Coenzymatic properties of low molecular-weight and macromolecular N6-derivatives of NAD+ and NADP+ with dehydrogenases of interest for organic synthesis

The extrusion of sulfur from acyl derivatives of 2,1-benzisothiazol-3(1H)-one (1) is autocatalytic. The catalyst is low-molecular-weight sulfur. Addition of cyclohexasulfur (5) to solutions of theseacyl derivatives increases the rate of such reactions.

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Structural Characterization of the Symbiotically Important Low-Molecular-Weight Succinoglycan ofSinorhizobium meliloti

Journal of Bacteriology ◽

10.1128/jb.181.21.6788-6796.1999 ◽

1999 ◽

Vol 181 (21) ◽

pp. 6788-6796 ◽

Cited By ~ 96

Author(s):

Lai-Xi Wang ◽

Ying Wang ◽

Brett Pellock ◽

Graham C. Walker

Keyword(s):

Molecular Weight ◽

Nuclear Magnetic Resonance ◽

Sinorhizobium Meliloti ◽

Structural Basis ◽

Low Molecular Weight ◽

Considerable Heterogeneity ◽

Chromatographic Techniques ◽

Detailed Structural Analysis ◽

Derivatives Of

ABSTRACT The production of succinoglycan by Sinorhizobium meliloti Rm1021 is required for successful nodule invasion by the bacterium of its host plant, alfalfa. Rm1021 produces succinoglycan, an acidic exopolysaccharide composed of an octasaccharide repeating unit modified with acetyl, succinyl, and pyruvyl moieties, in both low- and high-molecular-weight forms. Low-molecular-weight (LMW) succinoglycan, previously thought to consist of monomers, trimers, and tetramers of the repeating unit, has been reported as being capable of promoting the formation of nitrogen-fixing nodules by succinoglycan-deficient derivatives of strain Rm1021. We have determined that the three size classes of LMW succinoglycan species are in fact monomers, dimers, and trimers of the repeating unit and that the trimer is the species active in promoting nodule invasion. A detailed structural analysis of the components of LMW succinoglycan by using various chromatographic techniques, along with nuclear magnetic resonance analyses, has revealed that there is considerable heterogeneity within the LMW succinoglycan oligomers in terms of noncarbohydrate substitutions, and we have determined the structural basis of this heterogeneity.

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Antiplatelet Actions Of Low Molecular Weight Peptides And Their Derivatives

10.1055/s-0038-1652145 ◽

1981 ◽

Author(s):

Jawed Fareed ◽

Harry L Messmore ◽

Daniel A Walz

Keyword(s):

Molecular Weight ◽

Molecular Mechanisms ◽

Free Acid ◽

Acid Amide ◽

Antiplatelet Agents ◽

Low Molecular Weight ◽

Clot Retraction ◽

Induced Aggregation ◽

Derivatives Of ◽

Aggregation Of Platelets

We have reported on the antiserine protease actions of low molecular weight peptides with arginine and lysine at the carboxyl terminus and their derivatives. In order to investigate the action of these peptides and their analogues on other components of hemostasis we studied their effects on platelet function; aggregation and release reactions, clot retraction and serotonin uptake by platelets. D-Phe-Pro-Arg-NH-heptyl, D-Phe-Pro-Arg-O-heptyl, D-Phe-Pro-Arg-thiobenzyl, D-Phe-Pro-Arg-COOH, D-Phe-Pro-Arg-NH2, D-Phe-Pro-Arginal and similar derivatives of D-Pro-Phe-Arg, D-Phe-Phe-Arg and Val-leu-lys- were screened None of these peptides produced aggregation and release reactions in concentration >10 mM. D-Phe-Pro-Arg-thiobenzyl and D-Phe-Pro-Arginal produced a strong inhibition of thrombin induced aggregation and release reactions at sub ymolar levels. Both of these peptides also inhibited thrombin’s action in amidolytic and coagulant assays. D-Phe-Pro-Arg-thiobenzyl ester also produced a complete inhibition of arachidonic acid induced aggregation of platelets and showed varying inhibitory actions against ADP, epinephrine, collagen, and serotonin induced aggregation and release reactions. Although ristocetin induced aggregation was only slightly effected, a complete block of the release reaction was seen. ADP induced β-thrombo- globulin release was also inhibited by this peptide.Heptyl amide and esters of H-D-Phe-Pro-Arg-and free acid, amide and arginal forms of various other peptides exhibited relatively weaker antiplatelet actions. Our studies suggest that peptides with amino acid resembling serine protease sensitive sites can be molecularly manipulated to design potent antiplatelet agents. Furthermore these peptides may provide a useful probe to study the molecular mechanisms involved in the pathophysiology of thrombotic disorders and to design new antiplatelet drugs.

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Synthesis of a Chiral Meso-Like Ansa-Zirconocene Complex and its Use for the Catalytic Formation of Low Molecular Weight Polypropylene

Zeitschrift für Naturforschung B ◽

10.1515/znb-1995-0621 ◽

1995 ◽

Vol 50 (6) ◽

pp. 982-989 ◽

Cited By ~ 8

Author(s):

Sven Thiele ◽

Gerhard Erker ◽

Cornelia Fritze ◽

Christian Psiorz ◽

Roland Fröhlich

Keyword(s):

Crystal Structure ◽

Molecular Weight ◽

Double Bond ◽

Ambient Temperature ◽

Organic Synthesis ◽

Crystal Structure Analysis ◽

Low Molecular Weight ◽

X Ray ◽

Catalyst Systems ◽

Double Bond Shift

Reaction of lithium(neomenthylcyclopentadienid) 3 with dimethyldichlorosilane gives dimethylbis[3-(neomenthyl)cyclopentadienyl]silane 4 regioselectively as a mixture of double bond shift isomers (57% isolated). Deprotonation with 2 equiv. of butyllithium followed by treatment with zirconiumtetrachloride furnished a mixture of the three {dimethylsilylenbis[η5-3-(neomenthyl)cyclopentadienyl][zirconium dichloride diastereomers from which the pure meso-like isomer 6e [p -R (1′S ,3 ′R ,4 ′R),p -S (1′S ,3 ′R ,4 ′R)] was isolated by fractional crystallization. Complex 6 c was characterized by an X-ray crystal structure analysis. Its D 1 - Zr - D 2 angle of 126.8° is very similar as observed in bis(η-cyclopentadienyl) zirconium dichloride (D 1 and D 2 denote the centroids of the cyclopentadienyl rings). The homogeneous 6c/methylalumoxane Ziegler-type catalyst produces polypropylene of low molecular weight (Mη ≈ 670 at ambient temperature). Related catalyst systems may find interesting applications in organic synthesis.

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