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At least 631 records · Page 35Linked to original sources
PubMed1993

New NO-donors with antithrombotic and vasodilating activities, I: 3-Arylalkyl-N-nitroso-5-sydnone imines.

Nine nitrosimino title compounds were prepared. They inhibit the aggregation of human platelets induced by collagen with an IC50 = 0.7--33 mumol/L. The most active substance is the 3-phenylethyl derivative 6b. The in vitro effect is mediated by an active metabolite which is formed by a photochemical reaction in the aggregometer. As the corresponding and so far unknown sydnone-5-cyanimines have no effect on platelets the metabolite is most certainly a NO-species. The activity of the sydnone-5-nitrimine 5b is in the same order of magnitude (IC50 = 7.5 mumol/L) as in the nitrosimines of type 6. The most active compound 6b was investigated for antithrombotic properties in a thrombosis model, where the thrombus formation was induced by a laser-beam. 2 h after oral administration of 60 mg/kg of 6b to rats in venoles a 28% inhibition of thrombin formation was found. In arterioles this effect is more evident and a 48% inhibition is seen (the thrombus formation index is 2.6 and 3.9, respectively). These results suggest that the active metabolite is formed as well in vivo.

Fibrinolytic Agents↗
PubMed2006

Self-assembly of multinuclear complexes with enantiomerically pure chiral binaphthoxy imine ligands: effect of the alkyl spacer connecting two binaphthyl units on the metal binding.

Metal complexing behavior of enantiomerically pure alpha,omega-diiminoalkanes possessing the two terminal binaphthyl units (L1 and L2) was studied. The ligands L1 and L2 were prepared by the reaction of optically pure 2'-butoxy-3-formyl-2-hydroxy-1,1'-binaphthyl with propane and pentane diamines. Reactions of L1 and L2 with equimolar amount of Cu(OAc)2 afforded quantitatively multinuclear complexes 1. The structure of 1 was confirmed by MALDI-TOF MS spectroscopy, X-ray single-crystal-structure analysis, and UV/vis and CD spectroscopic analyses. The reaction of L1 having a 1,3-propanediyl spacer resulted in the formation of a self-assembled product, which was assigned as enantiopure trinuclear circular helicate 1a, while the ligand having a 1,5-pentanediyl spacer L2 gave a different self-assembled product, dinuclear side-by-side complex 1b. The circular dichroism (CD) spectrum of 1a in solution showed intense Cotton effects in both the pi-pi* transition of the naphthalene units and the LMCT region of the N,O-chelate moieties. The CD spectrum of 1b was completely different from that of 1a; in particular the Cotton effects in the LMCT region were very weak, contrary to those of 1a. These results suggest that 1a retains some chirality induced on the N,O-chelating moieties even in solution, while the induced chirality on the N,O-chelating moieties in 1b is not very significant, being consistent with the consequences of the X-ray single-crystal-structure studies.

Journal Article↗
PubMed1986

pH dependence of deuterium isotope effects and tritium exchange in the bovine plasma amine oxidase reaction: a role for single-base catalysis in amine oxidation and imine exchange.

The pH dependence of steady-state parameters for [1,1-1H2]- and [1,1-2H2]benzylamine oxidation and of tritium exchange from [2-3H]dopamine has been measured in the bovine plasma amine oxidase reaction. Deuterium isotope effects on kcat/Km for benzylamine are observed to be constant, near the intrinsic value of 13.5, over the experimental pH range, indicating that C-H bond cleavage is fully rate limiting for this parameter. As a consequence, pKa values derived from kcat/Km profiles, 8.0 +/- 0.1 (pK1) and 9.0 +/- 0.16 (pKs), can be ascribed to microscopic pKa values for the ionization of an essential active site residue (EB1) and substrate, respectively. Profiles for kcat and Dkcat show that EB1 undergoes a perturbation from 8.0 to 5.6 +/- 0.3 (pK1') in the presence of substrate; additionally, a second ionization, pK2 = 7.25 +/- 0.25, is observed to mediate but not be essential for enzyme reoxidation. The pH dependence of the ratio of tritium exchange to product formation for dopamine also indicates base catalysis with a pKexch = 5.5 +/- 0.01, which is within experimental error of pK1'. We conclude that the data presented herein support a single residue catalyzing both substrate oxidation and exchange, consistent with recent stereochemical results that implicate a syn relationship between these processes [Farnum, M., & Klinman, J.P. (1985) Fed. Proc., Fed. Am. Soc. Exp. Biol. 44, 1055]. This conclusion contrasts with earlier kinetic data in support of a large rate differential for the exchange of hydrogen from C-1 vs. C-2 of phenethylamine derivatives [Palcic, M.M., & Klinman, J.P. (1983) Biochemistry 22, 5957-5966].(ABSTRACT TRUNCATED AT 250 WORDS)

Amine Oxidase (Copper-Containing)↗
PubMed1988

Inhibition of alanine racemase by alanine phosphonate: detection of an imine linkage to pyridoxal 5'-phosphate in the enzyme-inhibitor complex by solid-state 15N nuclear magnetic resonance.

Inhibition of alanine racemase from the Gram-positive bacterium Bacillus stearothermophilus by (1-aminoethyl) phosphonic acid (Ala-P) proceeds via a two-step reaction pathway in which reactivation occurs very slowly. In order to determine the mechanism of inhibition, we have recorded low-temperature, solid-state 15N NMR spectra from microcrystals of the [15N]Ala-P-enzyme complex, together with spectra of a series of model compounds that provide the requisite database for the interpretation of the 15N chemical shifts. Proton-decoupled spectra of the microcrystals exhibit a line at approximately 150 ppm, which conclusively demonstrates the presence of a protonated Ala-P-PLP aldimine and thus clarifies the structure of the enzyme-inhibitor complex. We also report the pH dependence of Ala-P binding to alanine racemase.

Alanine Racemase↗