trzebicka, Barbara; Szweda, Roza

2015-10-01

This study describes a novel approach to the preparation of crosslinked polymeric nanoparticles of controlled sizes that can be degraded under basic conditions. For this purpose thermoresponsive copolymers containing azide and alkyne functions were obtained by ATRP of di(ethylene glycol) monomethyl ether methacrylate (D) and 2-aminoethyl methacrylate (A) followed by post polymerization modification. The amino groups of A were reacted with propargyl chloroformate or 2-azido-1,3-dimethylimidazolinium hexafluorophosphate, which led to two types of copolymers. Increasing the temperature of aqueous solutions of the mixed copolymers caused their aggregation into spherical nanoparticles composed of both types of chains. Their dimensions could be controlled by changing the concentration and heating rate of the solutions. Covalent stabilization of aggregated chains was performed by a ``click'' reaction between the azide and alkyne groups. Due to the presence of a carbamate bond the nanoparticles undergo pH dependent degradation under mild basic conditions. The proposed procedure opens a route to new carriers for the controlled release of active species.This study describes a novel approach to the preparation of crosslinked polymeric nanoparticles of controlled sizes that can be degraded under basic conditions. For this purpose thermoresponsive copolymers containing azide and alkyne functions were obtained by ATRP of di(ethylene glycol) monomethyl ether methacrylate (D) and 2-aminoethyl methacrylate (A) followed by post polymerization modification. The amino groups of A were reacted with propargyl chloroformate or 2-azido-1,3-dimethylimidazolinium hexafluorophosphate, which led to two types of copolymers. Increasing the temperature of aqueous solutions of the mixed copolymers caused their aggregation into spherical nanoparticles composed of both types of chains. Their dimensions could be controlled by changing the concentration and heating rate of the solutions. Covalent stabilization of aggregated chains was performed by a ``click'' reaction between the azide and alkyne groups. Due to the presence of a carbamate bond the nanoparticles undergo pH dependent degradation under mild basic conditions. The proposed procedure opens a route to new carriers for the controlled release of active species. Electronic supplementary information (ESI) available: GPC-MALLS chromatograms for P(D-co-A)_1 and P(D-co-A)_2 copolymers, absorbance spectra of P(D-co-A)_1, P(D-co-A)_2, P(D-co-A_Pr) and P(D-co-A_Az) after reaction with ninhydrine. See DOI: 10.1039/c5nr04448k

A three-enzyme cascade reaction through positional assembly of enzymes in a polymersome nanoreactor.

PubMed

van Dongen, Stijn F M; Nallani, Madhavan; Cornelissen, Jeroen J L M; Nolte, Roeland J M; van Hest, Jan C M

2009-01-01

Porous polymersomes based on block copolymers of isocyanopeptides and styrene have been used to anchor enzymes at three different locations, namely, in their lumen (glucose oxidase, GOx), in their bilayer membrane (Candida antarctica lipase B, CalB) and on their surface (horseradish peroxidase, HRP). The surface coupling was achieved by click chemistry between acetylene-functionalised anchors on the surface of the polymersomes and azido functions of HRP, which were introduced by using a direct diazo transfer reaction to lysine residues of the enzyme. To determine the encapsulation and conjugation efficiency of the enzymes, they were decorated with metal-ion labels and analysed by mass spectrometry. This revealed an almost quantitative immobilisation efficiency of HRP on the surface of the polymersomes and a more than statistical incorporation efficiency for CalB in the membrane and for GOx in the aqueous compartment. The enzyme-decorated polymersomes were studied as nanoreactors in which glucose acetate was converted by CalB to glucose, which was oxidised by GOx to gluconolactone in a second step. The hydrogen peroxide produced was used by HRP to oxidise 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) to ABTS(.+). Kinetic analysis revealed that the reaction step catalysed by HRP is the fastest in the cascade reaction.

A novel bio-orthogonal cross-linker for improved protein/protein interaction analysis.

PubMed

Nury, Catherine; Redeker, Virginie; Dautrey, Sébastien; Romieu, Anthony; van der Rest, Guillaume; Renard, Pierre-Yves; Melki, Ronald; Chamot-Rooke, Julia

2015-02-03

The variety of protein cross-linkers developed in recent years illustrates the current requirement for efficient reagents optimized for mass spectrometry (MS) analysis. To date, the most widely used strategy relies on commercial cross-linkers that bear an isotopically labeled tag and N-hydroxysuccinimid-ester (NHS-ester) moieties. Moreover, an enrichment step using liquid chromatography is usually performed after enzymatic digestion of the cross-linked proteins. Unfortunately, this approach suffers from several limitations. First, it requires large amounts of proteins. Second, NHS-ester cross-linkers are poorly efficient because of their fast hydrolysis in water. Finally, data analysis is complicated because of uneven fragmentation of complex isotopic cross-linked peptide mixtures. We therefore synthesized a new type of trifunctional cross-linker to overrule these limitations. This reagent, named NNP9, comprises a rigid core and bears two activated carbamate moieties and an azido group. NNP9 was used to establish intra- and intermolecular cross-links within creatine kinase, then to map the interaction surfaces between α-Synuclein (α-Syn), the aggregation of which leads to Parkinson's disease, and the molecular chaperone Hsc70. We show that NNP9 cross-linking efficiency is significantly higher than that of NHS-ester commercial cross-linkers. The number of cross-linked peptides identified was increased, and a high quality of MS/MS spectra leading to high sequence coverage was observed. Our data demonstrate the potential of NNP9 for an efficient and straightforward characterization of protein-protein interfaces and illustrate the power of using different cross-linkers to map thoroughly the surface interfaces within protein complexes.

The use of O-trifluoroacetyl protection and profound influence of the nature of glycosyl acceptor in benzyl-free arabinofuranosylation.

PubMed

Abronina, Polina I; Fedina, Ksenia G; Podvalnyy, Nikita M; Zinin, Alexander I; Chizhov, Alexander O; Kondakov, Nikolay N; Torgov, Vladimir I; Kononov, Leonid O

2014-09-19

The influence of O-trifluoroacetyl (TFA) groups at different positions of thioglycoside glycosyl donors on stereoselectivity of α-arabinofuranosylation leading to corresponding disaccharides was studied. It was shown that TFA group in thioglycoside glycosyl donors, when combined with 2-O-(triisopropylsilyl) (TIPS) non-participating group, may be regarded as an electron-withdrawing protecting group that may enhance 1,2-cis-selectivity in arabinofuranosylation, the results strongly depending on the nature of glycosyl acceptor. The reactivities of the glycosyl donors were compared with those of a similar thioglycoside with O-pentafluoropropionyl groups and the known phenyl 3,5-O-(di-tert-butylsilylene)-1-thio-α-d-arabinofuranosides with 2-O-TIPS and 2-O-benzyl groups. The 'matching' in the donor-acceptor combination was found to be critical for achieving both high reactivity of glycosyl donor and β-stereoselectivity of arabinofuranosylation. The use of glycosyl donors with TFA and silyl protection may be useful in the realization of the benzyl-free approach to oligoarabinofuranosides with azido group in aglycon-convenient building blocks for the preparation of neoglycoconjugates. Copyright © 2014 Elsevier Ltd. All rights reserved.

Genetically encoded photocross-linkers determine the biological binding site of exendin-4 peptide in the N-terminal domain of the intact human glucagon-like peptide-1 receptor (GLP-1R)

PubMed Central

Koole, Cassandra; Reynolds, Christopher A.; Mobarec, Juan C.; Hick, Caroline; Sexton, Patrick M.; Sakmar, Thomas P.

2017-01-01

The glucagon-like peptide-1 receptor (GLP-1R) is a key therapeutic target in the management of type II diabetes mellitus, with actions including regulation of insulin biosynthesis and secretion, promotion of satiety, and preservation of β-cell mass. Like most class B G protein-coupled receptors (GPCRs), there is limited knowledge linking biological activity of the GLP-1R with the molecular structure of an intact, full-length, and functional receptor·ligand complex. In this study, we have utilized genetic code expansion to site-specifically incorporate the photoactive amino acid p-azido-l-phenylalanine (azF) into N-terminal residues of a full-length functional human GLP-1R in mammalian cells. UV-mediated photolysis of azF was then carried out to induce targeted photocross-linking to determine the proximity of the azido group in the mutant receptor with the peptide exendin-4. Cross-linking data were compared directly with the crystal structure of the isolated N-terminal extracellular domain of the GLP-1R in complex with exendin(9–39), revealing both similarities as well as distinct differences in the mode of interaction. Generation of a molecular model to accommodate the photocross-linking constraints highlights the potential influence of environmental conditions on the conformation of the receptor·peptide complex, including folding dynamics of the peptide and formation of dimeric and higher order oligomeric receptor multimers. These data demonstrate that crystal structures of isolated receptor regions may not give a complete reflection of peptide/receptor interactions and should be combined with additional experimental constraints to reveal peptide/receptor interactions occurring in the dynamic, native, and full-length receptor state. PMID:28283573

Energetic Azido Compounds

DTIC Science & Technology

1980-03-28

Dr. F. Roberto Lt. S. Clift Naval Weapons Center 3 Mr. ;. Geisler Chi•a Lakre, CA 93555 4a Attn: Dr. A. Amsrer, Code 385 U.S. Army Research Office I...Research Naval: Weapons Center 1 Directorate of Chemical Sciences China Lake, CA 93555 Bolling Air Force Base Attn: Mr. H. Richter, Code 3858

Facile and selective covalent grafting of an RGD-peptide to electrospun scaffolds improves HUVEC adhesion.

PubMed

Dettin, Monica; Zamuner, Annj; Roso, Martina; Iucci, Giovanna; Samouillan, Valerie; Danesin, Roberta; Modesti, Michele; Conconi, Maria Teresa

2015-10-01

The development of a biomimetic surface able to promote endothelialization is fundamental in the search for blood vessel substitutes that prevent the formation of thrombi or hyperplasia. This study aims at investigating the effect of functionalization of poly-ε-caprolactone or poly(L-lactic acid-co-ɛ-caprolactone) electrospun scaffolds with a photoreactive adhesive peptide. The designed peptide sequence contains four Gly-Arg-Gly-Asp-Ser-Pro motifs per chain and a p-azido-Phe residue at each terminus. Different peptide densities on the scaffold surface were obtained by simply modifying the peptide concentration used in pretreatment of the scaffold before UV irradiation. Scaffolds of poly-ε-caprolactone embedded with adhesive peptides were produced to assess the importance of peptide covalent grafting. Our results show that the scaffolds functionalized with photoreactive peptides enhance adhesion at 24 h with a dose-dependent effect and control the proliferation of human umbilical vein endothelial cells, whereas the inclusion of adhesive peptide in the electrospun matrices by embedding does not give satisfactory results. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd.

1-(4-(6-Fluorobenzo [d] isoxazol-3-yl) piperidin-1-yl)-2-(4-(hydroxymethyl)-1H-1,2,3-triazol-1-yl) ethanone: Synthesis, spectroscopic characterization, Hirshfeld surface analysis, cytotoxic studies and docking studies

NASA Astrophysics Data System (ADS)

Govindhan, M.; Viswanathan, V.; Karthikeyan, S.; Subramanian, K.; Velmurugan, D.

2017-08-01

Compound 1-(4-(6-fluorobenzo[d] isoxazol-3-yl) piperidin-1-yl)-2-(4-(hydroxymethyl)-1H-1, 2,3-triazol-1-yl) ethanone was synthesized in good yield by using click chemistry approach with 2-azido-1-(4-(6-flurobenzo[d]isooxazol-3-yl)piperidin-1-yl)ethanone as a starting material. The synthesized compound was characterized using IR, NMR and MS studies. Thermal stability of the compound was analyzed by using TGA and DSC technique. The single crystal XRD analysis was taken part, to confirm the structure of the compound. The intercontacts in the crystal structure are analyzed using Hirshfeld surfaces computational method. Cytotoxicity of the synthesized compound was evaluated and the results were reported. The binding analysis carried out between the newly synthesized molecule with human serum albumin using fluorescence spectroscopy technique to understand the pharmacokinetics nature of the compound for further biological application. The molecular docking studies were evaluated for the compound to elucidate insights of new molecules in carrier protein.

An in vivo strategy to counteract post-administration anticoagulant activity of azido-Warfarin

NASA Astrophysics Data System (ADS)

Ursuegui, Sylvain; Recher, Marion; Krężel, Wojciech; Wagner, Alain

2017-05-01

Drugs, usually long acting and metabolically stable molecules, might be the source of adverse effects triggered by complex drug interactions, anaphylaxis and drug-induced coagulopathy. To circumvent this growing drug safety issue, we herein investigate the opportunity offered by bio-orthogonal chemistry for in vivo drug neutralization. We design a small-molecule anticoagulant drug (Warfarin) containing an azide group that acts as a safety pin. It allows drug deactivation and restoration of physiological coagulation via in vivo click reaction with a suitable cyclooctyne-based neutralizing agent. In this strategy, the new molecule formed by reaction of the drug and the antidote is deprived of biological activity and prone to fast renal clearance. This `Click & Clear' approach lays ground for new strategies in designing drugs with switchable biophysical properties.

Ethyl 2-{4-[(1,5-dibenzyl-2,4-dioxo-2,3,4,5-tetra-hydro-1H-1,5-benzo-diazepin-3-yl)meth-yl]-1H-1,2,3-triazol-1-yl}acetate.

PubMed

Jabli, Hind; Kandri Rodi, Y; Ladeira, Sonia; Essassi, El Mokhtar; Ng, Seik Weng

2009-12-12

The reaction of 1,5-dibenzyl-3-propargyl-1,5-benzodiazepine-2,4-dione with ethyl azido-acetate in the presence of copper sulfate pentahydrate and sodium ascorbate leads to the formation of the title regioisomer, C(30)H(29)N(5)O(4), which features a phenyl-ene ring fused with a seven-membered diazepinyl ring. The latter ring adopts a boat conformation (with the methyl-triazolylacetate-bearing C atom as the prow and the fused-ring C atoms as the stern). The benzyl groups connected to the diazepinyl ring jprotrude from the sides; the methyl-triazolylacetate substituent occupies an axial position.

The time of administration of 3'-azido-3'-deoxythymidine (AZT) determines its host toxicity with possible relevance to AZT chemotherapy.

PubMed Central

Zhang, R; Lu, Z; Diasio, C R; Liu, T; Soong, S J

1993-01-01

3'-Azido-3'-deoxythymidine (AZT) is the drug most widely used in the treatment of AIDS. Its major drug-related toxicity is bone marrow suppression, which limits the dose of AZT that can be used. It is essential that AZT be phosphorylated for antiviral effect. We have recently demonstrated that thymidine kinase (TK), the initial enzyme in AZT anabolism, follows a circadian pattern in rat bone marrow. The present study was undertaken to determine whether AZT toxicity is related to the time of its administration and whether the variation in toxicity is correlated with the circadian variation in TK activity. Male Sprague-Dawley rats were housed under standardized conditions of light and dark (lights on 0600 to 1800 and lights off 1800 to 0600) for 4 weeks. The animals were randomly divided into seven groups; six groups were administered AZT by intraperitoneal injection at the same dose of 750 mg/kg of body weight at various times (0400, 0800, 1200, 1600, 2000, and 2400), and one group was used as a control. AZT-related toxic effects, including bone marrow toxicity, differed significantly among the treatment groups, depending on the time of AZT administration (by analysis of variance and Cosinor analysis, P < 0.001). The least toxicity was observed in rats receiving AZT at 1600 (10 h after light onset [10 HALO], in late sleep span) and the greatest toxicity was observed in those injected at 0400 (22 HALO, in late activity span). To verify these results, we administered AZT by intraperitoneal injection at an approximately 50% lethal dose (1,500 mg/kg) to two groups of rats, one at 1200 (6 HALO, in the middle of the sleep span) and the other at 2400 (18 HALO, in the middle of the activity span). AZT lethality was significantly higher in rats receiving AZT at 2400 (18 HALO, in the middle of the activity span). Further statistical analysis demonstrated that the variation in AZT toxicity was correlated with the circadian variation in TK activity in bone marrow of the same species (peak activity at 0400 [22 HALO, in late activity span] and trough activity at 1600 [10 HALO, in late sleep span]), suggesting that the circadian variation in TK activity may be the biochemical basis for the observed circadian variation in AZT toxicity. These results may be useful in the design of improved AZT chemotherapeutic regimens. PMID:8239582

Selective dye-labeling of newly synthesized proteins in bacterial cells.

PubMed

Beatty, Kimberly E; Xie, Fang; Wang, Qian; Tirrell, David A

2005-10-19

We describe fluorescence labeling of newly synthesized proteins in Escherichia coli cells by means of Cu(I)-catalyzed cycloaddition between alkynyl amino acid side chains and the fluorogenic dye 3-azido-7-hydroxycoumarin. The method involves co-translational labeling of proteins by the non-natural amino acids homopropargylglycine (Hpg) or ethynylphenylalanine (Eth) followed by treatment with the dye. As a demonstration, the model protein barstar was expressed and treated overnight with Cu(I) and 3-azido-7-hydroxycoumarin. Examination of treated cells by confocal microscopy revealed that strong fluorescence enhancement was observed only for alkynyl-barstar treated with Cu(I) and the reactive dye. The cellular fluorescence was punctate, and gel electrophoresis confirmed that labeled barstar was localized in inclusion bodies. Other proteins showed little fluorescence. Examination of treated cells by fluorimetry demonstrated that cultures supplemented with Eth or Hpg showed an 8- to 14-fold enhancement in fluorescence intensity after labeling. Addition of a protein synthesis inhibitor reduced the emission intensity to levels slightly above background, confirming selective labeling of newly synthesized proteins in the bacterial cell.

Structure-activity relationships of C6-uridine derivatives targeting plasmodia orotidine monophosphate decarboxylase.

PubMed

Bello, Angelica M; Poduch, Ewa; Liu, Yan; Wei, Lianhu; Crandall, Ian; Wang, Xiaoyang; Dyanand, Christopher; Kain, Kevin C; Pai, Emil F; Kotra, Lakshmi P

2008-02-14

Malaria, caused by Plasmodia parasites, has re-emerged as a major problem, imposing its fatal effects on human health, especially due to multidrug resistance. In Plasmodia, orotidine 5'-monophosphate decarboxylase (ODCase) is an essential enzyme for the de novo synthesis of uridine 5'-monophosphate. Impairing ODCase in these pathogens is a promising strategy to develop novel classes of therapeutics. Encouraged by our recent discovery that 6-iodo uridine is a potent inhibitor of P. falciparum, we investigated the structure-activity relationships of various C6 derivatives of UMP. 6-Cyano, 6-azido, 6-amino, 6-methyl, 6- N-methylamino, and 6- N, N-dimethylamino derivatives of uridine were evaluated against P. falciparum. The mononucleotides of 6-cyano, 6-azido, 6-amino, and 6-methyl uridine derivatives were studied as inhibitors of plasmodial ODCase. 6-Azidouridine 5'-monophosphate is a potent covalent inhibitor of P. falciparum ODCase. 6-Methyluridine exhibited weak antimalarial activity against P. falciparum 3D7 isolate. 6- N-Methylamino and 6- N, N-dimethylamino uridine derivatives exhibited moderate antimalarial activities.

From Mesocates to Helicates: Structural, Magnetic and Chiro-Optical Studies on Nickel(II) Supramolecular Assemblies Derived from Tetradentate Schiff Bases.

PubMed

Mayans, Júlia; Font-Bardia, Mercè; Di Bari, Lorenzo; Arrico, Lorenzo; Zinna, Francesco; Pescitelli, Gennaro; Escuer, Albert

2018-05-28

The systematic reactions of a family of tetradentate pyridyl/imine and quinolyl/imine racemic or enantiopure Schiff bases with Ni(NO 3 ) 2 or Ni(ClO 4 ) 2 in the presence of sodium azide yielded, as a function of the starting racemic, chiral or achiral base, a set of chiral, meso or achiral complexes. In all cases, the compounds consist of two Ni II cations linked by a double azido bridge in its end-on coordination mode. All the dimers exhibit a mesocate supramolecular structure and one of them, the unprecedented mix of helicate and mesocate in 2:1 ratio. The transition from mesocate to helicate conformation has been reached by tuning the flexibility of the central spacers of the Schiff bases and the size of the substituents. Electronic circular dichroism (ECD) studies have been performed for two pairs of enantiomers and interpreted by means of DFT calculations. Susceptibility measurements show a ferromagnetic coupling between the Ni II cations mediated by the end-on azido bridges. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Selection and characterization of a mutant of feline immunodeficiency virus resistant to 2',3'-dideoxycytidine.

PubMed Central

Medlin, H K; Zhu, Y Q; Remington, K M; Phillips, T R; North, T W

1996-01-01

We have selected and plaque purified a mutant of feline immunodeficiency virus (FIV) that is resistant to 2',3'-dideoxycytidine (ddC). This mutant was selected in cultured cells in the continuous presence of 25 microM ddC. The mutant, designated DCR-5c, was fourfold resistant to ddC, threefold resistant to 2',3'-dideoxyinosine, and more than fourfold resistant to phosphonoformic acid. DCR-5c displayed little or no resistance to (-)-beta-2',3'-dideoxy-3'-thiacytidine, 3'-azido-3'-deoxythymidine, or 9-(2-phosphonylmethoxyethyl) adenine. Reverse transcriptase purified from DCR-5c was less susceptible to inhibition by ddCTP, phosphonoformic acid, ddATP, or azido-dTTP than the wild-type FIV reverse transcriptase. Sequence analysis of DCR-5c revealed a single base change (G to C at nucleotide 2342) in the reverse transcriptase-encoding region of FIV. This mutation results in substitution of His for Asp at codon 3 of FIV reverse transcriptase. The role of this mutation in ddC resistance was confirmed by site-directed mutagenesis. PMID:8849258

C-H Activation of Benzene by a Photoactivated Ni(II)(azide): Formation of a Transient Nickel Nitrido Complex.

PubMed

Vreeken, Vincent; Siegler, Maxime A; de Bruin, Bas; Reek, Joost N H; Lutz, Martin; van der Vlugt, Jarl Ivar

2015-06-08

Photochemical activation of nickel-azido complex 2 [Ni(N3)(PNP)] (PN(H)P=2,2'-di(isopropylphosphino)-4,4'-ditolylamine) in neat benzene produces diamagnetic complex 3 [Ni(Ph)(PN(P)N(H))], which is crystallographically characterized. DFT calculations support photoinitiated N2-loss of the azido complex to generate a rare, transient Ni(IV) nitrido species, which bears significant nitridyl radical character. Subsequent trapping of this nitrido through insertion into the Ni-P bond generates a coordinatively unsaturated Ni(II) imidophosphorane P=N donor. This species shows unprecedented reactivity toward 1,2-addition of a C-H bond of benzene to form 3. The structurally characterized chlorido complex 4 [Ni(Cl)(PN(P)N(H))] is generated by reaction of 3 with HCl or by direct photolysis of 2 in chlorobenzene. This is the first report of aromatic C-H bond activation by a trapped transient nitrido species of a late transition metal. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cabazitaxel is more active than first-generation taxanes in ABCB1(+) cell lines due to its reduced affinity for P-glycoprotein.

PubMed

Duran, George E; Derdau, Volker; Weitz, Dietmar; Philippe, Nicolas; Blankenstein, Jörg; Atzrodt, Jens; Sémiond, Dorothée; Gianolio, Diego A; Macé, Sandrine; Sikic, Branimir I

2018-04-19

The primary aim of this study was to determine cabazitaxel's affinity for the ABCB1/P-glycoprotein (P-gp) transporter compared to first-generation taxanes. We determined the kinetics of drug accumulation and retention using [ 14 C]-labeled taxanes in multidrug-resistant (MDR) cells. In addition, membrane-enriched fractions isolated from doxorubicin-selected MES-SA/Dx5 cells were used to determine sodium orthovanadate-sensitive ATPase stimulation after exposure to taxanes. Custom [ 3 H]-azido-taxane analogues were synthesized for the photoaffinity labeling of P-gp. The maximum intracellular drug concentration was achieved faster with [ 14 C]-cabazitaxel (5 min) than [ 14 C]-docetaxel (15-30 min). MDR cells accumulated twice as much cabazitaxel than docetaxel, and these levels could be restored to parental levels in the presence of the P-gp inhibitor PSC-833 (valspodar). Efflux in drug-free medium confirmed that MDR cells retained twice as much cabazitaxel than docetaxel. There was a strong association (r 2  = 0.91) between the degree of taxane resistance conferred by P-gp expression and the accumulation differences observed with the two taxanes. One cell model expressing low levels of P-gp was not cross-resistant to cabazitaxel while demonstrating modest resistance to docetaxel. Furthermore, there was a 1.9 × reduction in sodium orthovanadate-sensitive ATPase stimulation resulting from treatment with cabazitaxel compared to docetaxel. We calculated a dissociation constant (Kd) value of 1.7 µM for [ 3 H]-azido-docetaxel and ~ 7.5 µM for [ 3 H]-azido-cabazitaxel resulting in a 4.4 × difference in P-gp labeling, and cold docetaxel was a more effective competitor than cabazitaxel. Our studies confirm that cabazitaxel is more active in ABCB1(+) cell models due to its reduced affinity for P-gp compared to docetaxel.

Synthesis and evaluation of 3-modified 1D-myo-inositols as inhibitors and substrates of phosphatidylinositol synthase and inhibitors of myo-inositol uptake by cells.

PubMed

Johnson, S C; Dahl, J; Shih, T L; Schedler, D J; Anderson, L; Benjamin, T L; Baker, D C

1993-11-12

A number of 3-substituted 1D-myo-inositols were synthesized and evaluated as substrates for phosphatidylinositol synthase and uptake by intact cells. 1D-3-Amino-, -3-chloro-, and -3-(acetylthio)-3-deoxy-myo-inositols were all synthesized by nucleophilic displacement of the 6-O-(trifluoromethyl)sulfonyl group of 1L-1,2:3,4-di-O-cyclohexylidene-5-O-methyl-6-O-[(trifluoromethyl)-sulfon yl] - chiro-inositol (which was prepared from L-quebrachitol), respectively, by reaction with LiN3, followed by reduction of the azido function, and with LiCl and KSAc to give the O-protected compounds. O-Demethylation using BBr3 and concomitant acetal hydrolysis furnished the free-hydroxy 3-amino- and 3-chloro-3-deoxy-1D-myo-inositols. The 3-mercapto analogue was obtained by removal of the acetal groups of the acetylthio analogue, followed by acetylation and purification of the peracetate, and subsequent O-demethylation and deacetylation. The 3-deoxy derivative was synthesized from the 6-O-(imidazol-1-ylthiocarbonyl) compound via Barton-McCombie deoxygenation. The 3-azido derivative was directly synthesized from 1L-1-O-tosyl-chiro-inositol via displacement with azide. The 3-keto analogue was prepared by Pt-catalyzed air oxidation of 1L-chiro-inositol. The compounds were all evaluated as substrates for phosphatidylinositol (PtdIns) synthase from mouse brain. The 3-NH2, 3-F, 3-deoxy, and 3-keto analogues all showed activity as substrates, as measured by liberation of cytidine monophosphate. These compounds also showed inhibition of the reaction of myo-[3H]inositol with PtdIns synthase. These results taken together indicate that these compounds are likely to be incorporated into phospholipids. As a further indication that these compounds might be useful as probes for the PtdIns pathway, it was demonstrated that the 3-NH2, 3-F, and 3-deoxy compounds are taken up by intact fibroblast cells as evidenced by their competing with myo-[3H]inositol uptake.

Initial mechanisms for the decomposition of electronically excited energetic materials: 1,5′-BT, 5,5′-BT, and AzTT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuan, Bing; Yu, Zijun; Bernstein, Elliot R., E-mail: erb@lamar.Colostate.edu

2015-03-28

Decomposition of nitrogen-rich energetic materials 1,5′-BT, 5,5′-BT, and AzTT (1,5′-Bistetrazole, 5,5′-Bistetrazole, and 5-(5-azido-(1 or 4)H-1,2,4-triazol-3-yl)tetrazole, respectively), following electronic state excitation, is investigated both experimentally and theoretically. The N{sub 2} molecule is observed as an initial decomposition product from the three materials, subsequent to UV excitation, with a cold rotational temperature (<30 K). Initial decomposition mechanisms for these three electronically excited materials are explored at the complete active space self-consistent field (CASSCF) level. Potential energy surface calculations at the CASSCF(12,8)/6-31G(d) level illustrate that conical intersections play an essential role in the decomposition mechanism. Electronically excited S{sub 1} molecules can non-adiabatically relaxmore » to their ground electronic states through (S{sub 1}/S{sub 0}){sub CI} conical intersections. 1,5′-BT and 5,5′-BT materials have several (S{sub 1}/S{sub 0}){sub CI} conical intersections between S{sub 1} and S{sub 0} states, related to different tetrazole ring opening positions, all of which lead to N{sub 2} product formation. The N{sub 2} product for AzTT is formed primarily by N–N bond rupture of the –N{sub 3} group. The observed rotational energy distributions for the N{sub 2} products are consistent with the final structures of the respective transition states for each molecule on its S{sub 0} potential energy surface. The theoretically derived vibrational temperature of the N{sub 2} product is high, which is similar to that found for energetic salts and molecules studied previously.« less

Quantitative fabrication of functional polymer surfaces

NASA Astrophysics Data System (ADS)

Rengifo, Hernan R.

Polymeric surfaces and films have very broad applications in industry. They have been employed as anticorrosive, abrasive and decorative coatings for many years. More recently, the applications of functional polymer films in microelectronics, optics, nanocomposites, DNA microarrays, and enzyme immobilizations has drawn a lot of attention. There are a number of challenges associated with the implementation of functional polymeric surfaces, and these challenges are especially important in the field of surface modification. In this thesis, three different challenges in the field of polymeric functional surfaces are addressed: first of all, a set of rules for the molecular design are presented in chapters 3 and 4 according to the surface needs. Second, some latent energy source must be incorporated into the material design to quantitative modify a surface. Third, the morphology of the surface, the method use to fabricate the design surface and their new applications are presented in chapters 4 and 5. The new polymeric surface functionalization method described in Chapter 3 is based upon an end-functionalized diblock copolymer design to self-assemble at the surface of both hard and soft surfaces. It is demonstrated that alkyne end-functional diblock copolymers can be used to provide precise control over areal densities of reactive functionality. The areal density of alkyne functional groups is precisely controlled by adjusting the thickness of the block copolymer monolayer, which is accomplished by changing either the spin coating conditions (i.e., rotational speed and solution concentration) or the copolymer molecular weight. The modified surfaces are characterized by atomic force microscopy (AFM), contact angle, ellipsometry, fluorescent imaging and angle-dependent X-ray photoelectron spectroscopy (ADXPS) measurements. In Chapter 4, a simple means is demonstrated to covalently bond DNA to polymer-modified substrates; the method provides quantitative control of the DNA areal density. The approach is based upon synthesis of an alkyne-end-functional diblock copolymer alpha-alkyne-o-Br-poly(tBA- b-MMA). The block copolymer self-assembles to form a bilayer on the substrate and directs alkyne groups to the surface. Azido-functionalized DNA is immobilized on alkyne functionalized substrates by a "click" reaction. The density of immobilized DNA can be quantitatively controlled by varying the parameters used for spin-coating the polymer film or by adjusting the hydrophilicity of the polymer surface underlying the reactive alkyne functional groups. In Chapter 5, Layer by layer (LbL) assembly techniques construct multilayer thin films by sequential deposition of monomolecular layers of organic molecules. One of the drawbacks associated with their use is that monomolecular layers are usually held together by relatively weak forces such as Van der Waals, electrostatic and hydrogen bonding interactions, and can therefore be lacking in mechanical integrity. In this chapter, it is demonstrated that heterobifunctional polymers, functionalized with one azide chain terminus and a protected alkyne group as the other chain terminus, constitute a powerful and versatile means for the covalent layer-by-layer (CLbL) assembly of thin polymer films. Each monomolecular polymer layer is covalently bound to both the preceding and following layers to produce a robust multilayer structure. Because the coupling chemistry used, "click" chemistry, is highly chemoselective, the layering process is virtually independent of the chemical nature of the polymer so that the constitution of each layer can be selected at will. Unlike other layer-by-layer deposition techniques, the layer thickness in CLbL is not equivalent to the diameter of the polymer chain, but is related to the polymer chain length and can be controlled by adjustment of either the polymer molecular weight or the areal density of surface alkyne groups.

Mass Spectrometric Thermal Decomposition and Ultraviolet Irradiation Studies of Some Azido and Nitrato Polymeric Binders.

DTIC Science & Technology

1982-09-01

Edwards AFB, CA 93523 Attn: Mr. D. Siegel Attn: Dr. F. Roberto Office of Naval Research 1 AFSC Western Office Andrews AFB, Code DLFP 1030 East Green...Office space Sciences One Hallidie Plaza Suite 601 Bolling Air Force Base San Francisco, CA 94102 Washing.on, DC 20332 Attn: Dr. P. A. Miller Attn: Dr

Ultrafast primary processes of an iron-(III) azido complex in solution induced with 266 nm light.

PubMed

Vennekate, Hendrik; Schwarzer, Dirk; Torres-Alacan, Joel; Krahe, Oliver; Filippou, Alexander C; Neese, Frank; Vöhringer, Peter

2012-05-14

The ultrafast photo-induced primary processes of the iron-(III) azido complex, [Fe(III)N(3)(cyclam-acetato)] PF(6) (1), in acetonitrile solution at room temperature were studied using femtosecond spectroscopy with ultraviolet (UV) excitation and mid-infrared (MIR) detection. Following the absorption of a 266 nm photon, the complex undergoes an internal conversion back to the electronic doublet ground state at a time scale below 2 ps. Subsequently, the electronic ground state vibrationally cools with a characteristic time constant of 13 ps. A homolytic bond cleavage was also observed by the appearance of ground state azide radicals, which were identified by their asymmetric stretching vibration at 1659 cm(-1). The azide radical recombines in a geminate fashion with the iron containing fragment within 20 ps. The cage escape leading to well separated fragments after homolytic Fe-N bond breakage was found to occur with a quantum yield of 35%. Finally, non-geminate recombination at nanosecond time scales was seen to further reduce the photolytic quantum yield to below 20% at a wavelength of 266 nm. This journal is © the Owner Societies 2012

Synthesis and Catalytic Applications of Multi-Walled Carbon Nanotube-Polyamidoamine Dendrimer Hybrids.

PubMed

Desmecht, Antonin; Steenhaut, Timothy; Pennetreau, Florence; Hermans, Sophie; Riant, Olivier

2018-06-20

Polyamidoamine (PAMAM) dendrimers were covalently immobilized on multi-walled carbon nanotubes (MWNT) via two 'grafting to' strategies. We demonstrate the existence of non-covalent interactions between the two components but outline the superiority of our two grafting approaches, namely xanthate and click chemistry. MWNT surfaces were functionalized with activated ester and propargylic moieties prior to their reaction with PAMAM or azido-PAMAM dendrimers, respectively. The grafting of PAMAM generations 0 to 3 was evaluated with X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). The versatility of our hybrids was demonstrated by post-functionalization sequences involving copper alkyne-azide cycloaddition (CuAAC). We synthesized homogeneous supported iridium complexes at the extremities of the dendrimers. In addition, our materials were used as template for the encapsulation of Pd nanoparticles (NP), validating our nanocomposites for catalytic applications. The palladium-based catalyst was active for carbonylative coupling during 5 consecutive runs without loss of activity. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Azido, triazolyl, and alkynyl complexes of gold(I): syntheses, structures, and ligand effects.

PubMed

Robilotto, Thomas J; Deligonul, Nihal; Updegraff, James B; Gray, Thomas G

2013-08-19

Gold(I) triazolyl complexes are prepared in [3 + 2] cycloaddition reactions of (tertiary phosphine)gold(I) azides with terminal alkynes. Seven such triazolyl complexes, not previously prepared, are described. Reducible functional groups are accommodated. In addition, two new (N-heterocyclic carbene)gold(I) azides and two new gold(I) alkynyls are described. Eight complexes are crystallographically authenticated; aurophilic interactions appear in one structure only. The packing diagrams of gold(I) triazolyls all show intermolecular hydrogen bonding between N-1 of one molecule and N-3 of a neighbor. This hydrogen bonding permeates the crystal lattice. Density-functional theory calculations of (triphenylphosphine)gold(I) triazolyls and the corresponding alkynyls indicate that the triazolyl is a stronger trans-influencer than is the alkynyl, but the alkynyl is more electron-releasing. These results suggest that trans-influences in two-coordinate gold(I) complexes can be more than a simple matter of ligand donicity.

Functionalisation of lanthanide complexes via microwave-enhanced Cu(I)-catalysed azide-alkyne cycloaddition.

PubMed

Szíjjártó, Csongor; Pershagen, Elias; Borbas, K Eszter

2012-07-07

Cu(I)-catalysed azide-alkyne cycloaddition reactions were used to functionalise lanthanide(III)-complexes (Ln; La, Eu and Tb) incorporating alkyne or azide reactive groups. Microwave irradiation significantly accelerated the reactions, enabling full conversion to the triazole products in some cases in 5 min. Alkyl and aryl azides and alkyl and aryl alkynes could all serve as coupling partners. These reaction conditions proved efficient for cyclen-tricarboxylates and previously unreactive cyclen-tris-primary amide chelates. The synthesis of heterobimetallic (Eu/Tb, EuTb17 and Eu/La, EuLa17) and heterotrimetallic (Eu/La/Eu) complexes was achieved in up to 60% isolated yield starting from coumarin 2-appended alkynyl complexes Tb16 or La16 and an azido-Eu complex Eu4, and bis-alkynyl La-complex La5 and Eu4, respectively. EuTb17 displayed dual Eu(III) and Tb(III)-emission upon antenna-centred excitation.

Preparation of Metalloporphyrin-Bound Superparamagnetic Silica Particles via "Click" Reaction.

PubMed

Hollingsworth, Javoris V; Bhupathiraju, N V S Dinesh K; Sun, Jirun; Lochner, Eric; Vicente, M Graça H; Russo, Paul S

2016-01-13

A facile approach using click chemistry is demonstrated for immobilization of metalloporphyrins onto the surface of silica-coated iron oxide particles. Oleic-acid stabilized iron oxide nanocrystals were prepared by thermal decomposition of iron(III) acetylacetonate. Their crystallinity, morphology, and superparamagnetism were determined using X-ray diffraction, transmission electron microscopy, and a superconducting quantum interference device. Monodisperse core-shell particles were produced in the silica-coating of iron oxide via microemulsion synthesis. Surface modification of these particles was performed in two steps, which included the reaction of silica-coated iron oxide particles with 3-bromopropyltrichlorosilane, followed by azido-functionalization with sodium azide. Monoalkylated porphyrins were prepared using the Williamson ether synthesis of commercially available tetra(4-hydroxyphenyl) porphyrin with propargyl bromide in the presence of a base. (1)H NMR and matrix-assisted laser desorption ionization confirmed the identity of the compounds. The prepared monoalkyne porphyrins were zinc-metalated prior to their introduction to azide-functionalized, silica-coated iron oxide particles in the click reaction. X-ray photoelectron spectroscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy were used to characterize the surface chemistry after each step in the reaction. In addition, particle size was determined using dynamic light scattering and microscopy. The presented methodology is versatile and can be extended to other photoreactive systems, such as phthalocyanines and boron-dipyrromethane, which may lead to new materials for optical, photonic, and biological applications.

Syntheses, crystal structures, magnetic properties, and EPR spectra of tetranuclear copper(II) complexes featuring pairs of "roof-shaped" Cu2X2 dimers with hydroxide, methoxide, and azide bridges.

PubMed

Graham, B; Hearn, M T; Junk, P C; Kepert, C M; Mabbs, F E; Moubaraki, B; Murray, K S; Spiccia, L

2001-03-26

Hydroxo- and methoxo-bridged tetranuclear copper(II) complexes of the tetramacrocyclic ligand 1,2,4,5-tetrakis(1,4,7-triazacyclonon-1-ylmethyl)benzene (Ldur), have been prepared from [Cu4Ldur(H2O)8](ClO4)8.9H2O (1). Addition of base to an aqueous solution of 1 gave [Cu4Ldur(mu2-OH)4](ClO4)4 (2). Diffusion of MeOH into a DMF solution of 2 produces [Cu4Ldur(mu2-OMe)4](ClO4)4.HClO4.2/3MeOH (3), a complex which hydrolyzes on exposure to moisture regenerating 2. The structurally related azido-bridged complex, [Cu4Ldur(mu2-N3)4](PF6)4.4H2O.6CH3CN (4), was produced by reaction of Ldur with 4 molar equiv of Cu(OAc)2.H2O and NaN3 in the presence of excess KPF6. Compounds 2-4 crystallize in the triclinic space group P1 (No. 2) with a = 10.248(1) A, b = 12.130(2) A, c = 14.353(2) A, alpha = 82.23(1) degrees, beta = 80.79(1) degrees, gamma = 65.71(1) degrees, and Z = 1 for 2, a = 10.2985(4) A, b = 12.1182(4) A, c = 13.9705(3) A, alpha = 89.978(2) degrees, beta = 82.038(2) degrees, gamma = 65.095(2) degrees, and Z = 1 for 3, and a = 12.059(2) A, b = 12.554(2) A, c = 14.051(2) A, alpha = 91.85(1) degrees, beta = 98.22(1) degrees, gamma = 105.62(1) degrees, and Z = 1 for 4. The complexes feature pairs of isolated dibridged copper(II) dimers with "roof-shaped" Cu2(mu2-X)2 cores (X = OH-, OMe-, N3-), as indicated by the dihedral angle between the two CuX2 planes (159 degrees for 2, 161 degrees for 3, and 153 degrees for 4). This leads to Cu.Cu distances of 2.940(4) A for 2, 2.962(1) A for 3, and 3.006(5) A for 4. Variable-temperature magnetic susceptibility measurements indicate weak antiferromagnetic coupling (J = -27 cm(-1)) for the hydroxo-bridged copper(II) centers in 2 and very strong antiferromagnetic coupling (J = -269 cm(-1)) for the methoxo-bridged copper(II) centers in 3. Pairs of copper(II) centers in 4 display the strongest ferromagnetic interaction (J = 94 cm(-1)) reported thus far for bis(mu2-1,1-azido)-bridged dicopper units. Spectral measurements on a neat powdered sample of 4 at 33.9 GHz or 90 Ghz confirm the spin-triplet ground state for the azido-bridged copper(II) pairs.

"Click" on PLGA-PEG and hyaluronic acid: Gaining access to anti-leishmanial pentamidine bioconjugates.

PubMed

Scala, Angela; Piperno, Anna; Micale, Nicola; Mineo, Placido G; Abbadessa, Antonio; Risoluti, Roberta; Castelli, Germano; Bruno, Federica; Vitale, Fabrizio; Cascio, Antonio; Grassi, Giovanni

2017-12-08

Pentamidine (Pent), an antiparasitic drug used for the treatment of visceral leishmaniasis, has been modified with terminal azide groups and conjugated to two different polymer backbones (PLGA-PEG [PP] copolymer and hyaluronic acid [HA]) armed with alkyne end-groups. The conjugation has been performed by Copper Catalyzed Azido Alkyne Cycloaddition (CuAAC) using CuSO 4 /sodium ascorbate as metal source. The novel PP-Pent and HA-Pent bioconjugates are proposed, respectively, as non-targeted and targeted drug delivery systems against Leishmania infections. Moreover, Pent has been encapsulated into PP nanoparticles by the oil-in-water emulsion method, with the aim to compare the biological activity of the bioconjugates with that of the classical drug-loaded delivery system that physically entraps the therapeutic agent. Biological assays against Leishmania infantum amastigote-infected macrophages and primary macrophages revealed that Pent, either covalently conjugated with polymers or loaded into polymeric nanoparticles, turned out to be more potent and less toxic than the free Pent. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2017. © 2017 Wiley Periodicals, Inc.

Fungal growth inhibitory properties of new phytosphingolipid analogues.

PubMed

Mormeneo, D; Manresa, A; Casas, J; Llebaria, A; Delgado, A

2008-04-01

To study the growth inhibitory properties of a series of phytosphingosine (PHS) and phytoceramide (PHC) analogues. A panel of two yeast (Candida albicans and Saccharomyces cerevisiae) and six moulds (Aspergillus repens, Aspergillus niger, Penicillium chrysogenum, Cladosporium cladosporioides, Arthroderma uncinatum and Penicillium funiculosum) has been used in this study. A series of new PHS and PHC analogues differing at the sphingoid backbone and the functional group at C1 position were synthesized. Among PHS analogues, 1-azido derivative 1c, bearing the natural D-ribo stereochemistry, showed a promising growth inhibitory profile. Among PHC analogues, compound 12, with a bulky N-pivaloyl group and a Z double bond at C3 position of the sphingoid chain, was the most active growth inhibitor. Minimal inhibitory concentration values were in the range of 23-48 micromol l(-1) for 1c and 44-87 micromol l(-1) for 12. Only scattered data on the antifungal activity of phytosphingolipids have been reported in the literature. This is the first time that a series of analogues of this kind are tested and compared to discern their structural requirements for antifungal activity.

Human immunodeficiency virus types 1 and 2 exhibit comparable sensitivities to Zidovudine and other nucleoside analog inhibitors in vitro.

PubMed

Smith, Robert A; Gottlieb, Geoffrey S; Anderson, Donovan J; Pyrak, Crystal L; Preston, Bradley D

2008-01-01

Using an indicator cell assay that directly quantifies viral replication, we show that human immunodeficiency virus types 1 and 2 (HIV-1 and HIV-2, respectively) exhibit similar sensitivities to 3'-azido-3'-deoxythymidine (zidovudine) as well as other nucleoside analog inhibitors of reverse transcriptase. These data support the use of nucleoside analogs for antiviral therapy of HIV-2 infection.

Identification of the triazine receptor protein as a chloroplast gene product

PubMed Central

Steinback, Katherine E.; McIntosh, Lee; Bogorad, Lawrence; Arntzen, Charles J.

1981-01-01

The triazine herbicides inhibit photosynthesis by blocking electron transport at the second stable electron acceptor of photosystem II. This electron transport component of chloroplast thylakoid membranes is a protein-plastoquinone complex termed “B.” The polypeptide that is believed to be a component of the B complex has recently been identified as a 32- to 34-kilo-dalton polypeptide by using a photoaffinity labeling probe, azido-[14C]atrazine. A 34-kilodalton polypeptide of pea chloroplasts rapidly incorporates [35S]methionine in vivo and is also a rapidly labeled product of chloroplast-directed protein synthesis. Trypsin treatment of membranes tagged with azido-[14C]atrazine, [35S]methionine in vivo, or [35S]methionine in isolated intact chloroplasts results in identical, sequential alterations of the 34-kilo-dalton polypeptide to species of 32, then 18 and 16 kilodaltons. From the identical pattern of susceptibility to trypsin we conclude that the rapidly synthesized 34-kilodalton polypeptide that is a product of chloroplast-directed protein synthesis is identical to the triazine herbicide-binding protein of photosystem II. Chloroplasts of both triazine-susceptible and triazine-resistant biotypes of Amaranthus hybridus synthesize the 34-kilodalton polypeptide, but that of the resistant biotype does not bind the herbicide. Images PMID:16593133

Design and synthesis of unnatural heparosan and chondroitin building blocks

PubMed Central

Bera, Smritilekha; Linhardt, Robert J.

2011-01-01

Triazole linked heparosan and chondroitin disaccharide and tetrasaccharide building blocks were synthesized in a stereoselective manner by applying a very efficient Copper Catalyzed Azide-Alkyne Cycloadditions (CuAAC) reaction of appropriately substituted azido-glucuronic acid and propargyluted N-acetyl glucosamine and N-acetyl galactosamine derivative respectively. The resulting suitably substituted tetrasaccharide analogs can be easily converted into azide and alkyne unit for further synthesis of higher oligosaccharide analogs. PMID:21438620

trans-Bis(azido-kappaN)bis(pyridine-2-carboxamide-kappa2N1,O2)nickel(II).

PubMed

Daković, Marijana; Popović, Zora

2007-11-01

In the title compound, [Ni(N(3))(2)(C(6)H(6)N(2)O)(2)], the Ni(II) atom lies on an inversion centre. The distorted octahedral nickel(II) coordination environment contains two planar trans-related N,O-chelating picolinamide ligands in one plane and two monodentate azide ligands perpendicular to this plane. Molecules are linked into a three-dimensional framework by N-H...N hydrogen bonds.

Interaction of forskolin with the P-glycoprotein multidrug transporter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ming s, D.I.; Seamon, K.B.; Speicher, L.A.

1991-08-27

Forskolin and 1,9-dideoxyforskolin, an analogue that does not activate adenylyl cyclase, were tested for their ability to enhance the cytotoxic effects of adriamycin in human ovarian carcinoma cells, SKOV3, which are sensitive to adriamycin and express low levels of P-glycoprotein, and a variant cell line, SKVLB, which overexpresses the P-glycoprotein and has the multidrug reing ance (MDR) phenotype. Forskolin and 1,9-dideoxyforskolin both increased the cytotoxic effects of adriamycin in SKVLB cells, yet had no effect on SKOV3 cells. Two photoactive derivatives of forskolin have been synthesized, 7-O-((2-(3-(4-azido-3-({sup 125}I)iodophenyl)propionamido)ethyl)carbamyl)forskolin, {sup 125}I-6-AIPP-Fsk, and 6-O-((2-(3-(4-azido-3-({sup 125}I)iodophenyl)propionamido)ethyl)carbamyl)forskolin, {sup 125}I-6-AIPP-Fsk, which exhibit specificity for labelingmore » the glucose transporter and aing lyl cyclase, respectively. Both photolabels identified a 140-kDa protein in membranes from SKVLB cells whose labeling was inhibited by forskolin and 1,9-dideoxyforskolin. The data are consistent with forskolin binding to the P-glycoprotein analogous to that of other chemosensitizing drugs that have been shown to partially reverse MDR. The ability of forskolin photolabels to specifically label the transporter, the adenylyl cyclase, and the P-glycoprotein suggests that these proteins may share a common biing g domain for forskolin analogues.« less

Ferromagnetic interactions in Ru(III)-nitronyl nitroxide radical complex: a potential 2p4d building block for molecular magnets.

PubMed

Pointillart, Fabrice; Bernot, Kevin; Sorace, Lorenzo; Sessoli, Roberta; Gatteschi, Dante

2007-07-07

The reaction between [Ru(salen)(PPh3)Cl] and the 4-pyridyl-substituted nitronyl nitroxide radical (NITpPy) leads to the [Ru(salen)(PPh3)(NITpPy)](ClO4)(H2O)2 complex while the reaction with the azido anion (N3-) leads to the [Ru(salen)(PPh3)(N3)] complex 2 (where salen2- = N,N'-ethan-1,2-diylbis(salicylidenamine) and PPh3 = triphenylphosphine). Both compounds have been characterized by single crystal X-ray diffraction. The two crystal structures are composed by a [Ru(III)(salen)(PPh3)]+ unit where the Ru(III) ion is coordinated to a salen2- ligand and one PPh3 ligand in axial position. In 1 the Ru(III) ion is coordinated to the 4-pyridyl-substituted nitronyl nitroxide radical whereas in 2 the second axial position is occupied by the azido ligand. In both complexes the Ru(III) ions are in the same environment RuO2N3P, in a tetragonally elongated octhaedral geometry. The crystal packing of 1 reveals pi-stacking in pairs. While antiferromagnetic intermolecular interaction (J2 = 5.0 cm(-1)) dominates at low temperatures, ferromagnetic intramolecular interaction (J1 = -9.0 cm(-1)) have been found between the Ru(III) ion and the coordinated NITpPy.

A Novel Point Mutation at Position 156 of Reverse Transcriptase from Feline Immunodeficiency Virus Confers Resistance to the Combination of (−)-β-2′,3′-Dideoxy-3′-Thiacytidine and 3′-Azido-3′-Deoxythymidine

PubMed Central

Smith, Robert A.; Remington, Kathryn M.; Preston, Bradley D.; Schinazi, Raymond F.; North, Thomas W.

1998-01-01

Mutants of feline immunodeficiency virus (FIV) resistant to (−)-β-2′,3′-dideoxy-3′-thiacytidine (3TC) were selected by culturing virus in the presence of increasing stepwise concentrations of 3TC. Two plaque-purified variants were isolated from the original mutant population, and both of these mutants were resistant to 3TC. Surprisingly, these mutants were also phenotypically resistant to 3′-azido-3′-deoxythymidine (AZT) and to the combination of 3TC and AZT. Purified reverse transcriptase (RT) from one of these plaque-purified mutants was resistant to the 5′-triphosphates of 3TC and AZT. DNA sequence analysis of the RT-encoding region of the pol gene amplified from the plaque-purified mutants revealed a Pro-to-Ser mutation at position 156 of RT. A site-directed mutant of FIV engineered to contain this Pro-156-Ser mutation was resistant to 3TC, AZT, and the combination of 3TC and AZT, confirming the role of the Pro-156-Ser mutation in the resistance of FIV to these two nucleoside analogs. This represents the first report of a lentiviral mutant resistant to the combination of AZT and 3TC due to a single, unique point mutation. PMID:9499094

Cyclic AMP-receptor proteins in heart muscle of rats flown on Cosmos 1887

NASA Technical Reports Server (NTRS)

Mednieks, Maija I.; Popova, Irina A.; Grindeland, Richard E.

1991-01-01

The cellular compartmentalization of the cyclic AMP-receptor proteins in heart ventricular tissue obtained from rats flown on the Cosmos 1887 is determined. Photoaffinity labeling of soluble and particular cell fractions with a (32P)-8-azido analog of cyclic AMP is followed by electrophoretic separation of the proteins and by autoradiographic identification of the labeled isoforms of cAPK R subunits. It is shown that RII in the particulate subcellular fraction was significantly decreased in heart cells from rats in the flight group when compared to controls. Protein banding patterns in both the cytoplasmic fraction and in a fraction enriched in chromatin-bound proteins exhibited some variability in tissues of individual animals, but showed no changes that could be directly attributed to flight conditions. No significant change was apparent in the distribution of RI or RII cyclic AMP binding in the soluble fractions. It is inferred that the cardiac cell integrity or its protein content is not compromised under flight conditions.

o-Fluorination of aromatic azides yields improved azido-based fluorescent probes for hydrogen sulfide: synthesis, spectra, and bioimaging.

PubMed

Wei, Chao; Wang, Runyu; Wei, Lv; Cheng, Longhuai; Li, Zhifei; Xi, Zhen; Yi, Long

2014-12-01

Hydrogen sulfide (H2S) is an endogenously produced gaseous signaling molecule with multiple biological functions. To visualize the endogenous in situ production of H2S in real time, new coumarin- and boron-dipyrromethene-based fluorescent turn-on probes were developed for fast sensing of H2S in aqueous buffer and in living cells. Introduction of a fluoro group in the ortho position of the aromatic azide can lead to a greater than twofold increase in the rate of reaction with H2S. On the basis of o-fluorinated aromatic azides, fluorescent probes with high sensitivity and selectivity toward H2S over other biologically relevant species were designed and synthesized. The probes can be used to in situ to visualize exogenous H2S and D-cysteine-dependent endogenously produced H2S in living cells, which makes them promising tools for potential applications in H2S biology. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Production of Bombyx mori silk fibroin incorporated with unnatural amino acids.

PubMed

Teramoto, Hidetoshi; Kojima, Katsura

2014-07-14

Silk fibroin incorporated with unnatural amino acids was produced by in vivo feeding of p-chloro-, p-bromo-, and p-azido-substituted analogues of L-phenylalanine (Phe) to transgenic silkworms (Bombyx mori) that expressed a mutant of phenylalanyl-tRNA synthetase with expanded substrate recognition capabilities in silk glands. Cutting down the content of Phe in the diet was effective for increasing the incorporation of Phe analogues but simultaneously caused a decrease of fibroin production. The azide groups incorporated in fibroin were active as chemical handles for click chemistry in both the solubilized and the solid (fibrous) states. The azides survived degumming in the boiling alkaline solution that is required for complete removal of the sericin layer, demonstrating that AzPhe-incorporated silk fibroin could be a versatile platform to produce "clickable" silk materials in various forms. This study indicates the huge potential of UAA mutagenesis as a novel methodology to alter the characteristics of B. mori silk.

Synthesis of antifungal vaccines by conjugation of β-1,2 trimannosides with T-cell peptides and covalent anchoring of neoglycopeptide to tetanus toxoid.

PubMed

Cartmell, Jonathan; Paszkiewicz, Eugenia; Dziadek, Sebastian; Tam, Pui-Hang; Luu, Thanh; Sarkar, Susmita; Lipinski, Tomasz; Bundle, David R

2015-02-11

Selective strategies for the construction of novel three component glycoconjugate vaccines presenting Candida albicans cell wall glycan (β-1,2 mannoside) and polypeptide fragments on a tetanus toxoid carrier are described. The first of two conjugation strategies employed peptides bearing an N-terminal thiopropionyl residue for conjugation to a trisaccharide equipped with an acrylate linker and a C-terminal S-acetyl thioglycolyl moiety for subsequent linking of neoglycopeptide to bromoacetylated tetanus toxoid. Michael addition of acrylate trisaccharides to peptide thiol under mildly basic conditions gave a mixture of N- and C- terminal glyco-peptide thioethers. An adaptation of this strategy coordinated S-acyl protection with anticipated thioester exchange equilibria. This furnished a single chemically defined fully synthetic neoglycopeptide conjugate that could be anchored to a tetanus toxoid carrier and avoids the introduction of exogenous antigenic groups. The second strategy retained the N-terminal thiopropionyl residue but replaced the C-terminal S-acetate functionality with an azido group that allowed efficient, selective formation of neoglycopeptide thioethers and subsequent conjugation of these with propargylated tetanus toxoid, but introduced potentially antigenic triazole linkages. Copyright © 2014 Elsevier Ltd. All rights reserved.

Synthesis, characterization and functionalization of silicon nanoparticle based hybrid nanomaterials for photovoltaic and biological applications

NASA Astrophysics Data System (ADS)

Xu, Zejing

Silicon nanoparticles are attractive candidates for biological, photovoltaic and energy storage applications due to their size dependent optoelectronic properties. These include tunable light emission, high brightness, and stability against photo-bleaching relative to organic dyes (see Chapter 1). The preparation and characterization of silicon nanoparticle based hybrid nanomaterials and their relevance to photovoltaic and biological applications are described. The surface-passivated silicon nanoparticles were produced in one step from the reactive high-energy ball milling (RHEBM) of silicon wafers with various organic ligands. The surface structure and optical properties of the passivated silicon nanoparticles were systematically characterized. Fast approaches for purifying and at the same time size separating the silicon nanoparticles using a gravity GPC column were developed. The hydrodynamic diameter and size distribution of these size-separated silicon nanoparticles were determined using GPC and Diffusion Ordered NMR Spectroscopy (DOSY) as fast, reliable alternative approaches to TEM. Water soluble silicon nanoparticles were synthesized by grafting PEG polymers onto functionalized silicon nanoparticles with distal alkyne or azide moieties. The surface-functionalized silicon nanoparticles were produced from the reactive high-energy ball milling (RHEBM) of silicon wafers with a mixture of either 5-chloro-1-pentyne in 1-pentyne or 1,7 octadiyne in 1-hexyne to afford air and water stable chloroalkyl or alkynyl terminated nanoparticles, respectively. Nanoparticles with the ω-chloroalkyl substituents were easily converted to ω-azidoalkyl groups through the reaction of the silicon nanoparticles with sodium azide in DMF. The azido terminated nanoparticles were then grafted with monoalkynyl-PEG polymers using a copper catalyzed alkyne-azide cycloaddition (CuAAC) reaction to afford core-shell silicon nanoparticles with a covalently attached PEG shell. Covalently linked silicon nanoparticle clusters were synthesized via the CuAAC "click" reaction of functional silicon nanoparticles with α,ω-functional PEG polymers of various lengths. Dynamic light scattering studies show that the flexible globular nanoparticle arrays undergo a solvent dependent change in volume (ethanol> dichloromethane> toluene) similar in behavior to hydrogel nanocomposites. A novel light-harvesting complex and artificial photosynthetic material based on silicon nanoparticles was designed and synthesized. Silicon nanoparticles were used as nanoscaffolds for organizing the porphyrins to form light-harvesting complexes thereby enhancing the light absorption of the system. The energy transfer from silicon nanoparticles to porphyrin acceptors was investigated by both steady-state and time-resolved fluorescence spectroscopy. The energy transfer efficiency depended on the donor-acceptor ratio and the distance between the nanoparticle and the porphyrin ring. The addition of C60 resulted in the formation of silicon nanoparticle-porphyrin-fullerene nanoclusters which led to charge separation upon irradiation of the porphyrin ring. The electron-transfer process between the porphyrin and fullerene was investigated by femto-second transient absorption spectroscopy. Finally, the water soluble silicon nanoparticles were used as nanocarriers in photodynamic therapeutic application, in which can selectively deliver porphyrins into human embryonic kidney 293T (HEK293T) cells. In particular, the PEGylated alkynyl-porphyrins were conjugated onto the azido-terminated silicon nanoparticles via a CuAAC "click" reaction. The resultant PEGylated porphyrin grafted silicon nanoparticles have diameters around 13.5 +/- 3.8 nm. The cryo-TEM and conventional TEM analysis proved that the PEGylated porphyrin grafted silicon nanoparticle could form the micelle-like structures at higher concentration in water via self-assembly. The UV-Vis absorption analysis demonstrated that the silicon nanoparticle could reduce the porphyrin aggregation in water which can reduce the photophysical activity of porphyrin. In addition, the nanoparticle complex was capable of producing singlet oxygen when the porphyrin units were excited by light. The cell studies demonstrated that the silicon nanoparticle could deliver the porphyrin drugs into HEK293T cells and accumulate in the mitochondria where the porphyrin could serve as an efficient photosensitizer to kill the cells via mitochondrial apoptotic pathway.

One-step ligand exchange reaction as an efficient way for functionalization of magnetic nanoparticles

NASA Astrophysics Data System (ADS)

Mrówczyński, Radosław; Rednic, Lidia; Turcu, Rodica; Liebscher, Jürgen

2012-07-01

Novel magnetic Fe3O4 nanoparticles (NPs) covered by one layer of functionalized fatty acids, bearing entities (Hayashi catalyst, biotin, quinine, proline, and galactose) of high interest for practical application in nanomedicine or organocatalysis, were synthesized. The functionalized fatty acids were obtained by Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) of azido fatty acids with alkynes. All the magnetic NPs show superparamagnetic behavior with high values of magnetization and high colloidal stability in DCM solution.

Tetrazolo(1,5-A)pyridines and Furazano(4,5-B)pyridine-1-oxides as Energetic Materials

DTIC Science & Technology

1989-04-01

alpyridine was isolated, contaminated with about 10% of 16. The azido compound was charac- terized by IR and NMR spectroscopy, and the structure (15...Applications of Nuclear Magnetic Resonance Spectroscopy to Organic Chemistry," Record of Chemical Progress, 23 ( 1962 ), p. 223. 16. A. J. Boulton and A. R...Katritzky. "A New Heterocyclic Rearrangement," Proc. Chem. Soc. ( 1962 ), p. 257. 1 7. A. P. Chafin and D. W. Moore. Unpublished results; F. A. L. Anet

Inhibition of the norepinephrine transporter by χ-conotoxin dendrimers.

PubMed

Wan, Jingjing; Brust, Andreas; Bhola, Rebecca F; Jha, Prerna; Mobli, Mehdi; Lewis, Richard J; Christie, Macdonald J; Alewood, Paul F

2016-05-01

Peptide dendrimers are a novel class of macromolecules of emerging interest with the potential of delayed renal clearance due to their molecular size and enhanced activity due to the multivalency effect. In this work, an active analogue of the disulfide-rich χ-conotoxin χ-MrIA (χ-MrIA), a norepinephrine reuptake (norepinephrine transporter) inhibitor, was grafted onto a polylysine dendron. Dendron decoration was achieved by employing copper-catalyzed alkyne-azide cycloaddition with azido-PEG chain-modified χ-MrIA analogues, leading to homogenous 4-mer and 8-mer χ-MrIA dendrimers with molecular weights ranging from 8 to 22 kDa. These dendrimers were investigated for their impact on peptide secondary structure, in vitro functional activity, and potential anti-allodynia in vivo. NMR studies showed that the χ-MrIA tertiary structure was maintained in the χ-MrIA dendrimers. In a functional norepinephrine transporter reuptake assay, χ-MrIA dendrimers showed slightly increased potency relative to the azido-PEGylated χ-MrIA analogues with similar potency to the parent peptide. In contrast to χ-MrIA, no anti-allodynic action was observed when the χ-MrIA dendrimers were administered intrathecally in a rat model of neuropathic pain, suggesting that the larger dendrimer structures are unable to diffuse through the spinal column tissue and reach the norepinephrine transporter. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.

Stepwise-activable multifunctional peptide-guided prodrug micelles for cancerous cells intracellular drug release

NASA Astrophysics Data System (ADS)

Zhang, Jing; Li, Mengfei; Yuan, Zhefan; Wu, Dan; Chen, Jia-da; Feng, Jie

2016-10-01

A novel type of stepwise-activable multifunctional peptide-guided prodrug micelles (MPPM) was fabricated for cancerous cells intracellular drug release. Deca-lysine sequence (K10), a type of cell-penetrating peptide, was synthesized and terminated with azido-glycine. Then a new kind of molecule, alkyne modified doxorubicin (DOX) connecting through disulfide bond (DOX-SS-alkyne), was synthesized. After coupling via Cu-catalyzed azide-alkyne cycloaddition (CuAAC) click chemistry reaction, reduction-sensitive peptide-guided prodrug was obtained. Due to the amphiphilic property of the prodrug, it can assemble to form micelles. To prevent the nanocarriers from unspecific cellular uptake, the prodrug micelles were subsequently modified with 2,3-dimethyl maleic anhydride to obtain MPPM with a negatively charged outer shell. In vitro studies showed that MPPM could be shielded from cells under psychological environment. However, when arriving at mild acidic tumor site, the cell-penetrating capacity of MPPM would be activated by charge reversal of the micelles via hydrolysis of acid-labile β-carboxylic amides and regeneration of K10, which enabled efficient internalization of MPPM by tumor cells as well as following glutathione- and protease-induced drug release inside the cancerous cells. Furthermore, since the guide peptide sequences can be accurately designed and synthesized, it can be easily changed for various functions, such as targeting peptide, apoptotic peptide, even aptamers, only need to be terminated with azido-glycine. This method can be used as a template for reduction-sensitive peptide-guided prodrug for cancer therapy.

Preparation of a poly(3'-azido-3'-deoxythymidine-co-propargyl methacrylate-co-pentaerythritol triacrylate) monolithic column by in situ polymerization and a click reaction for capillary liquid chromatography of small molecules and proteins.

PubMed

Lin, Zian; Yu, Ruifang; Hu, Wenli; Zheng, Jiangnan; Tong, Ping; Zhao, Hongzhi; Cai, Zongwei

2015-07-07

Combining free radical polymerization with click chemistry via a copper-mediated azide/alkyne cycloaddition (CuAAC) reaction in a "one-pot" process, a facile approach was developed for the preparation of a poly(3'-azido-3'-deoxythymidine-co-propargyl methacrylate-co-pentaerythritol triacrylate) (AZT-co-PMA-co-PETA) monolithic column. The resulting poly(AZT-co-PMA-co-PETA) monolith showed a relatively homogeneous monolithic structure, good permeability and mechanical stability. Different ratios of monomers and porogens were used for optimizing the properties of a monolithic column. A series of alkylbenzenes, amides, anilines, and benzoic acids were used to evaluate the chromatographic properties of the polymer monolith in terms of hydrophobic, hydrophilic and cation-exchange interactions, and the results showed that the poly(AZT-co-PMA-co-PETA) monolith exhibited more flexible adjustment in chromatographic selectivity than that of the parent poly(PMA-co-PETA) and AZT-modified poly(PMA-co-PETA) monoliths. Column efficiencies for toluene, DMF, and formamide with 35,000-48,000 theoretical plates per m could be obtained at a linear velocity of 0.17 mm s(-1). The run-to-run, column-to-column, and batch-to-batch repeatabilities of the retention factors were less than 4.2%. In addition, the proposed monolith was also applied to efficient separation of sulfonamides, nucleobases and nucleosides, anesthetics and proteins for demonstrating its potential.

Replication of human immunodeficiency virus in monocytes. Granulocyte/macrophage colony-stimulating factor (GM-CSF) potentiates viral production yet enhances the antiviral effect mediated by 3'-azido- 2'3'-dideoxythymidine (AZT) and other dideoxynucleoside congeners of thymidine

PubMed Central

1989-01-01

We have investigated the influence of granulocyte-macrophage CSF (GM- CSF) on the replication of HIV-1 in cells of monocyte/macrophage (M/M) lineage, and its effect on the anti-HIV activity of several 2'3'- dideoxynucleoside congeners of thymidine in these cells in vitro. We found that replication of both HTLV-IIIBa-L (a monocytotropic strain of HIV-1) and HTLV-IIIB (a lymphocytotropic strain) is markedly enhanced in M/M, but not in lymphocytes exposed to GM-CSF in culture. Moreover, GM-CSF reduced the dose of HIV required to obtain productive infection in M/M. Even in the face of this increased infection, GM-CSF also enhanced the net anti-HIV activity of 3'-azido-2'3'-dideoxythymidine (AZT) and several related congeners: 2'3'-dideoxythymidine (ddT), 2'3'- dideoxy-2'3'-didehydrothymidine (D4T), and 3'-azido-2'3'-dideoxyuridine (AZddU). Inhibition of viral replication in GM-CSF-exposed M/M was achieved with concentrations of AZT and related drugs, which were 10- 100 times lower than those inhibitory for HIV-1 in monocytes in the absence of GM-CSF. Other dideoxynucleosides not related to AZT showed unchanged or decreased anti-HIV activity in GM-CSF-exposed M/M. To investigate the possible biochemical basis for these effects, we evaluated the metabolism of several drugs in M/M exposed to GM-CSF. We observed in these cells markedly increased levels of both parent and mono-, di-, and triphosphate anabolites of AZT and D4T compared with M/M not exposed to GM-CSF. By contrast, only limited increases of endogenous competing 2'-deoxynucleoside-5'-triphosphate pools were observed after GM-CSF exposure. Thus, the ratio of AZT-5'- triphosphate/2'-deoxythymidine-5'-triphosphate and 2'3'-dideoxy-2'3'- didehydrothymidine-5'-triphosphate/2'-deoxythymi dine- 5'-triphosphate is several-fold higher in GM-CSF-exposed M/M, and this may account for the enhanced activity of such drugs in these cells. Taken together, these findings suggest that GM-CSF increases HIV-1 replication in M/M, while at the same time enhancing the anti-HIV activity of AZT and related congeners in these cells. These results may have implications in exploring new therapeutic strategies in patients with severe HIV infection. PMID:2538549

Lymphocyte receptors for pertussis toxin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, C.G.; Armstrong, G.D.

1990-12-01

We have investigated human T-lymphocyte receptors for pertussis toxin by affinity isolation and photoaffinity labeling procedures. T lymphocytes were obtained from peripheral human blood, surface iodinated, and solubilized in Triton X-100. The iodinated mixture was then passed through pertussis toxin-agarose, and the fractions were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Autoradiography of the fixed, dried gels revealed several bands in the pertussis toxin-bound fraction that were not observed in fractions obtained from histone or fetuin-agarose. Further investigations employed a photoaffinity labeling reagent, sulfosuccinimidyl 2-(p-azido-salicylamido)-1,3'-dithiopropionate, to identify pertussis toxin receptors in freshly isolated peripheral blood monocytic cells, T lymphocytes, andmore » Jurkat cells. In all three cell systems, the pertussis toxin affinity probe specifically labeled a single protein species with an apparent molecular weight of 70,000 that was not observed when the procedure was performed in the presence of excess unmodified pertussis toxin. A protein comparable in molecular weight to the one detected by the photoaffinity labeling technique was also observed among the species that bound to pertussis toxin-agarose. The results suggest that pertussis toxin may bind to a 70,000-Da receptor in human T lymphocytes.« less

In vivo metabolic labeling of sialoglycans in the mouse brain by using a liposome-assisted bioorthogonal reporter strategy

PubMed Central

Xie, Ran; Dong, Lu; Du, Yifei; Zhu, Yuntao; Hua, Rui; Zhang, Chen; Chen, Xing

2016-01-01

Mammalian brains are highly enriched with sialoglycans, which have been implicated in brain development and disease progression. However, in vivo labeling and visualization of sialoglycans in the mouse brain remain a challenge because of the blood−brain barrier. Here we introduce a liposome-assisted bioorthogonal reporter (LABOR) strategy for shuttling 9-azido sialic acid (9AzSia), a sialic acid reporter, into the brain to metabolically label sialoglycoconjugates, including sialylated glycoproteins and glycolipids. Subsequent bioorthogonal conjugation of the incorporated 9AzSia with fluorescent probes via click chemistry enabled fluorescence imaging of brain sialoglycans in living animals and in brain sections. Newly synthesized sialoglycans were found to widely distribute on neuronal cell surfaces, in particular at synaptic sites. Furthermore, large-scale proteomic profiling identified 140 brain sialylated glycoproteins, including a wealth of synapse-associated proteins. Finally, by performing a pulse−chase experiment, we showed that dynamic sialylation is spatially regulated, and that turnover of sialoglycans in the hippocampus is significantly slower than that in other brain regions. The LABOR strategy provides a means to directly visualize and monitor the sialoglycan biosynthesis in the mouse brain and will facilitate elucidating the functional role of brain sialylation. PMID:27125855

Dideoxynucleoside resistance emerges with prolonged zidovudine monotherapy. The RV43 Study Group.

