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At least 793 records · Page 44Linked to original sources
PubMed1984

The specific capsular polysaccharide of Streptococcus pneumoniae type 15A (American type 30).

The specific capsular polysaccharide of Streptococcus pneumoniae type 15A (American type 30) is composed of D-galactose (three parts), D-glucose (one part), 2-acetamido-2-deoxy-D-glucose (one part), phosphate (one part), and glycerol (one part). Hydrolysis, periodate oxidation, methylation, optical rotation, and nuclear magnetic resonance studies showed that the polysaccharide is a high molecular weight linear polymer of a pentasaccharide repeating unit having the structure: (formula: see text)

Cell Membrane↗
PubMed1984

Structural analysis of the specific polysaccharide of Streptococcus pneumoniae type 9L (American type 49).

The specific capsular polysaccharide produced by Streptococcus pneumoniae type 9L (American type 49) is composed of D-galactose (one part), D-glucose (one part), D-glucuronic acid (one part), 2-acetamido-2-deoxy-D-mannose (one part), and 2-acetamido-2-deoxy-D-glucose (one part). Partial acid hydrolysis, periodate oxidation, nitrous acid deamination, optical rotation, methylation, and 13C and 1H nuclear magnetic resonance studies showed that the polysaccharide is an unbranched high molecular weight linear polymer of a repeating pentasaccharide unit having the structure: (formula; see text).

Chemical Phenomena↗
PubMed1985

The structure of the specific capsular polysaccharide of Streptococcus pneumoniae type 11F (American type 11).

The specific polysaccharide of Streptococcus pneumoniae type 11F (American type 11) is composed of 2-acetamido-2-deoxy-D-glucose (one part), D-glucose (one part), D-galactose (two parts), ribitol (one part), phosphate (one part), and O-acetyl (two parts). Hydrolysis, dephosphorylation, periodate oxidation, methylation, optical rotation, and 1H and 13C nuclear magnetic resonance studies showed that the polysaccharide is an unbranched linear polymer of a ribitol-phosphate substituted repeating tetrasaccharide unit having the structure: (Formula: see text). The specific capsular polysaccharides of S. pneumoniae type 11B and 11C (American types 76 and 53) were found to have the same tetrasaccharide repeating unit as the 11F polysaccharide, but differed from it in their mode of O-acetylation and the replacement of the ribitol phosphate by glycerol phosphate in the 11C specific polysaccharide.

Animals↗
PubMed1987

Structure of the lipopolysaccharide O-chain of Yersinia enterocolitica serotype O:5,27.

The cellular lipopolysaccharide produced by Yersinia enterocolitica serotype O:5,27 was of the S-type and composed of an antigenic O-chain polysaccharide linked through a core oligosaccharide region, which in turn was linked through 3-deoxy-D-manno-octulonosyl units to a lipid A moiety. The O-chain polysaccharide was composed of equal molar amounts of L-rhamnose and D-xylulose. By partial hydrolysis, periodate oxidation, methylation, specific optical rotation, and 13C and 1H nuclear magnetic resonance studies, the structure of the O-chain was established as being a linear backbone of alternating 1,3-linked alpha-L-rhamnopyranosyl and beta-L-rhamnopyranosyl units, to which 2,2-linked beta-D-threo-pent-2-ulofuranoside (D-xylulofuranoside) units were present on every L-rhamnopyranosyl residue, as shown below. (Formula: see text)

Carbohydrate Conformation↗
PubMed1988

Structure of the specific capsular polysaccharide of Streptococcus pneumoniae type 23F (American type 23).

The specific capsular polysaccharide of Streptococcus pneumoniae serotype 23F (American type 23) is composed of a repeating tetrasaccharide unit containing D-glucose (one part), D-galactose (one part), L-rhamnose (two parts), glycerol (one part), and phosphate (one part). By composition analysis, optical rotation, partial hydrolysis, periodate oxidation, methylation, and high-resolution 1H and 13C nuclear magnetic resonance studies, the elucidated unambiguous structure was in agreement with our earlier proposal but is at variance with structures proposed later by other authors. The structure of the type 23F pneumococcal polysaccharide is (formula; see text).

