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Vaterite microparticles, metastable form of calcium carbonate, are promising forms of delivery of medicinal compounds. For more efficient delivery of target molecules (increased incorporation and retention), vaterite microparticles must be functionalized with biopolymers. In this article the effect of polysaccharides, mucin and vaterite microparticles, as well as hybrid vaterite microparticles with the above-mentioned biopolymers was studied on platelet aggregation. It was found that fucoidan, heparin and dextran sulfate (when added to platelet-rich plasma) and mucin (when added to isolated platelets) initiated cell aggregation. Pectin and chondroitin sulfate inhibited ADP- and thrombin-induced aggregation in a dose-dependent manner, mucin suppressed ADP-induced, and dextran sulfate suppressed thrombin-induced platelet aggregation. Vaterite microparticles at a concentration of 100–1000 µg/mL did not affect the aggregation of isolated platelets, but caused 10–15% cell aggregation in plasma; at the same time, at a concentration of 1000 µg/mL vaterite microparticles prevented agonist-induced cell aggregation by ~30%. It has been established that hybrid vaterite microparticles with fucoidan or heparin, when added both to platelet-rich plasma and to isolated cells, are capable to initiate platelet aggregation. Vaterite microparticles functionalized with pectin or chondroitin sulfate had no effect on spontaneous cell aggregation, and did not affect (with chondroitin sulfate) or inhibit (with pectin) agonist-induced platelet aggregation. Thus, the use of hybrid vaterite microparticles with pectin or fucoidan/heparin may be promising for the delivery of drugs aimed at modulating (inhibition with pectin or activation with fucoidan/heparin) the platelet component of hemostasis. [ABSTRACT FROM AUTHOR]

We studied the properties of N6-chloroadenosine phosphates (ATP, ADP, and AMP chloramines) as compounds with potentially increased antiplatelet efficacy determined by their binding to the plasma membrane of platelets. Chloramine derivatives of ATP, ADP, and AMP do not differ in their optical absorption characteristics: their absorption spectra are in the range of 220-340 nm with a maximum at 264 nm. Chloramines of adenosine phosphates are characterized by high reactivity with respect to thiol compounds. In particular, the rate constants of the reaction of N6-chloroadenosine-5'-diphosphate with N-acetylcysteine, reduced glutathione, dithiothreitol, and cysteine reach 59,000, 250,000, 340,000, and 1,250,000 M—1×sec—1, respectively, and only 1.10±0.02 M—1×sec—1 with methionine. It has been found that N6-chloradenosine-5'-triphosphate is a strong inhibitor of platelet functions: it effectively suppresses ADP-induced cell aggregation (IC50 in the whole blood is 5 μM) and inhibits aggregation of preactivated platelets and induces dissociation of their aggregates. [ABSTRACT FROM AUTHOR]

PoxtA and OptrA are ATP binding cassette (ABC) proteins of the F subtype (ABCF). They confer resistance to oxazolidinone and phenicol antibiotics, such as linezolid and chloramphenicol, which stall translating ribosomes when certain amino acids are present at a defined position in the nascent polypeptide chain. These proteins are often encoded on mobile genetic elements, facilitating their rapid spread amongst Gram-positive bacteria, and are thought to confer resistance by binding to the ribosome and dislodging the bound antibiotic. However, the mechanistic basis of this resistance remains unclear. Here we refine the PoxtA spectrum of action, demonstrate alleviation of linezolid-induced context-dependent translational stalling, and present cryo-electron microscopy structures of PoxtA in complex with the Enterococcus faecalis 70S ribosome. PoxtA perturbs the CCA-end of the P-site tRNA, causing it to shift by ∼4 Å out of the ribosome, corresponding to a register shift of approximately one amino acid for an attached nascent polypeptide chain. We postulate that the perturbation of the P-site tRNA by PoxtA thereby alters the conformation of the attached nascent chain to disrupt the drug binding site. PoxtA confers resistance to ribosome-targeting oxazolidinone (linezolid) and chloramphenicol antibiotics. Here, Crowe-McAuliffe et al. provide structural insights into how binding of PoxtA to the ribosome indirectly promotes drug dissociation. [ABSTRACT FROM AUTHOR]