PubMed Central

Mayers, D L; Japour, A J; Arduino, J M; Hammer, S M; Reichman, R; Wagner, K F; Chung, R; Lane, J; Crumpacker, C S; McLeod, G X

1994-01-01

Human immunodeficiency virus type 1 (HIV-1) isolates resistant to zidovudine (ZDV) have previously been demonstrated to exhibit in vitro cross-resistance to other similar dideoxynucleoside agents which contain a 3'-azido group. However, cross-resistance to didanosine (ddI) or dideoxycytidine (ddC) has been less well documented. ZDV, ddI, and ddC susceptibility data have been collected from clinical HIV-1 isolates obtained by five clinical centers and their respective retrovirology laboratories. All subjects were treated only with ZDV. Clinical HIV-1 isolates were isolated, amplified, and assayed for drug susceptibility in standardized cultures of phytohemagglutinin-stimulated donor peripheral blood mononuclear cells obtained from healthy seronegative donors. All five cohorts showed a correlation between decreased in vitro susceptibility to ZDV and decreased susceptibility to ddI and ddC. For each 10-fold decrease in ZDV susceptibility, an average corresponding decrease of 2.2-fold in ddI susceptibility was observed (129 isolates studied; P < 0.001, Fisher's test of combined significance). Similarly, susceptibility to ddC decreased 2.0-fold for each 10-fold decrease in ZDV susceptibility (82 isolates studied; P < 0.001, Fisher's test of combined significance). These data indicate that a correlation exists between HIV-1 susceptibilities to ZDV and ddI or ddC for clinical HIV-1 isolates. PMID:8192457

Influence of dialkyne structure on the properties of new click-gels based on hyaluronic acid.

PubMed

Testa, Gabriella; Di Meo, Chiara; Nardecchia, Stefania; Capitani, Donatella; Mannina, Luisa; Lamanna, Raffaele; Barbetta, Andrea; Dentini, Mariella

2009-08-13

Hydrogels have been widely used in tissue engineering as a support for tissue formation and/or to deliver drug locally. A novel procedure for the in situ rapid chemical gelation of aqueous solutions of hyaluronan (HA) was employed. HA was functionalised with an arm bearing a terminal azido group (HAAA). When HAAA was mixed with a series of dialkyne reagents of different length, a 1,3-dipolar cycloaddition ("click-chemistry") reaction took place in the presence of catalytic amount of Cu(I) resulting in fast gelation at room temperature. The resulting gels were characterised in terms of degree of cross-linking by (1)H HR-MAS NMR. The kinetic of gelation and the determination of elastic moduli as well as the degree of swelling and the controlled release of a model drug, were studied as a function of chemical nature of the dialkyne group, catalyst concentration, HAAA concentration and temperature. All these variables allowed the swelling ratio and the extent of release of a drug, doxorubicin, entrapped within the gel, to be modulated. In all cases the kinetic of release reached the stationary state within 150 h. The height of the plateau was dependent on the overall (chemical and topological) degree of cross-linking.

Inorganic–organic hybrid materials through post-synthesis modification: Impact of the treatment with azides on the mesopore structure

PubMed Central

Keppeler, Miriam; Holzbock, Jürgen; Akbarzadeh, Johanna; Peterlik, Herwig

2011-01-01

Summary Hybrid, hierarchically organized, monolithic silica gels, comprising periodically arranged mesopores and a cellular macroscopic network, have been prepared through a co-condensation reaction of tetrakis(2-hydroxyethyl)orthosilicate with chloromethyl-trimethoxysilane or 3-(chloropropyl)-triethoxysilane. Subsequent conversion of the chloro groups into azido groups, by nucleophilic substitution with NaN3 in N,N-dimethylformamide, was conducted upon preservation of the monolithic structure. However, treatment with NaN3 had a strong influence on the structure in the mesoporous regime, with changes such as an increase of mesopore diameter, pore volume and lattice constants, as well as a concomitant decrease of the pore wall thickness, as confirmed by small angle X-ray scattering, transmission electron microscopy, and nitrogen sorption analysis. Similar effects were observed for unmodified silica gels by simple ageing in azide-containing media, whether a relatively small or a sterically demanding counter ion (Na+ or (H3C)4N+) was used. The structural modification did not seem to depend greatly on whether an organic aprotic solvent (N,N-dimethylformamide, 1,1,3,3-tetramethylurea, 1,3-dimethyl-2-imidazolidinone) or a protic solvent that can form hydrogen bonds, such as water, was used. PMID:22003454

Sequential Multicomponent Strategy for the Diastereoselective Synthesis of Densely Functionalized Spirooxindole-Fused Thiazolidines.

PubMed

Rainoldi, Giulia; Begnini, Fabio; de Munnik, Mariska; Lo Presti, Leonardo; Vande Velde, Christophe M L; Orru, Romano; Lesma, Giordano; Ruijter, Eelco; Silvani, Alessandra

2018-02-12

We developed two Ugi-type three-component reactions of spirooxindole-fused 3-thiazolines, isocyanides, and either carboxylic acids or trimethylsilyl azide, to give highly functionalized spirooxindole-fused thiazolidines. Two diverse libraries were generated using practical and robust procedures affording the products in typically good yields. The obtained thiazolidines proved to be suitable substrates for further transformations. Notably, both the Ugi-Joullié and the azido-Ugi reactions resulted highly diastereoselective, affording predominantly the trans-configured products, as confirmed by X-ray crystallographic analysis.

Synthesis, structural characterization, photo-physical and magnetic properties of cobalt salphen pseudo halide complexes showing meta-magnetic ordering

NASA Astrophysics Data System (ADS)

Nassief, A. R.; Abdel-Hafiez, M.; Hassen, A.; Khalil, A. S. G.; Saber, M. R.

2018-04-01

The solvo-thermal syntheses of [(CoSalphen)2Co (SCN)2]n (1), CoSalphen(NH3)(N3)(2), Na[CoIIIsalphen(N3)2](3), Na[CoIIIsalen(N3)2](4) and CoIIIsalen(NH3)(N3) (5) {salphen = N,N'-o-phenylene-bis(salicylideneimine)} are reported. The structural studies using X-ray diffraction measurements revealed that 1 crystalizes in a monoclinic C2/c space group. Two cobalt (II) metal centers in penta-coordinated and octahedral local coordination environments are bridged via alternating O and μ1,3 SCN bridges resulting in a novel 2D layered coordination polymer. Compound 2 is a trivalent mononuclear cobalt azido complex with an octahedral coordination environment. The magnetic investigations of 1 revealed ferromagnetic coupling (J = +49.1 cm-1) and meta-magnetic ordering. Time resolved photoluminescence studies of the complexes showed excited state lifetimes of (τ1 = 0.4675 ns, τ2 = 5.23 ns) for 1 and (τ1 = 0.5078 ns, τ2 = 6.79 ns) for 2.

Circular DNA by "Bis-Click" Ligation: Template-Independent Intramolecular Circularization of Oligonucleotides with Terminal Alkynyl Groups Utilizing Bifunctional Azides.

PubMed

Yang, Haozhe; Seela, Frank

2016-01-22

A highly effective and convenient "bis-click" strategy was developed for the template-independent circularization of single-stranded oligonucleotides by employing copper(I)-assisted azide-alkyne cycloaddition. Terminal triple bonds were incorporated at both ends of linear oligonucleotides. Alkynylated 7-deaza-2'-deoxyadenosine and 2'-deoxyuridine residues with different side chains were used in solid-phase synthesis with phosphoramidite chemistry. The bis-click ligation of linear 9- to 36-mer oligonucleotides with 1,4-bis(azidomethyl)benzene afforded circular DNA in a simple and selective way; azido modification of the oligonucleotide was not necessary. Short ethynyl side chains were compatible with the circularization of longer oligonucleotides, whereas octadiynyl residues were used for short 9-mers. Compared with linear duplexes, circular bis-click constructs exhibit a significantly increased duplex stability over their linear counterparts. The intramolecular bis-click ligation protocol is not limited to DNA, but may also be suitable for the construction of other macrocycles, such as circular RNAs, peptides, or polysaccharides. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Real-time and label-free ring-resonator monitoring of solid-phase recombinase polymerase amplification.

PubMed

Sabaté Del Río, Jonathan; Steylaerts, Tim; Henry, Olivier Y F; Bienstman, Peter; Stakenborg, Tim; Van Roy, Wim; O'Sullivan, Ciara K

2015-11-15

In this work we present the use of a silicon-on-insulator (SOI) chip featuring an array of 64 optical ring resonators used as refractive index sensors for real-time and label-free DNA detection. Single ring functionalisation was achieved using a click reaction after precise nanolitre spotting of specific hexynyl-terminated DNA capture probes to link to an azido-silanised chip surface. To demonstrate detectability using the ring resonators and to optimise conditions for solid-phase amplification, hybridisation between short 25-mer single stranded DNA (ssDNA) fragments and a complementary capture probe immobilised on the surface of the ring resonators was carried out and detected through the shift in the resonant wavelength. Using the optimised conditions demonstrated via the solid-phase hybridisation, a 144-bp double stranded DNA (dsDNA) was then detected directly using recombinase and polymerase proteins through on-chip target amplification and solid-phase elongation of immobilised forward primers on specific rings, at a constant temperature of 37°C and in less than 60min, achieving a limit of detection of 7.8·10(-13)M (6·10(5) copies in 50µL). The use of an automatic liquid handler injection instrument connected to an integrated resealable chip interface (RCI) allowed programmable multiple injection protocols. Air plugs between different solutions were introduced to prevent intermixing and a proportional-integral-derivative (PID) temperature controller minimised temperature based drifts. Published by Elsevier B.V.

Rare azido-bridged manganese(II) systems: syntheses, crystal structures, and magnetic properties.

PubMed

Ghosh, A K; Ghoshal, D; Zangrando, E; Ribas, J; Ray Chaudhuri, N

2005-03-21

Two new polymeric azido-bridged manganese complexes of formulas [Mn(N3)2 (bpee)]n (1) and {[Mn(N3)(dpyo)Cl(H2O)2](H2O)}n (2) [bpee, trans-1,2-bis(4-pyridyl)ethylene; dpyo, 4,4'-dipyridyl N,N'-dioxide] have been synthesized and characterized by single-crystal X-ray diffraction analysis and low-temperature magnetic study. Both the complexes 1 and 2 crystallize in the triclinic system, space group P1, with a = 8.877(3) A, b = 11.036(3) A, c = 11.584(4) A, alpha = 72.62(2) degrees, beta = 71.06(2) degrees, gamma = 87.98(3) degrees, and Z = 1 and a = 7.060(3) A, b = 10.345(3) A, c = 11.697(4) A, alpha = 106.86(2) degrees, beta = 113.33(2) degrees, gamma = 96.39(3) degrees, and Z = 2, respectively. Complex 1 exhibits a 2D structure of [-Mn(N3)2-]n chains, connected by bpee ligands, whose pyridine rings undergo pi-pi and C-H...pi interactions. This facilitates the rare arrangement of doubly bridged azide ligands with one end-on and two end-to-end (EO-EE-EE) sequence. Complex 2 is a neutral 1D polymer built up by [Mn(N3)(dpyo)Cl(H2O)2] units and lattice water molecules. The metals are connected by single EE azide ligands, which are arranged in a cis position to the Mn(II) center. The 1D zipped chains are linked by H-bonds involving lattice water molecules and show pi-pi stacking of dpyo pyridine rings to form a supramolecular 2D layered structure. The magnetic studies were performed in 2-300 K temperature range, and the data were fitted by considering an alternating chain of exchange interactions with S = 5/2 (considered as classical spin) with the spin Hamiltonians H = -Ji sigma(S(3i)S(3i+1) + S(3i+1)S(3i+2)) - J2 sigmaS(3i-1)S(3i) and H = -Ji sigmaS(2i)S(2i+1) - J2 sigmaS(2i+1)S(2i+2) for complexes 1 and 2, respectively. Complex 2 exhibits small antiferromagnetic coupling between the metal centers, whereas 1 exhibits a new case of topological ferromagnetism, which is very unusual.

Translation system engineering in Escherichia coli enhances non-canonical amino acid incorporation into proteins.

PubMed

Gan, Rui; Perez, Jessica G; Carlson, Erik D; Ntai, Ioanna; Isaacs, Farren J; Kelleher, Neil L; Jewett, Michael C

2017-05-01

The ability to site-specifically incorporate non-canonical amino acids (ncAAs) into proteins has made possible the study of protein structure and function in fundamentally new ways, as well as the bio synthesis of unnatural polymers. However, the task of site-specifically incorporating multiple ncAAs into proteins with high purity and yield continues to present a challenge. At the heart of this challenge lies the lower efficiency of engineered orthogonal translation system components compared to their natural counterparts (e.g., translation elements that specifically use a ncAA and do not interact with the cell's natural translation apparatus). Here, we show that evolving and tuning expression levels of multiple components of an engineered translation system together as a whole enhances ncAA incorporation efficiency. Specifically, we increase protein yield when incorporating multiple p-azido-phenylalanine(pAzF) residues into proteins by (i) evolving the Methanocaldococcus jannaschii p-azido-phenylalanyl-tRNA synthetase anti-codon binding domain, (ii) evolving the elongation factor Tu amino acid-binding pocket, and (iii) tuning the expression of evolved translation machinery components in a single vector. Use of the evolved translation machinery in a genomically recoded organism lacking release factor one enabled enhanced multi-site ncAA incorporation into proteins. We anticipate that our approach to orthogonal translation system development will accelerate and expand our ability to site-specifically incorporate multiple ncAAs into proteins and biopolymers, advancing new horizons for synthetic and chemical biotechnology. Biotechnol. Bioeng. 2017;114: 1074-1086. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Experimental Investigation on the Mechanism of Chelation-Assisted, Copper(II) Acetate-Accelerated Azide-Alkyne Cycloaddition

PubMed Central

Kuang, Gui-Chao; Guha, Pampa M.; Brotherton, Wendy S.; Simmons, J. Tyler; Stankee, Lisa A.; Nguyen, Brian T.; Clark, Ronald J.; Zhu, Lei

2011-01-01

A mechanistic model is formulated to account for the high reactivity of chelating azides (organic azides capable of chelation-assisted metal coordination at the alkylated azido nitrogen position) and copper(II) acetate (Cu(OAc)2) in copper(II)-mediated azide-alkyne cycloaddition (AAC) reactions. Fluorescence and 1H NMR assays are developed for monitoring the reaction progress in two different solvents – methanol and acetonitrile. Solvent kinetic isotopic effect and pre-mixing experiments give credence to the proposed different induction reactions for converting copper(II) to catalytic copper(I) species in methanol (methanol oxidation) and acetonitrile (alkyne oxidative homocoupling), respectively. The kinetic orders of individual components in a chelation-assisted, copper(II)-accelerated AAC reaction are determined in both methanol and acetonitrile. Key conclusions resulting from the kinetic studies include (1) the interaction between copper ion (either in +1 or +2 oxidation state) and a chelating azide occurs in a fast, pre-equilibrium step prior to the formation of the in-cycle copper(I)-acetylide, (2) alkyne deprotonation is involved in several kinetically significant steps, and (3) consistent with prior experimental and computational results by other groups, two copper centers are involved in the catalysis. The X-ray crystal structures of chelating azides with Cu(OAc)2 suggest a mechanistic synergy between alkyne oxidative homocoupling and copper(II)-accelerated AAC reactions, in which both a bimetallic catalytic pathway and a base are involved. The different roles of the two copper centers (a Lewis acid to enhance the electrophilicity of the azido group and a two-electron reducing agent in oxidative metallacycle formation, respectively) in the proposed catalytic cycle suggest that a mixed valency (+2 and +1) dinuclear copper species be a highly efficient catalyst. This proposition is supported by the higher activity of the partially reduced Cu(OAc)2 in mediating a 2-picolylazide-involved AAC reaction than the fully reduced Cu(OAc)2. Finally, the discontinuous kinetic behavior that has been observed by us and others in copper(I/II)-mediated AAC reactions is explained by the likely catalyst disintegration during the course of a relatively slow reaction. Complementing the prior mechanistic conclusions drawn by other investigators which primarily focus on the copper(I)/alkyne interactions, we emphasize the kinetic significance of copper(I/II)/azide interaction. This work not only provides a mechanism accounting for the fast Cu(OAc)2-mediated AAC reactions involving chelating azides, which has apparent practical implications, but suggests the significance of mixed-valency dinuclear copper species in catalytic reactions where two copper centers carry different functions. PMID:21809811

Rapid, Efficient and Versatile Strategies for Functionally Sophisticated Polymers and Nanoparticles: Degradable Polyphosphoesters and Anisotropic Distribution of Chemical Functionalities

NASA Astrophysics Data System (ADS)

Zhang, Shiyi

The overall emphasis of this dissertation research included two kinds of asymmetrically-functionalized nanoparticles with anisotropic distributions of chemical functionalities, three degradable polymers synthesized by organocatalyzed ring-opening polymerizations, and two polyphosphoester-based nanoparticle systems for various biomedical applications. Inspired by the many hierarchical assembly processes that afford complex materials in Nature, the construction of asymmetrically-functionalized nanoparticles with efficient surface chemistries and the directional organization of those building blocks into complex structures have attracted much attention. The first method generated a Janus-faced polymer nanoparticle that presented two orthogonally click-reactive surface chemistries, thiol and azido. This robust method involved reactive functional group transfer by templating against gold nanoparticle substrates. The second method produced nanoparticles with sandwich-like distribution of crown ether functionalities through a stepwise self-assembly process that utilized crown ether-ammonium supramolecular interactions to mediate inter-particle association and the local intra-particle phase separation of unlike hydrophobic polymers. With the goal to improve the efficiency of the production of degradable polymers with tunable chemical and physical properties, a new type of reactive polyphosphoester was synthesized bearing alkynyl groups by an organocatalyzed ring-opening polymerization, the chemical availability of the alkyne groups was investigated by employing "click" type azide-alkyne Huisgen cycloaddition and thiol-yne radical-mediated reactions. Based on this alkyne-functionalized polyphosphoester polymer and its two available "click" type reactions, two degradable nanoparticle systems were developed. To develop the first system, the well defined poly(ethylene oxide)-block-polyphosphester diblock copolymer was transformed into a multifunctional Paclitaxel drug conjugate by densely attaching the polyphosphoester block with azide-functionalized Paclitaxel by azide-alkyne Huisgen cycloaddition. This Paclitaxel drug conjugate provides a powerful platform for combinational cancer therapy and bioimaging due to its ultra-high Paclitaxel loading (> 65 wt%), high water solubility (>6.2 mg/mL for PTX) and easy functionalization. Another polyphosphoester-based nanoparticle system has been developed by a programmable process for the rapid and facile preparation of a family of nanoparticles with different surface charges and functionalities. The non-ionic, anionic, cationic and zwitterionic nanoparticles with hydrodynamic diameters between 13 nm to 21 nm and great size uniformity could be rapidly prepared from small molecules in 6 h or 2 days. The anionic and zwitterionic nanoparticles were designed to load silver ions to treat pulmonary infections, while the cationic nanoparticles are being applied to regulate lung injuries by serving as a degradable iNOS inhibitor conjugates. In addition, a direct synthesis of acid-labile polyphosphoramidate by organobase-catalyzed ring-opening polymerization and an improved two-step preparation of polyphosphoester ionomer by acid-assisted cleavage of phosphoramidate bonds on polyphosphoramidate were developed. Polyphosphoramidate and polyphosphoester ionomers may be applied to many applications, due to their unique chemical and physical properties.

Toxicology and Carcinogenesis Studies of Mixtures of 3'-Azido-3'-Deoxythymidine (AZT), Lamivudine (3TC), and Nevirapine (NVP) (CAS Nos. 30516-87-1, 134678-17-4, 129618-40-2) in Genetically Modified C3B6.129F1-Trp53(tm1Brd) N12 Haploinsufficient Mice (in utero and postnatal gavage studies).

PubMed

2013-10-01

3'-Azido-3'-deoxythymidine (AZT) is the most widely used and evaluated chemotherapeutic agent for the treatment of persons with acquired immune deficiency syndrome (AIDS). Antiviral therapy is essential for treatment and prevention of AIDS in adults and children infected with human immunodeficiency virus (HIV), and to prevent mother-to-child transmission of HIV during pregnancy and labor. The studies described in this report were designed to determine possible long-term sequelae from AZT treatment, often used in combination with other antiviral drugs, such as lamivudine (3TC) and nevirapine (NVP) in preventing mother-to-child transmission of HIV. Male and female heterozygous F1 p53+/- mice were exposed to AZT, 3TC, NVP, or combinations of the chemicals in utero on gestation days (GD) 12 through 18, then administered the same chemical or combination of chemicals by gavage from postnatal day (PND) 1 through PND 28 and then observed until 45 weeks of age. Vehicle control mice received only an aqueous solution containing 0.2% methylcellulose and 0.1% Tween 80. Mice were dosed twice daily until PND 28. Genetic toxicology studies were conducted in mouse peripheral blood erythrocytes. The study compared three combination doses of AZT, 3TC and NVP (AZT/3TC/NVP-L, AZT/3TC/NVP-M, and AZT/3TC/NVP-H) with the vehicle controls, and compared the individual components with each other at the highest dose (AZT-H, 3TC-H, NVP-H, AZT/3TC-H and AZT/3TC/NVP-H). Because exposure to AZT/3TC/NVP-M and AZT/3TC/NVP-H reduced pup survival, additional litters were required to provide sufficient pups to load the 45-week study. 45-WEEK STUDY: In general, survival was relatively high once the pup exposure phase had been completed, with at least 75% of the mice surviving to terminal sacrifice in all groups. For males, survival was significantly greater in the AZT/3TC/NVP-L and AZT/3TC/NVP-M groups relative to the vehicle control group. There were no significant differences in survival between high dose groups of the constituent chemicals in either sex; however, survival of females in the AZT/3TC-H group was significantly less than that in the vehicle control group. Early deaths were predominantly associated with occurrences of malignant lymphoma, mammary gland tumors, and osteosarcomas. In the combination dose comparison, males and females dosed with the AZT/3TC/NVP-H combination had significantly decreased body weights compared to the vehicle control groups from PND 11 when individual monitoring began until 20 (males) or 11 (females) weeks. In addition, mean body weights for the male and female AZT/3TC/NVP-M groups were significantly less than those of the vehicle control groups until 14 weeks. In the high dose comparison, mean body weights of the male and female AZT-H groups were significantly less than those of the vehicle control groups during some of the early weeks of dosing. In male and female mice, absolute brain weights of the combination dose groups decreased with increasing dose and, except in low dose males, the absolute brain weights of the dosed groups were significantly less than those of the vehicle control groups. When the high doses of the constituent chemicals were compared, absolute brain weights of the male and female AZT-H and AZT/3TC/NVP-H groups were significantly less than those of the vehicle control groups. However, relative brain weights were not significantly altered. Relative liver weights of male combination dose groups followed a positive trend with dose. When the high dose groups were compared, increases in relative liver weights of male mice appeared to be associated with AZT exposure. In combination dose groups, the absolute heart weight of AZT/3TC/NVP-H females was significantly greater than that of the vehicle control group, and there was a positive trend in absolute heart weights. There was also a positive trend for relative heart weights in these combination dose groups, though no individual group relative weight was significantly greater than that of the vehicle control group. In females, absolute heart weight was also significantly increased in the AZT/3TC-H group relative to the vehicle control group. A small but statistically significant increase in serum alanine aminotransferase activity was observed in the male AZT/3TC/NVP-H group compared to the vehicle control group. In the combination dose comparison, the incidences of hepatocellular adenoma and hepatocellular adenoma or carcinoma (combined) in the liver of all groups of males dosed with AZT/3TC/NVP were significantly increased compared to the vehicle control group. In the high dose comparison, the incidences of hepatocellular adenoma in males in the AZT-H group and hepatocellular adenoma and hepatocellular adenoma or carcinoma (combined) in males in the AZT/3TC-H and AZT/3TC/NVP-H groups were significantly greater than those in the vehicle control group; the incidences of these lesions in the 3TC-H and NVP-H groups were significantly less than those in the AZT/3TC/NVP-H group. The incidences of malignant lymphoma in males administered AZT-H or AZT/3TC-H and in females administered AZT/3TC/NVP-M, AZT/3TC/NVP-H, NVP-H, or AZT/3TC-H were slightly greater than those in the vehicle control groups. The incidence of mammary gland adenoacanthoma or adenocarcinoma (combined) in females administered 3TC-H was slightly greater than that in the vehicle control group. In the peripheral blood of 1-day-old male and female mice, the percentage of total reticulocytes (RETs) was significantly decreased in groups exposed to doses that contained AZT. In addition, the percentages of micronucleated normochromatic erythrocytes (NCEs) and micronucleated RETs were generally significantly increased in groups exposed to doses containing AZT, but not in the 3TC-H or NVP-H groups. The percentages of micronucleated NCEs in the AZT/3TC/NVP-H groups were greater than in the AZT-H and the AZT/3TC-H groups. In peripheral blood of male pups evaluated at PND 28, both the percentage of micronucleated RETs and the percentage of micronucleated NCEs were significantly increased in the group where 3TC was coadministered with AZT compared to the group administered only AZT. Under the conditions of this gavage study, there was clear evidence of carcinogenic activity of AZT alone in male heterozygous F1 p53+/- mice based on increased incidences of hepatocellular adenoma. There was clear evidence of carcinogenic activity of AZT in combination with 3TC, and AZT in combination with 3TC and NVP in male heterozygous F1 p53+/- mice based on increased incidences of hepatocellular adenoma and hepatocellular adenoma or carcinoma (combined). The occurrence of malignant lymphoma may have been related to treatment with AZT alone and with AZT in combination with 3TC. There was no evidence of carcinogenic activity of 3TC alone in male heterozygous F1 p53+/- mice administered 150 mg/kg. There was no evidence of carcinogenic activity of NVP alone in male heterozygous F1 p53+/- mice administered 168 mg/kg. There was equivocal evidence of carcinogenic activity of NVP alone, AZT in combination with 3TC, and AZT in combination with 3TC and NVP in female heterozygous F1 p53+/- mice based on the occurrence of malignant lymphoma. There was equivocal evidence of carcinogenic activity of 3TC alone in female heterozygous F1 p53+/- mice based on the occurrence of mammary gland adenoacanthoma or adenocarcinoma (combined). There was no evidence of carcinogenic activity of AZT alone in female heterozygous F1 p53+/- mice administered 240 mg/kg. Synonyms: (3'-AZIDO-3'-DEOXYTHYMIDINE) 3'-azido-2',3'-dideoxythymidine; azidodeoxythymidine; azidothymidine; 3'-azidothymidine; AZT; BW A509U; Compound S; 3'-deoxy-3'-azidothymidine; 3'-deoxy-(8CI) (9CI); ZDV; zidovudine. Trade name: Retrovir® [Combivir® with 3TC] Synonyms: (2',3'-DIDEOXY-3'-THIACYTIDINE) 3TC; 4-amino-1-[(2R,5S)-2-(hydroxymethyl)-1,3-oxathiolan-5-yl]-1,2-dihydropyrimidin-2-one; L-2',3'-dideoxy-3'-thiacytidine; lamivudine Trade name: Epivir® [Combivir® with AZT] Synonyms: (NEVIRAPINE) NVP; 11-cyclopropyl-4-methyl-5,11-dihydro-6H- dipyrido[3,2-b:2',3'-e][1,4]diazepin-6-one Trade name: Viramune®

Incorporation of a Doubly Functionalized Synthetic Amino Acid into Proteins for Creating Chemical and Light-Induced Conjugates.

PubMed

Yamaguchi, Atsushi; Matsuda, Takayoshi; Ohtake, Kazumasa; Yanagisawa, Tatsuo; Yokoyama, Shigeyuki; Fujiwara, Yoshihisa; Watanabe, Takayoshi; Hohsaka, Takahiro; Sakamoto, Kensaku

2016-01-20

Z-Lysine (ZLys) is a lysine derivative with a benzyloxycarbonyl group linked to the ε-nitrogen. It has been genetically encoded with the UAG stop codon, using the pair of an engineered variant of pyrrolysyl-tRNA synthetase (PylRS) and tRNA(Pyl). In the present study, we designed a novel Z-lysine derivative (AmAzZLys), which is doubly functionalized with amino and azido substituents at the meta positions of the benzyl moiety, and demonstrated its applicability for creating protein conjugates. AmAzZLys was incorporated into proteins in Escherichia coli, by using the ZLys-specific PylRS variant. AmAzZLys was then site-specifically incorporated into a camelid single-domain antibody specific to the epidermal growth factor receptor (EGFR). A one-pot reaction demonstrated that the phenyl amine and azide were efficiently linked to the 5 kDa polyethylene glycol and a fluorescent probe, respectively, through specific bio-orthogonal chemistry. The antibody was then tested for the ability to form a photo-cross-link between its phenylazide moiety and the antigen, while the amino group on the same ring was used for chemical labeling. When incorporated at a selected position in the antibody and exposed to 365 nm light, AmAzZLys formed a covalent bond with the EGFR ectodomain, with the phenylamine moiety labeled fluorescently prior to the reaction. The present results illuminated the versatility of the ZLys scaffold, which can accommodate multiple reactive groups useful for protein conjugation.

Azido and tetrazolo 1,2,4,5-tetrazine N-oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chavez, David E.; Parrish, Damon A.; Mitchell, Lauren

2017-02-23

This paper presents the synthesis and characterization of the oxidation products of 3,6-diazido-1,2,4,5-tetrazine (1) and 6-amino-[1,5-b]tetrazolo-1,2,4,5-tetrazine (2). 3,6-Diazido-1,2,4,5-tetrazine-1,4-dioxide was produced from oxidation with peroxytrifluoroacetic acid, and more effectively using hypofluorous acid, and 2 can be oxidized to two different products, 6-amino-[1,5-b]tetrazolo-1,2,4,5-tetrazine mono-N-oxide and di-N-oxide. These N-oxide compounds display promising performance properties as energetic materials.

Triazine herbicide resistance in the photosynthetic bacterium Rhodopseudomonas sphaeroides

PubMed Central

Brown, Alfred E.; Gilbert, Carl W.; Guy, Rachel; Arntzen, Charles J.

1984-01-01

The photoaffinity herbicide azidoatrazine (2-azido-4-ethylamino-6-isopropylamino-s-triazine) selectively labels the L subunit of the reaction center of the photosynthetic bacterium Rhodopseudomonas sphaeroides. Herbicide-resistant mutants retain the L subunit and have altered binding properties for methylthio- and chloro-substituted triazines as well as altered equilibrium constants for electron transfer between primary and secondary electron acceptors. We suggest that a subtle alteration in the L subunit is responsible for herbicide resistance and that the L subunit is the functional analog of the 32-kDa QB protein of chloroplast membranes. Images PMID:16593520

Selective posttranslational modification of phage-displayed polypeptides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsao, Meng-Lin; Tian, Feng; Schultz, Peter

The invention relates to posttranslational modification of phage-displayed polypeptides. These displayed polypeptides comprise at least one unnatural amino acid, e.g., an aryl-azide amino acid such as p-azido-L-phenylalanine, or an alkynyl-amino acid such as para-propargyloxyphenylalanine, which are incorporated into the phage-displayed fusion polypeptide at a selected position by using an in vivo orthogonal translation system comprising a suitable orthogonal aminoacyl-tRNA synthetase and a suitable orthogonal tRNA species. These unnatural amino acids advantageously provide targets for posttranslational modifications such as azide-alkyne [3+2] cycloaddition reactions and Staudinger modifications.

Selective posttranslational modification of phage-displayed polypeptides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsao, Meng-Lin; Tian, Feng; Schultz, Peter

The invention relates to posttranslational modification of phage-displayed polypeptides. These displayed polypeptides comprise at least one unnatural amino acid, e.g., an aryl-azide amino acid such as p-azido-L-phenylalanine, or an alkynyl-amino acid such as para-propargyloxyphenylalanine, which are incorporated into the phage-displayed fusion polypeptide at a selected position by using an in vivo orthogonal translation system comprising a suitable orthogonal aminoacyl-tRNA synthetase and a suitable orthogonal tRNA species. These unnatural amino acids advantageously provide targets for posttranslational modifications such as azide-alkyne [3+2]cycloaddition reactions and Staudinger modifications.

Synthesis and Immunological Properties of N-Modified GM3 Antigens as Therapeutic Cancer Vaccines

PubMed Central

Pan, Yanbin; Chefalo, Peter; Nagy, Nancy; Harding, Clifford; Guo, Zhongwu

2011-01-01

The problem of immunotolerance to GM3, an important tumor-associated trisaccharide antigen, seriously hinders its usage in cancer vaccine development. To solve this problem, the keyhole limpet hemocyanin (KLH) conjugates of a series of GM3 derivatives were synthesized and screened as therapeutic cancer vaccines. First, the β-linked anomeric azides of differently N-acylated GM3 analogs were prepared by a highly convergent procedure. Next, a pentenoyl group was linked to the reducing end of the carbohydrate antigens following selective reduction of the azido group. The linker was thereafter ozonolyzed to give an aldehyde functionality permitting the conjugation of the antigens to KLH via reductive amination. Finally, the immunological properties of the resultant glycoconjugates were studied in C57BL/6 mice by assessing the titers of specific antibodies induced by the GM3 analogs. While KLH-GM3 elicited low levels of immune response, the KLH conjugates of N-propionyl, N-butanoyl, N-iso-butanoyl and N-phenylacetyl GM3’s induced robust immune reactions with antibodies of multiple isotypes, indicating significantly improved and T-cell dependent immune responses that lead to isotype switching, affinity maturation and the induction of immunological ‘memory’. It was suggested that GM3PhAc-KLH is a promising vaccine candidate for glycoengineered immunotherapy of cancer with GM3 as the primary target. PMID:15689172

Interaction of Clostridium perfringens delta toxin with erythrocyte and liposome membranes and relation with the specific binding to the ganglioside GM2.

PubMed

Jolivet-Reynaud, C; Hauttecoeur, B; Alouf, J E

1989-01-01

The specific interaction of the cytolytic Clostridium perfringens delta toxin with membrane GM2 was indicated by: (i) characterization of this glycolipid in the membrane of sheep and goat erythrocytes, which are lysed by the toxin, whereas GM2 was undetectable in insensitive rabbit erythrocytes, (ii) demonstration of 125I-toxin binding to GM2, by autoradiography, following incubation with thin-layer chromatograms containing separated neuroblastoma gangliosides, and (iii) toxin fixation by phospholipid-cholesterol unilamellar vesicles containing either sheep gangliosides or GM2. In order to investigate the intramembrane events leading to membrane disruption following toxin binding, the photoreactive probe 12(4-azido-2-nitrophenoxy)stearoyl 1-14C glucosamine, which inserts into the outer layer and labels integral membrane proteins, was used to establish whether delta toxin penetrates into target cell membrane. No toxin labeling was found, suggesting that toxin action takes place at the membrane surface. This contention is supported by the observation that despite toxin binding, GM2 liposomes did not release entrapped 14C-glucose. Treatment of toxin with carboxypeptidases, but not aminopeptidases, abolished both toxin binding capacity onto erythrocytes and its combination with antitoxin neutralizing antibodies, suggesting that the carboxy terminal end of the toxin is critical for binding to cell membrane.

Par-4 dependent modulation of cellular β-catenin by medicinal plant natural product derivative 3-azido Withaferin A.

PubMed

Amin, Hina; Nayak, Debasis; Ur Rasool, Reyaz; Chakraborty, Souneek; Kumar, Anmol; Yousuf, Khalid; Sharma, Parduman Raj; Ahmed, Zabeer; Sharma, Neelam; Magotra, Asmita; Mukherjee, Debaraj; Kumar, Lekha Dinesh; Goswami, Anindya

2016-05-01

Here, we provide evidences that natural product derivative 3-azido Withaferin A (3-AWA) abrogated EMT and invasion by modulating β-catenin localization and its transcriptional activity in the prostate as well as in breast cancer cells. This study, for the first time, reveals 3-AWA treatment consistently sequestered nuclear β-catenin and augmented its cytoplasmic pool as evidenced by reducing β-catenin transcriptional activity in these cells. Moreover, 3-AWA treatment triggered robust induction of pro-apoptotic intracellular Par-4, attenuated Akt activity and rescued Phospho-GSK3β (by Akt) to promote β-catenin destabilization. Further, our in vitro studies demonstrate that 3-AWA treatment amplified E-cadherin expression along with sharp downregulation of c-Myc and cyclin D1 proteins. Strikingly, endogenous Par-4 knock down by siRNA underscored 3-AWA mediated inhibition of nuclear β-catenin was Par-4 dependent and suppression of Par-4 activity, either by Bcl-2 or by Ras transfection, restored the nuclear β-catenin level suggesting Par-4 mediated β-catenin regulation was not promiscuous. In vivo results further demonstrated that 3-AWA was effective inhibitor of tumor growth and immunohistochemical studies indicated that increased expression of total β-catenin and decreased expression of phospho-β-catenin and Par-4 in breast cancer tissues as compared to normal breast tissue suggesting Par-4 and β-catenin proteins are mutually regulated and inversely co-related in normal as well as cancer condition. Thus, strategic regulation of intracellular Par-4 by 3-AWA in diverse cancers could be an effective tool to control cancer cell metastasis. Conclusively, this report puts forward a novel approach of controlling deregulated β-catenin signaling by 3-AWA induced Par-4 protein. © 2015 Wiley Periodicals, Inc.

{μ-2-[(3-Amino-2,2-dimethyl-prop-yl)imino-meth-yl]-6-meth-oxy-phenolato-1:2κ(5)O(1),O(6):N,N',O(1)}{2-[(3-amino-2,2-dimethyl-prop-yl)imino-meth-yl]-6-meth-oxy-phenolato-1κ(3)N,N',O(1)}-μ-azido-1:2κ(2)N:N-azido-2κN-methanol-2κO-dinickel(II).

PubMed

Ghaemi, Akbar; Rayati, Saeed; Fayyazi, Kazem; Ng, Seik Weng; Tiekink, Edward R T

2012-08-01

Two distinct coordination geometries are found in the binuclear title complex, [Ni(2)(C(13)H(19)N(2)O(2))(2)(N(3))(2)(CH(3)OH)], as one Schiff base ligand is penta-dentate, coordinating via the anti-cipated oxide O, imine N and amine N atoms (as for the second, tridentate, ligand) but the oxide O is bridging and coordination also occurs through the meth-oxy O atom. The Ni(II) atoms are linked by a μ(2)-oxide atom and one end of a μ(2)-azide ligand, forming an Ni(2)ON core. The coordination geometry for the Ni(II) atom coordinated by the tridentate ligand is completed by the meth-oxy O atom derived from the penta-dentate ligand, with the resulting N(3)O(3) donor set defining a fac octa-hedron. The second Ni(II) atom has its cis-octa-hedral N(4)O(2) coordination geometry completed by the imine N and amine N atoms of the penta-dentate Schiff base ligand, a terminally coordinated azide N and a methanol O atom. The arrangement is stabilized by an intra-molecular hydrogen bond between the methanol H and the oxide O atom. Linear supra-molecular chains along the a axis are formed in the crystal packing whereby two amine H atoms from different amine atoms hydrogen bond to the terminal N atom of the monodentate azide ligand.

The antiretrovirus drug 3'-azido-3'-deoxythymidine increases the retrovirus mutation rate.

PubMed Central

Julias, J G; Kim, T; Arnold, G; Pathak, V K

1997-01-01

It was previously observed that the nucleoside analog 5-azacytidine increased the spleen necrosis virus (SNV) mutation rate 13-fold in one cycle of retrovirus replication (V. K. Pathak and H. M. Temin, J. Virol. 66:3093-3100, 1992). Based on this observation, we hypothesized that nucleoside analogs used as antiviral drugs may also increase retrovirus mutation rates. We sought to determine if 3'-azido-3'-deoxythymidine (AZT), the primary treatment for human immunodeficiency virus type 1 (HIV-1) infection, increases the retrovirus mutation rate. Two assays were used to determine the effects of AZT on retrovirus mutation rates. The strategy of the first assay involved measuring the in vivo rate of inactivation of the lacZ gene in one replication cycle of SNV- and murine leukemia virus-based retroviral vectors. We observed 7- and 10-fold increases in the SNV mutant frequency following treatment of target cells with 0.1 and 0.5 microM AZT, respectively. The murine leukemia virus mutant frequency increased two- and threefold following treatment of target cells with 0.5 and 1.0 microM AZT, respectively. The second assay used an SNV-based shuttle vector containing the lacZ alpha gene. Proviruses were recovered as plasmids in Escherichia coli, and the rate of inactivation of lacZ alpha was measured. The results indicated that treatment of target cells increased the overall mutation rate two- to threefold. DNA sequence analysis of mutant proviruses indicated that AZT increased both the deletion and substitution rates. These results suggest that AZT treatment of HIV-1 infection may increase the degree of viral variation and alter virus evolution or pathogenesis. PMID:9151812

The mononuclear nickel(II) complex bis(azido-κN)bis[2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole-κ2 N2 ,N3 ]nickel(II) protects tomato from Verticillium dahliae by inhibiting fungal growth and activating plant defences.

PubMed

Zine, Hanane; Rifai, Lalla Aicha; Koussa, Tayeb; Bentiss, Fouad; Guesmi, Salaheddine; Laachir, Abdelhakim; Makroum, Kacem; Belfaiza, Malika; Faize, Mohamed

2017-01-01

The antifungal properties of the nickel(II) complex bis(azido-κN)bis[2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole-κ 2 N 2 ,N 3 ]nickel(II) [NiL 2 (N 3 ) 2 ] and its parental ligand 2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole were examined to evaluate their ability to protect tomato plants against Verticillium dahliae. Our main objectives were to determine their effects on the in vitro growth of the pathogen, and their aptitude for controlling verticillium wilt and activating plant defence responses in the greenhouse. NiL 2 (N 3 ) 2 exhibited in vitro an elevated inhibition of radial growth of three strains of the pathogen. According to the strain, the EC 50 values ranged from 10 to 29 µg mL -1 for NiL 2 (N 3 ) 2 . In the greenhouse, it induced an elevated protection against V. dahliae when it was applied twice as foliar sprays at 50 µg mL -1 . It reduced the leaf alteration index by 85% and vessel browning by 96%. In addition, its protective ability was associated with the accumulation of H 2 O 2 and the activation of total phenolic content, as well as potentiation of the activity of peroxidase and polyphenol oxidase. These results demonstrated that the coordination of the ligand with Ni associated with the azide as a coligand resulted in an improvement in its biological activity by both inhibiting the growth of V. dahliae and activating plant defence responses. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

An Investigation of Siloxane Cross-linked Hydroxyapatite-Gelatin/Copolymer Composites for Potential Orthopedic Applications†

PubMed Central

Dyke, Jason Christopher; Knight, Kelly Jane; Zhou, Huaxing; Chiu, Chi-Kai; Ko, Ching-Chang; You, Wei

2012-01-01

Causes of bone deficiency are numerous, but biomimetic alloplastic grafts provide an alternative to repair tissue naturally. Previously, a hydroxyapatite-gelatin modified siloxane (HAp-Gemosil) composite was prepared by cross-linking (N, N′-bis[(3-trimethoxysilyl)propyl]ethylene diamine (enTMOS) around the HAp-Gel nanocomposite particles, to mimic the natural composition and properties of bone. However, the tensile strength remained too low for many orthopedic applications. It was hypothesized that incorporating a polymer chain into the composite could help improve long range interaction. Furthermore, designing this polymer to interact with the enTMOS siloxane cross-linked matrix would provide improved adhesion between the polymer and the ceramic composite, and improve mechanical properties. To this end, copolymers of L-Lactide (LLA), and a novel alkyne derivatized trimethylene carbonate, propargyl carbonate (PC), were synthesized. Incorporation of PC during copolymerization affects properties of copolymers such as molecular weight, Tg, and % PC incorporation. More importantly, PC monomers bear a synthetic handle, allowing copolymers to undergo post-polymerization functionalization with graft monomers to specifically tailor the properties of the final composite. For our investigation, P(LLA-co-PC) copolymers were functionalized by an azido-silane (AS) via copper catalyzed azide-alkyne cycloaddition (CuAAC) through terminal alkyne on PC monomers. The new functionalized polymer, P(LLA-co-PC)(AS) was blended with HAp-Gemosil, with the azido-silane linking the copolymer to the silsesquioxane matrix within the final composite. These HAp-Gemosil/P(LLA-co-PC)(AS) composites were subjected to mechanical and biological testing, and the results were compared with those from the HAp-Gemosil composites. This study revealed that incorporating a cross-linkable polymer served to increase the flexural strength of the composite by 50%, while maintaining the biocompatibility of HAp-Gemosil ceramics. PMID:23139457

pH-Responsive Dimeric Zinc(II) Phthalocyanine in Mesoporous Silica Nanoparticles as an Activatable Nanophotosensitizing System for Photodynamic Therapy.

PubMed

Wong, Roy C H; Chow, Sun Y S; Zhao, Shirui; Fong, Wing-Ping; Ng, Dennis K P; Lo, Pui-Chi

2017-07-19

An acid-cleavable acetal-linked zinc(II) phthalocyanine dimer with an azido terminal group (cPc) was prepared and conjugated to alkyne-modified mesoporous silica nanoparticles via copper(I)-catalyzed alkyne-azide cycloaddition reaction. For comparison, an amine-linked analogue (nPc) was also prepared as a non-acid-cleavable counterpart. These dimeric phthalocyanines were significantly self-quenched due to the close proximity of the phthalocyanine units inside the mesopores, resulting in much weaker fluorescence emission and singlet oxygen generation, both in N,N-dimethylformamide and in phosphate-buffered saline (PBS), compared with the free molecular counterparts. Under acidic conditions in PBS, the cPc-encapsulated nanosystem was activated in terms of fluorescence emission and singlet oxygen production. After internalization into human colon adenocarcinoma HT29 cells, it exhibited much higher intracellular fluorescence and photocytotoxicity compared to the nanosystem entrapped with nPc. The activation of this nanosystem was also demonstrated in tumor-bearing nude mice. The intratumoral fluorescence intensity increased gradually over 24 h, while for the nPc counterpart the fluorescence remained very weak. The results suggest that this nanosystem serves as a promising activatable nanophotosensitizing agent for photodynamic therapy.

Evaluation of Microemulsion and Lamellar Liquid Crystalline Systems for Transdermal Zidovudine Delivery.

PubMed

Carvalho, André Luis Menezes; Silva, José Alexsandro da; Lira, Ana Amélia Moreira; Conceição, Tamara Matos Freire; Nunes, Rogéria de Souza; de Albuquerque Junior, Ricardo Luiz Cavalcanti; Sarmento, Victor Hugo Vitorino; Leal, Leila Bastos; de Santana, Davi Pereira

2016-07-01

This study proposed to investigate and to compare colloidal carrier systems containing Zidovudine (3'-azido-3'-deoxythymidine) (AZT) for transdermal administration and optimization of antiretroviral therapy. Microemulsion (ME) and lamellar phase (LP) liquid crystal were obtained and selected from pseudoternary diagrams previously developed. Small-angle X-ray scattering and rheology analysis confirmed the presence of typical ME and liquid crystalline structures with lamellar arrangement, respectively. Both colloidal carrier systems, ME, and LP remained stable, homogeneous, and isotropic after AZT addition. In vitro permeation study (using pig ear skin) showed that the amount of permeated drug was higher for ME compared to the control and LP, obtaining a permeation enhancing effect on the order of approximately 2-fold (p < 0.05). Microscopic examination after in vivo skin irritation studies using mice suggested few histological changes in the skin of animals treated with the ME compared to the control group (hydrogel). Thus, ME proved to be adequate and have promising effects, being able to promote the drug permeation without causing apparent skin irritation. On the order hand, LP functioned as a drug reservoir reducing AZT partitioning into the skin. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Intestinal absorption of dideoxynucleosides: characterization using a multiloop in situ technique.

PubMed

Mirchandani, H L; Chien, Y W

1995-01-01

The intestinal absorption of dideoxynucleosides was studied in rabbits, using a closed-loop mesenteric-sampling in situ technique developed in this laboratory, and the kinetic profiles were characterized. Each of the dideoxynucleosides exhibited different dependence on the intestinal regions studied: 3'-azido-2',3'-dideoxythymidine was best absorbed from the ileum, while 2',3'-dideoxyinosine and 2',3'-dideoxycytidine were preferentially absorbed from the jejunum. The results were validated by the mass-balance approach; the percent of drug retained in the intestinal lumen and that degraded at the intestinal pH, by colonic flora, in the intestinal tissue, and in plasma were assessed.

Non-nucleoside building blocks for copper-assisted and copper-free click chemistry for the efficient synthesis of RNA conjugates.

PubMed

Jayaprakash, K N; Peng, Chang Geng; Butler, David; Varghese, Jos P; Maier, Martin A; Rajeev, Kallanthottathil G; Manoharan, Muthiah

2010-12-03

Novel non-nucleoside alkyne monomers compatible with oligonucleotide synthesis were designed, synthesized, and efficiently incorporated into RNA and RNA analogues during solid-phase synthesis. These modifications allowed site-specific conjugation of ligands to the RNA oligonucleotides through copper-assisted (CuAAC) and copper-free strain-promoted azide-alkyne cycloaddition (SPAAC) reactions. The SPAAC click reactions of cyclooctyne-oligonucleotides with various classes of azido-functionalized ligands in solution phase and on solid phase were efficient and quantitative and occurred under mild reaction conditions. The SPAAC reaction provides a method for the synthesis of oligonucleotide-ligand conjugates uncontaminated with copper ions.

An azido-oxazolidinone antibiotic for live bacterial cell imaging and generation of antibiotic variants.

PubMed

Phetsang, Wanida; Blaskovich, Mark A T; Butler, Mark S; Huang, Johnny X; Zuegg, Johannes; Mamidyala, Sreeman K; Ramu, Soumya; Kavanagh, Angela M; Cooper, Matthew A

2014-08-15

An azide-functionalised analogue of the oxazolidinone antibiotic linezolid was synthesised and shown to retain antimicrobial activity. Using facile 'click' chemistry, this versatile intermediate can be further functionalised to explore antimicrobial structure-activity relationships or conjugated to fluorophores to generate fluorescent probes. Such probes can report bacteria and their location in a sample in real time. Modelling of the structures bound to the cognate 50S ribosome target demonstrates binding to the same site as linezolid is possible. The fluorescent probes were successfully used to image Gram-positive bacteria using confocal microscopy. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Mapping of contact sites in complex formation between transducin and light-activated rhodopsin by covalent crosslinking: Use of a photoactivatable reagent

PubMed Central

Cai, Kewen; Itoh, Yoshiki; Khorana, H. Gobind

2001-01-01

Interaction of light-activated rhodopsin with transducin (T) is the first event in visual signal transduction. We use covalent crosslinking approaches to map the contact sites in interaction between the two proteins. Here we use a photoactivatable reagent, N-[(2-pyridyldithio)-ethyl], 4-azido salicylamide. The reagent is attached to the SH group of cytoplasmic monocysteine rhodopsin mutants by a disulfide-exchange reaction with the pyridylthio group, and the derivatized rhodopsin then is complexed with T by illumination at λ >495 nm. Subsequent irradiation of the complex at λ310 nm generates covalent crosslinks between the two proteins. Crosslinking was demonstrated between T and a number of single cysteine rhodopsin mutants. However, sites of crosslinks were investigated in detail only between T and the rhodopsin mutant S240C (cytoplasmic loop V-VI). Crosslinking occurred predominantly with Tα. For identification of the sites of crosslinks in Tα, the strategy used involved: (i) derivatization of all of the free cysteines in the crosslinked proteins with N-ethylmaleimide; (ii) reduction of the disulfide bond linking the two proteins and isolation of all of the Tα species carrying the crosslinked moiety with a free SH group; (iii) adduct formation of the latter with the N-maleimide moiety of the reagent, maleimido-butyryl-biocytin, containing a biotinyl group; (iv) trypsin degradation of the resulting Tα derivatives and isolation of Tα peptides carrying maleimido-butyryl-biocytin by avidin-agarose chromatography; and (v) identification of the isolated peptides by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. We found that crosslinking occurred mainly to two C-terminal peptides in Tα containing the amino acid sequences 310–313 and 342–345. PMID:11320237

Synthesis and first use of pyridine-2,6-diylbis(pyrazine-2-ylmethanone) in metal cluster chemistry: a {Mn(III)3Na2} complex with an ideal trigonal bipyramidal geometry.

PubMed

Giannopoulos, Dimosthenis P; Wilson-Konderka, Cody; Gagnon, Kevin J; Teat, Simon J; Escuer, Albert; Metallinos, Costa; Stamatatos, Theocharis C

2015-03-07

The successful organic synthesis of a new dipyrazole/pyridine-dicarbonyl organic molecule, namely pyridine-2,6-diylbis(pyrazine-2-ylmethanone) [(pz)CO(py)CO(pz)], followed by its employment in Mn coordination chemistry has yielded the neutral cluster compound [Mn3Na2O(N3)3(L)3] (1), where L(2-) is the (pz)C(CH2COCH3)(O(-))(py)C(CH2COCH3)(O(-))(pz) dianion. The latter group was formed in situ, presumably by the nucleophilic attack of the carbanion (-)CH2COCH3 to the carbonyl carbon atoms of (pz)CO(py)CO(pz), in the presence of Mn(n+) ions under basic conditions and in solvent Me2CO. Complex 1 possesses an almost ideal trigonal bipyramidal topology, with the two Na(I) ions occupying the apical positions and the three Mn(III) ions residing in the equatorial trigonal plane. The bridging ligation about the metal ions is provided by a μ3-O(2-) ion and six μ-OR(-) groups from the L(2-) ligand, while peripheral ligation is completed by three terminal azido groups and the pyridine N and carbonyl O atoms of L(2-). Magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions between the paramagnetic Mn(III) centres; the use of an anisotropic, equilateral Mn(III)3 triangle model allowed us to fit the magnetic data and obtain the best-fit parameters: J = -10.8 cm(-1), D = -5.3 cm(-1), and g = 1.99. The combined results demonstrate the rich chemical reactivity of carbonyl groups and the ability of poly-ketone ligands to stabilize cluster compounds with unprecedented structural motifs and interesting architectures.

Noscapinoids with anti-cancer activity against human acute lymphoblastic leukemia cells (CEM): a three dimensional chemical space pharmacophore modeling and electronic feature analysis.

PubMed

Naik, Pradeep K; Santoshi, Seneha; Joshi, Harish C

2012-01-01

We have identified a new class of microtubule-binding compounds-noscapinoids-that alter microtubule dynamics at stoichiometric concentrations without affecting tubulin polymer mass. Noscapinoids show great promise as chemotherapeutic agents for the treatment of human cancers. To investigate the structural determinants of noscapinoids responsible for anti-cancer activity, we tested 36 structurally diverse noscapinoids in human acute lymphoblastic leukemia cells (CEM). The IC(50) values of these noscapinoids vary from 1.2 to 56.0 μM. Pharmacophore models of anti-cancer activity were generated that identify two hydrogen bond acceptors, two aromatic rings, two hydrophobic groups, and one positively charged group as essential structural features. Additionally, an atom-based quantitative structure-activity relationship (QSAR) model was developed that gave a statistically satisfying result (R(2) = 0.912, Q(2) = 0.908, Pearson R = 0.951) and effectively predicts the anti-cancer activity of training and test set compounds. The pharmacophore model presented here is well supported by electronic property analysis using density functional theory at B3LYP/3-21*G level. Molecular electrostatic potential, particularly localization of negative potential near oxygen atoms of the dimethoxy isobenzofuranone ring of active compounds, matched the hydrogen bond acceptor feature of the generated pharmacophore. Our results further reveal that all active compounds have smaller lowest unoccupied molecular orbital (LUMO) energies concentrated over the dimethoxy isobenzofuranone ring, azido group, and nitro group, which is indicative of the electron acceptor capacity of the compounds. Results obtained from this study will be useful in the efficient design and development of more active noscapinoids.

Facile Synthesis and Proposed Mechanism of α,ω-Oxetanyl-Telechelic Poly(3-nitratomethyl-3-methyl oxetane) by an SN2(i) Nitrato Displacement Method in Basic Media

NASA Astrophysics Data System (ADS)

Desai, Hemant J.; Acheampong, Daniel O.; Hudson, Robert; Lacey, Richard; Stanley, Claire; Turner, Helen; Whitmore, Hannah; Torry, Simon; Golding, Peter; Erothu, Harikrishna; Topham, Paul

2017-01-01

The synthesis of a novel heterocyclic-telechelic polymer, α,ω-oxetanyl-telechelic poly(3-nitratomethyl-3-methyl oxetane), is described. Infrared spectroscopy (IR), gel permeation chromatography (GPC), and nuclear magnetic resonance (NMR) spectroscopy have been used to confirm the successful synthesis, demonstrating the presence of the telechelic-oxetanyl moieties. Synthesis of the terminal functionalities has been achieved via displacement of nitrato groups, in a manner similar to that employed with other leaving groups such as azido, bromo, and nitro, initiated by nucleophiles. In the present case, displacement occurs on the ends of a nitrato-functionalized polymer driven by the formation of sodium nitrate, which is supported by the polar aprotic solvent N,N-dimethyl formamide. The formation of an alkoxide at the polymer chain ends is favored and allows internal back-biting to the nearest carbon bearing the nitrato group, intrinsically in an SN2(i) reaction, leading to α,ω-oxetanyl functionalization. The telechelic-oxetanyl moieties have the potential to be cross-linked by chemical (e.g., acidic) or radiative (e.g., ultraviolet) curing methods without the use of high temperatures, usually below 100°C. This type of material was designed for future use as a contraband simulant, whereby it would form the predominant constituent of elastomeric composites comprising rubbery polymer with small quantities of solids, typically crystals of contraband substances, such as explosives or narcotics. This method also provides an alternative approach to ring closure and synthesis of heterocycles.

2D-IR Spectroscopy of an AHA Labeled Photoswitchable PDZ2 Domain.

PubMed

Stucki-Buchli, Brigitte; Johnson, Philip J M; Bozovic, Olga; Zanobini, Claudio; Koziol, Klemens L; Hamm, Peter; Gulzar, Adnan; Wolf, Steffen; Buchenberg, Sebastian; Stock, Gerhard

2017-12-14

We explore the capability of the non-natural amino acid azidohomoalanine (AHA) as an IR label to sense relatively small structural changes in proteins with the help of 2D IR difference spectroscopy. To that end, we AHA-labeled an allosteric protein (the PDZ2 domain from human tyrosine-phosphatase 1E) and furthermore covalently linked it to an azobenzene-derived photoswitch as to mimic its conformational transition upon ligand binding. To determine the strengths and limitations of the AHA label, in total six mutants have been investigated with the label at sites with varying properties. Only one mutant revealed a measurable 2D IR difference signal. In contrast to the commonly observed frequency shifts that report on the degree of solvation, in this case we observe an intensity change. To understand this spectral response, we performed classical MD simulations, evaluating local contacts of the AHA labels to water molecules and protein side chains and calculating the vibrational frequency on the basis of an electrostatic model. Although these simulations revealed in part significant and complex changes of the number of intraprotein and water contacts upon trans-cis photoisomerization, they could not provide a clear explanation of why this one label would stick out. Subsequent quantum-chemistry calculations suggest that the response is the result of an electronic interaction involving charge transfer of the azido group with sulfonate groups from the photoswitch. To the best of our knowledge, such an effect has not been described before.

Click Synthesis of Hydrophilic Maltose-Functionalized Iron Oxide Magnetic Nanoparticles Based on Dopamine Anchors for Highly Selective Enrichment of Glycopeptides.

PubMed

Bi, Changfen; Zhao, Yingran; Shen, Lijin; Zhang, Kai; He, Xiwen; Chen, Langxing; Zhang, Yukui

2015-11-11

The development of methods to isolate and enrich low-abundance glycopeptides from biological samples is crucial to glycoproteomics. Herein, we present an easy and one-step surface modification strategy to prepare hydrophilic maltose functionalized Fe3O4 nanoparticles (NPs). First, based on the chelation of the catechol ligand with iron atoms, azido-terminated dopamine (DA) derivative was assembled on the surface of magnetic Fe3O4 nanoparticles by sonication. Second, the hydrophilic maltose-functionalized Fe3O4 (Fe3O4-DA-Maltose) NPs were obtained via copper(I)-catalyzed azide-alkyne cycloaddition (click chemistry). The morphology, structure, and composition of Fe3O4-DA-Maltose NPs were investigated by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), X-ray photoelectron spectrometer (XPS), and vibrating sample magnetometer (VSM). Meanwhile, hydrophilicity of the obtained NPs was evaluated by water contact angle measurement. The hydrophilic Fe3O4-DA-Maltose NPs were applied in isolation and enrichment of glycopeptides from horseradish peroxidase (HRP), immunoglobulin (IgG) digests. The MALDI-TOF mass spectrometric analysis indicated that the novel NPs exhibited high detection sensitivity in enrichment from HRP digests at concentration as low as 0.05 ng μL(-1), a large binding capacity up to 43 mg g(-1), and good recovery for glycopeptides enrichment (85-110%). Moreover, the Fe3O4-DA-Maltose NPs were applied to enrich glycopeptides from human renal mesangial cells (HRMC) for identification of N-glycosylation sites. Finally, we identified 115 different N-linked glycopeptides, representing 93 gene products and 124 glycosylation sites in HRMC.

Site-specific antibody-liposome conjugation through copper-free click chemistry: a molecular biology approach for targeted photodynamic therapy (Conference Presentation)

NASA Astrophysics Data System (ADS)

Obaid, Girgis; Wang, Yucheng; Kuriakose, Jerrin; Broekgaarden, Mans; Alkhateeb, Ahmed; Bulin, Anne-Laure; Hui, James; Tsourkas, Andrew; Hasan, Tayyaba

2016-03-01

Nanocarriers, such as liposomes, have the ability to potentiate photodynamic therapy (PDT) treatment regimens by the encapsulation of high payloads of photosensitizers and enhance their passive delivery to tumors through the enhanced permeability and retention effect. By conjugating targeting moieties to the surface of the liposomal nanoconstructs, cellular selectivity is imparted on them and PDT-based therapies can be performed with significantly higher dose tolerances, as off-target toxicity is simultaneously reduced.1 However, the maximal benefits of conventional targeted nanocarriers, including liposomes, are hindered by practical limitations including chemical instability, non-selective conjugation chemistry, poor control over ligand orientation, and loss of ligand functionality following conjugation, amongst others.2 We have developed a robust, physically and chemically stable liposomal nanoplatform containing benzoporphyrin derivative photosensitizer molecules within the phospholipid bilayer and an optimized surface density of strained cyclooctyne moieties for `click' conjugation to azido-functionalized antibodies.3 The clinical chimeric anti-EGFR antibody Cetuximab is site-specifically photocrosslinked to a recombinant bioengineered that recognizes the antibody's Fc region, containing a terminal azide.4 The copper-free click conjugation of the bioengineered Cetuximab derivative to the optimized photosensitizing liposome provides exceptional control over the antibody's optimal orientation for cellular antigen binding. Importantly, the reaction occurs rapidly under physiological conditions, bioorthogonally (selectively in the presence of other biomolecules) and without the need for toxic copper catalysis.3 Such state-of-the-art conjugation strategies push the boundaries of targeted photodynamic therapy beyond the limitations of traditional chemical coupling techniques to produce more robust and effective targeted therapeutics with applications beyond conventional treatments.

General method for labeling siRNA by click chemistry with fluorine-18 for the purpose of PET imaging.

PubMed

Mercier, Frédéric; Paris, Jérôme; Kaisin, Geoffroy; Thonon, David; Flagothier, Jessica; Teller, Nathalie; Lemaire, Christian; Luxen, André

2011-01-19

The alkyne-azide Cu(I)-catalyzed Huisgen cycloaddition, a click-type reaction, was used to label a double-stranded oligonucleotide (siRNA) with fluorine-18. An alkyne solid support CPG for the preparation of monostranded oligonucleotides functionalized with alkyne has been developed. Two complementary azide labeling agents (1-(azidomethyl)-4-[(18)F]fluorobenzene) and 1-azido-4-(3-[(18)F]fluoropropoxy)benzene have been produced with 41% and 35% radiochemical yields (decay-corrected), respectively. After annealing with the complementary strand, the siRNA was directly labeled by click chemistry with [(18)F]fluoroazide to produce the [(18)F]-radiolabeled siRNA with excellent radiochemical yield and purity.

catena-Poly[[bis­[4-(dimethyl­amino)­pyridine-κN 1]cobalt(II)]-di-μ-azido-κ4 N 1:N 3

PubMed Central

Guenifa, Fatiha; Zeghouan, Ouahida; Hadjadj, Nasreddine; Bendjeddou, Lamia; Merazig, Hocine

2013-01-01

The title layered polymer, [Co(N3)2(C7H10N2)2]n, contains CoII, azide and 4-(dimethyl­amino)­pyridine (4-DMAP) species with site symmetries m2m, 2 and m, respectively. The Co2+ ion adopts an octa­hedral coordination geometry in which four N atoms from azide ligands lie in the equatorial plane and two 4-DMAP N atoms occupy the axial positions. The CoII atoms are connected by two bridging azide ligands, resulting in a chain parallel to the c axis. PMID:23476514

Novel fluorescent labelled affinity probes for diadenosine-5',5'''-P1,P4-tetraphosphate (Ap4A)-binding studies.

PubMed

Wright, Michael; Miller, Andrew D

2006-02-15

Tandem synthetic-biosynthetic procedures were used to prepare two novel fluorescent labelled affinity probes for diadenosine-5',5'''-P1,P4-tetraphosphate (Ap4A)-binding studies. These compounds (dial-mant-Ap4A and azido-mant-Ap4A) are shown to clearly distinguish known Ap4A-binding proteins from Escherichia coli (LysU and GroEL) and a variety of other control proteins. Successful labelling of chaperonin GroEL appears to be allosteric with respect to the well-characterized adenosine 5'-triphosphate (ATP)-binding site, suggesting that GroEL possesses a distinct Ap4A-binding site.

Identification of Crosslinked Peptides after Click-based Enrichment Using Sequential CID and ETD Tandem Mass Spectrometry

PubMed Central

Chowdhury, Saiful M.; Du, Xiuxia; Tolić, Nikola; Wu, Si; Moore, Ronald J.; Mayer, M. Uljana; Smith, Richard D.; Adkins, Joshua N.

2010-01-01

Chemical crosslinking combined with mass spectrometry can be a powerful approach for the identification of protein-protein interactions and for providing constraints on protein structures. However, enrichment of crosslinked peptides is crucial to reduce sample complexity before mass spectrometric analysis. In addition compact crosslinkers are often preferred to provide short spacer lengths, surface accessibility to the protein complexes, and must have reasonable solubility under condition where the native complex structure is stable. In this study, we present a novel compact crosslinker that contains two distinct features: 1) an alkyne tag and 2) a small molecule detection tag (NO2-) to maintain reasonable solubility in water. The alkyne tag enables enrichment of the crosslinked peptide after proteolytic cleavage after coupling of an affinity tag using alkyne-azido click chemistry. Neutral loss of the small NO2- moiety provides a secondary means of detecting crosslinked peptides in MS/MS analyses, providing additional confidence in peptide identifications. We show the labeling efficiency of this crosslinker, which we termed CLIP (Click-enabled Linker for Interacting Proteins) using ubiquitin. The enrichment capability of CLIP is demonstrated for crosslinked ubiquitin in highly complex E. coli cell lysates. Sequential CID-MS/MS and ETD-MS/MS of inter-crosslinked peptides (two peptides connected with a crosslinker) are also demonstrated for improved automated identification of crosslinked peptides. PMID:19496583

Synthesis and anti-HIV activity of novel N-1 side chain-modified analogs of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (HEPT).

PubMed

Pontikis, R; Benhida, R; Aubertin, A M; Grierson, D S; Monneret, C

1997-06-06

A series of 33 N-1 side chain-modified analogs of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (1, HEPT) were synthesized and evaluated for their anti-HIV-1 activity. In particular, the influence of substitution of the terminal hydroxy group of the acyclic structure of HEPT and the structural rigidity of this side chain were investigated. Halo (7, 8), azido (9), and amino (10-15) derivatives were synthesized from HEPT via the p-tosylate derivative 6. Acylation of the primary amine 15 afforded the amido analogs 16-20. The diaryl derivatives 26-29 were prepared by reaction of HEPT, or of the 6-(2-pyridylthio) analog 23, with diaryl disulfides in the presence of tri-n-butylphosphine. Compounds 39-41, in which the N-1 side chain is rigidified by incorporation of an E-configured double bond, were obtained by palladium(0)-catalyzed coupling of several different 6-(arylthio)uracil derivatives (37, 38) with allyl acetates 33. Compounds 13, 40a,c,d,f, and 41, incorporating an aromatic ring at the end of the acyclic side chain, were found to be more potent than the known diphenyl-substituted HEPT analog BPT (2), two of them, 40c,d, being 10-fold more active.

Forskolin photoaffinity labels with specificity for adenylyl cyclase and the glucose transporter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morris, D.I.; Robbins, J.D.; Ruoho, A.E.

1991-07-15

Two photolabels, N-(3-(4-azido-3-125I-phenyl)-propionamide)-6- aminoethylcarbamylforskolin(125I-6-AIPP-Fsk) and N-(3-(4-azido-3-125I-phenyl)propionamide)-7-aminoethylcarbamyl-7- desacetylforskolin (125I-7-AIPP-Fsk) were synthesized with specific activities of 2200 Ci/mmol and used to label adenylyl cyclase and the glucose transporter. The affinities of the photolabels for adenylyl cyclase were determined by their inhibition of (3H)forskolin binding to bovine brain membranes. 6-AIPP-Fsk and 7-AIPP-Fsk inhibited (3H)forskolin binding with IC50 values of 15 nM and 200 nM, respectively. 125I-6-AIPP-Fsk labeled a 115-kDa protein in control and GTP {gamma} S-preactivated bovine brain membranes. This labeling was inhibited by forskolin but not by 1,9-dideoxyforskolin or cytochalasin B. 125I-6-AIPP-Fsk labeling of partially purified adenylyl cyclase was inhibited by forskolinmore » but not by 1,9-dideoxyforskolin. 125I-7-AIPP-Fsk specifically labeled a 45-kDa protein and not a 115-kDa protein in control and GTP {gamma} S-preactivated brain membranes. This labeling was inhibited by forskolin, 1,9-dideoxyforskolin, cytochalasin B, and D-glucose but not cytochalasin E or L-glucose. Human erythrocyte membranes were photolyzed with 125I-6-AIPP-Fsk and 125I-7-AIPP-Fsk. 125I-7-AIPP-Fsk, but not 125I-6-AIPP-Fsk, strongly labeled a broad 45-70-kDa band. Forskolin, 7-bromoacetyl-7-desacetylforskolin, 1,9-dideoxyforskolin, cytochalasin B, and D-glucose, but not cytochalasin E or L-glucose, inhibited 125I-7-AIPP-Fsk labeling of the 45-70-kDa band. 125I-6-AIPP-Fsk and 125I-7-AIPP-Fsk are high affinity photolabels with specificity for adenylyl cyclase and the glucose transporter, respectively.« less

PAWR-mediated suppression of BCL2 promotes switching of 3-azido withaferin A (3-AWA)-induced autophagy to apoptosis in prostate cancer cells.

