Science.gov

Sample records for pendant hydroxyl groups

  1. Facile synthesis and characterization of novel biodegradable amphiphilic block copolymers bearing pendant hydroxyl groups.

    PubMed

    Hu, Gaicen; Fan, Xiaoshan; Xu, Bingcan; Zhang, Delong; Hu, Zhiguo

    2014-10-01

    Novel amphiphilic block copolymers bearing pendant hydroxyl groups polylactide-b-poly(3,3-bis(Hydroxymethyl-triazolylmethyl) oxetane)-b-polylactide (PLA-b-PHMTYO-b-PLA) were synthesized via a facile and efficient method. First, the block copolymer intermediates polylactide-b-poly(3,3-Diazidomethyloxetane)-b-polylactide (PLA-b-PBAMO-b-PLA) were synthesized through ring-opening polymerization of lactide using PBAMO as a macroinitiator. Following "Click" reaction of PLA-b-PBAMO-b-PLA with propargyl alcohol provided the targeted amphiphilic block copolymers PLA-b-PHMTYO-b-PLA with pendant hydroxyl groups. The composition and structure of prepared copolymers were characterized by (1)H nuclear magnetic resonance ((1)H NMR) spectroscopy, Fourier transform infrared (FT-IR) and gel permeation chromatography (GPC). The self-assembly behavior of the copolymers in water was investigated by transmission electron microscope (TEM), dynamic light scattering (DLS) and static light scattering (SLS). The results showed that the novel copolymers PLA-b-PHMTYO-b-PLA self-assembled into spherical micelles with diameters ranging from 100 nm to 200 nm in aqueous solution. These copolymers also exhibited low critical micellar concentrations (CMC: 6.9 × 10(-4)mg/mL and 3.9 × 10(-5)mg/mL, respectively). In addition, the in vitro cytotoxicity of these copolymers was determined in the presence of L929 cells. The results showed that the block copolymers PLA-b-PHMTYO-b-PLA exhibited better biocompatibility. Therefore, these well-defined copolymers are expected to find some applications in drug delivery or tissue engineering. PMID:25175206

  2. Polyimides with pendant alkyl groups

    NASA Technical Reports Server (NTRS)

    Jensen, B. J.; Young, P. R.

    1982-01-01

    The effect on selected polyimide properties when pendant alkyl groups were attached to the polymer backbone was investigated. A series of polymers were prepared using benzophenone tetracarboxylic acid dianhydride (BTDA) and seven different p-alkyl-m,p'-diaminobenzophenone monomers. The alkyl groups varied in length from C(1) (methyl) to C(9) (nonyl). The polyimide prepared from BTDA and m,p'-diaminobenzophenone was included as a control. All polymers were characterized by various chromatographic, spectroscopic, thermal, and mechanical techniques. Increasing the length of the pendant alkyl group resulted in a systematic decrease in glass transition temperature (Tg) for vacuum cured films. A 70 C decrease in Tg to 193 C was observed for the nonyl polymer compared to the Tg for the control. A corresponding systematic increase in Tg indicative of crosslinking, was observed for air cured films. Thermogravimetric analysis revealed a slight sacrifice in thermal stability with increasing alkyl length. No improvement in film toughness was observed.

  3. Polyphenylquinoxalines containing pendant phenylethynyl and ethynyl groups. [for thermoplastic resins

    NASA Technical Reports Server (NTRS)

    Hergenrother, P. M. (Inventor)

    1983-01-01

    Poly(phenylquinoxaline) prepolymers containing pendant phenylethynyl and ethynyl groups are disclosed along with the process for forming these polymers. Monomers and the process for producing same that are employed to prepare the polymers are also disclosed.

  4. On the rigidity of polynorbornenes with dipolar pendant groups.

    PubMed

    Lin, Wei-Yu; Murugesh, Modachur G; Sudhakar, Sundarraj; Yang, Hsiao-Ching; Tai, Hwan-Ching; Chang, Chia-Seng; Liu, Yi-Hung; Wang, Yu; Chen, I-Wen Peter; Chen, Chun-Hsien; Luh, Tien-Yau

    2005-12-16

    A range of polynorbornenes (PNBs) with fused dipolar pendant groups at C-5,6 positions was synthesized by ring-opening metathesis polymerization catalyzed by a ruthenium carbene complex (Grubbs I). Photophysical studies, EFISH measurements, and atomic force microscopy images have been used to investigate the structures and morphology of these polymers. These results suggest that the polymers may adopt rigid rod-like structures. The presence of the double bonds in PNBs appeared to be indispensable for the rigidity of the polymers. Interaction between unsaturated pendant groups may result in coherent alignment leading to a rod-like structure. PMID:16278915

  5. Polyimide characterization studies - Effect of pendant alkyl groups

    NASA Technical Reports Server (NTRS)

    Jensen, B. J.; Young, P. R.

    1984-01-01

    The effect on selected polyimide properties when pendant alkyl groups were attached to the polymer backbone was investigated. A series of polymers were prepared using benzophenone tetracarboxylic acid dianhydride (BTDA) and seven different p-alkyl-m,p'-diaminobenzophenone monomers. The alkyl groups varied in length from C(1) (methyl) to C(9) (nonyl). The polyimide prepared from BTDA and m,p'-diaminobenzophenone was included as a control. All polymers were characterized by various chromatographic, spectroscopic, thermal, and mechanical techniques. Increasing the length of the pendant alkyl group resulted in a systematic decrease in glass transition temperature (Tg) for vacuum cured films. A 70 C decrease in Tg to 193 C was observed for the nonyl polymer compared to the Tg for the control. A corresponding systematic increase in Tg indicative of crosslinking, was observed for air cured films. Thermogravimetric analysis revealed a slight sacrifice in thermal stability with increasing alkyl length. No improvement in film toughness was observed.

  6. Synthesis and photooxidation of styrene copolymer bearing camphorquinone pendant groups

    PubMed Central

    Moszner, Norbert; Lukáč, Ivan

    2012-01-01

    Summary (±)-10-Methacryloyloxycamphorquinone (MCQ) was synthesized from (±)-10-camphorsulfonic acid either by a known seven-step synthetic route or by a novel, shorter five-step synthetic route. MCQ was copolymerized with styrene (S) and the photochemical behavior of the copolymer MCQ/S was compared with that of a formerly studied copolymer of styrene with monomers containing the benzil (BZ) moiety (another 1,2-dicarbonyl). Irradiation (λ > 380 nm) of aerated films of styrene copolymers with monomers containing the BZ moiety leads to the insertion of two oxygen atoms between the carbonyl groups of BZ and to the formation of benzoyl peroxide (BP) as pendant groups on the polymer backbone. An equivalent irradiation of MCQ/S led mainly to the insertion of only one oxygen atom between the carbonyl groups of camphorquinone (CQ) and to the formation of camphoric anhydride (11) covalently bound to the polymer backbone. While the decomposition of pendant BP groups formed in irradiated films of styrene copolymers with pendant BZ groups leads to crosslinking, only small molecular-weight changes in irradiated MCQ/S were observed. PMID:22509202

  7. Ion Conduction in Polymerized Ionic Liquids with Different Pendant Groups

    SciTech Connect

    Fan, Fei; Wang, Yangyang; Hong, Tao; Heres, Maximilian F; Saito, Tomonori; Sokolov, Alexei P

    2015-01-01

    Polymerized ionic liquids (PolyILs) are promising candidates for energy storage and electrochemical devices applications. Understanding their ionic transport mechanism is the key for designing highly conductive PolyILs. By using broadband dielectric spectroscopy (BDS), rheology, and differential scanning calorimetry (DSC), a systematic study has been carried out to provide a better understanding of the ionic transport mechanism in PolyILs with different pendant groups. The variation of pendant groups results in different dielectric, mechanical, and thermal properties of these PolyILs. The Walden plot analysis shows that the data points for all these PolyILs fall above the ideal Walden line, and the deviation from the ideal line increases upon approaching the glass transition temperature (Tg). The conductivity for these PolyILs at their Tgs are much higher than the usually reported value 10 15 S/cm for polymer electrolytes, in which the ionic transport is closely coupled to the segmental dynamics. These results indicate a decoupling of ionic conductivity from the segmental relaxation in these materials. The degree of decoupling increases with the increase of the fragility of polymer segmental relaxation. We relate this observation to a decrease in polymer packing efficiency with an increase in fragility.

  8. Ion Conduction in Polymerized Ionic Liquids with Different Pendant Groups

    DOE PAGESBeta

    Fan, Fei; Wang, Yangyang; Hong, Tao; Heres, Maximilian F; Saito, Tomonori; Sokolov, Alexei P

    2015-01-01

    Polymerized ionic liquids (PolyILs) are promising candidates for energy storage and electrochemical devices applications. Understanding their ionic transport mechanism is the key for designing highly conductive PolyILs. By using broadband dielectric spectroscopy (BDS), rheology, and differential scanning calorimetry (DSC), a systematic study has been carried out to provide a better understanding of the ionic transport mechanism in PolyILs with different pendant groups. The variation of pendant groups results in different dielectric, mechanical, and thermal properties of these PolyILs. The Walden plot analysis shows that the data points for all these PolyILs fall above the ideal Walden line, and the deviationmore » from the ideal line increases upon approaching the glass transition temperature (Tg). The conductivity for these PolyILs at their Tgs are much higher than the usually reported value 10 15 S/cm for polymer electrolytes, in which the ionic transport is closely coupled to the segmental dynamics. These results indicate a decoupling of ionic conductivity from the segmental relaxation in these materials. The degree of decoupling increases with the increase of the fragility of polymer segmental relaxation. We relate this observation to a decrease in polymer packing efficiency with an increase in fragility.« less

  9. Polymer containing pendant silyl ether groups useful in enhanced oil recovery using CO sub 2 flooding

    SciTech Connect

    Irani, C.A.; Harris, T.V.; Pretzer, W.R.

    1991-06-11

    This patent describes improvement in a method for recovering oil from an underground oil-bearing earth formation penetrated by an injection well and a producing well, in which method carbon dioxide is injected into the formation to displace oil towards the producing well from which oil is produced to the surface. The improvement comprises injecting into the formation carbon dioxide, the viscosity of which is increased at least three- fold by the presence of a sufficient amount of a polymer containing pendant groups selected from the group consisting of silyl ether groups and polydialkylsiloxane groups and a sufficient amount of a cosolvent to form a solution of the polymer in the carbon dioxide, wherein the minimum solubility parameter of the polymer is reduced to 6.85 (cal/cc){sup 1/2} or less by control of the number of pendant groups and by the selection of the pendant groups.

  10. Polymer containing pendant tertiary alkyl amine groups useful in enhanced oil recovery using

    SciTech Connect

    Irani, C.A.; Harris, T.V.; Pretzer, W.R.

    1990-08-07

    This patent describes an improvement in a method for recovering oil from an underground oil-bearing earth formation penetrated by an injection well and a producing well, in which method carbon dioxide is injected into the formation to displace oil towards the producing well from which oil is produced to the surface. It comprises: injecting into the formation carbon dioxide, the viscosity of which is increased at least three-fold by the presence of a sufficient amount of a polymer containing pendant tertiary alkyl amine groups and a sufficient amount of a cosolvent to form a solution of the polymer in the carbon dioxide, wherein the minimum solubility parameter of the polymer is reduced to 6.85 (cal/cc)1/2 or less by control of the number of pendant tertiary alkyl amine groups and by the selection of the tertiary alkyl amine groups.

  11. Polymer containing pendant vinyl ether groups useful in enhanced oil recovery using

    SciTech Connect

    Irani, C.A.; Harris, T.V.; Aetzer, W.R.

    1990-08-07

    This patent describes an improvement in a method for recovering oil from an underground oil-bearing earth formation penetrated by an injection well and a producing well, in which method carbon dioxide is injected into the formation to displace oil towards the producing well from which oil is produced to the surface. It comprises: injecting into the formation carbon dioxide, the viscosity of which is increased at least three-fold by the presence of a sufficient amount of polymer containing pendant vinyl ether groups and a sufficient amount of a cosolvent to form a solution of the polymer in the carbon dioxide, wherein the minimum solubility parameter of the polymer is reduced to 6.85(cal/cc)1/1/2 or less by control of the number of pendant vinyl ether groups and by the selection of the vinyl ether groups.

  12. Synthetic transformations of a pendant nitrile moiety in group 4 metallocene complexes.

    PubMed

    Pinkas, Jiří; Císařová, Ivana; Kubišta, Jiří; Horáček, Michal; Lamač, Martin

    2013-05-21

    Functional group transformations at the group 4 metallocene framework have been demonstrated, which have provided relatively straightforward access to otherwise synthetically challenging derivatives. The pendant nitrile group in Ti and Zr metallocene complexes of the type [(η(5)-C5Me5)(η(5)-C5H4CMe2CH2CN)MCl2] was converted into an intramolecularly bound ketimido moiety by alkylation, which took place not only at the nitrile, but also at the metal centre. The choice of an alkylating reagent (alkyl/aryl lithium, Grignard reagent) was crucial: e.g., 2 equiv. of MeMgBr effected the alkylation only at the metal, yielding selectively complexes [(η(5)-C5Me5)(η(5)-C5H4CMe2CH2CN)MMe2], while the use of PhMgBr, PhLi, or MeLi instead gave selectively the ketimido complexes. Organyl lithium reagents were, however, not compatible with the titanocene derivatives. The metal-bound ketimides were subsequently cleaved off by the reaction with HCl, which afforded metallocene dichlorides with a pendant imino group. These compounds were easily protonated again at the nitrogen atom to produce a cationic iminium moiety. Aqueous hydrolysis of the imine or its respective hydrochloride proved to be viable in the case of Zr and it finally afforded a pendant ketone group attached to the zirconocene framework. PMID:23536005

  13. Chemistry and properties of imide oligomers containing pendant and terminal phenylethynyl groups

    SciTech Connect

    Smith, J.G. Jr.

    1996-12-31

    As part of a continuing effort to develop high performance/high temperature structural resins for aeronautical applications, oligomers containing latent reactive groups have been under investigation. Material requirements include ease of processability, retention of mechanical properties at elevated temperature, and no loss of mechanical properties after exposure to aircraft fluids such as hydraulic fluid, jet fuel, and cleaning fluids. The phenylethynyl group is an ideal latent reactive group. It has a relatively high cure temperature ({approximately}350{degrees}C) and a large processing window can be obtained with materials possessing the proper glass transition temperature. The thermally cured materials exhibit good retention of mechanical properties at elevated temperatures with no significant loss of properties after exposure to various solvents. To date, the phenylethynyl group has been incorporated either terminal or pendant to a variety of imide oligomers. Upon thermal cure, the phenylethynyl group undergoes chain extension, branching and/or crosslinking; however, the final cured product has not been well defined. As an extension of this work, a series of imide oligomers containing both pendant and terminal phenylethynyl groups (PTPEIs) were prepared as a means to improve retention of mechanical properties at elevated temperature while maintaining processability. The PTPEI oligomers were characterized, thermally cured and the cured polymers evaluated as unoriented thin films and adhesives. The chemistry, physical, and mechanical properties of these materials will be discussed.

  14. Copoly(arlene ether)s containing pendant sulfonic acid groups as proton exchange membrane

    SciTech Connect

    Kim, Yu Seung; Kim, Dae Sik; Robertson, Gilles; Guiver, Michael

    2008-01-01

    A copoly(arylene ether) (PAE) with high fluorine content and a copoly(arylene ether nitrile) (PAEN) with high nitrile content, each containing pendant phenyl sulfonic acids were synthesized. The P AE and PAEN were prepared from decafluorobiphenyl (DFBP) and difluorobenzonitrile (DFBN) respectively, by polycondensation with 2-phenylhydroquinone (PHQ) by conventional aromatic nucleophilic substitution reactions. The sulfonic acid groups were introduced by mild post-sulfonation exclusively on the para-position of the pendant phenyl ring in PHQ. The membrane properties of the resulting sulfonated copolymers sP AE and sP AEN were compared for fuel cell applications. The copolymers sPAE and sPAEN, each having a degree of sulfonation (DS) of 1.0 had high ion exchange capacities (IEC{sub v}(wet) (volume-based, wet state)) of 1.77 and 2.55 meq./cm{sup 3}, high proton conductivities of 135.4 and 140.1 mS/cm at 80 C, and acceptable volume-based water uptake of 44.5-51.9 vol% at 80 C, respectively, compared to Nafion. The data points of these copolymer membranes are located in the area of outstanding properties in the trade-off plot of alternative hydrocarbon polyelectrolyte membranes (PEM) for the relationship between proton conductivity versus water uptake (weight based or volume based). Furthermore, the relative selectivity derived from proton conductivity and methanol permeability is higher than that of Nafion.

  15. Copoly(arylene ether)s containing pendant sulfonic acid groups as proton exchange membranes

    SciTech Connect

    Dae Sik, Kim; Yu Seung, Kim; Gilles, Robertson; Guiver, Michael D

    2009-01-01

    A copoly(arylene ether) (PAE) with high fluorine content and a copoly(arylene ether nitrile) (PAEN) with high nitrile content, each containing pendant phenyl sulfonic acids were synthesized. The PAE and P AEN were prepared from decafluorobiphenyl (DFBP) and difluorobenzonitrile (DFBN) respectively, by polycondensation with 2phenylhydroquinone (PHQ) by conventional aromatic nucleophilic substitution reactions. sulfonic acid groups were introduced by mild post-sulfonation exclusively on the para-position of the pendant phenyl ring in PHQ. The membrane properties of the resulting sulfonated copolymers sPAE and sPAEN were compared for fuel cell applications. The copolymers sPAE and sPAEN, each having a degree of sulfonation (OS) of 1.0 had high ion exchange capacities (IEC{sub v})(wet) (volume-based, wet state) of 1.77 and 2.55 meq./cm3, high proton conductivities of 135.4 and 140.1 mS/cm at 80 C, and acceptable volume-based water uptake of 44.5 -51.9 vol% at 80 C, respectively, compared to Nafion. The data points of these copolymer membranes are located in the upper left-hand corner in the trade-off plot of alternative hydrocarbon polyelectrolyte membranes (PEM) for the relationship between proton conductivity versus water uptake (weight based or volume based), i.e., high proton conductivity and low water uptake. Furthermore, the relative selectivity derived from proton conductivity and methanol permeability is higher than that of Nafion.

  16. A ribozyme that triphosphorylates RNA 5′-hydroxyl groups

    PubMed Central

    Moretti, Janina E.; Müller, Ulrich F.

    2014-01-01

    The RNA world hypothesis describes a stage in the early evolution of life in which RNA served as genome and as the only genome-encoded catalyst. To test whether RNA world organisms could have used cyclic trimetaphosphate as an energy source, we developed an in vitro selection strategy for isolating ribozymes that catalyze the triphosphorylation of RNA 5′-hydroxyl groups with trimetaphosphate. Several active sequences were isolated, and one ribozyme was analyzed in more detail. The ribozyme was truncated to 96 nt, while retaining full activity. It was converted to a trans-format and reacted with rates of 0.16 min−1 under optimal conditions. The secondary structure appears to contain a four-helical junction motif. This study showed that ribozymes can use trimetaphosphate to triphosphorylate RNA 5′-hydroxyl groups and suggested that RNA world organisms could have used trimetaphosphate as their energy source. PMID:24452796

  17. Oligomers with pendant isocyanate groups as adhesives for dentin and other tissues.

    PubMed

    Lee, C H; Brauer, G M

    1989-03-01

    Oligomers containing pendant isocyanate groups were synthesized from various vinyl monomers, m-isopropenyldimethylbenzyl isocyanate (TMI), and 2-isocyanatoethyl methacrylate (IEM). The liquids were characterized by their refractive indices, infrared spectra, and percentage of isocynate groups in the molecule. Adhesive properties of these compounds were compared with those of oligomers prepared from methacrylate esters, IEM, and/or TMI which had been synthesized previously. Bond strengths of the sodium salt of ethylenediamine-tetraacetic acid (Na2EDTA adjusted to pH 7.4) and glutaraldehyde-treated dentin cemented to composite resin with dilute solutions of the oligomers and then stored in water were determined by the procedure of Kemper and Kilian (1975). These adhesive compositions, especially formulations synthesized from vinyl monomers, adhered at least as well to dentin as did other dentin bonding agents. Oligomers synthesized with methacrylate esters bonded more strongly to bone than did other hard-tissue adhesives. These oligomeric compositions are also excellent soft-tissue adhesives. For example, they provide a strong bond between a collagenous substrate (such as calfskin) and cured denture-base resin. Provided that their biological properties prove satisfactory, these compositions could find many applications as hard- and soft-tissue adhesives in clinical dentistry. PMID:2921392

  18. Hydrogen bonding and electron transfer between dimetal paddlewheel compounds containing pendant 2-pyridone functional groups.

    PubMed

    Wilkinson, Luke A; McNeill, Laura; Scattergood, Paul A; Patmore, Nathan J

    2013-08-19

    The compounds M2(TiPB)3(HDON) (TiPB = 2,4,6-triisopropylbenzoic acid; H2DON = 2,7-dihdroxy-1,8-napthyridine; M = Mo (1a) or W (1b)) and Mo2(TiPB)2(O2CCH2Cl)(HDON) (1c) which contain a pendant 2-pyridone functional group have been prepared. These compounds are capable of forming self-complementary hydrogen bonds, resulting in the formation of "dimers of dimers" ([1a-c]2) in CH2Cl2 solutions. Electrochemical studies reveal two successive one-electron redox processes for [1a-c]2 in CH2Cl2 solutions that correspond to successive oxidations of the dimetal core, indicating stabilization of the mixed-valence state. Only small changes in the value of Kc are observed upon changing the ancillary ligand or metal, implying that proton coupled mixed valency is responsible for the stabilization. Dimethylsulfoxide (DMSO) disrupts the hydrogen bonding interactions in these compounds, and a single oxidation process is observed in DMSO which shifts to lower potential as the number of HDON ligands increases. Further substitution of carboxylate ligands with HDON leads to the formation of Mo2(TiPB)2(HDON)2 (2) and Mo2(HDON)4 (3), which adopt trans-1,1 and cis-2,2 regioisomers in the solid-state. (1)H NMR spectroscopy indicates that there are at least two regioisomers present in solution for both compounds. The lowest energy transition in the electronic absorption spectra of these compounds corresponds to a M2-δ → HDON-π* transition. The electrochemical, spectroscopic and structural results were rationalized with the aid of density functional theory (DFT) calculations. PMID:23927688

  19. A Route to Aliphatic Poly(ester)s with Thiol Pendant Groups: From Monomer Design to Editable Porous Scaffolds.

    PubMed

    Fuoco, Tiziana; Finne-Wistrand, Anna; Pappalardo, Daniela

    2016-04-11

    Biodegradable aliphatic polyesters such as poly(lactide) and poly(ε-caprolactone), largely used in tissue engineering applications, lack suitable functional groups and biological cues to enable interactions with cells. Because of the ubiquity of thiol groups in the biological environment and the pliability of thiol chemistry, we aimed to design and synthesize poly(ester) chains bearing pendant thiol-protected groups. To achieve this, 3-methyl-6-(tritylthiomethyl)-1,4-dioxane-2,5-dione, a lactide-type monomer possessing a pendant thiol-protected group, was synthesized. This molecule, when used as a monomer in controlled ring-opening polymerization in combination with lactide and ε-caprolactone, appeared to be a convenient "building block" for the preparation of functionalized aliphatic copolyesters, which were easily modified further. A polymeric sample bearing pyridyl disulfide groups, able to bind a cysteine-containing peptide, was efficiently obtained from a two-step modification reaction. Porous scaffolds were then prepared by blending this latter copolymer sample with poly(l-lactide-co-ε-caprolactone) followed by salt leaching. A further disulfide exchange reaction performed in aqueous medium formed porous scaffolds with covalently linked arginine-glycine-aspartic acid sequences. The scaffolds were characterized by thermal and mechanical tests, and scanning electron microscopy surface images revealed a highly porous morphology. Moreover, a cytotoxicity test indicated good cell viability. PMID:26915640

  20. Effect of liquefaction temperature on hydroxyl groups of bio-oil from loblolly pine (Pinus taeda).

    PubMed

    Celikbag, Yusuf; Via, Brian K; Adhikari, Sushil; Wu, Yonnie

    2014-10-01

    Loblolly pine was liquefied with ethylene glycol at 100, 150, 200 and 250 °C in order to analyze the effect of liquefaction temperature on hydroxyl groups of bio-oil, and to determine the source and variation of hydroxyl groups. The optimum temperature was found to be 150-200 °C. Hydroxyl number (OHN) of the bio-oil was ranged from 632 to 1430 mg KOH/g. GC-MS analysis showed that 70-90% of OHN was generated from unreacted EG. (31)P NMR analysis showed that the majority of hydroxyl groups were aliphatic, and none of the bio-oil exhibited any detectable hydroxyl groups from phenolic sources. Finally, it was found that all bio-oils were stable in terms of OHN for 2 months when stored at -10 °C. PMID:25113882

  1. Amphiphilic block copolyesters bearing pendant cyclic ketal groups as nanocarriers for controlled release of camptothecin

    PubMed Central

    Wang, Xiaoying; Gurski, Lisa A.; Zhong, Sheng; Xu, Xian; Pochan, Darrin J.; Farach-Carson, Mary C.; Jia, Xinqiao

    2010-01-01

    Amphiphilic block copolymers consisting of hydrophilic poly(ethylene glycol) and hydrophobic polyester bearing pendent cyclic ketals were synthesized by ring-opening copolymerization of ε-caprolactone (CL) and 1,4,8-trioxaspiro-[4,6]-9-undecanone (TSU) using α-hydroxyl, ω-methoxy, polyethylene glycol as the initiator and stannous octoate as the catalyst. Compositional analyses indicate that TSU was randomly distributed in the hydrophobic blocks. When the TSU content in the copolymers increased, the polymer crystallinity decreased progressively and the glass transition temperature increased accordingly. Hydrophobic, anticancer drug, camptothecin (CPT), was successfully encapsulated in the block copolymer nanoparticles. The CPT encapsulation efficiency and release kinetics were strongly dependent on the copolymer composition and crystallinity. CPT release from nanoparticles constructed from copolymers containing 0, 39 and 100 mol% TSU in the hydrophobic block followed the same trend, with an initial burst of ~40% within one day followed by a moderate and slow release lasting up to 7 days. At a TSU content of 14 mol%, CPT was released in a continuous and controlled fashion with a reduced initial burst and a 73% cumulative release by day 7. In vitro cytoxicity assay showed that the blank nanoparticles were not toxic to the cultured bone metastatic prostate cancer cells (C4-2B). Compared to the free drug, the encapsulated CPT was more effective in inducing apoptotic responses in C4-2B cells. Modulating the physical characteristics of the amphiphilic copolymers via copolymerization offers a facile method for controlling the bioavailability of anticancer drugs ultimately increasing effectiveness and minimizing toxicity. PMID:20594408

  2. The Addition of A Pregnenolone Pendant Group Enhances the Anticancer Properties of Titanocene Dichloride in a MCF-7 Xenograft Model

    PubMed Central

    Ramos, Gladiany; Loperena, Yaliz; Ortiz, Giovanni; Reyes, Fiorella; Szeto, Ada; Vera, Jose; Velez, Javier; Morales, Jessica; Morrero, Deborah; Castillo, Linnette; Dharmawardhane, Surangani; Melendez, Enrique; Washington, A. Valance

    2014-01-01

    Background/Aim Titanocene dichloride held great promise as a chemotherapeutic compound in preclinical studies. However, subsequent clinical trials revealed hepatoxicity and nephrotoxicity, which limited its use in clinical applications. Therefore, we used steroid pendant groups to improve the targeting of titanocene in the MCF-7 breast cancer cell line, and demonstrated a 10-fold lower effective dose compared to titanocene in in vitro assays. The aim of the present study was to test the efficacy of a titanocene functionalized with pregnenolone (Ti-Preg) in an in vivo breast cancer model. Materials and Methods Xenografts from the MCF7 breast cancer cell line were implanted into athymic nu/nu mice to evaluate the potential of Ti-Preg as an anti-breast cancer agent. Results Ti-Preg demonstrated a significant inhibition of MCF-7 tumor growth when compared to vehicle and to titanocene controls. Conclusion Our findings demonstrate the potential of steroid pendent groups for targeting chemotherapeutics to steroid hormone-dependent cancer. PMID:24692689

  3. Diffusion of hydroxyl groups in silica glass through the binding interface

    NASA Astrophysics Data System (ADS)

    Sato, Naoya; Yamamoto, Takaki; Kuzuu, Nobu; Horikoshi, Hideharu; Niwa, Shohei

    2016-02-01

    Diffusion of hydroxyl groups in silica glass through an interface formed by binding between high-hydroxyl (ca. 1200 wt.ppm) and low-hydroxyl (ca. 130 wt.ppm)-containing silica glasses in the temperature range of 900-1150 °C was investigated. Although the theoretical curve with a hydroxyl-concentration-independent diffusion coefficient deviates from the experimental curve, the diffusion coefficients obtained by fitting to the experimental results by the least squares method coincided with the “effective diffusion coefficients” in the literature, which were obtained from the total absorption change in the IR absorption peak for the hydroxyl group using thin samples. By the analysis considering the hydroxyl concentration dependence of the diffusion coefficient, we showed that the diffusion coefficient is proportional to hydroxyl concentration at each temperature, which is consistent with the model of the diffusion: SiOSi + H2O = 2SiOH. On the basis of this scheme, we tried to evaluate the diffusion coefficients of molecular water using equilibrium constant in the literature.

  4. Block and random copolymers bearing cholic acid and oligo(ethylene glycol) pendant groups: aggregation, thermosensitivity, and drug loading.

    PubMed

    Shao, Yu; Jia, Yong-Guang; Shi, Changying; Luo, Juntao; Zhu, X X

    2014-05-12

    A series of block and random copolymers consisting of oligo(ethylene glycol) and cholic acid pendant groups were synthesized via ring-opening metathesis polymerization of their norbornene derivatives. These block and random copolymers were designed to have similar molecular weights and comonomer ratios; both types of copolymers showed thermosensitivity in aqueous solutions with similar cloud points. The copolymers self-assembled into micelles in water as shown by dynamic light scattering and transmission electron microscopy. The hydrodynamic diameter of the micelles formed by the block copolymer is much larger and exhibited a broad and gradual shrinkage from 20 to 54 °C below its cloud point, while the micelles formed by the random copolymers are smaller in size but exhibited some swelling in the same temperature range. Based on in vitro drug release studies, 78% and 24% paclitaxel (PTX) were released in 24 h from micelles self-assembled by the block and random copolymers, respectively. PTX-loaded micelles formed by the block and random copolymers exhibited apparent antitumor efficacy toward the ovarian cancer cells with a particularly low half-maximal inhibitory concentration (IC50) of 27.4 and 40.2 ng/mL, respectively. Cholic acid-based micelles show promise as a versatile and potent platform for cancer chemotherapy. PMID:24725005

  5. Block and Random Copolymers Bearing Cholic Acid and Oligo(ethylene glycol) Pendant Groups: Aggregation, Thermosensitivity, and Drug Loading

    PubMed Central

    2015-01-01

    A series of block and random copolymers consisting of oligo(ethylene glycol) and cholic acid pendant groups were synthesized via ring-opening metathesis polymerization of their norbornene derivatives. These block and random copolymers were designed to have similar molecular weights and comonomer ratios; both types of copolymers showed thermosensitivity in aqueous solutions with similar cloud points. The copolymers self-assembled into micelles in water as shown by dynamic light scattering and transmission electron microscopy. The hydrodynamic diameter of the micelles formed by the block copolymer is much larger and exhibited a broad and gradual shrinkage from 20 to 54 °C below its cloud point, while the micelles formed by the random copolymers are smaller in size but exhibited some swelling in the same temperature range. Based on in vitro drug release studies, 78% and 24% paclitaxel (PTX) were released in 24 h from micelles self-assembled by the block and random copolymers, respectively. PTX-loaded micelles formed by the block and random copolymers exhibited apparent antitumor efficacy toward the ovarian cancer cells with a particularly low half-maximal inhibitory concentration (IC50) of 27.4 and 40.2 ng/mL, respectively. Cholic acid-based micelles show promise as a versatile and potent platform for cancer chemotherapy. PMID:24725005

  6. Introduction of bridging and pendant organic groups into mesoporous alumina materials.

    PubMed

    Grant, Stacy M; Woods, Stephan M; Gericke, Arne; Jaroniec, Mietek

    2011-11-01

    Incorporation of organic functionalities into soft-templated mesoporous alumina was performed via organosilane-assisted evaporation induced self-assembly using aluminum alkoxide precursors and block copolymer templates. This strategy permits one to obtain mesoporous alumina-based materials with tailorable adsorption, surface and structural properties. Isocyanurate, ethane, mercaptopropyl, and ureidopropyl-functionalized mesoporous alumina materials were synthesized with relatively high surface area and large pore volume with uniform and wormhole-like mesopores. The presence of organosilyl groups within these hybrid materials was confirmed by IR or Raman spectroscopy and their concentration was determined by elemental analysis. PMID:21988174

  7. Tuning magnetic splitting of zigzag graphene nanoribbons by edge functionalization with hydroxyl groups

    SciTech Connect

    Zhang, Huizhen; Yang, Haifang; Li, Lin; Fu, Huixia; Ma, Wei; Niu, Chunyao; Sun, Jiatao; Meng, Sheng; Gu, Changzhi

    2015-03-21

    The electronic properties and relative stability of zigzag graphene nanoribbons are studied by varying the percentage of hydroxyl radicals for edge saturation using first principle calculations. The passivated structures of zigzag graphene nanoribbon have spin-polarized ground state with antiferromagnetic exchange coupling across the edge and ferromagnetic coupling along the edges. When the edges are specially passivated by hydroxyl, the potentials of spin exchange interaction across the two edges shift accordingly, resulting into a spin-semiconductor. Varying the concentration of hydroxyl groups can alter the maximum magnetization splitting. When the percentage of asymmetrically adsorbed hydroxyl reaches 50%, the magnetization splitting can reach a value as high as 275 meV due to the asymmetrical potential across the nanoribbon edges. These results would favor spintronic device applications based on zigzag graphene nanoribbons.

  8. Chemical modification and structure-activity relationships of pyripyropenes. 1. Modification at the four hydroxyl groups.

    PubMed

    Obata, R; Sunazuka, T; Li, Z; Tian, Z; Harigaya, Y; Tabata, N; Tomoda, H; Omura, S

    1996-11-01

    Four hydroxyl groups of pyripyropenes have been modified and evaluated for their ability to inhibit microsomal acyl-CoA:cholesterol acyltransferase (ACAT) activity in vitro and to lower cholesterol absorption in vivo in a cholesterol-fed hamster. 7-O-n-Valeryl derivative (8c) improved the in vitro ACAT inhibitory activity (IC50 = 13 nM) about 7 times better than pyripyropene A. Introduction of methanesulfonyl group at 11-hydroxyl group (17a) increased both in vitro activity (IC50 = 19 nM) and in vivo efficacy (ED50 = 10 mg/kg). PMID:8982343

  9. Entropy Loss of Hydroxyl Groups of Balanol upon Binding to Protein Kinase A

    NASA Astrophysics Data System (ADS)

    Gidofalvi, Gergely; Wong, Chung F.; McCammon, J. Andrew

    2002-09-01

    This article describes a short project for an undergraduate to learn several techniques for computer-aided drug design. The project involves estimating the loss of the rotational entropy of the hydroxyl groups of balanol upon its binding to the enzyme protein kinase A (PKA), as the entropy loss can significantly influence PKA balanol binding affinity. This work employs semiempirical quantum mechanical techniques for estimating the potential energy curves for the rotation of the hydroxyl groups of balanol in vacuum and in PKA, and solves the Poisson equation to correct the potential energy curves for hydration effects. Statistical mechanical principles are then applied to estimate the desired entropy loss from the potential energy curves. The analysis examines the influence of hydration effects on the rotational preference of the hydroxyl groups and the significance of the rotational entropy in determining binding affinity.

  10. IR spectroscopic study of hydroxyl groups of molecular sieves in the fundamental and combination tone regions

    NASA Astrophysics Data System (ADS)

    Löffler, E.; Zscherpel, U.; Peuker, Ch.; Staudte, B.

    1993-03-01

    The fundamental and combination vibrations of hydroxyl groups in zeolites (Y, ZSM-5) and silicoaluminophosphates (SAPO-5, -17, -34) are investigated. The influence of adsorbed molecules (C 6F 6, n-hexane) on the combination vibrations is also studied. Finally, remarks on quantitative evaluation of DRIFT spectra of NaHZSM-5 containing different amounts of bridging OH groups are given.

  11. Solution behavior and solid phase transitions of quaternary ammonium surfactants with head groups decorated by hydroxyl groups.

    PubMed

    Song, Binglei; Shang, Shibin; Song, Zhanqian

    2012-09-15

    Hydrogen bonds are strong intermolecular interactions, which are very important in molecular aggregation and new phase formation. Three long-chain quaternary ammonium surfactants, N,N-diethyl-N-(2-hydroxyethyl)-N-octadecylammonium bromide with one hydroxyl group, N-ethyl-N,N-bis (2-hydroxyethyl)-N-octadecylammonium bromide with two hydroxyl groups and N,N,N-tris (2-hydroxyethyl)-N-octadecylammonium bromide with three hydroxyl groups, abbreviated as SHQ, DHQ, and THQ, respectively, were synthesized in this work. Their solution behavior and solid phase transitions were investigated by surface tension, differential scanning calorimetry (DSC), X-ray diffraction (XRD), polarizing optical microscopy (POM), and Infrared (IR) spectroscopy. The hydrogen bonds introduced by the substituted hydroxyl groups promoted surfactant adsorption at the air/water interface and aggregation in solution. In the crystal state, an increased number of hydroxyl groups caused a larger tilt angle of the long axis of surfactant molecules with the layer normal. Above certain temperatures, SHQ and DHQ formed highly ordered smectic T and smectic A phases while THQ only formed less ordered smectic A phase. The weakened electrostatic attractions between opposite ions and the thicker polar sublayers of mesophases caused by the enhanced number of hydrogen bonds are responsible for the mesophase formation and transition of these surfactants. PMID:22762982

  12. Synthesis of acrylic copolymers consisting of multiple amine pendants for dispersing pigment.

    PubMed

    Chen, Yu-Min; Hsu, Ru-Siou; Lin, Hsiao-Chu; Chang, Shinn-Jen; Chen, Shih-Chun; Lin, Jiang-Jen

    2009-06-01

    A class of acrylic copolymers with narrow molecular weight distribution from butyl methacrylate and glycidyl methacrylate comonomers via atom transfer radical polymerization was synthesized. Various types of polarities including hydroxyl-amines, glycols, and carboxylic acids were then grafted onto the oxirane side groups. The resultant comb-like copolymers with different polar pendants were tested for homogenizing a representative Yellow pigment in 1,6-hexanediol diacrylate medium. Specifically, the polyacrylates with 1,3-diamine pendants (7-10 multiplicity on each polymer strain) enabled to homogeneously disperse the pigment than the analogous copolymers with hydroxyl or carboxylic acid groups. Ultimately, the pigment dispersion with an average size of ca. 20 nm in diameter, high transmittance and low viscosity was achieved. Furthermore, the pigment dispersion was allowed to UV-cure into a film, and for the first time, the primary structures of the pigment particles (ca. 50 nm in diameter) were observed by transmission electronic microscope. PMID:19364609

  13. Biosynthesis of polyhydroxyalkanoates containing hydroxyl group from glycolate in Escherichia coli.

    PubMed

    Insomphun, Chayatip; Kobayashi, Shingo; Fujiki, Tetsuya; Numata, Keiji

    2016-12-01

    Polyhydroxyalkanoates (PHAs) containing hydroxyl groups in a side chain were produced in recombinant Escherichia coli JM109 using glycolate as the sole carbon source. The propionate-CoA transferase (pct) gene from Megasphaera elsdenii and the β-ketothiolase (bktB) gene and phaCAB operon from Ralstonia eutropha H16 were introduced into E. coli JM109. A novel monomer containing a hydroxyl group, dihydroxybutyrate (DHBA), was the expected product of the condensation of glycolyl-CoA and acetyl-CoA by BktB. The recombinant strain produced a PHA containing 1 mol% DHBA. The incorporation of DHBA may have been restricted because the expression of phaAB1 competes for acetyl-CoA. The PHA containing DHBA units were evaluated regarding thermal properties, such as melting temperature, glass transition temperature and thermal degradation temperature. The current study demonstrates a potential use of PHA containing hydroxyl groups as renewable resources in biological materials. PMID:27075993

  14. The Juxtaposition of Ribose Hydroxyl Groups: The Root of Biological Catalysis and the RNA World?

    NASA Astrophysics Data System (ADS)

    Bernhardt, Harold S.