A technology has been developed for the preparation of novel chloramine compounds related to adenosine derivatives. The optical absorption characteristics of N6-сhloroadenosine-5'-phosphate (chloramine derivative of AMP) have been elucidated. It was shown that this compound absorbs light with wavelengths covering a range from 220 to 340 nm, the absorption maximum wavelength is 265 nm, and the minimum absorption occurs at 233 nm. The ability of N6-chloroadenosine phosphate to modify biologically significant compounds that contain the sulfhydryl (e.g., serum albumin) or sulfide (e.g., methionine residues in fibrinogen) functional groups has been studied. The quantitative indicator of this ability was the reaction rate constant. A spectrophotometer was used for recording the kinetic curve data on chloramine consumption after rapid mixing with sulfur-containing substrates and the rate constants were then calculated using a theoretical kinetic equation for bimolecular reactions. N6-chloroadenosine phosphate reacts very rapidly with thiol compounds; the rate constants for the reactions of N6-chloroadenosine phosphate with serum albumin, N-acetylcysteine, reduced glutathione, and cysteine (pH 7.4) reach 24 000, 58 000, 240 000, and 1 200 000 M–1 s–1, respectively. The difference in the rate constants is mainly due to the difference in the degree of dissociation of sulfhydryl groups. The rate constants for the reactions of N6-chloroadenosine phosphate with methionine, fibrinogen, and oxidized glutathione are 1.4 ± 0.09 M–1 s–1, 28 ± 1.6 M–1 s–1, and 0.230 ± 0.066 M–1 s–1, respectively. Thus, the chloramine derivative of АMP is characterized by increased reactivity towards the sulfhydryl group. It was found that N6-chloroadenosine phosphate effectively inhibits АDP-induced aggregation of isolated platelets and platelets in platelet-rich blood plasma. [ABSTRACT FROM AUTHOR]

Target protection proteins confer resistance to the host organism by directly binding to the antibiotic target. One class of such proteins are the antibiotic resistance (ARE) ATP-binding cassette (ABC) proteins of the F-subtype (ARE-ABCFs), which are widely distributed throughout Gram-positive bacteria and bind the ribosome to alleviate translational inhibition from antibiotics that target the large ribosomal subunit. Here, we present single-particle cryo-EM structures of ARE-ABCF-ribosome complexes from three Gram-positive pathogens: Enterococcus faecalis LsaA, Staphylococcus haemolyticus VgaALC and Listeria monocytogenes VgaL. Supported by extensive mutagenesis analysis, these structures enable a general model for antibiotic resistance mediated by these ARE-ABCFs to be proposed. In this model, ABCF binding to the antibiotic-stalled ribosome mediates antibiotic release via mechanistically diverse long-range conformational relays that converge on a few conserved ribosomal RNA nucleotides located at the peptidyltransferase center. These insights are important for the future development of antibiotics that overcome such target protection resistance mechanisms. Mitochondrial ribosomes (mitoribosomes) are characterized by a distinct architecture and thus biogenesis pathway. Here, cryo-EM structures of mitoribosome large subunit assembly intermediates elucidate final steps of 16 S rRNA folding, methylation and peptidyl transferase centre (PTC) completion, as well as functions of several mitoribosome assembly factors. [ABSTRACT FROM AUTHOR]

Objectives. To establish the characteristics of the influence of alcoholization on cognitive functions in patients with schizophrenia, Materials and methods. A total of 100 patients with paranoid schizophrenia were studied. A main group (MG) was identified with concomitant diagnosis of alcohol dependence (n = 50), along with a control group (n = 50). The characteristics of memory, attention, and thought were assessed, and the groups were compared in terms of the presence of concomitant addictive pathology. Results. Attention and short-term memory were at the borderline level and no statistically significant differences were seen between the groups studied. In the Benton test, the study group showed a predominance of errors of the schizophrenic type, while the control group was dominated by "organic" errors. A statistically significant dominance of mild decreases in thought were seen in the MG. Conclusions. Concomitant alcohol dependence was not a defining factor in cognitive impairments in patients with schizophrenia, though it introduced a distinct organic stigma to the structure of the patients' cognitive profile. "Organic" impairments to thought structure in patients with concomitant alcohol dependence were seen. The best measures of attention were seen in patients suffering from shift-like schizophrenia who were healthy in addiction terms. This suggests that the influence of the alcohol factor has different significance in the continuous and episodic/progressive types of schizophrenia. [ABSTRACT FROM AUTHOR]

