Maleic Acid Moiety Research Articles

Bioinspired, Size-Tunable Self-Assembly of Polymer-Lipid Bilayer Nanodiscs.

Polymer-based nanodiscs are valuable tools in biomedical research that can offer a detergent-free solubilization of membrane proteins maintaining their native lipid environment. Herein, we introduce a novel ca. 1.6 kDa SMA-based polymer with styrene:maleic acid moieties that can form nanodiscs containing a planar lipid bilayer which are useful to reconstitute membrane proteins for structural and functional studies. The physicochemical properties and the mechanism of formation of polymer-based nanodiscs are characterized by light scattering, NMR, FT-IR, and TEM. A remarkable feature is that nanodiscs of different sizes, from nanometer to sub-micrometer diameter, can be produced by varying the lipid-to-polymer ratio. The small-size nanodiscs (up to ca. 30 nm diameter) can be used for solution NMR spectroscopy studies whereas the magnetic-alignment of macro-nanodiscs (diameter of > ca. 40 nm) can be exploited for solid-state NMR studies on membrane proteins.

Bioinspired, Size‐Tunable Self‐Assembly of Polymer–Lipid Bilayer Nanodiscs

AbstractPolymer‐based nanodiscs are valuable tools in biomedical research that can offer a detergent‐free solubilization of membrane proteins maintaining their native lipid environment. Herein, we introduce a novel ca. 1.6 kDa SMA‐based polymer with styrene:maleic acid moieties that can form nanodiscs containing a planar lipid bilayer which are useful to reconstitute membrane proteins for structural and functional studies. The physicochemical properties and the mechanism of formation of polymer‐based nanodiscs are characterized by light scattering, NMR, FT‐IR, and TEM. A remarkable feature is that nanodiscs of different sizes, from nanometer to sub‐micrometer diameter, can be produced by varying the lipid‐to‐polymer ratio. The small‐size nanodiscs (up to ca. 30 nm diameter) can be used for solution NMR spectroscopy studies whereas the magnetic‐alignment of macro‐nanodiscs (diameter of > ca. 40 nm) can be exploited for solid‐state NMR studies on membrane proteins.

Preparation of Covalent Pseudo-Two-Dimensional Polymers in Water by Free Radical Polymerization

Two-dimensional (2D) polymer has attracted considerable attention due to its excellent properties. Although a number of 2D polymers have been reported, preparation of free-standing single-layer 2D polymers in solution is still a big challenge. Here we report a facile and highly efficient strategy for synthesis of free-standing single-layer covalent pseudo-2D polymers via free radical polymerization in water on a large scale. The strategy designated as “two-dimensional self-assembly polymerization (2DSP)” includes formation of supramolecular 2D nanosheets by self-assembly of bola-amphiphilic monomer that bearing two maleic acid moieties and transformation of supramolecular 2D nanosheets to covalent pseudo-2D polymers by copolymerization with vinyl monomers. We find that the counterion of the bola-amphiphile has a significant influence on formation of single-layer supramolecular 2D nanosheets, and the formation of 2D polymer sheets is highly related to the vinyl monomers. The unique 2D polymer sheets were used to prepare hydrogels with excellent mechanical properties.

Stability study on an anti-cancer drug 4-(3,5-bis(2-chlorobenzylidene)-4-oxo-piperidine-1-yl)-4-oxo-2-butenoic acid (CLEFMA) using a stability-indicating HPLC method

CLEFMA, 4-(3,5-bis(2-chlorobenzylidene)-4-oxo-piperidine-1-yl)-4-oxo-2-butenoic acid, is a new chemical entity with anti-cancer and anti-inflammatory activities. Here, we report its stability in solution against stress conditions of exposure to acid/base, light, oxidant, high temperature, and plasma. The identity of the degradation products was ascertained by mass and proton nuclear magnetic resonance spectroscopy. To facilitate this study, we developed and validated a reverse phase high performance liquid chromatography method for detection of CLEFMA and its degradation. The method was linear over a range of 1–100µg/mL; the accuracy and precision were within acceptable limits; it was stability-indicating as it successfully separated cis-/trans-isomers of CLEFMA as well as its degradation product. The major degradation product was produced from amide hydrolysis at maleic acid functionality caused by an acidic buffer, oxidant (3% hydrogen peroxide), or temperature stress (40–60°C). The log k-pH profile showed that CLEFMA was most stable at neutral pH. In accelerated stability study we found that the shelf-life (T90%) of CLEFMA at 25°C and 4°C was 45 days and 220 days, respectively. Upon exposure to UV-light (365nm), the normally prevalent trans-CLEFMA attained cis-configuration. This isomerization also involved the maleic acid moiety. CLEFMA was stable in plasma from which it could be efficiently extracted by an acetonitrile precipitation method. These results indicate that CLEFMA is sensitive to hydrolytic cleavage at its maleic acid moiety, and it is recommended that its samples should be stored under refrigerated and light-free conditions, and under inert environment.