PubMed

Rah, Bilal; ur Rasool, Reyaz; Nayak, Debasis; Yousuf, Syed Khalid; Mukherjee, Debaraj; Kumar, Lekha Dinesh; Goswami, Anindya

2015-01-01

An active medicinal component of plant origin with an ability to overcome autophagy by inducing apoptosis should be considered a therapeutically active lead pharmacophore to control malignancies. In this report, we studied the effect of concentration-dependent 3-AWA (3-azido withaferin A) sensitization to androgen-independent prostate cancer (CaP) cells which resulted in a distinct switching of 2 interrelated conserved biological processes, i.e. autophagy and apoptosis. We have observed 3 distinct parameters which are hallmarks of autophagy in our studies. First, a subtoxic concentration of 3-AWA resulted in an autophagic phenotype with an elevation of autophagy markers in prostate cancer cells. This led to a massive accumulation of MAP1LC3B and EGFP-LC3B puncta coupled with gradual degradation of SQSTM1. Second, higher toxic concentrations of 3-AWA stimulated ER stress in CaP cells to turn on apoptosis within 12 h by elevating the expression of the proapoptotic protein PAWR, which in turn suppressed the autophagy-related proteins BCL2 and BECN1. This inhibition of BECN1 in CaP cells, leading to the disruption of the BCL2-BECN1 interaction by overexpressed PAWR has not been reported so far. Third, we provide evidence that pawr-KO MEFs exhibited abundant autophagy signs even at toxic concentrations of 3-AWA underscoring the relevance of PAWR in switching of autophagy to apoptosis. Last but not least, overexpression of EGFP-LC3B and DS-Red-BECN1 revealed a delayed apoptosis turnover at a higher concentration of 3-AWA in CaP cells. In summary, this study provides evidence that 3-AWA is a strong anticancer candidate to abrogate protective autophagy. It also enhanced chemosensitivity by sensitizing prostate cancer cells to apoptosis through induction of PAWR endorsing its therapeutic potential.

Synthesis of the biologically active natural product cyclodepsipeptides apratoxin A and its analogues.

PubMed

Doi, Takayuki

2014-01-01

This paper describes the synthetic studies conducted on a marine natural product, cyclodepsipeptide apratoxin A. Total synthesis of the oxazoline analogue of apratoxin A was achieved. The conversion of oxazoline to thioamide, as well as thioamide formation from a serine-derived compound, were both unsuccessful. However, thiazoline formation from a cysteine-derived compound led to the total synthesis of apratoxin A. An in vivo study on synthetic apratoxin A revealed that it has potent antitumor activity, but with significant toxicity. Solid-phase synthesis of apratoxin A was accomplished using a preformed thiazoline derivative as a coupling unit. This method was used to synthesize several azido-containing analogues as precursors of molecular probes, and these analogues exhibited potent biological activity.

Linear ketenimines. Variable structures of C,C-dicyanoketenimines and C,C-bis-sulfonylketenimines.

PubMed

Finnerty, Justin; Mitschke, Ullrich; Wentrup, Curt

2002-02-22

C,C-dicyanoketenimines 10a-c were generated by flash vacuum thermolysis of ketene N,S-acetals 9a-c or by thermal or photochemical decomposition of alpha-azido-beta-cyanocinnamonitrile 11. In the latter reaction, 3,3-dicyano-2-phenyl-1-azirine 12 is also formed. IR spectroscopy of the keteniminines isolated in Ar matrixes or as neat films, NMR spectroscopy of 10c, and theoretical calculations (B3LYP/6-31G) demonstrate that these ketenimines have variable geometry, being essentially linear along the CCN-R framework in polar media (neat films and solution), but in the gas phase or Ar matrix they are bent, as is usual for ketenimines. Experiments and calculations agree that a single CN substituent as in 13 is not enough to enforce linearity, and sulfonyl groups are less effective that cyano groups in causing linearity. C,C-bis(methylsulfonyl)ketenimines 4-5 and a C-cyano-C-(methylsulfonyl)ketenimine 15 are not linear. The compound p-O2NC6H4N=C=C(COOMe)2 previously reported in the literature is probably somewhat linearized along the CCNR moiety. A computational survey (B3LYP/6-31G) of the inversion barrier at nitrogen indicates that electronegative C-substituents dramatically lower the barrier; this is also true of N-acyl substituents. Increasing polarity causes lower barriers. Although N-alkylbis(methylsulfonyl)ketenimines are not calculated to be linear, the barriers are so low that crystal lattice forces can induce planarity in N-methylbis(methylsulfonyl)ketenimine 3.

Synthesis of benzo-fused 1-azabicyclo[m.n.0]alkanes via the Schmidt reaction: a formal synthesis of gephyrotoxin.

PubMed

Pearson, W H; Fang, W

2000-10-20

The intramolecular capture of benzocyclobutyl, benzocyclopentyl, and benzocyclohexyl carbocations 7 by azides produces spirocyclic aminodiazonium ions 8, which undergo 1,2-C-to-N rearrangement with loss of dinitrogen to produce benzo-fused iminium ions resulting from either aryl (9) or alkyl (10) migration to the electron-deficient nitrogen atom. Reduction of the iminium ions affords regioisomeric benzo-fused 1-azabicyclo[m.n.0]alkanes, e.g., benzopyrrolizidines, benzoindolizidines, benzoquinolizidines, or perhydrobenzo[f]pyrrolo[1,2-a]azepines in two regioisomeric versions, anilines (e.g., 11-14) and benzylic amines (e.g., 15-18), the result of aryl and alkyl migrations, respectively. Generally, aryl migration is preferred, despite modeling that shows that the lowest energy aminodiazonium ions are those where the departing dinitrogen is preferentially antiperiplanar to the migrating alkyl group rather than the aryl group. The utility of this methodology was illustrated by a formal synthesis of the alkaloid gephyrotoxin 4. A dependence on the efficiency and regioselectivity of the Schmidt reaction upon subtle changes in the structure of the cation precursor was observed, necessitating the exploration of a variety of substrates. Fortunately, these materials were easily made. Ultimately, the azido-alkene 81 bearing a 2-bromoethyl side-chain was useful for the Schmidt reaction, producing the known benzo-fused indolizidine 49, which had been transformed by Ito et al. into gephyrotoxin 4. The synthesis of 49 required nine steps (five purifications) from commercially available 4-methoxy-1-indanone 60 and proceeded in 22% overall yield.

Detection of proteolytic activity by covalent tethering of fluorogenic substrates in zymogram gels.

PubMed

Deshmukh, Ameya A; Weist, Jessica L; Leight, Jennifer L

2018-05-01

Current zymographic techniques detect only a subset of known proteases due to the limited number of native proteins that have been optimized for incorporation into polyacrylamide gels. To address this limitation, we have developed a technique to covalently incorporate fluorescently labeled, protease-sensitive peptides using an azido-PEG3-maleimide crosslinker. Peptides incorporated into gels enabled measurement of MMP-2, -9, -14, and bacterial collagenase. Sensitivity analysis demonstrated that use of peptide functionalized gels could surpass detection limits of current techniques. Finally, electrophoresis of conditioned media from cultured cells resulted in the appearance of several proteolytic bands, some of which were undetectable by gelatin zymography. Taken together, these results demonstrate that covalent incorporation of fluorescent substrates can greatly expand the library of detectable proteases using zymographic techniques.

New Imidazole-based High Nitrogen Energetic Materials

NASA Astrophysics Data System (ADS)

Windler, G. Kenneth; Leonard, Philip; Schulze, Maxwell; Hartline, Ernest

2017-06-01

Energetic materials derive their power from energy release, usually in the form of gaseous products. The type and quantity of these products contribute to performance and detonation parameters. In particular, high-nitrogen materials produce large quantities of elemental nitrogen, and can be tuned via molecular structure for suitability as propellants (gas generators) or explosives. In this work, the five-membered nitrogen heterocycle imidazole is used as a substrate for a variety of high-nitrogen materials. Substitution of the imidazole ring directly with nitro-, azido-, diazo-, and tetrazole moieties allows for tunable properties of the resultant energetic material. Properties can be further tailored by salt formation at the acidic proton(s) on the molecules. The various combinations of these derivatives are presented, along with the substitution effects on physical, chemical, and explosive properties.

Site-selective post-translational modification of proteins using an unnatural amino acid, 3-azidotyrosine.

PubMed

Ohno, Satoshi; Matsui, Megumi; Yokogawa, Takashi; Nakamura, Masashi; Hosoya, Takamitsu; Hiramatsu, Toshiyuki; Suzuki, Masaaki; Hayashi, Nobuhiro; Nishikawa, Kazuya

2007-03-01

An efficient method for site-selective modification of proteins using an unnatural amino acid, 3-azidotyrosine has been developed. This method utilizes the yeast amber suppressor tRNA(Tyr)/mutated tyrosyl-tRNA synthetase pair as a carrier of 3-azidotyrosine in an Escherichia coli cell-free translation system, and triarylphosphine derivatives for specific modification of the azido group. Using rat calmodulin (CaM) as a model protein, we prepared several unnatural CaM molecules, each carrying an azidotyrosine at predetermined positions 72, 78, 80 or 100, respectively. Post-translational modification of these proteins with a conjugate compound of triarylphosphine and biotin produced site-selectively biotinylated CaM molecules. Reaction efficiency was similar among these proteins irrespective of the position of introduction, and site-specificity of biotinylation was confirmed using mass spectrometry. In addition, CBP-binding activity of the biotinylated CaMs was confirmed to be similar to that of wild-type CaM. This method is intrinsically versatile in that it should be easily applicable to introducing any other desirable compounds (e.g., probes and cross-linkers) into selected sites of proteins as far as appropriate derivative compounds of triarylphosphine could be chemically synthesized. Elucidation of molecular mechanisms of protein functions and protein-to-protein networks will be greatly facilitated by making use of these site-selectively modified proteins.

3'-Azido-2',3'-dideoxythymidine induced deficiency of thymidine kinases 1, 2 and deoxycytidine kinase in H9 T-lymphoid cells.

PubMed

Gröschel, Bettina; Kaufmann, Andreas; Höver, Gerold; Cinatl, Jaroslav; Doerr, Hans Wilhelm; Noordhuis, Paul; Loves, Willem J P; Peters, Godefridus J; Cinatl, Jindrich

2002-07-15

Continuous cultivation of T-lymphoid H9 cells in the presence of 3'-azido-2',3'-dideoxythymidine (AZT) resulted in a cell variant cross-resistant to both thymidine and deoxycytidine analogs. Cytotoxic effects of AZT, 2',3'-didehydro-3'-deoxythymidine as well as different deoxycytidine analogs such as 2',3'-dideoxycytidine, 2',2'-difluoro-2'-deoxycytidine (dFdC) and 1-ss-D-arabinofuranosylcytosine (Ara-C) were strongly reduced in H9 cells continuously exposed to AZT when compared to parental cells (>8.3-, >6.6-, >9.1-, 5 x 10(4)-, 5 x 10(3)-fold, respectively). Moreover, anti-HIV-1 effects of AZT, d4T, ddC and 2',3'-dideoxy-3'-thiacytidine (3TC) were significantly diminished (>222-, >25-, >400-, >200-fold, respectively) in AZT-resistant H9 cells. Study of cellular mechanisms responsible for cross-resistance to pyrimidine analogs in AZT-resistant H9 cells revealed decreased mRNA levels of thymidine kinase 1 (TK1) and lack of deoxycytidine kinase (dCK) mRNA expression. The loss of dCK gene expression was confirmed by western blot analysis of dCK protein as well as dCK enzyme activity assay. Moreover, enzyme activity of TK1 and TK2 was reduced in AZT-resistant cells. In order to determine whether lack of dCK affected the formation of the active triphosphate of the deoxycytidine analog dFdC, dFdCTP accumulation and retention was measured in H9 parental and AZT-resistant cells after exposure to 1 and 10 microM dFdC. Parental H9 cells accumulated about 30 and 100 pmol dFdCTP/10(6) cells after 4hr, whereas in AZT-resistant cells no dFdCTP accumulation was detected. These results demonstrate that continuous treatment of H9 cells in the presence of AZT selected for a thymidine analog resistant cell variant with cross-resistance to deoxycytidine analogs, due to deficiency in TK1, TK2, and dCK.

Incorporation of unnatural sugars for the identification of glycoproteins.

PubMed

Zaro, Balyn W; Hang, Howard C; Pratt, Matthew R

2013-01-01

Glycosylation is an abundant post-translational modification that alters the fate and function of its substrate proteins. To aid in understanding the significance of protein glycosylation, identification of target proteins is key. As with all proteomics experiments, mass spectrometry has been established as the desired method for substrate identification. However, these approaches require selective enrichment and purification of modified proteins. Chemical reporters in combination with bioorthogonal reactions have emerged as robust tools for identifying post-translational modifications including glycosylation. We provide here a method for the use of bioorthogonal chemical reporters for isolation and identification of glycosylated proteins. More specifically, this protocol is a representative procedure from our own work using an alkyne-bearing O-GlcNAc chemical reporter (GlcNAlk) and a chemically cleavable azido-azo-biotin probe for the identification of O-GlcNAc-modified proteins.

Click-MS: Tagless Protein Enrichment Using Bioorthogonal Chemistry for Quantitative Proteomics.

PubMed

Smits, Arne H; Borrmann, Annika; Roosjen, Mark; van Hest, Jan C M; Vermeulen, Michiel

2016-12-16

Epitope-tagging is an effective tool to facilitate protein enrichment from crude cell extracts. Traditionally, N- or C-terminal fused tags are employed, which, however, can perturb protein function. Unnatural amino acids (UAAs) harboring small reactive handles can be site-specifically incorporated into proteins, thus serving as a potential alternative for conventional protein tags. Here, we introduce Click-MS, which combines the power of site-specific UAA incorporation, bioorthogonal chemistry, and quantitative mass spectrometry-based proteomics to specifically enrich a single protein of interest from crude mammalian cell extracts. By genetic encoding of p-azido-l-phenylalanine, the protein of interest can be selectively captured using copper-free click chemistry. We use Click-MS to enrich proteins that function in different cellular compartments, and we identify protein-protein interactions, showing the great potential of Click-MS for interaction proteomics workflows.

SERS assay of telomerase activity at single-cell level and colon cancer tissues via quadratic signal amplification.

PubMed

Shi, Muling; Zheng, Jing; Liu, Changhui; Tan, Guixiang; Qing, Zhihe; Yang, Sheng; Yang, Jinfeng; Tan, Yongjun; Yang, Ronghua

2016-03-15

As an important biomarker and therapeutic target, telomerase has attracted extensive attention concerning its detection and monitoring. Recently, enzyme-assisted amplification approaches have provided useful platforms for the telomerase activity detection, however, further improvement in sensitivity is still hindered by the single-step signal amplification. Herein, we develop a quadratic signal amplification strategy for ultrasensitive surface-enhanced Raman scattering (SERS) detection of telomerase activity. The central idea of our design is using telomerase-induced silver nanoparticles (AgNPs) assembly and silver ions (Ag(+))-mediated cascade amplification. In our approach, each telomerase-aided DNA sequence extension could trigger the formation of a long double-stranded DNA (dsDNA), making numerous AgNPs assembling along with this long strand through specific Ag-S bond, to form a primary amplification element. For secondary amplification, each conjugated AgNP was dissolved into Ag(+), which can effectively induce the 4-aminobenzenethiol (4-ABT) modified gold nanoparticles (AuNPs@4-ABT) to undergo aggregation to form numerous "hot-spots". Through quadratic amplifications, a limit of detection down to single HeLa cell was achieved. More importantly, this method demonstrated good performance when applied to tissues from colon cancer patients, which exhibits great potential in the practical application of telomerase-based cancer diagnosis in early stages. To demonstrate the potential in screening the telomerase inhibitors and telomerase-targeted drugs, the proposed design is successfully employed to measure the inhibition of telomerase activity by 3'-azido-3'-deoxythymidine. Copyright © 2015 Elsevier B.V. All rights reserved.

Photoaffinity Labeling of the Plasmodium falciparum Chloroquine Resistance Transporter with a Novel Perfluorophenylazido Chloroquine†

PubMed Central

Lekostaj, Jacqueline K.; Natarajan, Jayakumar K.; Paguio, Michelle F.; Wolf, Christian; Roepe, Paul D.

2009-01-01

Several models describing how amino acid substitutions in the Plasmodium falciparum chloroquine resistance transporter (PfCRT) confer resistance to chloroquine (CQ) and other antimalarial drugs have been proposed. Further progress requires molecular analysis of interactions between purified reconstituted PfCRT protein and these drugs. We have thus designed and synthesized several perfluorophenyl azido (pfpa) CQ analogues for PfCRT photolabeling studies. One particularly useful probe (AzBCQ) places the pfpa group at the terminal aliphatic N of CQ via a flexible four-carbon ester linker and includes a convenient biotin tag. This probe photolabels PfCRT in situ with high specificity. Using reconstituted proteoliposomes harboring partially purified recombinant PfCRT, we analyze AzBCQ photolabeling versus competition with CQ and other drugs to probe the nature of the CQ binding site. We also inspect how pH, the chemoreversal agent verapamil (VPL), and various amino acid mutations in PfCRT that cause CQ resistance (CQR) affect the efficiency of AzBCQ photolabeling. Upon gel isolation of AzBCQ-labeled PfCRT followed by trypsin digestion and mass spectrometry analysis, we are able to define a single AzBCQ covalent attachment site lying within the digestive vacuolar-disposed loop between putative helices 9 and 10 of PfCRT. Taken together, the data provide important new insight into PfCRT function and, along with previous results, allow us to propose a model for a single CQ binding site in the PfCRT protein. PMID:18767816

Photoaffinity labeling of the Plasmodium falciparum chloroquine resistance transporter with a novel perfluorophenylazido chloroquine.

PubMed

Lekostaj, Jacqueline K; Natarajan, Jayakumar K; Paguio, Michelle F; Wolf, Christian; Roepe, Paul D

2008-09-30

Several models describing how amino acid substitutions in the Plasmodium falciparum chloroquine resistance transporter (PfCRT) confer resistance to chloroquine (CQ) and other antimalarial drugs have been proposed. Further progress requires molecular analysis of interactions between purified reconstituted PfCRT protein and these drugs. We have thus designed and synthesized several perfluorophenyl azido (pfpa) CQ analogues for PfCRT photolabeling studies. One particularly useful probe (AzBCQ) places the pfpa group at the terminal aliphatic N of CQ via a flexible four-carbon ester linker and includes a convenient biotin tag. This probe photolabels PfCRT in situ with high specificity. Using reconstituted proteoliposomes harboring partially purified recombinant PfCRT, we analyze AzBCQ photolabeling versus competition with CQ and other drugs to probe the nature of the CQ binding site. We also inspect how pH, the chemoreversal agent verapamil (VPL), and various amino acid mutations in PfCRT that cause CQ resistance (CQR) affect the efficiency of AzBCQ photolabeling. Upon gel isolation of AzBCQ-labeled PfCRT followed by trypsin digestion and mass spectrometry analysis, we are able to define a single AzBCQ covalent attachment site lying within the digestive vacuolar-disposed loop between putative helices 9 and 10 of PfCRT. Taken together, the data provide important new insight into PfCRT function and, along with previous results, allow us to propose a model for a single CQ binding site in the PfCRT protein.

Computational and Biochemical Docking of the Irreversible Cocaine Analog RTI 82 Directly Demonstrates Ligand Positioning in the Dopamine Transporter Central Substrate-binding Site*

PubMed Central

Dahal, Rejwi Acharya; Pramod, Akula Bala; Sharma, Babita; Krout, Danielle; Foster, James D.; Cha, Joo Hwan; Cao, Jianjing; Newman, Amy Hauck; Lever, John R.; Vaughan, Roxanne A.; Henry, L. Keith

2014-01-01

The dopamine transporter (DAT) functions as a key regulator of dopaminergic neurotransmission via re-uptake of synaptic dopamine (DA). Cocaine binding to DAT blocks this activity and elevates extracellular DA, leading to psychomotor stimulation and addiction, but the mechanisms by which cocaine interacts with DAT and inhibits transport remain incompletely understood. Here, we addressed these questions using computational and biochemical methodologies to localize the binding and adduction sites of the photoactivatable irreversible cocaine analog 3β-(p-chlorophenyl)tropane-2β-carboxylic acid, 4′-azido-3′-iodophenylethyl ester ([125I]RTI 82). Comparative modeling and small molecule docking indicated that the tropane pharmacophore of RTI 82 was positioned in the central DA active site with an orientation that juxtaposed the aryliodoazide group for cross-linking to rat DAT Phe-319. This prediction was verified by focused methionine substitution of residues flanking this site followed by cyanogen bromide mapping of the [125I]RTI 82-labeled mutants and by the substituted cysteine accessibility method protection analyses. These findings provide positive functional evidence linking tropane pharmacophore interaction with the core substrate-binding site and support a competitive mechanism for transport inhibition. This synergistic application of computational and biochemical methodologies overcomes many uncertainties inherent in other approaches and furnishes a schematic framework for elucidating the ligand-protein interactions of other classes of DA transport inhibitors. PMID:25179220

Antigen-antibody interaction. The immunodominant region of EDP208 pili.

PubMed

Worobec, E A; Paranchych, W; Parker, J M; Taneja, A K; Hodges, R S

1985-01-25

The EDP208 pilus contains a major antigenic determinant in the N-terminal dodecapeptide, as shown by E. A. Worobec, A. K. Taneja, R. S. Hodges, and W. Paranchych ((1983) J. Bacteriol. 153, 955-961). This peptide was chemically synthesized, coupled to bovine serum albumin with N-hydroxysuccinimidyl p-azido-benzoate, and used in immunoblot and enzyme-linked immunosorbent assays to show it was capable of reacting with anti-EDP208 pilus antibodies. Antibodies raised against the synthetic peptide conjugate were also capable of reacting with whole pili in these assays. To further examine the specific residues responsible for the antigenicity of this site, several peptide analogs were chemically synthesized. The relative affinity of these peptides for anti-EDP208 pilus antibodies was determined by a competitive enzyme-linked immunosorbent assay using the Fab fragment of anti-EDP208 pilus immunoglobulin G. From these results we established that the antigenic region of this peptide was the N-terminal pentapeptide, N-acetyl-Thr-Asp-Leu-Leu-Ala, and the key residues responsible for the antibody-antigen interaction are the N-acetyl-Thr1, Leu3, and Leu4. Hydrophobic interactions involving the methyl of the acetyl group and the leucine side chains make the largest contributions to the antigen-antibody interaction, while a lesser contribution is made by the Thr1 hydroxyl. The side chains of Asp2 and Ala5 contribute only weakly to the stabilization of the antigen-antibody complex.

Functionalized Congeners of P2Y1 Receptor Antagonists:

DOE Office of Scientific and Technical Information (OSTI.GOV)

de Castro, Sonia; Maruoka, Hiroshi; Hong, Kunlun

2010-01-01

The P2Y{sub 1} receptor is a prothrombotic G protein-coupled receptor (GPCR) activated by ADP. Preference for the North (N) ring conformation of the ribose moiety of adenine nucleotide 3',5'-bisphosphate antagonists of the P2Y{sub 1} receptor was established by using a ring-constrained methanocarba (a bicyclo[3.1.0]hexane) ring as a ribose substitute. A series of covalently linkable N{sup 6}-methyl-(N)-methanocarba-2'-deoxyadenosine-3',5'-bisphosphates containing extended 2-alkynyl chains was designed, and binding affinity at the human (h) P2Y{sub 1} receptor determined. The chain of these functionalized congeners contained hydrophilic moieties, a reactive substituent, or biotin, linked via an amide. Variation of the chain length and position of anmore » intermediate amide group revealed high affinity of carboxylic congener 8 (K{sub i} 23 nM) and extended amine congener 15 (K{sub i} 132 nM), both having a 2-(1-pentynoyl) group. A biotin conjugate 18 containing an extended {epsilon}-aminocaproyl spacer chain exhibited higher affinity than a shorter biotinylated analogue. Alternatively, click coupling of terminal alkynes of homologous 2-dialkynyl nucleotide derivatives to alkyl azido groups produced triazole derivatives that bound to the P2Y{sub 1} receptor following deprotection of the bisphosphate groups. The preservation of receptor affinity of the functionalized congeners was consistent with new P2Y{sub 1} receptor modeling and ligand docking. Attempted P2Y{sub 1} antagonist conjugation to PAMAM dendrimer carriers by amide formation or palladium-catalyzed reaction between an alkyne on the dendrimer and a 2-iodopurine-derivatized nucleotide was unsuccessful. A dialkynyl intermediate containing the chain length favored in receptor binding was conjugated to an azide-derivatized dendrimer, and the conjugate inhibited ADP-promoted human platelet aggregation. This is the first example of attaching a strategically functionalized P2Y receptor antagonist to a PAMAM dendrimer to produce a multivalent conjugate exhibiting a desired biological effect, i.e., antithrombotic action.« less

Site-specific incorporation of probes into RNA polymerase by unnatural-amino-acid mutagenesis and Staudinger-Bertozzi ligation

PubMed Central

Chakraborty, Anirban; Mazumder, Abhishek; Lin, Miaoxin; Hasemeyer, Adam; Xu, Qumiao; Wang, Dongye; Ebright, Yon W.; Ebright, Richard H.

2015-01-01

Summary A three-step procedure comprising (i) unnatural-amino-acid mutagenesis with 4-azido-phenylalanine, (ii) Staudinger-Bertozzi ligation with a probe-phosphine derivative, and (iii) in vitro reconstitution of RNA polymerase (RNAP) enables the efficient site-specific incorporation of a fluorescent probe, a spin label, a crosslinking agent, a cleaving agent, an affinity tag, or any other biochemical or biophysical probe, at any site of interest in RNAP. Straightforward extensions of the procedure enable the efficient site-specific incorporation of two or more different probes in two or more different subunits of RNAP. We present protocols for synthesis of probe-phosphine derivatives, preparation of RNAP subunits and the transcription initiation factor σ, unnatural amino acid mutagenesis of RNAP subunits and σ, Staudinger ligation with unnatural-amino-acid-containing RNAP subunits and σ, quantitation of labelling efficiency and labelling specificity, and reconstitution of RNAP. PMID:25665560

Histone Deacetylase Inhibitors through Click Chemistry

PubMed Central

Shen, Jie; Woodward, Robert; Kedenburg, James Patrick; Liu, Xianwei; Chen, Min; Fang, Lanyan; Sun, Duxin; Wang, Peng George

2012-01-01

Histone deacetylase inhibitors (HDACi) are a relatively new class of chemotherapy agents. Herein, we report a click-chemistry based approach to the synthesis of HDACi. Fourteen agents were synthesized from the combination of two alkyne and seven azido precursors. The inhibition of HDAC1 and HDAC8 was then determined by in vitro enzymatic assays, after which the cytotoxicity was evaluated in the NCI human cancer cell line screen. A lead compound 5g (NSC746457) was discovered that inhibited HDAC1 at an IC50 value of 104 ± 30 nM and proved quite potent in the cancer cell line screen with GI50 values ranging from 3.92 μM to 10 nM. Thus, this click HDACi design has provided a new chemical scaffold that has not only revealed a lead compound, but one which is easily amendable to further structural modifications given the modular nature of this approach. PMID:19007204

The history of antiretrovirals: key discoveries over the past 25 years.

PubMed

De Clercq, Erik

2009-09-01

Within 25 years after zidovudine (3'-azido-2',3'-dideoxythymidine, AZT) was first described as an inhibitor of HIV replication, 25 anti-HIV drugs have been formally approved for clinical use in the treatment of HIV infections: seven nucleoside reverse transcriptase inhibitors (NRTIs): zidovudine, didanosine, zalcitabine, stavudine, lamivudine, abacavir and emtricitabine; one nucleotide reverse transcriptase inhibitor (NtRTI): tenofovir [in its oral prodrug form: tenofovir disoproxil fumarate (TDF)]; four non-nucleoside reverse transcriptase inhibitors (NNRTIs): nevirapine, delavirdine, efavirenz and etravirine; ten protease inhibitors (PIs): saquinavir, ritonavir, indinavir, nelfinavir, amprenavir, lopinavir, atazanavir, fosamprenavir, tipranavir and darunavir; one fusion inhibitor (FI): enfuvirtide; one co-receptor inhibitor (CRI): maraviroc and one integrase inhibitor (INI): raltegravir. These compounds are used in various drug combination (some at fixed dose) regimens so as to achieve the highest possible benefit and tolerability, and to diminish the risk of virus-drug resistance development. (c) 2009 John Wiley & Sons, Ltd.

6-Deoxyhexoses from l-Rhamnose in the Search for Inducers of the Rhamnose Operon: Synergy of Chemistry and Biotechnology.

PubMed

Liu, Zilei; Yoshihara, Akihide; Kelly, Ciarán; Heap, John T; Marqvorsen, Mikkel H S; Jenkinson, Sarah F; Wormald, Mark R; Otero, José M; Estévez, Amalia; Kato, Atsushi; Fleet, George W J; Estévez, Ramón J; Izumori, Ken

2016-08-22

In the search for alternative non-metabolizable inducers in the l-rhamnose promoter system, the synthesis of fifteen 6-deoxyhexoses from l-rhamnose demonstrates the value of synergy between biotechnology and chemistry. The readily available 2,3-acetonide of rhamnonolactone allows inversion of configuration at C4 and/or C5 of rhamnose to give 6-deoxy-d-allose, 6-deoxy-d-gulose and 6-deoxy-l-talose. Highly crystalline 3,5-benzylidene rhamnonolactone gives easy access to l-quinovose (6-deoxy-l-glucose), l-olivose and rhamnose analogue with C2 azido, amino and acetamido substituents. Electrophilic fluorination of rhamnal gives a mixture of 2-deoxy-2-fluoro-l-rhamnose and 2-deoxy-2-fluoro-l-quinovose. Biotechnology provides access to 6-deoxy-l-altrose and 1-deoxy-l-fructose. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Potent Inhibitors against Newcastle Disease Virus Hemagglutinin-Neuraminidase.

PubMed

Rota, Paola; La Rocca, Paolo; Piccoli, Marco; Montefiori, Marco; Cirillo, Federica; Olsen, Lars; Orioli, Marica; Allevi, Pietro; Anastasia, Luigi

2018-02-06

Neuraminidase activity is essential for the infection and propagation of paramyxoviruses, including human parainfluenza viruses (hPIVs) and the Newcastle disease virus (NDV). Thus, many inhibitors have been developed based on the 2-deoxy-2,3-didehydro-d-N-acetylneuraminic acid inhibitor (DANA) backbone. Along this line, herein we report a series of neuraminidase inhibitors, having C4 (p-toluenesulfonamido and azido substituents) and C5 (N-perfluorinated chains) modifications to the DANA backbone, resulting in compounds with 5- to 15-fold greater potency than the currently most active compound, the N-trifluoroacetyl derivative of DANA (FANA), toward the NDV hemagglutinin-neuraminidase (NDV-HN). Remarkably, these inhibitors were found to be essentially inactive against the human sialidase NEU3, which is present on the outer layer of the cell membrane and is highly affected by the current NDV inhibitor FANA. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

7-Chloroquinolinotriazoles: synthesis by the azide-alkyne cycloaddition click chemistry, antimalarial activity, cytotoxicity and SAR studies.

PubMed

Pereira, Guilherme R; Brandão, Geraldo Célio; Arantes, Lucas M; de Oliveira, Háliton A; de Paula, Renata Cristina; do Nascimento, Maria Fernanda A; dos Santos, Fábio M; da Rocha, Ramon K; Lopes, Júlio César D; de Oliveira, Alaíde Braga

2014-02-12

Twenty-seven 7-chloroquinolinotriazole derivatives with different substituents in the triazole moiety were synthesized via copper-catalyzed cycloaddition (CuAAC) click chemistry between 4-azido-7-chloroquinoline and several alkynes. All the synthetic compounds were evaluated for their in vitro activity against Plasmodium falciparum (W2) and cytotoxicity to Hep G2A16 cells. All the products disclosed low cytotoxicity (CC50 > 100 μM) and five of them have shown moderate antimalarial activity (IC50 from 9.6 to 40.9 μM). As chloroquine analogs it was expected that these compounds might inhibit the heme polymerization and SAR studies were performed aiming to explain their antimalarial profile. New structural variations can be designed on the basis of the results obtained. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

Sensitive, site-specific, and stable vibrational probe of local protein environments: 4-azidomethyl-L-phenylalanine.

PubMed

Bazewicz, Christopher G; Liskov, Melanie T; Hines, Kevin J; Brewer, Scott H

2013-08-01

We have synthesized the unnatural amino acid (UAA), 4-azidomethyl-L-phenylalanine (pN₃CH₂Phe), to serve as an effective vibrational reporter of local protein environments. The position, extinction coefficient, and sensitivity to local environment of the azide asymmetric stretch vibration of pN₃CH₂Phe are compared to the vibrational reporters: 4-cyano-L-phenylalanine (pCNPhe) and 4-azido-L-phenylalanine (pN₃Phe). This UAA was genetically incorporated in a site-specific manner utilizing an engineered, orthogonal aminoacyl-tRNA synthetase in response to an amber codon with high efficiency and fidelity into two distinct sites in superfolder green fluorescent protein (sfGFP). This allowed for the dependence of the azide asymmetric stretch vibration of pN₃CH₂Phe to different protein environments to be measured. The photostability of pN₃CH₂Phe was also measured relative to the photoreactive UAA, pN₃Phe.

Exploring Covalent Allosteric Inhibition of Antigen 85C from Mycobacterium tuberculosis by Ebselen Derivatives

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goins, Christopher M.; Dajnowicz, Steven; Thanna, Sandeep

Previous studies identified ebselen as a potent in vitro and in vivo inhibitor of the Mycobacterium tuberculosis ( Mtb) antigen 85 (Ag85) complex, comprising three homologous enzymes required for the biosynthesis of the mycobacterial cell wall. In this study, the Mtb Ag85C enzyme was cocrystallized with azido and adamantyl ebselen derivatives, resulting in two crystallographic structures of 2.01 and 1.30 Å resolution, respectively. Both structures displayed the anticipated covalent modification of the solvent accessible, noncatalytic Cys209 residue forming a selenenylsulfide bond. Continuous difference density for both thiol modifiers allowed for the assessment of interactions that influence ebselen binding and inhibitormore » orientation that were unobserved in previous Ag85C ebselen structures. The k inact/ K I values for ebselen, adamantyl ebselen, and azido ebselen support the importance of observed constructive chemical interactions with Arg239 for increased in vitro efficacy toward Ag85C. To better understand the in vitro kinetic properties of these ebselen derivatives, the energetics of specific protein–inhibitor interactions and relative reaction free energies were calculated for ebselen and both derivatives using density functional theory. These studies further support the different in vitro properties of ebselen and two select ebselen derivatives from our previously published ebselen library with respect to kinetics and protein–inhibitor interactions. In both structures, the α9 helix was displaced farther from the enzyme active site than the previous Ag85C ebselen structure, resulting in the restructuring of a connecting loop and imparting a conformational change to residues believed to play a role in substrate binding specific to Ag85C. These notable structural changes directly affect protein stability, reducing the overall melting temperature by up to 14.5 °C, resulting in the unfolding of protein at physiological temperatures. Additionally, this structural rearrangement due to covalent allosteric modification creates a sizable solvent network that encompasses the active site and extends to the modified Cys209 residue. In all, this study outlines factors that influence enzyme inhibition by ebselen and its derivatives while further highlighting the effects of the covalent modification of Cys209 by said inhibitors on the structure and stability of Ag85C. Moreover, the results suggest a strategy for developing new classes of Ag85 inhibitors with increased specificity and potency.« less

Exploring Covalent Allosteric Inhibition of Antigen 85C from Mycobacterium tuberculosis by Ebselen Derivatives.

PubMed

Goins, Christopher M; Dajnowicz, Steven; Thanna, Sandeep; Sucheck, Steven J; Parks, Jerry M; Ronning, Donald R

2017-05-12

Previous studies identified ebselen as a potent in vitro and in vivo inhibitor of the Mycobacterium tuberculosis (Mtb) antigen 85 (Ag85) complex, comprising three homologous enzymes required for the biosynthesis of the mycobacterial cell wall. In this study, the Mtb Ag85C enzyme was cocrystallized with azido and adamantyl ebselen derivatives, resulting in two crystallographic structures of 2.01 and 1.30 Å resolution, respectively. Both structures displayed the anticipated covalent modification of the solvent accessible, noncatalytic Cys209 residue forming a selenenylsulfide bond. Continuous difference density for both thiol modifiers allowed for the assessment of interactions that influence ebselen binding and inhibitor orientation that were unobserved in previous Ag85C ebselen structures. The k inact /K I values for ebselen, adamantyl ebselen, and azido ebselen support the importance of observed constructive chemical interactions with Arg239 for increased in vitro efficacy toward Ag85C. To better understand the in vitro kinetic properties of these ebselen derivatives, the energetics of specific protein-inhibitor interactions and relative reaction free energies were calculated for ebselen and both derivatives using density functional theory. These studies further support the different in vitro properties of ebselen and two select ebselen derivatives from our previously published ebselen library with respect to kinetics and protein-inhibitor interactions. In both structures, the α9 helix was displaced farther from the enzyme active site than the previous Ag85C ebselen structure, resulting in the restructuring of a connecting loop and imparting a conformational change to residues believed to play a role in substrate binding specific to Ag85C. These notable structural changes directly affect protein stability, reducing the overall melting temperature by up to 14.5 °C, resulting in the unfolding of protein at physiological temperatures. Additionally, this structural rearrangement due to covalent allosteric modification creates a sizable solvent network that encompasses the active site and extends to the modified Cys209 residue. In all, this study outlines factors that influence enzyme inhibition by ebselen and its derivatives while further highlighting the effects of the covalent modification of Cys209 by said inhibitors on the structure and stability of Ag85C. Furthermore, the results suggest a strategy for developing new classes of Ag85 inhibitors with increased specificity and potency.

Exploring Covalent Allosteric Inhibition of Antigen 85C from Mycobacterium tuberculosis by Ebselen Derivatives

DOE PAGES

Goins, Christopher M.; Dajnowicz, Steven; Thanna, Sandeep; ...

2017-03-13

Previous studies identified ebselen as a potent in vitro and in vivo inhibitor of the Mycobacterium tuberculosis ( Mtb) antigen 85 (Ag85) complex, comprising three homologous enzymes required for the biosynthesis of the mycobacterial cell wall. In this study, the Mtb Ag85C enzyme was cocrystallized with azido and adamantyl ebselen derivatives, resulting in two crystallographic structures of 2.01 and 1.30 Å resolution, respectively. Both structures displayed the anticipated covalent modification of the solvent accessible, noncatalytic Cys209 residue forming a selenenylsulfide bond. Continuous difference density for both thiol modifiers allowed for the assessment of interactions that influence ebselen binding and inhibitormore » orientation that were unobserved in previous Ag85C ebselen structures. The k inact/ K I values for ebselen, adamantyl ebselen, and azido ebselen support the importance of observed constructive chemical interactions with Arg239 for increased in vitro efficacy toward Ag85C. To better understand the in vitro kinetic properties of these ebselen derivatives, the energetics of specific protein–inhibitor interactions and relative reaction free energies were calculated for ebselen and both derivatives using density functional theory. These studies further support the different in vitro properties of ebselen and two select ebselen derivatives from our previously published ebselen library with respect to kinetics and protein–inhibitor interactions. In both structures, the α9 helix was displaced farther from the enzyme active site than the previous Ag85C ebselen structure, resulting in the restructuring of a connecting loop and imparting a conformational change to residues believed to play a role in substrate binding specific to Ag85C. These notable structural changes directly affect protein stability, reducing the overall melting temperature by up to 14.5 °C, resulting in the unfolding of protein at physiological temperatures. Additionally, this structural rearrangement due to covalent allosteric modification creates a sizable solvent network that encompasses the active site and extends to the modified Cys209 residue. In all, this study outlines factors that influence enzyme inhibition by ebselen and its derivatives while further highlighting the effects of the covalent modification of Cys209 by said inhibitors on the structure and stability of Ag85C. Moreover, the results suggest a strategy for developing new classes of Ag85 inhibitors with increased specificity and potency.« less

The A2 Adenosine Receptor: Guanine Nucleotide Modulation of Agonist Binding Is Enhanced by Proteolysis

PubMed Central

NANOFF, CHRISTIAN; JACOBSON, KENNETH A.; STILES, GARY L.

2012-01-01

SUMMARY Agonist binding to the A2 adenosine receptor (A2AR) and its regulation by guanine nucleotides was studied using the newly developed radioligand 125l-2-[4-(2-{2-[(4-ammnophenyl)methylcarbonylamino]ethylaminnocarbonyl}ethyl)phenyl]ethylamino-5′-N-ethylcarboxamidoadenosine (1251-PAPA-APEC) and its photoaffinity analog 125l-azido-PAPA-APEC. A single protein of Mr 45,000, displaying the appropriate A2AR pharmacology, is Iabeled in membranes from bovine striatum, PC12 cells, and frog erythrocytes. In DDT1 MF2 cells the labeled protein has a slightly lower molecular weight. Incorporation of 125l-azido-PAPA-APEC into membranes from rabbit striatum, however, reveals two specifically labeled peptides (Mr ~47,O00 and 38,000), both of which display A2AR pharmacology. Inhibition of protease activity leads to a decrease in the amount of the Mr 38,000 protein, with only the Mr 47,000 protein remaining. This suggests that the Mr 38,000 peptide is a proteolytic product of the Mr 47,000 A2AR protein. In membranes containing the intact undigested A2AR protein, guanine nucleotides induce a small to insignificant decrease in agonist binding, which is atypical of stimulatory Gs-coupled receptors. This minimal effect is observed in rabbit striatal membranes prepared in the presence of protease inhibitors, as well as in the other tissues studied. Binding to rabbit stnatal membranes that possess the partially digested receptor protein, however, reveals a 50% reduction in maximal specific agonist binding upon addition of guanine nucleotides. Inhibition of proteolysis in rabbit striatum, on the other hand, results in a diminished ability of guanine nucleotides to regulate agonist binding. Thus, the enhanced effectiveness of guanine nucleotides in rabbit striatal membranes is associated with the generation of the Mr 38,000 peptide fragment. Guanosine 5′-(β,γ-imido)triphosphate reduces photoaffinity labeling by 55% in the Mr 38,000 protein, whereas the labeling is decreased by only 28% in the Mr 47,000 receptor protein. Our data, therefore, suggest that, unless proteolysis occurs, the A2AR in all tissues studied is tightly associated with the Gs protein and displays minimal guanine nucleotide modulation of agonist binding, which makes the A2AR an atypical stimulatory receptor. PMID:1899902

pH-responsive supramolecular self-assembly of well-defined zwitterionic ABC miktoarm star terpolymers.

PubMed

Liu, Hao; Li, Changhua; Liu, Hewen; Liu, Shiyong

2009-04-21

We report the first example of the synthesis and pH-responsive supramolecular self-assembly of double hydrophilic ABC miktoarm star terpolymers. Well-defined ABC miktoarm star terpolymers consisting of poly(ethylene glycol), poly(tert-butyl methacrylate), and poly(2-(diethylamino)ethyl methacrylate) arms [PEG(-b-PtBMA)-b-PDEA] were synthesized via the combination of consecutive click reactions and atom transfer radical polymerization (ATRP), starting from a trifunctional core molecule, 1-azido-3-chloro-2-propanol (ACP). The click reaction of monoalkynyl-terminated PEG with an excess of ACP afforded difunctional PEG bearing a chlorine and a secondary hydroxyl moiety at the chain end, PEG113(-Cl)-OH (1). After azidation with NaN3, PEG-based macroinitiator PEG113(-N3)-Br (3) was prepared by the esterification of PEG113(-N3)-OH (2) with 2-bromoisobutyryl bromide and then employed in the ATRP of tert-butyl methacrylate (tBMA). The obtained PEG(-N3)-b-PtBMA copolymers (4) possessed an azido moiety at the diblock junction point. The preparation of PEG(-b-PtBMA)-b-PDEA miktoarm star terpolymers was then achieved via the click reaction of 4 with an excess of monoalkynyl-terminated PDEA. The obtained miktoarm star terpolymers were successfully converted into PEG(-b-PMAA)-b-PDEA, where PMAA is poly(methacrylic acid). In aqueous solution, PEG(-b-PMAA)-b-PDEA zwitterionic ABC miktoarm star terpolymers can self-assemble into three types of micellar aggregates by simply adjusting solution pH at room temperature. Above pH 8, PDEA-core micelles stabilized by PEG/ionized PMAA hybrid coronas were formed due to the insolubility of PDEA block. In the range of pH 5-7, micelles possessing polyion complex cores formed as a result of charge compensation between partially ionized PMAA and partially protonated PDEA sequences. At pH<4, hydrogen bonding interactions between fully protonated PMAA and PEG led to the formation of another type of micellar aggregates possessing hydrogen-bonded complex cores stabilized by protonated PDEA coronas. The fully reversible pH-responsive formation of three types of aggregates were characterized by 1H NMR, dynamic and static laser light scattering (LLS), and transmission electron microscopy (TEM).

Immunophotoaffinity labeling of binders of 1-methyladenine, the oocyte maturation-inducing hormone of starfish

DOE Office of Scientific and Technical Information (OSTI.GOV)

Toraya, Tetsuo; Kida, Tetsuo; Kuyama, Atsushi

Starfish oocytes are arrested at the prophase stage of the first meiotic division in the ovary and resume meiosis by the stimulus of 1-methyladenine (1-MeAde), the oocyte maturation-inducing hormone of starfish. Putative 1-MeAde receptors on the oocyte surface have been suggested, but not yet been biochemically characterized. Immunophotoaffinity labeling, i.e., photoaffinity labeling combined with immunochemical detection, was attempted to detect unknown 1-MeAde binders including putative maturation-inducing hormone receptors in starfish oocytes. When the oocyte crude membrane fraction or its Triton X-100/EDTA extract was incubated with N{sup 6}-[6-(5-azido-2-nitrobenzoyl)aminohexyl]carboxamidomethyl-1-methyladenine and then photo-irradiated, followed by western blotting with antibody that was raised againstmore » a 1-MeAde hapten, a single band with M{sub r} of 47.5 K was detected. The band was lost when extract was heated at 100 °C. A similar 47.5 K band was detected in the crude membrane fraction of testis as well. Upon labeling with whole cells, this band was detected in immature and maturing oocytes, but only faintly in mature oocytes. As judged from these results, this 1-MeAde binder might be a possible candidate of the starfish maturation-inducing hormone receptors. - Highlights: • Synthesis of photoaffinity labeling reagents for 1-methyladenine binders of starfish. • Immunochemical detection of photoaffinity-labeled 1-methyladenine binders. • Immunophotoaffinity labeling of a 47.5 K 1-methyladenine binder in oocytes and testis. • A possible candidate of oocyte maturation-inducing hormone receptors of starfish.« less

Platelet-targeting sensor reveals thrombin gradients within blood clots forming in microfluidic assays and in mouse.

PubMed

Welsh, J D; Colace, T V; Muthard, R W; Stalker, T J; Brass, L F; Diamond, S L

2012-11-01

Thrombin undergoes convective and diffusive transport, making it difficult to visualize during thrombosis. We developed the first sensor capable of revealing inner clot thrombin dynamics. An N-terminal-azido thrombin-sensitive fluorescent peptide (ThS-P) with a thrombin-releasable quencher was linked to anti-CD41 using click chemistry to generate a thrombin-sensitive platelet binding sensor (ThS-Ab). Rapid thrombin cleavage of ThS-P (K(m) = 40.3 μm, k(cat) = 1.5 s(-1) ) allowed thrombin monitoring by ThS-P or ThS-Ab in blood treated with 2-25 pm tissue factor (TF). Individual platelets had > 20-fold more ThS-Ab fluorescence after clotting. In a microfluidic assay of whole blood perfusion over collagen ± linked TF (wall shear rate = 100 s(-1) ), ThS-Ab fluorescence increased between 90 and 450 s for 0.1-1 molecule-TF μm(-2) and co-localized with platelets near fibrin. Without TF, neither thrombin nor fibrin was detected on the platelet deposits by 450 s. Using a microfluidic device to control the pressure drop across a thrombus forming on a porous collagen/TF plug (521 s(-1) ), thrombin and fibrin were detected at the thrombus-collagen interface at a zero pressure drop, whereas 80% less thrombin was detected at 3200 Pa in concert with fibrin polymerizing within the collagen. With anti-mouse CD41 ThS-Ab deployed in a mouse laser injury model, the highest levels of thrombin arose between 40 and 160 s nearest the injury site where fibrin co-localized and where the thrombus was most mechanically stable. ThS-Ab reveals thrombin locality, which depends on surface TF, flow and intrathrombus pressure gradients. © 2012 International Society on Thrombosis and Haemostasis.

Synthesis and Evaluation of a Novel Adenosine-Ribose Probe for Global-Scale Profiling of Nucleoside and Nucleotide-Binding Proteins

PubMed Central

Mahajan, Shikha; Manetsch, Roman; Merkler, David J.; Stevens Jr., Stanley M.

2015-01-01

Proteomics is a powerful approach used for investigating the complex molecular mechanisms of disease pathogenesis and progression. An important challenge in modern protein profiling approaches involves targeting of specific protein activities in order to identify altered molecular processes associated with disease pathophysiology. Adenosine-binding proteins represent an important subset of the proteome where aberrant expression or activity changes of these proteins have been implicated in numerous human diseases. Herein, we describe an affinity-based approach for the enrichment of adenosine-binding proteins from a complex cell proteome. A novel N 6-biotinylated-8-azido-adenosine probe (AdoR probe) was synthesized, which contains a reactive group that forms a covalent bond with the target proteins, as well as a biotin tag for affinity enrichment using avidin chromatography. Probe specificity was confirmed with protein standards prior to further evaluation in a complex protein mixture consisting of a lysate derived from mouse neuroblastoma N18TG2 cells. Protein identification and relative quantitation using mass spectrometry allowed for the identification of small variations in abundance of nucleoside- and nucleotide-binding proteins in these samples where a significant enrichment of AdoR-binding proteins in the labeled proteome from the neuroblastoma cells was observed. The results from this study demonstrate the utility of this method to enrich for nucleoside- and nucleotide-binding proteins in a complex protein mixture, pointing towards a unique set of proteins that can be examined in the context of further understanding mechanisms of disease, or fundamental biological processes in general. PMID:25671571

Synthesis of some glycoside analogs and related compounds from 9-amino-6-(methylthio)-9H-purine.

PubMed

Temple, C; Kussner, C L; Montgomery, J A

1975-12-01

Additional information on the anticancer activity of 9-amino-9H-purine-6(1H)-thione and its derivatives was sought by the synthesis of some 9-(substituted amino)-6-(methylthio)-9H-purines in which the 9-substituent contained functional groups capable of either reversible or irreversible binding with an enzymatic site. Condensation of 9-amino-6-(methylthio)-9H-purine (1) with some carbonyl compounds followed by hydride reduction of the azomethine linkage in the intermediates leads to the 2-pyrrolylmethyl (8), 2,3,4-trihydroxybutyl (10), and the 1,5-dihydroxy-2- and 3-pentyl (11 and 12) compounds. A 4-hydroxybutyl derivative (13) was obtained by alkylation of 18, the 9-acetyl derivative of 1, with 4-chlorobutyl acetate followed by saponification. The cyclization of 13 and 11 with a sulfonyl chloride gave the 9-pyrrolidin-1-yl (27) and the 9-[2-(tosyloxymethyl)pyrrolidin-1-yl] (28), respectively. Acylation of 1 with ethyl L-2-pyrrolidine-5-carboxylate and ethyl 1-methyl-5-pyrrolidone-3-carboxylate, respectively, in Me2SO containing NaH gave the corresponding amides 15 and 17. Alkylation of 18 with 1-bromo-2-chloroethane and epichlorohydrin gave the N-(2-chloroethyl) and N-(1,2-epoxy-3-propyl) derivatives 19 and 20. The chloro group of the chlorobutyl derivative of 18 was displaced with KSCN and NaN3, respectively, to give the thiocyanate and azido derivatives 23 and 24. Hydrogenation of the latter gave the amine (25), which was acylated with ethyl chloroformate to give the (ethoxycarbonyl)amino compound 26. None of these compounds showed activity against L1210 leukemia cells implanted ip in mice on a single-dose schedule, suggesting that the activity observed in the simpler 9-aminopurines resulted from cleavage of the hydrazino linkage to give pH-purine-6(1H)-thione.

Octa- and nonanuclear nickel(II) polyoxometalate clusters: synthesis and electrochemical and magnetic characterizations.

PubMed

Pichon, Céline; Mialane, Pierre; Dolbecq, Anne; Marrot, Jérôme; Rivière, Eric; Bassil, Bassem S; Kortz, Ulrich; Keita, Bineta; Nadjo, Louis; Sécheresse, Francis

2008-12-01

Three high-nuclearity NiII-substituted polyoxometalate compounds functionalized by exogenous ligands have been synthesized and characterized. The octanuclear complexes in Na15[Na{(A-R-SiW9O34)Ni4(CH3COO)3(OH)3}2] . 4NaCl . 36H2O (1) and Na15[Na{(A-R-SiW9O34)Ni4(CH3COO)3(OH)2(N3)}2] . 32H2O (2) can be described as two {Ni4} subunits connected via a {Na(CH3COO)6} group, with the acetato ligands also ensuring in each subunit the connection between the paramagnetic centers. In 2, two azido groups replace two of the six mu-hydroxo ligands present in 1. The nonanuclear complex K7Na7[(A-R-SiW9O34)2Ni9(OH)6(H2O)6(CO3)3] . 42H2O (3) exhibits a double cubanestructure with two [(A-R-SiW9O34)Ni4(OH)3]5- subunits linked by three carbonato ligands. A ninth NiII center connected to one subunit via a carbonato ligand and a O=W group completes this asymmetric polyoxometalate.Electronic spectroscopy and electrochemical studies indicate that, while compounds 1-3 decompose in a pure aqueous medium, these complexes are very stable in a pH 6 acetate medium. The cyclic voltammetry pattern of each complex is constituted by a first eight-electron reduction wave followed by a second large-current intensity wave. The characteristics of the first waves of the complexes are clearly distinct from those obtained for their lacunary precursor [A-R-SiW9O34]10-, a feature that is due to the Ni centers in the complexes. Such observations of electroactive, stable, and highly nickel-rich polyoxometalates are not common. Measurements of the magnetic susceptibility revealed the occurrence of concomitant ferromagnetic and antiferromagnetic interactions in 1 and 3.For both of these compounds, the extension of the magnetic exchange has been determined by means of a spin Hamiltonian with three and four J constants, respectively.

High-yield cell-free synthesis of human EGFR by IRES-mediated protein translation in a continuous exchange cell-free reaction format

PubMed Central

Quast, Robert B.; Sonnabend, Andrei; Stech, Marlitt; Wüstenhagen, Doreen A.; Kubick, Stefan

2016-01-01

Cell-free protein synthesis systems derived from eukaryotic sources often provide comparatively low amounts of several μg per ml of de novo synthesized membrane protein. In order to overcome this, we herein demonstrate the high-yield cell-free synthesis of the human EGFR in a microsome-containing system derived from cultured Sf21 cells. Yields were increased more than 100-fold to more than 285 μg/ml by combination of IRES-mediated protein translation with a continuous exchange cell-free reaction format that allowed for prolonged reaction lifetimes exceeding 24 hours. In addition, an orthogonal cell-free translation system is presented that enabled the site-directed incorporation of p-Azido-L-phenylalanine by amber suppression. Functionality of cell-free synthesized receptor molecules is demonstrated by investigation of autophosphorylation activity in the absence of ligand and interaction with the cell-free synthesized adapter molecule Grb2. PMID:27456041

Calorimetric and spectroscopic studies of the interaction between zidovudine and human serum albumin

NASA Astrophysics Data System (ADS)

Pîrnău, Adrian; Mic, Mihaela; Neamţu, Silvia; Floare, Călin G.; Bogdan, Mircea

2018-02-01

A quantitative analysis of the interaction between zidovudine (AZT) and human serum albumin (HSA) was achieved using Isothermal titration calorimetry (ITC) in combination with fluorescence and 1H NMR spectroscopy. ITC directly measure the heat during a biomolecular binding event and gave us thermodynamic parameters and the characteristic association constant. By fluorescence quenching, the binding parameters of AZT-HSA interaction was determined and location to binding site I of HSA was confirmed. Via T1 NMR selective relaxation time measurements the drug-protein binding extent was evaluated as dissociation constants Kd and the involvement of azido moiety of zidovudine in molecular complex formation was put in evidence. All three methods indicated a very weak binding interaction. The association constant determined by ITC (3.58 × 102 M- 1) is supported by fluorescence quenching data (2.74 × 102 M- 1). The thermodynamic signature indicates that at least hydrophobic and electrostatic type interactions played a main role in the binding process.

"Click" star-shaped and dendritic PEGylated gold nanoparticle-carborane assemblies.

PubMed

Li, Na; Zhao, Pengxiang; Salmon, Lionel; Ruiz, Jaime; Zabawa, Mark; Hosmane, Narayan S; Astruc, Didier

2013-10-07

Carboranes that have a high boron content are key materials for boron neutron capture therapy (BNCT), while PEGylated gold nanoparticles (AuNPs) are also most useful in various aspects of nanomedicine including photothermotherapy, imaging and drug vectorization. Therefore, methods to assemble these key components have been investigated for the first time. Strategies and results are delineated in this article, and the nanomaterials have been characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), UV-vis., mass and multinuclear NMR data. A series of well-defined water-soluble bifunctional AuNPs containing carborane and polyethylene glycol (PEG) were synthesized through either two-step Cu(I)-catalyzed azide-alkyne cycloaddition CuAAC ("click") reactions at the periphery of azido-terminated AuNPs in the presence of the efficient catalyst [Cu(I)tren(CH2Ph)6][Br] or simply by direct stabilization of AuNPs using a tris-carborane thiol dendron or a hybrid dendron containing both PEG and carborane.

The Ligand Binding Region of the Sigma-1 Receptor: Studies Utilizing Photoaffinity Probes, Sphingosine and N-Alkylamines

PubMed Central

Ruoho, Arnold E.; Chu, Uyen B.; Ramachandran, Subramaniam; Fontanilla, Dominique; Mavlyutov, Timur; Hajipour, Abdol R.

2015-01-01

The sigma-1 receptor is a 26 kDa endoplasmic reticulum resident membrane protein that has been shown to have chaperone activity in addition to its promiscuous binding to pharmacological agents. Ligand binding domain(s) of the sigma-1 receptor have been identified using the E. coli expressed and purified receptor protein and novel radioiodinated azido photoaffinity probes followed by pro-teolytic and chemical cleavage strategies. The outcome of these experiments indicates that the sigma-1 receptor ligand binding regions are formed primarily by juxtaposition of its second and third hydrophobic domains, regions where the protein shares considerable homology with the fungal enzyme, sterol isomerase that is essential for the biosynthesis of ergosterol. Data indicate that these hydrophobic steroid binding domain like (SBDL) regions on the sigma-1 receptor are likely to interact selectively with N-alkyl amines such as the endogenous sphingolipids and with synthetic N-alkylamines and N-aralkylamines derivatives. A proposed model for the sigma-1 receptor is presented. PMID:22288412

Immunoregulatory effects of covalent antigen-antibody complexes. III. Enhancement or suppression depending on the time of administration of complex relative to a T-independent antigen.

PubMed Central

Tite, J P; Morrison, C A; Taylor, R B

1981-01-01

The photosensitive affinity label NAP (4-azido-2-nitrophenyl) was used to make a stable covalent-bonded monomeric immune complex (Ag2Ab) between rabbit anti-NAP antibody and a bihaptenic compound containing NAP linked to fluorescein (NAP-aminocaproyl-lysyl-Fl). This complex injected into mice had marked effects on their subsequent response to fluorescein coupled to a thymus-independent carrier (Fl-ficoll). Depending on the time at which the complex was administered relative to challenge, it was possible to obtain either enhancing or suppressive effects. The enhancing but not the suppressive effect of complex was dependent on immune recognition of the rabbit IgG carrier. While the suppressive effect probably results from complex-mediated inactivation of T-independent B cells, it is suggested that the enhancing effect results from priming of the T-dependent B cells by Fl-Ficoll followed by their triggering into antibody production by rabbit IgG-specific helper cells. PMID:7007223

Sensitive, Site-Specific, and Stable Vibrational Probe of Local Protein Environments: 4-Azidomethyl-L-Phenylalanine

PubMed Central

Bazewicz, Christopher G.; Liskov, Melanie T.; Hines, Kevin J.; Brewer, Scott H.

2013-01-01

We have synthesized the unnatural amino acid (UAA), 4-azidomethyl-Lphenylalanine (pN3CH2Phe), to serve as an effective vibrational reporter of local protein environments. The position, extinction coefficient, and sensitivity to local environment of the azide asymmetric stretch vibration of pN3CH2Phe are compared to the vibrational reporters: 4-cyano-L-phenylalanine (pCNPhe) and 4-azido-L-phenylalanine (pN3Phe). This UAA was genetically incorporated in a site-specific manner utilizing an engineered, orthogonal aminoacyl-tRNA synthetase in response to an amber codon with high efficiency and fidelity into two distinct sites in superfolder green fluorescent protein (sfGFP). This allowed for the dependence of the azide asymmetric stretch vibration of pN3CH2Phe to different protein environments to be measured. The photo-stability of pN3CH2Phe was also measured relative to the photoreactive UAA, pN3Phe. PMID:23865850

ZnO Nanorods Based Enzymatic Biosensor for Selective Determination of Penicillin

PubMed Central

Ibupoto, Zafar Hussain; Ali, Syed Muhammad Usman; Khun, Kimleang; Chey, Chan Oeurn; Nur, Omer; Willander, Magnus

2011-01-01

In this study, we have successfully demonstrated the fabrication of a biosensor based on well aligned single-crystal zinc oxide (ZnO) nanorods which were grown on gold coated glass substrate using a low temperature aqueous chemical growth (ACG) method. The ZnO nanorods were immobilized with penicillinase enzyme using the physical adsorption approach in combination with N-5-azido-2-nitrobenzoyloxysuccinimide (ANB-NOS) as cross linking molecules. The potentiometric response of the sensor configuration revealed good linearity over a large logarithmic concentration range from 100 µM to 100 mM. During the investigations, the proposed sensor showed a good stability with high sensitivity of ~121 mV/decade for sensing of penicillin. A quick electrochemical response of less than 5 s with a good selectivity, repeatability, reproducibility and a negligible response to common interferents such as Na1+, K1+, d-glucose, l-glucose, ascorbic acid, uric acid, urea, sucrose, lactose, glycine, penicilloic acid and cephalosporins, was observed. PMID:25585565

ZnO Nanorods Based Enzymatic Biosensor for Selective Determination of Penicillin.

PubMed

Ibupoto, Zafar Hussain; Ali, Syed Muhammad Usman; Khun, Kimleang; Chey, Chan Oeurn; Nur, Omer; Willander, Magnus

2011-10-27

In this study, we have successfully demonstrated the fabrication of a biosensor based on well aligned single-crystal zinc oxide (ZnO) nanorods which were grown on gold coated glass substrate using a low temperature aqueous chemical growth (ACG) method. The ZnO nanorods were immobilized with penicillinase enzyme using the physical adsorption approach in combination with N-5-azido-2-nitrobenzoyloxysuccinimide (ANB-NOS) as cross linking molecules. The potentiometric response of the sensor configuration revealed good linearity over a large logarithmic concentration range from 100 µM to 100 mM. During the investigations, the proposed sensor showed a good stability with high sensitivity of ~121 mV/decade for sensing of penicillin. A quick electrochemical response of less than 5 s with a good selectivity, repeatability, reproducibility and a negligible response to common interferents such as Na1+, K1+, d-glucose, l-glucose, ascorbic acid, uric acid, urea, sucrose, lactose, glycine, penicilloic acid and cephalosporins, was observed.

Synthesis of avibactam derivatives and activity on β-lactamases and peptidoglycan biosynthesis enzymes of mycobacteria.

PubMed

Edoo, Zainab; Iannazzo, Laura; Compain, Fabrice; Li de la Sierra Gallay, Inès; van Tilbeurgh, Herman; Fonvielle, Matthieu; Bouchet, Flavie; Le Run, Eva; Mainardi, Jean-Luc; Arthur, Michel; Ethève-Quelquejeu, Mélanie; Hugonnet, Jean-Emmanuel

2018-03-30

There is a renewed interest for β-lactams for treating infections due to Mycobacterium tuberculosis and M. abscessus since their β-lactamases are inhibited by classical (clavulanate) or new generation (avibactam) inhibitors, respectively. Here, we report access to an azido derivative of the diazabicyclooctane (DBO) scaffold of avibactam for functionalization by the Huisgen-Sharpless cycloaddition reaction. The amoxicillin-DBO combinations were active indicating that the triazole ring is compatible with drug penetration (minimal inhibitory concentration of 16 µg/ml for both species). Mechanistically, β-lactamase inhibition was not sufficient to account for the potentiation of amoxicillin by DBOs. Thus, we investigated the latter compounds as inhibitors of L,D-transpeptidases (LDTs), which are the main peptidoglycan polymerases in mycobacteria. The DBOs acted as slow-binding inhibitors of LDTs by S-carbamoylation indicating that optimization of DBOs for LDT inhibition is an attractive strategy to obtain drugs selectively active on mycobacteria. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Alkyne- and 1,6-elimination- succinimidyl carbonate - terminated heterobifunctional poly(ethylene glycol) for reversible "Click" PEGylation.

PubMed

Xie, Yumei; Duan, Shaofeng; Forrest, M Laird

2010-01-01

A new heterobifunctional (succinimidyl carbonate, SC)-activated poly(ethylene glycol) (PEG) with a reversible 1,6-elimination linker and a terminal alkyne for "click" chemistry was synthesized with high efficiency and low polydispersity. The α-alkyne-ω-hydroxyl PEG was first prepared using trimethylsilyl-2-propargyl alcohol as an initiator for ring-opening polymerization of ethylene oxide followed by mild deprotection with tetrabutylammonium fluoride. The hydroxy end was then modified with diglycolic anhydride to generate α-alkyne-ω-carboxylic acid PEG. The reversible 1, 6-elimination linker was introduced by conjugation of a hydroxymethyl phenol followed by activation with N,N'-disuccinimidyl carbonate to generate the heterobifunctional α-alkyne-ω-SC PEG. The terminal alkyne is available for "click" conjugation to azido ligands via 1,3-dipolar cycloaddition, and the succinimidyl carbonate will form a reversible conjugate to amines (e.g. in proteins) that can release the unaltered amine after base or enzyme catalyzed cleavage of the 1,6-linker.

A series of uranium (IV, V, VI) tritylimido complexes, their molecular and electronic structures and reactivity with CO2.

PubMed

Schmidt, Anna-Corina; Heinemann, Frank W; Maron, Laurent; Meyer, Karsten

2014-12-15

A series of uranium tritylimido complexes with structural continuity across complexes in different oxidation states, namely U(IV), U(V), and U(VI), is reported. This series was successfully synthesized by employing the trivalent uranium precursor, [(((nP,Me)ArO)3tacn)U(III)] (1) (where ((nP,Me)ArO)3tacn(3-) = trianion of 1,4,7-tris(2-hydroxy-5-methyl-3-neopentylbenzyl)-1,4,7-triazacyclononane), with the organic azides Me3SiN3, Me3SnN3, and Ph3CN3 (tritylazide). While the reaction with Me3SiN3 yields an inseparable mixture of both the azido and imido uranium complexes, applying the heavier Sn homologue yields the bis-μ-azido complex [{(((nP,Me)ArO)3tacn)U(IV)}2(μ-N3)2] (2) exclusively. In contrast to this one-electron redox chemistry, the reaction of precursor 1 with tritylazide solely leads to the two-electron oxidized U(V) imido [(((nP,Me)ArO)3tacn)U(V)(N-CPh3)] (3). Oxidation and reduction of 3 yield the corresponding U(VI) and U(IV) complexes [(((nP,Me)ArO)3tacn)U(VI)(N-CPh3)][B(C6F5)4] (4) and K[(((nP,Me)ArO)3tacn)U(IV)(N-CPh3)] (5), respectively. In addition, the U(V) imido 3 engages in a H atom abstraction reaction with toluene to yield the closely related amido complex [(((nP,Me)ArO)3tacn)U(IV)(N(H)-CPh3)] (6). Complex 6 and the three tritylimido complexes 3, 4, and 5, with oxidation states ranging from +IV to +VI and homologous core structures, were investigated by X-ray diffraction analyses and magnetochemical and spectroscopic studies as well as density functional theory (DFT) computational analysis. The series of structurally very similar imido complexes provides a unique opportunity to study electronic properties and to probe the uranium imido reactivity solely as a function of electron count of the metal-imido entity. Evidence for the U-N bond covalency and f-orbital participation in complexes 3-6 was drawn from the in-depth and comparative DFT study. The reactivity of the imido and amido complexes with CO2 was probed, and conclusions about the influence of the formal oxidation state are reported.

Nonlinear dynamics in the perceptual grouping of connected surfaces.

PubMed

Hock, Howard S; Schöner, Gregor

2016-09-01

Evidence obtained using the dynamic grouping method has shown that the grouping of an object's connected surfaces has properties characteristic of a nonlinear dynamical system. When a surface's luminance changes, one of its boundaries is perceived moving across the surface. The direction of this dynamic grouping (DG) motion indicates which of two flanking surfaces has been grouped with the changing surface. A quantitative measure of overall grouping strength (affinity) for adjacent surfaces is provided by the frequency of DG motion perception in directions promoted by the grouping variables. It was found that: (1) variables affecting surface grouping for three-surface objects evolve over time, settling at stable levels within a single fixation, (2) how often DG motion is perceived when a surface's luminance is perturbed (changed) depends on the pre-perturbation affinity state of the surface grouping, (3) grouping variables promoting the same surface grouping combine cooperatively and nonlinearly (super-additively) in determining the surface grouping's affinity, (4) different DG motion directions during different trials indicate that surface grouping can be bistable, which implies that inhibitory interactions have stabilized one of two alternative surface groupings, and (5) when alternative surface groupings have identical affinity, stochastic fluctuations can break the symmetry and inhibitory interactions can then stabilize one of the surface groupings, providing affinity levels are not too high (which results in bidirectional DG motion). A surface-grouping network is proposed within which boundaries vary in salience. Low salience or suppressed boundaries instantiate surface grouping, and DG motion results from changes in boundary salience. Copyright © 2015 Elsevier Ltd. All rights reserved.

Highly K+ -Selective Fluorescent Probes for Lifetime Sensing of K+ in Living Cells.

PubMed

Schwarze, Thomas; Mertens, Monique; Müller, Peter; Riemer, Janine; Wessig, Pablo; Holdt, Hans-Jürgen

2017-12-06

The new K + -selective fluorescent probes 1 and 2 were obtained by Cu I -catalyzed 1,3-dipolar azide alkyne cycloaddition (CuAAC) reactions of an alkyne-substituted [1,3]dioxolo[4,5-f][1,3]benzodioxole (DBD) ester fluorophore with azido-functionalized N-phenylaza-18-crown-6 ether and N-(o-isopropoxy) phenylaza-18-crown-6 ether, respectively. Probes 1 and 2 allow the detection of K + in the presence of Na + in water by fluorescence enhancement (2.2 for 1 at 2000 mm K + and 2.5 for 2 at 160 mm K + ). Fluorescence lifetime measurements in the absence and presence of K + revealed bi-exponential decay kinetics with similar lifetimes, however with different proportions changing the averaged fluorescence decay times (τ f(av) ). For 1 a decrease of τ f(av) from 12.4 to 9.3 ns and for 2 an increase from 17.8 to 21.8 ns was observed. Variation of the substituent in ortho position of the aniline unit of the N-phenylaza-18-crown-6 host permits the modulation of the K d value for a certain K + concentration. For example, substitution of H in 1 by the isopropoxy group (2) decreased the K d value from >300 mm to 10 mm. 2 was chosen for studying the efflux of K + from human red blood cells (RBC). Upon addition of the Ca 2+ ionophor ionomycin to a RBC suspension in a buffer containing Ca 2+ , the fluorescence of 2 slightly rose within 10 min, however, after 120 min a significant increase was observed. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polyphosphoester-Camptothecin Prodrug with Reduction-Response Prepared via Michael Addition Polymerization and Click Reaction.

PubMed

Du, Xueqiong; Sun, Yue; Zhang, Mingzu; He, Jinlin; Ni, Peihong

2017-04-26

Polyphosphoesters (PPEs), as potential candidates for biocompatible and biodegradable polymers, play an important role in material science. Various synthetic methods have been employed in the preparation of PPEs such as polycondensation, polyaddition, ring-opening polymerization, and olefin metathesis polymerization. In this study, a series of linear PPEs has been prepared via one-step Michael addition polymerization. Subsequently, camptothecin (CPT) derivatives containing disulfide bonds and azido groups were linked onto the side chain of the PPE through Cu(I)-catalyzed azidealkyne cyclo-addition "click" chemistry to yield a reduction-responsive polymeric prodrug P(EAEP-PPA)-g-ss-CPT. The chemical structures were characterized by nuclear magnetic resonance spectroscopy, gel permeation chromatography, Fourier transform infrared, ultraviolet-visible spectrophotometer, and high performance liquid chromatograph analyses, respectively. The amphiphilic prodrug could self-assemble into micelles in aqueous solution. The average particle size and morphology of the prodrug micelles were measured by dynamic light scattering and transmission electron microscopy, respectively. The results of size change under different conditions indicate that the micelles possess a favorable stability in physiological conditions and can be degraded in reductive medium. Moreover, the studies of in vitro drug release behavior confirm the reduction-responsive degradation of the prodrug micelles. A methyl thiazolyl tetrazolium assay verifies the good biocompatibility of P(EAEP-PPA) not only for normal cells, but also for tumor cells. The results of cytotoxicity and the intracellular uptake about prodrug micelles further demonstrate that the prodrug micelles can efficiently release CPT into 4T1 or HepG2 cells to inhibit the cell proliferation. All these results show that the polyphosphoester-based prodrug can be used for triggered drug delivery system in cancer treatment.

