Enhancing Cooperativity in Bifunctional Acid–Pd Catalysts with Carboxylic Acid-Functionalized Organic Monolayers

DOE PAGES

Coan, Patrick D.; Ellis, Lucas D.; Griffin, Michael B.; ...

2018-03-05

Here, cooperative catalysts containing a combination of noble metal hydrogenation sites and Bronsted acid sites are critical for many reactions, including the deoxygenation (DO) of biomass-derived oxygenates in the upgrading of pyrolysis oil. One route toward the design of cooperative catalysts is to tether two different catalytically active functions so that they are in close proximity while avoiding undesirable interactions that can block active sites. Here, we deposited carboxylic acid (CA)-functionalized organophosphonate monolayers onto Al 2O 3-supported Pd nanoparticle catalysts to prepare bifunctional catalysts containing both Bronsted acid and metal sites. Modification with phosphonic acids (PAs) improved activity and selectivitymore » for gas-phase DO reactions, but the degree of improvement was highly sensitive to both the presence and positioning of the CA group, suggesting a significant contribution from both the PA and CA sites. Short spacer lengths of 1-2 methylene groups between the phosphonate head and CA tail were found to yield the best DO rates and selectivities, whereas longer chains performed similarly to self-assembled monolayers having alkyl tails. Results from a combination of density functional theory and Fourier transform infrared spectroscopy suggested that the enhanced catalyst performance on the optimally positioned CAs was due to the generation of strong acid sites on the Al 2O 3 support adjacent to the metal. Furthermore, the high activity of these sites was found to result from a hydrogen-bonded cyclic structure involving cooperativity between the phosphonate head group and CA tail function. More broadly, these results indicate that functional groups tethered to supports via organic ligands can influence catalytic chemistry on metal nanoparticles.« less

Monolayer-directed Assembly and Magnetic Properties of FePt Nanoparticles on Patterned Aluminum Oxide

PubMed Central

Yildirim, Oktay; Gang, Tian; Kinge, Sachin; Reinhoudt, David N.; Blank, Dave H.A.; van der Wiel, Wilfred G.; Rijnders, Guus; Huskens, Jurriaan

2010-01-01

FePt nanoparticles (NPs) were assembled on aluminum oxide substrates, and their ferromagnetic properties were studied before and after thermal annealing. For the first time, phosph(on)ates were used as an adsorbate to form self-assembled monolayers (SAMs) on alumina to direct the assembly of NPs onto the surface. The Al2O3 substrates were functionalized with aminobutylphosphonic acid (ABP) or phosphonoundecanoic acid (PNDA) SAMs or with poly(ethyleneimine) (PEI) as a reference. FePt NPs assembled on all of these monolayers, but much less on unmodified Al2O3, which shows that ligand exchange at the NPs is the most likely mechanism of attachment. Proper modification of the Al2O3 surface and controlling the immersion time of the modified Al2O3 substrates into the FePt NP solution resulted in FePt NPs assembly with controlled NP density. Alumina substrates were patterned by microcontact printing using aminobutylphosphonic acid as the ink, allowing local NP assembly. Thermal annealing under reducing conditions (96%N2/4%H2) led to a phase change of the FePt NPs from the disordered FCC phase to the ordered FCT phase. This resulted in ferromagnetic behavior at room temperature. Such a process can potentially be applied in the fabrication of spintronic devices. PMID:20480007

Multifunctional Hybrid Multilayer Gate Dielectrics with Tunable Surface Energy for Ultralow-Power Organic and Amorphous Oxide Thin-Film Transistors.

PubMed

Byun, Hye-Ran; You, Eun-Ah; Ha, Young-Geun

2017-03-01

For large-area, printable, and flexible electronic applications using advanced semiconductors, novel dielectric materials with excellent capacitance, insulating property, thermal stability, and mechanical flexibility need to be developed to achieve high-performance, ultralow-voltage operation of thin-film transistors (TFTs). In this work, we first report on the facile fabrication of multifunctional hybrid multilayer gate dielectrics with tunable surface energy via a low-temperature solution-process to produce ultralow-voltage organic and amorphous oxide TFTs. The hybrid multilayer dielectric materials are constructed by iteratively stacking bifunctional phosphonic acid-based self-assembled monolayers combined with ultrathin high-k oxide layers. The nanoscopic thickness-controllable hybrid dielectrics exhibit the superior capacitance (up to 970 nF/cm 2 ), insulating property (leakage current densities <10 -7 A/cm 2 ), and thermal stability (up to 300 °C) as well as smooth surfaces (root-mean-square roughness <0.35 nm). In addition, the surface energy of the hybrid multilayer dielectrics are easily changed by switching between mono- and bifunctional phosphonic acid-based self-assembled monolayers for compatible fabrication with both organic and amorphous oxide semiconductors. Consequently, the hybrid multilayer dielectrics integrated into TFTs reveal their excellent dielectric functions to achieve high-performance, ultralow-voltage operation (< ± 2 V) for both organic and amorphous oxide TFTs. Because of the easily tunable surface energy, the multifunctional hybrid multilayer dielectrics can also be adapted for various organic and inorganic semiconductors, and metal gates in other device configurations, thus allowing diverse advanced electronic applications including ultralow-power and large-area electronic devices.

Chemical and charge transfer studies on interfaces of a conjugated polymer and ITO

NASA Astrophysics Data System (ADS)

David, Tanya M. S.; Arasho, Wondwosson; Smith, O'Neil; Hong, Kunlun; Bonner, Carl; Sun, Sam-Shajing

2017-08-01

Conjugated oligomers and polymers are very attractive for potential future plastic electronic and opto-electronic device applications such as plastic photo detectors and solar cells, thermoelectric devices, field effect transistors, and light emitting diodes. Understanding and optimizing charge transport between an active polymer layer and conductive substrate is critical to the optimization of polymer based electronic and opto-electronic devices. This study focused on the design, synthesis, self-assembly, and electron transfers and transports of a phosphonic acid end-functionalized polyphenylenevinylene (PPV) that was covalently attached and self-assembled onto an Indium Tin Oxide (ITO) substrate. This study demonstrated how atomic force microscopy (AFM) can be an effective characterization technique in conjunction with conventional electron transfer methods, including cyclic voltammetry (CV), towards determining electron transfer rates in polymer and polymer/conductor interface systems. This study found that the electron transfer rates of covalently attached and self-assembled films were much faster than the spin coated films. The knowledge from this study can be very useful for designing potential polymer based electronic and opto-electronic thin film devices.

Comparison of Zirconium Phosphonate-Modified Surfaces for Immobilizing Phosphopeptides and Phosphate-Tagged Proteins.

PubMed

Forato, Florian; Liu, Hao; Benoit, Roland; Fayon, Franck; Charlier, Cathy; Fateh, Amina; Defontaine, Alain; Tellier, Charles; Talham, Daniel R; Queffélec, Clémence; Bujoli, Bruno

2016-06-07

Different routes for preparing zirconium phosphonate-modified surfaces for immobilizing biomolecular probes are compared. Two chemical-modification approaches were explored to form self-assembled monolayers on commercially available primary amine-functionalized slides, and the resulting surfaces were compared to well-characterized zirconium phosphonate monolayer-modified supports prepared using Langmuir-Blodgett methods. When using POCl3 as the amine phosphorylating agent followed by treatment with zirconyl chloride, the result was not a zirconium-phosphonate monolayer, as commonly assumed in the literature, but rather the process gives adsorbed zirconium oxide/hydroxide species and to a lower extent adsorbed zirconium phosphate and/or phosphonate. Reactions giving rise to these products were modeled in homogeneous-phase studies. Nevertheless, each of the three modified surfaces effectively immobilized phosphopeptides and phosphopeptide tags fused to an affinity protein. Unexpectedly, the zirconium oxide/hydroxide modified surface, formed by treating the amine-coated slides with POCl3/Zr(4+), afforded better immobilization of the peptides and proteins and efficient capture of their targets.

Enhanced stability of ZnO-based inverted organic photovoltaic devices by phosphonic acid modification

NASA Astrophysics Data System (ADS)

MacLeod, Bradley; Tremolet de Villers, Bertrand; Cowan, Sarah; Ratcliff, Erin; Olson, Dana

2014-03-01

Solution-processed ZnO thin films are now commonly used as n-type bottom contacts in inverted-geometry organic photovoltaics (OPVs). The use of ZnO eliminates the need for highly-reactive top-contact (air-interface) electrode material, such as calcium and aluminum which are commonly used in conventional geometries, which enables operational lifetimes of unencapsulated devices to shift from minutes or hours to days. Modification of the ZnO film by self-assembled monolayers (SAMs) has been shown to enhance performance as well as air-stability during storage. We modify ZnO with dipolar phosphonic acids and observe enhanced performance and stability. We show for the first time devices measured under continuous illumination at one-sun intensity which have significantly enhanced stability when utilizing SAM-modified ZnO. These continuous-illumination stability measurements allow us to investigate the degradation mechanisms of these more stable inverted OPV devices. This work was was supported by of the Center for Interface Science: Solar Electric Materials (CISSEM), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001084.

Single-step synthesis of styryl phosphonic acids via palladium-catalyzed Heck coupling of vinyl phosphonic acid with aryl halides

DOE PAGES

McNichols, Brett W.; Koubek, Joshua T.; Sellinger, Alan

2017-10-27

Here, we have developed a single step palladium-catalyzed Heck coupling of aryl halides with vinyl phosphonic acid to produce functionalized (E)-styryl phosphonic acids. This pathway utilizes a variety of commercially available aryl halides, vinyl phosphonic acid and Pd(P(tBu) 3) 2 as catalyst. These conditions produce a wide range of styryl phosphonic acids with high purities and good to excellent yields (31–80%).

Single-step synthesis of styryl phosphonic acids via palladium-catalyzed Heck coupling of vinyl phosphonic acid with aryl halides

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

McNichols, Brett W.; Koubek, Joshua T.; Sellinger, Alan

Here, we have developed a single step palladium-catalyzed Heck coupling of aryl halides with vinyl phosphonic acid to produce functionalized (E)-styryl phosphonic acids. This pathway utilizes a variety of commercially available aryl halides, vinyl phosphonic acid and Pd(P(tBu) 3) 2 as catalyst. These conditions produce a wide range of styryl phosphonic acids with high purities and good to excellent yields (31–80%).

Stability of Phosphonic Self Assembled Monolayers (SAMs) on Cobalt Chromium (Co-Cr) Alloy under Oxidative conditions

PubMed Central

Bhure, Rahul; Abdel-Fattah, Tarek M.; Bonner, Carl; Hall, Felicia; Mahapatro, Anil

2011-01-01

Cobalt Chromium (Co-Cr) alloys has been widely used in the biomedical arena for cardiovascular, orthopedic and dental applications. Surface modification of the alloy allows us to tailor the interfacial properties to address critical challenges of Co-Cr alloy in medical applications. Self assembled monolayers (SAMs) of Octadecylphosphonic acid (ODPA) have been used to form thin films on the oxide layer of the Co-Cr alloy surface by solution deposition technique. The SAMs formed were investigated for their stability to oxidative conditions of ambient laboratory environment over periods of 1, 3, 7 and 14 days. The samples were then characterized for their stability using X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and Contact Angle Measurements. Detailed high energy XPS elemental scans confirmed the presence of the phosphonic monolayer after oxidative exposure which suggested that the SAMs were firmly attached to the oxide layer of Co-Cr alloy. AFM images gave topographical data of the surface and showed islands of SAMs on Co-Cr alloy surface, before and after SAM formation and also over the duration of the oxidative exposure. Contact angle measurements confirmed the hydrophobicity of the surface over 14 days. Thus the SAMs were found to be stable for the duration of the study. These SAMs could be subsequently tailored by modifying the terminal functional groups and could be used for various potential biomedical applications such as drug delivery, biocompatibility and tissue integration PMID:21603056

Lability and Basicity of Bipyridine-Carboxylate-Phosphonate Ligand Accelerate Single-Site Water Oxidation by Ruthenium-Based Molecular Catalysts

DOE PAGES

Shaffer, David W.; Xie, Yan; Szalda, David J.; ...

2017-09-24

Here, a critical step in creating an artificial photosynthesis system for energy storage is designing catalysts that can thrive in an assembled device. Single-site catalysts have an advantage over bimolecular catalysts because they remain effective when immobilized. Hybrid water oxidation catalysts described here, combining the features of single-site bis-phosphonate catalysts and fast bimolecular bis-carboxylate catalysts, have reached turnover frequencies over 100 s –1, faster than both related catalysts under identical conditions. The new [(bpHc)Ru(L) 2] (bpH 2cH = 2,2'-bipyridine-6-phosphonic acid-6'-carboxylic acid, L = 4-picoline or isoquinoline) catalysts proceed through a single-site water nucleophilic attack pathway. The pendant phosphonate base mediatesmore » O–O bond formation via intramolecular atom-proton transfer with a calculated barrier of only 9.1 kcal/mol. Additionally, the labile carboxylate group allows water to bind early in the catalytic cycle, allowing intramolecular proton-coupled electron transfer to lower the potentials for oxidation steps and catalysis. That a single-site catalyst can be this fast lends credence to the possibility that the oxygen evolving complex adopts a similar mechanism.« less

Lability and Basicity of Bipyridine-Carboxylate-Phosphonate Ligand Accelerate Single-Site Water Oxidation by Ruthenium-Based Molecular Catalysts

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

Shaffer, David W.; Xie, Yan; Szalda, David J.

Here, a critical step in creating an artificial photosynthesis system for energy storage is designing catalysts that can thrive in an assembled device. Single-site catalysts have an advantage over bimolecular catalysts because they remain effective when immobilized. Hybrid water oxidation catalysts described here, combining the features of single-site bis-phosphonate catalysts and fast bimolecular bis-carboxylate catalysts, have reached turnover frequencies over 100 s –1, faster than both related catalysts under identical conditions. The new [(bpHc)Ru(L) 2] (bpH 2cH = 2,2'-bipyridine-6-phosphonic acid-6'-carboxylic acid, L = 4-picoline or isoquinoline) catalysts proceed through a single-site water nucleophilic attack pathway. The pendant phosphonate base mediatesmore » O–O bond formation via intramolecular atom-proton transfer with a calculated barrier of only 9.1 kcal/mol. Additionally, the labile carboxylate group allows water to bind early in the catalytic cycle, allowing intramolecular proton-coupled electron transfer to lower the potentials for oxidation steps and catalysis. That a single-site catalyst can be this fast lends credence to the possibility that the oxygen evolving complex adopts a similar mechanism.« less

Synthesis and fabrication of sized-controlled nanoparticles: Using surface self-assemblies as building blocks for developing supralattices on nanocomposite materials

NASA Astrophysics Data System (ADS)

Yee, Chanel Kitmon

2001-10-01

A general one-phase synthesis for self-assembling thiols onto gold, platinum, palladium and iridium nanoparticles using tetrahydrofuran (THF) as the solvent, and lithium triethylborohydride (superhydride) as the reducing agent, is presented. Using the same synthetic procedure gold nanoparticles functionalized with 11-hydroxyundecane-1-thiol and 4'-bromo-4-mercaptobiphenyl were prepared to show that the availability and reflexibility of this method could lead to surface fabrication with various type of facial moieties. Alkyl selenide- and alkyl thiolate-functionalized gold nanoparticles were also prepared by the same method at 6°C. The properties were compared to their counterparts made at 25°C. The formation of the Se-Au bond and S-Au bonds was investigated by transmission Fourier transform infrared spectroscopy (FTIR), while the bond nature in each case was examined by x-ray photoelectron spectroscopy (XPS). Particle size was determined by Transmission Electron Microscopy (TEM), and further confirmed by ultraviolet spectroscopy (UV). Superparamagnetic Fe and Fe2O3 nanoparticles were synthesized by ultrasound irradiation and post-fabricated with alkyl sulfonic acids of various chain lengths and octadecyl phosphonic acid. TEM reveals nanoparticles of 5--10 mn in diameter. FTIR spectra suggest that the alkyl chains are packed in a solid-like assembly with packing disorder increasing with the decreasing chain length. The octadecyl sulfonic acid coating displays the lowest magnetization within the sulfonic acid series, which may be explained by the high packing and ordering of the alkyl chains on the particle surface. The smallest value of magnetization in the OPA case suggests that the spin-state of surface Fe3+ ions is affected by the bonded surfactant, and that the phosphonate empty d-orbitals increase magnetic interactions between neighboring Fe3+ spins. To build superstructures beyond the monolayer level, a general route for the attachment of amino-terminated biomolecules to nanoparticles was proposed. Thiophene thiolate-functionalized platinum nanoparticles were prepared and reacted with nitrosonium tetrafluoroborate to provide the nitroso-functionalized nanoparticles. The reaction of the nitroso group with primary amines to yield strong N=N bonds might provide a general route for the attachment of amino-terminated biomolecules to nanoparticles. The attachment of two cytidine molecules to platinum nanoparticles was accomplished, and experimental data were provided to demonstrate the intended grafting reaction.

Molecular architecture: construction of self-assembled organophosphonate duplexes and their electrochemical characterization.

PubMed

Cattani-Scholz, Anna; Liao, Kung-Ching; Bora, Achyut; Pathak, Anshuma; Hundschell, Christian; Nickel, Bert; Schwartz, Jeffrey; Abstreiter, Gerhard; Tornow, Marc

2012-05-22

Self-assembled monolayers of phosphonates (SAMPs) of 11-hydroxyundecylphosphonic acid, 2,6-diphosphonoanthracene, 9,10-diphenyl-2,6-diphosphonoanthracene, and 10,10'-diphosphono-9,9'-bianthracene and a novel self-assembled organophosphonate duplex ensemble were synthesized on nanometer-thick SiO(2)-coated, highly doped silicon electrodes. The duplex ensemble was synthesized by first treating the SAMP prepared from an aromatic diphosphonic acid to form a titanium complex-terminated one; this was followed by addition of a second equivalent of the aromatic diphosphonic acid. SAMP homogeneity, roughness, and thickness were evaluated by AFM; SAMP film thickness and the structural contributions of each unit in the duplex were measured by X-ray reflection (XRR). The duplex was compared with the aliphatic and aromatic monolayer SAMPs to determine the effect of stacking on electrochemical properties; these were measured by impedance spectroscopy using aqueous electrolytes in the frequency range 20 Hz to 100 kHz, and data were analyzed using resistance-capacitance network based equivalent circuits. For the 11-hydroxyundecylphosphonate SAMP, C(SAMP) = 2.6 ± 0.2 μF/cm(2), consistent with its measured layer thickness (ca. 1.1 nm). For the anthracene-based SAMPs, C(SAMP) = 6-10 μF/cm(2), which is attributed primarily to a higher effective dielectric constant for the aromatic moieties (ε = 5-10) compared to the aliphatic one; impedance spectroscopy measured the additional capacitance of the second aromatic monolayer in the duplex (2ndSAMP) to be C(Ti/2ndSAMP) = 6.8 ± 0.7 μF/cm(2), in series with the first.

Phosphonic acid: preparation and applications

PubMed Central

Sevrain, Charlotte M; Berchel, Mathieu; Couthon, Hélène

2017-01-01

The phosphonic acid functional group, which is characterized by a phosphorus atom bonded to three oxygen atoms (two hydroxy groups and one P=O double bond) and one carbon atom, is employed for many applications due to its structural analogy with the phosphate moiety or to its coordination or supramolecular properties. Phosphonic acids were used for their bioactive properties (drug, pro-drug), for bone targeting, for the design of supramolecular or hybrid materials, for the functionalization of surfaces, for analytical purposes, for medical imaging or as phosphoantigen. These applications are covering a large panel of research fields including chemistry, biology and physics thus making the synthesis of phosphonic acids a determinant question for numerous research projects. This review gives, first, an overview of the different fields of application of phosphonic acids that are illustrated with studies mainly selected over the last 20 years. Further, this review reports the different methods that can be used for the synthesis of phosphonic acids from dialkyl or diaryl phosphonate, from dichlorophosphine or dichlorophosphine oxide, from phosphonodiamide, or by oxidation of phosphinic acid. Direct methods that make use of phosphorous acid (H3PO3) and that produce a phosphonic acid functional group simultaneously to the formation of the P–C bond, are also surveyed. Among all these methods, the dealkylation of dialkyl phosphonates under either acidic conditions (HCl) or using the McKenna procedure (a two-step reaction that makes use of bromotrimethylsilane followed by methanolysis) constitute the best methods to prepare phosphonic acids. PMID:29114326

Phosphonic acid: preparation and applications.

PubMed

Sevrain, Charlotte M; Berchel, Mathieu; Couthon, Hélène; Jaffrès, Paul-Alain

2017-01-01

The phosphonic acid functional group, which is characterized by a phosphorus atom bonded to three oxygen atoms (two hydroxy groups and one P=O double bond) and one carbon atom, is employed for many applications due to its structural analogy with the phosphate moiety or to its coordination or supramolecular properties. Phosphonic acids were used for their bioactive properties (drug, pro-drug), for bone targeting, for the design of supramolecular or hybrid materials, for the functionalization of surfaces, for analytical purposes, for medical imaging or as phosphoantigen. These applications are covering a large panel of research fields including chemistry, biology and physics thus making the synthesis of phosphonic acids a determinant question for numerous research projects. This review gives, first, an overview of the different fields of application of phosphonic acids that are illustrated with studies mainly selected over the last 20 years. Further, this review reports the different methods that can be used for the synthesis of phosphonic acids from dialkyl or diaryl phosphonate, from dichlorophosphine or dichlorophosphine oxide, from phosphonodiamide, or by oxidation of phosphinic acid. Direct methods that make use of phosphorous acid (H 3 PO 3 ) and that produce a phosphonic acid functional group simultaneously to the formation of the P-C bond, are also surveyed. Among all these methods, the dealkylation of dialkyl phosphonates under either acidic conditions (HCl) or using the McKenna procedure (a two-step reaction that makes use of bromotrimethylsilane followed by methanolysis) constitute the best methods to prepare phosphonic acids.

Crystalline TiO 2 grafted with poly(2-methacryloyloxyethyl phosphorylcholine) via surface-initiated atom-transfer radical polymerization

NASA Astrophysics Data System (ADS)

Zhao, Yuancong; Tu, Qiufen; Wang, Jin; Huang, Qiongjian; Huang, Nan

2010-12-01

Crystalline TiO 2 films were prepared by unbalanced magnetron sputtering and the structure was confirmed by XRD. An organic layer of 11-hydroxyundecylphosphonic acid (HUPA) was prepared on the TiO 2 films by self-assembling, and the HUPA on TiO 2 films was confirmed by FTIR analysis. Simultaneously, hydroxyl groups were introduced in the phosphonic acid molecules to provide a functionality for further chemical modification. 2-Methacryloyloxyethyl phosphorylcholine (MPC), a biomimetic monomer, was chemically grafted on the HUPA surfaces at room temperature by surface-initiated atom-transfer radical polymerization. The surface characters of TiO 2 films modified by poly-MPC were confirmed by FTIR, XPS and SEM analysis. Platelet adhesion experiment revealed that poly-MPC modified surface was effective to inhibit platelet adhesion in vitro.

40 CFR 721.10243 - Phosphonic acid, P-[2-[bis(2-hydroxyethyl)amino]ethyl]-, bis(2-chloroethyl) ester.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Phosphonic acid, P-[2-[bis(2... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10243 Phosphonic acid, P-[2-[bis(2... to reporting. (1) The chemical substance identified as phosphonic acid, P-[2-[bis(2-hydroxyethyl...

40 CFR 721.10412 - Phosphonic acid ester (generic) (P-07-706).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Phosphonic acid ester (generic) (P-07... Specific Chemical Substances § 721.10412 Phosphonic acid ester (generic) (P-07-706). (a) Chemical substance... phosphonic acid ester (PMN P-07-706) is subject to reporting under this section for the significant new uses...

40 CFR 721.10412 - Phosphonic acid ester (generic) (P-07-706).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Phosphonic acid ester (generic) (P-07... Specific Chemical Substances § 721.10412 Phosphonic acid ester (generic) (P-07-706). (a) Chemical substance... phosphonic acid ester (PMN P-07-706) is subject to reporting under this section for the significant new uses...

40 CFR 721.10243 - Phosphonic acid, P-[2-[bis(2-hydroxyethyl)amino]ethyl]-, bis(2-chloroethyl) ester.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Phosphonic acid, P-[2-[bis(2... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10243 Phosphonic acid, P-[2-[bis(2... to reporting. (1) The chemical substance identified as phosphonic acid, P-[2-[bis(2-hydroxyethyl...

40 CFR 721.10412 - Phosphonic acid ester (generic) (P-07-706).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Phosphonic acid ester (generic) (P-07... Specific Chemical Substances § 721.10412 Phosphonic acid ester (generic) (P-07-706). (a) Chemical substance... phosphonic acid ester (PMN P-07-706) is subject to reporting under this section for the significant new uses...

Intermediate temperature proton conductors for PEM fuel cells based on phosphonic acid as protogenic group: a progress report.

PubMed

Steininger, H; Schuster, M; Kreuer, K D; Kaltbeitzel, A; Bingöl, B; Meyer, W H; Schauff, S; Brunklaus, G; Maier, J; Spiess, H W

2007-04-21

The melting behaviour and transport properties of straight chain alkanes mono- and difunctionalized with phosphonic acid groups have been investigated as a function of their length. The increase of melting temperature and decrease of proton conductivity with increasing chain length is suggested to be the consequence of an increasing ordering of the alkane segments which constrains the free aggregation of the phosphonic acid groups. However, the proton mobility is reduced to a greater extent than the proton diffusion coefficient indicating an increasing cooperativity of proton transport with increasing length of the alkane segment. The results clearly indicate that the "spacer concept", which had been proven successful in the optimization of the proton conductivity of heterocycle based systems, fails in the case of phosphonic acid functionalized polymers. Instead, a very high concentration of phosphonic acid functional groups forming "bulky" hydrogen bonded aggregates is suggested to be essential for obtaining very high proton conductivity. Aggregation is also suggested to reduce condensation reactions generally observed in phosphonic acid containing systems. On the basis of this understanding, the proton conductivities of poly(vinyl phosphonic acid) and poly(meta-phenylene phosphonic acid) are discussed. Though both polymers exhibit a substantial concentration of phosphonic acid groups, aggregation seems to be constrained to such an extent that intrinsic proton conductivity is limited to values below sigma = 10(-3) S cm(-1) at T = 150 degrees C. The results suggest that different immobilization concepts have to be developed in order to minimize the conductivity reduction compared to the very high intrinsic proton conductivity of neat phosphonic acid under quasi dry conditions. In the presence of high water activities, however, (as usually present in PEM fuel cells) the very high ion exchange capacities (IEC) possible for phosphonic acid functionalized ionomers (IEC >10 meq g(-1)) may allow for high proton conductivities in the intermediate temperature range (T approximately 120 -160 degrees C).

Organophosphonates: A review on environmental relevance, biodegradability and removal in wastewater treatment plants.

PubMed

Rott, Eduard; Steinmetz, Heidrun; Metzger, Jörg W

2018-02-15

The worldwide increasing consumption of the phosphonates 2-phosphonobutane-1,2,4-tricarboxylic acid [PBTC], 1-hydroxyethane 1,1-diphosphonic acid [HEDP], nitrilotris(methylene phosphonic acid) [NTMP], ethylenediamine tetra(methylene phosphonic acid) [EDTMP] and diethylenetriamine penta(methylene phosphonic acid) [DTPMP] over the past decades put phosphonates into focus of environmental scientists and agencies, as they are increasingly discussed in the context of various environmental problems. The hitherto difficult analysis of phosphonates contributed to the fact that very little is known about their concentrations and behavior in the environment. This work critically reviews the existing literature up to the year 2016 on the potential environmental relevance of phosphonates, their biotic and abiotic degradability, and their removal in wastewater treatment plants (WWTPs). Accordingly, despite their stability against biological degradation, phosphonates can be removed with relatively high efficiency (>80%) in WWTPs operated with chemical phosphate precipitation. In the literature, however, to our knowledge, there is no information as to whether an enhanced biological phosphorus removal alone is sufficient for such high removal rates and whether the achievable phosphonate concentrations in effluents are sufficiently low to prevent eutrophication. It is currently expected that phosphonates, although being complexing agents, do not remobilize heavy metals from sediments in a significant amount since the phosphonate concentrations required for this (>50μg/L) are considerably higher than the concentrations determined in surface waters. Various publications also point out that phosphonates are harmless to a variety of aquatic organisms. Moreover, degradation products thereof such as N-(phosphonomethyl)glycine and aminomethylphosphonic acid are regarded as being particularly critical. Despite their high stability against biological degradation, phosphonates contribute to eutrophication due to abiotic degradation (mainly photolysis). Furthermore, the literature reports on the fact that phosphonates in high concentrations interfere with phosphate precipitation in WWTPs. Thus, it is recommended to remove phosphonates, in particular from industrial wastewaters, before discharging them into water bodies or WWTPs. Copyright © 2017 Elsevier B.V. All rights reserved.

Disorder-derived, strong tunneling attenuation in bis-phosphonate monolayers.

PubMed

Pathak, Anshuma; Bora, Achyut; Liao, Kung-Ching; Schmolke, Hannah; Jung, Antje; Klages, Claus-Peter; Schwartz, Jeffrey; Tornow, Marc

2016-03-09

Monolayers of alkyl bisphosphonic acids (bisPAs) of various carbon chain lengths (C4, C8, C10, C12) were grown on aluminum oxide (AlO(x)) surfaces from solution. The structural and electrical properties of these self-assembled monolayers (SAMs) were compared with those of alkyl monophosphonic acids (monoPAs). Through contact angle (CA) and Kelvin-probe (KP) measurements, ellipsometry, and infrared (IR) and x-ray photoelectron (XPS) spectroscopies, it was found that bisPAs form monolayers that are relatively disordered compared to their monoPA analogs. Current-voltage (J-V) measurements made with a hanging Hg drop top contact show tunneling to be the prevailing transport mechanism. However, while the monoPAs have an observed decay constant within the typical range for dense monolayers, β(mono)  =  0.85  ±  0.03 per carbon atom, a surprisingly high value, β(bis) =  1.40  ±  0.05 per carbon atom, was measured for the bisPAs. We attribute this to a strong contribution of 'through-space' tunneling, which derives from conformational disorder in the monolayer due to strong interactions of the distal phosphonic acid groups; they likely form a hydrogen-bonding network that largely determines the molecular layer structure. Since bisPA SAMs attenuate tunnel currents more effectively than do the corresponding monoPA SAMs, they may find future application as gate dielectric modification in organic thin film devices.

Disorder-derived, strong tunneling attenuation in bis-phosphonate monolayers

NASA Astrophysics Data System (ADS)

Pathak, Anshuma; Bora, Achyut; Liao, Kung-Ching; Schmolke, Hannah; Jung, Antje; Klages, Claus-Peter; Schwartz, Jeffrey; Tornow, Marc

2016-03-01

Monolayers of alkyl bisphosphonic acids (bisPAs) of various carbon chain lengths (C4, C8, C10, C12) were grown on aluminum oxide (AlO x ) surfaces from solution. The structural and electrical properties of these self-assembled monolayers (SAMs) were compared with those of alkyl monophosphonic acids (monoPAs). Through contact angle (CA) and Kelvin-probe (KP) measurements, ellipsometry, and infrared (IR) and x-ray photoelectron (XPS) spectroscopies, it was found that bisPAs form monolayers that are relatively disordered compared to their monoPA analogs. Current-voltage (J-V) measurements made with a hanging Hg drop top contact show tunneling to be the prevailing transport mechanism. However, while the monoPAs have an observed decay constant within the typical range for dense monolayers, β mono  =  0.85  ±  0.03 per carbon atom, a surprisingly high value, β bis  =  1.40  ±  0.05 per carbon atom, was measured for the bisPAs. We attribute this to a strong contribution of ‘through-space’ tunneling, which derives from conformational disorder in the monolayer due to strong interactions of the distal phosphonic acid groups; they likely form a hydrogen-bonding network that largely determines the molecular layer structure. Since bisPA SAMs attenuate tunnel currents more effectively than do the corresponding monoPA SAMs, they may find future application as gate dielectric modification in organic thin film devices.

Functionalization of biodegradable magnesium alloy implants with alkylphosphonate self-assembled films.

PubMed

Grubač, Z; Metikoš-Huković, M; Babić, R; Rončević, I Škugor; Petravić, M; Peter, R

2013-05-01

Mg and Mg-alloys are promising materials for biodegradable implants. In order to slowdown the Mg-alloy (AZ91D) degradation and enhance its biocompatibility, the alloy surface was modified with alkylphosphonate self-assembling films. The binding configuration and the structural organization of alkylphosphonate monolayers on the Mg-alloy surface were investigated using contact angle measurements, FTIR, and XPS. Combination of FTIR and XPS data indicated the presence of several different bonding modes (mono-, di-, and tri dentate) of phosphonate head groups with the alloy surface. The existence of well organized and ordered self-assembled alkylphosphonate monolayers with good barrier protecting properties in a physiological solution is a key step in the development of biocompatible Mg-alloy implants. Copyright © 2013 Elsevier B.V. All rights reserved.

Alkyl phosphonic acids and sulfonic acids in the Murchison meteorite

NASA Technical Reports Server (NTRS)

Cooper, George W.; Onwo, Wilfred M.; Cronin, John R.

1992-01-01

Homologous series of alkyl phosphonic acids and alkyl sulfonic acids, along with inorganic orthophosphate and sulfate, are identified in water extracts of the Murchison meteorite after conversion to their t-butyl dimethylsilyl derivatives. The methyl, ethyl, propyl, and butyl compounds are observed in both series. Five of the eight possible alkyl phosphonic acids and seven of the eight possible alkyl sulfonic acids through C4 are identified. Abundances decrease with increasing carbon number as observed of other homologous series indigenous to Murchison. Concentrations range downward from approximately 380 nmol/gram in the alkyl sulfonic acid series, and from 9 nmol/gram in the alkyl phosphonic acid series.

Epoxy Phosphonate Crosslinkers for Providing Flame Resistance to Cotton Textiles

USDA-ARS?s Scientific Manuscript database

Two new monomers (2-methyl-oxiranylmethyl)-phosphonic acid dimethyl ester (3) and [2-(dimethoxy-phosphorylmethyl)-oxyranylmethyl]-phosphonic acid dimethyl ester (6) were prepared and used with dicyandiamide (7) and citric acid (8) to impart flame resistance to cotton plain weave, twill, and 80:20-co...

40 CFR 721.10370 - Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1).

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Phosphonic acid, p-octyl-, lanthanum... New Uses for Specific Chemical Substances § 721.10370 Phosphonic acid, p-octyl-, lanthanum (3+) salt... substance identified as phosphinic acid, p-octyl-, lanthanum (3+) salt (2:1) (PMN P-10-99; CAS No. 1186211...

40 CFR 721.10370 - Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1).

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Phosphonic acid, p-octyl-, lanthanum... New Uses for Specific Chemical Substances § 721.10370 Phosphonic acid, p-octyl-, lanthanum (3+) salt... substance identified as phosphinic acid, p-octyl-, lanthanum (3+) salt (2:1) (PMN P-10-99; CAS No. 1186211...

40 CFR 721.10370 - Phosphonic acid, p-octyl-, lanthanum (3+) salt (2:1).

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Phosphonic acid, p-octyl-, lanthanum... New Uses for Specific Chemical Substances § 721.10370 Phosphonic acid, p-octyl-, lanthanum (3+) salt... substance identified as phosphinic acid, p-octyl-, lanthanum (3+) salt (2:1) (PMN P-10-99; CAS No. 1186211...

Selective Removal of Lanthanides from Natural Waters, Acidic Streams and Dialysate

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

Yantasee, Wassana; Fryxell, Glen E.; Addleman, Raymond S.

2009-09-15

The increased demand for the lanthanides in commercial products result in increased production of lanthanide containing ores, increasing public exposure to the lanthanides, both from various commercial products and from production wastes/effluents. This work investigates lanthanide (La, Ce, Pr, Nd, Eu, Gd, Lu) binding properties of self-assembled monolayers on mesoporous silica supports (SAMMS®) that were functionalized with diphosphonic acid (DiPhos), acetamide phosphonic acid (AcPhos), propionamide phosphonic acid (ProPhos), and 1-hydroxy-2-pyridinone (1,2-HOPO) from natural waters (river, ground, and sea waters), acid solutions (to mimic certain industrial process streams), and dialysate and compares their performance to a high surface area activated carbon.more » The properties include sorption affinity, capacity, and sorption kinetics. Stability and regenerability of SAMMS materials were also investigated. Going from the acid side over to the alkaline side, the AcPhos- and DiPhos-SAMMS maintain their outstanding affinity for lanthanides, which enable the use of the materials in the systems where the pH may fluctuate. While the activated carbon is as effective as 1,2-HOPO-SAMMS for capturing lanthanides in natural (alkaline) waters, it has no affinity in acid solutions (pH 2.4) and low affinity in carbonate-rich dialysate. Over 99% of 100 ug/L of Gd in dialysate was removed by the ProPhos-SAMMS after ten minutes. SAMMS can be regenerated with an acid wash (0.5 M HCl) without losing the binding properties, for a number of regeneration cycles. In acid solutions, PhoPhos- and 1,2-HOPO-SAMMS have differing affinity along the lanthanide series, suggesting their potential for chromatographic lanthanide separations. Thus, SAMMS materials have a great potential to be used as sorbents in large scale treatment of lanthanides, lanthanide separation prior to analytical instruments, and sorbent dialyzers for lanthanide clearances.« less

The Effects of Phosphonic Acids in Dye-Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

James, Keith Edward

Novel methods for the construction of dye-sensitized solar cells (DSSCs) were developed. A thin dense underlayer of TiO2 was applied on fluorine-doped tin oxide (FTO) glass using as a precursor Tyzor AA-105. Subsequently a mesoporous film of P-25 TiO2 was applied by spreading a suspension uniformly over the surface of the underlayer and allowing the plate to slowly dry while resting on a level surface. After sintering at 500° C slides were treated with TCPP as a sensitizing dye and assembled into DSSCs. A novel method was used to seal the cells; strips of ParafilmRTM were used as spacers between the electrodes and to secure the electrodes together. The cells were filled with a redox electrolyte and sealed by dipping into molten paraffin. A series of phosphonic acids and one arsonic acid were employed as coadsorbates in DSSCs. The coadsorbates were found to compete for binding sites, resulting in lower levels of dye adsorption. The resulting loss of photocurrent was not linear with the reduction of dye loading, and in some cases photocurrent and efficiency were higher for cells with lower levels of dye loading. Electrodes were treated with coadsorbates by procedures including pre-adsorption, simultaneous (sim-adsorption), and post-adsorption, using a range of concentrations and treatment times and a variety of solvents. Most cells were tested using an iodide-triiodide based electrolyte (I3I-1) but some cells were tested using electrolytes based on a Co(II)/Co(III) redox couple (CoBpy electrolytes). Phosphonic acid post-adsorbates increased the Voc of cells using CoBpy electrolytes but caused a decrease in the Voc of cells using I3I-1 electrolyte. Phosphonic acids as sim-adsorbates resulted in a significant increase in efficiency and Jsc, and they show promise as a treatment for TCPP DSSCs.

Phosphoric and carboxylic methacrylate esters as bonding agents in self-adhesive resin cements

PubMed Central

Liu, Wenshu; Meng, Hongmei; Sun, Zhiguang; Jiang, Riwen; Dong, Chang-An; Zhang, Congxiao

2018-01-01

The aim of the present study was to investigate the effect of pH and phosphoric ester structure (phosphonate or phosphate) on the bond strength of different dental restorative materials. The following three self-adhesive resin cements were used in the present study: RelyX™ Unicem, Maxcem and Multilink Sprint The pH of each cement was measured using a pH meter. The cements were used to attach a variety of restorative materials to human dentin and the bond strength was measured by assessing shear strength using a universal testing machine. The pH values of RelyX Unicem, Maxcem and Multilink Sprint were 3.78, 1.78 and 3.42, respectively. Maxcem, a phosphate-based self-adhesive cement, was demonstrated to form the weakest bonds. No significant difference in bond strength was observed between RelyX Unicem and Multilink Sprint, which are phosphonate-based cements. The results of the present study suggest that the chemical structure of the functional monomer influences the performance of an adhesive material. Furthermore, the pH of acidic functional monomers containing phosphonate or phosphate groups has an effect on the strength of bonds formed between dentin and restorative materials. PMID:29731837

Nanocomposites of phosphonic-acid-functionalized polyethylenes with inorganic quantum dots.

PubMed

Rünzi, Thomas; Baier, Moritz C; Negele, Carla; Krumova, Marina; Mecking, Stefan

2015-01-01

Insertion of diethyl vinyl phosphonates and free vinyl phosphonic acid, respectively, into [(P^O)Pd(Me)(dmso)] ((P^O) = κ(2)-P,O-Ar2PC6H4SO2O with Ar = 2-MeOC6H4) (1-dmso) occurs in a 2,1- as well as 1,2-fashion, to form a four-and a five-membered chelate [(P^O)Pd{κ(2)-C,O-CH(P(O)(OR)2)CH2CH3}] and [(P^O)Pd{κ(2)-C,O-CH2CH(P(O)(OR)2)CH3}] (R = H, Et). No decomposition or other reactions of 1 by free phosphonic acid moieties occur. Copolymerization in a pressure reactor by 1-dmso yields linear random poly(ethylene-co-diethyl vinyl phosphonate) and poly(ethylene-co-vinyl phosphonic acid). In these copolymerizations, reversible coordination of the phosphonate moieties of free monomer as well as chelate formation by incorporated monomer retards chain growth as also evidenced by relative binding studies of diethyl phosphonate towards 1. Post-polymerization emulsification of poly(ethylene-co-vinyl phosphonic acid) together with CdSe/CdS quantum dots (QDs) yields submicron (ca. 50 nm from dynamic light scattering (DLS) and transmission electron microscopy (TEM)) polymer particles with the QDs embedded in the functionalized polyethylene in a nonaggregated fashion. This embedding benefits the fluorescence behavior in terms of continuous emission and life-time as revealed by wide-field fluorescence measurements. These composite particle dispersions are employed as a ″masterbatch" together with an aqueous high density polyethylene (HDPE) dispersion to generate thin films (by spin-coating) and bulk materials (from the melt), respectively, in which the inorganic nanoparticles remain highly disperse. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Discovery of a Phosphonoacetic Acid Derived Natural Product by Pathway Refactoring.

PubMed

Freestone, Todd S; Ju, Kou-San; Wang, Bin; Zhao, Huimin

2017-02-17

The activation of silent natural product gene clusters is a synthetic biology problem of great interest. As the rate at which gene clusters are identified outpaces the discovery rate of new molecules, this unknown chemical space is rapidly growing, as too are the rewards for developing technologies to exploit it. One class of natural products that has been underrepresented is phosphonic acids, which have important medical and agricultural uses. Hundreds of phosphonic acid biosynthetic gene clusters have been identified encoding for unknown molecules. Although methods exist to elicit secondary metabolite gene clusters in native hosts, they require the strain to be amenable to genetic manipulation. One method to circumvent this is pathway refactoring, which we implemented in an effort to discover new phosphonic acids from a gene cluster from Streptomyces sp. strain NRRL F-525. By reengineering this cluster for expression in the production host Streptomyces lividans, utility of refactoring is demonstrated with the isolation of a novel phosphonic acid, O-phosphonoacetic acid serine, and the characterization of its biosynthesis. In addition, a new biosynthetic branch point is identified with a phosphonoacetaldehyde dehydrogenase, which was used to identify additional phosphonic acid gene clusters that share phosphonoacetic acid as an intermediate.

Interface engineering in high-performance low-voltage organic thin-film transistors based on 2,7-dialkyl-[1]benzothieno[3,2-b][1]benzothiophenes.

PubMed

Amin, Atefeh Y; Reuter, Knud; Meyer-Friedrichsen, Timo; Halik, Marcus

2011-12-20

We investigated two different (2,7-dialkyl-[1]benzothieno[3,2-b][1]benzothiophenes; C(n)-BTBT-C(n), where n = 12 or 13) semiconductors in low-voltage operating thin-film transistors. By choosing functional molecules in nanoscaled hybrid dielectric layers, we were able to tune the surface energy and improve device characteristics, such as leakage current and hysteresis. The dipolar nature of the self-assembled molecules led to a shift in the threshold voltage. All devices exhibited high charge carrier mobilities of 0.6-7.0 cm(2) V(-1) s(-1). The thin-film morphology of BTBT was studied by means of atomic force microscopy (AFM), presented a dependency upon the surface energy of the self-assembled monolayer (SAM) hybrid dielectrics but not upon the device performance. The use of C(13)-BTBT-C(13) on hybrid dielectrics of AlO(x) and a F(15)C(18)-phosphonic acid monolayer led to devices with a hole mobility of 1.9 cm(2) V(-1) s(-1) at 3 V, on/off ratio of 10(5), small device-device variation of mobility, and a threshold voltage of only -0.9 V, thus providing excellent characteristics for further integration. © 2011 American Chemical Society

Adsorbed States of phosphonate derivatives of N-heterocyclic aromatic compounds, imidazole, thiazole, and pyridine on colloidal silver: comparison with a silver electrode.

PubMed

Podstawka, Edyta; Olszewski, Tomasz K; Boduszek, Bogdan; Proniewicz, Leonard M

2009-09-03

Here, we report a systematic surface-enhanced Raman spectroscopy (SERS) study of the structures of phosphonate derivatives of the N-heterocyclic aromatic compounds imidazole (ImMeP ([hydroxy(1H-imidazol-5-yl)methyl]phosphonic acid) and (ImMe)(2)P (bis[hydroxy-(1H-imidazol-4-yl)-methyl]phosphinic acid)), thiazole (BAThMeP (butylaminothiazol-2-yl-methyl)phosphonic acid) and BzAThMeP (benzylaminothiazol-2-yl-methyl)phosphonic acid)), and pyridine ((PyMe)(2)P (bis[(hydroxypyridin-3-yl-methyl)]phosphinic acid)) adsorbed on nanometer-sized colloidal particles. We compared these structures to those on a roughened silver electrode surface to determine the relationship between the adsorption strength and the geometry. For example, we showed that all of these biomolecules interact with the colloidal surface through aromatic rings. However, for BzAThMeP, a preferential interaction between the benzene ring and the colloidal silver surface is observed more so than that between the thiazole ring and this substrate. The PC(OH)C fragment does not take part in the adsorption process, and the phosphonate moiety of ImMeP and (ImMe)(2)P, being removed from the surface, only assists in this process.

A ω-mercaptoundecylphosphonic acid chemically modified gold electrode for uranium determination in waters in presence of organic matter.

PubMed

Merli, Daniele; Protti, Stefano; Labò, Matteo; Pesavento, Maria; Profumo, Antonella

2016-05-01

A chemically modified electrode (CME) on a gold surface assembled with a ω-phosphonic acid terminated thiol was investigated for its capability to complex uranyl ions. The electrode, characterized by electrochemical techniques, demonstrated to be effective for the determination of uranyl at sub-μgL(-1) level by differential pulse adsorptive stripping voltammetry (DPAdSV) in environmental waters, also in presence of humic matter and other potential chelating agents. The accuracy of the measurements was investigated employing as model probes ligands of different complexing capability (humic acids and EDTA). Copyright © 2016 Elsevier B.V. All rights reserved.

Preliminary assessment of developmental toxicity of Perfluorinated Phosphonic Acid in mice

EPA Science Inventory

Perfluorinated phosphonic acids (PFPAs) are a third member of the perfluoroalkyl acid (PFAA) family, and are structurally similar to the perfluoroalkyl sulfonates and perfluoroalkyl carboxylates. These emerging chemicals have recently been detected in the environment, particularl...

Developmental Toxicity of Perfluorinated Phosphonic Acids in Mice

EPA Science Inventory

Perfluorinated phosphonic acids (PFPAs) are a third member of the perfluoroalkyl acid (PFAA) family, and are structurally similar to the perfluoroalkyl sulfonates and perfluoroalkyl carboxylates. PFPAs are used primarily as a surfactant defoaming agent in pesticide production. Re...

Phosphonic Acids on an Atomically Defined Oxide Surface: The Binding Motif Changes with Surface Coverage.

PubMed

Schuschke, Christian; Schwarz, Matthias; Hohner, Chantal; Silva, Thais N; Fromm, Lukas; Döpper, Tibor; Görling, Andreas; Libuda, Jörg

2018-04-19

We have studied the anchoring mechanism of a phosphonic acid on an atomically defined oxide surface. Using time-resolved infrared reflection absorption spectroscopy, we investigated the reaction of deuterated phenylphosphonic acid (DPPA, C 6 H 5 PO 3 D 2 ) with an atomically defined Co 3 O 4 (111) surface in situ during film growth by physical vapor deposition. We show that the binding motif of the phosphonate anchor group changes as a function of coverage. At low coverage, DPPA binds in the form of a chelating tridentate phosphonate, while a transition to a chelating bidentate occurs close to monolayer saturation coverage. However, the coverage-dependent change in the binding motif is not associated with a major change of the molecular orientation, suggesting that the rigid phosphonate linker always maintains the DPPA in a strongly tilted orientation irrespective of the surface coverage.

Effects of Perfluorinated Phosphonic Acid Exposure during pregnancy in the mouse

EPA Science Inventory

Perfluorinated phosphonic acids (PFPAs) are a member of the perfluoroalkyl acid (PFAA) family, and are structurally similar to the perfluoroalkyl sulfonates and perfluoroalkyl carboxylates. These chemicals have recently been detected in the environment, particularly in surface wa...

Preparation of polyvinyl alcohol graphene oxide phosphonate film and research of thermal stability and mechanical properties.

PubMed

Li, Jihui; Song, Yunna; Ma, Zheng; Li, Ning; Niu, Shuai; Li, Yongshen

2018-05-01

In this article, flake graphite, nitric acid, peroxyacetic acid and phosphoric acid are used to prepare graphene oxide phosphonic and phosphinic acids (GOPAs), and GOPAs and polyvinyl alcohol (PVA) are used to synthesize polyvinyl alcohol graphene oxide phosphonate and phosphinate (PVAGOPs) in the case of faint acidity and ultrasound irradiation, and PVAGOPs are used to fabricate PVAGOPs film, and the structure and morphology of GOPAs, PVAGOPs and PVAGOPs film are characterized, and the thermal stability and mechanical properties of PVAGOPs film are investigated. Based on these, it has been proved that GOPAs consist of graphene oxide phosphonic acid and graphene oxide phosphinic acid, and there are CP covalent bonds between them, and PVAGOPs are composed of GOPAs and PVA, and there are six-member lactone rings between GOPAs and PVA, and the thermal stability and mechanical properties of PVAGOPs film are improved effectively. Copyright © 2018 Elsevier B.V. All rights reserved.

Quantitative structure-property relationship (correlation analysis) of phosphonic acid-based chelates in design of MRI contrast agent.

PubMed

Tiwari, Anjani K; Ojha, Himanshu; Kaul, Ankur; Dutta, Anupama; Srivastava, Pooja; Shukla, Gauri; Srivastava, Rakesh; Mishra, Anil K

2009-07-01

Nuclear magnetic resonance imaging is a very useful tool in modern medical diagnostics, especially when gadolinium (III)-based contrast agents are administered to the patient with the aim of increasing the image contrast between normal and diseased tissues. With the use of soft modelling techniques such as quantitative structure-activity relationship/quantitative structure-property relationship after a suitable description of their molecular structure, we have studied a series of phosphonic acid for designing new MRI contrast agent. Quantitative structure-property relationship studies with multiple linear regression analysis were applied to find correlation between different calculated molecular descriptors of the phosphonic acid-based chelating agent and their stability constants. The final quantitative structure-property relationship mathematical models were found as--quantitative structure-property relationship Model for phosphonic acid series (Model 1)--log K(ML) = {5.00243(+/-0.7102)}- MR {0.0263(+/-0.540)}n = 12 l r l = 0.942 s = 0.183 F = 99.165 quantitative structure-property relationship Model for phosphonic acid series (Model 2)--log K(ML) = {5.06280(+/-0.3418)}- MR {0.0252(+/- .198)}n = 12 l r l = 0.956 s = 0.186 F = 99.256.

Bifunctional phenyl monophosphonic/sulfonic acid ion exchange resin and process for using the same

DOEpatents

Alexandratos, Spiro; Shelley, Christopher A.; Horwitz, E. Philip; Chiarizia, Renato

2001-01-01

A cross-linked water-insoluble ion exchange resin comprised of polymerized monomers having a phenyl ring is disclosed. A contemplated resin contains (i) polymerized phenyl ring-containing monomers having a phosphonic acid ligand linked to the phenyl ring, (ii) about 2 to about 5 millimoles per gram (mmol/g) of phosphorus as phosphonic acid ligands, and (iii) a sufficient amount of a sulfonic acid ligand such that the ratio of mmol/g of phosphonic acid to mmol/g sulfonic acid is up to 3:1. A process for removing polyvalent metal cations from aqueous solution, and a process for removing iron(III) cations from acidic copper(II) cation-containing solutions that utilize the contemplated resin or other resins are disclosed.

Bifunctional phenyl monophosphonic/sulfonic acid ion exchange resin and process for using the same

DOEpatents

Alexandratos, Spiro; Shelley, Christopher A.; Horwitz, E. Philip; Chiarizia, Renato; Gula, Michael J.; Xue, Sui; Harvey, James T.

2002-01-01

A cross-linked water-insoluble ion exchange resin comprised of polymerized monomers having a phenyl ring is disclosed. A contemplated resin contains (i) polymerized phenyl ring-containing monomers having a phosphonic acid ligand linked to the phenyl ring, (ii) about 2 to about 5 millimoles per gram (mmol/g) of phosphorus as phosphonic acid ligands, and (iii) a sufficient amount of a sulfonic acid ligand such that the ratio of mmol/g of phosphonic acid to mmol/g sulfonic acid is up to 3:1. A process for removing polyvalent metal cations from aqueous solution, and a process for removing iron(III) cations from acidic copper(II) cation-containing solutions that utilize the contemplated resin or other resins are disclosed.

Discovery of phosphonic acid natural products by mining the genomes of 10,000 actinomycetes.

PubMed

Ju, Kou-San; Gao, Jiangtao; Doroghazi, James R; Wang, Kwo-Kwang A; Thibodeaux, Christopher J; Li, Steven; Metzger, Emily; Fudala, John; Su, Joleen; Zhang, Jun Kai; Lee, Jaeheon; Cioni, Joel P; Evans, Bradley S; Hirota, Ryuichi; Labeda, David P; van der Donk, Wilfred A; Metcalf, William W

2015-09-29

Although natural products have been a particularly rich source of human medicines, activity-based screening results in a very high rate of rediscovery of known molecules. Based on the large number of natural product biosynthetic genes in microbial genomes, many have proposed "genome mining" as an alternative approach for discovery efforts; however, this idea has yet to be performed experimentally on a large scale. Here, we demonstrate the feasibility of large-scale, high-throughput genome mining by screening a collection of over 10,000 actinomycetes for the genetic potential to make phosphonic acids, a class of natural products with diverse and useful bioactivities. Genome sequencing identified a diverse collection of phosphonate biosynthetic gene clusters within 278 strains. These clusters were classified into 64 distinct groups, of which 55 are likely to direct the synthesis of unknown compounds. Characterization of strains within five of these groups resulted in the discovery of a new archetypical pathway for phosphonate biosynthesis, the first (to our knowledge) dedicated pathway for H-phosphinates, and 11 previously undescribed phosphonic acid natural products. Among these compounds are argolaphos, a broad-spectrum antibacterial phosphonopeptide composed of aminomethylphosphonate in peptide linkage to a rare amino acid N(5)-hydroxyarginine; valinophos, an N-acetyl l-Val ester of 2,3-dihydroxypropylphosphonate; and phosphonocystoximate, an unusual thiohydroximate-containing molecule representing a new chemotype of sulfur-containing phosphonate natural products. Analysis of the genome sequences from the remaining strains suggests that the majority of the phosphonate biosynthetic repertoire of Actinobacteria has been captured at the gene level. This dereplicated strain collection now provides a reservoir of numerous, as yet undiscovered, phosphonate natural products.

Discovery of phosphonic acid natural products by mining the genomes of 10,000 actinomycetes

PubMed Central

Ju, Kou-San; Gao, Jiangtao; Doroghazi, James R.; Wang, Kwo-Kwang A.; Thibodeaux, Christopher J.; Li, Steven; Metzger, Emily; Fudala, John; Su, Joleen; Zhang, Jun Kai; Lee, Jaeheon; Cioni, Joel P.; Evans, Bradley S.; Hirota, Ryuichi; Labeda, David P.; van der Donk, Wilfred A.; Metcalf, William W.

2015-01-01

Although natural products have been a particularly rich source of human medicines, activity-based screening results in a very high rate of rediscovery of known molecules. Based on the large number of natural product biosynthetic genes in microbial genomes, many have proposed “genome mining” as an alternative approach for discovery efforts; however, this idea has yet to be performed experimentally on a large scale. Here, we demonstrate the feasibility of large-scale, high-throughput genome mining by screening a collection of over 10,000 actinomycetes for the genetic potential to make phosphonic acids, a class of natural products with diverse and useful bioactivities. Genome sequencing identified a diverse collection of phosphonate biosynthetic gene clusters within 278 strains. These clusters were classified into 64 distinct groups, of which 55 are likely to direct the synthesis of unknown compounds. Characterization of strains within five of these groups resulted in the discovery of a new archetypical pathway for phosphonate biosynthesis, the first (to our knowledge) dedicated pathway for H-phosphinates, and 11 previously undescribed phosphonic acid natural products. Among these compounds are argolaphos, a broad-spectrum antibacterial phosphonopeptide composed of aminomethylphosphonate in peptide linkage to a rare amino acid N5-hydroxyarginine; valinophos, an N-acetyl l-Val ester of 2,3-dihydroxypropylphosphonate; and phosphonocystoximate, an unusual thiohydroximate-containing molecule representing a new chemotype of sulfur-containing phosphonate natural products. Analysis of the genome sequences from the remaining strains suggests that the majority of the phosphonate biosynthetic repertoire of Actinobacteria has been captured at the gene level. This dereplicated strain collection now provides a reservoir of numerous, as yet undiscovered, phosphonate natural products. PMID:26324907

Water-soluble polymers and compositions thereof

DOEpatents

Smith, B.F.; Robison, T.W.; Gohdes, J.W.

1999-04-06

Water-soluble polymers including functionalization from the group of amino groups, carboxylic acid groups, phosphonic acid groups, phosphonic ester groups, acylpyrazolone groups, hydroxamic acid groups, aza crown ether groups, oxy crown ethers groups, guanidinium groups, amide groups, ester groups, aminodicarboxylic groups, permethylated polyvinylpyridine groups, permethylated amine groups, mercaptosuccinic acid groups, alkyl thiol groups, and N-alkylthiourea groups are disclosed.

Water-soluble polymers and compositions thereof

DOEpatents

Smith, Barbara F.; Robison, Thomas W.; Gohdes, Joel W.

2002-01-01

Water-soluble polymers including functionalization from the group of amino groups, carboxylic acid groups, phosphonic acid groups, phosphonic ester groups, acylpyrazolone groups, hydroxamic acid groups, aza crown ether groups, oxy crown ethers groups, guanidinium groups, amide groups, ester groups, aminodicarboxylic groups, permethylated polvinylpyridine groups, permethylated amine groups, mercaptosuccinic acid groups, alkyl thiol groups, and N-alkylthiourea groups are disclosed.

Water-soluble polymers and compositions thereof

DOEpatents

Smith, Barbara F.; Robison, Thomas W.; Gohdes, Joel W.

1999-01-01

Water-soluble polymers including functionalization from the group of amino groups, carboxylic acid groups, phosphonic acid groups, phosphonic ester groups, acylpyrazolone groups, hydroxamic acid groups, aza crown ether groups, oxy crown ethers groups, guanidinium groups, amide groups, ester groups, aminodicarboxylic groups, permethylated polyvinylpyridine groups, permethylated amine groups, mercaptosuccinic acid groups, alkyl thiol groups, and N-alkylthiourea groups are disclosed.

"Nickel Nanoflowers" with Surface-Attached Fluoropolymer Networks by C,H Insertion for the Generation of Metallic Superhydrophobic Surfaces.

PubMed

Hönes, Roland; Rühe, Jürgen

2018-05-08

Metallic superhydrophobic surfaces (SHSs) combine the attractive properties of metals, such as ductility, hardness, and conductivity, with the favorable wetting properties of nanostructured surfaces. Moreover, they promise additional benefits with respect to corrosion protection. For the modification of the intrinsically polar and hydrophilic surfaces of metals, a new method has been developed to deposit a long-term stable, highly hydrophobic coating, using nanostructured Ni surfaces as an example. Such substrates were chosen because the deposition of a thin Ni layer is a common choice for enhancing corrosion resistance of other metals. As the hydrophobic coating, we propose a thin film of an extremely hydrophobic fluoropolymer network. To form this network, a thin layer of a fluoropolymer precursor is deposited on the Ni substrate which includes a comonomer that is capable of C,H insertion cross-linking (CHic). Upon UV irradiation or heating, the cross-linker units become activated and the thin glassy film of the precursor is transformed into a polymer network that coats the surface conformally and permanently, as shown by extensive extraction experiments. To achieve an even higher stability, the same precursor film can also be transformed into a chemically surface-attached network by depositing a self-assembled monolayer of an alkane phosphonic acid on the Ni before coating with the precursor. During cross-linking, by the same chemical process, the growing polymer network will simultaneously attach to the alkane phosphonic acid layer at the surface of the metal. This strategy has been used to turn fractal Ni "nanoflower" surfaces grown by anisotropic electroplating into SHSs. The wetting characteristics of the obtained nanostructured metallic surfaces are studied. Additionally, the corrosion protection effect and the significant mechanical durability are demonstrated.

Durability of polymer/metal interfaces under cyclic loading

NASA Astrophysics Data System (ADS)

Du, Tianbao

Fatigue crack growth along metal/epoxy interface was examined in an aqueous environment and under mixed-mode conditions. A stress corrosion cracking mechanism was identified in this process. The fatigue crack growth rate in an aqueous environment was increased by several orders of magnitude and the fatigue threshold decreased by a factor of 10. The loss of adhesion in the aqueous environment was induced by the hydration of the surface oxide which resulted in a hydroxide with poor adhesion to the substrate metal. Self-assembled monolayer of long chain alkyl phosphonic acid and amino phosphonic acid were synthesized to enhance the adhesion and improve the durability of Al/epoxy interfacial bonding system. The same approach was taken to promote adhesion between copper and epoxy, where a two-component coupling system of 11-mercapto-1-undercanol and 3-aminopropyltriethoxysilane provided the most significant improvement in the copper/epoxy adhesion. The mixed-mode was applied by a piezoelectric actuator. Subcritical crack growth was observed along the epoxy/aluminum interface and the growth rate was found to depend on the magnitude of the applied electric field. Kinetics of the crack growth was correlated with the piezoelectric driving force. The resulting crack growth behavior was compared with the results from the conventional mechanical testing technique. Large differences were found between these two methods. Using this newly developed technique, effects of loading mode and frequency were studied. The fatigue resistance was found to increase with the mode II component and was expressed as a function of the KII/K I ratio. A strong frequency effect was observed for the subcritical crack growth along the Al/Epoxy interface, their fatigue resistance increased with the testing frequency.

Effects of self-assembled monolayer structural order, surface homogeneity and surface energy on pentacene morphology and thin film transistor device performance.

PubMed

Hutchins, Daniel Orrin; Weidner, Tobias; Baio, Joe; Polishak, Brent; Acton, Orb; Cernetic, Nathan; Ma, Hong; Jen, Alex K-Y

2013-01-04

A systematic study of six phosphonic acid (PA) self-assembled monolayers (SAMs) with tailored molecular structures is performed to evaluate their effectiveness as dielectric modifying layers in organic field-effect transistors (OFETs) and determine the relationship between SAM structural order, surface homogeneity, and surface energy in dictating device performance. SAM structures and surface properties are examined by near edge X-ray absorption fine structure (NEXAFS) spectroscopy, contact angle goniometry, and atomic force microscopy (AFM). Top-contact pentacene OFET devices are fabricated on SAM modified Si with a thermally grown oxide layer as a dielectric. For less ordered methyl- and phenyl-terminated alkyl ~(CH 2 ) 12 PA SAMs of varying surface energies, pentacene OFETs show high charge carrier mobilities up to 4.1 cm 2 V -1 s -1 . It is hypothesized that for these SAMs, mitigation of molecular scale roughness and subsequent control of surface homogeneity allow for large pentacene grain growth leading to high performance pentacene OFET devices. PA SAMs that contain bulky terminal groups or are highly crystalline in nature do not allow for a homogenous surface at a molecular level and result in charge carrier mobilities of 1.3 cm 2 V -1 s -1 or less. For all molecules used in this study, no causal relationship between SAM surface energy and charge carrier mobility in pentacene FET devices is observed.

Effects of self-assembled monolayer structural order, surface homogeneity and surface energy on pentacene morphology and thin film transistor device performance

PubMed Central

Hutchins, Daniel Orrin; Weidner, Tobias; Baio, Joe; Polishak, Brent; Acton, Orb; Cernetic, Nathan; Ma, Hong; Jen, Alex K.-Y.

2013-01-01

A systematic study of six phosphonic acid (PA) self-assembled monolayers (SAMs) with tailored molecular structures is performed to evaluate their effectiveness as dielectric modifying layers in organic field-effect transistors (OFETs) and determine the relationship between SAM structural order, surface homogeneity, and surface energy in dictating device performance. SAM structures and surface properties are examined by near edge X-ray absorption fine structure (NEXAFS) spectroscopy, contact angle goniometry, and atomic force microscopy (AFM). Top-contact pentacene OFET devices are fabricated on SAM modified Si with a thermally grown oxide layer as a dielectric. For less ordered methyl- and phenyl-terminated alkyl ~(CH2)12 PA SAMs of varying surface energies, pentacene OFETs show high charge carrier mobilities up to 4.1 cm2 V−1 s−1. It is hypothesized that for these SAMs, mitigation of molecular scale roughness and subsequent control of surface homogeneity allow for large pentacene grain growth leading to high performance pentacene OFET devices. PA SAMs that contain bulky terminal groups or are highly crystalline in nature do not allow for a homogenous surface at a molecular level and result in charge carrier mobilities of 1.3 cm2 V−1 s−1 or less. For all molecules used in this study, no causal relationship between SAM surface energy and charge carrier mobility in pentacene FET devices is observed. PMID:24086795

Immobilisation of an antibacterial drug to Ti6Al4V components fabricated using selective laser melting

NASA Astrophysics Data System (ADS)

Vaithilingam, Jayasheelan; Kilsby, Samuel; Goodridge, Ruth D.; Christie, Steven D. R.; Edmondson, Steve; Hague, Richard J. M.

2014-09-01

Bacterial infections from biomedical implants and surgical devices are a major problem in orthopaedic, dental and vascular surgery. Although the sources of contaminations that lead to bacterial infections are known, it is not possible to control or avoid such infections completely. In this study, an approach to immobilise Ciprofloxacin® (an antibacterial drug) to phosphonic acid based self-assembled monolayers (SAMs) adsorbed on a selectively laser melted (SLM) Ti6Al4V structure, has been presented. X-ray photoelectron spectroscopy (XPS) and static water contact angle measurements confirmed the attachment of SAMs and the drug. Results showed that Ciprofloxacin® is highly stable under the oxidative conditions used in this study. In-vitro stability was estimated by immersing the Ciprofloxacin® immobilised substrates in 10 mM of Tris-HCl buffer (pH-7.4) for 42 days. The Tris-HCl buffer was analysed using UV-vis spectrophotometry at 7, 14, 28 and 42 day time intervals to determine the release of the immobilised drug. The drug was observed to release in a sustained manner. 50% of the drug was released after 4 weeks with approximately 40% of the drug remaining after 6 weeks. Antibacterial susceptibility tests revealed that the immobilised drug was therapeutically active upon its release. This study demonstrates the potential to use self-assembled monolayers to modify SLM fabricated surfaces with therapeutics.

Isopropyl methyl phosphonic acid (IMPA)

Integrated Risk Information System (IRIS)

Isopropyl methyl phosphonic acid ( IMPA ) ; CASRN 1832 - 54 - 8 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assess

The Effects of Anchor Groups on (1) TiO2-Catalyzed Photooxidation and (2) Linker-Assisted Assembly on TiO2

NASA Astrophysics Data System (ADS)

Anderson, Ian Mark

Quantum dot-sensitized solar cells (QDSSCs) are a popular target for research due to their potential for highly efficient, easily tuned absorption. Typically, light is absorbed by quantum dots attached to a semiconductor substrate, such as TiO2, via bifunctional linker molecules. This research aims to create a patterned monolayer of linker molecules on a TiO2 film, which would in turn allow the attachment of a patterned layer of quantum dots. One method for the creation of a patterned monolayer is the functionalization of a TiO2 film with a linker molecule, followed by illumination with a laser at 355 nm. This initiates a TiO 2-catalyzed oxidation reaction, causing loss of surface coverage. A second linker molecule can then be adsorbed onto the TiO2 surface in the illuminated area. Towards that end, the behaviors of carboxylic and phosphonic acids adsorbed on TiO2 have been studied. TiO2 films were functionalized by immersion in solutions a single adsorbate and surface coverage was determined by IR spectroscopy. It is shown that phosphonic acids attain higher surface coverage than carboxylic acids, and will displace them from TiO2 when in a polar solvent. Alkyl chain lengths, which can influence stabilities of monolayers, are shown not to have an effect on this relationship. Equilibrium binding data for the adsorption of n-hexadecanoic acid to TiO2 from a THF solution are presented. It is shown that solvent polarity can affect monolayer stability; carboxylates and phosphonates undergo more desorption into polar solvents than nonpolar. Through illumination, it was possible to remove nearly all adsorbed linkers from TiO2. However, the illuminated areas were found not to be receptive to attachment by a second adsorbate. A possible reason for this behavior is presented. I also report on the synthesis and characterization of a straight-chain, thiol-terminated phosphonic acid. Initial experiments involving monolayer formation and quantum dot attachment are presented. Finally, it was found that quantum dots attach in high amounts to linker-functionalized TiO2 when suspended in pyridine. This increased surface attachment was present even when the linker molecule used lacked a functional group which would bind to the CdSe surface.

Interplay between Vacuum-Grown Monolayers of Alkylphosphonic Acids and the Performance of Organic Transistors Based on Dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene.

PubMed

Hannah, Stuart; Cardona, Javier; Lamprou, Dimitrios A; Šutta, Pavol; Baran, Peter; Al Ruzaiqi, Afra; Johnston, Karen; Gleskova, Helena

2016-09-28

Monolayers of six alkylphosphonic acids ranging from C8 to C18 were prepared by vacuum evaporation and incorporated into low-voltage organic field-effect transistors based on dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT). Similar to solution-assembled monolayers, the molecular order for vacuum-deposited monolayers improved with increasing length of the aliphatic tail. At the same time, Fourier transform infrared (FTIR) measurements suggested lower molecular coverage for longer phosphonic acids. The comparison of FTIR and vibration frequencies calculated by density functional theory indicated that monodentate bonding does not occur for any phosphonic acid. All monolayers exhibited low surface energy of ∼17.5 mJ/m(2) with a dominating Lifshitz-van der Waals component. Their surface roughness was comparable, while the nanomechanical properties were varied but not correlated to the length of the molecule. However, large improvement in transistor performance was observed with increasing length of the aliphatic tail. Upon going from C8 to C18, the mean threshold voltage decreased from -1.37 to -1.24 V, the field-effect mobility increased from 0.03 to 0.33 cm(2)/(V·s), the off-current decreased from ∼8 × 10(-13) to ∼3 × 10(-13) A, and for transistors with L = 30 μm the on-current increased from ∼3 × 10(-8) to ∼2 × 10(-6) A, and the on/off-current ratio increased from ∼3 × 10(4) to ∼4 × 10(6). Similarly, transistors with longer phosphonic acids exhibited much better air and bias-stress stability. The achieved transistor performance opens up a completely "dry" fabrication route for ultrathin dielectrics and low-voltage organic transistors.

Study of Perfluorophosphonic Acid Surface Modifications on Zinc Oxide Nanoparticles.

PubMed

Quiñones, Rosalynn; Shoup, Deben; Behnke, Grayce; Peck, Cynthia; Agarwal, Sushant; Gupta, Rakesh K; Fagan, Jonathan W; Mueller, Karl T; Iuliucci, Robbie J; Wang, Qiang

2017-11-28

In this study, perfluorinated phosphonic acid modifications were utilized to modify zinc oxide (ZnO) nanoparticles because they create a more stable surface due to the electronegativity of the perfluoro head group. Specifically, 12-pentafluorophenoxydodecylphosphonic acid, 2,3,4,5,6-pentafluorobenzylphosphonic acid, and (1H,1H,2H,2H-perfluorododecyl)phosphonic acid have been used to form thin films on the nanoparticle surfaces. The modified nanoparticles were then characterized using infrared spectroscopy, X-ray photoelectron spectroscopy, and solid-state nuclear magnetic resonance spectroscopy. Dynamic light scattering and scanning electron microscopy-energy dispersive X-ray spectroscopy were utilized to determine the particle size of the nanoparticles before and after modification, and to analyze the film coverage on the ZnO surfaces, respectively. Zeta potential measurements were obtained to determine the stability of the ZnO nanoparticles. It was shown that the surface charge increased as the alkyl chain length increases. This study shows that modifying the ZnO nanoparticles with perfluorinated groups increases the stability of the phosphonic acids adsorbed on the surfaces. Thermogravimetric analysis was used to distinguish between chemically and physically bound films on the modified nanoparticles. The higher weight loss for 12-pentafluorophenoxydodecylphosphonic acid and (1H,1H,2H,2H-perfluorododecyl)phosphonic acid modifications corresponds to a higher surface concentration of the modifications, and, ideally, higher surface coverage. While previous studies have shown how phosphonic acids interact with the surfaces of ZnO, the aim of this study was to understand how the perfluorinated groups can tune the surface properties of the nanoparticles.

In situ chemical functionalization of gallium nitride with phosphonic acid derivatives during etching.

PubMed

Wilkins, Stewart J; Greenough, Michelle; Arellano, Consuelo; Paskova, Tania; Ivanisevic, Albena

2014-03-04

In situ functionalization of polar (c plane) and nonpolar (a plane) gallium nitride (GaN) was performed by adding (3-bromopropyl) phosphonic acid or propyl phosphonic acid to a phosphoric acid etch. The target was to modulate the emission properties and oxide formation of GaN, which was explored through surface characterization with atomic force microscopy, X-ray photoelectron spectroscopy, photoluminescence (PL), inductively coupled plasma-mass spectrometry, and water contact angle. The use of (3-bromopropyl) phosphonic acid and propyl phosphonic acid in phosphoric acid demonstrated lower amounts of gallium oxide formation and greater hydrophobicity for both sample sets, while also improving PL emission of polar GaN samples. In addition to crystal orientation, growth-related factors such as defect density in bulk GaN versus thin GaN films residing on sapphire substrates were investigated as well as their responses to in situ functionalization. Thin nonpolar GaN layers were the most sensitive to etching treatments due in part to higher defect densities (stacking faults and threading dislocations), which accounts for large surface depressions. High-quality GaN (both free-standing bulk polar and bulk nonpolar) demonstrated increased sensitivity to oxide formation. Room-temperature PL stands out as an excellent technique to identify nonradiative recombination as observed in the spectra of heteroepitaxially grown GaN samples. The chemical methods applied to tune optical and physical properties of GaN provide a quantitative framework for future novel chemical and biochemical sensor development.

pH-Dependence of Binding Constants and Desorption Rates of Phosphonate- and Hydroxamate-Anchored [Ru(bpy)3]2+ on TiO2 and WO3.

