Two-step exposure of biological objects to infrared laser and microwave radiation]

The effect of two-step exposure of bacterial objects to infrared laser and microwave pulse radiations was studied. The effect is determined by the time interval between two excitation steps and pulse duration. It was shown that the biologically active dose of microwave radiation is much lower than that of infrared laser radiation; however, laser radiation induces a stronger cellular response. It was found that microwaves enhance the efficiency of infrared laser radiation.     

A Study of the Thermophysical Properties of Human Prostate Tumor Tissues in the Temperature Range from–160 to +40°C

Biophysics - A differential scanning calorimetry study of the specific isobaric heat capacity, phase-transition enthalpy, moisture content, and cryoscopic temperature for samples of benign and...     

Investigation of the complex antibiotic INA-5812

A concentrate with the antimicrobial activity has been isolated from the culture broth of Streptomyces roseoflavus INA-Ac-5812. Its further fractionation by reversed-phase HPLC has resulted in six fractions. It has been established by MALDI-TOF and ESI-MSⁿ precision mass-spectrometry methods that the main components of the complex antibiotic are several closely related compounds, presumably of a glycopeptide nature. The fraction containing an individual component with a mass of 1845.788 Da has been characterized by UV/Vis absorbance and fluorescence spectra, amino acid analysis, and derivatization with tris(2,6-dimethoxyphenyl)methyl cation. The activity of fractions against pathogenic microbes has been studied. The results allow the supposition that the INA-5812 antibiotic complex is a glyco- or lipoglycopeptide antibiotic of a new type, which is very promising for further study.     

Genetic effects of the decay of radionuclide products of nuclear fission in Saccharomyces cerevisiae cells. Lethal effects of the decay of 89Sr incorporated in cells of different ploidies and radiosensitivity

Decay of 89Sr incorporated in yeast cells produces a pronounced inactivating effect. The transmutation mainly contributes (about 80%) to cell inactivation. Haploid cells are more sensitive to 89Sr disintegration than diploid and tetraploid ones. A radiosensitive mutant XRS2, that is particularly sensitive to the transmutation effect of radionuclides, has proved to be sensitive to 89Sr transmutation as well. At the same time, another radiosensitive mutant, rad 54, does not virtually differ from the wild-type strain by its sensitivity to 89Sr decay.     

Effect of beta-lactam antibiotics on lipid bilayer membranes. II. Cephalosporin antibiotics

Interaction of cephalosporin antibiotics with flat bilayer lipid membranes (BLM) composed of vegetative or bacterial phospholipids was studied with respect to their effect on electroconductivity, capacity for binding to the bilayers and capacity for transmembrane transfer through the bilayers. By their effect on conductivity, the investigated cephalosporins could be divided into three groups: those having no effect on conductivity at the maximum concentrations (up to 1 mg/ml) i.e. cefoperazone, cefotaxime and ceftizoxime, those having an effect on conductivity at concentrations of 0.2 to 0.5 mg/ml i.e. cephalexin and cephalothin and those having a significant effect on conductivity at concentrations of 10 to 60 micrograms/ml i.e. N-acyl derivative of 7-ACA (substance 64) and 7-ACA derivative (substance 71). The cephalosporins had a capacity for binding to the bilayers and for incorporation into the bilayers. They penetrated to some extent through the bilayers composed of either vegetable or bacterial phospholipids. The lower rate of penetration through the BLM as compared to that of penicillins must be due to lower hydrophobicity of the cephalosporin molecules as compared to that of penicillins.     