A procedure for the direct photometric determination of rate constants for the oxidation of dithiothreitol (a thiol-compound example) by N-chlorotaurine and N-chloroglycine and their analogues that have a different structure of the reaction center was developed. The time dependences of the sum of the chloramine oxidant absorbance and the absorbance of dithiane (the product of the dithiothreitol conversion) were calculated for different values of the bimolecular rate constant. The value of the rate constant was considered as established when the best agreement between the calculated curve and the measured kinetic curve of absorbance was observed. The oxidative activities of monochloramine oxidants showed little difference: the rate constants for N-chlorotaurine, N-chloroglycine, and N-chloro-2,2-dimethyltaurine were equal to 170 ± 4, 235 ± 9.8, and 145 ± 4.3 M–1 s–1, respectively. When the reaction center structure was modified by introducing the substituents of the hydrogen atom into the chloramine group, the activities of the compounds changed dramatically: the rate constants for N-isopropyl-N-chlorotaurine, N,N-dichloro-2,2-dimethyltaurine and N-acetyl-N-chloro- 2,2-dimethyltaurine determined using the competitive kinetics method were 9 ± 0.5, 12 000 ± 950 and 25 300 ± 3000 M–1 s–1, respectively. The reactivity of N-chloroglycine and the structural analogues of taurine chloramine with respect to thiol-compounds correlates with the magnitude of the active chlorine charge. Predictions about the reactivity of unknown structural analogues of N-chloramino acids and N-chlorotaurine were obtained. [ABSTRACT FROM AUTHOR]

DNA is strictly compartmentalized within the nucleus to prevent autoimmunity; despite this, cyclic GMP-AMP synthase (cGAS), a cytosolic sensor of double-stranded DNA, is activated in autoinflammatory disorders and by DNA damage. Precisely how cellular DNA gains access to the cytoplasm remains to be determined. Here, we report that cGAS localizes to micronuclei arising from genome instability in a mouse model of monogenic autoinflammation, after exogenous DNA damage and spontaneously in human cancer cells. Such micronuclei occur after mis-segregation of DNA during cell division and consist of chromatin surrounded by its own nuclear membrane. Breakdown of the micronuclear envelope, a process associated with chromothripsis, leads to rapid accumulation of cGAS, providing a mechanism by which self-DNA becomes exposed to the cytosol. cGAS is activated by chromatin, and consistent with a mitotic origin, micronuclei formation and the proinflammatory response following DNA damage are cell-cycle dependent. By combining live-cell laser microdissection with single cell transcriptomics, we establish that interferon-stimulated gene expression is induced in micronucleated cells. We therefore conclude that micronuclei represent an important source of immunostimulatory DNA. As micronuclei formed from lagging chromosomes also activate this pathway, recognition of micronuclei by cGAS may act as a cell-intrinsic immune surveillance mechanism that detects a range of neoplasia-inducing processes. [ABSTRACT FROM AUTHOR]

We studied the effects of taurine chloramine and its structural analogues, antiplatelet agents, on the tertiary structure of bovine serum albumin by recording changes in its fluorescence spectrum. BSA was chosen as a model of the extracellular part of the purine P2Y12 receptor in platelets. For the detection of weak spectral shifts of the protein fluorescence, the index, which represents the ratio of the two light sums measured from approximately the middle of the spectrum towards the short- and longwave limits of its registration, was used. Administration of N-chlorotaurine and its analogues N-acetyl-N-chlorotaurine and N-isopropyl-N-chlorotaurine in albumin solution in equimolar concentrations cause weakening and red shift of the tryptophanyl fluorescence of the protein, indicating reorganization of the protein's tertiary structure, thereby changing the properties of the microenvironment of tryptophan residues, primarily, Trp 134. All these changes are probably due to a covalent modification of the sulfhydryl group of Cys34 residue. It was hypothesized that chloramines of taurine have the ability to inhibit the activity of the ADP P2Y12 receptor in platelets due to the modification of its sulfhydryl group and that the inhibitory effect on the ADP-binding site has an allosteric character. [ABSTRACT FROM AUTHOR]

