The role of modifications in oligonucleotides in sequence recognition by MvaI restriction endonuclease

The interaction of MvaI restriction endonuclease with 14-membered deoxyribonucleotide duplexes containing modifications within the recognition site (CCA/TGG) has been studied. Substitution of m5dC for the internal dC residue, as well as substitution of fl5dU or rU for dT did not influence the initial rate of hydrolysis (v0) of modified strands, whereas the hydrolysis of unmodified strands was inhibited in some cases. Furthermore, the substitution of a pyrophosphate bond for a scissile phosphodiester bond in one strand completely inhibited digestion in this strand without any decrease of the rate of hydrolysis of the unmodified strand. In contrast to EcoRII endonuclease, which recognizes the same DNA sequence, in the case of MvaI endonuclease substrate recognition is possible in a wide range of conformational, electronic and hydrophobic alterations within the recognition site.     

A comparative analysis of learning and exploratory behavior in rats with different resistances to stress exposures and to the brain monoamine level]

Wistar rats stable (S) to sound stimulus differed from the unstable (NS) ones by a heightened investigatory activity in condition of moderate stress in the open field test, by heightened reactivity to sensory stimuli of various modalities (somatosensory, visual and olfactory), lowered level of investigatory behaviour in the test of burrow chamber. S-rats differed from NS-animals by a higher ability to learning of goal-directed reaction and a lower ability to discrimination of different emotional influences. The results of biochemical analysis of the content of biogenic amines in various brain structures revealed in stable rats an increase of noradrenaline level and in non-stable ones--a higher level of dopamine and serotonin.     

Characteristics of the action of psychostimulants on learning and memory in rats

The effects of intraperitoneal injections of psychostimulant drugs: centrophenoxine (50 mg/kg) and peptide analog of tuftsin TP-1 (300 micrograms/kg) on the processes of elaboration and retention of conditioned reflex have been experimentally studied. The animals were trained with food reward in 30 trials per day. Psychostimulant drugs or saline were injected after the 10th trial. The elaboration of conditioned reflex was continued 30 min later. The retention was tested 24 h, 7 and 30 days later. It was established that both drugs induce an increase in memory traces stability during 30 days. These findings provide direct evidence that psychostimulant drugs, centrophenoxine and peptide substance TP-1, when injected during consolidation phase can enhance memory storage processes.     

DNA-like duplexes containing repetitive sequences. VIII. Synthesis and properties of DNA fragments--substrates of restriction endonuclease EcoRII

The optimal way of constructing a family of restriction endonuclease EcoRII substrates has been developed. The substrates are DNA-like duplexes containing regularly repeated native or modified sites of this enzyme as well as those of EcoRI and AluI. Synthesis of substrates was performed by water-soluble carbodiimide-induced polycondensation of two nonanucleotides, d(C-C-T-G-G-A-A-T-Tp) and d(C-C-A-G-G-A-G-C-Tp), as constituents of different complementary complexes. The products of reaction (degree of polymerization, 2-20) were isolated by G-200 gel-filtration. The yield of polymers was about 70%. The main products of reaction were dimers when dephosphorylated nonanucleotides (terminators of polycondensation) were used. The thermal stability of DNA-like duplexes is very high. The structure of the polymers obtained has been confirmed by UV-spectroscopy and by CD data as well as by the results of cleavage by EcoRI and AluI restriction endonucleases.