    2015-06-01

    We normally think of enzymes as being proteins; however, the RNA world hypothesis suggests that the earliest biological catalysts may have been composed of RNA. One of the oldest surviving RNA enzymes we are aware of is the peptidyl transferase centre (PTC) of the large ribosomal RNA, which joins amino acids together to form proteins. Recent evidence indicates that the enzymatic activity of the PTC is principally due to ribose 2 '-OHs. Many other reactions catalyzed by RNA and/or in which RNA is a substrate similarly utilize ribose 2 '-OHs, including phosphoryl transfer reactions that involve the cleavage and/or ligation of the ribose-phosphate backbone. It has recently been proposed by Yakhnin (2013) that phosphoryl transfer reactions were important in the prebiotic chemical evolution of RNA, by enabling macromolecules composed of polyols joined by phosphodiester linkages to undergo recombination reactions, with the reaction energy supplied by the phosphodiester bond itself. The almost unique juxtaposition of the ribose 2'-hydroxyl and 3'-oxygen in ribose-containing polymers such as RNA, which gives ribose the ability to catalyze such reactions, may have been an important factor in the selection of ribose as a component of the first biopolymer. In addition, the juxtaposition of hydroxyl groups in free ribose: (i) allows coordination of borate ions, which could have provided significant and preferential stabilization of ribose in a prebiotic environment; and (ii) enhances the rate of permeation by ribose into a variety of lipid membrane systems, possibly favouring its incorporation into early metabolic pathways and an ancestral ribose-phosphate polymer. Somewhat more speculatively, hydrogen bonds formed by juxtaposed ribose hydroxyl groups may have stabilized an ancestral ribose-phosphate polymer against degradation (Bernhardt and Sandwick 2014). I propose that the almost unique juxtaposition of ribose hydroxyl groups constitutes the root of both biological

  15. Metal-Chelating Polymers (MCPs) with Zwitterionic Pendant Groups Complexed to Trastuzumab Exhibit Decreased Liver Accumulation Compared to Polyanionic MCP Immunoconjugates.

    PubMed

    Liu, Peng; Boyle, Amanda J; Lu, Yijie; Adams, Jarrett; Chi, Yuechuan; Reilly, Raymond M; Winnik, Mitchell A

    2015-11-01

    Metal-chelating polymers (MCPs) can amplify the radioactivity delivered to cancer cells by monoclonal antibodies or their Fab fragments. We focus on trastuzumab (tmAb), which is used to target cancer cells that overexpress human epidermal growth factor receptor 2 (HER2). We report the synthesis and characterization of a biotin (Bi) end-capped MCP, Bi-PAm(DET-DTPA)36, a polyacrylamide with diethylenetriaminepentaacetic acid (DTPA) groups attached as monoamides to the polymer backbone by diethylenetriamine (DET) pendant groups. We compared its behavior in vivo and in vitro to a similar MCP with ethylenediamine (EDA) pendant groups (Bi-PAm(EDA-DTPA)40). These polymers were complexed to a streptavidin-modified Fab fragment of tmAb, then labeled with (111)In to specifically deliver multiple copies of (111)In to HER2+ cancer cells. Upon decay, (111)In emits γ-rays that can be used in single-photon emission computed tomography radioimaging, as well as Auger electrons that cause lethal double strand breakage of DNA. Our previous studies in Balb/c mice showed that radioimmunoconjugates (RICs) containing the Bi-PAm(EDA-DTPA)40 polymer had extremely short blood circulation time and high liver uptake and were, thus, unsuitable for in vivo studies. The polymer Bi-PAm(EDA-DTPA)40 carries negative charges on each pendant group at neutral pH and a net charge of (-1) on each pendant group when saturated with stable In(3+). To test our hypothesis that charge associated with the polymer repeat unit is a key factor affecting its biodistribution profile, we examined the biodistribution of RICs containing Bi-PAm(DET-DTPA)36. While this polymer is also negatively charged at neutral pH, it becomes a zwitterionic MCP upon saturation of the DTPA groups with stable In(3+) ions. In both nontumor bearing Balb/c mice and athymic mice implanted with HER2+ SKOV-3 human ovarian cancer tumors, we show that the zwitterionic MCP has improved biodistribution, higher blood levels of radioactivity

  16. The 4'-hydroxyl group of resveratrol is functionally important for direct activation of PPARα.

    PubMed

    Takizawa, Yoshie; Nakata, Rieko; Fukuhara, Kiyoshi; Yamashita, Hiroshi; Kubodera, Hideo; Inoue, Hiroyasu

    2015-01-01

    Long-term moderate consumption of red wine is associated with a reduced risk of developing lifestyle-related diseases such as cardiovascular disease and cancer. Therefore, resveratrol, a constituent of grapes and various other plants, has attracted substantial interest. This study focused on one molecular target of resveratrol, the peroxisome proliferator activated receptor α (PPARα). Our previous study in mice showed that resveratrol-mediated protection of the brain against stroke requires activation of PPARα; however, the molecular mechanisms involved in this process remain unknown. Here, we evaluated the chemical basis of the resveratrol-mediated activation of PPARα by performing a docking mode simulation and examining the structure-activity relationships of various polyphenols. The results of experiments using the crystal structure of the PPARα ligand-binding domain and an analysis of the activation of PPARα by a resveratrol analog 4-phenylazophenol (4-PAP) in vivo indicate that the 4'-hydroxyl group of resveratrol is critical for the direct activation of PPARα. Activation of PPARα by 5 μM resveratrol was enhanced by rolipram, an inhibitor of phosphodiesterase (PDE) and forskolin, an activator of adenylate cyclase. We also found that resveratrol has a higher PDE inhibitory activity (IC50 = 19 μM) than resveratrol analogs trans-4-hydroxystilbene and 4-PAP (IC50 = 27-28 μM), both of which has only 4'-hydroxyl group, indicating that this 4'-hydroxyl group of resveratrol is not sufficient for the inhibition of PDE. This result is consistent with that 10 μM resveratrol has a higher agonistic activity of PPARα than these analogs, suggesting that there is a feedforward activation loop of PPARα by resveratrol, which may be involved in the long-term effects of resveratrol in vivo. PMID:25798826

  17. Tuning the Moisture and Thermal Stability of Metal–Organic Frameworks through Incorporation of Pendant Hydrophobic Groups

    SciTech Connect

    Makal, Trevor A.; Wang, Xuan; Zhou, Hong-Cai

    2013-11-06

    An isostructural series of NbO-type porous metal–organic frameworks (MOFs) with different dialkoxy-substituents of formula Cu2(TPTC-OR) (TPTC-OR = 2',5'-di{alkyl}oxy-[1,1':4',1"-terphenyl]-3,3",5,5"-tetracarboxylate, R = Me, Et, nPr, nHex) has been synthesized and characterized. The moisture stability of the materials has been evaluated, and a new superhydrophobic porous MOF has been identified. The relationship between pendant side chain length and thermal stability has been analyzed by in situ synchrotron powder X-ray diffraction, showing decreased thermal stability as the side chain length is increased, contradictory to thermogravimetric decomposition studies. Additionally, the four materials exhibit moderate Brunauer–Emmett–Teller (BET) and Langmuir surface areas (1127–1396 m2 g–1 and 1414–1658 m2 g–1) and H2 capacity up to 1.9 wt % at 77 K and 1 bar.

  18. ToF‐SIMS analysis of a polymer microarray composed of poly(meth)acrylates with C6 derivative pendant groups

    PubMed Central

    Scurr, David J.

    2016-01-01

    Surface analysis plays a key role in understanding the function of materials, particularly in biological environments. Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) provides highly surface sensitive chemical information that can readily be acquired over large areas and has, thus, become an important surface analysis tool. However, the information‐rich nature of ToF‐SIMS complicates the interpretation and comparison of spectra, particularly in cases where multicomponent samples are being assessed. In this study, a method is presented to assess the chemical variance across 16 poly(meth)acrylates. Materials are selected to contain C6 pendant groups, and ten replicates of each are printed as a polymer microarray. SIMS spectra are acquired for each material with the most intense and unique ions assessed for each material to identify the predominant and distinctive fragmentation pathways within the materials studied. Differentiating acrylate/methacrylate pairs is readily achieved using secondary ions derived from both the polymer backbone and pendant groups. Principal component analysis (PCA) is performed on the SIMS spectra of the 16 polymers, whereby the resulting principal components are able to distinguish phenyl from benzyl groups, mono‐functional from multi‐functional monomers and acrylates from methacrylates. The principal components are applied to copolymer series to assess the predictive capabilities of the PCA. Beyond being able to predict the copolymer ratio, in some cases, the SIMS analysis is able to provide insight into the molecular sequence of a copolymer. The insight gained in this study will be beneficial for developing structure–function relationships based upon ToF‐SIMS data of polymer libraries. © 2016 The Authors Surface and Interface Analysis Published by John Wiley & Sons Ltd. PMID:27134321

  19. A functionalizable polyester with free hydroxyl groups and tunable physiochemical and biological properties

    PubMed Central

    You, Zhengwei; Cao, Haiping; Gao, Jin; Shin, Paul H.; Day, Billy W.; Wang, Yadong

    2010-01-01

    Polyesters with free functional groups allow facile modifications with biomolecules, which can lead to versatile biomaterials that afford controlled interactions with cells and tissues. Efficient synthesis of functionalizable polyesters is still a challenge that greatly limits the availability and widespread applications of biofunctionalized synthetic polymers. Here we report a simple route to prepare a functionalizable polyester, poly(sebacoyl diglyceride) (PSeD) bearing free hydroxyl groups. The key synthetic step is an epoxide ring-opening polymerization, instead of the traditional polycondensation, that produces poly(glycerol sebacate) (PGS) [1]. PSeD has a more defined structure with mostly linear backbone, more free hydroxyl groups, higher molecular weight, and lower polydispersity than PGS. Crosslinking PSeD with sebacic acid yields a polymer five times tougher and more elastic than cured PGS. PSeD exhibits good cytocompatibility in vitro. Furthermore, functionalization by glycine proceeds with high efficiency. This versatile synthetic platform can offer a large family of biodegradable, functionalized polymers with tunable physiochemical and biological properties useful for a wide range of biomedical applications. PMID:20149441

  20. Extraction characteristics of subcritical water depending on the number of hydroxyl group in flavonols.

    PubMed

    Cheigh, Chan-Ick; Yoo, Seo-Yeon; Ko, Min-Jung; Chang, Pahn-Shick; Chung, Myong-Soo

    2015-02-01

    This study compared the efficiencies of using subcritical water, hot water, and organic solvents to extract flavonols from black tea, celery, and ginseng leaf. The effect of key operating conditions was determined by varying the temperature (110-200°C), extraction time (5-15min), and pressure (about 10MPa) and the extracts were analysed quantitatively using HPLC. The yields of myricetin, quercetin, and kaempferol from plants were maximal at extraction temperatures of 170°C, 170°C and 200°C, respectively, and they depend on the number of hydroxyl groups included in the chemical structure of the flavonols, with more of those with fewer hydroxyl (OH) groups attached being extracted at higher temperatures. The results also showed that the yields of flavonols by subcritical water extraction were 2.0- to 22.7- and 1.8- to 23.6-fold higher than those obtained using the ethanol and methanol as traditional extraction methods, respectively. PMID:25172678

  1. Inhibition of Pseudomonas aeruginosa Swarming Motility by 1-Naphthol and Other Bicyclic Compounds Bearing Hydroxyl Groups

    PubMed Central

    Oura, Hiromu; Tashiro, Yosuke; Toyofuku, Masanori; Ueda, Kousetsu; Kiyokawa, Tatsunori; Ito, Satoshi; Takahashi, Yurika; Lee, Seunguk; Nojiri, Hideaki; Nakajima-Kambe, Toshiaki; Uchiyama, Hiroo; Futamata, Hiroyuki

    2015-01-01

    Many bacteria convert bicyclic compounds, such as indole and naphthalene, to oxidized compounds, including hydroxyindoles and naphthols. Pseudomonas aeruginosa, a ubiquitous bacterium that inhabits diverse environments, shows pathogenicity against animals, plants, and other microorganisms, and increasing evidence has shown that several bicyclic compounds alter the virulence-related phenotypes of P. aeruginosa. Here, we revealed that hydroxyindoles (4- and 5-hydroxyindoles) and naphthalene derivatives bearing hydroxyl groups specifically inhibit swarming motility but have minor effects on other motilities, including swimming and twitching, in P. aeruginosa. Further analyses using 1-naphthol showed that this effect is also associated with clinically isolated hyperswarming P. aeruginosa cells. Swarming motility is associated with the dispersion of cells from biofilms, and the addition of 1-naphthol maintained biofilm biomass without cell dispersion. We showed that this 1-naphthol-dependent swarming inhibition is independent of changes of rhamnolipid production and the intracellular level of signaling molecule cyclic-di-GMP (c-di-GMP). Transcriptome analyses revealed that 1-naphthol increases gene expression associated with multidrug efflux and represses gene expression associated with aerotaxis and with pyochelin, flagellar, and pilus synthesis. In the present study, we showed that several bicyclic compounds bearing hydroxyl groups inhibit the swarming motility of P. aeruginosa, and these results provide new insight into the chemical structures that inhibit the specific phenotypes of P. aeruginosa. PMID:25681177

  2. Inhibition of Pseudomonas aeruginosa swarming motility by 1-naphthol and other bicyclic compounds bearing hydroxyl groups.

    PubMed

    Oura, Hiromu; Tashiro, Yosuke; Toyofuku, Masanori; Ueda, Kousetsu; Kiyokawa, Tatsunori; Ito, Satoshi; Takahashi, Yurika; Lee, Seunguk; Nojiri, Hideaki; Nakajima-Kambe, Toshiaki; Uchiyama, Hiroo; Futamata, Hiroyuki; Nomura, Nobuhiko

    2015-04-01

    Many bacteria convert bicyclic compounds, such as indole and naphthalene, to oxidized compounds, including hydroxyindoles and naphthols. Pseudomonas aeruginosa, a ubiquitous bacterium that inhabits diverse environments, shows pathogenicity against animals, plants, and other microorganisms, and increasing evidence has shown that several bicyclic compounds alter the virulence-related phenotypes of P. aeruginosa. Here, we revealed that hydroxyindoles (4- and 5-hydroxyindoles) and naphthalene derivatives bearing hydroxyl groups specifically inhibit swarming motility but have minor effects on other motilities, including swimming and twitching, in P. aeruginosa. Further analyses using 1-naphthol showed that this effect is also associated with clinically isolated hyperswarming P. aeruginosa cells. Swarming motility is associated with the dispersion of cells from biofilms, and the addition of 1-naphthol maintained biofilm biomass without cell dispersion. We showed that this 1-naphthol-dependent swarming inhibition is independent of changes of rhamnolipid production and the intracellular level of signaling molecule cyclic-di-GMP (c-di-GMP). Transcriptome analyses revealed that 1-naphthol increases gene expression associated with multidrug efflux and represses gene expression associated with aerotaxis and with pyochelin, flagellar, and pilus synthesis. In the present study, we showed that several bicyclic compounds bearing hydroxyl groups inhibit the swarming motility of P. aeruginosa, and these results provide new insight into the chemical structures that inhibit the specific phenotypes of P. aeruginosa. PMID:25681177

  3. Coating morphology and surface composition of acrylic terpolymers with pendant catechol, OEG and perfluoroalkyl groups in varying ratio and the effect on protein adsorption.

    PubMed

    Zhong, Jun; Ji, Hua; Duan, Jiang; Tu, Haiyang; Zhang, Aidong

    2016-04-01

    This work aims at developing versatile low-biofouling polymeric coatings by using acrylic terpolymers (DOFs) that bear pendant catechol (D), oligo(ethylene glycol) (O), and perfluoroalkyl (F) groups in varying ratios. The polymers were endowed with the ability to form firmly coatings on virtually any surfaces and undergo surface microphase separation and self-assembly, as revealed by the surface enrichment of F pendants and the morphology variation from irregular solid domains to discrete crater-type aggregates of different size. The effect on protein adsorption was investigated using bovine serum albumin (BSA) and adhesive fibrinogen (Fib) as model proteins. The coating of DOF164 (low F content), which has morphology of discrete crater-type aggregates of ∼ 400 nm in size, adsorbed a least amount of protein but with a highest protein unit activity as determined by SPR and immunosorbent assay; whereas the coating of DOF1612 (high F content) showed a 12.3-fold higher adsorption capacity toward Fib. Interestingly, a 2.2-fold lower adsorption amount but with a 1.8-fold higher unit activity was found for Fib adsorbed on the DOF164 surface than on DOF250 (without F fraction), whose OEG segments being a widely recognized protein compatible material. The features of the DOF164 terpolymer presenting a robust coating ability and a minimal protein adsorption capacity while with a high protein unit activity suggest its potential application as a non-fouling surface-modifier for medical antifouling coatings and as a matrix material for selective protein immobilization and activity preservation in biosensor construction. PMID:26764109

  4. Water growth on metals and oxides: binding, dissociation and role of hydroxyl groups

    SciTech Connect

    Salmeron, M.; Bluhm, H.; Tatarkhanov, M.; Ketteler, G.; Shimizu, T.K.; Mugarza, A.; Deng, Xingyi; Herranz, T.; Yamamoto, S.; Nilsson, A.

    2008-09-01

    The authors discuss the role of the presence of dangling H bonds from water or from surface hydroxyl species on the wetting behavior of surfaces. Using Scanning Tunneling and Atomic Force Microscopies, and Photoelectron Spectroscopy, they have examined a variety of surfaces, including mica, oxides, and pure metals. They find that in all cases, the availability of free, dangling H-bonds at the surface is crucial for the subsequent growth of wetting water films. In the case of mica electrostatic forces and H-bonding to surface O atoms determine the water orientation in the first layer and also in subsequent layers with a strong influence in its wetting characteristics. In the case of oxides like TiO{sub 2}, Cu{sub 2}O, SiO{sub 2} and Al{sub 2}O{sub 3}, surface hydroxyls form readily on defects upon exposure to water vapor and help nucleate the subsequent growth of molecular water films. On pure metals, such as Pt, Pd, and Ru, the structure of the first water layer and whether or not it exhibits dangling H bonds is again crucial. Dangling H-bonds are provided by molecules with their plane oriented vertically, or by OH groups formed by the partial dissociation of water. By tying the two II atoms of the water molecules into strong H-bonds with pre-adsorbed O on Ru can also quench the wettability of the surface.

  5. IDENTIFICATION AND QUANTIFICATION OF AEROSOL POLAR OXYGENATED COMPOUNDS BEARING CARBOXYLIC AND/OR HYDROXYL GROUPS. 1. METHOD DEVELOPMENT

    EPA Science Inventory

    In this study, a new analytical technique was developed for the identification and quantification of multi-functional compounds containing simultaneously at least one hydroxyl or one carboxylic group, or both. This technique is based on derivatizing first the carboxylic group(s) ...

  6. Layer modulated smectic-C phase in liquid crystals with a terminal hydroxyl group

    NASA Astrophysics Data System (ADS)

    Kimoto, Yasuhiro; Nishizawa, Ayumi; Takanishi, Yoichi; Yoshizawa, Atsushi; Yamamoto, Jun

    2014-04-01

    We investigated local layer structures of the three smectic-C phases (SmC, SmC', and SmC″) in a liquid crystal with the terminal hydroxyl group using high resolution and microbeam x-ray diffraction. It is found that SmC is the conventional SmC1 phase and SmC″ is the bilayer SmC2 phase. The SmC' phase forms an in-plane modulation structure, so that this phase is the smectic-C antiphase. From the Fourier transform infrared spectroscopy, it is suggested that the intermolecular hydrogen bonding is important to induce the SmC' and SmC″ phases.

  7. Design of Poly(l-lactide)-Poly(ethylene glycol) Copolymer with Light-Induced Shape-Memory Effect Triggered by Pendant Anthracene Groups.

    PubMed

    Xie, Hui; He, Man-Jie; Deng, Xiao-Ying; Du, Lan; Fan, Cheng-Jie; Yang, Ke-Ke; Wang, Yu-Zhong

    2016-04-13

    A novel light-induced shape-memory material based on poly(l-lactide)-poly(ethylene glycol) copolymer is developed successfully by dangling the photoresponsive anthracene group on the PEG soft segment selectively. For synthesis strategy, the preprepared photoresponsive monomer N,N-bis(2-hydroxyethyl)-9-anthracene-methanamine (BHEAA) is first embedded into PEG chains; then, we couple this anthracene-functionalized PEG precursor with PLA precursor to result in PLA-PEG-A copolymer. The composition of target product can be well-defined by simply adjusting the feed ratio. The chemical structures of intermediate and final products are confirmed by (1)H NMR. Differential scanning calorimetry analysis of material reveals that the PEG soft segment became noncrystallizable when 4% or more BHEAA is introduced, and this feature is beneficial to the mobility of anthracene groups in polymer matrix. The static tensile tests show that the samples exhibit rubberlike mechanical properties except for the PLA-dominant one. The reversibility of [4 + 4] cycloaddition reaction between pendant anthracene groups in PLA-PEG-A film is demonstrated by UV-vis. Eventually, the light-induced shape-memory effect (LSME) is successfully realized in PLA-PEG-A. The results of cyclic photomechanical tests also reveal that the content of PLA hard segment as well as photosensitive anthracene moieties plays a crucial role in LSME. PMID:27031590

  8. 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. PMID:26509282

  9. The Effect of Terminal Hydroxyl Groups on the Self-Assembly of PEO in Water

    NASA Astrophysics Data System (ADS)

    Dormidontova, Elena E.

    2003-03-01

    Applying a mean field-like statistical model we explore the effect of terminal hydroxyl (-OH) groups on the properties of polyethylene oxide, PEO, which is extensively used in biomedical applications. The influence of terminal OH groups is two-fold: it allows PEO-PEO complex formation and additional water is adsorbed. Our theoretical modeling shows that the influence of PEO-PEO network formation on polymer properties is negligible till very high polymer concentration (>90%). At the same time the contribution of terminal OH groups to the overall PEO hydration (which is essential for inhibition of protein adsorption) is considerable, especially for short polymer chains (N<50). As a result, OH termination of short PEO chains may lead to stabilization of PEO solutions in the entire temperature and composition range. For longer chains, hydration via terminal OH groups becomes especially noticeable in the regions of poor hydration, i.e. at high polymer concentration and high temperature, that leads to some decrease of the phase separation region. As expected, very long PEO chains (N>500) have very small sensitivity to OH termination.

  10. Conformational influence of the ribose 2'-hydroxyl group: crystal structures of DNA-RNA chimeric duplexes

    NASA Technical Reports Server (NTRS)

    Egli, M.; Usman, N.; Rich, A.

    1993-01-01

    We have crystallized three double-helical DNA-RNA chimeric duplexes and determined their structures by X-ray crystallography at resolutions between 2 and 2.25 A. The two self-complementary duplexes [r(G)d(CGTATACGC)]2 and [d(GCGT)r(A)d(TACGC)]2, as well as the Okazaki fragment d(GGGTATACGC).r(GCG)d(TATACCC), were found to adopt A-type conformations. The crystal structures are non-isomorphous, and the crystallographic environments for the three chimeras are different. A number of intramolecular interactions of the ribose 2'-hydroxyl groups contribute to the stabilization of the A-conformation. Hydrogen bonds between 2'-hydroxyls and 5'-oxygens or phosphate oxygens, in addition to the previously observed hydrogen bonds to 1'-oxygens of adjacent riboses and deoxyriboses, are observed in the DNA-RNA chimeric duplexes. The crystalline chimeric duplexes do not show a transition between the DNA A- and B-conformations. CD spectra suggest that the Okazaki fragment assumes an A-conformation in solution as well. In this molecule the three RNA residues may therefore lock the complete decamer in the A-conformation. Crystals of an all-DNA strand with the same sequence as the self-complementary chimeras show a morphology which is different from those of the chimera crystals. Moreover, the oligonucleotide does not match any of the sequence characteristics of DNAs usually adopting the A-conformation in the crystalline state (e.g., octamers with short alternating stretches of purines and pyrimidines). In DNA-RNA chimeric duplexes, it is therefore possible that a single RNA residue can drive the conformational equilibrium toward the A-conformation.

  11. Study of sulfonated polyether ether ketone with pendant lithiated fluorinated sulfonic groups as ion conductive binder in lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Wei, Zengbin; Xue, Lixin; Nie, Feng; Sheng, Jianfang; Shi, Qianru; Zhao, Xiulan

    2014-06-01

    In an attempt to reduce the Li+ concentration polarization and electrolyte depletion from the electrode porous space, sulfonated polyether ether ketone with pendant lithiated fluorinated sulfonic groups (SPEEK-FSA-Li) is prepared and attempted as ionic conductivity binder. Sulfonated aromatic poly(ether ether ketone) exhibits strong adhesion and chemical stability, and lithiated fluorinated sulfonic side chains help to enhance the ionic conductivity and Li+ ion diffusion due to the charge delocalization over the sulfonic chain. The performances are evaluated by cyclic voltammetry, electrochemical impedance spectroscopy, charge-discharge cycle testing, 180° peel testing, and compared with the cathode prepared with polyvinylidene fluoride binder. The electrode prepared with SPEEK-FSA-Li binder forms the relatively smaller resistances of both the SEI and the charge transfer of lithium ion transport. This is beneficial to lithium ion intercalation and de-intercalation of the cathode during discharging-charging, therefore the cell prepared with SPEEK-FSA-Li shows lower charge plateau potential and higher discharge plateau potential. Compared with PVDF, the electrode with ionic binder shows smaller decrease in capacity with the increasing of cycle rate. Meanwhile, adhesion strength of electrode prepared with SPEEK-FSA-Li is more than five times greater than that with PVDF.

  12. Synthesis and characterization of novel sulfonated poly(arylene ether ketone) copolymers with pendant carboxylic acid groups for proton exchange membranes

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Cui, Zhiming; Zhao, Chengji; Shao, Ke; Li, Hongtao; Fu, Tiezhu; Na, Hui; Xing, Wei

    A series of novel side-chain-type sulfonated poly(arylene ether ketone)s with pendant carboxylic acid groups copolymers (C-SPAEKs) were synthesized by direct copolymerization of sodium 5,5‧-carbonyl-bis(2-fluorobenzenesulfonate), 4,4‧-difluorobenzophenone and 4,4‧-bis(4-hydroxyphenyl) valeric acid (DPA). The expected structure of the sulfonated copolymers was confirmed by FT-IR and 1H NMR. Membranes with good thermal and mechanical stability could be obtained by solvent cast process. It should be noted that the proton conductivity of these copolymers with high sulfonatation degree (DS > 0.6) was higher than 0.03 S cm -1 and increased with increasing temperature. At 80 °C, the conductivity of C-SPAEK-3 (DS = 0.6) and C-SPAEK-4 (DS = 0.8) reached up to 0.12 and 0.16 S cm -1, respectively, which were higher than that of Nafion 117 (0.10 S cm -1). Moreover, their methanol permeability was much lower than that of Nafion 117. These results showed that the synthesized materials might have potential applications as the proton exchange membranes for DMFCs.

  13. A dynamic NMR study of self-inclusion of a pendant group in amphiphilic 6-thiophenyl-6-deoxycyclodextrins

    NASA Astrophysics Data System (ADS)

    Dodziuk, H.; Chmurski, K.; Jurczak, J.; Koźmiński, W.; Lukin, O.; Sitkowski, J.; Stefaniak, L.

    2000-02-01

    The dynamic stereochemistry of amphiphilic derivatives of α-, β-, and γ-cyclodextrins ( 1- 3) has been investigated by means of variable temperature 1H and 13C NMR spectroscopy in DMF-d 7 solutions. The most significant spectral changes were detected for the smallest hexakis(6-thiophenyl-6-deoxy)-α-cyclodextrin ( 1) and they decrease with the increase of the macrocycle size. On the basis of ROESY measurements, these changes reflecting restricted movements of thiophenyl groups upon the temperature decrease were interpreted in terms of self-inclusion of at least one thiophenyl group. Molecular modeling of these compounds is consistent with these findings.

  14. Photoluminescence of oxygen vacancies and hydroxyl group surface functionalized SnO2 nanoparticles.

    PubMed

    Bonu, Venkataramana; Das, Arindam; Amirthapandian, S; Dhara, Sandip; Tyagi, Ashok Kumar

    2015-04-21

    We report, for the first time, the luminescence property of the hydroxyl group surface functionalized quantum dots (QDs) and nanoparticles (NPs) of SnO2 using low energy excitations of 2.54 eV (488 nm) and 2.42 eV (514.5 nm). This luminescence is in addition to generally observed luminescence from 'O' defects. The as-prepared SnO2 QDs are annealed at different temperatures under ambient conditions to create NPs with varying sizes. Subsequently, the average size of the NPs is calculated from the acoustic vibrations observed at low frequencies in the Raman spectra and by the transmission electron microscopy measurements. Detailed photoluminescence studies with 3.815 eV (325 nm) excitation reveal the nature of in-plane and bridging 'O' vacancies as well as adsorption and desorption occurring at different annealing temperatures. X-ray photoelectron spectroscopy studies also support this observation. The defect level related to the surface -OH functional groups shows a broad luminescence peak at around 1.96 eV in SnO2 NPs which is elaborated using temperature dependent studies. PMID:25774472

  15. Extraction of Cesium by a Calix[4]arene-Crown-6 Ether Bearing a Pendant amine Group

    SciTech Connect

    Harmon, Ben; Ensor, Dale; Delmau, Laetitia Helene; Moyer, Bruce A

    2007-01-01

    The goal of this work was to evaluate the role of the amino group of 5-aminomethylcalix[4]arene-[bis-4-(2-ethylhexyl)benzo-crown-6] (AMBEHB) in the extraction of cesium from acidic and basic mixtures of sodium nitrate and other concentrated salts. The extraction of cesium from nitrate media was measured as a function of extractant concentration, nitrate concentration, cesium concentration, and pH over the range 1-13. The initial studies showed a moderate decrease in the extraction of cesium in acidic media, which indicated the binding of cesium by the calixarene-crown was weakened by the protonation of the amine group. The results also indicated that a 1:1:1 Cs-ligand-nitrate complex is formed in the organic phase. To further evaluate AMBEHB, the empirical data were mathematically modeled to determine the formation constants of the complexes formed in the organic phase. The resulting formation constants showed that the attachment of the amine group to the calixarene-crown molecule reduced the binding stability for the cesium ion upon contact with an acidic solution. This supports the hypothesis of charge repulsion as the basis for more efficient stripping of cesium via pH-switching.

  16. Curable liquid hydrocarbon prepolymers containing hydroxyl groups and process for producing same

    NASA Technical Reports Server (NTRS)

    Rhein, R. A.; Ingham, J. D. (Inventor)

    1978-01-01

    Production of hydroxyl containing curable liquid hydrocarbon prepolymers by ozonizing a high molecular weight saturated hydrocarbon polymer such as polyisobutylene or ethylene propylene rubber is discussed. The ozonized material is reduced using reducing agents, preferably diisobutyl aluminum hydride, to form the hydroxyl containing liquid prepolymers having a substantially lower molecular weight than the parent polymer. The resulting curable liquid hydroxyl containing prepolymers can be poured into a mold and readily cured, with reactants such as toluene diisocyanate, to produce highly stable elastomers having a variety of uses such as binders for solid propellants.

  17. ENUMERATION OF CARBOHYDRATE HYDROXYL GROUPS BY SILYLATION AND MATRIX ASSISTED LASER DESORPTION/IONIZATION TIME-OF-FLIGHT MASS SPECTROMETRY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A method for enumerating hydroxyl group in analytes is described and applied to various carbohydrates and polyols. The analytes were derivatized in solution by using trimethylsilylimidazole (TMSI) and the products were analyzed without chromatography in a MALDI-TOF-MS. The mass spectra revealed co...

  18. Enumeration of sugars and sugar alcohols hydroxyl groups by aqueous-based acetylation and MALDI-TOF mass spectrometry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A method is described for enumerating hydroxyl groups on analytes in aqueous media is described, and applied to some common polyalcohols (erythritol, mannitol, and xylitol) and selected carbohydrates. The analytes were derivatized in water with vinyl acetate in presence of sodium phosphate buffer. ...

  19. Bis(alkyl) rare-earth complexes supported by a new tridentate amidinate ligand with a pendant diphenylphosphine oxide group. Synthesis, structures and catalytic activity in isoprene polymerization.

    PubMed

    Tolpygin, Aleksei O; Glukhova, Tatyana A; Cherkasov, Anton V; Fukin, Georgy K; Aleksanyan, Diana V; Cui, Dongmei; Trifonov, Alexander A

    2015-10-01

    A new tridentate amidine 2-[Ph2P(O)]C6H4NHC(tBu)[double bond, length as m-dash]N(2,6-Me2C6H3) (1) bearing a side chain pendant Ph2P[double bond, length as m-dash]O group was synthesized and proved to be a suitable ligand for coordination to rare-earths ions. Bis(alkyl) complexes {2-[Ph2P(O)]C6H4NC(tBu)N(2,6-Me2C6H3)}Ln(CH2SiMe3)2(THF)n (Ln = Y, n = 1 (3), Ln = Er, n = 1 (4), Ln = Lu, n = 0 (5)) were prepared using alkane elimination reactions of and Ln(CH2SiMe3)3(THF)2 (Ln = Y, Er, Lu) in hexane and were isolated in 50, 70 and 75% yields respectively. The X-ray studies revealed that complexes 2-5 feature intramolecular coordination of P[double bond, length as m-dash]O groups to metal ions. The lutetium complex 5 proved to be rather stable: at 20 °C its half-life time is 1155 h, while for the yttrium analogue the half-life time was found to be 63 h. Complexes 3-5 were evaluated as precatalysts for isoprene polymerization. The systems Ln/borate/AliBu3 (Ln = 3-5, borate = [PhNHMe2][B(C6F5)4], [Ph3C][B(C6F5)4]) turned out to be highly efficient in isoprene polymerization and enable complete conversion of 1000-10,000 equivalents of monomer into polymer at 20 °C within 0.5-2.5 h affording polyisoprenes with a very high content of 1,4-cis units (up to 96.6%) and from narrow (1.49) to moderate (3.54) polydispersities. A comparative study of catalytic performance of the related bis(alkyl) yttrium complexes supported by amidinate ligands of different denticities and structures [tBuC(N-2,6iPr2C6H4)2](-), [tBuC(N-2,6-iPr2C6H4)(N-2-MeOC6H4)](-) and {2-[Ph2P(O)]C6H4NC(tBu)N(2,6-Me2C6H3)}(-) demonstrated that the introduction of a pendant donor group (2-MeOC6H4 or Ph2P(O)) into a side chain of amidinate scaffolds results in a significant increase in catalytic activity. The amidinate ligand bearing a Ph2P(O)-group provides a high isoprene polymerization rate along with excellent control over regio- and stereoselectivities and allows us to obtain polyisoprenes with a reasonable

  20. Effects of the Hydroxyl Group on Phenyl Based Ligand/ERRγ Protein Binding

    PubMed Central

    2015-01-01

    Bisphenol-A (4,4′-dihydroxy-2,2-diphenylpropane, BPA, or BPA-A) and its derivatives, when exposed to humans, may affect functions of multiple organs by specific binding to the human estrogen-related receptor γ (ERRγ). We carried out atomistic molecular dynamics (MD) simulations of three ligand compounds including BPA-A, 4-α-cumylphenol (BPA-C), and 2,2-diphenylpropane (BPA-D) binding to the ligand binding domain (LBD) of a human ERRγ to study the structures and energies associated with the binding. We used the implicit Molecular Mechanics/Poisson–Boltzmann Surface Area (MM/PBSA) method to estimate the free energies of binding for the phenyl based compound/ERRγ systems. The addition of hydroxyl groups to the aromatic ring had only a minor effect on binding structures and a significant effect on ligand/protein binding energy in an aqueous solution. Free binding energies of BPA-D to the ERRγ were found to be considerably less than those of BPA-A and BPA-C to the ERRγ. These results are well correlated with those from experiments where no binding affinities were determined in the BPA-D/ERRγ complex. No conformational change was observed for the helix 12 (H-12) of ERRγ upon binding of these compounds preserving an active transcriptional conformation state. PMID:25098505

  1. Synthesis and evaluation of lanthanide ion DOTA-tetraamide complexes bearing peripheral hydroxyl groups

    PubMed Central

    Pasha, Azhar; Lin, Mai; Tircsó, Gyula; Rostollan, Cynthia L.; Woods, Mark; Kiefer, Garry E.; Sherry, A. Dean; Sun, Xiankai

    2009-01-01

    The use of lanthanide-based contrast agents for magnetic resonance imaging (MRI) has become an integral component of this important diagnostic modality. These inert chelates typically possess high thermodynamic stability constants that serve as a predictor for in vivo stability and low toxicity. Recently a new class of contrast agents was reported having a significantly lower degree thermodynamic stability while exhibiting biodistribution profiles indicative of high stability under biological conditions. These observations are suggestive that the nature of contrast agent stability is also dependent upon the kinetics of complex dissociation; a feature of potential importance when contemplating the design of new chelates for in vivo use. In this paper we present a study of the kinetics of acid catalyzed dissociation, thermodynamic stability, serum stability and biodistribution of a series of DOTA-tetraamide complexes that have been substituted with peripheral hydroxyl groups. The data indicate that these non-traditional contrast agents exhibit in vivo stability comparable to agents with much higher log KML values demonstrating the important contribution of kinetic inertness. PMID:19083028

  2. Distribution of Hydroxyl Groups in Kukersite Shale Oil: Quantitative Determination Using Fourier Transform Infrared (FT-IR) Spectroscopy.

    PubMed

    Baird, Zachariah Steven; Oja, Vahur; Järvik, Oliver

    2015-05-01

    This article describes the use of Fourier transform infrared (FT-IR) spectroscopy to quantitatively measure the hydroxyl concentrations among narrow boiling shale oil cuts. Shale oil samples were from an industrial solid heat carrier retort. Reference values were measured by titration and were used to create a partial least squares regression model from FT-IR data. The model had a root mean squared error (RMSE) of 0.44 wt% OH. This method was then used to study the distribution of hydroxyl groups among more than 100 shale oil cuts, which showed that hydroxyl content increased with the average boiling point of the cut up to about 350 °C and then leveled off and decreased. PMID:25811170

  3. A recyclable heavy fluorous tag carrying an allyl alcohol pendant group: design and evaluation toward applications in synthetic carbohydrate chemistry.

    PubMed

    Fukuda, Kazuo; Tojino, Mami; Goto, Kohtaro; Dohi, Hirofumi; Nishida, Yoshihiro; Mizuno, Mamoru

    2015-04-30

    Toward applications in synthetic carbohydrate chemistry, we converted our previous acid-resistant heavy fluorous tag [(Rf)3C-CH2-OH, 1] to allyl alcohol derivatives [(Rf)3C-CH2-O-(CH2)n-CH=CH-CH2-OH, 3 (n=1) or 4 (n=3)] by means of olefin cross metathesis. They were then subjected to β-glycosylation reactions by using a series of glycosyl donors, including glycosyl bromide and trichloroacetimidates. The terminal OH group in 3 and 4 was found to be β-glycosylated in moderate yield when 2,3,4,6-tetra-O-benzoyl-D-galactosyl trichloroacetimidate was used as the glycosyl donor. Upon a detachment reaction using Pd(PPh3)4, the initial heavy fluorous tag 1 was recovered in high yield (>90%) together with 1-hydroxy sugar, indicating that not only the allyl ether linkage in the glycosides but also the internal di-alkyl ether linkage in 4 be cleaved by the action of the Pd-catalyst enabling long-range olefin transmigration. Potential utility was demonstrated by using the tetra-O-benzoyl-β-D-galactosylated derivative of 3 in a series of deprotection, protection and glycosylation reactions, which were conductible in high yields without using chromatographic purification process. These findings prompt us to propose a general scheme in which the acid-resistant heavy fluorous compound 1 is applied as a recyclable tag in synthetic carbohydrate chemistry. PMID:25753904

  4. Unique Phase Behaviors in the Gemini Surfactant/EAN Binary System: The Role of the Hydroxyl Group.

    PubMed

    Li, Qintang; Wang, Xudong; Yue, Xiu; Chen, Xiao

    2015-12-22

    The hydroxyl group in the spacer of a cationic Gemini surfactant (12-3OH-12) caused dramatic changes of the phase behaviors in a protic ionic liquid (EAN). Here, the effects of the hydroxyl group on micellization and lyotropic liquid crystal formation were investigated through the surface tension, small-angle X-ray scattering, polarized optical microscopy, and rheological measurements. With the hydroxyl group in the spacer, the critical micellization concentration of 12-3OH-12 was found to be lower than that of the homologue without hydroxyl (12-3-12) and the 12-3OH-12 molecules packed more densely at the air/EAN interface. It was then interesting to observe a coexistence of two separated phases at wide concentration and temperature ranges in this 12-3OH-12/EAN system. Such a micellar phase separation was rarely observed in the ionic surfactant binary system. With the increase of surfactant concentration, the reverse hexagonal and bicontinuous cubic phases appeared in sequence, whereas only a reverse hexagonal phase was found in 12-3-12/EAN system. But, the hexagonal phases formed with 12-3OH-12 exhibited lower viscoelasticity and thermostability than those observed in 12-3-12/EAN system. Such unique changes in phase behaviors of 12-3OH-12 were ascribed to their enhanced solvophilic interactions of 12-3OH-12 and relatively weak solvophobic interactions in EAN. PMID:26634877

  5. Role of hydroxyl groups on the stability and catalytic activity of Au clusters on rutile surface

    SciTech Connect

    Kent, Paul R

    2011-01-01

    Hydroxyls are present as surface terminations of transition metal oxides under ambient conditions and may modify the properties of supported catalysts. We perform first-principles density functional theory calculations to investigate the role of hydroxyls on the catalytic activity of supported gold clusters on TiO{sub 2} (rutile). We find that they have a long-range effect increasing the adhesion of gold clusters on rutile. While hydroxyls make one gold atom more electronegative, a more complex charge-transfer scenario is observed on larger clusters which are important for catalytic applications. This enhances the molecular adsorption and coadsorption energies of CO and O{sub 2}, thereby increasing the catalytic activity of gold clusters for CO oxidation, consistent with reported experiments. Hydroxyls at the interface between gold and rutile surface are most important to this process, even when not directly bound to gold. As such, accurate models of catalytic processes on gold and other catalysts should include the effect of surface hydroxyls.