Controlling surface-segregation of a polymer to display carboxy groups on an outermost surface using perfluoroacyl groups.

PubMed

Nishimori, Keisuke; Kitahata, Shigeru; Nishino, Takashi; Maruyama, Tatsuo

2018-05-10

Controlling the surface properties of solid polymers is important for practical applications. We here succeeded in controlling the surface segregation of polymers to display carboxy groups on an outermost surface, which allowed the covalent immobilization of functional molecules via the carboxy groups on a substrate surface. Random methacrylate-based copolymers containing carboxy groups, in which carboxy groups were protected with perfluoroacyl (Rf) groups, were dip-coated on acrylic substrate surfaces. X-ray photoelectron spectroscopy and contact-angle measurements revealed that the Rf groups were segregated to the outermost surface of the dip-coated substrates. The Rf groups were removed by hydrolysis of the Rf esters in the copolymers, resulting in the display of carboxy groups on the surface. The quantification of carboxy groups on a surface revealed that the carboxy groups were reactive to a water-soluble solute in aqueous solution. The surface segregation was affected by the molecular structure of the copolymer used for dip-coating.

Susceptibility Testing by Polymerase Chain Reaction DNA Quantitation: A Method to Measure Drug Resistance of Human Immunodeficiency Virus Type 1 Isolates

NASA Astrophysics Data System (ADS)

Eron, Joseph J.; Gorczyca, Paul; Kaplan, Joan C.; D'Aquila, Richard T.

1992-04-01

Polymerase chain reaction (PCR) DNA quantitation (PDQ) susceptibility testing rapidly and directly measures nucleoside sensitivity of human immunodeficiency virus type 1 (HIV-1) isolates. PCR is used to quantitate the amount of HIV-1 DNA synthesized after in vitro infection of peripheral blood mononuclear cells. The relative amounts of HIV-1 DNA in cell lysates from cultures maintained at different drug concentrations reflect drug inhibition of virus replication. The results of PDQ susceptibility testing of 2- or 3-day cultures are supported by assays measuring HIV-1 p24 antigen production in supernatants of 7- or 10-day cultures. DNA sequence analyses to identify mutations in the reverse transcriptase gene that cause resistance to 3'-azido-3'-deoxythymidine also support the PDQ results. With the PDQ method, both infectivity titration and susceptibility testing can be performed on supernatants from primary cultures of peripheral blood mononuclear cells. PDQ susceptibility testing should facilitate epidemiologic studies of the clinical significance of drug-resistant HIV-1 isolates.

Molecular cloning and functional expression of the guinea pig alpha(1a)-adrenoceptor.

PubMed

González-Espinosa, C; Romero-Avila, M T; Mora-Rodríguez, D M; González-Espinosa, D; García-Sáinz, J A

2001-08-31

In the present paper, the cloning and expression of the guinea pig alpha(1A)-adrenoceptor is presented. The nucleotide sequence had an open reading frame of 1401 bp that encoded a 466 amino-acid protein with an estimated molecular mass of approximately 51.5 kDa. When the clone was expressed in Cos-1 cells, specific high-affinity binding of [(3)H]prazosin and [(3)H]tamsulosin was observed. Chloroethylclonidine treatment of membranes slightly decreased the total binding with both radioligands. Binding competition experiments using [(3)H]tamsulosin showed the following potency order: (a) for agonists: oxymetazoline >epinephrine>norepinephrine>methoxamine, and (b) for antagonists: prazosin> or 5-methyl-urapidil=benoxathian>phentolamine>BMY 7378 (8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4,5]decane-7,9-dione). Photoaffinity labeling using [(125)I-aryl]azido-prazosin revealed a major broad band with a molecular mass between 70 and 80 kDa. The receptor was functional, as evidenced by an epinephrine-increased production of [(3)H]inositol phosphates that was blocked by prazosin.

Induction of a melanoma-specific antibody response by a monovalent, but not a divalent, synthetic GM2 neoglycopeptide.

PubMed

Bay, S; Fort, S; Birikaki, L; Ganneau, C; Samain, E; Coïc, Y-M; Bonhomme, F; Dériaud, E; Leclerc, C; Lo-Man, R

2009-04-01

The GM2 ganglioside represents an important target for specific anticancer immunotherapy. We designed and synthesized a neoglycopeptide immunogen displaying one or two copies of the GM2 tetrasaccharidic moiety. These glycopeptides were prepared using the Huisgen cycloaddition, which enables the efficient ligation of the alkyne-functionalized biosynthesized GM2 with an azido CD4(+) T cell epitope peptide. It is worth noting that the GM2 can be produced on a gram scale in bacteria, which can be advantageous for a scale-up of the process. We show here for the first time that a fully synthetic glycopeptide, which is based on a ganglioside carbohydrate moiety, can induce human tumor cell-specific antibodies after immunization in mice. Interestingly, the monovalent, but not the divalent, form of GM2 peptide construct induced antimelanoma antibodies. Unlike traditional vaccines, this vaccine is a pure chemically-defined entity, a key quality for consistent studies and safe clinical evaluation. Therefore, such carbohydrate-peptide conjugate represents a promising cancer vaccine strategy for active immunotherapy targeting gangliosides.

Azide/alkyne-"click"-reactions of encapsulated reagents: toward self-healing materials.

PubMed

Gragert, Maria; Schunack, Marlen; Binder, Wolfgang H

2011-03-02

The successful encapsulation of reactive components for the azide/alkyne-"click"-reaction is reported featuring for the first time the use of a liquid polymer as reactive component. A liquid, azido-telechelic three-arm star poly(isobutylene) (M(n) = 3900 g · mol⁻¹) as well as trivalent alkynes were encapsulated into micron-sized capsules and embedded into a polymer-matrix (high-molecular weight poly(isobutylene), M(n) = 250,000 g · mol⁻¹). Using (Cu(I)Br(PPh₃)₃) as catalyst for the azide/alkyne-"click"-reaction, crosslinking of the two components at 40 °C is observed within 380 min and as fast as 10 min at 80 °C. Significant recovery of the tensile storage modulus was observed in a material containing 10 wt.-% and accordingly 5 wt.-% capsules including the reactive components within 5 d at room temperature, thus proving a new concept for materials with self-healing properties. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multiple Click-Selective tRNA Synthetases Expand Mammalian Cell-Specific Proteomics.

PubMed

Yang, Andrew C; du Bois, Haley; Olsson, Niclas; Gate, David; Lehallier, Benoit; Berdnik, Daniela; Brewer, Kyle D; Bertozzi, Carolyn R; Elias, Joshua E; Wyss-Coray, Tony

2018-06-13

Bioorthogonal tools enable cell-type-specific proteomics, a prerequisite to understanding biological processes in multicellular organisms. Here we report two engineered aminoacyl-tRNA synthetases for mammalian bioorthogonal labeling: a tyrosyl ( ScTyr Y43G ) and a phenylalanyl ( MmPhe T413G ) tRNA synthetase that incorporate azide-bearing noncanonical amino acids specifically into the nascent proteomes of host cells. Azide-labeled proteins are chemoselectively tagged via azide-alkyne cycloadditions with fluorophores for imaging or affinity resins for mass spectrometric characterization. Both mutant synthetases label human, hamster, and mouse cell line proteins and selectively activate their azido-bearing amino acids over 10-fold above the canonical. ScTyr Y43G and MmPhe T413G label overlapping but distinct proteomes in human cell lines, with broader proteome coverage upon their coexpression. In mice, ScTyr Y43G and MmPhe T413G label the melanoma tumor proteome and plasma secretome. This work furnishes new tools for mammalian residue-specific bioorthogonal chemistry, and enables more robust and comprehensive cell-type-specific proteomics in live mammals.

Synthesis of novel 13α-18-norandrostane-ferrocene conjugates via homogeneous catalytic methods and their investigation on TRPV1 receptor activation.

PubMed

Szánti-Pintér, Eszter; Wouters, Johan; Gömöry, Ágnes; Sághy, Éva; Szőke, Éva; Helyes, Zsuzsanna; Kollár, László; Skoda-Földes, Rita

2015-12-01

13α-Steroid-ferrocene derivatives were synthesized via two reaction pathways starting from an unnatural 16-keto-18-nor-13α-steroid. The unnatural steroid was converted to ferrocene derivatives via copper-catalyzed azide-alkyne cycloaddition or palladium-catalyzed aminocarbonylation. 16-Azido- and 16-N-(prop-2-ynyl)-carboxamido-steroids were synthesized as starting materials for azide-alkyne cycloaddition with the appropriate ferrocene derivatives. Based on our earlier work, aminocarbonylation of 16-iodo-16-ene and 16-iodo-15-ene derivatives was studied with ferrocenylmethylamine. The new products were obtained in moderate to good yields and were characterized by (1)H and (13)C NMR, IR and MS. The solid state structure of the starting material 13α-18-norandrostan-16-one and two carboxamide products were determined by X-ray crystallography. Evidences were provided that the N-propargyl-carboxamide compound as well as its ferrocenylmethyltriazole derivative are able to decrease the activation of TRPV1 receptor on TRG neurons. Copyright © 2015 Elsevier Inc. All rights reserved.

Stability and reactivity of 2-nitrosoamino-3,8-dimethylimidazo[4,5-f]quinoxaline.

PubMed

Lakshmi, Vijaya M; Hsu, Fong Fu; Schut, Herman A J; Zenser, Terry V

2006-02-01

2-Nitrosoamino-3,8-dimethylimidazo[4,5-f]quinoxaline (N-NO-MeIQx) is a nitrosation product of the food carcinogen 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and is proposed to form in vivo under inflammatory conditions. This study evaluated the stability and reactivity of N-NO-MeIQx to assess its possible role in the initiation of colon cancer by MeIQx. 14C-N-NO-MeIQx (4 microM) was incubated for 4 h over a range of pH values, and its stability was monitored by HPLC. At pH values from pH 7.4 to 9.0, N-NO-MeIQx was very stable with no detectable change observed. Glutathione (1 mM) did not alter stability at pH 7.4. As the pH decreased, this nitrosamine was less stable with only 48 +/- 1% remaining at pH 5.5 and none remaining at pH 3.5 or 2.0. Major products identified by electrospray ionization mass spectrometry were 3,8-dimethylimidazo[4,5-f]quinoxaline and 2-hydroxy-3,8-dimethylimidazo[4,5-f]quinoxaline. MeIQx was a minor product. At pH 2.0, the t(1/2) for N-NO-MeIQx was reduced from 2.1 +/- 0.2 to 1.2 +/- 0.1 min with 10 mM NaN3. This effect of azide was due to the formation of 2-azido-MeIQx. The binding of 14C-N-NO-MeIQx to DNA increased with decreasing pH. The 10-fold increase in binding observed at pH 2.0 as compared to pH 5.5 was completely inhibited by 10 mM NaN3 due to 2-azido-MeIQx formation. The reactivity of N-NO-MeIQx was compared to N-OH-MeIQx by evaluating adduct formation with 2'-deoxyguanosine 3'-monophosphate (dGp) by 32P-postlabeling. N-OH-MeIQx formed a single major adduct, N-(deoxyguanosin-8-yl)-MeIQx (dG-C8-MeIQx). Incubation of N-NO-MeIQx under inflammatory conditions (pH 5.5 +/- HOCl) produced dG-C8-MeIQx along with 4-6 other adducts. dG-C8-MeIQx formation increased in the presence of HOCl. Liver from a MeIQx-treated mouse contained dG-C8-MeIQx and two other adducts detected with N-NO-MeIQx but not N-OH-MeIQx. These results suggest that N-NO-MeIQx could be genotoxic, is activated by conditions that mediate inflammatory responses, and is a possible cancer risk factor for individuals with inflammation of the colon.

Stability and Reactivity of 2-Nitrosoamino-3,8-dimethylimidazo[4,5-f]quinoxaline

PubMed Central

Lakshmi, Vijaya M.; Hsu, Fong Fu; Schut, Herman A. J.; Zenser, Terry V.

2008-01-01

2-Nitrosoamino-3,8-dimethylimidazo[4,5-f]quinoxaline (N-NO-MeIQx) is a nitrosation product of the food carcinogen 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and proposed to form in vivo under inflammatory conditions. This study evaluated the stability and reactivity of N-NO-MeIQx to assess its possible role in initiation of colon cancer by MeIQx. 14C-N-NO-MeIQx (4 μM) was incubated for 4 hours over a range of pH values and its stability monitored by HPLC. At pH values from pH 7.4 to 9.0, N-NO-MeIQx was very stable with no detectable change observed. Glutathione (1 mM) did not alter stability at pH 7.4. As pH decreased, this nitrosamine was less stable with only 48 ± 1 % remaining at pH 5.5 and none remaining at pH 3.5 or 2.0. Major products identified by electrospray ionization mass spectrometry were 3,8-dimethylimidazo[4,5-f]quinoxaline and 2-hydroxy-3,8-dimethylimidazo[4,5-f]quinoxaline. MeIQx was a minor product. At pH 2.0, the t1/2 for N-NO-MeIQx was reduced from 2.1 ± 0.2 to 1.2 ± 0.1 min with 10 mM NaN3. This effect of azide was due to formation of 2-azido-MeIQx. The binding of 14C-N-NO-MeIQx to DNA increased with decreasing pH. The 10-fold increase in binding observed at pH 2.0 compared to pH 5.5 was completely inhibited by 10 mM NaN3 due to 2-azido-MeIQx formation. The reactivity of N-NO-MeIQx was compared to N-OH-MeIQx by evaluating adduct formation with 2′-deoxyguanosine 3′-monophosphate (dGp) by 32P-postlabeling. N-OH-MeIQx formed a single major adduct, N-(deoxyguanosin-8-yl)-MeIQx (dG-C8-MeIQx). Incubation of N-NO-MeIQx under inflammatory conditions (pH 5.5 ± HOCl) produced dG-C8-MeIQx along with 4 to 6 other adducts. dG-C8-MeIQx formation increased in the presence of HOCl. Liver from a MeIQx-treated mouse contained dG-C8-MeIQx and two other adducts detected with N-NO-MeIQx, but not N-OH-MeIQx. These results suggest that N-NO-MeIQx could be genotoxic, is activated by conditions that mediate inflammatory responses, and is a possible cancer risk factor for individuals with inflammation of the colon. PMID:16485910

Effect of simulated chairside grinding procedures using commercially available abrasive agents on the surface properties of zirconia.

PubMed

Sandhu, Ramandeep; Kheur, Mohit; Kheur, Supriya

2017-01-01

The aim of the present study was to assess the change in physical properties (surface roughness, surface hardness and phase transformation) after surface grinding of zirconia by using three commercially available abrasives. Thirty sintered zirconia specimens were prepared and divided into three groups namely Group M (grinded using Mani Dia diamond bur standard grit), Group T (grinded using Tri Hawk diamond bur coarse grit) and Group P (grinded using Predator carbide bur). A customised assembly was used to follow a standardised protocol for surface grinding. The surface roughness, surface hardness and phase transformation was recorded before and after the grinding procedure. ANOVA and Bonferroni post hoc test were used to assess the values obtained after the testing the surface roughness and surface hardness. The results of the present study revealed the average values of change in surface roughness as Group M (0.44 μ m) and Group T (1.235 μ m) and Group P (-0.88 μ m). The average values of change in surface hardness were Group T (19.578 HV), Group M (46.722 HV) and Group P (36.429 HV). The change in surface hardness was not statistically significant. There was no phase transformation seen after the grinding procedure. Carbide burs along with copious water irrigation when used to grind zirconia intra-orally produces has a polishing effect, minimal change in hardness & no phase transformation. The present study advocates the use of carbides for chair-side grinding of zirconia.

A comparison between the shear bond strength of brackets bonded to glazed and deglazed porcelain surfaces with resin-reinforced glass-ionomer cement and a bis-GMA resin adhesive.

PubMed

Lifshitz, Abraham B; Cárdenas, Marianela

2006-01-01

This study compared the shear bond strength of a light-cure resin-reinforced glass-ionomer cement with a bis-GMA light-cure resin system in the bonding of stainless steel brackets to glazed and deglazed porcelain surfaces. Porcelain surfaces were divided into 4 groups: group 1, deglazed porcelain surfaces with Transbond XT, group 2, glazed porcelain surfaces with Transbond XT; group 3, deglazed porcelain surfaces with Fuji Ortho LC; and group 4, porcelain surfaces with Fuji Ortho LC. Microetching with 50-microm aluminum oxide for 2 seconds at a distance of 5 mm deglazed the porcelain surfaces in groups 1 and 3. All brackets were bonded to the porcelain surfaces using the same procedure and light-cured for 40 seconds with a visible light. All samples were thermocycled between 5 degrees C and 55 degrees C for 300 cycles before testing for shear bond strength with a universal testing machine. The analysis of variance showed no significant difference (P < .05) among the 4 groups; ie, group 1, 10.12 MPa; group 2, 7.00 MPa; group 3, 6.78 MPa; and group 4, 11.15 MPa. The F test also failed to demonstrate any statistical difference among the groups. Conditioning the porcelain surfaces with 37% phosphoric acid immediately followed by a nonhydrolyzed silane coupling agent resulted in clinically adequate bond strength when using either a composite resin or a resin-reinforced glass-ionomer cement. Microetching of these porcelain surfaces apparently offers no bonding advantage.

Effect of simulated chairside grinding procedures using commercially available abrasive agents on the surface properties of zirconia

PubMed Central

Sandhu, Ramandeep; Kheur, Mohit; Kheur, Supriya

2017-01-01

Aim: The aim of the present study was to assess the change in physical properties (surface roughness, surface hardness and phase transformation) after surface grinding of zirconia by using three commercially available abrasives. Materials and Methods: Thirty sintered zirconia specimens were prepared and divided into three groups namely Group M (grinded using Mani Dia diamond bur standard grit), Group T (grinded using Tri Hawk diamond bur coarse grit) and Group P (grinded using Predator carbide bur). A customised assembly was used to follow a standardised protocol for surface grinding. The surface roughness, surface hardness and phase transformation was recorded before and after the grinding procedure. Statistical Analysis Used: ANOVA and Bonferroni post hoc test were used to assess the values obtained after the testing the surface roughness and surface hardness. Results: The results of the present study revealed the average values of change in surface roughness as Group M (0.44 μm) and Group T (1.235 μm) and Group P (-0.88 μm). The average values of change in surface hardness were Group T (19.578 HV), Group M (46.722 HV) and Group P (36.429 HV). The change in surface hardness was not statistically significant. There was no phase transformation seen after the grinding procedure. Clinical Significance: Carbide burs along with copious water irrigation when used to grind zirconia intra-orally produces has a polishing effect, minimal change in hardness & no phase transformation. The present study advocates the use of carbides for chair-side grinding of zirconia. PMID:28216841

Surface restructuring behavior of various types of poly(dimethylsiloxane) in water detected by SFG.

PubMed

Chen, Chunyan; Wang, Jie; Chen, Zhan

2004-11-09

Surface structures of several different poly(dimethylsiloxane) (PDMS) materials, tetraethoxysilane-cured hydroxy-terminated PDMS (TEOS-PDMS), platinum-cured vinyl-terminated PDMS (Pt-PDMS), platinum-cured vinyl-terminated poly(diphenylsiloxane)-co-poly(dimethylsiloxane) (PDPS-co-PDMS), and PDMS-co-polystyrene (PDMS-co-PS) copolymer in air and water have been investigated by sum frequency generation (SFG) vibrational spectroscopy. The SFG spectra collected from all PDMS surfaces in both air and water are dominated by methyl group stretches, indicating that all the surfaces are mainly covered by methyl groups. Other than surface-dominating methyl groups, some -Si-CH2-CH2- moieties on the Pt-PDMS surface have also been detected in air, which are present at cross-linking points. Information about the average orientation angle and angle distribution of the methyl groups on the PDMS surface has been evaluated. Surface restructuring of the methyl groups has been observed for all PDMS surfaces in water. Upon contacting water, the methyl groups on all PDMS surfaces tilt more toward the surface. The detailed restructuring behaviors of several PDMS surfaces in water and the effects of molecular weight on restructuring behaviors have been investigated. For comparison, in addition to air and water, surface structures of PDMS materials mentioned above in a nonpolar solvent, FC-75, have also been studied. By comparing the different response of phenyl groups to water on both PDPS-co-PDMS and PS-co-PDMS surfaces, we have demonstrated how the restructuring behaviors of surface phenyl groups are affected by the structural flexibility of the molecular chains where they are attached.

SFG and AFM Studies of Polymer Surface Monolayers

NASA Astrophysics Data System (ADS)

Somorjai, Gabor A.

2003-03-01

Sum frequency generation vibrational spectroscopy and atomic force microscopy techniques were utilized to study the structure and composition of polymer surfaces ranging from polyethylene and polypropylene to copolymers of polyurethane and polystyrene. The surface methyl groups aligned perpendicular to the surface above the glass transition temperature of polypropylene. Large side groups such as the phenyl group on polystyrene is also near the surface normal at the polymer-air interface. At the air interface hydrophobic groups are dominant on the polymer surface while at solid-water interface hydrophilic groups segregate to the surface. Minimizing surface energy is the cause of readjusting the surface composition at polymer-water interfaces as compared to polymer-air interfaces. Upon stretching the soft component of two-component polymer systems segregates to the surface and both the surface structure and the surface composition undergo reversible or irreversible changes depending on the magnitude of the stretch. Since the heart beat forces bio-polymers to stretch over 40 million times a year the molecular behavior due to stretching has important physiological consequences.

Polyisobutylene chain end transformations: Block copolymer synthesis and click chemistry functionalizations

NASA Astrophysics Data System (ADS)

Magenau, Andrew Jackson David

The primary objectives of this research were twofold: (1) development of synthetic procedures for combining quasiliving carbocationic polymerization (QLCCP) of isobutylene (IB) and reversible addition fragmentation chain transfer (RAFT) polymerization for block copolymer synthesis; (2) utilization of efficient, robust, and modular chemistries for facile functionalization of polyisobutylene (PIB). In the first study block copolymers consisting of PIB, and either PMMA or PS block segments, were synthesized by a site transformation approach combining living cationic and reversible addition-fragmentation chain transfer (RAFT) polymerizations. The initial PIB block was synthesized via quasiliving cationic polymerization using the TMPCl/TiCl4 initiation system and was subsequently converted into a hydroxylterminated PIB. Site transformation of the hydroxyl-terminated PIB into a macro chain transfer agent (PIB-CTA) was accomplished by N,N'-dicyclohexylcarbodiimide/dimethylaminopyridine-catalyzed esterification with 4-cyano-4-(dodecylsulfanylthiocarbonylsulfanyl)pentanoic acid. In the second study another site transformation approach was developed to synthesize a novel block copolymer, composed of PIB and PNIPAM segments. The PIB block was prepared via quasiliving cationic polymerization and end functionalized by in-situ quenching to yield telechelic halogen-terminated PIB. Azido functionality was obtained by displacement of the terminal halogen through nucleophilic substitution, which was confirmed by both 1H and 13C NMR. Coupling of an alkyne-functional chain transfer agent (CTA) to azido PIB was successfully accomplished through a copper catalyzed click reaction. Structure of the resulting PIB-based macro-CTA was verified with 1H NMR, FTIR, and GPC; whereas coupling reaction kinetics were monitored by real time variable temperature (VT) 1H NMR. In a third study, a click chemistry functionalization procedure was developed based upon the azide-alkyne 1,3-dipolar cycloaddition reaction. 1-(o-Azidoalkyl)pyrrolyl-terminated PIB was successfully synthesized both by substitution of the terminal halide of 1-(o-haloalkyl)pyrrolyl-terminated PIB with sodium azide and by in situ quenching of quasiliving PIB with a 1-(o-azidoalkyl)pyrrole. GPC indicated the absence of coupled PIB under optimized conditions, confirming exclusive mono-substitution on each pyrrole ring. In a fourth study, radical thiol-ene hydrothiolation "Click" chemistry was explored and adapted to easily and rapidly modify exo -olefin PIB with an array of thiol compounds bearing useful functionalities, including primary halogen, primary amine, primary hydroxyl, and carboxylic acid. The thiol-ene "click" procedure was shown to be applicable to both mono and difunctional exo-olefin polyisobutylene. Telechelic mono- and difunctional exo-olefin PIBs were synthesized via quasiliving cationic polymerization followed by quenching with the hindered amine, 1,2,2,6,6-pentamethylpiperidine. Lower reaction temperatures were found to increase exo-olefin conversion to near quantitative amounts. In the fifth study, thiol-terminated polyisobutylene (PIB-SH) was synthesized by reaction of thiourea with alpha,o-bromine-terminated PIB in a three step one-pot procedure. First the alkylisothiouronium salt was produced using a 1:1 (v:v) DMF:heptane cosolvent mixture at 90°C. Hydrolysis of the salt by aqueous base produced thiolate chain ends, which were then acidified to form the desired thiol functional group. An extension of this reaction was performed by a sequential thiol-ene/thiol-yne procedure to produce tetra-hydroxy functionalized PIB. 1H NMR was used to confirm formation of both alkyne and tetrahydroxyl functional species. Further utility of PIB-SH was demonstrated by base catalyzed thiol-isocyanate reactions. A model reaction was conducted with phenyl isocyanate in THF using triethylamine as the catalyst. Last, conversion of PIB-SH directly into a RAFT macro-CTA was accomplished, as shown by 1H NMR, by treatment of PIB-SH with triethylamine in carbon disulfide and subsequent alkylation with 2-bromopropionic acid. (Abstract shortened by UMI.)

Interrogating Surface Functional Group Heterogeneity of Activated Thermoplastics Using Super-Resolution Fluorescence Microscopy.

PubMed

ONeil, Colleen E; Jackson, Joshua M; Shim, Sang-Hee; Soper, Steven A

2016-04-05

We present a novel approach for characterizing surfaces utilizing super-resolution fluorescence microscopy with subdiffraction limit spatial resolution. Thermoplastic surfaces were activated by UV/O3 or O2 plasma treatment under various conditions to generate pendant surface-confined carboxylic acids (-COOH). These surface functional groups were then labeled with a photoswitchable dye and interrogated using single-molecule, localization-based, super-resolution fluorescence microscopy to elucidate the surface heterogeneity of these functional groups across the activated surface. Data indicated nonuniform distributions of these functional groups for both COC and PMMA thermoplastics with the degree of heterogeneity being dose dependent. In addition, COC demonstrated relative higher surface density of functional groups compared to PMMA for both UV/O3 and O2 plasma treatment. The spatial distribution of -COOH groups secured from super-resolution imaging were used to simulate nonuniform patterns of electroosmotic flow in thermoplastic nanochannels. Simulations were compared to single-particle tracking of fluorescent nanoparticles within thermoplastic nanoslits to demonstrate the effects of surface functional group heterogeneity on the electrokinetic transport process.

Two zinc(II) coordination complexes based on an asymmetric multidentate ligand: syntheses, structures, selective fluorescence sensing of iron(III) ions and thermal analyses.

PubMed

Liu, Yaru; Liu, Lan; Zhang, Xiao; Liang, Guorui; Gong, Xuebing

2018-01-01

The rational selection of ligands is vitally important in the construction of coordination complexes. Two novel Zn II complexes, namely bis(acetato-κO)bis[1-(1H-benzotriazol-1-ylmethyl)-2-propyl-1H-imidazole-κN 3 ]zinc(II) monohydrate, [Zn(C 13 H 15 N 5 ) 2 (C 2 H 3 O 2 ) 2 ]·H 2 O, (1), and bis(azido-κN 1 )bis[1-(1H-benzotriazol-1-ylmethyl)-2-propyl-1H-imidazole-κN 3 ]zinc(II), [Zn(C 13 H 15 N 5 ) 2 (N 3 ) 2 ], (2), constructed from the asymmetric multidentate imidazole ligand, have been synthesized under mild conditions and characterized by elemental analyses, IR spectroscopy and single-crystal X-ray diffraction analysis. Both complexes exhibit a three-dimensional supramolecular network directed by different intermolecular interactions between discrete mononuclear units. The complexes were also investigated by fluorescence and thermal analyses. The experimental results show that (1) is a promising fluorescence sensor for detecting Fe 3+ ions and (2) is effective as an accelerator of the thermal decomposition of ammonium perchlorate.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, J.Y.

Serial experiments were performed in order to understand and explore the Na/sup +/ transport system. In order to test possible covariation of cation and anion permeabilities, we applied inhibitors of cation or anion transport. Sulfonamide loop diuretics, furosemide and bumetanide, suppress 22/sub Na/sup +// influx into high permeability (HP) red cells but less into low permeability (LP) erythrocytes. These drugs also inhibit SO/sub 4/ = transport about 70% in both types of RBC. RBC pretreated with impermeant polyanions also show significantly decreased Na/sup +/ influx into HP but not LP RBC. However,a potent inhibitor of RBC anion transport, diisothiocyanostilbene disulfonatemore » (DIDS), has no influence on Na/sup +/ transport. Since the glucose channel is another transmembrane protein in erythrocyte membranes, the effects of the potent glucose transport inhibitors, phlorizin and phloretinyl-3'-benzylazide (PBAz), were measured. Both chemicals effect reduction of Na/sup +/ flux. Because radioactive PBAz is not available, we employed another potent Na/sup +/ channel blocker, /sup 32/P-8-azido-ATP, in an attempt to label HP and LP RBC membranes. Autoradiograms showed that /sup 32/P labels only band 4.2 and external iodination with /sup 125/I yields similar results.« less

DNA with Parallel Strand Orientation: A Nanometer Distance Study with Spin Labels in the Watson-Crick and the Reverse Watson-Crick Double Helix.

PubMed

Wunnicke, Dorith; Ding, Ping; Yang, Haozhe; Seela, Frank; Steinhoff, Heinz-Jürgen

2015-10-29

Parallel-stranded (ps) DNA characterized by its sugar-phosphate backbones pointing in the same direction represents an alternative pairing system to antiparallel-stranded (aps) DNA with the potential to inhibit transcription and translation. 25-mer oligonucleotides were selected containing only dA·dT base pairs to compare spin-labeled nucleobase distances over a range of 10 or 15 base pairs in ps DNA with those in aps DNA. By means of the copper(I)-catalyzed Huisgen-Meldal-Sharpless alkyne-azide cycloaddition, the spin label 4-azido-2,2,6,6-tetramethylpiperidine-1-oxyl was clicked to 7-ethynyl-7-deaza-2'-deoxyadenosine or 5-ethynyl-2'-deoxyuridine to yield 25-mer oligonucleotides incorporating two spin labels. The interspin distances between spin labeled residues were determined by pulse EPR spectroscopy. The results reveal that in ps DNA these distances are between 5 and 10% longer than in aps DNA when the labeled DNA segment is located near the center of the double helix. The interspin distance in ps DNA becomes shorter compared with aps DNA when one of the spin labels occupies a position near the end of the double helix.

Mechanism of ribonucleotide reductase from Herpes simplex virus type 1. Evidence for 3' carbon-hydrogen bond cleavage and inactivation by nucleotide analogs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ator, M.A.; Stubbe, J.; Spector, T.

1986-03-15

Isotope effects of 2.5, 2.1, and 1.0 were measured on the conversion of (3'-3H)ADP, (3'-H)UDP, and (5-3H) UDP to the corresponding 2'-deoxynucleotides by herpes simplex virus type 1 ribonucleotide reductase. These results indicate that the reduction of either purine or pyrimidine nucleotides requires cleavage of the 3' carbon-hydrogen bond of the substrate. The substrate analogs 2'-chloro-2'-deoxyuridine 5'-diphosphate (ClUDP), 2'-deoxy-2'-fluorouridine 5'-diphosphate, and 2'-azido-2'-deoxyuridine 5'-diphosphate were time-dependent inactivators of the herpes simplex virus type 1 ribonucleotide reductase. Incubation of (3'-3H)ClUDP with the enzyme was accompanied by time-dependent release of 3H to the solvent. Reaction of (beta-32P)ClUDP with the reductase resulted in themore » production of inorganic pyrophosphate. These results are consistent with the enzyme-mediated cleavage of the 3' carbon-hydrogen bond of ClUDP and the subsequent conversion of the nucleotide to 2-methylene-3(2H)furanone, as previously reported with the Escherichia coli ribonucleotide reductase.« less

Probing sialoglycans on fetal bovine fetuin with azido-sugars using glycosyltransferases.

PubMed

Wu, Zhengliang L; Huang, Xinyi; Burton, Andrew J; Swift, Karl A D

2016-04-01

Sialic acids are negatively charged sugar residues commonly found on the terminal positions of most glycoproteins. They play important roles in the stability and solubility of these proteins. Due to their unique positioning, they also frequently act as receptors for various ligands, and therefore are involved in numerous cell-cell and cell-pathogen interactions. Here, using in vitro incorporation of clickable monosaccharides with various glycosyltransferases, we probed the sialoglycans on fetal bovine fetuin. The incorporated monosaccharides were detected with chemiluminescence via click chemistry in a format of western blotting. The results indicate that the non-reducing end Gal residues on both N- and O-glycans are fully sialylated, but the peptide-linked GalNAc residues in O-glycans are not. The presence of sialyl core-1 glycan was repeatedly confirmed by probing with α-2,3-sialyltransferases, N-acetylgalactosaminide α-2,6-sialyltransferases and a β-1,6-N-acetylglucosaminyltransferase that is specific for core-1 glycan. The results also suggest the presence of a minute amount of sialyl Tn antigen on the protein. © The Author 2015. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Quantitative chemoproteomics for site-specific analysis of protein alkylation by 4-hydroxy-2-nonenal in cells.

PubMed

Yang, Jing; Tallman, Keri A; Porter, Ned A; Liebler, Daniel C

2015-03-03

Protein alkylation by 4-hydroxy-2-nonenal (HNE), an endogenous lipid derived electrophile, contributes to stress signaling and cellular toxicity. Although previous work has identified protein targets for HNE alkylation, the sequence specificity of alkylation and dynamics in a cellular context remain largely unexplored. We developed a new quantitative chemoproteomic platform, which uses isotopically tagged, photocleavable azido-biotin reagents to selectively capture and quantify the cellular targets labeled by the alkynyl analogue of HNE (aHNE). Our analyses site-specifically identified and quantified 398 aHNE protein alkylation events (386 cysteine sites and 12 histidine sites) in intact cells. This data set expands by at least an order of magnitude the number of such modification sites previously reported. Although adducts formed by Michael addition are thought to be largely irreversible, we found that most aHNE modifications are lost rapidly in situ. Moreover, aHNE adduct turnover occurs only in intact cells and loss rates are site-selective. This quantitative chemoproteomics platform provides a versatile general approach to map bioorthogonal-chemically engineered post-translational modifications and their cellular dynamics in a site-specific and unbiased manner.

Cell-free synthesis of functional human epidermal growth factor receptor: Investigation of ligand-independent dimerization in Sf21 microsomal membranes using non-canonical amino acids

PubMed Central

Quast, Robert B.; Ballion, Biljana; Stech, Marlitt; Sonnabend, Andrei; Varga, Balázs R.; Wüstenhagen, Doreen A.; Kele, Péter; Schiller, Stefan M.; Kubick, Stefan

2016-01-01

Cell-free protein synthesis systems represent versatile tools for the synthesis and modification of human membrane proteins. In particular, eukaryotic cell-free systems provide a promising platform for their structural and functional characterization. Here, we present the cell-free synthesis of functional human epidermal growth factor receptor and its vIII deletion mutant in a microsome-containing system derived from cultured Sf21 cells. We provide evidence for embedment of cell-free synthesized receptors into microsomal membranes and asparagine-linked glycosylation. Using the cricket paralysis virus internal ribosome entry site and a repetitive synthesis approach enrichment of receptors inside the microsomal fractions was facilitated thereby providing analytical amounts of functional protein. Receptor tyrosine kinase activation was demonstrated by monitoring receptor phosphorylation. Furthermore, an orthogonal cell-free translation system that provides the site-directed incorporation of p-azido-L-phenylalanine is characterized and applied to investigate receptor dimerization in the absence of a ligand by photo-affinity cross-linking. Finally, incorporated azides are used to generate stable covalently linked receptor dimers by strain-promoted cycloaddition using a novel linker system. PMID:27670253

[Influence of different surface treatments on porcelain surface topography].

PubMed

Tai, Yinxia; Zhu, Xianchun; Sen, Yan; Liu, Chang; Zhang, Xian; Shi, Xueming

2013-02-01

To evaluate the influence of different surface treatments on porcelain surface topography. Metal ceramic prostheses in 6 groups were treated according to the different surface treatment methods, and the surface topography was observed through scanning electron microscope (SEM). Group A was the control one (untreated), group B was etched by 9.6% hydrofluoric acid(HF), group C was deglazed by grinding and then etched by 9.6% HF, group D was treated with Nd: YAG laser irradiation(0.75 W) and HF etching, group E was treated with Nd: YAG laser irradiation (1.05 W) and HF etching, and group F was treated with laser irradiation (1.45 W) and HF etching. Surface topography was different in different groups. A lot of inerratic cracks with the shapes of rhombuses and grid, and crater with a shape of circle were observed on the ceramic surface after treatment with energy parameters of 1.05 W Nd: YAG laser irradiation and 9.6% HF etching (group E). Surface topography showed a lot of concaves on the inner wall of the cracks, and the concaves with diameter of 1-5 microm could be observed on the inner wall of the holes, which had a diameter of 20 microm under SEM. The use of Nd: YAG laser irradiation with the energy parameters of 1.05 W and the HF with a concentration of 9.6% can evenly coarsen the porcelain surface, that is an effective surface treatment method.

Profinite Completions of Burnside-Type Quotients of Surface Groups

NASA Astrophysics Data System (ADS)

Funar, Louis; Lochak, Pierre

2018-06-01

Using quantum representations of mapping class groups, we prove that profinite completions of Burnside-type surface group quotients are not virtually prosolvable, in general. Further, we construct infinitely many finite simple characteristic quotients of surface groups.

Synthesis of Selective Agonists for the α7 Nicotinic Acetylcholine Receptor with In Situ Click-Chemistry on Acetylcholine-Binding Protein Templates

PubMed Central

Yamauchi, John G.; Gomez, Kimberly; Grimster, Neil; Dufouil, Mikael; Nemecz, Ákos; Fotsing, Joseph R.; Ho, Kwok-Yiu; Talley, Todd T.; Sharpless, K. Barry; Fokin, Valery V.

2012-01-01

The acetylcholine-binding proteins (AChBPs), which serve as structural surrogates for the extracellular domain of nicotinic acetylcholine receptors (nAChRs), were used as reaction templates for in situ click-chemistry reactions to generate a congeneric series of triazoles from azide and alkyne building blocks. The catalysis of in situ azide-alkyne cycloaddition reactions at a dynamic subunit interface facilitated the synthesis of potentially selective compounds for nAChRs. We investigated compound sets generated in situ with soluble AChBP templates through pharmacological characterization with α7 and α4β2 nAChRs and 5-hydroxytryptamine type 3A receptors. Analysis of activity differences between the triazole 1,5-syn- and 1,4-anti-isomers showed a preference for the 1,4-anti-triazole regioisomers among nAChRs. To improve nAChR subtype selectivity, the highest-potency building block for α7 nAChRs, i.e., 3α-azido-N-methylammonium tropane, was used for additional in situ reactions with a mutated Aplysia californica AChBP that was made to resemble the ligand-binding domain of the α7 nAChR. Fourteen of 50 possible triazole products were identified, and their corresponding tertiary analogs were synthesized. Pharmacological assays revealed that the mutated binding protein template provided enhanced selectivity of ligands through in situ reactions. Discrete trends in pharmacological profiles were evident, with most compounds emerging as α7 nAChR agonists and α4β2 nAChR antagonists. Triazoles bearing quaternary tropanes and aromatic groups were most potent for α7 nAChRs. Pharmacological characterization of the in situ reaction products established that click-chemistry synthesis with surrogate receptor templates offered novel extensions of fragment-based drug design that were applicable to multisubunit ion channels. PMID:22784805

Neighborhood of 16S rRNA nucleotides U788/U789 in the 30S ribosomal subunit determined by site-directed crosslinking.

PubMed

Mundus, D; Wollenzien, P

1998-11-01

Site-specific photo crosslinking has been used to investigate the RNA neighborhood of 16S rRNA positions U788/ U789 in Escherichia coli 30S subunits. For these studies, site-specific psoralen (SSP) which contains a sulfhydryl group on a 17 A side chain was first added to nucleotides U788/U789 using a complementary guide DNA by annealing and phototransfer. Modified RNA was purified from the DNA and unmodified RNA. For some experiments, the SSP, which normally crosslinks at an 8 A distance, was derivitized with azidophenacylbromide (APAB) resulting in the photoreactive azido moiety at a maximum of 25 A from the 4' position on psoralen (SSP25APA). 16S rRNA containing SSP, SSP25APA or control 16S rRNA were reconstituted and 30S particles were isolated. The reconstituted subunits containing SSP or SSP25APA had normal protein composition, were active in tRNA binding and had the usual pattern of chemical reactivity except for increased kethoxal reactivity at G791 and modest changes in four other regions. Irradiation of the derivatized 30S subunits in activation buffer produced several intramolecular RNA crosslinks that were visualized and separated by gel electrophoresis and characterized by primer extension. Four major crosslink sites made by the SSP reagent were identified at positions U561/U562, U920/U921, C866 and U723; a fifth major crosslink at G693 was identified when the SSP25APA reagent was used. A number of additional crosslinks of lower frequency were seen, particularly with the APA reagent. These data indicate a central location close to the decoding region and central pseudoknot for nucleotides U788/U789 in the activated 30S subunit.

SEM Evaluation of Enamel Surface Changes and Enamel Microhardness around Orthodontic Brackets after Application of CO2 Laser, Er,Cr:YSGG Laser and Fluoride Varnish: An In vivo Study.

PubMed

Kaur, Tarundeep; Tripathi, Tulika; Rai, Priyank; Kanase, Anup

2017-09-01

One of the most undesirable consequences of orthodontic treatment is occurrence of enamel demineralization around orthodontic brackets. Numerous in vitro studies have reported the prevention of enamel demineralization by surface treatment with lasers and fluoride varnish. To evaluate the changes on the enamel surface and microhardness around orthodontic brackets after surface treatment by CO 2 laser, Er, Cr:YSGG laser and fluoride varnish in vivo. A double blind interventional study was carried out on 100 premolars which were equally divided into five groups, out of which one was the control group (Group 0). The intervention groups (Group I to IV) comprised of patients requiring fixed orthodontic treatment with all 4 first premolars extraction. Brackets were bonded on all 80 premolars which were to be extracted. Enamel surface treatment of Groups I, II and III was done by CO 2 laser, Er, Cr:YSGG laser and 5% sodium fluoride varnish respectively and Group IV did not receive any surface treatment. A modified T-loop was ligated to the bracket and after two months, the premolars were extracted. Surface changes were evaluated by Scanning Electron Microscopic (SEM) and microhardness testing. Comparison of mean microhardness between all the groups was assessed using post-hoc test with Bonferroni correction. Group I showed a melted enamel appearance with fine cracks and fissures while Group II showed a glossy, homogenous enamel surface with well coalesced enamel rods. Group III showed slight areas of erosions and Group IV presented areas of stripped enamel. Significant difference was observed between the mean microhardness (VHN) of Group I, Group II, Group III, Group IV and Group 0 with p<0.001. A significant difference of p<0.001 was observed while comparing Group I vs II,III,IV,0 and Group II vs III,IV,0. However, difference while comparing Group III vs IV was p=0.005 and difference between the mean microhardness of Group 0 vs Group III was non significant. Surface treatment with Er,Cr:YSGG laser causes a positive alteration of the enamel surface increasing its ability to resist demineralization with optimum microhardness as compared to CO 2 laser and sodium fluoride varnish.

Efficient 18F-Labeling of Large 37-Amino Acid pHLIP Peptide Analogues and their Biological Evaluation

PubMed Central

Daumar, Pierre; Wanger-Baumann, Cindy A.; Pillarsetty, NagaVaraKishore; Fabrizio, Laura; Carlin, Sean D.; Andreev, Oleg A.; Reshetnyak, Yana K.; Lewis, Jason S.

2012-01-01

Solid tumors often develop an acidic microenvironment, which plays a critical role in tumor progression and is associated with increased level of invasion and metastasis. The 37-residue pH (low) insertion peptide (pHLIP®) is under study as an imaging platform because of its unique ability to insert into cell membranes at a low extracellular pH (pHe<7). Labeling of peptides with [18F]-fluorine is usually performed via prosthetic groups using chemoselective coupling reactions. One of the most successful procedures involves the alkyne-azide copper(I) catalyzed cycloaddition (CuAAC). However, none of the known “click” methods have been applied to peptides as large as pHLIP. We designed a novel prosthetic group and extended the use of the CuAAC “click chemistry” for the simple and efficient 18F-labeling of large peptides. For the evaluation of this labeling approach, a D-amino acid analogue of WT-pHLIP and a L-amino acid control peptide K-pHLIP, both functionalized at the N-terminus with 6-azidohexanoic acid, were used. The novel 6-[18F]fluoro-2-ethynylpyridine prosthetic group, was obtained via nucleophilic substitution on the corresponding bromo-precursor after 10 min at 130 °C with a radiochemical yield of 27.5 ± 6.6% (decay corrected) with high radiochemical purity ≥ 98%. The subsequent CuI catalyzed “click” reaction with the azido functionalized pHLIP peptides was quantitative within 5 min at 70 °C in a mixture of water and ethanol using Cu-acetate and sodium L-ascorbate. [18F]-D-WT-pHLIP and [18F]-L-K-pHLIP were obtained with total radiochemical yields of 5–20% after HPLC purification. The total reaction time was only 85 min including formulation. In vitro stability tests revealed high stability of the [18F]-D-WT-pHLIP in human and mouse plasma after 120 min, with the parent tracer remaining intact at 65 and 85%, respectively. PET imaging and biodistribution studies in LNCaP and PC-3 xenografted mice with the [18F]-D-WT-pHLIP and the negative control [18F]-L-K-pHLIP revealed pH-dependent tumor retention. This reliable and efficient protocol promises to be useful for the 18F-labeling of large peptides such as pHLIP and will accelerate the evaluation of numerous [18F]-pHLIP analogues as potential PET tracers. PMID:22784215

Maltopentaose-conjugated CTA for RAFT polymerization generating nanostructured bioresource-block copolymer.

PubMed

Togashi, Daichi; Otsuka, Issei; Borsali, Redouane; Takeda, Koichi; Enomoto, Kazushi; Kawaguchi, Seigou; Narumi, Atsushi

2014-12-08

We now describe the synthesis of a new family of oligosaccharide-conjugated functional molecules, which act as chain transfer agents (CTAs) for the reversible addition-fragmentation chain transfer (RAFT) polymerization. The synthesis was started from the catalyst-free direct N-glycosyl reaction of 5-azidopentylamine onto maltopentaose (Mal5) in dry methanol at room temperature and subsequent N-protected reaction with acetic anhydride, producing a stable oligosaccharide-building block, such as Mal5 with an azidopentyl group (Mal5-N3). The azido group was hydrogenated using platinum dioxide (PtO2) as a catalyst to give Mal5 with aminopentyl group (Mal5-NH2), which was then reacted with CTA molecules bearing activated ester moieties. These reactions produced Mal5-modified macro-CTAs (Mal5-CTAs, 1), which were used for the RAFT polymerizations of styrene (St) and methyl methacrylate (MMA) in DMF. The polymerizations were performed using the [M]0/[1]0 values ranging from 50 to 600, affording the Mal5-hybrid amphiphilic block copolymers (BCPs), such as Mal5-polystyrene (2) and Mal5-poly(methyl methacrylate) (3), with a quantitative end-functionality and the controlled molecular weights between 4310 and 20 300 g mol(-1). The small-angle X-ray scattering (SAXS) measurements were accomplished for 2 and 3 to ensure their abilities to form phase separated structures in their bulk states with the increasing temperatures from 30 to 190 °C. The featured results were observed for 2 (ϕMal5 = 0.14) and 3 (ϕMal5 = 0.16) at temperatures above 100 °C, where ϕMal5 denotes the volume fraction of the Mal5 unit in the BCP sample. For both BCP samples, the primary scattering peaks q* were clearly observed together with the higher-ordered scattering peaks √2q* and √3q*. Thus, these Mal5-hybrid amphiphilic BCP samples have a body centered cubic (BCC) phase morphology. The domain spacing (d) values of the BCC morphology for 2 (ϕMal5 = 0.14) and 3 (ϕMal5 = 0.16) were 10.4 and 9.55 nm, respectively, which were determined using Bragg's relation (d = 2π/q*). The present RAFT agents were shown to eventually provide the phase separated structural polymeric materials in which 5.4 nm bioresource-spherical domains were periodically arrayed at the interval of about 10 nm.

Effect of a surface sealant on the color stability of composite resins after immersion in staining solution.

PubMed

Pedroso, Lauana Borges; Barreto, Luma Franciélle Cabreira; Miotti, Leonardo Lamberti; Nicoloso, Gabriel Ferreira; Durand, Leticia Brandão

2016-01-01

This study evaluated the influence of surface sealants on the color stability of 2 different composite resins after immersion in coffee. Four groups were created (n = 10): microhybrid composite, microhybrid with surface sealant, nanofilled composite, and nanofilled composite with surface sealant. Half of the specimens of each group were immersed in distilled water and half were immersed in coffee for 48 hours. Color was measured before and after immersion. Groups with surface sealants presented less color variation when compared with the groups without surface sealants. The nanofilled resin specimens presented the greatest color variation within the groups without sealant. The surface sealant positively influenced the color stability of composite resin specimens immersed in coffee. When surface sealant was not applied, the microhybrid specimens had better color stability than the nanofilled.

Radiographic evaluation of marginal bone level around implants with different neck designs after 1 year.

PubMed

Shin, Young-Kyu; Han, Chong-Hyun; Heo, Seong-Joo; Kim, Sunjai; Chun, Heoung-Jae

2006-01-01

To evaluate the influence of macro- and microstructure of the implant surface at the marginal bone level after functional loading. Sixty-eight patients were randomly assigned to 1 of 3 groups. The first group received 35 implants with a machined neck (Ankylos); the second group, 34 implants with a rough-surfaced neck (Stage 1); and the third, 38 implants with a rough-surfaced neck with microthreads (Oneplant). Clinical and radiographic examinations were conducted at baseline (implant loading) and 3, 6, and 12 months postloading. Two-way repeated analysis of variance (ANOVA) was used to test the significance of marginal bone change of each tested group at baseline, 3, 6, and 12 month follow-ups and 1-way ANOVA was also used to compare the bone loss of each time interval within the same implant group (P < .05). At 12 months, significant differences were noted in the amount of alveolar bone loss recorded for the 3 groups (P < .05). The group with the rough-surfaced microthreaded neck had a mean crestal bone loss of 0.18 +/- 0.16 mm; the group with the rough-surfaced neck, 0.76 +/- 0.21 mm; and the group with the machined neck, 1.32 +/- 0.27 mm. In the rough-surfaced group and the rough-surfaced microthreaded group, no statistically significant changes were observed after 3 months, whereas the machined-surface group showed significant bone loss for every interval (P < .05). To minimize marginal bone loss, in addition to the use of a rough surface at the marginal bone level, a macroscopic modification such as the addition of microthreads could be recommended. A rough surface and microthreads at the implant neck not only reduce crestal bone loss but also help with early biomechanical adaptation against loading in comparison to the machined neck design. A rough surface with microthreads at the implant neck was the most effective design to maintain the marginal bone level against functional loading.

Identification of the functional groups on the surface of nanoparticles formed in photonucleation of aldehydes generated during forest fire events

NASA Astrophysics Data System (ADS)

Dultsev, Fedor N.; Mik, Ivan A.; Dubtsov, Sergei N.; Dultseva, Galina G.

2014-11-01

We describe the new procedure developed to determine the functional groups on the surface of nanoparticles formed in photonucleation of furfural, one of the aldehydes generated during forest fire events. The procedure is based on the detection of nanoparticle rupture from chemically modified surface of the quartz crystal microbalance oscillating in the thickness shear mode under voltage sweep. The rupture force is determined from the voltage at which the rupture occurs. It depends on particle mass and on the affinity of the surface functional groups of the particle to the groups that are present on the modified QCM surface. It was demonstrated with the amine modification of the surface that the nanoparticles formed in furfural photonucleation contain carbonyl and carboxyl groups. The applicability of the method for the investigation of functional groups on the surface of the nanoparticles of atmospheric aerosol is demonstrated.

Effects of Oxygen Element and Oxygen-Containing Functional Groups on Surface Wettability of Coal Dust with Various Metamorphic Degrees Based on XPS Experiment

PubMed Central

Zhou, Gang; Xu, Cuicui; Cheng, Weimin; Zhang, Qi; Nie, Wen

2015-01-01

To investigate the difference of surface oxygen element and oxygen-containing functional groups among coal dusts with different metamorphic degrees and their influence on surface wettability, a series of X-ray photoelectron spectroscopy experiments on 6 coal samples are carried out. The result demonstrates that the O/C ratio of coal surface shows an overall increasing trend compared with the result of its elements analysis. As the metamorphic degree increases, the O/C ratio on the surface gradually declines and the hydrophilic groups tend to fall off from coal surface. It could be found that different coals show different surface distributions of carboxyl and hydroxyl which are considered as the greatest promoter to the wettability of coal surface. With the change of metamorphic degree, the distribution of ether group is irregular while the carbonyl distribution keeps stable. In general, as the metamorphic degree goes higher, the content of oxygen-containing polar group tends to reduce. According to the measurement results, the contact angle is negatively related to the content of oxygen element, surface oxygen, and polar groups. In addition, compared with surface oxygen content, the content of oxygen-containing polar group serves as a more reasonable indicator of coal dust wettability. PMID:26257980

Effect of surface preparation with Nd:YAG and Er,Cr:YSGG lasers on the repair bond strength of lithium disilicate glass ceramic to a silorane-based composite resin.

PubMed

Ebrahimi Chaharom, Mohammad Esmaeel; Pournaghi Azar, Fatemeh; Mohammadi, Narmin; Nasiri, Rezvan

2018-01-01

Background. This study was undertaken to evaluate the repair bond strength of lithium disilicate glass ceramic to a silorane-based composite resin after surface preparation with Nd:YAG and Er,Cr:YSGG lasers. Methods. A total of 102 lithium disilicate glass ceramic samples (IPS e.max Press), measuring 5 mm in diameter and 4 mm in thickness, were randomly assigned to 6 groups (n=17): group 1, no surface preparation (control); group 2, acid etching with 9.5% hydrofluoric acid (HF); group 3, surface preparation with 4.5-W Nd:YAG laser; group 4, surface preparation with 6-W Nd:YAG laser; group 5, surface preparation with 1.5-W Er,Cr:YSGG laser; and group 6, surface preparation with 6-W Er,Cr:YSGG laser. After preparation of surfaces and application of silane, all the samples were repaired with the use of a silorane-based composite resin, followed by storage in distilled water at a temperature of 37°C for 24 hours and thermocycling. Finally, the samples were subjected to a shearing bond strength test; the fracture modes were determined under a stereomi-croscope. Results. There were significant differences between the HF group and the other groups (P=0.000). Two-by-two comparisons of the other groups revealed no significant differences (P>0.05). Conclusion. Use of HF proved the most effective surface preparation technique to increase the repair bond strength between lithium disilicate glass ceramic and silorane-based composite resin; compared to the control group.

[Effect of SiO₂-ZrO₂slurry coating on surface performance of zirconia ceramic].

PubMed

Du, Qiao; Niu, Guangliang; Lin, Hong; Jiang, Ruodan

2015-11-01

To evaluate the effect of SiO₂-ZrO₂slurry coating on surface performance of zirconia ceramic. Seventy pre-sintered zirconia discs were randomly divided into seven groups with 10 discs per group. Sample discs in each group received one of the following seven different surface treatments, namely, sintered (group AS), sand blasting after sintered (group SB), coated with slurry of mole ratio of SiO₂to ZrO₂2:1 (group 2SiO₂-1ZrO₂), coated with slurry of mole ratio of SiO₂to ZrO₂1:1 (group 1SiO₂-1ZrO₂), coated with slurry of mole ratio of SiO₂to ZrO₂1:2 (group 1SiO₂-2ZrO₂), coated with slurry of mole ratio of SiO₂to ZrO₂1:3 (group 1SiO₂-3ZrO₂), coated with slurry of mole ratio of SiO₂to ZrO₂1:4 (group 1SiO₂-4ZrO₂). Profilometer, X-ray diffractometer (XRD), energy dispersive spectrometer, scanning electron microscopy (SEM) were used to analyze surface performance. The surface roughness of the discs in group AS was lower than those in the other groups [(0.33 ± 0.03) µm] (P < 0.05), there was no statistically significant difference (P > 0.05) among group 2SiO₂-1ZrO₂[(3.85 ± 0.38) µm], group 1SiO₂-1ZrO₂[(3.78 ± 0.56) µm] and group 1SiO₂-2ZrO₂[(4.06 ± 0.48) µm], and no difference (P > 0.05) was observed between group 1SiO₂-3ZrO₂[(1.02 ± 0.09) µm] and group 1SiO₂-4ZrO₂[(1.53 ± 0.23) µm] either. However, surface roughness in all coating groups was higher than those in group SB [(0.86 ± 0.05) µm] (P < 0.05). According to the XRD pattern, group AS and all coating groups consisted of 100% tetragonal airconia and monoclinic zirconia was detected at surface of group SB. Contents of surface silicon of coating groups increased significantly, however, no silicon was detected at sample surface of group AS and group SB. SEM showed that zirconia grains of coating exposed since part of silicon was etched by hydrofluoric acid, a three-dimensional network of intergrain nano-spaces was created. SiO₂-ZrO₂slurry coating could make surface of zirconia rough and increase Si content without creating monoclinic zirconia.

Reactivity of formic acid (HCOOD and DCOOH) at uranium and UO 2.0 surfaces

NASA Astrophysics Data System (ADS)

Manner, William L.; Lloyd, Jane A.; Paffett, Mark T.

1999-10-01

Interactions of DCOOH and HCOOD with uranium and UO 2.0 surfaces have been examined using surface-specific techniques of thermal desorption mass spectroscopy (TDMS), X-ray photoelectron spectroscopy (XPS), and static secondary ion mass spectroscopy (SSIMS). On the clean uranium surface, formate is the predominant product following formic acid adsorption at 100 K. A wide range of products is observed after annealing to 200 K, including formate, hydroxyl, O ads, and H ads (D ads) groups. Adsorbed formate decomposes by 300 K increasing the concentration of the remaining surface products. Surface-adsorbed carbon following TDMS measurements remains as the carbide, as indicated from XPS and SSIMS measurements. The only gaseous species created in high yields from the clean surface upon annealing are H 2, HD, and D 2. On the oxide surface (UO 2.0), adsorbed formate groups are more stable toward dissociation in comparison with the clean uranium surface. Between 100 and 300 K the predominant species on the UO 2.0 surface are surface formate and hydroxyl groups. Hydroxyl groups react between 300 and 350 K to release water from the surface. Adsorbed formate groups decompose between 400 and 500 K to release CO and H 2CO (D 2CO) groups from the oxide surface. Carbon was not detected on the oxide surface by XPS or SSIMS after annealing to 500 K, indicating that all carbon-containing species either desorb in the form of CO-containing products or migrate into the surface.

MAPs/bFGF-PLGA microsphere composite-coated titanium surfaces promote increased adhesion and proliferation of fibroblasts.

PubMed

Wang, Zhongshan; Wu, Guofeng; Bai, Shizhu; Feng, Zhihong; Dong, Yan; Zhou, Jian; Qin, Haiyan; Zhao, Yimin

2014-06-01

Infection and epithelial downgrowth are two major problems with maxillofacial transcutaneous implants, and both are mainly due to lack of stable closure of soft tissues at transcutaneous sites. Fibroblasts have been shown to play a key role in the formation of biological seals. In this work, titanium (Ti) model surfaces were coated with mussel adhesive proteins (MAPs) utilizing its unique adhesion ability on diverse inorganic and organic surfaces in wet environments. Prepared basic fibroblast growth factor (bFGF)-poly(lactic-co-glycolic acid) (PLGA) microspheres can be easily synthesized and combined onto MAPs-coated Ti surfaces, due to the negative surface charges of microspheres in aqueous solution, which is in contrast to the positive charges of MAPs. Titanium model surfaces were divided into three groups. Group A: MAPs/bFGF-PLGA microspheres composite-coated Ti surfaces. Group B: MAPs-coated Ti surfaces. Group C: uncoated Ti surfaces. The effects of coated Ti surfaces on adhesion of fibroblasts, cytoskeletal organization, proliferation, and extracellular matrix (ECM)-related gene expressions were examined. The results revealed increased adhesion (P < 0.05), enhanced actin cytoskeletal organization, and up-regulated ECM-related gene expressions in groups A and B compared with group C. Increased proliferation of fibroblasts during five days of incubation was observed in group A compared with groups B and C (P < 0.05). Collectively, the results from this in vitro study demonstrated that MAPs/bFGF-PLGA microspheres composite-coated Ti surfaces had the ability to increase fibroblast functionality. In addition, MAPs/bFGF-PLGA microsphere composite-coated Ti surfaces should be studied further as a method of promoting formation of stable biological seals around transcutaneous sites.

Characterizing high-energy-density propellants for space propulsion applications

NASA Astrophysics Data System (ADS)

Kokan, Timothy

There exists wide ranging research interest in high-energy-density matter (HEDM) propellants as a potential replacement for existing industry standard fuels for liquid rocket engines. The U.S. Air Force Research Laboratory, the U.S. Army Research Lab, the NASA Marshall Space Flight Center, and the NASA Glenn Research Center each either recently concluded or currently has ongoing programs in the synthesis and development of these potential new propellants. In order to perform conceptual designs using these new propellants, most conceptual rocket engine powerhead design tools (e.g. NPSS, ROCETS, and REDTOP-2) require several thermophysical properties of a given propellant over a wide range of temperature and pressure. These properties include enthalpy, entropy, density, viscosity, and thermal conductivity. Very little thermophysical property data exists for most of these potential new HEDM propellants. Experimental testing of these properties is both expensive and time consuming and is impractical in a conceptual vehicle design environment. A new technique for determining these thermophysical properties of potential new rocket engine propellants is presented. The technique uses a combination of three different computational methods to determine these properties. Quantum mechanics and molecular dynamics are used to model new propellants at a molecular level in order to calculate density, enthalpy, and entropy. Additivity methods are used to calculate the kinematic viscosity and thermal conductivity of new propellants. This new technique is validated via a series of verification experiments of HEDM compounds. Results are provided for two HEDM propellants: quadricyclane and 2-azido-N,N-dimethylethanamine (DMAZ). In each case, the new technique does a better job than the best current computational methods at accurately matching the experimental data of the HEDM compounds of interest. A case study is provided to help quantify the vehicle level impacts of using HEDM propellants. The case study consists of the National Aeronautics and Space Administration's (NASA) Exploration Systems Architecture Study (ESAS) Lunar Surface Access Module (LSAM). The results of this study show that the use of HEDM propellants instead of hypergolic propellants can lower the gross weight of the LSAM and may be an attractive alternative to the current baseline hypergolic propellant choice.

The effects of dentin and intaglio indirect ceramic optimized polymer restoration surface treatment on the shear bond strength of resin cement

NASA Astrophysics Data System (ADS)

Puspitarini, A.; Suprastiwi, E.; Usman, M.

2017-08-01

Ceramic optimized polymer (ceromer) bonds to the tooth substrate through resin cements. The bond strength between dentin, resin cement, and ceromer depends on the applied surface treatment. To analyze the effects of dentin and intaglio ceromer surface treatment on the shear bond strength self-adhesive resin cement. Forty-five dentin premolar and ceromer specimens were bonded with resin cement and divided into three groups as follows: in group 1, no treatment was applied; in group 2, dentin surface treatment was carried out with acid etching and a bonding agent; and in group 3, dentin surface treatment was carried out with acid etching, a bonding agent, and intaglio ceromer surface treatment with etching and silane. All specimens were incubated at 37 °C for 24 hours, and the shear bond strength was measured using a universal testing machine. Group 3 showed the highest shear bond strength, followed by group 2. The surface treatment of dentin and intaglio ceromer showed significantly improved shear bond strength in the group comparison. Dentin and intaglio ceromer surface treatment can improved the shear bond strength self-adhesive resin cement.

Scanning electron microscopy evaluation of the effect of etching agents on human enamel surface.

PubMed

Zanet, Caio G; Arana-Chavez, Victor E; Fava, Marcelo

2006-01-01

Acid etching promotes microporosities on enamel surface, which provide a better bonding surface to adhesive materials. The purpose of this study was to comparatively analyze the microstructure of enamel surface after etching with 37% phosphoric acid or with two self-etching primers, Non-rinse conditioner (NRC) and Clearfil SE Bond (CSEB) using scanning electron microscopy. Thirty sound premolars were divided into 3 groups with ten teeth each: Group 1: the buccal surface was etched with 37% phosphoric acid for 15 seconds; Group 2: the buccal surface was etched with NRC for 20 seconds; Group 3: the buccal surface was etched with CSEB for 20 seconds. Teeth from Group 1 were rinsed with water; teeth from all groups were air-dried for 15 seconds. After that, all specimens were processed for scanning electron microscopy and analyzed in a Jeol 6100 SEM. The results showed deeper etching when the enamel surface was etched with 37% phosphoric acid, followed by NRC and CSEB. It is concluded that 37% phosphoric acid is still the best agent for a most effective enamel etching.

The Effect of Hydrofluoric Acid Surface Treatment on the Cyclic Fatigue Resistance of K3 NiTi Instruments

PubMed Central

2017-01-01

The aim of this study was to investigate the effect of 50% hydrofluoric acid (HF) surface treatment on the cyclic fatigue resistance (CFR) of K3 NiTi instruments. Twenty as-received and twenty HF-treated K3 NiTi instruments were compared in CFR. The surface texture and fracture surface of two instrument groups were examined with a scanning electron microscope (SEM). Additionally, any change of Ni and Ti composition from both instrument groups was investigated using energy dispersive spectrometry. The results were analyzed with t-test. The HF-treated K3 group showed statistically higher cyclic fatigue resistance than as-received K3 group (P < 0.05). HF-treated K3 instruments showed smoother and rounded surface compared to as-received K3 under SEM observation. The fracture surfaces of both groups showed typical patterns of cyclic fatigue fracture. There was no difference in surface Ni and Ti composition between two groups. HF treatment of K3 instruments smoothed the file surface and increased the cyclic fatigue resistance, while it had no effect on surface ion composition and the file fracture pattern. PMID:28539854

Evaluation of the surface roughness of zirconia ceramics after different surface treatments.

PubMed

Kirmali, Omer; Akin, Hakan; Kapdan, Alper

2014-08-01

This study aimed to investigate the effects of different mechanical surface treatments of pre-sintered zirconium oxide (ZrO2) in an attempt to improve its bonding potential. One hundred and twenty IPS e-max ZirCAD (Ivoclar Vivadent) pre-sintered zirconia blocks (7 mm diameter, 3 mm height) received six different surface treatments (n = 20): Group C was untreated (control); Group E was Er:YAG laser irradiated; Group N was Nd:YAG laser irradiated; Group SB was sandblasted, Group SN was sandblasted and Nd:YAG laser irradiated; and Group SE was sandblasted and Er:YAG laser irradiated. After the surface treatments, the average surface roughness (Ra, µm) of each specimen was determined with a profilometer, then all the specimens were sintered. The surface roughness values were analysed through one-way ANOVA and Tukey's test. Changes in the morphological characteristics of ZrO2 were examined through scanning electron microscopy (SEM). Sintered sandblasted, Er:YAG laser treatment, sandblasted + Er:YAG laser and sandblasted + Nd:YAG laser irradiation resulted in a rougher surface than the other treatments. Nd:YAG laser irradiation alone was not effective in altering the zirconia surface morphology.

Effect of Reduced Phosphoric Acid Pre-etching Times 
on Enamel Surface Characteristics and Shear Fatigue Strength Using Universal Adhesives.

PubMed

Tsujimoto, Akimasa; Fischer, Nicholas; Barkmeier, Wayne; Baruth, Andrew; Takamizawa, Toshiki; Latta, Mark; Miyazaki, Masashi

2017-01-01

To examine the effect of reduced phosphoric acid pre-etching times on enamel fatigue bond strength of universal adhesives and surface characteristics by using atomic force microscopy (AFM). Three universal adhesives were used in this study (Clearfil Universal Bond [C], G-Premio Bond [GP], Scotchbond Universal Adhesive [SU]). Four pre-etching groups were employed: enamel pre-etched with phosphoric acid and immediately rinsed with an air-water spray, and enamel pre-etched with phosphoric acid for 5, 10, or 15 s. Ground enamel was used as the control group. For the initial bond strength test, 15 specimens per etching group for each adhesive were used. For the shear fatigue test, 20 specimens per etching group for each adhesive were loaded using a sine wave at a frequency of 20 Hz for 50,000 cycles or until failure occurred. Initial shear bond strengths and fatigue shear strengths of composite adhesively bonded to ground and pre-etched enamel were determined. AFM observations of ground and pre-etched enamel were also conducted, and surface roughness as well as surface area were evaluated. The initial shear bond strengths and fatigue shear strengths of the universal adhesives in the pre-etched groups were significantly higher than those of the control group, and were not influenced by the pre-etching time. Significantly higher surface roughness and surface area of enamel surfaces in pre-etched groups were observed compared with those in the control group. While the surface area was not significantly influenced by etching time, surface roughness of the enamel surfaces in the pre-etched groups significantly increased with pre-etching time. The results of this in vitro study suggest that reduced phosphoric acid pre-etching times do not impair the fatigue bond strength of universal adhesives. Although fatigue bond strength and surface area were not influenced by phosphoric-acid etching times, surface roughness increased with increasing etching time.

Tuning Optical Properties and Photocatalytic Activities of Carbon-based "Quantum Dots" Through their Surface Groups.

PubMed

Hu, Shengliang

2016-02-01

We report recent progress in tuning optical properties and photocatalytic activities of carbon-based quantum dots (carbon-based QDs) through their surface groups. It is increasingly clear that the properties of carbon-based QDs are more dependent on their surface groups than on their size. The present challenge remains as to how to control the type, number, and conformation of the heterogeneous groups on the surface of carbon-based QDs when considering their target applications. By reviewing the related achievements, this personal account aims to help us understand the roles different surface groups play in tuning the properties of carbon-based QDs. A number of significant accomplishments have demonstrated that surface groups possess strong power in engineering electronic structure and controlling photogenerated charge behaviors of carbon-based QDs. However, effective strategies for modifying carbon-based QDs with diverse heterogeneous groups are still needed. © 2015 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Histological Evaluation of Nano-Micro Titanium Implant Surface Treatment in Beagle Humerus.

PubMed

Yun, Kwidug; Kang, Seongsoo; Oh, Gyejeong; Lim, Hyunpil; Lee, Kwangmin; Yang, Hongso; Vang, Mongsook; Park, Sangwon

2016-02-01

The objective of this study was to investigate the effects of nano-micro titanium implant surface using histology in beagle dogs. A total of 48 screw-shaped implants (Megagen, Daegu, Korea) which dimensions were 4 mm in diameter and 8.5 mm in length, were used. The implants were classified into 4 groups (n = 12): machined surface (M group), RBM (Resorbable Blasting Media) surface (R group), nano surface which is nanotube formation on the machined surface (MA group) and nano-micro surface which is nanotube formation on the RBM surface (RA group). Anodic oxidation was performed at a constant voltage of 20 V for 10 min using a DC power supply (Fine Power F-3005; SG EMD, Anyang, Korea). The bone blocks were investigated using histology. There was no inflammation around implants, and new bone formation was shown along with the nano-micro titanium implant surfaces. The amount of bone formation was increased depending on time comparing 4 weeks and 12 weeks. At 12 weeks, lamellar bone was more formed along with the nano-micro titanium implant surfaces than 4 weeks. It indicated that nano-micro surface showed good result in terms of osseointegration.

MicroCT Analysis of Micro-Nano Titanium Implant Surface on the Osseointegration.