PubMed

Esarey, Samuel L; Bartlett, Bart M

2018-04-17

The binding constants and rate constants for desorption of the modified molecular dye [Ru(bpy) 3 ] 2+ anchored by either phosphonate or hydroxamate on the bipyridine ligand to anatase TiO 2 and WO 3 have been measured. In aqueous media at pH 1-10, repulsive electrostatic interactions between the negatively charged anchor and the negatively charged surface govern phosphonate desorption under neutral and basic conditions for TiO 2 anatase due to the high acidity of phosphonic acid (p K a,4 = 5.1). In contrast, the lower acidity of hydroxamate (p K a,1 = 6.5, p K a,2 = 9.1) leads to little change in adsorption/desorption properties as a function of pH from 1 to 7. The binding constant for hydroxamate is 10 3 in water, independent of pH in this range. These results are true for WO 3 as well, but are not reported at pH > 4 due to its Arrhenius acidity. Kinetics for desorption as a function of pH are reported, with a proposed mechanism for phosphonate desorption at high pH being the electrostatic repulsion of negative charges between the surface and the anionic anchor. Further, the hydroxamic acid anchor itself is likely the site of quasi-reversible redox activity in [Ru(bpy) 2 (2,2'-bpy-4,4'-(C(O)N(OH)) 2 )] 2+ , which does not lead to any measurable deterioration of the complex within 2 h of dark cyclic voltammogram scans in aqueous media. These results posit phosphonate as the preferred anchoring group under acidic conditions and hydroxamate for neutral/basic conditions.

Cellular membrane enrichment of self-assembling D-peptides for cell surface engineering.

PubMed

Wang, Huaimin; Wang, Youzhi; Han, Aitian; Cai, Yanbin; Xiao, Nannan; Wang, Ling; Ding, Dan; Yang, Zhimou

2014-06-25

We occasionally found that several self-assembling peptides containing D-amino acids would be preferentially enriched in cellular membranes at self-assembled stages while distributed evenly in the cytoplasma of cells at unassembled stages. Self-assembling peptides containing only Lamino acids distributed evenly in cytoplasma of cells at both self-assembled and unassembled stages. The self-assembling peptides containing D-amino acids could therefore be applied for engineering cell surface with peptides. More importantly, by integrating a protein binding peptide (a PDZ domain binding hexapeptide of WRESAI) with the self-assembling peptide containing D-amino acids, protein could also be introduced to the cell surface. This study not only provided a novel approach to engineer cell surface, but also highlighted the unusual properties and potential applications of self-assembling peptides containing D-amino acids in regenerative medicine, drug delivery, and tissue engineering.

A New Epoxy Bis-Phosphonate Crosslinker for Durable Fire Retardancy on Cotton

USDA-ARS?s Scientific Manuscript database

A new epoxy bis-phosphonate crosslinker for cotton [2-(dimethoxy-phosphorylmethyl)-oxiranylmethyl]-phosphonic acid dimethyl ester was prepared in two steps from 3-chloro-2-chloromethylpropene in 55% yield. The new monomer was characterized by proton and carbon NMR and GC-mass spectrometry. This cro...

Imidazoline phosphonic acids

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

Redmore, D.

1972-07-04

Nitrogen-heterocyclic phosphonic acids and derivatives are characterized by aminomethyl (or substituted methyl) phosphonic acids or derivatives thereof bonded directly or indirectly, i.e., through a N-side chain to the nitrogen atom in the heterocyclic ring, for example those containing in the molecule at least one of the following units: ..pi..Equation/sup -/ where represents a heterocyclic ring having a nitrogen atom on the ring; -R'N- represents an amino- terminated side chain attached directly to the ring nitrogen (which side chain may or may not be present); and ..pi..Equation/sup -/ represents a methyl (or substituted methyl) phosphonic acid group where M is hydrogen,more » an alcohol or a salt moiety, and X and Y are hydrogen or a substituted group such as alkyl, aryl, etc., of which one or 2 units may be present depending on the available nitrogen bonded by hydrogens, and to uses for these compounds, for example, as scale inhibitors, corrosion inhibitors, etc. (5 claims)« less

Determination of Fosetyl and Phosphonic Acid at 0.010 mg/kg Level by Ion Chromatography Tandem Mass Spectrometry.

PubMed

Bauer, Anna; Luetjohann, Jens; Rohn, Sascha; Kuballa, Juergen; Jantzen, Eckard

2018-01-10

A new sensitive, fast, and robust method using ion chromatography tandem mass spectrometry (IC-MS/MS) for the determination of fosetyl and phosphonic acid in plant-derived matrices was developed. For compensation of matrix effects and differences in recovery rates the isotopically labeled internal standard (ILIS) 18 O 3 -labeled phosphonic acid was added to the samples prior to the extraction of the target compounds. The validation of the method for the matrices tomato, apple, lemon, sultana, avocado, and wheat was performed according to the actual EU guidance document SANTE/11945/2015. The precision and accuracy were determined in five replicates at spiking levels of 0.010 and 0.100 mg/kg with recovery rates between 76 and 105% and RSDs between 1.2 and 17.8%. In this paper, it was achieved for the first time to detect both fosetyl and phosphonic acid at the reporting level of 0.010 mg/kg most relevant for organic plant food commodities.

DEGRADATION OF NITRILOTRIS (METHYLENEPHOSPHONIC ACID) AND RELATED (AMINO) PHOSPHONATE CHELATING AGENTS IN THE PRESENCE OF MANGANESE AND MOLECULAR OXYGEN. (R826376)

EPA Science Inventory

Phosphonates are used in an increasing variety of industrial and household
applications including cooling waters systems, oil production, textile industry,
and detergents. Phosphonates are not biodegraded during wastewater treatment but
instead are removed by adsor...

RADIATION STABILITY OF ORGANIC LIQUIDS. Semi-Annual Report No. 2 for July 1 to December 31, 1957

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

Wagner, R.M.

1958-01-14

Preliminary studies were completed on the nature and amount of the radiolysis products of dibutyl butanephosphonate, 50% dibutyl butanephosphonate- 50% Amsco 12582 mixture, diamyl pentanephosphonate, 50% diamyl pentanephosphonate- 50% Amsco 125-82 mixture, high level dose TBP, and dibutyl phosphoric acid, Results of analysis indicated that aliphatic phosphonates are superior to aliphatic phosphates, but inferior to aromaticaliphatic phosphonates in resistance to radiolytic degradation. Radiolysis data indicated that the phenyl group of phosphonates inhibited gas production when irradiated alone or in Amsco solution, howevcr the phenyl protective effect did not apply to acid production. Alipbatic phosphonates yielded lower G(acid) values than didmore » phenyl phosphonates, No large differences were observed in nature or yield of radiolysis products from the phosphonates. Comparison of radiolysis data of tributyl phosphate with that of aliphatic phosphonates, however, indicates reductions in G(gas) and G(acid) values of factors of 2 and 15, respectively due to the radiolytic stability of the phosphonate structure. Emulsification studies, comparing irradiated TBP and phosphonates, indicated no marked differences between the systems studied. The interpretation of results was complicated by the prevalence of three-phase phenomena due to the high dose levels employed. Tributyl phosphate, irradiated to 1900 whr/liter levels, was studied from the aspects of methods suitable for removal of radiolysis products, methods suitable for isolation of polymeric species, and identification of polymer constituents, Treatment of 1900 whr/liter TBP, diluted with Amsco 125-82 and virgin TBP, with a mixture of sodium and ammonium hydroxides was found to be more effective than simple caustic strip for restoring irradiated TBP to recycle condition. The effectiveness of the treatment was determined by measuring uranium distribution ratios using both spinner column and separatory funnel studies, Duolite A-2 anion exchange resin was used to remove acidic radiolysis products from 1900 whr/liter TBP prior to isolation of polymeric species by vacuum distillation, A G value of 0.91 for polymer was obtained. Cryoscopic studies with the polymer indicated a gross molecular weight of 840 to 850. G values for gas and polymer of 3.40 and 1.42 were obtained from irradiation of dibutyl phosphoric acid to 1280 whr/liter levels. These values are slightly higher than the corresponding values for tributyl phosphate. The solubility of thorium dibutyl phosphate in Amsco 125-82 was determined to be 0.1 g/liter at 26 C. Diethyl carbonate was evaluated as an extractant for uranium by separatory funnel and spinner column studies. The extraction is highly acid dependent and is sensitive to salt effects. Using 0.2M uranyl nitrate of both 6M and 8M nitric acid strengths as feeds at organic/ aqueous ratios of 1:2, uraniura separation factors of 0.45 and 0.82 were obtained. TBP-Amsco systems yield separation factors pf 5 under 2M nitric acid conditions. (For preceding period see AECCU-4051.) (auth)« less

Synthesis of a new family of acyclic nucleoside phosphonates, analogues of TPases transition states.

PubMed

Dayde, Bénédicte; Benzaria, Samira; Pierra, Claire; Gosselin, Gilles; Surleraux, Dominique; Volle, Jean-Noël; Pirat, Jean-Luc; Virieux, David

2012-05-07

A 6-step procedure was developed for the synthesis of a new family of acyclic nucleoside phosphonates (ANPs), "PHEEPA" [(2-pyrimidinyl-2-(2-hydroxyethoxy)ethyl)phosphonic acids] in overall yields ranging from 4.5% to 32%. These compounds, which possess on one side a hydroxy function and on the other side a phosphonate group, can be considered either as potential antiviral agents or as transition state analogues of nucleoside phosphorylases such as thymidine phosphorylase.

Overcoming the crystallization and designability issues in the ultrastable zirconium phosphonate framework system

DOE PAGES

Zheng, Tao; Yang, Zaixing; Gui, Daxiang; ...

2017-05-30

Metal-organic frameworks (MOFs) based on zirconium phosphonates exhibit superior chemical stability suitable for applications under harsh conditions. These compounds mostly exist as poorly crystallized precipitates, and precise structural information has therefore remained elusive. Furthermore, a zero-dimensional zirconium phosphonate cluster acting as secondary building unit has been lacking, leading to poor designability in this system. We overcome these challenges and obtain single crystals of three zirconium phosphonates that are suitable for structural analysis. Furthermore, these compounds are built by previously unknown isolated zirconium phosphonate clusters and exhibit combined high porosity and ultrastability even in fuming acids. SZ-2 possesses the largest voidmore » volume recorded in zirconium phosphonates and SZ-3 represents the most porous crystalline zirconium phosphonate and the only porous MOF material reported to survive in aqua regia. SZ-2 and SZ-3 can effectively remove uranyl ions from aqueous solutions over a wide pH range, and we have elucidated the removal mechanism.« less

Overcoming the crystallization and designability issues in the ultrastable zirconium phosphonate framework system

PubMed Central

Zheng, Tao; Yang, Zaixing; Gui, Daxiang; Liu, Zhiyong; Wang, Xiangxiang; Dai, Xing; Liu, Shengtang; Zhang, Linjuan; Gao, Yang; Chen, Lanhua; Sheng, Daopeng; Wang, Yanlong; Diwu, Juan; Wang, Jianqiang; Zhou, Ruhong; Chai, Zhifang; Albrecht-Schmitt, Thomas E.; Wang, Shuao

2017-01-01

Metal-organic frameworks (MOFs) based on zirconium phosphonates exhibit superior chemical stability suitable for applications under harsh conditions. These compounds mostly exist as poorly crystallized precipitates, and precise structural information has therefore remained elusive. Furthermore, a zero-dimensional zirconium phosphonate cluster acting as secondary building unit has been lacking, leading to poor designability in this system. Herein, we overcome these challenges and obtain single crystals of three zirconium phosphonates that are suitable for structural analysis. These compounds are built by previously unknown isolated zirconium phosphonate clusters and exhibit combined high porosity and ultrastability even in fuming acids. SZ-2 possesses the largest void volume recorded in zirconium phosphonates and SZ-3 represents the most porous crystalline zirconium phosphonate and the only porous MOF material reported to survive in aqua regia. SZ-2 and SZ-3 can effectively remove uranyl ions from aqueous solutions over a wide pH range, and we have elucidated the removal mechanism. PMID:28555656

Overcoming the crystallization and designability issues in the ultrastable zirconium phosphonate framework system

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

Zheng, Tao; Yang, Zaixing; Gui, Daxiang

Metal-organic frameworks (MOFs) based on zirconium phosphonates exhibit superior chemical stability suitable for applications under harsh conditions. These compounds mostly exist as poorly crystallized precipitates, and precise structural information has therefore remained elusive. Furthermore, a zero-dimensional zirconium phosphonate cluster acting as secondary building unit has been lacking, leading to poor designability in this system. We overcome these challenges and obtain single crystals of three zirconium phosphonates that are suitable for structural analysis. Furthermore, these compounds are built by previously unknown isolated zirconium phosphonate clusters and exhibit combined high porosity and ultrastability even in fuming acids. SZ-2 possesses the largest voidmore » volume recorded in zirconium phosphonates and SZ-3 represents the most porous crystalline zirconium phosphonate and the only porous MOF material reported to survive in aqua regia. SZ-2 and SZ-3 can effectively remove uranyl ions from aqueous solutions over a wide pH range, and we have elucidated the removal mechanism.« less

Self-assembled monolayers of alendronate on Ti6Al4V alloy surfaces enhance osteogenesis in mesenchymal stem cells

NASA Astrophysics Data System (ADS)

Rojo, Luis; Gharibi, Borzo; McLister, Robert; Meenan, Brian J.; Deb, Sanjukta

2016-07-01

Phosphonates have emerged as an alternative for functionalization of titanium surfaces by the formation of homogeneous self-assembled monolayers (SAMs) via Ti-O-P linkages. This study presents results from an investigation of the modification of Ti6Al4V alloy by chemisorption of osseoinductive alendronate using a simple, effective and clean methodology. The modified surfaces showed a tailored topography and surface chemistry as determined by SEM microscopy and RAMAN spectroscopy. X-ray photoelectron spectroscopy revealed that an effective mode of bonding is created between the metal oxide surface and the phosphate residue of alendronate, leading to formation of homogenous drug distribution along the surface. In-vitro studies showed that alendronate SAMs induce differentiation of hMSC to a bone cell phenotype and promote bone formation on modified surfaces. Here we show that this novel method for the preparation of functional coatings on titanium-based medical devices provides osseoinductive bioactive molecules to promote enhanced integration at the site of implantation.

Self-assembled monolayers of alendronate on Ti6Al4V alloy surfaces enhance osteogenesis in mesenchymal stem cells

PubMed Central

Rojo, Luis; Gharibi, Borzo; McLister, Robert; Meenan, Brian J.; Deb, Sanjukta

2016-01-01

Phosphonates have emerged as an alternative for functionalization of titanium surfaces by the formation of homogeneous self-assembled monolayers (SAMs) via Ti-O-P linkages. This study presents results from an investigation of the modification of Ti6Al4V alloy by chemisorption of osseoinductive alendronate using a simple, effective and clean methodology. The modified surfaces showed a tailored topography and surface chemistry as determined by SEM microscopy and RAMAN spectroscopy. X-ray photoelectron spectroscopy revealed that an effective mode of bonding is created between the metal oxide surface and the phosphate residue of alendronate, leading to formation of homogenous drug distribution along the surface. In-vitro studies showed that alendronate SAMs induce differentiation of hMSC to a bone cell phenotype and promote bone formation on modified surfaces. Here we show that this novel method for the preparation of functional coatings on titanium-based medical devices provides osseoinductive bioactive molecules to promote enhanced integration at the site of implantation. PMID:27468811

Self-assembling nucleic acid delivery vehicles via linear, water-soluble, cyclodextrin-containing polymers.

PubMed

Davis, M E; Pun, S H; Bellocq, N C; Reineke, T M; Popielarski, S R; Mishra, S; Heidel, J D

2004-01-01

Non-viral (synthetic) nucleic acid delivery systems have the potential to provide for the practical application of nucleic acid-based therapeutics. We have designed and prepared a tunable, non-viral nucleic acid delivery system that self-assembles with nucleic acids and centers around a new class of polymeric materials; namely, linear, water-soluble cyclodextrin-containing polymers. The relationships between polymer structure and gene delivery are illustrated, and the roles of the cyclodextrin moieties for minimizing toxicity and forming inclusion complexes in the self-assembly processes are highlighted. This vehicle is the first example of a polymer-based gene delivery system formed entirely by self-assembly.

Solid-State Densification of Spun-Cast Self-Assembled Monolayers for Use in Ultra-Thin Hybrid Dielectrics.

PubMed

Hutchins, Daniel O; Acton, Orb; Weidner, Tobias; Cernetic, Nathan; Baio, Joe E; Castner, David G; Ma, Hong; Jen, Alex K-Y

2012-11-15

Ultra-thin self-assembled monolayer (SAM)-oxide hybrid dielectrics have gained significant interest for their application in low-voltage organic thin film transistors (OTFTs). A [8-(11-phenoxy-undecyloxy)-octyl]phosphonic acid (PhO-19-PA) SAM on ultrathin AlO x (2.5 nm) has been developed to significantly enhance the dielectric performance of inorganic oxides through reduction of leakage current while maintaining similar capacitance to the underlying oxide structure. Rapid processing of this SAM in ambient conditions is achieved by spin coating, however, as-cast monolayer density is not sufficient for dielectric applications. Thermal annealing of a bulk spun-cast PhO-19-PA molecular film is explored as a mechanism for SAM densification. SAM density, or surface coverage, and order are examined as a function of annealing temperature. These SAM characteristics are probed through atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and near edge X-ray absorption fine structure spectroscopy (NEXAFS). It is found that at temperatures sufficient to melt the as-cast bulk molecular film, SAM densification is achieved; leading to a rapid processing technique for high performance SAM-oxide hybrid dielectric systems utilizing a single wet processing step. To demonstrate low-voltage devices based on this hybrid dielectric (with leakage current density of 7.7×10 -8 A cm -2 and capacitance density of 0.62 µF cm -2 at 3 V), pentacene thin-film transistors (OTFTs) are fabricated and yield sub 2 V operation and charge carrier mobilites of up to 1.1 cm 2 V -1 s -1 .

Solid-State Densification of Spun-Cast Self-Assembled Monolayers for Use in Ultra-Thin Hybrid Dielectrics

PubMed Central

Hutchins, Daniel O.; Acton, Orb; Weidner, Tobias; Cernetic, Nathan; Baio, Joe E.; Castner, David G.; Ma, Hong; Jen, Alex K.-Y.

2013-01-01

Ultra-thin self-assembled monolayer (SAM)-oxide hybrid dielectrics have gained significant interest for their application in low-voltage organic thin film transistors (OTFTs). A [8-(11-phenoxy-undecyloxy)-octyl]phosphonic acid (PhO-19-PA) SAM on ultrathin AlOx (2.5 nm) has been developed to significantly enhance the dielectric performance of inorganic oxides through reduction of leakage current while maintaining similar capacitance to the underlying oxide structure. Rapid processing of this SAM in ambient conditions is achieved by spin coating, however, as-cast monolayer density is not sufficient for dielectric applications. Thermal annealing of a bulk spun-cast PhO-19-PA molecular film is explored as a mechanism for SAM densification. SAM density, or surface coverage, and order are examined as a function of annealing temperature. These SAM characteristics are probed through atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and near edge X-ray absorption fine structure spectroscopy (NEXAFS). It is found that at temperatures sufficient to melt the as-cast bulk molecular film, SAM densification is achieved; leading to a rapid processing technique for high performance SAM-oxide hybrid dielectric systems utilizing a single wet processing step. To demonstrate low-voltage devices based on this hybrid dielectric (with leakage current density of 7.7×10−8 A cm−2 and capacitance density of 0.62 µF cm−2 at 3 V), pentacene thin-film transistors (OTFTs) are fabricated and yield sub 2 V operation and charge carrier mobilites of up to 1.1 cm2 V−1 s−1. PMID:24288423

ESTERASES OF THE POLYMORPHONUCLEAR LEUKOCYTE CAPABLE OF HYDROLYZING ACETYL DL-PHENYL-ALANINE β-NAPHTHYL ESTER

PubMed Central

Becker, Elmer L.; Ward, Peter A.

1969-01-01

Previous published work has led to the hypothesis that the activatable esterase of chemotaxis is a serine esterase of the rabbit polymorphonuclear leukocyte existing in an inert, phosphonate insusceptible form, which after activation is capable of hydrolyzing aromatic amino acid esters and being inhibited by phosphonates. In the present study, directed to the testing of this hypothesis, we have shown that rabbit peritoneal polymorphonuclear leukocytes contain three esterases capable of hydrolyzing the aromatic amino acid ester, acetyl DL-phenylalanine β-naphthyl ester. Two of these esterases, esterase 1 and esterase 2, are inhibited by various p-nitrophenyl ethyl phosphonate esters. The inhibition of each esterase is irreversible and progressive with time. When the logarithm of the esterase activity remaining after cell and inhibitor have been in contact for a constant time is plotted against the concentration of inhibitor, a straight line results. These results support the conclusion that both esterases are serine esterases. The third esterase, esterase 3, differs from the other two by its inability to be inactivated by any of the phosphonates no matter how high the concentration of phosphonate or prolonged the period of incubation of cell with phosphonate. The activity of esterase 1 is at least 10,000 times more easily inhibited by phosphonates than is that of esterase 2; incubating rabbit polymorphonuclear leukocytes for 15 min at 27°C with 10–9–10–8 M concentrations of various phosphonates inactivates esterase 1, but it required 10–6–10–4 M concentrations of the same phosphonates to inhibit esterase 2. The inhibition profiles of esterase 1 are distinctly different from those of esterase 2 when the two esterases are tested with the phenylalkylphosphonates, chloroalkylphosphonates, and alkylphosphonates. The inhibition profile of esterase 1 is essentially the same as that of the activatable esterase of chemotaxis obtained previously when the same three homologous series of phosphonates were tested for their ability to protect against deactivation by the chemotactic factor or give chemotactic-dependent inhibition. It is tentatively concluded that esterase 1 of the rabbit peritoneal neutrophil is the activated form of the activatable esterase of chemotaxis. PMID:5812915

Surface Patterning of Benzene Carboxylic Acids on Graphite: Influence of structure, solvent, and concentration on molecular self-assembly

NASA Astrophysics Data System (ADS)

Florio, Gina; Stiso, Kimberly; Campanelli, Joseph; Dessources, Kimberly; Folkes, Trudi

2012-02-01

Scanning tunneling microscopy (STM) was used to investigate the molecular self-assembly of four different benzene carboxylic acid derivatives at the liquid/graphite interface: pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid), trimellitic acid (1,2,4-benzenetricarboxylic acid), trimesic acid (1,3,5-benzenetricarboxylic acid), and 1,3,5-benzenetriacetic acid. A range of two dimensional networks are observed that depend sensitively on the number of carboxylic acids present, the nature of the solvent, and the solution concentration. We will describe our recent efforts to determine (a) the preferential two-dimensional structure(s) for each benzene carboxylic acid at the liquid/graphite interface, (b) the thermodynamic and kinetic factors influencing self-assembly (or lack thereof), (c) the role solvent plays in the assembly, (e) the effect of in situ versus ex situ dilution on surface packing density, and (f) the temporal evolution of the self-assembled monolayer. Results of computational analysis of analog molecules and model monolayer films will also be presented to aid assignment of network structures and to provide a qualitative picture of surface adsorption and network formation.

Construction of energy transfer pathways self-assembled from DNA-templated stacks of anthracene.

PubMed

Iwaura, Rika; Yui, Hiroharu; Someya, Yuu; Ohnishi-Kameyama, Mayumi

2014-01-05

We describe optical properties of anthracene stacks formed from single-component self-assembly of thymidylic acid-appended anthracene 2,6-bis[5-(3'-thymidylic acid)pentyloxy] anthracene (TACT) and the binary self-assembly of TACT and complementary 20-meric oligoadenylic acid (TACT/dA20) in an aqueous buffer. UV-Vis and emission spectra for the single-component self-assembly of TACT and the binary self-assembly of TACT/dA20 were very consistent with stacked acene moieties in both self-assemblies. Interestingly, time-resolved fluorescence spectra from anthracene stacks exhibited very different features of the single-component and binary self-assemblies. In the single-component self-assembly of TACT, a dynamic Stokes shift (DSS) and relatively short fluorescence lifetime (τ=0.35ns) observed at around 450nm suggested that the anthracene moieties were flexible. Moreover, a broad emission at 530nm suggested the formation of an excited dimer (excimer). In the binary self-assembly of TACT/dA20, we detected a broad, red-shifted emission component at 534nm with a lifetime (τ=0.4ns) shorter than that observed in the TACT single-component self-assembly. Combining these results with the emission spectrum of the binary self-assembly of TACT/5'-HEX dA20, we concluded that the energy transfer pathway was constructed by columnar anthracene stacks formed from the DNA-templated self-assembly of TACT. Copyright © 2013 Elsevier B.V. All rights reserved.

Americium(III) capture using phosphonic acid-functionalized silicas with different mesoporous morphologies: adsorption behavior study and mechanism investigation by EXAFS/XPS.

PubMed

Zhang, Wen; He, Xihong; Ye, Gang; Yi, Rong; Chen, Jing

2014-06-17

Efficient capture of highly toxic radionuclides with long half-lives such as Americium-241 is crucial to prevent radionuclides from diffusing into the biosphere. To reach this purpose, three different types of mesoporous silicas functionalized with phosphonic acid ligands (SBA-POH, MCM-POH, and BPMO-POH) were synthesized via a facile procedure. The structure, surface chemistry, and micromorphology of the materials were fully characterized by (31)P/(13)C/(29)Si MAS NMR, XPS, and XRD analysis. Efficient adsorption of Am(III) was realized with a fast rate to reach equilibrium (within 10 min). Influences including structural parameters and functionalization degree on the adsorption behavior were investigated. Slope analysis of the equilibrium data suggested that the coordination with Am(III) involved the exchange of three protons. Moreover, extended X-ray absorption fine structure (EXAFS) analysis, in combination with XPS survey, was employed for an in-depth probe into the binding mechanism by using Eu(III) as a simulant due to its similar coordination behavior and benign property. The results showed three phosphonic acid ligands were coordinated to Eu(III) in bidentate fashion, and Eu(P(O)O)3(H2O) species were formed with the Eu-O coordination number of 7. These phosphonic acid-functionalized mesoporous silicas should be promising for the treatment of Am-containing radioactive liquid waste.

Surface Functionalized Nanostructured Ceramic Sorbents for the Effective Collection and Recovery of Uranium from Seawater

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

Chouyyok, Wilaiwan; Pittman, Jonathan W.; Warner, Marvin G.

2016-05-02

The ability to collect uranium from seawater offers the potential for a nearly limitless fuel supply for nuclear energy. We evaluated the use of functionalized nanostructured sorbents for the collection and recovery of uranium from seawater. Extraction of trace minerals from seawater and brines is challenging due to the high ionic strength of seawater, low mineral concentrations, and fouling of surfaces over time. We demonstrate that rationally assembled sorbent materials that integrate high affinity surface chemistry and high surface area nanostructures into an application relevant micro/macro structure enables collection performance that far exceeds typical sorbent materials. High surface area nanostructuredmore » silica with surface chemistries composed of phosphonic acid, phosphonates, 3,4 hydroxypyridinone, and EDTA showed superior performance for uranium collection. A few phosphorous-based commercial resins, specifically Diphonix and Ln Resin, also performed well. We demonstrate an effective and environmentally benign method of stripping the uranium from the high affinity sorbents using inexpensive nontoxic carbonate solutions. The cyclic use of preferred sorbents and acidic reconditioning of materials was shown to improve performance. Composite thin films composed of the nanostructured sorbents and a porous polymer binder are shown to have excellent kinetics and good capacity while providing an effective processing configuration for trace mineral recovery from solutions. Initial work using the composite thin films shows significant improvements in processing capacity over the previously reported sorbent materials.« less

Synthesis and Structural Studies of Calcium and Magnesium Phosphinate and Phosphonate Compounds

NASA Astrophysics Data System (ADS)

Bampoh, Victoria Naa Kwale

The work presented herein describes synthetic methodologies leading to the design of a wide array of magnesium and calcium based phosphinate and phosphonates with possible applications as bone scaffolding materials or additives to bone cements. The challenge to the chemistry of the alkaline earth phosphonate target compounds includes poor solubility of compounds, and poorly understood details on the control of the metal's coordination environment. Hence, less is known on phosphonate based alkaline earth metal organic frameworks as compared to transition metal phosphonates. Factors governing the challenges in obtaining crystalline, well-defined magnesium and calcium solids lie in the large metal diameters, the absence of energetically available d-orbitals to direct metal geometry, as well as the overall weakness of the metal-ligand bonds. A significant part of this project was concerned with the development of suitable reaction conditions to obtain X-ray quality crystals of the reaction products to allow for structural elucidation of the novel compounds. Various methodologies to aid in crystal growth including hydrothermal methods and gel crystallization were employed. We have used phosphinate and phosphonate ligands with different number of phosphorus oxygen atoms as well as diphosphonates with different linker lengths to determine their effects on the overall structural features. An interesting correlation is observed between the dimensionality of products and the increasing number of donor oxygen atoms in the ligands as we progress from phosphinic acid to the phosphorous acids. As an example, monophosphinate ligand only yielded one-dimensional compounds, whereas the phosphonates crystallize as one and two-dimensional compounds, and the di- and triphosphonate based compounds display two or three-dimensional geometries. This thesis provides a selection of calcium and magnesium compounds with one-dimensional geometry, as represented in a calcium phosphinate to novel two-dimensional sheets of magnesium and pillared calcium phosphonates. The preparation of these novel compounds has led to the establishment of synthetic protocols that allow for the direct preparation of compounds with defined structural features.

Nanolayer formation on titanium by phosphonated gelatin for cell adhesion and growth enhancement

PubMed Central

Zhou, Xiaoyue; Park, Shin-Hye; Mao, Hongli; Isoshima, Takashi; Wang, Yi; Ito, Yoshihiro

2015-01-01

Phosphonated gelatin was prepared for surface modification of titanium to stimulate cell functions. The modified gelatin was synthesized by coupling with 3-aminopropylphosphonic acid using water-soluble carbodiimide and characterized by 31P nuclear magnetic resonance and gel permeation chromatography. Circular dichroism revealed no differences in the conformations of unmodified and phosphonated gelatin. However, the gelation temperature was changed by the modification. Even a high concentration of modified gelatin did not form a gel at room temperature. Time-of-flight secondary ion mass spectrometry showed direct bonding between the phosphonated gelatin and the titanium surface after binding. The binding behavior of phosphonated gelatin on the titanium surface was quantitatively analyzed by a quartz crystal microbalance. Ellipsometry showed the formation of a several nanometer layer of gelatin on the surface. Contact angle measurement indicated that the modified titanium surface was hydrophobic. Enhancement of the attachment and spreading of MC-3T3L1 osteoblastic cells was observed on the phosphonated gelatin-modified titanium. These effects on cell adhesion also led to growth enhancement. Phosphonation of gelatin was effective for preparation of a cell-stimulating titanium surface. PMID:26366080

Studies on the biodegradation of fosfomycin: growth of Rhizobium huakuii PMY1 on possible intermediates synthesised chemically.

PubMed

McGrath, John W; Hammerschmidt, Friedrich; Preusser, Werner; Quinn, John P; Schweifer, Anna

2009-05-07

The first step of the mineralisation of fosfomycin by R. huakuii PMY1 is hydrolytic ring opening with the formation of (1R,2R)-1,2-dihydroxypropylphosphonic acid. This phosphonic acid and its three stereoisomers were synthesised by chemical means and tested as their ammonium salts for mineralisation as evidenced by release of P(i). Only the (1R,2R)-isomer was degraded. A number of salts of phosphonic acids such as (+/-)-1,2-epoxybutyl-, (+/-)-1,2-dihydroxyethyl-, 2-oxopropyl-, (S)-2-hydroxypropyl-, (+/-)-1-hydroxypropyl- and (+/-)-1-hydroxy-2-oxopropylphosphonic acid were synthesised chemically, but none supported growth. In vitro C-P bond cleavage activity was however detected with the last phosphonic acid. A mechanism involving phosphite had to be discarded as it could not be used as a phosphorus source. R. huakuii PMY1 grew well on (R)- and (S)-lactic acid and hydroxyacetone, but less well on propionic acid and not on acetone or (R)- and (+/-)-1,2-propanediol. The P(i) released from (1R,2R)-1,2-dihydroxypropylphosphonic acid labelled with one oxygen-18 in the PO3H2 group did not stay long enough in the cells to allow complete exchange of 18O for 16O by enzymic turnover.

New water-soluble metal working fluids additives from phosphonic acid derivatives for aluminum alloy materials.

PubMed

Kohara, Ichitaro; Tomoda, Hideyuki; Watanabe, Shoji

2007-01-01

Water-soluble metal working fluids are used for processing of aluminum alloy materials. This short paper describes properties of new additives for water-soluble cutting fluids for aluminum alloy materials. Some alkyldiphosphonic acids were prepared with known method. Amine salts of these phosphonic acids showed anti-corrosion property for aluminum alloy materials. However, they have no hard water tolerance. Monoesters of octylphosphonic acid were prepared by the reaction of octylphosphonic acid dichloride with various alcohols in the presence of triethylamine. Amine salts of monoester of octylphosphonic acid with diethyleneglycol monomethyl ether, ethyleneglycol monomethyl ether and triethyleneglycol monomethyl ether showed both of a good anti-corrosion property for aluminum alloy materials and hard water tolerance.

Stereoselective synthesis of the 5'-hydroxy-5'-phosphonate derivatives of cytidine and cytosine arabinoside.

PubMed

Chen, Xuemei; Wiemer, Andrew J; Hohl, Raymond J; Wiemer, David F

2002-12-27

Both the (R)- and (S)-5'-hydroxy 5'-phosphonate derivatives of cytidine and cytosine arabinoside (ara-C) have been prepared via phosphite addition or a Lewis acid mediated hydrophosphonylation of appropriately protected 5'-nucleoside aldehydes. Phosphite addition to a cytosine aldehyde protected as the 2',3'-acetonide gave predominately the 5'R isomer, while phosphite addition to the corresponding 2',3'-bis TBS derivative favored the 5'S stereochemistry. In contrast, phosphite addition to the 2',3'-bis TBS protected aldehyde derived from ara-C gave only the 5'R adduct. However, TiCl(4)-mediated hydrophosphonylation of the same ara-C aldehyde favored the 5'S stereoisomer by a 2:1 ratio. Once all four of the diastereomers were in hand, the stereochemistry of these compounds could be assigned based on their spectral data or that obtained from their O-methyl mandelate derivatives. After hydrolysis of the phosphonate esters and various protecting groups, the four alpha-hydroxy phosphonic acids were tested for their ability to serve as substrates for the enzyme nucleoside monophosphate kinase and for their toxicity to K562 cells.

Self-assembly of myristic acid in the presence of choline hydroxide: effect of molar ratio and temperature.

PubMed

Arnould, Audrey; Perez, Adrian A; Gaillard, Cédric; Douliez, Jean-Paul; Cousin, Fabrice; Santiago, Liliana G; Zemb, Thomas; Anton, Marc; Fameau, Anne-Laure

2015-05-01

Salt-free catanionic systems based on fatty acids exhibit a broad polymorphism by simply tuning the molar ratio between the two components. For fatty acid combined with organic amino counter-ions, very few data are available on the phase behavior obtained as a function of the molar ratio between the counter-ion and the fatty acid. We investigated the choline hydroxide/myristic acid system by varying the molar ratio, R=n(choline hydroxide)/n(myristic acid), and the temperature. Myristic acid ionization state was determined by coupling pH, conductivity and infra-red spectroscopy measurements. Self-assemblies were characterized by small angle neutron scattering and microscopy experiments. Self-assembly thermal behavior was investigated by differential scanning calorimetry, wide angle X-ray scattering and nuclear magnetic resonance. For R<1, ionized and protonated myristic acid molecules coexisted leading to the formation of facetted self-assemblies and lamellar phases. The melting process between the gel and the fluid state of these bilayers induced a structural change from facetted or lamellar objects to spherical vesicles. For R>1, myristic acid molecules were ionized and formed spherical micelles. Our study highlights that both R and temperature are two key parameters to finely control the self-assembly structure formed by myristic acid in the presence of choline hydroxide. Copyright © 2015 Elsevier Inc. All rights reserved.

Extreme Activity of Drug Nanocrystals Coated with A Layer of Non-Covalent Polymers from Self-Assembled Boric Acid

NASA Astrophysics Data System (ADS)

Zhan, Honglei; Liang, Jun F.

2016-12-01

Non-covalent polymers have remarkable advantages over synthetic polymers for wide biomedical applications. In this study, non-covalent polymers from self-assembled boric acid were used as the capping reagent to replace synthetic polymers in drug crystallization. Under acidic pH, boric acid self-assembled on the surface of drug nanocrystals to form polymers with network-like structures held together by hydrogen bonds. Coating driven by boric acid self-assembly had negligible effects on drug crystallinity and structure but resulted in drug nanocrystals with excellent dispersion properties that aided in the formation of a more stable suspension. Boric acid coating improved drug stability dramatically by preventing drug molecules from undergoing water hydrolysis in a neutral environment. More importantly, the specific reactivity of orthoboric groups to diols in cell glycocalyx facilitated a rapid cross-membrane translocation of drug nanocrystals, leading to efficient intracellular drug delivery, especially on cancer cells with highly expressed sialic acids. Boric acid coated nanocrystals of camptothecin, an anticancer drug with poor aqueous solubility and stability, demonstrated extreme cytotoxic activity (IC50 < 5.0 μg/mL) to cancer cells compared to synthetic polymer coated CPT nanocrystals and free CPT. Surface coating using non-covalent polymers from self-assembled boric acid will have wide biomedical applications especially in biomaterials and drug delivery field.

Extreme Activity of Drug Nanocrystals Coated with A Layer of Non-Covalent Polymers from Self-Assembled Boric Acid.

PubMed

Zhan, Honglei; Liang, Jun F

2016-12-09

Non-covalent polymers have remarkable advantages over synthetic polymers for wide biomedical applications. In this study, non-covalent polymers from self-assembled boric acid were used as the capping reagent to replace synthetic polymers in drug crystallization. Under acidic pH, boric acid self-assembled on the surface of drug nanocrystals to form polymers with network-like structures held together by hydrogen bonds. Coating driven by boric acid self-assembly had negligible effects on drug crystallinity and structure but resulted in drug nanocrystals with excellent dispersion properties that aided in the formation of a more stable suspension. Boric acid coating improved drug stability dramatically by preventing drug molecules from undergoing water hydrolysis in a neutral environment. More importantly, the specific reactivity of orthoboric groups to diols in cell glycocalyx facilitated a rapid cross-membrane translocation of drug nanocrystals, leading to efficient intracellular drug delivery, especially on cancer cells with highly expressed sialic acids. Boric acid coated nanocrystals of camptothecin, an anticancer drug with poor aqueous solubility and stability, demonstrated extreme cytotoxic activity (IC 50  < 5.0 μg/mL) to cancer cells compared to synthetic polymer coated CPT nanocrystals and free CPT. Surface coating using non-covalent polymers from self-assembled boric acid will have wide biomedical applications especially in biomaterials and drug delivery field.

Extreme Activity of Drug Nanocrystals Coated with A Layer of Non-Covalent Polymers from Self-Assembled Boric Acid

PubMed Central

Zhan, Honglei; Liang, Jun F.

2016-01-01

Non-covalent polymers have remarkable advantages over synthetic polymers for wide biomedical applications. In this study, non-covalent polymers from self-assembled boric acid were used as the capping reagent to replace synthetic polymers in drug crystallization. Under acidic pH, boric acid self-assembled on the surface of drug nanocrystals to form polymers with network-like structures held together by hydrogen bonds. Coating driven by boric acid self-assembly had negligible effects on drug crystallinity and structure but resulted in drug nanocrystals with excellent dispersion properties that aided in the formation of a more stable suspension. Boric acid coating improved drug stability dramatically by preventing drug molecules from undergoing water hydrolysis in a neutral environment. More importantly, the specific reactivity of orthoboric groups to diols in cell glycocalyx facilitated a rapid cross-membrane translocation of drug nanocrystals, leading to efficient intracellular drug delivery, especially on cancer cells with highly expressed sialic acids. Boric acid coated nanocrystals of camptothecin, an anticancer drug with poor aqueous solubility and stability, demonstrated extreme cytotoxic activity (IC50 < 5.0 μg/mL) to cancer cells compared to synthetic polymer coated CPT nanocrystals and free CPT. Surface coating using non-covalent polymers from self-assembled boric acid will have wide biomedical applications especially in biomaterials and drug delivery field. PMID:27934922

Self-assembled nanotubes from single fluorescent amino acid

NASA Astrophysics Data System (ADS)

Babar, Dipak Gorakh; Sarkar, Sabyasachi

2017-04-01

Self-assembly of biomolecules has gained increasing attention as it generates various supramolecular structural assemblies having potential applications principally in biomedical sciences. Here, we show that amino acid like tryptophan or tyrosine readily aggregates as nanotubes via a simple self-assembly process. These were characterized by FTIR, scanning electron microscopy, and by fluorescence microscopy. Nanotubes prepared from tryptophan are having 200 nm inner diameter and those from tyrosine are having the same around 50 nm diameter.

Fabrication of sub-diffraction-limit molecular structures by scanning near-field photolithography

NASA Astrophysics Data System (ADS)

Ducker, Robert E.; Montague, Matthew T.; Sun, Shuqing; Leggett, Graham J.

2007-09-01

Using a scanning near-field optical microscope coupled to a UV laser, an approach we term scanning near-field photolithography (SNP), structures as small as 9 nm (ca. λ/30) may be fabricated in self-assembled monolayers of alkanethiols on gold surfaces. Selective exposure of the adsorbate molecules in the near field leads to photoconversion of the alkylthiolate to a weakly bound alkylsulfonate which may be displaced readily be a contrasting thiol, leading to a chemical pattern, or used as a resist for the selective etching of the underlying metal. A novel ultra-mild etch for gold is reported, and used to etch structures as small as 9 nm. Photopatterning of oligo(ethylene glycol) (OEG) terminated selfassembled monolayers facilitates the fabrication of biomolecular nanostructures. Selective removal of the protein-resistant OEG terminated adsorbates created regions that may be functionalized with a second thiol and derivatized with a biomolecule. Finally, the application of SNP to nanopatterning on oxide surfaces is demonstrated. Selective exposure of monolayers of phosphonic acids adsorbed onto aluminum oxide leads to cleavage of the P-C bond and desorption of the adsorbate molecule. Subsequent etching, using aqueous based, yields structures as small as 100 nm.

Genetically encoded photochemical covalent crosslinking within the Hcp-1 self-assembling bacterial secretion machinery.

PubMed

Antonczak, Alicja K; Milholland, Kedric; Tippmann, Eric M

2018-05-01

The target protein, Hcp1, was first described as part of the bacterial Type VI secretion system from Pseudomonas aeruginosa. The protein first self-assembles into a hexamer and then the hexamers further stack into a nanotubular structure. Hcp1 monomers were targeted for mutagenesis with two widely used photoactivatable amino acids: para-benzoyl phenylalanine or para-azidophenylalanine. The ability of these amino acids to form covalent adducts within the Hcp1 self-assembled system was investigated. Multiple residues, putatively of equal distance between the monomer-monomer interface were targeted. The efficiency of each amino acid to covalently link self-assembled hexamers was determined. The results demonstrate the choice and role of genetically encoded tools applied to complicated biological processes such as self-assembly and also suggested some structural dynamics of the Hcp-1 protein not obvious from crystallographic structures.

Diorganotin-based coordination polymers derived from sulfonate/phosphonate/phosphonocarboxylate ligands.

PubMed

Shankar, Ravi; Jain, Archana; Kociok-Köhn, Gabriele; Molloy, Kieran C

2011-02-21

The reactions of diorganotin precursors [R(2)Sn(OR(1))(OSO(2)R(1))](n) [R = R(1) = Me (1); R = Me, R(1) = Et (2)] with an equimolar amount of t-butylphosphonic acid (RT, 8-10 h) in methanol result in the formation of identical products, of composition [(Me(2)Sn)(3)(O(3)PBu(t))(2)(O(2)P(OH)Bu(t))(2)](n) (3). On the other hand, a similar reaction of 2, when carried out in dichloromethane, affords [(Me(2)Sn)(3)(O(3)PBu(t))(2)(OSO(2)Et)(2)·MeOH](n) (4). A plausible mechanism implicating the role of solvent in the formation of these compounds has been put forward. In addition, the synthesis of [(Me(2)Sn)(3)(O(3)PCH(2)CH(2)COOMe)(2)(OSO(2)Me)(2)](n) (5) and [R(2)Sn(O(2)P(OH)CH(2)CH(2)COOMe)(OSO(2)R(1))](n) [R = Et, R(1) = Me (6); R = (n)Bu, R(1) = Et (7)] has been achieved by reacting 1 and related diorganotin(alkoxy)alkanesulfonates with 3-phosphonopropionic acid in methanol. The formation of a methylpropionate functionality on the phosphorus center in these structural frameworks results from in situ esterification of the carboxylic group. X-ray crystallographic studies of 1-7 are presented. The structures of 1 and 2 represent one-dimensional (1D) coordination polymers composed of alternate [Sn-O](2) and [Sn-O-S-O](2) cyclic rings formed by μ(2)-alkoxo and sulfonate ligands, respectively. For 3-5 and 7, variable bonding modes of phosphonate and/or sulfonate ligands afford the construction of two- and three-dimensional self-assemblies that are comprised of trinuclear tin entities with an Sn(3)P(2)O(6) core as well as [Sn-O-P-O](2) and/or [Sn-O-S-O](2) rings. The formation of a 1D coordination polymer in 6 is unique in terms of repeating eight-membered cyclic rings containing Sn, O, P, and S heteroatoms. The contribution from hydrogen-bonding interactions is also found to be significant in these structures.

Properties of amphoteric polyurethane waterborne dispersions. II. Macromolecular self-assembly behavior.

PubMed

Dong, Anjie; Hou, Guoling; Sun, Duoxian

2003-10-15

Amphoteric polyurethane (APU) samples used in this paper were composed of hydrophobic soft segments and pendent -COOH and -CH(2)N(CH(3))(2) groups on the hard segments, which present the properties of both amphoteric polyelectrolytes and amphiphilic block copolymers. APU macromolecules can self-assemble into micelles in acidic and basic aqueous media by hydrophobic/hydrophilic interaction. The self-assembly behavior of APU in acidic and basic media was studied by transmission electron microscopy and light scattering methods. The spherical and hollow micelles of APU were observed respectively in acidic and basic aqueous media. The results indicate that the size and size distribution of APU self-assembly micelles largely depend on the ratio of -COOH to -CH(2)N(CH(3))(2) groups, density of ionizable groups, concentration of APU, and types of acid and base in the media.

Ultrasmall Peptides Self-Assemble into Diverse Nanostructures: Morphological Evaluation and Potential Implications

PubMed Central

Lakshmanan, Anupama; Hauser, Charlotte A.E.

2011-01-01

In this study, we perform a morphological evaluation of the diverse nanostructures formed by varying concentration and amino acid sequence of a unique class of ultrasmall self-assembling peptides. We modified these peptides by replacing the aliphatic amino acid at the C-aliphatic terminus with different aromatic amino acids. We tracked the effect of introducing aromatic residues on self-assembly and morphology of resulting nanostructures. Whereas aliphatic peptides formed long, helical fibers that entangle into meshes and entrap >99.9% water, the modified peptides contrastingly formed short, straight fibers with a flat morphology. No helical fibers were observed for the modified peptides. For the aliphatic peptides at low concentrations, different supramolecular assemblies such as hollow nanospheres and membrane blebs were found. Since the ultrasmall peptides are made of simple, aliphatic amino acids, considered to have existed in the primordial soup, study of these supramolecular assemblies could be relevant to understanding chemical evolution leading to the origin of life on Earth. In particular, we propose a variety of potential applications in bioengineering and nanotechnology for the diverse self-assembled nanostructures. PMID:22016623

Quantitative characterization of all single amino acid variants of a viral capsid-based drug delivery vehicle.

PubMed

Hartman, Emily C; Jakobson, Christopher M; Favor, Andrew H; Lobba, Marco J; Álvarez-Benedicto, Ester; Francis, Matthew B; Tullman-Ercek, Danielle

2018-04-11

Self-assembling proteins are critical to biological systems and industrial technologies, but predicting how mutations affect self-assembly remains a significant challenge. Here, we report a technique, termed SyMAPS (Systematic Mutation and Assembled Particle Selection), that can be used to characterize the assembly competency of all single amino acid variants of a self-assembling viral structural protein. SyMAPS studies on the MS2 bacteriophage coat protein revealed a high-resolution fitness landscape that challenges some conventional assumptions of protein engineering. An additional round of selection identified a previously unknown variant (CP[T71H]) that is stable at neutral pH but less tolerant to acidic conditions than the wild-type coat protein. The capsids formed by this variant could be more amenable to disassembly in late endosomes or early lysosomes-a feature that is advantageous for delivery applications. In addition to providing a mutability blueprint for virus-like particles, SyMAPS can be readily applied to other self-assembling proteins.

Gallium(III) complexes of NOTA-bis (phosphonate) conjugates as PET radiotracers for bone imaging.

PubMed

Holub, Jan; Meckel, Marian; Kubíček, Vojtěch; Rösch, Frank; Hermann, Petr

2015-01-01

Ligands with geminal bis(phosphonic acid) appended to 1,4,7-triazacyclonone-1,4-diacetic acid fragment through acetamide (NOTAM(BP) ) or methylenephosphinate (NO2AP(BP) ) spacers designed for (68) Ga were prepared. Ga(III) complexation is much faster for ligand with methylenephosphinate spacer than that with acetamide one, in both chemical (high reactant concentrations) and radiolabeling studies with no-carrier-added (68) Ga. For both ligands, formation of Ga(III) complex was slower than that with NOTA owing to the strong out-of-cage binding of bis(phosphonate) group. Radiolabeling was efficient and fast only above 60 °C and in a narrow acidity region (pH ~3). At higher temperature, hydrolysis of amide bond of the carboxamide-bis(phosphonate) conjugate was observed during complexation reaction leading to Ga-NOTA complex. In vitro sorption studies confirmed effective binding of the (68) Ga complexes to hydroxyapatite being comparable with that found for common bis(phosphonate) drugs such as pamindronate. Selective bone uptake was confirmed in healthy rats by biodistribution studies ex vivo and by positron emission tomography imaging in vivo. Bone uptake was very high, with SUV (standardized uptake value) of 6.19 ± 1.27 for [(68) Ga]NO2AP(BP) ) at 60 min p.i., which is superior to uptake of (68) Ga-DOTA-based bis(phosphonates) and [(18) F]NaF reported earlier (SUV of 4.63 ± 0.38 and SUV of 4.87 ± 0.32 for [(68) Ga]DO3AP(BP) and [(18) F]NaF, respectively, at 60 min p.i.). Coincidently, accumulation in soft tissue is generally low (e.g. for kidneys SUV of 0.26 ± 0.09 for [(68) Ga]NO2AP(BP) at 60 min p.i.), revealing the new (68) Ga complexes as ideal tracers for noninvasive, fast and quantitative imaging of calcified tissue and for metastatic lesions using PET or PET/CT. Copyright © 2014 John Wiley & Sons, Ltd.

Phosphonic acid based exchange resins

DOEpatents

Horwitz, E. Philip; Alexandratos, Spiro D.; Gatrone, Ralph C.; Chiarizia, Ronato

1995-01-01

An ion exchange resin for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene.

Nucleoside-O-Methyl-(H)-Phosphinates: Novel Monomers for the Synthesis of Methylphosphonate Oligonucleotides Using H-Phosphonate Chemistry.

PubMed

Kostov, Ondřej; Páv, Ondřej; Rosenberg, Ivan

2017-09-18

This unit comprises the straightforward synthesis of protected 2'-deoxyribonucleoside-O-methyl-(H)-phosphinates in both 3'- and 5'-series. These compounds represent a new class of monomers compatible with the solid-phase synthesis of oligonucleotides using H-phosphonate chemistry and are suitable for the preparation of both 3'- and 5'-O-methylphosphonate oligonucleotides. The synthesis of 4-toluenesulfonyloxymethyl-(H)-phosphinic acid as a new reagent for the preparation of O-methyl-(H)-phosphinic acid derivatives is described. © 2017 by John Wiley & Sons, Inc. Copyright © 2017 John Wiley & Sons, Inc.

Hierarchical mesostructured titanium phosphonates with unusual uniform lines of macropores.

PubMed

Ma, Tian-Yi; Lin, Xiu-Zhen; Zhang, Xue-Jun; Yuan, Zhong-Yong

2011-04-01

Organic-inorganic hybrid materials of mesostructured titanium phosphonates with unusual uniform lines of macropores were synthesized by using bis(hexamethylenetriamine) penta(methylenephosphonic acid) (BHMTPMP) as the coupling molecule, through a one-pot hydrothermal process without any surfactant assistance. A wormhole-like mesostructure and many uniform parallel lines of macropores divided by solid ridges in the same direction were confirmed by N(2) sorption, SEM and TEM observations. This novel macropore architecture has never been observed in other metal phosphonate materials, which may be directly related to the structure nature of BHMTPMP with extra long alkyl chains. The structural characterization of FT-IR and MAS NMR revealed the integrity of organic groups inside the hybrid framework. The hybrid materials were also used as adsorbents for heavy metal ions and CO(2), in order to clarify the impacts of the organic contents and organic types on the physicochemical properties of the synthesized hierarchical macro-/mesoporous phosphonate materials.

Phosphonic acid based ion exchange resins

DOEpatents

Horwitz, E. Philip; Alexandratos, Spiro D.; Gatrone, Ralph C.; Chiarizia, Ronato

1994-01-01

An ion exchange resin for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene disphosphonic acid with styrene, acrylonitrile and divinylbenzene.

Phosphonic acid based ion exchange resins

DOEpatents

Horwitz, E. Philip; Alexandratos, Spiro D.; Gatrone, Ralph C.; Chiarizia, Ronato

1996-01-01

An ion exchange resin for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene.

Acid monolayer functionalized iron oxide nanoparticle catalysts

NASA Astrophysics Data System (ADS)

Ikenberry, Myles

Superparamagnetic iron oxide nanoparticle functionalization is an area of intensely active research, with applications across disciplines such as biomedical science and heterogeneous catalysis. This work demonstrates the functionalization of iron oxide nanoparticles with a quasi-monolayer of 11-sulfoundecanoic acid, 10-phosphono-1-decanesulfonic acid, and 11-aminoundecanoic acid. The carboxylic and phosphonic moieties form bonds to the iron oxide particle core, while the sulfonic acid groups face outward where they are available for catalysis. The particles were characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), potentiometric titration, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectrometry (XPS), and dynamic light scattering (DLS). The sulfonic acid functionalized particles were used to catalyze the hydrolysis of sucrose at 80° and starch at 130°, showing a higher activity per acid site than the traditional solid acid catalyst Amberlyst-15, and comparing well against results reported in the literature for sulfonic acid functionalized mesoporous silicas. In sucrose catalysis reactions, the phosphonic-sulfonic nanoparticles (PSNPs) were seen to be incompletely recovered by an external magnetic field, while the carboxylic-sulfonic nanoparticles (CSNPs) showed a trend of increasing activity over the first four recycle runs. Between the two sulfonic ligands, the phosphonates produced a more tightly packed monolayer, which corresponded to a higher sulfonic acid loading, lower agglomeration, lower recoverability through application of an external magnetic field, and higher activity per acid site for the hydrolysis of starch. Functionalizations with 11-aminoundecanoic acid resulted in some amine groups binding to the surfaces of iron oxide nanoparticles. This amine binding is commonly ignored in iron oxide nanoparticle syntheses and functionalizations for biomedical and catalytic applications, affecting understandings of surface charge and other material properties.

Purification and Characterization of Phosphonoglycans from Glycomyces sp. Strain NRRL B-16210 and Stackebrandtia nassauensis NRRL B-16338

PubMed Central

Yu, Xiaomin; Price, Neil P. J.; Evans, Bradley S.

2014-01-01

Two related actinomycetes, Glycomyces sp. strain NRRL B-16210 and Stackebrandtia nassauensis NRRL B-16338, were identified as potential phosphonic acid producers by screening for the gene encoding phosphoenolpyruvate (PEP) mutase, which is required for the biosynthesis of most phosphonates. Using a variety of analytical techniques, both strains were subsequently shown to produce phosphonate-containing exopolysaccharides (EPS), also known as phosphonoglycans. The phosphonoglycans were purified by sequential organic solvent extractions, methanol precipitation, and ultrafiltration. The EPS from the Glycomyces strain has a mass of 40 to 50 kDa and is composed of galactose, xylose, and five distinct partially O-methylated galactose residues. Per-deutero-methylation analysis indicated that galactosyl residues in the polysaccharide backbone are 3,4-linked Gal, 2,4-linked 3-MeGal, 2,3-linked Gal, 3,6-linked 2-MeGal, and 4,6-linked 2,3-diMeGal. The EPS from the Stackebrandtia strain is comprised of glucose, galactose, xylose, and four partially O-methylated galactose residues. Isotopic labeling indicated that the O-methyl groups in the Stackebrandtia phosphonoglycan arise from S-adenosylmethionine. The phosphonate moiety in both phosphonoglycans was shown to be 2-hydroxyethylphosphonate (2-HEP) by 31P nuclear magnetic resonance (NMR) and mass spectrometry following strong acid hydrolysis of the purified molecules. Partial acid hydrolysis of the purified EPS from Glycomyces yielded 2-HEP in ester linkage to the O-5 or O-6 position of a hexose and a 2-HEP mono(2,3-dihydroxypropyl)ester. Partial acid hydrolysis of Stackebrandtia EPS also revealed the presence of 2-HEP mono(2,3-dihydroxypropyl)ester. Examination of the genome sequences of the two strains revealed similar pepM-containing gene clusters that are likely to be required for phosphonoglycan synthesis. PMID:24584498

Contrast Agents for Micro-Computed Tomography of Microdamage in Bone

DTIC Science & Technology

2009-01-01

carboxylate (reported in January 2009), phosphonate and bisphosphonate groups (Fig. 2). The presence of functional groups was verified by FT- IR (Fig. 3...carboxylic acid, (b) phosphonate or (c) bisphosphonate groups for calcium binding damaged tissue. (a) (b) (c) Fig. 3. FT- IR spectra for Au NPs...functional group. Quantitative measurements of the binding affinity were performed by adding hydroxyapatite (HA) crystals to functionalized Au NP solutions in

A self-assembling nanomedicine of conjugated linoleic acid-paclitaxel conjugate (CLA-PTX) with higher drug loading and carrier-free characteristic

NASA Astrophysics Data System (ADS)

Zhong, Ting; Yao, Xin; Zhang, Shuang; Guo, Yang; Duan, Xiao-Chuan; Ren, Wei; Dan Huang; Yin, Yi-Fan; Zhang, Xuan

2016-11-01

The main objective of this study was to demonstrate the proof-of-principle for the hypothesis that conjugated linoleic acid-paclitaxel conjugate (CLA-PTX), a novel fatty acid modified anti-cancer drug conjugate, could self-assemble forming nanoparticles. The results indicated that a novel self-assembling nanomedicine, CLA-PTX@PEG NPs (about 105 nm), with Cremophor EL (CrEL)-free and organic solvent-free characteristics, was prepared by a simple precipitation method. Being the ratio of CLA-PTX:DSPE-PEG was only 1:0.1 (w/w), the higher drug loading CLA-PTX@PEG NPs (about 90%) possessed carrier-free characteristic. The stability results indicated that CLA-PTX@PEG NPs could be stored for at least 9 months. The safety of CLA-PTX@PEG NPs was demonstrated by the MTD results. The anti-tumor activity and cellular uptake were also confirmed in the in vitro experiments. The lower crystallinity, polarity and solubility of CLA-PTX compared with that of paclitaxel (PTX) might be the possible reason for CLA-PTX self-assembling forming nanoparticles, indicating a relationship between PTX modification and nanoparticles self-assembly. Overall, the data presented here confirm that this drug self-delivery strategy based on self-assembly of a CLA-PTX conjugate may offer a new way to prepare nanomedicine products for cancer therapy involving the relationship between anticancer drug modification and self-assembly into nanoparticles.

Phosphorus sorption on marine carbonate sediment: phosphonate as model organic compounds.

PubMed

Huang, Xiao-Lan; Zhang, Jia-Zhong

2011-11-01

Organophosphonate, characterized by the presence of a stable, covalent, carbon to phosphorus (C-P) bond, is a group of synthetic or biogenic organophosphorus compounds. The fate of these organic phosphorus compounds in the environment is not well studied. This study presents the first investigation on the sorption of phosphorus (P) in the presence of two model phosphonate compounds, 2-aminothylphosphonoic acid (2-AEP) and phosphonoformic acid (PFA), on marine carbonate sediments. In contrast to other organic P compounds, no significant inorganic phosphate exchange was observed in seawater. P was found to adsorb on the sediment only in the presence of PFA, not 2-AEP. This indicated that sorption of P from phosphonate on marine sediment was compound specific. Compared with inorganic phosphate sorption on the same sediments, P sorption from organic phosphorus is much less in the marine environment. Further study is needed to understand the potential role of the organophosphonate compounds in biogeochemical cycle of phosphorus in the environment. Copyright © 2011 Elsevier Ltd. All rights reserved.

Development of Oseltamivir Phosphonate Congeners as Anti-Influenza Agents

PubMed Central

Cheng, Ting-Jen R.; Weinheimer, Steven; Tarbet, E. Bart; Jan, Jia-Tsrong; Cheng, Yih-Shyun E.; Shie, Jiun-Jie; Chen, Chun-Lin; Chen, Chih-An; Hsieh, Wei-Che; Huang, Pei-Wei; Lin, Wen-Hao; Wang, Shi-Yun; Fang, Jim-Min; Hu, Oliver Yoa-Pu; Wong, Chi-Huey

2012-01-01

Oseltamivir phosphonic acid (tamiphosphor, 3a), its monoethyl ester (3c), guanidino-tamiphosphor (4a) and its monoethyl ester (4c) are potent inhibitors of influenza neuraminidases. They inhibit the replication of influenza viruses, including the oseltamivir-resistant H275Y strain, at low nM to pM levels, and significantly protect mice from infection with lethal doses of influenza viruses when orally administered with 1 mg/kg or higher doses. These compounds are stable in simulated gastric fluid, liver microsomes and human blood, and are largely free from binding to plasma proteins. Pharmacokinetic properties of these inhibitors are thoroughly studied in dogs, rats and mice. The absolute oral bioavailability of these compounds was lower than 12%. No conversion of monoester 4c to phosphonic acid 4a was observed in rats after intravenous administration, but partial conversion of 4c was observed with oral administration. Advanced formulation may be investigated to develop these new anti-influenza agents for better therapeutic use. PMID:23009169

Removal of phosphonates from industrial wastewater with UV/FeII, Fenton and UV/Fenton treatment.

PubMed

Rott, Eduard; Minke, Ralf; Bali, Ulusoy; Steinmetz, Heidrun

2017-10-01

Phosphonates are an important group of phosphorus-containing compounds due to their increasing industrial use and possible eutrophication potential. This study involves investigations into the methods UV/Fe II , Fenton and UV/Fenton for their removal from a pure water matrix and industrial wastewaters. It could be shown that the degradability of phosphonates by UV/Fe II (6 kWh/m 3 ) in pure water crucially depended on the pH and was higher the less phosphonate groups a phosphonate contains. The UV/Fe II method is recommended in particular for the treatment of concentrates with nitrogen-free phosphonates, only little turbidity and a low content of organic compounds. Using Fenton reagent, the degradation of polyphosphonates was relatively weak in a pure water matrix (<20% transformation to o-PO 4 3- ). By means of the Photo-Fenton method (6 kWh/m 3 ), those phosphonates with the smallest numbers of phosphonate groups were easier degraded as well at pH 3.5 in a pure water matrix (o-PO 4 3- formation rates of up to 80%). Despite an incomplete transformation of organically bound phosphorus to o-PO 4 3- with Fenton reagent in an organically highly polluted wastewater (max. 15%), an almost total removal of the total P occurred. The most efficient total P elimination rates were achieved in accordance with the following Fenton implementation: reaction → sludge separation (acidic) → neutralization of the supernatant → sludge separation (neutral). Accordingly, a neutralization directly after the reaction phase led to a lower total P removal extent. Copyright © 2017 Elsevier Ltd. All rights reserved.

Phosphonic acid based exchange resins

DOEpatents

Horwitz, E.P.; Alexandratos, S.D.; Gatrone, R.C.; Chiarizia, R.

1995-09-12

An ion exchange resin is described for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene. 10 figs.

Aqueous corrosion of phosphide minerals from iron meteorites: a highly reactive source of prebiotic phosphorus on the surface of the early Earth.

PubMed

Pasek, Matthew A; Lauretta, Dante S

2005-08-01

We present the results of an experimental study of aqueous corrosion of Fe-phosphide under conditions relevant to the early Earth. The results strongly suggest that iron meteorites were an important source of reactive phosphorus (P), a requirement for the formation of P-based life. We further demonstrate that iron meteorites were an abundant source of phosphide minerals early in Earth history. Phosphide corrosion was studied in five different solutions: deionized water, deionized water buffered with sodium bicarbonate, deionized water with dissolved magnesium and calcium chlorides, deionized water containing ethanol and acetic acid, and deionized water containing the chlorides, ethanol, and acetic acid. Experiments were performed in the presence of both air and pure Ar gas to evaluate the effect of atmospheric chemistry. Phosphide corrosion in deionized water results in a metastable mixture of mixed-valence, P-bearing ions including pyrophosphate and triphosphate, key components for metabolism in modern life. In a pH-buffered solution of NaHCO(3), the condensed and reduced species diphosphonate is an abundant corrosion product. Corrosion in ethanol- and acetic acid-containing solutions yields additional P-bearing organic molecules, including acetyl phosphonate and a cyclic triphosphorus molecule. Phosphonate is a major corrosion product of all experiments and is the only P-bearing molecule that persists in solutions with high concentrations of magnesium and calcium chlorides, which suggests that phosphonate may have been a primitive oceanic source of P. The stability and reactivity of phosphonate and hypophosphite in solution were investigated to elucidate reaction mechanisms and the role of mineral catalysts on P-solution chemistry. Phosphonate oxidation is rapid in the presence of Fe metal but negligible in the presence of magnetite and in the control sample. The rate of hypophosphite oxidation is independent of reaction substrate.

Gold Electrodes Modified with Self-Assembled Monolayers for Measuring L-Ascorbic Acid: An Undergraduate Analytical Chemistry Laboratory Experiment

ERIC Educational Resources Information Center

Ito, Takashi; Perera, D. M. Neluni T.; Nagasaka, Shinobu

2008-01-01

This article describes an undergraduate electrochemistry laboratory experiment in which the students measure the L-ascorbic acid content of a real sample. Gold electrodes modified with self-assembled monolayers (SAMs) of thioctic acid and cysteamine are prepared to study the effects of surface modification on the electrode reaction of L-ascorbic…

Phosphonic acid based ion exchange resins

DOEpatents

Horwitz, E.P.; Alexandratos, S.D.; Gatrone, R.C.; Chiarizia, R.

1996-07-23

An ion exchange resin is described for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene. 10 figs.

Phosphonic acid based ion exchange resins

DOEpatents

Horwitz, E.P.; Alexandratos, S.D.; Gatrone, R.C.; Chiarizia, R.

1994-01-25

An ion exchange resin is described for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene. 9 figures.

Conductivity of gel polymer electrolytes doped with solutions of phosphonic acid or protic ionic liquids

NASA Astrophysics Data System (ADS)

Shmukler, Liudmila E.; Fadeeva, Yuliya A.; Glushenkova, Ekaterina V.; Nguyen, Van Thuc; Safonova, Liubov P.

2018-04-01

The proton-conducting gel electrolytes (PCGEs) based on PMMA, PVdF or PVdF-HFP doped with solutions of phosphonic acid or ammonium based protic ionic liquids (PILs) in DMF have been synthesized. Rather high values of the conductivity (10-4-10-3 S cm-1) have been reached at low dopant concentrations (up to 1 mol l-1). The influence of the nature of both polymeric matrix and dopant as well as dopant concentration on the conductivity values was discussed. It was established that the dependence of conductivity on the nature of dopant, but not the polymeric matrix, was more pronounced.

Asymmetric hydrogenation of α,β-unsaturated phosphonates with Rh-BisP* and Rh-MiniPHOS catalysts: Scope and mechanism of the reaction

PubMed Central

Gridnev, Ilya D.; Yasutake, Masaya; Imamoto, Tsuneo; Beletskaya, Irina P.

2004-01-01

Optically active 1,2-bis(alkylmethylphosphino)ethanes and bis(alkylmethylphosphino)methanes are unique diphosphine ligands combining the simple molecular structure and P-stereogenic asymmetric environment. This work shows that these ligands exhibit excellent enantioselectivity in rhodium-catalyzed asymmetric hydrogenation of α,β-unsaturated phosphonic acid derivatives. The enantioselective hydrogenation mechanism elucidated by NMR study is also described. PMID:15024119

Effective methylation of phosphonic acids related to chemical warfare agents mediated by trimethyloxonium tetrafluoroborate for their qualitative detection and identification by gas chromatography-mass spectrometry

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

Valdez, Carlos A.; Leif, Roald N.; Alcaraz, Armando

The effective methylation of phosphonic acids related to chemical warfare agents (CWAs) employing trimethyloxonium tetrafluoroborate (TMO·BF 4) for their qualitative detection and identification by gas chromatography-mass spectrometry (GC-MS) is presented. The methylation occurs in rapid fashion (1 h) and can be conveniently carried out at ambient temperature, thus providing a safer alternative to the universally employed diazomethane-based methylation protocols. Optimization of the methylation parameters led us to conclude that methylene chloride was the ideal solvent to carry out the derivatization, and that even though methylated products can be observed surfacing after only 1 h, additional time was not found tomore » be detrimental but beneficial to the process particularly when dealing with analytes at low concentrations (~10 μg mL -1). Due to its insolubility in methylene chloride, TMO·BF 4 conveniently settles to the bottom during the reaction and does not produce additional interfering by-products that may further complicate the GC-MS analysis. We demonstrated the method to successfully methylate a variety of Schedule 2 phosphonic acids, including their half esters, resulting in derivatives that were readily detected and identified using the instrument's spectral library. Most importantly, the method was shown to simultaneously methylate a mixture of the organophosphorus-based nerve agent hydrolysis products: pinacolyl methylphosphonate (PMPA), cyclohexyl methylphosphonate (CyMPA) and ethyl methylphosphonate (EMPA) (at a 10 μg mL -1 concentration each) in a fatty acid ester-rich organic matrix (OPCW-PT-O 3) featured in the 38th Organisation for the Prohibition of Chemical Weapons (OPCW) Proficiency Test. Additionally, the protocol was found to effectively methylate N,N-diethylamino ethanesulfonic acid and N,N-diisopropylamino ethanesulfonic acid that are products arising from the oxidative degradation of the V-series agents VR and VX respectively. This work described herein represents the first report on the use of TMO·BF 4 as a viable, stable and safe agent for the methylation of phosphonic acids and their half esters and within the context of an OPCW Proficiency Test sample analysis.« less

Effective methylation of phosphonic acids related to chemical warfare agents mediated by trimethyloxonium tetrafluoroborate for their qualitative detection and identification by gas chromatography-mass spectrometry

DOE PAGES

Valdez, Carlos A.; Leif, Roald N.; Alcaraz, Armando

2016-06-01

The effective methylation of phosphonic acids related to chemical warfare agents (CWAs) employing trimethyloxonium tetrafluoroborate (TMO·BF 4) for their qualitative detection and identification by gas chromatography-mass spectrometry (GC-MS) is presented. The methylation occurs in rapid fashion (1 h) and can be conveniently carried out at ambient temperature, thus providing a safer alternative to the universally employed diazomethane-based methylation protocols. Optimization of the methylation parameters led us to conclude that methylene chloride was the ideal solvent to carry out the derivatization, and that even though methylated products can be observed surfacing after only 1 h, additional time was not found tomore » be detrimental but beneficial to the process particularly when dealing with analytes at low concentrations (~10 μg mL -1). Due to its insolubility in methylene chloride, TMO·BF 4 conveniently settles to the bottom during the reaction and does not produce additional interfering by-products that may further complicate the GC-MS analysis. We demonstrated the method to successfully methylate a variety of Schedule 2 phosphonic acids, including their half esters, resulting in derivatives that were readily detected and identified using the instrument's spectral library. Most importantly, the method was shown to simultaneously methylate a mixture of the organophosphorus-based nerve agent hydrolysis products: pinacolyl methylphosphonate (PMPA), cyclohexyl methylphosphonate (CyMPA) and ethyl methylphosphonate (EMPA) (at a 10 μg mL -1 concentration each) in a fatty acid ester-rich organic matrix (OPCW-PT-O 3) featured in the 38th Organisation for the Prohibition of Chemical Weapons (OPCW) Proficiency Test. Additionally, the protocol was found to effectively methylate N,N-diethylamino ethanesulfonic acid and N,N-diisopropylamino ethanesulfonic acid that are products arising from the oxidative degradation of the V-series agents VR and VX respectively. This work described herein represents the first report on the use of TMO·BF 4 as a viable, stable and safe agent for the methylation of phosphonic acids and their half esters and within the context of an OPCW Proficiency Test sample analysis.« less

A multi-stimuli responive, self-assembling, boronic acid dipeptide

DOE PAGES

Jones, Brad Howard; Martinez, Alina Marissa; Wheeler, Jill S.; ...

2015-08-11

Modification of the dipeptide of phenylalanine, FF, with a boronic acid (BA) functionality imparts unique aqueous self-assembly behavior that responds to multiple stimuli. Changes in pH and ionic strength are used to trigger hydrogelation via the formation of nanoribbon networks. Thus, we show for the first time that the binding of polyols to the BA functionality can modulate a peptide between its assembled and disassembled states.

A Library of the Nanoscale Self-Assembly of Amino Acids on Metal Surfaces

NASA Astrophysics Data System (ADS)

Iski, Erin; Yitamben, Esmeralda; Guisinger, Nathan

2012-02-01

The investigation of the hierarchical self-assembly of amino acids on surfaces represents a unique test-bed for the origin of enantio-favoritism in biology and the transmission of chirality from single molecules to complete surface layers. These chiral systems, in particular the assembly of isoleucine and alanine on Cu(111), represent a direct link to the understanding of certain biological processes, specifically the preference for some amino acids to form alpha helices vs. beta-pleated sheets in the secondary structure of proteins. Low temperature, ultra-high vacuum, scanning tunneling microscopy (LT UHV-STM) is used to study the hierarchical self-assembly of different amino acids on a Cu(111) single crystal in an effort to build a library of their two-dimensional structure with molecular-scale resolution for enhanced protein and peptide studies. Both enantiopure and racemic structures are studied in order to elucidate how chirality can affect the self-assembly of the amino acids. In some cases, density functional theory (DFT) models can be used to confirm the experimental structure. The advent of such a library with fully resolved, two-dimensional structures at different molecular coverages would address some of the complex questions surrounding the preferential formation of alpha helices vs. beta-pleated sheets in proteins and lead to a better understanding of the key role played by these amino acids in protein sequencing.

Surface-enhanced Raman spectroscopic and surface plasmon resonance in situ study of self-assembly of 4-mercaptobenzoic acid on gold surface

NASA Astrophysics Data System (ADS)

Thi, Minh Do; Volka, Karel

2010-07-01

A feasibility study has been undertaken to assess the suitability of a commercially available SERS substrate for monitoring of self-assembling deposition process. Monolayer self-assembly of 4-mercaptobenzoic acid on SERS active substrate Klarite™ from absolute and acidified ethanol was studied and compared with deposition on SPR substrate from absolute ethanol. Changes in integral intensity of the phenyl bands at 1587 and 1076 cm -1 and ethanol band at 1451 cm -1 allow to follow structural changes in the monolayer. Stability of the monolayer assembled from acidified ethanol in contrast to the pure ethanol was demonstrated.

Two-component gelator isomers with different combination of amine and acid: Helical/non-helical morphology and selective adsorption of dyes.