  6. Self-organizing p-quinquephenyl building blocks incorporating lateral hydroxyl and methoxyl groups into supramolecular nano-assemblies.

    PubMed

    Lu, Zhaoyang; Zhong, Keli; Liu, Yang; Li, Zhaohua; Chen, Tie; Jin, Long Yi

    2016-05-01

    The self-assembling behavior of coil-rod-coil molecules 1a, 1b, and 2a, 2b was investigated using DSC, POM, SAXS, and AFM in bulk and aqueous solutions. These molecules contain p-quinquephenyl groups as rod segments incorporating lateral hydroxyl or methoxyl groups in the center positions and oligo(ethylene oxide)s as the coil segments. Molecules 1a and 1b, with lateral methoxyl groups in the rod segments, self-assemble into oblique columnar structures in the crystalline phase and transform into nematic phases. On the other hand, molecules 2a and 2b, with hydroxyl groups in the center of their rod segments, self-organize into hexagonal perforated lamellar and oblique columnar nano-structures in the crystalline and liquid crystalline phase, respectively. In aqueous solutions, these molecules aggregate into nano-ribbons and vesicles, depending on their lateral groups and oligo(ethylene oxide) chain lengths. These results imply that the lateral methoxyl or hydroxyl groups, present in the center of the rod segments, significantly influence the formation of various supramolecular nano-structures in the bulk state and in aqueous solution. This is achieved via tuning of the non-covalent interactions of the rod building blocks. PMID:27025276

  7. Anaerobic Activation of p-Cymene in Denitrifying Betaproteobacteria: Methyl Group Hydroxylation versus Addition to Fumarate

    PubMed Central

    Strijkstra, Annemieke; Trautwein, Kathleen; Jarling, René; Wöhlbrand, Lars; Dörries, Marvin; Reinhardt, Richard; Drozdowska, Marta; Golding, Bernard T.; Wilkes, Heinz

    2014-01-01

    The betaproteobacteria “Aromatoleum aromaticum” pCyN1 and “Thauera” sp. strain pCyN2 anaerobically degrade the plant-derived aromatic hydrocarbon p-cymene (4-isopropyltoluene) under nitrate-reducing conditions. Metabolite analysis of p-cymene-adapted “A. aromaticum” pCyN1 cells demonstrated the specific formation of 4-isopropylbenzyl alcohol and 4-isopropylbenzaldehyde, whereas with “Thauera” sp. pCyN2, exclusively 4-isopropylbenzylsuccinate and tentatively identified (4-isopropylphenyl)itaconate were observed. 4-Isopropylbenzoate in contrast was detected with both strains. Proteogenomic investigation of p-cymene- versus succinate-adapted cells of the two strains revealed distinct protein profiles agreeing with the different metabolites formed from p-cymene. “A. aromaticum” pCyN1 specifically produced (i) a putative p-cymene dehydrogenase (CmdABC) expected to hydroxylate the benzylic methyl group of p-cymene, (ii) two dehydrogenases putatively oxidizing 4-isopropylbenzyl alcohol (Iod) and 4-isopropylbenzaldehyde (Iad), and (iii) the putative 4-isopropylbenzoate-coenzyme A (CoA) ligase (Ibl). The p-cymene-specific protein profile of “Thauera” sp. pCyN2, on the other hand, encompassed proteins homologous to subunits of toluene-activating benzylsuccinate synthase (termed [4-isopropylbenzyl]succinate synthase IbsABCDEF; identified subunits, IbsAE) and protein homologs of the benzylsuccinate β-oxidation (Bbs) pathway (termed BisABCDEFGH; all identified except for BisEF). This study reveals that two related denitrifying bacteria employ fundamentally different peripheral degradation routes for one and the same substrate, p-cymene, with the two pathways apparently converging at the level of 4-isopropylbenzoyl-CoA. PMID:25261521

  8. Oxime ether lipids containing hydroxylated head groups are more superior siRNA delivery agents than their nonhydroxylated counterparts

    PubMed Central

    Gupta, Kshitij; Mattingly, Stephanie J; Knipp, Ralph J; Afonin, Kirill A; Viard, Mathias; Bergman, Joseph T; Stepler, Marissa; Nantz, Michael H; Puri, Anu; Shapiro, Bruce A

    2015-01-01

    Aim: To evaluate the structure–activity relationship of oxime ether lipids (OELs) containing modifications in the hydrophobic domains (chain length, degree of unsaturation) and hydrophilic head groups (polar domain hydroxyl groups) toward complex formation with siRNA molecules and siRNA delivery efficiency of resulting complexes to a human breast cancer cell line (MDA-MB-231). Materials & methods: Ability of lipoplex formation between oxime ether lipids with nucleic acids were examined using biophysical techniques. The potential of OELs to deliver nucleic acids and silence green fluorescent protein (GFP) gene was analyzed using MDA-MB-231 and MDA-MB-231/GFP cells, respectively. Results & conclusion: Introduction of hydroxyl groups to the polar domain of the OELs and unsaturation into the hydrophobic domain favor higher transfection and gene silencing in a cell culture system. PMID:26107486

  9. The influence of distribution of hydroxyl groups on vibrational spectra of fullerenol C60(OH)24 isomers: DFT study.

    PubMed

    Dawid, A; Górny, K; Gburski, Z

    2015-02-01

    The infrared and Raman spectra of C60(OH)24 molecule with uniform and non-uniform distribution of hydroxyl groups have been investigated using first principle DFT calculations at the B3LYP/6-31G(d,p) level of theory. The important features of the obtained geometries have been measured and compared to experimental results. The reference calculations of C60 molecule geometry and vibrational spectra have been made and compared to available experimental data. The striking differences of infrared spectra between C60(OH)24 molecule with uniform and non-uniform distribution of hydroxyl groups have been shown and discussed. The OH modes have been identified as the most sensitive to C60(OH)24 isomer configuration. The C-C stretching modes in the Raman spectra of the C60(OH)24 molecule have been found as a potential sensor of OH groups distribution over fullerene C60 surface. PMID:25223813

  10. Use of molecular dynamics to assess the biophysiological role of hydroxyl groups in glycerol dyalkyl glycerol teraethers

    NASA Astrophysics Data System (ADS)

    Huguet, Carme; Costenaro, Lionel; Fietz, Susanne; Daura, Xavier

    2015-04-01

    The cell membrane of some Archaea is constituted by lipids that span the whole membrane width and contain two alkyl chains bound by two glycerol groups (glycerol dyalkyl glycerol teraethers or GDGTs). These lipids confer stability to the membrane in mesophile to extremophile environments. Besides the more frequently studied isoprenoid archaeal lipids, both mono- and dihydroxy-GDGTs (OH-GDGT) have been recently reported to occur in marine sediments (1). OH-GDGTs contain up to two cyclopentane moieties and have been identified in both core and intact forms. In 2013, a correlation between OH-GDGTs and temperature was reported, with higher relative OH-GDGT abundances at high latitudes (2,3). The physiological function of the hydroxyl group in a GDGT is not yet known, but given the field results, it could be linked to an adaptation of the membrane to changes in temperature. For hydroxydiether lipid cores in methanogenic bacteria, it has been postulated that the hydroxyl group may alter the cell membrane properties: either extending the polar head group region or creating a hydrophilic pocket (4). It has also been suggested that the hydroxylation of the biphytany (l) moiety may result in enhanced membrane rigidity (1). To improve our understanding of the effect of the hydroxylation on physical properties of membranes, we performed molecular-dynamics simulations of GDGT membranes presenting and lacking these additional OH groups. This is an approach with a great development potential in the archaea lipid field, especially in relation to proxy validation. Our results indicate that the addition of an OH increases the membrane fluidity, thus providing an advantage in cold environments. We also observe a widening of the polar head group area, which could enhance transport. 1. Liu et al. 2012, GCA 2. Huguet et al. 2013, Org. Geochem 3. Fietz et al. 2013 4. Sprott et al. 1990. J. Biol. Chem. 265, 13735-13740.

  11. Synthesis of dendrigraft poly(ϵ-caprolactone)s using side hydroxyl groups for the grafting of branch chains.

    PubMed

    Cheng, Juan; Ling, Xiujun; Zhong, Zhenlin; Zhuo, Renxi

    2011-11-15

    Dendrigraft poly(ϵ-caprolactone)s with high molecular weight and narrow polydispersity are synthesized via a convenient generation-growth approach. Copolymerization of ϵ-caprolactone (CL) and 4-(2-benzoxyethoxy)-ϵ-caprolactone (BECL) with stannous octanoate as a catalyst affords a functionalized poly(ϵ-caprolactone) (PCL) with benzyl-protected hydroxyl side groups. After removal of benzyl groups by palladium-catalyzed hydrogenolysis, the graft copolymerization of CL and BECL onto the hydroxyl-bearing linear polyester (zero-generation) affords the first-generation graft polyester. Further deprotection and graft polymerization cycles led to dendrigraft polyesters. Molecular weights are multiplied in each graft copolymerization. The second-generation dendrigraft poly(ϵ-caprolactone) has an M(w) of 236 000 g·mol(-1) and M(w) /M(n) of 1.53. PMID:21928304

  12. An efficient approach to derive hydroxyl groups on the surface of barium titanate nanoparticles to improve its chemical modification ability.

    PubMed

    Chang, Shinn-Jen; Liao, Wei-Sheng; Ciou, Ci-Jin; Lee, Jyh-Tsung; Li, Chia-Chen

    2009-01-15

    Highly hydroxylated barium titanate (BaTiO(3)) nanoparticles have been prepared via an easy and gentle approach which oxidizes BaTiO(3) nanoparticles using an aqueous solution of hydrogen peroxide (H(2)O(2)). The hydroxylated BaTiO(3) surface reacts with sodium oleate (SOA) to form oleophilic layers that greatly enhance the dispersion of BaTiO(3) nanoparticles in organic solvents such as tetrahydrofuran, toluene, and n-octane. The results of Fourier transform infrared spectroscopy confirmed that the major functional groups on the surface of H(2)O(2)-treated BaTiO(3) nanoparticles are hydroxyl groups which are chemically active, favoring chemical bonding with SOA. The results of transmission electron microscopy of SOA-modified BaTiO(3) nanoparticles suggested that the oleate molecules were bonded to the surfaces of nanoparticles and formed a homogeneous layer having a thickness of about 2 nm. Furthermore, the improved dispersion capability of the modified BaTiO(3) nanoparticles in organic solvents was verified through analytic results of its settling and rheological behaviors. PMID:18977001

  13. Synthesis and evaluation of antibacterial polyurethane coatings made from soybean oil functionalized with dimethylphenylammonium iodide and hydroxyl groups.

    PubMed

    Bakhshi, Hadi; Yeganeh, Hamid; Mehdipour-Ataei, Shahram

    2013-06-01

    Preparation of antibacterial polyurethane coatings from novel functional soybean oil was considered in this work. First, epoxidized soybean oil (ESBO) as a low price and widely available renewable resource raw material was subjected to the reaction with aniline using an ionic liquid as a green catalyst. The intermediate phenylamine containing polyol (SAP) was then methylated by reaction with methyl iodide to produce a polyol (QAP) with pendant dimethylphenylammonium iodide groups. To regulate the physical and mechanical properties as well as biological characteristics of final coatings, QAP was mixed with different portions of a similar soybean oil-based polyol (MSP) without quaternary ammonium groups. The mixtures were reacted with isophorone diisocyanate to produce crosslinked polyurethane coatings. Evaluation of viscoelastic properties by DMA method revealed single phase structure with Tg in the range of 50-82°C. Stress-strain analysis of the prepared polyurethanes showed initial modulus, tensile strength, and elongation at break in the ranges of 13-299 MPa, 4.5-13.8 MPa, and 16-109%, respectively. Additionally, the coatings showed good adherence to aluminum and PVC substrates. The solvent extracted samples showed excellent biocompatibility as determined by monitoring L929 fibroblast cells morphology and MTT assay. Meanwhile, very promising antibacterial properties against both Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria with bacterial reduction in the range of 83-100% was observed. PMID:23172859

  14. Modulation of arachidonic acid metabolism by phenols: relation to positions of hydroxyl groups and peroxyl radical scavenging properties.

    PubMed

    Alanko, J; Riutta, A; Mucha, I; Vapaatalo, H; Metsä-Ketelä, T

    1993-01-01

    We have shown earlier that catecholamines have opposite regulative effects on prostaglandin (PG)E2 and leukotriene (LT)B4 formation with a receptor-independent mechanism in human polymorphonuclear leukocytes (PMNs) and whole blood. To shed further light on the mechanisms involved and structure-action relationship, we tested the effects of phenols (catechol, hydroquinone, phenol, and resorcinol) on the synthesis of PGE2 and LTB4 in human A23187-stimulated PMNs. To study the mechanism of how phenols influence PGE2 and LTB4 synthesis, their peroxyl radical-scavenging properties were analyzed. In general, low concentrations of phenols stimulated (catechol > hydroquinone > phenol) and high concentrations inhibited (resorcinol > catechol > hydroquinone > phenol) PGE2 formation. Resorcinol was different from the other phenols: It did not stimulate PGE2 synthesis at all, but it was effective inhibitor at high concentrations. Phenols had only an inhibitory effect on LTB4 formation (catechol = hydroquinone > phenol > resorcinol). The order of both stochiometric factors and reactivities of phenols for scavenging peroxyl radicals was catechol > hydroquinone > resorcinol > phenol. According to these results, phenols having hydroxyl groups in ortho- or paraposition have the greatest stimulative effect on PGE2 synthesis, the highest inhibitory action on LTB4 synthesis, and are good antioxidants. Resorcinol, having hydroxyl groups in the metaposition, behaves differently. It neither stimulates PGE2 nor inhibits LTB4 formation, but it is the most potent inhibitor of PGE2 formation. In spite of resorcinol's two hydroxyl groups, it mimics as an antioxidant phenol more than catechol and hydroquinone. PMID:8384148

  15. Glycerol dehydratation by the B12-independent enzyme may not involve the migration of a hydroxyl group: a computational study.

    PubMed

    Feliks, Mikolaj; Ullmann, G Matthias

    2012-06-21

    A combination of continuum electrostatic and density functional calculations has been employed to study the mechanism of the B(12)-independent glycerol dehydratase, a novel glycyl-radical enzyme involved in the microbial conversion of glycerol to 3-hydroxylpropionaldehyde. The calculations indicate that the dehydratation of glycerol by the B(12)-independent enzyme does not need to involve a mechanistically complicated migration of the middle hydroxyl group to one of the two terminal positions of a molecule, as previously suggested. Instead, the reaction can proceed in three elementary steps. First, a radical transfer from the catalytically active Cys433 to the ligand generates a substrate-related intermediate. Second, a hydroxyl group splits off at the middle position of the ligand and is protonated by the neighboring His164 to form a water molecule. The other active site residue Glu435 accepts a proton from one of the terminal hydroxyl groups of the ligand and a C═O double bond is created. Third, the reaction is completed by a radical back transfer from the product-related intermediate to Cys433. On the basis of our calculations, the catalytic functions of the active site residues have been suggested. Cys433 is a radical relay site; His164 and Glu435 make up a proton accepting/donating system; Asn156, His281, and Asp447 form a network of hydrogen bonds responsible for the electrostatic stabilization of the transition state. A synergistic participation of these residues in the reaction seems to be crucial for the catalysis. PMID:22626266

  16. Effect of active hydroxyl groups on the interfacial bond strength of titanium with segmented polyurethane through gamma-mercapto propyl trimethoxysilane.

    PubMed

    Sakamoto, Harumi; Hirohashi, Yohei; Saito, Haruka; Doi, Hisashi; Tsutsumi, Yusuke; Suzuki, Yoshiaki; Noda, Kazuhiko; Hanawa, Takao

    2008-01-01

    The objective of this study was to investigate the effect of active hydroxyl groups on a titanium (Ti) surface on the bond strength between Ti and segmented polyurethane (SPU) composite through gamma-mercapto propyl trimethoxysilane (gamma-MPS). Active hydroxyl groups on Ti surface oxide were controlled by immersion in hydrogen peroxide (H2O2) with different lengths of immersion time, and the resulting concentrations of active hydroxyl groups were evaluated using a zinc-complex substitution technique. For the H2O2-treated Ti, it was characterized using X-ray photoelectron spectroscopy and scanning electron spectroscopy. For the bond strength of Ti/ gamma-MPS/SPU interface, it was determined using a shear bond test. Results showed that the bond strength increased with increase in the concentration of active hydroxyl groups. In terms of durability after immersion in water at 310 K for 30 days, it was found that bond strength was improved with increase in active hydroxyl groups. Based on the results obtained, active hydroxyl groups on the surface oxide film were clearly one of the causes governing the interfacial bond strength. PMID:18309616

  17. Effect of alkyl chain length and hydroxyl group functionalization on the surface properties of imidazolium ionic liquids.

    PubMed

    Pensado, Alfonso S; Costa Gomes, Margarida F; Canongia Lopes, José N; Malfreyt, Patrice; Pádua, Agílio A H

    2011-08-14

    Properties of the surface of ionic liquids, such as surface tension, ordering, and charge and density profiles, were studied using molecular simulation. Two types of modification in the molecular structure of imidazolium cations were studied: the length of the alkyl side chain and the presence of a polar hydroxyl group at the end of the side chain. Four ionic liquids were considered: 1-ethyl-3-methylimidazolium tetrafluoroborate, [C(2)C(1)im][BF(4)]; 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate, [C(2)OHC(1)im][BF(4)]; 1-octyl-3-methylimidazolium tetrafluoroborate, [C(8)C(1)im][BF(4)] and 1-(8-hydroxyoctyl)-3-methylimidazolium tetrafluoroborate, [C(8)OHC(1)im][BF(4)]. The surface tension was calculated using both mechanical and thermodynamic definitions, with consistent treatment of the long-range corrections. The simulations reproduce the available experimental values of surface tension with a maximum deviation of ±10%. This energetic characterization of the interface is completed by microscopic structural analysis of orientational ordering at the interface and density profiles along the direction normal to the interface. The presence of the hydroxyl group modifies the local structure at the interface, leading to a less organized liquid phase. The results allow us to relate the surface tension to the structural ordering at the liquid-vacuum interface. PMID:21643581

  18. Number of free hydroxyl groups on bile acid phospholipids determines the fluidity and hydration of model membranes.

    PubMed

    Sreekanth, Vedagopuram; Bajaj, Avinash

    2013-10-10

    Interactions of synthetic phospholipids with model membranes determines the drug release capabilities of phospholipid vesicles at diseased sites. We performed 1,6-diphenyl-1,3,5-hexatriene (DPH)-based fluorescence anisotropy, Laurdan-based membrane hydration, and differential scanning calorimetry (DSC) studies to cognize the interactions of three bile acid phospholipids, lithocholic acid-phosphocholine (LCA-PC), deoxycholic acid-phosphocholine (DCA-PC), and cholic acid-phosphocholine (CA-PC) with model membranes. These studies revealed that bile acid phospholipids increases membrane fluidity in DCA-PC > CA-PC > LCA-PC order, indicating that induction of membrane fluidity is contingent on the number and positioning of free hydroxyl groups on bile acids. Similarly, DCA-PC causes maximum membrane perturbations due to the presence of a free hydroxyl group, whereas LCA-PC induces gel phase in membranes due to hydrophobic bile acid acyl chain interactions. These DCA-PC-induced membrane perturbations induce a drastic decrease in phase transition temperature (Tm) as determined by calorimetric studies, whereas doping of LCA-PC causes phase transition broadening without change in Tm. Doping of CA-PC induces membrane perturbations and membrane hydration like DCA-PC but sharpening of phase transition at higher doping suggests self-association of CA-PC molecules. Therefore these differential mode of interactions between bile acid phospholipids and model membranes would help in the future for their use in drug delivery. PMID:24079709

  19. Metallographic analysis of 3000-year-old Kanalski Vrh hoard pendant

    SciTech Connect

    Paulin, Andrej; Spaic, Savo; Zalar, Anton; Orel-Trampuz, Neva

    2003-11-15

    In a Late Bronze Age hoard at Kanalski Vrh in Slovenia, bronze pendants were found among numerous other artifacts. Among them a group of nine pendants of very similar compositions contained higher amounts of antimony, arsenic, nickel, cobalt, and iron, which suggested that speiss was added to bronze. Furthermore, most pendants had a silvery grey surface that differed from the common color of tin bronze, with about 13% Sn. One of the pendants was analysed by light optical and electron microscopy, Auger electron spectroscopy (AES), X-ray diffraction (XRD), and differential thermal analysis (DTA). Analyses revealed that the surface of the pendant was corroded, the copper alpha phase was eaten away, and the remaining eutectoid phase exhibited that silvery grey color. Comparison of chemical composition of the pendant and of compositions of speiss ingots found in the same hoard indicated that speisses could be used as alloying additions in making melts for casting pendants.

  20. A functional polyester carrying free hydroxyl groups promotes the mineralization of osteoblast and human mesenchymal stem cell extracellular matrix.

    PubMed

    Bi, Xiaoping; You, Zhengwei; Gao, Jin; Fan, Xianqun; Wang, Yadong

    2014-06-01

    Functional groups can control biointerfaces and provide a simple way to make therapeutic materials. We recently reported the design and synthesis of poly(sebacoyl diglyceride) (PSeD) carrying a free hydroxyl group in its repeating unit. This paper examines the use of this polymer to promote biomineralization for application in bone tissue engineering. PSeD promoted more mineralization of extracellular matrix secreted by human mesenchymal stem cells and rat osteoblasts than poly(lactic-co-glycolic acid) (PLGA), which is currently widely used in bone tissue engineering. PSeD showed in vitro osteocompatibility and in vivo biocompatibility that matched or surpassed that of PLGA, as well as supported the attachment, proliferation and differentiation of rat osteoblasts and human mesenchymal stem cells. This demonstrates the potential of PSeD for use in bone regeneration. PMID:24560799

  1. Investigation of water and hydroxyl groups associated with coal fly ash by thermal desorption and fourier transform infrared photoacoustic spectroscopies

    SciTech Connect

    Seaverson, L.M.; McClelland, J.F.; Burnet, G.; Anderegg, J.W.; Iles, M.K.

    1985-01-01

    Thermal desorption spectrometry (TDS) and Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) have been used in combination to analyze the water and hydroxyl groups associated with four coal fly ashes. Measurements using the former technique on these ashes resulted in identification of three water desorption regions in the temperature range from 25/sup 0/ to 1100/sup 0/C. The regions consisted of a small desorption peak at 50/sup 0/, a broad band from 180/sup 0/ to 400/sup 0/, and an intense peak from 400/sup 0/ to 590/sup 0/. No additional water desorption was observed up to 1100/sup 0/. A fourth ash gave a similar spectrum except that it lacked the intense last peak. The TDS spectra together with FT-IR/PAS spectra taken on samples exposed to pre- and post-desorption peak temperatures allowed the first TDS peak to be assigned to the desorption of physically adsorbed water, the broad band to desorption of hydrogenbonded surface hydroxyls, and the intense last peak to the decomposition of Ca(OH)/sub 2/.

  2. Band profile of hydroxyl groups in the infrared spectrum of hydrogen-bonded surface complexes: Ammonia on silicon dioxide

    SciTech Connect

    Pavlov, A.Y.; Tsyganenko, A.A.

    1994-07-01

    Dependences of the band maximum and band half-width of the stretching modes of surface OH and OD groups perturbed by ammonia adsorption on Aerosil were studied as functions of sample temperature, amount of adsorbed ammonia, and thermal treatment in vacuum. The appearance of a low-frequency wing was explained by the formation of polymer chains of OH groups coupled via adsorbed molecules. The latter tend to form a second bond with an oxygen atom of the neighboring OH group in addition to a hydrogen bond with a hydroxyl proton via nitrogen. The wide band at 3250 cm{sup -1} was assigned to NH groups of adsorbed molecules perturbed by H-bonding with oxygen. This band is observed as a shoulder of the coupled-OH group band. The large width of the latter as well as its temperature behavior was explained by differences in the arrangement of OH groups and by anharmonic coupling with the low-frequency vibrational modes of the complex. 14 refs., 4 figs., 4 tabs.

  3. Boron-doped bismuth oxybromide microspheres with enhanced surface hydroxyl groups: Synthesis, characterization and dramatic photocatalytic activity.

    PubMed

    Liu, ZhangSheng; Liu, JinLong; Wang, HaiYang; Cao, Gang; Niu, JiNan

    2016-02-01

    B-doped BiOBr photocatalysts were successfully synthesized via a facile solvothermal method with boric acid used as boron source. As-obtained products consist of novel hierarchical microspheres, whose nanosheet building units were formed by nanoparticles splicing. They showed dramatic photocatalytic efficiency toward the degradation of Rhodamine B (RhB) and phenol under the visible-light irradiation and the highest activity was achieved by 0.075B-BiOBr. The enhanced photocatalytic activity could be attributed to the enriched surface hydroxyl groups on B-doped BiOBr samples, which not only improved the adsorption of pollutant on the photocatalyst but also promoted the separation of photogenerated electron-hole pairs. In addition, it was found that the main reactive species responsible for the degradation of organic pollutant were h(+) and O2(-) radicals, instead of OH radicals. PMID:26590875

  4. Fine structures in vibrational circular dichroism spectra of chiral molecules with rotatable hydroxyl groups and their application in the analysis of local intermolecular interactions

    NASA Astrophysics Data System (ADS)

    Konno, Kohzo; Shiina, Isamu; Yui, Hiroharu

    2013-03-01

    The effect of hydroxyl group on vibrational circular dichroism is addressed. (-)-Menthol is investigated as a representative chiral molecule which has been widely used as a chiral starting material. Free rotation of the hydroxyl group in (-)-menthol allows it to exist in various conformations in solution. The variety of conformations inevitably affects local intermolecular interactions and the resultant efficiency of asymmetric syntheses. However, the precise relationship between the conformations and intermolecular interactions arising from rotation of the hydroxyl group has remained an unsolved issue despite the molecule's importance. Here, the conformations and interactions are investigated using vibrational circular dichroism (VCD). VCD is quite sensitive to slight differences in the conformation of chiral molecules and their local environment. We examined various conformers in (-)-menthol and compared the VCD spectrum with that of (-)-menthone. It revealed the rotation of the polar hydroxyl group sensitively affects the VCD activity, resulting in the emergence of various patterns in the corresponding VCD spectra, especially in the wavenumber regions at around 1064 cm-1 and 1254 cm-1. Among these regions, the latter one is further investigated to examine the feasibility of applying the sensitive response to the analysis on the local intermolecular environment. It includes solute-solvent interactions via hydroxyl groups, which is important for biomacromolecule structural stability and efficient stereoselective syntheses. As a consequence, distinctive fine structures in the VCD spectra, including an unpredicted band, are observed when varying temperature and concentration. Their possible assignment is also discussed.

  5. Influence of Hydroxyl Group Position and Temperature on Thermophysical Properties of Tetraalkylammonium Hydroxide Ionic Liquids with Alcohols

    PubMed Central

    Attri, Pankaj; Baik, Ku Youn.; Venkatesu, Pannuru; Kim, In Tae; Choi, Eun Ha

    2014-01-01

    In this work, we have explored the thermophysical properties of tetraalkylammonium hydroxide ionic liquids (ILs) such as tetrapropylammonium hydroxide (TPAH) and tetrabutylammonium hydroxide (TBAH) with isomers of butanol (1-butanol, 2-butanol and 2-methyl-2-propanol) within the temperature range 293.15–313.15 K, with interval of 5 K and over the varied concentration range of ILs. The molecular interactions between ILs and butanol isomers are essential for understanding the function of ILs in related measures and excess functions are sensitive probe for the molecular interactions. Therefore, we calculated the excess molar volume (VE) and the deviation in isentropic compressibility (Δκs) using the experimental values such as densities (ρ) and ultrasonic sound velocities (u) that are measured over the whole compositions range at five different temperatures (293.15, 298.15, 303.15, 308.15 and 313.15 K) and atmospheric pressure. These excess functions were adequately correlated by using the Redlich–Kister polynomial equation. It was observed that for all studied systems, the VE and Δκs values are negative for the whole composition range at 293.15 K. And, the excess function follows the sequence: 2-butanol>1-butanol>2-methyl-2-propanol, which reveals that (primary or secondary or tertiary) position of hydroxyl group influence the magnitude of interactions with ILs. The negative values of excess functions are contributions from the ion-dipole interaction, hydrogen bonding and packing efficiency between the ILs and butanol isomers. Hence, the position of hydroxyl group plays an important role in the interactions with ILs. The hydrogen bonding features between ILs and alcohols were analysed using molecular modelling program by using HyperChem 7. PMID:24489741

  6. Influence of hydroxyl group position and temperature on thermophysical properties of tetraalkylammonium hydroxide ionic liquids with alcohols.

    PubMed

    Attri, Pankaj; Baik, Ku Youn; Venkatesu, Pannuru; Kim, In Tae; Choi, Eun Ha

    2014-01-01

    In this work, we have explored the thermophysical properties of tetraalkylammonium hydroxide ionic liquids (ILs) such as tetrapropylammonium hydroxide (TPAH) and tetrabutylammonium hydroxide (TBAH) with isomers of butanol (1-butanol, 2-butanol and 2-methyl-2-propanol) within the temperature range 293.15-313.15 K, with interval of 5 K and over the varied concentration range of ILs. The molecular interactions between ILs and butanol isomers are essential for understanding the function of ILs in related measures and excess functions are sensitive probe for the molecular interactions. Therefore, we calculated the excess molar volume (V(E) ) and the deviation in isentropic compressibility (Δκs ) using the experimental values such as densities (ρ) and ultrasonic sound velocities (u) that are measured over the whole compositions range at five different temperatures (293.15, 298.15, 303.15, 308.15 and 313.15 K) and atmospheric pressure. These excess functions were adequately correlated by using the Redlich-Kister polynomial equation. It was observed that for all studied systems, the V(E) and Δκs values are negative for the whole composition range at 293.15 K. And, the excess function follows the sequence: 2-butanol>1-butanol>2-methyl-2-propanol, which reveals that (primary or secondary or tertiary) position of hydroxyl group influence the magnitude of interactions with ILs. The negative values of excess functions are contributions from the ion-dipole interaction, hydrogen bonding and packing efficiency between the ILs and butanol isomers. Hence, the position of hydroxyl group plays an important role in the interactions with ILs. The hydrogen bonding features between ILs and alcohols were analysed using molecular modelling program by using HyperChem 7. PMID:24489741

  7. A new synthesis of lysophosphatidylcholines and related derivatives. Use of p-toluenesulfonate for hydroxyl group protection.

    PubMed

    Rosseto, Renato; Bibak, Niloufar; DeOcampo, Rosemarie; Shah, Trishul; Gabrielian, Ara; Hajdu, Joseph

    2007-03-01

    A new stereoselective synthesis of lysophosphatidylcholines is reported. The synthesis is based upon (1) the use of 3-p-toluenesulfonyl-sn-glycerol to provide the stereocenter for construction of the optically active lysophospholipid molecule, (2) tetrahydropyranylation of the secondary alcohol function to achieve orthogonal protection of the sn-2- and sn-3-glycerol positions, and (3) elaboration of the phosphodiester headgroup using a 2-chloro-1,3,2-dioxaphospholane/trimethylamine sequence. In the course of developing the synthesis it has been discovered that methoxyacetate displacement of the sn-3-p-toluenesulfonate yields a reactive methoxyacetyl ester, which in turn can be selectively cleaved with methanol/tert-butylamine, while the ester group at the sn-1-position remains unaffected. The sequence has been shown to be suitable for preparation of spectroscopically labeled lysophosphatidylcholines. One of these compounds was readily converted to a double-labeled mixed-chain phosphatidylcholine applicable for real-time fluorescence resonance energy transfer (FRET) assay of lipolytic enzymes. In addition, the work led to new synthetic strategies based on chemoselective manipulation of the tosyl group in the presence of other base-labile groups such as FMOC derivatives that are often used for the protection of amino and hydroxyl groups in syntheses. PMID:17284078

  8. Heterogeneity of hydroxyl and deuteroxyl groups on the surface of TiO{sub 2} polymorphs

    SciTech Connect

    Contescu, C.; Popa, V.T.; Schwarz, J.A.

    1996-06-01

    Potentiometric titration data from pure rutile, anatase, and a commercial fumed titania (Degussa P25) were analyzed in terms of proton binding isotherms from which proton affinity distributions (PADs) of surface sites were obtained. As-received samples, whose thermal and storage history were not systematically controlled, as well as samples subjected to controlled calcination-rehydration-drying treatments were studied. The results indicated the occurrence of a limited number of surface groups on the two polymorphs. The behavior of pure rutile and anatase could be admixed to simulate the acid-base behavior of the commercial sample; on this basis the surface of fumed titania consists largely of anatase-like structures with a small contribution (7%) of rutile-like groups. The region of {nu}{sub OD} stretching vibrations of isolated -OD groups on extensively dehydroxylated samples was found to correlate with the pK`s determined from PADs. A qualitative assignment of measured pK values based on either the original MUSIC model (Hiemstra, T., de Wit, J.C.M., and Van Riemsdijk, W.H., J. Colloid Interface Sci. 133, 105 (1989)) or a refined version of it is presented.

  9. Stereochemical arrangement of hydroxyl groups in sugar and polyalcohol molecules as an important factor in effective cryopreservation.

    PubMed

    Turner, S; Senaratna, T; Touchell, D; Bunn, E; Dixon, K; Tan, B

    2001-02-01

    The efficacy of several sugars and polyalcohols in preculture medium was investigated using Anigozanthos viridis ssp terraspectans Hopper (Haemodoraceae), a threatened plant species endemic to the south west of Western Australia. A vitrification protocol involving preculturing of shoot apices for 3 days on different concentrations of sugars and polyalcohols, followed by incubation in plant vitrification solution 2 (PVS2) for 25 min, prior to immersion in liquid nitrogen (LN) and warming resulted in shoot tip survival ranging from 34 to 84%. High levels of survival were obtained with polyalcohols, compared to sucrose, glucose, trehalose and raffinose when used at the same molarity (0.4 M) or at the equivalent concentration of total hydroxyl (OH) groups present in molecules. In both cases glycerol proved more effective. When polyalcohols (ribitol and erythritol) with similar stereochemical arrangement of OH groups as glycerol were examined, at the same molarity (0.4 M) and with equivalent OH numbers, higher survival was achieved when the total number of OH groups present was the same as glycerol. Additionally, when the structural isomers mannitol/sorbitol and ribitol/xylitol were compared at the same molarity (0.4 M), the isomer with the higher number of OH groups along the same side resulted in significantly higher levels of post-LN survival. We propose that the mode of action of polyalcohols is based not on molarity, but on the total number of OH groups present in the medium. Furthermore, based on these results we propose that the orientation of OH groups is a determining factor in effective cryopreservation. PMID:11166436

  10. Short-step chemical synthesis of DNA by use of MMTrS group for protection of 5'-hydroxyl group.

    PubMed

    Shiraishi, Miyuki; Utagawa, Eri; Ohkubo, Akihiro; Sekine, Mitsuo; Seio, Kohji

    2007-01-01

    4-methoxytrithylthio (MMTrS) group was applied for the appropriately protected four canonical nucleosides. We prepared the phosphoroamidite units by use of these nucleosides and developed the synthesis of oligodeoxynucleotides without any acidic treatment. Moreover, the new DNA synthesis protocol was applied to an automated DNA synthesizer for the synthesis of longer oligodeoxynucleotides. PMID:18029620

  11. Neurosteroids: Can a 2alpha,3alpha-epoxy ring make up for the 3alpha-hydroxyl group?

    PubMed

    Kasal, Alexander; Buděšínský, Miloš; Mareš, Pavel; Krištofíková, Zdena; Leitão, Alcino J; Sá e Melo, Maria Luisa; Silva, Maria Manuel C

    2016-01-01

    Seven steroid epoxides were prepared from 5α-pregn-2-en-20-one and 5α-pregn-3-en-20-one and their side-chain derivatives. All compounds were tested in vitro for binding to γ-aminobutyric acid (GABAA) receptor, some of them also in vivo for anticonvulsant action. 2α,3α-Epoxy-5α-pregnan-20-one inhibited the TBPS binding to the GABAA receptor and showed a moderate anticonvulsant action in immature rats. In contrast, its 3α,4α-isomer was inactive. More polar epoxide derivatives, modified at the side chain were less active or inactive. Noteworthy, diol 20, the product of trans-diaxial opening of the 2α,3α-epoxide 4, was not able to inhibit the TBPS binding, showing that the activity of the epoxide is due to the compound itself and not to its hydrolytic product. The 3α-hydroxyl group is known to be essential for the GABAA receptor binding. Despite the shortness of in vivo effects which are probably due to metabolic inactivation of the products prepared, our results show that the 2α,3α-epoxy ring is another structural pattern with ability to bind the GABAAR. PMID:26631551

  12. Plasma enhanced chemical vapour deposition of silica onto Ti: Analysis of surface chemistry, morphology and functional hydroxyl groups

    PubMed Central

    Szili, Endre J.; Kumar, Sunil; Smart, Roger St. C.; Lowe, Rachel; Saiz, Eduardo; Voelcker, Nicolas H.

    2009-01-01

    Previously, we have developed and characterised a procedure for the deposition of thin silica films by a plasma enhanced chemical vapour deposition (PECVD) procedure using tetraethoxysilane (TEOS) as the main precursor. We have used the silica coatings for improving the corrosion resistance of metals and for enhancing the bioactivity of biomedical metallic implants. Recently, we have been fine-tuning the PECVD method for producing high quality and reproducible PECVD-silica (PECVD-Si) coatings on metals, primarily for biomaterial applications. In order to understand the interaction of the PECVD-Si coatings with biological species (such as proteins and cells), it is important to first analyse the properties of the silica films deposited using the optimised parameters. Therefore, this current investigation was carried out to analyse the characteristic features of PECVD-Si deposited on Ti substrates (PECVD-Si-Ti). We determined that the PECVD-Si coatings on Ti were conformal to the substrate surface, strongly adhered to the underlying substrate and were resistant to delamination. The PECVD-Si surface was composed of stoichiometric SiO2, showed a low carbon content (below 10 at.%) and was very hydrophilic (contact angle <10°). Finally, we also showed that the PECVD-Si coatings contain functional hydroxyl groups. PMID:19809536

  13. Horseradish peroxidase-catalyzed formation of hydrogels from chitosan and poly(vinyl alcohol) derivatives both possessing phenolic hydroxyl groups.

    PubMed

    Sakai, Shinji; Khanmohammadi, Mehdi; Khoshfetrat, Ali Baradar; Taya, Masahito

    2014-10-13

    Horseradish peroxidase-catalyzed cross-linking was applied to prepare hydrogels from aqueous solutions containing chitosan and poly(vinyl alcohol) derivatives both possessing phenolic hydroxyl groups (denoted as Ph-chitosan and Ph-PVA, respectively). Comparing the hydrogels prepared from the solution of 1.0% (w/v) Ph-chitosan and 3.0% (w/v) Ph-PVA and that of 3.0% (w/v) Ph-chitosan and 1.0% (w/v) Ph-PVA, the gelation time of the former hydrogel was 47 s, while was 10s longer than that of the latter one. The breaking point for the former hydrogel under stretching (114% strain) was approximately twice larger than that for the latter one. The swelling ratio of the former hydrogel in saline was about half of the latter one. Fibroblastic cells did not adhere on the former hydrogel but adhered and spread on the latter one. The growth of Escherichia coli cells was fully suppressed on the latter hydrogel during 48 h cultivation. PMID:25037368

  14. Effect of replacing a hydroxyl group with a methyl group on arsenic (V) species adsorption on goethite (alpha-FeOOH).