PubMed

Ban, Jaesam; Kang, Seongsoo; Kim, Jihyun; Lee, Kwangmin; Hyunpil, Lim; Vang, Mongsook; Yang, Hongso; Oh, Gyejeong; Kim, Hyunseung; Hwang, Gabwoon; Jung, Yongho; Lee, Kyungku; Park, Sangwon; Yunl, Kwidug

2015-01-01

This study was to investigate the effects of micro-nano titanium implant surface on the osseointegration. A total of 36 screw-shaped implants were used. The implant surfaces were classified into 3 groups (n = 12): machined surface (M group), nanosurface which is nanotube formation on the machined surface (MA group) and nano-micro surface which is nanotube formation on the RBM surface (RA group). Anodic oxidation was performed at a 20 V for 10 min with 1 M H3PO4 and 1.5 wt% HF solutions. The implants were installed on the humerus on 6 beagles. After 4 and 12 weeks, the morphometric analysis with micro CT (skyscan 1172, SKYSCAN, Antwerpen, Belgium) was done. The data were statistically analyzed with two-way ANOVA. Bone mineral density and bone volume were significantly increased depending on time. RA group showed the highest bone mineral density and bone volume at 4 weeks and 12 weeks significantly. It indicated that nano-micro titanium implant surface showed faster and more mature osseointegration.

F-theory models on K3 surfaces with various Mordell-Weil ranks — constructions that use quadratic base change of rational elliptic surfaces

NASA Astrophysics Data System (ADS)

Kimura, Yusuke

2018-05-01

We constructed several families of elliptic K3 surfaces with Mordell-Weil groups of ranks from 1 to 4. We studied F-theory compactifications on these elliptic K3 surfaces times a K3 surface. Gluing pairs of identical rational elliptic surfaces with nonzero Mordell-Weil ranks yields elliptic K3 surfaces, the Mordell-Weil groups of which have nonzero ranks. The sum of the ranks of the singularity type and the Mordell-Weil group of any rational elliptic surface with a global section is 8. By utilizing this property, families of rational elliptic surfaces with various nonzero Mordell-Weil ranks can be obtained by choosing appropriate singularity types. Gluing pairs of these rational elliptic surfaces yields families of elliptic K3 surfaces with various nonzero Mordell-Weil ranks. We also determined the global structures of the gauge groups that arise in F-theory compactifications on the resulting K3 surfaces times a K3 surface. U(1) gauge fields arise in these compactifications.

Evaluation Of The Shear Bond Strength Between Dentin And Dental Luting Cement Following Dentin Surface Treatment By 980 Nm Diode Laser And Desensitizing Agent

NASA Astrophysics Data System (ADS)

Ibrahim, T.; Gheith, M.

2011-09-01

Dentin hypersensitivity is described clinically as an exaggerated response to non-noxious sensory stimuli. Current treatment is concentrating on two approaches; to occlude the dentinal tubules or to block neural transmission. This is achieved through using dentin desensitizers and low power lasers. Forty eight freshly extracted human molar teeth were used in this study and divided equally into three groups. Group 1) control group, group 2) laser treated dentin surface group, and group 3) desensitizing agent dentin surface group. Scanning electron microscopic analysis of laser treated group showed melted globules, no carbonization, recrystalization and crystal growth of the apatite in some areas. In diode laser dentin surface treated group showed the highest shear bond strength mean value.

The effects of pulsed electromagnetic field (PEMF) on osteoblast-like cells cultured on titanium and titanium-zirconium surfaces.

PubMed

Atalay, Belir; Aybar, Buket; Ergüven, Mine; Emes, Yusuf; Bultan, Özgür; Akça, Kivanç; Yalçin, Serhat; Baysal, Uğur; Işsever, Halim; Çehreli, Murat Cavit; Bilir, Ayhan

2013-11-01

Commercially pure Ti, together with Ti Ni, Ti-6Al-4V, and Ti-6Al-7Nb alloys, are among the materials currently being used for this purpose. Titanium-zirconium (TiZr) has been developed that allows SLActive surface modification and that has comparable or better mechanical strength and improved biocompatibility compared with existing Ti alloys. Furthermore, approaches have targeted making the implant surface more hydrophilic, as with the Straumann SLActive surface, a modification of the SLA surface. The aim of this study is to evaluate the effects of pulsed electromagnetic field (PEMF) to the behavior of neonatal rat calvarial osteoblast-like cells cultured on commercially pure titanium (cpTi) and titanium-zirconium alloy (TiZr) discs with hydrophilic surface properties. Osteoblast cells were cultured on titanium and TiZr discs, and PEMF was applied. Cell proliferation rates, cell numbers, cell viability rates, alkaline phosphatase, and midkine (MK) levels were measured at 24 and 72 hours. At 24 hours, the number of cells was significantly higher in the TiZr group. At 72 hours, TiZr had a significantly higher number of cells when compared to SLActive, SLActive + PEMF, and machine surface + PEMF groups. At 24 hours, cell proliferation was significantly higher in the TiZr group than SLActive and TiZr + PEMF group. At 72 hours, TiZr group had higher proliferation rate than machine surface and TiZr + PEMF. Cell proliferation in the machine surface group was lower than both SLActive + PEMF and machine surface + PEMF. MK levels of PEMF-treated groups were lower than untreated groups for 72 hours. Our findings conclude that TiZr surfaces are similar to cpTi surfaces in terms of biocompatibility. However, PEMF application has a higher stimulative effect on cells cultured on cpTi surfaces when compared to TiZr.

The Effect of Femtosecond Laser Treatment on the Effectiveness of Resin-Zirconia Adhesive: An In Vitro Study

PubMed Central

Vicente Prieto, María; Gomes, Ana Luisa Caseiro; Montero Martín, Javier; Alvarado Lorenzo, Alfonso; Seoane Mato, Vicente; Albaladejo Martínez, Alberto

2016-01-01

Introduction: When aesthetics is compromised, dental ceramics are excellent materials for dental restorations; owing to their optical properties and biocompatibility, zirconia ceramics are particularly interesting. Self-adhesive resin cements are the most suitable for bonding to zirconia ceramics, but traditional adhesive chemistry is ineffective and surface treatments are required to improve the adhesive bonding between resin and zirconia. The aim of this study was to evaluate the effect of femtosecond laser treatment on the shear bond strength (SBS) of self-adhesive resin cement on zirconia surfaces and to contrast it with other different surface conditioning methods. Methods: Sixty square-shaped zirconia samples were divided randomly into four groups (n = 15) according to their surface conditioning method: the NT group - no surface treatment; the APA25 group - airborne abrasion with 25 μm alumina particles; the TSC group - tribochemical silica coating, and the FS group - femtosecond laser irradiation (800 nm, 4 mJ, 40 fs/pulse, 1 kHz). Self-adhesive resin cements were bonded at the centre of samples, and after 72 hours, they were tested for SBS with a universal testing machine at a crosshead speed of 0.5 mm/min, until fracture. Five zirconia surfaces for each group were subjected to a surface morphology analysis by scanning electron microscopy (SEM). The failure modes were noted and a third of the specimens were prepared to morphological analysis. Results: The NT group showed lower SBS values than the other groups. Femtosecond laser treatment demonstrated higher values than the control and APA25 groups and similar values to those of the TSC group. In the APA25 group, the surface conditioning method had values close to those of the TSC group, but lower than those obtained with femtosecond laser treatment. Conclusion: The treatment of zirconia with femtosecond laser irradiation created a consistent and profound surface roughness, improving the adhesive effectiveness of the zirconia-resin interface. PMID:28491255

Surface characterization studies of walnut-shell biochar catalysts for simultaneously removing of organic sulfur from yellow phosphorus tail gas

NASA Astrophysics Data System (ADS)

Song, Xin; Li, Kai; Ning, Ping; Wang, Chi; Sun, Xin; Tang, Lihong; Ruan, Haotian; Han, Shuang

2017-12-01

The influences of different preparation conditions for surface characteristics on removing organic sulfur were studied. From BET, XRD, FTIR, DRIFTS, TG/DTA, CO2-TPD results, it can be seen that these preparation conditions had great influences on the pore structure, specific surface area, crystal structure and surface functional groups. The micropore volume, amorphous structure and alkalinity site strength played major roles in desulfurization process. H2S was oxidized by oxygen containing functional groups, such as sbnd COO, sbnd Cdbnd O. H2O molecule could be converted into some groups, such as sbnd CH and Csbnd OH groups, and promoted the hydrolysis reaction. The strong alkalinity site was the key factor for chemical adsorption and hydrolysis. H2O molecule, sbnd CH, Csbnd OH groups promoted the hydrolysis reaction and sbnd COO, sbnd Cdbnd O groups promoted the oxidation of H2S on the surface of WSB. Meanwhile, the main desulfurization process over WSB after carbonization was adsorption and it changed to hydrolysis reaction after activation on the surface of WSB. Furthermore, the reaction mechanism was investigated by DRIFTS measurement according to the change of surface functional groups.

Surface characterization of nickel titanium orthodontic arch wires

PubMed Central

Krishnan, Manu; Seema, Saraswathy; Tiwari, Brijesh; Sharma, Himanshu S.; Londhe, Sanjay; Arora, Vimal

2015-01-01

Background Surface roughness of nickel titanium orthodontic arch wires poses several clinical challenges. Surface modification with aesthetic/metallic/non metallic materials is therefore a recent innovation, with clinical efficacy yet to be comprehensively evaluated. Methods One conventional and five types of surface modified nickel titanium arch wires were surface characterized with scanning electron microscopy, energy dispersive analysis, Raman spectroscopy, Atomic force microscopy and 3D profilometry. Root mean square roughness values were analyzed by one way analysis of variance and post hoc Duncan's multiple range tests. Results Study groups demonstrated considerable reduction in roughness values from conventional in a material specific pattern: Group I; conventional (578.56 nm) > Group V; Teflon (365.33 nm) > Group III; nitride (301.51 nm) > Group VI (i); rhodium (290.64 nm) > Group VI (ii); silver (252.22 nm) > Group IV; titanium (229.51 nm) > Group II; resin (158.60 nm). It also showed the defects with aesthetic (resin/Teflon) and nitride surfaces and smooth topography achieved with metals; titanium/silver/rhodium. Conclusions Resin, Teflon, titanium, silver, rhodium and nitrides were effective in decreasing surface roughness of nickel titanium arch wires albeit; certain flaws. Findings have clinical implications, considering their potential in lessening biofilm adhesion, reducing friction, improving corrosion resistance and preventing nickel leach and allergic reactions. PMID:26843749

Water Contact Angle Dependence with Hydroxyl Functional Groups on Silica Surfaces under CO2 Sequestration Conditions.

PubMed

Chen, Cong; Zhang, Ning; Li, Weizhong; Song, Yongchen

2015-12-15

Functional groups on silica surfaces under CO2 sequestration conditions are complex due to reactions among supercritical CO2, brine and silica. Molecular dynamics simulations have been performed to investigate the effects of hydroxyl functional groups on wettability. It has been found that wettability shows a strong dependence on functional groups on silica surfaces: silanol number density, space distribution, and deprotonation/protonation degree. For neutral silica surfaces with crystalline structure (Q(3), Q(3)/Q(4), Q(4)), as silanol number density decreases, contact angle increases from 33.5° to 146.7° at 10.5 MPa and 318 K. When Q(3) surface changes to an amorphous structure, water contact angle increases 20°. Water contact angle decreases about 12° when 9% of silanol groups on Q(3) surface are deprotonated. When the deprotonation degree increases to 50%, water contact angle decreases to 0. The dependence of wettability on silica surface functional groups was used to analyze contact angle measurement ambiguity in literature. The composition of silica surfaces is complicated under CO2 sequestration conditions, the results found in this study may help to better understand wettability of CO2/brine/silica system.

The effect of toothbrush bristle stiffness on nanohybrid surface roughness

NASA Astrophysics Data System (ADS)

Zairani, O.; Irawan, B.; Damiyanti, M.

2017-08-01

The surface of a restoration can be affected by toothpaste containing abrasive agents and the stiffness of toothbrush bristles. Objective: To identify the effect of toothbrush bristle stiffness on nanohybrid surface roughness. Methods: Sixteen nanohybrid specimens were separated into two groups. The first group was brushed using soft-bristle toothbrushes, and the second group was brushed using medium-bristle toothbrushes. Media such as aqua bides was used for brushing in both groups. Brushing was done 3 times for 5 minutes. Surface roughness was measured initially and at 5, 10, and 15 minutes using a surface roughness tester. Results: The results, tested with One-Way ANOVA and Independent Samples t Test, demonstrated that after brushing for 15 minutes, the soft-bristle toothbrush group showed a significantly different value (p < 0.05) of nanohybrid surface roughness. The group using medium-bristle toothbrushes showed the value of nano hybrid surface roughness significant difference after brushing for 10 minutes. Conclusion: Roughness occurs more rapidly when brushing with medium-bristle tooth brushes than when brushing with soft-bristle toothbrushes.

Spontaneous adsorption on a hydrophobic surface governed by hydrogen bonding.

PubMed

Dang, Fuquan; Hasegawa, Takeshi; Biju, Vasudevanpillai; Ishikawa, Mitsuru; Kaji, Noritada; Yasui, Takao; Baba, Yoshinobu

2009-08-18

Spontaneous adsorption from solution onto solid surface is a common phenomenon in nature, but the force that governs adsorption is still a matter of considerable debate. (1, 2) We found that surfactants and cellulose adsorb from solution onto a poly(methyl methacrylate) (PMMA) surface in an ordered and cooperative way governed by hydrogen bonding. The glucose rings of n-dodecyl-beta-D-maltoside (DDM) and hydroxyethylcellulose (HEC) stand perpendicular to the surface, H-bond to the surface COOMe groups with their C=O and Me-O bonds parallel to the surface, and form a tight monolayer. The non-H-bonded COOMe groups orient their C=O bonds perpendicular to the surface. In contrast, the glucose rings of hydrophobically modified hydroxyethylcellulose (HMHEC) lie flat with the side chains perpendicular to the surface and H-bond to the perpendicular-oriented C=O groups. The non-H-bonded COOMe groups orient their C=O bonds parallel but Me-O bonds near-perpendicular to the surface for stabilizing HMHEC. The current work provides a detailed picture of how surface-active molecules interact with a solid surface and self-assemble into greatly different architectures.

The effect of glazing and aging on the surface properties of CAD/CAM resin blocks

PubMed Central

Tuncer, Safa; Kara, Dilan; Demirci, Mustafa

2018-01-01

PURPOSE To investigate the effect of accelerated aging on surface properties of glazed CAD/CAM resin blocks using a 2D surface profilometer and a 3D non-contact optical profilometer. MATERIALS AND METHODS Three types of CAD/CAM resin restorative materials, LAVA Ultimate (3M ESPE, St Paul, MN, USA), VITA Enamic (Vita Zahnfabrik H. Rauter, Bad Säckingen, Germany), and Cerasmart (GC Corparation, Tokyo, Japan) were used for this study. CAD/CAM blocks were cut in 3-mm thickness slabs and divided into three groups; Group 1: control group (specimens polished with 600 grit SCI paper); Group 2: specimens sandblasted, silanized, and glazed with Optiglaze Color (GC); Group 3: glazed specimens subjected to 5000 thermocycles (n=15). The surface roughness (Ra and Rz) was evaluated using a profilometer and a 3D scanning instrument. Data were analyzed using two-way ANOVA and Tukey's post-hoc test (P<.05). RESULTS LAVA, VITA, and Cerasmart exhibited statistically similar Ra and Rz values for each group (P>.05). For VITA and Cerasmart, the specimens in Group 1 exhibited significantly higher Ra values than Group 2 (P<.05). Group 1 (0.502 Ra), Group 2 (0.384 Ra), and Group 3 (0.431 Ra) exhibited statistically similar Ra values for LAVA (P=.062). After 5000 thermocycles, surface roughness values did not change significantly for glazed LAVA, VITA, and Cerasmart (P>.05). CONCLUSION Glaze material Optiglaze Color makes CAD/CAM resin surfaces smooth and glazed CAD/CAM surfaces seem resistant to deterioration under 5000 thermocycles. PMID:29503714

The effect of glazing and aging on the surface properties of CAD/CAM resin blocks.

PubMed

Tekçe, Neslihan; Fidan, Sinan; Tuncer, Safa; Kara, Dilan; Demirci, Mustafa

2018-02-01

To investigate the effect of accelerated aging on surface properties of glazed CAD/CAM resin blocks using a 2D surface profilometer and a 3D non-contact optical profilometer. Three types of CAD/CAM resin restorative materials, LAVA Ultimate (3M ESPE, St Paul, MN, USA), VITA Enamic (Vita Zahnfabrik H. Rauter, Bad Säckingen, Germany), and Cerasmart (GC Corparation, Tokyo, Japan) were used for this study. CAD/CAM blocks were cut in 3-mm thickness slabs and divided into three groups; Group 1: control group (specimens polished with 600 grit SCI paper); Group 2: specimens sandblasted, silanized, and glazed with Optiglaze Color (GC); Group 3: glazed specimens subjected to 5000 thermocycles (n=15). The surface roughness (R a and R z ) was evaluated using a profilometer and a 3D scanning instrument. Data were analyzed using two-way ANOVA and Tukey's post-hoc test ( P <.05). LAVA, VITA, and Cerasmart exhibited statistically similar R a and R z values for each group ( P >.05). For VITA and Cerasmart, the specimens in Group 1 exhibited significantly higher R a values than Group 2 ( P <.05). Group 1 (0.502 R a ), Group 2 (0.384 R a ), and Group 3 (0.431 R a ) exhibited statistically similar R a values for LAVA ( P =.062). After 5000 thermocycles, surface roughness values did not change significantly for glazed LAVA, VITA, and Cerasmart ( P >.05). Glaze material Optiglaze Color makes CAD/CAM resin surfaces smooth and glazed CAD/CAM surfaces seem resistant to deterioration under 5000 thermocycles.

Method for producing hydrophobic aerogels

DOEpatents

Hrubesh, Lawrence W.; Poco, John F.; Coronado, Paul R.

1999-01-01

A method for treating a dried monolithic aerogel containing non-dispersed particles, with an organometallic surface modifying agent to produce hydrophobic aerogels. The dried, porous hydrophobic aerogels contain a protective layer of alkyl groups, such as methyl groups, on the modified surfaces of the pores of the aerogel. The alkyl groups at the aerogel surface typically contain at least one carbon-metal bond per group.

The effect of bridge exercise accompanied by the abdominal drawing-in maneuver on an unstable support surface on the lumbar stability of normal adults.

PubMed

Gong, Wontae

2015-01-01

[Purpose] The present study sought to investigate the influence on static and dynamic lumbar stability of bridge exercise accompanied by an abdominal drawing-in maneuver (ADIM) performed on an uneven support surface. [Subjects] A total of 30 participants were divided into an experimental group (15 participants) and a control group (15 participants). [Methods] The experimental group performed bridge exercise on an unstable surface, whereas the control group performed bridge exercise on a stable surface. The respective bridge exercises were performed for 30 minutes, 3 times per week, for 6 weeks. The static lumbar stability (SLS) and dynamic lumbar stability (DLS) of both the experimental group and the control group were measured using a pressure biofeedback unit. [Results] In the comparison of the initial and final results of the experimental and control groups, only the SLS and DLS of the experimental group were found to be statistically significant. [Conclusion] The results of the present study show that when using bridge exercise to improve SLS and DLS, performing the bridge exercise accompanied by ADIM on an uneven surface is more effective than performing the exercise on a stable surface.

Laser-treated stainless steel mini-screw implants: 3D surface roughness, bone-implant contact, and fracture resistance analysis

PubMed Central

Kang, He-Kyong; Chu, Tien-Min; Dechow, Paul; Stewart, Kelton; Kyung, Hee-Moon

2016-01-01

Summary Background/Objectives: This study investigated the biomechanical properties and bone-implant intersurface response of machined and laser surface-treated stainless steel (SS) mini-screw implants (MSIs). Material and Methods: Forty-eight 1.3mm in diameter and 6mm long SS MSIs were divided into two groups. The control (machined surface) group received no surface treatment; the laser-treated group received Nd-YAG laser surface treatment. Half in each group was used for examining surface roughness (Sa and Sq), surface texture, and facture resistance. The remaining MSIs were placed in the maxilla of six skeletally mature male beagle dogs in a randomized split-mouth design. A pair with the same surface treatment was placed on the same side and immediately loaded with 200g nickel–titanium coil springs for 8 weeks. After killing, the bone-implant contact (BIC) for each MSI was calculated using micro computed tomography. Analysis of variance model and two-sample t test were used for statistical analysis with a significance level of P <0.05. Results: The mean values of Sa and Sq were significantly higher in the laser-treated group compared with the machined group (P <0.05). There were no significant differences in fracture resistance and BIC between the two groups. Limitation: animal study Conclusions/Implications: Laser treatment increased surface roughness without compromising fracture resistance. Despite increasing surface roughness, laser treatment did not improve BIC. Overall, it appears that medical grade SS has the potential to be substituted for titanium alloy MSIs. PMID:25908868

Surface nucleation and independent growth of Ce(OH)4 within confinement space on modified carbon black surface to prepare nano-CeO2 without agglomeration

NASA Astrophysics Data System (ADS)

Zhang, Xinyue; Xia, Chunhui; Li, Kaitao; Lin, Yanjun

2018-06-01

Highly dispersed negative carboxyl groups can be formed on carbon black (CB) surface modified with strong nitric acid. Therefore positive cations can be uniformly absorbed by carboxyl groups and precipitated within a confinement space on modified CB surface to prepare highly dispersed nanomaterials. In this paper, the formation and dispersion status of surface negative carboxyl groups, adsorption status of Ce3+, surface confinement nucleation, crystallization and calcination process were studied by EDS, SEM, and laser particle size analysis. The results show that the carboxyl groups formed on modified CB surface are highly dispersed, and Ce3+ cations can be uniformly anchored by carboxyl groups. Therefore, highly dispersed Ce3+ can react with OH- within a confinement surface region to form positive nano-Ce(OH)4 nuclei which also can be adsorbed by electrostatic attraction. After independent growth of Ce(OH)4 without agglomeration, highly dispersed CeO2 nanoparticles without agglomeration can be prepared together with the help of effectively isolates by CO2 released in the combustion of CB.

Surface nucleation and independent growth of Ce(OH)4 within confinement space on modified carbon black surface to prepare nano-CeO2 without agglomeration

NASA Astrophysics Data System (ADS)

Zhang, Xinyue; Xia, Chunhui; Li, Kaitao; Lin, Yanjun

2018-04-01

Highly dispersed negative carboxyl groups can be formed on carbon black (CB) surface modified with strong nitric acid. Therefore positive cations can be uniformly absorbed by carboxyl groups and precipitated within a confinement space on modified CB surface to prepare highly dispersed nanomaterials. In this paper, the formation and dispersion status of surface negative carboxyl groups, adsorption status of Ce3+, surface confinement nucleation, crystallization and calcination process were studied by EDS, SEM, and laser particle size analysis. The results show that the carboxyl groups formed on modified CB surface are highly dispersed, and Ce3+ cations can be uniformly anchored by carboxyl groups. Therefore, highly dispersed Ce3+ can react with OH- within a confinement surface region to form positive nano-Ce(OH)4 nuclei which also can be adsorbed by electrostatic attraction. After independent growth of Ce(OH)4 without agglomeration, highly dispersed CeO2 nanoparticles without agglomeration can be prepared together with the help of effectively isolates by CO2 released in the combustion of CB.

Three-Dimensional Polypeptide Architectures Through Tandem Catalysis and Click Chemistry

NASA Astrophysics Data System (ADS)

Rhodes, Allison Jane

Rapid renal clearance, liver accumulation, proteolytic degradation and non-specificity are challenges small molecule drugs, peptides, proteins and nucleic acid therapeutics encounter en route to their intended destination within the body. Nanocarriers (i.e. dendritric polymers, vesicles, and micelles) of approximately 100 nm in diameter, shuttle small molecule drugs to their desired location through passive (EPR effect) and active (ligand-mediated) targeting, maximizing therapeutic efficiency. Polypeptide-based polymers are water-soluble, biocompatible, non-toxic and are therefore excellent candidates for nanocarriers. Dendritic polymers, including dendrimers, cylindrical brushes, and star polymers, are the newest class of nanomedicine drug delivery vehicles. The synthesis and characterization of dendritic polymers is challenging, with tedious and costly procedures. Dendritic polymers possess peripheral pendent functional groups that can potentially be used in ligand-mediated drug delivery vehicles and bioimaging applications. More specifically, cylindrical brushes are dendritic polymers where a single linear polymer (primary chain) has polymer chains (secondary chains) grafted to it. Recently, research groups have shown that cylindrical brush polymers are capable of nanoparticle and supramolecular structure self-assembly. The facile preparation of high-density brush copolypeptides by the "grafting from" approach will be discussed. This approach utilizes a novel, tandem catalytic methodology where alloc-alpha-aminoamide groups are installed within the side-chains of the alpha-amino-N-carboxyanhydride (NCA) monomer serving as masked initiators. These groups are inert during cobalt initiated NCA polymerization, and give alloc-alpha-aminoamide substituted polypeptide main-chains. The alloc-alpha-aminoamide groups are activated in situ using nickel to generate initiators for growth of side-chain brush segments. This method proves to be efficient, yielding well-defined, high-density brushes for applications in drug delivery and imaging. Here, we also report a method for the synthesis of soluble, well-defined, azido functionalized polypeptides in a straightforward, 3-step synthesis. Homo and diblock azidopolypeptides were prepared with controlled segment lengths via living polymerization using Co(PMe3)4 initiator. Through copper azide alkyne click chemistry (CuAAC) in organic solvent, azidopolypeptides were regioselectively and quantitatively modified with carboxylic acid (pH-responsive), amino acid and sugar functional groups. Finally, the advances towards well-defined hyperbranched polypeptides through alpha-amino-acid-N-thiocarboxyanhydrides (NTAs) will be discussed. Within the past 10 years, controlled NCA (alpha-amino acid-N-carboxyanhydride) ring-opening polymerization (ROP) has emerged, expanding the application of copolypeptide polymers in various drug delivery and tissue engineering motifs. Modification of NCA monomers to the corresponding alpha-amino-acid-N-thiocarboxyanhydride (NTA) will diversify ROP reactions, leading to more complex polypeptides (such as hyperbranched polymers), in addition to the possibility of performing these polymerizations under ambient conditions, which would greatly expand their potential utility. The project focuses on the preparation of hyperbranched polypeptides with well-defined architectures and controlled branching density in a one-pot reaction. This will be accomplished by taking advantage of the different selectivities of Co(PMe3)4 and depeNi(COD) polymerization initiators, and by exploiting the reactivity difference between NCA and the more stable NTA monomers.

Effects of surface-finishing protocols on the roughness, color change, and translucency of different ceramic systems.

PubMed

Akar, Gülcan Coşkun; Pekkan, Gürel; Çal, Ebru; Eskitaşçıoğlu, Gürcan; Özcan, Mutlu

2014-08-01

Surface-finishing protocols have a mechanical impact on ceramic surfaces that could eventually affect surface topography and light scattering. An optimum protocol is needed to avoid damaging the optical properties of ceramics. The purpose of this study was to determine the effects of different surface-finishing protocols on the surface roughness, color change, and translucency of ceramic and metal ceramic restorations. Standardized disk-shaped specimens (1.5 × 10 mm, n=128) were fabricated from 3 different ceramic core materials (aluminum oxide [Al2O3]-AL, zirconium oxide [ZrO2]-ZR, lithium disilicate [Li2Si2O5]-LIT), veneered (V) with dentin ceramics (n=32 per group), and placed in the following groups: ALV, ZRV, and LITV. The metal ceramic group acted as the control (n=32). Four different surface-finishing methods were tested. Airborne-particle abrasion with 50 μm Al2O3, polishing with adjustment kit, polishing with adjustment kit plus diamond polishing paste, and autoglazing (n=8 subgroup) were applied on the veneering ceramics. The specimens were analyzed with a profilometer for surface roughness, and color change and translucency were measured with a clinical spectrophotometer. Statistical analyses were performed with 1-way ANOVA and the Tukey honest significant difference tests (α=.05). Specimens treated with the airborne particle abrasion method showed significantly higher mean profilometer for surface roughness values in all groups (P<.05). The polishing with adjustment kit and autoglazing methods revealed statistically similar surface roughness values in all groups (P>.05). With the diamond polishing paste method, lower surface roughness values were achieved in the ZRV and metal ceramic groups acted as the control groups. Different surface-finishing methods affected the color change of the ceramic systems, except for ZRV. Surface-finishing protocols significantly affected the translucency values of the ALV, LITV, and metal ceramic groups (P<.05). No single surface-finishing protocol can be recommended to obtain the smoothest surface and the least color change without affecting translucency for the ceramics tested. The airborne-particle abrasion protocol created rougher surfaces and decreased translucency, and color change in zirconia was not affected by the finishing protocols. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

In vitro labeling strategies for in cellulo fluorescence microscopy of single ribonucleoprotein machines.

PubMed

Custer, Thomas C; Walter, Nils G

2017-07-01

RNA plays a fundamental, ubiquitous role as either substrate or functional component of many large cellular complexes-"molecular machines"-used to maintain and control the readout of genetic information, a functional landscape that we are only beginning to understand. The cellular mechanisms for the spatiotemporal organization of the plethora of RNAs involved in gene expression are particularly poorly understood. Intracellular single-molecule fluorescence microscopy provides a powerful emerging tool for probing the pertinent mechanistic parameters that govern cellular RNA functions, including those of protein coding messenger RNAs (mRNAs). Progress has been hampered, however, by the scarcity of efficient high-yield methods to fluorescently label RNA molecules without the need to drastically increase their molecular weight through artificial appendages that may result in altered behavior. Herein, we employ T7 RNA polymerase to body label an RNA with a cyanine dye, as well as yeast poly(A) polymerase to strategically place multiple 2'-azido-modifications for subsequent fluorophore labeling either between the body and tail or randomly throughout the tail. Using a combination of biochemical and single-molecule fluorescence microscopy approaches, we demonstrate that both yeast poly(A) polymerase labeling strategies result in fully functional mRNA, whereas protein coding is severely diminished in the case of body labeling. © 2016 The Protein Society.

Generation of therapeutic protein variants with the human serum albumin binding capacity via site-specific fatty acid conjugation.

PubMed

Cho, Jinhwan; Lim, Sung In; Yang, Byung Seop; Hahn, Young S; Kwon, Inchan

2017-12-21

Extension of the serum half-life is an important issue in developing new therapeutic proteins and expanding applications of existing therapeutic proteins. Conjugation of fatty acid, a natural human serum albumin ligand, to a therapeutic protein/peptide was developed as a technique to extend the serum half-life in vivo by taking advantages of unusually long serum half-life of human serum albumin (HSA). However, for broad applications of fatty acid-conjugation, several issues should be addressed, including a poor solubility of fatty acid and a substantial loss in the therapeutic activity. Therefore, herein we systematically investigate the conditions and components in conjugation of fatty acid to a therapeutic protein resulting in the HSA binding capacity without compromising therapeutic activities. By examining the crystal structure and performing dye conjugation assay, two sites (W160 and D112) of urate oxidase (Uox), a model therapeutic protein, were selected as sites for fatty acid-conjugation. Combination of site-specific incorporation of a clickable p-azido-L-phenylalanine to Uox and strain-promoted azide-alkyne cycloaddition allowed the conjugation of fatty acid (palmitic acid analog) to Uox with the HSA binding capacity and retained enzyme activity. Deoxycholic acid, a strong detergent, greatly enhanced the conjugation yield likely due to the enhanced solubility of palmitic acid analog.

Down-regulation of HSP60 Suppresses the Proliferation of Glioblastoma Cells via the ROS/AMPK/mTOR Pathway

PubMed Central

Tang, Haiping; Li, Jin; Liu, Xiaohui; Wang, Guihuai; Luo, Minkui; Deng, Haiteng

2016-01-01

Glioblastoma is a fatal and incurable cancer with the hyper-activated mTOR pathway. HSP60, a major chaperone for maintenance of mitochondrial proteostasis, is highly expressed in glioblastoma patients. To understand the effects of HSP60 on glioblastoma tumorigenesis and progression, we characterized the HSP60-knockdowned glioblastoma cells and revealed that HSP60 silencing markedly suppressed cell proliferation and promoted cell to undergo the epithelial-mesenchymal transition (EMT). Proteomic analysis showed that ribosomal proteins were significantly downregulated whereas EMT-associated proteins were up-regulated in HSP60-knockdowned U87 cells as confirmed by a distinct enrichment pattern in newly synthesized proteins with azido-homoalanine labeling. Biochemical analysis revealed that HSP60 knockdown increased reactive oxygen species (ROS) production that led to AMPK activation, similarly to the complex I inhibitor rotenone-induced AMPK activation. Activated AMPK suppressed mTORC1 mediated S6K and 4EBP1 phosphorylation to decrease protein translation, which slowed down cell growth and proliferation. On the other hand, high levels of ROS in HSP60 knockdowned or rotenone-treated U87 cells contributed to EMT. These results indicate that HSP60 silencing deactivates the mTOR pathway to suppress glioblastoma progression, suggesting that HSP60 is a potential therapeutic target for glioblastoma treatment. PMID:27325206

Target-Based Screen Against a Periplasmic Serine Protease That Regulates Intrabacterial pH Homeostasis in Mycobacterium tuberculosis

PubMed Central

2015-01-01

Mycobacterium tuberculosis (Mtb) maintains its intrabacterial pH (pHIB) near neutrality in the acidic environment of phagosomes within activated macrophages. A previously reported genetic screen revealed that Mtb loses this ability when the mycobacterial acid resistance protease (marP) gene is disrupted. In the present study, a high throughput screen (HTS) of compounds against the protease domain of MarP identified benzoxazinones as inhibitors of MarP. A potent benzoxazinone, BO43 (6-chloro-2-(2′-methylphenyl)-4H-1,3-benzoxazin-4-one), acylated MarP and lowered Mtb’s pHIB and survival during incubation at pH 4.5. BO43 had similar effects on MarP-deficient Mtb, suggesting the existence of additional target(s). Reaction of an alkynyl-benzoxazinone, BO43T, with Mycobacterium bovis variant bacille Calmette-Guérin (BCG) followed by click chemistry with azido-biotin identified both the MarP homologue and the high temperature requirement A1 (HtrA1) homologue, an essential protein. Thus, the chemical probe identified through a target-based screen not only reacted with its intended target in the intact cells but also implicated an additional enzyme that had eluded a genetic screen biased against essential genes. PMID:25457457

Effects of allicin on both telomerase activity and apoptosis in gastric cancer SGC-7901 cells.

PubMed

Sun, Li; Wang, Xu

2003-09-01

To investigate the effects of allicin on both telomerase activity and apoptosis in gastric cancer SGC-7901 cells. The gastric cancer SGC-7901 adenocarcinoma cells were treated with allicin and the cell cycle, inhibitory rate, apoptosis, telomerase activity and morphologic changes were studied by MTT assay, flow cytometry (FCM), TRAP-PCR-ELISA assay, light microscope, electron microscope respectively. Results were compared with that of AZT (3'-Azido-3'-deoxythymidine). SGC-7901 cells were suppressed after exposure to allicin of 0.016 mg/ml, 0.05 mg/ml, and 0.1 mg/ml for 48 h. Compared with the control, the difference was significant (P<0.05). Allicin could induce apoptosis of the cells in a dose-dependent and non-linear manner and increase the proportion of cells in the G(2)/M phase. Compared with the control, the difference was significant in terms of the percentage of cells in the G2/M phase (P<0.05). Allicin could inhibit telomerase activity in a time-dependent and dose-dependent pattern. After exposure to allicin at 0.016 mg/ml for 24 hours, SGC-7901 cells showed typical morphologic change. Allicin can inhibit telomerase activity and induce apoptosis of gastric cancer SGC-7901 cells. Allicin may be more effective than AZT.

A sensitive fluorescent sensor for quantification of alpha-fetoprotein based on immunosorbent assay and click chemistry.

PubMed

Xie, Qunfang; Weng, Xiuhua; Lu, Lijun; Lin, Zhenyu; Xu, Xiongwei; Fu, Caili

2016-03-15

A novel fluoresencent immunosensor for determination of cancer biomarkers such as alpha-fetoprotein (AFP) was designed by utilizing both the high specificity of antigen-antibody sandwich structure and the high sensitivity of the click chemistry based fluorescence detection. Instead of an enzyme or fluorophore, the CuO nanoparticles are labeled on the detection antibody, which was not susceptible to the change of the external environments. The CuO nanoparticles which were modified on the sandwich structure can be dissolved to produce Cu(2+) ions with the help of HCl and then the Cu(2+) ions were reduced by sodium ascorbate to produce Cu(+) ions which triggered the Cu(+) catalyzed alkyne-azide cycloaddition (CuAAC) reaction between the weak fluorescent compound (3-azido-7-hydroxycoumarin) and propargyl alcohol to form a strong fluorescent compound. A good linear relationship was observed between the fluorescence increase factor of the system and the concentration of AFP in the range of 0.025-5.0 ng/mL with a detection limit of 12 pg/mL (S/N=3). The proposed fluorescent sensor had been applied to detect AFP in the human serum samples and gave satisfactory results. Copyright © 2015 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kahoun, J.R.; Ruoho, A.E.

A carrier-free radioiodinated cocaine photoaffinity label, (-)-3-({sup 125}I)iodo-4-azidococaine (({sup 125}I)IACoc), has been synthesized and used as a probe for cocaine-binding proteins. Photoaffinity labeling with 0.5 nM ({sup 125}I)IACoc resulted in selective derivatization of a 26-kDa polypeptide with the pharmacology of a sigma receptor in membranes derived from whole rat brain, rat liver, and human placenta. ({sup 125}I)IACoc labeling of the 26-kDa polypeptide was also inhibited by 10 {mu}M imipramine, amitriptyline, fluoxetine, benztropine, and tetrabenazine. The size of the ({sup 125}I)I-ACoc-labeled proteins is consistent with the size of proteins photolabeled in guinea pig brain and liver membranes by using the sigmamore » photolabel azido-({sup 3}H)DTG. Kinetic analysis of ({sup 125}I)IACoc binding to rat liver microsomes revealed two sites with K{sub d} values of 19 and 126 pM, respectively. The presence or absence of proteolytic inhibitors during membrane preparation did not alter the size of the photolabeled sigma receptor, indicating that the 26-kDa polypeptide was not derived from a larger protein. In summary, ({sup 125}I)IACoc is a potent and highly specific photoaffinity label for the haloperidol-sensitive sigma receptor and will be useful for its biochemical and molecular characterization.« less

New fluorescent reagents specific for Ca{sup 2+}-binding proteins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ben-Hail, Danya; Lemelson, Daniela; Israelson, Adrian

2012-09-14

Highlights: Black-Right-Pointing-Pointer New reagents specifically inhibit the activity of Ca{sup 2+}-dependent proteins. Black-Right-Pointing-Pointer FITC-Ru and EITC-Ru allow for mechanism-independent probing of Ca{sup 2+}-binding proteins. Black-Right-Pointing-Pointer Changes in reagents fluorescence allow characterization of protein Ca{sup 2+}-binding properties. -- Abstract: Ca{sup 2+} carries information pivotal to cell life and death via its interactions with specific binding sites in a protein. We previously developed a novel photoreactive reagent, azido ruthenium (AzRu), which strongly inhibits Ca{sup 2+}-dependent activities. Here, we synthesized new fluorescent ruthenium-based reagents containing FITC or EITC, FITC-Ru and EITC-Ru. These reagents were purified, characterized and found to specifically interact with andmore » markedly inhibit Ca{sup 2+}-dependent activities but not the activity of Ca{sup 2+}-independent reactions. In contrast to many reagents that serve as probes for Ca{sup 2+}, FITC-Ru and EITC-Ru are the first fluorescent divalent cation analogs to be synthesized and characterized that specifically bind to Ca{sup 2+}-binding proteins and inhibit their activity. Such reagents will assist in characterizing Ca{sup 2+}-binding proteins, thereby facilitating better understanding of the function of Ca{sup 2+} as a key bio-regulator.« less

In Vivo Tumor Cell Targeting with “Click” Nanoparticles

PubMed Central

von Maltzahn, Geoffrey; Ren, Yin; Park, Ji-Ho; Min, Dal-Hee; Kotamraju, Venkata Ramana; Jayakumar, Jayanthi; Fogel, Valentina; Sailor, Michael J.; Ruoslahti, Erkki; Bhatia, Sangeeta N.

2008-01-01

The in vivo fate of nanomaterials strongly determines their biomedical efficacy. Accordingly, much effort has been invested into the development of library screening methods to select targeting ligands for a diversity of sites in vivo. Still, broad application of chemical and biological screens to the in vivo targeting of nanomaterials requires ligand attachment chemistries that are generalizable, efficient, covalent, orthogonal to diverse biochemical libraries, applicable under aqueous conditions, and stable in in vivo environments. To date, the copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition or “click” reaction has shown considerable promise as a method for developing targeted nanomaterials in vitro. Here, we investigate the utility of “click” chemistry for the in vivo targeting of inorganic nanoparticles to tumors. We find that “click” chemistry allows cyclic LyP-1 targeting peptides to be specifically linked to azido-nanoparticles and to direct their binding to p32-expressing tumor cells in vitro. Moreover, “click” nanoparticles are able to stably circulate for hours in vivo following intravenous administration (>5h circulation time), extravasate into tumors, and penetrate the tumor interstitium to specifically bind p32-expressing cells in tumors. In the future, in vivo use of “click” nanomaterials should expedite the progression from ligand discovery to in vivo evaluation and diversify approaches toward multifunctional nanoparticle development. PMID:18611045

A Single Zidovudine (AZT) Administration Delays Hepatic Cell Proliferation by Altering Oxidative State in the Regenerating Rat Liver.

PubMed

Butanda-Ochoa, Armando; Hernández-Espinosa, Diego Rolando; Olguín-Martínez, Marisela; Sánchez-Sevilla, Lourdes; Rodríguez, Mario R; Chávez-Rentería, Benito; Aranda-Fraustro, Alberto; Hernández-Muñoz, Rolando

2017-01-01

The 3'-azido-3'-deoxythymidine or Zidovudine (AZT) was the first antiretroviral drug used in the treatment of HIV patients, which has good effectiveness but also hepatotoxic side effects that include cell cycle arrest and oxidative/nitrative mitochondrial damage. Whether such an oxidative damage may affect the proliferative-regenerative capacity of liver remains to be clearly specified at doses commonly used in the clinical practice. In this study, we described the oxidative-proliferative effect of AZT administered at a common clinical dose in rat liver submitted to 70% partial hepatectomy (PH). The results indicate that AZT significantly decreased DNA synthesis and the number of mitosis in liver subjected to PH in a synchronized way with the promotion of organelle-selective lipid peroxidation events (especially those observed in plasma membrane and cytosolic fractions) and with liver enzyme release to the bloodstream. Then at the dose used in clinical practice AZT decreased liver regeneration but stimulates oxidative events involved during the proliferation process in a way that each membrane system inside the cell preserves its integrity in order to maintain the cell proliferative process. Here, the induction of large amounts of free ammonia in the systemic circulation could become a factor capable of mediating the deleterious effects of AZT on PH-induced rat liver regeneration.

Effect of repair resin type and surface treatment on the repair strength of heat-polymerized denture base resin.

PubMed

Alkurt, Murat; Yeşil Duymuş, Zeynep; Gundogdu, Mustafa

2014-01-01

Acrylic resin denture fracture is common in prosthodontic practice. When fractured denture bases are repaired, recurrent fractures frequently occur at the repair surface interface or adjacent areas. The purpose of this study was to evaluate the effect of different surface treatments on the flexural strength of the acrylic resin denture base repaired with heat-polymerized acrylic resin, autopolymerizing resin, and light-polymerized acrylic resin. Ninety-six specimens of heat-polymerized acrylic resin were prepared according to the American Dental Association Specification No. 12 (65.0 × 10.0 × 2.5 mm) and sectioned into halves to create a repair gap (3.0 × 10 × 2.5 mm). The sectioned specimens were divided into 3 groups according to their repair materials. The specimens from each group were divided into 4 subgroups according to their surface treatments: a control group without any surface treatment; an experimental group treated with methyl methacrylate monomer (MMA group); an experimental group treated with airborne-particle abrasion with aluminum oxide particles of 250-μm particle size (abrasion group); and an experimental group treated with erbium:yttrium-aluminum-garnet laser (laser group). After the surface treatments, the 3 materials were placed into the repair gaps and then polymerized. After all of the specimens had been ground and polished, they were stored in distilled water at 37°C for 1 week and subjected to a 3-point bend test. Data were analyzed with a 2-way analysis of variance, and the Tukey honestly significant difference test was performed to identify significant differences (α=.05). The effects of the surface treatments and repair resins on the surface of the denture base resin were examined with scanning electron microscopy. Significant differences were found among the groups in terms of repair resin type (P<.001). All surface-treated specimens had higher flexural strength than controls, except the surface treated with the methyl methacrylate in the heat-polymerized group. A significant difference between the control and abrasion groups (P=.013) was found. The scanning electron microscopy observations showed that the application of surface treatments modified the surface of the denture base resin. The repair procedure with heat-polymerized resin exhibited significantly higher flexural strength than that of the autopolymerized and light-polymerized resins. In addition, the airborne-particle abrasion with aluminum oxide particles of 250-μm particle size improved the flexural strength of the specimens tested. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

Evaluation of the Effect of Surface Polishing, Oral Beverages and Food Colorants on Color Stability and Surface Roughness of Nanocomposite Resins

PubMed Central

Kumari, R Veena; Nagaraj, Hema; Siddaraju, Kishore; Poluri, Ramya Krishna

2015-01-01

Background: It is beyond doubt that finishing and polishing of a composite restoration enhance its esthetics and, is also essential for the health of the periodontium. A variety of instruments are commonly used for finishing and polishing tooth-colored restorative materials Thus, it is important to understand which type of surface finishing treatments would significantly affect the staining and surface irregularities of the composite resin restoration. Still one of the properties of the composite resins that have to pass the test of time is its color stability. In modern day dentistry, a large emphasis is laid over esthetics. Hence, it is important to understand the various agents capable of adversely affecting the esthetics of a restoration due to its staining capacity. Thus, the aim of this in vitro study was to evaluate the effect of surface polishing, oral beverages and food colorants on the color stability and surface roughness of nanocomposite resins. Materials and Methods: 90 Disks of nanocomposites resin (Filtek Z350 XT) measuring 8 mm in diameter and 2 mm in thickness were fabricated using a custom made silicon mold. Pre-polishing surface roughness (Ra1) of all the 90 samples were measured using a Surface Profilometer. The nano-composite disks were then randomly divided into 3 groups with 30 samples in each group. Group I: Control group: The samples were not subjected to any polishing procedures. Group II: Sof-Lex group: Samples subjected to polishing using different grits of Sof-Lex disks. Group III: Diamond polishing paste group: Samples were subjected with a polishing paste consisting of diamond particles. Following polishing procedures, the surface roughness of all samples were measured again to obtain change in surface roughness due to polishing procedures (Ra2), pre immersion spectrophotometric value (ΔE1) was also recorded for baseline color of the samples. The samples were then divided into subgroups (A, B, C, D, E), by including every first sample in Subgroup A, second in Subgroup B, third in Subgroup C, fourth in Subgroup D, and fifth in Subgroup E. Each was immersed in the respective test solution for 10 min, twice a day for 30 days. Group A - Tea, Group B - Coffee, Group C - Cola, Group D - Turmeric, Group E - Control (artificial saliva). Post immersion profilometric value was recorded to evaluate roughness bought about by the solutions (Ra3) and spectrophotometric value was recorded to evaluate the color change in samples (ΔE2). Results were statistically analyzed using ANOVA. Results: Higher mean roughness (Ra2-Ra1) value was recorded in Sof-Lex, followed by Diamond polishing paste and Control group. Comparison of surface roughness caused due to beverages and food colorant solution showed subgroup C (Coca Cola) increased surface roughness in all groups (Group I, II, III). Subgroup D (Turmeric) had the highest discoloration potential (P < 0001) in all groups, followed by coffee, tea, coca-cola and artificial saliva. Sof-Lex polishing System showed most color stability. Conclusion: Polishing procedures significantly roughen the surface of the restoration compared to the unpolished Mylar controls. One-step polishing system (diamond polishing paste) produces a smoother surface compared to a multi-step system (Sof-Lex polishing disks). Turmeric solution caused maximum staining of the samples, to a visually perceptible level. PMID:26229373

[Effects of Nd: YAG laser irradiation on the root surfaces and adhesion of Streptococcus mutans].

PubMed

Yuanhong, Li; Zhongcheng, Li; Mengqi, Luo; Daonan, Shen; Shu, Zhang; Shu, Meng

2016-12-01

This study aimed to evaluate the effects of treatment with different powers of Nd: YAG laser irradiation on root surfaces and Streptococcus mutans (S. mutans) adhesion. Extracted teeth because of severe periodontal disease were divided into the following four groups: control group, laser group 1, laser group 2, and laser group 3. After scaling and root planning, laser group 1, laser group 2, and laser group 3 were separately treated with Nd: YAG laser irradiation (4/6/8 W, 60 s); however, the control group did not receive the treatment. Scanning electron microscopy (SEM) was used to determine the morphology. S. mutans were cultured with root slices from each group. Colony forming unit per mL (CFU·mL⁻¹) was used to count and compare the amounts of bacteria adhesion among groups. SEM was used to observe the difference of bacteria adhesion to root surfaces between control group (scaling) and laser group 2 (6 W, 60 s), thereby indicating the different bacteria adhesions because of different treatments. Morphology alterations indicated that root surfaces in control group contain obvious smear layer, debris, and biofilm; whereas the root surfaces in laser group contain more cracks with less smear layer and debris. The bacteria counting indicated that S. mutans adhesion to laser group was weaker than that of control group (P<0.05). No statistical significance among the laser groups (P>0.05) was observed. Morphology alterations also verified that S. mutans adhesion to laser group 2 (6 W, 60 s) was weaker than that of control group (scaling). This study demonstrated that Nd: YAG laser irradiation treatment after scaling can reduce smear layer, debris, and biofilm on the root surfaces as compared with conventional scaling. The laser treatment reduces the adhesion of S. mutans as well. However, Nd: YAG laser irradiation can cause cracks on the root surfaces. In this experiment, the optimum laser power of 6 W can thoroughly remove the smear layer and debris, as well as relatively improve the control of thermal damagee.

Fuel injector nozzle for an internal combustion engine

DOEpatents

Cavanagh, Mark S [Bloomington, IL; Urven, Jr., Roger L.; Lawrence, Keith E [Peoria, IL

2011-03-22

A direct injection fuel injector includes a nozzle tip having a plurality of passages allowing fluid communication between an inner nozzle tip surface portion and an outer nozzle tip surface portion and directly into a combustion chamber of an internal combustion engine. A first group of the passages have inner surface apertures located substantially in a first common plane. A second group of the passages have inner surface apertures located substantially in at least a second common plane substantially parallel to the first common plane. The second group has more passages than the first group.

Fuel Injector Nozzle For An Internal Combustion Engine

DOEpatents

Cavanagh, Mark S.; Urven, Jr.; Roger L.; Lawrence, Keith E.

2006-04-25

A direct injection fuel injector includes a nozzle tip having a plurality of passages allowing fluid communication between an inner nozzle tip surface portion and an outer nozzle tip surface portion and directly into a combustion chamber of an internal combustion engine. A first group of the passages have inner surface apertures located substantially in a first common plane. A second group of the passages have inner surface apertures located substantially in at least a second common plane substantially parallel to the first common plane. The second group has more passages than the first group.

Fuel injector nozzle for an internal combustion engine

DOEpatents

Cavanagh, Mark S.; Urven, Jr., Roger L.; Lawrence, Keith E.

2007-11-06

A direct injection fuel injector includes a nozzle tip having a plurality of passages allowing fluid communication between an inner nozzle tip surface portion and an outer nozzle tip surface portion and directly into a combustion chamber of an internal combustion engine. A first group of the passages have inner surface apertures located substantially in a first common plane. A second group of the passages have inner surface apertures located substantially in at least a second common plane substantially parallel to the first common plane. The second group has more passages than the first group.

Fuel injector nozzle for an internal combustion engine

DOEpatents

Cavanagh, Mark S.; Urven, Jr., Roger L.; Lawrence, Keith E.

2008-11-04

A direct injection fuel injector includes a nozzle tip having a plurality of passages allowing fluid communication between an inner nozzle tip surface portion and an outer nozzle tip surface portion and directly into a combustion chamber of an internal combustion engine. A first group of the passages have inner surface apertures located substantially in a first common plane. A second group of the passages have inner surface apertures located substantially in at least a second common plane substantially parallel to the first common plane. The second group has more passages than the first group.

Comparison surface characteristics and chemical composition of conventional metallic and nickel-free brackets.

PubMed

Shintcovsk, Ricardo Lima; Knop, Luegya Amorim Henriques; Gandini, Luiz Gonzaga; Martins, Lidia Parsekian; Pires, Aline Segatto

2015-01-01

This study aims at comparing conventional and nickel-free metal bracket surface characteristics with elemental composition by scanning electron microscopy (SEM), using energy dispersive spectroscopy (EDS). The sample consisted of 40 lower incisor brackets divided into four groups: ABZ = conventional brackets, Kirium Abzil 3M® (n = 10); RL = conventional brackets, Roth Light Morelli® (n = 10); NF = nickel-free brackets, Nickel-Free Morelli® (n = 10); and RM = nickel-free brackets, Roth Max Morelli® (n = 10). Qualitative evaluation of the bracket surface was performed using SEM, whereby surface features were described and compared. The elemental composition was analyzed by EDS. According to surface analysis, groups ABZ and RL showed a homogeneous surface, with better finishing, whereas the surfaces in groups NF and RM were rougher. The chemical components with the highest percentage were Fe, Cr and C. Groups NF and MR showed no nickel in their composition. In conclusion, the bracket surface of the ABZ and RL groups was more homogeneous, with grooves and pores, whereas the surfaces in groups NF and RM showed numerous flaws, cracks, pores and grooves. The chemical composition analysis confirmed that the nickel-free brackets had no Ni in their composition, as confirmed by the manufacturer's specifications, and were therefore safe to use in patients with a medical history of allergy to this metal.

Surface Coverage and Metallicity of ZnO Surfaces from First-Principles Calculations

NASA Astrophysics Data System (ADS)

Zhang, Xiao; Schleife, Andre; The Schleife research Group Team

Zinc oxide (ZnO) surfaces are widely used in different applications such as catalysis, biosensing, and solar cells. These surfaces are, in many cases, chemically terminated by hydroxyl groups. In experiment, a transition of the ZnO surface electronic properties from semiconducting to metallic was reported upon increasing the hydroxyl coverage to more than approximately 80 %. The reason for this transition is not well understood yet. We report on first-principles calculations based on density functional theory for the ZnO [ 10 1 0 ] surface, taking different amounts of hydroxyl coverage into account. We calculated band structures for fully relaxed configurations and verified the existence of this transition. However, we only find the fully covered surface to be metallic. We thus explore the possibility for clustering of the surface-terminating hydroxyl groups based on total-energy calculations. We also found that the valence band maximum consists of oxygen p states from both the surface hydroxyl groups and the surface oxygen atoms of the material. The main contribution to the metallicity is found to be from the hydroxyl groups.

Shear bond, wettability and AFM evaluations on CO2 laser-irradiated CAD/CAM ceramic surfaces.

PubMed

El Gamal, Ahmed; Medioni, Etienne; Rocca, Jean Paul; Fornaini, Carlo; Muhammad, Omid H; Brulat-Bouchard, Nathalie

2017-05-01

The purpose of this study is to determine the CO 2 laser irradiation in comparison with sandblasting (Sb), hydrofluoric acid (Hf) and silane coupling agent (Si) on shear bond strength (SBS), roughness (Rg) and wettability (Wt) of resin cement to CAD/CAM ceramics. Sixty (CAD/CAM) ceramic discs were prepared and distributed into six different groups: group A, control lithium disilicate (Li); group B, control zirconia (Zr); group C, Li: CO 2 /HF/Si; group D, Li: HF/Si; group E, Zr: CO 2 /Sb/Si; group F, Zr: Sb/Si. Result showed significant difference between irradiated and non-irradiated in terms of shear bond strength for zirconia ceramics (p value = 0.014). Moreover, partial surface wettability for irradiated and non-irradiated ceramics. Irradiated surface demonstrated more rough surface in lithium disilicate than zirconia ceramics. CO 2 irradiation could increase shear bond strength, surface roughness and wettability for both CAD/CAM ceramics.

Effect of Nd: YAG laser irradiation on surface properties and bond strength of zirconia ceramics.

PubMed

Liu, Li; Liu, Suogang; Song, Xiaomeng; Zhu, Qingping; Zhang, Wei

2015-02-01

This study investigated the effect of neodymium-doped yttrium aluminum garnet (Nd: YAG) laser irradiation on surface properties and bond strength of zirconia ceramics. Specimens of zirconia ceramic pieces were divided into 11 groups according to surface treatments as follows: one control group (no treatment), one air abrasion group, and nine laser groups (Nd: YAG irradiation). The laser groups were divided by applying with different output power (1, 2, or 3 W) and irradiation time (30, 60, or 90 s). Following surface treatments, the morphological characteristics of ceramic pieces was observed, and the surface roughness was measured. All specimens were bonded to resin cement. After, stored in water for 24 h and additionally aged by thermocycling, the shear bond strength was measured. Dunnett's t test and one-way ANOVA were performed as the statistical analyses for the surface roughness and the shear bond strength, respectively, with α = .05. Rougher surface of the ceramics could be obtained by laser irradiation with higher output power (2 and 3 W). However, cracks and defects were also found on material surface. The shear bond strength of laser groups was not obviously increased, and it was significantly lower than that of air abrasion group. No significant differences of the shear bond strength were found among laser groups treated with different output power or irradiation time. Nd: YAG laser irradiation cannot improve the surface properties of zirconia ceramics and cannot increase the bond strength of the ceramics. Enhancing irradiation power and extending irradiation time cannot induce higher bond strength of the ceramics and may cause material defect.

Evaluation of the Effect of Surface Polishing, Oral Beverages and Food Colorants on Color Stability and Surface Roughness of Nanocomposite Resins.

PubMed

Kumari, R Veena; Nagaraj, Hema; Siddaraju, Kishore; Poluri, Ramya Krishna

2015-07-01

It is beyond doubt that finishing and polishing of a composite restoration enhance its esthetics and, is also essential for the health of the periodontium. A variety of instruments are commonly used for finishing and polishing tooth-colored restorative materials Thus, it is important to understand which type of surface finishing treatments would significantly affect the staining and surface irregularities of the composite resin restoration. Still one of the properties of the composite resins that have to pass the test of time is its color stability. In modern day dentistry, a large emphasis is laid over esthetics. Hence, it is important to understand the various agents capable of adversely affecting the esthetics of a restoration due to its staining capacity. Thus, the aim of this in vitro study was to evaluate the effect of surface polishing, oral beverages and food colorants on the color stability and surface roughness of nanocomposite resins. 90 Disks of nanocomposites resin (Filtek Z350 XT) measuring 8 mm in diameter and 2 mm in thickness were fabricated using a custom made silicon mold. Pre-polishing surface roughness (Ra1) of all the 90 samples were measured using a Surface Profilometer. The nano-composite disks were then randomly divided into 3 groups with 30 samples in each group. Group I: The samples were not subjected to any polishing procedures. Group II: Sof-Lex group: Samples subjected to polishing using different grits of Sof-Lex disks. Group III: Diamond polishing paste group: Samples were subjected with a polishing paste consisting of diamond particles. Following polishing procedures, the surface roughness of all samples were measured again to obtain change in surface roughness due to polishing procedures (Ra2), pre immersion spectrophotometric value (ΔE1) was also recorded for baseline color of the samples. The samples were then divided into subgroups (A, B, C, D, E), by including every first sample in Subgroup A, second in Subgroup B, third in Subgroup C, fourth in Subgroup D, and fifth in Subgroup E. Each was immersed in the respective test solution for 10 min, twice a day for 30 days. Group A - Tea, Group B - Coffee, Group C - Cola, Group D - Turmeric, Group E - Control (artificial saliva). Post immersion profilometric value was recorded to evaluate roughness bought about by the solutions (Ra3) and spectrophotometric value was recorded to evaluate the color change in samples (ΔE2). Results were statistically analyzed using ANOVA. Higher mean roughness (Ra2-Ra1) value was recorded in Sof-Lex, followed by Diamond polishing paste and Control group. Comparison of surface roughness caused due to beverages and food colorant solution showed subgroup C (Coca Cola) increased surface roughness in all groups (Group I, II, III). Subgroup D (Turmeric) had the highest discoloration potential (P < 0001) in all groups, followed by coffee, tea, coca-cola and artificial saliva. Sof-Lex polishing System showed most color stability. Polishing procedures significantly roughen the surface of the restoration compared to the unpolished Mylar controls. One-step polishing system (diamond polishing paste) produces a smoother surface compared to a multi-step system (Sof-Lex polishing disks). Turmeric solution caused maximum staining of the samples, to a visually perceptible level.

Sensory interaction on static balance: a comparison concerning the history of falls of community-dwelling elderly.

PubMed

Ricci, Natalia Aquaroni; de Faria Figueiredo Gonçalves, Daniele; Coimbra, Arlete Maria Valente; Coimbra, Ibsen Bellini

2009-06-01

To determine whether elderly subjects with distinct histories of falls presented differences concerning the influence of sensory interaction on balance. Cross-sectional research. Ninety-six community-dwelling elderly subjects were divided into three groups, according to the history of falls within the past year (group 1, no falls; group 2, one fall; and group 3, recurrent falls). The Clinical Test of Sensory Interaction and Balance was used to evaluate the influence of sensory inputs on standing balance. The test required the subject to maintain stability during 30 s, under six conditions: (i) firm surface with eyes open; (ii) firm surface with eyes closed; (iii) firm surface with visual conflict; (iv) unstable surface with eyes open; (v) unstable surface with eyes closed; and (vi) unstable surface with visual conflict. The time expended on conditions and the number of abnormal cases were compared between groups. Each group was evaluated in relation to its performance in the progression of conditions. More abnormal cases occurred in group 3 compared to group 1 for conditions (iv) and (v); and compared to group 2 for condition (iv). Group 3 remained less time than group 1 under conditions (iv), (v) and (vi). Groups 1, 2 and 3 presented relevant decrements in trial duration from conditions (iv) to (v). For group 3, a significant decay was also noted from condition (i) to (ii). Sensorial interaction in the elderly varies according to their history of falls. Thus, it is possible to correctly guide the rehabilitation process and to prevent sensorial decays according to an individual's history of falls.

Automatic detection of sweep-meshable volumes

DOEpatents

Tautges,; Timothy J. , White; David, R [Pittsburgh, PA

2006-05-23

A method of and software for automatically determining whether a mesh can be generated by sweeping for a representation of a geometric solid comprising: classifying surface mesh schemes for surfaces of the representation locally using surface vertex types; grouping mappable and submappable surfaces of the representation into chains; computing volume edge types for the representation; recursively traversing surfaces of the representation and grouping the surfaces into source, target, and linking surface lists; and checking traversal direction when traversing onto linking surfaces.

Effect of the application of surface treatments before and after sintering on the flexural strength, phase transformation and surface topography of zirconia.

PubMed

Kurtulmus-Yilmaz, Sevcan; Aktore, Huseyin

2018-05-01

To evaluate the effects of airborne-particle abrasion (APA) and Er,Cr:YSGG laser irradiation on 4-point-flexural strength, phase transformation and morphologic changes of zirconia ceramics treated at pre-sintered or post-sintered stage. Three hundred and forty-two bar shaped zirconia specimens were milled with different sizes according to the flexural strength test (n = 10), X-ray diffraction (XRD) (n = 4) and field emission scanning electron microscope (FE-SEM) (n = 4) analyses. For each test protocol, specimens were divided into 4 main groups whether the surface treatments applied before or after sintering and whether the specimens received heat treatment or not as pre-sintered, post-sintered no-heat and post-sintered heat-treated groups, and a group was served as control. Main groups were further divided into 6 equal subgroups according to surface treatment method applied (2 W-, 3 W-, 4 W-, 5 W-, 6 W-laser irradiations and APA). Surface treatments were applied to pre-sintered groups before sintering and to post-sintered groups after sintering. Post-sintered heat-treated groups were subjected to veneer ceramic firing simulation after surface treatments. Flexural strength and flexural modulus values were statistically analysed and monoclinic phase content was calculated. Weibull analysis was used to evaluate strength reliability and fractographic analysis was conducted. Highest flexural strength values were detected at post-sintered no-heat APA and 4W-laser groups (P < 0.05). Pre-sintered groups showed statistically lower flexural strength values. Heat treatment decreased the strength of the specimens. Monoclinic phase content was only detected at post-sintered no-heat groups and the highest amount was detected at APA group. Rougher surfaces and deeper irregularities were detected at FE-SEM images pre-sintered groups. Application of surface treatments at pre-sintered stage may be detrimental for zirconia ceramics in terms of flexural strength. Treating the surface of zirconia ceramic before sintering process is not recommended due to significant decrease in flexural strength values. 2 W-4 W Er,Cr:YSGG laser irradiations can be regarded as alternative surface treatment methods when zirconia restoration would be subjected to veneer ceramic firing procedures. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effect of different surface treatments on the shear bond strength of nanofilled composite repairs

PubMed Central

Ahmadizenouz, Ghazaleh; Esmaeili, Behnaz; Taghvaei, Arnica; Jamali, Zahra; Jafari, Toloo; Amiri Daneshvar, Farshid; Khafri, Soraya

2016-01-01

Background. Repairing aged composite resin is a challenging process. Many surface treatment options have been proposed to this end. This study evaluated the effect of different surface treatments on the shear bond strength (SBS) of nano-filled composite resin repairs. Methods. Seventy-five cylindrical specimens of a Filtek Z350XT composite resin were fabricated and stored in 37°C distilled water for 24 hours. After thermocycling, the specimens were divided into 5 groups according to the following surface treatments: no treatment (group 1); air abrasion with 50-μm aluminum oxide particles (group 2); irradiation with Er:YAG laser beams (group 3); roughening with coarse-grit diamond bur + 35% phosphoric acid (group 4); and etching with 9% hydrofluoric acid for 120 s (group 5). Another group of Filtek Z350XT composite resin samples (4×6 mm) was fabricated for the measurement of cohesive strength (group 6). A silane coupling agent and an adhesive system were applied after each surface treatment. The specimens were restored with the same composite resin and thermocycled again. A shearing force was applied to the interface in a universal testing machine. Data were analyzed using one-way ANOVA and post hoc Tukey tests (P < 0.05). Results. One-way ANOVA indicated significant differences between the groups (P < 0.05). SBS of controls was significantly lower than the other groups; differences between groups 2, 3, 4, 5 and 6 were not significant. Surface treatment with diamond bur + 35% phosphoric acid resulted in the highest bond strength. Conclusion. All the surface treatments used in this study improved the shear bond strength of nanofilled composite resin used. PMID:27092209

Comparison of removal torques between laser-treated and SLA-treated implant surfaces in rabbit tibiae

PubMed Central

Kang, Nam-Seok; Li, Lin-Jie

2014-01-01

PURPOSE The purpose of this study was to compare removal torques and surface topography between laser treated and sandblasted, large-grit, acid-etched (SLA) treated implants. MATERIALS AND METHODS Laser-treated implants (experimental group) and SLA-treated implants (control group) 8 mm in length and 3.4 mm in diameter were inserted into both sides of the tibiae of 12 rabbits. Surface analysis was accomplished using a field emission scanning electron microscope (FE-SEM; Hitachi S-4800; Japan) under ×25, ×150 and ×1,000 magnification. Surface components were analyzed using energy dispersive spectroscopy (EDS). Rabbits were sacrificed after a 6-week healing period. The removal torque was measured using the MGT-12 digital torque meter (Mark-10 Co., Copiague, NY, USA). RESULTS In the experimental group, the surface analysis showed uniform porous structures under ×25, ×150 and ×1,000 magnification. Pore sizes in the experimental group were 20-40 mm and consisted of numerous small pores, whereas pore sizes in the control group were 0.5-2.0 mm. EDS analysis showed no significant difference between the two groups. The mean removal torque in the laser-treated and the SLA-treated implant groups were 79.4 Ncm (SD = 20.4; range 34.6-104.3 Ncm) and 52.7 Ncm (SD = 17.2; range 18.7-73.8 Ncm), respectively. The removal torque in the laser-treated surface implant group was significantly higher than that in the control group (P=.004). CONCLUSION In this study, removal torque values were significantly higher for laser-treated surface implants than for SLA-treated surface implants. PMID:25177474

Bioactivity of Ti-6Al-4V alloy implants treated with ibandronate after the formation of the nanotube TiO2 layer.

PubMed

Moon, So-Hee; Lee, Seung-Jae; Park, Il-Song; Lee, Min-Ho; Soh, Yun-Jo; Bae, Tae-Sung; Kim, Hyung-Seop

2012-11-01

Nanostructure surface of titanium implants treated with anodic oxidation, heat, and bisphosphonates, has been introduced to improve osseointegration of the implants. However, no information could be found about the efficiency of these approaches on Ti-6Al-4V alloy surfaces. This study examined the drug loading capacity of anodized nanotubular Ti-6Al-4V alloy surfaces in vitro as well as the bone response to surface immobilized bisphosphonates (BPs) on anodized nanotubular Ti-6Al-4V alloy surface in tibiae of rats. Ti-6Al-4V alloy titanium was divided into two groups: (1) control group (nontreated); (2) test group (anodized, heat-, and bisphosphonate-treated group). In vitro, amount of the drug released from the both groups' specimens was examined; all samples were 1 × 2 cm in size. In vivo, the 10 implants were placed inside of tibias of five rats. After 4 weeks, the bone response of the implants was evaluated using a removal torque test, and measuring bone contact and bone area. In addition, the surfaces of the extracted implants were observed by FE-SEM and EDS. In vitro, the drug loading capacity of the Ti-6Al-4V alloy surfaces was enhanced by anodizing surface modification. The values of the removal torque, bone contact, and bone area were significantly higher in the test group (p < 0.05). Furthermore, according to the EDS analysis, the amounts of Ca and P on the surface of the extracted implants were higher in the test group. Within the limits of this experiment, results of this research demonstrated that bisphosphonate-treated Ti-6Al-4V alloy implants with nanotubular surfaces have positive effects in bone-to-implant contact. Copyright © 2012 Wiley Periodicals, Inc.

Effect of artificial aging on the surface roughness and microhardness of resin-based materials.

PubMed

Santos, M Jacinta M C; Rêgo, Heleine Maria Chagas; Mukhopadhyay, Anuradha; El Najjar, Mai; Santos, Gildo C

2016-01-01

This study sought to verify the effects of aging on the surface roughness (Ra) and microhardness (Knoop hardness number [KHN]) of resin-based restorative materials protected with a surface sealer. Disc specimens of 2 resin-modified glass ionomers (RMGIs) and 1 composite resin (CR) were fabricated in a metal mold. Specimens of each material were divided into 1 group that was covered with surface sealer and 1 group that was not. Both groups of each material were then subdivided according to whether they were stored (aged) in cola or distilled water. Surface roughness and KHN values were obtained from each specimen before and after storage. After aging of the specimens, significantly higher Ra values were observed in the 2 RMGIs when they were not covered with a surface sealer, while the CR was not affected. The KHN values varied by materials and storage conditions (with and without a surface sealer). All the groups with a surface sealer exhibited increased Ra values after aging.

Evaluating the risk of decompression sickness for a yo-yo dive using a rat model.

PubMed

Ofir, Dror; Yanir, Yoav; Abramovich, Amir; Bar, Ronen; Arieli, Yehuda

2016-01-01

The frequent ascents made during yo-yo diving may contribute to gas bubble clearance but paradoxically may also increase the risk of central nervous system decompression illness (DCI). We evaluated the risk of DCI due to yo-yo dives with very short surface intervals, using a controlled animal model. Dives were conducted on air to a depth of 90 meters (10 atmospheres absolute) for 32 minutes of bottom time, at a descent/ascent rate of 10 meters/ minute. Sprague-Dawley rats weighing ~ 300 grams were divided randomly into three groups. Group A performed a square dive protocol without any surface intervals, Group B conducted a protocol that included two surface intervals during the dive, and Group C performed a protocol with three surface intervals. Ascent/descent rate for surface intervals, each lasting one minute, was also 10 meters/minute. Manifestations of DCI were observed in 13 of 16 animals in Group A (81.3%), six of 12 in Group B (58.3%), and two of 12 in Group C (16.7%). Mortality rates were similar in all groups. Surface intervals during dives breathing air significantly reduced DCI risk in the rat. Further studies are required using a larger animal model to reinforce the results of the present investigation.

