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Acid Units (acid + unit)
Selected AbstractsSynthesis and Enantioselective Discrimination of Chiral Fluorescence Receptors Bearing Amino Acid UnitsCHINESE JOURNAL OF CHEMISTRY, Issue 3 2007Kuo-Xi Xu Abstract Two chiral fluorescence receptors (1, 2) were synthesized, and their structures were characterized by IR, 1H NMR, 13C NMR, mass spectra and elemental analysis. The chiral recognition of receptors was studied by 1H NMR and fluorescence spectra. The results demonstrate that receptors and dibenzoyl tartrate anion formed a 1:1 complex. The receptor 1 exhibited a good enantioselective recognition ability toward the enantiomers of dibenzoyl tartrate anion. [source] Synthesis of 4H- indeno[1,2- b]thiophenes, 8H -indeno[2,1- b]-thiophenes and 8H -indeno[2,1- b]furans having acrylic acid unitJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2008Ki Joon Jeon Treatment of methyl propiolate and 2-(thiophen-2-yl)benzaldehyde, 2-(thiophen-3-yl)benzaldehyde or 2-(furan-3-yl)benzaldehyde with tetrabutylammonium iodide/zirconium (IV) chloride or treatment of methyl acrylate and the same aldehydes with 1,4-diazabicyclo[2,2,2]octane and triethanolamine induce an aldol-type reaction to furnish Baylis-Hillman adducts ,-iodo-,-(hydroxymethyl)acrylates or ,-(hydroxy-methyl)acrylates, respectively. These can be used for the preparation of indenothiophenes and indenofurans having acrylic acid unit by intramolecular Friedel-Crafts reaction with sulfuric acid in tetrachloromethane. [source] Structural characterization and identification of iridoid glycosides, saponins, phenolic acids and flavonoids in Flos Lonicerae Japonicae by a fast liquid chromatography method with diode-array detection and time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2009Lian-Wen Qi A fast liquid chromatography method with diode-array detection (DAD) and time-of-flight mass spectrometry (TOF-MS) has been developed for analysis of constituents in Flos Lonicerae Japonicae (FLJ), a traditional Chinese medicine derived from the flower bud of Lonicerajaponica. The chromatographic analytical time decreased to 25,min without sacrificing resolution using a column packed with 1.8-µm porous particles (4.6,×,50,mm), three times faster than the performance of conventional 5.0-µm columns (4.6,×,150,mm). Four major groups of compounds previously isolated from FLJ were structurally characterized by DAD-TOF-MS: iridoid glycosides showed maximum UV absorption at 240,nm; phenolic acids at 217, 242, and 326,nm; flavonoids at 255 and 355,nm; while saponins had no absorption. In electrospray ionization (ESI)-TOF-MS experiments, elimination of a glucose unit (162 Da), and successive losses of H2O, CH3OH and CO, were generally observed in iridoid glycosides; saponins were characterized by a series of identical aglycone ions; phenolic acids typically generated a base peak at [M,H,caffeoyl], by loss of a caffeic acid unit (162 Da) and several marked quinic acid moiety ions; cleavage of the glycosidic bond (loss of 162 or 308 Da), subsequent losses of H2O, CO, RDA and C-ring fragmentation were the most possible fragmentation pathways for flavonoids. By accurate mass measurements within 4,ppm error for each molecular ion and subsequent fragment ions, as well as the ,full mass spectral' information of TOF-MS, a total of 41 compounds including 13 iridoid glycosides, 11 phenolic acids, 7 saponins, and 10 flavonoids were identified in a methanolic extract of FLJ. Copyright © 2009 John Wiley & Sons, Ltd. [source] Glycan profiling of urine, amniotic fluid and ascitic fluid from galactosialidosis patients reveals novel oligosaccharides with reducing end hexose and aldohexonic acid residuesFEBS JOURNAL, Issue 14 2010Cees Bruggink Urine, amniotic fluid and ascitic fluid samples of galactosialidosis patients were analyzed and structurally characterized for free oligosaccharides using capillary high-performance anion-exchange chromatography with pulsed amperometric detection and online mass spectrometry. In addition to the expected endo-,- N- acetylglucosaminidase-cleaved products of complex-type sialylated N -glycans, O -sulfated oligosaccharide moieties were