    PubMed

    Zhang, J S; Stanforth, R S; Pehkonen, S O

    2007-02-01

    Arsenate and methylated arsenicals, such as dimethylarsinate (DMA) and monomethylarsonate (MMA), are being found with increasing frequency in natural water systems. The mobility and bioavailability of these arsenic species in the environment are strongly influenced by their interactions with mineral surface, especially iron and aluminum oxides. Goethite (alpha-FeOOH), one of the most abundant ferric (hydr)oxides in natural systems, has a high retention capacity for arsenic species. Unfortunately, the sorption mechanism for the species is not completely understood, which limits our ability to model their behavior in natural systems. The purpose of this study is to investigate the effect of replacing a hydroxyl group with a methyl group on the adsorption behaviors of arsenic (V) species using adsorption edges, the influence of the background electrolyte on arsenic adsorption, and their effect on the zeta potential of goethite. The affinity of the three species to the goethite surface decreases in the order of AsO4=MMA>DMA. The uptake of DMA and MMA is independent of the concentration of background electrolyte, indicating that both species form inner-sphere complexes on the goethite surface and the most charge of adsorbed DMA and MMA locates at the surface plane. Arsenate uptake increases with increasing concentrations of background electrolyte at pH above 4, possibly due to that the charge of adsorbed arsenate is distributed between the surface plane and another electrostatic plane. DMA and lower concentrations of MMA have small effect on the zeta potential, whereas the zeta potential of goethite decreases in the presence of arsenate. The small effect on zeta potential of DMA or MMA adsorption suggests that the sorption sites for the anions is not important in controlling the surface charge. This observation is inconsistent with most adsorption models that postulate a singly coordinated hydroxyls contributing to both the adsorption and the surface charge, but

  15. Structure-Activity Relationship of Synthetic 2-Phenylnaphthalenes with Hydroxyl Groups that Inhibit Proliferation and Induce Apoptosis of MCF-7 Cancer Cells

    PubMed Central

    Chang, Chi-Fen; Ke, Ci-Yi; Wu, Yang-Chang; Chuang, Ta-Hsien

    2015-01-01

    In this study, six 2-phenylnaphthalenes with hydroxyl groups were synthesized in high yields by the demethylation of the corresponding methoxy-2-phenylnaphthalenes, and one 2-phenylnaphthalene with an amino group was obtained by hydrogenation. All of the 2-phenylnaphthalene derivatives were evaluated for cytotoxicity, and the structure-activity relationship (SAR) against human breast cancer (MCF-7) cells was also determined. The SAR results revealed that cytotoxicity was markedly promoted by the hydroxyl group at the C-7 position of the naphthalene ring. The introduction of hydroxyl groups at the C-6 position of the naphthalene ring and the C-4' position of the phenyl ring fairly enhanced cytotoxicity, but the introduction of a hydroxyl group at the C-3' position of the phenyl ring slightly decreased cytotoxicity. Overall, 6,7-dihydroxy-2-(4'-hydroxyphenyl)naphthalene (PNAP-6h) exhibited the best cytotoxicity, with an IC50 value of 4.8 μM against the MCF-7 cell line, and showed low toxicity toward normal human mammary epithelial cells (MCF-10A). PNAP-6h led to cell arrest at the S phase, most likely due to increasing levels of p21 and p27 and decreasing levels of cyclin D1, CDK4, cyclin E, and CDK2. In addition, PNAP-6h decreased CDK1 and cyclin B1 expression, most likely leading to G2/M arrest, and induced morphological changes, such as nuclear shrinkage, nuclear fragmentation, and nuclear hypercondensation, as observed by Hoechst 33342 staining. PNAP-6h induced apoptosis, most likely by the promotion of Fas expression, increased PARP activity, caspase-7, caspase-8, and caspase-9 expression, the Bax/Bcl-2 ratio, and the phosphorylation of p38, and decreased the phosphorylation of ERK. This study provides the first demonstration of the cytotoxicity of PNAPs against MCF-7 cells and elucidates the mechanism underlying PNAP-induced cytotoxicity. PMID:26492346

  16. Non-contact atomic force microscopy study of hydroxyl groups on the spinel MgAl2O4(100) surface.

    PubMed

    Federici Canova, F; Foster, A S; Rasmussen, M K; Meinander, K; Besenbacher, F; Lauritsen, J V

    2012-08-17

    Atom-resolved non-contact atomic force microscopy (NC-AFM) studies of the magnesium aluminate (MgAl(2)O(4)) surface have revealed that, contrary to expectations, the (100) surface is terminated by an aluminum and oxygen layer. Theoretical studies have suggested that hydrogen plays a strong role in stabilizing this surface through the formation of surface hydroxyl groups, but the previous studies did not discuss in depth the possible H configurations, the diffusion behaviour of hydrogen atoms and how the signature of adsorbed H is reflected in atom-resolved NC-AFM images. In this work, we combine first principles calculations with simulated and experimental NC-AFM images to investigate the role of hydrogen on the MgAl(2)O(4)(100) surface. By means of surface energy calculations based on density functional theory, we show that the presence of hydrogen adsorbed on the surface as hydroxyl groups is strongly predicted by surface stability considerations at all relevant partial pressures of H(2) and O(2). We then address the question of how such adsorbed hydrogen atoms are reflected in simulated NC-AFM images for the most stable surface hydroxyl groups, and compare with experimental atom-resolved NC-AFM data. In the appendices we provide details of the methods used to simulate NC-AFM using first principles methods and a virtual AFM. PMID:22827936

  17. Phosphorus-nitrogen compounds: Part 28. Syntheses, structural characterizations, antimicrobial and cytotoxic activities, and DNA interactions of new phosphazenes bearing vanillinato and pendant ferrocenyl groups

    NASA Astrophysics Data System (ADS)

    Tümer, Yasemin; Asmafiliz, Nuran; Kılıç, Zeynel; Hökelek, Tuncer; Yasemin Koç, L.; Açık, Leyla; Yola, Mehmet Lütfi; Solak, Ali Osman; Öner, Yağmur; Dündar, Devrim; Yavuz, Makbule

    2013-10-01

    The gradually Cl replacement reactions of spirocyclic mono (1 and 2) and bisferrocenyl cyclotriphosphazenes (3-5) with the potassium salt of 4-hydroxy-3-methoxybenzaldehyde (potassium vanillinate) gave mono (1a-5a), geminal (gem-1b-5b), non-geminal (cis-1b, cis-5b and trans-2b-5b), tri (1c-5c) and tetra-substituted phosphazenes (1d-5d). Some phosphazenes have stereogenic P-center(s). The chirality of 4c was verified using chiral HPLC column. Electrochemical behaviors were influenced only by the number of ferrocene groups, but not the length of the amine chains and the substituent(s). The structures of the new phosphazenes were determined by FTIR, MS, 1H, 13C and 31P NMR, HSQC and HMBC spectral data. The solid-state structures of cis-1b and 4d were examined by single crystal X-ray diffraction techniques. The twelve phosphazene derivatives were screened for antimicrobial activity and the compounds 5a, cis-1b and 2c exhibited the highest antibacterial activity against G(+) and G(-) bacteria. In addition, it was found that overall gem-1b inhibited the growth of Mycobacterium tuberculosis. The compounds 1d, 2d and 4d were tested in HeLa cancer cell lines. Among these compounds, 2d had cytotoxic effect on HeLa cell in the first 48 h. Moreover, interactions between compounds 2a, gem-1b, gem-2b, cis-1b, 2c, 3c, 4c, 5c, 1d, 2d and 4d, and pBR322 plasmid DNA were investigated.

  18. Influence of lipids with hydroxyl-containing head groups on Fe2+ (Cu2+)/H2O2-mediated transformation of phospholipids in model membranes.

    PubMed

    Olshyk, Viktoriya N; Melsitova, Inna V; Yurkova, Irina L

    2014-01-01

    Under condition of ROS formation in lipid membranes, free radical reactions can proceed in both hydrophobic (peroxidation of lipids, POL) and polar (free radical fragmentation) parts of the bilayer. Free-radical fragmentation is typical for the lipids containing a hydroxyl group in β-position with respect to an ester or amide bond. The present study has been undertaken to investigate free-radical transformations of phospholipids in model membranes containing lipids able to undergo fragmentation in their polar part. Liposomes from egg yolk lecithin containing saturated or monounsaturated glycero- and sphingolipids were subjected to the action of an HO* - generating system - Fe(2+)(Cu(2+))/H2O2/Asc, and the POL products were investigated. In parallel with this, the effects of monoacylglycerols and scavengers of reactive species on Fe(2+)(Cu(2+))/H2O2/Asc - mediated free-radical fragmentation of phosphatidylglycerols were studied. Hydroxyl-containing sphingolipids and glycerolipids, which undergo free-radical fragmentation under such conditions, manifested antioxidant properties in the model membranes. In the absence of HO groups in the lipid structure, the effect was either pro-oxidant or neutral. Monoacylglycerols slowed down the rate of both peroxidation in the hydrophobic part and free-radical fragmentation in the hydrophilic part of phospholipid membrane. Scavengers of reactive species inhibited the fragmentation of phosphatidylglycerol substantially. Thus, the ability of hydroxyl-containing lipids to undergo free-radical fragmentation in polar part apparently makes a substantial contribution to the mechanism of their protector action. PMID:24189590

  19. Synthesis of MOF having hydroxyl functional side groups and optimization of activation process for the maximization of its BET surface area

    SciTech Connect

    Kim, Jongsik; Kim, Dong Ok; Kim, Dong Wook; Sagong, Kil

    2013-01-15

    To accomplish the postsynthetic modification of MOF with organic-metal precursors (OMPs) described in our previous researches more efficiently, synthesis of MOF (HCC-2) possessing relatively larger pore size as well as higher number of hydroxyl functional side groups per its base unit than those of HCC-1 has been successfully conducted via adopting 1,4-di-(4-carboxy-2,6-dihydroxyphenyl)benzene as an organic ligand and Zn(NO{sub 3}){sub 2}{center_dot}6H{sub 2}O as a metal source, respectively. Also, optimization about the Activation process of HCC-2 was performed to maximize its BET (Brunauer-Emmett-Teller) surface area which was proved to be proportional to the number of exposed active sites on which its postsynthetic modification occurred. However, Activation process having been validated to be so effective with the acquirement of highly-purified HCC-1 (CO{sub 2} supercritical drying step followed by vacuum drying step) was less satisfactory with the case of HCC-2. This might be attributed to relatively higher hydrophilicity and bulkier molecular structure of organic ligand of HCC-2. However, it was readily settled by simple modification of above Activation process. Moreover, indispensable residues composed of both DMF and its thermally degraded derivatives which were chemically attached via coordination bond with hydroxyl functionalities even after Activation process III might enable their H{sub 2} adsorption properties to be seriously debased compared to that of IRMOF-16 having no hydroxyl functionalities. - Graphical abstract: Synthesis of new-structured MOF (HCC-2) simultaneously possessing relatively larger pore size as well as higher number of hydroxyl functional side groups per its base unit at the same time than those of HCC-1 has been performed via adopting 1,4-di-(4-carboxy-2,6-dihydroxyphenyl)benzene as an organic ligand and Zn(NO{sub 3}){sub 2}{center_dot}6H{sub 2}O as a metal source, respectively. Also, the optimization of activation process for HCC-2

  20. Copper(II)-complex directed regioselective mono-p-toluenesulfonylation of cyclomaltoheptaose at a primary hydroxyl group position: an NMR and molecular dynamics-aided design.

    PubMed

    Law, Ho; Benito, Juan M; Fernández, José M García; Jicsinszky, Laszlo; Crouzy, Serge; Defaye, Jacques

    2011-06-16

    Interactions between cyclomaltoheptaose (β-cyclodextrin, βCD) and p-toluenesulfonyl chloride (TsCl) were investigated using MD simulations, both in vacuum, approximating the hydrophobic environment of the CD cavity, and with water as a solvent. In both cases, the minimum energy adiabatic paths, and the mean force potentials (MFP) for the insertion of TsCl along a reaction coordinate perpendicular to the CD plane, were calculated for the two possible orientations of TsCl. The results show a preferred entry of TsCl in the CD cavity with the sulfonyl chloride group pointing to the primary hydroxyls rim. In each orientation, two energy minima for the complex are detected in vacuum that reflect the H-H contacts between host and guest observed by NMR spectroscopy (ROESY, NOESY). These separate minima collapsed into a single broader minimum, when the solvent was introduced in the simulations. The resulting association constant between TsCl and βCD (K(a) ≈ 100 M(-1)) is in good agreement with the NMR results (K(a) = 102 ± 12 M(-1)) in deuterated water solution at 298 K. Advantage has been taken of the dynamics of the reagent inclusion to set up a one step process involving a transient Cu(2+) chelate at the secondary hydroxyls rim position for the electrophilic monoactivation of βCD at the primary hydroxyls rim using water as solvent. PMID:21591775

  1. Dehydration and Stabilization of a Reactive Tertiary Hydroxyl Group in Solid Oral Dosage Forms of BMS-779788.

    PubMed

    Adams, Monica L; Sharma, Vijayata; Gokhale, Madhushree; Huang, Yande; Stefanski, Kevin; Su, Ching; Hussain, Munir A

    2016-04-01

    BMS-779788 contains a reactive tertiary hydroxyl attached to a weakly basic imidazole ring. Propensity of the carbinol toward dehydration to yield the corresponding alkene, BMS-779788-ALK, was evaluated. Elevated levels of BMS-779788-ALK were observed in excipient compatibility samples. Stability studies revealed that BMS-779788 degrades to BMS-779788-ALK in capsules and tablets prepared by both dry and wet granulation processes. An acid-catalyzed dehydration mechanism, in which the heterocyclic core contributes resonance stability to the cationic intermediate via charge transfer to the imidazole ring, was proposed. Therefore, neutralization via a buffered (pH 7.0) granulating solution was used to mitigate dehydration. Solution studies revealed degradation of BMS-779788 to BMS-779788-ALK over the pH range of 1-7.5. Reversibility was confirmed by initiating reactions with BMS-779788-ALK over the same pH range. Accordingly, a simple reversible scheme can be used to describe reactions initiated with either BMS-779788 or BMS-779788-ALK. To eliminate potential for charge delocalization across the heterocycle and probe the degradation mechanism, the imidazole ring of BMS-779788 was methylated (BMS-779788-Me). The propensity for acid-catalyzed dehydration was then evaluated. The acid stability of BMS-779788-Me confirmed that the heterocyclic core contributes to reactivity liability of the tertiary hydroxyl. PMID:26921118

  2. Preparation of hydroxylated polyethylene surfaces.

    PubMed

    Zand, A; Walter, N; Bahu, M; Ketterer, S; Sanders, M; Sikorski, Y; Cunningham, R; Beholz, L

    2008-01-01

    The surfaces of high-density or ultra-high-molecular-weight polyethylenes were hydroxylated using a two-step process. The wetting and wear properties of the untreated (virgin) and surface hydroxylated polyethylenes were compared. The introduction of hydroxyl groups provided an increase in surface hydrophilicity resulting in reduced wear. Hydrophilicity was analyzed by optical analysis of water contact angle. Wear was determined by weight loss under conditions of a reciprocating pin-on-plate apparatus with the panels immersed in water or calf serum. These results suggest that hydroxylation of polyethylene friction-bearing orthopedic surfaces may lead to a longer joint life. PMID:18318959

  3. Numerical simulations of pendant droplets

    NASA Astrophysics Data System (ADS)

    Pena, Carlos; Kahouadji, Lyes; Matar, Omar; Chergui, Jalel; Juric, Damir; Shin, Seungwon

    2015-11-01

    We simulate the evolution of a three-dimensional pendant droplet through pinch-off using a new parallel two-phase flow solver called BLUE. The parallelization of the code is based on the technique of algebraic domain decomposition where the velocity field is solved by a parallel GMRes method for the viscous terms and the pressure by a parallel multigrid/GMRes method. Communication is handled by MPI message passing procedures. The method for the treatment of the fluid interfaces uses a hybrid Front Tracking/Level Set technique which defines the interface both by a discontinuous density field as well as by a local triangular Lagrangian mesh. This structure allows the interface to undergo large deformations including the rupture and coalescence of fluid interfaces. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.

  4. The effect of ethanol on hydroxyl and carbonyl groups in biopolyol produced by hydrothermal liquefaction of loblolly pine: (31)P-NMR and (19)F-NMR analysis.

    PubMed

    Celikbag, Yusuf; Via, Brian K; Adhikari, Sushil; Buschle-Diller, Gisela; Auad, Maria L

    2016-08-01

    The goal of this study was to investigate the role of ethanol and temperature on the hydroxyl and carbonyl groups in biopolyol produced from hydrothermal liquefaction of loblolly pine (Pinus spp.) carried out at 250, 300, 350 and 390°C for 30min. Water and water/ethanol mixture (1/1, wt/wt) were used as liquefying solvent in the HTL experiments. HTL in water and water/ethanol is donated as W-HTL and W/E-HTL, respectively. It was found that 300°C and water/ethanol solvent was the optimum liquefaction temperature and solvent, yielding up to 68.1wt.% bio-oil and 2.4wt.% solid residue. (31)P-NMR analysis showed that biopolyol produced by W-HTL was rich in phenolic OH while W/E-HTL produced more aliphatic OH rich biopolyols. Moreover, biopolyols with higher hydroxyl concentration were produced by W/E-HTL. Carbonyl groups were analyzed by (19)F-NMR, which showed that ethanol reduced the concentration of carbonyl groups. PMID:27126078

  5. The Hydroxyl at Position C1 of Genipin Is the Active Inhibitory Group that Affects Mitochondrial Uncoupling Protein 2 in Panc-1 Cells

    PubMed Central

    Hou, Jianwei; Ding, Yue; Zhang, Tong; Zhang, Yong; Wang, Jianying; Shi, Chenchen; Fu, Wenwei; Cai, Zhenzhen

    2016-01-01

    Genipin (GNP) effectively inhibits uncoupling protein 2 (UCP2), which regulates the leakage of protons across the inner mitochondrial membrane. UCP2 inhibition may induce pancreatic adenocarcinoma cell death by increasing reactive oxygen species (ROS) levels. In this study, the hydroxyls at positions C10 (10-OH) and C1 (1-OH) of GNP were hypothesized to be the active groups that cause these inhibitory effects. Four GNP derivatives in which the hydroxyl at position C10 or C1 was replaced with other chemical groups were synthesized and isolated. Differences in the inhibitory effects of GNP and its four derivatives on pancreatic carcinoma cell (Panc-1) proliferation were assessed. The effects of GNP and its derivatives on apoptosis, UCP2 inhibition and ROS production were also studied to explore the relationship between GNP’s activity and its structure. The derivatives with 1-OH substitutions, geniposide (1-GNP1) and 1-ethyl-genipin (1-GNP2) lacked cytotoxic effects, while the other derivatives that retained 1-OH, 10-piv-genipin (10-GNP1) and 10-acetic acid-genipin (10-GNP2) exerted biological effects similar to those of GNP, even in the absence of 10-OH. Thus, 1-OH is the key functional group in the structure of GNP that is responsible for GNP’s apoptotic effects. These cytotoxic effects involve the induction of Panc-1 cell apoptosis through UCP2 inhibition and subsequent ROS production. PMID:26771380

  6. Structure-Activity Relationship of Oligomeric Flavan-3-ols: Importance of the Upper-Unit B-ring Hydroxyl Groups in the Dimeric Structure for Strong Activities.

    PubMed

    Hamada, Yoshitomo; Takano, Syota; Ayano, Yoshihiro; Tokunaga, Masahiro; Koashi, Takahiro; Okamoto, Syuhei; Doi, Syoma; Ishida, Masahiko; Kawasaki, Takashi; Hamada, Masahiro; Nakajima, Noriyuki; Saito, Akiko

    2015-01-01

    Proanthocyanidins, which are composed of oligomeric flavan-3-ol units, are contained in various foodstuffs (e.g., fruits, vegetables, and drinks) and are strongly biologically active compounds. We investigated which element of the proanthocyanidin structure is primarily responsible for this functionality. In this study, we elucidate the importance of the upper-unit of 4-8 condensed dimeric flavan-3-ols for antimicrobial activity against Saccharomyces cerevisiae (S. cerevisiae) and cervical epithelioid carcinoma cell line HeLa S3 proliferation inhibitory activity. To clarify the important constituent unit of proanthocyanidin, we synthesized four dimeric compounds, (-)-epigallocatechin-[4,8]-(+)-catechin, (-)-epigallocatechin-[4,8]-(-)-epigallocatechin, (-)-epigallocatechin-[4,8]-(-)-epigallocatechin-3-O-gallate, and (+)-catechin-[4,8]-(-)-epigallocatechin and performed structure-activity relationship (SAR) studies. In addition to antimicrobial activity against S. cerevisiae and proliferation inhibitory activity on HeLa S3 cells, the correlation of 2,2-diphenyl-l-picrylhydrazyl radical scavenging activity with the number of phenolic hydroxyl groups was low. On the basis of the results of our SAR studies, we concluded that B-ring hydroxyl groups of the upper-unit of the dimer are crucially important for strong and effective activity. PMID:26501251

  7. Mechanistic Insights of Ethanol Steam Reforming over Ni–CeO x (111): The Importance of Hydroxyl Groups for Suppressing Coke Formation

    DOE PAGESBeta

    Liu, Zongyuan; Duchoň, Tomáš; Wang, Huanru; Peterson, Erik W.; Zhou, Yinghui; Luo, Si; Zhou, Jing; Matolín, Vladimir; Stacchiola, Dario J.; Rodriguez, José A.; et al

    2015-07-30

    We have studied the reaction of ethanol and water over Ni–CeO2-x(111) model surfaces to elucidate the mechanistic steps associated with the ethanol steam reforming (ESR) reaction. Our results provide insights about the importance of hydroxyl groups to the ESR reaction over Ni-based catalysts. Systematically, we have investigated the reaction of ethanol on Ni–CeO2-x(111) at varying Ce³⁺ concentrations (CeO1.8–2.0) with absence/presence of water using a combination of soft X-ray photoelectron spectroscopy (sXPS) and temperature-programmed desorption (TPD). Consistent with previous reports, upon annealing, metallic Ni formed on reduced ceria while NiO was the main component on fully oxidized ceria. Ni⁰ is themore » active phase leading to both the C–C and C–H cleavage of ethanol but is also responsible for carbon accumulation or coking. We have identified a Ni₃C phase that formed prior to the formation of coke. At temperatures above 600K, the lattice oxygen from ceria and the hydroxyl groups from water interact cooperatively in the removal of coke, likely through a strong metal–support interaction between nickel and ceria that facilitates oxygen transfer.« less

  8. Mechanistic Insights of Ethanol Steam Reforming over Ni–CeO x (111): The Importance of Hydroxyl Groups for Suppressing Coke Formation

    SciTech Connect

    Liu, Zongyuan; Duchoň, Tomáš; Wang, Huanru; Peterson, Erik W.; Zhou, Yinghui; Luo, Si; Zhou, Jing; Matolín, Vladimir; Stacchiola, Dario J.; Rodriguez, José A.; Senanayake, Sanjaya D.

    2015-07-30

    We have studied the reaction of ethanol and water over Ni–CeO2-x(111) model surfaces to elucidate the mechanistic steps associated with the ethanol steam reforming (ESR) reaction. Our results provide insights about the importance of hydroxyl groups to the ESR reaction over Ni-based catalysts. Systematically, we have investigated the reaction of ethanol on Ni–CeO2-x(111) at varying Ce³⁺ concentrations (CeO1.8–2.0) with absence/presence of water using a combination of soft X-ray photoelectron spectroscopy (sXPS) and temperature-programmed desorption (TPD). Consistent with previous reports, upon annealing, metallic Ni formed on reduced ceria while NiO was the main component on fully oxidized ceria. Ni⁰ is the active phase leading to both the C–C and C–H cleavage of ethanol but is also responsible for carbon accumulation or coking. We have identified a Ni₃C phase that formed prior to the formation of coke. At temperatures above 600K, the lattice oxygen from ceria and the hydroxyl groups from water interact cooperatively in the removal of coke, likely through a strong metal–support interaction between nickel and ceria that facilitates oxygen transfer.

  9. Photo and Chemical Reduction of Copper onto Anatase-Type TiO2 Nanoparticles with Enhanced Surface Hydroxyl Groups as Efficient Visible Light Photocatalysts.

    PubMed

    Eskandarloo, Hamed; Badiei, Alireza; Behnajady, Mohammad A; Mohammadi Ziarani, Ghodsi

    2015-01-01

    In this study, the photocatalytic efficiency of anatase-type TiO2 nanoparticles synthesized using the sol-gel low-temperature method, were enhanced by a combined process of copper reduction and surface hydroxyl groups enhancement. UV-light-assisted photo and NaBH4 -assisted chemical reduction methods were used for deposition of copper onto TiO2. The surface hydroxyl groups of TiO2 were enhanced with the assistance of NaOH modification. The prepared catalysts were immobilized on glass plates and used as the fixed-bed systems for the removal of phenazopyridine as a model drug contaminant under visible light irradiation. NaOH-modified Cu/TiO2 nanoparticles demonstrated higher photocatalytic efficiency than that of pure TiO2 due to the extending of the charge carriers lifetime and enhancement of the adsorption capacity of TiO2 toward phenazopyridine. The relationship of structure and performance of prepared nanoparticles has been established by using various techniques, such as XRD, XPS, TEM, EDX, XRF, TGA, DRS and PL. The effects of preparation variables, including copper content, reducing agents rate (NaBH4 concentration and UV light intensity) and NaOH concentration were investigated on the photocatalytic efficiency of NaOH-modified Cu/TiO2 nanoparticles. PMID:25809844

  10. Infrared spectroscopy of OD vibrators in minerals at natural dilution: hydroxyl groups in talc and kaolinite, and structural water in beryl and emerald.

    PubMed

    de Donato, Philippe; Cheilletz, Alain; Barres, Odile; Yvon, Jacques

    2004-05-01

    An infrared (IR) study of natural deuteration is conducted on minerals containing hydroxyl groups (talc and kaolinite) and channel-water-bearing minerals (beryl and emerald). In talc, the OD valence vibration is located at 2710 cm(-1), corresponding to OD groups surrounded by 3 Mg atoms. In kaolinite, the OD valence vibrations are located at 2671 cm(-1) (inner OD group), 2712, 2706, and 2700 cm(-1) (three inner-surface OD groups). In beryl and emerald, natural deuteration of channel water is observed for the first time by infrared microspectroscopy. In beryl from Minas Gerais (Brazil), the OD profiles are characterized by four bands at 2735, 2686, 2672, and 2641 cm(-1). In emeralds from Colombia and Brazil, the OD profiles are characterized by five or four bands, respectively, at 2816, 2737, 2685, 2673, and 2641 cm(-1) (Colombia) and 2730, 2684, 2672, and 2640 cm(-1) (Brazil). The band at 2816 cm(-1) can be assigned to -OD or OD(-), and bands at 2686-2684, 2673-2672, and 2641-2640 cm(-1) can be assigned to type-I and type-II HOD molecules. The band at 2737-2730 cm(-1) is partially disturbed by combination bands of the mineral. Such OD profiles are different from those obtained by artificial deuteration at higher OD dilution. PMID:15165327

  11. Oxidation of amino groups by hydroxyl radicals in relation to the oxidation degree of the alpha-carbon.

    PubMed

    Leitner, N Karpel Vel; Berger, P; Legube, B

    2002-07-15

    Nitrogen organic compounds constitute a large class of aqueous pollutants. These compounds include not only azoic structures, nitrogen heterocycles, and nitrous groups but also amides and amines. This work consisted in studying the OH* induced oxidation of simple primary amines in dilute aqueous solution with special attention to mineralization of the nitrogen group as a function of the nature of the alpha-carbon. H2O2/UV and gamma-irradiation processes were used for the production of OH* radicals, and the molecules studied were one alpha-amino acid i.e., glycine (HOOCCH2NH2), and two primary amides i.e., acetamide (CH3CONH2) and oxamic acid (HOOCCONH2). It was shown that the oxidation of glycine leads to the formation of ammonia, whereas the acetamide molecule is first oxidized into oxamic acid ending in complete mineralization with production of nitrates. Reaction mechanisms are proposed which account for the observed inorganic nitrogen end product depending on the oxidation degree of the carbon atoms of the molecules. It follows that the present study will allow for prediction of the fate of nitrogen resulting from the oxidation of primary amino groups by OH* radicals. PMID:12141487

  12. The Effect of Methyl, Hydroxyl, and Ketone Functional Groups on the Heterogeneous Oxidation of Succinic Acid Aerosol by OH Radicals

    NASA Astrophysics Data System (ADS)

    Chan, M.; Zhang, H.; Wilson, K. R.

    2013-12-01

    The heterogeneous oxidation of atmospheric organic aerosols can influence their effects on climate, human health, and visibility. During oxidation, functionalization occurs when an oxygenated functional group is added to a molecule, leaving the carbon skeleton intact. Fragmentation involves carbon-carbon bond cleavage and produces two products with smaller carbon numbers than the parent compound. To gain better insights into how the molecular structure of more oxygenated organic compounds affects heterogeneous reactivity, succinic acid aerosols are photo-oxidized in an aerosol flow tube reactor, and the reaction products are analyzed using Direct Analysis in Real Time Mass Spectrometry for online chemical analysis. The effect of various functional groups (CH3, OH, C=O) along the carbon backbone on the heterogeneous reaction mechanisms are also investigated using model compounds. For this series of compounds, the formation of more oxygenated products through functionalization can be explained by well-known condensation-phase reactions such as Russell and Bennett and Summers. The number of fragmentation products is found to increase with the presence of OH and CH3 groups. This can be attributed to the increased number of tertiary carbons, enhancing the fragmentation after multiple oxidation steps. Smaller dicaids (oxalic acid and malonic acid) can be formed through the fragmentation processes in the heterogeneous oxidation of succinic acid. The effect of molecular structure on reaction kinetics, volatilization, and the relative importance of functionalization and fragmentation pathways will be discussed.

  13. Infrared study of the interaction between Lewis bases and surface hydroxyl groups of {Pt}/{Cab-O-Sil}

    NASA Astrophysics Data System (ADS)

    Sárkány, János

    1997-06-01

    Transmission IR spectroscopic study at 298 K has revealed strong H-bonds between Lewis bases (LBs) containing one, [1-O], or two, [2-O], sp 3 hybridized O atoms and the surface OH groups of Cab-O-Sil. LB [1-O] (10 torr = 1.333 kPa) caused a greater | Δν(OH)| (470-520 cm -1) than did LB [2-O] (385-470 cm -1). In contrast with expectations, the intensity of the OH band at 3660 cm -1 decreased to a greater extent for LB [2-O] than for LB [1-O]. The results were interpreted on the basis of chargetransfer theory. The estimated sequence of electron-donating ability (EDA) was: oxepane > oxane > oxolane > diethyl ether ≥ 1,4-dioxane > 1,3-dioxepane > 1,3-dioxane > 1,3-dioxolane.

  14. Mechanical vibrations of pendant liquid droplets.

    PubMed

    Temperton, Robert H; Smith, Michael I; Sharp, James S

    2015-07-01

    A simple optical deflection technique was used to monitor the vibrations of microlitre pendant droplets of deuterium oxide, formamide, and 1,1,2,2-tetrabromoethane. Droplets of different volumes of each liquid were suspended from the end of a microlitre pipette and vibrated using a small puff of nitrogen gas. A laser was passed through the droplets and the scattered light was collected using a photodiode. Vibration of the droplets resulted in the motion of the scattered beam and time-dependent intensity variations were recorded using the photodiode. These time-dependent variations were Fourier transformed and the frequencies and widths of the mechanical droplet resonances were extracted. A simple model of vibrations in pendant/sessile drops was used to relate these parameters to the surface tension, density and viscosity of the liquid droplets. The surface tension values obtained from this method were found to be in good agreement with results obtained using the standard pendant drop technique. Damping of capillary waves on pendant drops was shown to be similar to that observed for deep liquid baths and the kinematic viscosities obtained were in agreement with literature values for all three liquids studied. PMID:26189195

  15. Gelation of Copolymers Photo-crosslinked by Pendant Benzophenones

    NASA Astrophysics Data System (ADS)

    Christensen, Scott; Hayward, Ryan C.

    2011-03-01

    Copolymers containing pendant benzophenone (BP) groups provide a simple and powerful route to crosslinkable polymer films. While the solution state photo-chemistry of BP is well established, and crosslinking of polymers blended with BP has been studied in detail, the process of crosslinking by covalently attached BP has received comparatively little attention. We have prepared copolymers of BP with several different monomers, and studied gelation as a function of BP content and degree of photochemical conversion. We seek to understand the influence of polymer chemistry on crosslinking efficiency, to guide choices of materials for photo- crosslinkable polymer films and to provide a route for tailoring morphology in polymer blends.

  16. Well-defined poly(2-hydroxyl-3-(2-hydroxyethylamino)propyl methacrylate) vectors with low toxicity and high gene transfection efficiency.

    PubMed

    Xu, F J; Chai, M Y; Li, W B; Ping, Y; Tang, G P; Yang, W T; Ma, J; Liu, F S

    2010-06-14

    Successful gene delivery vectors for clinical translation should have high transfection efficiency and minimal toxicity. In this work, well-defined poly(2-hydroxyl-3-(2-hydroxyethylamino)propyl methacrylate) (PGEA) vectors with flanking cationic secondary amine and nonionic hydroxyl units were prepared via the ring-opening reaction of the pendant epoxide groups of poly(glycidyl methacrylate) with the amine moieties of ethanolamine. It was found that PGEA carriers possess very low toxicity (<10% of the toxicity of branched polyethylenimine (PEI, 25 kDa), while exhibiting surprisingly excellent transfection efficiency (higher than or comparable to that of PEI (25 kDa)) in different cell lines. A series of transfection and cytotoxicity assays revealed that PGEAs are highly promising as a new class of safe and efficient gene delivery vectors for future clinical gene therapies. PMID:20426406

  17. Hydroxyl Fatty Acids and Hydroxyl Oils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soybean oil is produced domestically in large supply, averaging over 20 billion pounds per year with an annual carryover of more than one billion pounds. It is important to find new uses for this surplus soybean oil. Hydroxyl fatty acids and hydroxyl oils are platform materials for specialty chemi...

  18. Replacement of the carboxylic acid group of prostaglandin F2α with a hydroxyl or methoxy substituent provides biologically unique compounds

    PubMed Central

    Woodward, D F; Krauss, A H-P; Chen, J; Gil, D W; Kedzie, K M; Protzman, C E; Shi, L; Chen, R; Krauss, H A; Bogardus, A; Dinh, H T T; Wheeler, L A; Andrews, S W; Burk, R M; Gac, T; Roof, M B; Garst, M E; Kaplan, L J; Sachs, G; Pierce, K L; Regan, J W; Ross, R A; Chan, M F

    2000-01-01

    Replacement of the carboxylic acid group of PGF2α with the non-acidic substituents hydroxyl (-OH) or methoxy (-OCH3) resulted in an unexpected activity profile.Although PGF2α 1-OH and PGF2α 1-OCH3 exhibited potent contractile effects similar to 17-phenyl PGF2α in the cat lung parenchymal preparation, they were approximately 1000 times less potent than 17-phenyl PGF2α in stimulating recombinant feline and human FP receptors.In human dermal fibroblasts and Swiss 3T3 cells PGF2α 1-OH and PGF2α 1-OCH3 produced no Ca2+ signal until a 1 μM concentration was exceeded. Pretreatment of Swiss 3T3 cells with either 1 μM PGF2α 1-OH or PGF2α 1-OCH3 did not attenuate Ca2+ signal responses produced by PGF2α or fluprostenol. In the rat uterus, PGF2α 1-OH was about two orders of magnitude less potent than 17-phenyl PGF2α whereas PGF2α 1-OCH3 produced only a minimal effect.Radioligand binding studies on cat lung parenchymal plasma membrane preparations suggested that the cat lung parenchyma does not contain a homogeneous population of receptors that equally respond to PGF2α1-OH, PGF2α1-OCH3, and classical FP receptor agonists.Studies on smooth muscle preparations and cells containing DP, EP1, EP2, EP3, EP4, IP, and TP receptors indicated that the activity of PGF2α 1-OH and PGF2α 1-OCH3 could not be ascribed to interaction with these receptors.The potent effects of PGF2α 1-OH and PGF2α 1-OCH3 on the cat lung parenchyma are difficult to describe in terms of interaction with the FP or any other known prostanoid receptor. PMID:10952685

  19. DNA Binding Hydroxyl Radical Probes

    PubMed Central

    Tang, Vicky J; Konigsfeld, Katie M; Aguilera, Joe A; Milligan, Jamie R

    2011-01-01

    The hydroxyl radical is the primary mediator of DNA damage by the indirect effect of ionizing radiation. It is a powerful oxidizing agent produced by the radiolysis of water and is responsible for a significant fraction of the DNA damage associated with ionizing radiation. There is therefore an interest in the development of sensitive assays for its detection. The hydroxylation of aromatic groups to produce fluorescent products has been used for this purpose. We have examined four different chromophores which produce fluorescent products when hydroxylated. Of these, the coumarin system suffers from the fewest disadvantages. We have therefore examined its behavior when linked to a cationic peptide ligand designed to bind strongly to DNA. PMID:22125376

  20. Structure–activity relationship of Au/ZrO2 catalyst on formation of hydroxyl groups and its influence on CO oxidation

    SciTech Connect

    Karwacki, Christopher J.; Ganesh, P.; Kent, Paul R. C.; Gordon, Wesley O.; Peterson, Gregory W.; Niu, Jun Jie; Gogotsi, Yury

    2013-01-01

    The effect of changes in morphology and surface hydroxyl species upon thermal treatment of zirconia on the oxidation activity of Au/ZrO2 catalyst was studied. We observed using transmission fourier transform infrared (FTIR) spectroscopy progressive changes in the presence of monodentate (type I), bidentate (type II) and hydrogen bridged species (type III) for each of the thermally treated (85 to 500 C) supports consisting of bare zirconia and Au/ZrO2 catalysts. Furthermore, structural changes in zirconia were accompanied by an increase in crystal size (7 to 58 nm) and contraction of the supports porosity (SSA 532 to 7 m2/g) with increasing thermal treatment. Deposition of gold nanoparticles under similar preparation conditions on different thermally treated zirconia resulted in changes in the mean gold cluster size, ranging from 3.7 to 5.6 nm. Changes in the surface hydroxyl species, support structure and size of the gold centers are important parameters responsible for the observed decrease (> 90 %) in CO conversion activity for the Au/ZrO2 catalysts. Density functional theory calculations provide evidence of increased CO binding to Au nanoclusters in the presence of surface hydroxyls on zirconia, which increases charge transfer at the perimeter of the gold nanocluster on zirconia support. This further helps in reducing a model CO-oxidation reaction barrier in the presence of surface hydroxyls. This work demonstrates the need to understand the structure-activity relationship of both the support and active particles for the design of catalytic materials.

  1. Structure-activity relationship of Au-ZrO2 catalyst on formation of hydroxyl groups and its influence on CO oxidation

    SciTech Connect

    Karwacki, Christopher J; Ganesh, Panchapakesan; Kent, P. R. C.; Gordon, Wesley O; Peterson, Gregory W; Niu, Jun Jie; Gogotsi, Yury G.

    2013-01-01

    The effect of changes in morphology and surface hydroxyl species upon thermal treatment of zirconia on the oxidation activity of Au/ZrO2 catalyst was studied. We observed using transmission Fourier transform infrared (FTIR) spectroscopy progressive changes in the presence of monodentate (type I), bidentate (type II) and hydrogen bridged species (type III) for each of the thermally treated (85 to 500 C) supports consisting of bare zirconia and Au/ZrO2 catalysts. Furthermore, structural changes in zirconia were accompanied by an increase in crystal size (7 to 58 nm) and contraction of the supports porosity (SSA 532 to 7 m2 g 1) with increasing thermal treatment. Deposition of gold nanoparticles under similar preparation conditions on different thermally treated zirconia resulted in changes in the mean gold cluster size, ranging from 3.7 to 5.6 nm. Changes in the surface hydroxyl species, support structure and size of the gold centers are important parameters responsible for the observed decrease (>90%) in CO conversion activity for the Au/ZrO2 catalysts. Density functional theory calculations provide evidence of increased CO binding to Au nanoclusters in the presence of surface hydroxyls on zirconia, which increases charge transfer at the perimeter of the gold nanocluster on zirconia support. This further helps in reducing a model CO-oxidation reaction barrier in the presence of surface hydroxyls. This work demonstrates the need to understand the structure activity relationship of both the support and active particles for the design of catalytic materials.

  2. The effects of amine/nitro/hydroxyl groups on the benzene rings of redox additives on the electrochemical performance of carbon-based supercapacitors.