PubMed

Han, Xiaoyu; Liu, Jiahui; Zhao, Chaoyue; Zhang, Bao; Xu, Xiufang; Song, Jian

2018-09-01

Hydrogels induced by two-component gelator isomers based on the different amine/acid interactions were investigated. Scanning electron microscopy and atomic force microscopy images of the xerogel obtained from the two hydrogels revealed different assembly morphologies. While left-handed helical fibers were observed for the amine-acid based xerogel, acid-amine underwent self-assembly to afford smooth fibers. Fourier transform infrared spectroscopy, fluorescence, and X-ray diffraction measurements combined with density functional theory calculations suggested that the different self-assembly patterns of gelators resulted in opposite electric charges on the xerogel surfaces, in line with Zeta potential measurements. Based on these opposite charges resulting from their different self-assemblies, both xerogels demonstrated efficient dye adsorption abilities with different selectivities. Interestingly, the adsorption performance was not influenced by the salt in the dye solution. Furthermore, the xerogels still showed high dye adsorption efficiency after four cycles. These results provide a two-component hydrogel method for the purification of dye-polluted water systems, while also paving the way for future design of functionalized supramolecular self-assembly systems. Copyright © 2018 Elsevier Inc. All rights reserved.

SYNTHESIS OF MIXED FULL AND SEMIESTERS OF PHOSPHOROUS ACID AS ORGANIC MOTOR OIL ADDITIVES,

DTIC Science & Technology

The synthesis of mixed full and semiesters of phosphonic acid was effected using alkylphenols produced by the chemical industry. By condensation of...industrial alkylphenol or the condensation of acid chloride of di-(alkylphenyl)-phosphorous acid with diethylamine, the corresponding mixed full and semiesters

Ordered Self-Assembled Monolayers of Peptide Nucleic Acids with DNA Recognition Capability

NASA Astrophysics Data System (ADS)

Briones, C.; Mateo-Marti, E.; Gómez-Navarro, C.; Parro, V.; Román, E.; Martín-Gago, J. A.

2004-11-01

We report on the formation of ordered self-assembled monolayers (SAMs) of single-stranded peptide nucleic acids (ssPNA). In spite of their remarkable length (7nm) thiolated PNAs assemble standing up on gold surfaces similarly to the SAMs of short alkanethiols. SAMs of ssPNA recognize complementary nucleic acids, acting as specific biosensors that discriminate even a point mutation in target ssDNA. These results are obtained by surface characterization techniques that avoid labeling of the target molecule: x-ray photoemission, x-ray absorption and atomic force microscopy.

Construction of supramolecular helical nanofibers using renewable biomaterials: self-assembly of a cytidylic acid-appended bolaamphiphile in lemon juice.

PubMed

Iwaura, Rika; Ohnishi-Kameyama, Mayumi

2012-07-07

We performed the self-assembly of a 1,18-cytidylic acid-appended bolaamphiphile (C18C) in lemon juice, which contained citric acid, and succeeded in forming left-handed helical nanofibers with diameters, lengths, and pitches of ca. 6-7 nm, several hundred nm to 5 μm, and ca. 30-40 nm, respectively.

Development of Ultrafiltration Membrane-Separation Technology for Energy-Efficient Water Treatment and Desalination Process

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

Yim, Woosoon; Bae, Chulsung

The growing scarcity of fresh water is a major political and economic challenge in the 21st century. Compared to thermal-based distillation technique of water production, pressure driven membrane-based water purification process, such as ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO), can offer more energy-efficient and environmentally friendly solution to clean water production. Potential applications also include removal of hazardous chemicals (i.e., arsenic, pesticides, organics) from water. Although those membrane-separation technologies have been used to produce drinking water from seawater (desalination) and non-traditional water (i.e., municipal wastewater and brackish groundwater) over the last decades, they still have problems in ordermore » to be applied in large-scale operations. Currently, a major huddle of membrane-based water purification technology for large-scale commercialization is membrane fouling and its resulting increases in pressure and energy cost of filtration process. Membrane cleaning methods, which can restore the membrane properties to some degree, usually cause irreversible damage to the membranes. Considering that electricity for creating of pressure constitutes a majority of cost (~50%) in membrane-based water purification process, the development of new nano-porous membranes that are more resistant to degradation and less subject to fouling is highly desired. Styrene-ethylene/butylene-styrene (SEBS) block copolymer is one of the best known block copolymers that induces well defined morphologies. Due to the polarity difference of aromatic styrene unit and saturated ethylene/butylene unit, these two polymer chains self-assemble each other and form different phase-separated morphologies depending on the ratios of two polymer chain lengths. Because the surface of SEBS is hydrophobic which easily causes fouling of membrane, incorporation of ionic group (e,g, sulfonate) to the polymer is necessary to reduces fouling. Recently, sulfonated SEBS became commercially available and has been extensively explored for membrane-mediated water purification technology. The sulfonated block copolymer creates a well developed nano-sale phase-separated morphologies composed of hydrophilic domains (sulfonated polystyrene) and hydrophobic domains (polyethylene/polybutylene). The hydrophilic domains determines transport properties (water transport, salt and/or ion rejection, etc) and the hydrophobic domains provides mechanical stability of the membrane. Unfortunately, a high degree of sulfonation of SEBS induces excessive swelling and deterioration of mechanical stability of the membrane. In an effort to develop robust polymeric membrane materials for water purification technology, phosphonic acid-functionalized SEBS membranes are investigated during this report period. In compare to sulfonated polymers, the corresponding phosphonated polymers are known to swell less because of the formation of extensive hydrogen bonding networks between phosphonates. In addition to the expected better mechanical stability, phosphonated polymers has another advantage over sulfonated polymers for the use water purification membrane; each phosphonate can accommodate two ions while each sulfonate accommodates only one ion. Membrane properties (ion type, ionic density, etc) of new membranes will be studied and their separation performance will be evaluated in water purification and desalination process. Through systematic study of the relationship of chemical structure–surface property–membrane performance, we aim to better understand the nature of membrane fouling and develop more fouling-resistant water purification membranes. The basic understanding of this relationship will lead to the development of advanced membrane materials which can offer a solution to environmentally sustainable production of fresh water.« less

Formation and Characterization of Self-Assembled Phenylboronic Acid Derivative Monolayers toward Developing Monosaccharide Sensing-Interface

PubMed Central

Chen, Hongxia; Lee, Minsu; Lee, Jaebeom; Kim, Jae-Ho; Gal, Yeong-Soon; Hwang, Yoon-Hwae; An, Won Gun; Koh, Kwangnak

2007-01-01

We designed and synthesized phenylboronic acid as a molecular recognition model system for saccharide detection. The phenylboronic acid derivatives that have boronic acid moiety are well known to interact with saccharides in aqueous solution; thus, they can be applied to a functional interface of saccharide sensing through the formation of self-assembled monolayer (SAM). In this study, self-assembled phenylboronic acid derivative monolayers were formed on Au surface and carefully characterized by atomic force microscopy (AFM), Fourier transform infrared reflection absorption spectroscopy (FTIR-RAS), surface enhanced Raman spectroscopy (SERS), and surface electrochemical measurements. The saccharide sensing application was investigated using surface plasmon resonance (SPR) spectroscopy. The phenylboronic acid monolayers showed good sensitivity of monosaccharide sensing even at the low concentration range (1.0 × 10−12 M). The SPR angle shift derived from interaction between phenylboronic acid and monosaccharide was increased with increasing the alkyl spacer length of synthesized phenylboronic acid derivatives.

40 CFR 721.1705 - Benzoic acid, 3-amino-, diazotized, coupled with 6-amino-4-hydroxy-2-naphthalenesulfonic acid...

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Benzoic acid, 3-amino-, diazotized, coupled with 6-amino-4-hydroxy-2-naphthalenesulfonic acid, diazotized, (3-aminophenyl)phosphonic acid and... Significant New Uses for Specific Chemical Substances § 721.1705 Benzoic acid, 3-amino-, diazotized, coupled...

40 CFR 721.1705 - Benzoic acid, 3-amino-, diazotized, coupled with 6-amino-4-hydroxy-2-naphthalenesulfonic acid...

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Benzoic acid, 3-amino-, diazotized, coupled with 6-amino-4-hydroxy-2-naphthalenesulfonic acid, diazotized, (3-aminophenyl)phosphonic acid and... Significant New Uses for Specific Chemical Substances § 721.1705 Benzoic acid, 3-amino-, diazotized, coupled...

Cooperation of Amphiphilicity and Crystallization for Regulating the Self-Assembly of Poly(ethylene glycol)-block-poly(lactic acid) Copolymers.

PubMed

Wang, Zhen; Cao, Yuanyuan; Song, Jiaqi; Xie, Zhigang; Wang, Yapei

2016-09-20

Tuning the amphiphilicity of block copolymers has been extensively exploited to manipulate the morphological transition of aggregates. The introduction of crystallizable moieties into the amphiphilic copolymers also offers increasing possibilities for regulating self-assembled structures. In this work, we demonstrate a detailed investigation of the self-assembly behavior of amphiphilic poly(ethylene glycol)-block-poly(l-lactic acid) (PEG-b-PLLA) diblock copolymers with the assistance of a common solvent in aqueous solution. With a given length of the PEG block, the molecular weight of the PLA block has great effect on the morphologies of self-assembled nanoaggregates as a result of varying molecular amphiphilicity and polymer crystallization. Common solvents including N,N-dimethylformamide, dioxane, and tetrahydrofuran involved in the early stage of self-assembly led to the change in chain configuration, which further influences the self-assembly of block copolymers. This study expanded the scope of PLA-based copolymers and proposed a possible mechanism of the sphere-to-lozenge and platelet-to-cylinder morphological transitions.

Light-emitting self-assembled peptide nucleic acids exhibit both stacking interactions and Watson-Crick base pairing.

PubMed

Berger, Or; Adler-Abramovich, Lihi; Levy-Sakin, Michal; Grunwald, Assaf; Liebes-Peer, Yael; Bachar, Mor; Buzhansky, Ludmila; Mossou, Estelle; Forsyth, V Trevor; Schwartz, Tal; Ebenstein, Yuval; Frolow, Felix; Shimon, Linda J W; Patolsky, Fernando; Gazit, Ehud

2015-04-01

The two main branches of bionanotechnology involve the self-assembly of either peptides or DNA. Peptide scaffolds offer chemical versatility, architectural flexibility and structural complexity, but they lack the precise base pairing and molecular recognition available with nucleic acid assemblies. Here, inspired by the ability of aromatic dipeptides to form ordered nanostructures with unique physical properties, we explore the assembly of peptide nucleic acids (PNAs), which are short DNA mimics that have an amide backbone. All 16 combinations of the very short di-PNA building blocks were synthesized and assayed for their ability to self-associate. Only three guanine-containing di-PNAs-CG, GC and GG-could form ordered assemblies, as observed by electron microscopy, and these di-PNAs efficiently assembled into discrete architectures within a few minutes. The X-ray crystal structure of the GC di-PNA showed the occurrence of both stacking interactions and Watson-Crick base pairing. The assemblies were also found to exhibit optical properties including voltage-dependent electroluminescence and wide-range excitation-dependent fluorescence in the visible region.

Investigating the effects of peptoid substitutions in self-assembly of Fmoc-diphenylalanine derivatives.

PubMed

Rajbhandary, Annada; Nilsson, Bradley L

2017-03-01

Low molecular weight agents that undergo self-assembly into fibril networks with hydrogel properties are promising biomaterials. Most low molecular weight hydrogelators are discovered empirically or serendipitously due to imperfect understanding of the mechanisms of self-assembly, the packing structure of self-assembled materials, and how the self-assembly process corresponds to emergent hydrogelation. Herein, the mechanisms of self-assembly and hydrogelation of N-fluorenylmethoxycarbonyl diphenylalanine (Fmoc-PhePhe), a well-studied low molecular weight hydrogelator, is probed by systematic comparison with derivatives in which Phe residues are replaced by corresponding N-benzyl glycine peptoid (Nphe) analogs. Peptoids are peptidomimetics that shift display of side chain functionality from the α-carbon to the terminal nitrogen. This alters the hydrogen bonding capacity, the side chain presentation geometry, amide cis/trans isomerization equilibrium, and β-sheet potential of the peptoid relative to the corresponding amino acid in the context of peptidic polymers. It was found that amino acid/peptoid hybrids Fmoc-Phe-Nphe and Fmoc-Nphe-Phe have altered fibril self-assembly propensity and reduced hydrogelation capacity relative to the parent dipeptide, and that fibril self-assembly of the dipeptoid, Fmoc-Nphe-Nphe, is completely curtailed. These findings provide insight into the potential of low molecular weight peptoids and peptide/peptoid hybrids as hydrogelation agents and illuminate the importance of hydrogen bonding and π-π interaction geometry in facilitating self-assembly of Fmoc-Phe-Phe. © 2016 Wiley Periodicals, Inc.

Surface modification of poly(D,L-lactic acid) scaffolds for orthopedic applications: a biocompatible, nondestructive route via diazonium chemistry.

PubMed

Mahjoubi, Hesameddin; Kinsella, Joseph M; Murshed, Monzur; Cerruti, Marta

2014-07-09

Scaffolds made with synthetic polymers such as polyesters are commonly used in bone tissue engineering. However, their hydrophobicity and the lack of specific functionalities make their surface not ideal for cell adhesion and growth. Surface modification of these materials is thus crucial to enhance the scaffold's integration in the body. Different surface modification techniques have been developed to improve scaffold biocompatibility. Here we show that diazonium chemistry can be used to modify the outer and inner surfaces of three-dimensional poly(D,L-lactic acid) (PDLLA) scaffolds with phosphonate groups, using a simple two-step method. By changing reaction time and impregnation procedure, we were able to tune the concentration of phosphonate groups present on the scaffolds, without degrading the PDLLA matrix. To test the effectiveness of this modification, we immersed the scaffolds in simulated body fluid, and characterized them with scanning electron microscopy, X-ray photoelectron spectroscopy, Raman, and infrared spectroscopy. Our results showed that a layer of hydroxyapatite particles was formed on all scaffolds after 2 and 4 weeks of immersion; however, the precipitation was faster and in larger amounts on the phosphonate-modified than on the bare PDLLA scaffolds. Both osteogenic MC3T3-E1 and chondrogenic ATDC5 cell lines showed increased cell viability/metabolic activity when grown on a phosphonated PDLLA surface in comparison to a control PDLLA surface. Also, more calcium-containing minerals were deposited by cultures grown on phosphonated PDLLA, thus showing the pro-mineralization properties of the proposed modification. This work introduces diazonium chemistry as a simple and biocompatible technique to modify scaffold surfaces, allowing to covalently and homogeneously bind a number of functional groups without degrading the scaffold's polymeric matrix.

Utilization of Glyphosate as Phosphate Source: Biochemistry and Genetics of Bacterial Carbon-Phosphorus Lyase

PubMed Central

Zechel, David L.; Jochimsen, Bjarne

2014-01-01

SUMMARY After several decades of use of glyphosate, the active ingredient in weed killers such as Roundup, in fields, forests, and gardens, the biochemical pathway of transformation of glyphosate phosphorus to a useful phosphorus source for microorganisms has been disclosed. Glyphosate is a member of a large group of chemicals, phosphonic acids or phosphonates, which are characterized by a carbon-phosphorus bond. This is in contrast to the general phosphorus compounds utilized and metabolized by microorganisms. Here phosphorus is found as phosphoric acid or phosphate ion, phosphoric acid esters, or phosphoric acid anhydrides. The latter compounds contain phosphorus that is bound only to oxygen. Hydrolytic, oxidative, and radical-based mechanisms for carbon-phosphorus bond cleavage have been described. This review deals with the radical-based mechanism employed by the carbon-phosphorus lyase of the carbon-phosphorus lyase pathway, which involves reactions for activation of phosphonate, carbon-phosphorus bond cleavage, and further chemical transformation before a useful phosphate ion is generated in a series of seven or eight enzyme-catalyzed reactions. The phn genes, encoding the enzymes for this pathway, are widespread among bacterial species. The processes are described with emphasis on glyphosate as a substrate. Additionally, the catabolism of glyphosate is intimately connected with that of aminomethylphosphonate, which is also treated in this review. Results of physiological and genetic analyses are combined with those of bioinformatics analyses. PMID:24600043

Self-assembly of cinnamic acid-capped gold nanoparticles

NASA Astrophysics Data System (ADS)

Wang, Li; Wei, Gang; Sun, Lanlan; Liu, Zhiguo; Song, Yonghai; Yang, Tao; Sun, Yujing; Guo, Cunlan; Li, Zhuang

2006-06-01

In this work, a new capping agent, cinnamic acid (CA) was used to synthesize Au nanoparticles (NPs) under ambient conditions. The size of the NPs can be controlled by adjusting the concentration of reductant (in our experiment sodium borohydride was used) or CA. The CA-stabilized Au NPs can self-assemble into 'nanowire-like' or 'pearl-necklace-like' nanostructures by adjusting the molar ratio of CA to HAuCl4 or by tuning the pH value of the Au colloidal solution. The process of Au NPs self-assembly was investigated by UV-vis spectroscopy and transmission electron microscopy. The results reveal that the induced dipole-dipole interaction is the driving force of Au NP linear assemblies.

Current Understanding of Perfluoroalkyl Acid Toxicology

EPA Science Inventory

The perfluoroalkyl acids (PFAAs) are a family of organic chemicals consisting of a perfluorinated carbon backbone (4-14 carbons in length) and an anionic head group (sulfonate, carboxylate or phosphonate). These compounds have excellent surface-tension reducing properties and hav...

Glyphosate catabolism by Pseudomonas sp

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

Shinabarger, D.L.

1986-01-01

The pathway for the degradation of glyphosate (N-phosphonomethylglycine) by Pseudomonas sp. PG2982 has been determined using metabolic radiolabeling experiments. Radiorespirometry experiments utilizing (3-/sup 14/C) glyphosate revealed that approximately 50-59% of the C3 carbon was oxidized to CO/sub 2/. Fractionation of stationary phase cells labeled with (3-/sup 14/C)glyphosate revealed that from 45-47% of the assimilated C3 carbon is distributed to proteins and that amino acids methionine and serine are highly labeled. The nucleic acid bases adenine and guanine received 90% of the C3 label that was incorporated into nucleic acids, and the only pyrimidine base labeled was thymine. Pulse labeling ofmore » PG2982 cells with (3-/sup 14/C)glyphosate revealed that (3-/sup 14/C)sarcosine is an intermediate in glyphosate degradation. Examination of crude extracts prepared from PG2982 cells revealed the presence of an enzyme that oxidizes sarcosine to glycine and formaldehyde. These results indicate that the first step in glyphosate degradation by PG2982 is cleavage of the carbon-phosphorus bond, resulting in the release of sarcosine and a phosphate group. The phosphate group is utilized as a source of phosphorus, and the sarcosine is degraded to glycine and formaldehyde. Phosphonate utilization by Pseudomonas sp. PG2982 was investigated. Each of the ten phosphonates tested were utilized as a sole source of phosphorus by PG2982. Representative compounds tested included alkylphosphonates, 1-amino-substituted alkylphosphonates, amino-terminal phosphonates, and an arylphosphonate. PG2982 cultures degraded phenylphosphonate to benzene and produced methane from methylphosphonate. The data indicate that PG2982 is capable of cleaving the carbon-phosphorus bond of several structurally different phosphonates.« less

Role of Achiral Nucleobases in Multicomponent Chiral Self-Assembly: Purine-Triggered Helix and Chirality Transfer.

PubMed

Deng, Ming; Zhang, Li; Jiang, Yuqian; Liu, Minghua

2016-11-21

Chiral self-assembly is a basic process in biological systems, where many chiral biomolecules such as amino acids and sugars play important roles. Achiral nucleobases usually covalently bond to saccharides and play a significant role in the formation of the double helix structure. However, it remains unclear how the achiral nucleobases can function in chiral self-assembly without the sugar modification. Herein, we have clarified that purine nucleobases could trigger N-(9-fluorenylmethox-ycarbonyl) (Fmoc)-protected glutamic acid to self-assemble into helical nanostructures. Moreover, the helical nanostructure could serve as a matrix and transfer the chirality to an achiral fluorescence probe, thioflavin T (ThT). Upon chirality transfer, the ThT showed not only supramolecular chirality but also circular polarized fluorescence (CPL). Without the nucleobase, the self-assembly processes cannot happen, thus providing an example where achiral molecules played an essential role in the expression and transfer of the chirality. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Phosphonate-anchored monolayers for antibody binding to magnetic nanoparticles.

PubMed

Benbenishty-Shamir, Helly; Gilert, Roni; Gotman, Irena; Gutmanas, Elazar Y; Sukenik, Chaim N

2011-10-04

Targeted delivery of magnetic iron oxide nanoparticles (IONPs) to a specific tissue can be achieved by conjugation with particular biological ligands on an appropriately functionalized IONP surface. To take best advantage of the unique magnetic properties of IONPs and to maximize their blood half-life, thin, strongly bonded, functionalized coatings are required. The work reported herein demonstrates the successful application of phosphonate-anchored self-assembled monolayers (SAMs) as ultrathin coatings for such particles. It also describes a new chemical approach to the anchoring of antibodies on the surface of SAM-coated IONPs (using nucleophilic aromatic substitution). This anchoring strategy results in stable, nonhydrolyzable, covalent attachment and allows the reactivity of the particles toward antibody binding to be activated in situ, such that prior to the activation the modified surface is stable for long-term storage. While the SAMs do not have the well-packed crystallinity of other such monolayers, their structure was studied using smooth model substrates based on an iron oxide layer on a double-side polished silicon wafer. In this way, atomic force microscopy, ellipsometry, and contact angle goniometry (tools that could not be applied to the nanoparticles' surfaces) could contribute to the determination of their monomolecular thickness and uniformity. Finally, the successful conjugation of IgG antibodies to the SAM-coated IONPs such that the antibodies retain their biological activity is verified by their complexation to a secondary fluorescent antibody. © 2011 American Chemical Society

Organophosphonates utilization by soil strains of Ochrobactrum anthropi and Achromobacter sp.

PubMed

Ermakova, Inna T; Shushkova, Tatyana V; Sviridov, Alexey V; Zelenkova, Nina F; Vinokurova, Natalya G; Baskunov, Boris P; Leontievsky, Alexey A

2017-07-01

Four bacterial strains from glyphosate- or alkylphosphonates-contaminated soils were tested for ability to utilize different organophosphonates. All studied strains readily utilized methylphosphonic acid and a number of other phosphonates, but differed in their ability to degrade glyphosate. Only strains Ochrobactrum anthropi GPK 3 and Achromobacter sp. Kg 16 utilized this compound after isolation from enrichment cultures with glyphosate. Achromobacter sp. MPK 7 from the same enrichment culture, similar to Achromobacter sp. MPS 12 from methylphosphonate-polluted source, required adaptation to growth on GP. Studied strains varied significantly in their growth parameters, efficiency of phosphonates degradation and characteristic products of this process, as well as in their energy metabolism. These differences give grounds to propose a possible model of interaction between these strains in microbial consortium in phosphonate-contaminated soils.

Novel alpha-hydroxy phosphonic acids via castor oil

USDA-ARS?s Scientific Manuscript database

Hydroxy fatty acids (HFAs) have found a number of uses in today’s market, with uses ranging from materials to pharmaceuticals. Castor oil has served as a versatile HFA; its principle component, ricinoleic acid, can be isolated from castor oil and has been modified extensively for a number of applica...

Hydrothermal syntheses, characterizations and crystal structures of a new lead(II) carboxylate-phosphonate with a double layer structure and a new nickel(II) carboxylate-phosphonate containing a hydrogen-bonded 2D layer with intercalation of ethylenediamines

NASA Astrophysics Data System (ADS)

Song, Jun-Ling; Mao, Jiang-Gao; Sun, Yan-Qiong; Zeng, Hui-Yi; Kremer, Reinhard K.; Clearfield, Abraham

2004-03-01

Hydrothermal reactions of N, N-bis(phosphonomethyl)aminoacetic acid (HO 2CCH 2N(CH 2PO 3H 2) 2) with metal(II) salts afforded two new metal carboxylate-phosphonates, namely, Pb 2[O 2CCH 2N(CH 2PO 3)(CH 2PO 3H)]·H 2O ( 1) and {NH 3CH 2CH 2NH 3}{Ni[O 2CCH 2N(CH 2PO 3H) 2](H 2O) 2} 2 ( 2). Among two unique lead(II) ions in the asymmetric unit of complex 1, one is five coordinated by five phosphonate oxygen atoms from 5 ligands, whereas the other one is five-coordinated by a tridentate chelating ligand (1 N and 2 phosphonate O atoms) and two phosphonate oxygen atoms from two other ligands. The carboxylate group of the ligand remains non-coordinated. The bridging of above two types of lead(II) ions through phosphonate groups resulted in a <002> double layer with the carboxylate group of the ligand as a pendant group. These double layers are further interlinked via hydrogen bonds between the carboxylate groups into a 3D network. The nickel(II) ion in complex 2 is octahedrally coordinated by a tetradentate chelating ligand (two phosphonate oxygen atoms, one nitrogen and one carboxylate oxygen atoms) and two aqua ligands. These {Ni[O 2CCH 2N(CH 2PO 3H) 2][H 2O] 2} - anions are further interlinked via hydrogen bonds between non-coordinated phosphonate oxygen atoms to form a <800> hydrogen bonded 2D layer. The 2H-protonated ethylenediamine cations are intercalated between two layers, forming hydrogen bonds with the non-coordinated carboxylate oxygen atoms. Results of magnetic measurements for complex 2 indicate that there is weak Curie-Weiss behavior with θ=-4.4 K indicating predominant antiferromagnetic interaction between the Ni(II) ions. Indication for magnetic low-dimension magnetism could not be detected.

Assembling new technologies at the interface of materials science and biology

NASA Astrophysics Data System (ADS)

Stendahl, John C.

Molecular self-assembly can be used to construct advanced materials by taking cues from nature and harnessing noncovalent interactions. This bottom-up approach affords molecular level precision that can cultivate pathways to improved materials function. The graduate research presented in this thesis integrates molecular self-assembly with traditional concepts in chemistry and materials science, with the ultimate goal of developing innovative solutions in technology and medicine. In the field of polymer engineering, self-assembly was used to create supramolecular nanoribbons that, when incorporated into polystyrene, modify its microstructure and significantly enhance its toughness and ductility. In medicine, self-assembly was used to create ordered, chemically functional materials to improve interactions with cells and other constituents of the biological environment. One system that was investigated is based on a triblock molecule in which cholesterol is connected to a lysine dendron by a flexible oligo-(L-lactic acid) spacer. These molecules self-assemble into polar surface coatings on fibrous poly(L-lactic acid) scaffolds that improve the scaffold's wettability and increase its retention of cells during seeding. Another self-assembling system that was investigated for biomedical applications is a family of molecules referred to as peptide amphiphiles (PA's). PA's consist of hydrophobic alkyl tails connected to short, hydrophilic peptides that incorporate biological signaling epitopes. These molecules spontaneously assemble into networks of well-defined nanofibers in aqueous environments, with the signaling epitopes presented in high density on the nanofiber exteriors. Nanofiber assembly is triggered by charge screening on the peptides and is able to produce self-supporting gels in concentrations of less than 1.0 wt.-%. The assembly process and mechanical properties of PA gels was investigated in detail with vibrational spectroscopy and oscillatory rheology. PA nanofibers were used in conjunction with fibrous poly(L-lactic acid] fabrics to create chemically functional scaffolds to facilitate islet cell transplantation. In transplant studies in diabetic mice, the use of scaffolds for islet delivery was shown to significantly improve transplant outcomes over free islet injections. Together, these studies illustrate that molecular self-assembly can be used to create functional materials for a variety of applications. These materials utilize noncovalent interactions to produce supramolecular structures that have important impacts on properties.

Perfluoroalkyl acids : Recent activities and research progress

EPA Science Inventory

The perfluoroalkyl acids (PFAAs) are a family of man-made fluorinated organic chemicals consisting of a carbon backbone typically of four to fourteen in length and a charged functional moiety (primarily carboxylate, sulfonate or phosphonate). The two most widely known PFAAs are ...

Reaction chemistry and ligand exchange at cadmium selenide nanocrystal surfaces

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

Owen, Jonathan; Park, Jungwon; Trudeau, Paul-Emile

Chemical modification of nanocrystal surfaces is fundamentally important to their assembly, their implementation in biology and medicine, and greatly impacts their electrical and optical properties. However, it remains a major challenge owing to a lack of analytical tools to directly determine nanoparticle surface structure. Early nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) studies of CdSe nanocrystals prepared in tri-n-octylphosphine oxide (1) and tri-n-octylphosphine (2), suggested these coordinating solvents are datively bound to the particle surface. However, assigning the broad NMR resonances of surface-bound ligands is complicated by significant concentrations of phosphorus-containing impurities in commercial sources of 1, andmore » XPS provides only limited information about the nature of the phosphorus containing molecules in the sample. More recent reports have shown the surface ligands of CdSe nanocrystals prepared in technical grade 1, and in the presence of alkylphosphonic acids, include phosphonic and phosphinic acids. These studies do not, however, distinguish whether these ligands are bound datively, as neutral, L-type ligands, or by X-type interaction of an anionic phosphonate/phosphinate moiety with a surface Cd{sup 2+} ion. Answering this question would help clarify why ligand exchange with such particles does not proceed generally as expected based on a L-type ligand model. By using reagents with reactive silicon-chalcogen and silicon-chlorine bonds to cleave the ligands from the nanocrystal surface, we show that our CdSe and CdSe/ZnS core-shell nanocrystal surfaces are likely terminated by X-type binding of alkylphosphonate ligands to a layer of Cd{sup 2+}/Zn{sup 2+} ions, rather than by dative interactions. Further, we provide spectroscopic evidence that 1 and 2 are not coordinated to our purified nanocrystals.« less

Role of four conserved aspartic acid residues of EF-loops in the metal ion binding and in the self-assembly of ciliate Euplotes octocarinatus centrin.

PubMed

Liu, Wen; Duan, Lian; Sun, Tijian; Yang, Binsheng

2016-12-01

Ciliate Euplotes octocarinatus centrin (EoCen) is an EF-hand calcium-binding protein closely related to the prototypical calcium sensor protein calmodulin. Four mutants (D37K, D73K, D110K and D146K) were created firstly to elucidate the importance of the first aspartic acid residues (Asp37, Asp73, Asp110 and Asp146) in the beginning of the four EF-loops of EoCen. Aromatic-sensitized Tb 3+ fluorescence indicates that the aspartic acid residues are very important for the metal-binding of EoCen, except for Asp73 (in EF-loop II). Resonance light scattering (RLS) measurements for different metal ions (Ca 2+ and Tb 3+ ) binding proteins suggest that the order of four conserved aspartic acid residues for contributing to the self-assembly of EoCen is Asp37 > Asp146 > Asp110 > Asp73. Cross-linking experiment also exhibits that Asp37 and Asp146 play critical role in the self-assembly of EoCen. Asp37, in site I, which is located in the N-terminal domain, plays the most important role in the metal ion-dependent self-assembly of EoCen, and there is cooperativity between N-terminal and C-terminal domain (especially the site IV). In addition, the dependence of Tb 3+ induced self-assembly of EoCen and the mutants on various factors, including ionic strength and pH, were characterized using RLS. Finally, 2-p-toluidinylnaphthalene-6-sulfonate (TNS) binding, ionic strength and pH control experiments indicate that in the process of EoCen self-assembly, molecular interactions are mediated by both electrostatic and hydrophobic forces, and the hydrophobic interaction has the important status.

Effect of short-chain fatty acids on the formation of amylose microparticles by amylosucrase.

PubMed

Lim, Min-Cheol; Park, Kyu-Hwan; Choi, Jong-Hyun; Lee, Da-Hee; Letona, Carlos Andres Morales; Baik, Moo-Yeol; Park, Cheon-Seok; Kim, Young-Rok

2016-10-20

Amylose microparticles can be produced by self-assembly of amylose molecules through an amylosucrase-mediated synthesis. Here we investigated the role of short-chain fatty acids in the formation of amylose microparticles and the fate of these fatty acids at the end of the reaction. The rate of self-assembly and production yields of amylose microparticles were significantly enhanced in the presence of fatty acids. The effect was dependent on the length of the fatty acid carbon tail; butanoic acid (C4) was the most effective, followed by hexanoic acid (C6) and octanoic acid (C8). The amylose microparticles were investigated by carrying out SEM, XRD, Raman, NMR, FT-IR and DSC analysis. The size, morphology and crystal structure of the resulting amylose microparticles were comparable with those of amylose microparticles produced without fatty acids. The results indicated the carboxyl group of the fatty acid to be responsible for promoting the self-assembly of amylose chains to form microparticles. The fatty acids were eventually removed from the microstructure through the tight association of amylose double helices to form the amylose microparticles. Copyright © 2016 Elsevier Ltd. All rights reserved.

Nonequilibrium Self-Assembly of π-Conjugated Oligopeptides in Solution.

PubMed

Li, Bo; Li, Songsong; Zhou, Yuecheng; Ardoña, Herdeline Ann M; Valverde, Lawrence R; Wilson, William L; Tovar, John D; Schroeder, Charles M

2017-02-01

Supramolecular assembly is a powerful method that can be used to generate materials with well-defined structures across multiple length scales. Supramolecular assemblies consisting of biopolymer-synthetic polymer subunits are specifically known to exhibit exceptional structural and functional diversity as well as programmable control of noncovalent interactions through hydrogen bonding in biopolymer subunits. Despite recent progress, there is a need to control and quantitatively understand assembly under nonequilibrium conditions. In this work, we study the nonequilibrium self-assembly of π-conjugated synthetic oligopeptides using a combination of experiments and analytical modeling. By isolating an aqueous peptide solution droplet within an immiscible organic layer, the rate of peptide assembly in the aqueous solution can be controlled by tuning the transport rate of acid that is used to trigger assembly. Using this approach, peptides are guided to assemble under reaction-dominated and diffusion-dominated conditions, with results showing a transition from a diffusion-limited reaction front to spatially homogeneous assembly as the transport rate of acid decreases. Interestingly, our results show that the morphology of self-assembled peptide fibers is controlled by the assembly kinetics such that increasingly homogeneous structures of self-assembled synthetic oligopeptides were generally obtained using slower rates of assembly. We further developed an analytical reaction-diffusion model to describe oligopeptide assembly, and experimental results are compared to the reaction-diffusion model across a range of parameters. Overall, this work highlights the importance of molecular self-assembly under nonequilibrium conditions, specifically showing that oligopeptide assembly is governed by a delicate balance between reaction kinetics and transport processes.

Multidimensional Self-Assembled Structures of Alkylated Cellulose Oligomers Synthesized via in Vitro Enzymatic Reactions.

PubMed

Yataka, Yusuke; Sawada, Toshiki; Serizawa, Takeshi

2016-10-04

The self-assembly of biomolecules into highly ordered nano-to-macroscale structures is essential in the construction of biological tissues and organs. A variety of biomolecular assemblies composed of nucleic acids, peptides, and lipids have been used as molecular building units for self-assembled materials. However, crystalline polysaccharides have rarely been utilized in self-assembled materials. In this study, we describe multidimensional self-assembled structures of alkylated cellulose oligomers synthesized via in vitro enzymatic reactions. We found that the alkyl chain length drastically affected the assembled morphologies and allomorphs of cellulose moieties. The modulation of the intermolecular interactions of cellulose oligomers by alkyl substituents was highly effective at controlling their assembly into multidimensional structures. This study proposes a new potential of crystalline oligosaccharides for structural components of molecular assemblies with controlled morphologies and crystal structures.

Effective methylation of phosphonic acids related to chemical warfare agents mediated by trimethyloxonium tetrafluoroborate for their qualitative detection and identification by gas chromatography-mass spectrometry.

PubMed

Valdez, Carlos A; Leif, Roald N; Alcaraz, Armando

2016-08-24

The effective methylation of phosphonic acids related to chemical warfare agents (CWAs) employing trimethyloxonium tetrafluoroborate (TMO·BF4) for their qualitative detection and identification by gas chromatography-mass spectrometry (GC-MS) is presented. The methylation occurs in rapid fashion (1 h) and can be conveniently carried out at ambient temperature, thus providing a safer alternative to the universally employed diazomethane-based methylation protocols. Optimization of the methylation parameters led us to conclude that methylene chloride was the ideal solvent to carry out the derivatization, and that even though methylated products can be observed surfacing after only 1 h, additional time was not found to be detrimental but beneficial to the process particularly when dealing with analytes at low concentrations (∼10 μg mL(-1)). Due to its insolubility in methylene chloride, TMO·BF4 conveniently settles to the bottom during the reaction and does not produce additional interfering by-products that may further complicate the GC-MS analysis. The method was demonstrated to successfully methylate a variety of Schedule 2 phosphonic acids, including their half esters, resulting in derivatives that were readily detected and identified using the instrument's spectral library. Most importantly, the method was shown to simultaneously methylate a mixture of the organophosphorus-based nerve agent hydrolysis products: pinacolyl methylphosphonate (PMPA), cyclohexyl methylphosphonate (CyMPA) and ethyl methylphosphonate (EMPA) (at a 10 μg mL(-1) concentration each) in a fatty acid ester-rich organic matrix (OPCW-PT-O3) featured in the 38th Organisation for the Prohibition of Chemical Weapons (OPCW) Proficiency Test. In addition, the protocol was found to effectively methylate N,N-diethylamino ethanesulfonic acid and N,N-diisopropylamino ethanesulfonic acid that are products arising from the oxidative degradation of the V-series agents VR and VX respectively. The work described herein represents the first report on the use of TMO·BF4 as a viable, stable and safe agent for the methylation of phosphonic acids and their half esters and within the context of an OPCW Proficiency Test sample analysis. Copyright © 2016 Elsevier B.V. All rights reserved.

Nanoscale Platelet Formation by Monounsaturated and Saturated Sophorolipids under Basic pH Conditions.

PubMed

Cuvier, Anne-Sophie; Babonneau, Florence; Berton, Jan; Stevens, Christian V; Fadda, Giulia C; Péhau-Arnaudet, Gérard; Le Griel, Patrick; Prévost, Sylvain; Perez, Javier; Baccile, Niki

2015-12-21

The self-assembly behavior of the yeast-derived bolaamphiphile sophorolipid (SL) is generally studied under acidic/neutral pH conditions, at which micellar and fibrillar aggregates are commonly found, according to the (un)saturation of the aliphatic chain: the cis form, which corresponds to the oleic acid form of SL, spontaneously forms micelles, whereas the saturated form, which corresponds to the stearic acid form of SL, preferentially forms chiral fibers. By using small-angle light and X-ray scattering (SLS, SAXS) combined with high-sensitivity transmission electron microscopy imaging under cryogenic conditions (cryo-TEM), the nature of the self-assembled structures formed by these two compounds above pH 10, which is the pH at which they are negatively charged due to the presence of a carboxylate group, has been explored. Under these conditions, these compounds self-assemble into nanoscale platelets, despite the different molecular structures. This work shows that the electrostatic repulsion forces generated by COO(-) mainly drive the self-assembly process at basic pH, in contrast with that found at pH below neutrality, at which self-assembly is driven by van der Waals forces and hydrogen bonding, and thus, is in agreement with previous findings on carbohydrate-based gemini surfactants. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Generation and exploitation of acyclic azomethine imines in chiral Brønsted acid catalysis

NASA Astrophysics Data System (ADS)

Hashimoto, Takuya; Kimura, Hidenori; Kawamata, Yu; Maruoka, Keiji

2011-08-01

Successful implementation of a catalytic asymmetric synthesis strategy to produce enantiomerically enriched compounds requires the adoption of suitable prochiral substrates. The combination of an azomethine imine electrophile with various nucleophiles could give straightforward access to a number of synthetically useful chiral hydrazines, but is used rarely. Here we report the exploitation of acyclic azomethine imines as a new type of prochiral electrophile. They can be generated in situ by the condensation of N‧-benzylbenzoylhydrazide with a variety of aldehydes in the presence of a catalytic amount of an axially chiral dicarboxylic acid. By trapping these electrophiles with alkyl diazoacetate or (diazomethyl)phosphonate nucleophiles, we produced a diverse array of chiral α-diazo-β-hydrazino esters and phosphonates with excellent enantioselectivities.

Opal-like Multicolor Appearance of Self-Assembled Photonic Array.

PubMed

Arnon, Zohar A; Pinotsi, Dorothea; Schmidt, Matthias; Gilead, Sharon; Guterman, Tom; Sadhanala, Aditya; Ahmad, Shahab; Levin, Aviad; Walther, Paul; Kaminski, Clemens F; Fändrich, Marcus; Kaminski Schierle, Gabriele S; Adler-Abramovich, Lihi; Shimon, Linda J W; Gazit, Ehud

2018-06-20

Molecular self-assembly of short peptide building blocks leads to the formation of various material architectures that may possess unique physical properties. Recent studies had confirmed the key role of biaromaticity in peptide self-assembly, with the diphenylalanine (FF) structural family as an archetypal model. Another significant direction in the molecular engineering of peptide building blocks is the use of fluorenylmethoxycarbonyl (Fmoc) modification, which promotes the assembly process and may result in nanostructures with distinctive features and macroscopic hydrogel with supramolecular features and nanoscale order. Here, we explored the self-assembly of the protected, noncoded fluorenylmethoxycarbonyl-β,β-diphenyl-Ala-OH (Fmoc-Dip) amino acid. This process results in the formation of elongated needle-like crystals with notable aromatic continuity. By altering the assembly conditions, arrays of spherical particles were formed that exhibit strong light scattering. These arrays display vivid coloration, strongly resembling the appearance of opal gemstones. However, unlike the Rayleigh scattering effect produced by the arrangement of opal, the described optical phenomenon is attributed to Mie scattering. Moreover, by controlling the solution evaporation rate, i.e., the assembly kinetics, we were able to manipulate the resulting coloration. This work demonstrates a bottom-up approach, utilizing self-assembly of a protected amino acid minimal building block, to create arrays of organic, light-scattering colorful surfaces.

Determination of polyfluoroalkyl phosphoric acid diesters, perfluoroalkyl phosphonic acids, perfluoroalkyl phosphinic acids, perfluoroalkyl carboxylic acids, and perfluoroalkane sulfonic acids in lake trout from the Great Lakes region.

PubMed

Guo, Rui; Reiner, Eric J; Bhavsar, Satyendra P; Helm, Paul A; Mabury, Scott A; Braekevelt, Eric; Tittlemier, Sheryl A

2012-11-01

A comprehensive method to extract perfluoroalkyl carboxylic acids, perfluoroalkane sulfonic acids, perfluoroalkyl phosphonic acids, perfluoroalkyl phosphinic acids, and polyfluoroalkyl phosphoric acid diesters simultaneously from fish samples has been developed. The recoveries of target compounds ranged from 78 % to 121 %. The new method was used to analyze lake trout (Salvelinus namaycush) from the Great Lakes region. The results showed that the total perfluoroalkane sulfonate concentrations ranged from 0.1 to 145 ng/g (wet weight) with perfluorooctane sulfonate (PFOS) as the dominant contaminant. Concentrations in fish between lakes were in the order of Lakes Ontario ≈ Erie > Huron > Superior ≈ Nipigon. The total perfluoroalkyl carboxylic acid concentrations ranged from 0.2 to 18.2 ng/g wet weight. The aggregate mean perfluorooctanoic acid (PFOA) concentration in fish across all lakes was 0.045 ± 0.023 ng/g. Mean concentrations of PFOA were not significantly different (p > 0.1) among the five lakes. Perfluoroalkyl phosphinic acids were detected in lake trout from Lake Ontario, Lake Erie, and Lake Huron with concentration ranging from non-detect (ND) to 0.032 ng/g. Polyfluoroalkyl phosphoric acid diesters were detected only in lake trout from Lake Huron, at levels similar to perfluorooctanoic acid.

Relative binding affinity of carboxylate-, phosphonate-, and bisphosphonate-functionalized gold nanoparticles targeted to damaged bone tissue

NASA Astrophysics Data System (ADS)

Ross, Ryan D.; Cole, Lisa E.; Roeder, Ryan K.

2012-10-01

Functionalized Au NPs have received considerable recent interest for targeting and labeling cells and tissues. Damaged bone tissue can be targeted by functionalizing Au NPs with molecules exhibiting affinity for calcium. Therefore, the relative binding affinity of Au NPs surface functionalized with either carboxylate ( l-glutamic acid), phosphonate (2-aminoethylphosphonic acid), or bisphosphonate (alendronate) was investigated for targeted labeling of damaged bone tissue in vitro. Targeted labeling of damaged bone tissue was qualitatively verified by visual observation and backscattered electron microscopy, and quantitatively measured by the surface density of Au NPs using field-emission scanning electron microscopy. The surface density of functionalized Au NPs was significantly greater within damaged tissue compared to undamaged tissue for each functional group. Bisphosphonate-functionalized Au NPs exhibited a greater surface density labeling damaged tissue compared to glutamic acid- and phosphonic acid-functionalized Au NPs, which was consistent with the results of previous work comparing the binding affinity of the same functionalized Au NPs to synthetic hydroxyapatite crystals. Targeted labeling was enabled not only by the functional groups but also by the colloidal stability in solution. Functionalized Au NPs were stabilized by the presence of the functional groups, and were shown to remain well dispersed in ionic (phosphate buffered saline) and serum (fetal bovine serum) solutions for up to 1 week. Therefore, the results of this study suggest that bisphosphonate-functionalized Au NPs have potential for targeted delivery to damaged bone tissue in vitro and provide motivation for in vivo investigation.

Quantifying quality in DNA self-assembly

PubMed Central

Wagenbauer, Klaus F.; Wachauf, Christian H.; Dietz, Hendrik

2014-01-01

Molecular self-assembly with DNA is an attractive route for building nanoscale devices. The development of sophisticated and precise objects with this technique requires detailed experimental feedback on the structure and composition of assembled objects. Here we report a sensitive assay for the quality of assembly. The method relies on measuring the content of unpaired DNA bases in self-assembled DNA objects using a fluorescent de-Bruijn probe for three-base ‘codons’, which enables a comparison with the designed content of unpaired DNA. We use the assay to measure the quality of assembly of several multilayer DNA origami objects and illustrate the use of the assay for the rational refinement of assembly protocols. Our data suggests that large and complex objects like multilayer DNA origami can be made with high strand integration quality up to 99%. Beyond DNA nanotechnology, we speculate that the ability to discriminate unpaired from paired nucleic acids in the same macromolecule may also be useful for analysing cellular nucleic acids. PMID:24751596

Synthetic Analogs of Phospholipid Metabolites as Antimalarials.

DTIC Science & Technology

1979-07-01

phosphatidic acid analogs containing ether and phosphonate groups; completely non-hydrolyzable lecithin analogs containing phosphinate and ether groups...The phosphatidic acid and lecithin target compounds were successfully synthesized and submitted, together with a number of intermediates. A model of a... Phosphatidic acid analogs ......................... 5 Z.Z Lecithin Analogs .................................. 6 2.3 Analogs of Cytidine Diphosphate

Assembly of barcode-like nucleic acid nanostructures.

PubMed

Wang, Pengfei; Tian, Cheng; Li, Xiang; Mao, Chengde

2014-10-15

Barcode-like (BC) nanopatterns from programmed self-assembly of nucleic acids (DNA and RNA) are reported. BC nanostructures are generated by the introduction of open spaces at selected sites to an otherwise closely packed, plain, rectangle nucleic acid nanostructure. This strategy is applied to nanostructures assembled from both origami approach and single stranded tile approach. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Demonstration of spread-on peel-off consumer products for sampling surfaces contaminated with pesticides and chemical warfare agent signatures.

PubMed

Behringer, Deborah L; Smith, Deborah L; Katona, Vanessa R; Lewis, Alan T; Hernon-Kenny, Laura A; Crenshaw, Michael D

2014-08-01

A terrorist attack using toxic chemicals is an international concern. The utility of rubber cement and latex body paint as spray-on/spread-on peel-off collection media for signatures attributable to pesticides and chemical warfare agents from interior building and public transportation surfaces two weeks post-deposition is demonstrated. The efficacy of these media to sample escalator handrail, stainless steel, vinyl upholstery fabric, and wood flooring is demonstrated for two pesticides and eight chemicals related to chemical warfare agents. The chemicals tested are nicotine, parathion, atropine, diisopropyl methylphosphonate, dimethyl methylphosphonate, dipinacolyl methylphosphonate, ethyl methylphosphonic acid, isopropyl methylphosphonic acid, methylphosphonic acid, and thiodiglycol. Amounts of each chemical found are generally greatest when latex body paint is used. Analytes with low volatility and containing an alkaline nitrogen or a sulfur atom (e.g., nicotine and parathion) usually are recovered to a greater extent than the neutral phosphonate diesters and acidic phosphonic acids (e.g., dimethyl methylphosphonate and ethyl methylphosphonic acid). Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Tailoring peptide amphiphiles and their assemblies for biomedical applications

NASA Astrophysics Data System (ADS)

Lin, Brian

Peptide amphiphiles (PAs) are molecules composed of a peptide conjugated to a hydrophobic moiety, commonly a fatty acid. They closely resemble the structure of naturally occurring lipopeptides, produced by microbes as signaling and antimicrobial agents. The amphiphilic nature of PAs in concert with the large number of discovered functional peptides inspired scientists to exploit this molecular architecture for producing synthetic self-assembled bioactive materials. PA assemblies are sought after for a wide breadth of applications including disease therapy, regenerative medicine, and catalysis. However, with PAs, the peptide chemistry is a double-edged sword. The peptide component contributes significantly to both the activity and self-assembly. The physiochemical properties of different PAs lead to unique aggregation stability and morphological characteristics which are unpredictable, a priori. Therefore it is challenging to design bioactive PAs and control their self-assembly, simultaneously. This limitation slows the development of PAs for medical use. In this dissertation, methods to control the self-assembly of PAs and the effects of acylating a functional peptide will be discussed. In one part, efforts to direct the self-assembly of PAs into small spherical aggregates, a morphology infrequently observed, will be described. In another section, a strategy to control the stability of PA assemblies will be discussed. In the last section, a pH-responsive membrane perturbing peptide was modified with fatty acid tails and the properties of the resulting PAs will be presented. This dissertation provides some fundamental insight for the use and design of PA self-assemblies.

Electrooxidation of pyrrole-terminated self-assembled lipoic acid derivatives

NASA Astrophysics Data System (ADS)

Cabrita, Joana F.; Viana, Ana S.; Eberle, Christoph; Montforts, Franz-Peter; Mourato, Ana; Abrantes, Luisa M.

2009-08-01

New pyrrole derivatives, pyrrolyl lipoic acid (Py-LA 3) and dipyrrolyl lipoic acid (Py 2-LA 2) have been used for surface attachment and immobilisation on gold surfaces, by self-assembly. The electrooxidation of the surface-confined pyrroles was analysed by cyclic voltammetry and the modified electrodes morphological and thickness changes addressed by scanning probe microscopy and ellipsometry. The data support the formation of oligomers as a result of the pendant-pyrrolyl units ease oxidation but provide no evidence of an effective subsequent polymerisation.

Self-assembly modes of glycyrrhetinic acid esters in view of the crystal packing of related triterpene molecules.

PubMed

Langer, Dominik; Wicher, Barbara; Szczołko, Wojciech; Gdaniec, Maria; Tykarska, Ewa

2016-08-01

The crystal structures of three ester derivatives of glycyrrhetinic acid (GE) are reported. X-ray crystallography revealed that despite differences in the size of the ester substituents (ethyl, isopropyl and 2-morpholinoethyl) the scheme of molecular self-assembly is similar in all three cases but differs significantly from that observed in other known GE esters. According to our analysis, the two basic patterns of self-assembly of GE esters observed in their unsolvated crystals correspond to two distinct orientations of the ester groups relative to the triterpene backbone. Moreover, comparison of the self-assembly modes of GE esters in their unsolvated forms with the supramolecular organization of GE and carbenoxolone in their solvated crystals revealed that ester substituents replace solvent molecules hydrogen bonded to the COOH group at the triterpene skeleton, resulting in similar packing arrangements of these compounds.

Preparation and use of crystalline bis-monoorganic phosphonate and phosphate salts of tetravalent metals

DOEpatents

Maya, L.

1980-06-26

A method of preparing and using the crystalline organic derivatives of the tetravalent metal phosphates and phosphonates provides for the contacting of an aqueous solution of a metal nitrate, with a solution of an organophosphorus acid for a period of time at room temperature that is sufficient for the formation of a metal phosphate product, and thereafter recovering said product. According to the invention, the product of the disclosed process is used in effecting analytical separations, such as ion exchange and chromatography.

Marine methane paradox explained by bacterial degradation of dissolved organic matter

NASA Astrophysics Data System (ADS)

Repeta, Daniel J.; Ferrón, Sara; Sosa, Oscar A.; Johnson, Carl G.; Repeta, Lucas D.; Acker, Marianne; Delong, Edward F.; Karl, David M.

2016-12-01

Biogenic methane is widely thought to be a product of archaeal methanogenesis, an anaerobic process that is inhibited or outcompeted by the presence of oxygen and sulfate. Yet a large fraction of marine methane delivered to the atmosphere is produced in high-sulfate, fully oxygenated surface waters that have methane concentrations above atmospheric equilibrium values, an unexplained phenomenon referred to as the marine methane paradox. Here we use nuclear magnetic resonance spectroscopy to show that polysaccharide esters of three phosphonic acids are important constituents of dissolved organic matter in seawater from the North Pacific. In seawater and pure culture incubations, bacterial degradation of these dissolved organic matter phosphonates in the presence of oxygen releases methane, ethylene and propylene gas. Moreover, we found that in mutants of a methane-producing marine bacterium, Pseudomonas stutzeri, disrupted in the C-P lyase phosphonate degradation pathway, methanogenesis was also disabled, indicating that the C-P lyase pathway can catalyse methane production from marine dissolved organic matter. Finally, the carbon stable isotope ratio of methane emitted during our incubations agrees well with anomalous isotopic characteristics of seawater methane. We estimate that daily cycling of only about 0.25% of the organic matter phosphonate inventory would support the entire atmospheric methane flux at our study site. We conclude that aerobic bacterial degradation of phosphonate esters in dissolved organic matter may explain the marine methane paradox.

Frit inlet field-flow fractionation techniques for the characterization of polyion complex self-assemblies.

PubMed

Till, Ugo; Gaucher, Mireille; Amouroux, Baptiste; Gineste, Stéphane; Lonetti, Barbara; Marty, Jean-Daniel; Mingotaud, Christophe; Bria, Carmen R M; Williams, S Kim Ratanathanawongs; Violleau, Frédéric; Mingotaud, Anne-Françoise

2017-01-20

Polymer self-assemblies joining oppositely charged chains, known as polyion complexes (PICs), have been formed using poly(ethyleneoxide - b - acrylic acid)/poly(l-lysine), poly(ethyleneoxide-b-acrylic acid)/dendrigraft poly(l-lysine) and poly[(3-acrylamidopropyl) trimethylammonium chloride - b - N - isopropyl acrylamide]/poly(acrylic acid). The self-assemblies have been first characterized in batch by Dynamic Light Scattering. In a second step, their analysis by Flow Field-Flow Fractionation techniques (FlFFF) was examined. They were shown to be very sensitive to shearing, especially during the focus step of the fractionation, and this led to an incompatibility with asymmetrical FlFFF. On the other hand, Frit Inlet FlFFF proved to be very efficient to observe them, either in its symmetrical (FI-FlFFF) or asymmetrical version (FI-AsFlFFF). Conditions of elution were found to optimize the sample recovery in pure water. Spherical self-assemblies were detected, with a size range between 70-400nm depending on the polymers. Compared to batch DLS, FI-AsFlFFF clearly showed the presence of several populations in some cases. The influence of salt on poly(ethyleneoxide-b-acrylic acid) (PEO-PAA) 6000-3000/dendrigraft poly(l-lysine) (DGL 3) was also assessed in parallel in batch DLS and FI-AsFlFFF. Batch DLS revealed a first process of swelling of the self-assembly for low concentrations up to 0.8M followed by the dissociation. FI-AsFlFFF furthermore indicated a possible ejection of DGL3 from the PIC assembly for concentrations as low as 0.2M, which could not be observed in batch DLS. Copyright © 2016 Elsevier B.V. All rights reserved.

Synthesis of lesquerella a-hydroxy phosphonates

USDA-ARS?s Scientific Manuscript database

Hydroxy fatty acids (HFAs) have found a number of uses in today’s market, with uses ranging from industrial materials to pharmaceuticals. Castor oil, which is obtained from castor seeds, has served as a source of a versatile HFA; its principle component, ricinoleic acid, can be isolated from castor ...

Synthesis and Characterization of Fatty Acid/Amino Acid Self-Assemblies

PubMed Central

Gajowy, Joanna; Bolikal, Durgadas; Kohn, Joachim; El Fray, Miroslawa

2014-01-01

In this paper, we discuss the synthesis and self-assembling behavior of new copolymers derived from fatty acid/amino acid components, namely dimers of linoleic acid (DLA) and tyrosine derived diphenols containing alkyl ester pendent chains, designated as “R” (DTR). Specific pendent chains were ethyl (E) and hexyl (H). These poly(aliphatic/aromatic-ester-amide)s were further reacted with poly(ethylene glycol) (PEG) and poly(ethylene glycol methyl ether) of different molecular masses, thus resulting in ABA type (hydrophilic-hydrophobic-hydrophilic) triblock copolymers. We used Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies to evaluate the chemical structure of the final materials. The molecular masses were estimated by gel permeation chromatography (GPC) measurements. The self-organization of these new polymeric systems into micellar/nanospheric structures in aqueous environment was evaluated using ultraviolet/visible (UV-VIS) spectroscopy, dynamic light scattering (DLS) and transmission electron microscopy (TEM). The polymers were found to spontaneously self-assemble into nanoparticles with sizes in the range 196–239 nm and critical micelle concentration (CMC) of 0.125–0.250 mg/mL. The results are quite promising and these materials are capable of self-organizing into well-defined micelles/nanospheres encapsulating bioactive molecules, e.g., vitamins or antibacterial peptides for antibacterial coatings on medical devices. PMID:25347356

A sensitive capacitive immunosensor for direct detection of human heart fatty acid-binding protein (h-FABP).

PubMed

Mihailescu, Carmen-Marinela; Stan, Dana; Iosub, Rodica; Moldovan, Carmen; Savin, Mihaela

2015-01-01

The fabrication of a capacitive interdigitated immunosensor (CID) based on a mixed self-assembled monolayer (mSAM) film for the direct detection of heart fatty-acid binding protein (h-FABP) without any labeling is described. The capacitance changes of mSAMs vs. homogenous ordered self-assembled monolayers (hSAMs) on gold work electrodes/covalently bonded antibodies/buffered medium are utilized for monitoring the specific antibody-antigen interaction. Capacitance measurements in the absence and presence of Faradaic currents were performed. The electrochemical properties of mixed monolayers were compared with those of a pure monolayer of 11-mercaptoundecanoic acid (MUA) self-assembled on gold surfaces. Taking into account the stability of the studied monolayers during the electrochemical experiments with the Faradaic process, the best SAM functionalization method was used for developing a sensitive capacitive immunosensor with a non-Faradaic process for direct immune detection of human h-FABP. Under the optimized conditions, the proposed mixed self-assembled monolayer (mSAM1) on gold electrode exhibited good insulating properties such as a capacitive behavior when detecting h-FABP from human serum in the range of 98 pg ml(-1)-100 ng ml(-1), with a detection limit of 0.836 ng ml(-1) comparative with a homogenous self-assembled monolayer (hSAM). Copyright © 2014 Elsevier B.V. All rights reserved.

Enrichment and low-level determination of glyphosate, aminomethylphosphonic acid and glufosinate in drinking water after cleanup by cation exchange resin.

PubMed

Küsters, Markus; Gerhartz, Michael

2010-04-01

For the determination of glyphosate, aminomethylphosphonic acid and glufosinate in drinking water, different procedures of enrichment and cleanup were examined using anion exchange or SPE. In many cases interactions of, e.g. alkaline earth metal ions especially calcium could be observed during enrichment and cleanup resulting in loss of analytes. For that reason, a novel cleanup and enrichment procedure for the determination of these phosphonic acid herbicides has been developed in drinking water using cation-exchange resin. In summary, the cleanup procedure with cation-exchange resin developed in this study avoids interactions as described above and is applicable to calcium-rich drinking water samples. After derivatization with 9-fluorenylmethylchloroformate followed by LC with fluorescence detection, LOD of 12, 14 and 12 ng/L and mean recoveries from real-world drinking water samples of 98+/-9, 100+/-16 and 101+/-11% were obtained for glyphosate, aminomethylphosphonic acid and glufosinate, respectively. The low LODs and the high precision permit the analysis of these phosphonic acid herbicides according to the guidelines of the European Commission.

pH and Amphiphilic Structure Direct Supramolecular Behavior in Biofunctional Assemblies

DOE PAGES

Moyer, Tyson J.; Finbloom, Joel A.; Chen, Feng; ...

2014-10-13

Supramolecular self-assembly offers promising new ways to control nanostructure morphology and respond to external stimuli. A pH-sensitive self-assembled system was developed to both control nanostructure shape and respond to the acidic microenvironment of tumors using self-assembling peptide amphiphiles (PAs). Here, by incorporating an oligo-histidine H 6 sequence, we developed two PAs that self-assembled into distinct morphologies on the nanoscale, either as nanofibers or spherical micelles, based on the incorporation of the aliphatic tail on the N-terminus or near the C-terminus, respectively. Both cylinder and sphere-forming PAs demonstrated reversible disassembly between pH 6.0 and 6.5 upon protonation of the histidine residuesmore » in acidic solutions. These PAs were then characterized and assessed for their potential to encapsulate hydrophobic chemotherapies. The H 6-based nanofiber assemblies encapsulated camptothecin (CPT) with up to 60% efficiency, a 7-fold increase in CPT encapsulation relative to spherical micelles. Additionally, pH-sensitive nanofibers showed improved tumor accumulation over both spherical micelles and nanofibers that did not change morphologies in acidic environments. We have demonstrated that the morphological transitions upon changes in pH of supramolecular nanostructures affect drug encapsulation and tumor accumulation. Lastly, our findings also suggest that these supramolecular events can be tuned by molecular design to improve the pharmacologic properties of nanomedicines.« less

Site-selective chemical modification of chymotrypsin using peptidyl derivatives bearing optically active diphenyl 1-amino-2-phenylethylphosphonate: Stereochemical effect of the diphenyl phosphonate moiety.

PubMed

Ono, Shin; Nakai, Takahiko; Kuroda, Hirofumi; Miyatake, Ryuta; Horino, Yoshikazu; Abe, Hitoshi; Umezaki, Masahito; Oyama, Hiroshi

2016-11-04

Diphenyl (α-aminoalkyl)phosphonates act as mechanism-based inhibitors against serine proteases by forming a covalent bond with the hydroxy group of the active center Ser residue. Because the covalent bond was found to be broken and replaced by 2-pyridinaldoxime methiodide (2PAM), we employed a peptidyl derivative bearing diphenyl 1-amino-2-phenylethylphosphonate moiety (Phe(p) (OPh)2 ) to target the active site of chymotrypsin and to selectively anchor to Lys175 in the vicinity of the active site. Previously, it was reported that the configuration of the α-carbon of phosphorus in diphenyl (α-aminoalkyl)phosphonates affects the inactivation reaction of serine proteases, i.e., the (R)-enantiomeric diphenyl phosphonate is comparable to l-amino acids and it effectively reacts with serine proteases, whereas the (S)-enantiomeric form does not. In this study, we evaluated the stereochemical effect of the phosphonate moiety on the selective chemical modification. Epimeric dipeptidyl derivatives, Ala-(R or S)-Phe(p) (OPh)2 , were prepared by separation with RP-HPLC. A tripeptidyl (R)-epimer (Ala-Ala-(R)-Phe(p) (OPh)2 ) exhibited a more potent inactivation ability against chymotrypsin than the (S)-epimer. The enzyme inactivated by the (R)-epimer was more effectively reactivated with 2PAM than the enzyme inactivated by the (S)-epimer. Finally, N-succinimidyl (NHS) active ester derivatives, NHS-Suc-Ala-Ala- (R or S)-Phe(p) (OPh)2 , were prepared, and we evaluated their action when modifying Lys175 in chymotrypsin. We demonstrated that the epimeric NHS derivative that possessed the diphenyl phosphonate moiety with the (R)-configuration effectively modified Lys175 in chymotrypsin, whereas that with the (S)-configuration did not. These results demonstrate the utility of peptidyl derivatives that bear an optically active diphenyl phosphonate moiety as affinity labeling probes in protein bioconjugation. © 2015 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 521-530, 2016. © 2015 Wiley Periodicals, Inc.

Insight into the collagen assembly in the presence of lysine and glutamic acid: An in vitro study.

PubMed

Liu, Xinhua; Dan, Nianhua; Dan, Weihua

2017-01-01

The aim of this study is to evaluate the effects of two different charged amino acids in collagen chains, lysine and glutamic acid, on the fibrillogenesis process of collagen molecules. The turbidity, zeta potential, and fiber diameter analysis suggest that introducing the positively charged lysine into collagen might improve the sizes or amounts of the self-assembled collagen fibrils significantly. Conversely, the negatively charged glutamic acid might restrict the self-assembly of collagen building blocks into a higher order structure. Meanwhile, the optimal fibrillogenesis condition is achieved when the concentration of lysine reaches to 1mM. Both scanning electron microscopy (SEM) and atomic force microscope (AFM) analysis indicates that compared to pure collagen fibrils, the reconstructed collagen-lysine co-fibrils exhibit a higher degree of inter-fiber entanglements with more straight and longer fibrils. Noted that the specific D-period patterns of the reconstructed collagen fibrils could be clearly discernible and the width of D-banding increases steadily after introducing lysine. Besides, the kinetic and thermodynamic collagen self-assembly analysis confirms that the rate constants of both the first and second assembly phase decrease after introducing lysine, and lysine could promote the process of collagen fibrillogenesis obeying the laws of thermodynamics. Copyright © 2016 Elsevier B.V. All rights reserved.

The sources, fate, and toxicity of chemical warfare agent degradation products.

PubMed Central

Munro, N B; Talmage, S S; Griffin, G D; Waters, L C; Watson, A P; King, J F; Hauschild, V

1999-01-01

We include in this review an assessment of the formation, environmental fate, and mammalian and ecotoxicity of CW agent degradation products relevant to environmental and occupational health. These parent CW agents include several vesicants: sulfur mustards [undistilled sulfur mustard (H), sulfur mustard (HD), and an HD/agent T mixture (HT)]; nitrogen mustards [ethylbis(2-chloroethyl)amine (HN1), methylbis(2-chloroethyl)amine (HN2), tris(2-chloroethyl)amine (HN3)], and Lewisite; four nerve agents (O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX), tabun (GA), sarin (GB), and soman (GD)); and the blood agent cyanogen chloride. The degradation processes considered here include hydrolysis, microbial degradation, oxidation, and photolysis. We also briefly address decontamination but not combustion processes. Because CW agents are generally not considered very persistent, certain degradation products of significant persistence, even those that are not particularly toxic, may indicate previous CW agent presence or that degradation has occurred. Of those products for which there are data on both environmental fate and toxicity, only a few are both environmentally persistent and highly toxic. Major degradation products estimated to be of significant persistence (weeks to years) include thiodiglycol for HD; Lewisite oxide for Lewisite; and ethyl methyl phosphonic acid, methyl phosphonic acid, and possibly S-(2-diisopropylaminoethyl) methylphosphonothioic acid (EA 2192) for VX. Methyl phosphonic acid is also the ultimate hydrolysis product of both GB and GD. The GB product, isopropyl methylphosphonic acid, and a closely related contaminant of GB, diisopropyl methylphosphonate, are also persistent. Of all of these compounds, only Lewisite oxide and EA 2192 possess high mammalian toxicity. Unlike other CW agents, sulfur mustard agents (e.g., HD) are somewhat persistent; therefore, sites or conditions involving potential HD contamination should include an evaluation of both the agent and thiodiglycol. Images Figure 1 Figure 3 Figure 5 PMID:10585900

A self-assembled Ni(cyclam)-BTC network on ITO for an oxygen evolution catalyst in alkaline solution.

PubMed

Leem, Yun Jin; Cho, Keumnam; Oh, Kyung Hee; Han, Sung-Hwan; Nam, Ki Min; Chang, Jinho

2017-03-25

A self-assembled Ni(cyclam)-BTC film was formed on ITO in an acidic solution. Ni(cyclam)-BTC exhibited an enhanced electro-catalytic property for the oxygen evolution reaction (OER), which was strongly relevant to the Ni(iii)/Ni(iv) redox reaction activated by the potential dynamic process. A possible formation mechanism of Ni(cyclam)-BTC by self-assembly on ITO was also proposed.

Balancing the intermolecular forces in peptide amphiphiles for controlling self-assembly transitions.

PubMed

Buettner, C J; Wallace, A J; Ok, S; Manos, A A; Nicholl, M J; Ghosh, A; Tweedle, M F; Goldberger, J E

2017-06-21

While the influence of alkyl chain length and headgroup size on self-assembly behaviour has been well-established for simple surfactants, the rational control over the pH- and concentration-dependent self-assembly behaviour in stimuli responsive peptides remains an elusive goal. Here, we show that different amphiphilic peptides can have similar self-assembly phase diagrams, providing the relative strengths of the attractive and repulsive forces are balanced. Using palmitoyl-YYAAEEEEK(DO3A:Gd)-NH 2 and palmitoyl-YAAEEEEK(DO3A:Gd)-NH 2 as controls, we show that reducing hydrophobic attractive forces through fewer methylene groups in the alkyl chain will lead to a similar self-assembly phase diagram as increasing the electrostatic repulsive forces via the addition of a glutamic acid residue. These changes allow creation of self-assembled MRI vehicles with slightly different micelle and nanofiber diameters but with minimal changes in the spin-lattice T 1 relaxivity. These findings reveal a powerful strategy to design self-assembled vehicles with different sizes but with similar self-assembly profiles.

Mechanical characteristics of beta sheet-forming peptide hydrogels are dependent on peptide sequence, concentration and buffer composition

PubMed Central

Müller, Michael; König, Finja; Meyer, Nina; Gattlen, Jasmin; Pieles, Uwe; Peters, Kirsten; Kreikemeyer, Bernd; Mathes, Stephanie; Saxer, Sina

2018-01-01

Self-assembling peptide hydrogels can be modified regarding their biodegradability, their chemical and mechanical properties and their nanofibrillar structure. Thus, self-assembling peptide hydrogels might be suitable scaffolds for regenerative therapies and tissue engineering. Owing to the use of various peptide concentrations and buffer compositions, the self-assembling peptide hydrogels might be influenced regarding their mechanical characteristics. Therefore, the mechanical properties and stability of a set of self-assembling peptide hydrogels, consisting of 11 amino acids, made from four beta sheet self-assembling peptides in various peptide concentrations and buffer compositions were studied. The formed self-assembling peptide hydrogels exhibited stiffnesses ranging from 0.6 to 205 kPa. The hydrogel stiffness was mostly affected by peptide sequence followed by peptide concentration and buffer composition. All self-assembling peptide hydrogels examined provided a nanofibrillar network formation. A maximum self-assembling peptide hydrogel dissolution of 20% was observed for different buffer solutions after 7 days. The stability regarding enzymatic and bacterial digestion showed less degradation in comparison to the self-assembling peptide hydrogel dissolution rate in buffer. The tested set of self-assembling peptide hydrogels were able to form stable scaffolds and provided a broad spectrum of tissue-specific stiffnesses that are suitable for a regenerative therapy. PMID:29657766

Self-assembling multimeric nucleic acid constructs

DOEpatents

Cantor, Charles R.; Niemeyer, Christof M.; Smith, Cassandra L.; Sano, Takeshi; Hnatowich, Donald J.; Rusckowski, Mary

1999-10-12

The invention is directed to constructs and compositions containing multimeric forms of nucleic acid. Multimeric nucleic acids comprise single-stranded nucleic acids attached via biotin to streptavidin and bound with a functional group. These constructs can be utilized in vivo to treat or identify diseased tissue or cells. Repeated administrations of multimeric nucleic acid compositions produce a rapid and specific amplification of nucleic acid constructs and their attached functional groups. For treatment purposes, functional groups may be toxins, radioisotopes, genes or enzymes. Diagnostically, labeled multimeric constructs may be used to identify specific targets in vivo or in vitro. Multimeric nucleic acids may also be used in nanotechnology and to create self-assembling polymeric aggregates such as membranes of defined porosity, microcircuits and many other products.

Self-assembling multimeric nucleic acid constructs

DOEpatents

Cantor, Charles R.; Niemeyer, Christof M.; Smith, Cassandra L.; Sano, Takeshi; Hnatowich, Donald J.; Rusckowski, Mary

1996-01-01

The invention is directed to constructs and compositions containing multimeric forms of nucleic acid. Multimeric nucleic acids comprise single-stranded nucleic acids attached via biotin to streptavidin and bound with a functional group. These constructs can be utilized in vivo to treat or identify diseased tissue or cells. Repeated administrations of multimeric nucleic acid compositions produce a rapid and specific amplification of nucleic acid constructs and their attached functional groups. For treatment purposes, functional groups may be toxins, radioisotopes, genes or enzymes. Diagnostically, labeled multimeric constructs may be used to identify specific targets in vivo or in vitro. Multimeric nucleic acids may also be used in nanotechnology and to create self-assembling polymeric aggregates such as membranes of defined porosity, microcircuits and many other products.

Self-assembling multimeric nucleic acid constructs

DOEpatents

Cantor, C.R.; Niemeyer, C.M.; Smith, C.L.; Sano, Takeshi; Hnatowich, D.J.; Rusckowski, M.

1996-10-01

The invention is directed to constructs and compositions containing multimeric forms of nucleic acid. Multimeric nucleic acids comprise single-stranded nucleic acids attached via biotin to streptavidin and bound with a functional group. These constructs can be utilized in vivo to treat or identify diseased tissue or cells. Repeated administrations of multimeric nucleic acid compositions produce a rapid and specific amplification of nucleic acid constructs and their attached functional groups. For treatment purposes, functional groups may be toxins, radioisotopes, genes or enzymes. Diagnostically, labeled multimeric constructs may be used to identify specific targets in vivo or in vitro. Multimeric nucleic acids may also be used in nanotechnology and to create self-assembling polymeric aggregates such as membranes of defined porosity, microcircuits and many other products. 5 figs.

Exciplex formation and energy transfer in a self-assembled metal-organic hybrid system.

PubMed

Haldar, Ritesh; Rao, K Venkata; George, Subi J; Maji, Tapas Kumar

2012-05-07

Exciting assemblies: A metal-organic self-assembly of pyrenebutyric acid (PBA), 1,10-phenanthroline (o-phen), and Mg(II) shows solid-state fluorescence originating from a 1:1 PBA-o-phen exciplex. This exciplex fluorescence is sensitized by another residual PBA chromophore through an excited-state energy-transfer process. The solvent polarity modulates the self-assembly and the corresponding exciplex as well as the energy transfer, resulting in tunable emission of the hybrid (see figure). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Influence of Lactic Acid Concentration on the Separation of Light Rare Earth Elements by Continuous Liquid-Liquid Extraction with 2-Ethylhexyl Phosphonic Acid Mono-2-ethylhexyl Ester

NASA Astrophysics Data System (ADS)

de Carvalho Gomes, Rafael; Seruff, Luciana Amaral; Scal, Maira Labanca Waineraich; Vera, Ysrael Marrero

2018-02-01

The separation of rare earth elements (REEs) using solvent extraction adding complexing agents appears to be an alternative to saponification of the extractant. We evaluated the effect of lactic acid concentration on didymium (praseodymium and neodymium) and lanthanum extraction with 2-ethylhexyl phosphonic acid mono-2-ethyl hexyl ester [HEH(EHP)] as extractant. First, we investigated in batch experiments the separation of lanthanum (La) and didymium (Pr and Nd) using McCabe-Thiele diagrams to estimate the number of extraction stages when the feed solution was or was not conditioned with lactic acid. Additionally, we conducted continuous liquid-liquid extraction experiments and evaluated the influence of lactic acid concentration on the REE extraction and separation. The tests showed that the extraction percentage of REEs and the separation factor Pr/La increased when the lactic acid concentration increased, but the didymium purity decreased. Lanthanum, praseodymium, and neodymium extraction rate were 23.0, 89.7, and 99.2 pct, respectively, with 1:1 aqueous/organic volume flow rate and feed solution doped with 0.52 mol L-1 lactic acid. The highest didymium purity reached was 92.0 pct with 0.26 mol L-1 lactic acid concentration.

