Jerzy Gebicki

1-Methylnicotinamide (MNA), a primary metabolite of nicotinamide, exerts anti-thrombotic activity mediated by a cyclooxygenase-2/prostacyclin pathway

1‐methylnicotinamide (MNA) has been considered to be an inactive metabolite of nicotinamide. Here we assessed the anti‐thrombotic activity of MNA in vivo.

The Effect of Ultrasound on Heme Enzymes in Aqueous Solution

The effect of cavitating 22 kHz ultrasound on aqueous solutions of hydrogen peroxide-consuming enzymes, catalase and peroxidases, both plant (horseradish peroxidase) and animal (lactoperoxidase) was studied. Catalase did not undergo inactivation during sonication, whereas activity of peroxidases decreased with increased duration of sonication. It is suggested, basing on the absorption spectra, that some conformational changes occur in peroxidases upon sonolysis. It is concluded from the experiments with free radical scavengers that partial enzyme inactivation and modification has not a chemical but a mechanical basis.

Pulse radiolysis of catalase in solution. I: Reactions of O2− with catalase and its compound I

The time-course of absorption changes of oxygen-saturated solutions of bovine-liver catalase after pulse radiolysis have been studied. The rate constant of formation of Compound I due to the reaction of catalase with hydrogen peroxide has been estimated to be 2.0 x 10(7) dm3mol-1s-1. Radiation generated superoxide radicals reduce Compound I to Compound II with a rate constant of 5.0 x 10(6) dm3mol-1s-1. The formation of Compound III in the direct reaction of O2- with catalase has also been observed.

IR evidence for the formation of weakly bound complexes BF3CO and BF3N2

Abstract Weakly bound complexes of BF 3 with CO and with N 2 have been prepared by controlled condensation of a gaseous mixture on a cold CsI window and characterized by FTIR spectroscopy.

Kinetic studies on the interaction of ferricytochrome c with anionic surfactants.

The kinetics of absorbance and fluorescence changes of cytochrome c as induced by an aqueous solution of the anionic surfactant sodium dodecyl sulfate (SDS) or sodium bis(2-ethylhexyl)sulfosuccinate (AOT) are studied. The results are compared with far-UV circular dichroism (CD) spectra. Both surfactants cause similar alterations in the secondary structure of cytochrome c, while their influence on the heme environment of cytochrome c is different. In the presence of AOT below and above critical micellar concentration a conversion of the low-spin native cytochrome c to a denatured low-spin protein not having methionine ligand takes place. In the presence of SDS micelles conversion of the native protein to a denatured mixed-spin form occurs. The changes in the heme group induced by both surfactants occur independently of the alterations in tertiary structure.

Antithrombotic Effects of Pyridinium Compounds Formed from Trigonelline upon Coffee Roasting

Coffee may exert a preventive effect on arterial thrombosis. Trigonelline is one of the most abundant compounds in coffee that undergoes pyrolysis upon roasting of coffee beans. The aim of the present study was to identify pyridinium compounds formed upon trigonelline pyrolysis and coffee roasting and to investigate the effect of three of them, i.e., 1-methylpyridine and 1,3- and 1,4-dimethylpyridine, on experimentally induced arterial thrombosis in rats. 1,3- and 1,4-dimethylpyridine but not 1-methylpyridine inhibited arterial thrombus formation. 1,3-Dimethylpyridine inhibited platelet aggregation and reduced fibrin formation in platelet-rich plasma, whereas 1,4-dimethylpyridine increased the plasma level of 6-keto-PGF1α. 1,4-Dimethylpyridine slightly increased rat tissue plasminogen activator plasma activity. In summary, we demonstrated that pyridinium compounds display mild antithrombotic properties due to stimulation by prostacyclin release (1,4-dimethylpyridine) and inhibition of platelet aggregation (1,3-dimethylpyridine). Those pyridinium compounds may, to some extent, be responsible for the beneficial effects of coffee drinking.

Electron processes in AOT reverse micelles. Part 1.—Absorption spectra and lifetimes of hydrated electrons as studied by pulse radiolysis

Pulse radiolysis has been applied to produce hydrated electrons in reverse micelles of AOT in heptane or methylcyclohexane at various water contents. The observed influence of the water : AOT ratio on the spectral properties of eaq– and on its lifetime have been critically compared with results published in the literature. The influence of the hydrocarbon solvent on the spectra properties of eaq– is discussed.

Pulse radiolytic investigation of perfluorinated surfactants in aqueous solutions

Pulse radiolysis studies were performed for aqueous solutions of ammonium perfluorooctanoate, tetraethylammonium perfluorooctyl sulfonate, and an ammonium salt of a carboxylic perfluoropolyether derivative. The protiated system of sodium octanoate was also examined for comparison. The rate constants of hydrated electron (e−aq) and ·OH radical reactions with these amphiphiles, and absorption spectra of the intermediate products are reported for the first time. It is demonstrated that the critical micellar concentrations (CMC) can be determined from the kinetic data. The observed differences in e−aq reactivity towards fluorinated amphiphiles above CMC are rationalized in terms of different charge density at the micellar interface.

LASER FLASH PHOTOLYSIS STUDY OF PHENYLCARBENE, o-TOLYLCARBENE AND MESITYLCARBENE

Laser flash photolysis (LFP, XeCl, 308 nm, 20 ns) of phenyldiazomethane (PDM), o-tolydiazomethane (TDM) and mesitydiazomethane (MDM) produces phenylcarbene (PC), o-tolycarbene (TC) and mesitylcarbene (MSC), respectively. Transient spectra of PC and TC could not be detected in pentane at ambient temperature; however, these carbenes could be trapped with pyridine to form UV–Vis-active ylides. The rate of formation of these ylides was resolved in CF2ClCFCl2 (Freon-113) and yields, after analysis, values of kpyr and τ, where kpyr is the absolute rate constant of the reaction of the spin equilibrated carbene with pyridine and τ is the carbene lifetime in Freon-113 in the absence of pyridine. LFP of MDM produces the transient spectra of both triplet MSC and 3,5-dimethyl-1,2-benzoquinodimethane (3,5-BQM). The lifetime of 3MSC in pentane is ca 500 ns. 3MSC reacts with pyridine with an apparent rate constant of kpyr=1·35×107 M−1 s−1. The decay of 3MSC in a variety of solvents does not lead to increased absorption of 3,5-BQM in solution, nor does the presence of a carbene scavenger (methanol) lead to a reduction in yield of 3,5-dimethyl-1,2-benzoquinodimethane upon LFP of precursor. Thus, the decay of 3MSC in solution does not lead to the formation of quinodimethane. This species (3,5-BQM) is formed, instead, by a hydrogen atom transfer in the excited state of the precursor. Product analysis reveals that the excited state rearrangement which forms xylylene is a minor process. Photolysis of MDM in a nitrogen matrix at 10 K leads to the UV–Vis spectra of matrix-isolated triplet mesitylcarbene and 3,5-BQM. The carbene rearranges slowly to 3,5-BQM in the cryogenic matrix, in contrast to its behavior in solution.

Reactions of heme peroxidases with peroxynitrite.

The interaction of peroxynitrite, produced by ozonation of azide, with two heme peroxidases (horseradish peroxidase and lactoperoxidase) was studied. Enzymes retained full activity after incubation with peroxynitrite at neutral pH. Lactoperoxidase alone was found to catalyze peroxynitrite decomposition, whereas horseradish peroxidase accelerated peroxynitrite decomposition only in the presence of certain substrates. For example, in the presence of guaiacol the catalyzing effect was clear, but in the presence of trolox was only noticeable.