    PubMed

    Huang, Xuan; Wang, Qian; Chen, Xiang Ying; Zhang, Zhong Jie

    2016-04-21

    In this work, a series of porous carbon materials with hierarchical porosities have been synthesized via a template carbonization method, in which cheap CaCO3 serves as a template and glucose as a carbon precursor. During the carbonization process, CO2 produced by the decomposition of the CaCO3 template can act as an internal activating agent, significantly improving microporosity and mesoporosity. All the carbon materials obtained by regulating the ratio of glucose to CaCO3 exhibit the amorphous features with a low graphitization degree. Among them, the carbon-1 : 2 sample shows a high BET surface area of up to 818.5 m(2) g(-1) and a large total pore volume of 1.78 cm(3) g(-1) as well as a specific capacitance of 107.0 F g(-1) at 1 A g(-1). In addition, a series of hydroquinone (HQ), p-aminophenol (PAP) and p-nitrophenol (PNP) as novel redox additives that can produce pseudo-capacitances have been added into the KOH electrolyte for promoting the total capacitive performances via redox reactions at the electrode-electrolyte interface. As expected, a 2.5-fold increase in the galvanostatic capacitance of 240.0 F g(-1) in the HQ-0.5 electrolyte occurs, compared with the conventional KOH electrolyte. Similarly, the PAP-0.5 electrolyte and the PNP-0.5 electrolyte also show a high specific capacitance of 184.0 F g(-1) at 2 A g(-1) (156.6 F g(-1) at 3 A g(-1)) and 153.0 F g(-1) at 3 A g(-1), respectively. Additionally, the three kinds of electrolytes exhibit excellent cyclic stability. The remarkable improvement of supercapacitors is attributed to the quick reversible Faradaic reactions of amine and hydroxyl groups adhering to the phenyl rings, which largely accelerates electron migration and brings additional pseudocapacitive contribution for carbon-based supercapacitors. PMID:27030290

  3. Water concentrations and hydrogen isotope compositions of alkaline basalt-hosted clinopyroxene megacrysts and amphibole clinopyroxenites: the role of structural hydroxyl groups and molecular water

    NASA Astrophysics Data System (ADS)

    Kovács, István; Demény, Attila; Czuppon, György; Lécuyer, Christophe; Fourel, Francois; Xia, Qun-Ke; Liu, Jia; Pintér, Zsanett; Király, Edit; Török, Kálmán; Szabó, Ábel; Deloule, Etienne; Falus, György; Fancsik, Tamás; Zajacz, Zoltán; Sándorné Kovács, Judit; Udvardi, Beatrix

    2016-05-01

    The aim of this study was to determine both `water' contents (as OH- and H2O) and δD values of several clinopyroxene samples from alkaline basalts. These parameters were first obtained from five clinopyroxene samples using both the classical `off-line' vacuum extraction technique and the `on-line' high-temperature pyrolysis technique. Blanks measured with the `on-line' gas extraction techniques were low enough to prevent any contamination by atmospheric water vapour. The comparison of data has revealed that our `on-line' procedure is more effective for the extraction of `water' from clinopyroxenes and, consequently, this `on-line' technique was applied to ten additional clinopyroxene samples. Sample δD values cover a similar range from -95 to -45 ‰ (VSMOW) regardless of the studied locations, whereas the total `water' content varies from ~115 to ~2570 ppm. The structural hydroxyl content of clinopyroxene samples measured by micro-FTIR spectrometry varies from ~0 to 476 ppm expressed in molecular water equivalent. The total `water' concentrations determined by mass spectrometry differ considerably from structural hydroxyl contents constrained by micro-FTIR, thus indicating that considerable proportion of the `water' may be present in (nano)-inclusions. The structural hydroxyl concentration—apart from clinopyroxenes separated from amphibole clinopyroxenite xenoliths—correlates positively with the δD values of clinopyroxene megacrysts for each locality, indicating that structurally bond hydrogen in clinopyroxenes may have δD values higher than molecular water in inclusions. This implies that there may be a significant hydrogen isotope fractionation for structural hydroxyl during crystallization of clinopyroxene, while for molecular water there may be no or only negligible isotope fractionation.

  4. Synthesis and Reactivity of Tripodal Complexes Containing Pendant Bases

    SciTech Connect

    Blacquiere, Johanna M.; Pegis, Michael L.; Raugei, Simone; Kaminsky, Werner; Forget, Amelie; Cook, Sarah; Taguchi, Taketo; Borovik, Andrew S.; Mayer, James M.

    2014-09-02

    The synthesis of a new tripodal ligand family is reported, with tertiary-amine groups in the second-coordination sphere. The ligands are tris(amido)amine derivatives, with the pendant amines attached via a peptide coupling strategy. They were designed to be used in new catalysts for the oxygen reduction reaction (ORR), in which the pendant acid/base group could improve catalyst performance. Two members of the new ligand family were each metallated with Co(II) and Zn(II) to afford trigonal monopyramidal complexes. Reaction of the cobalt complexes, [Co(L)]-, with dioxygen reversibly generates a small amount of a Co(III)-superoxo species, which was characterized by EPR. Protonation of the zinc complex Zn[N{CH2CH2NC(O)CH2N(CH2Ph)2}3)-– ([Zn(TNBn)]-) with one equivalent of acid occurs with displacement and dissociation of an amide ligand. Addition of excess acid to the any of the complexes [M(L)]- results in complete proteolysis and formation of the ligands H3L. This decomposition limits the use of these complexes as catalysts for the ORR. An alternative ligand with two pyridyl arms was also prepared but could not be metallated. These studies highlight the importance of stability of the primary-coordination sphere of ORR electrocatalysts to both oxidative and acidic conditions. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

  5. The Stability of Two Connected Pendant Drops

    NASA Technical Reports Server (NTRS)

    Slobozhanin, Lev A.; Alexander, J. Iwan

    2004-01-01

    The stability of an equilibrium system of two drops suspended from circular holes is examined. The drop surfaces are disconnected surfaces of a connected liquid body. For holes of equal radii and identical pendant drops axisymmetric perturbations are always the most dangerous. The stability region for two identical drops differs considerably from that for a single drop. Loss of stability leads to a transition from a critical system of identical drops to a stable system of axisymmetric non-identical. This system of non-identical drops reaches its own stability limit (to isochoric or non-isochoric paturbations). For non-identical drops, loss of stability results in dripping or streaming from the holes. Critical volumes for non-identical drops have been calculated as functions of the Bond number, B. For unequal hole radii, stability regions have been constructed for a set of hole radius, K. The dependence of critical volumes on K and B is analyzed.

  6. The radiocarbon hydroxyl technique

    NASA Technical Reports Server (NTRS)

    Campbell, Malcolm J.; Sheppard, John C.

    1994-01-01

    The Radiocarbon Technique depends upon measuring the rate of oxidation of CO in an essentially unperturbed sample of air. The airborne technique is slightly different. Hydroxyl concentrations can be calculated directly; peroxyl concentrations can be obtained by NO doping.

  7. Enhanced catalytic four-electron dioxygen (O2) and two-electron hydrogen peroxide (H2O2) reduction with a copper(II) complex possessing a pendant ligand pivalamido group.

    PubMed

    Kakuda, Saya; Peterson, Ryan L; Ohkubo, Kei; Karlin, Kenneth D; Fukuzumi, Shunichi

    2013-05-01

    A copper complex, [(PV-tmpa)Cu(II)](ClO4)2 (1) [PV-tmpa = bis(pyrid-2-ylmethyl){[6-(pivalamido)pyrid-2-yl]methyl}amine], acts as a more efficient catalyst for the four-electron reduction of O2 by decamethylferrocene (Fc*) in the presence of trifluoroacetic acid (CF3COOH) in acetone as compared with the corresponding copper complex without a pivalamido group, [(tmpa)Cu(II)](ClO4)2 (2) (tmpa = tris(2-pyridylmethyl)amine). The rate constant (k(obs)) of formation of decamethylferrocenium ion (Fc*(+)) in the catalytic four-electron reduction of O2 by Fc* in the presence of a large excess CF3COOH and O2 obeyed first-order kinetics. The k(obs) value was proportional to the concentration of catalyst 1 or 2, whereas the k(obs) value remained constant irrespective of the concentration of CF3COOH or O2. This indicates that electron transfer from Fc* to 1 or 2 is the rate-determining step in the catalytic cycle of the four-electron reduction of O2 by Fc* in the presence of CF3COOH. The second-order catalytic rate constant (k(cat)) for 1 is 4 times larger than the corresponding value determined for 2. With the pivalamido group in 1 compared to 2, the Cu(II)/Cu(I) potentials are -0.23 and -0.05 V vs SCE, respectively. However, during catalytic turnover, the CF3COO(-) anion present readily binds to 2 shifting the resulting complex's redox potential to -0.35 V. The pivalamido group in 1 is found to inhibit anion binding. The overall effect is to make 1 easier to reduce (relative to 2) during catalysis, accounting for the relative k(cat) values observed. 1 is also an excellent catalyst for the two-electron two-proton reduction of H2O2 to water and is also more efficient than is 2. For both complexes, reaction rates are greater than for the overall four-electron O2-reduction to water, an important asset in the design of catalysts for the latter. PMID:23509853

  8. Unusual cyclic terpenoids with terminal pendant prenyl moieties: from occurrence to synthesis.

    PubMed

    Kulcitki, Veaceslav; Harghel, Petru; Ungur, Nicon

    2014-12-01

    The paper reviews the known examples of cyclic terpenoids produced from open chain polyenic precursors by an "unusual" biosynthetic pathway, involving selective electrophilic attack on an internal double bond followed by cyclization. The resulting compounds possess cyclic backbones with pendant terminal prenyl groups. Synthetic approaches applied for the synthesis of such specifically functionalized compounds are also discussed, as well as biological activity of reported representatives. PMID:25118808

  9. Remote Neural Pendants In A Welding-Control System

    NASA Technical Reports Server (NTRS)

    Venable, Richard A.; Bucher, Joseph H.

    1995-01-01

    Neural network integrated circuits enhance functionalities of both remote terminals (called "pendants") and communication links, without necessitating installation of additional wires in links. Makes possible to incorporate many features into pendant, including real-time display of critical welding parameters and other process information, capability for communication between technician at pendant and host computer or technician elsewhere in system, and switches and potentiometers through which technician at pendant exerts remote control over such critical aspects of welding process as current, voltage, rate of travel, flow of gas, starting, and stopping. Other potential manufacturing applications include control of spray coating and of curing of composite materials. Potential nonmanufacturing uses include remote control of heating, air conditioning, and lighting in electrically noisy and otherwise hostile environments.

  10. 10. Detail view of pendant lamps, laminated arch beams and ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. Detail view of pendant lamps, laminated arch beams and ceiling structure, facing north - Mountain Home Air Force Base, Base Chapel, 350 Willow Street, Cantonment Area, Mountain Home, Elmore County, ID

  11. Tyr254 hydroxyl group acts as a two-way switch mechanism in the coupling of heterotropic and homotropic effects in Escherichia coli glucosamine-6-phosphate deaminase.

    PubMed

    Montero-Morán, G M; Horjales, E; Calcagno, M L; Altamirano, M M

    1998-05-26

    The involvement of tyrosine residues in the allosteric function of the enzyme glucosamine 6-phosphate deaminase from Escherichia coli was first proposed on the basis of a theoretical analysis of the sequence and demonstrated by spectrophotometric experiments. Two tyrosine residues, Tyr121 and Tyr254, were indicated as involved in the mechanism of cooperativity and in the allosteric regulation of the enzyme [Altamirano et al. (1994) Eur. J. Biochem. 220, 409-413]. Tyr121 replacement by threonine or tryptophan altered the symmetric character of the T --> R transition [Altamirano et al. (1995) Biochemistry 34, 6074-6082]. From crystallographic data of the R allosteric conformer, Tyr254 has been shown to be part of the allosteric pocket [Oliva et al. (1995) Structure 3, 1323-1332]. Although it is not directly involved in binding the allosteric activator, N-acetylglucosamine 6-phosphate, Tyr 254 is hydrogen bonded through its phenolic hydroxyl to the backbone carbonyl from residue 161 in the neighboring polypeptide chain. Kinetic and binding experiments with the mutant form Tyr254-Phe of the enzyme reveal that this replacement caused an uncoupling of the homotropic and heterotropic effects. Homotropic cooperativity diminished and the allosteric activation pattern changed from one of the K-type in the wild-type deaminase to a mixed K-V pattern. On the other hand, Tyr254-Trp deaminase is kinetically closer to a K-type enzyme and it has a higher catalytic efficiency than the wild-type protein. These results show that the interactions of Tyr254 are fundamental in coupling binding in the active site to events occurring in the allosteric pocket of E. coli glucosamine 6-P deaminase. PMID:9601045

  12. Hydroxyl radicals in indoor environments

    NASA Astrophysics Data System (ADS)

    Sarwar, Golam; Corsi, Richard; Kimura, Yosuke; Allen, David; Weschler, Charles J.

    Indoor hydroxyl radical concentrations were estimated using a new indoor air quality model which employs the SAPRC-99 atmospheric chemistry model to simulate indoor homogenous reactions. Model results indicate that typical indoor hydroxyl radical concentrations are lower than typical outdoor summertime urban hydroxyl radical levels of 5-10×10 6 molecules cm -3; however, indoor levels can be similar to or greater than typical nighttime outdoor hydroxyl radical levels of approximately 5×10 4 molecules cm -3. Effects of selected parameters on indoor hydroxyl radical concentrations are presented herein. Indoor hydroxyl radical concentrations are predicted to increase non-linearly with increasing outdoor ozone concentrations, indoor alkene emission rates, and air exchange rates. Indoor hydroxyl radical concentrations decrease with increasing outdoor nitric oxide concentrations. Indoor temperature and indoor light intensity have moderate impacts on indoor hydroxyl radical concentrations. Outdoor hydroxyl radical concentrations, outdoor nitrate (NO 3rad ) radical concentrations, outdoor hydroperoxy radical concentrations, and hydroxyl radical removal by indoor surfaces are predicted to have no appreciable impact on indoor hydroxyl radical concentrations. Production of hydroxyl radicals in indoor environments appears to be controlled primarily by reactions of alkenes with ozone, and nitric oxide with hydroperoxy radical. Estimated indoor hydroxyl radical levels may potentially affect indoor air quality. Two examples are presented in which reactions of d-limonene and α-pinene with indoor hydroxyl radicals produce aldehydes, which may be of greater concern than the original compounds.

  13. Crosslinking of aromatic polyamides via pendant propargyl groups

    NASA Technical Reports Server (NTRS)

    St.clair, A. K.; St.clair, T. L.; Barrick, J. D.; Campbell, F. J.

    1980-01-01

    Methods for crosslinking N-methyl substituted aromatic polyamides were investigated in an effort to improve the applicability of these polymers as matrix resins for Kavlar trademark fiber composites. High molecular weight polymers were prepared from isophthaloyl dichloride and 4,4'- bis(methylamino)diphenylmethane with varying proportions of the N,N'bispropargyl diamine incorporated as a crosslinking agent. The propargylcontaining diamines were crosslinked thermally and characterized by infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Attempts were also made to crosslink polyamide films by exposure to ultraviolet light, electron beam, and gamma radiation.

  14. Titanium "constrained geometry" complexes with pendant arene groups.

    PubMed

    Dureen, Meghan A; Brown, Christopher C; Morton, Jason G M; Stephan, Douglas W

    2011-03-28

    The synthesis of the proligands C(5)Me(4)HSiMe(2)N(H)R) (R = CMe(2)Ph 1, 2-C(6)H(4)Ph 2) was accomplished via a straightforward salt metathesis reaction of the appropriate lithium amide and ClSiMe(2)(C(5)Me(5)H). Generation of the dilithio salt and reaction with TiCl(3)·(THF)(3) followed by oxidation gave C(5)Me(4)SiMe(2)N(C(6)H(4)Ph)TiCl(2) (3) in low yield. In contrast, deprotonation of 1 and 2 and reaction with (Me(2)N)(2)TiCl(2) afforded C(5)Me(4)(SiMe(2)NR)Ti(NMe(2))(2) (R = CMe(2)Ph 4, 2-C(6)H(4)Ph 5), respectively, in good yields Treatment with MeI gave the analogs C(5)Me(4)(SiMe(2)NR)TiI(2) (R = CMe(2)Ph 6, 2-C(6)H(4)Ph 7). Reduction of 7 with potassium graphite afforded C(5)Me(4)(SiMe(2)NC(6)H(4)Ph)Ti 8. Treatment of 6 and 7 with MeMgBr afforded C(5)Me(4)(SiMe(2)NR)TiMe(2) (R = CMe(2)Ph 9, 2-C(6)H(4)Ph 10). Complexes 9 and 10 in combination with the activator [Ph(3)C][B(C(6)F(5))(4)] catalyzed the polymerization of styrene and ethylene. Copolymerization was also investigated. While the catalyst derived from 10 showed poor activity, compound 9 showed markedly higher activity than 10 and (C(5)Me(4))SiMe(2)(NtBu)]TiMe(2). PMID:21298170

  15. LINE-1 gene hypomethylation and p16 gene hypermethylation in HepG2 cells induced by low-dose and long-term triclosan exposure: The role of hydroxyl group.

    PubMed

    Zeng, Liudan; Ma, Huimin; Pan, Shangxia; You, Jing; Zhang, Gan; Yu, Zhiqing; Sheng, Guoying; Fu, Jiamo

    2016-08-01

    Triclosan (TCS), a frequently used antimicrobial agent in pharmaceuticals and personal care products, exerts liver tumor promoter activities in mice. Previous work showed high-dose TCS (1.25-10μM) induced global DNA hypomethylation in HepG2 cells. However, whether or how tumor suppressor gene methylation changed in HepG2 cells after low-dose and long-term TCS exposure is still unknown. We investigate here the effects and mechanisms of DNA methylation of global DNA(GDM), repetitive genes, and liver tumor suppressor gene (p16) after exposing HepG2 cells to low-dose TCS (0.625-5nM)for two weeks using HPLC-MS/MS, Methylight, Q-MSP, Pyrosequencing, and Massarray methods. We found that low-dose TCS exposure decreased repetitive elements LINE-1 methylation levels, but not global DNA methylation, through down-regulating DNMT1 (DNA methyltransferase 1) and MeCP2 (methylated DNA binding domain) expression, and up-regulating 8-hydroxy-2-deoxyguanosine (8-OHdG) levels. Interestingly, low-dose TCS elevated p16 gene methylation and inhibited p16 expression, which were not observed in high-dose (10μM) group. Meanwhile, methyl-triclosan could not induce these two types of DNA methylation changes, suggesting the involvement of hydroxyl in TCS-mediated DNA methylation changes. Collectively, our results suggested low concentrations of TCS adversely affected HepG2 cells through DNA methylation dysregulation, and hydroxyl group in TCS played an important role in the effects. This study provided a better understanding on hepatotoxicity of TCS at environmentally relevant concentrations through epigenetic pathway. PMID:26970259

  16. The role of hydroxyl group acidity on the activity of silica-supported secondary amines for the self-condensation of n-butanal.

    PubMed

    Shylesh, Sankaranarayanapillai; Hanna, David; Gomes, Joseph; Canlas, Christian G; Head-Gordon, Martin; Bell, Alexis T

    2015-02-01

    The catalytic activity of secondary amines supported on mesoporous silica for the self-condensation of n-butanal to 2-ethylhexenal can be altered significantly by controlling the Brønsted acidity of M--OH species present on the surface of the support. In this study, M--OH (M=Sn, Zr, Ti, and Al) groups were doped onto the surface of SBA-15, a mesoporous silica, prior to grafting secondary propyl amine groups on to the support surface. The catalytic activity was found to depend critically on the synthesis procedure, the nature and amount of metal species introduced and the spatial separation between the acidic sites and amine groups. DFT analysis of the reaction pathway indicates that, for weak Brønsted acid groups, such as Si--OH, the rate-limiting step is C--C bond formation, whereas for stronger Brønsted acid groups, such as Ti and Al, hydrolysis of iminium species produced upon C--C bond formation is the rate-limiting step. Theoretical analysis shows further that the apparent activation energy decreases with increasing Brønsted acidity of the M--OH groups, consistent with experimental observation. PMID:25314616

  17. New and extended parameterization of the thermodynamic model AIOMFAC: calculation of activity coefficients for organic-inorganic mixtures containing carboxyl, hydroxyl, carbonyl, ether, ester, alkenyl, alkyl, and aromatic functional groups

    NASA Astrophysics Data System (ADS)

    Zuend, A.; Marcolli, C.; Booth, A. M.; Lienhard, D. M.; Soonsin, V.; Krieger, U. K.; Topping, D. O.; McFiggans, G.; Peter, T.; Seinfeld, J. H.

    2011-09-01

    We present a new and considerably extended parameterization of the thermodynamic activity coefficient model AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) at room temperature. AIOMFAC combines a Pitzer-like electrolyte solution model with a UNIFAC-based group-contribution approach and explicitly accounts for interactions between organic functional groups and inorganic ions. Such interactions constitute the salt-effect, may cause liquid-liquid phase separation, and affect the gas-particle partitioning of aerosols. The previous AIOMFAC version was parameterized for alkyl and hydroxyl functional groups of alcohols and polyols. With the goal to describe a wide variety of organic compounds found in atmospheric aerosols, we extend here the parameterization of AIOMFAC to include the functional groups carboxyl, hydroxyl, ketone, aldehyde, ether, ester, alkenyl, alkyl, aromatic carbon-alcohol, and aromatic hydrocarbon. Thermodynamic equilibrium data of organic-inorganic systems from the literature are critically assessed and complemented with new measurements to establish a comprehensive database. The database is used to determine simultaneously the AIOMFAC parameters describing interactions of organic functional groups with the ions H+, Li+, Na+, K+, NH4+, Mg2+, Ca2+, Cl-, Br-, NO3-, HSO4-, and SO42-. Detailed descriptions of different types of thermodynamic data, such as vapor-liquid, solid-liquid, and liquid-liquid equilibria, and their use for the model parameterization are provided. Issues regarding deficiencies of the database, types and uncertainties of experimental data, and limitations of the model, are discussed. The challenging parameter optimization problem is solved with a novel combination of powerful global minimization algorithms. A number of exemplary calculations for systems containing atmospherically relevant aerosol components are shown. Amongst others, we discuss aqueous mixtures of ammonium sulfate with

  18. New and extended parameterization of the thermodynamic model AIOMFAC: calculation of activity coefficients for organic-inorganic mixtures containing carboxyl, hydroxyl, carbonyl, ether, ester, alkenyl, alkyl, and aromatic functional groups

    NASA Astrophysics Data System (ADS)

    Zuend, A.; Marcolli, C.; Booth, A. M.; Lienhard, D. M.; Soonsin, V.; Krieger, U. K.; Topping, D. O.; McFiggans, G.; Peter, T.; Seinfeld, J. H.

    2011-05-01

    We present a new and considerably extended parameterization of the thermodynamic activity coefficient model AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) at room temperature. AIOMFAC combines a Pitzer-like electrolyte solution model with a UNIFAC-based group-contribution approach and explicitly accounts for interactions between organic functional groups and inorganic ions. Such interactions constitute the salt-effect, may cause liquid-liquid phase separation, and affect the gas-particle partitioning of aerosols. The previous AIOMFAC version was parameterized for alkyl and hydroxyl functional groups of alcohols and polyols. With the goal to describe a wide variety of organic compounds found in atmospheric aerosols, we extend here the parameterization of AIOMFAC to include the functional groups carboxyl, hydroxyl, ketone, aldehyde, ether, ester, alkenyl, alkyl, aromatic carbon-alcohol, and aromatic hydrocarbon. Thermodynamic equilibrium data of organic-inorganic systems from the literature are critically assessed and complemented with new measurements to establish a comprehensive database. The database is used to determine simultaneously the AIOMFAC parameters describing interactions of organic functional groups with the ions H+, Li+, Na+, K+, NH4+, Mg2+, Ca2+, Cl-, Br-, NO3-, HSO4-, and SO42-. Detailed descriptions of different types of thermodynamic data, such as vapor-liquid, solid-liquid, and liquid-liquid equilibria, and their use for the model parameterization are provided. Issues regarding deficiencies of the database, types and uncertainties of experimental data, and limitations of the model, are discussed. The challenging parameter optimization problem is solved with a novel combination of powerful global minimization algorithms. A number of exemplary calculations for systems containing atmospherically relevant aerosol components are shown. Amongst others, we discuss aqueous mixtures of ammonium sulfate with

  19. The Important Role of the Hydroxyl Group on the Conformational Adaptability in Bis(l-threoninato)copper(II) Compared to Bis(l-allo-threoninato)copper(II): Quantum Chemical Study.

    PubMed

    Marković, Marijana; Ramek, Michael; Loher, Claudia; Sabolović, Jasmina

    2016-08-01

    Detailed structural properties of physiological bis(amino acidato)copper(II) complexes are generally unknown in solutions. This paper examines how stereochemical differences between the essential amino acid l-threonine and its diastereomer l-allo-threonine, which is rarely present in nature, may affect relative stabilities of bis(l-threoninato)copper(II) and bis(l-allo-threoninato)copper(II) in the gas phase and aqueous solution. These amino acids can bind to Cu(II) via the nitrogen and carboxylato oxygen atoms, the nitrogen and hydroxyl oxygen atoms, and the carboxylato and hydroxyl oxygen atoms. We term these coordination modes G, No, and Oo, respectively. The density functional theory (DFT) calculations with the B3LYP functional of the conformational landscapes for all possible coordination modes of both complexes revealed their very similar stability in the gas phase and in aqueous solution. The conformational analyses resulted in 196 and 267 conformers of isolated copper(II) chelates with l-threonine and l-allo-threonine, respectively. The G-G coordination mode is the most stable, both in the gas phase and aqueous solution. Very similar energy values of the lowest-energy solvated cis and trans G-G conformers in implicitly accounted water medium are in accord with the experimental results that these isomers are present in aqueous solution at physiological pH values. The transition-state structures, activation Gibbs free energies, and reaction rates calculated using DFT/B3LYP and MP2 for the transformations from the most stable cis G-G and trans Oo-G conformers to trans G-G ones for the first time reveal several alternate coordination-mode transformation mechanisms in the copper(II) complexes with amino acids other than glycine. The trans Oo-G conformers are kinetically more stable than cis G-G ones in the gas phase. The only significant difference found between the two complexes is a more suitable position of the hydroxyl group in physiological bis

  20. Modifications of the 7-Hydroxyl Group of the Transthyretin Ligand Luteolin Provide Mechanistic Insights into Its Binding Properties and High Plasma Specificity

    PubMed Central

    Nilsson, Lina; Larsson, Andreas; Begum, Afshan; Iakovleva, Irina; Carlsson, Marcus; Brännström, Kristoffer; Sauer-Eriksson, A. Elisabeth; Olofsson, Anders

    2016-01-01

    Amyloid formation of the plasma protein transthyretin (TTR) has been linked to familial amyloid polyneuropathy and senile systemic amyloidosis. Binding of ligands within its natural hormone binding site can stabilize the tetrameric structure and impair amyloid formation. We have recently shown that the flavonoid luteolin stabilizes TTR in human plasma with a very high selectivity. Luteolin, however, is inactivated in vivo via glucuronidation for which the preferred site is the hydroxy group at position 7 on its aromatic A-ring. We have evaluated the properties of two luteolin variants in which the 7-hydroxy group has been exchanged for a chlorine (7-Cl-Lut) or a methoxy group (7-MeO-Lut). Using an in vitro model, based on human liver microsomes, we verified that these modifications increase the persistence of the drug. Crystal structure determinations show that 7-Cl-Lut binds similarly to luteolin. The larger MeO substituent cannot be accommodated within the same space as the chlorine or hydroxy group and as a result 7-MeO-Lut binds in the opposite direction with the methoxy group in position 7 facing the solvent. Both 7-Cl-Lut and 7-MeO-Lut qualify as high-affinity binders, but in contrast to luteolin, they display a highly non-specific binding to other plasma components. The binding of the two conformations and the key-interactions to TTR are discussed in detail. Taken together, these results show a proof-of-concept that the persistence of luteolin towards enzymatic modification can be increased. We reveal two alternative high-affinity binding modes of luteolin to TTR and that modification in position 7 is restricted only to small substituents if the original orientation of luteolin should be preserved. In addition, the present work provides a general and convenient method to evaluate the efficacy of TTR-stabilizing drugs under conditions similar to an in vivo environment. PMID:27050398

  1. Modifications of the 7-Hydroxyl Group of the Transthyretin Ligand Luteolin Provide Mechanistic Insights into Its Binding Properties and High Plasma Specificity.

    PubMed

    Nilsson, Lina; Larsson, Andreas; Begum, Afshan; Iakovleva, Irina; Carlsson, Marcus; Brännström, Kristoffer; Sauer-Eriksson, A Elisabeth; Olofsson, Anders

    2016-01-01

    Amyloid formation of the plasma protein transthyretin (TTR) has been linked to familial amyloid polyneuropathy and senile systemic amyloidosis. Binding of ligands within its natural hormone binding site can stabilize the tetrameric structure and impair amyloid formation. We have recently shown that the flavonoid luteolin stabilizes TTR in human plasma with a very high selectivity. Luteolin, however, is inactivated in vivo via glucuronidation for which the preferred site is the hydroxy group at position 7 on its aromatic A-ring. We have evaluated the properties of two luteolin variants in which the 7-hydroxy group has been exchanged for a chlorine (7-Cl-Lut) or a methoxy group (7-MeO-Lut). Using an in vitro model, based on human liver microsomes, we verified that these modifications increase the persistence of the drug. Crystal structure determinations show that 7-Cl-Lut binds similarly to luteolin. The larger MeO substituent cannot be accommodated within the same space as the chlorine or hydroxy group and as a result 7-MeO-Lut binds in the opposite direction with the methoxy group in position 7 facing the solvent. Both 7-Cl-Lut and 7-MeO-Lut qualify as high-affinity binders, but in contrast to luteolin, they display a highly non-specific binding to other plasma components. The binding of the two conformations and the key-interactions to TTR are discussed in detail. Taken together, these results show a proof-of-concept that the persistence of luteolin towards enzymatic modification can be increased. We reveal two alternative high-affinity binding modes of luteolin to TTR and that modification in position 7 is restricted only to small substituents if the original orientation of luteolin should be preserved. In addition, the present work provides a general and convenient method to evaluate the efficacy of TTR-stabilizing drugs under conditions similar to an in vivo environment. PMID:27050398

  2. Stability of a pendant droplet in gas metal arc welding

    SciTech Connect

    Murray, P.E.

    1998-07-01

    The authors develop a model of metal transfer in gas metal arc welding and compute the critical mass of a pendant droplet in order to ascertain the size and frequency of droplets detaching from the consumable metal electrode. These results are used to predict the mode of metal transfer for a range of voltage and current encompassing free flight transfer, and the transition between globular and spray transfer. This model includes an efficient method to compute the stability of a pendant droplet and the location of the liquid bridge connecting the primary droplet and the residual liquid remaining after detachment of the primary droplet.

  3. Catalytic selective etherification of hydroxyl groups in 5-hydroxymethylfurfural over H4SiW12O40/MCM-41 nanospheres for liquid fuel production.

    PubMed

    Che, Penghua; Lu, Fang; Zhang, Junjie; Huang, Yizheng; Nie, Xin; Gao, Jin; Xu, Jie

    2012-09-01

    5-Hydroxymethylfurfural (HMF) is an important biomass-derived building block, but production and sustainable utilization of HMF remain challenging due to reactions of the highly reactive functional groups of this compound. H(4)SiW(12)O(40)/MCM-41 nanospheres were developed that exhibit 84.1% selectivity to 5-ethoxymethylfurfural (EMF) when HMF conversion reaches 92.0%, during etherification of 5-hydroxymethylfurfural (HMF) with ethanol under mild conditions. The catalyst could be reused, and its activity remained unaffected over five cycles. The strong acidity of the catalyst significantly enhanced etherification. The acetalized byproducts, 5-(diethoxymethyl)-2-furanmethanol and the HMF-dimer (5,5'(oxy-bis(methylene))bis-2-furfural), can be converted into HMF and then transformed to the main product, EMF, by using this catalyst to shift the reaction equilibrium. PMID:22749371

  4. Hydrolysis mechanisms of BNPP mediated by facial copper(II) complexes bearing single alkyl guanidine pendants: cooperation between the metal centers and the guanidine pendants.

    PubMed

    Zhang, Xuepeng; Liu, Xueping; Phillips, David Lee; Zhao, Cunyuan

    2016-01-28

    The hydrolysis mechanisms of DNA dinucleotide analogue BNPP(-) (bis(p-nitrophenyl) phosphate) catalyzed by mononuclear/dinuclear facial copper(ii) complexes bearing single alkyl guanidine pendants were investigated using density functional theory (DFT) calculations. Active catalyst forms have been investigated and four different reaction modes are proposed accordingly. The [Cu2(L(1))2(μ-OH)](3+) (L(1) is 1-(2-guanidinoethyl)-1,4,7-triazacyclononane) complex features a strong μ-hydroxo mediated antiferromagnetic coupling between the bimetallic centers and the corresponding more stable open-shell singlet state. Three different reaction modes involving two catalysts and a substrate were proposed for L(1) entries and the mode 1 in which an inter-complex nucleophilic attack by a metal bound hydroxide was found to be more favorable. In the L(3)-involved reactions (L(3) is 1-(4-guanidinobutyl)-1,4,7-triazacyclononane), the reaction mode in which an in-plane intracomplex scissoring-like nucleophilic attack by a Cu(ii)-bound hydroxide was found to be more competitive. The protonated guanidine pendants in each proposed mechanism were found to play crucial roles in stabilizing the reaction structures via hydrogen bonds and in facilitating the departure of the leaving group via electrostatic attraction. The calculated results are consistent with the experimental observations that the Cu(ii)-L(3) complexes are hydrolytically more favorable than their L(1)-involved counterparts. PMID:26688285

  5. Equilibrium shapes of pendant monodisperse microbubbles suspension droplets

    NASA Astrophysics Data System (ADS)

    Fernandez, Juan Manuel; Campo-Cortes, Francisco

    2014-11-01

    The formation and stability of pendant droplets are a great value for both fundamental and engineering applications. In their pioneering work, Bashforth and Adams obtained the profile of a pendant pure liquid droplet by integrating the Young-Laplace equation. Since then, the stable and unstable conditions that govern the equilibrium of a pendant liquid droplet are well characterized. Here, we study the formation of droplets containing inside a suspension of monodisperse microbubbles. In this study, we present the different morphologies of these pendant multiphase droplets from the tip of a capillary tube of radius R for different average densities of the suspension droplet, defined as ρa =ρgαg +ρlαl where αg and αl are respectively the gas and liquid volume fractions. Experimental droplet profiles are compared with the theoretical predictions obtained by integrating the Young-Laplace equation. For low gas volume gas fraction (high liquid volume fraction), the suspension droplet shape (and consequently its maximum critical volume for stable equilibrium) is defined by the average Bond number, ρa gR2 / σ . However, for dense suspensions, αg > 0 . 7 , the presence of microbubbles greatly changes the mode of drop formation.

  6. Pendant-Drop Surface-Tension Measurement On Molten Metal

    NASA Technical Reports Server (NTRS)

    Man, Kin Fung; Thiessen, David

    1996-01-01

    Method of measuring surface tension of molten metal based on pendant-drop method implemented in quasi-containerless manner and augmented with digital processing of image data. Electrons bombard lower end of sample rod in vacuum, generating hanging drop of molten metal. Surface tension of drop computed from its shape. Technique minimizes effects of contamination.

  7. Nano-anisotropic surface coating based on drug immobilized pendant polymer to suppress macrophage adhesion response.

    PubMed

    Kaladhar, K; Renz, H; Sharma, C P

    2015-04-01

    Exploring drug molecules for material design, to harness concepts of nano-anisotropy and ligand-receptor interactions, are rather elusive. The aim of this study is to demonstrate the bottom-up design of a single-step and bio-interactive polymeric surface coating, based on drug based pendant polymer. This can be applied on to polystyrene (PS) substrates, to suppress macrophage adhesion and spreading. The drug molecule is used in this coating for two purposes. The first one is drug as a "pendant" group, to produce nano-anisotropic properties that can enable adhesion of the coatings to the substrate. The second purpose is to use the drug as a "ligand", to produce ligand-receptor interaction, between the bound ligand and receptors of albumin, to develop a self-albumin coat over the surface, by the preferential binding of albumin in biological environment, to reduce macrophage adhesion. Our in silico studies show that, diclofenac (DIC) is an ideal drug based "ligand" for albumin. This can also act as a "pendant" group with planar aryl groups. The combination of these two factors can help to harness, both nano-anisotropic properties and biological functions to the polymeric coating. Further, the drug, diclofenac (DIC) is immobilized to the polyvinyl alcohol (PVA), to develop the pendant polymer (PVA-DIC). The interaction of bound DIC with the albumin is a ligand-receptor based interaction, as per the studies by circular dichroism, differential scanning calorimetry, and SDS-PAGE. The non-polar π-π* interactions are regulating; the interactions between PVA bound DIC-DIC interactions, leading to "nano-anisotropic condensation" to form distinct "nano-anisotropic segments" inside the polymeric coating. This is evident from, the thermo-responsiveness and uniform size of nanoparticles, as well as regular roughness in the surface coating, with similar properties as that of nanoparticles. In addition, the hydrophobic DIC-polystyrene (PS) interactions, between the PVA

  8. Conjugated polymer network films of poly(p-phenylene vinylene) with hole-transporting carbazole pendants: dual photoluminescence and electrochromic behavior.

    PubMed

    Ponnapati, Ramakrishna; Felipe, Mary Jane; Muthalagu, Vetrichelvan; Puno, Katherine; Wolff, Birte; Advincula, Rigoberto

    2012-03-01

    A series of poly(p-phenylene vinylene) (PPV) copolymers functionalized with hole-transport and electrochemically active carbazole units as pendant moieties is reported. These polymers exhibit photoluminescence properties by virtue of the PPV analogous backbone. They were also designed as precursor polymer bearing the electroactive carbazole group to form conjugated polymer network (CPN) films by electrodeposition. The electrochemical polymerization of the pendant units eventually lead to a dual property electro-optically active thin film - photoluminescence (PL) behavior that can be attenuated with CPN formation, and a reversible doping and dedoping processes at controlled potentials that lead to an electrochromic behavior. This reveals the ability to incorporate complementary optical and electro-optical properties within the same film using the CPN approach. It should be possible to design and synthesize other PPV π-conjugated polymers with efficient pendant hole-transport groups exhibiting tunable PL and electrochromism with cross-linking. PMID:22329863

  9. Peptidyl-CCA deacylation on the ribosome promoted by induced fit and the O3′-hydroxyl group of A76 of the unacylated A-site tRNA

    SciTech Connect

    Simonović, Miljan; Steitz, Thomas A.

    2008-11-24

    The last step in ribosome-catalyzed protein synthesis is the hydrolytic release of the newly formed polypeptide from the P-site bound tRNA. Hydrolysis of the ester link of the peptidyl-tRNA is stimulated normally by the binding of release factors (RFs). However, an unacylated tRNA or just CCA binding to the ribosomal A site can also stimulate deacylation under some nonphysiological conditions. Although the sequence of events is well described by biochemical studies, the structural basis of the mechanism underlying this process is not well understood. Two new structures of the large ribosomal subunit of Haloarcula marismortui complexed with a peptidyl-tRNA analog in the P site and two oligonucleotide mimics of unacylated tRNA, CCA and CA, in the A site show that the binding of either CA or CCA induces a very similar conformational change in the peptidyl-transferase center as induced by aminoacyl-CCA. However, only CCA positions a water molecule appropriately to attack the carbonyl carbon of the peptidyl-tRNA and stabilizes the proper orientation of the ester link for hydrolysis. We, thus, conclude that both the ability of the O3'-hydroxyl group of the A-site A76 to position the water and the A-site CCA induced conformational change of the PTC are critical for the catalysis of the deacylation of the peptidyl-tRNA by CCA, and perhaps, an analogous mechanism is used by RFs.

  10. Hydroxyl speciation in felsic magmas

    NASA Astrophysics Data System (ADS)

    Malfait, Wim J.; Xue, Xianyu

    2014-09-01

    The hydroxyl speciation of hydrous, metaluminous potassium and calcium aluminosilicate glasses was investigated by 27Al-1H cross polarization and quantitative 1H MAS NMR spectroscopy. Al-OH is present in both the potassium and the calcium aluminosilicate glasses and its 1H NMR partial spectrum was derived from the 27Al-1H cross polarization data. For the calcium aluminosilicate glasses, the abundance of Al-OH could not be determined because of the low spectral resolution. For the potassium aluminosilicate glasses, the fraction of Al-OH was quantified by fitting its partial spectrum to the quantitative 1H NMR spectra. The degree of aluminum avoidance and the relative tendency for Si-O-Si, Si-O-Al and Al-O-Al bonds to hydrolyze were derived from the measured species abundances. Compared to the sodium, lithium and calcium systems, potassium aluminosilicate glasses display a much stronger degree of aluminum avoidance and a stronger tendency for the Al-O-Al linkages to hydrolyze. Combining our results with those for sodium aluminosilicate glasses (Malfait and Xue, 2010a), we predict that the hydroxyl groups in rhyolitic and phonolitic magmas are predominantly present as Si-OH (84-89% and 68-78%, respectively), but with a significant fraction of Al-OH (11-16% and 22-32%, respectively). For both rhyolitic and phonolitic melts, the AlOH/(AlOH + SiOH) ratio is likely smaller than the Al/(Al + Si) ratio for the lower end of the natural temperature range but may approach the Al/(Al + Si) ratio at higher temperatures.

  11. A Straight Forward Route for the Development of Metal-Organic Frameworks Functionalized with Aromatic -OH Groups: Synthesis, Characterization, and Gas (N2, Ar, H2, CO2, CH4, NH3) Sorption Properties

    SciTech Connect

    Spanopoulos, Ioannis; Xydias, Pantelis; Malliakas, Christos D; Trikalitis, Pantelis N

    2013-01-09

    A facile and general methodology for the development of metal–organic frameworks (MOFs) functionalized with pendant, aromatic hydroxyl (-OH) groups is presented. Extensive gas-sorption studies in representative and important MOFs functionalized with free aromatic -OH groups such as the IRMOF-8 and DUT-6 (or MOF-205), denoted here as 1 and 2, revealed a high CO2/CH4 selectivity for 1 (13.6 at 273 K and 1 bar) and a high NH3 uptake of 16.4 mol kg–1 at 298 K and 1 bar for 2.

  12. Hydroxylated PBDEs induce developmental arrest in zebrafish

    SciTech Connect

    Usenko, Crystal Y. Hopkins, David C.; Trumble, Stephen J. Bruce, Erica D.