Surface characteristics and bioactivity of oxide film on titanium metal formed by thermal oxidation.

PubMed

Park, Yeong-Joon; Song, Ho-Jun; Kim, In; Yang, Hong-So

2007-04-01

In this study, we characterized the surface of oxide film formed on titanium metal through the use of thermal treatment and investigated the effect of surface characteristics on the bioactivity of titanium. The as-received sample group was prepared by polishing and cleaning CP-Ti as a control group, and thermally oxidized sample groups were prepared by heat treating at 530, 600, 700, 800, 900, and 1000 degrees C respectively. Micro-morphology, crystalline structure, chemical composition, and binding state were evaluated using FE-SEM, XRD, and XPS. The bioactivity of sample groups was investigated by observing the degree of calcium phosphate formation from immersion testing in MEM. The surface characterization tests showed that hydroxyl group content in titanium oxide film was increased, as the density of titanium atoms was high and the surface area was large. In MEM immersion test, initial calcium phosphate formation was dependent upon the thickness of titanium oxide, and resultant calcium phosphate formation depended on the content of the hydroxyl group of the titanium oxide film surface.

On the organization and thermal behavior of functional groups on Ti3C2 MXene surfaces in vacuum

NASA Astrophysics Data System (ADS)

Persson, Ingemar; Näslund, Lars-Åke; Halim, Joseph; Barsoum, Michel W.; Darakchieva, Vanya; Palisaitis, Justinas; Rosen, Johanna; Persson, Per O. Å.

2018-03-01

The two-dimensional (2D) MXene Ti3C2T x is functionalized by surface groups (T x ) that determine its surface properties for, e.g. electrochemical applications. The coordination and thermal properties of these surface groups has, to date, not been investigated at the atomic level, despite strong variations in the MXene properties that are predicted from different coordinations and from the identity of the functional groups. To alleviate this deficiency, and to characterize the functionalized surfaces of single MXene sheets, the present investigation combines atomically resolved in situ heating in a scanning transmission electron microscope (STEM) and STEM simulations with temperature-programmed x-ray photoelectron spectroscopy (TP-XPS) in the room temperature to 750 °C range. Using these techniques, we follow the surface group coordination at the atomic level. It is concluded that the F and O atoms compete for the DFT-predicted thermodynamically preferred site and that at room temperature that site is mostly occupied by F. At higher temperatures, F desorbs and is replaced by O. Depending on the O/F ratio, the surface bare MXene is exposed as F desorbs, which enables a route for tailored surface functionalization.

Comparison of the effect of resin infiltrant, fluoride varnish, and nano-hydroxy apatite paste on surface hardness and streptococcus mutans adhesion to artificial enamel lesions.

PubMed

Aziznezhad, Mahdiye; Alaghemand, Homayoon; Shahande, Zahra; Pasdar, Nilgoon; Bijani, Ali; Eslami, Abdolreza; Dastan, Zohre

2017-03-01

Dental caries is a major public health problem, and Streptococcus mutans is considered the main causal agent of dental caries. This study aimed to compare the effect of three re-mineralizing materials: resin infiltrant, fluoride varnish, and nano-hydroxy apatite paste on the surface hardness and adhesion of Streptococcus mutans as noninvasive treatments for initial enamel lesions. This experimental study was conducted from December 2015 through March 2016 in Babol, Iran. Artificial enamel lesions were created on 60 enamel surfaces, which were divided into two groups: Group A and Group B (30 subjects per group). Group A was divided into three subgroups (10 samples in each subgroup), including fluoride varnish group, nano-hydroxy apatite paste group (Nano P paste), and resin infiltrant group (Icon-resin). In Group A, the surface hardness of each sample was measured in three stages: First, on an intact enamel (baseline); second, after creating artificial enamel lesions; third, after application of re-mineralizing materials. In Group B, the samples were divided into five subgroups, including intact enamel, demineralized enamel, demineralized enamel treated with fluoride varnish, Nano P paste, and Icon-resin. In Group B, standard Streptococcus mutans bacteria adhesion (PTCC 1683) was examined and reported in terms of colony forming units (CFU/ml). Then, data were analyzed using ANOVA, Kruskal-Wallis, Mann-Whitney, and post hoc tests. In Group A, after treatment with re-mineralizing materials, the Icon-resin group had the highest surface hardness among the studied groups, then the Nano P paste group and fluoride varnish group, respectively (p = 0.035). In Group B, in terms of bacterial adhesion, fluoride varnish group had zero bacterial adhesion level, and then the Nano P paste group, Icon-resin group, intact enamel group, and the de-mineralized enamel group showed bacterial adhesion increasing in order (p < 0.001). According to the study among the examined materials, the resin infiltrant increased the tooth surface hardness as the intact enamel and fluoride varnish had the highest reduction level for bacterial adhesion. Nano P paste had an effect between the two materials, both in increasing surface hardness and reducing bacterial adhesion.

In-Vitro Comparative Study of In-office and Home Bleaching Agents on Surface Micro-morphology of Enamel.

PubMed

Fatima, Nazish

2016-01-01

To evaluate the effect of home-use bleaching agent containing 16% Carbamide Peroxide (CP) and in-office bleaching agent with 38% Hydrogen Peroxide (HP) on surface micro-morphology of enamel. An experimental study. The discs were prepared at Material Engineering Department of NED University of Engineering and Technology, Karachi, and surface morphology was analyzed at Centralized Science Laboratory of Karachi University, Pakistan. Duration of study was one year from January to December 2012. Forty five sound human third molar crowns, extracted for periodontal reason, were included in the study. Longitudinal sections were made using diamond disks (0.2 mm) under water lubrication to obtain enamel slabs measuring (3 mm x 3 mm). The slabs were embedded in polystyrene resin by using 2.0 cm diameter PVC molds, leaving the outer enamel surface uncovered by the resin. Ninety dental enamel slabs were prepared. The slabs were then randomly divided into 3 groups. Each group contained thirty specimens (n=30). Group 1 was kept in artificial saliva at 37°C in incubator (Memart, Germany) during whole experiment. Group 2 was treated with power whitening gel (White Smile 2011, Germany). Group 3 was treated with tooth whitening pen (White Smile 2011, Germany). The most central region or the region that was most representative of the entire surface area was used. The SEM (Jeol-Japan-JSM6380A, JAPAN) micrographs were examined to determine the type of surface presented. The enamel changes were classified as no or mild alteration, moderate alteration and severe altered surface. Regarding micro-morphology, the enamel surface of control groups showed smooth surface in general with some scattered clear scratches due to the polishing procedure. The specimens bleached in group 2 and group 3, represented areas of mild erosion. Bleaching with 38% Hydrogen Peroxide (HP) and 16% Carbamide Peroxide (CP) resulted in mild changes in surface micro-morphology of enamel.

Effects of a micro/nano rough strontium-loaded surface on osseointegration

PubMed Central

Li, Yongfeng; Qi, Yaping; Gao, Qi; Niu, Qiang; Shen, Mingming; Fu, Qian; Hu, Kaijin; Kong, Liang

2015-01-01

We developed a hierarchical hybrid micro/nanorough strontium-loaded Ti (MNT-Sr) surface fabricated through hydrofluoric acid etching followed by magnetron sputtering and evaluated the effects of this surface on osseointegration. Samples with a smooth Ti (ST) surface, micro Ti (MT) surface treated with hydrofluoric acid etching, and strontium-loaded nano Ti (NT-Sr) surface treated with SrTiO3 target deposited via magnetron sputtering technique were investigated in parallel for comparison. The results showed that MNT-Sr surfaces were prepared successfully and with high interface bonding strength. Moreover, slow Sr release could be detected when the MNT-Sr and NT-Sr samples were immersed in phosphate-buffered saline. In in vitro experiments, the MNT-Sr surface significantly improved the proliferation and differentiation of osteoblasts compared with the other three groups. Twelve weeks after the four different surface implants were inserted into the distal femurs of 40 rats, the bone–implant contact in the ST, MT, NT-Sr, and MNT-Sr groups were 39.70%±6.00%, 57.60%±7.79%, 46.10%±5.51%, and 70.38%±8.61%, respectively. In terms of the mineral apposition ratio, the MNT-Sr group increased by 129%, 58%, and 25% compared with the values of the ST, MT, and NT-Sr groups, respectively. Moreover, the maximal pullout force in the MNT-Sr group was 1.12-, 0.31-, and 0.69-fold higher than the values of the ST, MT, and NT-Sr groups, respectively. These results suggested that the MNT-Sr surface has a synergistic effect of hierarchical micro/nano-topography and strontium for enhanced osseointegration, and it may be a promising option for clinical use. Compared with the MT surface, the NT-Sr surface significantly improved the differentiation of osteoblasts in vitro. In the in vivo animal experiment, the MT surface significantly enhanced the bone-implant contact and maximal pullout force than the NT-Sr surface. PMID:26213468

Ability of barrier coat S-PRG coating to arrest artificial enamel lesions in primary teeth.

PubMed

Hosoya, Yumiko; Ando, Susumu; Otani, Hideji; Yukinari, Tetsuhiro; Miyazaki, Masashi; Garcia-Godoy, Franklin

2013-10-01

To evaluate the effects of a surface pre-reacted glass-ionomer (S-PRG) filled coating material to arrest artificial enamel lesions in primary teeth. Buccal and lingual enamel was demineralized in 0.1 M lactic acid buffer solution (pH 4.75) for 5 days and then divided in the PRG-applied and non-PRG areas. Proximal surfaces were used as a control area without demineralization and coating application. Teeth were divided into three groups (n = 4) according to the 1-week immersion in different solutions: Group 1 (distilled water), Group 2 (demineralizing solution) and Group 3 (artificial saliva). Hardness and Young's modulus by nano-indentation test, and elemental contents and ultrastructure by SEM/EDX analysis were obtained. Data were statistically analyzed using ANOVA and Fisher's PLSD at alpha = 0.05. Only for the non-PRG area in Group 1, the hardness and Young's modulus of the demineralized surface enamel were significantly lower than those of the enamel 30-60 microm beneath the surface. Demineralized enamel of non-PRG and PRG-applied areas showed similar SEM views. Only for the non-PRG area in Group 2 and control area in Group 3, the Ca/P of the surface enamel was significantly higher than that of the enamel 5-10 microm beneath the surface. There was no significant difference of the Ca/P among the measuring points from the surface to 10 microm depth of enamel for the PRG applied area in Group 2.

Spectroscopic and first principles investigation on 4-[(4-pyridinylmethylene)amino]-benzoic acid bearing pyridyl and carboxyl anchoring groups

NASA Astrophysics Data System (ADS)

Zhang, Lei; Wang, Qiaoyi

2018-03-01

We report a combined experimental and computational investigation on the structure and photophysics of 4-[(4-pyridinylmethylene)amino]-benzoic acid, a functional molecule bearing two anchoring groups for attachment onto a TiO2 surface and perovskite surface, for potential solar cell application. This molecule possesses interesting adsorption properties in perovskite solar cell because the pyridyl group serves as the Lewis base and targets Lewis acidic sites in the perovskite surface, while the carboxyl group targets TiO2 surface, improving the coupling between the perovskite surface and the TiO2 surface. The electronic structures of the molecule and its photochemistry are revealed by the UV-vis absorption spectra and the fluorescence spectra under visible light irradiation, which are combined with density functional theory (DFT) and time-dependent density functional theory (TDDFT) analysis. Considering the bi-anchoring groups and the conjugated π system embedded in the molecule, we anticipate it can molecular engineer the TiO2/perovskite interface in perovskite solar cell.

Evaluation of modified titanium surfaces physical and chemical characteristics

NASA Astrophysics Data System (ADS)

Lukaszewska-Kuska, Magdalena; Leda, Bartosz; Gajdus, Przemyslaw; Hedzelek, Wieslaw

2017-11-01

Development of dental implantology is focused, among other things, on devising active surface of the implant, conditioning acceleration of the implant's integration with the bone. Increased roughness, characteristic for group of implants with developed surface, altered topography and chemically modified implant's surface determines increased implants stability. In this study four different titanium surfaces modifications: turned (TS); aluminium oxide-blasted (Al2O3); resorbable material blasted (RBM); sandblast and then etched with a mixture of acids (SAE), were evaluated in terms of surfaces topography and chemical composition prior to in vivo analysis. Topography analysis revealed two groups: one with smooth, anisotropic, undeveloped TS surface and the second group with remaining surfaces presenting rough, isotropic, developed surfaces with added during blasting procedure aluminium for Al2O3 and calcium and phosphorus for RBM. Physical and chemical modifications of titanium surface change its microstructure (typical for SAE) and increase its roughness (highest for Al2O3-blasted and RBM surfaces). The introduced modifications develop titanium surface - 10 times for SAE surfaces, 16 times for Al2O3-blasted surfaces, and 20 times for RBM surfaces.

Effect of different pH solvents on micro-hardness and surface topography of dental nano-composite: An in vitro analysis

PubMed Central

Khan, Aftab Ahmed; Siddiqui, Adel Zia; Al-Kheraif, Abdulaziz A; Zahid, Ambreen; Divakar, Darshan Devang

2015-01-01

Objective: Erosion of tooth surface is attributed to recent shift in diet pattern and frequent use of beverages. The aim of this research was to evaluate the effects of different beverages on surface topography and hardness of nano-filled composite material. Methods: Sixty flat disc shaped resin composite samples were fabricated and placed in distilled water for 24 hours. After 24 hours test samples were dried and divided into 4 groups. Group A (n=15) specimens were placed in tight amber bottle comprising 25 ml of artificial saliva. Similarly Group B, C and D were stored in equal amounts of orange juice, milk and coca cola drink respectively. Samples were checked for hardness and surface changes were evaluated with scanning electron microscopy. Results: There were strong significant difference observed in samples immersed in orange juice and artificial saliva. A strong significant difference was seen between Group D and Group A. Group A and Group C showed no significant difference. The micro-hardness test showed reduced values among all samples. Conclusion: Beverages consumed daily have a negative influence on hardness and surface degradation of nano-filled dental composite. Comparatively, nano-filled composites possess higher surface area to volume ratio of their fillers particle size may lead to higher surface roughness than other resin based dental biomaterials. PMID:26430417

Effect of Various Laser Surface Treatments on Repair Shear Bond Strength of Aged Silorane-Based Composite

PubMed Central

Alizadeh Oskoee, Parnian; Savadi Oskoee, Siavash; Rikhtegaran, Sahand; Pournaghi-Azar, Fatemeh; Gholizadeh, Sarah; Aleyasin, Yasaman; Kasrae, Shahin

2017-01-01

Introduction: Successful repair of composite restorations depends on a strong bond between the old composite and the repair composite. This study sought to assess the repair shear bond strength of aged silorane-based composite following surface treatment with Nd:YAG, Er,Cr:YSGG and CO2 lasers. Methods: Seventy-six Filtek silorane composite cylinders were fabricated and aged by 2 months of water storage at 37°C. The samples were randomly divided into 4 groups (n=19) of no surface treatment (group 1) and surface treatment with Er,Cr:YSGG (group 2), Nd:YAG (group 3) and CO2 (group 4) lasers. The repair composite was applied and the shear bond strength was measured. The data were analyzed using one-way analysis of variance (ANOVA) and Tukey posthoc test. Prior to the application of the repair composite, 2 samples were randomly selected from each group and topographic changes on their surfaces following laser irradiation were studied using a scanning electron microscope (SEM). Seventeen other samples were also fabricated for assessment of cohesive strength of composite. Results: The highest and the lowest mean bond strength values were 8.99 MPa and 6.69 MPa for Er,Cr:YSGG and control groups, respectively. The difference in the repair bond strength was statistically significant between the Er,Cr:YSGG and other groups. Bond strength of the control, Nd:YAG and CO2 groups was not significantly different. The SEM micrographs revealed variable degrees of ablation and surface roughness in laser-treated groups. Conclusion: Surface treatment with Er,Cr:YSGG laser significantly increase the repair bond strength of aged silorane-based composite resin. PMID:29071025

[Adhesion of oral microorganisms on dental porcelain polished and glazed].

PubMed

Wang, Yi-ning; Wen, Guo-jiang; Shi, Bin; Pan, Xin-hua

2003-09-01

This study compared the roughness of porcelain polished or glazed surfaces and the adhesion of oral streptococcus mutans to them in vitro. 30 porcelain samples were made. Porcelain samples in group A were polished with diamond paste. Porcelain samples were glazed in group B and were polished with Al2O3 (240#) bur in group C. Their roughness values were measured by profilometer. Standardized cell suspensions were incubated with test samples for one hour at 37 degrees C, then retained cells were counted by image analysis (percentage area of a microscopic field covered by cells). Roughness values of group A, B, C were respectively (0.1987 +/- 0.057) microm, (0.1990 +/- 0.091) microm, (0.4260 +/- 0.174) microm. There was no significantly difference between group A and group B. The roughness samples in group C were significantly rougher than that in the other groups. The amount of retained cells in group A, group B, group C was respectively (15.92 +/- 4.37)%, (16.39 +/- 6.31)% and (41.48 +/- 12.1)%. There was no significant difference between the cell adhesion on porcelain surface glazed and polished, but more bacteria adhered on the porcelain surface in group C. Porcelain surface polished treatment was clinically acceptable compared with its glazed. They all exhibited the least amount of bacteria adhesion. The more porcelain surface was rough, the more bacteria adhered on it.

Chemical modification of TiO2 surfaces with methylsilanes and characterization by infrared absorption spectroscopy

NASA Technical Reports Server (NTRS)

Finklea, H. O.; Vithanage, R.

1982-01-01

Infrared absorption spectra of methylsilanes bonded to a TiO2 powder were obtained. The reacting silanes include Me sub (4-n)SiX sub n (n=1-4; X=Cl, OMe) and hexamethyldisilazane (HMDS). Reactions were performed on hydroxylated-but-anhydrous TiO2 surfaces in the gas phase. IR spectra confirm the presence of a bonded silane layer. Terminal surface OH groups are found to react more readily than bridging OH groups. By-products of the modification adsorp tenaciously to the surface. The various silanes show only small differences in their ability to sequester surface OH groups. Following hydrolysis in moist air, Si-OH groups are observed only for the tetrafunctional silanes.

Method for Improving Mg Doping During Group-III Nitride MOCVD

DOEpatents

Creighton, J. Randall; Wang, George T.

2008-11-11

A method for improving Mg doping of Group III-N materials grown by MOCVD preventing condensation in the gas phase or on reactor surfaces of adducts of magnesocene and ammonia by suitably heating reactor surfaces between the location of mixing of the magnesocene and ammonia reactants and the Group III-nitride surface whereon growth is to occur.

Group IV nanocrystals with ion-exchangeable surface ligands and methods of making the same

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wheeler, Lance M.; Nichols, Asa W.; Chernomordik, Boris D.

Methods are described that include reacting a starting nanocrystal that includes a starting nanocrystal core and a covalently bound surface species to create an ion-exchangeable (IE) nanocrystal that includes a surface charge and a first ion-exchangeable (IE) surface ligand ionically bound to the surface charge, where the starting nanocrystal core includes a group IV element.

The effect of silane applied to glass ceramics on surface structure and bonding strength at different temperatures

PubMed Central

Eraslan, Oguz

2016-01-01

PURPOSE To evaluate the effect of various surface treatments on the surface structure and shear bond strength (SBS) of different ceramics. MATERIALS AND METHODS 288 specimens (lithium-disilicate, leucite-reinforced, and glass infiltrated zirconia) were first divided into two groups according to the resin cement used, and were later divided into four groups according to the given surface treatments: G1 (hydrofluoric acid (HF)+silane), G2 (silane alone-no heat-treatment), G3 (silane alone-then dried with 60℃ heat-treatment), and G4 (silane alone-then dried with 100℃ heat-treatment). Two different adhesive luting systems were applied onto the ceramic discs in all groups. SBS (in MPa) was calculated from the failure load per bonded area (in N/mm2). Subsequently, one specimen from each group was prepared for SEM evaluation of the separated-resin–ceramic interface. RESULTS SBS values of G1 were significantly higher than those of the other groups in the lithium disilicate ceramic and leucite reinforced ceramic, and the SBS values of G4 and G1 were significantly higher than those of G2 and G3 in glass infiltrated zirconia. The three-way ANOVA revealed that the SBS values were significantly affected by the type of resin cement (P<.001). FIN ceramics had the highest rate of cohesive failure on the ceramic surfaces than other ceramic groups. AFM images showed that the surface treatment groups exhibited similar topographies, except the group treated with HF. CONCLUSION The heat treatment was not sufficient to achieve high SBS values as compared with HF acid etching. The surface topography of ceramics was affected by surface treatments. PMID:27141250

Evaluation of surface roughness of enamel after various bonding and clean-up procedures on enamel bonded with three different bonding agents: An in-vitro study

PubMed Central

Goel, Amit; Singh, Atul; Gupta, Tarun

2017-01-01

Background The purpose of this study was to analyze and compare the enamel surface roughness before bonding and after debonding, to find correlation between the adhesive remnant index and its effect on enamel surface roughness and to evaluate which clean-up method is most efficient to provide a smoother enamel surface. Material and Methods 135 premolars were divided into 3 groups containing 45 premolars in each group. Group I was bonded by using moisture insensitive primer, Group II by using conventional orthodontic adhesive and Group III by using self-etching primer. Each group was divided into 3 sub-groups on the basis of type of clean-up method applied i,e scaling followed by polishing, tungsten carbide bur and Sof-Lex disc. Enamel surface roughness was measured and compared before bonding and after clean-up. Results Evaluation of pre bonding and post clean-up enamel surface roughness (Ra value) with the t test showed that Post clean-up Ra values were greater than Pre bonding Ra values in all the groups except in teeth bonded with self-etching primer cleaned with Sof-Lex disc. Reliability of ARI score taken at different time interval tested with Kruskal Wallis test suggested that all the readings were reliable. Conclusions No clean-up procedure was able to restore the enamel to its original smoothness. Self-etching primer and Sof-Lex disc clean-up method combination restored the enamel surface roughness (Ra value) closest to its pre-treatment value. Key words:Enamel surface roughness, clean-up method, adhesive remnant index. PMID:28512535

Effect of ultraviolet light irradiation on bond strength of fiber post: Evaluation of surface characteristic and bonded area of fiber post with resin cement.

PubMed

Reza, Fazal; Ibrahim, Nur Sukainah

2015-01-01

Fiber post is cemented to a root canal to restore coronal tooth structure. This research aims to evaluate the effect of ultraviolet (UV) irradiation on bond strength of fiber post with resin cement. A total of 40 of the two types of fiber posts, namely, FRC Prostec (FRC) and Fiber KOR (KOR), were used for the experiment. UV irradiation was applied on top of the fiber post surface for 0, 15, 20, and 30 min. The irradiated surface of the fiber posts (n = 5) were immediately bonded with resin cement (Rely X U200) after UV irradiation. Shear bond strength (SBS) MPa was measured, and the dislodged area of post surfaces was examined with scanning electron microscopes. Changes in surface roughness (Ra) of the FRC group after UV irradiation were observed (n = 3) using atomic force microscopy. Data of SBS were statistically analyzed using one-way analysis of variance, followed by multiple comparisons (P < 0.05). SBS was significantly higher for 20 min of UV irradiation of the FRC group while significantly higher SBS was observed with 15 min of UV irradiation of the KOR group. Resin cement was more evident (cohesive failure) on the dislodged post surface of the UV treated groups compared with the control. The surface roughness of the FRC post was Ra = 175.1 nm and Ra = 929.2 nm for the control and the 20 min group, respectively. Higher surface roughness of the UV irradiated group indicated formation of mechanical retention on the fiber post surface. Evidence of cohesive failure was observed which indicated higher SBS of fiber post with the UV irradiated group.

Effect of ultraviolet light irradiation on bond strength of fiber post: Evaluation of surface characteristic and bonded area of fiber post with resin cement

PubMed Central

Reza, Fazal; Ibrahim, Nur Sukainah

2015-01-01

Objective: Fiber post is cemented to a root canal to restore coronal tooth structure. This research aims to evaluate the effect of ultraviolet (UV) irradiation on bond strength of fiber post with resin cement. Materials and Methods: A total of 40 of the two types of fiber posts, namely, FRC Prostec (FRC) and Fiber KOR (KOR), were used for the experiment. UV irradiation was applied on top of the fiber post surface for 0, 15, 20, and 30 min. The irradiated surface of the fiber posts (n = 5) were immediately bonded with resin cement (Rely X U200) after UV irradiation. Shear bond strength (SBS) MPa was measured, and the dislodged area of post surfaces was examined with scanning electron microscopes. Changes in surface roughness (Ra) of the FRC group after UV irradiation were observed (n = 3) using atomic force microscopy. Data of SBS were statistically analyzed using one-way analysis of variance, followed by multiple comparisons (P < 0.05). Results: SBS was significantly higher for 20 min of UV irradiation of the FRC group while significantly higher SBS was observed with 15 min of UV irradiation of the KOR group. Resin cement was more evident (cohesive failure) on the dislodged post surface of the UV treated groups compared with the control. The surface roughness of the FRC post was Ra = 175.1 nm and Ra = 929.2 nm for the control and the 20 min group, respectively. Conclusions: Higher surface roughness of the UV irradiated group indicated formation of mechanical retention on the fiber post surface. Evidence of cohesive failure was observed which indicated higher SBS of fiber post with the UV irradiated group. PMID:25713488

Backward propagating branch of surface waves in a semi-bounded streaming plasma system

NASA Astrophysics Data System (ADS)

Lim, Young Kyung; Lee, Myoung-Jae; Seo, Ki Wan; Jung, Young-Dae

2017-06-01

The influence of wake and magnetic field on the surface ion-cyclotron wave is kinetically investigated in a semi-bounded streaming dusty magnetoplasma in the presence of the ion wake-field. The analytic expressions of the frequency and the group velocity are derived by the plasma dielectric function with the spectral reflection condition. The result shows that the ion wake-field enhances the wave frequency and the group velocity of the surface ion-cyclotron wave in a semi-bounded dusty plasma. It is found that the frequency and the group velocity of the surface electrostatic-ion-cyclotron wave increase with an increase of the strength of the magnetic field. It is interesting to find out that the group velocity without the ion flow has the backward propagation mode in a semi-bounded dusty plasma. The variations due to the frequency and the group velocity of the surface ion-cyclotron wave are also discussed.

Effect of surface treatments on the bond strength of soft denture lining materials to an acrylic resin denture base.

PubMed

Gundogdu, Mustafa; Yesil Duymus, Zeynep; Alkurt, Murat

2014-10-01

Adhesive failure between acrylic resin and resilient liner material is commonly encountered in clinical practice. The purpose of this study was to evaluate the effect of different surface treatments on the bond strength of 2 different resilient lining materials to an acrylic resin denture base. Ninety-six dumbbell-shaped specimens were fabricated from heat-polymerized acrylic resin, and 3 mm of the material was cut from the thin midsection. The specimens were divided into 6 groups according to their surface treatments: no surface treatment (control group), 36% phosphoric acid etching (acid group), erbium:yttrium-aluminum-garnet (Er:YAG) laser (laser group), airborne-particle abrasion with 50-μm Al2O3 particles (abrasion group), an acid+laser group, and an abrasion+laser group. The specimens in each group were divided into 2 subgroups according to the resilient lining material used: heat-polymerized silicone based resilient liner (Molloplast B) and autopolymerized silicone-based resilient liner (Ufi Gel P). After all of the specimens had been polymerized, they were stored in distilled water at 37°C for 1 week. A tensile bond strength test was then performed. Data were analyzed with a 2-way ANOVA, and the Sidak multiple comparison test was used to identify significant differences (α=.05). The effects of the surface treatments and resilient lining materials on the surface of the denture base resin were examined with scanning electron microscopy. The tensile bond strength was significantly different between Molloplast B and Ufi Gel P (P<.001). The specimens of the acid group had the highest tensile bond strength, whereas those of the abrasion group had the lowest tensile bond strength. The scanning electron microscopy observations showed that the application of surface treatments modified the surface of the denture base resin. Molloplast B exhibited significantly higher bond strength than Ufi Gel P. Altering the surface of the acrylic resin denture base with 36% phosphoric acid etching increased bond strength. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Aberration compensation between anterior and posterior corneal surfaces after Small incision lenticule extraction and Femtosecond laser-assisted laser in-situ keratomileusis.

PubMed

Li, Xiaojing; Wang, Yan; Dou, Rui

2015-09-01

To investigate the aberration compensation between anterior and posterior corneal surfaces after SMILE and FS-LASIK. Fifty-five subjects (55 eyes) undergoing SMILE and 51 subjects (51 eyes) undergoing FS-LASIK were enrolled in this study. Wavefront aberrations of anterior and posterior corneal surfaces and the whole cornea at 6 mm in diameter were measured using a Scheimpflug Camera preoperatively and one, three and 6 months postoperatively. The compensation factor (CF), where CF = 1 - (aberration of the whole cornea/aberration of anterior corneal surface), was calculated. Spherical aberration of the posterior surface and the whole cornea remained stable after SMILE. However, spherical aberration of posterior surface increased significantly at 6 months in the FS-LASIK group. The total higher-order aberration (tHOA) of the anterior surface and the whole cornea was lower at 6 months than at one and 3 months (p = 0.001 and 0.001, respectively) in the FS-LASIK group. Meanwhile, in the SMILE group, no significant difference in tHOA was found between various postoperative time points. There were significant decreases in the CF of tHOA compared with preoperative values in both groups. The CF of spherical aberration reduced significantly in both groups at 3 and 6 mm in diameter one, three and 6 months postoperatively. Significant decreases in the CF of vertical coma were found at three and 6 months postoperatively in the FS-LASIK group compared with preoperative values at 6 mm in diameter (p = 0.021 and 0.008, respectively). The change in CF (ΔCF) of spherical aberration was smaller in the SMILE group than in the FS-LASIK group at one and 3 months postoperatively (p = 0.003 and p < 0.0001, respectively). The ΔCF of spherical aberration was significantly lower in moderately myopic subjects than in subjects with high myopia at 1 month in the SMILE group (p = 0.041) and at one, three and 6 months in the FS-LASIK group (p = 0.014, 0.020, and 0.004, respectively). The posterior corneal surface plays an important role in compensating for spherical aberration of the anterior corneal surface. The compensation mechanisms of spherical aberration and higher-order aberration between anterior and posterior corneal surfaces were disrupted by the SMILE and the FS-LASIK procedures. The change in the CF of spherical aberration was smaller in the SMILE group compared with the FS-LASIK group, especially in subjects with high myopia. © 2015 The Authors Ophthalmic & Physiological Optics © 2015 The College of Optometrists.

[Influence of different porcelain surface treatment method on the bonding of metal brackets to porcelain].

PubMed

Fan, Cun-Hui; Chen, Jie; Liu, Xin-Qiang; Ma, Xin

2005-08-01

To investigate the influence of different porcelain surface treatment methods on the shear bond strength of metal brackets bonded to porcelain. 80 porcelain facets were divided randomly into two groups according to different adhesive material that was used to bond metal brackets. Adhesive material were Jing-Jin enamel adhesive and light-cured composite resin. Each group was further divided into 4 subgroups according to different surface treatment methods, which were acid etching with 37% phosphoric acid (H3PO4), acid etching with 9.6% hydrofluoric acid (HF), deglazing by grinding and silanating the porcelain surface. All specimens were stored in 37 degrees C water for 24 hours and then the shear bond strength and the porcelain fracture after debonding was determined. The porcelain surfaces after HF etching, H3PO4 etching and deglazing by grinding were examined by scanning electron microscopy respectively. The shear bond strengths in the HF etching groups, the deglazing groups and the silanating groups were much greater than that in the phosphoric etching groups (P < 0.01). Adequate orthodontic bonding strength was achieved both when bonded with light-cured composite resin after deglazing by grinding and when bonded with either of these adhesives after HF etching or surface silanating. There were no differences in the rates of porcelain fractures among groups (P > 0.05). HF etching, deglazing by grinding and silanating can all increase the shear bond strength between metal bracket and porcelain. Surface silanating of porcelain is a better surface treatment when metal brackets bonded to porcelain.

Surface developmental dyslexia is as prevalent as phonological dyslexia when appropriate control groups are employed.

PubMed

Wybrow, Dean P; Hanley, J Richard

2015-01-01

Previous investigations of the incidence of developmental surface and phonological dyslexia using reading-age-matched control groups have identified many more phonological dyslexics (poor nonword reading relative to irregular-word reading) than surface dyslexics (poor irregular-word reading relative to nonword reading). However, because the measures that have been used to estimate reading age include irregular-word reading ability, they appear inappropriate for assessing the incidence of surface dyslexia. The current study used a novel method for generating control groups whose reading ability was matched to that of the dyslexic sample. The incidence of surface dyslexia was assessed by comparing dyslexic performance with that of a control group who were matched with the dyslexics on a test of nonword reading. The incidence of phonological dyslexia was assessed with reference to a control group who were matched with the dyslexics at irregular-word reading. These control groups led to the identification of an approximately equal number of children with surface and phonological dyslexia. It appeared that selecting control participants who were matched with dyslexics for reading age led to the recruitment of individuals with relatively high nonword reading scores relative to their irregular-word reading scores compared with other types of control group. The theoretical implications of these findings are discussed.

Change in surface roughness of esthetic restorative materials after exposure to different immersion regimes in a cola drink.

PubMed

Bajwa, Navroop Kaur; Pathak, Anuradha

2014-01-01

Context. An in vitro study carried out to evaluate and compare the effect of Cola drink on surface roughness of esthetic restorative materials. Purpose. To compare the effect of different immersion regimes in a Cola drink on surface roughness of esthetic restorative materials. Method. Two hundred samples were grouped into 4 equal groups of 50 samples each: Group I: conventional glass ionomer, Group II: resin modified glass ionomer, Group III: polyacid-modified resin composite, Group IV: Composite resin. Each group was further subdivided into 5 subgroups of 10 samples each. Subgroup A (Control Subgroup). Samples were kept immersed in artificial saliva. Subgroup B. Samples were immersed in Cola drink once a day. Subgroup C. Samples were immersed in Cola drink, 3 times a day. Subgroup D. Samples were immersed in Cola drink 5 times a day. Subgroup E. Samples were immersed in Cola drink 10 times a day. Each immersion lasted 5 minutes. The immersion protocol was repeated for 7 days. Results. Maximum surface roughness was seen in Group I conventional glass ionomer cement, followed by Group II resin modified glass ionomer, Group III polyacid modified resin composite, and Group IV composite resin samples. Conclusion. Resistance to change in surface roughness is more in resin based restorative materials as compared to glass ionomer based materials.

Change in Surface Roughness of Esthetic Restorative Materials after Exposure to Different Immersion Regimes in a Cola Drink

PubMed Central

Bajwa, Navroop Kaur; Pathak, Anuradha

2014-01-01

Context. An in vitro study carried out to evaluate and compare the effect of Cola drink on surface roughness of esthetic restorative materials. Purpose. To compare the effect of different immersion regimes in a Cola drink on surface roughness of esthetic restorative materials. Method. Two hundred samples were grouped into 4 equal groups of 50 samples each: Group I: conventional glass ionomer, Group II: resin modified glass ionomer, Group III: polyacid-modified resin composite, Group IV: Composite resin. Each group was further subdivided into 5 subgroups of 10 samples each. Subgroup A (Control Subgroup). Samples were kept immersed in artificial saliva. Subgroup B. Samples were immersed in Cola drink once a day. Subgroup C. Samples were immersed in Cola drink, 3 times a day. Subgroup D. Samples were immersed in Cola drink 5 times a day. Subgroup E. Samples were immersed in Cola drink 10 times a day. Each immersion lasted 5 minutes. The immersion protocol was repeated for 7 days. Results. Maximum surface roughness was seen in Group I conventional glass ionomer cement, followed by Group II resin modified glass ionomer, Group III polyacid modified resin composite, and Group IV composite resin samples. Conclusion. Resistance to change in surface roughness is more in resin based restorative materials as compared to glass ionomer based materials. PMID:25006464

Shear-bond-strength of orthodontic brackets to aged nano-hybrid composite-resin surfaces using different surface preparation.

PubMed

Demirtas, Hatice Kubra; Akin, Mehmet; Ileri, Zehra; Basciftci, Faruk Ayhan

2015-01-01

The aim of this study was to evaluate the effects of different surface preparation methods on the shear bond strength (SBS) of orthodontic metal brackets to aged nano-hybrid resin composite surfaces in vitro. A total of 100 restorative composite resin discs, 6 mm in diameter and 3 mm thick, were obtained and treated with an ageing procedure. After ageing, the samples were randomly divided as follows according to surface preparation methods: (1)Control, (2)37% phosphoric acid gel, (3)Sandblasting, (4)Diamond bur, (5)Air-flow and 20 central incisor teeth were used for the control etched group. SBS test were applied on bonded metal brackets to all samples. SBS values and residual adhesives were evaluated. Analysis of variance showed a significant difference (p<0.001) between the groups. Sandblasted group had the highest SBS value (12.85 MPa) in experimental groups. The sandblasting surface treatment is recommended as an effective method of bonding orthodontic metal brackets to nano-hybrid composite resin surfaces.

Effect of surface treatments on shear bond strength of resin composite bonded to CAD/CAM resin-ceramic hybrid materials

PubMed Central

Güngör, Merve Bankoğlu; Bal, Bilge Turhan; Ünver, Senem; Doğan, Aylin

2016-01-01

PURPOSE The purpose of this study was to assess the effect of surface treatments on shear bond strength of resin composite bonded to thermocycled and non-thermocycled CAD/CAM resin-ceramic hybrid materials. MATERIALS AND METHODS 120 specimens (10×10×2 mm) from each material were divided into 12 groups according to different surface treatments in combination with thermal aging procedures. Surface treatment methods were airborne-particle abrasion (abraded with 50 micron alumina particles), dry grinding (grinded with 125 µm grain size bur), and hydrofluoric acid (9%) and silane application. According to the thermocycling procedure, the groups were assigned as non-thermocycled, thermocycled after packing composites, and thermocycled before packing composites. The average surface roughness of the non-thermocycled specimens were measured after surface treatments. After packing composites and thermocycling procedures, shear bond strength (SBS) of the specimens were tested. The results of surface roughness were statistically analyzed by 2-way Analysis of Variance (ANOVA), and SBS results were statistically analyzed by 3-way ANOVA. RESULTS Surface roughness of GC were significantly lower than that of LU and VE (P<.05). The highest surface roughness was observed for dry grinding group, followed by airborne particle abraded group (P<.05). Comparing the materials within the same surface treatment method revealed that untreated surfaces generally showed lower SBS values. The values of untreated LU specimens showed significantly different SBS values compared to those of other surface treatment groups (P<.05). CONCLUSION SBS was affected by surface treatments. Thermocycling did not have any effect on the SBS of the materials except acid and silane applied GC specimens, which were subjected to thermocycling before packing of the composite resin. PMID:27555894

A Three Month Comparative Evaluation of the Effect of Different Surface Treatment Agents on the Surface Integrity and Softness of Acrylic based Soft Liner: An In vivo Study

PubMed Central

Mahajan, Neerja; Naveen, Y. G.; Sethuraman, Rajesh

2017-01-01

Introduction Acrylic based soft liners are cost effective, yet are inferior in durability as compared to silicone based liners. Hence, this study was conducted to evaluate if the softness and surface integrity of acrylic based soft liner can be maintained by using different surface treatment agents. Aim To comparatively evaluate the effects of Varnish, Monopoly and Kregard surface treatment agents on the surface integrity and softness of acrylic based soft liner at baseline, at one month and after three months. Materials and Methods A total of 37 participants who required conventional maxillary dentures were selected according to the determined inclusion and exclusion criteria of the study. In the maxillary denture on the denture bearing surface, eight palatal recesses (5 mm x 3 mm) were made and filled with acrylic based soft liner (Permasoft). The soft liners in these recesses were given surface treatment and divided as control (uncoated), Varnish, Monopoly and Kregard groups. The hardness and surface integrity were evaluated with Shore A Durometer and Scanning Electron Microscope (SEM) respectively at baseline, one month and three months interval. Surface integrity between groups was compared using Kruskal-Wallis test. Intergroup comparison for hardness was done using ANOVA and Tukey’s HSD post-hoc tests. Results Amongst all the groups tested, surface integrity was maintained in the Kregard group, as compared to control, Varnish and Monopoly groups for all three time intervals (p< 0.001). Kregard treated samples also demonstrated significantly higher softness at all the time intervals (p<0.001). Conclusion Surface treatment with Kregard demonstrated better surface integrity and softness at all the time intervals. PMID:29207842

Modeling the Acid-Base Properties of Montmorillonite Edge Surfaces.

PubMed

Tournassat, Christophe; Davis, James A; Chiaberge, Christophe; Grangeon, Sylvain; Bourg, Ian C

2016-12-20

The surface reactivity of clay minerals remains challenging to characterize because of a duality of adsorption surfaces and mechanisms that does not exist in the case of simple oxide surfaces: edge surfaces of clay minerals have a variable proton surface charge arising from hydroxyl functional groups, whereas basal surfaces have a permanent negative charge arising from isomorphic substitutions. Hence, the relationship between surface charge and surface potential on edge surfaces cannot be described using the Gouy-Chapman relation, because of a spillover of negative electrostatic potential from the basal surface onto the edge surface. While surface complexation models can be modified to account for these features, a predictive fit of experimental data was not possible until recently, because of uncertainty regarding the densities and intrinsic pK a values of edge functional groups. Here, we reexamine this problem in light of new knowledge on intrinsic pK a values obtained over the past decade using ab initio molecular dynamics simulations, and we propose a new formalism to describe edge functional groups. Our simulation results yield reasonable predictions of the best available experimental acid-base titration data.

Effect of sealant agents on the color stability and surface roughness of nanohybrid composite resins.

PubMed

Dede, Doğu Ömür; Şahin, Onur; Koroglu, Aysegül; Yilmaz, Burak

2016-07-01

The effect of sealant agents on the surface roughness and color stability of nanohybrid composite resins is unknown. The purpose of this in vitro study was to evaluate the effect of sealant agents on the surface roughness and color stability of 4 nanohybrid composite resin materials. Forty disks (10×2 mm) were fabricated for each nanohybrid composite resin material (Z-550, Tetric EvoCeram, Clearfill Majesty, Ice) (N=160) and divided into 4 surface treatment groups: 1 conventional polishing (control) and 3 different sealant agent (Palaseal, Optiglaze, BisCover) coupling groups (n=10). The specimens were thermocycled, and surface roughness (Ra) values were obtained with a profilometer. Scanning electron microscope images were also recorded. CIELab color parameters of each specimen were measured with a spectrophotometer before and after 7 days of storage in a coffee solution. Color differences were calculated by the CIEDE 2000 (ΔE00) formula. The data were statistically analyzed by 2-way ANOVA and by the Tukey HSD test (α=.05). The surface treatment technique significantly affected the Ra values of the composite resins tested (P<.001). The interaction between the surface treatment technique and composite resin material was also significant for ΔE00 values (P<.05). Within the composite resin groups, significant decreases in Ra were observed only for the Palaseal agent coupled composite resin groups (except Ice) compared with the control groups (P<.05). Scanning electron microscope images revealed rougher surfaces with conventionally polished groups compared with test groups. Conventionally polished groups had the highest ΔE00 (3.09 to 3.49) values for each composite resin group, except for BisCover applied Clearfill Majesty (P<.05). Within the composite resin groups, significant differences were observed between the color change seen with BisCover and other sealants for Clearfill Majesty composite resin (P<.05). Using Palaseal agent on all tested composite resins except for Ice produced smoother surfaces. All surface sealant agents provided less discoloration of nanohybrid composite resins after coffee staining compared with conventional polishing except for BisCover applied Clearfill Majesty composite resin. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Surface roughness of glass ionomer cements indicated for uncooperative patients according to surface protection treatment

PubMed Central

Pacifici, Edoardo; Bossù, Maurizio; Giovannetti, Agostino; La Torre, Giuseppe; Guerra, Fabrizio; Polimeni, Antonella

2013-01-01

Summary Background Even today, use of Glass Ionomer Cements (GIC) as restorative material is indicated for uncooperative patients. Aim The study aimed at estimating the surface roughness of different GICs using or not their proprietary surface coatings and at observing the interfaces between cement and coating through SEM. Materials and methods Forty specimens have been obtained and divided into 4 groups: Fuji IX (IX), Fuji IX/G-Coat Plus (IXC), Vitremer (V), Vitremer/Finishing Gloss (VFG). Samples were obtained using silicone moulds to simulate class I restorations. All specimens were processed for profilometric evaluation. The statistical differences of surface roughness between groups were assessed using One-Way Analysis of Variance (One-Way ANOVA) (p<0.05). The Two-Way Analysis of Variance (Two-Way ANOVA) was used to evaluate the influence of two factors: restoration material and presence of coating. Coated restoration specimens (IXC and VFG) were sectioned perpendicular to the restoration surface and processed for SEM evaluation. Results No statistical differences in roughness could be noticed between groups or factors. Following microscopic observation, interfaces between restoration material and coating were better for group IXC than for group VFG. Conclusions When specimens are obtained simulating normal clinical procedures, the presence of surface protection does not significantly improve the surface roughness of GICs. PMID:24611090

Surface roughness of glass ionomer cements indicated for uncooperative patients according to surface protection treatment.

PubMed

Pacifici, Edoardo; Bossù, Maurizio; Giovannetti, Agostino; La Torre, Giuseppe; Guerra, Fabrizio; Polimeni, Antonella

2013-01-01

Even today, use of Glass Ionomer Cements (GIC) as restorative material is indicated for uncooperative patients. The study aimed at estimating the surface roughness of different GICs using or not their proprietary surface coatings and at observing the interfaces between cement and coating through SEM. Forty specimens have been obtained and divided into 4 groups: Fuji IX (IX), Fuji IX/G-Coat Plus (IXC), Vitremer (V), Vitremer/Finishing Gloss (VFG). Samples were obtained using silicone moulds to simulate class I restorations. All specimens were processed for profilometric evaluation. The statistical differences of surface roughness between groups were assessed using One-Way Analysis of Variance (One-Way ANOVA) (p<0.05). The Two-Way Analysis of Variance (Two-Way ANOVA) was used to evaluate the influence of two factors: restoration material and presence of coating. Coated restoration specimens (IXC and VFG) were sectioned perpendicular to the restoration surface and processed for SEM evaluation. No statistical differences in roughness could be noticed between groups or factors. Following microscopic observation, interfaces between restoration material and coating were better for group IXC than for group VFG. When specimens are obtained simulating normal clinical procedures, the presence of surface protection does not significantly improve the surface roughness of GICs.

Influence of nano alumina coating on the flexural bond strength between zirconia and resin cement

PubMed Central

Mumcu, Emre; Şen, Murat

2018-01-01

PURPOSE The purpose of this in vitro study is to examine the effects of a nano-structured alumina coating on the adhesion between resin cements and zirconia ceramics using a four-point bending test. MATERIALS AND METHODS 100 pairs of zirconium bar specimens were prepared with dimensions of 25 mm × 2 mm × 5 mm and cementation surfaces of 5 mm × 2 mm. The samples were divided into 5 groups of 20 pairs each. The groups are as follows: Group I (C) – Control with no surface modification, Group II (APA) – airborne-particle-abrasion with 110 µm high-purity aluminum oxide (Al2O3) particles, Group III (ROC) – airborne-particle-abrasion with 110 µm silica modified aluminum oxide (Al2O3 + SiO2) particles, Group IV (TCS) – tribochemical silica coated with Al2O3 particles, and Group V (AlC) – nano alumina coating. The surface modifications were assessed on two samples selected from each group by atomic force microscopy and scanning electron microscopy. The samples were cemented with two different self-adhesive resin cements. The bending bond strength was evaluated by mechanical testing. RESULTS According to the ANOVA results, surface treatments, different cement types, and their interactions were statistically significant (P<.05). The highest flexural bond strengths were obtained in nanostructured alumina coated zirconia surfaces (50.4 MPa) and the lowest values were obtained in the control group (12.00 MPa), both of which were cemented using a self-adhesive resin cement. CONCLUSION The surface modifications tested in the current study affected the surface roughness and flexural bond strength of zirconia. The nano alumina coating method significantly increased the flexural bond strength of zirconia ceramics. PMID:29503713

Influence of oscillating and rotary cutting instruments with electric and turbine handpieces on tooth preparation surfaces.

PubMed

Geminiani, Alessandro; Abdel-Azim, Tamer; Ercoli, Carlo; Feng, Changyong; Meirelles, Luiz; Massironi, Domenico

2014-07-01

Rotary and nonrotary cutting instruments are used to produce specific characteristics on the axial and marginal surfaces of teeth being prepared for fixed restorations. Oscillating instruments have been suggested for tooth preparation, but no comparative surface roughness data are available. To compare the surface roughness of simulated tooth preparations produced by oscillating instruments versus rotary cutting instruments with turbine and electric handpieces. Different grit rotary cutting instruments were used to prepare Macor specimens (n=36) with 2 handpieces. The surface roughness obtained with rotary cutting instruments was compared with that produced by oscillating cutting instruments. The instruments used were as follows: coarse, then fine-grit rotary cutting instruments with a turbine (group CFT) or an electric handpiece (group CFE); coarse, then medium-grit rotary cutting instruments with a turbine (group CMT) or an electric handpiece (group CME); coarse-grit rotary cutting instruments with a turbine handpiece and oscillating instruments at a low-power (group CSL) or high-power setting (group CSH). A custom testing apparatus was used to test all instruments. The average roughness was measured for each specimen with a 3-dimensional optical surface profiler and compared with 1-way ANOVA and the Tukey honestly significant difference post hoc test for multiple comparisons (α=.05). Oscillating cutting instruments produced surface roughness values similar to those produced by similar grit rotary cutting instruments with a turbine handpiece. The electric handpiece produced smoother surfaces than the turbine regardless of rotary cutting instrument grit. Rotary cutting instruments with electric handpieces produced the smoothest surface, whereas the same instruments used with a turbine and oscillating instruments achieved similar surface roughness. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

[Correlation between axial length and corneal curvature and spherical aberration].

PubMed

Wang, X J; Bao, Y Z

2017-04-11

Objective: To discuss the correlation between axial length and corneal curvature and corneal spherical aberration in a group of cataract patients with axial length greater than 24 mm. Methods: Retrospective case series. This study comprised 117 (234 eyes) age-related cataract patients. There were 51 men (43.59%) and 66 women (56.41%) with mean age of (69.0±8.7) years (range from 52.0 to 85.0 years). The average axial length was 27.6±1.8 (range from 24.2 to 31.9 mm). We devided them into four groups according to the axial length. A-scan was used to measure the axial length and Pentacam was used to get the corneal curvature and corneal spherical aberration of both anterior and posterior surface. kolmogorov-smirnov test was used to check the normal distribution. ANOVA test was used to compare eachcorneal parameter among different groups. Pearson correlation analysis was used to obtain the correlation of corneal parameters in groups. Results: There were correlations between the axial length and the anterior and posterior corneal curvature ( r=- 0.213, r= 0.174, respectively, P< 0.05). No correlation was found between the axial length and anterior or posterior corneal spherical aberration ( r=- 0.114, 0.055, respectively, P> 0.05). Mean values of corneal anterior surface curvature were (45.26±1.60) D (group 1), (44.17±1.45) D (group 2), (44.40±1.99)D (group 3), and (44.53±1.69) D (group 4) respectively. Mean values of corneal posterior surface curvature were(-6.57±0.26)D (group 1), ( - 6.40±0.24)D (group 2), ( - 6.41±0.38)D (group 3), and (-6.43±0.26)D (group 4) respectively. There were significant difference of corneal anterior and posterior surface curvature among 4 groups ( P= 0.004, P= 0.001). There was significant difference of corneal curvature of anterior surface in group 1 compared to group 2 and group 3( P< 0.01, P= 0.01). There was significant difference of curvature of posterior surface in group 1 compared to group 2 and group 3, respectively ( P< 0.01). Mean values of anterior surface corneal spherical aberration were (2.09±0.53) μm (group 1), (1.90±0.44) μm (group 2), (2.00±0.74) μm (group 3), and (1.78±0.52) μm (group 4) respectively. Mean values of posterior surface corneal spherical aberration were (2.69±1.15) μm (group 1), (2.46±1.16) μm (group 2), (2.92±2.51) μm (group 3), and (2.69±1.13) μm (group 4) respectively. No correlation was found in anterior and posterior surface corneal spherical aberration( P> 0.05) among different groups. Conclusions: The eye with a longer axial length have a flatter cornea. Cornea fails to compensate for axial length elongation when the axial length is longer than 28mm. The corneal spherical aberration varies among individuals, which suggests us to do the customized measurement before cataract surgery to make a decision on choosing the aspherical intraocular lens. (Chin J Ophthalmol, 2017, 53: 255-259) .

Evaluation of experimental coating to improve the zirconia-veneering ceramic bond strength.

PubMed

Matani, Jay D; Kheur, Mohit; Jambhekar, Shantanu Subhashchandra; Bhargava, Parag; Londhe, Aditya

2014-12-01

To evaluate the shear bond strength (SBS) between zirconia and veneering ceramic following different surface treatments of zirconia. The efficacy of an experimental zirconia coating to improve the bond strength was also evaluated. Zirconia strips were fabricated and were divided into four groups as per their surface treatment: polished (control), airborne-particle abrasion, laser irradiation, and application of the experimental coating. The surface roughness and the residual monoclinic content were evaluated before and after the respective surface treatments. A scanning electron microscope (SEM) analysis of the experimental surfaces was performed. All specimens were subjected to shear force in a universal testing machine. The SBS values were analyzed with one-way ANOVA followed by Bonferroni post hoc for groupwise comparisons. The fractured specimens were examined to observe the failure mode. The SBS (29.17 MPa) and roughness values (0.80) of the experimental coating group were the highest among the groups. The residual monoclinic content was minimal (0.32) when compared to the remaining test groups. SEM analysis revealed a homogenous surface well adhered to an undamaged zirconia base. The other test groups showed destruction of the zirconia surface. The analysis of failure following bond strength testing showed entirely cohesive failures in the veneering ceramic in all study groups. The experimental zirconia surface coating is a simple technique to increase the microroughness of the zirconia surface, and thereby improve the SBS to the veneering ceramic. It results in the least monoclinic content and produces no structural damage to the zirconia substructure. © 2014 by the American College of Prosthodontists.

The CPP-ACP relieved enamel erosion from a carbonated soft beverage: an in vitro AFM and XRD study.

PubMed

Wang, C P; Huang, S B; Liu, Y; Li, J Y; Yu, H Y

2014-03-01

To investigate the CPP-ACP's effect on enamel against carbonated beverage erosion and explore the potential mechanism. A total of 30 enamel samples were prepared from sound bovine incisors, divided into 3 groups. Samples in the control group were kept in artificial saliva. Specimens' surfaces were smeared with a CPP-ACP agent (Tooth Mousse, TM) for 3 min, rinsed with distilled water for 10s, merged into cola (Coca Cola, CC) for 4 intervals of 2 min, rinsed again for the TM+CC group. In the CC group, specimens were treated solely with cola for 4 intervals (2 min each). The cycles were applied at 0, 12, 24, 36, 48 and 60 h. The surface microhardness (SMH) alterations were measured using a microhardness tester, the surface profiles were analyzed using the atomic force microscope, and the surface crystalline amount (I%) and crystallinity (FWHM) were analyzed using X-ray diffractometer. The SMH were significantly decreased in CC group, showing the largest SMH alteration; the reduction of SMH in TM+CC group was lower than that in CC group, still larger than control. After cycles, the TM+CC group showed rougher surfaces than control, while the CC group had the roughest surfaces. The TM+CC had an I% higher than the CC, and lower than the control. The TM+CC group had a FWHM lower than CC, higher than control. CPP-ACP was able to relieve the erosion on enamel from carbonated beverage. Copyright © 2013 Elsevier Ltd. All rights reserved.

Effects of staining and bleaching on a nanohybrid composite with or without surface sealant

PubMed Central

Halacoglu, Derya Merve; Yamanel, Kıvanc; Basaran, Saffet; Tuncer, Duygu; Celik, Cigdem

2016-01-01

Objective: The effect of different staining solutions and a bleaching procedure on color stability and surface roughness of a nanohybrid resin composite were evaluated with or without liquid resin polishing (RP). Materials and Methods: Ninety-six disc-shaped resin composite specimens (A1 Shade, Z550 Filtek 3M ESPE, St. Paul, MN, USA) were prepared and divided randomly into two groups (n = 48). Liquid RP (BisCover LV, Bisco Inc., Schaumburg, IL, USA) was applied in one group (RP) and not in the other (P). Specimen color and surface roughness were determined using a colorimeter and profilometer, respectively. After baseline measurements, each group was divided into four subgroups (n = 12) for immersion in a control (distilled water) or three different staining solutions (ice tea, red wine, and cola) for 1 week. Color and surface roughness were then reevaluated. After measurements, all specimens were bleached using a 35% hydrogen peroxide gel. The color and surface roughness of the specimens were reevaluated. Statistical Analysis: Data were subjected to an analysis of variance for repeated measurements among the groups (P < 0.05). Results: Staining and bleaching did not change the surface roughness of the RP and P groups (P > 0.05). Discoloration in the red wine group was higher than for the other staining solutions for the RP (P < 0.001) and P groups (P = 0.018). Conclusion: Application of liquid RP did not enhance the color stability and surface roughness of the composite resin restoration. PMID:27403054

Storage Medium Affects the Surface Porosity of Dental Cements.

PubMed

Saghiri, M Ali; Shabani, Asal; Asatourian, Armen; Sheibani, Nader

2017-08-01

Calcium silicate-based cements physical properties is influenced by environmental changes. Here, we intended to evaluate the effect of storage medium on surface porosity of root Mineral Trioxide Aggregate (MTA) and Biodentine cement. A total of 40 polyethylene tubes were selected and divided into two groups: Group A (MTA) and Group B (Biodentine). Each group was subdivided into two subgroups (n=10). In subgroups A1 and B1, tubes were transferred to Distilled Water (DW), while samples of subgroup A2 and B2 were transferred to Synthetic Tissue Fluid (STF) as storage medium and samples were stored for three days. All specimens were then placed in a desiccator for 24 hours and then subject to surface porosity evaluation by Scanning Electron Microscopy (SEM) at ×500, ×1000, ×2000 and ×5000 magnifications. The number and the surface porosities were determined by Image J analysis. Data were analyzed by ANOVA at level of significance of p<0.05. The lowest surface porosity was observed in MTA samples stored in STF and the highest was in Biodentine samples stored in DW. Significant differences were noted between groups and subgroups of each group (p< 0.05). MTA samples stored in DW and STF showed significantly lower surface porosities compared to Biodentine samples (p < 0.05). Storage medium can drastically affect the surface porosity of tested calcium silicate-based cements. However, MTA showed lower surface porosity compared to Biodentine cement, which can result in lower microleakage in applied area.

Comparison of surface abrasion produced on the enamel surface by a standard dentifrice using three different toothbrush bristle designs: A profilometric in vitro study

PubMed Central

Kumar, Sandeep; Kumari, Minal; Acharya, Shashidhar; Prasad, Ram

2014-01-01

Aim: The aim was to assess, in vitro, the effect on surface abrasivity of enamel surface caused by three different types (flat trim, zig-zag, bi-level) of toothbrush bristle design. Materials and Methods: Twenty-four freshly extracted, sound, human incisor teeth were collected for this study. The enamel slab was prepared, which were mounted, on separate acrylic bases followed by subjected to profilometric analysis. The surface roughness was measured using the profilometer. The specimen were divided into three groups, each group containing eight mounted specimens, wherein, Group 1 specimens were brushed with flat trim toothbrush; Group 2 brushed with zig-zag and Group 3 with bi-level bristle design. A commercially available dentifrice was used throughout the study. A single specimen was brushed for 2 times daily for 2 min period for 1 week using a customized brushing apparatus. The pre- and post-roughness value change were analyzed and recorded. Statistical test: Kruskal–Wallis test and Mann–Whitney U-test. Result: The results showed that surface abrasion was produced on each specimen, in all the three groups, which were subjected to brushing cycle. However, the bi-level bristle design (350% increase in roughness, P = 0.021) and zig-zag bristle design (160% increase in roughness, P = 0.050) showed significantly higher surface abrasion when compared with flat trim bristle design toothbrush. Conclusion: Flat trim toothbrush bristle produces least surface abrasion and is relatively safe for use. PMID:25125852

Evaluation of an alternative technique to optimize direct bonding of orthodontic brackets to temporary crowns.

PubMed

Dias, Francilena Maria Campos Santos; Pinzan-Vercelino, Célia Regina Maio; Tavares, Rudys Rodolfo de Jesus; Gurgel, Júlio de Araújo; Bramante, Fausto Silva; Fialho, Melissa Nogueira Proença

2015-01-01

To compare shear bond strength of different direct bonding techniques of orthodontic brackets to acrylic resin surfaces. The sample comprised 64 discs of chemically activated acrylic resin (CAAR) randomly divided into four groups: discs in group 1 were bonded by means of light-cured composite resin (conventional adhesive); discs in group 2 had surfaces roughened with a diamond bur followed by conventional direct bonding by means of light-cured composite resin; discs in group 3 were bonded by means of CAAR (alternative adhesive); and discs in group 4 had surfaces roughened with a diamond bur followed by direct bonding by means of CAAR. Shear bond strength values were determined after 24 hours by means of a universal testing machine at a speed of 0.5 mm/min, and compared by analysis of variance followed by post-hoc Tukey test. Adhesive remnant index (ARI) was measured and compared among groups by means of Kruskal-Wallis and Dunn tests. Groups 3 and 4 had significantly greater shear bond strength values in comparison to groups 1 and 2. Groups 3 and 4 yielded similar results. Group 2 showed better results when compared to group 1. In ARI analyses, groups 1 and 2 predominantly exhibited a score equal to 0, whereas groups 3 and 4 predominantly exhibited a score equal to 3. Direct bonding of brackets to acrylic resin surfaces using CAAR yielded better results than light-cured composite resin. Surface preparation with diamond bur only increased shear bond strength in group 2.

Comparison of Linear and Hyperbranched Polyether Lipids for Liposome Shielding by 18F-Radiolabeling and Positron Emission Tomography.

PubMed

Wagener, Karolin; Worm, Matthias; Pektor, Stefanie; Schinnerer, Meike; Thiermann, Raphael; Miederer, Matthias; Frey, Holger; Rösch, Frank

2018-04-27

Multifunctional and highly biocompatible polyether structures play a key role in shielding liposomes from degradation in the bloodstream, providing also multiple functional groups for further attachment of targeting moieties. In this work hyperbranched polyglycerol ( hbPG) bearing lipids with long alkyl chain anchor are evaluated with respect to steric stabilization of liposomes. The branched polyether lipids possess a hydrophobic bis(hexadecyl)glycerol membrane anchor for the liposomal membrane. hbPG was chosen as a multifunctional alternative to PEG, enabling the eventual linkage of multiple targeting vectors. Different hbPG lipids ( M n = 2900 and 5200 g mol -1 ) were examined. A linear bis(hexadecyl)glycerol-PEG lipid ( M n = 3000 g mol -1 ) was investigated as well, comparing hbPG and PEG with respect to shielding properties. Radiolabeling of the polymers was carried out using 1-azido-2-(2-(2-[ 18 F]fluoroethoxy)ethoxy)ethane ([ 18 F]F-TEG-N) 3 via copper-catalyzed alkyne-azide cycloaddition with excellent radiochemical yields exceeding 95%. Liposomes were prepared by the thin-film hydration method followed by repeated extrusion. Use of a custom automatic extrusion device gave access to reproducible sizes of the liposomes (hydrodynamic radius of 60-94 nm). The in vivo fate of the bis(hexadecyl)glycerol polyethers and their corresponding assembled liposome structures were evaluated via noninvasive small animal positron emission tomography (PET) imaging and biodistribution studies (1 h after injection and 4 h after injection) in mice. Whereas the main uptake of the nonliposomal polyether lipids was observed in the kidneys and in the bladder after 1 h due to rapid renal clearance, in contrast, the corresponding liposomes showed uptake in the blood pool as well as in organs with good blood supply, that is, heart and lung over the whole observation period of 4 h. The in vivo behavior of all three liposomal formulations was comparable, albeit with remarkable differences in splenic uptake. Overall, liposomes shielded by the branched polyglycerol lipids show a favorable biodistribution with greatly prolonged blood circulation times, rendering them promising novel nanovesicles for drug transport and targeting.

Zeta Potential Measurements on Solid Surfaces for in Vitro Biomaterials Testing: Surface Charge, Reactivity Upon Contact With Fluids and Protein Absorption

PubMed Central

Ferraris, Sara; Cazzola, Martina; Peretti, Veronica; Stella, Barbara; Spriano, Silvia

2018-01-01

Surface properties of biomaterials (e.g., roughness, chemical composition, charge, wettability, and hydroxylation degree) are key features to understand and control the complex interface phenomena that happens upon contact with physiological fluids. Numerous physico-chemical techniques can be used in order to investigate in depth these crucial material features. Among them, zeta potential measurements are widely used for the characterization of colloidal suspensions, but actually poorly explored in the study of solid surfaces, even if they can give significant information about surface charge in function of pH and indirectly about surface functional groups and reactivity. The aim of the present research is application of zeta potential measurements of solid surfaces for the in vitro testing of biomaterials. In particular, bare and surface modified Ti6Al4V samples have been compared in order to evaluate their isoelectric points (IEPs), surface charge at physiological pH, in vitro bioactivity [in simulated body fluid (SBF)] and protein absorption. Zeta potential titration was demonstrated as a suitable technique for the surface characterization of surface treated Ti6Al4V substrates. Significant shift of the isoelectric point was recorded after a chemical surface treatment (because of the exposition of hydroxyl groups), SBF soaking (because of apatite precipitation IEP moves close to apatite one) and protein absorption (IEP moves close to protein ones). Moreover, the shape of the curve gives information about exposed functional groups (e.g., a plateau in the basic range appears due to the exposition of acidic OH groups and in the acidic range due to exposition of basic NH2 groups). PMID:29868575

A surface structural model for ferrihydrite I: Sites related to primary charge, molar mass, and mass density

NASA Astrophysics Data System (ADS)

Hiemstra, Tjisse; Van Riemsdijk, Willem H.

2009-08-01

A multisite surface complexation (MUSIC) model for ferrihydrite (Fh) has been developed. The surface structure and composition of Fh nanoparticles are described in relation to ion binding and surface charge development. The site densities of the various reactive surface groups, the molar mass, the mass density, the specific surface area, and the particle size are quantified. As derived theoretically, molecular mass and mass density of nanoparticles will depend on the types of surface groups and the corresponding site densities and will vary with particle size and surface area because of a relatively large contribution of the surface groups in comparison to the mineral core of nanoparticles. The nano-sized (˜2.6 nm) particles of freshly prepared 2-line Fh as a whole have an increased molar mass of M ˜ 101 ± 2 g/mol Fe, a reduced mass density of ˜3.5 ± 0.1 g/cm 3, both relatively to the mineral core. The specific surface area is ˜650 m 2/g. Six-line Fh (5-6 nm) has a molar mass of M ˜ 94 ± 2 g/mol, a mass density of ˜3.9 ± 0.1 g/cm 3, and a surface area of ˜280 ± 30 m 2/g. Data analysis shows that the mineral core of Fh has an average chemical composition very close to FeOOH with M ˜ 89 g/mol. The mineral core has a mass density around ˜4.15 ± 0.1 g/cm 3, which is between that of feroxyhyte, goethite, and lepidocrocite. These results can be used to constrain structural models for Fh. Singly-coordinated surface groups dominate the surface of ferrihydrite (˜6.0 ± 0.5 nm -2). These groups can be present in two structural configurations. In pairs, the groups either form the edge of a single Fe-octahedron (˜2.5 nm -2) or are present at a single corner (˜3.5 nm -2) of two adjacent Fe octahedra. These configurations can form bidentate surface complexes by edge- and double-corner sharing, respectively, and may therefore respond differently to the binding of ions such as uranyl, carbonate, arsenite, phosphate, and others. The relatively low PZC of ferrihydrite can be rationalized based on the estimated proton affinity constant for singly-coordinated surface groups. Nanoparticles have an enhanced surface charge. The charging behavior of Fh nanoparticles can be described satisfactory using the capacitance of a spherical Stern layer condenser in combination with a diffuse double layer for flat plates.

Breast surface radiation dose during coronary CT angiography: reduction by breast displacement and lead shielding.

PubMed

Foley, Shane J; McEntee, Mark F; Achenbach, Stephan; Brennan, Patrick C; Rainford, Louise S; Dodd, Jonathan D

2011-08-01

The purpose of this study was to prospectively evaluate the effect of cranial breast displacement and lead shielding on in vivo breast surface radiation dose in women undergoing coronary CT angiography. Fifty-four women (mean age, 59.2 ± 9.8 years) prospectively underwent coronary 64-MDCT angiography for evaluation of chest pain. The patients were randomly assigned to a control group (n = 16), breast displacement group (n = 22), or breast displacement plus lead shielding group (n = 16). Thermoluminescent dosimeters (TLDs) were placed superficially on each breast quadrant and the areolar region of both breasts. Breast surface radiation doses, the degree of breast displacement, and coronary image quality were compared between groups. A phantom dose study was conducted to compare breast doses with z-axis positioning on the chest wall. A total of 1620 TLD dose measurements were recorded. Compared with control values, the mean breast surface dose was reduced 23% in the breast displacement group (24.3 vs 18.6 mGy, p = 0.015) and 36% in the displacement plus lead shielding group (24.3 vs 15.6 mGy, p = 0.0001). Surface dose reductions were greatest in the upper outer (displacement alone, 66%; displacement plus shielding, 63%), upper inner (65%, 58%), and areolar quadrants (44%, 53%). The smallest surface dose reductions were recorded for A-cup breasts: 7% for the displacement group and 3% for the displacement plus lead group (p = 0.741). Larger reductions in surface dose were recorded for B-cup (25% and 56%, p = 0.273), C-cup (38% and 60%, p = 0.001), and D-cup (31% and 25%, p = 0.095) sizes. Most of the patients (79%) had either good (< 50% of breast above scan range) or excellent (< 75% of breast above the scan range) breast displacement. No significant difference in coronary image quality was detected between groups. The phantom dose study showed that surface TLD measurements were underestimates of absorbed tissue dose by a mean of 9% and that a strong negative correlation exists between the amount of cranial displacement and breast dose. Use of breast displacement during coronary CTA substantially reduces the radiation dose to the breast surface.

Reactions of methyl groups on a non-reducible metal oxide: The reaction of iodomethane on stoichiometric α-Cr 2O 3(0001)

DOE PAGES

Dong, Yujung; Brooks, John D.; Chen, Tsung-Liang; ...

2015-06-10

The reaction of iodomethane on the nearly stoichiometric α-Cr 2O 3(0001) surface produces gas phase ethylene, methane, and surface iodine adatoms. The reaction is first initiated by the dissociation of iodomethane into surface methyl fragments, -CH 3, and iodine adatoms. Methyl fragments bound at surface Cr cation sites undergo a rate-limiting dehydrogenation reaction to methylene, =CH 2. The methylene intermediates formed from methyl dehydrogenation can then undergo coupling reactions to produce ethylene via two principle reaction pathways: (1) direct coupling of methylene and (2) methylene insertion into the methyl surface bond to form surface ethyl groups which undergo β-H eliminationmore » to produce ethylene. The liberated hydrogen also combines with methyl groups to form methane. Iodine adatoms from the dissociation of iodomethane deactivate the surface by simple site blocking of the surface Cr 3+ cations.« less

Modification of polycarbonate surface in oxidizing plasma

NASA Astrophysics Data System (ADS)

Ovtsyn, A. A.; Smirnov, S. A.; Shikova, T. G.; Kholodkov, I. V.

2017-11-01

The properties of the surface of the film polycarbonate Lexan 8010 were experimentally studied after treatment in a DC discharge plasma in oxygen and air at pressures of 50-300 Pa and a discharge current of 80 mA. The contact angles of wetting and surface energies are measured. The topography of the surface was investigated by atomic force microscopy. The chemical composition of the surface was determined from the FT-IR spectroscopy data in the variant of total internal reflection, as well as X-ray photoelectron spectroscopy. Treatment in the oxidizing plasma leads to a change in morphology (average roughness increases), an increase in the surface energy, and the concentration of oxygen-containing groups (hydroxyl groups, carbonyl groups in ketones or aldehydes and in oxyketones) on the surface of the polymer. Possible reasons for the difference in surface properties of polymer under the action of oxygen and air plasma on it are discussed.