Glycyrrhetinic Acid-Poly(ethylene glycol)-glycyrrhetinic Acid Tri-Block Conjugates Based Self-Assembled Micelles for Hepatic Targeted Delivery of Poorly Water Soluble Drug

PubMed Central

Xu, Ting; Liu, Chi; Chen, Can; Song, Xiangrong; Zheng, Yu

2013-01-01

The triblock 18β-glycyrrhetinic acid-poly(ethylene glycol)-18β-glycyrrhetinic acid conjugates (GA-PEG-GA) based self-assembled micelles were synthesized and characterized by FTIR, NMR, transmission electron microscopy, and particle size analysis. The GA-PEG-GA conjugates having the critical micelle concentration of 6 × 10−5 M were used to form nanosized micelles, with mean diameters of 159.21 ± 2.2 nm, and then paclitaxel (PTX) was incorporated into GA-PEG-GA micelles by self-assembly method. The physicochemical properties of the PTX loaded GA-PEG-GA micelles were evaluated including in vitro cellular uptake, cytotoxicity, drug release profile, and in vivo tissue distribution. The results demonstrate that the GA-PEG-GA micelles had low cytotoxicity and good ability of selectively delivering drug to hepatic cells in vitro and in vivo by the targeting moiety glycyrrhetinic acid. In conclusion, the GA-PEG-GA conjugates have potential medical applications for targeted delivery of poor soluble drug delivery. PMID:24376388

Self-assembled multilayers and photoluminescence properties of a new water-soluble poly(para-phenylene)

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

Shi, X.; Li, D.; Luett, M.

1998-07-01

This paper reports the synthesis and characterizations of a new water-soluble poly(paraphenylene) (PPP) and its applications in preparing self-assembled multi-layer films. This new water-soluble conducting polymer was prepared through the sulfonation reaction of poly(p-quarterphenylene-2,2{prime}-dicarboxylic acid). The incorporation of sulfonate groups has dramatically improved PPP's solubility in water at a wide pH range, whereas previous PPP is only slightly soluble in basic solutions. Dilute aqueous solutions of this polymer with acidic, neutral or basic pH emit brilliant blue light while irradiated with UV light. The sulfonated PPP emits from 350 nm to 455 nm with a maximum intensity at 380 nm.more » Self-assembled multilayers of this sulfonated PPP were constructed with a positively charged polymer poly(diallyl dimethyl ammonium chloride) and characterized with various surface analyses. Conductive (RuO{sub 2} and ITO), semiconductive (Si wafer), and non-conductive (SiO{sub 2}) substrates were used in the preparation of self-assembled multilayers. Electrical, optical and structural properties of these novel self-assembled thin films will be discussed.« less

Self-assembled multilayers and photoluminescence properties of a new water-soluble poly(para-phenylene)

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

Shi, X.; Li, D.Q.; Luett, M.

1998-03-01

This paper reports the synthesis and characterizations of a new water-soluble poly(para-phenylene) (PPP) and its applications in preparing self-assembled multilayer films. This new water-soluble conducting polymer was prepared through the sulfonation reaction of poly(p-quarterphenylene-2,2{prime}-dicarboxylic acid). The incorporation of sulfonate groups has dramatically improved PPP`s solubility in water at a wide pH range, whereas previous PPP is only slightly soluble in basic solutions. Dilute aqueous solutions of this polymer with acidic, neutral or basic pH emit brilliant blue light while irradiated with UV light. The sulfonated PPP emits from 350 nm to 455 nm with a maximum intensity at 380 nm.more » Self-assembled multilayers of this sulfonated PPP were constructed with a positively charged polymer poly(diallyl dimethyl ammonium chloride) and characterized with various surface analyses. Conductive (RuO{sub 2} and ITO), semiconductive (Si wafer), and non-conductive (SiO{sub 2}) substrates were used in the preparation of self-assembled multilayers. Electrical, optical and structural properties of these novel self-assembled thin films will be discussed.« less

Fluoroalkenylphosphonates

NASA Astrophysics Data System (ADS)

Kadyrov, A. A.; Rokhlin, E. M.

1988-09-01

In this review we survey the methods for the preparation of derivatives of fluoroalkenylphosphonic acid and their reactions. The main methods for obtaining these compounds are based on the reactions of fluoroolefins with phosphites and also on the elimination of halogens, hydrogen halides and alkyl halides from fluoroalkylphosphonates or fluorine-containing phosphorus ylides. The chemical properties of fluoroalkenylphosphonates are due to the combined effect of the fluorine atoms and the phosphonate group. Their reactions with different reagents leads to modifications of the phosphonate group, addition to the C=C bond, replacement of the vinyl halogen atom, and cleavage of the C-P bond. The bibliography includes 96 references.

Substituted Phosphonic Analogues of Phenylglycine as Inhibitors of Phenylalanine Ammonia Lyase from Potatoes.

PubMed

Wanat, Weronika; Talma, Michał; Hurek, Józef; Pawełczak, Małgorzata; Kafarski, Paweł

2018-06-08

A series of phosphonic acid analogues of phenylglycine variously substituted in phenyl ring have been synthesized and evaluated for their inhibitory activity towards potato L-phenylalanine ammonia lyase. Most of the compounds appeared to act as moderate (micromolar) inhibitors of the enzyme. Analysis of their binding performed using molecular modeling have shown that they might be bound either in active site of the enzyme or in the non-physiologic site. The latter one is located in adjoining deep site nearby the to the entrance channel for substrate into active site. Copyright © 2018. Published by Elsevier B.V.

Synthesis, Self-Assembly, and Drug-Release Properties of New Amphipathic Liquid Crystal Polycarbonates

PubMed Central

Xie, Yujiao; Liu, Xiaofeng; Hu, Zhuang; Hou, Zhipeng; Chen, Zhangpei; Hu, Jianshe; Yang, Liqun

2018-01-01

New amphiphilic liquid crystal (LC) polycarbonate block copolymers containing side-chain cholesteryl units were synthesized. Their structure, thermal stability, and LC phase behavior were characterized with Fourier transform infrared (FT-IR) spectrum, 1H NMR, gel permeation chromatographic (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), polarizing optical microscope (POM), and XRD methods. The results demonstrated that the LC copolymers showed a double molecular arrangement of a smectic A phase at room temperature. With the elevating of LC unit content in such LC copolymers, the corresponding properties including decomposition temperature (Td), glass temperature (Tg), and isotropic temperature (Ti) increased. The LC copolymers showed pH-responsive self-assembly behavior under the weakly acidic condition, and with more side-chain LC units, the self-assembly process was faster, and the formed particle size was smaller. It indicated that the self-assembly driving force was derived from the orientational ability of LC. The particle size and morphologies of self-assembled microspheres loaded with doxorubicin (DOX), together with drug release tracking, were evaluated by dynamic light scattering (DLS), SEM, and UV–vis spectroscopy. The results showed that DOX could be quickly released in a weakly acidic environment due to the pH response of the self-assembled microspheres. This would offer a new strategy for drug delivery in clinic applications. PMID:29584691

Nano Cu interaction with single amino acid tyrosine derived self-assemblies; study through XRD, AFM, confocal Raman microscopy, SERS and DFT methods

NASA Astrophysics Data System (ADS)

Govindhan, Raman; Karthikeyan, Balakrishnan

2017-12-01

3,5-Bis(trifluoromethyl)benzylamine derivatives of single amino acid tyrosine produced self-assembled nanotubes (BTTNTs) as simple Phe-Phe. It has been observed that tyrosine derivative gives exclusively micro and nano tubes irrespective of the concentration of the precursor monomer. However, the introduced xenobiotic trifluoromethyl group (TFM) present in key backbone positionsof the self assembly gives the specific therapeutic function has been highlighted. Herein this work study of such self assembled nanotubes were studied through experimental and theoretical methods. The interaction of nanocopper cluster with the nanotubes (Cu@BTTNTs) were extensively studied by various methods like XRD, AFM, confocal Raman microscopy, SERS and theoretical methods like Mulliken's atomic charge analysis. SERS reveals that the interactions of Cu cluster with NH2, OH, NH and phenyl ring π-electrons system of BTTNTs. DFT studies gave the total dipole moment values of Cu@BTTNTs and explained the nature of interaction.

Self-assembling bisphosphonates into nanofibers to enhance their inhibitory capacity on bone resorption

NASA Astrophysics Data System (ADS)

Tang, Anming; Qian, Yu; Liu, Shuang; Wang, Weijuan; Xu, Bing; Qin, An; Liang, Gaolin

2016-05-01

Osteoporosis (OP) is an important aging-related disease and the effective prevention/treatment of this disease remains challenging. Considering the acidic microenvironment of bone resorption lacunae, herein, we rationally designed two pamidronate (Pami)-derivative and alendronate (Alen)-derivative hydrogelators Pami-D and Alen-D which self-assemble into nanofibers to form supramolecular hydrogels under acidic conditions. Cell viability assay, osteoclastogenesis, osteoclastic gene expression, and in vitro bone resorption results indicated that both Pami-D and Alen-D have better inhibitory effects on osteoclastic formation and bone resorption than Pami and Alen, respectively. We anticipate that our new drugs Pami-D and Alen-D could ``smartly'' self-assemble and locally concentrate the drugs at bone resorption lacunae in vivo and subsequently prevent/treat osteoporosis more efficiently.Osteoporosis (OP) is an important aging-related disease and the effective prevention/treatment of this disease remains challenging. Considering the acidic microenvironment of bone resorption lacunae, herein, we rationally designed two pamidronate (Pami)-derivative and alendronate (Alen)-derivative hydrogelators Pami-D and Alen-D which self-assemble into nanofibers to form supramolecular hydrogels under acidic conditions. Cell viability assay, osteoclastogenesis, osteoclastic gene expression, and in vitro bone resorption results indicated that both Pami-D and Alen-D have better inhibitory effects on osteoclastic formation and bone resorption than Pami and Alen, respectively. We anticipate that our new drugs Pami-D and Alen-D could ``smartly'' self-assemble and locally concentrate the drugs at bone resorption lacunae in vivo and subsequently prevent/treat osteoporosis more efficiently. Electronic supplementary information (ESI) available: Experiment methods and details; syntheses and characterization of Pami-D and Alen-D; HPLC conditions; Fig. S1-S15, Schemes S1 and S2, Tables S1 and S2. See DOI: 10.1039/c6nr00843g

Self-assembled polyhydroxy fatty acids vesicles: a mechanism for plant cutin synthesis.

PubMed

Heredia-Guerrero, José A; Benítez, José J; Heredia, Antonio

2008-03-01

Despite its biological importance, the mechanism of formation of cutin, the polymeric matrix of plant cuticles, has not yet been fully clarified. Here, for the first time, we show the participation in the process of lipid vesicles formed by the self-assembly of endogenous polyhydroxy fatty acids. The accumulation and fusion of these vesicles (cutinsomes) at the outer part of epidermal cell wall is proposed as the mechanism for early cuticle formation.

Amino Acid Chirality and Ferrocene Conformation Guided Self-Assembly and Gelation of Ferrocene-Peptide Conjugates.

PubMed

Adhikari, Bimalendu; Singh, Charanpreet; Shah, Afzal; Lough, Alan J; Kraatz, Heinz-Bernhard

2015-08-03

The self-assembly and gelation behavior of a series of mono- and disubstituted ferrocene (Fc)-peptide conjugates as a function of ferrocene conformation and amino acid chirality are described. The results reveal that ferrocene-peptide conjugates self-assemble into organogels by controlling the conformation of the central ferrocene core, through inter- versus intramolecular hydrogen bonding in the attached peptide chain(s). The chirality controlled assembling studies showed that two monosubstituted Fc conjugates FcCO-LFLFLA-OMe and FcCO-LFLFDA-OMe form gels with nanofibrillar network structures, whereas the other two diastereomers FcCO-DFLFLA-OMe and FcCO-LFDFLA-OMe exclusively produced straight nanorods and non-interconnected small fibers, respectively. This suggests the potential tuning of gelation behavior and nanoscale morphology by altering the chirality of constituted amino acids. The current study confirms the profound effect of diastereomerism and no influence of enantiomers on gelation. Correspondingly, the diastereomeric and enantiomeric Fc[CO-FFA-OMe]2 were constructed for the study of chirality-organized structures. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface modification of titania powder P25 with phosphate and phosphonic acids--effect on thermal stability and photocatalytic activity.

PubMed

Djafer, Lahcène; Ayral, André; Boury, Bruno; Laine, Richard M

2013-03-01

Phosphorus is frequently reported as a doping element for TiO(2) as photocatalyst; however, the previously reported methods used to prepare P-doped TiO(2) do not allow control over the location of the phosphorus either in the bulk or at the surface or both. In this study, we report on the surface modification of Evonik P25 with phosphonic (H(3)PO(3)) and octylphosphonic acid [C(8)H(17)-PO(OH)(2)], done to limit the introduction of phosphorus only to the photocatalyst surface. The effect of this element on the thermal behavior and photocatalytic properties is reported through characterization using elemental analyses, solid state (31)P NMR, X-ray powder diffraction, N(2) porosimetry, dilatometry, etc. Thus, the objective of the work reported here is to focus on the role(s) that phosphorus plays only at TiO(2) crystallite surfaces. For comparison, other samples were treated with phosphoric acid. Copyright © 2012 Elsevier Inc. All rights reserved.

Nafion/silane nanocomposite membranes for high temperature polymer electrolyte membrane fuel cell.

PubMed

Ghi, Lee Jin; Park, Na Ri; Kim, Moon Sung; Rhee, Hee Woo

2011-07-01

The polymer electrolyte membrane fuel cell (PEMFC) has been studied actively for both potable and stationary applications because it can offer high power density and be used only hydrogen and oxygen as environment-friendly fuels. Nafion which is widely used has mechanical and chemical stabilities as well as high conductivity. However, there is a drawback that it can be useless at high temperatures (> or = 90 degrees C) because proton conducting mechanism cannot work above 100 degrees C due to dehydration of membrane. Therefore, PEMFC should be operated for long-term at high temperatures continuously. In this study, we developed nanocomposite membrane using stable properties of Nafion and phosphonic acid groups which made proton conducting mechanism without water. 3-Aminopropyl triethoxysilane (APTES) was used to replace sulfonic acid groups of Nafion and then its aminopropyl group was chemically modified to phosphonic acid groups. The nanocomposite membrane showed very high conductivity (approximately 0.02 S/cm at 110 degrees C, <30% RH).

Novel quinolinone-phosphonic acid AMPA antagonists devoid of nephrotoxicity.

PubMed

Cordi, Alex A; Desos, Patrice; Ruano, Elisabeth; Al-Badri, Hashim; Fugier, Claude; Chapman, Astrid G; Meldrum, Brian S; Thomas, Jean-Yves; Roger, Anita; Lestage, Pierre

2002-10-01

We reported previously the synthesis and structure-activity relationships (SAR) in a series of 2-(1H)-oxoquinolines bearing different acidic functions in the 3-position. Exploiting these SAR, we were able to identify 6,7-dichloro-2-(1H)-oxoquinoline-3-phosphonic acid compound 3 (S 17625) as a potent, in vivo active AMPA antagonist. Unfortunately, during the course of the development, nephrotoxicity was manifest at therapeutically effective doses. Considering that some similitude exists between S 17625 and probenecid, a compound known to protect against the nephrotoxicity and/or slow the clearance of different drugs, we decided to synthesise some new analogues of S 17625 incorporating some of the salient features of probenecid. Replacement of the chlorine in position 6 by a sulfonylamine led to very potent AMPA antagonists endowed with good in vivo activity and lacking nephrotoxicity potential. Amongst the compounds evaluated, derivatives 7a and 7s appear to be the most promising and are currently evaluated in therapeutically relevant stroke models.

Directed surface attachment of nanomaterials via coiled-coil-driven self-assembly

NASA Astrophysics Data System (ADS)

White, Simon J.; Johnson, Steven; Szymonik, Michal; Wardingley, Richard A.; Pye, Douglas; Davies, A. Giles; Wälti, Christoph; Stockley, Peter G.

2012-12-01

Numerous nanoscale devices and materials have been fabricated in recent years using a variety of biological scaffolds. However, the interfacing of these devices and materials into existing circuits and ordered arrays has proved problematic. Here, we describe a simple solution to this problem using self-assembly of the peptide coiled-coil heterodimer ACID:BASE to immobilize M13 bacteriophage particles to specific locations on a patterned gold surface. Surface plasmon resonance demonstrated that free ACID peptides will assemble onto a surface derivatized with BASE. We then displayed the ACID peptide on the pIX coat protein of M13 and showed that these phage particles permit formation of the coiled-coil resulting in specific surface attachment. The ACID:immobilized BASE affinities appear to be similar for free peptide and phage-displayed ACID. Finally, we fabricated two gold electrodes, separated by a 200 nm gap, coated one of them with BASE and showed that this allows localization of the M13:ACID onto the functionalized electrode.

Peptide Conjugates of Benzene Carboxylic Acids as Agonists and Antagonists of Amylin Aggregation.

PubMed

Profit, Adam A; Vedad, Jayson; Desamero, Ruel Z B

2017-02-15

Human islet amyloid polypeptide (hIAPP), also known as amylin, is a 37 residue peptide hormone that is stored and co-secreted with insulin. hIAPP plays a pivotal role in type 2 diabetes and is the major component of amyloid deposits found in the pancreas of patients afflicted with the disease. The self-assembly of hIAPP and the formation of amyloid is linked to the death of insulin producing β-cells. Recent findings suggest that soluble hIAPP oligomers are the cytotoxic species responsible for β-cell loss whereas amyloid fibrils themselves may indeed be innocuous. Potential avenues of therapeutic intervention include the development of compounds that prevent hIAPP self-assembly as well as those that reduce or eliminate lag time and rapidly accelerate the formation of amyloid fibrils. Both of these approaches minimize temporal exposure to soluble cytotoxic hIAPP oligomers. Toward this end our laboratory has pursued an electrostatic repulsion approach to the development of potential inhibitors and modulators of hIAPP self-assembly. Peptide conjugates were constructed in which benzene carboxylic acids of varying charge were employed as electrostatic disrupting elements and appended to the N-terminal of the hIAPP 22-29 (NFGAILSS) self-recognition sequence. The self-assembly kinetics of conjugates were characterized by turbidity measurements and the structure of aggregates probed by Raman and CD spectroscopy while the morphology was assessed using transmission electron microscopy. Several benzene carboxylic acid peptide conjugates failed to self-assemble and some were found to inhibit the aggregation of full-length amylin while others served to enhance the rate of amyloid formation and/or increase the yield of amyloid produced. Studies reveal that the geometric display of free carboxylates on the benzene ring of the conjugates plays an important role in the activity of conjugates. In addition, a number of free benzene carboxylic acids were found to modulate amylin self-assembly on their own. The results of these investigations confirm the viability of the electrostatic repulsion approach to the modulation of amyloid formation and may aid the design and development of potential therapeutic agents.

3D-QSAR studies and molecular docking on [5-(4-amino-1 H-benzoimidazol-2-yl)-furan-2-yl]-phosphonic acid derivatives as fructose-1,6-biphophatase inhibitors

NASA Astrophysics Data System (ADS)

Lan, Ping; Xie, Mei-Qi; Yao, Yue-Mei; Chen, Wan-Na; Chen, Wei-Min

2010-12-01

Fructose-1,6-biphophatase has been regarded as a novel therapeutic target for the treatment of type 2 diabetes mellitus (T2DM). 3D-QSAR and docking studies were performed on a series of [5-(4-amino-1 H-benzoimidazol-2-yl)-furan-2-yl]-phosphonic acid derivatives as fructose-1,6-biphophatase inhibitors. The CoMFA and CoMSIA models using thirty-seven molecules in the training set gave r cv 2 values of 0.614 and 0.598, r 2 values of 0.950 and 0.928, respectively. The external validation indicated that our CoMFA and CoMSIA models possessed high predictive powers with r 0 2 values of 0.994 and 0.994, r m 2 values of 0.751 and 0.690, respectively. Molecular docking studies revealed that a phosphonic group was essential for binding to the receptor, and some key features were also identified. A set of forty new analogues were designed by utilizing the results revealed in the present study, and were predicted with significantly improved potencies in the developed models. The findings can be quite useful to aid the designing of new fructose-1,6-biphophatase inhibitors with improved biological response.

Self-assembling multidomain peptide fibers with aromatic cores

USDA-ARS?s Scientific Manuscript database

Self-assembling multidomain peptides have been shown to have desirable properties, such as the ability to form hydrogels that rapidly recover following shear-thinning and the potential to be tailored by amino acid selection to vary their elasticity and encapsulate and deliver proteins and cells. Her...

Chiral recognition and selection during the self-assembly process of protein-mimic macroanions

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

Yin, Panchao; Zhang, Zhi-Ming; Lv, Hongjin

The research on chiral recognition and chiral selection is not only fundamental in resolving the puzzle of homochirality, but also instructive in chiral separation and stereoselective catalysis. Here we report the chiral recognition and chiral selection during the self-assembly process of two enantiomeric wheel-shaped macroanions, [Fe28(μ3-O)8(Tart)16(HCOO)24]20- (Tart=D- or L-tartaric acid tetra-anion). The enantiomers are observed to remain self-sorted and self-assemble into their individual assemblies in their racemic mixture solution. The addition of chiral co-anions can selectively suppress the self-assembly process of the enantiomeric macroanions, which is further used to separate the two enantiomers from their mixtures on the basis ofmore » the size difference between the monomers and the assemblies. We believe that delicate long-range electrostatic interactions could be responsible for such high-level chiral recognition and selection.« less

Molecular Level Understanding of Interfaces and Excited State Electronic Structure in Organic Solar Cells Using Soft X-ray Techniques

NASA Astrophysics Data System (ADS)

Gliboff, Matthew

Transparent conductive oxides like indium tin oxide (ITO) are common substrates for optoelectronic devices, including organic light emitting diodes and organic solar cells. Tailoring the interface between the oxide and the active layer by adjusting the work function or wettability of the oxide can improve the performance of these devices in both emissive and photovoltaic applications. Molecular design of self-assembled monolayers (SAMs) allows for a range of surface properties using the same oxide material. The molecular ordering and conformation adopted by the SAMs determine properties such as work function and wettability at these critical interfaces. I use angle-dependent near edge x-ray absorption fine structure (NEXAFS) spectroscopy, to determine the molecular orientations of a variety of dipolar phosphonic acid surface modifiers. For a model system, phenylphosphonic acid on indium zinc oxide, the SAMs prove to be surprisingly well-oriented, with the phenyl ring adopting a well-defined tilt angle of 12-16° from the surface normal. The NEXAFS results agree with polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) results and orientations calculated from density functional theory (DFT). These results not only provide a detailed picture of the molecular structure of a technologically important class of SAMs, but they also resolve a long-standing ambiguity regarding the vibrational-mode assignments for phosphonic acids on oxide surfaces, thus improving the utility of PM-IRRAS for future studies. The effect of fluorination on the orientation of these phosponic-acid SAMs is non-trivial, due to the combined effects of the fluorination on binding mode and steric packing. The latter effects are found to be more dominant in aliphatic SAMs, leading to a more upright orientation in the fluorinated SAM. In the aromatic case, the fluorinated SAM adopted a less upright orientation which I attribute to changes in binding mode. The relationship between structure and performance in active layer polymers for organic electronics is not yet well understood. To gain insight into the effect of the excited state electronic structure on device performance, we examine two similar donor-acceptor polymers: PCPDTBT and PCDTBT, which produce devices with internal quantum efficiency (IQE) of 70% and 100% respectively. We use time-dependent density functional theory (TD-DFT) in combination with near edge x-ray absorption fine structure (NEXAFS) and resonant Auger spectroscopy to predict the electronic structure of the lowest unoccupied molecular orbital (LUMO). The resonant Auger results are found to be independent of film morphology and likely dominated by monomer structure. We show that the degree of LUMO localization onto the benzothiadiazole acceptor group in each polymer is similar, indicating that that the differences in IQE between these two polymers are driven by larger-scale morphology and not explained by the electronic structure of the excited state.

Chelating Tendencies of Bioactive Aminophosphonates

PubMed Central

Lázár, István; Kafarski, Pawel

1994-01-01

The metal-binding abilities of a wide variety of bioactive aminophosphonates, from the simple aminoethanephosphonic acids to the rather large macrocyclic polyaza derivatives, are discussed with special emphasis on a comparison of the analogous carboxylic acid and phosphonic acid systems. Examples are given of the biological importance of metal ion – aminophosphonate interactions in living systems, and also of their actual and potential applicability in medicine. PMID:18476237

General Linker Diversification Approach to Bivalent Ligand Assembly: Generation of an Array of Ligands for the Cation-Independent Mannose 6-Phosphate Receptor.

PubMed

Fei, Xiang; Zavorka, Megan E; Malik, Guillaume; Connelly, Christopher M; MacDonald, Richard G; Berkowitz, David B

2017-08-18

A generalized strategy is presented for the rapid assembly of a set of bivalent ligands with a variety of linking functionalities from a common monomer. Herein, an array of phosphatase-inert mannose-6-phosphonate-presenting ligands for the cation-independent-mannose 6-phosphate receptor (CI-MPR) is constructed. Receptor binding affinity varies with linking functionality-the simple amide and 1,5-triazole(tetrazole) being preferred over the 1,4-triazole. This approach is expected to find application across chemical biology, particularly in glycoscience, wherein multivalency often governs molecular recognition.

Self-Assembly of Large Amyloid Fibers

NASA Astrophysics Data System (ADS)

Ridgley, Devin M.

Functional amyloids found throughout nature have demonstrated that amyloid fibers are potential industrial biomaterials. This work introduces a new "template plus adder" cooperative mechanism for the spontaneous self-assembly of micrometer sized amyloid fibers. A short hydrophobic template peptide induces a conformation change within a highly alpha-helical adder protein to form beta-sheets that continue to assemble into micrometer sized amyloid fibers. This study utilizes a variety of proteins that have template or adder characteristics which suggests that this mechanism may be employed throughout nature. Depending on the amino acid composition of the proteins used the mixtures form amyloid fibers of a cylindrical ( 10 mum diameter, 2 GPa Young's modulus) or tape (5- 10 mum height, 10-20 mum width and 100-200 MPa Young's modulus) morphology. Processing conditions are altered to manipulate the morphology and structural characteristics of the fibers. Spectroscopy is utilized to identify certain amino acid groups that contribute to the self-assembly process. Aliphatic amino acids (A, I, V and L) are responsible for initiating conformation change of the adder proteins to assemble into amyloid tapes. Additional polyglutamine segments (Q-blocks) within the protein mixtures will form Q hydrogen bonds to reinforce the amyloid structure and form a cylindrical fiber of higher modulus. Atomic force microscopy is utilized to delineate the self-assembly of amyloid tapes and cylindrical fibers from protofibrils (15-30 nm width) to fibers (10-20 mum width) spanning three orders of magnitude. The aliphatic amino acid content of the adder proteins' alpha-helices is a good predictor of high density beta-sheet formation within the protein mixture. Thus, it is possible to predict the propensity of a protein to undergo conformation change into amyloid structures. Finally, Escherichia coli is genetically engineered to express a template protein which self-assembles into large amyloid fibers when combined with extracellular myoglobin, an adder protein. The goal of this thesis is to produce, manipulate and characterize the self-assembly of large amyloid fibers for their potential industrial biomaterial applications. The techniques used throughout this study outline various methods to design and engineer amyloid fibers of a tailored modulus and morphology. Furthermore, the mechanisms described here may offer some insight into naturally occurring amyloid forming systems.

Structure-Property Relationship of Phenylene-Based Self-Assembled-Monolayers for Record Low Work Function of Indium Tin Oxide.

PubMed

Benneckendorf, Frank S; Hillebrandt, Sabina; Ullrich, Florian; Rohnacher, Valentina; Hietzschold, Sebastian; Jänsch, Daniel; Freudenberg, Jan; Beck, Sebastian; Mankel, Eric; Jaegermann, Wolfram; Pucci, Annemarie; Bunz, Uwe H F; Müllen, Klaus

2018-06-20

Studying the structure-property relations of tailored dipolar phenyl and biphenylphosphonic acids we report self-assembled monolayers with a significant decrease of the work function (WF) of indium-tin oxide (ITO) electrodes. While the strengths of the dipoles are varied through the different molecular lengths and the introduction of electron-withdrawing fluorine atoms, the surface energy is kept constant through the electron-donating N,N dimethylamine head groups. The self-assembled monolayer formation and its modification of the electrodes are investigated via infrared reflection absorption spectroscopy, contact angle measurements, and photoelectron spectroscopy. The WF decrease of ITO correlates with increasing molecular dipoles. The lowest ever recorded WF of 3.7 eV is achieved with the fluorinated biphenylphosphonic acid.

Facile synthesis of novel two- and three-dimensional coordination polymers containing dialkyltin phosphonate-based tri/tetra-nuclear clusters with appended sulfonate groups.

PubMed

Shankar, Ravi; Jain, Archana; Singh, Atul Pratap; Kociok-Köhn, Gabriele; Molloy, Kieran C

2009-04-20

The coordination-driven self-assemblies of mixed-ligand dialkyltin derivatives, [(Et(2)Sn)(4) (O(2)P(OH)Me)(2)(O(3)PMe)(2)(OSO(2)Et)(2) x 2 H(2)O](n) 1, [(Et(2)Sn)(3)(O(3)PMe)(2)(OSO(2)Me)(2) x CHCl(3)](n) 2, and [(Me(2)Sn)(3)(O(3)PBu(t))(2)(OSO(2)Me)(2) x 2 CHCl(3)](n) 3 have been achieved by reacting the tin precursors, [R(2)Sn(OR(1))(OSO(2)R(1))](n) (R = Et, R(1) = Et (1a), Me (2a); R = Me, R(1) = Me (3a)) with an equimolar amount of methylphosphonic/t-butylphosphonic acid under mild conditions (rt, 8 h, CH(2)Cl(2)). These have been characterized by IR and multinuclear ((1)H, (13)C, (31)P, and (119)Sn) NMR spectroscopy as well as single crystal X-ray diffraction. The asymmetric unit of 1 is composed of a tetranuclear, Sn(4)(mu(2)-PO(2))(2)(mu(3)-PO(3))(2) core bearing an appended ethanesulfonate group on each terminal tin (Sn2) atom and two P(OH)...O hydrogen bonded water molecules. The ladder-like structural motif thus formed is extended into one-dimensional polymeric chains by virtue of bridging bidentate mode of the sulfonate groups. These chains are linked by O-H...O(S) hydrogen bonds involving H(2)O molecules and oxygen atoms of the sulfonate groups. The asymmetric units of 2 and 3 are composed of trinuclear tin clusters with a Sn(3)(mu(3)-PO(3))(2) core and two dangling methanesulfonate groups which are covalently bonded to the tin centers. The construction of three-dimensional self-assemblies is effected by variable bonding modes (mu(2), mu(3) in 2; mu(2) in 3) of the methanesulfonate groups. Both the structural motifs possess five- and six-coordinated tin atoms and form rectangular channels which are occupied by CHCl(3) molecules.

Strong Fluorescent Smart Organogel as a Dual Sensing Material for Volatile Acid and Organic Amine Vapors.

PubMed

Xue, Pengchong; Yao, Boqi; Wang, Panpan; Gong, Peng; Zhang, Zhenqi; Lu, Ran

2015-11-23

An L-phenylalanine derivative (C12PhBPCP) consisting of a strong emission fluorophore with benzoxazole and cyano groups is designed and synthesized to realize dual responses to volatile acid and organic amine vapors. The photophysical properties and self-assembly of the said derivative in the gel phase are also studied. C12PhBPCP can gelate organic solvents and self-assemble into 1 D nanofibers in the gels. UV/Vis absorption spectral results show H-aggregate formation during gelation, which indicates strong exciton coupling between fluorophores. Both wet gel and xerogel emit strong green fluorescence because the cyano group suppresses fluorescence quenching in the self-assemblies. Moreover, the xerogel film with strong green fluorescence can be used as a dual chemosensor for quantitative detection of volatile acid and organic amine vapors with fast response times and low detection limits owing to its large surface area and amplified fluorescence quenching. The detection limits are 796 ppt and 25 ppb for gaseous aniline and trifluoroacetic acid (TFA), respectively. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

THE ROLE OF COMPETITION EFFECT IN THE SELF-ASSEMBLY STRUCTURE OF 3,5-DIPHENYLBENZOIC ACID AND 2,2‧:6‧,2″-TERPYRIDINE-4‧-CARBOXYLIC ACID ON Ag(110)

NASA Astrophysics Data System (ADS)

Hu, Yufen; Li, Wei; Lu, Yan; Wang, Zhongping; Leng, Xinli; Liao, Qinghua; Liu, Xiaoqing; Wang, Li

The self-assembly structures of 2,2‧:6‧,2‧‧-terpyridine-4‧-carboxylic acid (C16H11N3O2; YN) molecules and 3,5-diphenylbenzoic acid (C19H14O2; YC) molecules on Ag(110) surface have been investigated by scanning tunneling microscopy (STM) and Density Functional Theory (DFT) calculation. The YC molecules form two different well-organized structures due to the π-π stacking and dipole-dipole interactions. When three C atoms of YC molecules are replaced by three N atoms to form YN molecules, the main driving force to form ordered assembly structures of YN molecule is changed to metal-organic coordination bond and hydrogen bond. The dramatic changes of main driving force between YC/Ag(110) and YN/Ag(110) system demonstrate that the N atoms are apt to form metal-organic coordination bond and hydrogen bond but dipole-dipole interactions and π-π stacking are relative to C atoms. These findings further reveal that the optimization design of organic molecules could vary the main driving force and then lead to the change of the molecular self-assembly structures.

A copper-phosphonate network as a high-performance heterogeneous catalyst for the CO2 cycloaddition reactions and alcoholysis of epoxides.

PubMed

Ai, Jing; Min, Xue; Gao, Chao-Ying; Tian, Hong-Rui; Dang, Song; Sun, Zhong-Ming

2017-05-23

A novel 3D copper-phosphonate network, with the general formula Cu 7 (H 1 L) 2 (TPT) 3 (H 2 O) 6 , namely compound 1, has been synthesized using a rigid tetrahedral linker tetraphenylsilane tetrakis-4-phosphonic acid (H 8 L) and a nitrogen-containing ancillary ligand (TPT: [5-(4-(1H-1,2,4-triazol-1-yl)phenyl)-1H-tetrazole]) under hydrothermal conditions. The compound was fully characterized using PXRD, ICP, IR, TGA and elemental analysis. Compound 1 can be used as an efficient catalyst for the CO 2 coupling reaction that is greatly superior to many conventional MOF-based catalysts, where porosity is always mentioned and used. In addition, it shows excellent catalytic performance for ring-opening reactions with epoxides under ambient conditions. Additionally, compound 1 can be recycled at least three times without a significant compromise in the activity in the two catalytic reactions.

Potential New Ligand Systems for Binding Uranyl Ions in Seawater Environments

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

Arnold, John

2014-12-13

Work began this quarter on a new project involving a combined computational and biosynthetic approach to selective recognition of uranyl ion in aqueous solution. This project exploits the results of computational studies to discover new ligand classes. Synthetic studies will follow to generate target systems for uranyl binding and determination of binding constants. The process will be iterative, with results from computation informing synthesis, and vice versa. The theme of the ligand classes to be examined initially will be biologically based. New phosphonate-containing α-amino acid N-carboxyanhydride (NCA) monomers were used recently to prepare well-defined phosphonate-containing poly-peptides and block copolypeptides. Ourmore » first approach is to utilize these phosphate- and phosphonate-containing NCAs for the coordination of uranyl. The work includes the laboratory-scale preparation of a series of NCAs and the full thermodynamic and spectroscopic characterization of the resulting uranyl complexes. We are also evaluating the sequestering activity in different physiological and environmental conditions of these copolymers as well as their biodegradability.« less

The supramolecular architecture of tris(naphthalene-1,5-diaminium) bis(5-aminonaphthalen-1-aminium) octakis[hydrogen (5-carboxypyridin-3-yl)phosphonate].

PubMed

Wilk, Magdalena; Janczak, Jan; Videnova-Adrabinska, Veneta

2012-09-01

The asymmetric unit of the title compound, 3C(10)H(12)N(2)(2+)·2C(10)H(11)N(2)(+)·8C(6)H(5)NO(5)P(-), contains one and a half naphthalene-1,5-diaminium cations, in which the half-molecule has inversion symmetry, one 5-aminonaphthalen-1-aminium cation and four hydrogen (5-carboxypyridin-3-yl)phosphonate anions. The crystal structure is layered and consists of hydrogen-bonded anionic monolayers between which the cations are arranged. The acid monoanions are organized into one-dimensional chains along the [101] direction via hydrogen bonds established between the phosphonate sites. (C)O-H···N(py) hydrogen bonds (py is pyridine) crosslink the chains to form an undulating (010) monolayer. The cations serve both to balance the charge of the anionic network and to connect neighbouring layers via multiple hydrogen bonds to form a three-dimensional supramolecular architecture.

A report on emergent uranyl binding phenomena by an amidoxime phosphonic acid co-polymer

DOE PAGES

Abney, C. W.; Das, S.; Mayes, R. T.; ...

2016-08-01

Development of technology to harvest the uranium dissolved in seawater would enable access to vast quantities of this critical metal for nuclear power generation. Amidoxime polymers are the most promising platform for achieving this separation, yet design of advanced adsorbents is hindered by uncertainty regarding the uranium binding mode. In this work we use XAFS to investigate the uranium coordination environment in an amidoxime-phosphonic acid copolymer adsorbent. In contrast to the binding mode predicted computationally and from small molecule studies, a cooperative chelating model is favoured, attributable to emergent behavior resulting from inclusion of amidoxime in a polymer. Samples exposedmore » to seawater also display a feature consistent with a 2-oxo-bridged transition metal, suggesting formation of an in situ specific binding site. As a result, these findings challenge long held assumptions and provide new opportunities for the design of advanced adsorbent materials.« less

Effect of amino acid sequence and pH on nanofiber formation of self-assembling peptides EAK16-II and EAK16-IV.

PubMed

Hong, Yooseong; Legge, Raymond L; Zhang, S; Chen, P

2003-01-01

Atomic force microscopy (AFM) and axisymmetric drop shape analysis-profile (ASDA-P) were used to investigate the mechanism of self-assembly of peptides. The peptides chosen consisted of 16 alternating hydrophobic and hydrophilic amino acids, where the hydrophilic residues possess alternating negative and positive charges. Two types of peptides, AEAEAKAKAEAEAKAK (EAK16-II) and AEAEAEAEAKAKAKAK (EAK16-IV), were investigated in terms of nanostructure formation through self-assembly. The experimental results, which focused on the effects of the amino acid sequence and pH, show that the nanostructures formed by the peptides are dependent on the amino acid sequence and the pH of the solution. For pH conditions around neutrality, one of the peptides used in this study, EAK16-IV, forms globular assemblies and has lower surface tension at air-water interfaces than another peptide, EAK16-II, which forms fibrillar assemblies at the same pH. When the pH is lowered below 6.5 or raised above 7.5, there is a transition from globular to fibrillar structures for EAK16-IV, but EAK16-II does not show any structural transition. Surface tension measurements using ADSA-P showed different surface activities of peptides at air-water interfaces. EAK16-II does not show a significant difference in surface tension for the pH range between 4 and 9. However, EAK16-IV shows a noticeable decrease in surface tension at pH around neutrality, indicating that the formation of globular assemblies is related to the molecular hydrophobicity.

Self-assembly of gibberellic amide assemblies and their applications in the growth and fabrication of ordered gold nanoparticles

NASA Astrophysics Data System (ADS)

Smoak, Evan M.; Carlo, Andrew D.; Fowles, Catherine C.; Banerjee, Ipsita A.

2010-01-01

Gibberellins are a group of naturally occurring diterpenoid based phytohormones that play a vital role in plant growth and development. In this work, we have studied the self-assembly of gibberellic acid, a phytohormone, which belongs to the family of gibberellins, and designed amide derivatives of gibberellic acid (GA3) for the facile, green synthesis of gold nanoparticles. It was found that the derivatives self-assembled into nanofibers and nanoribbons in aqueous solutions at varying pH. Further, upon incubation with tetrachloroaurate, the self-assembled GA3-amide derivatives efficiently nucleated and formed gold nanoparticles when heated to 60 °C. Energy dispersive x-ray spectroscopy, transmission electron microscopy and scanning electron microscopy analyses revealed that uniform coatings of gold nanoparticles in the 10-20 nm range were obtained at low pH on the nanowire surfaces without the assistance of additional reducing agents. This simple method for the development of morphology controlled gold nanoparticles using a plant hormone derivative opens doors for a new class of plant biomaterials which can efficiently yield gold nanoparticles in an environmentally friendly manner. The gold encrusted nanowires formed using biomimetic methods may lead on to the formation of conductive nanowires, which may be useful for a wide range of applications such as in optoelectronics and sensors. Further, the spontaneous formation of highly organized nanostructures obtained from plant phytohormone derivatives such as gibberellic acid is of particular interest as it might help in further understanding the supramolecular assembly mechanism of more highly organized biological structures.

New Drug Self-Assembles and Delivers Itself to Its Target | Center for Cancer Research

Cancer.gov

Viruses self-assemble with high precision and disassemble upon fusion with the cell membrane and deliver this way their cargo to the interior of the cells. Using this talent, viruses are able to inject whole proteins and large nucleic acid molecules into certain types of cells.

Solvent-Tuned Self-Assembled Nanostructures of Chiral l/d-Phenylalanine Derivatives of Protoporphyrin IX

PubMed Central

Bobe, Mr Sharad R; Al Kobaisi, Mohammad; Bhosale, Sheshanath V; Bhosale, Sidhanath V

2015-01-01

Protoporphyrin IX is a naturally occurring amphiphilic porphyrin with a rigid hydrophobic nonpolar core and two polar propionic acid substitutions on the porphyrin ring. This molecule can be modified on the hydrophilic group, which can lead to strengthened π–π-stacking and spontaneous self-assembly into novel nanostructures. Herein, we use l- phenylalanine and d-phenylalanine to modify protoporphyrin IX, and use the two derivatives for solvophobic-controlled self-assembly. Both derivatives possess two important features: 1) the aromatic core of the porphyrin for dispersive interactions and 2) a chiral amino acid to maximize the influence of chirality on selfassembly. These derivatives lead to the formation of a variety of nanostructure morphologies, such as spheres, nanofibers, lamellar structures, and thread-like and spherical shells. Solution-based self-assembly was determined by UV/Vis, fluorescence, and circular dichroism spectroscopy, and the formed nanostructures were characterized by scanning electron microscopy (SEM). Such engineered porphyrin derivatives could have potential applications in energy transport and storage, supramolecular chemistry, materials science, and medicine. PMID:26478848

Solvent-Tuned Self-Assembled Nanostructures of Chiral l/d-Phenylalanine Derivatives of Protoporphyrin IX.

PubMed

Bobe, Mr Sharad R; Al Kobaisi, Mohammad; Bhosale, Sheshanath V; Bhosale, Sidhanath V

2015-08-01

Protoporphyrin IX is a naturally occurring amphiphilic porphyrin with a rigid hydrophobic nonpolar core and two polar propionic acid substitutions on the porphyrin ring. This molecule can be modified on the hydrophilic group, which can lead to strengthened π-π-stacking and spontaneous self-assembly into novel nanostructures. Herein, we use l- phenylalanine and d-phenylalanine to modify protoporphyrin IX, and use the two derivatives for solvophobic-controlled self-assembly. Both derivatives possess two important features: 1) the aromatic core of the porphyrin for dispersive interactions and 2) a chiral amino acid to maximize the influence of chirality on selfassembly. These derivatives lead to the formation of a variety of nanostructure morphologies, such as spheres, nanofibers, lamellar structures, and thread-like and spherical shells. Solution-based self-assembly was determined by UV/Vis, fluorescence, and circular dichroism spectroscopy, and the formed nanostructures were characterized by scanning electron microscopy (SEM). Such engineered porphyrin derivatives could have potential applications in energy transport and storage, supramolecular chemistry, materials science, and medicine.

Self assembling proteins

DOEpatents

Yeates, Todd O.; Padilla, Jennifer; Colovos, Chris

2004-06-29

Novel fusion proteins capable of self-assembling into regular structures, as well as nucleic acids encoding the same, are provided. The subject fusion proteins comprise at least two oligomerization domains rigidly linked together, e.g. through an alpha helical linking group. Also provided are regular structures comprising a plurality of self-assembled fusion proteins of the subject invention, and methods for producing the same. The subject fusion proteins find use in the preparation of a variety of nanostructures, where such structures include: cages, shells, double-layer rings, two-dimensional layers, three-dimensional crystals, filaments, and tubes.

Polymer Directed Self-Assembly of pH-Responsive Antioxidant Nanoparticles

PubMed Central

Tang, Christina; Amin, Devang; Messersmith, Phillip B.; Anthony, John E.; Prud’homme, Robert K.

2015-01-01

We have developed pH-responsive, multifunctional nanoparticles based on encapsulation of an antioxidant, tannic acid (TA), using Flash NanoPrecipitation, a polymer directed self-assembly method. Formation of insoluble coordination complexes of tannic acid and iron during mixing drives nanoparticle assembly. Tuning the core material to polymer ratio, the size of the nanoparticles can be readily tuned between 50 and 265 nm. The resulting nanoparticle is pH-responsive, i.e. stable at pH 7.4 and soluble under acidic conditions due to the nature of the coordination complex. Further, the coordination complex can be coprecipitated with other hydrophobic materials such as therapeutics or imaging agents. For example, coprecipitation with a hydrophobic fluorescent dye creates fluorescent nanoparticles. In vitro, the nanoparticles have low cytotoxicity show antioxidant activity. Therefore, these particles may facilitate intracellular delivery of antioxidants. PMID:25760226

Hexagonally Ordered Arrays of α-Helical Bundles Formed from Peptide-Dendron Hybrids

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

Barkley, Deborah A.; Rokhlenko, Yekaterina; Marine, Jeannette E.

Combining monodisperse building blocks that have distinct folding properties serves as a modular strategy for controlling structural complexity in hierarchically organized materials. We combine an α-helical bundle-forming peptide with self-assembling dendrons to better control the arrangement of functional groups within cylindrical nanostructures. Site-specific grafting of dendrons to amino acid residues on the exterior of the α-helical bundle yields monodisperse macromolecules with programmable folding and self-assembly properties. The resulting hybrid biomaterials form thermotropic columnar hexagonal mesophases in which the peptides adopt an α-helical conformation. Bundling of the α-helical peptides accompanies self-assembly of the peptide-dendron hybrids into cylindrical nanostructures. The bundle stoichiometrymore » in the mesophase agrees well with the size found in solution for α-helical bundles of peptides with a similar amino acid sequence.« less

MICROCHIP ENZYMATIC ASSAY OF ORGANOPHOSPHATE NERVE AGENTS. (R830900)

EPA Science Inventory

An on-chip enzymatic assay for screening organophosphate (OP) nerve agents, based on a pre-column reaction of organophosphorus hydrolase (OPH), electrophoretic separation of the phosphonic acid products, and their contactless-conductivity detection, is described. Factors affec...

Self-assembled bionanostructures: proteins following the lead of DNA nanostructures

PubMed Central

2014-01-01

Natural polymers are able to self-assemble into versatile nanostructures based on the information encoded into their primary structure. The structural richness of biopolymer-based nanostructures depends on the information content of building blocks and the available biological machinery to assemble and decode polymers with a defined sequence. Natural polypeptides comprise 20 amino acids with very different properties in comparison to only 4 structurally similar nucleotides, building elements of nucleic acids. Nevertheless the ease of synthesizing polynucleotides with selected sequence and the ability to encode the nanostructural assembly based on the two specific nucleotide pairs underlay the development of techniques to self-assemble almost any selected three-dimensional nanostructure from polynucleotides. Despite more complex design rules, peptides were successfully used to assemble symmetric nanostructures, such as fibrils and spheres. While earlier designed protein-based nanostructures used linked natural oligomerizing domains, recent design of new oligomerizing interaction surfaces and introduction of the platform for topologically designed protein fold may enable polypeptide-based design to follow the track of DNA nanostructures. The advantages of protein-based nanostructures, such as the functional versatility and cost effective and sustainable production methods provide strong incentive for further development in this direction. PMID:24491139

Gallium(III) chelates of mixed phosphonate-carboxylate triazamacrocyclic ligands relevant to nuclear medicine: Structural, stability and in vivo studies.

PubMed

Prata, Maria I M; André, João P; Kovács, Zoltán; Takács, Anett I; Tircsó, Gyula; Tóth, Imre; Geraldes, Carlos F G C

2017-12-01

Three triaza macrocyclic ligands, H 6 NOTP (1,4,7-triazacyclononane-N,N',N″-trimethylene phosphonic acid), H 4 NO2AP (1,4,7-triazacyclononane-N-methylenephosphonic acid-N',N″-dimethylenecarboxylic acid), and H 5 NOA2P (1,4,7-triazacyclononane-N,N'-bis(methylenephosphonic acid)-N″-methylene carboxylic acid), and their gallium(III) chelates were studied in view of their potential interest as scintigraphic and PET (Positron Emission Tomography) imaging agents. A 1 H, 31 P and 71 Ga multinuclear NMR study gave an insight on the structure, internal dynamics and stability of the chelates in aqueous solution. In particular, the analysis of 71 Ga NMR spectra gave information on the symmetry of the Ga 3+ coordination sphere and the stability of the chelates towards hydrolysis. The 31 P NMR spectra afforded information on the protonation of the non-coordinated oxygen atoms from the pendant phosphonate groups and on the number of species in solution. The 1 H NMR spectra allowed the analysis of the structure and the number of species in solution. 31 P and 1 H NMR titrations combined with potentiometry afforded the measurement of the protonation constants (log K Hi ) and the microscopic protonation scheme of the triaza macrocyclic ligands. The remarkably high thermodynamic stability constant (log K GaL =34.44 (0.04) and stepwise protonation constants of Ga(NOA2P) 2- were determined by potentiometry and 69 Ga and 31 P NMR titrations. Biodistribution and gamma imaging studies have been performed on Wistar rats using the radiolabeled 67 Ga(NO2AP) - and 67 Ga(NOA2P) 2- chelates, having both demonstrated to have renal excretion. The correlation of the molecular properties of the chelates with their pharmacokinetic properties has been analysed. Copyright © 2017 Elsevier Inc. All rights reserved.

Inhibitors of the alpha-ketoglutarate dehydrogenase complex alter [1-13C]glucose and [U-13C]glutamate metabolism in cerebellar granule neurons.

PubMed

Santos, Sónia Sá; Gibson, Gary E; Cooper, Arthur J L; Denton, Travis T; Thompson, Charles M; Bunik, Victoria I; Alves, Paula M; Sonnewald, Ursula

2006-02-15

Diminished activity of the alpha-ketoglutarate dehydrogenase complex (KGDHC), an important component of the tricarboxylic acid (TCA) cycle, occurs in several neurological diseases. The effect of specific KGDHC inhibitors [phosphonoethyl ester of succinyl phosphonate (PESP) and the carboxy ethyl ester of succinyl phosphonate (CESP)] on [1-13C]glucose and [U-13C]glutamate metabolism in intact cerebellar granule neurons was investigated. Both inhibitors decreased formation of [4-13C]glutamate from [1-13C]glucose, a reduction in label in glutamate derived from [1-13C]glucose/[U-13C]glutamate through a second turn of the TCA cycle and a decline in the amounts of gamma-aminobutyric acid (GABA), aspartate, and alanine. PESP decreased formation of [U-13C]aspartate and total glutathione, whereas CESP decreased concentrations of valine and leucine. The findings are consistent with decreased KGDHC activity; increased alpha-ketoglutarate formation; increased transamination of alpha-ketoglutarate with valine, leucine, and GABA; and new equilibrium position of the aspartate aminotransferase reaction. Overall, the findings also suggest that some carbon derived from alpha-ketoglutarate may bypass the block in the TCA cycle at KGDHC by means of the GABA shunt and/or conversion of valine to succinate. The results suggest the potential of succinyl phosphonate esters for modeling the biochemical and pathophysiological consequences of reduced KGDHC activity in brain diseases.

The Hydrolytic Stability and Degradation Mechanism of a Hierarchically Porous Metal Alkylphosphonate Framework

PubMed Central

Lv, Kai; Yang, Chu-Ting; Liu, Yi; Hu, Sheng; Wang, Xiao-Lin

2018-01-01

To aid the design of a hierarchically porous unconventional metal-phosphonate framework (HP-UMPF) for practical radioanalytical separation, a systematic investigation of the hydrolytic stability of bulk phase against acidic corrosion has been carried out for an archetypical HP-UMPF. Bulk dissolution results suggest that aqueous acidity has a more paramount effect on incongruent leaching than the temperature, and the kinetic stability reaches equilibrium by way of an accumulation of a partial leached species on the corrosion conduits. A variation of particle morphology, hierarchical porosity and backbone composition upon corrosion reveals that they are hydrolytically resilient without suffering any great degradation of porous texture, although large aggregates crack into sporadic fractures while the nucleophilic attack of inorganic layers cause the leaching of tin and phosphorus. The remaining selectivity of these HP-UMPFs is dictated by a balance between the elimination of free phosphonate and the exposure of confined phosphonates, thus allowing a real-time tailor of radionuclide sequestration. Moreover, a plausible degradation mechanism has been proposed for the triple progressive dissolution of three-level hierarchical porous structures to elucidate resultant reactivity. These HP-UMPFs are compared with benchmark metal-organic frameworks (MOFs) to obtain a rough grading of hydrolytic stability and two feasible approaches are suggested for enhancing their hydrolytic stability that are intended for real-life separation protocols. PMID:29538348

Swell Gels to Dumbbell Micelles: Construction of Materials and Nanostructure with Self-assembly

NASA Astrophysics Data System (ADS)

Pochan, Darrin

2007-03-01

Bionanotechnology, the emerging field of using biomolecular and biotechnological tools for nanostructure or nanotecnology development, provides exceptional opportunity in the design of new materials. Self-assembly of molecules is an attractive materials construction strategy due to its simplicity in application. By considering peptidic or charged synthetic polymer molecules in the bottom-up materials self-assembly design process, one can take advantage of inherently biomolecular attributes; intramolecular folding events, secondary structure, and electrostatic interactions; in addition to more traditional self-assembling molecular attributes such as amphiphilicty, to define hierarchical material structure and consequent properties. Several molecular systems will be discussed. Synthetic block copolymers with charged corona blocks can be assembled in dilute solution containing multivalent organic counterions to produce micelle structures such as toroids. These ring-like micelles are similar to the toroidal bundling of charged semiflexible biopolymers like DNA in the presence of multivalent counterions. Micelle structure can be tuned between toroids, cylinders, and disks simply by using different concentrations or molecular volumes of organic counterion. In addition, these charged blocks can consist of amino acids as monomers producing block copolypeptides. In addition to the above attributes, block copolypeptides provide the control of block secondary structure to further control self-assembly. Design strategies based on small (less than 24 amino acids) beta-hairpin peptides will be discussed. Self-assembly of the peptides is predicated on an intramolecular folding event caused by desired solution properties. Importantly, the intramolecular folding event impart a molecular-level mechanism for environmental responsiveness at the material level (e.g. infinite change in viscosity of a solution to a gel with changes in pH, ionic strength, temperature).

The self-assembled behavior of DNA bases on the interface.

PubMed

Liu, Lei; Xia, Dan; Klausen, Lasse H; Dong, Mingdong

2014-01-27

A successful example of self-assembly in a biological system is that DNA can be an excellent agent to self-assemble into desirable two and three-dimensional nanostructures in a well-ordered manner by specific hydrogen bonding interactions between the DNA bases. The self-assembly of DNA bases have played a significant role in constructing the hierarchical nanostructures. In this review article we will introduce the study of nucleic acid base self-assembly by scanning tunneling microscopy (STM) at vacuum and ambient condition (the liquid/solid interface), respectively. From the ideal condition to a more realistic environment, the self-assembled behaviors of DNA bases are introduced. In a vacuum system, the energetic advantages will dominate the assembly formation of DNA bases, while at ambient condition, more factors such as conformational freedom and the biochemical environment will be considered. Therefore, the assemblies of DNA bases at ambient condition are different from the ones obtained under vacuum. We present the ordered nanostructures formed by DNA bases at both vacuum and ambient condition. To construct and tailor the nanostructure through the interaction between DNA bases, it is important to understand the assembly behavior and features of DNA bases and their derivatives at ambient condition. The utilization of STM offers the advantage of investigating DNA base self-assembly with sub-molecular level resolution at the surface.

The Self-Assembled Behavior of DNA Bases on the Interface

PubMed Central

Liu, Lei; Xia, Dan; Klausen, Lasse H.; Dong, Mingdong

2014-01-01

A successful example of self-assembly in a biological system is that DNA can be an excellent agent to self-assemble into desirable two and three-dimensional nanostructures in a well-ordered manner by specific hydrogen bonding interactions between the DNA bases. The self-assembly of DNA bases have played a significant role in constructing the hierarchical nanostructures. In this review article we will introduce the study of nucleic acid base self-assembly by scanning tunneling microscopy (STM) at vacuum and ambient condition (the liquid/solid interface), respectively. From the ideal condition to a more realistic environment, the self-assembled behaviors of DNA bases are introduced. In a vacuum system, the energetic advantages will dominate the assembly formation of DNA bases, while at ambient condition, more factors such as conformational freedom and the biochemical environment will be considered. Therefore, the assemblies of DNA bases at ambient condition are different from the ones obtained under vacuum. We present the ordered nanostructures formed by DNA bases at both vacuum and ambient condition. To construct and tailor the nanostructure through the interaction between DNA bases, it is important to understand the assembly behavior and features of DNA bases and their derivatives at ambient condition. The utilization of STM offers the advantage of investigating DNA base self-assembly with sub-molecular level resolution at the surface. PMID:24473140

Interfacial assembly structures and nanotribological properties of saccharic acids.

PubMed

Shi, Hongyu; Liu, Yuhong; Zeng, Qingdao; Yang, Yanlian; Wang, Chen; Lu, Xinchun

2017-01-04

Saccharides have been recognized as potential bio-lubricants because of their good hydration ability. However, the interfacial structures of saccharides and their derivatives are rarely studied and the molecular details of interaction mechanisms have not been well understood. In this paper, the supramolecular assembly structures of saccharic acids (including galactaric acid and lactobionic acid), mediated by hydrogen bonds O-HN and O-HO, were successfully constructed on a highly oriented pyrolytic graphite (HOPG) surface by introducing pyridine modulators and were explicitly revealed by using scanning tunneling microscopy (STM). Furthermore, friction forces were measured in the saccharic acid/pyridine co-assembled system by atomic force microscopy (AFM), revealing a larger value than a pristine saccharic acid system, which could be attributed to the stronger tip-assembled molecule interactions that lead to the higher potential energy barrier needed to overcome. The effort on saccharide-related supramolecular self-assembly and nanotribological behavior could provide a novel and promising pathway to explore the interaction mechanisms underlying friction and reveal the structure-property relationship at the molecular level.

SEPARATION OF EUROPIUM FROM OTHER LANTHANIDE RAE EARTHS BY SOLVENT EXTRACTION

DOEpatents

Peppard, D.F.; Horwitz, E.P.; Mason, G.W.

1963-02-12

This patent deals with a process of separating europium from other lanthanides present in aqueous hydrochloric or sulfuric acid solutions. The europium is selectively reduced to the divalent state with a divalent chromium salt formed in situ from chromium(III) salt plus zinc amalgam. The other trivalent lanthanides are then extracted away from the divalent europium with a nitrogen-flushed phosphoric acid ester or a phosphonic acid ester. (AEC)

Molecular water oxidation catalyst

DOEpatents

Gratzel, Michael; Munavalli, Shekhar; Pern, Fu-Jann; Frank, Arthur J.

1993-01-01

A dimeric composition of the formula: ##STR1## wherein L', L", L'", and L"" are each a bidentate ligand having at least one functional substituent, the ligand selected from bipyridine, phenanthroline, 2-phenylpyridine, bipyrimidine, and bipyrazyl and the functional substituent selected from carboxylic acid, ester, amide, halogenide, anhydride, acyl ketone, alkyl ketone, acid chloride, sulfonic acid, phosphonic acid, and nitro and nitroso groups. An electrochemical oxidation process for the production of the above functionally substituted bidentate ligand diaqua oxo-bridged ruthenium dimers and their use as water oxidation catalysts is described.

Insect cell expression of recombinant imidazoleglycerolphosphate dehydratase of Arabidopsis and wheat and inhibition by triazole herbicides.

PubMed Central

Tada, S; Hatano, M; Nakayama, Y; Volrath, S; Guyer, D; Ward, E; Ohta, D

1995-01-01

Imidazoleglycerolphosphate dehydratase (IGPD; EC 4.2.1.19), which is involved in the histidine biosynthetic pathway of Arabidopsis thaliana and wheat (Triticum aestivum), has been expressed in insect cells using the baculovirus expression vector system. N-terminal amino acid sequencing indicated that recombinant IGPDs (rIGPDs) were produced as mature forms via nonspecific proteolytic cleavages in the putative transit peptide region. The wheat rIGPD contained one Mn atom per subunit, and the Mn was involved in the assembly of the subunits to form active IGPDs. Protein-blotting analysis, using antibodies raised against the wheat rIGPD, indicated that IGPD was located in the chloroplasts of wheat. The rIGPDs of Arabidopsis and wheat, which were 86% identical in their primary structures deduced from the cDNAs, exhibited similar properties in terms of the molecular mass, pH optimum, and the Km for the substrate, imidazoleglycerolphosphate. However, the nonselective herbicides 3-amino-1,2,4-triazole and a newly synthesized triazole [(1R*, 3R*)-[3-hydroxy-3-(2H-[1,2,4]triazole-3-yl)-cyclohexyl]- phosphonic acid], inhibited Arabidopsis and wheat IGPDs in a mixed-type and a competitive manner, respectively. PMID:7480319

Phosphonate removal from discharged circulating cooling water using iron-carbon micro-electrolysis.

PubMed

Zhou, Zhen; Qiao, Weimin; Lin, Yangbo; Shen, Xuelian; Hu, Dalong; Zhang, Jianqiao; Jiang, Lu-Man; Wang, Luochun

2014-01-01

Phosphonate is a commonly used corrosion and scale inhibitor for a circulating cooling water (CCW) system. Its discharge could cause eutrophication of receiving waters. The iron-carbon (Fe/C) micro-electrolysis technology was used to degrade and remove phosphonate from discharged CCW. The influences of initial pH, Fe/C ratio (FCR) and temperature on phosphonate removal were investigated in a series of batch tests and optimized by response surface methodology. The quadratic model of phosphonate removal was obtained with satisfactory degrees of fitness. The optimum conditions with total phosphorus removal efficiency of 95% were obtained at pH 7.0, FCR of 1.25, and temperature of 45 °C. The phosphonate removal mechanisms were also studied. Phosphonate removal occurred predominantly via two consecutive reactive phases: the degradation of phosphonate complexes (Ca-phosphonate) and the precipitation of Fe/C micro-electrolysis products (PO₄(3-), Ca²⁺ and Fe³⁺).

pH responsive micelle self-assembled from a new amphiphilic peptide as anti-tumor drug carrier.

PubMed

Liang, Ju; Wu, Wen-Lan; Xu, Xiao-Ding; Zhuo, Ren-Xi; Zhang, Xian-Zheng

2014-02-01

An acid-responsive amphiphilic peptide that contains KKGRGDS sequence in hydrophilic head and VVVVVV sequence in hydrophobic tail was designed and prepared. In neutral or basic medium, this amphiphilic peptide can self-assemble into micelles through hydrogen bonding and hydrophobic interactions. If changing the solution pH to an acidic environment, the electrostatic repulsion interaction among the ionized lysine (K) residues will prevent the self-assembly of the amphiphilic peptide, leading to the dissociation of micelles. The anti-tumor drug of doxorubicin (DOX) was chosen and loaded into the self-assembled micelles of the amphiphilic peptide to investigate the influence of external pH change on the drug release behavior. As expected, the micelles show a sustained DOX release in neutral medium (pH 7.0) but fast release behavior in acidic medium (pH 5.0). When incubating these DOX-loaded micelles with HeLa and COS7 cells, due to the over-expression of integrins on cancer cells, the micelles can efficiently use the tumor-targeting function of RGD sequence to deliver the drug into HeLa cells. Combined with the low cytotoxicity of the amphiphilic peptide against both HeLa and COS7 cells, the amphiphilic peptide reported in this work may be promising in clinical application for targeted drug delivery. Copyright © 2013 Elsevier B.V. All rights reserved.

Free fatty acids electronically bridge the self-assembly of a three-component nanocomplex consisting of amylose, protein, and free fatty acids.

PubMed

Zhang, Genyi; Maladen, Michelle; Campanella, Osvaldo H; Hamaker, Bruce R

2010-08-25

The self-assembly of a ternary complex, which is formed through heating and cooling of a mixture of amylose (1.0 mg/mL), whey protein isolate (50 μg/mL), and free fatty acids (FFAs, 250 μg/mL) was investigated. High-performance size-exclusion chromatography-multi-angle laser light scattering (HPSEC-MALLS) analysis showed that the complex is a water-soluble supramolecule (Mw = 6-7 × 10(6)), with a radius of gyration of 20-100 nm, indicating a nanoscale complex. Experimental results using 1-monostearyl-rac-glycerol (MSG) or cetyl alcohol that is similar to FFA in structure (except the headgroup) indicate that FFAs are the bridge between thermodynamically incompatible amylose and protein molecules and their functional carboxyl group is essential to the formation of the complex. Additionally, the effects of pH and salt treatments suggest that electrostatic interactions between negatively charged carboxyl groups of FFAs and polyionic protein are the foundation for the self-assembly of the complex. The fact that FFA is one important component in the self-assembled complex with an estimated molar ratio of 6:1:192 (amylose/protein/FFA, ∼4-5% FFA) demonstrates that it might be used as a nanocarrier for the controlled release of lipophilic functional materials to maintain their stability, bioactivity, and more importantly water solubility.

Inhibition of dog and human gastric lipases by enantiomeric phosphonate inhibitors: a structure-activity study.

PubMed

Miled, Nabil; Roussel, Alain; Bussetta, Cécile; Berti-Dupuis, Liliane; Rivière, Mireille; Buono, Gérard; Verger, Robert; Cambillau, Christian; Canaan, Stéphane

2003-10-14

The crystal structures of gastric lipases in the apo form [Roussel, A., et al. (1999) J. Biol. Chem. 274, 16995-17002] or in complex with the (R(P))-undecyl butyl phosphonate [C(11)Y(4)(+)] [Roussel, A., et al. (2002) J. Biol. Chem. 277, 2266-2274] have improved our understanding of the structure-activity relationships of acid lipases. In this report, we have performed a kinetic study with dog and human gastric lipases (DGL and HGL, respectively) using several phosphonate inhibitors by varying the absolute configuration of the phosphorus atom and the chain length of the alkyl/alkoxy substituents. Using the two previously determined structures and that of a new crystal structure obtained with the other (S(P))-phosphonate enantiomer [C(11)Y(4)(-)], we constructed models of phosphonate inhibitors fitting into the active site crevices of DGL and HGL. All inhibitors with a chain length of fewer than 12 carbon atoms were found to be completely buried in the catalytic crevice, whereas longer alkyl/alkoxy chains were found to point out of the cavity. The main stereospecific determinant explaining the stronger inhibition of the S(P) enantiomers is the presence of a hydrogen bond involving the catalytic histidine as found in the DGL-C(11)Y(4)(-) complex. On the basis of these results, we have built a model of the first tetrahedral intermediate corresponding to the tristearoyl-lipase complex. The triglyceride molecule completely fills the active site crevice of DGL, in contrast with what is observed with other lipases such as pancreatic lipases which have a shallower and narrower active site. For substrate hydrolysis, the supply of water molecules to the active site might be achieved through a lateral channel identified in the protein core.

Effects of radiation, acid, and base on the extractant dihexyl-(diethylcarbamoyl)methyl) phosphonate

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

Bahner, C.T.; Shoun, R.R.; McDowell, W.J.

1981-11-01

The effects of exposure to gamma radiation (/sup 60/Co) and of contact with acidic and basic aqueous solutions on dihexyl((diethylcarbamoyl)methyl)phosphonate (DHDECMP) were studied. Gamma radiation decomposes DHDECMP into a variety of products. The most troublesome of those are the acidic compounds that cause problems in stripping the actinides and lanthanides from the extractant at low acid concentrations. The rate of degradation of DHDECMP by radiation is about the same or only slightly higher than that of tri-n-butyl phosphate (TBP). It is relatively easy to remove the radiation-produced impurities by equilibration (scrubbing) with sodium carbonate or sodium hydroxide or by columnmore » chromatographic methods. The hydrolysis of DHDECMP in contact with aqueous solutions containing less than 3 M HNO/sub 3/ is not more severe than that of TBP under the same conditions but is significant above that acid concentration. Hydrolysis of DHDECMP in contact with aqueous sodium hydroxide solution does occur, but it should not pose an important problem with the short contact times such as those anticipated for the removal of the radiation-induced degradation products by caustic scrubbing. Results of various chromatographic tests to characterize the degradation products of DHDECMP are also given.« less

Analysis of Phosphonic Acids: Validation of Semi-Volatile Analysis by HPLC-MS/MS by EPA Method MS999

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

Owens, J; Vu, A; Koester, C

The Environmental Protection Agency's (EPA) Region 5 Chicago Regional Laboratory (CRL) developed a method titled Analysis of Diisopropyl Methylphosphonate, Ethyl Hydrogen Dimethylamidophosphate, Isopropyl Methylphosphonic Acid, Methylphosphonic Acid, and Pinacolyl Methylphosphonic Acid in Water by Multiple Reaction Monitoring Liquid Chromatography/Tandem Mass Spectrometry: EPA Version MS999. This draft standard operating procedure (SOP) was distributed to multiple EPA laboratories and to Lawrence Livermore National Laboratory, which was tasked to serve as a reference laboratory for EPA's Environmental Reference Laboratory Network (ERLN) and to develop and validate analytical procedures. The primary objective of this study was to validate and verify the analytical procedures describedmore » in EPA Method MS999 for analysis of the listed phosphonic acids and surrogates in aqueous samples. The gathered data from this validation study will be used to: (1) demonstrate analytical method performance; (2) generate quality control acceptance criteria; and (3) revise the SOP to provide a validated method that would be available for use during a homeland security event. The data contained in this report will be compiled, by EPA CRL, with data generated by other EPA Regional laboratories so that performance metrics of EPA Method MS999 can be determined.« less

Fully packed capillary electrochromatographic microchip with self-assembly colloidal silica beads.

PubMed

Park, Jongman; Lee, Dami; Kim, Won; Horiike, Shigeyoshi; Nishimoto, Takahiro; Lee, Se Hwan; Ahn, Chong H

2007-04-15

A fully packed capillary electrochromatographic (CEC) microchip showing improved solution and chip handling was developed. Microchannels for the CEC microchip were patterned on a cyclic olefin copolymer substrate by injection molding and packed fully with 0.8-microm monodisperse colloidal silica beads utilizing a self-assembly packing technique. The silica packed chip substrate was covered and thermally press-bonded. After fabrication, the chip was filled with buffer solution by self-priming capillary action. The self-assembly packing at each channel served as a built-in nanofilter allowing quick loading of samples and running buffer solution without filtration. Because of a large surface area-to-volume ratio of the silica packing, reproducible control of electroosmotic flow was possible without leveling of the solutions in the reservoirs resulting 1.3% rsd in migration rate. The capillary electrophoretic separation characteristics of the chip were studied using fluorescein isothiocyanate (FITC)-derivatized amino acids as probe molecules. A mixture of FITC and four FITC-derivatized amino acids was successfully separated with 2-mm separation channel length.

Charged triblock copolymer self-assembly into charged micelles

NASA Astrophysics Data System (ADS)

Chen, Yingchao; Zhang, Ke; Zhu, Jiahua; Wooley, Karen; Pochan, Darrin; Department of Material Science; Engineering University of Delaware Team; Department of Chemistry Texas A&M University Collaboration

2011-03-01

Micelles were formed through the self-assembly of amphiphlic block copolymer poly(acrylic acid)-block-poly(methyl acrylate)-block-polystyrene (PAA-PMA-PS). ~Importantly, the polymer is complexed with diamine molecules in pure THF solution prior to water titration solvent processing-a critical aspect in the control of final micelle geometry. The addition of diamine triggers acid-base complexation ~between the carboxylic acid PAA side chains and amines. ~Remarkably uniform spheres were found to form close-packed patterns when forced into dried films and thin, solvated films when an excess of amine was used in the polymer assembly process. Surface properties and structural features of these hexagonal-packed spherical micelles with charged corona have been explored by various characterization methods including Transmission Electron Microscopy (TEM), cryogenic TEM, z-potential analysis and Dynamic Light Scattering. The forming mechanism for this pattern and morphology changes against external stimulate such as salt will be discussed.

Effect of Hyaluronic Acid on the Self Assembling Behaviour of PEO-PPO Copolymers in Aqueous Solution

NASA Astrophysics Data System (ADS)

Mayol, L.; Borzacchiello, A.; Quaglia, F.; La Rotonda, M. I.; Ambrosio, L.

2008-07-01

The influence of hyaluronic acid (HA) on the self assembling properties of pluronic (PEO-PPO-PEO block copolymers) blends has been studied with the aim of engineering thermosensitive and mucoadhesive polymeric platforms for drug delivery. The gelation temperature (Tgel), viscoelastic properties and mucoadhesive force of the systems were investigated and optimised by means of rheological analyses. Pluronic micellar radius was evaluated by Photon Correlation Spectroscopy (PCS). The addition of Low Molecular Weight HA did not hamper the self assembling process of pluronics just delaying the gelation temperature of few Celsius degrees. Furthermore, HA presence led to a strong increase of the pluronics gel rheological properties. PCS results show, in formulations containing HA, aggregates with hydrodynamic diameters values much higher than those of pluronic micelles. Mucoadhesive experiments indicate the possibility of interactions between the pluronic/HA gel and mucus glycoproteins.

Self-assembled nanoparticle of common food constituents that carries a sparingly soluble small molecule.

PubMed

Bhopatkar, Deepak; Feng, Tao; Chen, Feng; Zhang, Genyi; Carignano, Marcelo; Park, Sung Hyun; Zhuang, Haining; Campanella, Osvaldo H; Hamaker, Bruce R

2015-05-06

A previously reported nanoparticle formed through the self-assembly of common food constituents (amylose, protein, and fatty acids) was shown to have the capacity to carry a sparingly soluble small molecule (1-naphthol) in a dispersed system. Potentiometric titration showed that 1-naphthol locates in the lumen of the amylose helix of the nanoparticle. This finding was further supported by calorimetric measurements, showing higher enthalpies of dissociation and reassociation in the presence of 1-naphthol. Visually, the 1-naphthol-loaded nanoparticle appeared to be well-dispersed in aqueous solution. Molecular dynamics simulation showed that the self-assembly was favorable, and at 500 ns, the 1-naphthol molecule resided in the helix of the amylose lumen in proximity to the hydrophobic tail of the fatty acid. Thus, sparingly soluble small molecules, such as some nutraceuticals or drugs, could be incorporated and delivered by this soft nanoparticle carrier.

Homopolymer self-assembly into stable nanoparticles: concerted action of hydrophobic association and hydrogen bonding in thermoresponsive poly(alkylacrylic acid)s.