Antifungal activity of tautomycin and related compounds against Sclerotinia sclerotiorum

The potential of tautomycin to control oilseed rape stem rot was investigated in this paper. Tautomycin produced by Streptomyces spiroverticillatus strongly inhibited Sclerotinia sclerotiorum, which causes oilseed rape stem rot. Tautomycin showed great inhibition of the mycelial growth of S. sclerotiorum on potato dextrose agar (PDA) plates. The values of EC(50) and MIC were 3.26 × 10(-4) mM and 6.52 × 10(-4) mM, respectively. Tautomycin treatment also resulted in morphological abnormalities of S. sclerotiorum such as hyphal swellings and abnormally branched shapes, which were observed microscopically. Sclerotia of S. sclerotiorum soaked in the tautomycin solution for 24 h remained viable, but their ability to undergo myceliogenic germination on PDA plates was completely inhibited when the concentration of tautomycin reached 6.52 × 10(-4) mM. Tautomycin-treated oilseed rape leaves were found to have a low incidence of leaf blight caused by S. sclerotiorum. The activity of the protein phosphatase (PP) in S. sclerotiorum decreased by 41.6% and 52.6% when treated with 3.30 × 10(-4) mM and 6.52 × 10(-4) mM tautomycin, respectively. Cellular constituents also leaked from S. sclerotiorum cells incubated with tautomycin. The results suggest that the antimicrobial activity of tautomycin is due to the inhibition of the PP and then a change of membrane permeability. This paper also investigated related compounds that possess either a maleic anhydride or maleic acid moiety. Results showed 2,3-dimethylmaleic anhydride, diphenylmaleic anhydride and dimethyl maleate demonstrated significant activity against S. sclerotiorum. The values of EC(50) for these three compounds were 0.31 mM, 0.15 mM and 3.99 mM, respectively. The MIC values obtained for these compounds were 1.11 mM, 0.56 mM and 9.58 mM, respectively.

Preparation of highly dispersed gold nanoparticles inside the porous support assisted by amphiphilic vinyl maleate copolymer

An amphiphilic copolymer composed of maleic acid and alkyl (C 18) vinyl monomer was encapsulated into the porous support. A series of colloidal gold nanoparticles of known size was substantially immobilized in the composite porous supports based on cross-linked polyacrylate ester and cross-linked polystyrene resin. Maleic acid moiety of the amphiphilic copolymer can act as a stabilizer for gold nanoparticles in analogy to citric acid, whereas alkyl chains play a role for the stable accommodation of the amphiphilic copolymer. Maleic acid stabilizes the gold nanoparticles by flexing the geometrical arrangement of the linear polymer. Presence of C 18 alkyl chain in the poly(C 18-vinyl maleate) is indispensable to act as spacing group that prevents mutual aggregation of gold nanoparticles. On the other hand, gold nanoparticles with average diameter of less than 8 nm were spontaneously formed by treatment of the composite resin beads with aqueous HAuCl 4 solution, subsequently dispersed inside the pores of resin beads as observed by TEM. We have also elucidated the catalytic activity of the material with the hydrogenation of cinnamaldehyde in supercritical carbon dioxide. Notably, apparent size effect of gold was observed in the selectivity of the reaction.