Organizational and economic approaches to solving the problems of the reprocessing and disposal of spent nuclear fuel are examined. The capacity shortage for reprocessing spent nuclear fuel is equal to 510–530 tons/yr. It is shown that the financial resources needed to create storage and reprocessing facilities for spent fuel can be obtained by increasing the cost of electricity produced by NPP, which can equal 0.013–0.02 rubles/(kW·h). [ABSTRACT FROM AUTHOR]

Small regulatory RNA (sRNA) is a unique noncoding RNA involved in regulation of gene expression in both eukaryotic and bacterial cells. This short review discusses examples of positive and negative translation regulation by sRNAs in bacteria and participation of Hfq in these processes. The importance of structure investigation of nucleotide-protein and RNA-protein complexes for designing a model of Hfq interaction with both mRNA and sRNA simultaneously is demonstrated. [ABSTRACT FROM AUTHOR]

Bacterial Hfq proteins are structural homologs of archaeal and eukaryotic Sm/Lsm proteins, which are characterized by a 5-stranded β-sheet and an N-terminal α-helix. Previously, it was shown that archaeal Lsm proteins (SmAP) could produce long fibrils spontaneously, in contrast to the Hfq from Escherichia coli that could form similar fibrils only after special treatment. The organization of these fibrils is significantly different, but the reason for the dissimilarity has not been found. In the present work, we studied the process of fibril formation by bacterial protein Hfq from Pseudomonas aeruginosa and archaeal protein SmAP from Methanococcus jannaschii. Both proteins have high homology with E. coli Hfq. We found that Hfq from P. aeruginosa could form fibrils after substitutions in the conserved Sm2 motif only. SmAP from M. jannaschii, like other archaeal Lsm proteins, form fibrils spontaneously. Despite differences in the fibril formation conditions, the architecture of both was similar to that described for E. coli Hfq. Therefore, universal nature of fibril architecture formed by Hfq proteins is suggested. [ABSTRACT FROM AUTHOR]

A number of molecular characteristics for the N-chlorotaurine structural analogs, amino acid chloramines, and related compounds have been computed by the ab initio B3LYP/6-31G method. In particular, the characteristics were the Mulliken atomic charges for the chloramine part and adjacent atoms. The quantitative measure of the capabilities of the chloramines to react with the methionine sulfide group or the sulfhydryl group of reduced glutathione was their reaction rate constants. The constants available in the literature and those found in our experiments have been depicted with an exponential equation of multiple correlations. In the case of the reaction with methionine, the high determination coefficient ( R) was obtained with five independent variables, which were the charges of available chlorine, nitrogen, and carbon bonded with nitrogen, the bond length between the nitrogen and carbon atoms, and the molecular weight. The equation was used to predict the rate constant values for the reactions between methionine and compounds containing available chlorine. The prediction showed that the structural analogs of N-chlorotaurine bearing two methyl groups at β-carbon of taurine are remarkable for the low value of the rate constant under discussion. [ABSTRACT FROM AUTHOR]

We studied the effects of amide and N-alkyl analogs of taurine chloramine on rabbit plasma coagulation and platelet aggregation. Alkyl analog N-isopropyl-N-chlorotaurine produced greater increase in plasma coagulation time after its activation by the contact method or with thrombin than amide analog N-propionyl-N-chlorotaurine. In case of coagulation induced by the tissue factor, the test analogs produced similar effect. Inhibition of platelet aggregation in platelet-rich plasma under the effect of N-isopropyl-N-chlorotaurine depended on the nature of the agonist. Aggregation was suppressed stronger under conditions of collagen stimulation than in response to ADP agonist. Estimated partial charges of the chlorine atom in amide analogs were 5-fold higher than in N-alkyl analogs. This fact determined the difference in the chemoselective interaction with sulfur-containing amino acid residues in targets and the specific features of anticoagulation and antiaggregant effects of two analogs of taurine chloramine. [ABSTRACT FROM AUTHOR]

Hfq is a thermostable RNA-binding bacterial protein that forms a uniquely shaped homohexamer. Based on sequence and structural similarity, Hfq belongs to the like-Sm (LSm) protein family. In spite of a rather high degree of homology between archaeal and eukaryotic LSm proteins, their quaternary structure is different, usually consisting of five to eight monomers. In this work, the importance of conserved intersubunit hydrogen bonds for the Hfq spatial organization was tested. The structures and stabilities for the Gln8Ala, Asn28Ala, Asp40Ala, and Tyr55Ala Hfq mutants were determined. All these proteins have the same hexamer organization, but their stability is different. Elimination of a single intersubunit hydrogen bond due to Gln8Ala, Asp40Ala, and Tyr55Ala substitutions results in decreased stability of the Hfq hexamer. Tyr55Ala Hfq as well as the earlier studied His57Ala Hfq has reduced protein thermostability, which seems to correspond to an opening of the protein hydrophobic core. [ABSTRACT FROM AUTHOR]

