The Antiplatelet Effect and Chemical Activity of N6-Chloroadenosine Phosphate

Biophysics - A technology has been developed for the preparation of novel chloramine compounds related to adenosine derivatives. The optical absorption characteristics of...     

Changes in erythrocyte and thrombocyte aggregation after ultraviolet irradiation

Lipid peroxidation which occurs in blood serum under ultraviolet irradiation was studied. The products of these reaction suppress ADP-induced aggregation of native platelets. The rouleaux-forming capacity increased after UV-irradiation of plasma and serum albumin. Under UV-irradiation the aggregates of albumin molecules are supposed to form the aggregates of albumin molecules which bind the erythrocytes in rouleaux.     

Chemiluminescence in a stimulated polymorphonuclear leukocytes--luminol system: suppression by thiols

The effect of some scavengers of thiol nature, which eliminate all reactive oxygen species and oxidants with reactive chlorine, on the luminol-enhanced chemiluminescence of polymorphonuclear leukocytes was studied. The use of two scavengers of this type (penetrating and not penetrating into the cell) made it possible to separate the luminescence of cell structures from the luminescence generated by oxidants in the surrounding medium. It was found that about a half of luminol luminescence is due to its oxidation in the medium surrounding the cell, and it is completely inhibited by the nonpenetrating reduced glutathione. The cell itself is a source of a considerable portion of luminescence, and this luminescence is quenched by penetrating sulfhydryl compounds such as dithiothreitol and N-acethyl cysteine. Reduced glutathione, which penetrates into cells and whose action is due only to the sulfhydryl group, is recommended as a candidate for the selective neutralization of extracellular oxidants.     

An essential saccharide binding domain for the mAb 2C7 established for Neisseria gonorrhoeae LOS by ES-MS and MSn

A study of bacterial surface oligosaccharides were investigated among different strains of Neisseria gonorrhoeae to correlate structural features essential for binding to the MAb 2C7. This epitope is widely expressed and conserved in gonococcal isolates, characteristics essential to an effective candidate vaccine antigen. Sample lipooligosaccharides (LOS), was prepared by a modification of the hot phenol-water method from which de-O-acetylated LOS and oligosaccharide (OS) components were analyzed by ES-MS-CID-MS and ES-MSnin a triple quadrupole and an ion trap mass spectrometer, respectively. Previously documented natural heterogeneity was apparent from both LOS and OS preparations which was admixed with fragments induced by hydrazine and mild acid treatment. Natural heterogeneity was limited to phosphorylation and antenni extensions to the alpha-chain. Mild acid hydrolysis to release OS also hydrolyzed the beta(1-->6) glycosidic linkage of lipid A. OS structures were determined by collisional and resonance excitation combined with MS and multistep MSn which provided sequence information from both neutral loss, and nonreducing terminal fragments. A comparison of OS structures, with earlier knowledge of MAb binding, enzyme treatment, and partial acid hydrolysis indicates a generic overlapping domain for 2C7 binding. Reoccurring structural features include a Hepalpha(1-->3)Hepbeta(1-->5)KDO trisaccharide core branched on the nonreducing terminus (Hep-2) with an alpha(1-->2) linked GlcNAc (gamma-chain), and an alpha-linked lactose (beta-chain) residue. From the central heptose (Hep-1), a beta(1-->4) linked lactose (alpha-chain), moiety is required although extensions to this residue appear unnecessary.      

Anti-aggregation action of hypochlorite on the thrombocytes

Sodium hypochlorite at concentrations higher than 1 mM suppresses ADP-dependent aggregation of blood platelets. The effect was associated with the process of cell modification. Blood platelet aggregation may be depressed partially by ADP destruction. Products of ADP-sodium hypochlorite interaction may lead to the induction of blood platelet aggregation, which is not so intensive than the ADP-induced one.     