    2012-07-01

    The ubiquitous spread of polybrominated diphenyl ethers (PBDEs) has led to concerns regarding the metabolites of these congeners, in particular hydroxylated PBDEs. There are limited studies regarding the biological interactions of these chemicals, yet there is some concern they may be more toxic than their parent compounds. In this study three hydroxylated PBDEs were assessed for toxicity in embryonic zebrafish: 3-OH-BDE 47, 5-OH-BDE 47, and 6-OH-BDE 47. All three congeners induced developmental arrest in a concentration-dependent manner; however, 6-OH-BDE 47 induced adverse effects at lower concentrations than the other congeners. Furthermore, all three induced cell death; however apoptosis was not observed. In short-term exposures (24–28 hours post fertilization), all hydroxylated PBDEs generated oxidative stress in the region corresponding to the cell death at 5 and 10 ppm. To further investigate the short-term effects that may be responsible for the developmental arrest observed in this study, gene regulation was assessed for embryos exposed to 0.625 ppm 6-OH-BDE 47 from 24 to 28 hpf. Genes involved in stress response, thyroid hormone regulation, and neurodevelopment were significantly upregulated compared to controls; however, genes related to oxidative stress were either unaffected or downregulated. This study suggests that hydroxylated PBDEs disrupt development, and may induce oxidative stress and potentially disrupt the cholinergic system and thyroid hormone homeostasis. -- Highlights: ► OH-PBDEs induce developmental arrest in a concentration-dependent manner. ► Hydroxyl group location influences biological interaction. ► OH-PBDEs induce oxidative stress. ► Thyroid hormone gene regulation was disrupted following exposure. ► To our knowledge, this is the first whole organism study of OH-PBDE toxicity.

  13. Are Displaced Miogeoclinal Rocks present in metamorphic pendants in the central and southern Sierra Nevada

    NASA Astrophysics Data System (ADS)

    Gelbach, L. B.; Stanley, R.; Chang, J.; van Guilder, E.; Paterson, S. R.; Memeti, V.

    2009-12-01

    In high flux arcs regional tectonic events are largely preserved in small host rock pendants. It has been proposed in the Sierran arc, California that a block of passive margin sediments (Snow Lake block) has been displaced to its present location from an uncertain origin. Members of the USC undergraduate team research program have studied two pendants, the Boyden Cave pendant and further north, the Iron Mountain pendant to determine if passive margin sediments exist in these areas. The Boyden Cave pendant was composed of Cretaceous metasedimentary rocks and metavolcanics potentially resembling a Mesozoic overlap sequence seen elsewhere in Sierran pendants on top of the passive margin metasediments. Further west, the area contained limestones and very pure quartzites of unknown ages that could have miogeoclinal origins. The Iron Mountain pendant has been mapped also as part of the Snow Lake Block, but we believe this to be incorrect. The Iron Mountain pendant is composed of a mix of volcanic, volcaniclastic, and sedimentary rocks associated with a hypabyssal pluton and may represent an old caldera, possibly of Mesozoic age. If correct this pendant represents some of the most western and potentially youngest Mesozoic volcanics preserved in this part of the arc. Zircon dating and geochemistry underway will allow us to better constrain the likely ages and protolith of quartzites from Boyden Cave and if the Iron Mountain pendant represents a Cretaceous caldera complex.

  14. Towards a full understanding of the nature of Ni(II) species and hydroxyl groups over highly siliceous HZSM-5 zeolite supported nickel catalysts prepared by a deposition-precipitation method.

    PubMed

    Chen, Bao-Hui; Chao, Zi-Sheng; He, Hao; Huang, Chen; Liu, Ya-Juan; Yi, Wen-Jun; Wei, Xue-Ling; An, Jun-Fang

    2016-02-14

    Highly siliceous HZSM-5 zeolite supported nickel catalysts prepared by a deposition-precipitation (D-P) method were characterized by Fourier transform infrared (FT-IR), hydrogen temperature programmed reduction (H2-TPR), X-ray diffraction (XRD), N2-absorption/desorption, field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and (27)Al magic-angle nuclear magnetic resonance (MAS NMR) techniques. The results showed that the D-P of nickel species occurred predominantly on the internal surface of highly siliceous HZSM-5 zeolite, in which the internal silanol groups located on the hydroxylated mesopores or nanocavities played a key role. During the D-P process, nickel hydroxide was first deposited-precipitated via olation/polymerization of neutral hydroxoaqua nickel species over the HZSM-5 zeolite. With the progress of the D-P process, 1 : 1 nickel phyllosilicate was formed over the HZSM-5 via the hetero-condensation/polymerization between charged hydroxoaqua nickel species and monomer silicic species generated due to the partial dissolution of the HZSM-5 framework. The 1 : 1 nickel phyllosilicate could also be generated via the hydrolytic adsorption of hydroxoaqua nickel species and their subsequent olation condensation. After calcination, the deposited-precipitated nickel hydroxide was decomposed into nickel oxide, while the 1 : 1 nickel phyllosilicate was transformed into 2 : 1 nickel phyllosilicate. According to the above mechanism, Ni(ii) species were present both in the form of nickel oxide and 2 : 1 nickel phyllosilicate, which were mutually separated from each other, being highly dispersed over HZSM-5 zeolite. PMID:26745008

  15. Interaction of Gold Clusters with a Hydroxylated Surface

    SciTech Connect

    Jiang, Deen; Overbury, Steven {Steve} H; Dai, Sheng

    2011-01-01

    We explore the interaction between gold nanoclusters and a fully hydroxylated surface, Mg(OH){sub 2}'s basal plane, by using a density functional theory-enabled local basin-hopping technique for global-minimum search. We find strong interaction of gold nanoclusters with the surface hydroxyls via a short bond between edge Au atoms and O atoms of the -OH groups. We expect that this strong interaction is ubiquitous on hydroxylated support surfaces and helps the gold nanoclusters against sintering, thereby contributing to their CO-oxidation activity at low temperatures.

  16. Evaluation of alcoholic hydroxyl derivatives for chemically amplified extreme ultraviolet resist

    NASA Astrophysics Data System (ADS)

    Furukawa, Kikuo; Kozawa, Takahiro; Tagawa, Seiichi

    2009-03-01

    Extreme ultraviolet (EUV) lithography is the most favorable process as next-generation lithography. For the development of EUV resists, phenolic materials such as poly (4-hydroxystyrene) have been investigated. Phenolic hydroxyl groups of polymers play an important role in acid diffusion, dissolution kinetics, and adhesion to substrates. Besides these important roles, phenolic hydroxyl groups are also an effective proton source in acid generation in EUV resists. However, the roles of alcohol hydroxyl groups have not been well-studied. To clarify the difference between phenolic and alcoholic hydroxyl groups upon exposure to EUV radiation, we synthesized acrylic terpolymers containing alcoholic hydroxyl groups as model photopolymers and exposed the resist samples based on these polymers to EUV radiation. On the basis of the lithographic performances of these resist samples, we evaluated the characteristics of alcoholic hydroxyl groups upon exposure to EUV radiation. We discuss the relationship between the chemical structures of these derivatives and lithographic performance.

  17. Hydroxyl Motion in Mg(OH)2

    NASA Astrophysics Data System (ADS)

    Itoh, Yutaka; Isobe, Masahiko

    2015-11-01

    We report on pulsed 1H NMR studies of the hydroxyl OH groups in magnesium hydroxide Mg(OH)2 at 77-355 K at 42.5772 MHz. The Fourier-transformed NMR spectra show the superposition of broad and narrow components. The broad NMR spectrum is assigned to dipole-coupled protons on a rigid lattice in the bulk Mg(OH)2, while the narrow NMR spectrum is assigned to extrinsic protons, e.g., conduction protons facilitated by lattice defects. We found a monotonically decreasing linewidth of the broad NMR spectrum on heating. The monotonic decrease in the linewidth is associated with hopping protons around a threefold axis (rotational hydroxyl protons).

  18. Mesomorphic and luminescent properties of disubstituted polyacetylenes bearing biphenyl pendants

    NASA Astrophysics Data System (ADS)

    Lam, Jacky W. Y.; Law, Chi Kong; Dong, Yuping; Wang, Jiannong; Ge, Weikun; Tang, Ben Zhong

    2003-01-01

    Liquid crystalline and light emitting properties of two new disubstituted polyacetylenes bearing biphenyl pendants (-{(R)CC[(CH 2) 4OCO-Biph-OC 7H 15]} n-, RCH 3 ( 1), C 6H 5 ( 2), Biph=4,4 '-biphenylyl) were investigated. Whereas 1 formed enantiotropic nematic phase, 2 was non-mesomorphic. Upon photoexcitation, the THF solutions of 1 and 2 emitted strong UV and blue light of 369 and 460 nm, respectively, whose quantum efficiencies were higher than that of poly(1-phenyl-1-octyne), a highly luminescent disubstituted polyacetylene.

  19. Measurement of surface and interfacial tension using pendant drop tensiometry.

    PubMed

    Berry, Joseph D; Neeson, Michael J; Dagastine, Raymond R; Chan, Derek Y C; Tabor, Rico F

    2015-09-15

    Pendant drop tensiometry offers a simple and elegant solution to determining surface and interfacial tension - a central parameter in many colloidal systems including emulsions, foams and wetting phenomena. The technique involves the acquisition of a silhouette of an axisymmetric fluid droplet, and iterative fitting of the Young-Laplace equation that balances gravitational deformation of the drop with the restorative interfacial tension. Since the advent of high-quality digital cameras and desktop computers, this process has been automated with high speed and precision. However, despite its beguiling simplicity, there are complications and limitations that accompany pendant drop tensiometry connected with both Bond number (the balance between interfacial tension and gravitational forces) and drop volume. Here, we discuss the process involved with going from a captured experimental image to a fitted interfacial tension value, highlighting pertinent features and limitations along the way. We introduce a new parameter, the Worthington number, Wo, to characterise the measurement precision. A fully functional, open-source acquisition and fitting software is provided to enable the reader to test and develop the technique further. PMID:26037272

  20. Sequential and competitive adsorption of peptides at pendant PEO layers.

    PubMed

    Wu, Xiangming; Ryder, Matthew P; McGuire, Joseph; Snider, Joshua L; Schilke, Karl F

    2015-06-01

    Earlier work provided direction for development of responsive drug delivery systems based on modulation of the structure, amphiphilicity, and surface density of bioactive peptides entrapped within pendant polyethylene oxide (PEO) brush layers. In this work, we describe the sequential and competitive adsorption behavior of such peptides at pendant PEO layers. Three cationic peptides were used for this purpose: the arginine-rich, amphiphilic peptide WLBU2, a peptide chemically identical to WLBU2 but of scrambled sequence (S-WLBU2), and the non-amphiphilic peptide poly-L-arginine (PLR). Optical waveguide lightmode spectroscopy (OWLS) was used to quantify the rate and extent of peptide adsorption and elution at surfaces coated with PEO. UV spectroscopy and time-of-flight secondary ion mass spectrometry (TOF-SIMS) were used to quantify the extent of peptide exchange during the course of sequential and competitive adsorption. Circular dichroism (CD) was used to evaluate conformational changes after adsorption of peptide mixtures at PEO-coated silica nanoparticles. Results indicated that amphiphilic peptides are able to displace adsorbed, non-amphiphilic peptides in PEO layers, while non-amphiphilic peptides were not able to displace more amphiphilic peptides. In addition, peptides of greater amphiphilicity dominated the adsorption at the PEO layer from mixtures with less amphiphilic or non-amphiphilic peptides. PMID:25909181

  1. A Quasi-Containerless Pendant Drop Method for Surface Tension Measurements of Molten Metals and Alloys

    NASA Technical Reports Server (NTRS)

    Thiessen, David B.; Man, Kin F.

    1994-01-01

    A quasi-containerless pendant drop method for measuring the surface tension of molten metals and alloys is being developed. The technique involves melting the end of a high-purity metal rod by bombardment with an electron beam to form a pendant drop under ultra-high vacuum conditions to minimize surface contamination.

  2. Gravity model and structural implications of the Goddard Pendant, Sierra Nevada, California.

    USGS Publications Warehouse

    du Bray, E.A.; Oliver, H.W.

    1981-01-01

    A subsurface model for the Goddard pendant is constructed from a residual gravity high of about 7mGal over the pendant. The model, which is the simplest and most geologically reasonable possibility, shows a metamorphic block that tapers with depth and extends about 3.5km below the surface. The structures in the Goddard pendant are similar in style and orientation to those in other Sierra Nevada pendants, indicating that the country rock was neither deformed nor rotated during pluton emplacement. Consequently, emplacement must have been a passive rather than a forceful process. The pendant itself represents a piece of country rock trapped between plutons which are dome shaped in cross section. -Authors

  3. Hydroxyl radical detection in vivo

    SciTech Connect

    Chevion, M.; Floyd, R.A.

    1986-05-01

    Hydroxyl radicals have been implicated as the actual species responsible for the deleterious effects of active oxygen in biology. However, in most cases, its presence has only been inferred by circumstantial evidence. Using electrochemical detection coupled to HPLC separation technique the authors can identify and quantitate (at sub-picomole level) the hydroxylated products of 3 aromatic compounds (phenol, salicylate, and 2-deoxy-guanosine) as a direct measure of hydroxyl radical formation. Firstly, the authors showed that mixing ascorbate with copper ions (in the absence of presence of a protein) yields catechols, dihydroxybenzoic acids and 8-OH-deoxy-guanosine (8-OHdG). This approach has been used to study the formation of OH in vivo. Human granulocytes stimulated with TPA showed that 8-OHdG was formed in the cellular DNA at high levels (one 8-OHdG/800 DNA bases). Unstimulated granulocytes contained 8-OHdG below detection level. Formation of 8-OHdG in the TPA-stimulated granulocytes DNA was decreased by the addition of SOD and catalase. Using salicylate as an in vivo scavenger of hydroxyl radicals the authors showed that the level of trapped-dihydroxybenzoic acids is increased approx.8 and approx.3 fold in the lungs and liver of paraquat-poisoned mice, respectively, as compared to normal animals. Similarly, the detected level of dihydroxybenzoic acids in the hearts of adriamycin-treated rats was increased over 100-fold as compared to the hearts of control animals.

  4. 7-alpha-hydroxylation of cholestanol by rat liver microsomes.

    PubMed

    Shefer, S; Hauser, S; Mosbach, E H

    1968-05-01

    In a study of the mechanism whereby 5alpha-bile acids are formed from cholestanol, the 7alpha-hydroxylation of cholestanol was investigated in rat liver preparations in vitro. It was found that in the presence of NADPH and oxygen, rat liver microsomes catalyzed the 7alpha-hydroxylation of cholestanol to the same extent as that of cholesterol. The rate of the hydroxylation was enhanced by prior treatment of the experimental rats with cholestyramine (a bile acid sequestrant) or by establishment of bile fistulas-i.e., by partial or complete removal of bile acids from the enterohepatic circulation. The 7-hydroxylation reaction was further stimulated by pretreatment of the animals with phenobarbital, a drug known to produce increased biosynthesis of hepatic endoplasmic membranes. The 7alpha-hydroxylase was inhibited by the reaction product, by sterols with 7-keto or 7beta-hydroxyl groups, and also by mono- and dihydroxy bile acids of the 5beta-series, although cholic acid or taurocholate produced no inhibition unless added in high concentrations. The results of these studies are in accord with the concept that the presence of a Delta(5)-double bond is not required for the enzymatic formation of the 7alpha-hydroxy derivative. The rate of this hydroxylation reaction in vitro appears to depend on the concentration of bile salts in the enterohepatic circulation of the experimental animals from whom the microsomes were obtained. PMID:5650927

  5. Selective hydroxylation of alkanes by an extracellular fungal peroxygenase.

    PubMed

    Peter, Sebastian; Kinne, Matthias; Wang, Xiaoshi; Ullrich, René; Kayser, Gernot; Groves, John T; Hofrichter, Martin

    2011-10-01

    Fungal peroxygenases are novel extracellular heme-thiolate biocatalysts that are capable of catalyzing the selective monooxygenation of diverse organic compounds, using only H(2)O(2) as a cosubstrate. Little is known about the physiological role or the catalytic mechanism of these enzymes. We have found that the peroxygenase secreted by Agrocybe aegerita catalyzes the H(2)O(2)-dependent hydroxylation of linear alkanes at the 2-position and 3-position with high efficiency, as well as the regioselective monooxygenation of branched and cyclic alkanes. Experiments with n-heptane and n-octane showed that the hydroxylation proceeded with complete stereoselectivity for the (R)-enantiomer of the corresponding 3-alcohol. Investigations with a number of model substrates provided information about the route of alkane hydroxylation: (a) the hydroxylation of cyclohexane mediated by H(2)(18)(2) resulted in complete incorporation of (18)O into the hydroxyl group of the product cyclohexanol; (b) the hydroxylation of n-hexane-1,1,1,2,2,3,3-D(7) showed a large intramolecular deuterium isotope effect [(k(H)/k(D))(obs)] of 16.0 ± 1.0 for 2-hexanol and 8.9 ± 0.9 for 3-hexanol; and (c) the hydroxylation of the radical clock norcarane led to an estimated radical lifetime of 9.4 ps and an oxygen rebound rate of 1.06 × 10(11) s(-1). These results point to a hydrogen abstraction and oxygen rebound mechanism for alkane hydroxylation. The peroxygenase appeared to lack activity on long-chain alkanes (> C(16)) and highly branched alkanes (e.g. tetramethylpentane), but otherwise exhibited a broad substrate range. It may accordingly have a role in the bioconversion of natural and anthropogenic alkane-containing structures (including alkyl chains of complex biomaterials) in soils, plant litter, and wood. PMID:21812933

  6. Experimental verification of a pendant ice formation model

    SciTech Connect

    Szilder, K.; Forest, T.; Lozowski, E.P.

    1995-12-31

    A random walk model has been developed to predict the growth of pendant ice formations and icicles. The model allows an efficient representation of water flow along the surface, dripping from lower extremities, and freezing of water. Using a simple analysis, the microscopic model parameters are expressed as functions of the macroscopic physical conditions. To verify the random walk model, a series of laboratory experiments was conducted in an icing wind tunnel. A horizontal thin wire was exposed to vertically falling supercooled spray and the formation of icicles underneath the wire was examined. Model verification based on a comparison with the experimental results demonstrates quantitatively and qualitatively the credibility and value of this model approach. Future model development will involve the quantitative simulation of ice accretion on objects of complex geometry, such as offshore structures, ships, and transmission lines.

  7. Effective inhibition of hydroxyl radicals by hydroxylated biphenyl compounds.

    PubMed

    Taira, J; Ikemoto, T; Mimura, K; Hagi, A; Murakami, A; Makino, K

    1993-01-01

    In aqueous media, approximate rate constants for the reactions between hydroxyl radicals (.OH) and biphenyl compounds such as dehydrodieugenol, magnolol, honokiol, dehydrodidihydroeugenol, dehydrodivanillyl alcohol, and dehydrodicreosol were estimated by competition reactions for .OH between these biphenyls and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). By measuring the decrease in the height of the EPR signals of the .OH spin adduct, rate constants in the order of 10(9) to 10(10) M were measured. PMID:8282234

  8. H 3SiOH and F 3SiOH as models for isolated hydroxyl groups of amorphous silica: an ab initio study of the adducts with dihydrogen and carbon monoxide

    NASA Astrophysics Data System (ADS)

    Senchenya, I. N.; Civalleri, B.; Ugliengo, P.; Garrone, E.

    1998-09-01

    Ab initio calculations have been performed at both the self-consistent field (SCF) and the second-order Møller-Plesset (MP2) levels of theory, using both double-zeta plus polarisation functions basis sets and augmented correlation-consistent valence-polarised (aug-cc-pVDZ and aug-cc-pVTZ) ones, to compare the acidic and vibration features and the geometry of H 3SiOH, the model usually adopted for the isolated hydroxyls of silica, with those of its fluorinated analogue, F 3SiOH. Their complexes with H 2 and CO have also been studied. Passing from the MP2/DZP level of computation to MP2/aug-cc-pVDZ and MP2/aug-cc-pVTZ levels results in a considerable improvement of calculated data for H 3SiOH and its complexes when compared with experimental data. H 3SiOH is, however, less acidic than isolated hyroxyls of silica. In contrast, the use of F 3SiOH as a model yields an overestimation of the acidic properties; e.g., the stretching O-H mode frequency shifts caused by hydrogen-bond interaction with the base molecules. The combined use of both models may provide guidelines for prediction of the adducts of the isolated hydroxyl of silica with small molecules.

  9. Pendant Dynamics of Ethylene-Oxide Containing Polymers with Diverse Backbones

    NASA Astrophysics Data System (ADS)

    Bartels, Joshua; Wang, Jing-Han Helen; Chen, Quan; Runt, James; Colby, Ralph

    In the last twenty years, a wide variety of ion conducting polymers have used ether oxygens to facilitate ion conduction, and it is therefore important to understand the dynamics of ether oxygens (EOs) when attached to different polymer backbones. Four different EO-containing polymer architectures are studied by dielectric spectroscopy to understand the backbone effect on the EO dipoles. Polysiloxanes, polyphosphazenes, polymethylmethacrylates, and a polyester ether are compared, with different EO pendant lengths for the siloxane and methylmethacrylate backbones. The flexible polysiloxanes and polyphosphazene backbones impart superior segmental mobility with a glass transition temperature 15 K lower than that of the organic backbone polymers. Short EO pendants are found to impart a lower static dielectric constant at comparable EO content as compared to longer EO pendants of either inorganic or organic backbones. The long-pendant polymethylmethacrylate polymers show two relaxations corresponding to fast EOs near the pendant tail end and slow EOs close to the slower backbone, whereas the long-pendant polysiloxane shows a single relaxation due to the siloxane backbone relaxing faster than the EO pendant. Supported by the NSF Division of Materials Research Polymers Program through Grants DMR-1404586 (RHC) and DMR-1505953 (JR).

  10. An Iminium Salt Organocatalyst for Selective Aliphatic C-H Hydroxylation.

    PubMed

    Wang, Daoyong; Shuler, William G; Pierce, Conor J; Hilinski, Michael K

    2016-08-01

    The first examples of catalysis of aliphatic C-H hydroxylation by an iminium salt are presented. The method allows the selective organocatalytic hydroxylation of unactivated 3° C-H bonds at room temperature using hydrogen peroxide as the terminal oxidant. Hydroxylation of an unactivated 2° C-H bond is also demonstrated. Furthermore, improved functional group compatibility over other catalytic methods is reported in the form of selectivity for aliphatic C-H hydroxylation over alcohol oxidation. On the basis of initial mechanistic studies, an oxaziridinium species is proposed as the active oxidant. PMID:27391543

  11. Sensing system for detection and control of deposition on pendant tubes in recovery and power boilers

    DOEpatents

    Kychakoff, George; Afromowitz, Martin A; Hugle, Richard E

    2005-06-21

    A system for detection and control of deposition on pendant tubes in recovery and power boilers includes one or more deposit monitoring sensors operating in infrared regions and about 4 or 8.7 microns and directly producing images of the interior of the boiler. An image pre-processing circuit (95) in which a 2-D image formed by the video data input is captured, and includes a low pass filter for performing noise filtering of said video input. An image segmentation module (105) for separating the image of the recovery boiler interior into background, pendant tubes, and deposition. An image-understanding unit (115) matches derived regions to a 3-D model of said boiler. It derives a 3-D structure the deposition on pendant tubes in the boiler and provides the information about deposits to the plant distributed control system (130) for more efficient operation of the plant pendant tube cleaning and operating systems.

  12. Determinants of regioselective hydroxylation in the fungal polysaccharide monooxygenases.

    PubMed

    Vu, Van V; Beeson, William T; Phillips, Christopher M; Cate, Jamie H D; Marletta, Michael A

    2014-01-15

    The ubiquitous fungal polysaccharide monooxygenases (PMOs) (also known as GH61 proteins, LPMOs, and AA9 proteins) are structurally related but have significant variation in sequence. A heterologous expression method in Neurospora crassa was developed as a step toward connecting regioselectivity of the chemistry to PMO phylogeny. Activity assays, as well as sequence and phylogenetic analyses, showed that the majority of fungal PMOs fall into three major groups with distinctive active site surface features. PMO1s and PMO2s hydroxylate glycosidic positions C1 and C4, respectively. PMO3s hydroxylate both C1 and C4. A subgroup of PMO3s (PMO3*) hydroxylate C1. Mutagenesis studies showed that an extra subdomain of about 12 amino acids contribute to C4 oxidation in the PMO3 family. PMID:24350607

  13. Removal and recovery of toxic metal ions from aqueous waste sites using polymer pendant ligands

    SciTech Connect

    Fish, D.

    1996-10-01

    The purpose of this project is to investigate the use of polymer pendant ligand technology to remove and recover toxic metal ions from DOE aqueous waste sites. Polymer pendant lgiands are organic ligands, anchored to crosslinked, modified divinylbenzene-polystyrene beads, that can selectively complex metal ions. The metal ion removal step usually occurs through a complexation or ion exchange phenomena, thus recovery of the metal ions and reuse of the beads is readily accomplished.

  14. Influence of hydroxyl substitution on flavanone antioxidants properties.

    PubMed

    Masek, Anna; Chrzescijanska, Ewa; Latos, Malgorzata; Zaborski, Marian

    2017-01-15

    The aim of our study was to determine the effect of the position of the hydroxyl group on the antioxidant properties of flavonoid derivatives. For this purpose, we performed electrochemical analysis and quantum-mechanical calculations to describe the mechanisms of electrochemical oxidation, and we selected the two methods of ABTS (2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) and DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate), which allowed us to determine the ability to scavenge free radicals. On the basis of the research, we found that the derivatives of flavonoids, which have a hydroxyl group substituted at the R-3 position on the C ring, have outstanding antioxidant activity. Flavone, which had an OH group substituted at the R-6 and R-7 position on the ring A, showed similar antioxidant activity to flavone without -OH groups in the structure and slightly higher activity than the di-substituted flavone on the ring A. PMID:27542504

  15. Quantifying nisin adsorption behavior at pendant PEO layers

    PubMed Central

    Dill, Justen K.; Auxier, Julie A.; Schilke, Karl F.; McGuire, Joseph

    2013-01-01

    The antimicrobial peptide nisin shows potent activity against Gram-positive bacteria including the most prevalent implant-associated pathogens. Its mechanism of action minimizes the opportunity for the rise of resistant bacteria and it does not appear to be toxic to humans, suggesting good potential for its use in antibacterial coatings for selected medical devices. A more quantitative understanding of nisin loading and release from polyethylene oxide (PEO) brush layers will inform new strategies for drug storage and delivery, and in this work optical waveguide lightmode spectroscopy was used to record changes in adsorbed mass during cyclic adsorption-elution experiments with nisin, at uncoated and PEO-coated surfaces. PEO layers were prepared by radiolytic grafting of Pluronic® surfactant F108 or F68 to silanized silica surfaces, producing long- or short-chain PEO layers, respectively. Kinetic patterns were interpreted with reference to a model accounting for history-dependent adsorption, in order to evaluate rate constants for nisin adsorption and desorption, as well as the effect of pendant PEO on the lateral clustering behavior of nisin. Nisin adsorption was observed at the uncoated and F108-coated surfaces, but not at the F68-coated surfaces. Nisin showed greater resistance to elution by peptide-free buffer at the uncoated surface, and lateral rearrangement and clustering of adsorbed nisin was apparent only at the uncoated surface. We conclude peptide entrapment at the F108-coated surface is governed by a hydrophobic inner region of the PEO brush layer that is not sufficient for nisin entrapment in the case of the shorter PEO chains of the F68-coated surface. PMID:23445762

  16. Pumping the stellar hydroxyl maser

    NASA Technical Reports Server (NTRS)

    Dickinson, Dale F.

    1987-01-01

    IRAS far-IR flux data for 163 OH maser stars were analyzed to quantify the contributions 35 and 53 microns inversions make to pumping of the hydroxyl maser. The 35 microns transition is from the 3,3 ground state to the 1,5 rotationally excited level and subsequent decay; the 53 microns transition is a change from the ground state to the 1,3 excited level and relaxation. The stars examined included Mira, short period semi-regular and long-period semi-regular variables. Both transition lines had rough parity in contributing to the approximately 8 percent pumping efficiency at 1612 MHz. However, the individual contributions of the lines could not be determined for the stellar population studied.

  17. Construction of a peptide with an electroactive daunomycin like a pendant arm to detect ovalbumin.

    PubMed

    Sugawara, Kazuharu; Kadoya, Toshihiko; Kuramitz, Hideki

    2015-02-01

    In this study, a peptide-1 (RNRCKGTDVQAW) constructing lysozyme was conjugated with an electroactive daunomycin in order to voltammetrically detect ovalbumin (OVA). Hetero-bifunctional cross-linking agents with four kinds of ethylene chains in differing lengths were used to bind the peptide-1 and daunomycin. After a cross-linking agent had reacted with an amino group of daunomycin, the compound was introduced into the peptide to the cysteine residue in the peptide using a pendant arm. The OVA was sensed via a change in the electrode response of the daunomycin moiety, based on the binding between the peptide and the OVA. The adsorption of the peptide probe on the electrode increased with increases in the ethylene chain. The binding constants between the peptide probes and the OVA, however, did not depend on the length of the chain. This was because the ethylene chain influenced the binding. When the peptide and the daunomycin were bound using N-(6-maleimidocaproyloxy) sulfosuccinimide, the electrode response of the peptide probe was the most sensitive from among the four cross-linking agents. The calibration curve of the OVA using the peptide probe was linear and ranged from 1.5×10(-11) to 3.0×10(-10)M. Furthermore, this method could be applied to the electrochemical sensing of the OVA in egg whites and in fetal bovine serum. PMID:25604822

  18. Generation of hydroxyl radicals during ascites experimentally induced in broilers.

    PubMed

    Arab, H A; Jamshidi, R; Rassouli, A; Shams, G; Hassanzadeh, M H

    2006-04-01

    Increased metabolic rates, pulmonary hypertension and cardiac dysfunction are the most important features of the ascites syndrome in broiler chickens. However, the mechanism of cell injury causing the pathogenesis of the syndrome is not clearly understood. Our study aimed to examine the generation of hydroxyl radicals (OH*) in broiler chickens experiencing ascites. The hundred and fifty 1-d-old chickens were purchased from a local hatchery and reared in an open poultry house for 46 d. They were divided at random into three groups and ascites was induced in two groups by exposing them to low temperature or administration of triiodothyronine (T(3)). The third group served as control and was reared normally. Haematological, biochemical and pathological tests were used to determine the incidence of ascites: including total red blood cell (RBC), packed cell volume (PCV), release of alanine transaminase (ALT) and aspartate transaminase (AST) and ratio of right ventricular weight to total ventricular weight (RV/TV). A salicylate hydroxylation method was used to examine the generation of hydroxyl radicals (OH*) in treated groups. TWo hydroxylated salicylic acid metabolites, 2,3- and 2,5-dihydroxy benzoic acid (2,3- and 2,5-DHBA), were measured by HPLC to detect the generation of OH*. An ascites syndrome was observed in T(3) and low-temperature treated groups, as shown by necropsy changes and increases in f RBC, PCV, ALT, AST and the ratio of RV/TV. Concentrations of 2,3- and 2,5-DHBA were increased in groups experiencing ascites compared to control group. It is suggested that reactive oxygen species that is OH* ions, may be involved in the pathogenesis of the ascites syndrome in broiler chickens. PMID:16641033

  19. Modulation of Symmetry-Breaking Intramolecular Charge-Transfer Dynamics Assisted by Pendant Side Chains in π-Linkers in Quadrupolar Diketopyrrolopyrrole Derivatives.

    PubMed

    Kim, Woojae; Sung, Jooyoung; Grzybowski, Marek; Gryko, Daniel T; Kim, Dongho

    2016-08-01

    The effect of the length of pendant side chains in centrosymmetric quadrupolar molecules on dynamics of their most perplexing photophysical phenomenon, i.e., symmetry-breaking intramolecular charge transfer, has been discovered. Unexpectedly, considerable influence of length of these pendant side chains in π-linkers arose as a structural factor enabling the control of the degree of fluorescence solvatochromism. The symmetry-breaking intramolecular charge-transfer dynamics has been described on quadrupolar diketopyrrolopyrrole derivatives possessing fluorene moieties as π-linkers and diarylamino groups as electron donors. On the basis of the evolution of transient fluorescence spectra obtained by a femtosecond broadband fluorescence up-conversion spectroscopy, it was found that the relative contribution of diffusive solvation and torsional relaxation in overall spectral relaxation can be modulated by the length of pendant side chain in π-linkers. Consequently, we demonstrated that this modulation plays a significant role in determining the photophysical properties of diketopyrrolopyrroles in a polar medium. PMID:27455383

  20. Creation of localized spins in graphene by ring-opening of epoxy derived hydroxyl

    PubMed Central

    Chen, Jie; Zhang, Weili; Sun, Yuanyuan; Zheng, Yongping; Tang, Nujiang; Du, Youwei

    2016-01-01

    Creation of high-density localized spins in the basal plane of graphene sheet by introduction of sp3-type defects is considered to be a potential route for the realization of high-magnetization graphene. Theoretical and experimental studies confirmed that hydroxyl can be an effective sp3-type candidate for inducing robust magnetic moment. However, the artificial generation of hydroxyl groups for creating high-density spins on the basal plane of graphene sheet is very scarce. Here we demonstrate that high-content hydroxyl groups can be generated on the basal plane of graphene oxide (GO) sheet by ring opening of epoxy groups. We show that by introduction of 10.74 at.% hydroxyl groups, the density of localized spins of GO can be significantly increased from 0.4 to 5.17 μB/1000 C. Thus, this study provided an effective method to obtain graphene with high-density localized spins. PMID:27225991

  1. Creation of localized spins in graphene by ring-opening of epoxy derived hydroxyl

    NASA Astrophysics Data System (ADS)

    Chen, Jie; Zhang, Weili; Sun, Yuanyuan; Zheng, Yongping; Tang, Nujiang; Du, Youwei

    2016-05-01

    Creation of high-density localized spins in the basal plane of graphene sheet by introduction of sp3-type defects is considered to be a potential route for the realization of high-magnetization graphene. Theoretical and experimental studies confirmed that hydroxyl can be an effective sp3-type candidate for inducing robust magnetic moment. However, the artificial generation of hydroxyl groups for creating high-density spins on the basal plane of graphene sheet is very scarce. Here we demonstrate that high-content hydroxyl groups can be generated on the basal plane of graphene oxide (GO) sheet by ring opening of epoxy groups. We show that by introduction of 10.74 at.% hydroxyl groups, the density of localized spins of GO can be significantly increased from 0.4 to 5.17 μB/1000 C. Thus, this study provided an effective method to obtain graphene with high-density localized spins.

  2. Creation of localized spins in graphene by ring-opening of epoxy derived hydroxyl.

    PubMed

    Chen, Jie; Zhang, Weili; Sun, Yuanyuan; Zheng, Yongping; Tang, Nujiang; Du, Youwei

    2016-01-01

    Creation of high-density localized spins in the basal plane of graphene sheet by introduction of sp(3)-type defects is considered to be a potential route for the realization of high-magnetization graphene. Theoretical and experimental studies confirmed that hydroxyl can be an effective sp(3)-type candidate for inducing robust magnetic moment. However, the artificial generation of hydroxyl groups for creating high-density spins on the basal plane of graphene sheet is very scarce. Here we demonstrate that high-content hydroxyl groups can be generated on the basal plane of graphene oxide (GO) sheet by ring opening of epoxy groups. We show that by introduction of 10.74 at.% hydroxyl groups, the density of localized spins of GO can be significantly increased from 0.4 to 5.17 μB/1000 C. Thus, this study provided an effective method to obtain graphene with high-density localized spins. PMID:27225991

  3. Structural development of Saddlebag Lake pendant, eastern Sierra Nevada, California: Implications for crustal evolution

    SciTech Connect

    Schweickert, R.A.; Lahren, M.M. . Dept. of Geological Sciences)

    1993-04-01

    Saddlebag Lake pendant provides an important window into the structural development of wallrocks of the Sierra Nevada batholith, and provides constraints on a number of regional tectonic events. Sixteen mappable stratigraphic units crop out within ten major thrust sheets. Stratigraphic cutoffs and estimated 35-degree average ramp angles yield minimum total thrust displacements of 25 km. Adding displacements required by flats, thickness variations among stratigraphic units, internal folds, and internal strains within thrust sheets yields an estimate of 50--60 km of shortening. Although only estimates, these figures indicate that a significant zone of Triassic and Jurassic( ) contractional deformation exists within the pendant, offering little support for extensional tectonic scenarios for Sierran wallrocks that have been proposed. In addition, map and structural relations preclude the existence of intrabatholithic breaks with proposed dextral displacements of up to 210 km, along the eastern edge of the pendant. The authors conclude that this part of the eastern Sierra experienced only the following tectonic events: (1) Antler deformation; (2) Permo-Triassic( ) Golconda thrusting; (3) large-magnitude Late Triassic thrusting during arc volcanism and plutonism; (4) Late Jurassic or Early Cretaceous east-vergent thrusting, folding, and cleavage development. Evidence also exists along the western edge of the pendant for pre-90 Ma dextral shear following the above events. They infer that the latter event may signal development of the Mojave-Snow Lake fault west of Saddlebag Lake pendant.

  4. Hydroxylation of a metal-supported hexagonal boron nitride monolayer by oxygen induced water dissociation.

    PubMed

    Guo, Yufeng; Guo, Wanlin

    2015-07-01

    Hydroxylated hexagonal boron nitride (h-BN) nanosheets exhibit potential application in nanocomposites and functional surface coating. Our first-principles calculations reveal possible hydroxylation of a h-BN monolayer on a Ni substrate by surface O adatom induced spontaneous dissociation of water molecules. Here one H atom is split from a water molecule by bonding with the O adatom on the B atom and the resulting O-H radical then bonds with an adjacent B atom, which leads to two hydroxyl groups formed on h-BN/Ni. Hydroxylation slightly influences the electronic properties of a Ni-supported h-BN layer. Similar water dissociation and hydroxylation can occur on the surface of O functionalized h-BN/Cu depending on the O adsorption configuration. Metal substrates play an important catalytic role in enhancing the chemical reactivity of O adatoms on h-BN with water molecules through transferring additional charges to them. PMID:26051363

  5. Molecular modeling of the pendant chain in Nafion{reg_sign}

    SciTech Connect

    Paddison, S.J.; Zawodzinski, T.A.

    1998-03-01

    Ion transport through perfluorosulfonic acid ionomers such as Nafion{reg_sign} is controlled by both the microstructure of the polymer and the charge and water distribution in the hydrated polymer. The authors present here the results of theoretical calculations on the side chain of Nafion{reg_sign}, establishing microscopic information for the modeling of water modeling of water modeling of water and proton transport in the membrane. Optimized geometries for the trifluoromethane sulfonic acid fragment (CF{sub 3}SO{sub 3}H), the di-trifluoromethane ether fragment (CF{sub 3}OCF{sub 3}), and the side chain (CF{sub 3}{single_bond}OCF{sub 2}CF(CF{sub 3})OCF{sub 2}CF{sub 2}SO{sub 3}H) were determined by means of both ab initio Hartree Fock theory with second order Moeller-Plesset electron correlation corrections, and density functional theory with Becke`s three parameter hybrid method. Several rotational potential energy surfaces were calculated to assess chain flexibility and proton accessibility. A probe water molecule was added to each of the fragments to characterize hydrophilic sites. These calculations confirmed that the sulfonic acid group is hydrophilic and the ethers are hydrophobic. Molecular dynamics simulations were then performed on the side chain to check the conditions required to stretch the pendant chain. Thermal averages of several structural parameters assessing the flexibility and stretch of the chain were computed from selected conformations produced in the simulation and these results indicate that although the sulfonate group is free to rotate, the chain stretches little. The construction of a potential energy surface for rotation about the second ether group suggests that the side chain exists in a folded or curled up conformation. A physical continuum dielectric solvent model was used to obtain free energies of electrostatic interaction of the fragments and the full chain with the solvent.

  6. Substrate specificity for the 12beta-hydroxylation of bufadienolides by Alternaria alternata.

    PubMed

    Ye, Min; Guo, Dean

    2005-05-25

    Hydroxylation is an important route to synthesize more hydrophilic compounds of pharmaceutical significance. Microbial hydroxylation offers advantages over chemical means for its high specificity. In this study, a fungal strain Alternaria alternata AS 3.4578 was found to be able to catalyze the specific 12beta-hydroxylation of a variety of cytotoxic bufadienolides. Cinobufagin and resibufogenin could be completely metabolized by A. alternata to generate their 12beta-hydroxylated products in high yields (>90%) within 8 h of incubation. A. alternata could also convert 3-epi-desacetylcinobufagin into 3-epi-12beta-hydroxyl desacetylcinobufagin as the major product (70% yield). C-3 dehydrogenated products were detected in these reactions in fair yields, while their accumulation was relatively slow. The 12beta-hydroxylation of bufadienolides could be significantly inhibited by the substitution of 1beta-, 5-, or 16alpha-hydroxyl groups, and the 14beta,15beta-epoxy ring appeared to be a necessary structural requirement for the specificity. For the biotransformation of bufalin, a 14beta-OH bufadienolide, this reaction was not specific, and accompanied by 7beta-hydroxylation as a parallel and competing metabolic route. The biotransformation products were identified by comparison with authentic samples or tentatively characterized by high-performance liquid chromatography-diode array detection-atmospheric pressure chemical ionization-mass spectrometry analyses. PMID:15862355

  7. RF-Hydroxysite: a random forest based predictor for hydroxylation sites.

    PubMed

    Ismail, Hamid D; Newman, Robert H; Kc, Dukka B

    2016-07-19

    Protein hydroxylation is an emerging posttranslational modification involved in both normal cellular processes and a growing number of pathological states, including several cancers. Protein hydroxylation is mediated by members of the hydroxylase family of enzymes, which catalyze the conversion of an alkyne group at select lysine or proline residues on their target substrates to a hydroxyl. Traditionally, hydroxylation has been identified using expensive and time-consuming experimental methods, such as tandem mass spectrometry. Therefore, to facilitate identification of putative hydroxylation sites and to complement existing experimental approaches, computational methods designed to predict the hydroxylation sites in protein sequences have recently been developed. Building on these efforts, we have developed a new method, termed RF-hydroxysite, that uses random forest to identify putative hydroxylysine and hydroxyproline residues in proteins using only the primary amino acid sequence as input. RF-Hydroxysite integrates features previously shown to contribute to hydroxylation site prediction with several new features that we found to augment the performance remarkably. These include features that capture physicochemical, structural, sequence-order and evolutionary information from the protein sequences. The features used in the final model were selected based on their contribution to the prediction. Physicochemical information was found to contribute the most to the model. The present study also sheds light on the contribution of evolutionary, sequence order, and protein disordered region information to hydroxylation site prediction. The web server for RF-hydroxysite is available online at . PMID:27292874

  8. Formation and decomplexation kinetics of copper(ii) complexes with cyclen derivatives having mixed carboxylate and phosphonate pendant arms.