A search for proteins which interact with the eRF1 termination translation factor encoded by SUP45 gene in yeast Saccharomyces cerevisiae was carried out by screening yeast genes located on a multicopy plasmid. This approach allowed finding the ECM23 gene whose increased expression led to lower viability of the sup45 nonsense mutants. Overexpression ECM23 gene led also to an antisuppressor effect, although the amount of the eRF1protein was not changed. Possible mechanisms of how ECM23 can affect the viability of the sup45 nonsense mutants are discussed. [ABSTRACT FROM AUTHOR]

Repair of interstrand crosslinks (ICLs) requires the coordinated action of the intra-S-phase checkpoint and the Fanconi anaemia pathway, which promote ICL incision, translesion synthesis and homologous recombination (reviewed in refs 1, 2). Previous studies have implicated the 3′-5′ superfamily 2 helicase HELQ in ICL repair in Drosophila melanogaster (MUS301 (ref. 3)) and Caenorhabditis elegans (HELQ-1 (ref. 4)). Although in vitro analysis suggests that HELQ preferentially unwinds synthetic replication fork substrates with 3′ single-stranded DNA overhangs and also disrupts protein-DNA interactions while translocating along DNA, little is known regarding its functions in mammalian organisms. Here we report that HELQ helicase-deficient mice exhibit subfertility, germ cell attrition, ICL sensitivity and tumour predisposition, with Helq heterozygous mice exhibiting a similar, albeit less severe, phenotype than the null, indicative of haploinsufficiency. We establish that HELQ interacts directly with the RAD51 paralogue complex BCDX2 and functions in parallel to the Fanconi anaemia pathway to promote efficient homologous recombination at damaged replication forks. Thus, our results reveal a critical role for HELQ in replication-coupled DNA repair, germ cell maintenance and tumour suppression in mammals. [ABSTRACT FROM AUTHOR]

RNA-binding proteins play a significant role in many processes of RNA metabolism, such as splicing and processing, regulation of DNA transcription and RNA translation, etc. Among the great number of RNA-binding proteins, so-called RNA-chaperones occupy an individual niche; they were named for their ability to assist RNA molecules to gain their accurate native spatial structure. When binding with RNAs, they possess the capability of altering (melting) their secondary structure, thus providing a possibility for formation of necessary intramolecular contacts between individual RNA sites for proper folding. These proteins also have an additional helper function in RNA-RNA and RNA-protein interactions. Members of such class of the RNA-binding protein family are Sm and Sm-like proteins (Sm-Like, LSm). The presence of these proteins in bacteria, archaea, and eukaryotes emphasizes their biological significance. These proteins are now attractive for researchers because of their implication in many processes associated with RNAs in bacterial and archaeal cells. This review is focused on a comparison of architecture of bacterial and archaeal LSm proteins and their interaction with different RNA molecules. [ABSTRACT FROM AUTHOR]

Results are presented from studies of the change in the internal stress of a polyacrylonitrile fiber during heat treatment. It is shown that the increase in stress during deformation and heat treatment and its decrease during relaxation can be explained by representing the structure of the polymer in the form of stable and unstable grids superimposed on one another. The sub-units of the grids are formed by chains of the amorphous phase, the stable nodes are formed by crystallites and chemical bonds, and the unstable nodes are formed by microscopic blocks of the amorphous phase and van der Waals interactions. [ABSTRACT FROM AUTHOR]

It is proposed that the Wiechert model be used to describe the structure of a polyacrylonitrile (PAN) fiber. The model which is used includes a Hookian element and two Maxwellian elements with variable parameters. The temperature dependence of the parameters of the model are determined. The proposed method can be used to analyze and describe the structure of the fiber on the basis of indirect parameters and to predict the fiber's behavior during its deformation and heat treatment. In particular, the method can be used to determine the optimum elongation of a PAN fiber during its thermal stabilization as part of the process of carbon fiber production. [ABSTRACT FROM AUTHOR]

