Formation of triplexes wherein the (G,T)-containing strand passes over from one purine strand of DNA duplex to the other was studied by chemical ligation and electrophoresis under nondenaturing conditions. Oligodeoxyribonucleotides with adjacent purine and pyrimidine regions were shown to be capable of forming stable bimolecular triplexes with cyclic oligonucleotides as well as with Linear ones that form a triple helix by both Watson-Crick and Hoogsteen base pairing.

A novel reaction involving the internucleotide phosphate of double-stranded DNA was proposed to obtain cross-linked DNA duplexes containing a reactive interstrand monosubstituted pyrophosphate group. The reaction takes place between activated terminal phosphate group linked to an oligonucleotide probe via a spacer unit, and proximal internucleotide phosphate, group of complementary oligonucleotide. Propane-, butane-, heptane-, and dodecandioles as well as 1,2-dideoxy-D-ribofuranose served as spacer units. Activation of the probe terminal phosphate was carried out using 1-ethyl-3(3'-dimethylaminopropyl)carbodiimide. The yield of the cross-linked duplexes was the highest with probes including propylene- or 1,2-dideoxy-D-ribofuranoside spacer units; it amounted up to 40%. Some properties of these compounds were investigated. It was found that the trisubstituted pyrophosphate group was selectively cleaved by nucleophilic agents such as N-methylimidazole and ethylendiamine. This reaction proceeds in aqueous media and results in transfer of one of oligonucleotide residues of the covalently bound duplex to the nucleophilic agent. The nucleophilic substitution proceeds simultaneously at both phosphates of the trisubstituted pyrophosphate group.

Techniques for preparing catalytically active corrin complexes of cobalt with monofunctional e-carboxyl- and e-amino groups in a macroligand are suggested. Two methods of the covalent attachment of such Co-corrin complexes to the terminal 3'- and 5'-phosphate groups of oligodeoxyribonucleotides were studied: the introduction of the complex to the oligonucleotide after oligonucleotide synthesis in aqueous solution and in the course of automated solid-phase oligonucleotide synthesis. Introducing of the Co-corrin complex during solid-phase synthesis was more efficient. It was demonstrated that the oligonucleotide probe thus obtained was able to act as a nuclease in the presence of ascorbic acid, the location of the clearage sites being determined by the addressing oligonucleotide.

Mixed oligomers, representing oligonucleotides connected with long nonnucleotide spacers, have been synthesized using phosphoramidite chemistry. The oligonucleotide moieties of the mixed oligomers fully or partially correspond in the structure to the consensus elements of -35 (TTGACA) and -10 (TATAATG) regions of prokaryotic promoters, The nonnucleotide spacers, approximating in size 17-membered DNA fragments, were synthesized using phosphoramidite derivatives of polyethylene glycol (PEG600), tetraethylene glycol or dodecanediol. It is shown that the oligonucleotide moieties of the mixed oligomers can form <<normal>> DNA like antiparallel complementary complexes, being the substrates of T4 DNA ligase. To obtain the DNA-Like polymers with alternating natural and nonnatural regions or cyclic structures, the enzymatic ligation of different complexes of the oligomers synthesized was studied.

Two self-complementary decadeoxyribonucleotides TAATGC* ATTA (where C* is a derivative of 5-methyl cytosine with a carboxy- or aminofunction attached through a spacer to the exocyclic amino group) were synthesized. Carbodiimide induced condensation of the amino and carboxyl groups in the opposite strands to give the crosslinks with a yield up to 20%. Cross-linking of two opposite strands in the duplex formed by the self-complementary aliphatic amino group-containing decanucleotide was performed with the use of glutaric aldehyde with a similar efficiency. The structure of the dimers obtained and position of the crosslinks were confirmed by the Maxam-Gilbert method. Efficiencies of the T4 DNA ligase-induced polycondensations of the double-stranded modified decanucleotides and of the cross-linked products differed significantly.

A synthesis of phosphoroamidite derivative of 2'-amino-2'-deoxyuridine which allows one to introduce point modifications into any position of the oligodeoxyribonucleotide chain by means of the standard solid phase phosphoroamidite method has been developed.

The DNA ligase-induced assembly of synthetic oligodeoxyribonucleotides on polymer supports was used to obtain immobilized DNA, containing the T7 RNA polymerase promoter and coding for a 14-membered oligoribonucleotide. The obtained template can carry out RNA synthesis in a flowing-type reactor. Sepharose 4B and Toyopear HW-55 were used as supports.

Studies were carried out on the efficiency of hybridase cleavage of RNA in perfect and imperfect hybrid duplexes consisting of three 'components: 1) individual RNA or polyribonucleotides; 2) synthetic complementary oligodeoxyribonucleotides; 3) Escherichia coli RNase H. In most experiments, the RNA was hydrolyzed predominantly in perfect hybrid duplexes formed from the RNA target and the complementary oligonucleotide probes. A number of imperfect hybrid duplexes containing a central pair of noncomplementary bases were found in which efficient hybridase cleavage of RNA also occurred.

Transcription of synthetic DNA by T7 RNA polymerase was used to obtain oligoribonucleotides of defined sequence. The enzyme's ability to transcribe DNA immobilized on hydrazide-sepharose was revealed. DNA templates used in such synthesis can be constructed by means of enzymatic (DNA ligase) or chemical ligation (cyanogen bromide).

Surgical desympathization of skeletal muscle fibre does not change the resting membrane potential or input resistance of muscle fibre membrane, but induces extrajunctional sensitivity to acetylcholine though lesser by half than that after anatomical muscle denervation. Raucedil injection and nerve stump transplantation on the muscle do not cause any changes in muscle membrane. The data obtained suggest the sympathetic nervous system participation in neurotropic control of muscle membrane sensitivity to acetylcholine.