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S A Strel'tsov

Publications and source records attributed to S A Strel'tsov.

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

[Intramolecular compactization of circular DNA in interaction with dansyl hydrazide trivaline leading to a formation of a new type of structure--triple rings].

Compactization of supercoiled circular plasmid pBR322 caused by interaction with synthetic oligopeptide dansyl hydrazide trivaline capable of beta-structure formation was studied by electron microscopy. The results show that at rising input peptide concentration circular DNA molecules undergo intramolecular structural transition with the formation of compact ring structures. The compact ring structures are formed by the fiber having the thickness of 60 A. The analysis of morphology of intermediate structures and the contour length measurements enable us to conclude that 60 A-fiber contains three lying side-by-side and interwound double-stranded DNA segments. Thus, the compact ring structures are addressed to as triple rings. The triple ring have one special point, where the triple region ends are locked by a duplex DNA segment. The mechanisms responsible for the triple ring formation may be of importance for DNA and chromatin compactization processes in vivo.

DNA, Circular↗
PubMedDate not supplied

[Spatial structure of DNA complex with the oligopeptide dansyl hydrazide trivaline].

The structure of complexes between double-stranded DNA and oligopeptide dansyl hydrazide trivaline was studied by linear dichroism, electron microscopy and hydrodynamical methods. The results show that the binding of the oligopeptide to DNA is a cooperative process that leads to the formation of particles significantly differing in the structure from free DNA. The linear dichroism studies were carried out in a wide range of flow-speed gradients. From the theoretical analysis of these data a conclusion can be drawn that the DNA-oligopeptide complexes possesses a higher rigidity as compared with that of free DNA. The hydrodynamical behaviour of these particles is consistent with the rigid rod-like structure of the particles with a long axis nearly parallel to the DNA helix axis in the complexes. The sedimentation patterns of the complexes suggest the existence of the fast and slow sedimenting species. The sedimentation coefficient measured for a fast sedimenting species is about 3 times higher than that of free DNA. The linear dichroism spectra obtained for the floworiented DNA-oligopeptide complexes correlate with the existence of a superhelical organization of DNA in the complex. This offers a possibility for the determining of the angle of the DNA local axis inclination with respect to the superhelix axis. On electron micrographs the DNA-oligopeptide complexes look like rod-shaped structures with the thickness of about 180 A and 80 A on the rotatory-shadowed preparations and on the uranylacetate stained preparations, respectively. The rod-shaped structures are formed by two interwound DNA molecules. The superhelix has a pitch of about 150 A with an angle of twist inclination of about 40 degrees. These values are in good agreement with the optical anisotropic data. It is suggested that the complex structure is stabilized by periodically spaced hydrophobic contacts between the dimeric oligopeptide species bound to the DNA molecules.

DNA↗
PubMedDate not supplied

[Specific reaction between oligovaline and nucleic acids].

The DNA binding activity of trivaline dansyl hydrazide was investigated by circular dichroism, UV spectrophotometry and fluorescence methods. It is shown that these peptides in the absence of DNA can adopt statistical coil and antiparallel beta-conformation and can exist in aqueous solution as monomers, dimers and higher orders aggregates depending upon the concentration and the presence of N- and C-blocking groups. The aggregation and disaggregation processes are very slow especially for N- and C-protected peptides. Our observations show that oligopeptides in the monomeric and dimeric forms bind to double-stranded DNA and RNA whereas tetramers and higher order aggregates exhibit no DNA binding activity. The binding of monomers is a cooperative process favoring the formation of deformed antiparallel beta-structure between adjacently bound monomers. The binding constant of dimeric oligovaline species to GC-rich DNA sequences is about 5 fold higher than that found from the binding of oligovaline to poly(dA) . poly(dT). The binding of dimers takes place in the minor DNA groove as revealed from our observations that oligovaline binds to T6 phage DNA containing massive glucose and diglucose residues in the major groove. The backbone C=0 groups of oligovaline probably serve as specific reaction centres for the interaction with guanine 2-amino groups in the minor DNA groove.

Chemical Phenomena↗
PubMedDate not supplied

[The hierarchy of complexes and compact structures of trivaline with nucleic acids. II. Interaction of trivaline with single-stranded RNA (using poly(U) as an example)].

It has been shown by equilibrium dialysis that at a poly(U) concentration above the "critical" one, the complete polymer saturation with trivaline reaches approximately 0.7, i.e., in these conditions the peptide dimer occupied on poly(U) a site of three bases in length. It has been shown by flow linear dichroism that trivaline beta-dimers preferentially binding with the single-stranded polymer rather than with the double-stranded one. It has been shown by electron microscopy that "the highest" compact structure of trivaline-poly(C) consists of dozens of "biduplex" structures. Beginning with a dimer trivaline-poly(U) complex, we proposed a schematic model for other complexes and compact structures of these molecules.