The quantum mechanics computation of the reactivities of chloramine derivatives of amino acids and taurine has been accomplished. A pair of computational indices that reflect a predisposition of alpha amino acid chloramines to chemical decay have been revealed. One of the indices was the dihedral angle for the chain of four atoms: carbons at beta- and alpha-positions, carbon of the carboxyl group, and carbonyl oxygen. The second index was the sum of partial charges for three or two carbon atoms in the chain. The amino acid chloramines with high values of the indices showed enhanced stability. Partial charges for active chlorine in known chloramines having different structures have been computed. The charges correlate with the rate constants of the reaction between chloramines and the thiol group of reduced glutathione. New derivatives of taurine chloramines have been constructed via the introduction of different substituents into the chloramine part. Among them, the amidoderivatives had the greatest charges of active chlorine (0.19-0.23). It was found in the study of the reactions of N-acetyl-N-chlorotaurine and N-propyonyl-N-chlorotaurine with amino acids and peptides possessing the thiol, thioester, or disulphide groups that the amidoderivatives manifested the thiol chemoselectivity. N-acetyl-N-chlorotaurine and N-propionyl-N-chlorotaurine suppress the aggregation activity of blood platelets under their activation by the agonists ADP and collagen. It is not excluded that the amidoderivatives studied prevent platelet aggregation by a modification of the critical thiol group in the purine receptor P2Y12. [ABSTRACT FROM AUTHOR]

In order to create effective therapeutically signifi cant oligonucleotide structures, a series of analogs of thrombin-binding aptamer d(GGTTGGTGTGGTTGG) containing thiophosphoryl substitutions were synthesized. The anticoagulation effects of the resultant thrombin-binding aptamer analogs were evaluated and the effects of local thiomodifications on their structure and function were studied, including the effects on stability in blood plasma and resistance to DNA nucleases. A promising modified oligonucleotide (LL11) was found with the structure modified only in TT loops. It retains antithrombin properties of thrombin-binding aptamer, but is more resistant to biodegradation. [ABSTRACT FROM AUTHOR]

At present, the machinery supporting the viability of organisms possessing nonsense mutations in essential genes is not entirely understood. Nonsense mutants of Saccharomyces cerevisiae yeast containing a premature translation termination codon in the essential SUP45 gene are known. These strains are viable in the absence of mutant suppressor tRNAs; hence, the existence of alternative mechanisms providing nonsense suppression and mutant viability is conjectured. Analysis of clones obtained by transformation of a strain bearing a nonsense-mutant allele of SUP45 with a multicopy yeast genomic library revealed three genes encoding wild-type tRNATyr and four genes encoding wild-type tRNAGln, which increased nonsense mutant viability. Moreover, overexpression of these genes leads to an increase in the amount of the full-length eRF1 protein in cells and compensates for heat sensitivity in the nonsense mutants. Probable ways of tRNATyr and tRNAGln influence on the increase in the viability of strains with nonsense mutations in SUP45 are discussed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Nonlethal nonsense mutations obtained earlier in the essential gene SUP45 encoding the translation termination factor eRF1 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 trucated 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°C. When grown under nonpermissive conditions (37°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. [ABSTRACT FROM AUTHOR]

Abstract  Alanine and taurine sharply potentiate antiaggregant effects of hypochlorite on platelets in platelet-rich plasma. This effect is determined by more pronounced action of chloramine derivatives, products of interaction of added amino acids with hypochlorite. Platelets are more sensitive to the inhibitory effects of amino acid chloramine derivatives (biogenic chloramines) compared to erythrocytes and neutrophils. The antiaggregant effects of biobenic amines, as covalent platelet inhibitors, in platelet-rich plasma are characterized by their increased reaction capacity with molecular targets in cells. Quantitative parameter of this initial selectivity (ratio of rate constant of inactivation of platelet receptors to rate constant of side reaction with plasma proteins) far surpasses 1. N,N-Dichlorotaurine is a perspective antiaggreant among the studied biogenic chloramines. This agent is stable and exhibits specific pharmacological activity in all test systems, including animal model of thrombosis. [ABSTRACT FROM AUTHOR]