Multifaceted adsorption of α-cyano-4-hydroxycinnamic acid on silver colloidal and island surfaces

NASA Astrophysics Data System (ADS)

Jung, Dawoon; Jeon, Kooknam; Yeo, Juhyun; Hussain, Shafqat; Pang, Yoonsoo

2017-12-01

The surface adsorption of organic nitrile compounds on the silver colloidal and island surfaces has been studied using surface-enhanced Raman scattering (SERS). α-Cyano-4-hydroxycinnamic acid (CHCA) with nitrile and carboxyl groups shows various surface adsorption on the silver surfaces. In acidic conditions, the surface adsorption of CHCA via the nitrile group with a more or less tilted geometry to the surface was found. When the solution pH increases, the carboxylate and nitrile groups of deprotonated CHCA participate in the surface adsorption, whereas the molecular plane of CHCA becomes more parallel to the surface. The ν(Ctbnd N) band in SERS of CHCA is the indicator of the surface adsorption geometry. The strongly red-shifted and broadened ν(Ctbnd N) band in SERS represents the surface adsorption via π-electrons of the Ctbnd N bond (side-on geometry; π-coordination). Nitriles adsorbed on the surface via the nonbonding electron pair of the nitrogen atom (end-on geometry; σ-coordination) often cause the blue-shifts and small band broadening in ν(Ctbnd N) in SERS. The surface adsorption geometry of organic nitriles based on many previous experimental results was further confirmed by the surface adsorption of CHCA on the silver island surfaces and dinitrile compounds on the silver colloidal surfaces.

[Effect of resin infiltration on microhardness of artificial caries lesions].

PubMed

Liu, Yonghong; Deng, Hui; Tang, Longmei; Zhang, Zhiyong

2015-12-01

To compare the changes of enamel surface and cross-sectional microhardness of artificial caries immediately and after the twice demineralization through coating resin infiltration, fluoride varnish and fissure sealant. A total of forty bovine lower incisors enamel samples with artificial caries lesions by the demineralization liquid were used in the experiment. The specimens were then randomly divided into four groups as group A(resin infiltration), B(fluoride varnish), C (fissure sealant), D(control), 10 specimens in each group. The samples were sectioned vertically into two halves through the centre. One half of each sample the surface and cross-sectional microhardness was measured. The other half was put into demineralization liquid for 14 days, then the surface and cross-sectional microhardness was measured again. The cross section morphology of the samples was observed by scanning electron microscope. The surface of enamel had the highest microhardness value, and with the increase of cross- sectional depth, the microhardness value declined gradually. Variance analysis showed that the difference was statistically significant in the cross-section of different depth among the four groups(P<0.05). The microhardness values of the surface and the cross- section at 40 µm of each group in immediate measure showed the values were significantly higher in group A, B and C than in group D. There was no significant difference in the microhardness value of cross-section at 80 µm between group A[(324 ± 17) kg/mm(2)] and group C[(316 ± 20) kg/mm(2)], but they were significantly higher than group D. There was no significant difference between group B[(303 ± 13) kg/mm(2)] and group D[(294 ± 23) kg/mm(2)]. At 120 µm level, the microhardness value of group A was significantly higher than those of the other three groups. After the twice demineralization, the enamel surface microhardness value of the specimens was the same as the first measurement. In the cross-section at 40 µm level, the microhardness value was equal to the value of cross-section at 80 µm level of the first measurement. In the cross- section at 80 µm and 120 µm level, the microhardness value of group A was significantly higher than those of the other three groups. Resin infiltration can effectively strengthen microhardness of enamel surface and cross-section of different depth of artificial caries.

Effect of a multi-layer infection control barrier on the micro-hardness of a composite resin

PubMed Central

HWANG, In-Nam; HONG, Sung-Ok; LEE, Bin-Na; HWANG, Yun-Chan; OH, Won-Mann; CHANG, Hoon-Sang

2012-01-01

Objective The aim of this study was to evaluate the effect of multiple layers of an infection control barrier on the micro-hardness of a composite resin. Material and Methods One, two, four, and eight layers of an infection control barrier were used to cover the light guides of a high-power light emitting diode (LED) light curing unit (LCU) and a low-power halogen LCU. The composite specimens were photopolymerized with the LCUs and the barriers, and the micro-hardness of the upper and lower surfaces was measured (n=10). The hardness ratio was calculated by dividing the bottom surface hardness of the experimental groups by the irradiated surface hardness of the control groups. The data was analyzed by two-way ANOVA and Tukey's HSD test. Results The micro-hardness of the composite specimens photopolymerized with the LED LCU decreased significantly in the four- and eight-layer groups of the upper surface and in the two-, four-, and eight-layer groups of the lower surface. The hardness ratio of the composite specimens was <80% in the eight-layer group. The micro-hardness of the composite specimens photopolymerized with the halogen LCU decreased significantly in the eight-layer group of the upper surface and in the two-, four-, and eight-layer groups of the lower surface. However, the hardness ratios of all the composite specimens photopolymerized with barriers were <80%. Conclusions The two-layer infection control barrier could be used on high-power LCUs without decreasing the surface hardness of the composite resin. However, when using an infection control barrier on the low-power LCUs, attention should be paid so as not to sacrifice the polymerization efficiency. PMID:23138746

Effect of Er:YAG laser irradiation on bonding property of zirconia ceramics to resin cement.

PubMed

Lin, Yihua; Song, Xiaomeng; Chen, Yaming; Zhu, Qingping; Zhang, Wei

2013-12-01

This study aimed to investigate whether or not an erbium: yttrium-aluminum-garnet (Er:YAG) laser could improve the bonding property of zirconia ceramics to resin cement. Surface treatments can improve the bonding properties of dental ceramics. However, little is known about the effect of Er:YAG laser irradiated on zirconia ceramics. Specimens of zirconia ceramic pieces were made, and randomly divided into 11 groups according to surface treatments, including one control group (no treatment), one air abrasion group, and nine Er:YAG laser groups. The laser groups were subdivided by applying different energy intensities (100, 200, or 300 mJ) and irradiation times (5, 10, or 15 sec). After surface treatments, ceramic pieces had their surface morphology observed, and their surface roughness was measured. All specimens were bonded to resin cement. Shear bond strength was measured after the bonded specimens were stored in water for 24 h, and additionally aged by thermocycling. Statistical analyses were performed using one way analysis of variance (ANOVA) and Tukey's test for shear bond strength, and Dunnett's t test for surface roughness, with α=0.05. Er:YAG laser irradiation changed the morphological characteristics of zirconia ceramics. Higher energy intensities (200, 300 mJ) could roughen the ceramics, but also caused surface cracks. There were no significant differences in the bond strength between the control group and the laser groups treated with different energy intensities or irradiation times. Air abrasion with alumina particles induced highest surface roughness and shear bond strength. Er:YAG laser irradiation cannot improve the bonding property of zirconia ceramics to resin cement. Enhancing irradiation intensities and extending irradiation time have no benefit on the bond of the ceramics, and might cause material defect.

Effect of the association between citric acid and EDTA on root surface etching.

PubMed

Manzolli Leite, Fabio Renato; Nascimento, Gustavo Giacomelli; Manzolli Leite, Elza Regina; Leite, Amauri Antiquera; Cezar Sampaio, Josá Eduardo

2013-09-01

This study aims to compare the clot stabilization on root surfaces conditioned with citric acid and ethylenediamine-tetraacetic acid (EDTA). Scaled root samples (n = 100) were set in fve groups: group I-control group (saline solution); group II (24% EDTA); group III (25% citric acid); group IV (EDTA + citric acid); group V (citric acid + EDTA). Fifty samples were assessed using the root surface modifcation index (RSMI). The other 50 received a blood drop after conditioning. Clot formation was assessed using blood elements adhesion index (BEAI). A blind examiner evaluated photomicrographs. Statistical analysis considered p < 0.05. Groups-III and G-V attained the best results for RSMI and BEAI in comparison to control. The worst results for clot stabilization were seen in group-II. EDTA employment before citric acid (group-IV) reduced clot formation in comparison to citric acid use alone (group-III). Root conditioning with citric acid alone and before EDTA had the best results for smear layer removal and clot stabilization. EDTA inhibited clot stabilization on root surface and must have a residual activity once it has diminished clot adhesion to root even after citric acid conditioning. Thus, EDTA can be used to neutralize citric acid effects on periodontal cells without affecting clot stabilization. Clinical signifcance: To demonstrate that citric acid use on root surfaces previously affected by periodontal disease may favor clot stabilization and may have a benefcial effect on surgical outcomes. Also, EDTA can be used to neutralize citric acid effects on periodontal cells.

The multilevel analysis of surface acting and mental health: A moderation of positive group affective tone

NASA Astrophysics Data System (ADS)

Lee, Meng-Shiu; Huang, Jui-Chan; Wu, Tzu-Jung

2017-06-01

The purpose of this study is to investigate the relationship among surface acting, mental health, and positive group affective tone. According to the prior theory, this study attempts to establish a comprehensive research framework among these variables, and furthermore tests the moderating effect of positive group affective tone. Data were collected from 435 employees in 52 service industrial companies by questionnaire, and this study conducted multilevel analysis. The results showed that surface acting will negatively affect the mental health. In addition, the positive group affective tone have significant moderating effect on the relationship among surface acting and mental health. Finally, this study discusses managerial implications and highlights future research suggestions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, Daniel P.; Tymińska, Nina; Zurek, Eva, E-mail: ezurek@buffalo.edu

Dispersion corrected Density Functional Theory calculations were employed to study the adsorption of benzenes derivatized with functional groups encompassing a large region of the activated/deactivated spectrum to the Ag(111) surface. Benzenes substituted with weak activating or deactivating groups, such as methyl and fluoro, do not have a strong preference for adsorbing to a particular site on the substrate, with the corrugations in the potential energy surface being similar to those of benzene. Strong activating (N(CH{sub 3}){sub 2}) and deactivating (NO{sub 2}) groups, on the other hand, possess a distinct site preference. The nitrogen in the former prefers to lie abovemore » a silver atom (top site), but in the latter a hollow hexagonal-closed-packed (H{sub hcp}) site of the Ag(111) surface is favored instead. Benzenes derivatized with classic activating groups donate electron density from their highest occupied molecular orbital to the surface, and those functionalized with deactivating groups withdraw electron density from the surface into orbitals that are unoccupied in the gas phase. For benzenes functionalized with two substituents, the groups that are strongly activating or deactivating control the site preference and the other groups assume sites that are, to a large degree, dictated by their positions on the benzene ring. The relative stabilities of the ortho, meta, and para positional isomers of disubstituted benzenes can, in some cases, be modified by adsorption to the surface.« less

[Effects of different surface conditioning agents on the bond strength of resin-opaque porcelain composite].

PubMed

Liu, Wenjia; Fu, Jing; Liao, Shuang; Su, Naichuan; Wang, Hang; Liao, Yunmao

2014-04-01

The objective of this research is to evaluate the effects of different silane coupling agents on the bond strength between Ceramco3 opaque porcelain and indirect composite resin. Five groups of Co-Cr metal alloy substrates were fabricated according to manufacturer's instruction. The surface of metal alloy with a layer of dental opaque porcelain was heated by fire. After the surface of opaque porcelain was etched, five different surface treatments, i.e. RelyX Ceramic Primer (RCP), Porcelain Bond Activator and SE Bond Primer (mixed with a proportion of 1:1) (PBA), Shofu Porcelain Primer (SPP), SE bond primer (SEP), and no primer treatment (as a control group), were used to combine P60 and opaque porcelain along with resin cement. Shear bond strength of specimens was tested in a universal testing machine. The failure modes of specimens in all groups were observed and classified into four types. Selected specimens were subjected to scanning electron microscope and energy disperse spectroscopy to reveal the relief of the fracture surface and to confirm the failure mode of different types. The experimental results showed that the values of the tested items in all the tested groups were higher than that in the control group. Group PBA exhibited the highest value [(37.52 +/- 2.14) MPa] and this suggested a fact that all of the specimens in group PBA revealed combined failures (failure occurred in metal-porcelain combined surface and within opaque porcelain). Group SPP and RCP showed higher values than SEP (P < 0.05) and most specimens of SPP and RCP performed combined failures (failure occurred in bond surface and within opaque porcelain or composite resin) while all the specimens in group SEP and control group revealed adhesive failures. Conclusions could be drawn that silane coupling agents could reinforce the bond strength of dental composite resin to metal-opaque porcelain substrate. The bond strength between dental composite resin and dental opaque porcelain could meet the clinical requirements.

Tensile bond strength between auto-polymerized acrylic resin and acrylic denture teeth treated with MF-MA solution.

PubMed

Thongrakard, Ticha; Wiwatwarrapan, Chairat

2016-08-01

This study evaluated the effect of chemical surface treatment using methyl formate-methyl acetate (MF-MA) solution on the tensile bond strength between acrylic denture teeth and auto-polymerized acrylic resin. Seventy maxillary central incisor acrylic denture teeth for each of three different brands (Yamahachi New Ace; Major Dent; Cosmo HXL) were embedded with incisal edge downwards in auto-polymerized resin in polyethylene pipes and ground with silicone carbide paper on their ridge lap surfaces. The teeth of each brand were divided into seven groups (n=10): no surface treatment (control group), MF-MA solution at a ratio of 25:75 (v/v) for 15 seconds, 30 seconds, 60 seconds, 120 seconds, 180 seconds, and MMA for 180 seconds. Auto-polymerized acrylic resin (Unifast Trad) was applied to the ground surface and polymerized in a pressure cooker. A tensile strength test was performed with a universal testing machine. Statistical analysis of the results was performed using two-way analysis of variance (ANOVA) and post-hoc Dunnett T3 test (α=.05). The surface treatment groups had significantly higher mean tensile bond strengths compared with the control group (P<.05) when compared within the same brand. Among the surface treatment groups of each brand, there were no significantly different tensile bond strengths between the MF-MA groups and the MMA 180 second group (P>.05), except for the Yamahachi New Ace MF-MA 180-second group (P<.05). 15-second MF-MA solution can be an alternative chemical surface treatment for repairing a denture base and rebonding acrylic denture teeth with auto-polymerized acrylic resin, for both conventional and cross-linked teeth.

Effect of immersion time of restorative glass ionomer cements and immersion duration in calcium chloride solution on surface hardness.

PubMed

Shiozawa, Maho; Takahashi, Hidekazu; Iwasaki, Naohiko; Wada, Takahiro; Uo, Motohiro

2014-12-01

The objective of this study was to evaluate the effect of immersion time of restorative glass ionomer cements (GICs) and immersion duration in calcium chloride (CaCl2) solution on the surface hardness. Two high-viscosity GICs, Fuji IX GP and GlasIonomer FX-II, were selected. Forty-eight specimens were randomly divided into two groups. Sixty minutes after being mixed, half of them were immersed in a 42.7wt% CaCl2 solution for 10, 30, or 60min (Group 1); the remaining specimens were immersed after an additional 1-week of storage (Group 2). The surface hardness of the specimens was measured and analyzed with two-way ANOVA and the Tukey HSD test (α=0.05). The surface compositions were examined using energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The surface hardness of Group 1 significantly increased as the immersion duration in CaCl2 increased; that of Group 2 significantly increased only after 60-minute CaCl2 immersion. After CaCl2 immersion, the amounts of Ca increased as the immersion duration increased. The surface hardness after CaCl2 immersion significantly correlated with the amount of Ca in Group 1, but not in Group 2. The binding energy of the Ca2p peak was similar to that of calcium polyalkenoate. These findings indicated that the Ca ions from the CaCl2 solution created chemical bonds with the carboxylic acid groups in the cement matrix. Immersion of GICs in CaCl2 solution at the early stage of setting was considered to enhance the formation of the polyacid salt matrix; as a result, the surface hardness increased. Copyright © 2014. Published by Elsevier Ltd.

Effects of pH values of hydrogen peroxide bleaching agents on enamel surface properties.

PubMed

Xu, B; Li, Q; Wang, Y

2011-01-01

This study investigated the influence of pH values of bleaching agents on the properties of the enamel surface. Sixty freshly extracted premolars were embedded in epoxy resin and mesiodistally sectioned through the buccal aspect into two parts. The sectioned slabs were distributed among six groups (n=10) and treated using different solutions. Group HCl was treated with HCl solution (pH=3.0) and served as a positive control. Group DW, stored in distilled water (pH=7.0), served as a negative control. Four treatment groups were treated using 30% hydrogen peroxide solutions with different pH values: group HP3 (pH=3.0), group HP5 (pH=5.0), group HP7 (pH=7.0), and group HP8 (pH=8.0). The buccal slabs were subjected to spectrophotometric evaluations. Scanning electron microscopy investigation and Micro-Raman spectroscopy were used to evaluate enamel surface morphological and chemical composition alterations. pH value has a significant influence on the color changes after bleaching (p<0.001). Tukey's multiple comparisons revealed that the order of color changes was HP8, HP7>HP5, HP3>HCl>DW. No obvious morphological alterations were detected on the enamel surface in groups DW, HP7, and HP8. The enamel surface of groups HCl and HP3 showed significant alterations with an erosion appearance. No obvious chemical composition changes were detected with respect to Micro-Raman analysis. Within the limitations of this study, it was concluded that no obvious morphological or chemical composition alterations of enamel surface were detected in the neutral or alkaline bleaching solutions. Bleaching solutions with lower pH values could result in more significant erosion of enamel, which represented a slight whitening effect.

Influence of tooth brushing on adhesion strength of orthodontic brackets bonded to porcelain.

PubMed

Durgesh, Bangalore H; Alhijji, Saleh; Hashem, Mohamed I; Al Kheraif, AbdulAziz A; Durgesh, Pavithra; Elsharawy, Mohamed; Vallittu, Pekka K

2016-09-28

Adhesive resin composite, which is used to bond orthodontic bracket to tooth surface is exposed to the influence of wear by tooth brushing and wear may influence loosening of the bracket. The aim of this study was to evaluate in vitro the effect of tooth brushing on the adhesion strength of orthodontic brackets bonded to surface treated porcelain. A total of 90 glazed porcelain fused to metal facets (PFM) were randomly assigned into 3 groups according to the surface treatment to be received. Group 1 was conditioned with hydrofluoric acid (HF), group 2 conditioned with grit-blasting (GB) and group 3 conditioned with tribochemical silica coating (RC). The groups were evaluated for surface roughness (Ra) before and after surface treatment. Next, 15 samples from each group were subjected to brushing and remaining 15 samples served as the baseline (n=15). Adhesion strength (shear bond strength)was recorded using a universal testing machine. Data collected were analyzed by ANOVA and Tukey's multiple comparison post hoc analysis. Tooth brushing decreased the bond strength in all groups. The highest adhesion strength (baseline and after brushing) was observed in group 3 (26.8 ± 1.77 MPa and 23.57 ± 1.02 MPa) and the lowest was found in group 1 (9.6 ± 1.5 MPa and 5.87 ± 0.77 MPa). Group 3 specimens exhibited the highest Ra (1.24 ± 0.08). It was found that tooth brushing of the exposed adhesive resin composite at the bracket-bonding substrate interface lowers the bonding strength regardless of the surface treatment of the substrate.

Effects of sol-gel processed silica coating on bond strength of resin cements to glass-infiltrated alumina ceramic.

PubMed

Xie, Haifeng; Wang, Xiaozu; Wang, Yu; Zhang, Feimin; Chen, Chen; Xia, Yang

2009-02-01

The aim of this study was to verify the effects of sol-gel processed silica coating on the bond strength between resin cement and glass-infiltrated aluminum oxide ceramic. Silica coatings were prepared on glass-infiltrated aluminum oxide ceramic surface via the sol-gel process. Atomic Force Microscope (AFM), Fourier Transmission Infrared spectrum (FTIR), and Energy Dispersive X-ray Spectroscopy (EDS) were used for coating characterization. Forty-eight blocks of glass-infiltrated aluminum oxide ceramic were fabricated. The ceramic surfaces were polished following sandblasting. Three groups of specimens (16 for each group) with different surface treatment were prepared. Group P: no treatment; group PO: treated with silane solution; group PTO: silica coating via sol-gel process, followed by silane application. Composite cylinders were luted with resin cement to the test specimens. Half of the specimens in each group were stored in distilled water for 24 h and the other half were stored in distilled water for 30 days before shear loading in a universal testing machine until failure. Selected ceramic surfaces were analyzed to identify the failure mode using a scanning electron microscopy (SEM). Nanostructured silica coatings were prepared on glass-infiltrated aluminum oxide ceramic surfaces by the sol-gel process. The silicon element on the ceramic surface increased significantly after the coating process. The mean shear bond strength values (standard deviation) before artificial aging were: group P: 1.882 +/- 0.156 MPa; group PO: 2.177 +/- 0.226 MPa; group PTO: 3.574 +/- 0.671 MPa. Statistically significant differences existed between group PTO and group P, and group PTO and groups PO. The failure mode for group P and group PO was adhesive, while group PTO was mixed. The mean shear bond strength values (standard deviation) after artificial aging were: group P: 1.594 +/- 0.111 MPa; group PO: 2.120 +/- 0.339 MPa; group PTO: 2.955 +/- 0.113 MPa. Statistically significant differences existed between each two groups after artificial aging, group P had the lowest bond durability, and group PTO had the highest bond durability. The sol-gel process is an effective way to prepare silica coating on dental glass-infiltrated alumina ceramic. Sol-gel processed silica coating can improve the resin bond strength of glass-infiltrated alumina ceramic.

Effects of polishing on surface roughness, gloss and color of surface reaction type pre-reacted glass-ionomer filled resin composite.

PubMed

Hosoya, Yumiko; Shiraishi, Takanobu; Odatsu, Tetsuro; Miyazaki, Masashi; García-Godoy, Franklin

2011-06-01

To evaluate the effects of polishing on surface roughness, gloss and color of different shades of surface reaction type pre-reacted glass-ionomer (S-PRG) filled nano-hybrid resin composite. Resin disks of 15 mm diameter and 2 mm thickness and final polish with 1000-grit SiC paper, super fine cut diamond (FG) point, silicon (MFR) point and Super-Snap mini-disk red (SNAP) were made with Beautifil II shades: A2, A20, Inc). One week after curing, the surface roughness, gloss and color were measured. Data was analyzed with ANOVA and Fisher's PLSD with alpha= 0.05 For all shades, the order of roughness (Ra) ranked according to groups of 1000-grit SiC > FG > MFR > SNAP with significant differences among all groups. For all shades, the order of gloss ranked according to groups of SNAP > MFR > FG > 1000-grit SiC with significant differences among the groups except for between MFR and FG without significant difference. The influence of the surface roughness on color differed among the polishing groups and shades. However, the values of the color differences (deltaE*ab) between the polishing groups of all shades were imperceptible to the naked eye.

Contact lens-related dry eye and ocular surface changes with mapping technique in long-term soft silicone hydrogel contact lens wearers.

PubMed

Sengor, Tomris; Aydin Kurna, Sevda; Ozbay, Nurver; Ertek, Semahat; Aki, Suat; Altun, Ahmet

2012-01-01

To evaluate ocular surface changes in long-term silicone hydrogel contact lens wearers. Thirty patients were included in this study. Twenty patients (40 eyes) using contact lenses constituted group 1 and 10 (20 eyes) volunteers constituted group 2. The duration of average contact lens usage was 7.74 ± 3.3 years. Ocular surface was evaluated by surface staining, tear film break-up time (TBUT), Schirmer I test, and conjunctival impression cytology with color-coded mapping technique and by the Ocular Surface Disease Index (OSDI). The mean break-up time was lower and staining scores were higher in group 1 (p<0.001) but Schirmer values were not significantly different from group 2 (p>0.05). The mean OSDI score was 34.59 ± 11.93 to 19.28 ± 6.7 in group 1 and 2. Increased metaplastic predominant changes of grade II and III were observed in the interpalpebral and perilimbal areas in group 1. Significant correlations were observed in TBUT, cornea staining, and grade II to grade III metaplasia ratios between duration of the lens usage and contact lens wear time in a day. Silicone hydrogel lenses produce significant changes on tear film and impression cytology of the ocular surface in long-term use.

Ionization state of L-phenylalanine at the air-water interface.

PubMed

Griffith, Elizabeth C; Vaida, Veronica

2013-01-16

The ionization state of organic molecules at the air-water interface and the related problem of the surface pH of water have significant consequences on the catalytic role of the surface in chemical reactions and are currently areas of intense research and controversy. In this work, infrared reflection-absorption spectroscopy (IRRAS) is used to identify changes in the ionization state of L-phenylalanine in the surface region versus the bulk aqueous solution. L-phenylalanine has the unique advantage of possessing two different hydrophilic groups, a carboxylic acid and an amine base, which can deprotonate and protonate respectively depending on the ionic environment they experience at the water surface. In this work, the polar group vibrations in the surface region are identified spectroscopically in varying bulk pH solutions, and are subsequently compared with the ionization state of the polar groups of molecules residing in the bulk environment. The polar groups of L-phenylalanine at the surface transition to their deprotonated state at bulk pH values lower than the molecules residing in the bulk, indicating a decrease in their pK(a) at the surface, and implying an enhanced hydroxide ion concentration in the surface region relative to the bulk.

Subjective Visual Performance and Objective Optical Quality With Intraocular Lens Glistening and Surface Light Scattering.

PubMed

Luo, Furong; Bao, Xuan; Qin, Yingyan; Hou, Min; Wu, Mingxing

2018-06-01

To evaluate the long-term effect of glistenings and surface light scattering of intraocular lenses (IOLs) on visual and optical performance after cataract surgery. Pseudophakic eyes that underwent standard phacoemulsification and two types of hydrophobic acrylic spherical IOL implantation without complications for at least 5 years were included in this retrospective study. Participants were divided into the glistenings, surface light scattering, and control groups according to the current condition of the IOLs. Then participants received a follow-up examination including uncorrected and corrected distance visual acuity (UDVA and CDVA), contrast sensitivity, straylight, and intraocular higher order aberrations, as well as point spread function (PSF) and modulation transfer function (MTF). A total of 140 eyes were included in the study. UDVA, CDVA, and glare sensitivity were not significantly different among the three groups (P > .05). However, compared with the control group, the IOLs of the glistenings and surface light scattering groups were associated with significantly lower contrast sensitivity under no glare conditions. Furthermore, eye with glistenings exhibited the highest straylight value (P < .05), whereas no difference was found between the surface light scattering and control groups. In contrast to the control group, the spherical aberration increased and the mean values of PSF and MTF decreased in the glistenings and surface light scattering groups. Both glistenings and surface light scattering tend to impair subjective visual performance, such as contrast sensitivity, and potentially affect objective optical quality, including straylight, spherical aberration, PSF, and MTF. [J Refract Surg. 2018;34(6):372-378.]. Copyright 2018, SLACK Incorporated.

[Ocular Surface Evaluation in Patients Treated with Prostaglandin Analogues Considering Preservative Agent].

PubMed

Mlčáková, E; Mlčák, P; Karhanová, M; Langová, K; Marešová, K

The aim of this study was to evaluate the ocular surface in patients treated with prostaglandin analogues considering contained preservative agent. 60 patients with glaucoma or ocular hypertension treated with prostaglandin analogue monotherapy were enrolled in this observational study. 20 patients with glaucoma suspect or ocular hypertension without local or systemic glaucoma medication formed the control group. Demographic data and medical history were recorded for each participant. Patients filled in the Ocular surface disease index© (OSDI) questionnaire and underwent an ophthalmological examination including assessment of conjunctival hyperaemia according to Efron, tear film break up time (BUT) and fluorescein staining according to the Oxford grading scheme. Treated participants were divided into 3 groups according to the preservative contained in the currently used prostaglandin analogue: the preservative-free group (18 patients), the polyquaternium group (17 patients) and the benzalkonium chloride (BAK) group (25 patients). The control group had significantly lower fluorescein staining than the preservative-free group (p=0.001), the polyquaternium group (p=0.007) and the BAK group (p=0.002). The conjunctival hyperaemia was significantly lower in the preservative-free group compared to the polyquaternium group (p=0.011). There was no significant difference among the other groups. The difference neither in the OSDI score nor in the BUT was statistically important. This study confirmed that the ocular surface is worse in patients treated with prostaglandin analogue monotherapy than in people without glaucoma medication. A significant difference among treated patients depending on a preservative agent was not proved.Key words: benzalkonium chloride, glaucoma, ocular surface disease, preservatives, prostaglandin analogues.

Overview on the Surface Functionalization Mechanism and Determination of Surface Functional Groups of Plasma Treated Carbon Nanotubes.

PubMed

Saka, Cafer

2018-01-02

The use of carbon materials for many applications is due to the unique diversity of structures and properties ranging from chemical bonds between the carbon atoms of the materials to nanostructures, crystallite alignment, and microstructures. Carbon nanotubes and other nanoscale carbonaceous materials draw much attention due to their physical and chemical properties, such as high strength, high resistance to corrosion, electrical and thermal conductivity, stability and a qualified adsorbent. Carbon-based nanomaterials, which have a relatively large specific area and layered structure, can be used as an adsorbent for efficient removal of organic and inorganic contaminants. However, one of the biggest obstacles to the development of carbon-based nanomaterials adsorbents is insolubility and the lack of functional groups on the surface. There are several approaches to introduce functional groups on carbon nanotubes. One of these approaches, plasma applications, now has an important place in the creation of surface functional groups as a flexible, fast, and environmentally friendly method. This review focuses on recent information concerning the surface functionalization and modification of plasma treated carbon nanotube. This review considers the surface properties, advantages, and disadvantages of plasma-applied carbon nanotubes. It also examines the reaction mechanisms involved in the functional groups on the surface.

Method of bonding functional surface materials to substrates and applications in microtechnology and anti-fouling

DOEpatents

Feng, Xiangdong; Liu, Jun; Liang, Liang

2001-01-01

A simple and effective method to bond a thin coating of poly(N-isopropylacylamide) (NIPAAm) on a glass surface by UV photopolymerization, and the use of such a coated surface in nano and micro technology applications. A silane coupling agent with a dithiocarbamate group is provided as a photosensitizer preferably, (N,N'-diethylamine) dithiocarbamoylpropyl-(trimethoxy) silane (DATMS). The thiocarbamate group of the sensitizer is then bonded to the glass surface by coupling the silane agent with the hydroxyl groups on the glass surface. The modified surface is then exposed to a solution of NIPAAm and a crosslinking agent which may be any organic molecule having an acrylamide group and at least two double bonds in its structure, such as N, N'-methylenebisacrylamide, and a polar solvent which may be any polar liquid which will dissolve the monomer and the crosslinking agent such as acetone, water, ethanol, or combinations thereof. By exposing the glass surface to a UV light, free radicals are generated in the thiocarbamate group which then bonds to the crosslinking agent and the NIPAAm. Upon bonding, the crosslinking agent and the NIPAAm polymerize to form a thin coating of PNIPAAm bonded to the glass. Depending upon the particular configuration of the glass, the properties of the PNIPAAm allow applications in micro and nano technology.

Method of bonding functional surface materials to substrates and applications in microtechnology and antifouling

DOEpatents

Feng, Xiangdong; Liu, Jun; Liang, Liang

1999-01-01

A simple and effective method to bond a thin coating of poly(N-isopropylacylamide) (NIPAAm) on a glass surface by UV photopolymerization, and the use of such a coated surface in nano and micro technology applications. A silane coupling agent with a dithiocarbamate group is provided as a photosensitizer, preferably, (N,N'-diethylamine)dithiocarbamoylpropyl-(trimethoxy)silane (DATMS). The thiocarbamate group of the sensitizer is then bonded to the glass surface by coupling the silane agent with the hydroxyl groups on the glass surface. The modified surface is then exposed to a solution of NIPAAm and a crosslinking agent which may be any organic molecule having an acrylamide group and at least two double bonds in its structure, such as N,N'-methylenebisacrylamide, and a polar solvent which may be any polar liquid which will dissolve the monomer and the crosslinking agent such as acetone, water, ethanol, or combinations thereof. By exposing the glass surface to a UV light, free radicals are generated in the thiocarbamate group which then bonds to the crosslinking agent and the NIPAAm. Upon bonding, the crosslinking agent and the NIPAAm polymerize to form a thin coating of PNIPAAm bonded to the glass. Depending upon the particular configuration of the glass, the properties of the PNIPAAm allow applications in micro and nano technology.

Influence of handpiece maintenance sprays on resin bonding to dentin.

PubMed

Sugawara, Toyotarou; Kameyama, Atsushi; Haruyama, Akiko; Oishi, Takumi; Kukidome, Nobuyuki; Takase, Yasuaki; Tsunoda, Masatake

2010-01-01

To investigate the influence of maintenance spray on resin bonding to dentin. The crown of extracted, caries-free human molars was transversally sectioned with a model trimmer to prepare the dentin surfaces from mid-coronal sound dentin, and then uniformly abraded with #600 silicon carbide paper. The dentin surfaces were randomly divided into three groups: oil-free spray group where maintenance cleaner for air bearing handpieces was sprayed onto the dentin surface for 1 s and rinsed with water spray for 30 s; oil-containing spray group where maintenance cleaner for micro motor handpieces was sprayed onto the dentin surface for 1 s and rinsed with water spray for 30 s; and control group where the surface was rinsed with water spray for 30 s and then air-dried. These surfaces were then bonded with Clearfil SE Bond (Kuraray Medical), and resin composite (Clearfil AP-X, Kuraray Medical) build-up crowns were incrementally constructed on the bonded surfaces. After storage for 24 h in 37°C water, the bonded teeth were sectioned into hour-glass shaped slices (0.7-mm thick) perpendicular to the bonded surfaces. The specimens were then subjected to microtensile bond strength (μTBS) testing at a crosshead speed of 1.0 mm/min. Data were analyzed with one-way ANOVA and the Tukey-Kramer test. Maintenance spray-contaminated specimens (oil-free and oil-containing spray groups) showed significantly lower μTBS than control specimens (P < 0.05). However, there was no significant difference between the spray-contaminated groups (P > 0.05). Maintenance spray significantly reduces the bond strength of Clearfil SE Bond to dentin.

Storage Medium Affects the Surface Porosity of Dental Cements

PubMed Central

Shabani, Asal; Asatourian, Armen; Sheibani, Nader

2017-01-01

Introduction Calcium silicate-based cements physical properties is influenced by environmental changes. Aim Here, we intended to evaluate the effect of storage medium on surface porosity of root Mineral Trioxide Aggregate (MTA) and Biodentine cement. Materials and Methods A total of 40 polyethylene tubes were selected and divided into two groups: Group A (MTA) and Group B (Biodentine). Each group was subdivided into two subgroups (n=10). In subgroups A1 and B1, tubes were transferred to Distilled Water (DW), while samples of subgroup A2 and B2 were transferred to Synthetic Tissue Fluid (STF) as storage medium and samples were stored for three days. All specimens were then placed in a desiccator for 24 hours and then subject to surface porosity evaluation by Scanning Electron Microscopy (SEM) at ×500, ×1000, ×2000 and ×5000 magnifications. The number and the surface porosities were determined by Image J analysis. Data were analyzed by ANOVA at level of significance of p<0.05. Results The lowest surface porosity was observed in MTA samples stored in STF and the highest was in Biodentine samples stored in DW. Significant differences were noted between groups and subgroups of each group (p< 0.05). MTA samples stored in DW and STF showed significantly lower surface porosities compared to Biodentine samples (p < 0.05). Conclusion Storage medium can drastically affect the surface porosity of tested calcium silicate-based cements. However, MTA showed lower surface porosity compared to Biodentine cement, which can result in lower microleakage in applied area. PMID:28969288

Effect of different surface treatments on adhesion of In-Ceram Zirconia to enamel and dentin substrates.

PubMed

Saker, Samah; Ibrahim, Fatma; Ozcan, Mutlu

2013-08-01

Resin bonding of In-Ceram Zirconia (ICZ) ceramics is still a challenge, especially for minimally invasive applications. This study evaluated the adhesion of ICZ to enamel and dentin after different surface treatments of the ceramic. ICZ ceramic specimens (diameter: 6 mm; thickness: 2 mm) (N = 100) were fabricated following the manufacturer's instructions and randomly assigned to 5 groups (n = 20), according to the surface treatment methods applied. The groups were as follows: group C: no treatment; group SB: sandblasting; group SCS-S: CoJet+silane; group SCS-P: CoJet+Alloy Primer; group GE-S: glaze+ hydrofluoric acid etching (9.6%) for 60 s+silane. Each group was randomly divided into two subgroups to be bonded to either enamel or dentin (n = 10 per group) using MDP-based resin cement (Panavia F2.0). All the specimens were subjected to thermocycling (5000x, 5°C-55°C). The specimens were mounted in a universal testing machine and tensile force was applied to the ceramic/cement interface until failure occurred (1 mm/min). After evaluating all the debonded specimens under SEM, the failure types were defined as either "adhesive" with no cement left on the ceramic surface (score 0) or "mixed" with less than 1/2 of the cement left adhered to the surface with no cohesive failure of the substrate (score 1). The data were statistically evaluated using 2-way ANOVA and Tukey's tests (α = 0.05). The highest tensile bond strength for the enamel surfaces was obtained in group GE-S (18.1 ± 2 MPa) and the lowest in group SB (7.1 ± 1.4 MPa). Regarding dentin, group CSC-P showed the highest (12 ± 1.3 MPa) and SB the lowest tensile bond strength (5.7 ± 0.4 MPa). Groups SB, CSC-S, CSC-P, and GE-S did not show significant differences between the different surface treatments on either enamel or dentin surfaces (p < 0.05, p < 0.001, respectively). Groups CSC-P and GE-S presented similar bond strength for both the enamel and dentin substrates (p < 0.8 and p < 0.9), respectively. While on enamel substrates, exclusively adhesive failures from ICZ (score 0) were found, on dentin exclusively mixed failures were observed (score 1). Adhesion of ICZ to both enamel and dentin can be improved when ceramics are glazed, etched, and silanized, or sandblasted, primed, and cemented with an MDP-based cement.

Evaluation of the Surface Treatment on Bone Healing in a Transmucosal 1-mm Area of Implant Abutment: An Experimental Study in the Rabbit Tibia.

PubMed

Gehrke, Sergio Alexandre; da Silva Neto, Ulisses Tavares

2016-06-01

The objective of the present study was to investigate the effect on bone tissue healing patterns in 1-mm area treated in the transmucosal surface of the abutment in the tibia of rabbits. Forty-six abutments were divided into two groups: control group (CG) with 14 abutments with smooth surface and experimental group (EG) with 32 abutments presenting a 1-mm area of the transmucosal surface treated through sandblasting with microparticles of titanium oxide followed by acid etching. Five samples of each group were analyzed using an optical laser profilometer for surface roughness characterization. Thirty-six Morse taper implants (3.5 mm in diameter and 7 mm in length) were inserted 1.5 mm subcrestal into the tibiae of nine rabbits. The implants were removed after 8, 10, and 12 weeks for histological analysis. The histological slides were prepared and analyzed qualitatively in relation to the new bone at the interface bone-abutment and quantitatively, in relation to bone height from the base of the implant. These data were computed and statistically compared inside the groups using analysis of variance and the U-test between groups for same time. Both groups exhibited bone growth in the direction and over the surface of the abutments, with good healing. However, the EG group showed an increased height of bone formation in the crestal direction, and highly significant differences were observed (p < .001) between these measured values. Under the limitations of the present study, histological follow-up at 8, 10, and 12 weeks showed that transmucosal 1-mm area of implant abutment with treatment of the surface facilitated the maintenance of bone height around the abutment compared with the same abutment with the totally smooth surface. © 2015 Wiley Periodicals, Inc.

Effect of surface hydroxyl groups on heat capacity of mesoporous silica

NASA Astrophysics Data System (ADS)

Marszewski, Michal; Butts, Danielle; Lan, Esther; Yan, Yan; King, Sophia C.; McNeil, Patricia E.; Galy, Tiphaine; Dunn, Bruce; Tolbert, Sarah H.; Hu, Yongjie; Pilon, Laurent

2018-05-01

This paper quantifies the effect of surface hydroxyl groups on the effective specific and volumetric heat capacities of mesoporous silica. To achieve a wide range of structural diversity, mesoporous silica samples were synthesized by various methods, including (i) polymer-templated nanoparticle-based powders, (ii) polymer-templated sol-gel powders, and (iii) ambigel silica samples dried by solvent exchange at room temperature. Their effective specific heat capacity, specific surface area, and porosity were measured using differential scanning calorimetry and low-temperature nitrogen adsorption-desorption measurements. The experimentally measured specific heat capacity was larger than the conventional weight-fraction-weighted specific heat capacity of the air and silica constituents. The difference was attributed to the presence of OH groups in the large internal surface area. A thermodynamic model was developed based on surface energy considerations to account for the effect of surface OH groups on the specific and volumetric heat capacity. The model predictions fell within the experimental uncertainty.

Highly porous and mechanically strong ceramic oxide aerogels

NASA Technical Reports Server (NTRS)

Johnston, James C. (Inventor); Leventis, Nicholas (Inventor); Ilhan, Ulvi F. (Inventor); Meador, Mary Ann B. (Inventor); Fabrizio, Eve F. (Inventor)

2012-01-01

Structurally stable and mechanically strong ceramic oxide aerogels are provided. The aerogels are cross-linked via organic polymer chains that are attached to and extend from surface-bound functional groups provided or present over the internal surfaces of a mesoporous ceramic oxide particle network via appropriate chemical reactions. The functional groups can be hydroxyl groups, which are native to ceramic oxides, or they can be non-hydroxyl functional groups that can be decorated over the internal surfaces of the ceramic oxide network. Methods of preparing such mechanically strong ceramic oxide aerogels also are provided.

Highly porous and mechanically strong ceramic oxide aerogels

NASA Technical Reports Server (NTRS)

Fabrizio, Eve F. (Inventor); Leventis, Nicholas (Inventor); Ilhan, Ulvi F. (Inventor); Meador, Mary Ann B. (Inventor); Johnston, James C. (Inventor)

2010-01-01

Structurally stable and mechanically strong ceramic oxide aerogels are provided. The aerogels are cross-linked via organic polymer chains that are attached to and extend from surface-bound functional groups provided or present over the internal surfaces of a mesoporous ceramic oxide particle network via appropriate chemical reactions. The functional groups can be hydroxyl groups, which are native to ceramic oxides, or they can be non-hydroxyl functional groups that can be decorated over the internal surfaces of the ceramic oxide network. Methods of preparing such mechanically strong ceramic oxide aerogels also are provided.

WISEP J004701.06+680352.1: An Intermediate Surface Gravity, Dusty Brown Dwarf in the AB Dor Moving Group

DTIC Science & Technology

2015-02-01

reserved. WISEP J004701.06+680352.1: AN INTERMEDIATE SURFACE GRAVITY, DUSTY BROWN DWARF IN THE AB DOR MOVING GROUP John E. Gizis1,9, Katelyn N...pc. The three-dimensional space mo- tion identifies it as a member of the AB Dor Moving Group, an identification supported by our classification of...SUBTITLE WISEP J004701+680352.1: An Intermediate Surface Gravity, Dusty Brown Dwarf In The AB Dor Moving Group 5a. CONTRACT NUMBER 5b. GRANT NUMBER

Plasma surface modification of polypropylene track-etched membrane to improve its performance properties

NASA Astrophysics Data System (ADS)

Kravets, L. I.; Elinson, V. M.; Ibragimov, R. G.; Mitu, B.; Dinescu, G.

2018-02-01

The surface and electrochemical properties of polypropylene track-etched membrane treated by plasma of nitrogen, air and oxygen are studied. The effect of the plasma-forming gas composition on the surface morphology is considered. It has been found that the micro-relief of the membrane surface formed under the gas-discharge etching, changes. Moreover, the effect of the non-polymerizing gas plasma leads to formation of oxygen-containing functional groups, mostly carbonyl and carboxyl. It is shown that due to the formation of polar groups on the surface and its higher roughness, the wettability of the plasma-modified membranes improves. In addition, the presence of polar groups on the membrane surface layer modifies its electrochemical properties so that conductivity of plasma-treated membranes increase.

DETA/NONOate, a nitric oxide donor, produces antidepressant effects by promoting hippocampal neurogenesis.

PubMed

Hua, Yao; Huang, Xin-Yan; Zhou, Li; Zhou, Qi-Gang; Hu, Yao; Luo, Chun-Xia; Li, Fei; Zhu, Dong-Ya

2008-10-01

Increasing evidence suggests that depression may be associated with a lack of hippocampal neurogenesis. Our recent study shows that endogenous nitric oxide (NO) contributes to chronic mild stress (CMS)-induced depression by suppressing hippocampal neurogenesis. The aim of this study was to investigate the effects of exogenous NO in CMS-induced depression in young adult mice. In normal mice, administration of a pure NO donor (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl) aminio] diazen-1-ium-1,2-diolate (DETA/NONOate; 0.4 mg/kg, i.p., for 7 days) produced an antidepressant-like effect and significantly increased hippocampal neurogenesis. The mice exposed to CMS exhibited behavioral changes typical of depression and impaired neurogenesis in the hippocampus. Treatment with DETA/NONOate (0.4 mg/kg, i.p., for 7 days) reversed CMS-induced behavioral despair and hippocampal neurogenesis impairment. We treated mice with a telomerase inhibitor 3'-azido-deoxythymidine (AZT; 100 mg/kg, i.p., for 14 days) to disrupt neurogenesis. From day 4 to day 11 of AZT treatment, mice were injected with DETA/NONOate (0.4 mg/kg, i.p., for 7 days). Disrupting hippocampal neurogenesis blocked the antidepressant effect of DETA/NONOate. Our findings suggest that exogenous NO benefits chronic stress-induced depression by stimulating hippocampal neurogenesis and may represent a novel approach for the treatment of depressive disorders.

Structural Characterization of the Molecular Events during a Slow Substrate-Product Transition in Orotidine 5'-Monophosphate Decarboxylase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fujihashi, Masahiro; Wei, Lianhu; Kotra, Lakshmi P

2009-04-06

Crystal structures of substrate-product complexes of Methanobacterium thermoautotrophicum orotidine 5'-monophosphate decarboxylase, obtained at various steps in its catalysis of the unusual transformation of 6-cyano-uridine 5'-monophosphate (UMP) into barbituric acid ribosyl monophosphate, show that the cyano substituent of the substrate, when bound to the active site, is first bent significantly from the plane of the pyrimidine ring and then replaced by an oxygen atom. Although the K72A and D70A/K72A mutants are either catalytically impaired or even completely inactive, they still display bending of the C6 substituent. Interestingly, high-resolution structures of the D70A and D75N mutants revealed a covalent bond between C6more » of UMP and the Lys72 side chain after the -CN moiety's release. The same covalent bond was observed when the native enzyme was incubated with 6-azido-UMP and 6-iodo-UMP; in contrast, the K72A mutant transformed 6-iodo-UMP to barbituric acid ribosyl 5'-monophosphate. These results demonstrate that, given a suitable environment, native orotidine 5'-monophosphate decarboxylase and several of its mutants are not restricted to the physiologically relevant decarboxylation; they are able to catalyze even nucleophilic substitution reactions but consistently maintain distortion on the C6 substituent as an important feature of catalysis.« less

Structural characterization of the molecular events during a slow substrate-product transition in orotidine 5'-monophosphate decarboxylase.

PubMed

Fujihashi, Masahiro; Wei, Lianhu; Kotra, Lakshmi P; Pai, Emil F

2009-04-17

Crystal structures of substrate-product complexes of Methanobacterium thermoautotrophicum orotidine 5'-monophosphate decarboxylase, obtained at various steps in its catalysis of the unusual transformation of 6-cyano-uridine 5'-monophosphate (UMP) into barbituric acid ribosyl monophosphate, show that the cyano substituent of the substrate, when bound to the active site, is first bent significantly from the plane of the pyrimidine ring and then replaced by an oxygen atom. Although the K72A and D70A/K72A mutants are either catalytically impaired or even completely inactive, they still display bending of the C6 substituent. Interestingly, high-resolution structures of the D70A and D75N mutants revealed a covalent bond between C6 of UMP and the Lys72 side chain after the -CN moiety's release. The same covalent bond was observed when the native enzyme was incubated with 6-azido-UMP and 6-iodo-UMP; in contrast, the K72A mutant transformed 6-iodo-UMP to barbituric acid ribosyl 5'-monophosphate. These results demonstrate that, given a suitable environment, native orotidine 5'-monophosphate decarboxylase and several of its mutants are not restricted to the physiologically relevant decarboxylation; they are able to catalyze even nucleophilic substitution reactions but consistently maintain distortion on the C6 substituent as an important feature of catalysis.

Human immunodeficiency virus type 1 pol gene mutations which cause decreased susceptibility to 2',3'-dideoxycytidine.

PubMed Central

Fitzgibbon, J E; Howell, R M; Haberzettl, C A; Sperber, S J; Gocke, D J; Dubin, D T

1992-01-01

To investigate whether human immunodeficiency virus type 1 pol gene mutations are selected during prolonged 2',3'-dideoxycytidine (ddC) therapy, we used the polymerase chain reaction to amplify a portion of the reverse transcriptase segment of the pol gene from the peripheral blood mononuclear cell DNA of a patient with AIDS before and after an 80-week course of ddC therapy. The consensus sequence from the second sample contained a unique double mutation (ACT to GAT) in the codon for reverse transcriptase amino acid 69, causing substitution of aspartic acid (Asp) for the wild-type threonine (Thr). A mutation (ACA to ATA) also occurred in the codon for position 165, causing substitution of isoleucine (Ile) for Thr. The GAT (Asp) codon was introduced into the pol gene of a molecular clone of human immunodeficiency virus via site-directed mutagenesis. Following transfection, mutant and wild-type viruses were tested for susceptibility to ddC by a plaque reduction assay. The mutant virus was fivefold less susceptible to ddC than the wild type; cross-resistance to 3'-azido-3'-deoxythymidine or 2'3'-dideoxyinosine was not found. The Ile-165 mutation did not confer additional ddC resistance. The Asp-69 substitution may have contributed to the generation of resistant virus in this patient. Images PMID:1317143

Characterization of Streptococcus pneumoniae thymidylate kinase: steady-state kinetics of the forward reaction and isothermal titration calorimetry.

PubMed Central

Petit, Chantal M; Koretke, Kristin K

2002-01-01

Thymidylate kinase (TMK) catalyses the phosphorylation of dTMP to form dTDP in both the de novo and salvage pathways of dTTP synthesis. The tmk gene from the bacterial pathogen Streptococcus pneumoniae was identified. The gene, encoding a 212-amino-acid polypeptide (23352 Da), was cloned and overexpressed in Escherichia coli with an N-terminal hexahistidine tag. The enzyme was purified to homogeneity, and characterized in the forward reaction. The pH profile of TMK indicates that its activity is optimal at pH 8.5. The substrate specificity of the enzyme was examined; it was found that not only ATP, but also dATP and to a lesser extent CTP, could act as phosphate donors, and dTMP and dUMP could serve as phosphate acceptors. Furthermore, AZT-MP (3'-azido-3'-deoxythymidine 5'-monophosphate) was shown not to be a substrate for S. pneumoniae TMK. Steady-state kinetics and inhibition studies with adenosine 5'-[beta-thio]diphosphate and dTDP in addition to isothermal titration calorimetry were performed. The data showed that binding follows an ordered pathway, in which ATP binds first with a K(m) of 235 +/- 46 microM and a K(d) of 116 +/- 3 microM, and dTMP binds secondly with a K(m) of 66 +/- 12 microM and a K(d) of 53 +/- 2 microM. PMID:11964185

Efficient enzymatic synthesis and dual-colour fluorescent labelling of DNA probes using long chain azido-dUTP and BCN dyes

PubMed Central

Ren, Xiaomei; El-Sagheer, Afaf H.; Brown, Tom

2016-01-01

A sterically undemanding azide analogue of dTTP (AHP dUTP) with an alkyl chain and ethynyl attachment to the nucleobase was designed and incorporated into DNA by primer extension, reverse transcription and polymerase chain reaction (PCR). An azide-modified 523 bp PCR amplicon with all 335 thymidines replaced by AHP dU was shown to be a perfect copy of the template from which it was amplified. Replacement of thymidine with AHP dU increases duplex stability, accounting in part for the high incorporation efficiency of the azide-modified triphosphate. Single-stranded azide-labelled DNA was conveniently prepared from PCR products by λ-exonuclease digestion and streptavidin magnetic bead isolation. Efficient fluorescent labelling of single and double-stranded DNA was carried out using dyes functionalized with bicyclo[6.1.0]non-4-yne (BCN) via the strain-promoted alkyne-azide cycloaddition (SPAAC) reaction. This revealed that the degree of labelling must be carefully controlled to achieve optimum fluorescence and avoid fluorescence quenching. Dual-coloured probes were obtained in a single tube fluorescent labelling reaction; and varying the ratios of the two dyes provides a simple method to prepare DNA probes with unique fluorescent signatures. AHP dUTP is a versatile clickable nucleotide with potentially wide applications in biology and nanotechnology including single molecule studies and synthesis of modified aptamer libraries via SELEX. PMID:26819406

Biotin-Containing Reduced Graphene Oxide-Based Nanosystem as a Multieffect Anticancer Agent: Combining Hyperthermia with Targeted Chemotherapy.

PubMed

Mauro, Nicolò; Scialabba, Cinzia; Cavallaro, Gennara; Licciardi, Mariano; Giammona, Gaetano

2015-09-14

Among the relevant properties of graphene derivatives, their ability of acting as an energy-converting device so as to produce heat (i.e., thermoablation and hyperthermia) was more recently taken into account for the treatment of solid tumors. In this pioneering study, for the first time, the in vitro RGO-induced hyperthermia was assessed and combined with the stimuli-sensitive anticancer effect of a biotinylated inulin-doxorubicin conjugate (CJ-PEGBT), hence, getting to a nanosystem endowed with synergic anticancer effects and high specificity. CJ-PEGBT was synthesized by linking pentynoic acid and citraconic acid to inulin. The citraconylamide pendants, used as pH reversible spacer, were exploited to further conjugate doxorubicin, whereas the alkyne moiety was orthogonally functionalized with an azido PEG-biotin derivative by copper(II) catalyzed 1,3-dipolar cycloaddition. DSC measures, AFM, and UV spectrophotometry were employed to systematically investigate adsorption of CJ-PEGBT onto RGO and its physicochemical stability in aqueous media, demonstrating that a stable π-staked nanosystem can be obtained. In vitro tests using cancer breast cells (MCF-7) showed the ability of the RGO/CJ-PEGBT of efficiently killing cancer cells both via a selective laser beam thermoablation and hyperthermia-triggered chemotherapy. If compared with the nonbiotinylated nanosystem, including virgin RGO and the free conjugate, RGO/CJ-PEGBT is endowed with a smart combination of properties which warrant potential as an anticancer nanomedicine.

Genetically encoding a light switch in an ionotropic glutamate receptor reveals subunit-specific interfaces.

PubMed

Zhu, Shujia; Riou, Morgane; Yao, C Andrea; Carvalho, Stéphanie; Rodriguez, Pamela C; Bensaude, Olivier; Paoletti, Pierre; Ye, Shixin

2014-04-22

Reprogramming receptors to artificially respond to light has strong potential for molecular studies and interrogation of biological functions. Here, we design a light-controlled ionotropic glutamate receptor by genetically encoding a photoreactive unnatural amino acid (UAA). The photo-cross-linker p-azido-L-phenylalanine (AzF) was encoded in NMDA receptors (NMDARs), a class of glutamate-gated ion channels that play key roles in neuronal development and plasticity. AzF incorporation in the obligatory GluN1 subunit at the GluN1/GluN2B N-terminal domain (NTD) upper lobe dimer interface leads to an irreversible allosteric inhibition of channel activity upon UV illumination. In contrast, when pairing the UAA-containing GluN1 subunit with the GluN2A subunit, light-dependent inactivation is completely absent. By combining electrophysiological and biochemical analyses, we identify subunit-specific structural determinants at the GluN1/GluN2 NTD dimer interfaces that critically dictate UV-controlled inactivation. Our work reveals that the two major NMDAR subtypes differ in their ectodomain-subunit interactions, in particular their electrostatic contacts, resulting in GluN1 NTD coupling more tightly to the GluN2B NTD than to the GluN2A NTD. It also paves the way for engineering light-sensitive ligand-gated ion channels with subtype specificity through the genetic code expansion.

Advanced drug and gene delivery systems based on functional biodegradable polycarbonates and copolymers.

PubMed

Chen, Wei; Meng, Fenghua; Cheng, Ru; Deng, Chao; Feijen, Jan; Zhong, Zhiyuan

2014-09-28

Biodegradable polymeric nanocarriers are one of the most promising systems for targeted and controlled drug and gene delivery. They have shown several unique advantages such as excellent biocompatibility, prolonged circulation time, passive tumor targeting via the enhanced permeability and retention (EPR) effect, and degradation in vivo into nontoxic products after completing their tasks. The current biodegradable drug and gene delivery systems exhibit, however, typically low in vivo therapeutic efficacy, due to issues of low loading capacity, inadequate in vivo stability, premature cargo release, poor uptake by target cells, and slow release of therapeutics inside tumor cells. To overcome these problems, a variety of advanced drug and gene delivery systems has recently been designed and developed based on functional biodegradable polycarbonates and copolymers. Notably, polycarbonates and copolymers with diverse functionalities such as hydroxyl, carboxyl, amine, alkene, alkyne, halogen, azido, acryloyl, vinyl sulfone, pyridyldisulfide, and saccharide, could be readily obtained by controlled ring-opening polymerization. In this paper, we give an overview on design concepts and recent developments of functional polycarbonate-based nanocarriers including stimuli-sensitive, photo-crosslinkable, or active targeting polymeric micelles, polymersomes and polyplexes for enhanced drug and gene delivery in vitro and in vivo. These multifunctional biodegradable nanosystems might be eventually developed for safe and efficient cancer chemotherapy and gene therapy. Copyright © 2014 Elsevier B.V. All rights reserved.

A Single Zidovudine (AZT) Administration Delays Hepatic Cell Proliferation by Altering Oxidative State in the Regenerating Rat Liver

PubMed Central

Butanda-Ochoa, Armando; Hernández-Espinosa, Diego Rolando; Olguín-Martínez, Marisela; Sánchez-Sevilla, Lourdes; Rodríguez, Mario R.; Chávez-Rentería, Benito; Aranda-Fraustro, Alberto

2017-01-01

The 3′-azido-3′-deoxythymidine or Zidovudine (AZT) was the first antiretroviral drug used in the treatment of HIV patients, which has good effectiveness but also hepatotoxic side effects that include cell cycle arrest and oxidative/nitrative mitochondrial damage. Whether such an oxidative damage may affect the proliferative-regenerative capacity of liver remains to be clearly specified at doses commonly used in the clinical practice. In this study, we described the oxidative-proliferative effect of AZT administered at a common clinical dose in rat liver submitted to 70% partial hepatectomy (PH). The results indicate that AZT significantly decreased DNA synthesis and the number of mitosis in liver subjected to PH in a synchronized way with the promotion of organelle-selective lipid peroxidation events (especially those observed in plasma membrane and cytosolic fractions) and with liver enzyme release to the bloodstream. Then at the dose used in clinical practice AZT decreased liver regeneration but stimulates oxidative events involved during the proliferation process in a way that each membrane system inside the cell preserves its integrity in order to maintain the cell proliferative process. Here, the induction of large amounts of free ammonia in the systemic circulation could become a factor capable of mediating the deleterious effects of AZT on PH-induced rat liver regeneration. PMID:28479956

Chemical surface deposition of ultra-thin semiconductors

DOEpatents

McCandless, Brian E.; Shafarman, William N.

2003-03-25

A chemical surface deposition process for forming an ultra-thin semiconducting film of Group IIB-VIA compounds onto a substrate. This process eliminates particulates formed by homogeneous reactions in bath, dramatically increases the utilization of Group IIB species, and results in the formation of a dense, adherent film for thin film solar cells. The process involves applying a pre-mixed liquid coating composition containing Group IIB and Group VIA ionic species onto a preheated substrate. Heat from the substrate causes a heterogeneous reaction between the Group IIB and VIA ionic species of the liquid coating composition, thus forming a solid reaction product film on the substrate surface.

[Effects of sintered bone modified with surface mineralization/P24 peptide composite biomaterial on the adhesion, proliferation and osteodifferentiation of MC3T3-E1 cells].

PubMed

Li, Jingfeng; Zheng, Qixin; Guo, Xiaodong; Chen, Liaobin

2014-10-01

In the present research, the effects of sintered bone modified with surface mineralization/P24 peptide composite biomaterials on the adhesion, proliferation and osteodifferentiation of MC3T3-E1 cells were investigated. The experiments were divided into three groups due to biomaterials used: Group A (composite materials of sintered bone modified with surface mineralization and P24, a peptide of bone morphogenetic protein-2); Group B (sintered bone modified with surface mineralization) and Group C (sintered bone only). The three groups were observed by scanning electron microscopy (SEM) before the experiments, respectively. Then MC3T3-E1 cells were cultured on the surfaces of the three kinds of material, respectively. The cell adhesion rate was assessed by precipitation method. The proliferative ability of MC3T3-E1 cells were measured with MTT assay. And the ALP staining and measurement of alkaline phosphatase (ALP) activity were performed to assess the differentiation of cells into osteoblasts. The SEM results showed that the materials in the three groups retained the natural pore structure and the pore sizes were in the range between 200-850 μm. The adhesive ratio measurements and MTT assay suggested that adhesion and proliferation of MC3T3-E1 cells in Group A were much higher than those in Group B and Group C (P < 0.05). The ALP staining and ALP activity of MC3T3-E1 cells in Group A were significantly higher than those in Group B and Group C (P < 0.05). The sintered bone modified with surface mineralization/P24 composite material was confirmed to improve the adhesion rate and proliferation and osteodifferentiation of MC3T3-E1 cells, and maintained their morphology.

The Effects of Size, Shape, and Surface Functional Group of Gold Nanostructures on Their Adsorption and Internalization by Cells

PubMed Central

Cho, Eun Chul; Au, Leslie; Zhang, Qiang; Xia, Younan

2010-01-01

In this study, we examined the effects of size, shape, and surface chemistry of gold nanostructures on their uptake (including both adsorption and internalization) by SK-BR-3 breast cancer cells. We used both spherical and cubic Au nanostructures (nanospheres and nanocages, respectively) of two different sizes, and their surface was modified with poly(ethylene glycol) (PEG), antibody anti-HER2, or poly(allyamine hydrochloride) (PAA). Our results showed that the size of the Au nanostructures influenced their uptake by the cells in a similar way regardless of the surface chemistry, while the shape dependency could vary depending on the surface functional group. In addition, the cells preferred to take up the Au nanostructures covered by different surface groups in the following order: PAA>> anti-HER2> PEG. The fraction of Au nanostructures attached to the cell surface was also dependent on the aforementioned parameters. PMID:20029850

A comprehensive review of techniques for biofunctionalization of titanium

PubMed Central

2011-01-01

A number of surface modification techniques using immobilization of biofunctional molecules of Titanium (Ti) for dental implants as well as surface properties of Ti and Ti alloys have been developed. The method using passive surface oxide film on titanium takes advantage of the fact that the surface film on Ti consists mainly of amorphous or low-crystalline and non-stoichiometric TiO2. In another method, the reconstruction of passive films, calcium phosphate naturally forms on Ti and its alloys, which is characteristic of Ti. A third method uses the surface active hydroxyl group. The oxide surface immediately reacts with water molecules and hydroxyl groups are formed. The hydroxyl groups dissociate in aqueous solutions and show acidic and basic properties. Several additional methods are also possible, including surface modification techniques, immobilization of poly(ethylene glycol), and immobilization of biomolecules such as bone morphogenetic protein, peptide, collagen, hydrogel, and gelatin. PMID:22324003

Effect of sandblasting on surface roughness of zirconia-based ceramics and shear bond strength of veneering porcelain.

PubMed

He, Min; Zhang, Zutai; Zheng, Dongxiang; Ding, Ning; Liu, Yan

2014-01-01

This study aims to investigate the effect of sandblasting on the surface roughness of zirconia and the shear bond strength of the veneering porcelain. Pre-sintered zirconia plates were prepared and divided into four groups. Group A were not treated at all; group B were first sandblasted under 0.2 MPa pressure and then densely sintered; group C and D were sintered first, and then sandblasted under 0.2 MPa and 0.4 MPa pressures respectively. Surface roughness was measured and 3D roughness was reconstructed for the specimens, which were also analyzed with X-ray diffractometry. Finally after veneering porcelain sintering, shear bond tests were conducted. Sandblasting zirconia before sintering significantly increased surface roughness and the shear bond strength between zirconia and veneering porcelain (p<0.05). Sandblasting zirconia before sintering is a useful method to increase surface roughness and could successfully improve the bonding strength of veneering porcelain.

Effectiveness of silica-lasing method on the bond strength of composite resin repair to Ni-Cr alloy.

PubMed

Madani, Azam S; Astaneh, Pedram Ansari; Nakhaei, Mohammadreza; Bagheri, Hossein G; Moosavi, Horieh; Alavi, Samin; Najjaran, Niloufar Tayarani

2015-04-01

The aim of this study was to evaluate the effectiveness of silica-lasing method for improving the composite resin repair of metal ceramic restorations. Sixty Ni-Cr cylindrical specimens were fabricated. The bonding surface of all specimens was airborne-particle abraded using 50 μm aluminum oxide particles. Specimens were divided into six groups that received the following surface treatments: group 1-airborne-particle abrasion alone (AA); group 2-Nd:YAG laser irradiation (LA); group 3-silica coating (Si-CO); group 4-silica-lasing (metal surface was coated with slurry of opaque porcelain and irradiated by Nd:YAG laser) (Si-LA); group 5-silica-lasing plus etching with HF acid (Si-LA-HF); group 6-CoJet sand lased (CJ-LA). Composite resin was applied on metal surfaces. Specimens were thermocycled and tested in shear mode in a universal testing machine. The shear bond strength values were analyzed using ANOVA and Tukey's tests (α = 0.05). The mode of failure was determined, and two specimens in each group were examined by scanning electron microscopy and wavelength dispersive X-ray spectroscopy. Si-CO showed significantly higher shear bond strength in comparison to other groups (p < 0.001). The shear bond strength values of the LA group were significantly higher than those of the AA group (p < 0.05). No significant difference was found among lased groups (LA, Si-LA, Si-LA-HF, CJ-LA; p > 0.05). The failure mode was 100% adhesive for AA, Si-LA, Si-LA-HF, and CJ-LA. LA and Si-CO groups showed 37.5% and 87.5% cohesive failure, respectively. Silica coating of Ni-Cr alloy resulted in higher shear bond strength than those of other surface treatments. © 2014 by the American College of Prosthodontists.

[Effect of surface organic modified nano-silicon-oxide on mechanical properties of A-2186 silicone elastomers].

PubMed

Guo, Nan; Jiao, Ting

2011-08-01

To study the effect of surface organic modified nano-silicon-oxide (SiO(x)) on mechanical properties of A-2186 silicone elastomers. Surface organic modified nano-silicon-oxide (SiO(x)) was added into A-2186 silicone elastomers by weight percentage of 2%, 4% and 6%. The one without addition served as a control. Standard specimens were made according to American Society for Testing Materials (ASTM). Their tensile strength, elongation at break, tear strength, and Shore A hardness were measured. The results were analyzed statistically by SPSS 10.0 software package. The tensile strength in the experimental groups was significantly lower than the control group (P<0.001).The elongation in the experimental groups was lower than the control group, but there was no significant difference between the 2wt% group and the control group (P=0.068). The tear strength in both the 2wt= group and 4wt= group were higher than the control group, and the difference was statistically significant; in addition, the tear strength in 2wt= group was higher than 4wt= group, which also showed statistical significance (P<0.001). With the increase of the added amount of surface modified nano-SiO(x), Shore A hardness increased and there was significant difference among them (P<0.001). Adding surface modified nano-SiO(x) has an effect on mechanical properties of A-2186 silicone elastomer, when 2wt= and 4wt= are added, tear strength of A-2186 improves significantly, with an increase of Shore A hardness and an decrease of tensile strength.

Molecular Structures and Sorption Mechanisms of Biochars as Heterogeneous Carbon Materials

NASA Astrophysics Data System (ADS)

Chen, Baoliang; Chen, Zaiming; Xiao, Xin; Fang, Qile

2015-04-01

Surface functional groups such as carboxyl play a vital role in the environmental applications of biochar as a soil amendment. However, the quantification of oxygen-containing groups on a biochar surface still lacks systematical investigation. An integrated method combining chemical and spectroscopic techniques was established to quantitatively identify the chemical states, dissociation constants (pKa), and contents of oxygen-containing groups on dairy manure-derived biochars prepared at 100-700 °C. The dissociation pH of carboxyl groups on the biochar surface covered a wide range of pH values (pH 2-11), due to the varied structural micro-environments and chemical states. For low temperature biochars (≤350 °C), carboxyl existed not only as hydrogen-bonded carboxyl and unbonded carboxyl groups but also formed esters at the surface of biochars. The esters consumed OH‒ via saponification in the alkaline pH region and enhanced the dissolution of organic matter from biochars. For high temperature biochars (≥500 °C), esters came from carboxyl were almost eliminated via carbonization (ester pyrolysis), while lactones were developed. The surface density of carboxyl groups on biochars decreased sharply with the increase of the biochar-producing temperature, but the total contents of the surface carboxyls for different biochars were comparable (with a difference < 3-fold) as a result of the expanded surface area at high pyrolytic temperatures. Understanding the wide pKa ranges and the abundant contents of carboxyl groups on biochars is a prerequisite to recognition of the multi-functional applications and biogeochemical cycling of biochars. A schematic diagram for the dissociation of acid/base groups on biochar surfaces and their related functions was depicted. The protonated biochars favor inorganic anion adsorption and ionizable organic chemical sorption, while the deprotonated biochars favor cationic nutrient retention, heavy metal immobilization, and the release of dissolved materials. For low temperature biochars (i.e., DM100, DM250 and DM350), the acid/base group dissociation directly controls the pH buffering properties of biochars. The resulting surface charges regulate biochars in nutrient retention, sorption/immobilization of hazardous pollutants and biochar particle dispersing properties. Meanwhile, dissociation of acid/base groups affects carbon and silica biogeochemical cycling by regulating the release of organic matter from the cleavage of esters and dissolution of the Si-containing minerals. For high temperature biochars (i.e., DM500 and DM700), the effect of acid/base dissociation on organic matter dissolution is eliminated, but other functions are similar. CGs are the major acid/base groups on biochar surfaces. In field applications, such abundant CGs are worthy of concern in terms of multiple functions of biochars, such as soil pH adjustment, soil nutrient retention, and toxic metals immobilization.

Tooth Whitening And Temperature Rise With Two Bleaching Activation Methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abu-ElMagd, D. M.; El-Sayad, I. I.; Abd El-Gawad, L. M.

2009-09-27

To measure the tooth whitening and the surface and Intrapulpal temperature increase in vitro on freshly extracted upper human central incisors after chemical, Zoom AP light and diode laser activated bleaching. Thirty caries-free upper human incisors were selected. Teeth were divided into three equal groups according to the methods of activation of the bleaching agent (n = 10). A whitening gel containing hydrogen peroxide was applied to the buccal surface of all teeth. Group I was bleached using chemically activated hydrogen peroxide gel, for three applications of 15 min each. Group II was bleached with high intensity advanced power Zoommore » activation light (Zoom AP), for three applications of 15 min each. Group III was bleached with diode laser activation technique, where the teeth were irradiated with 2 Watt diode laser for three applications of 30 sec each. The whitening degree was assessed using an image analysis system, while temperature rise was recorded using a thermocouple on the external tooth surface and Intrapulpal. The degree of whitening increased significantly in all groups. However, the percentage of whitening was not statistically significantly different between the three groups. In addition, group II showed statistically significant higher mean rise in both surface and pulp temperatures than group I and group III. Chemical bleaching produces the same whitening effect as Zoom AP light and laser, with no surface or pulpal temperature rise. Laser application is faster and produces less surface and pulp temperature increase than Zoom AP light. Diode laser used to activate bleaching gels is not considered dangerous to the vitality of dental pulp using power settings of 2 W.« less

Polymethyl methacrylate-co-methacrylic acid coatings with controllable concentration of surface carboxyl groups: A novel approach in fabrication of polymeric platforms for potential bio-diagnostic devices

NASA Astrophysics Data System (ADS)

Hosseini, Samira; Ibrahim, Fatimah; Djordjevic, Ivan; Koole, Leo H.

2014-05-01

The generally accepted strategy in development of bio-diagnostic devices is to immobilize proteins on polymeric surfaces as a part of detection process for diseases and viruses through antibody/antigen coupling. In that perspective, polymer surface properties such as concentration of functional groups must be closely controlled in order to preserve the protein activity. In order to improve the surface characteristics of transparent polymethacrylate plastics that are used for diagnostic devices, we have developed an effective fabrication procedure of polymethylmetacrylate-co-metacrylic acid (PMMA-co-MAA) coatings with controlled number of surface carboxyl groups. The polymers were processed effectively with the spin-coating technique and the detailed control over surface properties is here by demonstrated through the variation of a single synthesis reaction parameter. The chemical structure of synthesized and processed co-polymers has been investigated with nuclear magnetic resonance spectroscopy (NMR) and matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-ToF-MS). The surface morphology of polymer coatings have been analyzed with atomic force microscopy (AFM) and scanning electron microscopy (SEM). We demonstrate that the surface morphology and the concentration of surface -COOH groups (determined with UV-vis surface titration) on the processed PMMA-co-MAA coatings can be precisely controlled by variation of initial molar ratio of reactants in the free-radical polymerization reaction. The wettability of developed polymer surfaces also varies with macromolecular structure.