DNA↗
PubMedDate not supplied

[Oxytetracycline binding to E. coli ribosomes].

Binding of oxytetracycline to E. coli ribosomes was studied by equilibrium dialysis. The results are consistent with the existence of two classes of binding sites for the antibiotic on ribosomes having different reactivities. There is one strong binding site as well as about 500 weak ones. The association constant for strong complexes is about 10(3) times greater than the value for weak ones. Oxytetracycline and tetracycline bind to ribosomes as magnesium chelates. Increase of the concentration of Mg2+ leads to the formation of two types of magnesium chelates of the antibiotic: chelate 1 which is formed at a relatively low concentration of Mg2+ and has a stiochiometry 1:1, and chelate 2 which probably corresponds to the attachment of second ion to the antibiotic molecule. The strong binding of oxytetracycline to ribosomes prevents the template dependent association of aminoacyl-tRNA with ribosomes. However, no changes in the extent of the antibiotic binding were found upon addition of aminoacyl-tRNA, poly(U) and chloramphenicol to oxytetracycline-ribosome complexes. It has been suggested that inhibiting effect of oxytetracycline on the protein synthesis involves an allosteric mechanism.

Binding Sites↗
PubMedDate not supplied

[The hierarchy of complexes and compact structures of trivaline with nucleic acids. I. Interaction of trivaline with double-stranded DNA].

It was shown that trivaline-poly(U) complexes have no appreciable fluorescence at any peptide concentration if the polymer concentration is less than critical. By electron microscopy it was shown that dsDNA molecules undergo a second step of compactization if polymer and peptide concentrations are high enough. The diameter of this rod-like particles is over 40 nm. If the polymer concentration is less than critical, dsDNA molecules form with trivaline extended structures of dissimilar morphology. We propose a scheme of trivaline-dsDNA complexes and compact structure formation, beginning from a dimer complex. It is consistent with the results of equilibrium dialysis, fluorescence, electron microscopy, flow linear and circular dichroism measurements.

Circular Dichroism↗
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[The hierarchy of complexes and compact structures of trivaline with nucleic acids. III. Complexes of trivaline with trinucleotides forms a rod-like structure with length of about 1000 A in solution].

We demonstrated the ability of trivaline in the course of interaction with certain trinucleotides in solution to form extended fibre-like structures with lengths of up to several thousand angstroms. Such structures were observed for complexes of trivaline with both deoxyribo- and ribonucleotides with homopurine, homopyrimidine, or random sequences, with or without terminal 5'-phosphate. A model of organization of such structures is proposed. It is based on tetramer complex of trivaline with short nucleotides, two structural units of which, consisting of trivaline tetramer and two trinucleotides, form the octamer complex. It has three perpendicular axes of symmetry of the second order. The spatial location of bases in this structure is additionally fixed by nucleopeptide interactions. The latter create favourable conditions for arranging hydrogen bonds between trinucleotides belonging to different tetramer complexes and stacking interactions between the bases of each nucleotide. Octamer complexes are able to form regular aggregates in the form of a "stack", consisting of dozens of elementary units. These aggregates can be electron microscopically visualized as extended fibre-like structures.

Microscopy, Electron↗
PubMedDate not supplied

[Trivaline initiates formation of homo- and heteroquadruplex DNA structures].

Formation of heterologous (calf thymus double-stranded DNA) and homologous (linearized pBR322 plasmid double-stranded DNA) quadruplexes upon binding with the simple aliphatic tripeptide derivative (dansyl hydrazide trivaline) was examined by fluorimetry, flow linear and circular dichroism and electron microscopy. The morphology of the rod-like compact particles formed due to the association of double-stranded DNA segments proved to be the same for both DNAs, whereas the stability of the compact DNA structure upon tripeptide removal from the complex with DNA differed substantially for homologous versus non-homologous double-stranded DNA used. The increase of NaCl concentration in the solution up to 30 mM removes the peptide from both types of the complexes completely. At the same time at 20 mM NaCl calf thymus DNA quadruplexes readily dissociate, whereas the structures formed by plasmid DNA retain their morphology in the solution containing NaCl with concentrations up to 40 mM and are only partially disrupted at even higher NaCl concentration. These results provide the analogy between trivaline-DNA model complexes and RecA-DNA binding.

Animals↗