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V N Potaman

Publications and source records attributed to V N Potaman.

31 records · Page 2Linked to original sources
PubMed1993

High-performance liquid chromatography of the photoproducts of nucleic acid components. III. Detection of the secondary structure differences in sequence isomeric self-complementary oligonucleotides.

Reversed-phase high-performance liquid chromatography (RP-HPLC) was used to detect differences in the secondary structures of two self-complementary oligodeoxyribonucleotides. The [d(CCTTTAAAGG)]2 duplex assumes an ordinary B-conformation in aqueous solution, while [d(GGAAATTTCC)]2 is known to contain in its central part a stretch of a more rigid B'-form conformation with significantly lowered fluctuational mobility of base pairs. The latter factor causes a marked difference in the amounts of thymine cyclobutane photodimers formed under UV irradiation of corresponding duplexes as revealed by chromatography of two single-stranded oligonucleotides. Increasing the temperature below the duplex melting temperature (stimulation of the B'-B structural transition) results in an increase in photodimer formation that was inhibited in the B'-form. Thus, we demonstrate the usefulness of RP-HPLC for duplex DNA structural studies.

Base Sequence↗
PubMed1993

HPLC photofingerprinting of conformational peculiarities and transitions in oligonucleotide duplexes.

Two self-complementary sequence-isomeric decadeoxyribonucleotides were exposed to UV light under conditions in which they assume duplex structures. After that they were analyzed in the denatured state by reversed-phase high-performance liquid chromatography (HPLC). Characterization of the separated photoproducts allowed localization of cyclobutane pyrimidine dimers in the sequences of the modified oligonucleotides. For [d(GGAAATTTCC)]2, which is known to contain in its central part a stretch of rigid B'-conformation with decreased mobility of constituent bases, lower yields of thymine dimers, as compared with that for ordinary B-form [d(CCTTTAAAGG)]2, were found. On the contrary, mixed thymine-cytosine heterodimers generated in the former oligonucleotide demonstrate the increase in photoreactivity of these residues at the B'-B junction. This is probably due to the peculiar conformation adopted by this decanucleotide. Stimulation of B'-B transition, by increasing the temperature before melting, reduced an inhibition of thymine photodimer formation. During the melting of both oligonucleotides yields of all identified photoinduced cyclobutadipyrimidines were reduced. Possible influences of some metal cations on the stability of the B'-form were also studied by this photoprobing technique. The present study demonstrates the feasibility of HPLC photofingerprinting as a new approach for structural analysis of nucleic acids.

Base Sequence↗
PubMed1992

Use of tetrabutylammonium salts of amino acids in peptide synthesis.

Tetrabutylammonium (TBA) salts of amino acids and peptides have increased solubility, as compared with that of alkali metals salts, in organic solvents. We have compared the reaction rates for tripeptide formation in methylene chloride from Boc-Gly-Phe activated with various phenols, N-oxysuccinimide and azide, and TBA-salt of tryptophan, as well as Trp-OCH3. H-Trp-O-.TBA+ as an amino component significantly accelerates the rate of reaction. Although a significant degree of racemization has been found, the use of TBA-salt of amino acids and peptides is justified in many cases due to high conversion rates.

Amino Acid Sequence↗
PubMed1991

Entry of the synthetic ACTH(4-10) analogue into the rat brain following intravenous injection.

In view of known central effects of N-terminal ACTH fragments, a possibility of their entry into the brain was studied. Rat blood and brain extracts after intravenous injection of the tritiated synthetic ACTH(4-10) analogue, Met-Glu-His-Phe-Pro-Gly-Pro, were subjected to a high-performance liquid chromatographic analysis. At two time points the labelled peptide was detected in brain extracts. The brain to blood ratios of peptide content in brain and blood were found to be significantly higher than those calculated for a distribution of labelled bovine serum albumin in rat brain capillaries and blood. This strongly suggests that this peptide penetrates into the brain tissues, its quantity not exceeding 0.01% of dose injected. Peptide diffusion through the vascular epithelium of brain capillaries could account for the data obtained.

Adrenocorticotropic Hormone↗
PubMed1991

N-terminal degradation of ACTH(4-10) and its synthetic analog semax by the rat blood enzymes.