Layer‐by‐layer assembly of weak‐strong copolymer polyelectrolytes: A route to morphological control of thin films

AbstractMultilayer films were assembled from a strong polyelectrolyte (poly(diallyldimethylammonium chloride), PDADMAC) and a copolymer containing both strongly charged styrene sulfonate moieties and weakly charged maleic acid moieties (poly(4‐styrenesulfonic acid‐co‐maleic acid), PSSMA). Growth of PSSMA/PDADMAC multilayers was linear, as characterized by UV‐vis spectroscopy and quartz crystal microgravimetry. The influence of both the pH of the PSSMA adsorption solutions and the ratio of SS:MA in the PSSMA on multilayer properties was investigated. Fourier transform infrared spectroscopy results showed that the ionization of carboxylic acid groups in PSSMA/PDADMAC multilayers did not vary significantly with changes in the PSSMA assembly pH. However, the multilayers showed different thicknesses, surface morphologies, and stability to post‐assembly pH treatment. We also demonstrate that PSSMA/PDADMAC multilayers are significantly more stable than PSSMA/PAH multilayers after post‐assembly pH treatment (i.e. the films remain intact when exposed to pH extremes). In addition, the surface morphology of two films (PSSMA 1:1 assembled at pH 5.8, post‐treated at pH 2 and PSSMA 3:1 assembled at pH 5.8, post‐treated at pH 11) changed significantly when the films were exposed to solutions of different pH and, in the former case, this change in film morphology was reversible. The porous morphology after treatment at pH 2 could be reversed to give a significantly smoother film after subsequent exposure to water for 24 h. Our results demonstrate that by the rational choice of the assembly pH of PSSMA, stable and pH‐responsive films can be obtained via the sequential assembly of PSSMA and PDADMAC. These films have potential in controlled release applications where film stability and pH‐responsive behavior are essential. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4341‐4351, 2007

Surface Rheology of Monolayers of Poly(1-alkylene-co-maleic acid) at the Air/Water Interface: Surface Light Scattering Studies

The surface viscoelasticity of poly(1-alkylene-co-maleic acid) (PXcMA) with side chains varying from C4 to C16 was investigated at the air/water interface using the technique of surface light scattering (SLS). In the dilute surface mass density regime, the side chain length of the 1-alkylene has been shown to produce a wide range of surface viscoelastic films, from an elasticity-dominant film to a viscosity-dominant film. On the other hand, in the semidilute surface mass density regime, the film viscoelasticity is scarcely affected by the side chain length. Rather, the viscoelastic parameters are shown to scale with the inverse of surface mass density, i.e., area per monomer A. An inference is drawn that interactions between the hydrophilic polymer head of maleic acid moiety and the interface dominate in this regime. The loss tangent value varies with the side chain length in the dilute regime, whereas it no longer depends on the side chain length in the semidilute regime, where it collapses onto a limiting scaling behavior hitherto unknown: tan δ ∼ A-10 ∼ Π2.

Electroacoustic characterization of electrokinetics in concentrated pigment dispersions: 3-Cyano-4-(4′-butanesulfonamidophenyl)-5-furylidene-furan-2-one

The surface and colloid chemistry of organic pigment dispersions have largely been ignored in the literature, although organic pigments play a crucial role in classical and ink jet printing and imaging. This paper presents detailed measurements of an aqueous dispersion of the title compound, prepared without added surfactant, and examines the adsorption of various anionic surfactants via electrokinetic sonic amplitude (ESA) measurements. Quantitative adsorption data are compared with adsorption isotherms obtained via phase separation methods and are found to be in good agreement. Determination of saturation monolayer adsorption is significantly faster and more convenient using ESA measurement technology. However, some of the surfactants examined exhibited multilayer or partial multilayer adsorption. A surfactant modeled after the title compound was synthesized and exhibited particularly effective stabilization, although the adsorption appears slightly weaker than the classical surfactants studied. The intrinsic negative surface charge observed in aqueous dispersion of the title compound was identified as due to mechanicochemical activation of surface molecules to hydrolyze the furanone ring to the α-cyano maleic acid moiety. Electrophoretic mobility measurements as a function of volume fraction at various ionic strengths indicate that increasing electrophoretic mobility magnitudes accompanying increasing NaCl concentrations were due to preferential adsorption of chloride to the particle surfaces.