    PubMed

    Ševčík, R; Vaněk, J; Michalicová, R; Lubal, P; Hermann, P; Santos, I C; Santos, I; Campello, M P C

    2016-08-01

    The kinetic properties of Cu(ii) complexes of H4dota and its analogues with one (H5do3ap), two in the 1,7-position (trans-H6do2a2p), three (H7doa3p) and four (H8dotp) phosphonic acid pendant arms were investigated. The formation of a Cu(ii) complex with H4dota, trans-H6do2a2p and H8dotp at a slightly acidic pH is faster for the phosphonic acid derivatives than for H4dota, but with no simple dependence on the number of -CH2PO3H2 substituents (trans-H6do2a2p > H8dotp > H4dota; pH 4-6). Relative differences in the reactivity among the differently protonated species (HnL(x-)) of the same ligand are successively decreased with the more phosphonic acid groups in the ligand. The faster complexation is probably caused by the higher ability of phosphonates to bind the metal ion and/or to assist in the transfer of protons from the ring amine groups to the bulk water. The acid-assisted decomplexation kinetics of the complexes was followed in highly acidic solutions ([H(+)] = 0.01-5 M) and at different temperatures (15-70 °C) to determine the activation parameters of the reaction. The kinetic inertness of the Cu(ii) complexes follows the order: H4dota > H5do3ap > trans-H6do2a2p > H7doa3p > H8dotp. To obtain information on the influence of additional pendant arms, analogous data were obtained for trans-H2do2a. The ligand is less reactive than H4dota, but the kinetic inertness of its Cu(ii) complex is similar to that of the H4dota complex. As it was considered that the published thermodynamics data on the Cu(ii)-H8dotp system are probably incorrect, the system was re-investigated. It showed a very high stability for the [Cu(dotp)](6-) species and the easy formation of several Cu2L species in the presence of an excess of the metal ion. Also, the structure of the (H6doa3p)(-) anion in the solid state was determined. These experimental data demonstrate that the substitution of acetic acid pendant arms by methylphosphonic acid ones in H4dota-like ligands increases the rate of

  9. Bacterial metabolism of hydroxylated biphenyls.

    PubMed Central

    Higson, F K; Focht, D D

    1989-01-01

    Isolates able to grow on 3- or 4-hydroxybiphenyl (HB) as the sole carbon source were obtained by enrichment culture. The 3-HB degrader Pseudomonas sp. strain FH12 used an NADPH-dependent monooxygenase restricted to 3- and 3,3'-HBs to introduce an ortho-hydroxyl. The 4-HB degrader Pseudomonas sp. strain FH23 used either a mono- or dioxygenase to generate a 2,3-diphenolic substitution pattern which allowed meta-fission of the aromatic ring. By using 3-chlorocatechol to inhibit catechol dioxygenase activity, it was found that 2- and 3-HBs were converted by FH23 to 2,3-HB, whereas biphenyl and 4-HB were attacked by dioxygenation. 4-HB was metabolized to 2,3,4'-trihydroxybiphenyl. Neither organism attacked chlorinated HBs. The degradation of 3- and 4-HBs by these strains is therefore analogous to the metabolism of biphenyl, 2-HB, and naphthalene in the requirement for 2,3-catechol formation. PMID:2729993

  10. A characterization study of a hydroxylated polycrystalline tin oxide surface

    NASA Technical Reports Server (NTRS)

    Hoflund, Gar B.; Grogan, Austin L., Jr.; Asbury, Douglas A.; Schryer, David R.

    1989-01-01

    In this study Auger electron spectroscopy, electron spectroscopy for chemical analysis (ESCA) and electron-stimulated desorption (ESD) have been used to examine a polycrystalline tin oxide surface before and after annealing in vacuum at 500 C. Features due to surface hydroxyl groups are present in both the ESCA and ESD spectra, and ESD shows that several chemical states of hydrogen are present. Annealing at 500 C causes a large reduction in the surface hydrogen concentration but not complete removal.

  11. Surface studies of hydroxylated multi-wall carbon nanotubes

    SciTech Connect

    Bradley, Robert; Cassity, Kelby; Andrews, Rodney; Meier, Mark; Osbeck, Susan; Andreu, Aurik; Johnston, Colin; Crossley, Alison

    2012-01-01

    CVD grown MWCNTs, of typical diameter 5 to 50 nm and with approximately 15-20 concentric graphene layers in the multi-walls, have been surface functionalised using the Fenton hydroxylation reaction. HRTEM reveals little physical difference between the treated and untreated materials; images from both exhibit similar multi-wall structure and contain evidence for some low-level disruption of the very outermost layers. Raman spectra from the two types of nanotubes are almost identical displaying the disorder (D) peaks at approximately 1350 cm{sup -1} and graphite (G) peaks at approximately 1580 cm{sup -1}, characteristic of graphene-based carbon materials, in approximately equal intensity ratios. Equilibrium adsorption data for nitrogen at 77 K leads to BET surface areas of 60.4 m{sup 2} g{sup -1} for the untreated and 71.8 m{sup 2} g{sup -1} for the hydroxylated samples; the increase in area being due to separation of the tube-bundles during functionalization. This is accompanied by a decrease in measured porosity, mostly at high relative pressures of nitrogen, i.e. where larger (meso 2-5 nm and macro >5 nm) pores are being filled, which is consistent with an attendant loss of inter-tube capillarity. X-ray photoelectron spectroscopy (XPS) shows that hydroxylation increases the nanotube surface oxygen level from 4.3 at.% to 22.3 at.%; chemical shift data indicate that approximately 75% of that oxygen is present as hydroxyl (-OH) groups. Water vapour adsorption by the hydroxylated surfaces leads to Type II isotherms which are characteristic of relatively high numbers of hydrogen bonding interactions compared to the untreated materials which exhibit Type III curves. This difference in polar surface energy is confirmed by calorimetric enthalpies of immersion in water which are -54 mJ m{sup -2} for the untreated and -192 mJ m{sup -2} for the hydroxylated materials. The treated materials therefore have significantly increased water wettability/dispersivity and a greater

  12. 3D QSAR studies of hydroxylated polychlorinated biphenyls as potential xenoestrogens.

    PubMed

    Ruiz, Patricia; Ingale, Kundan; Wheeler, John S; Mumtaz, Moiz

    2016-02-01

    Mono-hydroxylated polychlorinated biphenyls (OH-PCBs) are found in human biological samples and lack of data on their potential estrogenic activity has been a source of concern. We have extended our previous in silico 2D QSAR study through the application of advance techniques such as docking and 3D QSAR to gain insights into their estrogen receptor (ERα) binding. The results support our earlier findings that the hydroxyl group is the most important feature on the compounds; its position, orientation and surroundings in the structure are influential for the binding of OH-PCBs to ERα. This study has also revealed the following additional interactions that influence estrogenicity of these chemicals (a) the aromatic interactions of the biphenyl moieties with the receptor, (b) hydrogen bonding interactions of the p-hydroxyl group with key amino acids ARG394 and GLU353, (c) low or no electronegative substitution at para-positions of the p-hydroxyl group, (d) enhanced electrostatic interactions at the meta position on the B ring, and (e) co-planarity of the hydroxyl group on the A ring. In combination the 2D and 3D QSAR approaches have led us to the support conclusion that the hydroxyl group is the most important feature on the OH-PCB influencing the binding to estrogen receptors, and have enhanced our understanding of the mechanistic details of estrogenicity of this class of chemicals. Such in silico computational methods could serve as useful tools in risk assessment of chemicals. PMID:26598992

  13. Adamantyl-Substituted Retinoid-Derived Molecules That Interact with the Orphan Nuclear Receptor Small Heterodimer Partner: Effects of Replacing the 1-Adamantyl or Hydroxyl Group on Inhibition of Cancer Cell Growth, Induction of Cancer Cell Apoptosis, and Inhibition of Src Homology 2 Domain-Containing Protein Tyrosine Phosphatase-2 Activity

    PubMed Central

    Dawson, Marcia I.; Xia, Zebin; Jiang, Tao; Ye, Mao; Fontana, Joseph A.; Farhana, Lulu; Patel, Bhaumik; Xue, Li Ping; Bhuiyan, Mohammad; Pellicciari, Roberto; Macchiarulo, Antonio; Nuti, Roberto; Zhang, Xiao-Kun; Han, Young-Hoon; Tautz, Lutz; Hobbs, Peter D.; Jong, Ling; Waleh, Nahid; Chao, Wan-ru; Feng, Gen-Sheng; Pang, Yuhong; Su, Ying

    2014-01-01

    (E)-4-[3-(1-Adamantyl)-4′-hydroxyphenyl]-3-chlorocinnamic acid (3-Cl-AHPC) induces the cell-cycle arrest and apoptosis of leukemia and cancer cells. Studies demonstrated that 3-Cl-AHPC bound to the atypical orphan nuclear receptor small heterodimer partner (SHP). Although missing a DNA-binding domain, SHP heterodimerizes with the ligand-binding domains of other nuclear receptors to repress their abilities to induce or inhibit gene expression. 3-Cl-AHPC analogues having the 1-adamantyl and phenolic hydroxyl pharmacophoric elements replaced with isosteric groups were designed, synthesized, and evaluated for their inhibition of proliferation and induction of human cancer cell apoptosis. Structure–anticancer activity relationship studies indicated the importance of both groups to apoptotic activity. Docking of 3-Cl-AHPC and its analogues to an SHP computational model that was based on the crystal structure of ultraspiracle complexed with 1-stearoyl-2-palmitoylglycero-3-phosphoethanolamine suggested why these 3-Cl-AHPC groups could influence SHP activity. Inhibitory activity against Src homology 2 domain-containing protein tyrosine phosphatase 2 (Shp-2) was also assessed. The most active Shp-2 inhibitor was found to be the 3′-(3,3-dimethylbutynyl) analogue of 3-Cl-AHPC. PMID:18759424

  14. HETEROGENOUS PHOTOREACTION OF FORMALDEHYDE WITH HYDROXYL RADICALS

    EPA Science Inventory

    Atmospheric heterogeneous photoreactions occur between formaldehyde and hydroxyl radicals to produce formic acid. hese photoreactions not only occur in clouds, but also in other tropospheric hydrometeors such as precipitation and dew droplets. xperiments were performed by irradia...

  15. Protonation Studies of a Mono-Dinitrogen Complex of Chromium Supported by a 12-Membered Phosphorus Macrocycle Containing Pendant Amines

    SciTech Connect

    Mock, Michael T.; Pierpont, Aaron W.; Egbert, Jonathan D.; O'Hagan, Molly J.; Chen, Shentan; Bullock, R. Morris; Dougherty, William G.; Kassel, W. S.; Rousseau, Roger J.

    2015-05-18

    The first example of a mono-dinitrogen Cr0 complex, Cr(N2)(dmpe)(PPh3NBn3), 2(N2), (PPh3NBn3 = 1,5,9-tribenzyl-3,7,11-triphenyl-1,5,9-triaza-3,7,11-triphosphacyclododecane; dmpe = 1,2-bis(dimethylphosphino)ethane) containing a pentaphosphine coordination environment is described. 2(N2) is supported by a unique facially coordinating 12-membered phosphorus macrocycle containing pendant amine groups in the second coordination sphere. Treatment of 2(N2) at -78 °C with 1 equiv of [H(OEt2)2][B(C6F5)4] results in protonation of the metal center, generating the 7-coordinate Cr(II)-N2 hydride complex, [Cr(H)(N2)(dmpe)(PPh3NBn3)][B(C6F5)4], [2(H)(N2)]+. Treatment of 2(15N2) with excess triflic acid at -50 °C afforded a trace amount of 15NH4+ from the reduction of the coordinated 15N2 ligand (electrons originate from Cr). Augmenting the acid reactivity studies, electronic structure calculations evaluated the pKa values of three sites of 2(N2) (metal center, pendant amine, and N2 ligand) to elucidate possible Cr-NxHy intermediates involved in the N2 reduction pathways from the protonation of 2(N2). This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Computational resources provided by the National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  16. Steroid and sterol 7-hydroxylation: ancient pathways.

    PubMed

    Lathe, Richard

    2002-11-01

    B-ring hydroxylation is a major metabolic pathway for cholesterols and some steroids. In liver, 7 alpha-hydroxylation of cholesterols, mediated by CYP7A and CYP39A1, is the rate-limiting step of bile acid synthesis and metabolic elimination. In brain and other tissues, both sterols and some steroids including dehydroepiandrosterone (DHEA) are prominently 7 alpha-hydroxylated by CYP7B. The function of extra-hepatic steroid and sterol 7-hydroxylation is unknown. Nevertheless, 7-oxygenated cholesterols are potent regulators of cell proliferation and apoptosis; 7-oxygenated derivatives of DHEA, pregnenolone, and androstenediol can have major effects in the brain and in the immune system. The receptor targets involved remain obscure. It is argued that B-ring modification predated steroid evolution: non-enzymatic oxidation of membrane sterols primarily results in 7-oxygenation. Such molecules may have provided early growth and stress signals; a relic may be found in hydroxylation at the symmetrical 11-position of glucocorticoids. Early receptor targets probably included intracellular sterol sites, some modern steroids may continue to act at these targets. 7-Hydroxylation of DHEA may reflect conservation of an early signaling pathway. PMID:12398993

  17. Structural insights into the epimerization of β-1,4-linked oligosaccharides catalyzed by cellobiose 2-epimerase, the sole enzyme epimerizing non-anomeric hydroxyl groups of unmodified sugars.

    PubMed

    Fujiwara, Takaaki; Saburi, Wataru; Matsui, Hirokazu; Mori, Haruhide; Yao, Min

    2014-02-01

    Cellobiose 2-epimerase (CE) reversibly converts d-glucose residues into d-mannose residues at the reducing end of unmodified β1,4-linked oligosaccharides, including β-1,4-mannobiose, cellobiose, and lactose. CE is responsible for conversion of β1,4-mannobiose to 4-O-β-d-mannosyl-d-glucose in mannan metabolism. However, the detailed catalytic mechanism of CE is unclear due to the lack of structural data in complex with ligands. We determined the crystal structures of halothermophile Rhodothermus marinus CE (RmCE) in complex with substrates/products or intermediate analogs, and its apo form. The structures in complex with the substrates/products indicated that the residues in the β5-β6 loop as well as those in the inner six helices form the catalytic site. Trp-322 and Trp-385 interact with reducing and non-reducing end parts of these ligands, respectively, by stacking interactions. The architecture of the catalytic site also provided insights into the mechanism of reversible epimerization. His-259 abstracts the H2 proton of the d-mannose residue at the reducing end, and consistently forms the cis-enediol intermediate by facilitated depolarization of the 2-OH group mediated by hydrogen bonding interaction with His-200. His-390 subsequently donates the proton to the C2 atom of the intermediate to form a d-glucose residue. The reverse reaction is mediated by these three histidines with the inverse roles of acid/base catalysts. The conformation of cellobiitol demonstrated that the deprotonation/reprotonation step is coupled with rotation of the C2-C3 bond of the open form of the ligand. Moreover, it is postulated that His-390 is closely related to ring opening/closure by transferring a proton between the O5 and O1 atoms of the ligand. PMID:24362032

  18. Aromatic hydroxylation by Fenton reagents (reactive intermediate [Lx+FeIIOOH(BH+)], not free hydroxyl radical (HO.)).

    PubMed

    Hage, J P; Llobet, A; Sawyer, D T

    1995-10-01

    Several iron complexes [FeII(bpy)2(2+), FeII(OPPh3)4(2+), and FeII(PA)2] in combination with hydrogen peroxide (HOOH) catalytically hydroxylate aromatic substrates (ArH). The base-induced nucleophilic addition of HOOH to the electrophilic iron center yields the reactive intermediate of Fenton reagents [FeIILx2+ + HOOH<-->Lx+FeIIOOH(BH+)(1)]. The latter includes a 'stabilized' hydroxyl radical that is able to replace an aromatic hydrogen (H) with a hydroxyl group (HO) via an initial addition reaction. With PhCH3 and PhCH2CH3 as substrates free HO. (from the radiolysis of H2O) reacts via aryl addition (97 and 85%, respectively) to give Ar-Ar as the predominant product, whereas 1 favors H-atom abstraction from the alkyl group (50 and 80%, respectively) and the only detectable products from aryl addition are the respective substituted phenols (o:p-ArOH). Other substituted benzenes (PhX) undergo addition by free HO at the ortho and para aryl carbons (o:p ratio, 2), followed by dimerization and elimination of two H2O molecules to yield substituted biphenyls. In contrast, 1 reacts with PhX to yield substituted phenol (ArOH; o:p ratio, 0.5-1.1). With phenol (PhOH) as the substrate, reaction with 1 yields mainly catechol (o-Ar(OH)2; o:p ratio, 20). In a solvent matrix of MeCN:H2O (3:1 mol:mol ratio) the reaction efficiencies with FeII(bpy)2(2+) and FeII(OPPh3)4(2+) for the hydroxylation of benzene to phenol are 36 and 42%, respectively (product per HOOH). PMID:8564405

  19. Polythiophenes based on pyrene as pendant group: Synthesis, structural characterization and luminescent properties

    NASA Astrophysics Data System (ADS)

    González-Juárez, E.; Güizado-Rodríguez, M.; Barba, V.; Melgoza-Ramírez, M.; Rodríguez, M.; Ramos-Ortíz, G.; Maldonado, J. L.

    2016-01-01

    Novel polythiophenes (PTs) derived from 3-alkylthiophenes (R = hexyl, octyl) and a thiophene functionalized with pyrene chromophore were synthesized. A homopolymer and copolymers were obtained by using different stoichiometric ratios, and their photophysical properties were investigated. Physicochemically characterized by FT-IR, 1H NMR, UV-vis, DSC-TGA and GPC as well as fluorescence spectroscopy, the new PTs reached moderate molecular weight distributions, exhibited good thermal properties and were easily processable for depositing films of satisfactory optical quality with third-order nonlinear optical susceptibilities of approximately 10-12 esu. The new PTs showed absorption and emission bands ranging from 346 to 430 nm, and from 450 to 570 nm, respectively, with quantum yields between 0.07 and 0.25. In addition, nanoparticles were obtained from the PTs by using the mini-emulsion technique. Their spectroscopic characteristics and morphology were determined by means of UV-vis spectroscopy and SEM analysis.

  20. Ln(iii)-complexes of a DOTA analogue with an ethylenediamine pendant arm as pH-responsive PARACEST contrast agents.

    PubMed

    Krchová, T; Gálisová, A; Jirák, D; Hermann, P; Kotek, J

    2016-02-28

    A novel macrocyclic DO3A derivative containing a linear diamine pendant arm, H3do3aNN, was prepared and its protonation and complexation properties were studied by means of potentiometry. It determined ligand consecutive protonation constants log K(An) = 12.62, 10.28, 9.67, 8.30, 3.30 and 1.58 and stability constants of selected lanthanide (Eu(iii), Yb(iii)) complexes log K(EuL) = 23.16 and log KYbL = 22.76. The complexes could be protonated on the pendant amino group(s) with log K(HLM) ≈ 5.6 and log K(H2LM) ≈ 4.8. Solution structures of both complexes were studied by NMR spectroscopy. The study revealed that the complex species exist exclusively in the form of twisted-square-antiprismatic (TSA) isomers. The complexes show significant pH dependence of the Chemical Exchange Saturation Transfer (CEST) between their amino groups and the bulk water molecules in the pH range of 5-8. Thus, the pH dependence of the magnetization transfer ratio of CEST signals can be used for pH determination using magnetic resonance imaging techniques in a pH range relevant for in vivo conditions. PMID:26795214

  1. Structure, electronic properties, and aggregation behavior of hydroxylated carbon nanotubes

    NASA Astrophysics Data System (ADS)

    López-Oyama, A. B.; Silva-Molina, R. A.; Ruíz-García, J.; Gámez-Corrales, R.; Guirado-López, R. A.

    2014-11-01

    We present a combined experimental and theoretical study to analyze the structure, electronic properties, and aggregation behavior of hydroxylated multiwalled carbon nanotubes (OH-MWCNT). Our MWCNTs have average diameters of ˜2 nm, lengths of approximately 100-300 nm, and a hydroxyl surface coverage θ˜0.1. When deposited on the air/water interface the OH-MWCNTs are partially soluble and the floating units interact and link with each other forming extended foam-like carbon networks. Surface pressure-area isotherms of the nanotube films are performed using the Langmuir balance method at different equilibration times. The films are transferred into a mica substrate and atomic force microscopy images show that the foam like structure is preserved and reveals fine details of their microstructure. Density functional theory calculations performed on model hydroxylated carbon nanotubes show that low energy atomic configurations are found when the OH groups form molecular islands on the nanotube's surface. This patchy behavior for the OH species is expected to produce nanotubes having reduced wettabilities, in line with experimental observations. OH doping yields nanotubes having small HOMO-LUMO energy gaps and generates a nanotube → OH direction for the charge transfer leading to the existence of more hole carriers in the structures. Our synthesized OH-MWCNTs might have promising applications.

  2. Structure, electronic properties, and aggregation behavior of hydroxylated carbon nanotubes.

    PubMed

    López-Oyama, A B; Silva-Molina, R A; Ruíz-García, J; Gámez-Corrales, R; Guirado-López, R A

    2014-11-01

    We present a combined experimental and theoretical study to analyze the structure, electronic properties, and aggregation behavior of hydroxylated multiwalled carbon nanotubes (OH-MWCNT). Our MWCNTs have average diameters of ~2 nm, lengths of approximately 100-300 nm, and a hydroxyl surface coverage θ~0.1. When deposited on the air/water interface the OH-MWCNTs are partially soluble and the floating units interact and link with each other forming extended foam-like carbon networks. Surface pressure-area isotherms of the nanotube films are performed using the Langmuir balance method at different equilibration times. The films are transferred into a mica substrate and atomic force microscopy images show that the foam like structure is preserved and reveals fine details of their microstructure. Density functional theory calculations performed on model hydroxylated carbon nanotubes show that low energy atomic configurations are found when the OH groups form molecular islands on the nanotube's surface. This patchy behavior for the OH species is expected to produce nanotubes having reduced wettabilities, in line with experimental observations. OH doping yields nanotubes having small HOMO-LUMO energy gaps and generates a nanotube → OH direction for the charge transfer leading to the existence of more hole carriers in the structures. Our synthesized OH-MWCNTs might have promising applications. PMID:25381534

  3. Hydroxyl functionalized thermosensitive microgels with quadratic crosslinking density distribution.

    PubMed

    Elmas, Begum; Tuncel, Murvet; Senel, Serap; Patir, S; Tuncel, Ali

    2007-09-01

    N-isopropylacrylamide (NIPA) based uniform thermosensitive microgels were synthesized by dispersion polymerization by using relatively hydrophilic crosslinking agents with hydroxyl functionality. Glycerol dimethacrylate (GDMA), pentaerythritol triacrylate (PETA) and pentaerythritol propoxylate triacrylate (PEPTA) were used as crosslinking agents with different hydrophilicities. A protocol was first proposed to determine the crosslinking density distribution in the thermosensitive microgel particles by confocal laser scanning microscopy (CLSM). The microgels were fluorescently labeled by using hydroxyl group of the crosslinking agent. The CLSM observations performed with the microgels synthesized by three different crosslinking agents showed that the crosslinking density exhibited a quadratic decrease with the increasing radial distance in the spherical microgel particles. This structure led to the formation of more loose gel structure on the particle surface with respect to the center. Then the use of hydrophilic crosslinking agents in the dispersion polymerization of NIPA made possible the synthesis of thermosensitive microgels carrying long, flexible and chemically derivatizable (i.e., hydroxyl functionalized) fringes on the surface by a single-stage dispersion polymerization. The microgels with all crosslinking agents exhibited volume phase transition with the increasing temperature. The microgel obtained by the most hydrophilic crosslinking agent, GDMA exhibited higher hydrodynamic diameters in the fully swollen form at low temperatures than those obtained by PETA and PEPTA. Higher hydrodynamic size decrease from fully swollen form to the fully shrunken form was also observed with the same microgel. PMID:17532327

  4. Structure, electronic properties, and aggregation behavior of hydroxylated carbon nanotubes

    SciTech Connect

    López-Oyama, A. B.; Silva-Molina, R. A.; Ruíz-García, J.; Guirado-López, R. A.; Gámez-Corrales, R.

    2014-11-07

    We present a combined experimental and theoretical study to analyze the structure, electronic properties, and aggregation behavior of hydroxylated multiwalled carbon nanotubes (OH–MWCNT). Our MWCNTs have average diameters of ∼2 nm, lengths of approximately 100–300 nm, and a hydroxyl surface coverage θ∼0.1. When deposited on the air/water interface the OH–MWCNTs are partially soluble and the floating units interact and link with each other forming extended foam-like carbon networks. Surface pressure-area isotherms of the nanotube films are performed using the Langmuir balance method at different equilibration times. The films are transferred into a mica substrate and atomic force microscopy images show that the foam like structure is preserved and reveals fine details of their microstructure. Density functional theory calculations performed on model hydroxylated carbon nanotubes show that low energy atomic configurations are found when the OH groups form molecular islands on the nanotube's surface. This patchy behavior for the OH species is expected to produce nanotubes having reduced wettabilities, in line with experimental observations. OH doping yields nanotubes having small HOMO–LUMO energy gaps and generates a nanotube → OH direction for the charge transfer leading to the existence of more hole carriers in the structures. Our synthesized OH–MWCNTs might have promising applications.

  5. Hydroxyl radical oxidation of feruloylated arabinoxylan.

    PubMed

    Bagdi, Attila; Tömösközi, Sándor; Nyström, Laura

    2016-11-01

    Feruloylated arabinoxylan (AX) has a unique capacity to form covalent gels in the presence of certain oxidizing agents. The present study demonstrates that hydroxyl radical oxidation does not provoke ferulic acid dimerization and thus oxidative gelation. We studied the hydroxyl radical mediated oxidation of an alkali-extracted AX preparation (purity: 92g/100g dry matter) that showed gel-forming capability upon peroxidase/hydrogen peroxide treatment. Hydroxyl radicals were produced with ascorbate-driven Fenton reaction and the radical formation was monitored with electron paramagnetic resonance, using a POBN/EtOH spin trapping system. Oxidation was carried out at different catalytic concentrations of iron (50 and 100μM) and at different temperatures (20°C, 50°C, and 80°C). It was demonstrated that hydroxyl radical oxidation does not provoke gel formation, but viscosity decrease in AX solution, which suggests polymer degradation. Furthermore, it was demonstrated that hydroxyl radical formation in AX solution can be initiated merely by increasing temperature. PMID:27516272

  6. Stratigraphy and structure of the Strawberry Mine roof pendant, central Sierra Nevada, California

    USGS Publications Warehouse

    Nokleberg, W.J.

    1981-01-01

    The Strawberry mine roof pendant, 90 km northeast of Fresno, Calif., is composed of a sequence of metasedimentary rocks of probable Early Jurassic age and a sequence of metaigneous rocks of middle Cretaceous age. The metasedimentary rocks are a former miogeosynclinal sequence of marl and limestone now metamorphosed to calc-silicate hornfels and marble. A pelecypod found in the calc-silicate hornfels has been tentatively identified as a Mesozoic bivalve, possibly Inoceramus pseudomytiloides of Early Jurassic age. These metasedimentary rocks are similar in lithology, structure, and gross age to the metasedimentary rocks of the Boyden Cave roof pendant and are assigned to the Lower Jurassic Kings sequence. The younger metaigneous rocks are metamorphosed shallow-in trusi ve rocks that range in composi tion from granodiorite to rhyolite. These rocks are similar in composition and age to the metavolcanic rocks of the surrounding Merced Peak quadrangle and nearby Ritter Range, and probably represent necks or dikes that were one source for the meta volcanic rocks. The roof pendant is intruded by several plutons, ranging in composition from dioritic to highly felsic, that constitute part of the granodiorite of Jackass Lakes, also M middle Cretaceous age. The contemporaneous suites of metaigneous, metavolcanic, and plutonic rocks in the region represent a middle Cretaceous period of calc-alkalic volcanism and plutonism in the central Sierra Nevada and are interpreted as part of an Andean-type volcanic-plutonic arc. Three deformations are documented in the roof pendant. The first deformation is reflected only in the metasedimentary rocks and consists of northeast-to east-west-trending folds. Similar structures occur in the Boyden Cave roof pendant and in the Calaveras Formation and represent a Middle Jurassic regional deformation. Evidence of the second deformation occurs in the metasedimentary and metaigneous rocks and consists of folds, faults, minor structures, and

  7. Neodymium Fluorescence Quenching by Hydroxyl Groups in Phosphate Laser Glasses

    SciTech Connect

    Ehrmann, P R; Carlson, K; Campbell, J H; Click, C A; Brow, R K

    2003-09-02

    Non-radiative losses due to OH fluorescence quenching of the Nd{sup 3+} {sup 4}F{sub 3/2} state are quantified over a range of OH concentrations from 4 x 10{sup 18}/cm{sup 3} to 4 x 10{sup 20}/cm{sup 3} and Nd doping levels from 0.4 to 9 x 10{sup 20}/cm{sup 3} in two K{sub 2}O-MgO-Al{sub 2}O{sub 3}-P{sub 2}O{sub 5} metaphosphate glasses having different K/Mg ratios ({approx}1/1 and 2/1). The quenching rate is found to vary linearly with the Nd and OH concentrations as predicted by Forster-Dexter theory. However, in contrast to theory the OH quenching rate extrapolates to a non-zero value at low Nd{sup 3+} doping levels. It is proposed that at low Nd{sup 3+} concentrations the OH is correlated with Nd sites in the glass. The quenching strength of OH on a per ion basis is found to be weak compared to other common transition metal impurities (e.g. Fe{sup 2+}, Co{sup 2+}, Ni{sup 2+}, Cu{sup 2+}). Nevertheless, OH dominates the Nd quenching in phosphate glass because under most processing conditions OH is present at concentrations 10{sup 2} to 10{sup 3} greater than transition metal ion impurities. A correlation of the quenching strength of OH and common metal impurity ions with the degree of spectral overlap of the impurity absorption bands and the four {sup 4}F{sub 3/2} to {sup 4}I{sub J} transitions shows good agreement.

  8. Hole-transporting and emitting pendant polymers for organic electroluminescent devices

    NASA Astrophysics Data System (ADS)

    Kageyama, Hiroshi; Mutaguchi, Daisuke; Hashimoto, Keisuke; Nagamatsu, Daisuke; Tanaka, Masatake; Okumoto, Kenji; Ohsedo, Yutaka; Shirota, Yasuhiko

    2006-08-01

    New hole-transporting pendant polymers with high glass-transition temperatures (Tgs) above 200 °C were designed and synthesized. Multilayer organic electroluminescent (EL) devices using the new polymers as the hole-transport layer and quinacridone-doped tris(8-quinolinolato)aluminum as the emitting layer exhibited high performance. One of the hole-transporting polymers functioned well as a hole injection buffer layer in organic EL devices. New green- and orange-emitting pendant polymers with high Tgs and desired ambipolar character were also designed and synthesized. Organic EL devices using these emitting polymers also exhibited good performance. One of the hole-transporting polymer showed a high hole carrier mobility of over 10 -3 cm2V -1s -1 at an electric field of 1.0 × 10 5 Vcm -1, as determined by a time-of-flight method.

  9. Infrared absorption and vibrational circular dichroism spectra of poly(vinyl ether) containing diastereomeric menthols as pendants

    NASA Astrophysics Data System (ADS)

    McCann, Jennifer L.; Rauk, Arvi; Wieser, Hal

    1997-06-01

    The absorption and vibrational circular dichroism (VCD) spectra in the 1700 to 830 cm -1 region are reported and qualitatively interpreted for poly(vinyl ether) with (+)-menthol (I), (+)-isomenthol (II) and (+)-neomenthol (III) as pendants.

  10. Sensing system for detection and control of deposition on pendant tubes in recovery and power boilers

    DOEpatents

    Kychakoff, George; Afromowitz, Martin A.; Hogle, Richard E.

    2008-10-14

    A system for detection and control of deposition on pendant tubes in recovery and power boilers includes one or more deposit monitoring sensors operating in infrared regions of about 4 or 8.7 microns and directly producing images of the interior of the boiler, or producing feeding signals to a data processing system for information to enable a distributed control system by which the boilers are operated to operate said boilers more efficiently. The data processing system includes an image pre-processing circuit in which a 2-D image formed by the video data input is captured, and includes a low pass filter for performing noise filtering of said video input. It also includes an image compensation system for array compensation to correct for pixel variation and dead cells, etc., and for correcting geometric distortion. An image segmentation module receives a cleaned image from the image pre-processing circuit for separating the image of the recovery boiler interior into background, pendant tubes, and deposition. It also accomplishes thresholding/clustering on gray scale/texture and makes morphological transforms to smooth regions, and identifies regions by connected components. An image-understanding unit receives a segmented image sent from the image segmentation module and matches derived regions to a 3-D model of said boiler. It derives a 3-D structure the deposition on pendant tubes in the boiler and provides the information about deposits to the plant distributed control system for more efficient operation of the plant pendant tube cleaning and operating systems.

  11. Direct Hydroxylation and Amination of Arenes via Deprotonative Cupration.

    PubMed

    Tezuka, Noriyuki; Shimojo, Kohei; Hirano, Keiichi; Komagawa, Shinsuke; Yoshida, Kengo; Wang, Chao; Miyamoto, Kazunori; Saito, Tatsuo; Takita, Ryo; Uchiyama, Masanobu

    2016-07-27

    Deprotonative directed ortho cupration of aromatic/heteroaromatic C-H bond and subsequent oxidation with t-BuOOH furnished functionalized phenols in high yields with high regio- and chemoselectivity. DFT calculations revealed that this hydroxylation reaction proceeds via a copper (I → III → I) redox mechanism. Application of this reaction to aromatic C-H amination using BnONH2 efficiently afforded the corresponding primary anilines. These reactions show broad scope and good functional group compatibility. Catalytic versions of these transformations are also demonstrated. PMID:27348154

  12. Catalytic Oxidation of Alcohol via Nickel Phosphine Complexes with Pendant Amines

    SciTech Connect

    Weiss, Charles J.; Das, Partha Pratim; Higgins, Deanna LM; Helm, Monte L.; Appel, Aaron M.

    2014-09-05

    Nickel complexes were prepared with diphosphine ligands that contain pendant amines, and these complexes catalytically oxidize primary and secondary alcohols to their respective aldehydes and ketones. Kinetic and mechanistic studies of these prospective electrocatalysts were performed to understand what influences the catalytic activity. For the oxidation of diphenylmethanol, the catalytic rates were determined to be dependent on the concentration of both the catalyst and the alcohol. The catalytic rates were found to be independent of the concentration of base and oxidant. The incorporation of pendant amines to the phosphine ligand results in substantial increases in the rate of alcohol oxidation with more electron-donating substituents on the pendant amine exhibiting the fastest rates. We thank Dr. John C. Linehan, Dr. Elliott B. Hulley, Dr. Jonathan M. Darmon, and Dr. Elizabeth L. Tyson for helpful discussions. Research by CJW, PD, DLM, and AMA was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Research by MLH was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle.

  13. Horseradish peroxidase catalyzed hydroxylations: mechanistic studies.

    PubMed

    Dordick, J S; Klibanov, A M; Marletta, M A

    1986-05-20

    The hydroxylation of phenol to hydroquinone and catechol in the presence of dihydroxyfumaric acid and oxygen catalyzed by horseradish peroxidase was studied under conditions where the product yield was high and the side reactions were minimal. The reaction is partially uncoupled with a molar ratio of dihydroxyfumaric acid consumed to hydroxylated products of 12:1. Hydrogen peroxide does not participate in the reaction as evidenced by the lack of effect of catalase and by the direct addition of hydrogen peroxide. Conversely, superoxide and hydroxyl radicals are involved as their scavengers are potent inhibitors. Experiments were all consistent with the involvement of compound III (oxygenated ferrous complex) of peroxidase in the reaction. Compound III is stable in the presence of phenol alone but decomposes rapidly in the presence of both phenol and dihydroxyfumaric acid with the concomitant formation of product. Therefore, phenol and dihydroxyfumaric acid must be present with compound III in order for the hydroxylation reaction to occur. A mechanism consistent with the experimental results is proposed. PMID:3718931

  14. Targeted acylation for all the hydroxyls of (+)-catechin and evaluation of their individual contribution to radical scavenging activity.

    PubMed

    Hong, Shan; Liu, Songbai

    2016-04-15

    The reactivity profile of all the hydroxyl groups in (+)-catechin towards acylation and their respective contribution to radical scavenging activity were systematically explored in this work. Selective acylation of the hydroxyls on different rings was carried out employing either a basic or acidic activation strategy. Monoacylation of B ring was achieved effectively with the aid of dimethyltin dichloride. Monoacylation of A ring was accomplished by sequential protection and deprotection of B and C rings. Based on specific acylation of all the individual hydroxyls of (+)-catechins, the structure radical scavenging activity relationship of each hydroxyl of (+)-catechin was established. It was demonstrated that the vicinal phenolic hydroxyls on B ring played the most important role in the ABTS radical scavenging activity and those on A and C rings made a much smaller contribution. This study has laid solid groundwork for further modification of the catechins and improvement of their properties. PMID:26616969

  15. Determination of surface-accessible acidic hydroxyls and surface area of lignin by cationic dye adsorption.

    PubMed

    Sipponen, Mika Henrikki; Pihlajaniemi, Ville; Littunen, Kuisma; Pastinen, Ossi; Laakso, Simo

    2014-10-01

    A new colorimetric method for determining the surface-accessible acidic lignin hydroxyl groups in lignocellulose solid fractions was developed. The method is based on selective adsorption of Azure B, a basic dye, onto acidic hydroxyl groups of lignin. Selectivity of adsorption of Azure B on lignin was demonstrated using lignin and cellulose materials as adsorbents. Adsorption isotherms of Azure B on wheat straw (WS), sugarcane bagasse (SGB), oat husk, and isolated lignin materials were determined. The maximum adsorption capacities predicted by the Langmuir isotherms were used to calculate the amounts of surface-accessible acidic hydroxyl groups. WS contained 1.7-times more acidic hydroxyls (0.21 mmol/g) and higher surface area of lignin (84 m(2)/g) than SGB or oat husk materials. Equations for determining the amount of surface-accessible acidic hydroxyls in solid fractions of the three plant materials by a single point measurement were developed. A method for high-throughput characterization of lignocellulosic materials is now available. PMID:25033327

  16. Novel pendant-type macrocyclic bifunctional chelating agents: (Carboxymethyl)amino derivatives of 2-(4-nitrobenzyl)-1,4,7,10-tetraazacyclo-dodecane-N,N{prime},N{double_prime},N{prime}{double_prime}-tetraacetic acid and their complex formation with yttrium(III)

    SciTech Connect

    Takenouchi, Kazuya; Tabe, Masayasu; Watanabe, Kenzo

    1993-11-19

    The authors investigated novel synthetic routes to pendant-type {rho}-NO{sub 2}-BZ-DOTA, 1 and 2, containing a (carboxymethyl) amino group appended to the DOTA structure via a methylene (1) and an ethylene (2) spacer, respectively. The complexation of Yttrium (III) with these chelates is reported. 1 fig., 1 tab.

