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Biomedical subjects

A S Krylov

Publications and source records attributed to A S Krylov.

24 records · Page 2Linked to original sources
PubMedDate not supplied

[Antigenic structure of endotoxins from Bacillus thuringiensis].

The proteins of parasporal crystals of 9 strains of entomopathogenic bacteria of the Bacillus thuringiensis group of different H-serotypes were studied by different methods. Electrophoresis showed that crystals from the bacteria of 1, 3, 4, 5, 8, and 10 serotypes contained 1-2 proteins with a molecular weight of 130-145 kD and an additional fraction with a molecular weight of 55-120 kD. Double-radial immunodiffusion revealed that the crystals of all the serotypes studied are immunologically related. The proteins contained at least 3 types of antigens that can be detected either separately or all together when being tested with different antisera. The ELISA technique showed that the crystal proteins homologous with respect of antigens gave, as a rule, similar titration results.

Antigens, Bacterial↗
PubMedDate not supplied

[Reaction of fluorescent labeled analogs of the antibiotic distamycin A with synthetic polydeoxyribonucleotides].

Interaction of DNA with the analogs of the antibiotic distamycin A having different numbers of pyrrolcarboxamide units and labeled with dansyl was studied. The intensity of fluorescence of these analogs increases markedly when they bind to DNA. It is shown that the introduction of dansyl into the analog molecules does not change their binding characteristics. The binding isotherms of the analogs to synthetic polydeoxyribonucleotides were obtained. Analysis of the experimental data leads to the following conclusions: 1. The free energy of binding of the analogs to poly(dA1 . poly(dT) depends linearly on the number of pyrrolcarboxamide units in the molecule of the analog whereas attachment of each pyrrolcarboxamide unit produces change of 2 kcal/mole in the free energy. 2. Attachment of a pyrrolcarboxamide unit to GC pair results in the free energy change of 0.95 kcal/mole. 3. Adenine and thymine are close but not equivalent by the energy of binding to the analogs of distamycin A. 4. The binding of analogs to poly(dA . poly(dT) is a cooperative process, presumably dependent on the conformational changes induced by the binding of analogs to DNA.

Chemical Phenomena↗
PubMedDate not supplied

[Mechanism of AT base pairs recognition by molecules of dye "Hoechst 33258"].

Experimental studies are reported on the binding of the dye "Hoechst 33 258" to DNA and synthetic polynucleotides. A stereochemical model of binding of the dye to DNA is proposed. According to the model, the molecules of the dye are located in the minor groove of DNA, each covering 4 base pairs. The benzimidazole backbone of the dye tends to form a helix isogeometric to that of DNA in the B form. The specifisity of "Hoechst 33 258" binding to At pairs involves hydrogen bonding of two NH-groups of benzimidazole rings and CH3N+H group of the piperazine ring to O2 oxygenes of thymines and N3 nitrogens of adenines facing the minor groove of the DNA double helix.

Adenine↗
PubMedDate not supplied

[Structure of DNA complexes with regular polypeptides].

The conformation of some regular polypeptides: (Lys-Ala)50, (Lys-Ala2)37, (Lys-Ala2)26, (Lys-Ala3)18, (Lys3-Pro)29, (Orn3-Gly)28 was studied by means of CD. The complexes of these polypeptides with DNA were obtained by the methods of jump-dilution of a two-components mixture from 2 M NaCl to 0.05 M NaCl. The extent of DNA covering by the polypeptides was compared using binding isoterms of ethidium on DNA and DNA-polypeptide complex. The length, L, which polypeptides cover on DNA was estimated by means of energy transfer between the dyes absorbed on the complexes. The CD spectra of the complexes revealed a high sensitivity to changes of the environmental conditions. Small variations in the temperature and ionic strength produces marked changes in the CD spectra of the complexes. It was suggested that observed CD changes are due to both the structural relaxation of the complexes and the existence of liquid-crystal domains in solution.

Chemical Phenomena↗
PubMedDate not supplied

[Interactions between distamycin A analogs bound to DNA].

The experimental binding isotherms of the distamycin A analog to 8 natural and synthetic DNAs were analyzed. The shapes of binding isotherms suggest that the bound ligand molecule induces transitions of DNA (B-form) into two perturbated conformation states. These transitions are responsible for the existence of positive and negative cooperative effects on binding of distamycin analogs to DNA. At low levels of binding positive cooperative effects play a dominating role whereas at high levels of binding negative cooperative effects are observed. These cooperative effects can be described by the aid of a potential of pairwise interactions between nearest neighbour bound antibiotic molecules. A detailed analysis of experimental binding isotherms shows that characteristic distances over which these interactions are extended depend on the AT content of DNA. The energetical and structural parameters characterising the allosteric transitions of DNA to the perturbated states are obtained.

Allosteric Regulation↗