The paradox of viable <Emphasis Type="Italic">sup45</Emphasis> STOP mutations: a necessary equilibrium between translational readthrough,activity and stability of the protein

The mechanisms leading to non-lethality of nonsense mutations in essential genes are poorly understood. Here, we focus on the factors influencing viability of yeast cells bearing premature termination codons (PTCs) in the essential gene SUP45 encoding translation termination factor eRF1. Using a dual reporter system we compared readthrough efficiency of the natural termination codon of SUP45 gene, spontaneous sup45-n (nonsense) mutations, nonsense mutations obtained by site-directed mutagenesis (76Q → TAA, 242R → TGA, 317L → TAG). The nonsense mutations in SUP45 gene were shown to be situated in moderate contexts for readthrough efficiency. We showed that readthrough efficiency of some of the mutations present in the sup45 mutants is not correlated with full-length Sup45 protein amount. This resulted from modification of both sup45 mRNA stability which varies 3-fold among sup45-n mutants and degradation rate of mutant Sup45 proteins. Our results demonstrate that some substitutions in the place of PTCs decrease Sup45 stability. The viability of sup45 nonsense mutants is therefore supported by diverse mechanisms that control the final amount of functional Sup45 in cells.     

Kinetic characteristics of luminol chemiluminescence caused by chloramine compounds

The decaying part of the kinetic curves of luminol chemiluminescence (0.02 mM) induced by N-chlorphenylalanine is approximated by an exponential dependence, which varies insignificantly as chloramine concentration is changed from 0.2 to 0.7 mM. On the whole, the chemiluminescence of luminol is a result of its oxidation, which occurs in three stages with the formation of two intermediate products. N-Chlorphenylalanine is involved in the process at the initial stage. The reciprocal of the time the luminescence reaches a maximum increases linearly with the growth of N-chlorphenylalanine concentration. According to the calculations using the equations that reflect three stages of luminol conversion in the presence of excess chloramine, the rate constant for the initial stage is about 10(3) l/(mol.min). The rate constant for one stage of the conversion of luminol oxidation product is approximately 0.2 min-1, and the rate constant of the other is severalfold greater. Luminol chemiluminescence induced by low concentrations of N,N-dichlortaurine is more durable. Probably, it is composed of two types of emission one of which slowly decays.     

Viable nonsense mutants for the SUP45 gene in the yeast Saccharomyces cerevisiae are lethal at increased temperature

Nonlethal nonsense mutations obtained earlier in the essential gene SUP45 encoding the translation termination eRFI factor in the yeast Saccharomyces cerevisiae were further characterized. Strains carrying these mutations retain the viability, since the full-length eRF1 protein is present in these strains, although in decreased amounts as compared to wild-type cells, together with a truncated eRF1. All nonsense mutations are likely to be located in a weak termination context, because a change in the stop codon UGAA (in the case of mutation sup45-107) to UAGA (sup45-107.2) led to the alteration of the local context from a weak to strong and to the lethality of the strain carrying sup45-107.2. All nonsense mutations studied are characterized by thermosensitivity expressed as cell mortality after cultivation at 37 degrees C. When grown under nonpermissive conditions (37 degrees C), cells of nonsense mutants sup45-104, sup45-105. and sup45-107 display a decrease in the amount of the truncated eRF1 protein without reduction in the amount of the full-length eRF1 protein. The results of this study suggest that the N-terminal eRF1 fragment is indispensable for cell viability of nonsense mutants due to the involvement in termination of translation.     

Investigation of bacteriorhodopsin-intermediate relaxation by means of temperature pulse

The kinetics of bacteriorhodopsin action are investigated by means of the temperature pulse method. The temperature jump is provided by a short laser pulse (wavelengths λ₁ = 2.94 μm or λ₂ = 10.6 μm). The kinetics of evolution of the spectral intermediates M-412 and O-640 are investigated. A very fast increase in the O-640 form is observed as a result of the temperature jump. The experimental results are most consistent with the physical model based on electron resonance tunneling and permitting two protons transported per cycle. A branched scheme of the bacteriorhodopsin photocycle and corresponding mathematical equations are discussed.     

Commensals of Mytilus galloprovincialis in the Black Sea: Urastoma cyprinae (Turbellaria) and Polydora ciliata (Polychaeta)

The intensity of infection of the mussel Mytilus galloprovincialis Lamarck in the Black Sea by the turbellarian Urastoma cyprinae (Graff), which lives on its gills, was found to be higher in larger hosts, reaching a maximum in mussels of 50–70 mm length. Greater numbers occured in mussels inhabiting a silty bottom than in cultivated mussels suspended above the bottom. Over the period 1982–1987, U. cyprinae was most numerous in winter and especially so in years that were colder. The spionid polychaete Polydora ciliata (Johnston) also infects M. galloprovincialis, burrowing into the shell. Young spionids of up to 1 mm length occured in mussels with a shell length of 35 mm. Numbers of this commensal reached a maximum in mussels of intermediate size.