PubMed

Sedlák, Marián

2012-03-01

A new approach to polymer self-assembly was presented recently [M. Sedlák, Č. Koňák, J. Dybal, Macromolecules 2009, 2, 7430-7438 and 7439-7446.] (1, 2) where stable polymeric nanoparticles were formed from poly(ethylacrylic acid) homopolymers without any assembly triggering additives, simply by heating polymer solution under conditions of thermosensitivity to certain temperature. In the current Article, we present successful results on poly(propylacrylic acid), which is a more hydrophobic polymer. We also present results on a less hydrophobic polymer from this series, poly(methacrylic acid), from which nanoparticles cannot be formed. Comparison of results on all three polymers gives a solid physicochemical insight and supports the molecular mechanism of the self-assembly previously suggested: The solvent quality gradually worsens upon heating of a thermosensitive polymer solution, and polymer-polymer contacts are preferred over polymer-solvent contacts, which leads to the formation of polymer assemblies. The presence of a significant amount of charge on chains prevents macroscopic phase separation. Upon subsequent cooling to laboratory temperature, the assemblies (nanoparticles) should eventually dissolve; however, this is not the case due to the fact that polymer chains brought to a close proximity at elevated temperatures become hydrogen-bonded. In addition, hydrogen bonds strengthen upon cooling. Mainly carboxylic-carboxylate hydrogen bonds (COOH····COO(-)) are responsible for the irreversibility of the process and the stability of nanoparticles. Conclusions are supported by results from static and dynamic light scattering, FTIR spectroscopy, and cryo-TEM microscopy. Size of nanoparticles can be monitored during the growth and custom-tailored by tuning critical parameters, especially the degree of ionization, temperature, and time of heating. Nanoparticles are stable over long periods of time. They are stable in a broad range of salt concentrations, including physiological conditions, and possess a mild acceptable degree of polydispersity.

Static and dynamic investigations of poly(aspartic acid) and Pluronic F127 complex prepared by self-assembling in aqueous solution

NASA Astrophysics Data System (ADS)

Nita, Loredana E.; Chiriac, Aurica P.; Bercea, Maria; Nistor, Manuela T.

2015-12-01

The present investigation is focused on evaluation of self-assembling ability in aqueous solutions of two water soluble polymers: poly(aspartic acid) (PAS) and Pluronic F127 (PL). The intermolecular complexes, realized between polyacid and neutral copolymer surfactant in different ratios, have been studied by combining various characterization techniques as rheology, DLS, spectroscopy, microscopy, chemical imaging, and zeta potential determination, measurements performed in static and/or dynamic conditions. In static conditions, when the equilibrium state between PAS/PL polymeric pair was reached, and depending on the polymers mixture composition, and of experimental rheological conditions, positive or negative deviations from the additive rule are registered. Conformational changes of the macromolecular chains and correspondingly physical interactions are generated between PL and PAS for self-assembly and the formation of interpolymer complex as suprastructure with micellar configuration. The phenomenon was better evidenced in case of 1/1 wt ratio between the two polymers. In dynamic conditions of determination, during ;in situ; evaluation of the hydrodynamic diameter, zeta potential and conductivity, when the equilibrium state is not reached and as result either the intermolecular bonds are not achieved, the self-assembling process is not so obvious evidenced.

Self-assembly of proglycinin and hybrid proglycinin synthesized in vitro from cDNA

PubMed Central

Dickinson, Craig D.; Floener, Liliane A.; Lilley, Glenn G.; Nielsen, Niels C.

1987-01-01

An in vitro system was developed that results in the self-assembly of subunit precursors into complexes that resemble those found naturally in the endoplasmic reticulum. Subunits of glycinin, the predominant seed protein of soybeans, were synthesized from modified cDNAs using a combination of the SP6 transcription and the rabbit reticulocyte translation systems. Subunits produced from plasmid constructions that encoded either Gy4 or Gy5 gene products, but modified such that their signal sequences were absent, self-assembled into trimers equivalent in size to those precursors found in the endoplasmic reticulum. In contrast, proteins synthesized in vitro from Gy4 constructs failed to self-assemble when the signal sequence was left intact (e.g., preproglycinin) or when the coding sequence was modified to remove 27 amino acids from an internal hydrophobic region, which is highly conserved among the glycinin subunits. Various hybrid subunits were also produced by trading portions of Gy4 and Gy5 cDNAs and all self-assembled in our system. The in vitro assembly system provides an opportunity to study the self-assembly of precursors and to probe for regions important for assembly. It will also be helpful in attempts to engineer beneficial nutritional changes into this important food protein. Images PMID:16593868

Modulating β-lactoglobulin nanofibril self-assembly at pH 2 using glycerol and sorbitol.

PubMed

Dave, Anant C; Loveday, Simon M; Anema, Skelte G; Jameson, Geoffrey B; Singh, Harjinder

2014-01-13

β-Lactoglobulin (β-lg) forms fibrils when heated at 80 °C, pH 2, and low ionic strength (<0.015 mM). When formed at protein concentrations <3%, these fibrils are made up of peptides produced from the acid hydrolysis of the β-lg monomer. The present study investigated the effects of the polyhydroxy alcohols (polyols) glycerol and sorbitol (0-50% w/v) on β-lg self-assembly at pH 2. Glycerol and sorbitol stabilize native protein structure and modulate protein functionality by preferential exclusion. In our study, both polyols decreased the rate of β-lg self-assembly but had no effect on the morphology of fibrils. The mechanism of these effects was studied using circular dichroism spectroscopy and SDS-PAGE. Sorbitol inhibited self-assembly by stabilizing β-lg against unfolding and hydrolysis, resulting in fewer fibrillogenic species, whereas glycerol inhibited nucleation without inhibiting hydrolysis. Both polyols increased the viscosity of the solutions, but viscosity appeared to have little effect on fibril assembly, and we believe that self-assembly was not diffusion-limited under these conditions. This is in agreement with previous reports for other proteins assembling under different conditions. The phenomenon of peptide self-assembly can be decoupled from protein hydrolysis using glycerol.

Synthesis of conformationally locked L-deoxythreosyl phosphonate nucleosides built on a bicyclo[3.1.0]hexane template.

PubMed

Saneyoshi, Hisao; Deschamps, Jeffrey R; Marquez, Victor E

2010-11-19

Two conformationally locked versions of l-deoxythreosyl phosphonate nucleosides (2 and 3) were synthesized to investigate the preference of HIV reverse transcriptase for a conformation displaying either a fully diaxial or fully diequatorial disposition of substituents. Synthesis of the enantiomeric 4-(6-amino-9H-purin-9-yl)bicyclo[3.1.0]hexan-2-ol carbocyclic nucleoside precursors (diaxially disposed) proceeded straightforwardly from commercially available (1R,4S)-4-hydroxy-2-cyclopent-2-enyl-1-yl acetate employing a hydroxyl-directed Simmons-Smith cyclopropanation that culminated with a Mitsunobu coupling of the purine base. For the more complicated 1-(6-amino-9H-purin-9-yl)bicyclo[3.1.0]hexan-3-ol carbocyclic nucleoside precursors (diequatorially disposed), the obligatory linear approach required the syntheses of key 1-aminobicyclo[3.1.0.]hexan-3-yl benzoate precursors that were assembled via the amide variant of the Kulinkovich reaction involving the intramolecular cyclopropanation of a substituted δ-vinylamide. Completion of the purine ring was achieved by conventional approaches but with much improved yields through the use of a microwave reactor. The syntheses of the phosphonates and the corresponding diphosphates were achieved by conventional means. None of the diphosphates, which were supposed to act as nucleoside triphosphate mimics, could compete with dATP even when present in a 10-fold excess.

Templated bilayer self-assembly of fully conjugated π-expanded macrocyclic oligothiophenes complexed with fullerenes

PubMed Central

Cojal González, José D.; Iyoda, Masahiko; Rabe, Jürgen P.

2017-01-01

Fully conjugated macrocyclic oligothiophenes exhibit a combination of highly attractive structural, optical and electronic properties, and multifunctional molecular thin film architectures thereof are envisioned. However, control over the self-assembly of such systems becomes increasingly challenging, the more complex the target structures are. Here we show a robust self-assembly based on hierarchical non-covalent interactions. A self-assembled monolayer of hydrogen-bonded trimesic acid at the interface between an organic solution and graphite provides host-sites for the epitaxial ordering of Saturn-like complexes of fullerenes with oligothiophene macrocycles in mono- and bilayers. STM tomography verifies the formation of the templated layers. Molecular dynamics simulations corroborate the conformational stability and assign the adsorption sites of the adlayers. Scanning tunnelling spectroscopy determines their rectification characteristics. Current–voltage characteristics reveal the modification of the rectifying properties of the macrocycles by the formation of donor–acceptor complexes in a densely packed all-self-assembled supramolecular nanostructure. PMID:28281557

Templated bilayer self-assembly of fully conjugated π-expanded macrocyclic oligothiophenes complexed with fullerenes

NASA Astrophysics Data System (ADS)

Cojal González, José D.; Iyoda, Masahiko; Rabe, Jürgen P.

2017-03-01

Fully conjugated macrocyclic oligothiophenes exhibit a combination of highly attractive structural, optical and electronic properties, and multifunctional molecular thin film architectures thereof are envisioned. However, control over the self-assembly of such systems becomes increasingly challenging, the more complex the target structures are. Here we show a robust self-assembly based on hierarchical non-covalent interactions. A self-assembled monolayer of hydrogen-bonded trimesic acid at the interface between an organic solution and graphite provides host-sites for the epitaxial ordering of Saturn-like complexes of fullerenes with oligothiophene macrocycles in mono- and bilayers. STM tomography verifies the formation of the templated layers. Molecular dynamics simulations corroborate the conformational stability and assign the adsorption sites of the adlayers. Scanning tunnelling spectroscopy determines their rectification characteristics. Current-voltage characteristics reveal the modification of the rectifying properties of the macrocycles by the formation of donor-acceptor complexes in a densely packed all-self-assembled supramolecular nanostructure.

Controlling Self-Assembly of Engineered Peptides on Graphite by Rational Mutation

PubMed Central

So, Christopher R.; Hayamizu, Yuhei; Yazici, Hilal; Gresswell, Carolyn; Khatayevich, Dmitriy; Tamerler, Candan; Sarikaya, Mehmet

2012-01-01

Self-assembly of proteins on surfaces is utilized in many fields to integrate intricate biological structures and diverse functions with engineered materials. Controlling proteins at bio-solid interfaces relies on establishing key correlations between their primary sequences and resulting spatial organizations on substrates. Protein self-assembly, however, remains an engineering challenge. As a novel approach, we demonstrate here that short dodecapeptides selected by phage display are capable of self-assembly on graphite and form long-range ordered biomolecular nanostructures. Using atomic force microscopy and contact angle studies, we identify three amino-acid domains along the primary sequence that steer peptide ordering and lead to nanostructures with uniformly displayed residues. The peptides are further engineered via simple mutations to control fundamental interfacial processes, including initial binding, surface aggregation and growth kinetics, and intermolecular interactions. Tailoring short peptides via their primary sequence offers versatile control over molecular self-assembly, resulting in well-defined surface properties essential in building engineered, chemically rich, bio-solid interfaces. PMID:22233341

Self-assembly of nucleic acids, silk and hybrid materials thereof.

PubMed

Humenik, Martin; Scheibel, Thomas

2014-12-17

Top-down approaches based on etching techniques have almost reached their limits in terms of dimension. Therefore, novel assembly strategies and types of nanomaterials are required to allow technological advances. Self-assembly processes independent of external energy sources and unlimited in dimensional scaling have become a very promising approach. Here,we highlight recent developments in self-assembled DNA-polymer, silk-polymer and silk-DNA hybrids as promising materials with biotic and abiotic moieties for constructing complex hierarchical materials in ‘bottom-up’ approaches. DNA block copolymers assemble into nanostructures typically exposing a DNA corona which allows functionalization, labeling and higher levels of organization due to its specific addressable recognition properties. In contrast, self-assembly of natural silk proteins as well as their recombinant variants yields mechanically stable β-sheet rich nanostructures. The combination of silk with abiotic polymers gains hybrid materials with new functionalities. Together, the precision of DNA hybridization and robustness of silk fibrillar structures combine in novel conjugates enable processing of higher-order structures with nanoscale architecture and programmable functions.

Water ordering controls the dynamic equilibrium of micelle-fibre formation in self-assembly of peptide amphiphiles.

PubMed

Deshmukh, Sanket A; Solomon, Lee A; Kamath, Ganesh; Fry, H Christopher; Sankaranarayanan, Subramanian K R S

2016-08-24

Understanding the role of water in governing the kinetics of the self-assembly processes of amphiphilic peptides remains elusive. Here, we use a multistage atomistic-coarse-grained approach, complemented by circular dichroism/infrared spectroscopy and dynamic light scattering experiments to highlight the dual nature of water in driving the self-assembly of peptide amphiphiles (PAs). We show computationally that water cage formation and breakage near the hydrophobic groups control the fusion dynamics and aggregation of PAs in the micellar stage. Simulations also suggest that enhanced structural ordering of vicinal water near the hydrophilic amino acids shifts the equilibrium towards the fibre phase and stimulates structure and order during the PA assembly into nanofibres. Experiments validate our simulation findings; the measured infrared O-H bond stretching frequency is reminiscent of an ice-like bond which suggests that the solvated water becomes increasingly ordered with time in the assembled peptide network, thus shedding light on the role of water in a self-assembly process.

Self-assembly of nucleic acids, silk and hybrid materials thereof

NASA Astrophysics Data System (ADS)

Humenik, Martin; Scheibel, Thomas

2014-12-01

Top-down approaches based on etching techniques have almost reached their limits in terms of dimension. Therefore, novel assembly strategies and types of nanomaterials are required to allow technological advances. Self-assembly processes independent of external energy sources and unlimited in dimensional scaling have become a very promising approach. Here, we highlight recent developments in self-assembled DNA-polymer, silk-polymer and silk-DNA hybrids as promising materials with biotic and abiotic moieties for constructing complex hierarchical materials in ‘bottom-up’ approaches. DNA block copolymers assemble into nanostructures typically exposing a DNA corona which allows functionalization, labeling and higher levels of organization due to its specific addressable recognition properties. In contrast, self-assembly of natural silk proteins as well as their recombinant variants yields mechanically stable β-sheet rich nanostructures. The combination of silk with abiotic polymers gains hybrid materials with new functionalities. Together, the precision of DNA hybridization and robustness of silk fibrillar structures combine in novel conjugates enable processing of higher-order structures with nanoscale architecture and programmable functions.

Computational design of a homotrimeric metalloprotein with a trisbipyridyl core

DOE PAGES

Mills, Jeremy H.; Sheffler, William; Ener, Maraia E.; ...

2016-12-08

Metal-chelating heteroaryl small molecules have found widespread use as building blocks for coordination-driven, self-assembling nanostructures. The metal-chelating noncanonical amino acid (2,2'-bipyridin-5yl)alanine (Bpy-ala) could, in principle, be used to nucleate specific metalloprotein assemblies if introduced into proteins such that one assembly had much lower free energy than all alternatives. Here in this paper, we describe the use of the Rosetta computational methodology to design a self-assembling homotrimeric protein with [Fe(Bpy-ala) 3] 2+ complexes at the interface between monomers. X-ray crystallographic analysis of the homotrimer showed that the design process had near-atomic-level accuracy: The all-atom rmsd between the design model and crystalmore » structure for the residues at the protein interface is ~1.4 Å. These results demonstrate that computational protein design together with genetically encoded noncanonical amino acids can be used to drive formation of precisely specified metal-mediated protein assemblies that could find use in a wide range of photophysical applications.« less

Computational design of a homotrimeric metalloprotein with a trisbipyridyl core

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

Mills, Jeremy H.; Sheffler, William; Ener, Maraia E.

Metal-chelating heteroaryl small molecules have found widespread use as building blocks for coordination-driven, self-assembling nanostructures. The metal-chelating noncanonical amino acid (2,2'-bipyridin-5yl)alanine (Bpy-ala) could, in principle, be used to nucleate specific metalloprotein assemblies if introduced into proteins such that one assembly had much lower free energy than all alternatives. Here in this paper, we describe the use of the Rosetta computational methodology to design a self-assembling homotrimeric protein with [Fe(Bpy-ala) 3] 2+ complexes at the interface between monomers. X-ray crystallographic analysis of the homotrimer showed that the design process had near-atomic-level accuracy: The all-atom rmsd between the design model and crystalmore » structure for the residues at the protein interface is ~1.4 Å. These results demonstrate that computational protein design together with genetically encoded noncanonical amino acids can be used to drive formation of precisely specified metal-mediated protein assemblies that could find use in a wide range of photophysical applications.« less

Time-resolved viscoelastic properties of self-assembling iron oxide nanocube superlattices probed by quartz crystal microbalance with dissipation monitoring.

PubMed

Kapuscinski, Martin; Agthe, Michael; Bergström, Lennart

2018-07-15

Self-assembly of nanoparticles into superlattices can be used to create hierarchically structured materials with tailored functions. We have used the surface sensitive quartz crystal microbalance with dissipation monitoring (QCM-D) technique in combination with video microscopy (VM) to obtain time-resolved information on the mass increase and rheological properties of evaporation-induced self-assembly of nanocubes. We have recorded the frequency and dissipation shifts during growth and densification of superlattices formed by self-assembly of oleic acid capped, truncated iron oxide nanocubes and analyzed the time-resolved QCM-D data using a Kelvin-Voigt viscoelastic model. We show that the nanoparticles first assemble into solvent-containing arrays dominated by a viscous response followed by a solvent-releasing step that results in the formation of rigid and well-ordered superlattices. Our findings demonstrate that QCM-D can be successfully used to follow self-assembly and assist in the design of optimized routes to produce well-ordered superlattices. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Self-assembly of peptide-amphiphile nanofibers: the roles of hydrogen bonding and amphiphilic packing.

PubMed

Paramonov, Sergey E; Jun, Ho-Wook; Hartgerink, Jeffrey D

2006-06-07

The role of hydrogen bonding and amphiphilic packing in the self-assembly of peptide-amphiphiles (PAs) was investigated using a series of 26 PA derivatives, including 19 N-methylated variants and 7 alanine mutants. These were studied by circular dichroism spectroscopy, a variety of Fourier transform infrared spectroscopies, rheology, and vitreous ice cryo-transmission electron microscopy. From these studies, we have been able to determine which amino acids are critical for the self-assembly of PAs into nanofibers, why the nanofiber is favored over other possible nanostructures, the orientation of hydrogen bonding with respect to the nanofiber axis, and the constraints placed upon the portion of the peptide most intimately associated with the biological environment. Furthermore, by selectively eliminating key hydrogen bonds, we are able to completely change the nanostructure resulting from self-assembly in addition to modifying the macroscopic mechanical properties associated with the assembled gel. This study helps to clarify the mechanism of self-assembly for peptide amphiphiles and will thereby help in the design of future generations of PAs.

Layer-by-Layer Molecular Assemblies for Dye-Sensitized Photoelectrosynthesis Cells Prepared by Atomic Layer Deposition

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

Wang, Degao; Sheridan, Matthew V.; Shan, Bing

2017-08-30

In a Dye Sensitized Photoelectrosynthesis Cell (DSPEC) the relative orientation of catalyst and chromophore play important roles. Here we introduce a new, robust, Atomic Layer Deposition (ALD) procedure for the preparation of assemblies on wide bandgap semiconductors. In the procedure, phosphonated metal complex precursors react with metal ion bridging to an external chromophore or catalyst to give assemblies bridged by Al(III), Sn(IV), Ti(IV), or Zr(IV) metal oxide units as bridges. The procedure has been extended to chromophore-catalyst assemblies for water oxidation catalysis. A SnO2 bridged assembly on SnO2/TiO2 core/shell electrodes undergoes water splitting with an incident photon conversion efficiency (IPCE)more » of 17.1% at 440 nm. Reduction of water at a Ni(II)-based catalyst on NiO films has been shown to give H2. Compared to conventional solution-based procedures, the ALD approach offers significant advantages in scope and flexibility for the preparation of stable surface structures.« less

Functionalization of SiO2 Surfaces for Si Monolayer Doping with Minimal Carbon Contamination.

PubMed

van Druenen, Maart; Collins, Gillian; Glynn, Colm; O'Dwyer, Colm; Holmes, Justin D

2018-01-17

Monolayer doping (MLD) involves the functionalization of semiconductor surfaces followed by an annealing step to diffuse the dopant into the substrate. We report an alternative doping method, oxide-MLD, where ultrathin SiO 2 overlayers are functionalized with phosphonic acids for doping Si. Similar peak carrier concentrations were achieved when compared with hydrosilylated surfaces (∼2 × 10 20 atoms/cm 3 ). Oxide-MLD offers several advantages over conventional MLD, such as ease of sample processing, superior ambient stability, and minimal carbon contamination. The incorporation of an oxide layer minimizes carbon contamination by facilitating attachment of carbon-free precursors or by impeding carbon diffusion. The oxide-MLD strategy allows selection of many inexpensive precursors and therefore allows application to both p- and n-doping. The phosphonic acid-functionalized SiO 2 surfaces were investigated using X-ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy, whereas doping was assessed using electrochemical capacitance voltage and Hall measurements.

Controlling the Surface Chemistry of Graphite by Engineered Self-Assembled Peptides

PubMed Central

Khatayevich, Dmitriy; So, Christopher R.; Hayamizu, Yuhei; Gresswell, Carolyn; Sarikaya, Mehmet

2012-01-01

The systematic control over surface chemistry is a long-standing challenge in biomedical and nanotechnological applications for graphitic materials. As a novel approach, we utilize graphite-binding dodecapeptides that self-assemble into dense domains to form monolayer thick long-range ordered films on graphite. Specifically, the peptides are rationally designed through their amino acid sequences to predictably display hydrophilic and hydrophobic characteristics while maintaining their self-assembly capabilities on the solid substrate. The peptides are observed to maintain a high tolerance for sequence modification, allowing the control over surface chemistry via their amino acid sequence. Furthermore, through a single step co-assembly of two different designed peptides, we predictably and precisely tune the wettability of the resulting functionalized graphite surfaces from 44 to 83 degrees. The modular molecular structures and predictable behavior of short peptides demonstrated here give rise to a novel platform for functionalizing graphitic materials that offers numerous advantages, including non-invasive modification of the substrate, bio-compatible processing in an aqueous environment, and simple fusion with other functional biological molecules. PMID:22428620

Dynamic peptide libraries for the discovery of supramolecular nanomaterials

NASA Astrophysics Data System (ADS)

Pappas, Charalampos G.; Shafi, Ramim; Sasselli, Ivan R.; Siccardi, Henry; Wang, Tong; Narang, Vishal; Abzalimov, Rinat; Wijerathne, Nadeesha; Ulijn, Rein V.

2016-11-01

Sequence-specific polymers, such as oligonucleotides and peptides, can be used as building blocks for functional supramolecular nanomaterials. The design and selection of suitable self-assembling sequences is, however, challenging because of the vast combinatorial space available. Here we report a methodology that allows the peptide sequence space to be searched for self-assembling structures. In this approach, unprotected homo- and heterodipeptides (including aromatic, aliphatic, polar and charged amino acids) are subjected to continuous enzymatic condensation, hydrolysis and sequence exchange to create a dynamic combinatorial peptide library. The free-energy change associated with the assembly process itself gives rise to selective amplification of self-assembling candidates. By changing the environmental conditions during the selection process, different sequences and consequent nanoscale morphologies are selected.

Dynamic peptide libraries for the discovery of supramolecular nanomaterials.

PubMed

Pappas, Charalampos G; Shafi, Ramim; Sasselli, Ivan R; Siccardi, Henry; Wang, Tong; Narang, Vishal; Abzalimov, Rinat; Wijerathne, Nadeesha; Ulijn, Rein V

2016-11-01

Sequence-specific polymers, such as oligonucleotides and peptides, can be used as building blocks for functional supramolecular nanomaterials. The design and selection of suitable self-assembling sequences is, however, challenging because of the vast combinatorial space available. Here we report a methodology that allows the peptide sequence space to be searched for self-assembling structures. In this approach, unprotected homo- and heterodipeptides (including aromatic, aliphatic, polar and charged amino acids) are subjected to continuous enzymatic condensation, hydrolysis and sequence exchange to create a dynamic combinatorial peptide library. The free-energy change associated with the assembly process itself gives rise to selective amplification of self-assembling candidates. By changing the environmental conditions during the selection process, different sequences and consequent nanoscale morphologies are selected.

Phosphonate Analogs of 2-Oxoglutarate Perturb Metabolism and Gene Expression in Illuminated Arabidopsis Leaves

PubMed Central

Araújo, Wagner L.; Tohge, Takayuki; Nunes-Nesi, Adriano; Daloso, Danilo M.; Nimick, Mhairi; Krahnert, Ina; Bunik, Victoria I.; Moorhead, Greg B. G.; Fernie, Alisdair R.

2012-01-01

Although the role of the 2-oxoglutarate dehydrogenase complex (2-OGDHC) has previously been demonstrated in plant heterotrophic tissues its role in photosynthetically active tissues remains poorly understood. By using a combination of metabolite and transcript profiles we here investigated the function of 2-OGDHC in leaves of Arabidopsis thaliana via use of specific phosphonate inhibitors of the enzyme. Incubation of leaf disks with the inhibitors revealed that they produced the anticipated effects on the in situ enzyme activity. In vitro experiments revealed that succinyl phosphonate (SP) and a carboxy ethyl ester of SP are slow-binding inhibitors of the 2-OGDHC. Our results indicate that the reduced respiration rates are associated with changes in the regulation of metabolic and signaling pathways leading to an imbalance in carbon-nitrogen metabolism and cell homeostasis. The inducible alteration of primary metabolism was associated with altered expression of genes belonging to networks of amino acids, plant respiration, and sugar metabolism. In addition, by using isothermal titration calorimetry we excluded the possibility that the changes in gene expression resulted from an effect on 2-oxoglutarate (2OG) binding to the carbon/ATP sensing protein PII. We also demonstrated that the 2OG degradation by the 2-oxoglutarate dehydrogenase strongly influences the distribution of intermediates of the tricarboxylic acid (TCA) cycle and the GABA shunt. Our results indicate that the TCA cycle activity is clearly working in a non-cyclic manner upon 2-OGDHC inhibition during the light period. PMID:22876250

Role of Thermal Process on Self-Assembled Structures of 4′-([2,2′:6′,2″-Terpyridin]-4′-Yl)-[1,1′-Biphenyl]-4-Carboxylic Acid on Au(III)

PubMed Central

Liu, Xiaoqing; Wang, Yongli; Song, Xin; Chen, Feng; Ouyang, Hongping; Zhang, Xueao; Cai, Yingxiang; Liu, Xiaoming; Wang, Li

2013-01-01

The role of dynamic processes on self-assembled structures of 4′-([2,2′:6′, 2″-terpyridin]-4′-yl)-[1,1′-biphenyl]-4-carboxylic acid (l) molecules on Au(III) has been studied by scanning tunneling microscopy. The as-deposited monolayer is closed-packed and periodic in a short-range due to dipole forces. A thermal annealing process at 110 degrees drives such disordered monolayer into ordered chain-like structures, determined by the combination of the dipole forces and hydrogen bonding. Further annealing at 130 degrees turns the whole monolayer into a bowknot-like structure in which hydrogen bonding plays the dominant role in the formation of assembled structures. Such dependence of an assembled structure on the process demonstrates that an assembled structure can be regulated and controlled not only by the molecular structure but also by the thermal process to form the assembled structure. PMID:23478440

Development of short and highly potent self-assembling elastin-derived pentapeptide repeats containing aromatic amino acid residues.

PubMed

Taniguchi, Suguru; Watanabe, Noriko; Nose, Takeru; Maeda, Iori

2016-01-01

Tropoelastin is the primary component of elastin, which forms the elastic fibers that make up connective tissues. The hydrophobic domains of tropoelastin are thought to mediate the self-assembly of elastin into fibers, and the temperature-mediated self-assembly (coacervation) of one such repetitive peptide sequence (VPGVG) has been utilized in various bio-applications. To elucidate a mechanism for coacervation activity enhancement and to develop more potent coacervatable elastin-derived peptides, we synthesized two series of peptide analogs containing an aromatic amino acid, Trp or Tyr, in addition to Phe-containing analogs and tested their functional characteristics. Thus, position 1 of the hydrophobic pentapeptide repeat of elastin (X(1)P(2)G(3)V(4)G(5)) was substituted by Trp or Tyr. Eventually, we acquired a novel, short Trp-containing elastin-derived peptide analog (WPGVG)3 with potent coacervation ability. From the results obtained during this process, we determined the importance of aromaticity and hydrophobicity for the coacervation potency of elastin-derived peptide analogs. Generally, however, the production of long-chain synthetic polypeptides in quantities sufficient for commercial use remain cost-prohibitive. Therefore, the identification of (WPGVG)3, which is a 15-mer short peptide consisting simply of five natural amino acids and shows temperature-dependent self-assembly activity, might serve as a foundation for the development of various kinds of biomaterials. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd.

Self-assembled one dimensional functionalized metal-organic nanotubes (MONTs) for proton conduction.

PubMed

Panda, Tamas; Kundu, Tanay; Banerjee, Rahul

2012-06-04

Two self-assembled isostructural functionalized metal-organic nanotubes have been synthesized using 5-triazole isophthalic acid (5-TIA) with In(III) and Cd(II). In- and Cd-5TIA possess one-dimensional (1D) nanotubular architecture and show proton conductivity along regular 1D channels, measured as 5.35 × 10(-5) and 3.61 × 10(-3) S cm(-1) respectively.

Preparations and properties of anti-corrosion additives of water-soluble metal working fluids for aluminum alloy materials.

PubMed

Watanabe, Shoji

2008-01-01

This short review describes various types of anti-corrosion additives of water-soluble metal working fluids for aluminum alloy materials. It is concerned with synthetic additives classified according to their functional groups; silicone compounds, carboxylic acids and dibasic acids, esters, Diels-Alder adducts, various polymers, nitrogen compounds, phosphoric esters, phosphonic acids, and others. Testing methods for water-soluble metal working fluids for aluminum alloy materials are described for a practical application in a laboratory.

Liquid—liquid interface-mediated Au—ZnO composite membrane using ‘thiol-ene’ click chemistry

NASA Astrophysics Data System (ADS)

Ali, Mohammed; Ghosh, Sujit Kumar

2015-07-01

A nanoparticle-decorated composite membrane has been devised at the water/CCl4 interface based on the self-assembly of ligand-stabilized gold and zinc oxide nanoparticles, exploiting the ‘thiol-ene’ click chemistry between the thiol groups of 11-mercaptoundecanoic acid-stabilized ZnO nanoparticles and the ene functionality of cinnamic acid attached to gold nanoparticles. The interfacial assembly of ultrasmall particles leads to a multilayer film that exhibits charge-dependent permeability of amino acid molecules across the membrane.

A Self-Assembled Aggregate Composed of a Fatty Acid Membrane and the Building Blocks of Biological Polymers Provides a First Step in the Emergence of Protocells

PubMed Central

Black, Roy A.; Blosser, Matthew C.

2016-01-01

We propose that the first step in the origin of cellular life on Earth was the self-assembly of fatty acids with the building blocks of RNA and protein, resulting in a stable aggregate. This scheme provides explanations for the selection and concentration of the prebiotic components of cells; the stabilization and growth of early membranes; the catalysis of biopolymer synthesis; and the co-localization of membranes, RNA and protein. In this article, we review the evidence and rationale for the formation of the proposed aggregate: (i) the well-established phenomenon of self-assembly of fatty acids to form vesicles; (ii) our published evidence that nucleobases and sugars bind to and stabilize such vesicles; and (iii) the reasons why amino acids likely do so as well. We then explain how the conformational constraints and altered chemical environment due to binding of the components to the membrane could facilitate the formation of nucleosides, oligonucleotides and peptides. We conclude by discussing how the resulting oligomers, even if short and random, could have increased vesicle stability and growth more than their building blocks did, and how competition among these vesicles could have led to longer polymers with complex functions. PMID:27529283

Biomimetic Oxygen-Evolving Photobacteria Based on Amino Acid and Porphyrin Hierarchical Self-Organization.

PubMed

Liu, Kai; Zhang, Han; Xing, Ruirui; Zou, Qianli; Yan, Xuehai

2017-12-26

Biomimetic organization provides a promising strategy to develop functional materials and understand biological processes. However, how to mimic complex biological systems using simple biomolecular units remains a great challenge. Herein, we design and fabricate a biomimetic cyanobacteria model based on self-integration of small bioinspired molecules, including amphiphilic amino acid, 3,4-dihydroxyphenylalanine (DOPA), and metalloporphyrin and cobalt oxide nanoparticles (Co 3 O 4 NPs), with the assistance of chemical conjugation and molecular self-assembly. The assembled amino acid fiber can be modified by DOPA to form covalently bound DOPA melanin containing hydroxyl and quinone species via Schiff base reaction. The adhering template can further tune the self-assembly of metalloporphyrin and Co 3 O 4 NPs into J-aggregation and dispersive distribution, respectively, mainly via coordination binding. Metalloporphyrin molecules in the resulting hybrid fibers capture light; quinone species accept the excited electrons, and Co 3 O 4 NPs catalyze water oxidation. Thus, the essential components of the photosystem-II protein complex in cyanobacteria are simplified and engineered into a simple framework, still retaining a similar photosynthetic mechanism. In addition, this architecture leads to efficient coupling of antenna, quinone-type reaction center, and photocatalyst, which increases the flux of light energy from antenna to reaction center for charge separation, resulting in enhanced oxygen evolution rate with excellent sustainability.

Perfluoroalkyl acids: recent research highlights | Science ...

EPA Pesticide Factsheets

Perfluorinated compounds are organic chemicals in which all hydrogen molecules of the carbon-chain are substituted by fluorine molecules. Generally, there are two types of perfluorinated compounds, the perfluoroalkanes that are primarily used clinically for oxygenation and respiratory ventilation, and the perfluoroalkyl acids (PFAAs). Environmentally relevant PFAAs are a family of about 30 chemicals that consist of a carbon backbone typically 4-14 molecules in length and a charged functional group composed of either sulfonates, carboxylates or phosphonates (and to a lesser extent, phosphinates). While many (>100) derivatives ofPFAAs (such as alcohols, amides, esters and acids) are used for industrial and consumer applications, they can be degraded or metabolized to PFAAs as end-stage products. Thus, PFAAs, rather than their intermediates or derivatives, have drawn the most public attention and research interest. The most widely known PFAAs are the eight-carbon (C8) sulfonate (perfluorooctane sulfonate, PFOS) and carboxylate (perfluorooctanoic acid, PFOA), although the C4 (perfluorobutane) and C6 (perfluorohexane) sulfonates, as well as the C4, C6 and C9 (perfluorononanoic) carboxylates have also been used in commerce. The perfluoroalkyl phosphonates (PFPAs) are fairly new entities for this class ofchemicals. They are typically used as leveling and wetting agents, and defoaming additives in the production of pesticides. They were considered biologically inert by

Determination of perfluoroalkyl carboxylic, sulfonic, and phosphonic acids in food.

PubMed

Ullah, Shahid; Alsberg, Tomas; Vestergren, Robin; Berger, Urs

2012-11-01

A sensitive and accurate method was developed and validated for simultaneous analysis of perfluoroalkyl carboxylic acids, sulfonic acids, and phosphonic acids (PFPAs) at low picograms per gram concentrations in a variety of food matrices. The method employed extraction with acetonitrile/water and cleanup on a mixed-mode co-polymeric sorbent (C8 + quaternary amine) using solid-phase extraction. High-performance liquid chromatographic separation was achieved on a C18 column using a mobile phase gradient containing 5 mM 1-methyl piperidine for optimal chromatographic resolution of PFPAs. A quadrupole time-of-flight high-resolution mass spectrometer operating in negative ion mode was used as detector. Method detection limits were in the range of 0.002 to 0.02 ng g(-1) for all analytes. Sample preparation (extraction and cleanup) recoveries at a spiking level of 0.1 ng g(-1) to a baby food composite were in the range of 59 to 98 %. A strong matrix effect was observed in the analysis of PFPAs in food extracts, which was tentatively assigned to sorption of PFPAs to the injection vial in the solvent-based calibration standard. The method was successfully applied to a range of different food matrices including duplicate diet samples, vegetables, meat, and fish samples.

URBAN CONTRIBUTIONS OF GLYSPHOSATE AND ITS DEGRADATE AMPA TO STREAMS IN THE UNITED STATES

EPA Science Inventory

Glyphosate is the most widely used herbicide in the world, being routinely applied to control weeds in both agricultural and urban settings. Microbial degradation of glyphosate produces aminomethyl phosphonic acid (AMPA). The high polarity and water-solubility of glyphosate and A...

Two-carbon homologation of aldehydes and ketones to a,ß-unsaturated aldehydes

USDA-ARS?s Scientific Manuscript database

Phosphonate reagents were developed for the two-carbon homologation of aldehydes or ketones to unbranched- or methyl-branched a,ß-unsaturated aldehydes. The phosphonate reagents, diethyl methylformyl-2-phosphonate dimethylhydrazone and diethyl ethylformyl-2-phosphonate dimethylhydrazone, contained a...

pH-modulated self-assembly of colloidal nanoparticles in a dual-droplet inkjet printing process.

PubMed

Al-Milaji, Karam Nashwan; Radhakrishnan, Vinod; Kamerkar, Prajakta; Zhao, Hong

2018-06-05

Interfacial self-assembly has been demonstrated as a powerful driving mechanism for creating various nanostructured assemblies. In this work, we employed a dual-droplet printing process and interfacial self-assembly mechanism to produce deposits with controlled assembly structures of colloidal nanoparticles. We hypothesize that pH modulation of the droplet will influence the interfacial self-assembly through the multibody interactions, e.g. particle-particle, particle-interface, and particle-substrate interactions, correspondingly affecting the deposition morphology of the colloidal nanoparticles. During the dual-droplet printing, a wetting droplet, containing colloidal nanoparticles, was jetted over a supporting droplet that contains water only. pH modulation was carried out to the supporting droplet. The self-assembly of two kinds of functionalized polystyrene (PS) nanoparticles (carboxyl-PS and sulfate-PS) was systematically investigated under various pH conditions. Depending on the pH level of the supporting droplet, deposits of carboxyl-PS particles ranging from clear ring-like patterns to nearly uniform monolayer depositions have been obtained. On the other hand, the sulfate-PS particles, even at extreme basic and acidic environments, successfully assemble into nearly monolayer depositions. The multibody interactions are discussed. Such findings can be harnessed in manufacturing high-performance optical and electronic devices. Copyright © 2018 Elsevier Inc. All rights reserved.

Synthesis of phosphonic acid silver-graphene oxide nanomaterials with photocatalytic activity through ultrasonic-assisted method.

PubMed

Li, Yongshen; Song, Yunna; Ma, Zheng; Niu, Shuai; Li, Jihui; Li, Ning

2018-06-01

In this article, phosphonic acid silver-graphene oxide nanomaterials (Nano-PAS-GO) was synthesized from silver nitrate (AgNO 3 ) solution and phosphoric graphene oxide (PGO) via the convenient ultrasonic-assisted method, and the structure and morphology were characterized, and the photocatalytic activity and recyclability were evaluated through photocatalyzing degradation of Rhodamin B (RhB) aqueous solution, and the possible photocatalytic mechanism was also discussed. Based on those, it was confirmed that Nano-PAS-GO has been synthesized from AgNO 3 solution and PGO colloidal suspension under ultrasonic-assisted condition, and Nano-PAS-GO has consisted of phosphoric acid silver nanoparticles and GO with 2D lattice (2D GO lattice) connected in the form of C-P bonds, and the photodegradation rate of Nano-PAS-GO for RhB aqueous solution has reached 93.99%, and Nano-PAS-GO has possessed the nicer recyclability when the photocatalytic time was 50 min. From those results, the strong and stable interface . between PAS nanoparticles and 2D GO lattice connected in the form of the covalent bonds has effectively inhibited the occurrence of the photocorrosion phenomenon. Copyright © 2018 Elsevier B.V. All rights reserved.

Interaction of solid organic acids with carbon nanotube field effect transistors

NASA Astrophysics Data System (ADS)

Klinke, Christian; Afzali, Ali; Avouris, Phaedon

2006-10-01

A series of solid organic acids were used to p-dope carbon nanotubes. The extent of doping is shown to be dependent on the pKa value of the acids. Highly fluorinated carboxylic acids and sulfonic acids are very effective in shifting the threshold voltage and making carbon nanotube field effect transistors to be more p-type devices. Weaker acids like phosphonic or hydroxamic acids had less effect. The doping of the devices was accompanied by a reduction of the hysteresis in the transfer characteristics. In-solution doping survives standard fabrication processes and renders p-doped carbon nanotube field effect transistors with good transport characteristics.

Self-Assembly of Natural and Synthetic Drug Amphiphiles into Discrete Supramolecular Nanostructures

PubMed Central

Lock, Lye Lin; LaComb, Michelle; Schwarz, Kelly; Cheetham, Andrew G.; Lin, Yi-an; Zhang, Pengcheng

2014-01-01

Molecular assembly provides an effective approach to construct discrete supramolecular nanostructures of various sizes and shapes in a simple manner. One important technological application of the resulting nanostructures is their potential use as anticancer drug carriers to facilitate targeted delivery to tumour sites and consequently to improve clinical outcomes. In this carrier-assisted delivery strategy, anticancer drugs have been almost exclusively considered as the cargo to be carried and delivered, and their potential as molecular building blocks has been largely ignored. In this discussion, we report the use of anticancer drugs as molecular building units to create discrete supramolecular nanostructures that contain a high and quantitative drug loading and also have the potential for self-delivery. We first show the direct assembly of two amphiphilic drug molecules (methotrexate and folic acid) into discrete nanostructures. Our results reveal that folic acid exhibits rich self-assembly behaviours via Hoogsteen hydrogen bonding in various solvent conditions, whereas methotrexate was unable to assemble into any well-defined nanostructures under the same conditions, despite its similar chemical structures. Considering the low water solubility of most anticancer drugs, hydrophilic segments must be conjugated to the drug in order to bestow the necessary amphiphilicity. We have demonstrated this for camptothecin through the attachment of β-sheet-forming peptides with overall hydrophilicity. We found that the intermolecular interactions among camptothecin segments and those among β-sheet peptides act together to define the formation of stable one-dimensional nanostructures in dilute solutions, giving rise to nanotubes or nanofibers depending upon the processing conditions used. These results lead us to believe that self-assembly of drugs into discrete nanostructures not only offers an innovative way to craft self-delivering anticancer drugs, but also extends the paradigm of using molecular assembly as a toolbox to achieve functional nanostructures, to a new area which is specifically focused on the direct assembly of functional molecules (e.g. drugs, or imaging agents) into nanostructures of their own. PMID:24611283

Frictional response of fatty acids on steel.

PubMed

Sahoo, Rashmi R; Biswas, S K

2009-05-15

Self-assembled monolayers of fatty acids were formed on stainless steel by room-temperature solution deposition. The acids are covalently bound to the surface as carboxylate in a bidentate manner. To explore the effect of saturation in the carbon backbone on friction in sliding tribology, we study the response of saturated stearic acid (SA) and unsaturated linoleic acid (LA) as self-assembled monolayers using lateral force microscopy and nanotribometry and when the molecules are dispersed in hexadecane, using pin-on-disc tribometry. Over a very wide range (10 MPa-2.5 GPa) of contact pressures it is consistently demonstrated that the unsaturated linoleic acid molecules yield friction which is significantly lower than that of the saturated stearic acid. It is argued, using density functional theory predictions and XPS of slid track, that when the molecular backbone of unsaturated fatty acids are tilted and pressed strongly by a probe, in tribological contact, the high charge density of the double bond region of the backbone allows coupling with the steel substrate. The interaction yields a low friction carboxylate soap film on the substrate. The saturated fatty acid does not show this effect.

H-Bonding Assisted Self-Assembly of Anionic and Neutral Ligand on Metal: A Comprehensive Strategy To Mimic Ditopic Ligands in Olefin Polymerization.

PubMed

Mote, Nilesh R; Patel, Ketan; Shinde, Dinesh R; Gaikwad, Shahaji R; Koshti, Vijay S; Gonnade, Rajesh G; Chikkali, Samir H

2017-10-16

Self-assembly of two neutral ligands on a metal to mimic bidentate ligand coordination has been frequently encountered in the recent past, but self-assembly of an anionic ligand on a metal template alongside a neutral ligand remains an elusive target. Such a self-assembly is hampered by additional complexity, wherein a highly negatively charged anion can form intermolecular hydrogen bonding with the supramolecular motif, leaving no scope for self-assembly with neutral ligand. Presented here is the self-association of anionic ligand 3-ureidobenzoic acid (2a) and neutral ligand 1-(3-(diphenylphosphanyl)phenyl)urea (1a) on a metal template to yield metal complex [{COOC 6 H 4 NH(CO)NH 2 }{Ph 2 PC 6 H 4 NH(CO)NH 2 }PdMeDMSO] (4a). The identity of 4a was established by NMR and mass spectroscopy. Along the same lines, 3-(3-phenylureido)benzoic acid (2b) and 1-(3-(diphenylphosphanyl)phenyl)-3-phenylurea (1b) self-assemble on a metal template to produce palladium complex [{COOC 6 H 4 NH(CO)NHPh}{Ph 2 PC 6 H 4 NH(CO)NHPh}PdMePy] (5c). The existence of 5c was confirmed by Job plot, 1-2D NMR spectroscopy, deuterium labeling, IR spectroscopy, UV-vis spectroscopy, model complex synthesis, and DFT calculations. These solution and gas phase investigations authenticated the presence of intramolecular hydrogen bonding between hydrogen's of 1b and carbonyl oxygen of 2b. The generality of the supramolecular approach has been validated by preparing six complexes from four monodentate ligands, and their synthetic utility was demonstrated in ethylene polymerization. Complex 4a was found to be the most active, leading to the production of highly branched polyethylene with a molecular weight of 55700 g/mol and melting temperature of 112 °C.

Self-assembly of keratin peptides: Its implication on the performance of electrospun PVA nanofibers

PubMed Central

Kadirvelu, Kavitha; Fathima, Nishter Nishad

2016-01-01

Drawing inspiration from the field of designer self-assembling materials, this work is aimed to focus on the self-assembling nature of extracted peptides. Hair keratin, a proteinacious reject in tanning industry has been chosen since they have been extracted and used for wide range of applications. Keratin source was subjected to five hydrolysis treatments (viz., sulphitolysis, β-mercaptoethanol, ionic liquid, thioglycolic acid and alkali) and assayed for functional groups. This was followed by the prediction of secondary structure using circular dichroism, determining the microstructural level to which the extracted peptide has self-assembled. Sulphitolysis and thioglycolic acid based hydrolysates exist in monomeric conformation, whereas β-mercaptoethanol based hydrolysate exhibited dimeric conformation. The subsequent part of the study is to incorporate these peptides into the nanofibers to study the structural implication of keratin peptides on its characteristics. Accordingly, the peptides were electrospun with PVA and subjected to morphological, mechanical, thermal and biological characterizations. Monomeric nanofiber mat has high tensile strength of around 5.5 MPa and offered lower mass transport resistance, whereas dimeric mat has high Tm of around 290 °C and was more biocompatible. These results help in understanding the extraction-structure-function aspect of the hydrolysates stressing the role of extraction methods on the choice of application. PMID:27812004

Molecular Structure of a Helical ribbon in a Peptide Self-Assembly

NASA Astrophysics Data System (ADS)

Hwang, Wonmuk; Marini, Davide; Kamm, Roger D.; Zhang, Shuguang

2002-03-01

We have studied the molecular structure of nanometer scale helical ribbons observed during self-assembly of the peptide KFE8 (amino acid sequence: FKFEFKFE) (NanoLetters (2002, in press)). By analyzing the hydrogen bonding patterns between neighboring peptide backbones, we constructed a number of possible β-sheets. Using all possible combinations of these, we built helical ribbons with dimensions close to those found experimentally and performed molecular dynamics simulations to identify the most stable structure. Solvation effects were implemented by the analytic continuum electrostatics (ACE) model developed by Schaefer and Karplus (J. Phys. Chem. 100, 1578 (1996)). By applying electrostatic double layer theory, we incorporated the effect of pH by scaling the amount of charge on the sidechains. Our results suggest that the helical ribbon is comprised of a double β-sheet where the inner and the outer helices have distinct hydrogen bonding patterns. Our approach has general applicability to the study of helices formed by the self-assembly of β-sheet forming peptides with various amino acid sequences.

Hybrid gels assembled from Fmoc-amino acid and graphene oxide with controllable properties.

PubMed

Xing, Pengyao; Chu, Xiaoxiao; Li, Shangyang; Ma, Mingfang; Hao, Aiyou

2014-08-04

A supramolecular gel is obtained from the self-assembly of an ultralow-molecular-weight gelator (N-fluorenyl-9-methoxycarbonyl glutamic acid) in good and poor solvents. The gelators can self-assemble into a lamellar structure, which can further form twisted fibers and nanotubes in the gel phase. Rheological studies show that the gels are robust and rigid, and are able to rapidly self-recover to a gel after being destroyed by shear force. Fluorescence experiments reveal the aggregation-induced emission effects of the gel system; the fluorescence intensity is significantly enhanced by gel formation. Graphene oxide (GO) is introduced into the system efficiently to give a hybrid material, and the interaction between gelators-GO sheets is studied. Rheological and fluorescent studies imply that the mechanical properties and the fluorescent emission of the hybrid materials can be fine-tuned by controlling the addition of GO. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Eco-friendly microwave-assisted protocol to prepare hyaluronan-fatty acid conjugates and to induce their self-assembly process.

PubMed

Calce, Enrica; Mercurio, Flavia Anna; Leone, Marilisa; Saviano, Michele; De Luca, Stefania

2016-06-05

An environmentally sustainable and energy-efficient synthetic process has been developed to prepare hyaluronan-based nano-sized material. It consists in a microwave-promoted acylation of the hydroxyl function of the polysaccharide with natural fatty acids, performed under solvent-free conditions. The efficient interaction of the solid reagents with the MW radiation accounts for the obtained high yielded products. The self-assembly process of the obtained compounds very fast occurred in an aqueous medium under MW-radiation, thus allowing the development of a green protocol for the nano-particles preparation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Formation of vesicles through solvent assisted self-assembly of hydrophobic pentapeptides: encapsulation and pH responsive release of dyes by the vesicles.

PubMed

Kar, Sudeshna; Drew, Michael G B; Pramanik, Animesh

2011-09-01

In the biomimetic design two hydrophobic pentapetides Boc-Ile-Aib-Leu-Phe-Ala-OMe (I) and Boc-Gly-Ile-Aib-Leu-Phe-OMe (II) (Aib: α-aminoisobutyric acid) containing one Aib each are found to undergo solvent assisted self-assembly in methanol/water to form vesicular structures, which can be disrupted by simple addition of acid. The nanovesicles are found to encapsulate dye molecules that can be released by the addition of acid as confirmed by fluorescence microscopy and UV studies. The influence of solvent polarity on the morphology of the materials generated from the peptides has been examined systematically, and shows that fibrillar structures are formed in less polar chloroform/petroleum ether mixture and vesicular structures are formed in more polar methanol/water. Single crystal X-ray diffraction studies reveal that while β-sheet mediated self-assembly leads to the formation of fibrillar structures, the solvated β-sheet structure leads to the formation of vesicular structures. The results demonstrate that even hydrophobic peptides can generate vesicular structures from polar solvent which may be employed in model studies of complex biological phenomena.

Cooperative Subunit Refolding of a Light-Harvesting Protein through a Self-Chaperone Mechanism.

PubMed

Laos, Alistair J; Dean, Jacob C; Toa, Zi S D; Wilk, Krystyna E; Scholes, Gregory D; Curmi, Paul M G; Thordarson, Pall

2017-07-10

The fold of a protein is encoded by its amino acid sequence, but how complex multimeric proteins fold and assemble into functional quaternary structures remains unclear. Here we show that two structurally different phycobiliproteins refold and reassemble in a cooperative manner from their unfolded polypeptide subunits, without biological chaperones. Refolding was confirmed by ultrafast broadband transient absorption and two-dimensional electronic spectroscopy to probe internal chromophores as a marker of quaternary structure. Our results demonstrate a cooperative, self-chaperone refolding mechanism, whereby the β-subunits independently refold, thereby templating the folding of the α-subunits, which then chaperone the assembly of the native complex, quantitatively returning all coherences. Our results indicate that subunit self-chaperoning is a robust mechanism for heteromeric protein folding and assembly that could also be applied in self-assembled synthetic hierarchical systems. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Peptide self-assembly: thermodynamics and kinetics.

PubMed

Wang, Juan; Liu, Kai; Xing, Ruirui; Yan, Xuehai

2016-10-21

Self-assembling systems play a significant role in physiological functions and have therefore attracted tremendous attention due to their great potential for applications in energy, biomedicine and nanotechnology. Peptides, consisting of amino acids, are among the most popular building blocks and programmable molecular motifs. Nanostructures and materials assembled using peptides exhibit important potential for green-life new technology and biomedical applications mostly because of their bio-friendliness and reversibility. The formation of these ordered nanostructures pertains to the synergistic effect of various intermolecular non-covalent interactions, including hydrogen-bonding, π-π stacking, electrostatic, hydrophobic, and van der Waals interactions. Therefore, the self-assembly process is mainly driven by thermodynamics; however, kinetics is also a critical factor in structural modulation and function integration. In this review, we focus on the influence of thermodynamic and kinetic factors on structural assembly and regulation based on different types of peptide building blocks, including aromatic dipeptides, amphiphilic peptides, polypeptides, and amyloid-relevant peptides.

PROCESS FOR THE RECOVERY OF METALS FROM HIGH-LIME CARNOTITE ORES

DOEpatents

Grinstead, R.R.

1959-01-20

A process is presented for recovering uranium values from a high-lime carnotite ore comprising contacting the ore dispersed in a finely divided state with a concentrated mineral acid, adding an industrial orgnnic solvent containing alkyl ontho or pyro phosphoric acids, alkyl phosphates or alkyl phosphonates so as to effect an organic phase into which the metal value is leached and then recovering the metal value from the organic phase.

Applying AFM-based nanofabrication for measuring the thickness of nanopatterns: the role of head groups in the vertical self-assembly of omega-functionalized n-alkanethiols.

PubMed

Kelley, Algernon T; Ngunjiri, Johnpeter N; Serem, Wilson K; Lawrence, Steve O; Yu, Jing-Jiang; Crowe, William E; Garno, Jayne C

2010-03-02

Molecules of n-alkanethiols with methyl head groups typically form well-ordered monolayers during solution self-assembly for a wide range of experimental conditions. However, we have consistently observed that, for either carboxylic acid or thiol-terminated n-alkanethiols, under certain conditions nanografted patterns are generated with a thickness corresponding precisely to a double layer. To investigate the role of head groups for solution self-assembly, designed patterns of omega-functionalized n-alkanethiols were nanografted with systematic changes in concentration. Nanografting is an in situ approach for writing patterns of thiolated molecules on gold surfaces by scanning with an AFM tip under high force, accomplished in dilute solutions of desired ink molecules. As the tip is scanned across the surface of a self-assembled monolayer under force, the matrix molecules are displaced from the surface and are immediately replaced with fresh molecules from solution to generate nanopatterns. In this report, side-by-side comparison of nanografted patterns is achieved for different matrix molecules using AFM images. The chain length and head groups (i.e., carboxyl, hydroxyl, methyl, thiol) were varied for the nanopatterns and matrix monolayers. Interactions such as head-to-head dimerization affect the vertical self-assembly of omega-functionalized n-alkanethiol molecules within nanografted patterns. At certain threshold concentrations, double layers were observed to form when nanografting with head groups of carboxylic acid and dithiols, whereas single layers were generated exclusively for nanografted patterns with methyl and hydroxyl groups, regardless of changes in concentration.

Hydrogels constructed via self-assembly of beta-hairpin molecules

NASA Astrophysics Data System (ADS)

Ozbas, Bulent

There is a recent and growing interest in hydrogel materials that are formed via peptide self-assembly for tissue engineering applications. Peptide based materials are excellent candidates for diverse applications in biomedical field due to their responsive behavior and complex self-assembled structures. However, there is very limited information on the self-assembly and resultant network and mechanical properties of these types of hydrogels. The main goal of this dissertation is to investigate the self-assembly mechanism and viscoelastic properties of hydrogels that can be altered by changing solution conditions as well as the primary structure of the peptide. These hydrogels are formed via intramolecular folding and consequent self-assembly of 20 amino acid long beta-hairpin peptide molecules (Max1). The peptide molecules are locally amphiphilic with two linear strands of alternating hydrophobic valine and hydrophilic lysine amino acids connected with a Dproline-LProline turn sequence. Circular dichroism and FTIR spectroscopy show that at physiological conditions peptides are unfolded in the absence of salt. By raising the ionic strength of the solution electrostatic interactions between charged lysines are screened and the peptide arms are forced into a beta-sheet secondary structure stabilized by the turn sequence. These folded molecules intermolecularly assemble via hydrophobic collapse and hydrogen bonding into a three dimensional network. Folding and self-assembly of these molecules can also be triggered by increasing temperature and/or pH of the peptide solution. In addition, the random-coil to beta-sheet transition of the beta-hairpin peptides is pH and, with proper changes in the peptide sequence, thermally reversible. Rheological measurements demonstrate that the resultant supramolecular structure forms an elastic material, whose structure, and thus modulus, can be tuned by magnitude of the stimulus. Hydrogels recover their initial viscoelastic properties after cessation of high magnitude of strain due to the physically crosslinked network structure and strong inter-fibrillar interactions. These interactions can be turned off by either condensing anions or covalently attaching PEG chains on lysine-decorated fibrillar surfaces. TEM, SANS, and rheological data reveal that the elasticity arises from a network consisting of semiflexible fibrillar assemblies that are monodisperse in width. The experimental results are compared with scaling relationships developed for permanently crosslinked semiflexible biopolymer networks. (Abstract shortened by UMI.)

Metal-oxide assisted surface treatment of polyimide gate insulators for high-performance organic thin-film transistors.

PubMed

Kim, Sohee; Ha, Taewook; Yoo, Sungmi; Ka, Jae-Won; Kim, Jinsoo; Won, Jong Chan; Choi, Dong Hoon; Jang, Kwang-Suk; Kim, Yun Ho

2017-06-14

We developed a facile method for treating polyimide-based organic gate insulator (OGI) surfaces with self-assembled monolayers (SAMs) by introducing metal-oxide interlayers, called the metal-oxide assisted SAM treatment (MAST). To create sites for surface modification with SAM materials on polyimide-based OGI (KPI) surfaces, the metal-oxide interlayer, here amorphous alumina (α-Al 2 O 3 ), was deposited on the KPI gate insulator using spin-coating via a rapid sol-gel reaction, providing an excellent template for the formation of a high-quality SAM with phosphonic acid anchor groups. The SAM of octadecylphosphonic acid (ODPA) was successfully treated by spin-coating onto the α-Al 2 O 3 -deposited KPI film. After the surface treatment by ODPA/α-Al 2 O 3 , the surface energy of the KPI thin film was remarkably decreased and the molecular compatibility of the film with an organic semiconductor (OSC), 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-C 10 ), was increased. Ph-BTBT-C 10 molecules were uniformly deposited on the treated gate insulator surface and grown with high crystallinity, as confirmed by atomic force microscopy (AFM) and X-ray diffraction (XRD) analysis. The mobility of Ph-BTBT-C 10 thin-film transistors (TFTs) was approximately doubled, from 0.56 ± 0.05 cm 2 V -1 s -1 to 1.26 ± 0.06 cm 2 V -1 s -1 , after the surface treatment. The surface treatment of α-Al 2 O 3 and ODPA significantly decreased the threshold voltage from -21.2 V to -8.3 V by reducing the trap sites in the OGI and improving the interfacial properties with the OSC. We suggest that the MAST method for OGIs can be applied to various OGI materials lacking reactive sites using SAMs. It may provide a new platform for the surface treatment of OGIs, similar to that of conventional SiO 2 gate insulators.

Novel Self-Assembling Amino Acid-Derived Block Copolymer with Changeable Polymer Backbone Structure.

PubMed

Koga, Tomoyuki; Aso, Eri; Higashi, Nobuyuki

2016-11-29

Block copolymers have attracted much attention as potentially interesting building blocks for the development of novel nanostructured materials in recent years. Herein, we report a new type of self-assembling block copolymer with changeable polymer backbone structure, poly(Fmoc-Ser) ester -b-PSt, which was synthesized by combining the polycondensation of 9-fluorenylmethoxycarbonyl-serine (Fmoc-Ser) with the reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene (St). This block copolymer showed the direct conversion of the backbone structure from polyester to polypeptide through a multi O,N-acyl migration triggered by base-induced deprotection of Fmoc groups in organic solvent. Such polymer-to-polymer conversion was found to occur quantitatively without decrease in degree of polymerization and to cause a drastic change in self-assembling property of the block copolymer. On the basis of several morphological analyses using FTIR spectroscopy, atomic force, and transmission and scanning electron microscopies, the resulting peptide block copolymer was found to self-assemble into a vesicle-like hollow nanosphere with relatively uniform diameter of ca. 300 nm in toluene. In this case, the peptide block generated from polyester formed β-sheet structure, indicating the self-assembly via peptide-guided route. We believe the findings presented in this study offer a new concept for the development of self-assembling block copolymer system.

pH-Controlled Assembly of DNA Tiles

DOE PAGES

Amodio, Alessia; Adedeji, Abimbola Feyisara; Castronovo, Matteo; ...

2016-09-15

We demonstrate a strategy to trigger and finely control the assembly of supramolecular DNA nanostructures with pH. Control is achieved via a rationally designed strand displacement circuit that responds to pH and activates a downstream DNA tile self-assembly process. We observe that the DNA structures form under neutral/basic conditions, while the self-assembly process is suppressed under acidic conditions. The strategy presented here demonstrates a modular approach toward building systems capable of processing biochemical inputs and finely controlling the assembly of DNA-based nanostructures under isothermal conditions. In particular, the presented architecture is relevant for the development of complex DNA devices ablemore » to sense and respond to molecular markers associated with abnormal metabolism.« less

pH-Controlled Assembly of DNA Tiles

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

Amodio, Alessia; Adedeji, Abimbola Feyisara; Castronovo, Matteo

We demonstrate a strategy to trigger and finely control the assembly of supramolecular DNA nanostructures with pH. Control is achieved via a rationally designed strand displacement circuit that responds to pH and activates a downstream DNA tile self-assembly process. We observe that the DNA structures form under neutral/basic conditions, while the self-assembly process is suppressed under acidic conditions. The strategy presented here demonstrates a modular approach toward building systems capable of processing biochemical inputs and finely controlling the assembly of DNA-based nanostructures under isothermal conditions. In particular, the presented architecture is relevant for the development of complex DNA devices ablemore » to sense and respond to molecular markers associated with abnormal metabolism.« less

Polyaniline nanotubes and their dendrites doped with different naphthalene sulfonic acids

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

Zhang Zhiming; Chemistry and Chemical Engineering College, Ocean University of China, Qingdao 266003; Wei Zhixiang

2005-03-01

Polyaniline (PANI) nanotubes (130-250 nm in average diameter) doped with {alpha}-naphthalene sulfonic acid ({alpha}-NSA), {beta}-naphthalene sulfonic acid ({beta}-NSA) and 1,5-naphthalene disulfonic acid were synthesized via a self-assembly process. It was found that the formation yield, morphology (hollow or solid), size, crystalline and electrical properties of the nanostructures are affected by the position and number of -SO{sub 3}H groups attached to the naphthalene ring of NSA as well as the synthesis conditions. Moreover, these nanotubes aggregate to form a dendritic morphology when the polymerization is performed at a static state. The micelles composed of dopant or dopant/anilinium cations might act inmore » a template-like fashion in forming self-assembled PANI nanotubes, which was further confirmed by X-ray diffraction measurements, while the aggregated morphology of the nanotubes might result from polymer chain interactions including {pi}-{pi} interactions, hydrogen and ionic bonds.« less

Biochemical synthesis of novel, self-assembling glycolipids from ricinoleic acid by a recombinant α-glucosidase from Geobacillus sp.

PubMed

Konishi, Masa-aki; Fukuoka, Tokuma; Shimane, Yasuhiro; Mori, Kozue; Nagano, Yuriko; Ohta, Yukari; Kitamoto, Dai; Hatada, Yuji

2011-01-01

To explore a novel glycolipid, we performed biochemical reactions using a recombinant α-glucosidase from Geobacillus sp. which shows excellent transglycosylation reaction to hydroxyl groups in a variety of compounds. Two different glycolipids (GL-1 and GL-2) were prepared from ricinoleic acid using a recombinant α-glucosidase from Geobacillus sp. The molecular structure of GL-1 was confirmed as 12-O-α-D-glucopyranosyl-9-hexadecenoic acid by 1D and 2D NMR analyses. According to MALDI-TOF/MS, GL-1 and GL-2 showed single major peaks at m/z 483.82 and 645.97, respectively. The peaks corresponded to the [M + Na](+) ions of the glycolipids. GL-2 was estimated as 12-O-α-D-glucopyranosyl-(4'-O-α-glucopyranosyl)-9-hexadecenoic acid. Light polarization microscopy revealed that GL-2 easily formed self-assembled vesicles in aqueous solution.

Two-stages of chiral selectivity in the molecular self-assembly of tryptophan

NASA Astrophysics Data System (ADS)

Guisinger, Nathan

Both chirality and molecular assembly are essential and key components to life. In this study we explore the molecular assembly of the amino acid tryptophan (both L- and D- chiralities) on Cu(111). Our investigation utilizes low temperature scanning tunneling microscopy to observe resulting assemblies at the molecular scale. We find that depositing a racemic mixture of both L- and D- tryptophan results in the assembly of basic 6 molecule ``Lego'' structures that are enantiopure. These enantiopure ``Legos'' further assemble into 1-dimensional chains one block at a time. These resulting chains are also enantiopure with chiral selectivity occurring at two stages of assembly. Utilizing scanning tunneling spectroscopy we are able to probe the electronic structure of the chiral Legos that give insight into the root of the observed selectivity. Two-stages of chiral selectivity in the molecular self-assembly of tryptophan.

Bacterial Degradation of Phosphonates Bound to High-Molecular-Weight Dissolved Organic Matter Produces Methane and Other Hydrocarbons

NASA Astrophysics Data System (ADS)

Sosa, O.; Ferron Smith, S.; Karl, D. M.; DeLong, E.; Repeta, D.

2016-02-01

The biological degradation of dissolved organic matter (DOM) plays important roles in the carbon cycle and energy balance of the ocean. Yet, the biochemical pathways that drive DOM turnover remain to be fully characterized. In this study, we tested the ability of two open ocean bacterial isolates (a Pseudomonas stutzeri strain (Gammaproteobacteria) and a Sulfitobacter isolate (Alphaproteobacteria)) to degrade DOM phosphonates. Each isolate encoded a complete phosphonate degradation pathway in its genome, and each was able to degrade simple alkyl-phosphonates like methyl phosphonate, releasing methane (or other short chain hydrocarbon gases) as a result. We found that cultures incubated in the presence of HMW DOM polysaccharides also produced methane and other trace gases under aerobic conditions. To demonstrate that phosphonates were the source of these gases, we constructed a P. stutzeri mutant disabled in the phosphonate degradation pathway. Unlike the wild type, the mutant strain was deficient in the production of methane and other gases from HMW DOM-associated phosphonates. These observations support the hypothesis that DOM-bound methyl phosphonates may be a significant source of methane in the water column, and that bacterial degradation of these compounds likely contribute to the subsurface methane maxima observed throughout the world's oceans.

Construction and Self-Assembly of Single-Chain Polymer Nanoparticles via Coordination Association and Electrostatic Repulsion in Water.

PubMed

Zhu, Zhengguang; Xu, Na; Yu, Qiuping; Guo, Lei; Cao, Hui; Lu, Xinhua; Cai, Yuanli

2015-08-01

Simultaneous coordination-association and electrostatic-repulsion interactions play critical roles in the construction and stabilization of enzymatic function metal centers in water media. These interactions are promising for construction and self-assembly of artificial aqueous polymer single-chain nanoparticles (SCNPs). Herein, the construction and self-assembly of dative-bonded aqueous SCNPs are reported via simultaneous coordination-association and electrostatic-repulsion interactions within single chains of histamine-based hydrophilic block copolymer. The electrostatic-repulsion interactions are tunable through adjusting the imidazolium/imidazole ratio in response to pH, and in situ Cu(II)-coordination leads to the intramolecular association and single-chain collapse in acidic water. SCNPs are stabilized by the electrostatic repulsion of dative-bonded block and steric shielding of nonionic water-soluble block, and have a huge specific surface area of function metal centers accessible to substrates in acidic water. Moreover, SCNPs can assemble into micelles, networks, and large particles programmably in response to the solution pH. These unique media-sensitive phase-transformation behaviors provide a general, facile, and versatile platform for the fabrication of enzyme-inspired smart aqueous catalysts. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Analysis of nucleotides and oligonucleotides immobilized as self-assembled monolayers by static secondary ion mass spectrometry.

PubMed

Patrick, J S; Cooks, R G; Pachuta, S J

1994-11-01

Nucleic acid constituents can be bound to a metal surface in the form of self-assembled monolayers. Binding is achieved either through ionic interactions with a self-assembled 2-aminoethanethiol monolayer or by direct covalent binding of a dithiophosphate oligonucleotide to a metal surface through a sulfur-metal bond. Nucleotides, polynucleotides (both normal and a dithiophosphate analog) and double-stranded DNA have all been bound to surfaces. When the surfaces are interrogated using static secondary ion mass spectrometry (SIMS), the surface-bound nucleic acid constituents are observed in the form of the characteristic protonated nucleic acid base ions (BH2+). While a silver foil substrate was found to provide the highest absolute signal, vapor-deposited gold yields the best signal-to-noise ratio for ionically bound deoxyguanosine monophosphate. Under comparable conditions, a Cs+ projectile produces a 10-fold increase in the secondary ion signal relative to a Ga+ projectile. The experiment has been extended to a triple-quadrupole instrument where tandem mass spectrometric experiments on ionically immobilized dGMP showed the characteristic loss of ammonia from the released BH2+ ion. When a 'biomimetic' surface formed by ionically immobilizing double-stranded DNA is exposed to a solution containing ethidium bromide, ions corresponding to the non-covalent adduct are readily detectable using SIMS. This adduct and the nucleic acid constituents can be monitored at levels below 10 fmol.

Self-assembly of hybrid organic-inorganic polyoxovanadates: functionalised mixed-valent clusters and molecular cages.

PubMed

Breen, John M; Clérac, Rodolphe; Zhang, Lei; Cloonan, Suzanne M; Kennedy, Elaine; Feeney, Martin; McCabe, Thomas; Williams, D Clive; Schmitt, Wolfgang

2012-03-14

Herein we report the intra- and inter-molecular assembly of a {V(5)O(9)} subunit. This mixed-valent structural motif can be stabilised as [V(5)O(9)(L(1-3))(4)](5-/9-) (1-3) by a range of organoarsonate ligands (L(1)-L(3)) whose secondary functionalities influence its packing arrangement within the crystal structures. Variation of the reaction conditions results in the dodecanuclear cage structure [V(12)O(14)(OH)(4)(L(1))(10)](4-) (4) where two modified convex building units are linked via two dimeric {O(4)V(IV)(OH)(2)V(IV)O(4)} moieties. Bi-functional phosphonate ligands, L(4)-L(6) allow the intramolecular connectivity of the {V(5)O(9)} subunit to give hybrid capsules [V(10)O(18)(L(4-6))(4)](10-) (5-7). The dimensions of the electrophilic cavities of the capsular entities are determined by the incorporated ligand type. Mass spectrometry experiments confirm the stability of the complexes in solution. We investigate and model the temperature-dependent magnetic properties of representative complexes 1, 4, 6 and 7 and provide preliminary cell-viability studies of three different cancer cell lines with respect to Na(8)H(2)[6]·36H(2)O and Na(8)H(2)[7]·2DMF·29H(2)O.

Discovery of phosphonic acid natural products by mining the genomes of 10,000 actinomycetes

USDA-ARS?s Scientific Manuscript database

Although natural products have been a particularly rich source of human medicines, the rate at which new molecules are being discovered is declining precipitously. Based on the large number of natural product biosynthetic genes in microbial genomes, many have suggested “genome mining” as an approach...

40 CFR 704.95 - Phosphonic acid, [1,2-ethanediyl-bis[nitrilobis-(methylene)

Code of Federal Regulations, 2010 CFR

2010-07-01

... of the substance for which the report is submitted. (ii) Company name and headquarters address. (iii... transaction; the import site may in some cases be the organization's headquarters office in the United States... Abstracts Service Registry Number of the substance for which the report is submitted. (ii) Company name and...

The Self-Assembly of Nanogold for Optical Metamaterials

NASA Astrophysics Data System (ADS)

Nidetz, Robert A.

2011-12-01

Optical metamaterials are an emerging field that enables manipulation of light like never before. Producing optical metamaterials requires sub-wavelength building blocks. The focus here was to develop methods to produce building blocks for metamaterials from nanogold. Electron-beam lithography was used to define an aminosilane patterned chemical template in order to electrostatically self-assemble citrate-capped gold nanoparticles. Equilibrium self-assembly was achieved in 20 minutes by immersing chemical templates into gold nanoparticle solutions. The number of nanoparticles that self-assembled on an aminosilane dot was controlled by manipulating the diameters of the dots and nanoparticles. Adding salt to the nanoparticle solution enabled the nanoparticles to self-assemble in greater numbers on the same sized dot. However, the preparation of the nanoparticle solution containing salt was sensitive to spikes in the salt concentration which led to aggregation of the nanoparticles and non-specific deposition. Gold nanorods were also electrostatically self-assembled. Polyelectrolyte-coated gold nanorods were patterned with limited success. A polyelectrolyte chemical template also patterned gold nanorods, but the gold nanorods preferred to pattern on the edges of the pattern. Ligand-exchanged gold nanorods displayed the best self-assembly, but suffered from slow kinetics. Self-assembled gold nanoparticles were cross-linked with poly(diallyldimethylammonium chloride). The poly(diallyldimethylammonium chloride) allowed additional nanoparticles to pattern on top of the already patterned nanoparticles. Cross-linked nanoparticles were lifted-off of the substrate by sonication in a sodium hydroxide solution. The presence of van der Waals forces and/or amine bonding prevent the nanogold from lifting-off without sonication. A good-solvent evaporation process was used to self-assemble poly(styrene) coated gold nanoparticles into spherical microbead assemblies. The use of larger nanoparticles and larger poly(styrene) ligands resulted in larger and smaller assemblies, respectively. Stirring the solution resulted in a wider size distribution of microbead assemblies due to the stirring's shear forces. Two undeveloped methods to self-assemble nanogold were investigated. One method used block-copolymer thin films as chemical templates to direct the electrostatic self-assembly of nanogold. Another method used gold nanorods that are passivated with different ligands on different faces. The stability of an alkanethiol ligand in different acids and bases was investigated to determine which materials could be used to produce Janus nanorods.

Novel morphology change of Au-Methotrexate conjugates: From nanochains to discrete nanoparticles.

PubMed

Wang, Wei-Yuan; Zhao, Xiu-Fen; Ju, Xiao-Han; Wang, Yu; Wang, Lin; Li, Shu-Ping; Li, Xiao-Dong

2016-12-30

A novel morphology change of Au-methotrexate (Au-MTX) conjugates that could transform from nanochains to discrete nanoparticles was achieved by a simple, one-pot, and hydrothermal growth method. Herein, MTX was used efficiently as a complex-forming agent, reducing agent, capping agent, and importantly a targeting anticancer drug. The formation mechanism suggested a similarity with the molecular imprinting technology. The Au-MTX complex induced the MTX molecules to selectively adsorb on different crystal facets of gold nanoparticles (AuNPs) and then formed gold nanospheres. Moreover, the abundantly binding MTX molecules promoted directional alignment of these gold nanospheres to further form nanochains. More interestingly, the linear structures gradually changed into discrete nanoparticles by adding different amount of ethylene diamine tetra (methylene phosphonic acid) (EDTMPA) into the initial reaction solution, which likely arose from the strong electrostatic effect of the negatively charged phosphonic acid groups. Compared with the as-prepared nanochains, the resultant discrete nanoparticles showed almost equal drug loading capacity but with higher drug release control, colloidal stability, and in vitro anticancer activity. Copyright © 2016 Elsevier B.V. All rights reserved.