Chromatography, Gas↗
PubMed1988

The structures of the two lipopolysaccharide O-chains produced by Salmonella boecker.

Salmonella boecker, which belongs to group 0:6, 14(H) and shows the antigenic factors 6, 14, [1], and [25], defined by the Kauffmann-White system, produces two lipopolysaccharides differing from each other in the structures of their 0-poly-saccharide moieties. By glycose composition, partial hydrolysis, nitrous acid deamination, methylation, optical rotation, and 1H and 13C nuclear magnetic resonance studies, the O-polysaccharides were demonstrated to be high-molecular-weight polymers (I and II) composed of either structurally related repeating tetrasaccharide or repeating pentasaccharide units having the structures and (table; see text).

Carbohydrate Sequence↗
PubMed1990

Structures of polar lipids from the thermophilic, deep-sea archaeobacterium Methanococcus jannaschii.

Cells of Methanococcus jannaschii, grown at 65 degrees C in a defined medium, contained 7% of lipid composed of 87% polar and 13% neutral components. Within the polar fraction 16 lipids were resolved by thin-layer chromatography, 4 of which were present in trace amounts. Staining reactions demonstrated that the more abundant lipids were glycolipids, aminophospholipids, and an aminophosphoglycolipid. Most of the polar fraction (82%) consisted of five diether lipids, which were purified and their structures were resolved largely through nuclear magnetic resonance, mass spectrometry, and optical rotation methods. Macrocyclic diethers had the head groups phosphoethanolamine-(1----6)-beta-D-glucopyranose, beta-D-glucopyranose, and beta-D-glucopyranosyl-(1----6)-beta-D-glucopyranose. Phosphoethanolamine was identified as a head group for both the noncyclized and macrocylic diether core lipids. The neutral lipids were mainly acyclic C30 isoprenoids, predominantly dihydro-, hexahydro, and octahydro-squalenes.

Carbohydrate Conformation↗
PubMed2001

Physical chemistry of nucleic acids.

The Watson-Crick double helix of DNA was first revealed in 1953. Since then a wide range of physical chemical methods have been applied to DNA and to its more versatile relative RNA to determine their structures and functions. My major goal is to predict the folded structure of any RNA from its sequence. We have used bulk and single-molecule measurements of thermodynamics and kinetics, plus various spectroscopic methods (UV absorption, optical rotation, circular dichroism, circular intensity differential scattering, fluorescence, NMR) to approach this goal.

DNA↗
PubMed1982

The cardiac effects of d- and l-disopyramide in normal subjects: a noninvasive study.

Commercially available disopyramide is a racemic mixture of equal parts of dextrorotatory (d-) and levorotatory (l-) optical isomers. We studied the cardiac effects of i.v. administration of each isomer and the racemic mixture (dl-) in six normal males by digitized echocardiography, systolic time intervals and ECG. Both isomers and the racemic mixture produced equally marked dose-dependent negative inotropic effects (28.1 +/- 11.8% mean maximal reduction in fractional shortening of left ventricular dimension) and diastolic effects (28.6 +/- 24.1% mean maximal reduction in peak left ventricular filling rate). However, only the d-isomer prolonged QTc duration (by 13.6 +/- 5.2% at maximum, p less than 0.001 vs l-isomer). We conclude that disopyramide, in the doses used, produces marked adverse effects on left ventricle systolic and diastolic function in normal subjects independent of optical rotation. The production of these effects by the l-isomer without affecting QTc duration suggests different subcellular mechanisms for the myocardial depressant effects and some of the electrophysiologic effects of disopyramide.

Adult↗
PubMed2004

Synthesis and characterization of novel polyurethane cationomers with dipeptide sequences and alkylammonium groups.