Degradation of a regulatory peptide ACTH(4-10) and its synthetic analog semax in rat blood and serum was studied using high-performance liquid chromatography. About one third to one half of the serum degrading activity could be ascribed to bestatin-sensitive aminopeptidase which cleaved first and second N-terminal residues Met and Glu producing relatively stable intermediates. Comparable areas under the degradation/accumulation curves for intact peptides and intermediates implied that the latter can contribute to effects of intact peptides. Semax turned out to be more stable than ACTH(4-10) against the action of other enzymes that took part in degradation.

Adrenocorticotropic Hormone↗
PubMed1989

[A method of screening artificial substrates for proteolytic enzymes].

A method of screening of proteolytic enzyme's substrates is proposed. An equimolar mixture of substrates consisting of peptide and easily detectable chromophore moieties (all chromophores in the mixture must be different) is subjected to enzymatic treatment. The cleaved chromophore groups, which are products of the substrate proteolysis, are quantitatively determined by chromatography. The Kcat/Km ratio is greater for substrates with higher initial rate accumulation of proteolysis products. The method is illustrated by screening of peptide derivatives of aminonaphtalene sulphonamides for trypsin assay. Proteolysis products are determined by HPLC with absorption detection or by TLC with fluorescence detection.

Chemical Phenomena↗
PubMed1981

Study of DNA films by the CD, X-ray and polarization microscopy techniques.

DNA films with psi +/- CD spectra have been investigated. X-ray analysis has shown the sign of the psi spectra to be independent of the secondary structure of DNA. The appearance of the psi spectra is attended by the formation of a characteristic polygonal texture of the cholesteric type in the DNA film.

Animals↗
PubMed1980

Sedimentation of DNA in ethanol-water solutions within the interval of B to A transition.

Sedimentation of DNA ethanol-water solutions has been studied over the range of ethanol concentrations corresponding to the B to A transition (65-80% ethanol, v/v). High ethanol concentrations (more than 75%) have been found to promote aggregate formation in solution. The molecular weight of DNA under fixed ionic conditions in solution (5x10(-4)M NaCl) has been shown to influence the value of ethanol concentration at which aggregates appear. On the other hand, the fact that DNA molecular weight has not been found to exert any influence on B to A transition curves obtained from CD measurements suggests that the changes observed in DNA CD spectra on adding ethanol to the solution are independent of aggregate formation. The date obtained show that, first, aggregation is not a necessary condition for the DNA transition from the B to the A-conformation and, second, changes in CD spectra of DNA under the influence of ethanol are not related to the process of aggregation.

DNA↗
PubMedDate not supplied

Degradation of ACTH/MSH(4-10) and its synthetic analog semax by rat serum enzymes: an inhibitor study.

Degradation of the behaviorally active peptide ACTH/MSH(4-10) and its synthetic analog semax was studied in serum in the presence of several specific peptidase inhibitors. Bestatin and puromycin were used to inhibit aminopeptidase activity, lisinopril for angiotensin-converting enzyme, phosphoramidon for neutral endopeptidase 24.11, and Z-Pro-prolinal for prolyl endopeptidase. Bestatin inhibited up to 66%, puromycin about 33%, and lisinopril about 15% of total degrading activity against both ACTH/MSH(4-10) and semax. Involvement of neutral endopeptidase and prolyl endopeptidase in hydrolysis of the two peptides was less definitive. These studies showed that aminopeptidases and angiotensin-converting enzyme are responsible for the major part of the hydrolysis of ACTH/MSH(4-10) and semax in rat serum.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

[A possible approach to the analysis of protease mixtures].

A problem of quantitative assay of proteases in complex mixtures is solved by using a set of peptide substrates with detectable (chromogenic or fluorogenic) groups (DGs). Quantitation of separate DGs released in reaction of enzyme mixture with a set of substrates is carried out in chromatographic analysis of reaction products. Reaction of peptide derivatives of aminonaphthalene sulfamides with a mixture of thrombin and proteases from viper venom shows the amounts of produced DGs to be proportional to the amounts of both thrombin and venom proteases, confirming the validity of proposed approach. There are cases of mutual influence of some components in proteases mixtures as illustrated by inhibition of trypsin activity in presence of viper venom; one determines enzyme activities in this specific mixture rather than their amounts.

Animals↗
PubMedDate not supplied

[Diagram of DNA states in water-salt-ethanol mixtures].

A detailed study of the behaviour of DNA in water-salt-ethanol mixtures has been carried out. We have made a diagram of DNA states in these mixtures and established the ranges of ethanol and salt concentrations corresponding to A and B conformations of DNA. We have also identified the ranges of strong DNA aggregation characterized by intense psi + and psi- CD spectra.

Animals↗