detected. Moreover, novel carbohydrate moieties with reducing-end hexose residues were detected. On the basis of structural features such as a hexose,N -acetylhexosamine,hexose,hexose consensus sequence and di-sialic acid units, these oligosaccharides are thought to represent, at least in part, glycan moieties of glycosphingolipids. In addition, C1 -oxidized, aldohexonic acid-containing versions of most of these oligosaccharides were observed. These observations suggest an alternative catabolism of glycosphingolipids in galactosialidosis patients: oligosaccharide moieties from glycosphingolipids would be released by a hitherto unknown ceramide glycanase activity. The results show the potential and versatility of the analytical approach for structural characterization of oligosaccharides in various body fluids. [source] Tyrosine sulfation and N-glycosylation of human heparin cofactor II from plasma and recombinant Chinese hamster ovary cells and their effects on heparin bindingFEBS JOURNAL, Issue 3 2002Christoph Böhme The structure of post-translational modifications of human heparin cofactor II isolated from human serum and from recombinant Chinese hamster ovary cells and their effects on heparin binding have been characterized. Oligosaccharide chains were found attached to all three potential N-glycosylation sites in both protein preparations. The carbohydrate structures of heparin cofactor II circulating in blood are complex-type diantennary and triantennary chains in a ratio of 6 : 1 with the galactose being > 90% sialylated with ,2,6 linked N-acetylneuraminic acid. About 50% of the triantennary structures contain one sLex motif. Proximal ,1,6 fucosylation of oligosacharides from Chinese hamster ovary cell-derived HCII was detected in >,90% of the diantennary and triantennary glycans, the latter being slightly less sialylated with exclusively ,2,3-linked N -acetylneuraminic acid units. Applying the ESI-MS/ MS-MS technique, we demonstrate that the tryptic peptides comprising tyrosine residues in positions 60 and 73 were almost completely sulfated irrespective of the protein's origin. Treatment of transfected Chinese hamster ovary cells with chlorate or tunicamycin resulted in the production of heparin cofactor II molecules that eluted with higher ionic strength from heparin,Sepharose, indicating that tyrosine sulfation and N-linked glycans may affect the inhibitor's interaction with glycosaminoglycans. [source] A versatile approach for the syntheses of poly(ester amide)s with pendant functional groupsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2009Katelyn M. Atkins Abstract Poly(ester amide)s (PEAs) are emerging as promising materials for a wide range of biomedical applications due to their potential for both hydrolytic and enzymatic degradation, as well as the ease with which their properties can be tuned by the choice of monomers. The incorporation of pendant functional handles along the PEA backbone has the potential to further expand their applications by allowing the charge and hydrophilicity of the polymers to be altered, and facilitating the conjugation of active molecules such as drugs, targeting groups, and cell signaling molecules. Described here is a simple and versatile strategy based on orthogonal protecting groups, by which L -lysine and L- aspartic acid can be incorporated into several families of PEAs based on monomers including the diacids succinic and terephthalic acid, the diols 1,4-butanediol and 1,8-octanediol, and the amino acids L- alanine and L- phenylalanine. All polymers were thoroughly characterized by nuclear magnetic resonance spectroscopy, infrared spectroscopy, size exclusion chromatography, thermogravimetric analysis, and differential scanning calorimetry. It was demonstrated that the side chain protecting groups could be readily removed, allowing the pendant amines or carboxylic acids to be functionalized. In particular, the carboxylic acid groups on a polymer containing L- aspartic acid units were converted to N -hydroxysuccinimidyl esters, providing a useful template for further derivatization. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3757,3772, 2009 [source] Enzymatic Hydrolysis of , - and , -Oligo(L -aspartic acid)s by Poly(aspartic acid) Hydrolases-1 and 2 from Sphingomonas sp.MACROMOLECULAR BIOSCIENCE, Issue 3 2004Abstract Summary: The enzymatic hydrolysis of , - and , -oligo(L -aspartic acid)s by PAA hydrolase-1 and PAA hydrolase-2 (purified from Sphingomonas sp. KT-1) was performed to elucidate the mechanism of the microbial degradation by Sphingomonas sp. KT-1 of the thermally synthesized ,,, -poly(D,L -aspartic acid) (tPAA). GPC analysis of the hydrolyzed products of , - and , -tetra(L -aspartic acid)s by PAA hydrolase-1 has showed that PAA hydrolase-1 is capable of hydrolyzing only the specific amide bonds between , -aspartic acid units. The RP-HPLC analysis of the enzymatic hydrolysis of , -oligo(L -aspartic acid)s (4 and 5 mers) by PAA hydrolase-1 has suggested that the enzymatic hydrolysis of , -oligo(L -aspartic acid)s occurs via an endo-mode cleavage. In contrast, PAA hydrolase-2 hydrolyzed both , - and , -oligo(L -aspartic acid)s via an exo-mode cleavage to yield L -aspartic acid as a final product. A kinetic study on the enzymatic hydrolysis of , -oligo(L -aspartic acid)s (3 to 7 mers) by PAA hydrolase-2 has indicated that Km values are almost independent of the number of monomer units in oligomers of 4 to 7 mers, while that Vmax values are markedly dependent on the chain length and show a maximum value at 5 mer. A proposed mechanism of the enzymatic hydrolysis of tPAA by PAA hydrolase-1 and PAA hydrolase-2 in the cell of Sphingomonas sp. KT-1. [source] Synthesis and Characterization of Supramolecular Polymeric Materials Containing Azopyridine UnitsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 22 2006Marta Millaruelo Abstract Summary: The synthesis and characterization of a series of supramolecular polymeric complexes formed by H-bonding interactions between benzoic acid and azopyridine derivatives are described. A series of polymeric networks have been synthesized using a polymethacrylate bearing benzoic acid units as side groups, and several polymers with azopyridine as H-acceptor side groups. Furthermore, low-molecular-weight pyridine derivatives have been used to prepare an homologous side-chain polymer, and a network with azopyridine as a non-covalent crosslinker. Special attention was paid to the thermal and mesomorphic properties of these materials, which were studied by DSC, POM, and XRD. Micrograph of the mesomorphic melt of a sample taken at 130,°C on cooling from the isotropic state. [source] Molar Mass and Structural Characteristics of Poly[(lactide- co -(aspartic acid)] Block CopolymersMACROMOLECULAR SYMPOSIA, Issue 1 2008Ida Poljan Abstract Summary: We report on various synthetic procedures for the preparation of biodegradable and biocompatible poly(lactide- co -aspartic acid) block copolymers based on natural monomeric units , lactic acid and aspartic acid. Multiblock poly(lactide- co -aspartic acid) copolymers of different comonomer composition were synthesized by heating a mixture of L-aspartic acid and L,L-lactide in melt without the addition of any catalyst or solvent and with further alkaline hydrolysis of the cyclic succinimide rings to aspartic acid units. Diblock poly(lactide- co -aspartic acid) copolymers with different block lengths were prepared by copolymerization of amino terminated poly(, -benzyl-L-aspartate) homopolymer and L,L-lactide with subsequent deprotection of the benzyl protected carboxyl group by hydrogenolysis. The differences in the structure, composition, molar mass characteristics, and water-solubility of the synthesized multiblock and diblock poly(lactide- co -aspartic acid) copolymers are discussed. [source] Control of Biocatalytic Transformations by Programmed DNA AssembliesCHEMISTRY - A EUROPEAN JOURNAL, Issue 12 2010Ronit Freeman Abstract This study demonstrates the self-assembly of inhibitor/enzyme-tethered nucleic acid fragments or enzyme I-, enzyme II-modified nucleic acids into functional nanostructures that lead to the controlled inhibition of the enzyme or the activation of an enzyme cascade. In one system, the anti-cocaine aptamer subunits are modified with monocarboxy methylene blue (MB+) as the inhibitor and with choline oxidase (ChOx). The cocaine-induced