Catechol siderophore, produced by thermoresistent strain of Bacillus licheniformis VK21

Thermophilic and thermoresistant strains of bacilli were screened on a medium containing Chrome Azurol S for producers of siderophores. It was found that the Bacillus licheniformis VK21 strain dramatically increases secretion of the metabolite, a chelator of Fe3+, in response to addition of manganese(II) salts. The growth of the producer on a minimum medium containing MnSO4 under the conditions of iron deficiency is accompanied by the accumulation of a catechol product, the content of which reaches a maximum at the beginning of the stationary growth phase of culture. In the presence of FeCl3, the amount of the catechol product in the medium considerably decreases. The siderophore, called SVK21, was isolated from the cultural medium and purified by reversed phase HPLC, and its siderophore function was confirmed by the test for the restoration of growth of producer cells in a medium containing EDTA. The UV spectrum of the siderophore has absorption maxima at 248 and 315 nm. According to amino acid analysis and NMR spectrometry, the metabolite SVK21 is 2,3-dihydroxybenzoyl-glycyl-threonine. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2003, vol. 29, no. 6; see also http://www.maik.ru.     

Antimicrobial peptides containing arginine

Tetradecapeptides (RLARLAR)₂, D-(RLARLAR)₂, (RLARLAA)₂, and (RLGRLGR)₂ were synthesized by a solid phase method using Fmoc-amino acids. The antibacterial activity of the synthesized peptides was studied against Escherichia coli cells. The minimum inhibitory concentration (MIC) was, correspondingly, 3, 1, 3, and 12 M, which is comparable with MIC of such natural antimicrobial peptides as temporin, magainin, and dermaseptin. It was found that all of the synthesized peptides have no effect on human erythrocytes and rat thymocytes. The peptides form -helices in 30% trifluoroethanol and in 2.5 mM SDS, which have amphipathic structure.     

The bioutilization of thiodiglycol (a breakdown product of mustard gas): isolation of degraders and investigation of degradation conditions

The Alcaligenes xylosoxydans subsp. denitrificans strain TD1 capable of degrading thiodiglycol (TDG), a breakdown product of mustard gas, was isolated from soil contaminated with breakdown products of this chemical warfare agent. The selected stable variant of TD1 (strain TD2) can grow on TDG with a lag phase of 4-8 h and a specific growth rate of 0.04-0.045 h-1. Optimal conditions for the biodegradation of TDG (pH, the concentration of TDG in the medium, and its relative content with respect to the bacterial biomass) were determined. TDG was found to be degraded with the formation of diglycolsulfoxide and thiodiglycolic acid. The data obtained can be used to develop approaches to the bioremediation of mustard gas-contaminated soils.     

SO2 污染油菜对桃蚜的影响

ＳＯ_２污染油菜对桃蚜的影响龚佩瑜,吴坤君,李秀珍（中国科学院动物研究所北京１０００８０）ＳＯ２是我国大气污染的主要成分,它是一种对生物影响很大的污染物。ｓｏ。曾被用作熏蒸剂来防治害虫,但只有在浓度很高时才有效。更多的观察表明,ｓｏ：污染有利于蚜虫的?..     

Mechanism of aspartyl proteinase action. VII. Noncovalent complexes of HIV-1 aspartyl proteinase with substrate and substrate-like inhibitors

A computer model of a noncovalent complex of HIV-1 aspartyl protease with substrate-like inhibitor JG-365 was a priori constructed by using the approaches of theoretical conformational analysis and molecular mechanics. The root mean square deviation of the calculated conformation of the inhibitor from the X-ray diffraction analysis data was 0.87 A. These results enabled the a priori calculation of the structure of noncovalent complex of HIV-1 protease with a hexapeptide fragment of its native specific substrate Ser-Gln-Asn-Tyr-Pro-Ile-Val. The only possible orientation of the cleavable peptide bond in this and the nucleophilic water molecule relative to the catalytically active Asp residues of the enzyme (Asp25 and Asp125) was found that provides for the chemical transformation of the substrate to a tetrahedral intermediate. An action mechanism of enzymes of this class was proposed on the basis of the analysis of calculated distances. We showed that neither steric distortion of the cleavable bond nor the formation of unfavorable contacts in molecules of the enzymes and their substrates accompany the optimum orientation of substrate molecules at the active sites of HIV-1 aspartyl proteases and rhizopuspepsin.     

Branched antimicrobial peptides

Branched peptides E(RLAR)2, E[E(RLAR)2]2, E(KLAR)2, and E[E(KLAR)2]2 were synthesized on the basis of tetrapeptides RLAR and KLAR and glutamic acid bis(pentafluorophenyl) ester. Their minimal antimicrobial concentrations were shown to decrease along with increase in branching, achieving 12 microM for Escherichia coli cells, which is comparable to antimicrobial activities of temporin, magainin, and dermaseptin. The branched peptides were found not to act on human erythrocytes.     

Active and passive properties of carotid arteries]

A mathematical model of carotid arteries is constructed from the known experimental data. Passive properties of the vascular wall are characterized by an alternating module of elasticity, the active ones by the specific power of muscle contraction. Its maximum value (0,023 n/m-3) is shown to be reached with intravascular pressure 190 mm Hg. The dependence of inner radius on the power of muscle contraction is studied at different values of intravascular pressure. It is shown that theactive properties of carotid arteries are essentially determined by their passive properties and depend on the stretching of the vessel wall.