Preparation of proton conducting membranes containing bifunctional titania nanoparticles

NASA Astrophysics Data System (ADS)

Aslan, Ayşe; Bozkurt, Ayhan

2013-07-01

Throughout this work, the synthesis and characterization of novel proton conducting nanocomposite membranes including binary and ternary mixtures of sulfated nano-titania (TS), poly(vinyl alcohol) (PVA), and nitrilotri(methyl phosphonic acid) (NMPA) are discussed. The materials were produced by means of two different approaches where in the first, PVA and TS (10-15 nm) were admixed to form a binary system. The second method was the ternary nanocomposite membranes including PVA/TS/NMPA that were prepared at several compositions to get PVA-TS-(NMPA) x . The interaction of functional nano particles and NMPA in the host matrix was explored by FT-IR spectroscopy. The homogeneous distribution of bifunctional nanoparticles in the membrane was confirmed by SEM micrographs. The spectroscopic measurements and water/methanol uptake studies suggested a complexation between PVA and NMPA, which inhibited the leaching of the latter. The thermogravimetry analysis results verified that the presence of TS in the composite membranes suppressed the formation of phosphonic acid anhydrides up to 150 °C. The maximum proton conductivity has been measured for PVA-TS-(NMPA)3 as 0.003 S cm-1 at 150 °C.

The architectonics of programmable RNA and DNA nanostructures.

PubMed

Jaeger, Luc; Chworos, Arkadiusz

2006-08-01

The past several years have witnessed the emergence of a new world of nucleic-acid-based architectures with highly predictable and programmable self-assembly properties. For almost two decades, DNA has been the primary material for nucleic acid nanoconstruction. More recently, the dramatic increase in RNA structural information led to the development of RNA architectonics, the scientific study of the principles of RNA architecture with the aim of constructing RNA nanostructures of any arbitrary size and shape. The remarkable modularity and the distinct but complementary nature of RNA and DNA nanomaterials are revealed by the various self-assembly strategies that aim to achieve control of the arrangement of matter at a nanoscale level.

Self-assembly into soft materials of molecules derived from naturallyoccurring fatty-acids

NASA Astrophysics Data System (ADS)

Zhang, Mohan

The self-assembly of molecular gelators has provided an attractive route for the construction of nanostructured materials with desired functionalities. A well-defined paradigm for the design of molecular gels is needed, but none has yet been established. One of the important challenges to defining this paradigm is the creation of structure-property correlations for gelators at different distance scales. This dissertation centers on gaining additional insights in the relationship between small changes in gelator structures derived from long-chain, naturally-occurring fatty acids and the properties of the corresponding gels. This approach offers a reasonable method to probe the rational design of molecular gelators. (Abstract shortened by ProQuest.).

Isotopic Measurements of Organic Sulfonates From The Murchison Meteorite

NASA Technical Reports Server (NTRS)

Cooper, G. W.; Chang, S.; DeVincenzi, Donald L. (Technical Monitor)

1995-01-01

Organic sulfonates and phosphonates have been extracted from the Murchison meteorite for stable isotope measurements. Preliminary stable isotope measurements of individual alkyl sulfonates, R-SO3H (R=C(sub n)H(sub 2n+l)), are shown. These compounds were found in aqueous extracts of Murchison. Both groups show trends similar to other homologous series of organic compounds indigenous to Murchison. Molecular abundances decrease with increasing carbon number, and all possible isomers at each carbon number (through C-4) are present. Carbon isotope measurements of the sulfonates show a decrease in the C-13/C-12 ratio with increasing carbon number. The overall objectives of this project are to obtain dime element carbon, hydrogen, and sulfur - intramolecular isotopic analyses of individual sulfonates, and isotopic measurement of carbon and hydrogen of the phosphonates as a group. The Murchison meteorite is the best characterized carbonaceous chondrite with respect to organic chemistry. The finding of organic sulfonates and phosphonates in Murchison is of interest because they are the first well-characterized series of sulfur and phosphorus containing organic compounds found in meteorites. Also, meteorites, comets, and interplanetary dust particles may have been involved in chemical evolution on the early Earth. Because of the critical role of organic phosphorus and sulfur in all living systems, it is particularly interesting to see examples of abiotic syntheses of these classes of compounds. The study of the isotopic composition of the sulfonates and phosphonates can yield insight into their possible interstellar origin as well as their mechanisms of synthesis in the early solar system. Previous isotopic analyses of other classes of organic compounds indigenous to meteorites, e.g., amino acids, carboxylic acids, and hydrocarbons indicate the possibility that interstellar molecules were incorporated into meteorite parent bodies. In these compounds the ratios of heavy to light isotopes of hydrogen (D/H), carbon (C-13/C-12), and nitrogen (N-15/N-14), are anomalous relative to bulk terrestrial and meteoritic values. In some cases, the D/H ratios approach those observed for molecules in interstellar clouds.

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

PubMed

Sun, Chaode; Bittman, Robert

2004-10-29

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

RAFT Nano-constructs: surfing to biological applications.

PubMed

Boturyn, Didier; Defrancq, Eric; Dolphin, Gunnar T; Garcia, Julian; Labbe, Pierre; Renaudet, Olivier; Dumy, Pascal

2008-02-01

Biologically programmed molecular recognition provides the basis of all natural systems and supplies evolution-optimized functional materials from self-assembly of a limited number of molecular building blocks. Biomolecules such as peptides, nucleic acids and carbohydrates represent a diverse supply of structural building blocks for the chemist to design and fabricate new functional nanostructured architectures. In this context, we review here the chemistry we have developed to conjugate peptides with nucleic acids, carbohydrates, and organic molecules, as well as combinations thereof using a template-assembled approach. With this methodology, we have prepared new integrated functional systems exhibiting designed properties in the field of nanovectors, biosensors as well as controlled peptide self-assembly. Thus this molecular engineering approach allows for the rational design of systems with integrated tailor-made properties and paves the way to more elaborate applications by bottom-up design in the domain of nanobiosciences.

Integrating DNA strand displacement circuitry to the nonlinear hybridization chain reaction.

PubMed

Zhang, Zhuo; Fan, Tsz Wing; Hsing, I-Ming

2017-02-23

Programmable and modular attributes of DNA molecules allow one to develop versatile sensing platforms that can be operated isothermally and enzyme-free. In this work, we present an approach to integrate upstream DNA strand displacement circuits that can be turned on by a sequence-specific microRNA analyte with a downstream nonlinear hybridization chain reaction for a cascading hyperbranched nucleic acid assembly. This system provides a two-step amplification strategy for highly sensitive detection of the miRNA analyte, conducive for multiplexed detection. Multiple miRNA analytes were tested with our integrated circuitry using the same downstream signal amplification setting, showing the decoupling of nonlinear self-assembly with the analyte sequence. Compared with the reported methods, our signal amplification approach provides an additional control module for higher-order DNA self-assembly and could be developed into a promising platform for the detection of critical nucleic-acid based biomarkers.

Dissipative and Autonomous Square-Wave Self-Oscillation of a Macroscopic Hybrid Self-Assembly under Continuous Light Irradiation.

PubMed

Ikegami, Tomonori; Kageyama, Yoshiyuki; Obara, Kazuma; Takeda, Sadamu

2016-07-11

Building a bottom-up supramolecular system to perform continuously autonomous motions will pave the way for the next generation of biomimetic mechanical systems. In biological systems, hierarchical molecular synchronization underlies the generation of spatio-temporal patterns with dissipative structures. However, it remains difficult to build such self-organized working objects via artificial techniques. Herein, we show the first example of a square-wave limit-cycle self-oscillatory motion of a noncovalent assembly of oleic acid and an azobenzene derivative. The assembly steadily flips under continuous blue-light irradiation. Mechanical self-oscillation is established by successively alternating photoisomerization processes and multi-stable phase transitions. These results offer a fundamental strategy for creating a supramolecular motor that works progressively under the operation of molecule-based machines. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nucleic Acid Binding by Mason-Pfizer Monkey Virus CA Promotes Virus Assembly and Genome Packaging

PubMed Central

Füzik, Tibor; Píchalová, Růžena; Schur, Florian K. M.; Strohalmová, Karolína; Křížová, Ivana; Hadravová, Romana; Rumlová, Michaela; Briggs, John A. G.

2016-01-01

ABSTRACT The Gag polyprotein of retroviruses drives immature virus assembly by forming hexameric protein lattices. The assembly is primarily mediated by protein-protein interactions between capsid (CA) domains and by interactions between nucleocapsid (NC) domains and RNA. Specific interactions between NC and the viral RNA are required for genome packaging. Previously reported cryoelectron microscopy analysis of immature Mason-Pfizer monkey virus (M-PMV) particles suggested that a basic region (residues RKK) in CA may serve as an additional binding site for nucleic acids. Here, we have introduced mutations into the RKK region in both bacterial and proviral M-PMV vectors and have assessed their impact on M-PMV assembly, structure, RNA binding, budding/release, nuclear trafficking, and infectivity using in vitro and in vivo systems. Our data indicate that the RKK region binds and structures nucleic acid that serves to promote virus particle assembly in the cytoplasm. Moreover, the RKK region appears to be important for recruitment of viral genomic RNA into Gag particles, and this function could be linked to changes in nuclear trafficking. Together these observations suggest that in M-PMV, direct interactions between CA and nucleic acid play important functions in the late stages of the viral life cycle. IMPORTANCE Assembly of retrovirus particles is driven by the Gag polyprotein, which can self-assemble to form virus particles and interact with RNA to recruit the viral genome into the particles. Generally, the capsid domains of Gag contribute to essential protein-protein interactions during assembly, while the nucleocapsid domain interacts with RNA. The interactions between the nucleocapsid domain and RNA are important both for identifying the genome and for self-assembly of Gag molecules. Here, we show that a region of basic residues in the capsid protein of the betaretrovirus Mason-Pfizer monkey virus (M-PMV) contributes to interaction of Gag with nucleic acid. This interaction appears to provide a critical scaffolding function that promotes assembly of virus particles in the cytoplasm. It is also crucial for packaging the viral genome and thus for infectivity. These data indicate that, surprisingly, interactions between the capsid domain and RNA play an important role in the assembly of M-PMV. PMID:26912613

Novel agrochemical conjugates with self-assembling behaviour.

PubMed

Liu, Qingtao; Graham, Bim; Hawley, Adrian; Dong, Yao-Da; Boyd, Ben J

2018-02-15

That conjugation of agrichemicals to pro-assembly hydrophobic moieties will enable enhanced compatibility and loading with host lyotropic liquid crystalline carrier matrix, and potentially self-assemble in their own right in aqueous environments. A series of lipid-like agrochemical-conjugates were synthesized using specific amphiphilic entities conjugated onto the agrochemicals, picloram and 2,4-dichlorophenoxyacetic acid (2,4-D). The self-assembly behaviour and compatibility of the novel entities when incorporated into phytantriol and monoolein-based liquid crystalline systems were examined using small angle X-ray scattering, cryo-TEM and polarized optical microscopy. Compared to agrochemical-conjugates with simple alkyl ester groups, the esterification of the agrochemicals with amphiphilic groups such as phytantriol and monoolein led to greater structural compatibility and consequently a greater loading of the agrochemicals in the liquid crystalline systems without destabilizing phase structure. Picloram-monoolein and picloram-monoelaidin can self-assemble to form lamellar structures in water. However, certain agrochemical-conjugates such as picloram-monoelaidin and picloram-PEGn-oleate showed poor compatibility with liquid crystalline systems, resulting in phase separation. Copyright © 2017 Elsevier Inc. All rights reserved.

Molecular self-assembly in substituted alanine derivatives: XRD, Hirshfeld surfaces and DFT studies

NASA Astrophysics Data System (ADS)

Rajalakshmi, Periasamy; Srinivasan, Navaneethakrishnan; Sivaraman, Gandhi; Razak, Ibrahim Abdul; Rosli, Mohd Mustaqim; Krishnakumar, Rajaputi Venkatraman

2014-06-01

The molecular assemblage in the crystal structures of three modified chiral amino acids, two of which are isomeric D- and L-pairs boc-L-benzothienylalanine (BLA), boc-D-benzothienylalanine (BDA) and the other boc-D-naphthylalanine (NDA) differing from this pair very slightly in the chemical modification introduced, is accurately described. The aggregation of amino acid molecules is similar in all the crystals and may be described as a twisted double helical ladder in which two complementary long helical chains formed through O-H⋯O hydrogen bonds are interconnected through the characteristic head-to-tail N-H⋯O hydrogen bonds. Thus the molecular aggregation enabled through classical hydrogen bonds may be regarded as a mimic of the characteristic double helical structure of DNA. Also, precise structural information involving these amino acid molecules with lower symmetry exhibiting higher trigonal symmetry in their self-assembly is expected to throw light on the nature and strength of intermolecular interactions and their role in self-assembly of molecular aggregates, which are crucial in developing new or at least supplement existing crystal engineering strategies. Single crystal X-ray analysis and their electronic structures were calculated at the DFT level with a detailed analysis of Hirshfeld surfaces and fingerprint plots facilitating a comparison of intermolecular interactions in building different supramolecular architectures.

Distinct self-interaction domains promote Multi Sex Combs accumulation in and formation of the Drosophila histone locus body

PubMed Central

Terzo, Esteban A.; Lyons, Shawn M.; Poulton, John S.; Temple, Brenda R. S.; Marzluff, William F.; Duronio, Robert J.

2015-01-01

Nuclear bodies (NBs) are structures that concentrate proteins, RNAs, and ribonucleoproteins that perform functions essential to gene expression. How NBs assemble is not well understood. We studied the Drosophila histone locus body (HLB), a NB that concentrates factors required for histone mRNA biosynthesis at the replication-dependent histone gene locus. We coupled biochemical analysis with confocal imaging of both fixed and live tissues to demonstrate that the Drosophila Multi Sex Combs (Mxc) protein contains multiple domains necessary for HLB assembly. An important feature of this assembly process is the self-interaction of Mxc via two conserved N-terminal domains: a LisH domain and a novel self-interaction facilitator (SIF) domain immediately downstream of the LisH domain. Molecular modeling suggests that the LisH and SIF domains directly interact, and mutation of either the LisH or the SIF domain severely impairs Mxc function in vivo, resulting in reduced histone mRNA accumulation. A region of Mxc between amino acids 721 and 1481 is also necessary for HLB assembly independent of the LisH and SIF domains. Finally, the C-terminal 195 amino acids of Mxc are required for recruiting FLASH, an essential histone mRNA-processing factor, to the HLB. We conclude that multiple domains of the Mxc protein promote HLB assembly in order to concentrate factors required for histone mRNA biosynthesis. PMID:25694448

Improved insulin loading in poly(lactic-co-glycolic) acid (PLGA) nanoparticles upon self-assembly with lipids.

PubMed

García-Díaz, María; Foged, Camilla; Nielsen, Hanne Mørck

2015-03-30

Polymeric nanoparticles are widely investigated as drug delivery systems for oral administration. However, the hydrophobic nature of many polymers hampers effective loading of the particles with hydrophilic macromolecules such as insulin. Thus, the aim of this work was to improve the loading of insulin into poly(lactic-co-glycolic) acid (PLGA) nanoparticles by pre-assembly with amphiphilic lipids. Insulin was complexed with soybean phosphatidylcholine or sodium caprate by self-assembly and subsequently loaded into PLGA nanoparticles by using the double emulsion-solvent evaporation technique. The nanoparticles were characterized in terms of size, zeta potential, insulin encapsulation efficiency and loading capacity. Upon pre-assembly with lipids, there was an increased distribution of insulin into the organic phase of the emulsion, eventually resulting in significantly enhanced encapsulation efficiencies (90% as compared to 24% in the absence of lipids). Importantly, the insulin loading capacity was increased up to 20% by using the lipid-insulin complexes. The results further showed that a main fraction of the lipid was incorporated into the nanoparticles and remained associated to the polymer during release studies in buffers, whereas insulin was released in a non-complexed form as a burst of approximately 80% of the loaded insulin. In conclusion, the protein load in PLGA nanoparticles can be significantly increased by employing self-assembled protein-lipid complexes. Copyright © 2014 Elsevier B.V. All rights reserved.

Self-assembly of fatty acids on hydroxylated Al surface and effects of their stability on wettability and nanoscale organization.

PubMed

Liascukiene, Irma; Steffenhagen, Marie; Asadauskas, Svajus J; Lambert, Jean-François; Landoulsi, Jessem

2014-05-27

The self-assembly of fatty acids (FA) on the surfaces of inorganic materials is a relevant way to control their wetting properties. While the mechanism of adsorption on model flat substrate is well described in the literature, interfacial processes remain poorly documented on nanostructured surfaces. In this study, we report the self-assembly of a variety of FA on a hydroxylated Al surface which exhibits a random nanoscale organization. Our results revealed a peculiar fingerprint due to the FA self-assembly which consists in the formation of aligned nanopatterns in a state of hierarchical nanostructuration, regardless of the molecular structure of the FA (chain length, level of unsaturation). After a significant removal of adsorbed FA using UV/O3 treatment, a complete wetting was reached, and a noticeable disturbance of the surface morphology was observed, evidencing the pivotal role of FA molecules to maintain these nanostructures. The origin of wetting properties was investigated prior to and after conditioning of FA-modified samples taking into account key parameters, namely the surface roughness and its composition. For this purpose, the Wenzel roughness, defined as the third moment of power spectral density, was used, as it is sensitive to high spatial frequency and thus to the obtained hierarchical level of nanostructuration. Our results revealed that no correlation can be made between water contact angles (θ(w)) and the Wenzel roughness. By contrast, θ(w) strongly increased with the amount of -CHx- groups exhibited by adsorbed FA. These findings suggest that the main origin of hydrophobization is the presence of self-assembled molecules and that the surface roughness has only a small contribution to the wettability.

The Potential of Self-assembling Peptides for Enhancement of In Vitro Remineralisation of White Spot Lesions as Measured by Quantitative Laser Fluorescence.

PubMed

Golland, Luca; Schmidlin, Patrick R; Schätzle, Marc

To test the remineralisation potential of a single application of self-assembling peptides or acidic fluoride solution using quantitative light-induced fluorescence (QLF) in vitro. Bovine enamel disks were prepared, and white spot lesions were created on one half of the disk with an acidic buffer solution. After demineralisation, disks were allocated into three groups of 11 specimens each. Group A served as a control group and received no treatment. Group B had a single application of fluoride, and group C was treated once with self-assembling peptides. All disks were embedded in a plastic mold (diameter 15 mm, height 9 mm) with an a-silicone, and remineralisation was initiated using a pH-cycling protocol for five days. Four experimental regions on each disk were measured prior to the start of the study (T0), after demineralisation (T1) and after the remineralisation process (T2) using QLF. After demineralisation, all areas showed a distinct loss of fluorescence, with no statistically significant difference between the groups (ΔF from -69.3 to -10.2). After remineralisation, samples of group B (treated with fluoride) showed a statistically significant fluorescence increase (ΔF from T1 to T2 15.2 ± 7.3) indicating remineralisation, whereas the samples of control group A and group C (treated with self-assembling peptides) showed no significant changes in ΔF of 1.1 ± 1.9 and 2.5 ± 1.9, respectively. Application of self-assembling peptides on demineralised bovine enamel did not lead to increased fluorescence using QLF, indicating either lack of remineralisation or irregular crystals. Increased fluorescence using QLF indicated mineral gain following a single application of a highly concentrated fluoride.

Non-amyloidogenic peptide tags for the regulatable self-assembling of protein-only nanoparticles.

PubMed

Unzueta, Ugutz; Ferrer-Miralles, Neus; Cedano, Juan; Zikung, Xu; Pesarrodona, Mireia; Saccardo, Paolo; García-Fruitós, Elena; Domingo-Espín, Joan; Kumar, Pradeep; Gupta, Kailash C; Mangues, Ramón; Villaverde, Antonio; Vazquez, Esther

2012-11-01

Controlling the self-assembling of building blocks as nanoscale entities is a requisite for the generation of bio-inspired vehicles for nanomedicines. A wide spectrum of functional peptides has been incorporated to different types of nanoparticles for the delivery of conventional drugs and nucleic acids, enabling receptor-specific cell binding and internalization, endosomal escape, cytosolic trafficking, nuclear targeting and DNA condensation. However, the development of architectonic tags to induce the self-assembling of functionalized monomers has been essentially neglected. We have examined here the nanoscale architectonic capabilities of arginine-rich cationic peptides, that when displayed on His-tagged proteins, promote their self-assembling as monodisperse, protein-only nanoparticles. The scrutiny of the cross-molecular interactivity cooperatively conferred by poly-arginines and poly-histidines has identified regulatable electrostatic interactions between building blocks that can also be engineered to encapsulate cargo DNA. The combined use of cationic peptides and poly-histidine tags offers an unusually versatile approach for the tailored design and biofabrication of protein-based nano-therapeutics, beyond the more limited spectrum of possibilities so far offered by self-assembling amyloidogenic peptides. Copyright © 2012 Elsevier Ltd. All rights reserved.

Giant surfactants of poly(ethylene oxide)- b-polystyrene-(molecular nanoparticle): nanoparticle-driven self-assembly with sub-10-nm nanostructures in thin films

NASA Astrophysics Data System (ADS)

Hsu, Chih-Hao; Lin, Zhiwei; Dong, Xue-Hui; Hsieh, I.-Fan; Cheng, Stephen Z. D.

2014-03-01

Giant surfactants are built upon precisely attaching shape- and volume-persistent molecular nanoparticles (MNP) to polymeric flexible tails. The unique class of self-assembling materials, giant surfactants, has been demonstrated to form self-assembled ordered nanostructures, and their self-assembly behaviors are remarkably sensitive to primary chemical structures. In this work, two sets of giant surfactants with functionalized MNP attached to diblock copolymer tails were studied in thin films. Carboxylic acid-functionalized [60]fullerene (AC60) tethered with PEO- b-PS (PEO-PS-AC60) represents an ABA' (hydrophilic-hydrophobic-hydrophilic) giant surfactant, and fluoro-functionalized polyhedral oligomeric silsesquioxane (FPOSS) tethered with PEO- b-PS (PEO-PS-FPOSS) represents an ABC (hydrophilic-hydrophobic-omniphobic) one. The dissimilar chemical natures of the MNPs result in different arrangement of MNPs in self-assembled structures, the dispersion of AC60 in PEO domain and the single domain of FPOSS. Moreover, the chemically bonded MNPs could induce the originally disordered small molecular PEO- b-PS to form ordered cylindrical and lamellar structure, as evidenced by TEM and GISAXS, leading to sub-10-nm nanostructures of copolymer in the thin film state.

Computational studies of sequence-specific driving forces in peptide self-assembly

NASA Astrophysics Data System (ADS)

Jeon, Joohyun

Peptides are biopolymers made from various sequences of twenty different types of amino acids, connected by peptide bonds. There are practically an infinite number of possible sequences and tremendous possible combinations of peptide-peptide interactions. Recently, an increasing number of studies have shown a stark variety of peptide self-assembled nanomaterials whose detailed structures depend on their sequences and environmental factors; these have end uses in medical and bio-electronic applications, for example. To understand the underlying physics of complex peptide self-assembly processes and to delineate sequence specific effects, in this study, I use various simulation tools spanning all-atom molecular dynamics to simple lattice models and quantify the balance of interactions in the peptide self-assembly processes. In contrast to the existing view that peptides' aggregation propensities are proportional to the net sequence hydrophobicity and inversely proportional to the net charge, I show the more nuanced effects of electrostatic interactions, including the cooperative effects between hydrophobic and electrostatic interactions. Notably, I suggest rather unexpected, yet important roles of entropies in the small scale oligomerization processes. Overall, this study broadens our understanding of the role of thermodynamic driving forces in peptide self-assembly.

Ultrasonic-assisted synthesis of polyvinyl alcohol/phytic acid polymer film and its thermal stability, mechanical properties and surface resistivity.

PubMed

Li, Jihui; Li, Yongshen; Song, Yunna; Niu, Shuai; Li, Ning

2017-11-01

In this paper, polyvinyl alcohol/phytic acid polymer (PVA/PA polymer) was synthesized through esterification reaction of PVA and PA in the case of acidity and ultrasound irradiation and characterized, and PVA/PA polymer film was prepared by PVA/PA polymer and characterized, and the influence of dosage of PA on the thermal stability, mechanical properties and surface resistivity of PVA/PA polymer film were researched, and the influence of sonication time on the mechanical properties of PVA/PA polymer film was investigated. Based on those, it was concluded that the hydroxyl group on the chain of PVA and the phosphonic group on PA were connected together in the form of phosphonate bond, and the hydroxyl group on the chain of PVA were connected together in the form of ether bond after the intermolecular dehydration; in the meantime, it was also confirmed that PVA/PA polymer film prepared from 1.20mL of PA not only had the high thermal stability and favorable ductility but also the low surface resistivity in comparison with PVA/PA polymer film with 0.00mL of PA, and the ductility of PVA/PA polymer film was very sensitive to the sonication time. Copyright © 2017. Published by Elsevier B.V.

Water Ordering Controls the Dynamic Equilibrium of Micelle-Fiber Formation in Self-Assembly of Peptide Amphiphiles

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

Deshmukh, Sanket; Solomon, Lee A.; Kamath, Ganesh

Understanding the role of water in governing the kinetics of the self-assembly processes of amphiphilic peptides has still remained elusive. Here, using a multi-stage atomistic-coarse-grained approach, complemented by circular dichroism/infra-red spectroscopy and dynamic light scattering experiments, we highlight the dual nature of water in dictating the mechanism and dynamics of self-assembly of peptide amphiphiles (PAs). Our computational study shows that (i) Water cage formation and breakage near the hydrophobic groups controls the fusion dynamics and aggregation of PAs in the micellar stage, and (ii) Enhanced structural ordering of vicinal water near the hydrophilic amino acids shifts the equilibrium towards themore » fiber phase and stimulates structure and order in the PAs when they assemble into a hexagonal nanofiber architecture. Finally, spectroscopy and microscopy studies authenticate our computational observation that water ordering near the PAs increases with increase in time. The measured infra-red O-H bond stretch frequency reminiscent of ice-like suggests that the solvated water becomes increasingly solid-like with increased structural order in the assembled peptide network – thus shedding light on the role of water in a self-assembly process.« less

Water Ordering Controls the Dynamic Equilibrium of Micelle-Fiber Formation in Self-Assembly of Peptide Amphiphiles

DOE PAGES

Deshmukh, Sanket; Solomon, Lee A.; Kamath, Ganesh; ...

2016-08-24

Understanding the role of water in governing the kinetics of the self-assembly processes of amphiphilic peptides has still remained elusive. Here, using a multi-stage atomistic-coarse-grained approach, complemented by circular dichroism/infra-red spectroscopy and dynamic light scattering experiments, we highlight the dual nature of water in dictating the mechanism and dynamics of self-assembly of peptide amphiphiles (PAs). Our computational study shows that (i) Water cage formation and breakage near the hydrophobic groups controls the fusion dynamics and aggregation of PAs in the micellar stage, and (ii) Enhanced structural ordering of vicinal water near the hydrophilic amino acids shifts the equilibrium towards themore » fiber phase and stimulates structure and order in the PAs when they assemble into a hexagonal nanofiber architecture. Finally, spectroscopy and microscopy studies authenticate our computational observation that water ordering near the PAs increases with increase in time. The measured infra-red O-H bond stretch frequency reminiscent of ice-like suggests that the solvated water becomes increasingly solid-like with increased structural order in the assembled peptide network – thus shedding light on the role of water in a self-assembly process.« less

Folic-Acid-Targeted Self-Assembling Supramolecular Carrier for Gene Delivery.

PubMed

Liao, Rongqiang; Yi, Shouhui; Liu, Manshuo; Jin, Wenling; Yang, Bo

2015-07-27

A targeting gene carrier for cancer-specific delivery was successfully developed through a "multilayer bricks-mortar" strategy. The gene carrier was composed of adamantane-functionalized folic acid (FA-AD), an adamantane-functionalized poly(ethylene glycol) derivative (PEG-AD), and β-cyclodextrin-grafted low-molecular-weight branched polyethylenimine (PEI-CD). Carriers produced by two different self-assembly schemes, involving either precomplexation of the PEI-CD with the FA-AD and PEG-AD before pDNA condensation (Method A) or pDNA condensation with the PEI-CD prior to addition of the FA-AD and PEG-AD to engage host-guest complexation (Method B) were investigated for their ability to compact pDNA into nanoparticles. Cell viability studies show that the material produced by the Method A assembly scheme has lower cytotoxicity than branched PEI 25 kDa (PEI-25KD) and that the transfection efficiency is maintained. These findings suggest that the gene carrier, based on multivalent host-guest interactions, could be an effective, targeted, and low-toxicity carrier for delivering nucleic acid to target cells. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A novel fullerene lipoic acid derivative: Synthesis and preparation of self-assembled monolayers on gold

NASA Astrophysics Data System (ADS)

Viana, A. S.; Leupold, S.; Eberle, C.; Shokati, T.; Montforts, F.-P.; Abrantes, L. M.

2007-11-01

Synthesis and preparation of self-assembled monolayers of a novel fullerene lipoic acid derivative on gold are reported. The presence of densely packed SAMs was confirmed by ellipsometry and cyclic voltammetry. The electrochemical response of the modified electrode in organic media exhibits the first two redox peaks characteristic of the extended π-electron system of fullerene. C 60 surface coverage (1.4 × 10 -10 mol cm -2) has been electrochemically determined by the redox process of the adsorbed fullerene moiety and by reductive desorption of the SAM in strong alkaline solution. Electrochemical data indicate that all four sulphur atoms are involved in the self-assembly process, providing an increase of SAM stability in comparison to mono or di-thiolated appended molecules. Visualisation of discrete fullerene molecules by scanning tunnelling microscopy supplied further evidence for gold modification and molecular distribution on the surface. Mixed monolayers of hexanethiol and fullerene derivatives in a proportion of 1:2 have been also studied with the purpose of controlling the amount and distribution of fullerene units on the gold surface.

Structural coloration of chitosan coated cellulose fabrics by electrostatic self-assembled poly (styrene-methyl methacrylate-acrylic acid) photonic crystals.

PubMed

Yavuz, Gönül; Zille, Andrea; Seventekin, Necdet; Souto, Antonio P

2018-08-01

The structural coloration of a chitosan-coated woven cotton fabric obtained by glutaraldehyde-stabilized deposition of electrostatic self-assembled monodisperse and spherically uniform (250 nm) poly (styrene-methyl methacrylate-acrylic acid) photonic crystal nanospheres (P(St-MMA-AA)) was investigated. Bright iridescent coatings displaying different colors in function of the viewing angle were obtained. The SEM, diffuse reflectance spectroscopy, TGA, DSC and FTIR analyses confirm the presence of structural color and the glutaraldehyde and chitosan ability to provide durable chemical bonding between cotton fabric and photonic crystal (PCs) coating with the highest degradation temperature and the lowest enthalpy. The coatings are characterized by a mixture of face-centered cubic and hexagonal close-packed arrays alternating random packing regions. For the first time a cost-efficient structural coloration with high washing and light fastness using self-assembled P(St-MMA-AA) photonic crystals was successfully developed onto woven cotton fabric using chitosan and/or glutaraldehyde as stabilizing agent opening new strategies for the development of dye-free coloration of textiles. Copyright © 2018 Elsevier Ltd. All rights reserved.

Anti-cooperative supramolecular polymerization: a new K2-K model applied to the self-assembly of perylene bisimide dye proceeding via well-defined hydrogen-bonded dimers.

PubMed

Gershberg, Jana; Fennel, Franziska; Rehm, Thomas H; Lochbrunner, Stefan; Würthner, Frank

2016-03-01

A perylene bisimide dye bearing amide functionalities at the imide positions derived from amino acid l-alanine and a dialkoxy-substituted benzyl amine self-assembles into tightly bound dimers by π-π-stacking and hydrogen bonding in chloroform. In less polar or unpolar solvents like toluene and methylcyclohexane, and in their mixtures, these dimers further self-assemble into extended oligomeric aggregates in an anti-cooperative process in which even numbered aggregates are highly favoured. The stepwise transition from dimers into oligomers can not be properly described by conventional K 2 - K model, and thus a new K 2 - K aggregation model has been developed, which interpretes the present anti-cooperative supramolecular polymerization more appropriately. The newly developed K 2 - K model will be useful to describe self-assembly processes of a plethora of other π-conjugated molecules that are characterized by a favored dimer species.

Self-assembling peptide nanofiber hydrogels in tissue engineering and regenerative medicine: Progress, design guidelines, and applications.

PubMed

Koutsopoulos, Sotirios

2016-04-01

Until the mid-1980s, mainly biologists were conducting peptide research. This changed with discoveries that opened new paths of research involving the use of peptides in bioengineering, biotechnology, biomedicine, nanotechnology, and bioelectronics. Peptide engineering and rational design of novel peptide sequences with unique and tailor-made properties further expanded the field. The discovery of short self-assembling peptides, which upon association form well-defined supramolecular architectures, created new and exciting areas of research. Depending on the amino acid sequence, the pH, and the type of the electrolyte in the medium, peptide self-assembly leads to the formation of nanofibers, which are further organized to form a hydrogel. In this review, the application of ionic complementary peptides which self-assemble to form nanofiber hydrogels for tissue engineering and regenerative medicine will be discussed through a selective presentation of the most important work performed during the last 25 years. © 2016 Wiley Periodicals, Inc.

Controllable self-assembly of sodium caseinate with a zwitterionic vitamin-derived bolaamphiphile.

PubMed

Sun, Li-Hui; Sun, Yu-Long; Yang, Li-Jun; Zhang, Jian; Chen, Zhong-Xiu

2013-11-06

The control of self-assembly of sodium caseinate (SC) including the formation of mixed layers, microspheres, or nanoparticles is highly relevant to the microstructure of food and the design of promising drug delivery systems. In this paper, we designed a structure-switchable zwitterionic bolaamphiphile, 1,12-diaminododecanediorotate (DDO), from orotic acid, which has special binding sites and can guide the self-assembly of SC. Complexation between SC and DDO was investigated using dynamic light scattering, transmission electron microscopy, differential scanning calorimetry, and fluorescence spectra measurements. Monomeric DDO was bound to the negatively charged sites on the SC micelle and made the structure of SC more compact with decreased electrostatic repulsion between the head groups. Vesicular DDO led to reassociation of vesicles with enlarged size via preferable hydrophobic interactions. Moreover, the aggregation between SC and DDO was found to be temperature-dependent and reversible. This research provides an effective way to control the reversible self-assembly of SC by the zwitterionic vitamin-derived bolaamphiphile.

Dancing with chemical formulae of antivirals: a personal account.

PubMed

De Clercq, Erik

2013-09-15

A chemical structure is a joy forever, and this is how I perceived the chemical structures of a number of antiviral compounds with which I have been personally acquainted over the past 3 decades: (1) amino acid esters of acyclovir (i.e. valaciclovir); (2) 5-substituted 2'-deoxyuridines (i.e. brivudin); (3) 2',3'-dideoxynucleoside analogues (i.e. stavudine); (4) acyclic nucleoside phosphonates (ANPs) (i.e. cidofovir, adefovir); (5) tenofovir disoproxil fumarate (TDF) and drug combinations therewith; (6) tenofovir alafenamide (TAF, GS-7340), a new phosphonoamidate prodrug of tenofovir; (7) pro-prodrugs of PMEG (i.e. GS-9191 and GS-9219); (8) new ANPs: O-DAPy and 5-aza-C phosphonates; (9) non-nucleoside reverse transcriptase inhibitors (NNRTIs): HEPT and TIBO derivatives; and (10) bicyclam derivatives (i.e. AMD3100). Copyright © 2013 Elsevier Inc. All rights reserved.

Effects of self-assembly of 3-phosphonopropionic acid, 3-aminopropyltrimethoxysilane and dopamine on the corrosion behaviors and biocompatibility of a magnesium alloy.

PubMed

Pan, Chang-Jiang; Hou, Yu; Wang, Ya-Nan; Gao, Fei; Liu, Tao; Hou, Yan-Hua; Zhu, Yu-Fu; Ye, Wei; Wang, Ling-Ren

2016-10-01

Magnesium based alloys are attracting tremendous interests as the novel biodegradable metallic biomaterials. However, the rapid in vivo degradation and the limited surface biocompatibility restrict their clinical applications. Surface modification represents one of the important approaches to control the corrosion rate of Mg based alloys and to enhance the biocompatibility. In the present study, in order to improve the corrosion resistance and surface biocompatibility, magnesium alloy (AZ31B) was modified by the alkali heating treatment followed by the self-assembly of 3-phosphonopropionic acid, 3-aminopropyltrimethoxysilane (APTMS) and dopamine, respectively. The results of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectra (XPS) indicated that the molecules were successfully immobilized on the magnesium alloy surface by the self-assembly. An excellent hydrophilic surface was obtained after the alkali heating treatment and the water contact angle increased to some degree after the self-assembly of dopamine, APTMS and 3-phosphonopropionic acid, however, the hydrophilicity of the modified samples was better than that of the pristine magnesium substrate. Due to the formation of the passivation layer after the alkali heating treatment, the corrosion resistance of the magnesium alloy was obviously improved. The corrosion rate further decreased to varying degrees after the self-assembly surface modification. The blood compatibility of the pristine magnesium was significantly improved after the surface modification. The hemolysis rate was reduced from 56% of the blank magnesium alloy to 18% of the alkali heating treated sample and the values were further reduced to about 10% of dopamine-modified sample and 7% of APTMS-modified sample. The hemolysis rate was below 5% for the 3-phosphonopropionic acid modified sample. As compared to the pristine magnesium alloy, fewer platelets were attached and activated on the modified surfaces and the activated partial thromboplastin times (APTT) were prolonged to some degree. Furthermore, the modified samples showed good cytocompatibility. Endothelial cells exhibited the improved proliferative profiles in terms of CCK-8 assay as compared to those on the pristine magnesium alloy. The modified samples showed better endothelial cell adhesion and spreading than the pristine magnesium alloy. Taking all these results into consideration, the method of this study can be used to modify the magnesium alloy surface to improve the corrosion resistance and biocompatibility simultaneously. Copyright © 2016 Elsevier B.V. All rights reserved.

Reductionist Approach in Peptide-Based Nanotechnology.

PubMed

Gazit, Ehud

2018-06-20

The formation of ordered nanostructures by molecular self-assembly of proteins and peptides represents one of the principal directions in nanotechnology. Indeed, polyamides provide superior features as materials with diverse physical properties. A reductionist approach allowed the identification of extremely short peptide sequences, as short as dipeptides, which could form well-ordered amyloid-like β-sheet-rich assemblies comparable to supramolecular structures made of much larger proteins. Some of the peptide assemblies show remarkable mechanical, optical, and electrical characteristics. Another direction of reductionism utilized a natural noncoded amino acid, α-aminoisobutryic acid, to form short superhelical assemblies. The use of this exceptional helix inducer motif allowed the fabrication of single heptad repeats used in various biointerfaces, including their use as surfactants and DNA-binding agents. Two additional directions of the reductionist approach include the use of peptide nucleic acids (PNAs) and coassembly techniques. The diversified accomplishments of the reductionist approach, as well as the exciting future advances it bears, are discussed.

A fluorescent organic cage for picric acid detection.

PubMed

Acharyya, Koushik; Mukherjee, Partha Sarathi

2014-12-25

Dynamic covalent imine chemistry has been utilized to synthesize a fluorescent [3+2] self-assembled nanoscopic organic cage. The fluorescent nature of the reduced analogue of the cage was further exploited for the highly selective detection of the explosive picric acid (PA).

Light-induced Self-Assembly and Diffusion of Nanoclusters

NASA Astrophysics Data System (ADS)

Lian, Wenxuan

Novel methods to build multiple types of three-dimensional structures from various nanoscale components are the most exciting and challenging questions in nano-science. The properties of the assembled structures can be potentially and designed, but the development of such approaches is challenging. In order to realize such rational assembly, a tunable interaction medium is often introduced into the system. Soft matter, such as polymers, surfactants and biomolecules are used to modify the surfaces of the nanoscale building blocks. Deoxyribonucleic acid (DNA) strands are known as polynucleotides since they are composed of simpler units called nucleotides. There are unique base pairing rules that are predictable and programmable, which can be used to regulate self-assembly process with high degree of control. Besides controlling static structure, it is important to develop methods for controlling systems in dynamic matter, with chemical stimuli or external fields. For example, here we study the use of azobezene-trimethylammonium bromide (AzoTAB) as a molecular agent that can control self-assembly via light excitation. In this thesis, DNA assisted self-assembly was conducted. The ability of AzoTAB as a light induced surfactant to control DNA assisted self-assembly was confirmed. The mechanism of AzoTAB as a light controlled self-assembly promoter was studied. In the second project, diffusion of nanoclusters was studied. The presence of polymers brings strong entanglement with nanoclusters. This entanglement is more obvious when the nanocluster is a framed structure like the octahedron in the study. The diffusion coefficient of the octahedron becomes larger during traveling. The following up studies are required to elucidate the origin of the observed effect.

Development of simulation approach for two-dimensional chiral molecular self-assembly driven by hydrogen bond at the liquid/solid interface

NASA Astrophysics Data System (ADS)

Qin, Yuan; Yao, Man; Hao, Ce; Wan, Lijun; Wang, Yunhe; Chen, Ting; Wang, Dong; Wang, Xudong; Chen, Yonggang

2017-09-01

Two-dimensional (2D) chiral self-assembly system of 5-(benzyloxy)-isophthalic acid derivative/(S)-(+)-2-octanol/highly oriented pyrolytic graphite was studied. A combined density functional theory/molecular mechanics/molecular dynamics (DFT/MM/MD) approach for system of 2D chiral molecular self-assembly driven by hydrogen bond at the liquid/solid interface was thus proposed. Structural models of the chiral assembly were built on the basis of scanning tunneling microscopy (STM) images and simplified for DFT geometry optimization. Merck Molecular Force Field (MMFF) was singled out as the suitable force field by comparing the optimized configurations of MM and DFT. MM and MD simulations for hexagonal unit model which better represented the 2D assemble network were then preformed with MMFF. The adhesion energy, evolution of self-assembly process and characteristic parameters of hydrogen bond were obtained and analyzed. According to the above simulation, the stabilities of the clockwise and counterclockwise enantiomorphous networks were evaluated. The calculational results were supported by STM observations and the feasibility of the simulation method was confirmed by two other systems in the presence of chiral co-absorbers (R)-(-)-2-octanol and achiral co-absorbers 1-octanol. This theoretical simulation method assesses the stability trend of 2D enantiomorphous assemblies with atomic scale and can be applied to the similar hydrogen bond driven 2D chirality of molecular self-assembly system.

Concentration-dependent multiple chirality transition in halogen-bond-driven 2D self-assembly process

NASA Astrophysics Data System (ADS)

Miao, Xinrui; Li, Jinxing; Zha, Bao; Miao, Kai; Dong, Meiqiu; Wu, Juntian; Deng, Wenli

2018-03-01

The concentration-dependent self-assembly of iodine substituted thienophenanthrene derivative (5,10-DITD) is investigated at the 1-octanic acid/graphite interface using scanning tunneling microscopy. Three kinds of chiral arrangement and transition of 2D molecular assembly mainly driven by halogen bonding is clearly revealed. At high concentration the molecules self-assembled into a honeycomb-like chiral network. Except for the interchain van der Waals forces, this pattern is stabilized by intermolecular continuous Cdbnd O⋯I⋯S halogen bonds in each zigzag line. At moderate concentration, a chiral kite-like nanoarchitecture are observed, in which the Cdbnd O⋯I⋯S and I⋯Odbnd C halogen bonds, along with the molecule-solvent Cdbnd O⋯I⋯H halogen bonds are the dominated forces to determine the structural formation. At low concentration, the molecules form a chiral cyclic network resulting from the solvent coadsorption mainly by molecule-molecule Cdbnd O⋯I⋯S halogen bonds and molecule-solvent Cdbnd O⋯I⋯H halogen bonds. The density of molecular packing becomes lower with the decreasing of the solution concentration. The solution-concentration dependent self-assembly of thienophenanthrene derivative with iodine and ester chain moieties reveals that the type of intermolecular halogen bond and the number of the co-adsorbing 1-octanic acids by molecule-solvent Cdbnd O⋯I⋯H halogen bonds determine the formation and transformation of chirality. This research emphasizes the role of different types of halogen (I) bonds in the controllable supramolecular structures and provides an approach for the fabrication of chirality.

Aliphatic peptides show similar self-assembly to amyloid core sequences, challenging the importance of aromatic interactions in amyloidosis.

PubMed

Lakshmanan, Anupama; Cheong, Daniel W; Accardo, Angelo; Di Fabrizio, Enzo; Riekel, Christian; Hauser, Charlotte A E

2013-01-08

The self-assembly of abnormally folded proteins into amyloid fibrils is a hallmark of many debilitating diseases, from Alzheimer's and Parkinson diseases to prion-related disorders and diabetes type II. However, the fundamental mechanism of amyloid aggregation remains poorly understood. Core sequences of four to seven amino acids within natural amyloid proteins that form toxic fibrils have been used to study amyloidogenesis. We recently reported a class of systematically designed ultrasmall peptides that self-assemble in water into cross-β-type fibers. Here we compare the self-assembly of these peptides with natural core sequences. These include core segments from Alzheimer's amyloid-β, human amylin, and calcitonin. We analyzed the self-assembly process using circular dichroism, electron microscopy, X-ray diffraction, rheology, and molecular dynamics simulations. We found that the designed aliphatic peptides exhibited a similar self-assembly mechanism to several natural sequences, with formation of α-helical intermediates being a common feature. Interestingly, the self-assembly of a second core sequence from amyloid-β, containing the diphenylalanine motif, was distinctly different from all other examined sequences. The diphenylalanine-containing sequence formed β-sheet aggregates without going through the α-helical intermediate step, giving a unique fiber-diffraction pattern and simulation structure. Based on these results, we propose a simplified aliphatic model system to study amyloidosis. Our results provide vital insight into the nature of early intermediates formed and suggest that aromatic interactions are not as important in amyloid formation as previously postulated. This information is necessary for developing therapeutic drugs that inhibit and control amyloid formation.

Dynamics of dissipative self-assembly of particles interacting through oscillatory forces

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

Tagliazucchi, M.; Szleifer, I.

Dissipative self-assembly is the formation of ordered structures far from equilibrium, which continuously uptake energy and dissipate it into the environment. Due to its dynamical nature, dissipative self-assembly can lead to new phenomena and possibilities of self-organization that are unavailable to equilibrium systems. Understanding the dynamics of dissipative self-assembly is required in order to direct the assembly to structures of interest. In the present work, Brownian dynamics simulations and analytical theory were used to study the dynamics of self-assembly of a mixture of particles coated with weak acids and bases under continuous oscillations of the pH. The pH of themore » system modulates the charge of the particles and, therefore, the interparticle forces oscillate in time. This system produces a variety of self-assembled structures, including colloidal molecules, fibers and different types of crystalline lattices. The most important conclusions of our study are: (i) in the limit of fast oscillations, the whole dynamics (and not only those at the non-equilibrium steady state) of a system of particles interacting through time-oscillating interparticle forces can be described by an effective potential that is the time average of the time-dependent potential over one oscillation period; (ii) the oscillation period is critical to determine the order of the system. In some cases the order is favored by very fast oscillations while in others small oscillation frequencies increase the order. In the latter case, it is shown that slow oscillations remove kinetic traps and, thus, allow the system to evolve towards the most stable non-equilibrium steady state.« less

Recent advances in self-assembled monolayers based biomolecular electronic devices.

PubMed

Arya, Sunil K; Solanki, Pratima R; Datta, Monika; Malhotra, Bansi D

2009-05-15

Self-assembled monolayers (SAMs) have aroused much interest due to their potential applications in biosensors, biomolecular electronics and nanotechnology. This has been largely attributed to their inherent ordered arrangement and controllable properties. SAMs can be formed by chemisorption of organic molecules containing groups like thiols, disulphides, amines, acids or silanes, on desired surfaces and can be used to fabricate biomolecular electronic devices. We focus on recent applications of organosulphur compounds (thiols) based SAMs to biomolecular electronic devices in the last about 3 years.

Selective Surface Acoustic Wave-Based Organophosphorus Sensor Employing a Host-Guest Self-Assembly Monolayer of β-Cyclodextrin Derivative

PubMed Central

Pan, Yong; Mu, Ning; Shao, Shengyu; Yang, Liu; Wang, Wen; Xie, Xiao; He, Shitang

2015-01-01

Self-assembly and molecular imprinting technologies are very attractive technologies for the development of artificial recognition systems and provide chemical recognition based on need and not happenstance. In this paper, we employed a β-cyclodextrin derivative surface acoustic wave (SAW) chemical sensor for detecting the chemical warfare agents (CWAs) sarin (O-Isoprophyl methylphosphonofluoridate, GB). Using sarin acid (isoprophyl hydrogen methylphosphonate) as an imprinting template, mono[6-deoxy-6-[(mercaptodecamethylene)thio

An unprecedented Fe(36) phosphonate cage.

PubMed

Beavers, Christine M; Prosvirin, Andrey V; Prosverin, Andrey V; Cashion, John D; Dunbar, Kim R; Richards, Anne F

2013-02-18

The reaction of 2-pyridylphosphonic acid (LH(2)) with iron(II) perchlorate and iron(III) nitrate afforded an interconnected, double-layered, cationic iron cage, [{Fe(36)L(44)(H(2)O)(48)}](20+) (1a), the largest interconnected, polynuclear ferric cage reported to date. Magnetic studies on 1a revealed antiferromagnetic coupling between the spins on adjacent Fe(III) ions.

Molecular self-assembly using peptide nucleic acids.

PubMed

Berger, Or; Gazit, Ehud

2017-01-01

Peptide nucleic acids (PNAs) are extensively studied for the control of genetic expression since their design in the 1990s. However, the application of PNAs in nanotechnology is much more recent. PNAs share the specific base-pair recognition characteristic of DNA together with material-like properties of polyamides, both proteins and synthetic polymers, such as Kevlar and Nylon. The first application of PNA was in the form of PNA-amphiphiles, resulting in the formation of either lipid integrated structures, hydrogels or fibrillary assemblies. Heteroduplex DNA-PNA assemblies allow the formation of hybrid structures with higher stability as compared with pure DNA. A systematic screen for minimal PNA building blocks resulted in the identification of guanine-containing di-PNA assemblies and protected guanine-PNA monomer spheres showing unique optical properties. Finally, the co-assembly of PNA with thymine-like three-faced cyanuric acid allowed the assembly of poly-adenine PNA into fibers. In summary, we believe that PNAs represent a new and important family of building blocks which converges the advantages of both DNA- and peptide-nanotechnologies. © 2016 Wiley Periodicals, Inc.

Design and synthesis of polyphosphazenes: Hard tissue scaffolding biomaterials and physically crosslinked elastomers

NASA Astrophysics Data System (ADS)

Modzelewski, Tomasz

The work in this thesis is divided into two main parts. The first part examines the synthesis and characterization of polyphosphazenes as potential scaffolding materials usable for hard tissue repair. The goal of this work was to design polymers containing acidic functional groups in an attempt to encourage the deposition of calcium hydroxyapatite when the polymer is exposed to simulated body fluids. The second part examines the development of a new polymeric architecture which generates elastomeric properties without the use of traditional covalent or physical crosslinks. The goal was to examine the effects of this new architecture on the physical and mechanical properties of the final polymers. Chapter 1 provides a general background for the two main focus areas mentioned above. More specifically: a brief explanation is provided of the necessary physical and chemical properties of a suitable hard tissue engineering scaffolding substrate, and the basis of those requirements; together with an examination of the traditional ways in which elastomeric properties are introduced into a polymeric sample. Chapter 2 details the design and synthesis of polyphosphazenes bearing phosphonic acid and phosphoester side groups using two different routes. The first route utilized a linker unit which was functionalized with phosphoesters prior to its attachment to the polyphosphazene backbone, while the second route involved attachment of the same linking group to the polyphosphazene backbone before the introduction of the phosphoester moieties. In both cases, the samples were treated with iodotrimethylsilane to cleave the ester bonds and afford the parent phosphonic acid. Both routes proved successful. However, varying difficulties were encountered for each route. In Chapter 3 we examine the ability of the phosphonic acid functionalized polyphosphazenes described in Chapter 2 to mineralize calcium hydroxyapatite when exposed to simulated body fluid, which has the same ion concentration as human blood plasma. Scanning electron microscopy studies revealed that those polymers which were synthesized by phosphonation of the linker group after its attachment to the polymer backbone had a higher degree of inorganic deposition along the surface. However, these polymers had a lowed overall concentration of phosphonate groups per polymer chain. The inability to fully remove the ester protecting groups proved to be a key driving force for this increased activity. In addition, Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) analysis was utilized along with X-ray scattering to provide confirmation that the deposited phase was calcium hydroxyapatite, the natural mineral of bone. Chapter 4 describes the development of a family of carboxylic acid functionalized polyphosphazenes and the examination of their ability to mineralize calcium hydroxyapatite when exposed to simulated body fluids. The acid moieties in this system are introduced by the incorporation of the allyl esters of beta-alanine or gamma-amino butyric acid, followed by deesterification to afford the parent carboxylic acid. These samples show a significant increase in their ability to nucleate the growth of calcium hydroxyapatite along their surface, with the best sample doubling in mass within 4 weeks, which is a major improvement over the phosphonic acid functionalized samples described in Chapter 3. Chapter 5 contains an account of a new polymer architecture which imparts elastomeric properties without the use of traditional covalent or physical crosslinks. The polymers were synthesized with sterically bulky cyclotriphosphazene side groups linked directly to the polyphosphazene backbone using a hydroquinone linker. The geometry of the linking unit, as well as the large bulk of the side groups themselves, allowed the cyclotriphosphazene units to protrude away from the polymer backbone in a manner similar to the oars on a Viking long ship. This allowed them to interact physically with the oar's on adjacent polymer chains, and lock the chains in place, similar to the way in which the oars on one ship will interdigitate with the oars of another ship if they get too close. Chapter 6 expands the chemistry of the non-traditional elastomers described in Chapter 5. Specifically, the substituent groups on the cyclotriphosphazene groups are changed from 2,2,2- trifluoroethoxy to phenoxy, while the remaining chlorine atoms along the polymer backbone are still replaced with 2,2,2-trifluoroethoxide. The new polymers are shown to have better mechanical properties then the polymers described in Chapter 5. Chapter 7 describes a further extension of the ideas in Chapters 5 and 6. Specifically it involves the synthesis and mechanical testing of polyphosphazenes bearing oligo-p-phenylene groups co-substituted with 2,2,2-trifluoroethoxide. The oligo-phenylene groups are incorporated to act as variable length cross-linking moieties to further expand the new family of non-traditional polyphosphazene elastomers. The mechanical and physical properties of these polymers reveal a strong dependence on both the length and concentration of the oligo-phenylene minor co-substituent groups. (Abstract shortened by UMI.).

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

Abdelbaky, Mohammed S.M.; Amghouz, Zakariae; Department of Materials Science and Metallurgical Engineering, University of Oviedo, Campus Universitario, 33203 Gijón

Novel metal phosphonate [CuLi(PPA)] [H{sub 3}PPA=3-phosphonopropionic acid] was synthesized hydrothermally and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, scanning electron microscopy, infrared spectroscopy, and thermogravimetric analysis. It crystallizes in the space group C2/c, with cell parameters a=21.617(2) Å, b=4.9269(2) Å, c=14.342(1) Å, β=132.3(2)°, and Z=8. Its framework is built up from a main trimer, acting as a secondary building unit (SBU), which is formed by vertex-shared between two (LiO{sub 4}) and one (Cu(1)O{sub 4}) polyhedra. These units repeat along b-axis forming infinite inorganic chains, these chains are in turn cross-linked by corner sharing with (Cu(2)O{sub 4}) polyhedra to producemore » inorganic layers lying in the bc-plane. The neighboring layers are connected through the PPA ligand, leading to a 3D pillared-layered structure. The topological analysis reveals that the compound exhibits 3,4,10-c net. Finally, magnetic susceptibility measurement of this compound over the temperature range of 2–300 K reveals the occurrence of weak antiferromagnetic intrachain interactions. - Graphical abstract: Hydrothermal synthesis and structural characterization of a novel lithium-copper phosphonate, formulated as [CuLi(PPA)] (H{sub 3}PPA=3-phosphonopropionic acid), have been reported. This compound has a 3D pillared-layered structure with 3,4,10-c net topology. The magnetic susceptibility data over the temperature range of 2–300 K reveals the occurrence of weak antiferromagnetic interactions. - Highlights: • Novel metal phosphonate, [CuLi(PPA)] (1), has been synthesized and characterized. • Compound 1 has a 3D pillared-layered structure with 3,4,10-c net topology. • Magnetic susceptibility data reveals the occurrence of weak antiferromagnetic interactions.« less

Human Growth Hormone Adsorption Kinetics and Conformation on Self-Assembled Monolayers

PubMed Central

Buijs, Jos; Britt, David W.; Hlady, Vladimir

2012-01-01

The adsorption process of the recombinant human growth hormone on organic films, created by self-assembly of octadecyltrichlorosilane, arachidic acid, and dipalmitoylphosphatidylcholine, is investigated and compared to adsorption on silica and methylated silica substrates. Information on the adsorption process of human growth hormone (hGH) is obtained by using total internal reflection fluorescence (TIRF). The intensity, spectra, and quenching of the intrinsic fluorescence emitted by the growth hormone’s single tryptophan are monitored and related to adsorption kinetics and protein conformation. For the various alkylated hydrophobic surfaces with differences in surface density and conformational freedom it is observed that the adsorbed amount of growth hormone is relatively large if the alkyl chains are in an ordered structure while the amounts adsorbed are considerably lower for adsorption onto less ordered alkyl chains of fatty acid and phospholipid layers. Adsorption on methylated surfaces results in a relatively large conformational change in the growth hormone’s structure, as displayed by a 7 nm blue shift in emission wavelength and a large increase in the effectiveness of fluorescence quenching. Conformational changes are less evident for hGH adsorption onto the fatty acid and phospholipid alkyl chains. Adsorption kinetics on the hydrophilic head groups of the self-assembled monolayers are similar to those on solid hydrophilic surfaces. The relatively small conformational changes in the hGH structure observed for adsorption on silica are even further reduced for adsorption on fatty acid head groups. PMID:25125795

Assembly of citrate gold nanoparticles on hydrophilic monolayers

NASA Astrophysics Data System (ADS)

Vikholm-Lundin, Inger; Rosqvist, Emil; Ihalainen, Petri; Munter, Tony; Honkimaa, Anni; Marjomäki, Varpu; Albers, Willem M.; Peltonen, Jouko

2016-08-01

Self-assembled monolayers (SAMs) as model surfaces were linked onto planar gold films thorough lipoic acid or disulfide groups. The molecules used were polyethylene glycol (EG-S-S), N-[tris-(hydroxymethyl)methyl]acrylamide polymers with and without lipoic acid (Lipa-pTHMMAA and pTHMMAA) and a lipoic acid triazine derivative (Lipa-MF). All the layers, but Lipa-MF with a primary amino group were hydroxyl terminated. The layers were characterized by contact angle measurements and atomic force microscopy, AFM. Citrate stabilized nanoparticles, AuNPs in water and phosphate buffer were allowed to assemble on the layers for 10 min and the binding was followed in real-time with surface plasmon resonance, SPR. The SPR resonance curves were observed to shift to higher angles and become increasingly damped, while also the peaks strongly broaden when large nanoparticles assembled on the surface. Both the angular shift and the damping of the curve was largest for nanoparticles assembling on the EG-S-S monolayer. High amounts of particles were also assembled on the pTHMMAA layer without the lipoic acid group, but the damping of the curve was considerably lower with a more even distribution of the particles. Topographical images confirmed that the highest number of particles were assembled on the polyethylene glycol monolayer. By increasing the interaction time more particles could be assembled on the surface.

A direct conversion of benzylic and allylic alcohols to phosphonates

PubMed Central

Barney, Rocky J.; Richardson, Rebekah M.; Wiemer, David F.

2011-01-01

Benzyl phosphonate esters often serve as reagents in Horner-Wadsworth-Emmons reactions. In most cases, they can be prepared from benzylic alcohols via formation of the corresponding halide followed by an Arbuzov reaction. To identify a more direct synthesis of phosphonate esters, we have developed a one-flask procedure for conversion of benzylic and allylic alcohols to the corresponding phosphonates through treatment with triethyl phosphite and ZnI2. PMID:21405073

Recent advances in H-phosphonate chemistry. Part 1. H-phosphonate esters: synthesis and basic reactions.

PubMed

Sobkowski, Michal; Kraszewski, Adam; Stawinski, Jacek

2015-01-01

This review covers recent progress in the preparation of H-phosphonate mono- and diesters, basic studies on mechanistic and stereochemical aspects of this class of phosphorus compounds, and their fundamental chemistry in terms of transformation of P-H bonds into P-heteroatom bonds. Selected recent applications of H-phosphonate derivatives in basic organic phosphorus chemistry and in the synthesis of biologically important phosphorus compounds are also discussed.

Efficient inverted bulk-heterojunction polymer solar cells with self-assembled monolayer modified zinc oxide.

PubMed

Kim, Wook Hyun; Lyu, Hong-Kun; Han, Yoon Soo; Woo, Sungho

2013-10-01

The performance of poly(3-hexylthiophen) (P3HT) and [6, 6]phenyl C61 butyric acid methyl ester ([60]PCBM)-based inverted bulk-heterojunction (BHJ) polymer solar cells (PSCs) is enhanced by the modification of zinc oxide (ZnO)/BHJ interface with carboxylic-acid-functionalized self-assembled monolayers (SAMs). Under simulated solar illumination of AM 1.5 (100 mW/cm2), the inverted devices fabricated with SAM-modified ZnO achieved an enhanced power conversion efficiency (PCE) of 3.34% due to the increased fill factor and photocurrent density as compared to unmodified cells with PCE of 2.60%. This result provides an efficient method for interface engineering in inverted BHJ PSCs.

A highly directional fourfold hydrogen-bonding motif for supramolecular structures through self-assembly of fullerodendrimers.

PubMed

Hahn, Uwe; González, Juan J; Huerta, Elisa; Segura, Margarita; Eckert, Jean-François; Cardinali, François; de Mendoza, Javier; Nierengarten, Jean-François

2005-11-04

Supramolecular dendrimers resulting from the dimerization of fullerene-functionalized dendrons through a quadruple hydrogen-bonding motif were prepared. The synthetic strategy is based on the esterification of a tert-butoxycarbonyl (Boc)-protected 2-ureido-4-[1H]pyrimidinone precursor possessing an alcohol function with fullerodendrons bearing a carboxylic acid unit at the focal point. Subsequent acidic treatment to cleave the protecting group and reaction of the resulting amine with octylisocyanate affords the targeted compounds. As demonstrated by the results of MALDI-TOF mass spectrometry and 1H NMR spectroscopy, both of the 2-ureido-4-[1H]pyrimidinone derivatives form self-assembled dimers spontaneously through hydrogen-bonding interactions, thus leading to supramolecular structures containing two or ten fullerene moieties.

Synthesis, kinetic evaluation, and utilization of a biotinylated dipeptide proline diphenyl phosphonate for the disclosure of dipeptidyl peptidase IV-like serine proteases.

PubMed

Gilmore, Brendan F; Carson, Louise; McShane, Laura L; Quinn, Derek; Coulter, Wilson A; Walker, Brian

2006-08-18

In this study, we report on the synthesis, kinetic characterisation, and application of a novel biotinylated and active site-directed inactivator of dipeptidyl peptidase IV (DPP-IV). Thus, the dipeptide-derived proline diphenyl phosphonate NH(2)-Glu(biotinyl-PEG)-Pro(P)(OPh)(2) has been prepared by a combination of classical solution- and solid-phase methodologies and has been shown to be an irreversible inhibitor of porcine DPP-IV, exhibiting an over all second-order rate constant (k(i)/K(i)) for inhibition of 1.57 x 10(3) M(-1) min(-1). This value compares favourably with previously reported rates of inactivation of DPP-IV by dipeptides containing a P(1) proline diphenyl phosphonate grouping [B. Boduszek, J. Oleksyszyn, C.M. Kam, J. Selzler, R.E. Smith, J.C. Powers, Dipeptide phophonates as inhibitors of dipeptidyl peptidase IV, J. Med. Chem. 37 (1994) 3969-3976; B.F. Gilmore, J.F. Lynas, C.J. Scott, C. McGoohan, L. Martin, B. Walker, Dipeptide proline diphenyl phosphonates are potent, irreversible inhibitors of seprase (FAPalpha), Biochem, Biophys. Res. Commun. 346 (2006) 436-446.], thus demonstrating that the incorporation of the side-chain modified (N-biotinyl-3-(2-(2-(3-aminopropyloxy)-ethoxy)-ethoxy)-propyl) glutamic acid residue at the P(2) position is compatible with inhibitor efficacy. The utilisation of this probe for the detection of both purified dipeptidyl peptidase IV and the disclosure of a dipeptidyl peptidase IV-like activity from a clinical isolate of Porphyromonas gingivalis, using established electrophoretic and Western blotting techniques previously developed by our group, is also demonstrated.

Hierarchical self-assembly, coassembly, and self-organization of novel liquid crystalline lattices and superlattices from a twin-tapered dendritic benzamide and its four-cylinder-bundle supramolecular polymer.

PubMed

Percec, Virgil; Bera, Tushar K; Glodde, Martin; Fu, Qiongying; Balagurusamy, Venkatachalapathy S K; Heiney, Paul A

2003-02-17

The synthesis and structural analysis of the twin-dendritic benzamide 10, based on the first-generation, self-assembling, tapered dendrons 3,4,5-tris(4'-dodecyloxybenzyloxy)benzoic acid and 3,4,5-tris(4'-dodecyloxybenzyloxy)-1-aminobenzene, and the polymethacrylate, 20, which contains 10 as side groups, are presented. Benzamide 10 self-assembles into a supramolecular cylindrical dendrimer that self-organizes into a columnar hexagonal (Phi(h)) liquid crystalline (LC) phase. Polymer 20 self-assembles into an imperfect four-cylinder-bundle supramolecular dendrimer, and creates a giant vesicular supercylinder that self-organizes into a columnar nematic (N(c)) LC phase which displays short-range hexagonal order. In mixtures of 20 and 10, 10 acts as a guest and 20 as a host to create a perfect four-cylinder-bundle host-guest supramolecular dendrimer that coorganizes with 10. A diversity of Phi(h), simple rectangular columnar (Phi(r-s)) and centered rectangular columnar (Phi(r-c)), superlattices are produced at different ratios between 20 and 10. This diversity of LC lattices and superlattices is facilitated by the architecture of the twin-dendritic building block, polymethacrylate, the host-guest supramolecular assembly, and by hydrogen bonding along the center of the supramolecular cylinders generated from 10 and 20.

Stochastic simulations of fatty-acid proto-cell models

NASA Astrophysics Data System (ADS)

Mavelli, F.; Ruiz-Mirazo, K.

2007-06-01

In this contribution we tackle the problem of simulating the time behavior of self-assembling fatty acid vesicles in different experimental conditions. These systems have been (and are being) explored by various labs as possible precursor models of cellular compartments. By means of our recently developed stochastic simulation platform ('ENVIRONMENT') we are able to reproduce quite satisfactorily experimental data that have been reported on the different growth behavior of this type of proto-cellular systems, depending on the level of osmotic pressure they are under. The work here presented is part of a more general attempt to gain insight into the problem of how self-assembling vesicles (closed bilayer structures) could progressively turn into minimal self-producing and self-reproducing cells: i.e., into interesting candidates for (proto-)biological systems. This involves crossing the traditional gap between in silico and in vitro approaches, as we try to do here, convinced that major adavances in the field require the correct integration of both theoretical and experimental endeavors.

Self-assembling of 2,3-phenyl/thienyl-substituted acrylic acids over polycrystalline gold

NASA Astrophysics Data System (ADS)

Csankó, K.; Kozma, G.; Valkai, L.; Kukovecz, Á.; Kónya, Z.; Sipos, P.; Pálinkó, I.

2013-07-01

Self-assembling layers were formed from sulfur-containing cinnamic acid analogues over polycrystalline Au surface. The horizontal organising forces were strong O-H⋯O and weaker C-H⋯S hydrogen bonds (the former interaction kept together the acid dimers serving as the fundamental unit, while the latter was crucial in the construction of the 2D layers), while the vertical organisation forces were provided by Au-S covalent bonds. Measurements by atomic force, scanning electron, infrared and Raman microscopies attested that the dimers were situated in a nearly perpendicular fashion to the Au surface providing a ˜30-40 nm thick organic "carpet" and out of this layer occasionally, peaks with height of ˜100-120 nm grew out. The outgrowth of these surface structures were most probably governed by the defects of the polycrystalline metal surface.

In Vitro Investigation of Crosstalk between Fatty Acid and Polyketide Synthases in the Andrimid Biosynthetic Assembly Line.

PubMed

Ishikawa, Fumihiro; Sugimoto, Hiroyasu; Kakeya, Hideaki

2016-11-17

Andrimid (Adm) synthase, which belongs to the type II system of enzymes, produces Adm in Pantoea agglomerans. The adm biosynthetic gene cluster lacks canonical acyltransferases (ATs) to load the malonyl group to acyl carrier proteins (ACPs), thus suggesting that a malonyl-CoA ACP transacylase (MCAT) from the fatty acid synthase (FAS) complex provides the essential AT activity in Adm biosynthesis. Here we report that an MCAT is essential for catalysis of the transacylation of malonate from malonyl-CoA to AdmA polyketide synthase (PKS) ACP in vitro. Catalytic self-malonylation of AdmA (PKS ACP) was not observed in reactions without MCAT, although many type II PKS ACPs are capable of catalyzing self-acylation. This lack of self-malonylation was explained by amino acid sequence analysis of the AdmA PKS ACP and the type II PKS ACPs. The results show that MCAT from the organism's FAS complex can provide the missing AT activity in trans, thus suggesting a protein-protein interaction between the fatty acid and polyketide synthases in the Adm assembly line. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Designed Proteins Induce the Formation of Nanocage-containing Extracellular Vesicles

PubMed Central

Votteler, Jörg; Ogohara, Cassandra; Yi, Sue; Hsia, Yang; Nattermann, Una; Belnap, David M.; King, Neil P.; Sundquist, Wesley I.

2017-01-01

Complex biological processes are often performed by self-organizing nanostructures comprising multiple classes of macromolecules, such as ribosomes (proteins and RNA) or enveloped viruses (proteins, nucleic acids, and lipids). Approaches have been developed for designing self-assembling structures consisting of either nucleic acids1,2 or proteins3–5, but strategies for engineering hybrid biological materials are only beginning to emerge6,7. Here, we describe the design of self-assembling protein nanocages that direct their own release from human cells inside small vesicles in a manner that resembles some viruses. We refer to these hybrid biomaterials as Enveloped Protein Nanocages (EPNs). Robust EPN biogenesis required protein sequence elements that encode three distinct functions: membrane binding, self-assembly, and recruitment of the Endosomal Sorting Complexes Required for Transport (ESCRT) machinery8. A variety of synthetic proteins with these functional elements induced EPN biogenesis, highlighting the modularity and generality of the design strategy. Biochemical and electron cryomicroscopic (cryo-EM) analyses revealed that one design, EPN-01, comprised small (~100 nm) vesicles containing multiple protein nanocages that closely matched the structure of the designed 60-subunit self-assembling scaffold9. EPNs that incorporated the vesicular stomatitis viral glycoprotein (VSV-G) could fuse with target cells and deliver their contents, thereby transferring cargoes from one cell to another. These studies show how proteins can be programmed to direct the formation of hybrid biological materials that perform complex tasks, and establish EPNs as a novel class of designed, modular, genetically-encoded nanomaterials that can transfer molecules between cells. PMID:27919066

Cell-free protein synthesis and assembly on a biochip

NASA Astrophysics Data System (ADS)

Heyman, Yael; Buxboim, Amnon; Wolf, Sharon G.; Daube, Shirley S.; Bar-Ziv, Roy H.

2012-06-01

Biologically active complexes such as ribosomes and bacteriophages are formed through the self-assembly of proteins and nucleic acids. Recapitulating these biological self-assembly processes in a cell-free environment offers a way to develop synthetic biodevices. To visualize and understand the assembly process, a platform is required that enables simultaneous synthesis, assembly and imaging at the nanoscale. Here, we show that a silicon dioxide grid, used to support samples in transmission electron microscopy, can be modified into a biochip to combine in situ protein synthesis, assembly and imaging. Light is used to pattern the biochip surface with genes that encode specific proteins, and antibody traps that bind and assemble the nascent proteins. Using transmission electron microscopy imaging we show that protein nanotubes synthesized on the biochip surface in the presence of antibody traps efficiently assembled on these traps, but pre-assembled nanotubes were not effectively captured. Moreover, synthesis of green fluorescent protein from its immobilized gene generated a gradient of captured proteins decreasing in concentration away from the gene source. This biochip could be used to create spatial patterns of proteins assembled on surfaces.

Pectin-Lipid Self-Assembly: Influence on the Formation of Polyhydroxy Fatty Acids Nanoparticles

PubMed Central

Guzman-Puyol, Susana; Benítez, José Jesús; Domínguez, Eva; Bayer, Ilker Sefik; Cingolani, Roberto; Athanassiou, Athanassia; Heredia, Antonio; Heredia-Guerrero, José Alejandro

2015-01-01

Nanoparticles, named cutinsomes, have been prepared from aleuritic (9,10,16-trihidroxipalmitic) acid and tomato fruit cutin monomers (a mixture of mainly 9(10),16-dihydroxypalmitic acid (85%, w/w) and 16-hydroxyhexadecanoic acid (7.5%, w/w)) with pectin in aqueous solution. The process of formation of the nanoparticles of aleuritic acid plus pectin has been monitored by UV-Vis spectrophotometry, while their chemical and morphological characterization was analyzed by ATR-FTIR, TEM, and non-contact AFM. The structure of these nanoparticles can be described as a lipid core with a pectin shell. Pectin facilitated the formation of nanoparticles, by inducing their aggregation in branched chains and favoring the condensation between lipid monomers. Also, pectin determined the self-assembly of cutinsomes on highly ordered pyrolytic graphite (HOPG) surfaces, causing their opening and forming interconnected structures. In the case of cutin monomers, the nanoparticles are fused, and the condensation of the hydroxy fatty acids is strongly affected by the presence of the polysaccharide. The interaction of pectin with polyhydroxylated fatty acids could be related to an initial step in the formation of the plant biopolyester cutin. PMID:25915490

Microrheological Characterization of Collagen Systems: From Molecular Solutions to Fibrillar Gels

PubMed Central

Shayegan, Marjan; Forde, Nancy R.

