Kinetics of DNA-distaxin complex-formation

Kinetics of DNA--distaxines complexes formation was studied spectrophotometrically by means of the stop--flow method. It has been found that increase of number of bulky pyrrolcarboxamide group in the row of distaxines: -0, -1, -2, - slows down the binding reactions and increases the number of their stages.     

Allele specificity of genetic recombination in T4 phage using the indicator crossing study method]

The diagrams of relative correction ability of eighteen rII mutants of T4 phage were constructed on the basis of two-factor crosses, which were grouped into indicator series. In each series a pair of closely linked compared markers was crossed against indicator ones, the latter being distant enough so as to avoid simultaneous correction with the compared marker. The differences between the frequencies of wild type recombinants in crosses of two compared markers with indicator ones remained constant within the series and can be used as a measure of the differences between the compared markers in their correction ability. Mutants of base substitution type have small but statistically significant differences in correction ability. Simultaneous substitution of two bases in one codon yields a mutant which shows higher correction ability when compared to the mutant obtained as a result of substitution of only one base in the same codon. Frame shift mutants show much wider range of correctibility: some of them are corrected more rarely and others more frequently than base substitution mutants are.     

Acceptor specificity of mannosyl transferases from Salmonella of serotypes C2 and C3

Synthetic mono- and disaccharide derivatives of moraprenyl pyrophosphate were studied as mannose acceptors during the assembly of the repeating unit Rha-Man-Man-Gal of the Salmonella newport (serogroup C2) and S. kentucky (serogroup C3) O-antigens. Mannosyl transferases revealed strict specificity towards the configuration of terminal monosaccharide residue at C1 as well as to the type of linkage between monosaccharide residues in the disaccharide acceptor. The specificity of mannosyl transferases towards the structure of subterminal monosaccharide was not absolute. Alpha-D-Glucose and alpha-D-mannose derivatives were found not to serve as mannosyl residue acceptors, whereas those of alpha-D-talose, alpha-D-fucose, 4-deoxy-D-xylo-hexose and Man (alpha 1-3) glucose were substrates in enzymatic mannosylation with formation of polyprenyl pyrophosphate trisaccharides. These derivatives could serve as substrates for two subsequent enzymatic reactions: rhamnosylation and polymerization of the repeating units, yielding 40-60% of the polysaccharides.     

Incorporation of paratose residue into Salmonella O-specific polysaccharides using enzymatic reactions]

The block mechanism of O-specific polysaccharides biosynthesis was demonstrated for Salmonella nitra (serogroup A) and S. haifa (serogroup B). Due to the moderate specificity of glycosyl transferases from S. nitra, S. typhimurium, S. haifa and S. kentucky (serogroup C3) towards the 3,6-dideoxyhexose structure a paratose residue can be incorporated into the polysaccharide chain instead of an abequose residue, and vice versa.     

Doses levorin display an antiandrogenic action?

The antiandrogenic effect of levorin on immature castrated rats treated with exogenic testosterone was studied. In a dose of 200 mg/kg levorin lowered the cholesterin blood levels in the rats, inhibited the testosterone-induced increase in RNA concentration in the ventral and dorsal prostate and the seminal vesicles and to a less extent suppressed the growth of the accessory sexual glands. However, the antiandrogenic effect was observed with the use of levorin in the dose producing a pronounced toxic action evident from death of a part of the animals and a marked decrease in the animal body weight. This fact casts doubt on specificity of the levorin effect. Apparently, in high doses levorin impairs metabolism as a whole which cannot but affect the response of the sexual glands to administration of testosterone.     

Localization of DNA Sequences Tightly Associated with the Synaptonemal Complex in Compositional Fractions of the Golden Hamster Genome*

Synaptonemal complex (SC) isolated from spermatocyte nuclei after their exhaustive hydrolysis by DNase II contains DNA sequences tightly associated with it (SCAR DNA). Here, the compositional properties of a cloned family of golden hamster SCAR DNA were studied. For this purpose, 27 SCAR DNA clones were hybridized with compositionally fractionated golden hamster genomic DNA. The sequences of the SCAR DNA family were mainly localized in the GC-poor isochore families L1 and L2, which accounted for 63% of hybridization signals. The remaining 37% of signals pertained to the GC-rich isochore families H1 and H2. Thus, SCAR DNA proved to be distributed throughout the genome, irrespective of differences in density and sequence type between isochore families. Moreover, the SCAR DNA sequences containing the regions of homology with LINE/SINE repeats were found in all the isochore families. The compositional localization of SCAR DNA is in agreement with the hypothesis that the SC and SCAR DNA participate in chromatin reorganization during meiosis prophase I, which should result in the attachment of chromatin loops to the lateral elements of SC throughout its length.