self-assembly of the aptamer subunits complex results in the inhibition of ChOx by MB+. In a further configuration, two nucleic acids of limited complementarity are functionalized at their 3, and 5, ends with glucose oxidase (GOx) and horseradish peroxidase (HRP), respectively, or with MB+ and ChOx. In the presence of a target DNA sequence, synergistic complementary base-pairing occurs, thus leading to stable supramolecular Y-shaped nanostructures of the nucleic acid units. A GOx/HRP bienzyme cascade or the programmed inhibition of ChOx by MB+ is demonstrated in the resulting nucleic acid nanostructures. A quantitative theoretical model that describes the nucleic acid assemblies and that results in the inhibition of ChOx by MB+ or in the activation of the GOx/HRP cascade, respectively, is provided. [source] Modular Solid-Phase Synthetic Approach To Optimize Structural and Electronic Properties of Oligoboronic Acid Receptors and Sensors for the Aqueous Recognition of OligosaccharidesCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2004Duane Stones Dr. Abstract This article describes the design and optimization of the first entirely modular, parallel solid-phase synthetic approach for the generation of well-defined polyamine oligoboronic acid receptors and fluorescence sensors for complex oligosaccharides. The synthetic approach allows an effective building of the receptor polyamine backbone, followed by the controlled diversification of the amine benzylic side chains. This approach enabled the testing, in a modular fashion, of the effect of different arylboronic acid units substituted with unencumbering para electron-withdrawing or electron-donating groups. The feasibility of this approach toward automated synthesis was also investigated with the assembly of a sublibrary of receptors by means of the Irori MiniKan technology. Several sublibraries of anthracene-capped sensors containing two or three arylboronic acids were synthesized, and their binding to a series of model disaccharides was examined in neutral aqueous media. The calculation of association constants by fluorescence titrations confirmed that subtle changes in the structures of the interamine spacers in the polyamine backbone can have a significant effect on the stability of the resulting complexes. Most importantly, this study led to the determination of the preferred electronic characteristics for the arylboronate units, and suggests that a new generation of receptors containing very electron-poor arylboronic acids could lead to a significant improvement of binding affinities. [source] Water Soluble Cruciforms: Effect of Surfactants on FluorescenceCHEMISTRY - AN ASIAN JOURNAL, Issue 2 2009Juan Tolosa Dr. Abstract Brighten up! Adding surfactants to aqueous solutions of three different water-soluble cruciforms (XF) improves their fluorescence quantum yields. Additionally, changes are observed in the emission wavelength of the XF around the critical micelle concentration (cmc) of the surfactant. Three 1,4-bis-(aminostyryl)-2,5-bis(phenylethynyl) benzenes carrying four, six, or eight acetic acid units were investigated for their surfactochromicity. Anionic, cationic, and nonionic surfactants as well as a surfactant-like protein (bovine serum albumin, BSA) were added to buffered solutions of the XFs in water, causing,in most cases,the fluorescence quantum yield to increase significantly and a blue- or red-shifted emission to be observed. The addition of cationic (cetyltrimethylammonium bromide, CTAB) and neutral (Brij 35, TWEEN 20 and Triton X-100) surfactants to XFs causes a red shift in their emission at low or very low surfactant concentrations that we attribute to surfactant-induced excimer formation. The fluorescence quantum yield is in most cases a monotonous function of surfactant concentration. For the investigated ionic surfactants, the fluorescence quantum yield of the XFs does not change much after the critical micelle concentration (CMC) of the surface is reached. However, in the case of non-ionic surfactants, the fluorescence quantum yields of the XFs starts to increase after the CMC has been reached, suggesting that different effects are involved. [source] | |||||||||||||