The antiaggregant effect of two reactive oxidants— N,N-dichlorotaurine (a biogenic chloramine) and sodium hypochlorite—on the initial ADP-induced aggregation of rabbit blood platelets was studied. Platelet aggregation in reconstituted platelet-rich plasma was measured nephelometrically; an increase in the intensity of small-angle light scattering served as an index of aggregation. Addition of chloramine at relatively small concentrations (no greater than 1 mM available chlorine) directly to the reconstituted platelet-rich plasma suppressed the initial aggregation (formation of small aggregates) several times more strongly than preincubation of native plasma with chloramine. This suggests that N,N-dichlorotaurine realizes its antiaggregant effect on the platelet-rich plasma by directly interacting with cells. The effects of the inhibition of platelet aggregation in two variants of addition of high concentrations of N,N-dichlorotaurine did not differ significantly. In this case, a large amount of residual unreacted chloramine remained in the plasma, which caused the suppression of platelet aggregation during subsequent reconstitution of the platelet-rich plasma. Similar data were obtained in studying the antiaggregant effect of hypochlorite. N,N-Dichlorotaurine and hypochlorite at concentrations of 0.2–0.3 and 0.15 mM, respectively, strongly inhibited the initial aggregation of isolated platelets (approximately 2·108 cells/ml) preliminarily activated for 1.5 min by addition of 0.1–0.5 μM ADP. However, the antiaggregants had a more profound suppressive effect on the aggregation of unstimulated platelets. The antiaggregant effects of N,N-dichlorotaurine and hypochlorite probably stem from the oxidative modification of the sulfur-containing groups in platelet plasma membrane. [ABSTRACT FROM AUTHOR]

In this study, we investigated the pathways (including the formation of hydroxyl radicals and chloramines) leading to luminol chemiluminescence induced by hypochlorite generated in a suspension of stimulated rabbit polymorphonuclear leukocytes. Chemiluminescence of leukocytes stimulated by phorbol myristate acetate, which was enhanced by luminol (0.02 mM), did not change in the presence of dimethyl sulfoxide at moderate concentrations (0.02–2.6 mM), under which the latter should manifest the specific ability to scavenge hydroxyl radicals. This indicates that stimulation of polymorphonuclear leukocytes is not accompanied by the generation of hydroxyl radicals with the involvement of superoxide anion and hypochlorite synthesized by myeloperoxidase. At high concentrations of dimethyl sulfoxide (260 mM), chemiluminescence markedly declined because dimethyl sulfoxide directly reacts with hypochlorite. The luminol emission intensity considerably increased after its addition to a suspension of leukocytes that were preliminarily stimulated for 10 min. This effect was caused by the accumulation of hydrogen peroxide rather than chloramines. Exogenous amino acids and taurine at high concentrations (3–15 mM) quench chemiluminescence. All these data indicate that chemiluminescence in the system studied is largely determined by the direct initial reaction of hypochlorite with luminol, the emission intensity increasing as a result of oxidation of luminol transformation products by hydrogen peroxide. [ABSTRACT FROM AUTHOR]

An original nephelometric method allows one to measure initial platelet aggregation after a long-term storage of platelet concentrate. This attests to a high level of platelet activity despite the fact that final platelet aggregation cannot be detected by usual turbidimetric method. N-chloroalanine more slowly inhibits initial platelet aggregation in comparison with sodium hypochlorite, which implies different mechanisms of their membrane-modifying effects. [ABSTRACT FROM AUTHOR]

In enantioselective hydrogenation of ethyl acetoacetate on a Raney nickel catalyst modified with (+)-tartaric acid, we found an inhibiting effect of the reaction products, namely, racemic ethyl β-hydroxybutyrate and (-)-ethyl β-hydroxybutyrate, and also of acetic acid, pyridine, and thiophene, and we determined their relative adsorption coefficients. [ABSTRACT FROM AUTHOR]

Comparison of antiaggregation capacity of N-chloramine acids with different position of the chloramine group in the molecule showed that in the most efficient compounds the distance between the chloramine and carboxyl groups was 3–5 carbon atoms. This feature of antiaggregation activity was not related to the difference in oxidation capacity of N-chloramine acids. It was hypothesized that the revealed structural dependence of antiaggregation activity of N-chloramine acids is determined by the structure of platelet membrane, in particular, the presence of a negatively charged group near the site of interaction between N-chloramine acids and platelet membrane. [ABSTRACT FROM AUTHOR]