  17. Tunable photoluminescence and spectrum split from fluorinated to hydroxylated graphene

    NASA Astrophysics Data System (ADS)

    Gong, Peiwei; Wang, Jinqing; Sun, Weiming; Wu, Di; Wang, Zhaofeng; Fan, Zengjie; Wang, Honggang; Han, Xiuxun; Yang, Shengrong

    2014-02-01

    Tunable control over the functionalization of graphene is significantly important to manipulate its structure and optoelectronic properties. Yet the chemical inertness of this noble carbon material poses a particular challenge for its decoration without forcing reaction conditions. Here, a mild, operationally simple and controllable protocol is developed to synthesize hydroxylated graphene (HOG) from fluorinated graphene (FG). We successfully demonstrate that under designed alkali environment, fluorine atoms on graphene framework are programmably replaced by hydroxyl groups via a straightforward substitution reaction pathway. Element constituent analyses confirm that homogeneous C-O bonds are successfully grafted on graphene. Rather different from graphene oxide, the photoluminescence (PL) emission spectrum of the obtained HOG becomes split when excited with UV radiation. More interestingly, such transformation from FG facilitates highly tunable PL emission ranging from greenish white (0.343, 0.392) to deep blue (0.156, 0.094). Additionally, both experimental data and density function theory calculation indicate that the chemical functionalization induced structural rearrangement is more important than the chemical decoration itself in tuning the PL emission band tail and splitting energy gaps. This work not only presents a new way to effectively fabricate graphene derivatives with tunable PL performance, but also provides an enlightening insight into the PL origin of graphene related materials.Tunable control over the functionalization of graphene is significantly important to manipulate its structure and optoelectronic properties. Yet the chemical inertness of this noble carbon material poses a particular challenge for its decoration without forcing reaction conditions. Here, a mild, operationally simple and controllable protocol is developed to synthesize hydroxylated graphene (HOG) from fluorinated graphene (FG). We successfully demonstrate that under designed

  18. Aromatic hydroxylations in peroxidations by haemoglobin systems.

    PubMed

    Esclade, L; Guillochon, D; Thomas, D

    1986-07-01

    The catalytic activity of haemoglobin on aromatic substrates was studied in three systems: NADH-methylene blue-haemoglobin, ascorbic acid-haemoglobin, and red blood cells. Aniline and phenol but not acetanilide or p-toluidine are hydroxylated by haemoglobin. Dealkylations are not observed. Hydroxylations are postulated to be intermediate reactions in peroxidations catalysed by haemoglobin. The lifetime of the products depends on the presence of electron donors, such as NADH or ascorbic acid, in the medium. In the red blood cells where endogenous electron donors are recycled, levels of the products are higher and their lifetime is longer. This could have implications on drug metabolism by haemoglobin, as haemoglobin is present in large quantities in the organism. PMID:3751116

  19. Design of Novel β-Carboline Derivatives with Pendant 5-Bromothienyl and Their Evaluation as Phosphodiesterase-5 Inhibitors

    PubMed Central

    El-Gamil, Dalia S.; Ahmed, Nermin S.; Gary, Bernard D.; Piazza, Gary A.; Engel, Matthias; Hartmann, Rolf W.; Abadi, Ashraf H.

    2016-01-01

    New derivatives with the tetrahydro-β-carboline-imidazolidinedione and tetrahydro-β-carboline-piperazinedione scaffolds and a pendant bromothienyl moiety at C-5/C-6 were synthesized and tested for their ability to inhibit PDE5 in vitro. The following SAR can be concluded: The tetracyclic scaffold is essential for PDE5 inhibition; the ethyl group is the most suitable among the adopted N-substituents on the terminal ring (hydantoin/piperazinedione); the appropriate stereochemistry of C-5/C-6 derived from the aldehyde rather than C-11a/C-12a derived from tryptophan appears crucial for inhibition of PDE5; surprisingly, derivatives with the hydantoin terminal ring are more active than their analogs with the piperazinedione ring; the selectivity versus PDE5 relative to PDE11 with cGMP as a substrate is mainly a function of the substitution and stereochemistry pattern of the external ring, in other words of the interaction with the H-loop residues of the isozymes. Thirteen derivatives showed PDE5 inhibitory activity with IC50 values in the range of 0.16–5.4 μm. Compound 8 was the most potent PDE5 inhibitor and showed selectivity towards PDE5 versus other PDEs, with a selectivity index of 49 towards PDE5 rather than PDE11 with cGMP as the substrate. PMID:23307609

  20. Palladium-catalysed hydroxylation and alkoxylation.

    PubMed

    Enthaler, Stephan; Company, Anna

    2011-10-01

    The formation of oxygen-carbon bonds is one of the fundamental transformations in organic synthesis. In this regard the application of palladium-based catalysts has been extensively studied during recent years. Nowadays it is an established methodology and the success has been proven in manifold synthetic procedures. This tutorial review summarizes the advances on palladium-catalysed C-O bond formation, means hydroxylation and alkoxylation reactions. PMID:21643619

  1. Green organocatalytic α-hydroxylation of ketones.

    PubMed

    Voutyritsa, Errika; Theodorou, Alexis; Kokotos, Christoforos G

    2016-06-28

    An efficient and green method for the α-hydroxylation of substituted ketones has been developed. This method includes the in situ conversion of various ketones into the corresponding silyl enol ethers and their oxidation to the corresponding α-hydroxy ketones. Two protocols have been established leading either to protected α-hydroxy carbonyls or free α-hydroxy ketones. Both procedures are easy to follow and lead to good to high yields for a variety of ketones. PMID:26867154

  2. A theoretical study of O2 activation by the Au7-cluster on Mg(OH)2: roles of surface hydroxyls and hydroxyl defects.

    PubMed

    Jia, Chuanyi; Fan, Weiliu

    2015-11-11

    Using density functional theory (DFT) calculations, we investigated O2 activation by the Au7-cluster supported on the perfect and hydroxyl defective Mg(OH)2(0001) surface. It is revealed that hydroxyl groups on the perfect Mg(OH)2(0001) surface can not only enhance the stability of the Au7-cluster, but also help the adsorption of the O2 molecule through hydrogen-bonding interactions with the 2nd-layered interfacial Au sites. Density of states (DOS) analysis shows that the d-band centers of the 2nd-layered interfacial Au atoms are very close to the Fermi level, which thereby reduce the Pauli repulsion and promote the O2 adsorption. These two responses make the 2nd-layered interfacial Au atoms favor O2 activation. Interestingly, the surface hydrogen atoms activated by the 1st-layered Au atoms can facilitate the O2 dissociation process as well. Such a process is dynamically favorable and more inclined to occur at low temperatures compared to the direct dissociation process. Meanwhile, the hydroxyl defects of Mg(OH)2(0001) located right under the Au7-cluster can also up-shift the d-band centers of the surrounding Au atoms toward the Fermi level, enhancing its catalytic activity for O2 dissociation. In contrast, the d-band center of Au atoms surrounding the hydroxyl defect near the Au7-cluster exhibits an effective down-shift to lower energies, and therefore holds low activity. These results unveiled the roles of surface hydroxyls and hydroxyl defects on the Au/Mg(OH)2 catalyst in O2 activation and could provide a theoretical guidance for chemists to efficiently synthesize Au/hydroxide catalysts. PMID:26529519

  3. Hydroxylation of p-substituted phenols by tyrosinase: further insight into the mechanism of tyrosinase activity.

    PubMed

    Muñoz-Muñoz, Jose Luis; Berna, Jose; García-Molina, María del Mar; Garcia-Molina, Francisco; Garcia-Ruiz, Pedro Antonio; Varon, Ramon; Rodriguez-Lopez, Jose N; Garcia-Canovas, Francisco

    2012-07-27

    A study of the monophenolase activity of tyrosinase by measuring the steady state rate with a group of p-substituted monophenols provides the following kinetic information: k(cat)(m) and the Michaelis constant, K(M)(m). Analysis of these data taking into account chemical shifts of the carbon atom supporting the hydroxyl group (δ) and σ(p)(+), enables a mechanism to be proposed for the transformation of monophenols into o-diphenols, in which the first step is a nucleophilic attack on the copper atom on the form E(ox) (attack of the oxygen of the hydroxyl group of C-1 on the copper atom) followed by an electrophilic attack (attack of the hydroperoxide group on the ortho position with respect to the hydroxyl group of the benzene ring, electrophilic aromatic substitution with a reaction constant ρ of -1.75). These steps show the same dependency on the electronic effect of the substituent groups in C-4. Furthermore, a study of a solvent deuterium isotope effect on the oxidation of monophenols by tyrosinase points to an appreciable isotopic effect. In a proton inventory study with a series of p-substituted phenols, the representation of [Formula: see text] / [Formula: see text] against n (atom fractions of deuterium), where [Formula: see text] is the catalytic constant for a molar fraction of deuterium (n) and [Formula: see text] is the corresponding kinetic parameter in a water solution, was linear for all substrates. These results indicate that only one of the proton transfer processes from the hydroxyl groups involved the catalytic cycle is responsible for the isotope effects. We suggest that this step is the proton transfer from the hydroxyl group of C-1 to the peroxide of the oxytyrosinase form (E(ox)). After the nucleophilic attack, the incorporation of the oxygen in the benzene ring occurs by means of an electrophilic aromatic substitution mechanism in which there is no isotopic effect. PMID:22732412

  4. Investigating Hydroxyl at Asteroid 951 Gaspra

    NASA Astrophysics Data System (ADS)

    Granahan, James C.

    2015-11-01

    Recent investigations [Granahan, 2011; 2014] of Galileo Near Infrared Mapping Spectrometer (NIMS) observations of asteroid 951 Gaspra have detected an infrared absorption feature near 2.8 micrometers. These were detected in NIMS data acquired by the Galileo spacecraft on October 29, 1991 at wavelengths ranging from 0.7 - 5.2 micrometers [Carlson et al., 1992]. This abstract presents a summary of the investigation to identify the material creating the 2.8 micrometer spectral absorption feature. The current best match for the observed 951 Gaspra feature is the phyllosilicate bound hydroxyl signature present in a thermally desiccated QUE 99038 carbonaceous chondrite as measured by Takir et al. [2013].The 951 Gaspra absorption feature has been compared to a variety of hydroxyl bearing signatures. Many phyllosilicates, hydroxyl bearing minerals, have absorption minima at different positions (2.7 or 2.85 micrometers). It also differs from similar absorptions in a potential R chondrite analog, LAP 04840. The spectra LAP 04840 has a 2.7 micrometer feature due to biotite and a 2.9 micrometer feature due to adsorbed water [Klima et al., 2007]. 2.8 micrometer absorption minima have been found for adsorbed hydroxyl on the Moon [McCord et al., 2011] and various carbonaceous chondrites [Calvin and King, 1997; Takir et al., 2013]. The best match, with a minimum Euclidean distance difference to the 951 Gaspra feature, is found in the spectrum of QUE 99038 [Takir et al., 2013]. This spectrum is the product of an infrared measurement of a sample that had its adsorbed water baked off and removed in a vacuum chamber. The remaining hydroxyl in the sample belongs to a mixture of phyllosilicates dominated by the presence of cronstedtite.References: Calvin, W. M., and T. V. King (1997), Met. Planet. Sci., 32, 693-702. Carlson, R. W., et al. (1992), Bull. American Astro. Soc., 24, 932. Granahan, J. C. (2011), Icarus, 213, 265-272. Granahan, J. C. (2014), 45th LPSC, #1092. Klima, R., C. et

  5. Protonation Studies of a Tungsten Dinitrogen Complex Supported by a Diphosphine Ligand Containing a Pendant Amine

    SciTech Connect

    Weiss, Charles J.; Egbert, Jonathan D.; Chen, Shentan; Helm, Monte L.; Bullock, R. Morris; Mock, Michael T.

    2014-04-28

    Treatment of trans-[W(N2)2(dppe)(PEtNMePEt)] (dppe = Ph2PCH2CH2PPh2; PEtNMePEt = Et2PCH2N(Me)CH2PEt2) with three equivalents of tetrafluoroboric acid (HBF4∙Et2O) at -78 °C generated the seven-coordinate tungsten hydride trans-[W(N2)2(H)(dppe)(PEtNMePEt)][BF4]. Depending on the temperature of the reaction, protonation of a pendant amine is also observed, affording trans-[W(N2)2(H)(dppe)(PEtNMe(H)PEt)][BF4]2, with formation of the hydrazido complex, [W(NNH2)(dppe)(PEtNMe(H)PEt)][BF4]2, as a minor product. Similar product mixtures were obtained using triflic acid (HOTf). Upon acid addition to the carbonyl analogue, cis-[W(CO)2(dppe)(PEtNMePEt)], the seven-coordinate carbonyl-hydride complex, trans-[W(CO)2(H)(dppe)(PEtN(H)MePEt)][OTf]2 was generated. The mixed diphosphine complex without the pendant amine in the ligand backbone, trans-[W(N2)2(dppe)(depp)] (depp = Et2P(CH2)3PEt2), was synthesized and treated with HBF4∙Et2O, selectively generating a hydrazido complex, [W(NNH2)(F)(dppe)(depp)][BF4]. Computational analysis was used to probe proton affinity of three sites of protonation, the metal, pendant amine, and N2 ligand in these complexes. Room temperature reactions with 100 equivalents of HOTf produced NH4+ from reduction of the N2 ligand (electrons come from W). The addition of 100 equivalents HOTf to trans-[W(N2)2(dppe)(PEtNMePEt)] afforded 0.88 ± 0.02 equivalents NH4+, while 0.36 ± 0.02 equivalents of NH4+was formed upon treatment of trans-[W(N2)2(dppe)(depp)], the complex without the pendant amine. This work was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy Office of Science, Office of Basic Energy Sciences. Computational resources were provided by the National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory. Pacific Northwest National Laboratory is operated by Battelle for DOE.

  6. Moving Protons with Pendant Amines: Proton Mobility in a Nickel Catalyst for Oxidation of Hydrogen

    SciTech Connect

    O'Hagan, Molly; Shaw, Wendy J.; Raugei, Simone; Chen, Shentan; Yang, Jenny Y.; Kilgore, Uriah J.; DuBois, Daniel L.; Bullock, R. Morris

    2011-05-19

    Proton transport is ubiquitous in chemical and biological processes, including the reduction of dioxygen to water, the reduction of CO₂ to formate, and the production/oxidation of hydrogen. In this work we describe intramolecular proton transfer between Ni and positioned pendant amines for the hydrogen oxidation electrocatalyst [Ni(PCy₂NBn₂H)₂]²⁺ (PCy₂NBn₂ = 1,5-dibenzyl-3,7-dicyclohexyl-1,5-diaza-3,7-diphosphacyclooctane). Rate constants are determined by variable-temperature one-dimensional NMR techniques and two-dimensional EXSY experiments. Computational studies provide insight into the details of the proton movement and energetics of these complexes. Intramolecular proton exchange processes are observed for two of the three experimentally observable isomers of the doubly protonated Ni(0) complex, [Ni(PCy₂NBn₂H)₂]²⁺, which have N–H bonds but no Ni–H bonds. For these two isomers, with pendant amines positioned endo to the Ni, the rate constants for proton exchange range from 10⁴ to 10⁵ s⁻¹ at 25 °C, depending on isomer and solvent. No exchange is observed for protons on pendant amines positioned exo to the Ni. Analysis of the exchange as a function of temperature provides a barrier for proton exchange of ΔG = 11–12 kcal/mol for both isomers, with little dependence on solvent. Density functional theory calculations and molecular dynamics simulations support the experimental observations, suggesting metal-mediated intramolecular proton transfers between nitrogen atoms, with chair-to-boat isomerizations as the rate-limiting steps. Because of the fast rate of proton movement, this catalyst may be considered a metal center surrounded by a cloud of exchanging protons. The high intramolecular proton mobility provides information directly pertinent to the ability of pendant amines to accelerate proton transfers during catalysis of hydrogen oxidation

  7. Lasing characteristics of a pendant drop deformed by an applied electric field.

    PubMed

    Pu, X Y; Lee, W K

    2000-04-01

    The lasing properties of an oval-shaped resonant cavity (ORC) with a continuously variable aspect ratio have been studied. The ORC was formed with a dye-doped pendant drop placed inside a variable static electric field. When the drop ORC was pumped by a nitrogen laser, lasing from the ORC was found to have strong directional emission characteristics and an intensity enhancement factor as great as 19.5. Calculated results of light rays escaping from ORC's by refraction are in good agreement with the experimental data. PMID:18064081

  8. Compound pendant drop tensiometry for interfacial tension measurement at zero bond number.

    PubMed

    Neeson, Michael J; Chan, Derek Y C; Tabor, Rico F

    2014-12-30

    A widely used method to determine the interfacial tension between fluids is to quantify the pendant drop shape that is determined by gravity and interfacial tension forces. Failure of this method for small drops or small fluid density differences is a critical limitation in microfluidic applications and when only small fluid samples are available. By adding a small spherical particle to the interface to apply an axisymmetric deformation, both the particle density and the interfacial tension can be simultaneously and precisely determined, providing an accurate and elegant solution to a long-standing problem. PMID:25494530

  9. Hydroxylation of organic polymer surface: method and application.

    PubMed

    Yang, Peng; Yang, Wantai

    2014-03-26

    It may be hardly believable that inert C-H bonds on a polymeric material surface could be quickly and efficiently transformed into C-OH by a simple and mild way. Thanks to the approaches developed recently, it is now possible to transform surface H atoms of a polymeric substrate into monolayer OH groups by a simple/mild photochemical reaction. Herein the method and application of this small-molecular interfacial chemistry is highlighted. The existence of hydroxyl groups on material surfaces not only determines the physical and chemical properties of materials but also provides effective reaction sites for postsynthetic sequential modification to fulfill the requirements of various applications. However, organic synthetic materials based on petroleum, especially polyolefins comprise mainly C and H atoms and thus present serious surface problems due to low surface energy and inertness in reactivity. These limitations make it challenging to perform postsynthetic surface sequential chemical derivatization toward enhanced functionalities and properties and also cause serious interfacial problems when bonding or integrating polymer substrates with natural or inorganic materials. Polymer surface hydroxylation based on direct conversion of C-H bonds on polymer surfaces is thus of significant importance for academic and practical industrial applications. Although highly active research results have reported on small-molecular C-H bond activation in solution (thus homogeneous), most of them, featuring the use of a variety of transition metals as catalysts, present a slow reaction rate, a low atom economy and an obvious environmental pollution. In sharp contrast to these conventional C-H activation strategies, the present Spotlight describes a universal confined photocatalytic oxidation (CPO) system that is able to directly convert polymer surface C-H bonds to C-OSO3(-) and, subsequently, to C-OH through a simple hydrolysis. Generally speaking, these newly implanted hydroxyl

  10. Hydroxyl radical mediated DNA base modification by manmade mineral fibres.

    PubMed Central

    Leanderson, P; Söderkvist, P; Tagesson, C

    1989-01-01

    Manmade mineral fibres (MMMFs) were examined for their ability to hydroxylate 2-deoxyguanosine (dG) to 8-hydroxydeoxyguanosine (8-OH-dG), a reaction that is mediated by hydroxyl radicals. It appeared that (1) catalase and the hydroxyl radical scavengers, dimethylsulphoxide and sodium benzoate, inhibited the hydroxylation, whereas Fe2+ and H2O2 potentiated it; (2) pretreatment of MMMFs with the iron chelator, deferoxamine, or with extensive heat (200-400 degrees C), attenuated the hydroxylation; (3) the hydroxylation obtained by various MMMFs varied considerably; (4) there was no apparent correlation between the hydroxylation and the surface area of different MMMFs, although increasing the surface area of a fibre by crushing it increased its hydroxylating capacity; and (5) there was good correlation between the hydroxylation of dG residues in DNA and the hydroxylation of pure dG in solution for the 16 different MMMFs investigated. These findings indicate that MMMFs cause a hydroxyl radical mediated DNA base modification in vitro and that there is considerable variation in the reactivity of different fibre species. The DNA modifying ability seems to depend on physical or chemical characteristics, or both, of the fibre. PMID:2765416

  11. Hydroxyl orientations in cellobiose and other polyhydroxy compounds – modeling versus experiment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Theoretical and experimental gas-phase studies of carbohydrates show that their hydroxyl groups are located in homodromic partial rings that resemble cooperative hydrogen bonds, albeit with long H…O distances and small O-H…O angles. On the other hand, anecdotal experience with disaccharide crystal ...

  12. DFT STUDY OF ALPHA-MALTOSE: INFLUENCE OF HYDROXYL ORIENTATIONS ON THE GLYCOSIDIC BOND

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The result of DFT geometry optimization of 68 unique alpha-maltose conformers at the B3LYP/6-311++G** level of theory is described. Particular attention is paid to the hydroxyl group rotational positions and their influence on the glycosidic bond dihedral angles. The orientation of lone pair elect...

  13. Development of a Concise Synthesis of Ouabagenin and Hydroxylated Corticosteroid Analogues

    PubMed Central

    2016-01-01

    The natural product ouabagenin is a complex cardiotonic steroid with a highly oxygenated skeleton. This full account describes the development of a concise synthesis of ouabagenin, including the evolution of synthetic strategy to access hydroxylation at the C19 position of a steroid skeleton. In addition, approaches to install the requisite butenolide moiety at the C17 position are discussed. Lastly, methodology developed in this synthesis has been applied in the generation of novel analogues of corticosteroid drugs bearing a hydroxyl group at the C19 position. PMID:25594682

  14. Hydroxyl-decorated Graphene Systems: Organic metal-free Ferroelectrics, Multiferroics, and Proton battery Cathode Materials

    NASA Astrophysics Data System (ADS)

    Wu, Menghao; Burton, J. D.; Tsymbal, Evgeny; Zeng, Xiao; Jena, Puru; Jena's Group Team, Prof.; Burton's Group Team, Prof.; Tsymbal's Group Team, Prof.; Zeng's Group Team, Prof.

    2013-03-01

    Through density-functional-theory calculations we show that hydroxylized graphene systems are ideal candidates for light-weight organic ferroelectric materials with giant polarizations. For example, the polarization of semi-hydroxylized graphane and graphone as well as fully hydroxylized graphane are, respectively, 41.1, 43.7, 67.7 μC/cm2, much higher than any organic ferroelectric materials known to date. In addition, hydroxylized graphone is multiferroic due to the coexistence of ferroeletricity and ferromagnetism. Zigzag graphene nanoribbons decorated by hydroxyl groups also exhibit ferroelectric properties with a large polarization of 27.0 μC/cm2. Moreover, proton vacancies at the end of ribbons can induce large dipole moments that can be reversed by both hopping of protons and rotation of O-H bonds under an electric field. These materials have the potential as high-capacity cathode materials with specific capacity six times larger than lead-acid batteries and five times that of lithium-ion batteries.

  15. Mechanism of the N-hydroxylation of primary and secondary amines by cytochrome P450.

    PubMed

    Seger, Signe T; Rydberg, Patrik; Olsen, Lars

    2015-04-20

    Cytochrome P450 enzymes (CYPs) metabolize alkyl- and arylamines, generating several different products. For the primary and secondary amines, some of these reactions result in hydroxylated amines, which may be toxic. Thus, when designing new drugs containing amine groups, it is important to be able to predict if a given compound will be a substrate for CYPs, in order to avoid toxic metabolites, and hence to understand the mechanism that is utilized by CYPs. Two possible mechanisms, for the N-hydroxylation of primary and secondary amines mediated by CYPs, are studied by density functional theory (DFT) for four different amines (aniline, N-methylaniline, propan-2-amine, and dimethylamine). The hydrogen abstraction and rebound mechanism is found to be preferred over a direct oxygen transfer mechanism for all four amines. However, in contrast to the same mechanism for the hydroxylation of aliphatic carbon atoms, the rebound step is shown to be rate-limiting in most cases. PMID:25651340

  16. Aromatic-Hydroxyl Interaction of a Lignin Model Compound on SBA-15, Present at Pyrolysis Temperatures

    DOE PAGESBeta

    Kandziolka, III, Michael V.; Kidder, Michelle; Gill, Lance W.; Wu, Zili; Savara, Aditya Ashi

    2014-07-14

    An aromatic alpha-aryl ether compound (a benzyl phenyl ether analogue) was covalently grafted to mesoporous silica SBA-15, to create BPEa-SBA-15. The BPEa-SBA-15 was subjected to successive heating cycles up to 600 °C, with in situ monitoring by DRIFTS. It was found that the toluene moiety coordinates to SBA-15 surface silanol hydroxyl groups via an aromatic–hydroxyl interaction. This interaction is evidenced by a red-shift of the aromatic C–H stretches, as well as a red-shift and broadening of the surface hydroxyl O–H stretches, which are features characteristic of a hydrogen bond. These features remain present during heating until ~400 °C whereupon themore » ether linkage of BPEa-SBA-15 is cleaved, accompanied by loss of the toluene moiety.« less

  17. Aromatic-Hydroxyl Interaction of a Lignin Model Compound on SBA-15, Present at Pyrolysis Temperatures

    SciTech Connect

    Kandziolka, III, Michael V.; Kidder, Michelle; Gill, Lance W.; Wu, Zili; Savara, Aditya Ashi

    2014-07-14

    An aromatic alpha-aryl ether compound (a benzyl phenyl ether analogue) was covalently grafted to mesoporous silica SBA-15, to create BPEa-SBA-15. The BPEa-SBA-15 was subjected to successive heating cycles up to 600 °C, with in situ monitoring by DRIFTS. It was found that the toluene moiety coordinates to SBA-15 surface silanol hydroxyl groups via an aromatic–hydroxyl interaction. This interaction is evidenced by a red-shift of the aromatic C–H stretches, as well as a red-shift and broadening of the surface hydroxyl O–H stretches, which are features characteristic of a hydrogen bond. These features remain present during heating until ~400 °C whereupon the ether linkage of BPEa-SBA-15 is cleaved, accompanied by loss of the toluene moiety.

  18. Polymer resins with amino acid containing pendants for sorption of bilirubin. II. Polyamide resins with various basic amino acids.

    PubMed

    Henning, D S; Brown, G R; St-Pierre, L E

    1986-01-01

    Short peptides, three to eight amino acids in length, containing various combinations of alanine, arginine, lysine, histidine and tyrosine have been synthesized onto water-swellable polyamide resin by the solid phase peptide synthesis method. The amount of bilirubin adsorbed from aqueous buffer solution (pH = 7.8) by the resins increases with increasing basicity of the amino acids in the pendant. As the number of basic amino acids on the pendant is increased from one to five a 4.7 fold enhancement in the adsorption capacity is seen for arginine while a 9.3 fold enhancement is obtained for lysine. A corresponding increase in length for the non-basic histidine results in a 6 fold enhancement. With alanine the adsorption capacity is uneffected by an increase in pendant length. PMID:3957453

  19. Terpene hydroxylation with microbial cytochrome P450 monooxygenases.

    PubMed

    Janocha, Simon; Schmitz, Daniela; Bernhardt, Rita

    2015-01-01

    Terpenoids comprise a highly diverse group of natural products. In addition to their basic carbon skeleton, they differ from one another in their functional groups. Functional groups attached to the carbon skeleton are the basis of the terpenoids' diverse properties. Further modifications of terpene olefins include the introduction of acyl-, aryl-, or sugar moieties and usually start with oxidations catalyzed by cytochrome P450 monooxygenases (P450s, CYPs). P450s are ubiquitously distributed throughout nature, involved in essential biological pathways such as terpenoid biosynthesis as well as the tailoring of terpenoids and other natural products. Their ability to introduce oxygen into nonactivated C-H bonds is unique and makes P450s very attractive for applications in biotechnology. Especially in the field of terpene oxidation, biotransformation methods emerge as an attractive alternative to classical chemical synthesis. For this reason, microbial P450s depict a highly interesting target for protein engineering approaches in order to increase selectivity and activity, respectively. Microbial P450s have been described to convert industrial and pharmaceutically interesting terpenoids such as ionones, limone, valencene, resin acids, and triterpenes (including steroids) as well as vitamin D3. Highly selective and active mutants have been evolved by applying classical site-directed mutagenesis as well as directed evolution of proteins. As P450s usually depend on electron transfer proteins, mutagenesis has also been applied to improve the interactions between P450s and their respective redox partners. This chapter provides an overview of terpenoid hydroxylation reactions catalyzed by bacterial P450s and highlights the achievements made by protein engineering to establish productive hydroxylation processes. PMID:25682070

  20. Monitoring protein phosphorylation by acrylamide pendant Phos-Tag™ in various plants

    PubMed Central

    Bekešová, Slávka; Komis, George; Křenek, Pavel; Vyplelová, Petra; Ovečka, Miroslav; Luptovčiak, Ivan; Illés, Peter; Kuchařová, Anna; Šamaj, Jozef

    2015-01-01

    The aim of the present study is to rationalize acrylamide pendant Phos-Tag™ in-gel discrimination of phosphorylated and non-phosphorylated plant protein species with standard immunoblot analysis, and optimize sample preparation, efficient electrophoretic separation and transfer. We tested variants of the method including extraction buffers suitable for preservation of phosphorylated protein species in crude extracts from plants and we addressed the importance of the cation (Mn2+ or Zn2+) used in the gel recipe for efficient transfer to PVDF membranes for further immunoblot analysis. We demonstrate the monitoring of Medicago sativa stress-induced mitogen activated protein kinase (SIMK) in stress-treated wild type plants and transgenic SIMKK RNAi line. We further show the hyperosmotically-induced phosphorylation of the previously uncharacterized HvMPK4 of barley. The method is validated using inducible phosphorylation of barley and wheat α-tubulin and of Arabidopsis MPK6. Acrylamide pendant Phos-Tag™offers a flexible tool for studying protein phosphorylation in crops and Arabidopsis circumventing radioactive labeling and the use of phosphorylation specific antibodies. PMID:26029234

  1. Ionic polymer cluster energetics: Computational analysis of pendant chain stiffness and charge imbalance

    NASA Astrophysics Data System (ADS)

    Weiland, Lisa Mauck; Leo, Donald J.

    2005-06-01

    In recent years there has been considerable study of the potential mechanisms underlying the electromechanical response of ionic-polymer-metal composites. The most recent models have been based on the response of the ion-containing clusters that are formed when the material is synthesized. Most of these efforts have employed assumptions of uniform ion distribution within spherical cluster shapes. This work investigates the impact of dispensing with these assumptions in order to better understand the parameters that impact cluster shape, size, and ion transport potential. A computational micromechanics model applying Monte Carlo methodology is employed to predict the equilibrium state of a single cluster of a solvated ionomeric polymer. For a constant solvated state, the model tracks the position of individual ions within a given cluster in response to ion-ion interaction, mechanical stiffness of the pendant chain, cluster surface energy, and external electric-field loading. Results suggest that cluster surface effects play a significant role in the equilibrium cluster state, including ion distribution; pendant chain stiffness also plays a role in ion distribution but to a lesser extent. Moreover, ion pairing is rarely complete even in cation-rich clusters; this in turn supports the supposition of the formation of anode and cathode boundary layers.

  2. Tectonic evolution of the Oak Creek Volcanic Roof Pendant, eastern Sierra Nevada, California

    SciTech Connect

    Longiaru, S.

    1987-01-01

    Detailed mapping, newly obtained U/Pb age analyses, and finite strain studies completed on a deformed volcanic roof pendant within the eastern Sierra indicate that: (1) little or no penetrative deformation affected the area during the Late Jurassic, and (2) the penetrative structure postdates the Nevadan orogeny by approximately 50 million years. The pendant consists of two volcanic sequences: a steeply dipping, homoclinal series of felsic ash flows and intermediate flows of Mid- to Late Jurassic age and an unconformably overlying series of felsic ash flows and mafic tuffs of Late Cretaceous age. Both sequences possess a single, well-developed, subvertical foliation that trends NNW. Quantitative strain analyses indicate that both the Jurassic and Cretaceous volcanic sequences underwent identical compressional strains of 30-40% shortening. This observation precludes the possibility that significant ductile deformation accompanied the rotation of the Jurassic volcanic rocks and suggests that the penetrative fabric developed within both units is Late Cretaceous in age. Isotopic age determinations on adjacent undeformed or only weakly deformed granitic plutons further indicate that the peak of deformation occurred prior to 102 Ma. Structural considerations and arguments based on the orientation of dikes of the Independence suite suggest that rotation of the Jurassic volcanic sequence took place prior to 148 Ma. in an extensional regime rather than during a Nevadan compressional event as generally interpreted.

  3. The effect of pendant-arm modification and ring size on the dynamics of cyclic polyamines

    NASA Astrophysics Data System (ADS)

    Wyrwał, Joanna; Schroeder, Grzegorz; Kowalewski, Jozef; Aski, Sahar Nikkhou

    2006-07-01

    Carbon-13 relaxation studies have been performed on two cyclic polyamines—1,4,8,11-tetraazacyclotetradecane, N4R4_H, (cyclam) and 1,4,7,10,13,16-hexaazacyclooctadecane, N6R6_H, (hexacyclen), and on two synthesized N-substituted cyclam derivatives—1,4,8,11-tetrahexanoyl-1,4,8,11-tetraazacyclotetradecane, N4R4_CO(CH 2) 4CH 3, with aliphatic and 1,4,8,11-tetranaftalenesulfonyl-1,4,8,11-tetraazacyclotetradecane, N4R4_SO 2C 10H 7, with aromatic substituents. Longitudinal T1 relaxation and NOE measurements were performed in extreme narrowing region for basic polyamines and outside extreme narrowing region for substituted derivatives at room temperature and for magnetic strengths 400 and 500 MHz. The main ring and the pendant-arms in substituted compounds were considered separately. The obtained relaxation rates and NOE factors for N4R4_CO(CH 2) 4CH 3 and N4R4_SO 2C 10H 7 molecules were fitted to overall and internal correlation times and order parameters using Lipari-Szabo 'model-free' formalism. The chemical shift anisotropy was determined for N4R4_SO 2C 10H 7 compound. The meaningful differences were observed between carbons in the main part of molecules and carbons from pendant-arms.

  4. Role of hydroxyl radical during electrolytic degradation of contaminants.

    PubMed

    Li, Liang; Goel, Ramesh K

    2010-09-15

    The role of hydroxyl radical is investigated in electrochemical oxidation of organic contaminants with naphthalene as a model compound. The strategy employed was competitive kinetic for hydroxyl radical between naphthalene and other hydroxyl scavengers if the hydroxyl radical is produced in situ at the anode by the electrolysis of water. Methanol, d3-methanol, acetone and d6-acetone were used as competitors for hydroxyl radical and their molar concentrations were calculated based on their reaction constants with hydroxyl radical. The hydroxyl radical was not responsible for naphthalene loss in these experiments. The first order reaction rate constants in the batch experiments containing only naphthalene, 2 mM of each of acetone and d6-acetone were 0.093, 0.094 and 0.118 h(-1), respectively. Higher concentrations (4 mM) acetone and d6-acetone did not affect naphthalene degradation. Rate constants using methanol and d6-methanol as competitors for hydroxyl radical in batch degradations test were 0.128 and 0.099 h(-1), respectively. Based on the naphthalene degradation trends and reaction rate constants, it was concluded that, under the given set of conditions, hydroxyl radical was not responsible for naphthalene degradation during electrolytic degradation tests. This research suggests that the role of hydroxyl radical should be considered very carefully in modeling such indirect electrolytic oxidation processes. PMID:20580488

  5. Hydroxylated ornithine lipids increase stress tolerance in Rhizobium tropici CIAT899

    PubMed Central

    Vences-Guzmán, Miguel Ángel; Guan, Ziqiang; Ormeño-Orrillo, Ernesto; González-Silva, Napoleón; López-Lara, Isabel M.; Martínez-Romero, Esperanza; Geiger, Otto; Sohlenkamp, Christian

    2011-01-01

    Ornithine lipids (OLs) are widespread among gram-negative bacteria. Their basic structure consists of a 3-hydroxy fatty acyl group attached in amide linkage to the α-amino group of ornithine and a second fatty acyl group ester-linked to the 3-hydroxy position of the first fatty acid. OLs can be hydroxylated within the secondary fatty acyl moiety and this modification has been related to increased stress tolerance. Rhizobium tropici, a nodule-forming α-proteobacterium known for its stress tolerance, forms four different OLs. Studies of the function of these OLs have been hampered due to lack of knowledge about their biosynthesis. Here we describe that OL biosynthesis increases under acid stress and that OLs are enriched in the outer membrane. Using a functional expression screen, the OL hydroxylase OlsE was identified, which in combination with the OL hydroxylase OlsC is responsible for the synthesis of modified OLs in R. tropici. Unlike described OL hydroxylations, the OlsE-catalyzed hydroxylation occurs within the ornithine moiety. Mutants deficient in OlsE or OlsC and double mutants deficient in OlsC/OlsE were characterized. R. tropici mutants deficient in OlsC-mediated OL hydroxylation are more susceptible to acid and temperature stress. All three mutants lacking OL hydroxylases are affected during symbiosis. PMID:21205018

  6. Kinetics of hydrogen peroxide decomposition by catalase: hydroxylic solvent effects.

    PubMed

    Raducan, Adina; Cantemir, Anca Ruxandra; Puiu, Mihaela; Oancea, Dumitru

    2012-11-01

    The effect of water-alcohol (methanol, ethanol, propan-1-ol, propan-2-ol, ethane-1,2-diol and propane-1,2,3-triol) binary mixtures on the kinetics of hydrogen peroxide decomposition in the presence of bovine liver catalase is investigated. In all solvents, the activity of catalase is smaller than in water. The results are discussed on the basis of a simple kinetic model. The kinetic constants for product formation through enzyme-substrate complex decomposition and for inactivation of catalase are estimated. The organic solvents are characterized by several physical properties: dielectric constant (D), hydrophobicity (log P), concentration of hydroxyl groups ([OH]), polarizability (α), Kamlet-Taft parameter (β) and Kosower parameter (Z). The relationships between the initial rate, kinetic constants and medium properties are analyzed by linear and multiple linear regression. PMID:22565543

  7. [Angiotensin-converting enzyme inhibitors as neutralizers of hydroxyl radical].

    PubMed

    Mira, M L; Silva, M M; Queirós, M J; Manso, C

    1992-05-01

    Angiotensin converting enzyme inhibitors are utilized in the treatment of essential hypertension and of chronic cardiac failure. They are also employed in the treatment of the myocardial lesion of ischemia-reperfusion, which involves oxygen free radicals. In the present study we investigated the possibility of three angiotensin converting enzyme inhibitors (captopril, enalapril, lisinopril) to act as hydroxyl radical scavengers. The rate constants for reactions of those compounds with .OH were determined using the deoxyribose method. All there compounds proved to be good scavengers of .OH with rate constants of about 10(10)M-1s-1 and are iron chelators specially enalapril. The fact that captopril possesses a thiol group does not confer an higher antioxidative capacity. These results suggest that scavenging of oxygen free radicals may be a possible mechanism contributing to the therapeutic effect of angiotensin converting enzyme inhibitors. PMID:1325814

  8. Methyl substituted polyimides containing carbonyl and ether connecting groups

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M. (Inventor); Havens, Stephen J. (Inventor)

    1992-01-01

    Polyimides were prepared from the reaction of aromatic dianhydrides with novel aromatic diamines having carbonyl and ether groups connecting aromatic rings containing pendant methyl groups. The methyl substituent polyimides exhibit good solubility and form tough, strong films. Upon exposure to ultraviolet irradiation and/or heat, the methyl substituted polyimides crosslink to become insoluble.

  9. Post-Functionalized Polymer Brushes for Bio-Separation: Tuning GFP Adsorption via Functional Group Display

    NASA Astrophysics Data System (ADS)

    Diamanti, Steve; Arifuzzaman, Shafi; Genzer, Jan; Naik, Rajesh; Vaia, Richard

    2007-03-01

    An inexpensive and robust biosensor platform that can be tuned to separate and/or detect complex mixtures of biomolecules while minimizing reagents would be of great use for military, homeland security, and medical diagnostic applications. Gradient surfaces of poly(2-hydroxyethyl methacrylate) (PHEMA) brushes have been previously shown to spatially localize biomolecule binding, while minimizing non-specific adsorption of the same biomolecule on other regions of the gradient specimen. In order to further improve the specificity and to provide latent functionality for detection of the binding events, post-polymerization modification of PHEMA with various functional groups has been investigated. Using standard succinimide-based coupling, hydroxyl pendants of PHEMA brushes were conjugated to oligo-peptides, alkanes and oligo(ethylene glycol) (OEG) through an alpha-terminus primary amine. Ellipsometry, contact angle, XPS and ER-FTIR spectroscopy indicated that coupling occurred with efficiencies ranging from 10-40%. Post-functionalization of PHEMA with OEG and hexadecane allows manipulation of the hydrophilicity of the surface and thus tuning of Green Fluorescent Protein (GFP) binding.

  10. Ultraviolet irradiation-induced substitution of fluorine with hydroxyl radical for mass spectrometric analysis of perfluorooctane sulfonyl fluoride.

    PubMed

    Wang, Peng; Tang, Xuemei; Huang, Lulu; Kang, Jie; Zhong, Hongying

    2016-01-28

    A rapid and solvent free substitution reaction of a fluorine atom in perfluorooctane sulfonyl fluoride (PFOSF) with a hydroxyl radical is reported. Under irradiation of ultraviolet laser on semiconductor nanoparticles or metal surfaces, hydroxyl radicals can be generated through hole oxidization. Among all fluorine atoms of PFOSF, highly active hydroxyl radicals specifically substitute the fluorine of sulfonyl fluoride functional group. Resultant perfluorooctane sulfonic acid is further ionized through capture of photo-generated electrons that switch the neutral molecules to negatively charged odd electron hypervalent ions. The unpaired electron subsequently initiates α O-H bond cleavage and produces perfluorooctane sulfonate negative ions. Hydroxyl radical substitution and molecular dissociation of PFOSF have been confirmed by masses with high accuracy and resolution. It has been applied to direct mass spectrometric imaging of PFOSF adsorbed on surfaces of plant leaves. PMID:26755143