Shear Bond Strength of Three Orthodontic Bonding Systems on Enamel and Restorative Materials

PubMed Central

Ebeling, Jennifer; Schauseil, Michael; Stein, Steffen; Roggendorf, Matthias; Korbmacher-Steiner, Heike

2016-01-01

Objective. The aim of this in vitro study was to determine the shear bond strength (SBS) and adhesive remnant index (ARI) score of two self-etching no-mix adhesives (iBond™ and Scotchbond™) on different prosthetic surfaces and enamel, in comparison with the commonly used total etch system Transbond XT™. Materials and Methods. A total of 270 surfaces (1 enamel and 8 restorative surfaces, n = 30) were randomly divided into three adhesive groups. In group 1 (control) brackets were bonded with Transbond XT primer. In the experimental groups iBond adhesive (group 2) and Scotchbond Universal adhesive (group 3) were used. The SBS was measured using a Zwicki 1120™ testing machine. The ARI and SBS were compared statistically using the Kruskal–Wallis test (P ≤ 0.05). Results. Significant differences in SBS and ARI were found between the control group and experimental groups. Conclusions. Transbond XT showed the highest SBS on human enamel. Scotchbond Universal on average provides the best bonding on all other types of surface (metal, composite, and porcelain), with no need for additional primers. It might therefore be helpful for simplifying bonding in orthodontic procedures on restorative materials in patients. If metal brackets have to be bonded to a metal surface, the use of a dual-curing resin is recommended. PMID:27738633

Evaluation of primary tooth enamel surface morphology and microhardness after Nd:YAG laser irradiation and APF gel treatment--an in vitro study.

PubMed

Banda, Naveen Reddy; Vanaja Reddy, G; Shashikiran, N D

2011-01-01

Laser irradiation and fluoride has been used as a preventive tool to combat dental caries in permanent teeth, but little has been done for primary teeth which are more prone to caries. The purpose of this study was to evaluate microhardness alterations in the primary tooth enamel after Nd-YAG laser irradiation alone and combined with topical fluoride treatment either before or after Nd-YAG laser irradiation. Ten primary molars were sectioned and assigned randomly to: control group, Nd-YAG laser irradiation, Nd-YAG lasing before APF and APF followed by Nd-YAG lasing. The groups were evaluated for microhardness. Surface morphological changes were observed using SEM. Statistical comparisons were performed. The control group's SEM showed a relatively smooth enamel surface and lasing group had fine cracks and porosities. In the lasing + fluoride group a homogenous confluent surface was seen. In the fluoride + lasing group an irregular contour with marked crack propagation was noted. There was a significant increase in the microhardness of the treatment groups. Nd-YAG laser irradiation and combined APF treatment of the primary tooth enamel gave morphologically hardened enamel surface which can be a protective barrier against a cariogenic attack.

Shear Bond Strength of Three Orthodontic Bonding Systems on Enamel and Restorative Materials.

PubMed

Hellak, Andreas; Ebeling, Jennifer; Schauseil, Michael; Stein, Steffen; Roggendorf, Matthias; Korbmacher-Steiner, Heike

2016-01-01

Objective. The aim of this in vitro study was to determine the shear bond strength (SBS) and adhesive remnant index (ARI) score of two self-etching no-mix adhesives (iBond ™ and Scotchbond ™ ) on different prosthetic surfaces and enamel, in comparison with the commonly used total etch system Transbond XT ™ . Materials and Methods . A total of 270 surfaces (1 enamel and 8 restorative surfaces, n = 30) were randomly divided into three adhesive groups. In group 1 (control) brackets were bonded with Transbond XT primer. In the experimental groups iBond adhesive (group 2) and Scotchbond Universal adhesive (group 3) were used. The SBS was measured using a Zwicki 1120 ™ testing machine. The ARI and SBS were compared statistically using the Kruskal-Wallis test ( P ≤ 0.05). Results . Significant differences in SBS and ARI were found between the control group and experimental groups. Conclusions . Transbond XT showed the highest SBS on human enamel. Scotchbond Universal on average provides the best bonding on all other types of surface (metal, composite, and porcelain), with no need for additional primers. It might therefore be helpful for simplifying bonding in orthodontic procedures on restorative materials in patients. If metal brackets have to be bonded to a metal surface, the use of a dual-curing resin is recommended.

Prenatally administered HMB modifies the enamel surface roughness in spiny mice offspring: An atomic force microscopy study.

PubMed

Świetlicka, Izabela; Muszyński, Siemowit; Tomaszewska, Ewa; Dobrowolski, Piotr; Kwaśniewska, Anita; Świetlicki, Michał; Skic, Anna; Gołacki, Krzysztof

2016-10-01

The aim of this research was to check the effect of the prenatally administered β-hydroxy β-methylbutyrate (HMB) on the development of enamel surface of the spiny mice offspring. The spiny mice dams were randomly assigned into three groups: control group (not supplemented with HMB) and two experimental groups in which powdered HMB was given at the daily dosage of 0.2g/kg of body weight (group I) and 0.02g/kg of body weight (group II) during the last period of gestation. Newborn pups were euthanized by CO 2 inhalation. The morphology of incisor teeth was analysed using atomic force microscopy (AFM) in semi-contact mode in the height, magnitude and phase domains. Height images became a basis for determination of surface roughness parameters. Conducted study indicated that maternal HMB administration markedly influences enamel development. Enamel of offspring's teeth in both experimental groups was characterized by significantly smaller values of indices describing surface roughness and profile. HMB supplementation influenced the calculated parameters regardless of the diet type and offspring sex, however higher dose of HMB caused stronger changes in enamel surface's physical properties and could be observed in higher intensity in the male group. HMB administration caused reduction in the irregularities of enamel surface, thereby possibly reducing the probability of bacteria adhesion and caries development. These observations may serve to improve nutrition and supplementation of animals and could be a lead for further research. Copyright © 2016 Elsevier Ltd. All rights reserved.

In situ and ex situ spectroscopic monitoring of biochar's surface functional groups

USDA-ARS?s Scientific Manuscript database

A number of studies described the higher heating temperature (HHT) as the primary pyrolysis parameter dictating the biochar property: surface functional group and fixed carbon contents, O/C, H/C ratios, and Brunauer-Emmett-Teller (BET) surface area. In order to produce desirable biochar properties ...

Evaluation of the surface roughness of three heat-cured acrylic denture base resins with different conventional lathe polishing techniques: A comparative study.

PubMed

Rao, Duggineni Chalapathi; Kalavathy, N; Mohammad, H S; Hariprasad, A; Kumar, C Ravi

2015-01-01

Surface roughness promotes adhesion and colonization of denture plaque. Therefore, it is important to know the effects of polishing and finishing on the surface roughness of various acrylic resin materials. To evaluate and compare the effects of different conventional lathe polishing techniques on heat cured acrylic resins in producing surface roughness. Three different commercially available heat-cured acrylic resin materials namely DPI, Meliodent and Trevalon Hi were selected. 30 Specimens of each acrylic material (30 x 3 = 90, 10 x 60 x 2mm) were prepared and divided into 5 groups, each group consisted of 6 Nos. of specimens per material(6x3=18) and were grouped as Group A(unfinished), Group B (finished), Group C (Polishing Paste), Group D (Polishing Cake) and Group E (Pumice and Gold rouge). The resulted surface roughness (μm) was measured using Perthometer and observed under Scanning Electron Microscope. The values obtained were subjected statistical analyses. Among the materials tested, better results were obtained with Trevalon Hi followed by Meliodent and DPI. Among the polishing methods used, superior results were obtained with universal polishing paste followed by polishing cake; Pumice and Gold rouge. Although Pumice and Gold rouge values produced greater roughness value, they were well within the threshold value of 0.2 mm.

Comparative evaluation of surface topography of tooth prepared using erbium, chromium: Yttrium, scandium, gallium, garnet laser and bur and its clinical implications.

PubMed

Verma, Mahesh; Kumari, Pooja; Gupta, Rekha; Gill, Shubhra; Gupta, Ankur

2015-01-01

Erbium, chromium: Yttrium, scandium, gallium, garnet (Er, Cr: YSGG) laser has been successfully used in the ablation of dental hard and soft tissues. It has been reported that this system is also useful for preparing tooth surfaces and etching, but no consensus exist in the literature regarding the advantage of lasers over conventional tooth preparation technique. Labial surfaces of 25 extracted human maxillary central incisors were divided into two halves. Right half was prepared with diamond bur and left half with Er, Cr; YSGG laser and a reduction of 0.3-0.5 mm was carried out. Topography of prepared surfaces of five teeth were examined under scanning electron microscope (SEM). The remaining samples were divided into 4 groups of 10 specimens each based on the surface treatment received: One group was acid etched and other was nonetched. Composite resin cylinders were bonded on prepared surfaces and shear bond strength was assessed using a universal testing machine. The SEM observation revealed that the laser prepared surfaces were clean, highly irregular and devoid of a smear layer. Bur prepared surfaces were relatively smooth but covered with smear layer. Highest bond strength was shown by laser prepared acid etched group, followed by bur prepared the acid etched group. The bur prepared nonacid etched group showed least bond strength. Er, Cr: YSGG laser can be used for preparing tooth and bond strength value achieved by laser preparation alone without surface treatment procedure lies in the range of clinical acceptability.

Effect of various tooth whitening modalities on microhardness, surface roughness and surface morphology of the enamel.

PubMed

Kwon, So Ran; Kurti, Steven R; Oyoyo, Udochukwu; Li, Yiming

2015-09-01

The purpose of this study was to evaluate the effect of four whitening modalities on surface enamel as assessed with microhardness tester, profilometer, and scanning electron microscopy (SEM). Whitening was performed according to manufacturer's directions for over-the-counter (OTC), dentist dispensed for home use (HW) and in-office (OW) whitening. Do-it-yourself (DIY) whitening consisted of a strawberry and baking soda mix. Additionally, negative and positive controls were used. A total of 120 enamel specimens were used for microhardness testing at baseline and post-whitening. Following microhardness testing specimens were prepared for SEM observations. A total of 120 enamel specimens were used for surface roughness testing at baseline and post-whitening (n = 20 per group). Rank-based Analysis of Covariance was performed to compare microhardness and surface roughness changes. Tests of hypotheses were two-sided with α = 0.05. There was a significant difference in Knoop hardness changes (ΔKHN) among the groups (Kruskal-Wallis test, p < 0.0001). Significant hardness reduction was observed in the positive control and DIY group (p < 0.0001). Mean surface roughness changes (ΔRa) were significantly different among the groups (Kruskal-Wallis test, p < 0.0001). Surface roughness increased in the OTC group (p = 0.03) and in the positive control (p < 0.0001). The four whitening modalities-DIY, OTC, HW and OW induced minimal surface morphology changes when observed with SEM. It can be concluded that none of the four whitening modalities adversely affected enamel surface morphology. However, caution should be advised when using a DIY regimen as it may affect enamel microhardness and an OTC product as it has the potential to increase surface roughness.

Titanium Surface Roughing Treatments contribute to Higher Interaction with Salivary Proteins MG2 and Lactoferrin.

PubMed

Cavalcanti, Yuri Wanderley; Soare, Rodrigo Villamarim; Leite Assis, Marina Araújo; Zenóbio, Elton Gonçalves; Girundi, Francisco Mauro da Silva

2015-02-01

Some surface treatments performed on titanium can alter the composition of salivary pellicle formed on this abiotic surface. Such treatments modify the titanium's surface properties and can promote higher adsorption of proteins, which allow better integration of titanium to the biotic system. This study aimed to evaluate the interactions between salivary proteins and titanium disks with different surface treatments. Machined titanium disks (n = 48) were divided into four experimental groups (n = 12), according to their surface treatments: surface polishing (SP); acid etching (A); spot-blasting plus acid etching (SB-A); spot-blasting followed by acid etching and nano-functionalization (SB-A-NF). Titanium surfaces were characterized by surface roughness and scanning electron microscopy (SEM). Specimens were incubated with human saliva extracted from submandibular and sublingual glands. Total salivary protein adsorbed to titanium was quantified and samples were submitted to western blotting for mucin glycoprotein 2 (MG2) and lactoferrin identification. Surface roughness was statistically higher for SB-A and SB-A-NF groups. Scanning electron microscopy images confirmed that titanium surface treatments increased surface roughness with higher number of porous and scratches for SB-A and SB-A-NF groups. Total protein adsorption was significantly higher for SB-A and SB-A-NF groups (p < 0.05), which also presented higher interactions with MG2 and lactoferrin proteins. The roughing of titanium surface by spot-blasting plus acid etching treatments contribute to higher interaction with salivary proteins, such as MG2 and lactoferrin. Titanium surface roughing increases the interactions of the substratum with salivary proteins, which can influence the integration of dental implants and their components to the oral environment. However, those treatments should be used carefully intraorally, avoiding increase biofilm formation.

Development of fibrin-free intraocular lens with photochemical surface modification

NASA Astrophysics Data System (ADS)

Sato, Yuji; Tanizawa, Katsuya; Anai, Hiroyuki; Sato, Nobuhiro; Sato, Yuki; Ajiki, Tooru; Parel, Jean-Marie; Murahara, Masataka

2004-07-01

Having substituted the hydrophilic and hydrophobic groups alternately on the soft acrylic resin intraocular lens (IOL) surface by using an ArF excimer laser and a Xe2 excimer lamp, we have developed the IOL that is free from fibrin. Acrylic resin or PMMA lens has been used as an intraocular lens for 50 years. However, protein and fat are stuck onto the IOL surface after a long implantation, which opacifies the surface (after-cataract). Thus, we designed the micro domain structures of hydrophilic and hydrophobic groups on the IOL surface for fibrin-free. Firstly, the IOL was irradiated with the Xe2 excimer lamp in the presence of perfluoropolyether in order to make it hydrophobic. By this photochemical reaction, the CF3 functional groups were substituted on the IOL surface. Secondly, the ArF laser was projected on the IOL through the mask pattern in reduced size in the presence of water in order to be hydrophilic. With the photochemical reaction, the OH groups were substituted at the part exposed. The fibrin adsorption test of the modified IOL surface was carried out with FT-IR; which revealed that the fibrin-sticking rate of the treated sample has decreased by 23% compared with that of the non-treated sample. As a result, the fibrin-free IOL has been made by modifying the surface of the IOL to have the micro domain structures of the hydrophilic and hydrophobic groups that are arrayed alternately. In conclusion, the ideal intraocular lens has been demonstrated.

Effect of Er,Cr:YSGG laser on the surface of composite restoratives during in-office tooth bleaching.

PubMed

Dionysopoulos, Dimitrios; Strakas, Dimitrios; Tsitrou, Effrosyni; Tolidis, Kosmas; Koumpia, Effimia

2016-07-01

The aim of this in vitro study was to investigate the effect of Er,Cr:YSGG laser on the surface roughness and microhardness of various composite restoratives during in-office tooth bleaching. Five highly viscous composite restoratives and three flowable composite restoratives were investigated. Thirty cylindrical specimens of each material were made using Teflon molds. The specimens of each composite were randomly divided into three groups (n = 10). Group 1 specimens did not receive bleaching treatment, group 2 received a conventional in-office bleaching treatment, and group 3 received a laser-assisted in-office bleaching treatment using an Er,Cr:YSGG laser. Two-way ANOVA was used to determine significant interactions between materials and bleaching methods. One-way ANOVA and Tukey's post hoc test were used to compare the mean surface microhardness and roughness between materials for each treatment group (a = 0.05). Τhere were no significant differences in surface microhardness between the two bleached experimental groups for all the tested composites (p > 0.05). The reduction of surface microhardness after bleaching procedures ranged from 0.72 to 16.93 % for the specimens received conventional treatment and from 1.30 to 11.51 % for those received laser-assisted treatment. Moreover, there were no significant differences in Ra values between the experimental groups (p > 0.05) in all cases. The increase of surface roughness after the bleaching treatments was negligible and was between 0.43 and 4.78 %. The use of Er,Cr:YSGG laser during in-office tooth bleaching treatment did not affect the surface microhardness and roughness of the tested composite restorative materials.

Effects of thermal cycling on surface roughness, hardness and flexural strength of polymethylmethacrylate and polyamide denture base resins.

PubMed

Ayaz, Elif Aydoğan; Bağış, Bora; Turgut, Sedanur

2015-10-16

The purpose of this study was to evaluate the effects of thermal cycling on the surface roughness, hardness and flexural strength of denture resins. Polyamide (PA; Deflex and Valplast) and polymethylmethacrylate (PMMA; QC-20 and Acron MC) denture materials were selected. A total of 180 specimens were fabricated and then divided into 3 groups. The first group (group 1) acted as a control and was not thermocycled. The second group (group 2) was subjected to thermocycling for 10,000 cycles in artificial saliva and 5,000 cycles in distilled water. The last group (group 3) was thermocycled for 20,000 cycles in artificial saliva and 10,000 cycles in distilled water. The surface roughness were measured with a profilometer. The hardness of the resins were measured with a Vickers Hardness Tester using a 100-gf load. The flexural strength test was performed using the universal test machine with a crosshead speed of 5 mm/min. Data were analyzed using statistical software. The results of the measurements in the 3 different tests were analyzed by Kruskal-Wallis test with Bonferroni correction. Multiple comparisons were made by Conover and Wilcoxon tests. There was a significant difference between the PMMA and PA groups in terms of surface roughness, hardness and transverse strength before and after thermal cycling (p<0.001). Thermal cycling did not change the surface roughness, hardness and flexural strength values of either the PMMA or PA group (p>0.001).

The effect of different cleaning methods on the surface and temperature of failed titanium implants: an in vitro study.

PubMed

Hakki, Sema S; Tatar, Gulsah; Dundar, Niyazi; Demiralp, Burak

2017-04-01

The aims of this in vitro study are to compare the efficacy of different cleaning methods in removing debris of failed implants and to detect thermal changes of the implants treated by various scaling instruments. Twenty-seven failed implants and two unused implants as control were included to this study-group 1: plastic curette (P), group 2: titanium curette (T), group 3: carbon curette (C), group 4: titanium brush (TB), group 5: Er:YAG laser (laser 1 (L1) 100 mJ/pulse at 10 Hz), group 6: Er:YAG laser (laser 2 (L2) 150 mJ/pulse at 10 Hz), group 7: Er:YAG laser (laser 3 (L3) 200 mJ/pulse at 10 Hz), group 8: ultrasonic scaler appropriate for titanium (US), group 9: air abrasive method (AA) + citric acid, and group 10: implantoplasty (I). The changes on the treated/untreated titanium surfaces and remnant debris were observed by scanning electron microscopy (SEM). Temperature of the implants before and after treatment was detected using a thermocouple. The use of air abrasive and citric acid combination and Er:YAG laser groups was found as the best methods for the decontamination of titanium surfaces of failed implant. When the hand instruments were compared, titanium curette was found better than both the plastic and the carbon curettes which leave plastics and carbon remnants on the titanium surface. The temperature was higher after hand instrumentation when compared to other experimental groups (p < 0.05). Within the limitations of the present in vitro model, it can be concluded that the best method for decontamination of the implant surface is the use of air abrasives and Er:YAG laser.

VARIABLE CHARGE SOILS: MINERALOGY AND CHEMISTRY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Ranst, Eric; Qafoku, Nikolla; Noble, Andrew

2016-09-19

Soils rich in particles with amphoteric surface properties in the Oxisols, Ultisols, Alfisols, Spodosols and Andisols orders (1) are considered to be variable charge soils (2) (Table 1). The term “variable charge” is used to describe organic and inorganic soil constituents with reactive surface groups whose charge varies with pH and ionic concentration and composition of the soil solution. Such groups are the surface carboxyl, phenolic and amino functional groups of organic materials in soils, and surface hydroxyl groups of Fe and Al oxides, allophane and imogolite. The hydroxyl surface groups are also present on edges of some phyllosilicate mineralsmore » such as kaolinite, mica, and hydroxyl-interlayered vermiculite. The variable charge is developed on the surface groups as a result of adsorption or desorption of ions that are constituents of the solid phase, i.e., H+, and the adsorption or desorption of solid-unlike ions that are not constituents of the solid phase. Highly weathered soils and subsoils (e.g., Oxisols and some Ultisols, Alfisols and Andisols) may undergo isoelectric weathering and reach a “zero net charge” stage during their development. They usually have a slightly acidic to acidic soil solution pH, which is close to either the point of zero net charge (PZNC) (3) or the point of zero salt effect (PZSE) (3). They are characterized by high abundances of minerals with a point of zero net proton charge (PZNPC) (3) at neutral and slightly basic pHs; the most important being Fe and Al oxides and allophane. Under acidic conditions, the surfaces of these minerals are net positively charged. In contrast, the surfaces of permanent charge phyllosilicates are negatively charged regardless of ambient conditions. Variable charge soils therefore, are heterogeneous charge systems.« less

Light transmittance and surface roughness of a feldspathic ceramic CAD-CAM material as a function of different surface treatments.

PubMed

Ural, Çağrı; Duran, İbrahim; Evmek, Betül; Kavut, İdris; Cengiz, Seda; Yuzbasioglu, Emir

2016-07-15

The aim of the present study was to determine the effect of different surface treatments on light transmission of aesthetic feldspathic ceramics used in CAD-CAM chairside restorations. Forty eight feldspatic ceramic test specimens were prepared from prefabricated CAD-CAM blocks by using a slow speed diamond saw. Test specimens were prepared and divided into 4 groups (n = 12). In the control group, no surface treatments were applied on the feldspathic ceramic surfaces. In the hydrofluoric acid group, the bonding surfaces of feldspathic ceramics were etched with 9.5 % hydrofluoric acid. In the sandblasting group the feldspathic ceramic surfaces were air-abraded with 30-μm alumium oxide (Al2O3) particles and Er:YAG laser was used to irradiate the ceramic surfaces. The incident light power given by the LED device and the transmitted light power through each ceramic sample was registered using a digital LED radiometer device. Each polymerization light had a light guide with 8-mm-diameter tips. Light transmission of feldspathic ceramic samples was determined by placing it on the radiometer and irradiating the specimen for 10 s at the highest setting for each light polymerization. All specimens were coated with gold using a sputter coater and examined under a field emission scanning electron microscope. Surface roughness measurement each group were evaluated with 3D optical surface and tactile profilometers. One-way ANOVA test results revealed that both surface conditioning method significantly affect the light transmittance (F:412.437; p < 0.001) and the surface roughness values (F:16.386; p < 0.001). Al2O3 and Er-YAG laser application reduced the light transmission significantly (p < 0.05). The laser and Al2O3 applications reduced the light transmission of 1.5 mm thickness feldspathic ceramic material below the value of 400 mW/cm(2) which is critical limit for safe polymerization.

Influence of surface sealing on color stability and roughness of composite submitted to ultraviolet-accelerated aging.

PubMed

Catelan, Anderson; Suzuki, Thaís Yumi Umeda; Becker, Francisco; Briso, André Luiz Fraga; Dos Santos, Paulo Henrique

2017-05-01

In the present study, we evaluated the influence of surface sealing on color stability and surface roughness of a composite resin after accelerated artificial aging. Thirty-two specimens of a composite were prepared. After 24 h, the specimens were polished and divided into four groups (n = 8), according to the surface sealant used, including the control, which had no sealant application. Baseline color was measured according to the CIELab system using a reflection spectrophotometer. Surface roughness was determined using a profilometer with a cut-off of 0.25 mm. After these tests, specimens were aged for 252 h in an ultraviolet (UV)-accelerated aging chamber. Color stability was determined by difference between coordinates obtained before and after the aging procedure. Data of color change and roughness were evaluated by anova and Fisher's exact test (α = 0.05). The results showed that the unsealed group had the highest color change compared to other groups (P = 0.0289), and there was no significant difference between groups sealed with surface sealant (P > 0.05). The artificial aging caused an increase in roughness values independent of the experimental group studied (P = 0.0015). The sealed composites showed lower color change after UV aging, but all groups showed clinically-acceptable color change, and only liquid polish decreased roughness. © 2016 John Wiley & Sons Australia, Ltd.

Novel β-TCP Coated Titanium Nanofiber Surface for Enhanced Bone Growth.

PubMed

Lim, Hyun-Pil; Park, Sang-Won; Yun, Kwi-Dug; Park, Chan; Ji, Min-Kyung; Oh, Gye-Jeong; Lee, Jong-Tak; Lee, Kwangmin

2018-02-01

In this study, we examined the effect of β-tricalcium phosphate (β-TCP) coating on alkali-treated CP Grade II titanium surface via RF magnetron sputtering on osteoblast like cell (MC3T3-E1) viability and bone formation in rat tibia. The specimens were divided into three groups; commercially pure titanium (control group), alkali-treated titanium with nanofiber structure (NF group) and β-TCP coating on alkali-treated titanium with nanofiber structure (TNF group). The surface characteristics of specimens were observed under a field emission scanning electron microscope (FE-SEM), and contact angle was measured. The cell viability was assessed in vitro after 1 day, 3 days and 7 days. Implants of 2.0 mm diameter and 5.0 mm length were inserted into the tibia of rats. After 4 wks, the histomorphometric analysis was performed. Group NF and group TNF showed improved hydrophilicity of Ti. Group TNF showed significantly higher cell viability (P < 0.05) after 7 days. The bone to implant contact (BIC) ratio of the control group, NF group, and TNF group were 32.3%, 35.5%, and 63.9%, respectively. The study results suggested that β-TCP coated alkali-treated titanium surface via RF magnetron sputtering might be effective in implant dentistry due to enhanced hydrophilicity, improved cell response, and better osseointegration.

Introducing multiple bio-functional groups on the poly(ether sulfone) membrane substrate to fabricate an effective antithrombotic bio-interface.

PubMed

Wang, Lingren; He, Min; Gong, Tao; Zhang, Xiang; Zhang, Lincai; Liu, Tao; Ye, Wei; Pan, Changjiang; Zhao, Changsheng

2017-11-21

It has been widely recognized that functional groups on biomaterial surfaces play important roles in blood compatibility. To construct an effective antithrombotic bio-interface onto the poly(ether sulfone) (PES) membrane surface, bio-functional groups of sodium carboxylic (-COONa), sodium sulfonic (-SO 3 Na) and amino (-NH 2 ) groups were introduced onto the PES membrane surface in three steps: the synthesis of PES with carboxylic (-COOH) groups (CPES) and water-soluble PES with sodium sulfonic (-SO 3 Na) groups and amino (-NH 2 ) groups (SNPES); the introduction of carboxylic groups onto the PES membrane by blending CPES with PES; and the grafting of SNPES onto CPES/PES membranes via the coupling of amino groups and carboxyl groups. The physical/chemical properties and bioactivities were dependent on the proportions of the additives. After introducing bio-functional groups, the excellent hemocompatibility of the modified membranes was confirmed by the inhibited platelet adhesion and activation, prolonged clotting times, suppressed blood-related complement and leukocyte-related complement receptor activations. Furthermore, cell tests indicated that the modified membranes showed better cytocompatibility in endothelial cell proliferation than the pristine PES membrane due to the synergistic promotion of the functional groups. To sum up, these results suggested that modified membranes present great potential in fields using blood-contacting materials, such as hemodialysis and surface endothelialization.

The effect of root surface conditioning on smear layer removal in periodontal regeneration (a scanning electron microscopic study)

NASA Astrophysics Data System (ADS)

Fidyawati, D.; Soeroso, Y.; Masulili, S. L. C.

2017-08-01

The role of root surface conditioning treatment on smear layer removal of human teeth is affected by periodontitis in periodontal regeneration. The objective of this study is to analyze the smear layer on root surface conditioned with 2.1% minocycline HCl ointment (Periocline), and 24% EDTA gel (Prefgel). A total of 10 human teeth indicated for extraction due to chronic periodontitis were collected and root planed. The teeth were sectioned in thirds of the cervical area, providing 30 samples that were divided into three groups - minocycline ointment treatment, 24% EDTA gel treatment, and saline as a control. The samples were examined by scanning electron microscope. No significant differences in levels of smear layer were observed between the minocycline group and the EDTA group (p=0.759). However, there were significant differences in the level of smear layer after root surface treatment in the minocycline and EDTA groups, compared with the control group (p=0.00). There was a relationship between root surface conditioning treatment and smear layer levels following root planing.

Nonfouling Characteristics of Dextran-Containing Surfaces

PubMed Central

Martwiset, Surangkhana; Koh, Anna E.; Chen, Wei

2008-01-01

Hydroxyl groups in dextrans have been selectively oxidized to aldehyde groups by sodium periodate in a controlled fashion with percentage of conversion ranging from 6% to 100%. Dextrans (10 k, 70 k, 148 k, 500 k, and 2 000 kDa) and oxidized 10 k dextrans have been successfully grafted to functionalized silicon surfaces. The effect of molecular weight on protein adsorption is not nearly as striking as that of the extent of oxidation. When ∼ 25% of the hydroxyl groups have been converted to aldehyde groups, there is negligible protein adsorption on surfaces containing the oxidized polysaccharides. Conformations of grafted polymers depend strongly on their chemical structures, i.e. the relative amounts of –OH and –CHO groups. That the dependence of the chain conformation as well as the protein resistance on the balance of the hydrogen bond donors (-OH) and the acceptors (-OH and –CHO) implies the importance of chemical structure of surface molecules, specifically the interactions between surface and surrounding water molecules on protein adsorption. Oxidized dextrans are potential poly(ethylene glycol)-alternatives for nonfouling applications. PMID:16952261

Metastability in plyometric training on unstable surfaces: a pilot study

PubMed Central

2014-01-01

Background In the past, plyometric training (PT) has been predominantly performed on stable surfaces. The purpose of this pilot study was to examine effects of a 7-week lower body PT on stable vs. unstable surfaces. This type of exercise condition may be denoted as metastable equilibrium. Methods Thirty-three physically active male sport science students (age: 24.1 ± 3.8 years) were randomly assigned to a PT group (n = 13) exercising on stable (STAB) and a PT group (n = 20) on unstable surfaces (INST). Both groups trained countermovement jumps, drop jumps, and practiced a hurdle jump course. In addition, high bar squats were performed. Physical fitness tests on stable surfaces (hexagonal obstacle test, countermovement jump, hurdle drop jump, left-right hop, dynamic and static balance tests, and leg extension strength) were used to examine the training effects. Results Significant main effects of time (ANOVA) were found for the countermovement jump, hurdle drop jump, hexagonal test, dynamic balance, and leg extension strength. A significant interaction of time and training mode was detected for the countermovement jump in favor of the INST group. No significant improvements were evident for either group in the left-right hop and in the static balance test. Conclusions These results show that lower body PT on unstable surfaces is a safe and efficient way to improve physical performance on stable surfaces. PMID:25089202

Protein immobilization onto various surfaces using a polymer-bound isocyanate

NASA Astrophysics Data System (ADS)

Kang, Hyun-Jin; Cha, Eun Ji; Park, Hee-Deung

2015-01-01

Silane coupling agents have been widely used for immobilizing proteins onto inorganic surfaces. However, the immobilization method using silane coupling agents requires several treatment steps, and its application is limited to only surfaces containing hydroxyl groups. The aim of this study was to develop a novel method to overcome the limitations of the silane-based immobilization method using a polymer-bound isocyanate. Initially, polymer-bound isocyanate was dissolved in organic solvent and then was used to dip-coat inorganic surfaces. Proteins were then immobilized onto the dip-coated surfaces by the formation of urea bonds between the isocyanate groups of the polymer and the amine groups of the protein. The reaction was verified by FT-IR in which NCO stretching peaks disappeared, and CO and NH stretching peaks appeared after immobilization. The immobilization efficiency of the newly developed method was insensitive to reaction temperatures (4-50 °C), but the efficiency increased with reaction time and reached a maximum after 4 h. Furthermore, the method showed comparable immobilization efficiency to the silane-based immobilization method and was applicable to surfaces that cannot form hydroxyl groups. Taken together, the newly developed method provides a simple and efficient platform for immobilizing proteins onto surfaces.

Molecular basis of crystal morphology-dependent adhesion behavior of mefenamic acid during tableting.

PubMed

Waknis, Vrushali; Chu, Elza; Schlam, Roxana; Sidorenko, Alexander; Badawy, Sherif; Yin, Shawn; Narang, Ajit S

2014-01-01

The molecular basis of crystal surface adhesion leading to sticking was investigated by exploring the correlation of crystal adhesion to oxidized iron coated atomic force microscope (AFM) tips and bulk powder sticking behavior during tableting of two morphologically different crystals of a model drug, mefenamic acid (MA), to differences in their surface functional group orientation and energy. MA was recrystallized into two morphologies (plates and needles) of the same crystalline form. Crystal adhesion to oxidized iron coated AFM tips and bulk powder sticking to tablet punches was assessed using a direct compression formulation. Surface functional group orientation and energies on crystal faces were modeled using Accelrys Material Studio software. Needle-shaped morphology showed higher sticking tendency than plates despite similar particle size. This correlated with higher crystal surface adhesion of needle-shaped morphology to oxidized iron coated AFM probe tips, and greater surface energy and exposure of polar functional groups. Higher surface exposure of polar functional groups correlates with higher tendency to stick to metal surfaces and AFM tips, indicating involvement of specific polar interactions in the adhesion behavior. In addition, an AFM method is identified to prospectively assess the risk of sticking during the early stages of drug development.

The In vitro Evaluation of the effect of xyliwhite, probiotic, and the conventional toothpastes on the enamel roughness and microhardness.

PubMed

Maden, E Arat; Altun, C; Polat, G Guven; Basak, F

2018-03-01

The aim of this study was to evaluate the effect of fluoride, Xylitol, Probiotic, and Whitening toothpastes on the permanent teeth enamel roughness and microhardness. One hundred and twenty teeth were randomly divided into 2 groups, each group having 60 samples. G1: The group in which enamel roughness was examined (n = 60). G2: The group in which enamel microhardness was examined (n = 60). Then, these groups were randomly divided into 4 groups among themselves (n = 15). Each group was brushed using four different toothpastes for 1 week with a battery-powered toothbrush in the morning and evening for 2 min. Vicker's hardness tester was used to measure the changes in microhardness, and the profilometer was used to measure the changes in surface roughness. No statistically significant differences were found on surface roughness and microhardness values measured after tooth brushing process in group brushed with Colgate MaxFresh toothpaste (P > 0.01). Statistically significant decrease was observed on Vicker's hardness values measured after tooth brushing process in groups brushed with Ipana White Power Carbonate toothpaste, Xyliwhite Toothpaste Gel, and Periobiotic Probiotic Toothpaste (P < 0.01). Statistically significant increase was observed on surface roughness values in groups brushed with Ipana White Power Carbonate toothpaste, Xyliwhite Toothpaste Gel, Periobiotic Probiotic Toothpaste (P < 0.01). As a result, Colgate MaxFresh abrasive-free toothpaste with fluoride has no effect on permanent tooth enamel surface roughness and microhardness. Xyliwhite, Periobiotic, and Ipana White Power Carbonate-containing abrasive toothpastes led to changes negatively on permanent tooth enamel surface roughness and microhardness.

Modulatory effects by neodymium-doped yttrium aluminum garnet laser on fibroblast attachment to single rooted tooth surfaces following ultrasonic scaling and root planning: An in vitro study

PubMed Central

Negi, Shanta; Krishnamurthy, Malathi; Ganji, Kiran Kumar; Pendor, Sunil

2015-01-01

Context: One of the most important goals of periodontal therapy is connective tissue reattachment to previously diseased root surfaces. In the recent years, laser therapy has been considered as an important tool in improving the treatment of periodontal disease. Aims: To evaluate the neodymium-doped yttrium aluminum garnet (Nd: YAG) lasers effects on root surfaces affected by periodontal disease and compare this treatment with scaling and root planning (SRP) in terms of fibroblast attachment. Materials and Methods: A sample of 30 single-rooted human teeth extracted because of advanced periodontal disease was used in this study. Sixty specimens obtained by longitudinal sectioning were randomly divided in three groups. Group A control (untreated); Group B SRP; Group C laser (Nd: YAG) and ultrasonic scaling. All specimens were incubated with fibroblast suspension and then fixed and observed under scanning electron microscope. Results: With a median of 8, the control group (Group A) exhibited the least number of total fibroblasts among all the three groups. The laser and scaling - treated group (Group C) showed the highest number of fibroblasts (median = 49, mean ± standard deviation [SD] = 48.28 ± 17.18), followed by SRP only (Group B, median = 22, mean ± SD = 22.24 ± 8.67). Conclusions: Nd: YAG laser irradiation at specific energy densities can be used as a useful tool to condition the root surfaces, enhancing fibroblast attachment. Hence aiding in re-establishment of the connective tissue attachment to the root surfaces of previously diseased teeth. PMID:25810589

Topically applied 1% voriconazole induces dysplastic changes on the ocular surface: animal study.

PubMed

Arikan, Gul; Karatas, Ezgi; Lebe, Banu; Ayhan, Ziya; Utine, Canan Asli; Kutsoylu, Oya Eren; Gunenc, Uzeyir; Yilmaz, Osman

2018-04-26

To identify the risk of inducing ocular surface dysplasia following topical administration of 1% voriconazole eye drop. Fourteen noninflamed healthy eyes of 14 white adult New Zealand rabbits were included in the study. The rabbits were randomly divided into two groups comprised of 7 rabbits each. Group 1 received topical 1% voriconazole and Group 2 received topical saline as the control group. In all animals, right eye was selected for the study. In Group 1 (Voriconazole Group), single drop of voriconazole was instilled every 10 min consecutively for 17 times a day for 60 days. In Group 2 (Control Group), single drop of saline was instilled every 10 min consecutively for 17 times a day for 60 days. At two months, animals were sacrificed and study eyes were enucleated with the eyelids. The specimens were stained with hematoxylin-eosin and histopathologic changes in cornea, bulbar and palpebral conjunctiva were evaluated under light microscope. There were no macroscopically visible lesions on the ocular surface of any rabbits. Histopathological evaluation showed mild to moderate dysplasia localized mainly in the limbus and extending to the adjacent cornea and bulbar conjunctiva in all rabbits in Voriconazole Group. Severe dysplasia or carcinoma in situ was not observed. In the Control Group, dysplasia was not observed, at all. This animal study provides a possible relationship between topically administered 1% voriconazole and ocular surface dysplasia. We recommend ophthalmologists to be aware of the risk of ocular surface dysplasia in patients received voriconazole eye drop.

Effect of finishing instrumentation using NiTi hand files on volume, surface area and uninstrumented surfaces in C-shaped root canal systems.

PubMed

Amoroso-Silva, P; Alcalde, M P; Hungaro Duarte, M A; De-Deus, G; Ordinola-Zapata, R; Freire, L G; Cavenago, B C; De Moraes, I G

2017-06-01

To assess the effect of 90°-oscillatory instrumentation with hand files on several morphological parameters (volume, surface area and uninstrumented surface) in C-shaped root canals after instrumentation using a single-file reciprocation system (Reciproc; VDW, Munich, Germany) and a Self-Adjusting File System (SAF; ReDent Nova, Ra'anana, Israel). Twenty mandibular second molars with C-shaped canals and C1 canal configurations were divided into two groups (n = 10) and instrumented with Reciproc and SAF instruments. A size 30 NiTi hand K-file attached to a 90°-oscillatory motion handpiece was used as final instrumentation in both groups. The specimens were scanned using micro-computed tomography after all procedures. Volume, surface area increase and uninstrumented root canal surface were analysed using CTAn software (Bruker-microCT, Kontich, Belgium). Also, the uninstrumented root canal surface was calculated for each canal third. All values were compared between groups using the Mann-Whitney test and within groups using the Wilcoxon's signed-rank test. Instrumentation with Reciproc significantly increased canal volume compared with instrumentation with SAF. Additionally, the canal volumes were significantly increased after 90°-oscillatory instrumentation (between and within group comparison; (P < 0.05)). Regarding the increase in surface area after all instrumentation protocols, statistical analysis only revealed significant differences in the within groups comparison (P < 0.05). Reciproc and SAF instrumentation yielded an uninstrumented root canal surface of 28% and 34%, respectively, which was not significantly different (P > 0.05). Final oscillatory instrumentation significantly reduced the uninstrumented root canal surface from 28% to 9% (Reciproc) and from 34% to 15% (SAF; P < 0.05). The apical and middle thirds exhibited larger uninstrumented root canal surfaces after the first instrumentation that was significantly reduced after oscillatory instrumentation (P < 0.05). The Reciproc and SAF system were associated with similar morphological parameters after instrumentation of mandibular second molars with C-shaped canals except for a higher canal volume increase in the Reciproc group compared to the SAF. Furthermore, the final use of 90°-oscillatory instrumentation using NiTi hand files significantly decreased the uninstrumented canal walls that remained after Reciproc and SAF instrumentation. © 2016 International Endodontic Journal. Published by John Wiley & Sons Ltd.

Smart Biointerface with Photoswitched Functions between Bactericidal Activity and Bacteria-Releasing Ability.

PubMed

Wei, Ting; Zhan, Wenjun; Yu, Qian; Chen, Hong

2017-08-09

Smart biointerfaces with capability to regulate cell-surface interactions in response to external stimuli are of great interest for both fundamental research and practical applications. Smart surfaces with "ON/OFF" switchability for a single function such as cell attachment/detachment are well-known and useful, but the ability to switch between two different functions may be seen as the next level of "smart". In this work reported, a smart supramolecular surface capable of switching functions reversibly between bactericidal activity and bacteria-releasing ability in response to UV-visible light is developed. This platform is composed of surface-containing azobenzene (Azo) groups and a biocidal β-cyclodextrin derivative conjugated with seven quaternary ammonium salt groups (CD-QAS). The surface-immobilized Azo groups in trans form can specially incorporate CD-QAS to achieve a strongly bactericidal surface that kill more than 90% attached bacteria. On irradiation with UV light, the Azo groups switch to cis form, resulting in the dissociation of the Azo/CD-QAS inclusion complex and release of dead bacteria from the surface. After the kill-and-release cycle, the surface can be easily regenerated for reuse by irradiation with visible light and reincorporation of fresh CD-QAS. The use of supramolecular chemistry represents a promising approach to the realization of smart, multifunctional surfaces, and has the potential to be applied to diverse materials and devices in the biomedical field.

Surface field theories of point group symmetry protected topological phases

NASA Astrophysics Data System (ADS)

Huang, Sheng-Jie; Hermele, Michael

2018-02-01

We identify field theories that describe the surfaces of three-dimensional bosonic point group symmetry protected topological (pgSPT) phases. The anomalous nature of the surface field theories is revealed via a dimensional reduction argument. Specifically, we study three different surface field theories. The first field theory is quantum electrodynamics in three space-time dimensions (QED3) with four flavors of fermions. We show this theory can describe the surfaces of a majority of bosonic pgSPT phases protected by a single mirror reflection, or by Cn v point group symmetry for n =2 ,3 ,4 ,6 . The second field theory is a variant of QED3 with charge-1 and charge-3 Dirac fermions. This field theory can describe the surface of a reflection symmetric pgSPT phase built by placing an E8 state on the mirror plane. The third field theory is an O (4 ) nonlinear sigma model with a topological theta term at θ =π , or, equivalently, a noncompact CP1 model. Using a coupled wire construction, we show this is a surface theory for bosonic pgSPT phases with U (1 ) ×Z2P symmetry. For the latter two field theories, we discuss the connection to gapped surfaces with topological order. Moreover, we conjecture that the latter two field theories can describe surfaces of more general bosonic pgSPT phases with Cn v point group symmetry.

Surface zwitterionization: Effective method for preventing oral bacterial biofilm formation on hydroxyapatite surfaces

NASA Astrophysics Data System (ADS)

Lee, Myoungjin; Kim, Heejin; Seo, Jiae; Kang, Minji; Kang, Sunah; Jang, Joomyung; Lee, Yan; Seo, Ji-Hun

2018-01-01

In this study, we conducted surface zwitterionization of hydroxyapatite (HA) surfaces by immersing them in the zwitterionic polymer solutions to provide anti-bacterial properties to the HA surface. Three different monomers containing various zwitterionic groups, i.e., phosphorylcholine (PC), sulfobetaine (SB), and carboxybetaine (CB), were copolymerized with the methacrylic monomer containing a Ca2+-binding moiety, using the free radical polymerization method. As a control, functionalization of the copolymer containing the Ca2+-binding moiety was synthesized using a hydroxy group. The stable immobilization of the zwitterionic functional groups was confirmed by water contact angle analysis and X-ray photoelectron spectroscopy (XPS) measurement conducted after the sonication process. The zwitterionized HA surface showed significantly decreased protein adsorption, whereas the hydroxyl group-coated HA surface showed limited efficacy. The anti-bacterial adhesion property was confirmed by conducting Streptococcus mutans (S. mutans) adhesion tests for 6 h and 24 h. When furanone C-30, a representative anti-quorum sensing molecule for S. mutans, was used, only a small amount of bacteria adhered after 6 h and the population did not increase after 24 h. In contrast, zwitterionized HA surfaces showed almost no bacterial adhesion after 6 h and the effect was retained for 24 h, resulting in the lowest level of oral bacterial adhesion. These results confirm that surface zwitterionization is a promising method to effectively prevent oral bacterial adhesion on HA-based materials.

Evaluate the Effect of Commercially Available Denture Cleansers on Surface Hardness and Roughness of Denture Liners at Various Time Intervals

PubMed Central

Mohammed, Hilal S.; Singh, Sumeet; Hari, Prasad A.; Amarnath, G. S.; Kundapur, Vinaya; Pasha, Naveed; Anand, M.

2016-01-01

Background and objective: Chemical cleansing by denture cleansers is first choice for denture plaque control. The most common problems while using denture cleansers are hardening, porosity, odor sorption, water sorption, solubility, and colour change, bacterial and fungal growth. Chemical cleansing procedures have been found to have an effect on the physical and mechanical properties of denture liners. Thus, this study was conducted to evaluate the effect of commercially available denture cleansers on surface hardness and roughness of acrylic and silicon based denture liners at various time interval. Method: Two autopolymerising denture liners Kooliner (acrylic) and GC reline soft (silicon) were tested with two commercially available denture cleansers, polident and efferdent plus. Total of 120 specimens were prepared and all the specimens were divided into six groups based on the relining materials and denture cleansers used. Surface hardness and surface roughness was tested using Shore A durometer and profilometer respectively at the end of day 1, day 7, day 30 and day 90. All the specimens were stored in artificial saliva throughout the study. Cleanser solution was prepared daily by adding Polident and Efferdent plus denture cleanser tablet into 250ml of enough very warm (not hot) water. Acrylic and silicon liner groups were cleansed in a solution of denture cleanser and water for 15 minutes daily, rinsed with water and stored in artificial saliva at room temperature. The data was analyzed with one way ANOVA and independent t-test. Result: The acrylic soft lining showed gradual hardening and increase in surface roughness after immersion in denture cleanser and also with time. Acrylic liner material showed maximum hardness and roughness with Polident followed by Efferdent plus and water (control group). Silicone lining material showed a slight difference in hardness and roughness between the test group and control group. There was a slight increase in hardness in all the groups with time. Very slight increase in mean surface roughness of all the silicon liner groups from day 1 to day 90 was observed. A statistically significant change was noted between and within the all silicon liner groups on day 7, day 30 and day 90. Conclusion: The average surface hardness and surface roughness were lower in silicon liner material than acrylic liner material. Maximum surface roughness was noted by Polident followed by Efferdent Plus and Water for both acrylic liner group and silicon liner group. PMID:28190983

Optimization of amino group density on surfaces of titanium dioxide nanoparticles covalently bonded to a silicone substrate for antibacterial and cell adhesion activities.

PubMed

Okada, Masahiro; Yasuda, Shoji; Kimura, Tsuyoshi; Iwasaki, Mitsunobu; Ito, Seishiro; Kishida, Akio; Furuzono, Tsutomu

2006-01-01

A composite consisting of titanium dioxide (TiO2) particle, the surface of which was modified with amino groups, and a silicone substrate through covalent bonding at their interface was developed, and antibacterial and cell adhesion activities of the composite were evaluated. The density of the amino groups on the TiO2 particle surface was controlled by the reaction time of the modification reaction. The degradation rate of CH3CHO in the presence of the TiO2 particles under UV irradiation decreased with an increase in the amino group density on the TiO2 surface. On the other hand, the number of L929 cells adhering on the TiO2/silicone composite increased with an increase in the amino group density. From the above two results, the optimum density of amino groups for both photoreactivity and cell adhesiveness was estimated to be 2.0-4.0 molecules/nm2. The optimum amino group-modified TiO2/silicone composite sheet (amino group density, 3.0 molecules/nm2) showed an effective antibacterial activity for Escherichia coli bacteria under UV irradiation. (c) 2005 Wiley Periodicals, Inc

Surface shape analysis with an application to brain surface asymmetry in schizophrenia.

PubMed

Brignell, Christopher J; Dryden, Ian L; Gattone, S Antonio; Park, Bert; Leask, Stuart; Browne, William J; Flynn, Sean

2010-10-01

Some methods for the statistical analysis of surface shapes and asymmetry are introduced. We focus on a case study where magnetic resonance images of the brain are available from groups of 30 schizophrenia patients and 38 controls, and we investigate large-scale brain surface shape differences. Key aspects of shape analysis are to remove nuisance transformations by registration and to identify which parts of one object correspond with the parts of another object. We introduce maximum likelihood and Bayesian methods for registering brain images and providing large-scale correspondences of the brain surfaces. Brain surface size-and-shape analysis is considered using random field theory, and also dimension reduction is carried out using principal and independent components analysis. Some small but significant differences are observed between the the patient and control groups. We then investigate a particular type of asymmetry called torque. Differences in asymmetry are observed between the control and patient groups, which add strength to other observations in the literature. Further investigations of the midline plane location in the 2 groups and the fitting of nonplanar curved midlines are also considered.

Role of oxygen functional groups for structure and dynamics of interfacial water on low rank coal surface: a molecular dynamics simulation

NASA Astrophysics Data System (ADS)

You, Xiaofang; Wei, Hengbin; Zhu, Xianchang; Lyu, Xianjun; Li, Lin

2018-07-01

Molecular dynamics simulations were employed to study the effects of oxygen functional groups for structure and dynamics properties of interfacial water molecules on the subbituminous coal surface. Because of complex composition and structure, the graphite surface modified by hydroxyl, carboxyl and carbonyl groups was used to represent the surface model of subbituminous coal according to XPS results, and the composing proportion for hydroxyl, carbonyl and carboxyl is 25:3:5. The hydration energy with -386.28 kJ/mol means that the adsorption process between water and coal surface is spontaneous. Density profiles for oxygen atoms and hydrogen atoms indicate that the coal surface properties affect the structural and dynamic characteristics of the interfacial water molecules. The interfacial water exhibits much more ordering than bulk water. The results of radial distribution functions, mean square displacement and local self-diffusion coefficient for water molecule related to three oxygen moieties confirmed that the water molecules prefer to absorb with carboxylic groups, and adsorption of water molecules at the hydroxyl and carbonyl is similar.

Proton NMR studies of functionalized nanoparticles in aqueous environments

NASA Astrophysics Data System (ADS)

Tataurova, Yulia Nikolaevna

Nanoscience is an emerging field that can provide potential routes towards addressing critical issues such as clean and sustainable energy, environmental remediation and human health. Specifically, porous nanomaterials, such as zeolites and mesoporous silica, are found in a wide range of applications including catalysis, drug delivery, imaging, environmental protection, and sensing. The characterization of the physical and chemical properties of nanocrystalline materials is essential to the realization of these innovative applications. The great advantage of porous nanocrystals is their increased external surface area that can control their biological, chemical and catalytic activities. Specific functional groups synthesized on the surface of nanoparticles are able to absorb heavy metals from the solution or target disease cells, such as cancer cells. In these studies, three main issues related to functionalized nanomaterials will be addressed through the application of nuclear magnetic resonance (NMR) techniques including: 1) surface composition and structure of functionalized nanocrystalline particles; 2) chemical properties of the guest molecules on the surface of nanomaterials, and 3) adsorption and reactivity of surface bound functional groups. Nuclear magnetic resonance (NMR) is one of the major spectroscopic techniques available for the characterization of molecular structure and conformational dynamics with atomic level detail. This thesis deals with the application of 1H solution state NMR to porous nanomaterial in an aqueous environment. Understanding the aqueous phase behavior of functionalized nanomaterials is a key factor in the design and development of safe nanomaterials because their interactions with living systems are always mediated through the aqueous phase. This is often due to a lack of fundamental knowledge in interfacial chemical and physical phenomena that occur on the surface of nanoparticles. The use of solution NMR spectroscopy results in high-resolution NMR spectra. This technique is selective for protons on the surface organic functional groups due to their motional averaging in solution. In this study, 1H solution NMR spectroscopy was used to investigate the interface of the organic functional groups in D2O. The pKa for these functional groups covalently bound to the surface of nanoparticles was determined using an NMR-pH titration method based on the variation in the proton chemical shift for the alkyl group protons closest to the amine group with pH. The adsorption of toxic contaminants (chromate and arsenate anions) on the surface of functionalized silicalite-1 and mesoporous silica nanoparticles has been studied by 1H solution NMR spectroscopy. With this method, the surface bound contaminants are detected. The analysis of the intensity and position of these peaks allows quantitative assessment of the relative amounts of functional groups with adsorbed metal ions. These results demonstrate the sensitivity of solution NMR spectroscopy to the electronic environment and structure of the surface functional groups on porous nanomaterials.

[Effects of different surface modifications on micro-structure and adhesion of zirconia ceramic: an in vitro study].

PubMed

Siwen, Li; Shishi, Li; Yanhong, Wang; Hongmei, Ma

2017-02-01

This study evaluated the effect of different mechanical-chemical surface treatments on the characteristics, microstructure, and composition of zirconia ceramics and on the zirconia-dentin adhesion. The sintered commercial zirconia blocks (IPS e.max ZirCAD) were sectioned into 126 beams (6 mm×6 mm×5 mm) and randomly assigned to seven experimental groups (n=18). The zirconia block specimens were further treated as follows: (A) untreated, as control; (B) sandblasted with 50 μm Al2O3; (C) sandblasted with 50 μm Al2O3+30 μm silica powder; (D) sandblasted with 50 μm Al2O3+30% silica-sol coating; (E) sandblasted with 110 μm Al2O3; (F) sandblasted with 110 μm Al2O3+30 μm silica powder; and (G) sandblasted with 110 μm Al2O3+30% silica-sol coating. The surface roughness (Ra) of zirconia ceramics using X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) after seven surface treatments was analyzed. Seventy specimens of dentin surfaces were prepared. A dual-cure resin cement was applied into zirconia surfaces with its corresponding adhesive components to dentin. Shear bond strength (SBS) of each sample was measured using a universal testing machine. The data were analyzed by ANOVA using SPSS 17.0 software. Ra of zirconia were significantly different compared with the control group (P<0.05). The crystalline transformation from tetragonal phase to monoclinic phase was observed after surface modification. Monoclinic volume content of the heat-treated group was highest than that in other groups. The content of element Si in the heat-treated group was higher than that in other treatment groups accompanied by a decrease in elements Zr, Y, and Hf after being treated by two silica-coating methods. Air abrasion significantly increased the micro-cracks in the ceramic surface and caused the grain boundaries to disappear. A serious shrinkage of the thin silica film can be observed after sintering procedure. This process induced cracks and the film to strip away slightly from the surfaces of Y-TZP substrate. The SBS values from large to small were F and G groups, C and D groups, B and E groups (P<0.05), and control group (P<0.05). Alumina sandblasting, silica powder abrasion, and silica-sol coating affect the surface morphology, structure, and composition of the tooth. This effect can also achieve the improved micro-mechanical interlocking or chemical bonding and finally increase the bond strength between zirconia and tooth. Alumina sandblasting followed by silica coating is an effective technique to increase the bonding strength between the zirconia ceramic and dentin.
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SEM evaluation of human gingival fibroblasts growth onto CAD/CAM zirconia and veneering ceramic for zirconia

PubMed Central

Zizzari, Vincenzo; Borelli, Bruna; De Colli, Marianna; Tumedei, Margherita; Di Iorio, Donato; Zara, Susi; Sorrentino, Roberto; Cataldi, Amelia; Gherlone, Enrico Felice; Zarone, Fernando; Tetè, Stefano

2013-01-01

Summary Aim To evaluate the growth of Human Gingival Fibroblasts (HGFs) cultured onto sample discs of CAD/CAM zirconia and veneering ceramic for zirconia by means of Scanning Electron Microscope (SEM) analysis at different experimental times. Methods A total of 26 experimental discs, divided into 2 groups, were used: Group A) CAD/CAM zirconia (3Y-TZP) discs (n=13); Group B) veneering ceramic for zirconia discs (n=13). HGFs were obtained from human gingival biopsies, isolated and placed in culture plates. Subsequently, cells were seeded on experimental discs at 7,5×103/cm2 concentration and cultured for a total of 7 days. Discs were processed for SEM observation at 3h, 24h, 72h and 7 days. Results In Group A, after 3h, HGFs were adherent to the surface and showed a flattened profile. The disc surface covered by HGFs resulted to be wider in Group A than in Group B samples. At SEM observation, after 24h and 72h, differences in cell attachment were slightly noticeable between the groups, with an evident flattening of HGFs on both surfaces. All differences between Group A and group B became less significant after 7 days of culture in vitro. Conclusions SEM analysis of HGFs showed differences in terms of cell adhesion and proliferation, especially in the early hours of culture. Results showed a better adhesion and cell growth in Group A than in Group B, especially up to 72h in vitro. Differences decreased after 7 days, probably because of the rougher surface of CAD/CAM zirconia, promoting better cell adhesion, compared to the smoother surface of veneering ceramic. PMID:24611089

Microhardness of resin composites polymerized by plasma arc or conventional visible light curing.

PubMed

Park, S Ho; Krejci, I; Lutz, F

2002-01-01

This study evaluated the effectiveness of the plasma arc curing (PAC) unit for composite curing. To compare its effectiveness with conventional quartz tungsten halogen (QTH) light curing units, the microhardness of two composites (Z100 and Tetric Ceram) that had been light cured by the PAC or QTH units, were compared according to the depth from the composite surface. In addition, linear polymerization shrinkage was compared using a custom-made linometer between composites which were light cured by PAC or QTH units. Measuring polymerization shrinkage for two resin composites (Z100 and Tetric Ceram) was performed after polymerization with either QTH or PAC units. In the case of curing with the PAC unit, the composite was light cured with Apollo 95E for two (Group 1), three (Group 2), six (Group 3) or 2 x 6 (Group 4) seconds. For light curing with the QTH unit, the composite was light cured for 60 seconds with Optilux 500 (Group 5). The linear polymerization shrinkage of composites was determined in the linometer. Two resin composites were used to measure microhardness. Two-mm thick samples were light cured for three seconds (Group 1), six seconds (Group 2) or 12 (2 x 6) seconds (Group 3) with Apollo 95E or they were conventionally light cured with Optilux 500 for 30 seconds (Group 4) or 60 seconds (Group 5). For 3 mm thick samples, the composites were light cured for six seconds (Group 1), 12 (2 x 6) seconds (Group 2) or 18 (3 x 6) seconds (Group 3) with Apollo 95E or they were conventionally light cured with Optilux 500 for 30 seconds (Group 4) or 60 seconds (Group 5). Twenty samples were assigned to each group. The microhardness of the upper and lower surfaces was measured with a Vickers hardness-measuring instrument under load. The difference in microhardness between the upper and lower surfaces in each group was analyzed by paired t-test. For the upper or lower surfaces, one-way ANOVA with Tukey was used. For Tetric Ceram, the amount of polymerization shrinkage was lower when cured with the Apollo 95E for two or three seconds than when cured for six and 12 (2 x 6) seconds, or for 60 seconds with Optilux 500 (p<0.05). For Z100, the amount of linear polymerization shrinkage was lower when cured with the Apollo 95E for two, three and six seconds than for 12 (2 x 6) seconds with Apollo 95E or for 60 seconds with the Optilux 500 (p<0.05). The results of the microhardness test indicated that there was no statistically significant difference in microhardness between groups for the upper surface. However, for the lower surface, when the composites were light cured with Apollo 95E for three seconds as recommended by the manufacturer, microhardness of the lower surface was usually lower than that of the upper surface and did not cure sufficiently. Conclusively, when compared with conventional QTH unit, the PAC unit, Apollo 95E did not properly cure the lower composite surface when the layer thickness exceeded 2 mm. In addition, three seconds of curing time, which the manufacturer recommended, was insufficient for optimal curing of composites.

Electrical resistance behavior of oxyfluorinated graphene under oxidizing and reducing gas exposure.

PubMed

Im, Ji Sun; Bae, Tae-Sung; Shin, Eunjeong; Lee, Young-Seak

2014-03-01

The electrical resistance behavior of graphene was studied under oxidizing and reducing gas exposure. The graphene surface was modified via oxyfluorination to obtain a specific surface area and oxygen functional groups. Fluorine radicals provided improved pore structure and introduction of an oxygen functional group. A high-performance gas sensor was obtained based on enlarged target gas adsorption sites and an enhanced electron charge transfer between the target gas and carbon surface via improved pore structure and the introduction of oxygen functional groups, respectively.

Effects of Local and Systemic Zoledronic Acid Application on Titanium Implant Osseointegration: An Experimental Study Conducted on Two Surface Types.

PubMed

Dundar, Serkan; Yaman, Ferhan; Gecor, Orhan; Cakmak, Omer; Kirtay, Mustafa; Yildirim, Tuba Talo; Karaman, Tahir; Benlidayi, Mehmet Emre

2017-06-01

The aim of this study was to evaluate the effects of local and systemic zoledronic acid (ZA) applications on titaniumoksit ceramic blasted (TiO-CB)- and sandblasted large acid-grit (SLA)-surfaced titanium implant osseointegration. Twelve New Zealand White rabbits were used in the study, divided into 6 groups: the TiO-CB (TiO-CB-CNT) (n = 2) and SLA (SLA-CNT) (n = 2) control groups in which TiO-CB- and SLA-surfaced titanium implants were surgically inserted into rabbit tibias but no treatment was applied; the TiO-CB (TiO-CB-LZA) (n = 2) and SLA (SLA-LZA) (n = 2) local ZA groups in which 1 mL of normal saline solution containing 2 mg of ZA was injected into sockets and after this the implants were integrated; and the TiO-CB (TiO-CB-SZA) (n = 2) and SLA (SLA-SZA) (n = 2) systemic ZA groups in which a single infusion of 0.1 mg/kg of ZA was administered during surgical implant insertion. Following a period of osseointegration, bone implant contact (BIC) was recorded as a proportion of the total implant surface length in direct contact with the bone. Results of this study indicate that BIC was greater in the systemic ZA application groups than in the local ZA application groups, and BIC was greater in the local ZA groups than in the controls. Statistically significant differences in BIC were not detected between the TiO-CB- and SLA-surfaced implants in all the groups. Furthermore, this study did not reveal significant differences between the 2 types of surfaces due to similar average roughness values. Overall, systemic ZA application was found to be more effective in increasing BIC than local ZA application based on the results obtained by testing 2 implant surfaces.

Measuring surface temperature and grading pathological changes of airway tissue in a canine model of inhalational thermal injury.

PubMed

Zhao, Ran; Di, La-na; Zhao, Xiao-zhuo; Wang, Cheng; Zhang, Guo-an

2013-06-01

Airway tissue shows unexpected invulnerability to heated air. The mechanisms of this phenomenon are open to debate. This study was designed to measure the surface temperatures at different locations of the airway, and to explore the relationship between the tissue's surface temperature and injury severity. Twenty dogs were randomly divided into four groups, including three experimental groups (six dogs in each) to inhale heated air at 70-80 °C (group I), 150-160 °C (group II) and 310-320 °C (group III) and a control group (two dogs, only for histological observation). Injury time was 20 min. Mucosal surface temperatures of the epiglottis (point A), cricoid cartilage (point B) and lower trachea (point C) were measured. Dogs in group I-III were divided into three subgroups (two in each), to be assayed at 12, 24 and 36 h after injury, respectively. For each dog, four tissue parts (epiglottis, larynx, lower trachea and terminal bronchiole) were microscopically observed and graded according to an original pathological scoring system (score range: 0-27). Surface temperatures of the airway mucosa increased slowly to 40.60±3.29 °C, and the highest peak temperature was 48.3 °C (group III, point A). The pathological score of burned tissues was 4.12±4.94 (0.0-18.0), suggesting slight to moderate injuries. Air temperature and airway location both influenced mucosal temperature and pathological scores very significantly, and there was a very significant positive correlation between tissue temperature and injury severity. Compared to the inhalational air hyperthermia, airway surface temperature was much lower, but was still positively correlated with thermal injury severity. Copyright © 2012 Elsevier Ltd and ISBI. All rights reserved.

Evaluation of Temperature Elevation During Root Canal Treatment with Dual Wavelength Laser: 2780 nm Er,Cr:YSGG and 940 nm Diode.

PubMed

Al-Karadaghi, Tamara Sardar; Gutknecht, Norbert; Jawad, Hussein A; Vanweersch, Leon; Franzen, Rene

2015-09-01

The purpose of this study was to evaluate the effects of dual wavelength (2780 nm Er,Cr:YSGG and 940 nm diode) laser with radial firing tip (RFT) on the external root surface and sub-surfaces, in terms of temperature changes during laser-assisted root canal treatment. A significant factor that may limit the use of lasers in endodontics is the possible thermal injury to tooth supporting structures. A total of 50 sound single-rooted extracted teeth were divided randomly into two groups (n = 25). Group A, irradiated with Er,Cr:YSGG laser at 1.06 W, 50 Hz, and 50 μs was a control group, and group B was irradiated with dual wavelength of Er,Cr:YSGG laser with the same settings as group A and a diode laser of 0.51 W at 4 ms and 10 ms pulse duration. K-type thermocouples were used to record temperature changes at the cervical, middle, and apical root thirds, on root surfaces and sub-surfaces, arising from delivery of laser energy through RFT. Temperature elevation in group B was significantly higher in the middle and apical thirds of the prepared samples than in group A (p < 0.0001). Group B presented a mean temperature elevation of 5.07°C on the apical surface region corresponding to a 1.48 mm dentin thickness, whereas a mean temperature increase of 7.72°C was recorded corresponding to dentin thickness of 0.95 mm. Within the studied parameters, the dual wavelength laser did not result in adverse thermal changes on the external root surface in vitro.

Quantitative blood group typing using surface plasmon resonance.

PubMed

Then, Whui Lyn; Aguilar, Marie-Isabel; Garnier, Gil

2015-11-15

The accurate and reliable typing of blood groups is essential prior to blood transfusion. While current blood typing methods are well established, results are subjective and heavily reliant on analysis by trained personnel. Techniques for quantifying blood group antibody-antigen interactions are also very limited. Many biosensing systems rely on surface plasmon resonance (SPR) detection to quantify biomolecular interactions. While SPR has been widely used for characterizing antibody-antigen interactions, measuring antibody interactions with whole cells is significantly less common. Previous studies utilized SPR for blood group antigen detection, however, showed poor regeneration causing loss of functionality after a single use. In this study, a fully regenerable, multi-functional platform for quantitative blood group typing via SPR detection is achieved by immobilizing anti-human IgG antibody to the sensor surface, which binds to the Fc region of human IgG antibodies. The surface becomes an interchangeable platform capable of quantifying the blood group interactions between red blood cells (RBCs) and IgG antibodies. As with indirect antiglobulin tests (IAT), which use IgG antibodies for detection, IgG antibodies are initially incubated with RBCs. This facilitates binding to the immobilized monolayer and allows for quantitative blood group detection. Using the D-antigen as an example, a clear distinction between positive (>500 RU) and negative (<100 RU) RBCs is achieved using anti-D IgG. Complete regeneration of the anti-human IgG surface is also successful, showing negligible degradation of the surface after more than 100 regenerations. This novel approach is validated with human-sourced whole blood samples to demonstrate an interesting alternative for quantitative blood grouping using SPR analysis. Crown Copyright © 2015. Published by Elsevier B.V. All rights reserved.

The improvement of dry eye after cataract surgery by intraoperative using ophthalmic viscosurgical devices on the surface of cornea

PubMed Central

He, Yuan; Li, Jia; Zhu, Jingfen; Jie, Ying; Wang, Ningli; Wang, Jun

2017-01-01

Abstract Backgroud: This study aimed to investigate the protective effect of intraoperative used hydroxypropyl methylcellulose (HPMC 2%) on the ocular surface after cataract surgery. Methods: A total of 149 eyes (149 patients) diagnosed with age-related cataract, age 69.19 ± 9.74 years, were enrolled in this prospective, parallel-design, continuous, randomised controlled study. Patients were randomly assigned to receive HPMC 2% (study group) or balanced salt solution (control group) during the surgery to moisturize the cornea surface. The Ocular Surface Disease Index, Schirmer test without topical anesthetics, tear break-up time, and corneal fluorescein staining were assessed preoperatively, 1 day, 1 week, and 1 month after the surgery, respectively. Results: The Schirmer test value of male patients in the study group at 1 week postoperation was higher than that of male patients in the control group (P = .019). For patients diagnosed with dry eye before the surgery, Schirmer test value in the male patients in the study group at 1 month after surgery was higher than that in the male patients in the control group (P = .037). Furthermore, for the cluster of preoperative dry eye patients whose surgical time was longer than median, corneal fluorescein staining of the patients in the study group was superior to that of the patients in the control group (P = .032). Conclusion: Intraoperative use of HPMC 2% on the cornea surface could improve clinical outcomes of tear film and ocular surface health to some degree, especially in the patients diagnosed with dry eye before the surgery, male patients, and patients whose surgical time was relatively longer. PMID:29390284

The effect of Er:YAG laser irradiation on the bond stability of self-etch adhesives at different dentin depths.

PubMed

Karadas, Muhammet; Çağlar, İpek

2017-07-01

The aim of this study was to evaluate the effect of Er:YAG laser irradiation on the micro-shear bond strength of self-etch adhesives to the superficial dentin and the deep dentin before and after thermocycling. Superficial dentin and deep dentin surfaces were prepared by flattening of the occlusal surfaces of extracted human third molars. The deep or superficial dentin specimens were randomized into three groups according to the following surface treatments: group I (control group), group II (Er:YAG laser; 1.2 W), and group III (Er:YAG laser; 0.5 W). Clearfil SE Bond or Clearfil S 3 Bond was applied to each group's dentin surfaces. After construction of the composite blocks on the dentin surface, the micro-shear bond testing of each adhesive was performed at 24 h or after 15,000 thermal cycles. The data were analyzed using a univariate analysis of variance and Tukey's test (p < 0.05). Laser irradiation in superficial dentin did not significantly affect bond strength after thermocycling (p > 0.05). However, deep-dentin specimens irradiated with laser showed significantly higher bond strengths than did control specimens after thermocycling (p < 0.05). Thermocycling led to significant deterioration in the bond strengths of all deep-dentin groups. The stable bond strength after thermocycling was measured for all of the superficial-dentin groups. No significant difference was found between the 0.5 and 1.2 W output power settings. In conclusion, the effect of laser irradiation on the bond strength of self-etch adhesives may be altered by the dentin depth. Regardless of the applied surface treatment, deep dentin showed significant bond degradation.

[Influence of surface chemical properties and pore structure characteristics of activated carbon on the adsorption of nitrobenzene from aqueous solution].

PubMed

Liu, Shou-Xin; Chen, Xi; Zhang, Xian-Quan

2008-05-01

Commercial activated carbon was treated by HNO3 oxidation and then subsequently heat treated under N2 atmosphere. Effect of surface chemical properties and pore structure on the adsorption performance of nitrobenzene was investigated. N2/77K adsorption isotherm and scanning electron microscopy (SEM) were used to characterize the pore structure and surface morphology of carbon. Boehm titration, Fourier transform infrared spectroscopy (FTIR), the point of zero charge (pH(PZC)) measurement and elemental analysis were used to characterize the surface properties. The results reveal that HNO3 oxidation can modify the surface chemical properties, increase the number of acidic surface oxygen-containing groups and has trivial effect on the pore structure of carbon. Further heat treatment can cause the decomposition of surface oxygen-containing groups, and increase the external surface area and the number of mesopores. Adsorption capacity of nitrobenzene on AC(NO-T), AC(raw) and AC(NO) was 1011.31, 483.09 and 321.54 mg x g(-1), respectively. Larger external surface area and the number of meso-pores, together with the less acid surface oxygen-containing groups were the main reason for the larger adsorption capacity AC(NO-T).