2013-01-01

Collagen is the most abundant protein in the extracellular matrix (ECM), where its structural organization conveys mechanical information to cells. Using optical-tweezers-based microrheology, we investigated mechanical properties both of collagen molecules at a range of concentrations in acidic solution where fibrils cannot form and of gels of collagen fibrils formed at neutral pH, as well as the development of microscale mechanical heterogeneity during the self-assembly process. The frequency scaling of the complex shear modulus even at frequencies of ∼10 kHz was not able to resolve the flexibility of collagen molecules in acidic solution. In these solutions, molecular interactions cause significant transient elasticity, as we observed for 5 mg/ml solutions at frequencies above ∼200 Hz. We found the viscoelasticity of solutions of collagen molecules to be spatially homogeneous, in sharp contrast to the heterogeneity of self-assembled fibrillar collagen systems, whose elasticity varied by more than an order of magnitude and in power-law behavior at different locations within the sample. By probing changes in the complex shear modulus over 100-minute timescales as collagen self-assembled into fibrils, we conclude that microscale heterogeneity appears during early phases of fibrillar growth and continues to develop further during this growth phase. Experiments in which growing fibrils dislodge microspheres from an optical trap suggest that fibril growth is a force-generating process. These data contribute to understanding how heterogeneities develop during self-assembly, which in turn can help synthesis of new materials for cellular engineering. PMID:23936454

Structure-activity relationships of amide-phosphonate derivatives as inhibitors of the human soluble epoxide hydrolase.

PubMed

Kim, In-Hae; Park, Yong-Kyu; Nishiwaki, Hisashi; Hammock, Bruce D; Nishi, Kosuke

2015-11-15

Structure-activity relationships of amide-phosphonate derivatives as inhibitors of the human soluble epoxide hydrolase (sEH) were investigated. First, a series of alkyl or aryl groups were substituted on the carbon alpha to the phosphonate function in amide compounds to see whether substituted phosphonates can act as a secondary pharmacophore. A tert-butyl group (16) on the alpha carbon was found to yield most potent inhibition on the target enzyme. A 4-50-fold drop in inhibition was induced by other substituents such as aryls, substituted aryls, cycloalkyls, and alkyls. Then, the modification of the O-substituents on the phosphonate function revealed that diethyl groups (16 and 23) were preferable for inhibition to other longer alkyls or substituted alkyls. In amide compounds with the optimized diethylphosphonate moiety and an alkyl substitution such as adamantane (16), tetrahydronaphthalene (31), or adamantanemethane (36), highly potent inhibitions were gained. In addition, the resulting potent amide-phosphonate compounds had reasonable water solubility, suggesting that substituted phosphonates in amide inhibitors are effective for both inhibition potency on the human sEH and water solubility as a secondary pharmacophore. Copyright © 2015 Elsevier Ltd. All rights reserved.

Molecular Self-Assembly of Short Aromatic Peptides: From Biology to Nanotechnology and Material Science

NASA Astrophysics Data System (ADS)

Gazit, Ehud

2013-03-01

The formation of ordered amyloid fibrils is the hallmark of several diseases of unrelated origin. In spite of grave clinical consequence, the mechanism of amyloid formation is not fully understood. We have suggested, based on experimental and bioinformatic analysis, that aromatic interactions may provide energetic contribution as well as order and directionality in the molecular-recognition and self-association processes that lead to the formation of these assemblies. This is in line with the well-known central role of aromatic-stacking interactions in self-assembly processes. Our works on the mechanism of aromatic peptide self-assembly, lead to the discovery that the diphenylalanine recognition motif self-assembles into peptide nanotubes with a remarkable persistence length. Other aromatic homodipeptides could self-assemble in nano-spheres, nano-plates, nano-fibrils and hydrogels with nano-scale order. We demonstrated that the peptide nanostructures have unique chemical, physical and mechanical properties including ultra-rigidity as aramides, semi-conductive, piezoelectric and non-linear optic properties. We also demonstrated the ability to use these peptide nanostructures as casting mold for the fabrication of metallic nano-wires and coaxial nano-cables. The application of the nanostructures was demonstrated in various fields including electrochemical biosensors, tissue engineering, and molecular imaging. Finally, we had developed ways for depositing of the peptide nanostructures and their organization. We had use inkjet technology as well as vapour deposition methods to coat surface and from the peptide ``nano-forests''. We recently demonstrated that even a single phenylalanine amino-acid can form well-ordered fibrilar assemblies.

Separation and detection of VX and its methylphosphonic acid degradation products on a microchip using indirect laser-induced fluorescence.

PubMed

Heleg-Shabtai, Vered; Gratziany, Natzach; Liron, Zvi

2006-05-01

The application of indirect LIF (IDLIF) technique for on-chip electrophoretic separation and detection of the nerve agent O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothiolate (VX) and its major phosphonic degradation products, ethyl methylphosphonic acid (EMPA) and methylphosphonic acid (MPA) was demonstrated. Separation and detection of MPA degradation products of VX and the nerve agent isopropyl methylphosphonofluoridate (GB) are presented. The negatively charged dye eosin was found to be a good fluorescent marker for both the negatively charged phosphonic acids and the positively charged VX, and was chosen as the IDLIF visualization fluorescent dye. Separation and detection of VX, EMPA, and MPA in a simple-cross microchip were completed within less than a minute, and consumed only a 50 pL sample volume. A characteristic system peak that appeared in all IDLIF electropherograms served as an internal standard that increased the reliability of peak identification. The negative peak of both VX and the MPAs is in agreement with indirect detection theory and with previous reports in the literature. The LOD of VX and EMPA by IDLIF was 30 and 37 microM, respectively. Despite the fact that the detection sensitivity is relatively low, the rapid simultaneous on-chip analysis of both VX and its degradation products as well as the separation and detection of the MPA degradation products of both VX and GB, increases detection reliability and may present a choice when sensitivity is not critical compared with speed and simplicity of the assay.

40 CFR 721.10677 - Alkyl phosphonate (generic).

Code of Federal Regulations, 2014 CFR

2014-07-01

... CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10677 Alkyl phosphonate (generic). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as alkyl phosphonate (PMN P-12-584...

Diversity and abundance of phosphonate biosynthetic genes in nature

USDA-ARS?s Scientific Manuscript database

Phosphonates, molecules containing direct C-P bonds, comprise a structurally diverse class of natural products with interesting and useful biological properties. Although their synthesis in protozoa was discovered more than fifty years ago, the extent and diversity of phosphonate production in natur...

Designer nanomaterials using chiral self-assembling peptide systems and their emerging benefit for society.

PubMed

Luo, Zhongli; Zhang, Shuguang

2012-07-07

Chirality is absolutely central in chemistry and biology. The recent findings of chiral self-assembling peptides' remarkable chemical complementarity and structural compatibility make it one of the most inspired designer materials and structures in nanobiotechnology. The emerging field of designer chemistry and biology further explores biological and medical applications of these simple D,L- amino acids through producing marvellous nanostructures under physiological conditions. These self-assembled structures include well-ordered nanofibers, nanotubes and nanovesicles. These structures have been used for 3-dimensional tissue cultures of primary cells and stem cells, sustained release of small molecules, growth factors and monoclonal antibodies, accelerated wound-healing in reparative and regenerative medicine as well as tissue engineering. Recent advances in molecular designs have also led to the development of 3D fine-tuned bioactive tissue culture scaffolds. They are also used to stabilize membrane proteins including difficult G-protein coupled receptors for designing nanobiodevices. One of the self-assembling peptides has been used in human clinical trials for accelerated wound-healings. It is our hope that these peptide materials will open doors for more and diverse clinical uses. The field of chiral self-assembling peptide nanobiotechnology is growing in a number of directions that has led to many surprises in areas of novel materials, synthetic biology, clinical medicine and beyond.

Characterization of charged polymer self-assemblies by multidetector thermal field-flow fractionation in aqueous mobile phases.

PubMed

Greyling, Guilaume; Pasch, Harald

2018-01-12

Charged block copolymer self-assemblies, such as charged micelles, have attracted much attention as versatile drug delivery systems due to their readily tunable characteristics such as size and surface charge. However, current column-based analytical techniques are not suitable to fractionate and comprehensively characterize charged micelles in terms of size, molar mass, chemical composition and morphology. Multidetector thermal field-flow fractionation (ThFFF) is shown to be a unique characterization platform that can be used to characterize charged micelles in terms of size, molar mass, chemical composition and morphology in aqueous mobile phases with various ionic strengths and pH. This is demonstrated by the characterization of poly(methacrylic acid)-b-poly(methyl methacrylate) self-assemblies in high pH buffers as well as the characterization of cationic poly(2-vinyl pyridine)-b-polystyrene and poly(4-vinyl pyridine)-b-polystyrene self-assemblies in low pH buffers. Moreover, it is shown that ThFFF is capable of separating charged micelles according to the corona composition. These investigations prove convincingly that ThFFF is broadly applicable to the comprehensive characterization of amphiphilic self-assemblies even when aqueous mobile phases are used. Copyright © 2017 Elsevier B.V. All rights reserved.

Film Self-Assembly of Oppositely Charged Macromolecules Triggered by Electrochemistry through a Morphogenic Approach.

PubMed

Dochter, Alexandre; Garnier, Tony; Pardieu, Elodie; Chau, Nguyet Trang Thanh; Maerten, Clément; Senger, Bernard; Schaaf, Pierre; Jierry, Loïc; Boulmedais, Fouzia

2015-09-22

The development of new surface functionalization methods that are easy to use, versatile, and allow local deposition represents a real scientific challenge. Overcoming this challenge, we present here a one-pot process that consists in self-assembling, by electrochemistry on an electrode, films made of oppositely charged macromolecules. This method relies on a charge-shifting polyanion, dimethylmaleic-modified poly(allylamine) (PAHd), that undergoes hydrolysis at acidic pH, leading to an overall switching of its charge. When a mixture of the two polyanions, PAHd and poly(styrenesulfonate) (PSS), is placed in contact with an electrode, where the pH is decreased locally by electrochemistry, the transformation of PAHd into a polycation (PAH) leads to the continuous self-assembly of a nanometric PAH/PSS film by electrostatic interactions. The pH decrease is obtained by the electrochemical oxidation of hydroquinone, which produces protons locally over nanometric distances. Using a negatively charged enzyme, alkaline phosphatase (AP), instead of PSS, this one-pot process allows the creation of enzymatically active films. Under mild conditions, self-assembled PAH/AP films have an enzymatic activity which is adjustable simply by controlling the self-assembly time. The selective functionalization of microelectrode arrays by PAH/AP was achieved, opening the route toward miniaturized biosensors.

Metal-Dependent Amyloid β-Degrading Catalytic Antibody Construct

PubMed Central

Nishiyama, Yasuhiro; Taguchi, Hiroaki; Hara, Mariko; Planque, Stephanie A.; Mitsuda, Yukie; Paul, Sudhir

2015-01-01

Catalytic antibodies (catabodies) that degrade target antigens rapidly are rare. We describe the metal-dependence of catabody construct 2E6, an engineered heterodimer of immunoglobulin light chain variable domains that hydrolyzes amyloid β peptides (Aβ) specifically. In addition to the electrophilic phosphonate inhibitor of serine proteases, the metal chelators ethylenediaminetetraacetic acid (EDTA) and 1,10-phenanthroline completely inhibited the hydrolysis of Aβ by catabody 2E6. Formation of catabody-electrophilic phosphonate inhibitor adducts was unaffected by EDTA, suggesting that the metal exerts a favorable effect on a catalytic step after the initial catabody nucleophilic attack on Aβ. The EDTA inactivated catabody failed to disaggregate fibrillar Aβ, indicating the functional importance of the Aβ hydrolytic activity. Treating the EDTA-inactivated catabody with Zn2+ or Co2+ restored the Aβ hydrolytic activity, and Zn2+-induced catabody conformational transitions were evident by fluorescence emission spectroscopy. The studies reveal the absolute catabody dependence on a metal cofactor. PMID:24698848

Biomimetic Hierarchical Assembly of Helical Supraparticles from Chiral Nanoparticles

DOE PAGES

Zhou, Yunlong; Marson, Ryan L.; van Anders, Greg; ...

2016-02-22

Chiroptical materials found in butterflies, beetles, stomatopod crustaceans, and other creatures are attributed to biocomposites with helical motifs and multiscale hierarchical organization. These structurally sophisticated materials self-assemble from primitive nanoscale building blocks, a process that is simpler and more energy efficient than many top-down methods currently used to produce similarly sized three-dimensional materials. In this paper, we report that molecular-scale chirality of a CdTe nanoparticle surface can be translated to nanoscale helical assemblies, leading to chiroptical activity in the visible electromagnetic range. Chiral CdTe nanoparticles coated with cysteine self-organize around Te cores to produce helical supraparticles. D-/L-Form of the aminomore » acid determines the dominant left/right helicity of the supraparticles. Coarse-grained molecular dynamics simulations with a helical pair-potential confirm the assembly mechanism and the origin of its enantioselectivity, providing a framework for engineering three-dimensional chiral materials by self-assembly. Finally, the helical supraparticles further self-organize into lamellar crystals with liquid crystalline order, demonstrating the possibility of hierarchical organization and with multiple structural motifs and length scales determined by molecular-scale asymmetry of nanoparticle interactions.« less

Self-assembly processes in the prebiotic environment

PubMed Central

Deamer, David; Singaram, Sara; Rajamani, Sudha; Kompanichenko, Vladimir; Guggenheim, Stephen

2006-01-01

An important question guiding research on the origin of life concerns the environmental conditions where molecular systems with the properties of life first appeared on the early Earth. An appropriate site would require liquid water, a source of organic compounds, a source of energy to drive polymerization reactions and a process by which the compounds were sufficiently concentrated to undergo physical and chemical interactions. One such site is a geothermal setting, in which organic compounds interact with mineral surfaces to promote self-assembly and polymerization reactions. Here, we report an initial study of two geothermal sites where mixtures of representative organic solutes (amino acids, nucleobases, a fatty acid and glycerol) and phosphate were mixed with high-temperature water in clay-lined pools. Most of the added organics and phosphate were removed from solution with half-times measured in minutes to a few hours. Analysis of the clay, primarily smectite and kaolin, showed that the organics were adsorbed to the mineral surfaces at the acidic pH of the pools, but could subsequently be released in basic solutions. These results help to constrain the range of possible environments for the origin of life. A site conducive to self-assembly of organic solutes would be an aqueous environment relatively low in ionic solutes, at an intermediate temperature range and neutral pH ranges, in which cyclic concentration of the solutes can occur by transient dry intervals. PMID:17008220

Catalytic diversity in self-propagating peptide assemblies

NASA Astrophysics Data System (ADS)

Omosun, Tolulope O.; Hsieh, Ming-Chien; Childers, W. Seth; Das, Dibyendu; Mehta, Anil K.; Anthony, Neil R.; Pan, Ting; Grover, Martha A.; Berland, Keith M.; Lynn, David G.

2017-08-01

The protein-only infectious agents known as prions exist within cellular matrices as populations of assembled polypeptide phases ranging from particles to amyloid fibres. These phases appear to undergo Darwinian-like selection and propagation, yet remarkably little is known about their accessible chemical and biological functions. Here we construct simple peptides that assemble into well-defined amyloid phases and define paracrystalline surfaces able to catalyse specific enantioselective chemical reactions. Structural adjustments of individual amino acid residues predictably control both the assembled crystalline order and their accessible catalytic repertoire. Notably, the density and proximity of the extended arrays of enantioselective catalytic sites achieve template-directed polymerization of new polymers. These diverse amyloid templates can now be extended as dynamic self-propagating templates for the construction of even more complex functional materials.

Synthetic routes to 3(5)-phosphonylated pyrazoles

NASA Astrophysics Data System (ADS)

Goulioukina, N. S.; Makukhin, N. N.; Beletskaya, I. P.

2016-07-01

This review comprehensively covers the currently available synthetic routes to 3(5)-phosphonylated pyrazoles. There are demonstrated significant advances in this field over the last 10-15 years caused by the use of the Bestmann-Ohira reagent [as well as (diazomethyl)phosphonates and phosphonylated hydrazonoyl halides] in reactions with diverse dipolarophiles. 1,3-Dipolar cycloaddition of diazo compounds to α,β-unsaturated phosphonates as well as intramolecular heterocyclization of (1-diazoallyl)phosphonates and (3--diazo-1-propenyl)phosphonates are discussed. Synthetic potential of cyclocondensation of organophosphorus 1,3-dielectrophilic compounds with hydrazines is shown. Ways to introduce a phosphonate group into the pyrazole ring are considered. Examples of chemical transformations of 3(5)-phosphonylated pyrazoles are reported. The bibliography includes 88 references.

Development of the 2007 Chemical Decontaminant Source Document

DTIC Science & Technology

2009-03-01

Chemical Agent Simulant Specific DEM diethyl malonate MeS methyl salicylate PEG200 Polyethylene glycol 200 TEP triethyl phosphate Group 6...simulants • H-agent simulants o Methyl salicylate (MeS) o Chloroethyl phenyl sulfide (CEPS) o Chloroethyl ethyl sulfide (CEES) • VX simulants... Methyl bromide Ethyl phosphonothioic dichloride Sulfur dioxide Methyl chloroformate Ethyl phosphonic dichloride Sulfuric acid Methyl chlorosilane

Co-assembly of Peptide Amphiphiles and Lipids into Supramolecular Nanostructures Driven by Anion-π Interactions

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

Yu, Zhilin; Erbas, Aykut; Tantakitti, Faifan

Co-assembly of binary systems driven by specific non-covalent interactions can greatly expand the structural and functional space of supramolecular nanostructures. We report here on the self-assembly of peptide amphiphiles and fatty acids driven primarily by anion-π interactions. The peptide sequences investigated were functionalized with a perfluorinated phenylalanine residue to promote anion-π interactions with carboxylate headgroups in fatty acids. These interactions were verified here by NMR and circular dichroism experiments as well as investigated using atomistic simulations. Positioning the aromatic units close to the N-terminus of the peptide backbone near the hydrophobic core of cylindrical nanofibers leads to strong anion-π interactionsmore » between both components. With a low content of dodecanoic acid in this position, the cylindrical morphology is preserved. However, as the aromatic units are moved along the peptide backbone away from the hydrophobic core, the interactions with dodecanoic acid transform the cylindrical supramolecular morphology into ribbon-like structures. Increasing the ratio of dodecanoic acid to PA leads to either the formation of large vesicles in the binary systems where the anion-π interactions are strong, or a heterogeneous mixture of assemblies when the peptide amphiphiles associate weakly with dodecanoic acid. Our findings reveal how co-assembly involving designed specific interactions can drastically change supramolecular morphology and even cross from nano to micro scales.« less

Improving the Performance of Semiconductor Sensor Devices Using Surface Functionalization

NASA Astrophysics Data System (ADS)

Rohrbaugh, Nathaniel W.

As production and understanding of III-nitride growth has progressed, this class of material has been used for its semiconducting properties in the fields of computer processing, microelectronics, and LEDs. As understanding of materials properties has advanced, devices were fabricated to be sensitive to environmental surroundings such as pH, gas, or ionic concentration. Simultaneously the world of pharmaceuticals and environmental science has come to the age where the use of wearable devices and active environmental sensing can not only help us learn more about our surroundings, but help save lives. At the crossroads of these two fields work has been done in marrying the high stability and electrical properties of the III-nitrides with the needs of a growing sensor field for various environments and stimuli. Device architecture can only get one so far, and thus the need for well understood surface functionalization techniques has arisen in the field of III-nitride environmental sensing. Many existing schemes for functionalization involve chemistries that may be unfriendly to a biological environment, unstable in solution, or expensive to produce. One possible solution to these issues is the work presented here, which highlights a surface modification scheme utilizing phosphonic acid based chemistry and biomolecular attachment. This dissertation presents a set of studies and experiments quantifying and analyzing the response behaviors of AlGaN/GaN field effect transistor (FET) devices via their interfacial electronic properties. Additional investigation was done on the modification of these surfaces, effects of stressful environmental conditions, and the utility of the phosphonic acid surface treatments. Signals of AlGaN/GaN FETs were measured as IDrain values and in the earliest study an average signal increase of 96.43% was observed when surfaces were incubated in a solution of a known recognition peptide sequence (SVSVGMKPSPRP). This work showed that even without a form of surface modification the devices were capable of generating a response in the presence of a charged biomolecule. Solution exposure tests done devices showed that incubating peptides on the device surfaces produced a weak interaction and following 24 hrs of soaking no signs of peptide remained via XPS analysis. Subsequent testing was done to incorporate the phosphonic acid functionalization techniques shown previously by other members of this lab to the AlGaN/GaN surfaces as a remedy to this solution instability. In this second study FETs were modified using a heated phosphoric acid:ethephon etch followed by an incubation in TAT-C peptide. Resulting IV measurements done on the samples showed a shift in threshold voltage of the FETs following the etching procedure followed by a recovery of this shift from prolonged solution exposure. In total samples were given 168 hours of soaking and showed persistent peptide presence through the N 1s peak from XPS scans. FETs modified with this phosphonic acid derivative were examined in a third study under a simulated pollutant sensing scenario by measuring varied concentrations of Hg via a phytochelatin peptide bound to FET surfaces. HNO3 used in the Hg stock solution led to degradation of the FET signal but did not remove the phytochelatin layer. This led to a compensation effect in sensing the highest levels of Hg, lower concentrations however were successfully tested and showed varied responses from the FETs relative to the Hg content. In a concluding study on devices work was done to understand broader effects on the AlGaN/GaN FETs relative to a simulated biological sensing environment. Here an effect was noted from the addition of a biological fouling solution to the FETs and an increase in this effect when the biofouling was done to a phosphonic modified FET surface. Additionally devices were modified and soaked for 5 weeks and showed no shift or degradation in signal. Lastly in controlling for gate width of the FET it was found that the shorter 50 im gates were more susceptible to environmental interference than the 100 and 150 im gated devices. Thus this work has shown that modifying AlGaN/GaN devices with phosphonic acid derivatives is a viable functionalization method that is both adaptable and stable in solution over time. In moving forward, opportunities are available for testing a larger variety of analytes in both the medical and environmental fields. The final goal for this technology would be the fabrication and design of a multi-device sensing unit leading to eventual production of these sensors on an industrial scale for the use in future personal medical devices or environmental monitoring systems.

Molybdenum-oxide based unique polyprotic nanoacids showing different deprotonations and related assembly processes in solution.

PubMed

Kistler, Melissa L; Liu, Tianbo; Gouzerh, Pierre; Todea, Ana Maria; Müller, Achim

2009-07-14

We report the self-assembly processes in solution of three Keplerate-type molybdenum-oxide based clusters {Mo72V30}, {Mo72Cr30} and {Mo72Fe30} (all with diameters of approximately 2.5 nm). These clusters behave as unique weak polyprotic acids owing to the external water ligands attached to the non-Mo metal centers. Whereas the Cr and Fe clusters have 30 water ligands attached at the 30 M3+ centers pointing outside, {Mo72V30} has 20 water ligands coordinated to vanadium atoms, of which only 10 are pointing outside. The self-assembly processes of the Keplerates leading to supramolecular blackberry-type structures are influenced by the effective charge densities on the cluster surfaces, which can be tuned by the pH values and solvent properties. As expected, {Mo72Cr30} and {Mo72Fe30} behave similarly in aqueous solution due to their analogous structures and in both cases the self-assembly follows the partial deprotonation of the external water ligands attached to the non-Mo metal centers. However, the M-OH2 functionalities differ not only in acidity but also lability, i.e. in different residence times of the H2O ligands. In contrast to {Mo72Cr30} and {Mo72Fe30}, the {Mo72V30} clusters carry a rather large number of negative charges so that their solution properties are different. They exist as discrete macroions in dilute aqueous solution, and form only in mixed water/organic solvent (like acetone) blackberry-type structures whose size increases with acetone content. The comparison of the properties of the clusters allows more general information about the interesting self-assembly phenomenon to be unveiled.

Kinetic control of block copolymer self-assembly into multicompartment and novel geometry nanoparticles

NASA Astrophysics Data System (ADS)

Chen, Yingchao; Wang, Xiaojun; Zhang, Ke; Wooley, Karen; Mays, Jimmy; Percec, Virgil; Pochan, Darrin

2012-02-01

Micelles with the segregation of hydrophobic blocks trapped in the same nanoparticle core have been produced through co-self-assembly of two block copolymers in THF/water dilute solution. The dissolution of two block copolymer sharing the same polyacrylic acid PAA blocks in THF undergoes consequent aggregation and phase separation through either slow water titration or quick water addition that triggers the micellar formation. The combination and comparison of the two water addition kinetic pathways are the keys of forming multicompartment structures at high water content. Importantly, the addition of organic diamine provides for acid-base complexation with the PAA side chains which, in turn, plays the key role of trapping unlike hydrophobic blocks from different block copolymers into one nanoparticle core. The kinetic control of solution assembly can be applied to other molecular systems such as dendrimers as well as other block copolymer molecules. Transmission electron microscopy, cryogenic transmission electron microscopy, light scattering have been applied to characterize the micelle structures.

In vivo production of RNA nanostructures via programmed folding of single-stranded RNAs.

PubMed

Li, Mo; Zheng, Mengxi; Wu, Siyu; Tian, Cheng; Liu, Di; Weizmann, Yossi; Jiang, Wen; Wang, Guansong; Mao, Chengde

2018-06-06

Programmed self-assembly of nucleic acids is a powerful approach for nano-constructions. The assembled nanostructures have been explored for various applications. However, nucleic acid assembly often requires chemical or in vitro enzymatical synthesis of DNA or RNA, which is not a cost-effective production method on a large scale. In addition, the difficulty of cellular delivery limits the in vivo applications. Herein we report a strategy that mimics protein production. Gene-encoded DNA duplexes are transcribed into single-stranded RNAs, which self-fold into well-defined RNA nanostructures in the same way as polypeptide chains fold into proteins. The resulting nanostructure contains only one component RNA molecule. This approach allows both in vitro and in vivo production of RNA nanostructures. In vivo synthesized RNA strands can fold into designed nanostructures inside cells. This work not only suggests a way to synthesize RNA nanostructures on a large scale and at a low cost but also facilitates the in vivo applications.

Deviation between the chemistry of Ce(IV) and Pu(IV) and routes to ordered and disordered heterobimetallic 4f/5f and 5f/5f phosphonates

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

Diwu, Juan; Wang, Shuao; Good, Justin J.

2011-06-06

The heterobimetallic actinide compound UO₂Ce(H₂O)[C₆H₄(PO₃H)₂]₂·H₂O was prepared via the hydrothermal reaction of U(VI) and Ce(IV) in the presence of 1,2-phenylenediphosphonic acid. We demonstrate that this is a kinetic product that is not stable with respect to decomposition to the monometallic compounds. Similar reactions have been explored with U(VI) and Ce(III), resulting in the oxidation of Ce(III) to Ce(IV) and the formation of the Ce(IV) phosphonate, Ce[C₆H₄(PO₃H)(PO₃H₂)][C₆H₄(PO₃H)(PO₃)]·2H₂O, UO₂Ce(H₂O)[C₆H₄(PO₃H)₂]₂·H₂O, and UO₂[C₆H₄(PO₃H)₂](H₂O)·H₂O. In comparison, the reaction of U(VI) with Np(VI) only yields Np[C₆H₄(PO₃H)₂]₂·2H₂O and aqueous U(VI), whereas the reaction of U(VI) with Pu(VI) yields the disordered U(VI)/Pu(VI) compound, (U 0.9Pu 0.1)O₂[C₆H₄(PO₃H)₂](H₂O)·H₂O, and themore » Pu(IV) phosphonate, Pu[C₆H₄(PO₃H)(PO₃H₂)][C₆H₄(PO₃H)(PO₃)]·2H₂O. The reactions of Ce(IV) with Np(VI) yield disordered heterobimetallic phosphonates with both M[C₆H₄(PO₃H)(PO₃H₂)][C₆H₄(PO₃H)(PO₃)]·2H₂O (M = Ce, Np) and M[C₆H₄(PO₃H)₂]₂·2H₂O (M = Ce, Np) structures, as well as the Ce(IV) phosphonate Ce[C₆H₄(PO₃H)(PO₃H₂)][C₆H₄(PO₃H)(PO₃)]·2H₂O. Ce(IV) reacts with Pu(IV) to yield the Pu(VI) compound, PuO₂[C₆H₄(PO₃H)₂](H₂O)·3H₂O, and a disordered heterobimetallic Pu(IV)/Ce(IV) compound with the M[C₆H₄(PO₃H)(PO₃H₂)][C₆H₄(PO₃H)(PO₃)]·2H₂O (M = Ce, Pu) structure. Mixtures of Np(VI) and Pu(VI) yield disordered heterobimetallic Np(IV)/Pu(IV) phosphonates with both the An[C₆H₄(PO₃H)(PO₃H₂)][C₆H₄(PO₃H)(PO₃)]·2H₂O (M = Np, Pu) and An[C₆H₄(PO₃H)₂]₂·2H₂O (M = Np, Pu) formulas.« less

Selective Attachment of Nucleic Acid Molecules to Patterned Self-Assembled Surfaces.

DTIC Science & Technology

1994-12-01

of different sequence is accomplished by placement of 8 liquid portions of nucleic acids at the desired position on the 9 filter. This method is...acids are selectively 24 bound from regions to which nucleic acids are excluded, other than 25 by placement of liquid aliquots (generally >1 Al) of...is typically non-covalent (i.e., ionic 16 bonding, or, less often, hydrogen bonding). Advantageously, non- 17 covalent bonding of nucleic acid

Chaperone gelator for the chiral self-assembly of all proteinogenic amino acids and their enantiomers.

PubMed

Chen, Jie; Wang, Tianyu; Liu, Minghua

2016-05-04

A concept of a chaperone gelator that can assist non-gelator molecules to form gels is proposed. Such a new gelator was developed and found to tune all the proteinogenic l-amino acids, as well as their enantiomers into supramolecular gels.

Elastin-like Polypeptide (ELP) Charge Influences Self-Assembly of ELP-mCherry Fusion Proteins.

PubMed

Mills, Carolyn E; Michaud, Zachary; Olsen, Bradley D

2018-05-23

Self-assembly of protein-polymer bioconjugates presents an elegant strategy for controlling nanostructure and orientation of globular proteins in functional materials. Recent work has shown that genetic fusion of globular protein mCherry to an elastin-like polypeptide (ELP) yields similar self-assembly behavior to these protein-polymer bioconjugates. In the context of studying protein-polymer bioconjugate self-assembly, the mutability of the ELP sequence allows several different properties of the ELP block to be tuned orthogonally while maintaining consistent polypeptide backbone chemistry. This work uses this ELP sequence tunability in combination with the precise control offered by genetic engineering of an amino acid sequence to generate a library of four novel ELP sequences that are used to study the combined effect of charge and hydrophobicity on ELP-mCherry fusion protein self-assembly. Concentrated solution self-assembly is studied by small-angle X-ray scattering (SAXS) and depolarized light scattering (DPLS). These experiments show that fusions containing a negatively charged ELP block do not assemble at all, and fusions with a charge balanced ELP block exhibit a weak propensity for assembly. By comparison, the fusion containing an uncharged ELP block starts to order at 40 wt % in solution and at all concentrations measured has sharper, more intense SAXS peaks than other fusion proteins. These experiments show that charge character of the ELP block is a stronger predictor of self-assembly behavior than the hydrophobicity of the ELP block. Dilute solution small-angle neutron scattering (SANS) on the ELPs alone suggests that all ELPs used in this study (including the uncharged ELP) adopt dilute solution conformations similar to those of traditional polymers, including polyampholytes and polyelectrolytes. Finally, dynamic light scattering studies on ELP-mCherry blends shows that there is no significant complexation between the charged ELPs and mCherry. Therefore, it is proposed that the superior self-assembly of fusion proteins containing uncharged ELP block is due to effective repulsions between charged and uncharged blocks due to local charge correlation effects and, in the case of anionic ELPs, repulsion between like charges within the ELP block.

Fabrication and properties of light-emitting diodes based on self-assembled multilayers of poly(phenylene vinylene)

NASA Astrophysics Data System (ADS)

Fou, A. C.; Onitsuka, O.; Ferreira, M.; Rubner, M. F.; Hsieh, B. R.

1996-05-01

Light-emitting diodes have been fabricated from self-assembled multilayers of poly(p-phenylene vinylene) (PPV) and two different polyanions; polystyrene sulfonic acid (SPS) and polymethacrylic acid (PMA). The type of polyanion used to assemble the multilayer thin films was found to dramatically influence the behavior and performance of devices fabricated with indium tin oxide and aluminum electrodes. Light-emitting devices fabricated from PMA/PPV multilayers were found to exhibit luminance levels in the range of 20-60 cd/m2, a thickness dependent turn-on voltage and classical rectifying behavior with rectification ratios greater than 105. In sharp contrast, the devices based on SPS/PPV exhibited near symmetric current-voltage curves, thickness independent turn-on voltages and much lower luminance levels. The significant difference in device behavior observed between these two systems is primarily due to a doping effect induced either chemically or electrochemically by the sulfonic acid groups of SPS. It was also found that the performance of these devices depends on the type of layer that is in contact with the Al top electrode thereby making it possible to manipulate device efficiency at the molecular level.

Direct patterning of negative nanostructures on self-assembled monolayers of 16-mercaptohexadecanoic acid on Au(111) substrate via dip-pen nanolithography

NASA Astrophysics Data System (ADS)

Zheng, Zhikun; Yang, Menglong; Liu, Yaqing; Zhang, Bailin

2006-11-01

Both bare and self-assembled monolayer (SAM) protected gold substrate could be etched by allyl bromide according to atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS) and inductively coupled plasma mass spectrometric (ICPMS) analysis results. With this allyl bromide ink material, negative nanopatterns could be fabricated directly by dip-pen nanolithography (DPN) on SAMs of 16-mercaptohexadecanoic acid (MHA) on Au(111) substrate. A tip-promoted etching mechanism was proposed where the gold-reactive ink could penetrate the MHA resist film through tip-induced defects resulting in local corrosive removal of the gold substrate. The fabrication mechanism was also confirmed by electrochemical characterization, energy dispersive spectroscopy (EDS) analysis and fabrication of positive nanopatterns via a used DPN tip.

Nucleic acid encoding a self-assembling split-fluorescent protein system

DOEpatents

Waldo, Geoffrey S.; Cabantous, Stephanie

2014-04-01

The invention provides a protein labeling and detection system based on self-complementing fragments of fluorescent and chromophoric proteins. The system of the invention is exemplified with various combinations of self-complementing fragments derived from Aequorea victoria Green Fluorescent Protein (GFP), which are used to detect and quantify protein solubility in multiple assay formats, both in vitro and in vivo.

Nucleic acid encoding a self-assembling split-fluorescent protein system

DOEpatents

Waldo, Geoffrey S [Santa Fe, NM; Cabantous, Stephanie [Los Alamos, NM

2011-06-07

The invention provides a protein labeling and detection system based on self-complementing fragments of fluorescent and chromophoric proteins. The system of the invention is exemplified with various combinations of self-complementing fragments derived from Aequorea victoria Green Fluorescent Protein (GFP), which are used to detect and quantify protein solubility in multiple assay formats, both in vitro and in vivo.

Nucleic acid encoding a self-assembling split-fluorescent protein system

DOEpatents

Waldo, Geoffrey S.; Cabantous, Stephanie

2015-07-14

The invention provides a protein labeling and detection system based on self-complementing fragments of fluorescent and chromophoric proteins. The system of the invention is exemplified with various combinations of self-complementing fragments derived from Aequorea victoria Green Fluorescent Protein (GFP), which are used to detect and quantify protein solubility in multiple assay formats, both in vitro and in vivo.

Ionically self-assembled monolayers (ISAMs)

NASA Astrophysics Data System (ADS)

Janik, John

2001-04-01

Ionically self-assembled monolayers (ISAMs), fabricated by alternate adsorption of cationic and anionic components, yield exceptionally homogeneous thin films with sub-nanometer control of the thickness and relative special location of the component materials. Using organic electrochromic materials such as polyaniline, we report studies of electrochromic responses in ISAM films. Reversible changes in the absorption spectrum are observed with the application of voltages on the order of 1.0 V. Measurements are made using both liquid electrolytes and in all-solid state devices incorporating solid polyelectrolytes such as poly(2-acylamido 2-methyl propane sulfonic acid) (PAMPS).

Lipid-peptide-polymer conjugates and nanoparticles thereof

DOEpatents

Xu, Ting; Dong, He; Shu, Jessica

2015-06-02

The present invention provides a conjugate having a peptide with from about 10 to about 100 amino acids, wherein the peptide adopts a helical structure. The conjugate also includes a first polymer covalently linked to the peptide, and a hydrophobic moiety covalently linked to the N-terminus of the peptide, wherein the hydrophobic moiety comprises a second polymer or a lipid moiety. The present invention also provides helix bundles form by self-assembling the conjugates, and particles formed by self-assembling the helix bundles. Methods of preparing the helix bundles and particles are also provided.

Modeling the self-assembly of functionalized fullerenes on solid surfaces using Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Bubnis, Gregory J.

Since their discovery 25 years ago, carbon fullerenes have been widely studied for their unique physicochemical properties and for applications including organic electronics and photovoltaics. For these applications it is highly desirable for crystalline fullerene thin films to spontaneously self-assemble on surfaces. Accordingly, many studies have functionalized fullerenes with the aim of tailoring their intermolecular interactions and controlling interactions with the solid substrate. The success of these rational design approaches hinges on the subtle interplay of intermolecular forces and molecule-substrate interactions. Molecular modeling is well-suited to studying these interactions by directly simulating self-assembly. In this work, we consider three different fullerene functionalization approaches and for each approach we carry out Monte Carlo simulations of the self-assembly process. In all cases, we use a "coarse-grained" molecular representation that preserves the dominant physical interactions between molecules and maximizes computational efficiency. The first approach we consider is the traditional gold-thiolate SAM (self-assembled monolayer) strategy which tethers molecules to a gold substrate via covalent sulfur-gold bonds. For this we study an asymmetric fullerene thiolate bridged by a phenyl group. Clusters of 40 molecules are simulated on the Au(111) substrate at different temperatures and surface coverage densities. Fullerenes and S atoms are found to compete for Au(111) surface sites, and this competition prevents self-assembly of highly ordered monolayers. Next, we investigate self-assembled monolayers formed by fullerenes with hydrogen-bonding carboxylic acid substituents. We consider five molecules with different dimensions and symmetries. Monte Carlo cooling simulations are used to find the most stable solid structures of clusters adsorbed to Au(111). The results show cases where fullerene-Au(111) attraction, fullerene close-packing, and hydrogen-bonding interactions can cooperate to guide self-assembly or compete to hinder it. Finally, we consider three bis-fullerene molecules, each with a different "bridging group" covalently joining two fullerenes. To effectively study the competing "standing-up" and "lying-down" morphologies, we use Monte Carlo simulations in conjunction with replica exchange and force field biasing methods. For clusters adsorbed to smooth model surfaces, we determine free energy landscapes and demonstrate their utility for rationalizing and predicting self-assembly.

Solid-phase synthesis of self-assembling multivalent π-conjugated peptides

DOE PAGES

Sanders, Allix M.; Kale, Tejaswini S.; Katz, Howard E.; ...

2017-02-07

Here, we present a completely solid-phase synthetic strategy to create three- and four-fold peptide-appended π-electron molecules, where the multivalent oligopeptide presentation is dictated by the symmetries of reactive handles placed on discotic π-conjugated cores. Carboxylic acid and anhydride groups were viable amidation and imidation partners, respectively, and oligomeric π-electron discotic cores were prepared through Pd-catalyzed cross-couplings. Due to intermolecular hydrogen bonding between the three or four peptide axes, these π-peptide hybrids self-assemble into robust one-dimensional nanostructures with high aspect ratios in aqueous solution. The preparation of these systems via solid-phase methods will be detailed along with their self-assembly properties, asmore » revealed by steady-state spectroscopy and transmission electron microscopy and electrical characterization using field-effect transistor measurements.« less

Effect of Anions on Nanofiber Formation of β-sheet Propensity Amphiphile Peptide

NASA Astrophysics Data System (ADS)

Shamsudeen, H.; Tan, H. L.; Eshak, Z.

2018-05-01

Peptide self-assembly forms different nanostructures under simple alteration in the solution environment. Understanding the mechanism of the assembly will help us to control and tailor functional nanomaterials. This study aims to investigate the influence of anions on the self-assembly morphology and shape using a synthetic peptide of FFFFKK. Circular Dichoism (CD) and Environmental Scanning Electron Microscope (ESEM) were used to determine the secondary structure and self-assembly morphology, while Image J imaging software was used to measure diameter size. In the absence of anion, FFFFKK formed anti-parallel β-sheet that adopted sizeable fibrillar structure with a minimal increment over the first 7 hours of assembly. Irregular structure was observed in the presence of Iodide ion (I-) with a less stable secondary structure such as β-turn and β-loop. In the presence of perchlorate ion (ClO4 -), needle-like structure was observed with predominantly β-sheet structure. Our study showed that peptide morphology can be controlled by using different anions with careful selection of amino acid residues in peptide sequence.

The lathyrus toxin, {beta}-N-oxalyl-L-{alpha},{beta}-diaminopropionic acid (ODAP), and homocysteic acid sensitize CA1 pyramidal neurons to cystine and L-2-amino-6-phosphonohexanoic acid

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

Chase, L.A.; Peterson, N.L.; Koerner, J.F.

2007-02-15

A brief exposure of hippocampal slices to L-quisqualic acid (QUIS) sensitizes CA1 pyramidal neurons 30- to 250-fold to depolarization by certain excitatory amino acids analogues, e.g., L-2-amino-6-phosphonohexanoic acid (L-AP6), and by the endogenous compound, L-cystine. This phenomenon has been termed QUIS sensitization. A mechanism similar to that previously described for QUIS neurotoxicity has been proposed to describe QUIS sensitization. Specifically, QUIS has been shown to be sequestered into GABAergic interneurons by the System x{sub c} {sup -} and subsequently released by heteroexchange with cystine or L-AP6, resulting in activation of non-NMDA receptors. We now report two additional neurotoxins, the Lathyrusmore » excitotoxin, {beta}-N-oxalyl-L-{alpha},{beta}-diaminopropionic acid (ODAP), and the endogenous compound, L-homocysteic acid (HCA), sensitize CA1 hippocampal neurons > 50-fold to L-AP6 and > 10-fold to cystine in a manner similar to QUIS. While the cystine- or L-AP6-mediated depolarization can be inhibited by the non-NMDA receptor antagonist CNQX in ODAP- or QUIS-sensitized slices, the NMDA antagonist D-AP5 inhibits depolarization by cystine or L-AP6 in HCA-sensitized slices. Thus, HCA is the first identified NMDA agonist that induces phosphonate or cystine sensitization. Like QUIS sensitization, the sensitization evoked by either ODAP or HCA can be reversed by a subsequent exposure to 2 mM {alpha}-aminoadipic acid. Finally, we have demonstrated that there is a correlation between the potency of inducers for triggering phosphonate or cystine sensitivity and their affinities for System x{sub c} {sup -} and either the non-NMDA or NMDA receptor. Thus, the results of this study support our previous model of QUIS sensitization and have important implications for the mechanisms of neurotoxicity, neurolathyrism and hyperhomocystinemia.« less

A Novel Multi-Phosphonate Surface Treatment of Titanium Dental Implants: A Study in Sheep

PubMed Central

von Salis-Soglio, Marcella; Stübinger, Stefan; Sidler, Michéle; Klein, Karina; Ferguson, Stephen J.; Kämpf, Käthi; Zlinszky, Katalin; Buchini, Sabrina; Curno, Richard; Péchy, Péter; Aronsson, Bjorn-Owe; von Rechenberg, Brigitte

2014-01-01

The aim of the present study was to evaluate a new multi-phosphonate surface treatment (SurfLink®) in an unloaded sheep model. Treated implants were compared to control implants in terms of bone to implant contact (BIC), bone formation, and biomechanical stability. The study used two types of implants (rough or machined surface finish) each with either the multi-phosphonate Wet or Dry treatment or no treatment (control) for a total of six groups. Animals were sacrificed after 2, 8, and 52 weeks. No adverse events were observed at any time point. At two weeks, removal torque showed significantly higher values for the multi-phosphonate treated rough surface (+32% and +29%, Dry and Wet, respectively) compared to rough control. At 52 weeks, a significantly higher removal torque was observed for the multi-phosphonate treated machined surfaces (+37% and 23%, Dry and Wet, respectively). The multi-phosphonate treated groups showed a positive tendency for higher BIC with time and increased new-old bone ratio at eight weeks. SEM images revealed greater amounts of organic materials on the multi-phosphonate treated compared to control implants, with the bone fracture (from the torque test) appearing within the bone rather than at the bone to implant interface as it occurred for control implants. PMID:25215424

Direct observation of ultrafast coherent exciton dynamics in helical π-stacks of self-assembled perylene bisimides

PubMed Central

Sung, Jooyoung; Kim, Pyosang; Fimmel, Benjamin; Würthner, Frank; Kim, Dongho

2015-01-01

Ever since the discovery of dye self-assemblies in nature, there have been tremendous efforts to exploit biomimetic supramolecular assemblies for tailored artificial photon processing materials. This feature necessarily has resulted in an increasing demand for understanding exciton dynamics in the dye self-assemblies. In a sharp contrast with J-type aggregates, however, the detailed observation of exciton dynamics in H-type aggregates has remained challenging. In this study, as we succeed in measuring transient fluorescence from Frenkel state of π-stacked perylene tetracarboxylic acid bisimide dimer and oligomer aggregates, we present an experimental demonstration on Frenkel exciton dynamics of archetypal columnar π–π stacks of dyes. The analysis of the vibronic peak ratio of the transient fluorescence spectra reveals that unlike the simple π-stacked dimer, the photoexcitation energy in the columnar π-stacked oligomer aggregates is initially delocalized over at least three molecular units and moves coherently along the chain in tens of femtoseconds, preceding excimer formation process. PMID:26492820

Self-assembly behaviours of peptide-drug conjugates: influence of multiple factors on aggregate morphology and potential self-assembly mechanism

NASA Astrophysics Data System (ADS)

Fan, Qin; Ji, Yujie; Wang, Jingjing; Wu, Li; Li, Weidong; Chen, Rui; Chen, Zhipeng

2018-04-01

Peptide-drug conjugates (PDCs) as self-assembly prodrugs have the unique and specific features to build one-component nanomedicines. Supramolecular structure based on PDCs could form various morphologies ranging from nanotube, nanofibre, nanobelt to hydrogel. However, the assembly process of PDCs is too complex to predict or control. Herein, we investigated the effects of extrinsic factors on assembly morphology and the possible formation of nanostructures based on PDCs. To this end, we designed a PDC consisting of hydrophobic drug (S)-ketoprofen (Ket) and valine-glutamic acid dimeric repeats peptide (L-VEVE) to study their assembly behaviour. Our results showed that the critical assembly concentration of Ket-L-VEVE was 0.32 mM in water to form various nanostructures which experienced from micelle, nanorod, nanofibre to nanoribbon. The morphology was influenced by multiple factors including molecular design, assembly time, pH and hydrogen bond inhibitor. On the basis of experimental results, we speculated the possible assembly mechanism of Ket-L-VEVE. The π-π stacking interaction between Ket molecules could serve as an anchor, and hydrogen bonded-induced β-sheets and hydrophilic/hydrophobic balance between L-VEVE peptide play structure-directing role in forming filament-like or nanoribbon morphology. This work provides a new sight to rationally design and precisely control the nanostructure of PDCs based on aromatic fragment.

Self-assembly behaviours of peptide-drug conjugates: influence of multiple factors on aggregate morphology and potential self-assembly mechanism.

PubMed

Fan, Qin; Ji, Yujie; Wang, Jingjing; Wu, Li; Li, Weidong; Chen, Rui; Chen, Zhipeng

2018-04-01

Peptide-drug conjugates (PDCs) as self-assembly prodrugs have the unique and specific features to build one-component nanomedicines. Supramolecular structure based on PDCs could form various morphologies ranging from nanotube, nanofibre, nanobelt to hydrogel. However, the assembly process of PDCs is too complex to predict or control. Herein, we investigated the effects of extrinsic factors on assembly morphology and the possible formation of nanostructures based on PDCs. To this end, we designed a PDC consisting of hydrophobic drug ( S )-ketoprofen (Ket) and valine-glutamic acid dimeric repeats peptide (L-VEVE) to study their assembly behaviour. Our results showed that the critical assembly concentration of Ket-L-VEVE was 0.32 mM in water to form various nanostructures which experienced from micelle, nanorod, nanofibre to nanoribbon. The morphology was influenced by multiple factors including molecular design, assembly time, pH and hydrogen bond inhibitor. On the basis of experimental results, we speculated the possible assembly mechanism of Ket-L-VEVE. The π-π stacking interaction between Ket molecules could serve as an anchor, and hydrogen bonded-induced β-sheets and hydrophilic/hydrophobic balance between L-VEVE peptide play structure-directing role in forming filament-like or nanoribbon morphology. This work provides a new sight to rationally design and precisely control the nanostructure of PDCs based on aromatic fragment.

Titanium Surface Priming with Phase-Transited Lysozyme to Establish a Silver Nanoparticle-Loaded Chitosan/Hyaluronic Acid Antibacterial Multilayer via Layer-by-Layer Self-Assembly.

PubMed

Zhong, Xue; Song, Yunjia; Yang, Peng; Wang, Yao; Jiang, Shaoyun; Zhang, Xu; Li, Changyi

2016-01-01

The formation of biofilm around implants, which is induced by immediate bacterial colonization after installation, is the primary cause of post-operation infection. Initial surface modification is usually required to incorporate antibacterial agents on titanium (Ti) surfaces to inhibit biofilm formation. However, simple and effective priming methods are still lacking for the development of an initial functional layer as a base for subsequent coatings on titanium surfaces. The purpose of our work was to establish a novel initial layer on Ti surfaces using phase-transited lysozyme (PTL), on which multilayer coatings can incorporate silver nanoparticles (AgNP) using chitosan (CS) and hyaluronic acid (HA) via a layer-by-layer (LbL) self-assembly technique. In this study, the surfaces of Ti substrates were primed by dipping into a mixture of lysozyme and tris(2-carboxyethyl)phosphine (TCEP) to obtain PTL-functionalized Ti substrates. The subsequent alternating coatings of HA and chitosan loaded with AgNP onto the precursor layer of PTL were carried out via LbL self-assembly to construct multilayer coatings on Ti substrates. The results of SEM and XPS indicated that the necklace-like PTL and self-assembled multilayer were successfully immobilized on the Ti substrates. The multilayer coatings loaded with AgNP can kill planktonic and adherent bacteria to 100% during the first 4 days. The antibacterial efficacy of the samples against planktonic and adherent bacteria achieved 65%-90% after 14 days. The sustained release of Ag over 14 days can prevent bacterial invasion until mucosa healing. Although the AgNP-containing structure showed some cytotoxicity, the toxicity can be reduced by controlling the Ag release rate and concentration. The PTL priming method provides a promising strategy for fabricating long-term antibacterial multilayer coatings on titanium surfaces via the LbL self-assembly technique, which is effective in preventing implant-associated infections in the early stage.

Formation of hexagonal boron nitride nanoscrolls induced by inclusion and exclusion of self-assembling molecules in solution process

NASA Astrophysics Data System (ADS)

Hwang, Da Young; Suh, Dong Hack

2014-05-01

Unlike nanoscrolls of 2D graphene, those of 2D h-BN have not been demonstrated, except for only a few experimental reports. Nanoscrolls of h-BN with high yields and reproducibility are first synthesized by a simple solution process. Inner-tube diameters of BNSs including LCAs, N-(2-aminoethyl)-3α-hydroxy-5β-cholan-24-amide, a bile acid derivative and self-assembling material, can be controlled by adjusting the diameter of the LCA fiber which is grown by self-assembly. TEM and SEM images show that BNSs have a tube-like morphology and the inner-tube diameter of BNSs can be controlled in the range from 20 to 60 nm for a smaller diameter, up to 300 nm for a larger diameter by LCA fiber growth inside the BNSs. Finally, open cylindrical BNSs with hollow cores were obtained by dissolving LCAs inside BNSs.Unlike nanoscrolls of 2D graphene, those of 2D h-BN have not been demonstrated, except for only a few experimental reports. Nanoscrolls of h-BN with high yields and reproducibility are first synthesized by a simple solution process. Inner-tube diameters of BNSs including LCAs, N-(2-aminoethyl)-3α-hydroxy-5β-cholan-24-amide, a bile acid derivative and self-assembling material, can be controlled by adjusting the diameter of the LCA fiber which is grown by self-assembly. TEM and SEM images show that BNSs have a tube-like morphology and the inner-tube diameter of BNSs can be controlled in the range from 20 to 60 nm for a smaller diameter, up to 300 nm for a larger diameter by LCA fiber growth inside the BNSs. Finally, open cylindrical BNSs with hollow cores were obtained by dissolving LCAs inside BNSs. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr00897a

Probing the interaction of U (VI) with phosphonate-functionalized mesoporous silica using solid-state NMR spectroscopy

DOE PAGES

Uribe, Eva C.; Mason, Harris E.; Shusterman, Jennifer A.; ...

2016-05-30

The fundamental interaction of U (VI) with diethylphosphatoethyl triethoxysilane functionalized SBA-15 mesoporous silica is studied by macroscopic batch experiments and solid-state NMR spectroscopy. DPTS-functionalized silica has been shown to extract U (VI) from nitric acid solutions at or above pH 3. Extraction is dependent on pH and ionic strength. Single-pulse 31P NMR on U (VI) contacted samples revealed that U (VI)only interacts with a fraction of the ligands present on the surface. At pH 4 the U (VI) extraction capacity of the material is limited to 27–37% of the theoretical capacity, based on ligand loading. We combined single pulse 31Pmore » NMR on U (VI)-contacted samples with batch studies to measure a ligand-to-metal ratio of approximately 2 : 1 at pH 3 and 4. Batch studies and cross-polarization NMR measurements reveal that U (VI) binds to deprotonated phosphonate and/or silanol sites. We use 31P– 31P DQ-DRENAR NMR studies to compare the average dipolar coupling between phosphorus spins for both U (VI)-complexed and non-complexed ligand environments. Furthermore, these measurements reveal that U (VI) extraction is not limited by inadequate surface distribution of ligands, but rather by low stability of the surface phosphonate complex.« less

Structure of complexes of nitrilo tris methylene phosphonic acid with copper, [CuN(CH{sub 2}PO{sub 3}){sub 3}(H{sub 2}O){sub 3}] and Na{sub 4}[CuN(CH{sub 2}PO{sub 3}){sub 3}]{sub 2} · 19H{sub 2}O, as bactericides and inhibitors of scaling and corrosion

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

Somov, N. V., E-mail: somov@phys.unn.ru; Chausov, F. F., E-mail: chaus@uni.udm.ru

2015-03-15

Nitrilotris methylene phosphonate triaqua copper and octasodium bis(nitrilotris methylene phosphonate cuprate(II)) nonadecahydrate have been synthesized and investigated. [CuN(CH{sub 2}PO{sub 3}){sub 3}(H{sub 2}O){sub 3}] is crystallized in the sp. gr. P2{sub 1}/c, Z = 4, a = 9.2506(2) Å, b = 15.9815(2) Å, c = 9.5474(2) Å, β = 113.697(2)°. The copper atom is coordinated by oxygen atoms in the configuration of elongated octahedron; the ligand (of bridge type) links neighboring copper atoms. Na{sub 8}[CuN(CH{sub 2}PO{sub 3}){sub 3}]{sub 2} · 19H{sub 2}O is crystallized in the sp. gr. P2{sub 1}/c, Z = 2, a = 11.24550(10) Å, b = 17.38980(10) Å,more » c = 13.5852(2) Å, β = 127.8120(10)°. This complex is chelating; the copper atom closes three five-membered N-C-P-O-Cu cycles with a shared Cu-N bond. Copper is coordinated in a distorted trigonal-bipyramidal configuration.« less

Probing the interaction of U (VI) with phosphonate-functionalized mesoporous silica using solid-state NMR spectroscopy

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

Uribe, Eva C.; Mason, Harris E.; Shusterman, Jennifer A.

The fundamental interaction of U (VI) with diethylphosphatoethyl triethoxysilane functionalized SBA-15 mesoporous silica is studied by macroscopic batch experiments and solid-state NMR spectroscopy. DPTS-functionalized silica has been shown to extract U (VI) from nitric acid solutions at or above pH 3. Extraction is dependent on pH and ionic strength. Single-pulse 31P NMR on U (VI) contacted samples revealed that U (VI)only interacts with a fraction of the ligands present on the surface. At pH 4 the U (VI) extraction capacity of the material is limited to 27–37% of the theoretical capacity, based on ligand loading. We combined single pulse 31Pmore » NMR on U (VI)-contacted samples with batch studies to measure a ligand-to-metal ratio of approximately 2 : 1 at pH 3 and 4. Batch studies and cross-polarization NMR measurements reveal that U (VI) binds to deprotonated phosphonate and/or silanol sites. We use 31P– 31P DQ-DRENAR NMR studies to compare the average dipolar coupling between phosphorus spins for both U (VI)-complexed and non-complexed ligand environments. Furthermore, these measurements reveal that U (VI) extraction is not limited by inadequate surface distribution of ligands, but rather by low stability of the surface phosphonate complex.« less

Effect of noncovalent interaction on the self-assembly of a designed peptide and its potential use as a carrier for controlled bFGF release

PubMed Central

Liu, Yanfei; Zhang, Ling; Wei, Wei

2017-01-01

Peptide self-assembly is one of the promising bottom-up approaches for creating synthetic supermolecular architectures. Noncovalent interactions such as hydrophobic packing, electrostatic interaction, and polypeptide chain entropy (ΔSC) are the most relevant factors that affect the folding and self-assembly of peptides and the stability of supermolecular structures. The GVGV tetrapeptide is an abundant repeat in elastin, an extracellular matrix protein. In this study, four GVGV-containing peptides were designed with the aim of understanding the effects of these weak interactions on peptide self-assembly. Transmission electron microscopy, circular dichroism spectroscopy, dynamic light scattering measurements, and rheometry assays were used to study the structural features of the peptides. Because self-assembling peptides with different amino acid sequences may significantly affect protein release, basic fibroblast growth factor (bFGF) was used as a model molecule and encapsulated within the P2 (RLDLGVGVRLDLGVGV) hydrogel to study the release kinetics. The results showed that the balance among hydrophobic effects, electrostatic interactions, and chain entropy determined the molecular state and self-assembly of the peptide. Moreover, encapsulation of bFGF within the P2 hydrogel allowed its sustained release without causing changes in the secondary structure. The release profiles could be tuned by adjusting the P2 hydrogel concentration. Cell Counting Kit-8 and Western blot assays demonstrated that the encapsulated and released bFGFs were biologically active and capable of promoting the proliferation of murine fibroblast NIH-3T3 cells, most likely due to the activation of downstream signaling pathways. PMID:28176898

Key aromatic/hydrophobic amino acids controlling a cross-amyloid peptide interaction versus amyloid self-assembly.

PubMed

Bakou, Maria; Hille, Kathleen; Kracklauer, Michael; Spanopoulou, Anna; Frost, Christina V; Malideli, Eleni; Yan, Li-Mei; Caporale, Andrea; Zacharias, Martin; Kapurniotu, Aphrodite

2017-09-01

The interaction of the intrinsically disordered polypeptide islet amyloid polypeptide (IAPP), which is associated with type 2 diabetes (T2D), with the Alzheimer's disease amyloid-β (Aβ) peptide modulates their self-assembly into amyloid fibrils and may link the pathogeneses of these two cell-degenerative diseases. However, the molecular determinants of this interaction remain elusive. Using a systematic alanine scan approach, fluorescence spectroscopy, and other biophysical methods, including heterocomplex pulldown assays, far-UV CD spectroscopy, the thioflavin T binding assay, transmission EM, and molecular dynamics simulations, here we identified single aromatic/hydrophobic residues within the amyloid core IAPP region as hot spots or key residues of its cross-interaction with Aβ40(42) peptide. Importantly, we also find that none of these residues in isolation plays a key role in IAPP self-assembly, whereas simultaneous substitution of four aromatic/hydrophobic residues with Ala dramatically impairs both IAPP self-assembly and hetero-assembly with Aβ40(42). Furthermore, our experiments yielded several novel IAPP analogs, whose sequences are highly similar to that of IAPP but have distinct amyloid self- or cross-interaction potentials. The identified similarities and major differences controlling IAPP cross-peptide interaction with Aβ40(42) versus its amyloid self-assembly offer a molecular basis for understanding the underlying mechanisms. We propose that these insights will aid in designing intervention strategies and novel IAPP analogs for the management of type 2 diabetes, Alzheimer's disease, or other diseases related to IAPP dysfunction or cross-amyloid interactions. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

An aqueous, organic dye derivatized SnO 2 /TiO 2 core/shell photoanode

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

Wee, Kyung-Ryang; Sherman, Benjamin D.; Brennaman, M. Kyle

2016-01-01

Visible light driven water splitting in a dye-sensitized photoelectrochemical cell (DSPEC) based on a phosphonic acid-derivatized donor–π–acceptor (D–π–A) organic dye (P–A–π–D) is described with the dye anchored to an FTO|SnO 2/TiO 2core/shell photoanode in a pH 7 phosphate buffer solution.

Design of pH-sensitive methotrexate prodrug-targeted curcumin nanoparticles for efficient dual-drug delivery and combination cancer therapy.

PubMed

Xie, Jiajiang; Fan, Zhongxiong; Li, Yang; Zhang, Yinying; Yu, Fei; Su, Guanghao; Xie, Liya; Hou, Zhenqing

2018-01-01

We designed acid-labile methotrexate (MTX) targeting prodrug self-assembling nanoparticles loaded with curcumin (CUR) drug for simultaneous delivery of multi-chemotherapeutic drugs and combination cancer therapy. A dual-acting MTX, acting as both an anticancer drug and as a tumor-targeting ligand, was coupled to 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[aldehyde(polyethylene glycol)-2000] via Schiff's base reaction. The synthesized prodrug conjugate (DSPE-PEG-Imine-MTX) could be self-assembled into micellar nanoparticles (MTX-Imine-M) in aqueous solution, which encapsulated CUR into their core by hydrophobic interactions (MTX-Imine-M-CUR). The prepared MTX-Imine-M-CUR nanoparticles were composed of an inner hydrophobic DSPE/CUR core and an outside hydrophilic bishydroxyl poly (ethyleneglycol) (PEG) shell with a self-targeting MTX prodrug corona. The imine linker between 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[aldehyde(polyethyleneglycol)-2000] and MTX, as a dynamic covalent bond, was strong enough to remain intact in physiological pH, even though it is rapidly cleaved in acidic pH. The MTX-Imine-M-CUR could codeliver MTX and CUR selectively and efficiently into the cancer cells via folate receptor-mediated endocytosis followed by the rapid intracellular release of CUR and the active form of MTX via the acidity of endosomes/lysosomes. Moreover, the MTX-Imine-M-CUR resulted in significantly higher in vitro and in vivo anticancer activity than pH-insensitive DSPE-PEGAmide-MTX assembling nanoparticles loaded with CUR (MTX-Amide-M-CUR), MTX unconjugated DSPE-PEG assembling micellar nanoparticles loaded with CUR (M-CUR), combination of both free drugs, and individual free drugs. The smart system provided a simple, yet feasible, drug delivery strategy for targeted combination chemotherapy.

New biosensing platforms based on the layer-by-layer self-assembling of polyelectrolytes on Nafion/carbon nanotubes-coated glassy carbon electrodes.

PubMed

Rivas, Gustavo A; Miscoria, Silvia A; Desbrieres, Jacques; Barrera, Gustavo D

2007-01-15

We are proposing for the first time the use of a Nafion/multi-walled carbon nanotubes dispersion deposited on glassy carbon electrodes (GCE) as a new platform for developing enzymatic biosensors based on the self-assembling of a chitosan derivative and different oxidases. The electrodes are obtained by deposition of a layer of Nafion/multi-wall carbon nanotubes dispersion on glassy carbon electrodes, followed by the adsorption of a chitosan derivative as polycation and glucose oxidase, l-aminoacid oxidase or polyphenol oxidase, as polyanions and biorecognition elements. The optimum configuration for glucose biosensors has allowed a highly sensitive (sensitivity=(0.28+/-0.02)muAmM(-1), r=0.997), fast (4s in reaching the maximum response), and highly selective (0% interference of ascorbic acid and uric acid at maximum physiological levels) glucose quantification at 0.700V with detection and quantification limits of 0.035 and 0.107mM, respectively. The repetitivity for 10 measurements was 5.5%, while the reproducibility was 8.4% for eight electrodes. The potentiality of the new platform was clearly demonstrated by using the carbon nanotubes/Nafion layer as a platform for the self-assembling of l-aminoacid oxidase and polyphenol oxidase. Therefore, the platform we are proposing here, that combines the advantages of nanostructured materials with those of the layer-by-layer self-assembling of polyelectrolytes, opens the doors to new and exciting possibilities for the development of enzymatic and affinity biosensors using different transdution modes.

Intracellular self-assembly based multi-labeling of key viral components: Envelope, capsid and nucleic acids.

PubMed

Wen, Li; Lin, Yi; Zhang, Zhi-Ling; Lu, Wen; Lv, Cheng; Chen, Zhi-Liang; Wang, Han-Zhong; Pang, Dai-Wen

2016-08-01

Envelope, capsid and nucleic acids are key viral components that are all involved in crucial events during virus infection. Thus simultaneous labeling of these key components is an indispensable prerequisite for monitoring comprehensive virus infection process and dissecting virus infection mechanism. Baculovirus was genetically tagged with biotin on its envelope protein GP64 and enhanced green fluorescent protein (EGFP) on its capsid protein VP39. Spodoptera frugiperda 9 (Sf9) cells were infected by the recombinant baculovirus and subsequently fed with streptavidin-conjugated quantum dots (SA-QDs) and cell-permeable nucleic acids dye SYTO 82. Just by genetic engineering and virus propagation, multi-labeling of envelope, capsid and nucleic acids was spontaneously accomplished during virus inherent self-assembly process, significantly simplifying the labeling process while maintaining virus infectivity. Intracellular dissociation and transportation of all the key viral components, which was barely reported previously, was real-time monitored based on the multi-labeling approach, offering opportunities for deeply understanding virus infection and developing anti-virus treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Self-assembled polymeric nanoparticles as new, smart contrast agents for cancer early detection using magnetic resonance imaging.

PubMed

Mouffouk, Fouzi; Simão, Teresa; Dornelles, Daniel F; Lopes, André D; Sau, Pablo; Martins, Jorge; Abu-Salah, Khalid M; Alrokayan, Salman A; Rosa da Costa, Ana M; dos Santos, Nuno R

2015-01-01

Early cancer detection is a major factor in the reduction of mortality and cancer management cost. Here we developed a smart and targeted micelle-based contrast agent for magnetic resonance imaging (MRI), able to turn on its imaging capability in the presence of acidic cancer tissues. This smart contrast agent consists of pH-sensitive polymeric micelles formed by self-assembly of a diblock copolymer (poly(ethyleneglycol-b-trimethylsilyl methacrylate)), loaded with a gadolinium hydrophobic complex ((t)BuBipyGd) and exploits the acidic pH in cancer tissues. In vitro MRI experiments showed that (t)BuBipyGd-loaded micelles were pH-sensitive, as they turned on their imaging capability only in an acidic microenvironment. The micelle-targeting ability toward cancer cells was enhanced by conjugation with an antibody against the MUC1 protein. The ability of our antibody-decorated micelles to be switched on in acidic microenvironments and to target cancer cells expressing specific antigens, together with its high Gd(III) content and its small size (35-40 nm) reveals their potential use for early cancer detection by MRI.

Self-Assembly of Helical Ribbons

DTIC Science & Technology

1999-07-01

detergent, a phosphatidylcholine or a fatty acid , and a steroid analog of cholesterol. In almost all systems, two different pitch types of helical...quater- nary sterol systems (QSS), on a quaternary fatty acid system (QFAS), and on two lipid concentrate systems, as defined below. In addition to high...lipid concentrate; QSS, quaternary sterol systems; QFAS, quaternary fatty acid system; NaTC, sodium taurocholate; DOPC, 1,2-dioleoyl-glycero- 3

pH-programmable self-assembly of plasmonic nanoparticles: hydrophobic interaction versus electrostatic repulsion.

PubMed

Li, Weikun; Kanyo, Istvan; Kuo, Chung-Hao; Thanneeru, Srinivas; He, Jie

2015-01-21

We report a general strategy to conceptualize a new design for the pH-programmable self-assembly of plasmonic gold nanoparticles (AuNPs) tethered by random copolymers of poly(styrene-co-acrylic acid) (P(St-co-AA)). It is based on using pH as an external stimulus to reversibly change the surface charge of polymer tethers and to control the delicate balance of interparticle attractive and repulsive interactions. By incorporating -COOH moieties locally within PSt hydrophobic segments, the change in the ionization degree of -COOH moieties can dramatically disrupt the hydrophobic attraction within a close distance. pH acts as a key parameter to control the deprotonation of -COOH moieties and "programs" the assembled nanostructures of plasmonic nanoparticles in a stepwise manner. At a higher solution pH where -COOH groups of polymer tethers became highly deprotonated, electrostatic repulsion dominated the self-assembly and favored the formation of end-to-end, anisotropic assemblies, e.g. 1-D single-line chains. At a lower pH, the less deprotonated -COOH groups led to the decrease of electrostatic repulsion and the side-to-side aggregates, e.g. clusters and multi-line chains of AuNPs, became favorable. The pH-programmable self-assembly allowed us to engineer a "manual" program for a sequential self-assembly by changing the pH of the solution. We demonstrated that the two-step pH-programmable assembly could generate more sophisticated "multi-block" chains using two differently sized AuNPs. Our strategy offers a general means for the programmable design of plasmonic nanoparticles into the specific pre-ordained nanostructures that are potentially useful for the precise control over their plasmon coupling.

Physicochemical characterization of cellulose nanocrystal and nanoporous self-assembled CNC membrane derived from Ceiba pentandra.

PubMed

Mohamed, Mohamad Azuwa; W Salleh, W N; Jaafar, Juhana; Ismail, A F; Abd Mutalib, Muhazri; Mohamad, Abu Bakar; M Zain, M F; Awang, Nor Asikin; Mohd Hir, Zul Adlan

2017-02-10

This research involves the rare utilisation of the kapok fibre (Ceiba pentandra) as a raw material for the fabrication of cellulose nanocrystal (CNC) and self-assembled CNC membranes. The isolation of CNC from Ceiba pentandra began with the extraction of cellulose via the chemical alkali extraction by using 5wt% NaOH, followed by the typical acidified bleaching method and, finally, the CNC production through acid hydrolysis with 60wt% H 2 SO 4 at the optimum time of 60min. The prepared CNC was then employed for the preparation of self-assembled membrane through the water suspension casting evaporation technique. The obtained CNC membrane was characterised in terms of its composition, crystallinity, thermal stability, as well as, structural and morphological features with the use of several techniques including FTIR, XRD, AFM, TEM, FESEM, and TGA. The FESEM and AFM analyses had illustrated the achievement of a self-assembled CNC membrane with a smooth surface and a well-distributed nano-porous structure, with the porosity of 52.82±7.79%. In addition, the findings proved that the self-assembled CNC membrane displayed good adsorption capability indicated by the recorded efficiency of 79% and 85% for 10mg/L and 5mg/L of methylene blue in an aqueous solution, respectively. Copyright © 2016 Elsevier Ltd. All rights reserved.

Functional nanocomposites prepared by self-assembly and polymerization of diacetylene surfactants and silicic acid

NASA Technical Reports Server (NTRS)

Yang, Yi; Lu, Yunfeng; Lu, Mengcheng; Huang, Jinman; Haddad, Raid; Xomeritakis, George; Liu, Nanguo; Malanoski, Anthony P.; Sturmayr, Dietmar; Fan, Hongyou;

Self-Assembly Assisted Fabrication of Dextran-Based Nanohydrogels with Reduction-Cleavable Junctions for Applications as Efficient Drug Delivery Systems

PubMed Central

Wang, Hao; Dai, Tingting; Zhou, Shuyan; Huang, Xiaoxiao; Li, Songying; Sun, Kang; Zhou, Guangdong; Dou, Hongjing

2017-01-01

In order to overcome the key challenge in improving both fabrication efficiency and their drug delivery capability of anti-cancer drug delivery systems (ACDDS), here polyacrylic acid (PAA) grafted dextran (Dex) nanohydrogels (NGs) with covalent crosslinked structure bearing redox sensitive disulfide crosslinking junctions (Dex-SS-PAA) were synthesized efficiently through a one-step self-assembly assisted methodology (SAA). The Dex-SS-PAA were subsequently conjugated with doxorubicin through an acid-labile hydrazone bond (Dex-SS-PAA-DOX). The in vitro drug release behavior, anti-cancer effects in vivo, and biosafety of the as-prepared acid- and redox-dual responsive biodegradable NGs were systematically investigated. The results revealed that the Dex-SS-PAA-DOX exhibited pH- and redox-controlled drug release, greatly reduced the toxicity of free DOX, while exhibiting a strong ability to inhibit the growth of MDA-MB-231 tumors. Our study demonstrated that the Dex-SS-PAA-DOX NGs are very promising candidates as ACDDS for anti-cancer therapeutics. PMID:28071743

Characterization of self assembly layers of octadecanephosphonic acid by polarisation modulation FT-IRRA spectroscopy mapping

NASA Astrophysics Data System (ADS)

Steiner, G.; Sablinskas, V.; Savchuk, O.; Bariseviciute, R.; Jähne, E.; Adler, H. J.; Salzer, R.

2003-12-01

Self assembly layers were studied by a polarization modulation FT-spectroscopy mapping technique. The optical lay out is based on polarization modulation FT infrared reflection absorption spectroscopy (PM-FT-IRRAS). Here we report for the first time on a PM-FT-IRRAS mapping instrument. Octadecanephosphonic acid adsorbed on a patterned aluminum/gold surface was investigated. The nature of chemical bonding at particular surface areas was evaluated by principal component analysis. The most prominent features of the PM-FT-IRRA spectra are the P-O and PO stretching vibrations. It is shown that octadecanephosphonic acid is adsorbed both on Al 2O 3 and on Au. Moreover, PM-FT-IRRAS maps reveal areas of non-equivalent structural features. Lateral dimensions of these areas are in the micrometer range. Such non-equivalencies may control the inhibition potential of SAMs on ignoble metals, hence become crucial to the quality of products as biosensors or microelectronic components.

Crosslinked self-assemblies of lipoid acid-substituted low molecular weight (1800 Da) polyethylenimine as reductive-sensitive non-viral gene vectors

NASA Astrophysics Data System (ADS)

Chen, Xiaojiao; Yuan, Zhefan; Yi, Xiaoqing; Zhuo, Renxi; Li, Feng

2012-10-01

In this study, amphiphilic polyethylenimine-graft-thioctic acid (PEI-TA) and polyethylenimine-graft-lauric acid (PEI-LA) were synthesized. Both PEI-TA and PEI-LA could self-assemble into micelles. Due to the existence of disulfide-linked rings at the end of hydrophobic moieties, PEI-TA could form stable micelles with disulfide crosslinked cores (PEI-TA-SS). In comparison with the PEI-LA micelle, PEI-TA-SS possessed higher DNA binding ability according to the gel retardation assay and heparin replacement assay. In vitro transfection experiments indicated that PEI-TA-SS showed comparably high transfection efficiency as compared to 25 kDa PEI. More interestingly, the luciferase expression of PEI-TA-SS was superior to that of PEI-LA at low N/P ratio, which might be ascribed to the stronger binding capacity of PEI-TA-SS facilitating the entering of PEI-TA-SS/pDNA complexes into cells.

Self-Assembly Assisted Fabrication of Dextran-Based Nanohydrogels with Reduction-Cleavable Junctions for Applications as Efficient Drug Delivery Systems

NASA Astrophysics Data System (ADS)

Wang, Hao; Dai, Tingting; Zhou, Shuyan; Huang, Xiaoxiao; Li, Songying; Sun, Kang; Zhou, Guangdong; Dou, Hongjing

2017-01-01

In order to overcome the key challenge in improving both fabrication efficiency and their drug delivery capability of anti-cancer drug delivery systems (ACDDS), here polyacrylic acid (PAA) grafted dextran (Dex) nanohydrogels (NGs) with covalent crosslinked structure bearing redox sensitive disulfide crosslinking junctions (Dex-SS-PAA) were synthesized efficiently through a one-step self-assembly assisted methodology (SAA). The Dex-SS-PAA were subsequently conjugated with doxorubicin through an acid-labile hydrazone bond (Dex-SS-PAA-DOX). The in vitro drug release behavior, anti-cancer effects in vivo, and biosafety of the as-prepared acid- and redox-dual responsive biodegradable NGs were systematically investigated. The results revealed that the Dex-SS-PAA-DOX exhibited pH- and redox-controlled drug release, greatly reduced the toxicity of free DOX, while exhibiting a strong ability to inhibit the growth of MDA-MB-231 tumors. Our study demonstrated that the Dex-SS-PAA-DOX NGs are very promising candidates as ACDDS for anti-cancer therapeutics.