The REC41 gene of Saccharomyces cerevisiae: isolation and genetic analysis

Recombination-deficient strains have been proven useful for the understanding of the genetic control of homologous recombination. As the genetic screens used to isolate recombination-deficient (rec(-)) yeast mutants have not been saturated, we sought to develop a simple colony color assay to identify mutants with low or elevated rates of recombination. Using this system we isolated a collection of rec(-) mutants. We report the characterization of the REC41 gene identified in this way. REC41 is required for normal levels of interplasmid recombination and gamma-ray induced mitotic interchromosomal recombination. The rec41-1 mutant failed to grow at 37 degrees C. Microscopic analysis of plated cells showed that 45-50% of them did not form visible colonies at permissive temperature. Haploid cells of the rec41 mutant show the same gamma-ray sensitivity as wild type ones. However, the diploid rec41 mutant shows gamma-ray sensitivity which is comparable with heterozygous REC41/rec41-1 diploid cells. This fact indicates semidominance of the rec41-1 mutation. Diploid strains homozygous for the rec41 rad52 mutations had the same gamma-ray sensitivity as single rad52 diploids and exhibited dramatically decreased growth rate. The expression of the HO gene does not lead to inviability of rec41 cells. The rec41 mutation has an effect on meiosis, likely meiotic recombination, even in the heterozygous state. We cloned the REC41 gene. Sequence analysis revealed that the REC41 gene is encoded by ORF YDR245w. Earlier, this ORF was attributed to MNN10, BED1, SLC2, CAX5 genes. Two multicopy plasmids with suppressers of the rec41-1 mutation (pm21 and pm32) were isolated. The deletion analysis showed that only DNA fragments with the CDC43 and HAC1 genes can partially complement the rec41-1 mutation.     

Transferase and hydrolytic activities of the laminarinase from rhodothermus marinus and its M133A, M133C, and M133W mutants

Comparative studies of the transglycosylation and hydrolytic activities have been performed on the Rhodothermus marinus β-1,3-glucanase (laminarinase) and its M133A, M133C, and M133W mutants. The M133C mutant demonstrated near 20% greater rate of transglycosylation activity in comparison with the M133A and M133W mutants that was measured by NMR quantitation of nascent β(1-4) and β(1-6) linkages. To obtain kinetic probes for the wild-type enzyme and Met-133 mutants, p-nitrophenyl β-laminarin oligosaccharides of degree of polymerisation 2–8 were synthesized enzymatically. Catalytic efficiency values, k _cat/K _m, of the laminarinase catalysed hydrolysis of these oligosaccharides suggested possibility of four negative and at least three positive binding subsites in the active site. Comparison of action patterns of the wild-type and M133C mutant in the hydrolysis of the p-nitrophenyl-β-D-oligosac- charides indicated that the increased transglycosylation activity of the M133C mutant did not result from altered subsite affinities. The stereospecificity of the transglycosylation reaction also was unchanged in all mutants; the major transglycosylation products in hydrolysis of p-nitrophenyl laminaribioside were β-glucopyranosyl-β-1,3-D-glucopy- ranosyl-β-1,3-D-glucopyranose and β-glucopyranosyl-β-1, 3-D-glucopyranosyl-β-1,3-D-glucpyranosyl-β-1,3-D- glucopyranoxside. In a memoriam of Dr. Kirill N. Neustroev. All we, his friends and colleagues, mourn for his sudden death. He was a bright and talented scientist, brilliant manager and good friend.     

The rad2 mutation affects the molecular nature of UV and acridine-mustard-induced mutations in the ADE2 gene of Saccharomyces cerevisiae

We have studied the molecular nature of ade2 mutations induced by UV light and bifunctional acridine-mustard (BAM) in wild-type (RAD) and in excision-deficient (rad2) strains of the yeast, Saccharomyces cerevisiae. In the RAD strain, UV causes 45% GC → AT transitions among all mutations; in the rad2 strain this value is 77%. BAM was shown to be highly specific for frameshift mutagenesis: 60% frameshifts in the RAD strain, and as many as 84% frameshifts in the rad2 strain were induced. Therefore, the rad2 mutation affects the specificity of UV- and BAM-induced mutagenesis in yeast. Experimental data agree with the view that the majority of mutations in the RAD strain are induced by a prereplicative mechanism, whereas mutations in the RAD strain are induced by a prereplicative mechanism, whereas mutations in the rad2 strain are predominantly postreplicative events. Our results also suggest that: (1) cytosine-containing photoproducts are the substances responsible for major premutational damage to DNA; (2) a fraction of the mutations may arise in the course of excision repair of UV photoproducts.