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The article describes theoretical aspects of isolation and separation of DNA fragments by size using a polymeric sorbent. On this basis we presented a theoretical model of thermal desorption of DNA fragments of different length. Assuming that, under certain pH, interaction of DNA with the polymer sorbent is of an ion-dipole character and moving dipoles interact with the sorbent according to the Boltzmann distribution with the total charge of the DNA fragment in its pore, the expression for the interaction energy as a function of temperature is obtained. Equating the thermal energy to the interaction energy of the ion-dipole character, we have found the critical temperature of DNA separation from the sorbent. Account of the conformation of single-stranded DNA in the coil form leads to the dependence of DNA separation temperature, i.e., desorption, on the length of the DNA chain. The temperature for desorption increases symbatically to the contour length of DNA.

Method of ssDNA preparing in single-round PCR for microarray application is described. The approach is exemplified on genotyping of DARC gene. It is opposed to two-round PCR that consists of separate symmethric and asymmethric stages. Implementation of reaction in single round is achieved by means of low-melt excess internal primer application. The primer do not anneal during symmethric stage but after decreasing of annealing temperature on asymmethric stage. The results indicate effective oligonucleotide microarray genotyping. The approach reduces time requirements and risk of contamination.

The ss-DNA of the (+) and (-) chains of Ela DNA fragment was obtained by hydrolysis of the recombinant bacteriophages M13 mp8G and mp9G (where G is 1-1750 bp:, E1a region of oncogene SA7) in complexes with the 16 bp oligonucleotides containing AluI and BspRI sites of restriction and sequences complementary to E1a SA7. The obtained fragments overlap the E1a zones associated with the immortalizing potential of SA7.

A possible use of a previously described method of fractionation of highly polymeric DNAs on a column with benzoylated DEAE-cellulose is discussed. The method can be used for separation of renaturated and hybrid DNA molecules as well as for detection of single-stranded structures within the DNA. Using the method in question it was shown that the DNA of hepatoma 27 contains about 6% of single-stranded DNA structures.

A base composition of single-stranded DNA regions differed from those of total rat DNA mainly due to increase in content of 5-methylcytosine. Content of this base in the regions studied reduced with age and after cortisol administration. The single-stranded regions appear to shield the informative DNA sequences.

The present work is concerned with a sensitive and fast micromethod for separation of single- and double-stranded molecules of nucleic acid by hydroxyapatite (HAP) thin-layer chromatography. The thin layers were obtained by precipitation of ground HAP particules into the surface of the plates in water. Chromatography in sodium phosphate buffer makes it possible to separate from 1 to 50 micrograms of nucleic acids for 30--50 sec. Thereby double-stranded molecules remain at the starting line, whereas single-stranded DNA or RNA follow up the solvent. For quantitative assay of nucleic acids by HAP thin-layer chromatography, the plates were scanned in UV light, radioactivity was measured without extracting substances from HAP and DNA and RNA were eluted with the help of phosphate buffer. A simple and accurate determination method has been suggested consisting in dissolving HAP in perchloric acid followed by hydrolysis of nucleic acids and spectrophotometry of solutions. The retrieval of the material after chromatography in 99 +/- 2%, the mean determinations error is 2--3%. The conditions are described for extraction, after thin-layer chromatography, of desalted and concentrated DNA, ready for use in later experiments. The paper describes a method: for determination of the degree of DNA nativity; quantitative determination of DNA in solutions, containing admixtures; separation of synthesized RNA from its precursors and from the DNA template; assay of DNA thermostability; investigation of the kinetics of DNA reassociation and DNA-DNA hybridization. Some results obtained from hydroxyapatite thin-layer chromatography are discussed.