A synthetic approach to polyurethane cationomers containing S-pyroglutamyl-S-glutamic acid dipeptide (S-PyGlu-S-Glu) and alkylammonium groups is presented. Two segmented polycations, based on polycaprolactone diol, isophorone diisocyanate and dipeptide together with N-methyldiethanolamine, subsequently quaternized with dodecylbromide, were synthesized and characterized by IR spectroscopy, GPC, DSC and reduced viscosity measurements. Such polycations exhibited excellent film forming properties and their soft elastomeric nature provides adequate physical properties. Optical rotation varying from +10 (monomer) to -15 (polycation) could be associated with a configuration pertubation through the asymmetric carbon atoms of glutamic residues. Susceptibility of the cationic surface to heparinization and then to blood-polymer interaction suggested an anticoagulant activity of the heparinized polymeric films.

Anticoagulants↗
PubMed1968

Studies on collagenase from rheumatoid synovium in tissue culture.

Fragments of synovium from patients with rheumatoid arthritis survive in defined tissue culture medium in the absence of added serum and, after 3-4 days, release into the medium enzyme capable of degrading undenatured collagen. Maximal activity is observed at pH 7-9 but the enzyme is inactive at pH 5. At temperatures of 20 degrees and 27 degrees C, collagen molecules in solution are cleaved into 3/4 and 1/4 length fragments with minimal loss of negative optical rotation, but with loss in specific viscosity of approximately 60%. Above 30 degrees C the fragments begin to denature and denaturation is complete at 37 degrees C. If the enzyme is not inhibited at this stage the large fragments are broken down further to polypeptides of low molecular weight. Reconstituted collagen fibrils and native fibers at 37 degrees C are cleaved to the low molecular weight fragments, although the fibrils are resistant to breakdown at lower temperatures (20 degrees -27 degrees C). It is proposed that the production of such an enzyme by inflamed and proliferating rheumatoid synovium may be responsible for some of the destruction of collagenous structures that accompanies rheumatoid arthritis.

Adenosine Triphosphate↗
PubMed1989

Stereoselective reduction of acetohexamide in cytosol of rabbit liver.

The stereoselective reduction of acetohexamide, an oral antidiabetic drug, was studied by using the cytosol of rabbit liver. A major metabolite of acetohexamide was isolated in 41.5% yield from the enzyme reaction mixture, and identified as (-)-hydroxyhexamide by techniques including the melting point, thin-layer chromatography, infrared spectrometry and optical rotation. The enantiomeric purity of (-)-hydroxyhexamide was determined on the basis of the proton nuclear magnetic resonance (400 MHz) spectrum of ester (diasteromer) derived by the reaction of (-)-hydroxyhexamide with (R)-(+)-alpha-methoxy-alpha-trifluoromethylphenylacetyl chloride. The (-)-hydroxyhexamide isolated from the enzyme reaction mixture was almost 100% in that enantiomeric form. The metabolic reduction of acetohexamide in the cytosol of rabbit liver appeared to be catalyzed by some enzymes with the same stereoselectivity.

Acetohexamide↗
PubMed2002

Absolute structure of panaxytriol.

Diastereomeric mixture at C-3 of (9R,10R)-panaxytriol acetonide (3) and (9S,10S)-panaxytriol acetonide (4) were enantioselectively acetylated to give (3R)-acetates (3a-Ac, 4a-Ac) and (3S)-alcohols (3b, 4b) by enzyme mediated-acetylation using CHIRAZYME and vinyl acetate, respectively. Hydrolysis of (3R)-acetate (3a-Ac, 4a-Ac) with CHIRAZYME and phosphate buffer afforded (3R)-alcohols (3a, 4a), respectively. Deprotection of panaxytriol acetonides (3a, 3b, 4a, 4b) gave panaxatriol and its isomers, respectively. Comparison of optical rotation values of the synthetic panaxatriols with that of the natural one confirmed that the absolute configuration of panaxytriol sould be 3R,9R,10R.

Alkynes↗
PubMed2003

Studies on the constituents of Gentiana species. II. A new triterpenoid, and (S)-(+)- and (R)-(-)-gentiolactones from Gentiana lutea.

