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Acetyl Groups (acetyl + groups)
Selected AbstractsA Novel and Convenient Chemoselective Deprotection Method for Both Silyl and Acetyl Groups on Acidic Hydroxyl Groups such as Phenol and Carboxylic Acid by Using a Nitrogen Organic Base, 1,1,3,3-Tetramethylguanidine.CHEMINFORM, Issue 21 2003Kin-ichi Oyama No abstract is available for this article. [source] Structural Studies of the O-Chain Polysaccharide from Plesiomonas shigelloides Strain 302,73 (Serotype O1)EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2008Giuseppina Pieretti Abstract Plesiomonas shigelloides is a Gram-negative bacterium belonging to the Enterobacteriaceae family. It has been found in an aquatic environment in the tropical and subtropical regions and is responsible for many gastrointestinal infections in humans, which take place from drinking untreated water or eating uncooked shellfish. Plesiomonas shigelloides has also been reported to provoke extraintestinal infections such as meningitis and bacteremia in immunocompromised adults and neonates. Despite the emerging importance of this pathogenic microorganism, only three different O-antigens have been characterised so far. The structure of the O-chain of the lipopolysaccharide (LPS) from Plesiomonasshigelloides strain 302,73 (serotype O1) was determined by chemical analysis, 1D and 2D NMR spectroscopy and MALDI-TOF mass spectrometry. The polysaccharide was constituted by a linear pentasaccharidic repeating unit as follows: ,3)-,- L -PneNAc4OAc(1,4)-,- L -FucNAc(1,4)-,- L -FucNAc(1,4)-,- L -FucNAc(1,3)-,- D -QuiNAc4NHb(1, (PneNAc = 2-acetamido-2,6-dideoxy-talose, Hb = (S)-3-hydroxybutanoyl) PneNAc O -acetylation was not stoichiometric and was found to be about 75,%. The position of the O -acetyl group and the amount of acetylation were deduced by NMR spectroscopic analysis. All the monosaccharides included in the repeating unit were deoxyamino sugars, which most probably, together with the presence of O -acetyl groups, were responsible for the recovery of the LPS in the phenol layer of the phenol/water extract of dried bacteria cells.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Double-prodrugs of L -cysteine: Differential protection against acetaminophen-induced hepatotoxicity in miceJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 5 2002Daune L. Crankshaw Abstract A series of double-prodrugs of L -cysteine, designed to release L -cysteine in vivo and stimulate the biosynthesis of glutathione (GSH), were synthesized. To evaluate the hepatoprotective effectiveness of these double-prodrugs, male Swiss-Webster mice were administered acetaminophen (ACP) (2.45 mmol/kg (360 mg/kg), intraperitoneally (i.p.)). Prodrug (2.50 mmol/kg, i.p. or 1.25 mmol/kg, i.p., depending on the protocol) was administered 1 h before ACP as a priming dose. A supplementary dose of prodrug (2.5 mmol/kg, i.p. or 1.25 mmol/kg, i.p. depending on the protocol) was administered 0.5 h after ACP. The plasma alanine amino transferase (ALT) values, 24 h after ACP administration were transformed to logs and the 95% and 99% confidence intervals of the log values were plotted and compared for each group. Hepatoprotection was assessed by the degree of attenuation of plasma ALT levels. With these multiple dose schedules, the use of 2% carboxymethylcellulose as vehicle for the prodrugs was found to be detrimental; therefore, the prodrugs were dissolved in dilute aqueous base and the pH adjusted for administration. When a priming dose was given 1 h before ACP followed by a supplementary dose 0.5 h after ACP, only N,S -bis-acetyl- L -cysteine, where both the sulfhydryl and amino groups of L -cysteine were functionalized with the acetyl group, was found to be effective in protecting mice against the hepatotoxic effects of ACP. This suggests that these acetyl groups were rapidly hydrolyzed in vivo to liberate L -cysteine. In contrast, N -acetylation of 2(R,S)-methylthiazolidine-4(R)-carboxylic acid (MTCA) and its 2- n -propyl analog (PTCA), or N -acetylation of 2-oxothiazolidine-4-carboxylic acid (OTCA), reduced the hepatoprotective effects relative to the parent MTCA, PTCA, and OTCA, indicating that the release of L -cysteine in vivo from these N -acetylated thiazolidine prodrugs was metabolically unfavorable. The carbethoxy group, whether functionalized on the sulfhydryl or on the amino group of L -cysteine, or on the secondary amino group of MTCA, appears to be a poor "pro-moiety," since these carbethoxylated double-prodrugs of L -cysteine did not protect mice from ACP-induced hepatotoxicity. © 2002 Wiley Periodicals, Inc. J Biochem Mol Toxicol 16:235,244, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.10044 [source] Synthesis and hydrogel formation of fluorine-containing amphiphilic ABA triblock copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2001Kozo Matsumoto Abstract Fluorine-containing amphiphilic ABA triblock copolymers, poly(2-hydroxyethyl vinyl ether)- block -poly[2-(2,2,3,3,3-pentafluoropropoxy)ethyl vinyl ether]- block -poly(2-hydroxyethyl vinyl ether) [poly(HOVE- b -PFPOVE- b -HOVE)] (HFH), poly[2-(2,2,3,3,3-pentafluoropropoxy)ethyl vinyl ether]- block -poly(2-hydroxyethyl vinyl ether)- block -poly[2-(2,2,3,3,3-pentafluoropropoxy)ethyl vinyl ether] [poly(PFPOVE- b -HOVE- b -PFPOVE)] (FHF), and poly(n -butyl vinyl ether)- block -poly(2-hydroxyethyl vinyl ether)- block -poly(n -butyl vinyl ether) [poly(NBVE- b -HOVE- b -NBVE)] (LHL), were synthesized, and their behavior in water was investigated. The aforementioned polymers were prepared by sequential living cationic polymerization of 2-acetoxyethyl vinyl ether (AcOVE) and PFPOVE or NBVE, followed by hydrolysis of acetyl groups in polyAcOVE. FHF and LHL formed a hydrogel in water, whereas HFH gave a homogeneous aqueous solution. In addition, the gel-forming concentration of FHF was much lower than that of corresponding LHL. Surface-tension measurements of the aqueous polymer solutions revealed that all the triblock copolymers synthesized formed micelles or aggregates above about 1.0 × 10,4 mol/L. The surface tensions of HFH and FHF solutions above the critical micelle concentration were lower than those of LHL, indicating high surface activity of fluorine-containing triblock copolymers. Small-angle X-ray scattering measurements revealed that HFH formed a core-shell sperical micelle in 1 wt % aqueous solutions, whereas the other block copolymers caused more conplicated assembly in the solutions. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3751,3760, 2001 [source] Extraction and characterisation of hemicelluloses from maize stemPHYTOCHEMICAL ANALYSIS, Issue 5 2010Xiao-Feng Sun Abstract Introduction , Extraction and characterisation of hemicelluloses are very important for converting them into functional materials and chemicals. Objective , To develop a method for isolation of hemicelluloses from all cell walls. Methodology , Sequential steps using 90% dioxane, 80% acidic dioxane, 100% dimethyl sulphoxide and 8% NaOH were used for extraction of the hemicellulosic preparations (H1, H2, H3 and H4) from maize stem. Advanced NMR techniques were used for the analysis of native hemicelluloses. Results , Hemicelluloses with high yieldd were isolated from all cell walls, and contained arabinoxylan as the major polysaccharide. H3 was substituted by , - l -arabinofuranose, , - d -xylopyranose, and acetyl groups (degree of saturation = 0.12/0.09) at O -3/O -2 of xylan. H4 had a long continuous side chain of arabinose residues, and associated closely with non-cellulosic glucose. The hemicelluloses formed more linkages with guaiacyl lignins, and some p -coumaric acids built a bridge between hemicelluloses and lignin in maize stem. Conclusion , This modified method is successful for the isolation of hemicelluloses with high yields from all cell walls of maize stem. Copyright © 2010 John Wiley & Sons, Ltd. [source] Direct analysis of the extracellular proteome from two strains of Helicobacter pyloriPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 13 2007Todd G. Smith Abstract Helicobacter pylori extracellular proteins are of interest because of possible roles in pathogenesis, host recognition, and vaccine development. We utilized a unique approach by growing two strains (including one nonsequenced strain) in a defined serum-free medium and directly analyzing the proteins present in the culture supernatants by LC-MS/MS. Over 125 proteins were identified in the extracellular proteomes of two H. pylori strains. Forty-five of these proteins were enriched in the extracellular fraction when compared to soluble cell-associated protein samples. Our analysis confirmed and expanded on the previously reported H. pylori extracellular proteome. Extracellular proteins of interest identified here included cag pathogenicity island protein Cag24 (CagD); proteases HP0657 and HP1012; a polysaccharide deacetylase, HP0310, possibly involved in the hydrolysis of acetyl groups from host N -acetylglucosamine residues or from residues on the cell surface; and HP0953, an uncharacterized protein that appears to be restricted to Helicobacter species that colonize the gastric mucosa. In addition, our analysis found eight previously unidentified outer membrane proteins and two lipoproteins that could be important cell surface proteins. [source] Thiobarbiturates as Sirtuin Inhibitors: Virtual Screening, Free-Energy Calculations, and Biological TestingCHEMMEDCHEM, Issue 12 2008Urszula Uciechowska Abstract NAD+ -dependent histone deacetylases (sirtuins) are enzymes that cleave acetyl groups from lysine residues in histones and other proteins. Potent selective sirtuin inhibitors are interesting tools for the investigation of the biological functions of these enzymes and may be future drugs for the treatment of cancer or neurodegenerative diseases. Herein we present the results from a protein-based virtual screen of a commercial database with subsequent biological testing of the most promising compounds. The combination of docking and in,vitro experimental testing resulted in the identification of novel sirtuin inhibitors with thiobarbiturate structure. To rationalize the experimental results, free-energy calculations were carried out by molecular mechanics Poisson,Boltzmann/surface area (MM-PBSA) calculations. A significant correlation between calculated binding free energies and measured Sirt2 inhibitory activities was observed. The analyses suggested a molecular basis for the interaction of the identified thiobarbiturate derivatives with human Sirt2. Based on the docking and MM-PBSA calculations we synthesized and tested five further thiobarbiturates. The MM-PBSA method correctly predicted the activity of the novel thiobarbiturates. The identified compounds will be used to further explore the therapeutic potential of sirtuin inhibitors. [source] | ||||||||||