Poly[(N-Acetylimino)ethylene] Macromonomers with Maleic Moieties in the Dispersion Copolymerization with Styrene

Three different poly(N-acetyliminoethylene) (PNAI) macromonomers containing maleic acid moieties were tested as stabilizers for the preparation of polymer microparticles by dispersion polymerization in a polar media (alcohol/water). A comparative study on the effect of various factors, such as initiator nature and solvency of the reaction medium, on system stability and particle characteristics was performed. Styrene was used as the main monomer and ethanol, isopropanol and 2-butanol as organic solvents. Chemical and photochemical techniques were applied as initiation routes. The photoinitiators allow the synthesis of microparticles with low diameters and narrow size polydispersity in a high yield. The polymerization duration was significantly improved as compared to the methods available in the literature.

Total synthesis of D-(+)-showdomycin from syn-2,5-disubstituted tetrahydrofuran

D-(+)-Showdomycin, first isolated from Streptomyces showdoensis, has been synthesized starting from syn-2,5-disubstituted dihydrofuran 3. The key conversion was the functionalization of 2-thiophenylfuranyl group in 13 into maleic acid moiety in 12.

Grafting reactions and heparin adsorption of poly(amidoamine)-grafted poly(urethane amide)s

Differently terminated poly(amidoamine) (PAA) oligomers were grafted on the surface of poly(ether urethane amide)s (PEUAm), with fumaric or maleic acid moieties. The grafting reaction was Michael-type addition of amino groups to activated double bonds in the PEUAm backbone. PAAs having primary amino, or secondary amino end-groups were directly grafted on the surface of PEUAm sheets. For vinyl-terminated chains an α, Ω amino-polyether spacer was introduced initially, following the same addition mechanism. Ungrafted and grafted materials were characterized, besides other analytical techniques, by ATR FT-IR spectroscopy. The heparin adsorption on PEAUm films was analysed after its elution from heparinized samples, quantified by coagulation tests (aPTT), and related to the presence of the PAAs chains grafted on to the surface. Results indicate that PAA-grafted PEUAm elastomeric biomaterials, display enhanced heparin adsorption abilities.

Fluorescence probing of microdomains in aqueous solutions of polysoaps. 2. Study of the size of the microdomains

The fluorescence decay results in solutions of poly(disodium maleate-co-decylvinylether) and poly(disodium maleate-co-hexadecyl vinyl ether) referred to as PS10 and PS16 show that the microdomains are somewhat polydisperse in size. In the case of PS10 the number of repeat units per microdomain decreases nearly linearly upon increasing the degree of neutralization of the maleic acid moieties and is nearly independent of the polysoap concentration and polymerization degree as well as of the ionic strength and temperature. For PS16, the number of repeat units per microdomain is independent of the polymerization degree but increases much with temperature

Infrared Identification of Maleic Acid in Pharmaceutical Maleate Salts

Difficulties are encountered in the USP melting point identification test for maleic acid extracted from chlorpheniramine maleate. A general procedure is described for the isolation and infrared identification of the maleic acid moiety of pharmaceutical salts from drug substances or dosage forms. This procedure permits the concurrent infrared identification of the amine moiety.

Effect of Maleic Acid in Compendial UV Absorption Assays for Antihistamine Maleate Salts

Standard recoveries averaging 89.9% are reported for the NF XIII brompheniramine maleate tablet assay procedure, which employs UV comparison of unidentical sample and standard molecular species in the same medium. The data presented indicate that these low assay values are attributable to the chromophoric properties of the maleic acid moiety and its ability to protonate the α-pyridyl chromophore of the brompheniramine molecule in a neutral organic solvent.

Effect of Maleic Acid on the Ultraviolet Absorption of Some Antihistamine Maleate Salts

Abstract Several official compendial monographs contain assay procedures which compare the ultraviolet (UV) absorbance of a sample solution of a mineral acid salt of an antihistamine with that of a standard solution of the antihistamine maleate salt. The recovery data, UV absorbance values, and UV spectra presented show that erroneously low assay results are obtained when UV absorptions (below 280 nm) of antihistamine maleate sample solutions previously extracted from alkaline aqueous media into organic solvents are compared with antihistamine maleate standard sample solutions diluted directly in the same acid medium. Such errors are shown to be caused by the UV absorption properties of the maleic acid moiety.