A new triterpenoid, 12-ursene-3beta, 11alpha-diol 3-O-palmitate (1), has been isolated from the rhizomes and roots of Gentiana lutea, together with the artificial diene derivative, 9 (11), 12-ursadien-3beta-ol 3-O-palmitate (1a) and five known compounds (3-7). Their structures were established on the basis of spectral analysis. In addition, (+/-)-gentiolactone [(+/-)-2], isolated from this plant, was successfully separated into its enantiomers [(+)-2, (-)-2] for the first time, and the absolute configurations at C-9 of (+)-2, (-)-2 were assigned as S and R, respectively, from the optical rotations and the circular dichroism (CD) spectral data.

Gentiana↗
PubMed2004

Synthesis of panax acetylenes: chiral syntheses of acetylpanaxydol, PQ-3 and panaxydiol.

Acetylpanaxydol (1-Ac), PQ-3 (2) and panaxydiol (3) and their optical isomers were synthesized from L-(+)-diethyl tartrate. The absolute configurations of 1-Ac, 2 and 3 were determined to be 1-Ac (3R,9R,10S), 2 (9R,10S) and 3 (3R,10S), respectively, by comparisons of their optical rotations and the NMR data of their MTPA esters with those of natural products.

Acetylation↗
PubMed2004

Chiral discrimination on the host-guest-complexation of resorc[4]arenes with quarternary amines.

The interaction of inherently chiral resorc[4]arenes with different chiral ammonium ions was measured by ESI-MS. For that purpose one enantiomer of the ammonium guests was labeled with deuterium to distinguish the enantiomers by their mass. We synthesized the ammonium salts by reaction of chiral primary amines with either CH3I or CD3I and analyzed the resulting ammonium iodides by NMR and optical rotation. The complexation experiments were performed by mixing the chiral host with various ratios of the unlabeled guest and its labeled enantiomer. By analysis of the integrals of the host-guest complexes we observed a chiral discrimination effect and a secondary isotope effect as well.

Amines↗
PubMed2005

Production of L-sorbitol from L-fructose by Aureobasidium pullulans LP23 isolated from soy sauce mash.

A strain LP23 that can convert L-fructose to L-sorbitol was isolated from soy sauce mash and identified as Aureobasidium pullulans. The cells grown on L-arabinose were found to have relatively high L-fructose to L-sorbitol conversion potential. Addition of erythritol to the reaction mixture considerably accelerated the conversion rate of L-fructose to L-sorbitol. During the conversion reaction, erythritol was added to the reaction mixture at 8-h intervals to maintain the concentration of erythritol at 1.0%. The final conversion ratios were 82.8%, 95.3%, 92.4%, and 42.6% using washed cells when the concentrations of L-fructose were 1.0%, 2.0%, 5.0% and 10.0%, respectively. The product from L-fructose was identified as L-sorbitol by HPLC analysis, infrared spectroscopy, optical rotation and melting point measurements.

Ascomycota↗
PubMed2005

Production of L-talitol from L-psicose by Metschnikowia koreensis LA1 isolated from soy sauce mash.

A strain LA1 that can convert L-psicose to L-talitol was isolated from soy sauce mash and identified as Metschnikowia koreensis. The cells grown on L-arabitol were found to have relatively high conversion potential. Addition of D-sorbitol to the reaction mixture considerably accelerated the conversion rate of L-psicose to L-talitol. During the conversion reaction, D-sorbitol was added to the reaction mixture at 12-h intervals to maintain the concentration of D-sorbitol at 1.0%. The final conversion ratios were 81.4%, 75.2%, 73.0%, 60.4% and 43.5% using washed cells when the concentrations of L-psicose were 0.5%, 1.0%, 2.0%, 3.0% and 5.0%, respectively. The product from L-psicose was identified as L-talitol by HPLC analysis, and infrared spectroscopy, optical rotation and melting point measurements.

Biotechnology↗