Self-assembly of a double-helical complex of sodium.

PubMed

Bell, T W; Jousselin, H

1994-02-03

Spontaneous self-organization of helical and multiple-helical molecular structures occurs on several levels in living organisms. Key examples are alpha-helical polypeptides, double-helical nucleic acids and helical protein structures, including F-actin, microtubules and the protein sheath of the tobacco mosaic virus. Although the self-assembly of double-helical transition-metal complexes bears some resemblance to the molecular organization of double-stranded DNA, selection between monohelical, double-helical and triple-helical structures is determined largely by the size and geometrical preference of the tightly bound metal. Here we present an example of double-helical assembly induced by the weaker and non-directional interactions of an alkali-metal ion with an organic ligand that is pre-organized into a coil. We have characterized the resulting complex by two-dimensional NMR and fast-atom-bombardment mass spectrometry. These results provide a step toward the creation of molecular tubes or ion channels consisting of intertwined coils.

Self-Assembly of Narrowly Dispersed Brush Diblock Copolymers with Domain Spacing more than 100 nm

NASA Astrophysics Data System (ADS)

Gu, Weiyin; Sveinbjornsson, Benjamin; Hong, Sung Woo; Grubbs, Robert; Russell, Thomas

2012-02-01

Self-assembled structures of high molecular weight (MW), narrow molecular weight distribution brush block copolymers containing polylactic acid (PLA) and polystyrene (PS) side chains with similar MWs were studied in both the melt and thin films. The polynorbornene-backbone-based brush diblock copolymers containing approximately equal volume fractions of each block self-assembled into highly ordered lamellae with domain spacing over 100 nm, as revealed by SAXS, GISAXS and AFM. The domain size increased approximately linearly with backbone length, which indicated an extended conformation of the backbone in the ordered state. The length of side chains also played a significant role in terms of controlling the domain size. As the degree of polymerization (DP) increased, the symmetric brush diblock copolymers with longer side chains tended to form larger lamellar microdomains in comparison to those that have the same DP but shorter side chains.

Formation of hexagonal boron nitride nanoscrolls induced by inclusion and exclusion of self-assembling molecules in solution process.

PubMed

Hwang, Da Young; Suh, Dong Hack

2014-06-07

Unlike nanoscrolls of 2D graphene, those of 2D h-BN have not been demonstrated, except for only a few experimental reports. Nanoscrolls of h-BN with high yields and reproducibility are first synthesized by a simple solution process. Inner-tube diameters of BNSs including LCAs, N-(2-aminoethyl)-3α-hydroxy-5β-cholan-24-amide, a bile acid derivative and self-assembling material, can be controlled by adjusting the diameter of the LCA fiber which is grown by self-assembly. TEM and SEM images show that BNSs have a tube-like morphology and the inner-tube diameter of BNSs can be controlled in the range from 20 to 60 nm for a smaller diameter, up to 300 nm for a larger diameter by LCA fiber growth inside the BNSs. Finally, open cylindrical BNSs with hollow cores were obtained by dissolving LCAs inside BNSs.

Facile synthesis of self-assembled biporous NiO and its electrochemical properties

NASA Astrophysics Data System (ADS)

Muruganandham, M.; Suri, Rominder P. S.; Sillanpää, Mika; Lee, Gang-Juan; Wu, Jerry J.

2016-09-01

In this article, we report the synthesis of self-assembled bi-porous nickel oxide on a large scale without using any templates or matrix. Porous NiO microspheres composed of particles were obtained by thermal decomposition of nickel oxalate, which was prepared using nickel salt and oxalic acid as precursors. The as-obtained nickel oxalate and nickel oxide were characterized using X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), thermogravimetric analysis (TGA), and nitrogen adsorption-desorption analysis. The influence of various experimental conditions on the formation nickel oxalate and NiO were studied. The nitrogen adsorption-desorption analysis showed that the synthesized NiO possesses a biporous (both mesoporous and macroporous) surface structur. The NiO microspheres showed a discharge capacity of 2929 mAh g-1. A plausible mechanism for the NiO self-assembly was proposed.

Self-assembly of nitrogen-doped carbon nanoparticles: a new ratiometric UV-vis optical sensor for the highly sensitive and selective detection of Hg(2+) in aqueous solution.

PubMed

Ruan, Yudi; Wu, Lie; Jiang, Xiue

2016-05-23

Water-soluble nitrogen-doped carbon nanoparticles (N-CNPs) prepared by the one-step hydrothermal treatment of uric acid were found to show ratiometric changes in their UV-vis spectra due to Hg(2+)-mediated self-assembly. For the first time, such a property was developed into a UV-vis optical sensor for detecting Hg(2+) in aqueous solutions with high sensitively and selectively (detection limit = 1.4 nM). More importantly, this novel sensor exhibits a higher linear sensitivity over a wider concentration range compared with the fluorescence sensor based on the same N-CNPs. This work opens an exciting new avenue to explore the use of carbon nanoparticles in constructing UV-vis optical sensors for the detection of metal ions and the use of carbon nanoparticles as a new building block to self-assemble into superlattices.

High yield recombinant production of a self-assembling polycationic peptide for silica biomineralization.

PubMed

Zerfaß, Christian; Braukmann, Sandra; Nietzsche, Sandor; Hobe, Stephan; Paulsen, Harald

2015-04-01

We report the recombinant bacterial expression and purification at high yields of a polycationic oligopeptide, P5S3. The sequence of P5S3 was inspired by a diatom silaffin, a silica precipitating peptide. Like its native model, P5S3 exhibits silica biomineralizing activity, but furthermore has unusual self-assembling properties. P5S3 is efficiently expressed in Escherichia coli as fusion with ketosteroid isomerase (KSI), which causes deposition in inclusion bodies. After breaking the fusion by cyanogen bromide reaction, P5S3 was purified by cation exchange chromatography, taking advantage of the exceptionally high content of basic amino acids. The numerous cationic charges do not prevent, but may even promote counterion-independent self-assembly which in turn leads to silica precipitation. Enzymatic phosphorylation, a common modification in native silica biomineralizing peptides, can be used to modify the precipitation activity. Copyright © 2015 Elsevier Inc. All rights reserved.

How HIV-1 Gag assembles in cells: putting together pieces of the puzzle

PubMed Central

Lingappa, Jaisri R; Reed, Jonathan C; Tanaka, Motoko; Chutiraka, Kasana; Robinson, Bridget A

2014-01-01

During the late stage of the viral life cycle, HIV-1 Gag assembles into a spherical immature capsid, and undergoes budding, release, and maturation. Here we review events involved in immature capsid assembly from the perspective of five different approaches used to study this process: mutational analysis, structural studies, assembly of purified recombinant Gag, assembly of newly-translated Gag in a cell-free system, and studies in cells using biochemical and imaging techniques. We summarize key findings obtained using each approach, point out where there is consensus, and highlight unanswered questions. Particular emphasis is placed on reconciling data suggesting that Gag assembles by two different paths, depending on the assembly environment. Specifically, in assembly systems that lack cellular proteins, high concentrations of Gag can spontaneously assemble using purified nucleic acid as a scaffold. However, in the more complex intracellular environment, barriers that limit self-assembly are present in the form of cellular proteins, organelles, host defenses, and the absence of free nucleic acid. To overcome these barriers and promote efficient immature capsid formation in an unfavorable environment, Gag appears to utilize an energy-dependent, host-catalyzed, pathway of assembly intermediates in cells. Overall, we show how data obtained using a variety of techniques has led to our current understanding of HIV assembly. PMID:25066606

Chemical resistivity of self-assembled monolayer covalently attached to silicon substrate to hydrofluoric acid and ammonium fluoride

NASA Astrophysics Data System (ADS)

Saito, N.; Youda, S.; Hayashi, K.; Sugimura, H.; Takai, O.

2003-06-01

Self-assembled monolayers (SAMs) were prepared on hydrogen-terminated silicon substrates through chemical vapor deposition using 1-hexadecene (HD) as a precursor. The HD-SAMs prepared in an atmosphere under a reduced pressure (≈50 Pa) showed better chemical resistivities to hydrofluoric acid and ammonium fluoride (NH 4F) solutions than that of an organosilane SAM formed on oxide-covered silicon substrates. The surface covered with the HD-SAM was micro-patterned by vacuum ultraviolet photolithography and consequently divided into two areas terminated with HD-SAM or silicon dioxide. This micro-patterned sample was immersed in a 40 vol.% NH 4F aqueous solution. Surface images obtained by an optical microscopy clearly show that the micro-patterns of HD-SAM/silicon dioxide were successfully transferred into the silicon substrate.

Electrochemical Impedance Spectroscopy for Real-Time Detection of Lipid Membrane Damage Based on a Porous Self-Assembly Monolayer Support.

PubMed

Zhang, Meng; Zhai, Qingyu; Wan, Liping; Chen, Li; Peng, Yu; Deng, Chunyan; Xiang, Juan; Yan, Jiawei

2018-06-19

Layer-by-layer dissolution and permeable pore formation are two typical membrane damage pathways, which induce membrane function disorder and result in serious disease, such as Alzheimer's disease, Keshan disease, Sickle-cell disease, and so on. To effectively distinguish and sensitively monitor these two typical membrane damage pathways, a facile electrochemical impedance strategy was developed on a porous self-assembly monolayer (pSAM) supported bilayer lipid membrane (BLM). The pSAM was prepared by selectively electrochemical reductive desorption of the mercaptopropionic acid in a mixed mercaptopropionic acid/11-mercaptoundecanoic acid self-assembled monolayer, which created plenty of nanopores with tens of nanometers in diameter and several nanometers in height (defined as inner-pores). The ultralow aspect ratio of the inner-pores was advantageous to the mass transfer of electrochemical probe [Fe(CN) 6 ] 3-/4- , simplifying the equivalent electric circuit for electrochemical impedance spectroscopy analysis at the electrode/membrane interface. [Fe(CN) 6 ] 3-/4- transferring from the bulk solution into the inner-pore induce significant changes of the interfacial impedance properties, improving the detection sensitivity. Based on these, the different membrane damage pathways were effectively distinguished and sensitively monitored with the normalized resistance-capacitance changes of inner-pore-related parameters including the electrolyte resistance within the pore length ( R pore ) and the metal/inner-pore interfacial capacitance ( C pore ) and the charge-transfer resistance ( R ct-in ) at the metal/inner-pore interface.

Electrochemical and spectroscopic characterization of surface sol-gel processes.

PubMed

Chen, Xiaohong; Wilson, George S

2004-09-28

(3-Mercaptopropyl)trimethoxysilane (MTS) forms a unique film on a platinum substrate by self-assembly and sol-gel cross-linking. The gelating and drying states of the self-assembled MTS sol-gel films were probed by use of electrochemical and spectroscopic methods. The thiol moiety was the only active group within the sol-gel network. Gold nanoparticles were employed to detect the availability of the thiol group and their interaction further indicated the physicochemical states of the sol-gel inner structure. It was found that the thiol groups in the open porous MTS aerogel matrix were accessible to the gold nanoparticles while thiol groups in the compact MTS xerogel network were not accessible to the gold nanoparticles. The characteristics of the sol-gel matrix change with time because of its own irreversible gelating and drying process. The present work provides direct evidence of gold nanoparticle binding with thiol groups within the sol-gel structures and explains the different permeability of "aerogel" and "xerogel" films of MTS on the basis of electrochemical and spectroscopic results. Two endogenous species, hydrogen peroxide and ascorbic acid, were used to test the permeability of the self-assembled sol-gel film in different states. The MTS xerogel film on the platinum electrode was extremely selective against ascorbic acid while maintaining high sensitivity to hydrogen peroxide in contrast to the relatively high permeability of ascorbic acid in the MTS aerogel film. This study showed the potential of the MTS sol-gel film as a nanoporous material in biosensor development.

"Mixed-charge self-assembled monolayers" as a facile method to design pH-induced aggregation of large gold nanoparticles for near-infrared photothermal cancer therapy.

PubMed

Li, Huan; Liu, Xiangsheng; Huang, Nan; Ren, Kefeng; Jin, Qiao; Ji, Jian

2014-01-01

The acidic microenvironment of tumor tissues has proven to be one of the major differences from other normal tissues. The near-infrared (NIR) light irradiation of aggregated gold nanoparticles in a tumor acidic pH-induced manner could then provide an effect approach to treat solid tumors with the advantage of minimizing the undesired damage to normal tissues. Although it is well-known the aggregation of larger nanoparticles will result in a better NIR photothermal effect, the preparation of pH-sensitive gold nanoparticles in large sizes remains a big challenge because of their worse dispersive stability. In this paper, we introduce a facile way to endow large gold nanoparticles with tunable pH-aggregation behaviors by modifying the nanoparticle surface with mixed-charge self-assembly monolayers compromising positively and negatively charged thiol ligands. Four different size nanoparticles were used to study the general principle of tailoring the pH-induced aggregation behaviors of mixed-charge gold nanoparticles (MC-GNPs) by adjusting the surface ligand composition. With proper surface ligand composition, the MC-GNPs in four different sizes that all exhibited aggregation at tumor acidic pH were obtained. The biggest MC-GNPs showed the most encouraging aggregation-enhanced photothermal efficacy in vitro when they formed aggregates. The mixed-charge self-assembled monolayers were then proved as a facile method to design pH-induced aggregation of large gold nanoparticles for better NIR photothermal cancer therapy.

Site-selective growth of surface-anchored metal-organic frameworks on self-assembled monolayer patterns prepared by AFM nanografting

PubMed Central

Ladnorg, Tatjana; Welle, Alexander; Heißler, Stefan; Wöll, Christof

2013-01-01

Summary Surface anchored metal-organic frameworks, SURMOFs, are highly porous materials, which can be grown on modified substrates as highly oriented, crystalline coatings by a quasi-epitaxial layer-by-layer method (liquid-phase epitaxy, or LPE). The chemical termination of the supporting substrate is crucial, because the most convenient method for substrate modification is the formation of a suitable self-assembled monolayer. The choice of a particular SAM also allows for control over the orientation of the SURMOF. Here, we demonstrate for the first time the site-selective growth of the SURMOF HKUST-1 on thiol-based self-assembled monolayers patterned by the nanografting technique, with an atomic force microscope as a structuring tool. Two different approaches were applied: The first one is based on 3-mercaptopropionic acid molecules which are grafted in a 1-decanethiolate SAM, which serves as a matrix for this nanolithography. The second approach uses 16-mercaptohexadecanoic acid, which is grafted in a matrix of an 1-octadecanethiolate SAM. In both cases a site-selective growth of the SURMOF is observed. In the latter case the roughness of the HKUST-1 is found to be significantly higher than for the 1-mercaptopropionic acid. The successful grafting process was verified by time-of-flight secondary ion mass spectrometry and atomic force microscopy. The SURMOF structures grown via LPE were investigated and characterized by atomic force microscopy and Fourier-transform infrared microscopy. PMID:24205458

Synthesis and characterization of designed BMHP1-derived self-assembling peptides for tissue engineering applications

NASA Astrophysics Data System (ADS)

Silva, Diego; Natalello, Antonino; Sanii, Babak; Vasita, Rajesh; Saracino, Gloria; Zuckermann, Ronald N.; Doglia, Silvia Maria; Gelain, Fabrizio

2012-12-01

The importance of self-assembling peptides (SAPs) in regenerative medicine is becoming increasingly recognized. The propensity of SAPs to form nanostructured fibers is governed by multiple forces including hydrogen bonds, hydrophobic interactions and π-π aromatic interactions among side chains of the amino acids. Single residue modifications in SAP sequences can significantly affect these forces. BMHP1-derived SAPs is a class of biotinylated oligopeptides, which self-assemble in β-structured fibers to form a self-healing hydrogel. In the current study, selected modifications in previously described BMHP1-derived SAPs were designed in order to investigate the influence of modified residues on self-assembly kinetics and scaffold formation properties. The Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis demonstrated the secondary structure (β-sheet) formation in all modified SAP sequences, whereas atomic force microscopy (AFM) analysis further confirmed the presence of nanofibers. Furthermore, the fiber shape and dimension analysis by AFM showed flattened and twisted fiber morphology ranging from ~8 nm to ~70 nm. The mechanical properties of the pre-assembled and post assembled solution were investigated by rheometry. The shear-thinning behavior and rapid re-healing properties of the pre-assembled solutions make them a preferable choice for injectable scaffolds. The wide range of stiffnesses (G') -from ~1000 to ~27 000 Pa - exhibited by the post-assembled scaffolds demonstrated their potential for a variety of tissue engineering applications. The extra cellular matrix (ECM) mimicking (physically and chemically) properties of SAP scaffolds enhanced cell adhesion and proliferation. The capability of the scaffold to facilitate murine neural stem cell (mNSC) proliferation was evaluated in vitro: the increased mNSCs adhesion and proliferation demonstrated the potential of newly synthesized SAPs for regenerative medicine approaches.The importance of self-assembling peptides (SAPs) in regenerative medicine is becoming increasingly recognized. The propensity of SAPs to form nanostructured fibers is governed by multiple forces including hydrogen bonds, hydrophobic interactions and π-π aromatic interactions among side chains of the amino acids. Single residue modifications in SAP sequences can significantly affect these forces. BMHP1-derived SAPs is a class of biotinylated oligopeptides, which self-assemble in β-structured fibers to form a self-healing hydrogel. In the current study, selected modifications in previously described BMHP1-derived SAPs were designed in order to investigate the influence of modified residues on self-assembly kinetics and scaffold formation properties. The Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis demonstrated the secondary structure (β-sheet) formation in all modified SAP sequences, whereas atomic force microscopy (AFM) analysis further confirmed the presence of nanofibers. Furthermore, the fiber shape and dimension analysis by AFM showed flattened and twisted fiber morphology ranging from ~8 nm to ~70 nm. The mechanical properties of the pre-assembled and post assembled solution were investigated by rheometry. The shear-thinning behavior and rapid re-healing properties of the pre-assembled solutions make them a preferable choice for injectable scaffolds. The wide range of stiffnesses (G') -from ~1000 to ~27 000 Pa - exhibited by the post-assembled scaffolds demonstrated their potential for a variety of tissue engineering applications. The extra cellular matrix (ECM) mimicking (physically and chemically) properties of SAP scaffolds enhanced cell adhesion and proliferation. The capability of the scaffold to facilitate murine neural stem cell (mNSC) proliferation was evaluated in vitro: the increased mNSCs adhesion and proliferation demonstrated the potential of newly synthesized SAPs for regenerative medicine approaches. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr32656f

Autonomously Self-Adhesive Hydrogels as Building Blocks for Additive Manufacturing.

PubMed

Deng, Xudong; Attalla, Rana; Sadowski, Lukas P; Chen, Mengsu; Majcher, Michael J; Urosev, Ivan; Yin, Da-Chuan; Selvaganapathy, P Ravi; Filipe, Carlos D M; Hoare, Todd

2018-01-08

We report a simple method of preparing autonomous and rapid self-adhesive hydrogels and their use as building blocks for additive manufacturing of functional tissue scaffolds. Dynamic cross-linking between 2-aminophenylboronic acid-functionalized hyaluronic acid and poly(vinyl alcohol) yields hydrogels that recover their mechanical integrity within 1 min after cutting or shear under both neutral and acidic pH conditions. Incorporation of this hydrogel in an interpenetrating calcium-alginate network results in an interfacially stiffer but still rapidly self-adhesive hydrogel that can be assembled into hollow perfusion channels by simple contact additive manufacturing within minutes. Such channels withstand fluid perfusion while retaining their dimensions and support endothelial cell growth and proliferation, providing a simple and modular route to produce customized cell scaffolds.

Beyond DNA origami: A look on the bright future of nucleic acid nanotechnology

PubMed Central

Michelotti, Nicole; Johnson-Buck, Alexander; Manzo, Anthony J.

2012-01-01

Nucleic acid nanotechnology exploits the programmable molecular recognition properties of natural and synthetic nucleic acids to assemble structures with nanometer-scale precision. In 2006, DNA origami transformed the field by providing a versatile platform for self-assembly of arbitrary shapes from one long DNA strand held in place by hundreds of short, site-specific (spatially addressable) DNA ”staples”. This revolutionary approach has led to the creation of a multitude of 2D and 3D scaffolds that form the basis for functional nanodevices. Not limited to nucleic acids, these nanodevices can incorporate other structural and functional materials, such as proteins and nanoparticles, making them broadly useful for current and future applications in emerging fields such as nanomedicine, nanoelectronics, and alternative energy. PMID:22131292

Self-assembled inorganic clusters of semiconducting quantum dots for effective solar hydrogen evolution.

PubMed

Gao, Yu-Ji; Yang, Yichen; Li, Xu-Bing; Wu, Hao-Lin; Meng, Shu-Lin; Wang, Yang; Guo, Qing; Huang, Mao-Yong; Tung, Chen-Ho; Wu, Li-Zhu

2018-05-08

Owing to promoted electron-hole separation, the catalytic activity of semiconducting quantum dots (QDs) towards solar hydrogen (H2) production has been significantly enhanced by forming self-assembled clusters with ZnSe QDs made ex situ. Taking advantage of the favored interparticle hole transfer to ZnSe QDs, the rate of solar H2 evolution of CdSe QDs can be increased to ∼30 000 μmol h-1 g-1 with ascorbic acid as the sacrificial reagent, ∼150-fold higher than that of bare CdSe QDs clusters under the same conditions.

Electrochromic Behavior of Ionically Self-Assembled Thin Films

NASA Astrophysics Data System (ADS)

Janik, J. A.; Heflin, J. R.; Marciu, D.; Miller, M. B.; Davis, R. M.

2001-03-01

Ionically self-assembled monolayers (ISAMs), fabricated by alternate adsorption of cationic and anionic components, yield exceptionally homogeneous thin films with sub-nanometer control of the thickness and relative special location of the component materials. Using organic electrochromic materials such as polyaniline, we report studies of electrochromic responses in ISAM films. Reversible changes in the absorption spectrum are observed with the application of voltages on the order of 1.0 V. Measurements are made using both liquid electrolytes and in all-solid state devices incorporating solid polyelectrolytes such as poly(2-acylamido 2-methyl propane sulfonic acid) (PAMPS).

Quantum entanglement in photoactive prebiotic systems.

PubMed

Tamulis, Arvydas; Grigalavicius, Mantas

2014-06-01

This paper contains the review of quantum entanglement investigations in living systems, and in the quantum mechanically modelled photoactive prebiotic kernel systems. We define our modelled self-assembled supramolecular photoactive centres, composed of one or more sensitizer molecules, precursors of fatty acids and a number of water molecules, as a photoactive prebiotic kernel systems. We propose that life first emerged in the form of such minimal photoactive prebiotic kernel systems and later in the process of evolution these photoactive prebiotic kernel systems would have produced fatty acids and covered themselves with fatty acid envelopes to become the minimal cells of the Fatty Acid World. Specifically, we model self-assembling of photoactive prebiotic systems with observed quantum entanglement phenomena. We address the idea that quantum entanglement was important in the first stages of origins of life and evolution of the biospheres because simultaneously excite two prebiotic kernels in the system by appearance of two additional quantum entangled excited states, leading to faster growth and self-replication of minimal living cells. The quantum mechanically modelled possibility of synthesizing artificial self-reproducing quantum entangled prebiotic kernel systems and minimal cells also impacts the possibility of the most probable path of emergence of protocells on the Earth or elsewhere. We also examine the quantum entangled logic gates discovered in the modelled systems composed of two prebiotic kernels. Such logic gates may have application in the destruction of cancer cells or becoming building blocks of new forms of artificial cells including magnetically active ones.

pH-Sensitive polymer assisted self-aggregation of bis(pyrene) in living cells in situ with turn-on fluorescence

NASA Astrophysics Data System (ADS)

Duan, Zhongyu; Gao, Yu-Juan; Qiao, Zeng-Ying; Qiao, Shenglin; Wang, Yongmei; Hou, Chunyuan; Wang, Lei; Wang, Hao

2015-09-01

Supramolecular self-assemblies with various nanostructures in organic and aqueous solutions have been prepared with desired functions. However, in situ construction of self-assembled superstructures in physiological conditions to achieve expected biological functions remains a challenge. Here, we report a supramolecular system to realize the in situ formation of nanoaggregates in living cells. The bis(pyrene) monomers were dispersed inside of hydrophobic domains of pH-sensitive polymeric micelles and delivered to the lysosomes of cells. In the acidic lysosomes, the bis(pyrene) monomers were released and self-aggregated with turn-on fluorescence. We envision this strategy for in situ construction of supramolecular nanostructures in living cells will pave the way for molecular diagnostics in the future.

On the Reaction of Carbonyl Diphosphonic Acid with Hydroxylamine and O-alkylhydroxylamines: Unexpected Degradation of P-C-P Bridge.

PubMed

Khomich, Olga A; Yanvarev, Dmitry V; Novikov, Roman A; Kornev, Alexey B; Puljulla, Elina; Vepsäläinen, Jouko; Khomutov, Alex R; Kochetkov, Sergey N

2017-06-23

Derivatives of methylenediphosphonic acid possess wide spectra of biological activities and are used in enzymology as research tools as well as in practical medicine. Carbonyl diphosphonic acid is a promising starting building block for synthesis of functionally substituted methylenediphosphonates. Investigation of the interaction of carbonyl diphosphonic acid with hydroxylamine clearly demonstrates that it is impossible to isolate oxime within the pH range 2-12, while only cyanophosphonic and phosphoric acids are the products of the fast proceeding Beckmann-like fragmentation. In the case of O -alkylhydroxylamines, corresponding alcohols are found in the reaction mixtures in addition to cyanophosphonic and phosphoric acids. Therefore, two residues of phosphonic acid being attached to a carbonyl group provide new properties to this carbonyl group, making its oximes very unstable. This principally differs carbonyl diphosphonic acid from structurally related phosphonoglyoxalic acid and other α-ketophosphonates.

Self-assembly in solvates of 2,4-diamino-6-(4-methyl- phenyl)-1,3,5-triazine and in its molecular adducts with some aliphatic dicarboxylic acids

NASA Astrophysics Data System (ADS)

Nandy, Purnendu; Nayak, Amrita; Biswas, Sharmita Nandy; Pedireddi, V. R.

2016-03-01

Solid state structures of 2,4-diamino-6-(4-methylphenyl)-1,3,5-triazine, 1, in the form of methanol and dimethylsulfoxide (DMSO) solvates, as well as supramolecular assemblies of 1 with various aliphatic dicarboxylic acids, oxalic (a), malonic (b), succinic (c), glutaric (d) and adipic (e) have been reported. Analysis of the assemblies has been carried out by single crystal X-ray diffraction and thermal methods. Triazine 1 yields anhydrous molecular adducts with acids a-d, upon co-crystallization either from CH3OH and DMSO solvents. However acid e gives anhydrous adduct from DMSO solvent, while it gives a methanol adduct from CH3OH. Structure determination reveals that molecular adducts 1a, 1d and 1e are in a 2:1 ratio of 1 and the corresponding acid. However the ratio is 1:1, in 1b, perhaps due to the involvement of one of the acid groups in the intramolecular hydrogen bonding and in adduct 1c the ratio observed is 3:2. Structural features in all these assemblies have been rationalised in terms of various recognition patterns formed between the acceptor and donor groups. A noteworthy feature is that -COOH groups in acid a establish interaction with 1 through amino groups, while such interactions are observed to be through hetero -N atoms in case of the acids b-e.

Self-assembled pH-sensitive cholesteryl pullulan nanogel as a protein delivery vehicle.

PubMed

Morimoto, Nobuyuki; Hirano, Sayaka; Takahashi, Haruko; Loethen, Scott; Thompson, David H; Akiyoshi, Kazunari

2013-01-14

A self-assembled nanogel, derived from an acid-labile cholesteryl-modified pullulan (acL-CHP), was prepared by grafting vinyl ether-cholesterol substituents onto a 100 kD pullulan main chain polymer backbone. Stable nanogels are formed by acL-CHP self-assemblies at neutral pH. The hydrodynamic radius of the nanogels, observed to be 26.5 ± 5.1 nm at pH 7.0, increased by ~135% upon acidification of the solution to pH 4.0. SEC analysis of the acL-CHP nanogel at pH 4.0 showed that the grafts were nearly 80% degraded after 24 h, whereas little or no degradation was observed over the same time period for a pH stable analog (acS-CHP) at pH 4.0 or the acL-CHP at pH 7.0. Complexation of BSA with the acL-CHP nanogel was observed at pH 7.0 with subsequent release of the protein upon acidification. These findings suggest that stimuli-responsive, self-assembled nanogels can release protein cargo in a manner that is controlled by the degradation rate of the cholesterol-pullulan grafting moiety.

Rational synthesis of low-polydispersity block copolymer vesicles in concentrated solution via polymerization-induced self-assembly.

PubMed

Gonzato, Carlo; Semsarilar, Mona; Jones, Elizabeth R; Li, Feng; Krooshof, Gerard J P; Wyman, Paul; Mykhaylyk, Oleksandr O; Tuinier, Remco; Armes, Steven P

2014-08-06

Block copolymer self-assembly is normally conducted via post-polymerization processing at high dilution. In the case of block copolymer vesicles (or "polymersomes"), this approach normally leads to relatively broad size distributions, which is problematic for many potential applications. Herein we report the rational synthesis of low-polydispersity diblock copolymer vesicles in concentrated solution via polymerization-induced self-assembly using reversible addition-fragmentation chain transfer (RAFT) polymerization of benzyl methacrylate. Our strategy utilizes a binary mixture of a relatively long and a relatively short poly(methacrylic acid) stabilizer block, which become preferentially expressed at the outer and inner poly(benzyl methacrylate) membrane surface, respectively. Dynamic light scattering was utilized to construct phase diagrams to identify suitable conditions for the synthesis of relatively small, low-polydispersity vesicles. Small-angle X-ray scattering (SAXS) was used to verify that this binary mixture approach produced vesicles with significantly narrower size distributions compared to conventional vesicles prepared using a single (short) stabilizer block. Calculations performed using self-consistent mean field theory (SCMFT) account for the preferred self-assembled structures of the block copolymer binary mixtures and are in reasonable agreement with experiment. Finally, both SAXS and SCMFT indicate a significant degree of solvent plasticization for the membrane-forming poly(benzyl methacrylate) chains.

Amphiphilically modified chitosan cationic nanoparticles for drug delivery

NASA Astrophysics Data System (ADS)

You, Jie; Li, Wenfeng; Yu, Chang; Zhao, Chengguang; Jin, Langping; Zhou, Yili; Xu, Xuzhong; Dong, Siyang; Lu, Xincheng; Wang, Ouchen

2013-12-01

A series of amphiphilic N-(2-hydroxy)propyl-3-trimethylammonium-chitosan-cholic acid (HPTA-CHI-CA) polymers were synthesized by grafting cholic acid (CA) and glycidyltrimethylammonium chloride onto chitosan. The self-assembly behavior of HPTA-CHI-CA was studied by fluorescence technique. The polymers were able to self-assemble into NPs in phosphate buffered saline with a critical aggregation concentration (CAC) in the range of 66-26 mg/L and the CAC decreased with the increasing of the degree of substitution (DS) of CA. The size of cationic HPTA-CHI-CA NPs ranges from 170 to 220 nm (PDI < 0.2). It was found that doxorubicin (DOX) could be encapsulated into HPTA-CHI-CA NPs based on self-assembly. The drug loading content and efficiency varies depending on the DS of CA and feeding ratio of DOX to polymer. In vitro release studies suggested that DOX released slowly from HPTA-CHI-CA NPs without any burst initial release. Besides, the confocal microscopic measurements indicated that DOX-HPTA-CHI-CA NPs could easily be uptaken by breast cancer (MCF-7) cells and release DOX in cytoplasm. Anti-tumor efficacy results showed that DOX-HPTA-CHI-CA NPs have a significant activity of inhibition MCF-7 cells growth. These results suggest cationic HPTA-CHI-CA may have great potential for anticancer drug delivery.

Simultaneous determination of dopamine and uric acid using layer-by-layer graphene and chitosan assembled multilayer films.

PubMed

Weng, Xuexiang; Cao, Qingxue; Liang, Lixin; Chen, Jianrong; You, Chunping; Ruan, Yongmin; Lin, Hongjun; Wu, Lanju

2013-12-15

Multilayer films containing graphene (Gr) and chitosan (CS) were prepared on glassy carbon electrodes with layer-by-layer (LBL) assembly technique. After being characterized with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM), the electrochemical sensor based on the resulted films was developed to simultaneously determine dopamine (DA) and uric acid (UA). The LBL assembled electrode showed excellent electrocatalytic activity towards the oxidation of DA and UA. In addition, the self-assembly electrode possessed an excellent sensing performance for detection of DA and UA with a linear range from 0.1 μM to 140 µM and from 1.0 µM to 125 µM with the detection limit as low as 0.05 µM and 0.1 µM based on S/N=3, respectively. © 2013 Elsevier B.V. All rights reserved.

Immediate and Delayed Drug Therapy Effects on Low Dose Sarin Exposed Mice Myocardial Performance

DTIC Science & Technology

2011-03-01

to phosphorylate the serine hydroxyl residue in the active pocket of AChE, forming either a phosphoric or phosphonic acid ester which is extremely...London 2006). Brain natriuretic peptide exerts its 15 natriuretic, diuretic, and vasorelaxant effects through activation of its common receptor...exposed to asymptomatic levels would show no issues during normal activities , such garrison or non-field operations. However, this would quickly change

USSR and Eastern Europe Scientific Abstracts, Chemistry. Number 49

DTIC Science & Technology

1976-11-04

phosphorus tribromide with oxygen initia- tion leads to the synthesis of l-bromoalkane-2-phosphonous acid dibromides. References 8: 4 Russian, 4 Western. 1 ...are developed for synthesis of dialkylmethylphosphonates by nitration of ethoxyvinylphosphonates. References 21: 19 Russian, 2 Western. 1 / 1 USSR...spectroscopic data and reverse synthesis . Figures 2; References 3: 1 Russian, 2 Western. 1 / 1 28 USSR UDC 547.26� GOLOLOBOV, YU. G., BOLDESKUL, I

A Bispidol Chelator with a Phosphonate Pendant Arm: Synthesis, Cu(II) Complexation, and 64Cu Labeling.

PubMed

Gillet, Raphaël; Roux, Amandine; Brandel, Jérémy; Huclier-Markai, Sandrine; Camerel, Franck; Jeannin, Olivier; Nonat, Aline M; Charbonnière, Loïc J

2017-10-02

Here we present the synthesis and characterization of a new bispidine (3,7-diazabicyclo[3.3.1]nonane) ligand with N-methanephosphonate substituents (L 2 ). Its physicochemical properties in water, as well as those of the corresponding Cu(II) and Zn(II) complexes, have been evaluated by using UV-visible absorption spectroscopy, potentiometry, 1 H and 31 P NMR, and cyclic voltammetry. Radiolabeling experiments with 64 Cu II have been carried out, showing excellent radiolabeling properties. Quantitative complexation was achieved within 60 min under stoichiometric conditions, at room temperature and in the nanomolar concentration range. It was also demonstrated that the complexation occurred below pH 2. Properties have been compared to those of the analogue bispidol bearing a N-methanecarboxylate substituent (L 1 ). Although both systems meet the required criteria to be used as new chelator for 64/67 Cu in terms of the kinetics of formation, thermodynamic stability, selectivity for Cu(II), and kinetic inertness regarding redox- or acid-assisted decomplexation processes, substitution of the carboxylic acid function by the phosphonic moiety is responsible for a significant increase in the thermodynamic stability of the Cu(II) complex (+2 log units for pCu) and also leads to an increase in the radiochemical yields with 64 Cu II which is quantitative for L 2 .

Solar H2 evolution in water with modified diketopyrrolopyrrole dyes immobilised on molecular Co and Ni catalyst-TiO2 hybrids.

PubMed

Warnan, Julien; Willkomm, Janina; Ng, Jamues N; Godin, Robert; Prantl, Sebastian; Durrant, James R; Reisner, Erwin

2017-04-01

A series of diketopyrrolopyrrole (DPP) dyes with a terminal phosphonic acid group for attachment to metal oxide surfaces were synthesised and the effect of side chain modification on their properties investigated. The organic photosensitisers feature strong visible light absorption ( λ = 400 to 575 nm) and electrochemical and fluorescence studies revealed that the excited state of all dyes provides sufficient driving force for electron injection into the TiO 2 conduction band. The performance of the DPP chromophores attached to TiO 2 nanoparticles for photocatalytic H 2 evolution with co-immobilised molecular Co and Ni catalysts was subsequently studied, resulting in solar fuel generation with a dye-sensitised semiconductor nanoparticle system suspended in water without precious metal components. The performance of the DPP dyes in photocatalysis did not only depend on electronic parameters, but also on properties of the side chain such as polarity, steric hinderance and hydrophobicity as well as the specific experimental conditions and the nature of the sacrificial electron donor. In an aqueous pH 4.5 ascorbic acid solution with a phosphonated DuBois-type Ni catalyst, a DPP-based turnover number (TON DPP ) of up to 205 was obtained during UV-free simulated solar light irradiation (100 mW cm -2 , AM 1.5G, λ > 420 nm) after 1 day. DPP-sensitised TiO 2 nanoparticles were also successfully used in combination with a hydrogenase or platinum instead of the synthetic H 2 evolution catalysts and the platinum-based system achieved a TON DPP of up to 2660, which significantly outperforms an analogous system using a phosphonated Ru tris(bipyridine) dye (TON Ru = 431). Finally, transient absorption spectroscopy was performed to study interfacial recombination and dye regeneration kinetics revealing that the different performances of the DPP dyes are most likely dictated by the different regeneration efficiencies of the oxidised chromophores.

NMDA inhibits oxotremorine-induced acid secretion via the NO-dependent cyclic GMP system in rat stomach.

PubMed

Tsai, L H; Lee, Y J

2001-12-31

The mechanism of N-methyl-D-aspartate (NMDA) inhibits oxotremorine-induced acid secretion was examined in rat stomach, in relation to the cyclic GMP system. NMDA (10(-7) M) did not affect the spontaneous acid secretion from the everted preparations of isolated rat stomach, but inhibited the acid secretion stimulated by oxotremorine, and this effect of NMDA was antagonized by 2-amino-5-phosphonovaleric acid (AP-5), (+/-)3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) or N(G)-nitro-L-arginine (L-NNA). NMDA also elevated the cyclic GMP content of mucosal slices from rat stomach, and this effect of NMDA was antagonized by L-NNA. These results indicate that NMDA receptors are present in the rat stomach and regulate the gastric acid secretion. The mechanism underlying the effect of NMDA inhibits oxotremorine-induced acid secretion may be mediated by the NO-dependent cyclic GMP system.

Combining QD-FRET and microfluidics to monitor DNA nanocomplex self-assembly in real-time.

PubMed

Ho, Yi-Ping; Chen, Hunter H; Leong, Kam W; Wang, Tza-Huei

2009-08-26

Advances in genomics continue to fuel the development of therapeutics that can target pathogenesis at the cellular and molecular level. Typically functional inside the cell, nucleic acid-based therapeutics require an efficient intracellular delivery system. One widely adopted approach is to complex DNA with a gene carrier to form nanocomplexes via electrostatic self-assembly, facilitating cellular uptake of DNA while protecting it against degradation. The challenge lies in the rational design of efficient gene carriers, since premature dissociation or overly stable binding would be detrimental to the cellular uptake and therapeutic efficacy. Nanocomplexes synthesized by bulk mixing showed a diverse range of intracellular unpacking and trafficking behavior, which was attributed to the heterogeneity in size and stability of nanocomplexes. Such heterogeneity hinders the accurate assessment of the self-assembly kinetics and adds to the difficulty in correlating their physical properties to transfection efficiencies or bioactivities. We present a novel convergence of nanophotonics (i.e. QD-FRET) and microfluidics to characterize the real-time kinetics of the nanocomplex self-assembly under laminar flow. QD-FRET provides a highly sensitive indication of the onset of molecular interactions and quantitative measure throughout the synthesis process, whereas microfluidics offers a well-controlled microenvironment to spatially analyze the process with high temporal resolution (~milliseconds). For the model system of polymeric nanocomplexes, two distinct stages in the self-assembly process were captured by this analytic platform. The kinetic aspect of the self-assembly process obtained at the microscale would be particularly valuable for microreactor-based reactions which are relevant to many micro- and nano-scale applications. Further, nanocomplexes may be customized through proper design of microfludic devices, and the resulting QD-FRET polymeric DNA nanocomplexes could be readily applied for establishing structure-function relationships.

Subtle charge balance controls surface-nucleated self-assembly of designed biopolymers.

PubMed

Charbonneau, Céline; Kleijn, J Mieke; Cohen Stuart, Martien A

2014-03-25

We report the surface-nucleated self-assembly into fibrils of a biosynthetic amino acid polymer synthesized by the yeast Pichia pastoris. This polymer has a block-like architecture, with a central silk-like block labeled SH, responsible for the self-assembly into fibrils, and two collagen-like random coil end blocks (C) that colloidally stabilize the fibers in aqueous solution. The silk-like block contains histidine residues (pKa≈6) that are positively charged in the low pH region, which hinders self-assembly. In aqueous solution, CSHC self-assembles into fibers above a pH-dependent critical nucleation concentration Ccb. Below Ccb, where no self-assembly occurs in solution, fibril formation can be induced by a negatively charged surface (silica) in the pH range of 3.5-7. The density of the fibers at the surface and their length are controlled by a subtle balance in charge between the protein polymer and the silica surface, which is evidenced from the dependence on pH. With increasing number density of the fibers at the surface, their average length decreases. The results can be explained on the basis of a nucleation-and-growth mechanism: the surface density of fibers depends on the rate of nucleation, while their growth rate is limited by transport of proteins from solution. Screening of the charges on the surface and histidine units by adding NaCl influences the nucleation-and-growth process in a complicated fashion: at low pH, the growth is improved, while at high pH, the nucleation is limited. Under conditions where nucleation in the bulk solution is not possible, growth of the surface-nucleated fibers into the solution--away from the surface--can still occur.

Molecular Mechanism of Thioflavin-T Binding to the Surface of [beta]-Rich Peptide Self-Assemblies

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

Biancalana, Matthew; Makabe, Koki; Koide, Akiko

A number of small organic molecules have been developed that bind to amyloid fibrils, a subset of which also inhibit fibrillization. Among these, the benzothiol dye Thioflavin-T (ThT) has been used for decades in the diagnosis of protein-misfolding diseases and in kinetic studies of self-assembly (fibrillization). Despite its importance, efforts to characterize the ThT-binding mechanism at the atomic level have been hampered by the inherent insolubility and heterogeneity of peptide self-assemblies. To overcome these challenges, we have developed a minimalist approach to designing a ThT-binding site in a 'peptide self-assembly mimic' (PSAM) scaffold. PSAMs are engineered water-soluble proteins that mimicmore » a segment of beta-rich peptide self-assembly, and they are amenable to standard biophysical techniques and systematic mutagenesis. The PSAM beta-sheet contains rows of repetitive amino acid patterns running perpendicular to the strands (cross-strand ladders) that represent a ubiquitous structural feature of fibril-like surfaces. We successfully designed a ThT-binding site that recapitulates the hallmarks of ThT-fibril interactions by constructing a cross-strand ladder consisting of contiguous tyrosines. The X-ray crystal structures suggest that ThT interacts with the beta-sheet by docking onto surfaces formed by a single tyrosine ladder, rather than in the space between adjacent ladders. Systematic mutagenesis further demonstrated that tyrosine surfaces across four or more beta-strands formed the minimal binding site for ThT. Our work thus provides structural insights into how this widely used dye recognizes a prominent subset of peptide self-assemblies, and proposes a strategy to elucidate the mechanisms of fibril-ligand interactions.« less

Programmable In Vitro Coencapsidation of Guest Proteins for Intracellular Delivery by Virus-like Particles.

PubMed

Dashti, Noor H; Abidin, Rufika S; Sainsbury, Frank

2018-05-22

Bioinspired self-sorting and self-assembling systems using engineered versions of natural protein cages are being developed for biocatalysis and therapeutic delivery. The packaging and intracellular delivery of guest proteins is of particular interest for both in vitro and in vivo cell engineering. However, there is a lack of bionanotechnology platforms that combine programmable guest protein encapsidation with efficient intracellular uptake. We report a minimal peptide anchor for in vivo self-sorting of cargo-linked capsomeres of murine polyomavirus (MPyV) that enables controlled encapsidation of guest proteins by in vitro self-assembly. Using Förster resonance energy transfer, we demonstrate the flexibility in this system to support coencapsidation of multiple proteins. Complementing these ensemble measurements with single-particle analysis by super-resolution microscopy shows that the stochastic nature of coencapsidation is an overriding principle. This has implications for the design and deployment of both native and engineered self-sorting encapsulation systems and for the assembly of infectious virions. Taking advantage of the encoded affinity for sialic acids ubiquitously displayed on the surface of mammalian cells, we demonstrate the ability of self-assembled MPyV virus-like particles to mediate efficient delivery of guest proteins to the cytosol of primary human cells. This platform for programmable coencapsidation and efficient cytosolic delivery of complementary biomolecules therefore has enormous potential in cell engineering.

Multi-component hybrid hydrogels – understanding the extent of orthogonal assembly and its impact on controlled release† †Electronic supplementary information (ESI) available: Full experimental methods and further data from assays. See DOI: 10.1039/c7sc03301j Click here for additional data file.

PubMed Central

Vieira, Vânia M. P.; Hay, Laura L.

2017-01-01

This paper reports self-assembled multi-component hybrid hydrogels including a range of nanoscale systems and characterizes the extent to which each component maintains its own unique functionality, demonstrating that multi-functionality can be achieved by simply mixing carefully-chosen constituents. Specifically, the individual components are: (i) pH-activated low-molecular-weight gelator (LMWG) 1,3;2,4-dibenzylidenesorbitol-4′,4′′-dicarboxylic acid (DBS–COOH), (ii) thermally-activated polymer gelator (PG) agarose, (iii) anionic biopolymer heparin, and (iv) cationic self-assembled multivalent (SAMul) micelles capable of binding heparin. The LMWG still self-assembles in the presence of PG agarose, is slightly modified on the nanoscale by heparin, but is totally disrupted by the micelles. However, if the SAMul micelles are bound to heparin, DBS–COOH self-assembly is largely unaffected. The LMWG endows hybrid materials with pH-responsive behavior, while the PG provides mechanical robustness. The rate of heparin release can be controlled through network density and composition, with the LMWG and PG behaving differently in this regard, while the presence of the heparin binder completely inhibits heparin release through complexation. This study demonstrates that a multi-component approach can yield exquisite control over self-assembled materials. We reason that controlling orthogonality in such systems will underpin further development of controlled release systems with biomedical applications. PMID:29147525

Water oxidation by Ruthenium complexes incorporating multifunctional biipyridyl diphosphonate ligands

DOE PAGES

Xie, Yan; Shaffer, David W.; Lewandowska-Andralojc, Anna; ...

2016-05-11

Here, we describe herein the synthesis and characterization of ruthenium complexes with multifunctional bipyridyl diphosphonate ligands as well as initial water oxidation studies. In these complexes, the phosphonate groups provide redox-potential leveling through charge compensation and σ donation to allow facile access to high oxidation states. These complexes display unique pH-dependent electrochemistry associated with deprotonation of the phosphonic acid groups. The position of these groups allows them to shuttle protons in and out of the catalytic site and reduce activation barriers. A mechanism for water oxidation by these catalysts is proposed on the basis of experimental results and DFT calculations.more » The unprecedented attack of water at a neutral six-coordinate [Ru IV] center to yield an anionic seven-coordinate [Ru IV–OH] – intermediate is one of the key steps of a single-site mechanism in which all species are anionic or neutral. These complexes are among the fastest single-site catalysts reported to date.« less

Tuning the EDTA-induced self-assembly and plasmonic spectral properties of gold nanorods: application in surface-enhanced Raman scattering

NASA Astrophysics Data System (ADS)

Li, Jian-jun; Zhang, Ning; Wang, Jingyuan; Yang, Chun-yu; Zhu, Jian; Zhao, Jun-wu

2016-02-01

Self-assembly of cetyl trimethyl ammonium bromide-protected colloidal gold nanorods with different aspect ratios has been studied by adding the ethylene diamine tetraacetic acid (EDTA). Both the assembly strength and assembly configuration fashion of the gold nanorods could be tuned by changing the aspect ratio. For gold nanorods with small aspect ratio, side-by-side assembly takes the major role in the aggregation. In this case, the blue shift of the longitudinal absorption and the increase of the transverse absorption lead to the great uplift of the middle spectrum dip as the EDTA is increased. For gold nanorods with large aspect ratio, end-to-end assembly takes the major role in the aggregation. In this case, the longitudinal absorption peak fades down rapidly and a tailing absorption peak at longer wavelength uplifts greatly as the EDTA is increased. The surface-enhanced Raman scattering (SERS) activity of the assembled gold nanorods has been studied using alpha-fetoprotein (AFP) as the Raman active probe. It has been found that both the side-by-side assembly and end-to-end assembly of the gold nanorods could effectively improve the Raman signal of the AFP. And the gold nanorod substrate with side-by-side assembly has higher SERS activity.

DNA-Assembled Advanced Plasmonic Architectures.

PubMed

Liu, Na; Liedl, Tim

2018-03-28

The interaction between light and matter can be controlled efficiently by structuring materials at a length scale shorter than the wavelength of interest. With the goal to build optical devices that operate at the nanoscale, plasmonics has established itself as a discipline, where near-field effects of electromagnetic waves created in the vicinity of metallic surfaces can give rise to a variety of novel phenomena and fascinating applications. As research on plasmonics has emerged from the optics and solid-state communities, most laboratories employ top-down lithography to implement their nanophotonic designs. In this review, we discuss the recent, successful efforts of employing self-assembled DNA nanostructures as scaffolds for creating advanced plasmonic architectures. DNA self-assembly exploits the base-pairing specificity of nucleic acid sequences and allows for the nanometer-precise organization of organic molecules but also for the arrangement of inorganic particles in space. Bottom-up self-assembly thus bypasses many of the limitations of conventional fabrication methods. As a consequence, powerful tools such as DNA origami have pushed the boundaries of nanophotonics and new ways of thinking about plasmonic designs are on the rise.

Self-assembled arginine-rich peptides as effective antimicrobial agents.

PubMed

Mi, Gujie; Shi, Di; Herchek, Whitney; Webster, Thomas J

2017-04-01

Bacteria can adapt to their ever-changing environment to develop a resistance to commonly used antibiotics. This escalating evolution of bacteria coupled with a diminished number of effective antibiotics has caused a global healthcare crisis. New antimicrobials and novel approaches to tackle this problem are urgently needed. Antimicrobial peptides are of particular interest in this endeavor due to their broad spectrum antimicrobial properties as well as ability to combat multi-drug resistant bacteria. Most peptides have both hydrophobic and hydrophilic regions that enable them to be soluble in an aqueous solution, yet can insert into and subsequently disintegrate lipid rich membranes through diverse mechanisms. In this study, a novel class of cationic nanoparticles (formed by the self-assembly of an amphiphilic peptide) were shown to have strong antimicrobial properties against gram-positive bacteria, specifically Staphylococcus aureus, Staphylococcus epidermidis, and methicillin-resistant Staphylococcus aureus (MRSA) with minimal toxicity to human dermal fibroblasts. The particular self-assembled structure tested here included an arginine rich nanoparticle (C 17 H 35 GR7RGDS or amphiphilic peptide nanoparticles, APNPs) which incorporated seven arginine residues (imparting a positive charge to improve membrane interactions), a hydrophobic block which drove the self-assembly process, and the presence of an amino acid quadruplet arginine-glycine-aspartic acid-serine (RGDS) which may render these nanoparticles capable of attracting healthy cells while competing bacterial adherence to fibronectin, an adhesive protein found on cell surfaces. As such, this in vitro study demonstrated that the presently formulated APNPs should be further studied for a wide range of antibacterial applications where antibiotics are no longer useful. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1046-1054, 2017. © 2017 Wiley Periodicals, Inc.

Bacterial expression of self-assembling peptide hydrogelators

NASA Astrophysics Data System (ADS)

Sonmez, Cem

For tissue regeneration and drug delivery applications, various architectures are explored to serve as biomaterial tools. Via de novo design, functional peptide hydrogel materials have been developed as scaffolds for biomedical applications. The objective of this study is to investigate bacterial expression as an alternative method to chemical synthesis for the recombinant production of self-assembling peptides that can form rigid hydrogels under physiological conditions. The Schneider and Pochan Labs have designed and characterized a 20 amino acid beta-hairpin forming amphiphilic peptide containing a D-residue in its turn region (MAX1). As a result, this peptide must be prepared chemically. Peptide engineering, using the sequence of MAX1 as a template, afforded a small family of peptides for expression (EX peptides) that have different turn sequences consisting of natural amino acids and amenable to bacterial expression. Each sequence was initially chemically synthesized to quickly assess the material properties of its corresponding gel. One model peptide EX1, was chosen to start the bacterial expression studies. DNA constructs facilitating the expression of EX1 were designed in such that the peptide could be expressed with different fusion partners and subsequently cleaved by enzymatic or chemical means to afford the free peptide. Optimization studies were performed to increase the yield of pure peptide that ultimately allowed 50 mg of pure peptide to be harvested from one liter of culture, providing an alternate means to produce this hydrogel-forming peptide. Recombinant production of other self-assembling hairpins with different turn sequences was also successful using this optimized protocol. The studies demonstrate that new beta-hairpin self-assembling peptides that are amenable to bacterial production and form rigid hydrogels at physiological conditions can be designed and produced by fermentation in good yield at significantly reduced cost when compared to chemical synthesis.

Self-assembled block copolymer photonic crystal for selective fructose detection.

PubMed

Ayyub, Omar B; Ibrahim, Michael B; Briber, Robert M; Kofinas, Peter

2013-08-15

The use of one-dimensional photonic crystals fabricated from a self-assembled lamellar block copolymer as a sensitive and selective fructose sensor is investigated. The polystyrene-b-poly(2-vinyl pyridine) (PS-b-P2VP) films are functionalized with 2-(bromomethyl)phenylboronic acid. The boronic acid moiety confined within the lamellar morphology can reversibly bind to sugars such as fructose, imparting the photonic properties of the PS-b-P2VP film. The films exhibit a detection limit of 500 μM in water and 1mM in phosphate buffered saline. Exposure to a 50 mM solution of fructose invokes a highly visible color change from blue to orange. The films are also able to selectively recognize and respond to fructose in competitive studies in the presence of glucose, mannose and sucrose. Copyright © 2013 Elsevier B.V. All rights reserved.

Measurement of molecular length of self-assembled monolayer probed by localized surface plasmon resonance

NASA Astrophysics Data System (ADS)

Ito, Juri; Kajikawa, Kotaro

2016-02-01

We propose a method to measure the variation of the molecular length of self-assembled monolayers (SAMs) when it is exposed to solutions at different pH conditions. The surface immobilized gold nanospheres (SIGNs) shows strong absorption peak at the wavelengths of 600-800 nm when p-polarized light is illuminated. The peak wavelength depends on the length of the gap distance between the SIGNs and the substrate. The gap is supported by the SAM molecules. According to the analytical calculation based on multiple expansion, the relation between the peak wavelength of the SIGN structures and the gap distance is calculated, to evaluate the molecular length of the SAM through the optical absorption spectroscopy for the SIGN structures. The molecular length of the SIGN structure was measured in air, water, acidic, and basic solutions. It was found that the molecular lengths are longer in acidic solutions.

Interaction of bovine serum albumin protein with self assembled monolayer of mercaptoundecanoic acid

NASA Astrophysics Data System (ADS)

Poonia, Monika; Agarwal, Hitesh; Manjuladevi, V.; Gupta, R. K.

2016-05-01

Detection of proteins and other biomolecules in liquid phase is the essence for the design of a biosensor. The sensitivity of a sensor can be enhanced by the appropriate functionalization of the sensing area so as to establish the molecular specific interaction. In the present work, we have studied the interaction of bovine serum albumin (BSA) protein with a chemically functionalized surface using a quartz crystal microbalance (QCM). The gold-coated quartz crystals (AT-cut/5 MHz) were functionalized by forming self-assembled monolayer (SAM) of 11-Mercaptoundecanoic acid (MUA). The adsorption characteristics of BSA onto SAM of MUA on quartz crystal are reported. BSA showed the highest affinity for SAM of MUA as compared to pure gold surface. The SAM of MUA provides carboxylated surface which enhances not only the adsorption of the BSA protein but also a very stable BSA-MUA complex in the liquid phase.

Distinct self-interaction domains promote Multi Sex Combs accumulation in and formation of the Drosophila histone locus body.

PubMed

Terzo, Esteban A; Lyons, Shawn M; Poulton, John S; Temple, Brenda R S; Marzluff, William F; Duronio, Robert J

2015-04-15

Nuclear bodies (NBs) are structures that concentrate proteins, RNAs, and ribonucleoproteins that perform functions essential to gene expression. How NBs assemble is not well understood. We studied the Drosophila histone locus body (HLB), a NB that concentrates factors required for histone mRNA biosynthesis at the replication-dependent histone gene locus. We coupled biochemical analysis with confocal imaging of both fixed and live tissues to demonstrate that the Drosophila Multi Sex Combs (Mxc) protein contains multiple domains necessary for HLB assembly. An important feature of this assembly process is the self-interaction of Mxc via two conserved N-terminal domains: a LisH domain and a novel self-interaction facilitator (SIF) domain immediately downstream of the LisH domain. Molecular modeling suggests that the LisH and SIF domains directly interact, and mutation of either the LisH or the SIF domain severely impairs Mxc function in vivo, resulting in reduced histone mRNA accumulation. A region of Mxc between amino acids 721 and 1481 is also necessary for HLB assembly independent of the LisH and SIF domains. Finally, the C-terminal 195 amino acids of Mxc are required for recruiting FLASH, an essential histone mRNA-processing factor, to the HLB. We conclude that multiple domains of the Mxc protein promote HLB assembly in order to concentrate factors required for histone mRNA biosynthesis. © 2015 Terzo et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

Vertical Alignment of Single-Walled Carbon Nanotubes on Nanostructure Fabricated by Atomic Force Microscope

DTIC Science & Technology

2007-03-30

Langmuir - Blodgett and self-assembly methods, WNTs are patterned selectively onto various substrates [3,4]. hou et al. assembled SWNTs into aligned...dispersion usually decreases with increasing ionic concentration, it is suggested that chloride ions are produced by dissociating from acid chloride groups...patterns can be attributed to the Marangoni effect and diffusion-limited aggregation (DLA) in the liquid film during droplet evaporation t different

Collapsed state of polyglutamic acid results in amyloid spherulite formation

PubMed Central

Stehli, Daniel; Mulaj, Mentor; Miti, Tatiana; Traina, Joshua; Foley, Joseph; Muschol, Martin

2015-01-01

Self-assembly of proteins and peptides into amyloid fibrils involves multiple distinct intermediates and late-stage fibrillar polymorphs. Understanding the conditions and mechanisms that promote the formation of one type of intermediate and polymorph over the other represents a fundamental challenge. Answers to this question are also of immediate biomedical relevance since different amyloid aggregate species have been shown to have distinct pathogenic potencies. One amyloid polymorph that has received comparatively little attention are amyloid spherulites. Here we report that self-assembly of the intrinsically disordered polymer poly(L-glutamic) acid (PLE) can generate amyloid spherulites. We characterize spherulite growth kinetics, as well as the morphological, optical and tinctorial features of this amyloid polymorph previously unreported for PLE. We find that PLE spherulites share both tinctorial and structural characteristics with their amyloid fibril counterparts. Differences in PLE's molecular weight, polydispersity or chemistry could not explain the selective propensity toward either fibril or spherulite formation. Instead, we provide evidence that PLE polymers can exist in either a collapsed globule or an extended random coil conformation. The collapsed globule consistently produces spherulites while the extended coil assembles into disordered fibril bundles. This results suggests that these 2 PLE conformers directly affect the morphology of the resulting macroscopic amyloid assembly. PMID:28232889

Collapsed state of polyglutamic acid results in amyloid spherulite formation.

PubMed

Stehli, Daniel; Mulaj, Mentor; Miti, Tatiana; Traina, Joshua; Foley, Joseph; Muschol, Martin

2015-01-01

Self-assembly of proteins and peptides into amyloid fibrils involves multiple distinct intermediates and late-stage fibrillar polymorphs. Understanding the conditions and mechanisms that promote the formation of one type of intermediate and polymorph over the other represents a fundamental challenge. Answers to this question are also of immediate biomedical relevance since different amyloid aggregate species have been shown to have distinct pathogenic potencies. One amyloid polymorph that has received comparatively little attention are amyloid spherulites. Here we report that self-assembly of the intrinsically disordered polymer poly(L-glutamic) acid (PLE) can generate amyloid spherulites. We characterize spherulite growth kinetics, as well as the morphological, optical and tinctorial features of this amyloid polymorph previously unreported for PLE. We find that PLE spherulites share both tinctorial and structural characteristics with their amyloid fibril counterparts. Differences in PLE's molecular weight, polydispersity or chemistry could not explain the selective propensity toward either fibril or spherulite formation. Instead, we provide evidence that PLE polymers can exist in either a collapsed globule or an extended random coil conformation. The collapsed globule consistently produces spherulites while the extended coil assembles into disordered fibril bundles. This results suggests that these 2 PLE conformers directly affect the morphology of the resulting macroscopic amyloid assembly.

Botanicals and Phosphonate Show Potential to Replace Copper for Control of Potato Late Blight

PubMed Central

Forrer, Hans-Rudolf

2017-01-01

Potato late blight (PLB) caused by Phytophthora infestans (Pi) is the most harmful disease in potato production worldwide. In organic farming, copper is used despite its persistence in soil and toxicity to soil organisms. To replace copper, suspensions of powders from three promising botanicals, including bark of buckthorn (Frangula alnus, FA), roots of medicinal rhubarb (Rheum palmatum) and galls of the nutgall tree (Galla chinensis), were tested in multi-year field experiments. The current study shows for the first time that botanicals could replace copper under field conditions and best PLB reduction on leaves was achieved with FA, reaching a level close to that of 2 to 3 kg copper per hectare and year. Better results than with copper were achieved with Phosfik® (Ph), a phosphonate-based product. For both FA and Ph, the mode of action is based on induced resistance, for Ph also on direct fungicidal effects. A disadvantage of Ph is the accumulation of residues in potato tubers. Nevertheless, two to three applications with 2 to 3 L/ha of Ph would be feasible to not exceed a minimal risk level (MLR) of 20 mg/kg of phosphorous acid as proposed by the European Food Safety Authority. Due to an excellent environmental profile and a complex mode of action counteracting Pi resistance, phosphonate-based products would be most suitable for sustainable PLB management in integrated pest management (IPM) programmes. PMID:29371580

Integrated electrochemical gluconic acid biosensor based on self-assembled monolayer-modified gold electrodes. Application to the analysis of gluconic acid in musts and wines.

PubMed

Campuzano, S; Gamella, M; Serra, B; Reviejo, A J; Pingarrón, J M

2007-03-21

An integrated amperometric gluconic acid biosensor constructed using a gold electrode (AuE) modified with a self-assembled monolayer (SAM) of 3-mercaptopropionic acid (MPA) on which gluconate dehydrogenase (GADH, 0.84 U) and the mediator tetrathiafulvalene (TTF, 1.5 micromol) were coimmobilized by covering the electrode surface with a dialysis membrane is reported. The working conditions selected were Eapp=+0.15 V and 25+/-1 degrees C. The useful lifetime of one single TTF-GADH-MPA-AuE was surprisingly long. After 53 days of continuous use, the biosensor exhibited 86% of the original sensitivity. A linear calibration plot was obtained for gluconic acid over the 6.0x10(-7) to 2.0x10(-5) M concentration range, with a limit of detection of 1.9x10(-7) M. The effect of potential interferents (glucose, fructose, galactose, arabinose, and tartaric, citric, malic, ascorbic, gallic, and caffeic acids) on the biosensor response was evaluated. The behavior of the biosensor in a flow-injection system in connection with amperometric detection was tested. The analytical usefulness of the biosensor was evaluated by determining gluconic acid in wine and must samples, and the results obtained were validated by comparison with those provided by using a commercial enzyme test kit.

Exploring Step‐by‐Step Assembly of Nanoparticle:Cytochrome Biohybrid Photoanodes

PubMed Central

Hwang, Ee Taek; Orchard, Katherine L.; Hojo, Daisuke; Beton, Joseph; Lockwood, Colin W. J.; Adschiri, Tadafumi

2017-01-01

Abstract Coupling light‐harvesting semiconducting nanoparticles (NPs) with redox enzymes has been shown to create artificial photosynthetic systems that hold promise for the synthesis of solar fuels. High quantum yields require efficient electron transfer from the nanoparticle to the redox protein, a property that can be difficult to control. Here, we have compared binding and electron transfer between dye‐sensitized TiO2 nanocrystals or CdS quantum dots and two decaheme cytochromes on photoanodes. The effect of NP surface chemistry was assessed by preparing NPs capped with amine or carboxylic acid functionalities. For the TiO2 nanocrystals, binding to the cytochromes was optimal when capped with a carboxylic acid ligand, whereas for the CdS QDs, better adhesion was observed for amine capped ligand shells. When using TiO2 nanocrystals, dye‐sensitized with a phosphonated bipyridine Ru(II) dye, photocurrents are observed that are dependent on the redox state of the decaheme, confirming that electrons are transferred from the TiO2 nanocrystals to the surface via the decaheme conduit. In contrast, when CdS NPs are used, photocurrents are not dependent on the redox state of the decaheme, consistent with a model in which electron transfer from CdS to the photoanode bypasses the decaheme protein. These results illustrate that although the organic shell of NPs nanoparticles crucially affects coupling with proteinaceous material, the coupling can be difficult to predict or engineer. PMID:28920010

A synergetic analysis method for antifouling behavior investigation on PES ultrafiltration membrane with self-assembled TiO2 nanoparticles.

PubMed

Li, Xin; Li, Jiansheng; Fang, Xiaofeng; Bakzhan, Kariboz; Wang, Lianjun; Van der Bruggen, Bart

2016-05-01

Fouling of ultrafiltration (UF) membranes is a major impediment for their use in drinking water production. Mixed matrix membranes (MMMs) may have great opportunities in dealing with this challenge due to their hierarchical structures and multiple functionalities. In this study, a synergetic analysis method based on intermolecular adhesion force measurement and fouling process simulation was applied to investigate the fouling mechanism of polyethersulfone (PES) UF membranes containing in situ self-assembled TiO2 nanoparticles (NPs). The fouling resistance behavior and antifouling mechanism of the newly developed composite membranes were investigated with sodium alginate (SA), bovine serum albumin (BSA) and humic acid (HA) as model organic foulants. An improved antifouling effect was conspicuously observed for the composite membranes, expressed by a lower flux decline and significantly better cleaning efficiency. A strong correlation between the self-assembled structure of TiO2 NPs and the antifouling behavior of the composite membrane was observed. A lower magnitude and a narrower distribution of adhesion forces for the composite membrane suggest the effective suppression of foulants adsorption on the clean or fouled membrane. The simulation analysis indicates that the main fouling mechanism was standard blocking and cake filtration, further confirming the superiority of the NPs self-assembled structure in mitigating membrane fouling. This dual analysis method may provide a promising technological support for the application of modified UF membranes with self-assembled NPs in drinking water production. Copyright © 2016 Elsevier Inc. All rights reserved.

Two-carbon homologation of aldehydes and ketones to α,β-unsaturated aldehydes.

PubMed

Petroski, Richard J; Vermillion, Karl; Cossé, Allard A

2011-06-17

Phosphonate reagents were developed for the two-carbon homologation of aldehydes or ketones to unbranched- or methyl-branched α,β-unsaturated aldehydes. The phosphonate reagents, diethyl methylformyl-2-phosphonate dimethylhydrazone and diethyl ethylformyl-2-phosphonate dimethylhydrazone, contained a protected aldehyde group instead of the usual ester group. A homologation cycle entailed condensation of the reagent with the starting aldehyde, followed by removal of the dimethylhydrazone protective group with a biphasic mixture of 1 M HCl and petroleum ether. This robust two-step process worked with a variety of aldehydes and ketones. Overall isolated yields of unsaturated aldehyde products ranged from 71% to 86% after the condensation and deprotection steps.

Self-Assembled Soft Optical Negative Index Materials

DTIC Science & Technology

2008-08-05

within the MURI indicated that anodization of aluminum films provides hexagonal nano-hole arrays, which, when backfilled with e.g. silver via...bath determine pore size and spacing. Then AAO is removed with chromic and phosphoric acid at 70°C for 6 hrs. A 2nd anodization results in hexagonal...array of pores. Anodization time sets membrane thickness. Pores widened in acid such as phosphoric acid. The barrier layer is thinned by gradually

Structure of the Escherichia coli Phosphonate Binding Protein PhnD and Rationally Optimized Phosphonate Biosensors

PubMed Central

Alicea, Ismael; Marvin, Jonathan S.; Miklos, Aleksandr E.; Ellington, Andrew D.; Looger, Loren L.; Schreiter, Eric R.

2012-01-01

The phnD gene of Escherichia coli encodes the periplasmic binding protein of the phosphonate uptake and utilization pathway. We have crystallized and determined structures of E. coli PhnD (EcPhnD) in the absence of ligand and in complex with the environmentally abundant 2-aminoethylphosphonate (2AEP). Similar to other bacterial periplasmic binding proteins, 2AEP binds near the center of mass of EcPhnD in a cleft formed between two lobes. Comparison of the open, unliganded structure with the closed 2AEP-bound structure shows that the two lobes pivot around a hinge by ~70° between the two states. Extensive hydrogen bonding and electrostatic interactions stabilize 2AEP, which binds to EcPhnD with low nanomolar affinity. These structures provide insight into phosphonate uptake by bacteria and facilitated the rational design of high signal-to-noise phosphonate biosensors based both on coupled small molecule dyes and autocatalytic fluorescent proteins. PMID:22019591

The Metal Effect on Self-Assembling of Oxalamide Gelators Explored by Mass Spectrometry and DFT Calculations.

PubMed

Dabić, Dario; Brkljačić, Lidija; Tandarić, Tana; Žinić, Mladen; Vianello, Robert; Frkanec, Leo; Kobetić, Renata

2018-01-01

Gels formed by self-assembly of small organic molecules are of wide interest as dynamic soft materials with numerous possible applications, especially in terms of nanotechnology for functional and responsive biomaterials, biosensors, and nanowires. Four bis-oxalamides were chosen to show if electrospray ionization mass spectrometry (ESI-MS) could be used as a prediction of a good gelator and also to shed light on the gelation processes. By inspecting the gelation of several solvent, we showed that bis(amino acid)oxalamide 1 proved to be the most efficient, also being able of forming the largest observable assemblies in the gas phase. The formation of singly charged assemblies holding from one up to six monomer units is the outcome of the strong intermolecular H-bonds, particularly among terminal carboxyl groups. The variation of solvents from polar aprotic towards polar protic did not have any significant effects on the size of the assemblies. The addition of a salt such as NaOAc or Mg(OAc) 2 , depending on the concentration, altered the assembling. Computational analysis at the DFT level aided in the interpretation of the observed trends and revealed that individual gelator molecules spontaneously assemble to higher aggregates, but the presence of the Na + cation disrupts any gelator organization since it becomes significantly more favorable for gelator molecules to bind Na + cations up to the 3:1 ratio than to self-assemble, being fully in line with experimental observations reported here. Graphical Abstract ᅟ.

The Metal Effect on Self-Assembling of Oxalamide Gelators Explored by Mass Spectrometry and DFT Calculations

NASA Astrophysics Data System (ADS)

Dabić, Dario; Brkljačić, Lidija; Tandarić, Tana; Žinić, Mladen; Vianello, Robert; Frkanec, Leo; Kobetić, Renata

2018-01-01

Gels formed by self-assembly of small organic molecules are of wide interest as dynamic soft materials with numerous possible applications, especially in terms of nanotechnology for functional and responsive biomaterials, biosensors, and nanowires. Four bis-oxalamides were chosen to show if electrospray ionization mass spectrometry (ESI-MS) could be used as a prediction of a good gelator and also to shed light on the gelation processes. By inspecting the gelation of several solvent, we showed that bis(amino acid)oxalamide 1 proved to be the most efficient, also being able of forming the largest observable assemblies in the gas phase. The formation of singly charged assemblies holding from one up to six monomer units is the outcome of the strong intermolecular H-bonds, particularly among terminal carboxyl groups. The variation of solvents from polar aprotic towards polar protic did not have any significant effects on the size of the assemblies. The addition of a salt such as NaOAc or Mg(OAc)2, depending on the concentration, altered the assembling. Computational analysis at the DFT level aided in the interpretation of the observed trends and revealed that individual gelator molecules spontaneously assemble to higher aggregates, but the presence of the Na+ cation disrupts any gelator organization since it becomes significantly more favorable for gelator molecules to bind Na+ cations up to the 3:1 ratio than to self-assemble, being fully in line with experimental observations reported here. [Figure not available: see fulltext.

Block Copolymer Micelles as Nanocontainers for Controlled Release of Proteins from Biocompatible Oil Phases

PubMed Central

2009-01-01

Biocompatible oils are used in a variety of medical applications ranging from vaccine adjuvants to vehicles for oral drug delivery. To enable such nonpolar organic phases to serve as reservoirs for delivery of hydrophilic compounds, we explored the ability of block copolymer micelles in organic solvents to sequester proteins for sustained release across an oil−water interface. Self-assembly of the block copolymer, poly(ϵ-caprolactone)-block-poly(2-vinyl pyridine) (PCL-b-P2VP), was investigated in toluene and oleic acid, a biocompatible naturally occurring fatty acid. Micelle formation in toluene was characterized by dynamic light scattering (DLS) and atomic force microscopy (AFM) imaging of micelles cast onto silicon substrates. Cryogenic transmission electron microscopy confirmed a spherical morphology in oleic acid. Studies of homopolymer solubility implied that micelles in oleic acid consist of a P2VP corona and a PCL core, while P2VP formed the core of micelles assembled in toluene. The loading of two model proteins (ovalbumin (ova) and bovine serum albumin (BSA)) into micelles was demonstrated with loadings as high as 7.8% wt of protein per wt of P2VP in oleic acid. Characterization of block copolymer morphology in the two solvents after protein loading revealed spherical particles with similar size distributions to the as-assembled micelles. Release of ova from micelles in oleic acid was sustained for 12−30 h upon placing the oil phase in contact with an aqueous bath. Unique to the situation of micelle assembly in an oily phase, the data suggest protein is sequestered in the P2VP corona block of PCL-b-P2VP micelles in oleic acid. More conventionally, protein loading occurs in the P2VP core of micelles assembled in toluene. PMID:19235932

Fluoride-Mediated Dephosphonylation of α-Diazo-β-carbonyl Phosphonates.

PubMed

Phatake, Ravindra S; Mullapudi, Venkannababu; Wakchaure, Vivek C; Ramana, Chepuri V

2017-01-20

The possibility of fluoride-mediated selective dephosphonylation of α-diazo-β-carbonyl phosphonates such as the Ohira-Bestmann reagent has been proposed and executed. The resulting α-diazocarbonyl intermediates undergo a (3 + 2)-cycloaddition at room temperature with conjugated olefins and benzynes. Interestingly, under the current conditions, the resulting cycloaddition products underwent either N-acylation (with excess α-diazo-β-carbonyl phosphonates) or Michael addition (with conjugated olefins).