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Biomedical subjects

G I Chipens

Publications and source records attributed to G I Chipens.

At least 19 recordsLinked to original sources
PubMed1992

[Hidden symmetry of peptide and protein primary structures].

The internal symmetry of peptide chains was considered. To identify symmetrically located equivalent amino acids, the signatures method and the code of amino acid codon roots were applied. There was revealed the hidden symmetry of amino acid sequences of peptides and proteins as well as of their active centres. Amino acids having common codon roots in primary (and supposedly in the spatial "biologically active") molecular structures, are located symmetrically. Definition of local symmetry of peptide chains was proposed to use as one of the elements of complex analysis to determine location of molecular active centres.

Amino Acid Sequence↗
PubMed1992

[Folding of peptide chains during formation of the spatial structure of protein molecules is determined by the code of amino acid codon roots].

Basing on the analysis of a large number of protein sequences (Cserzo M., Simon I., 1989), the structure of the amino acid nearest neighbour pair whose occurrence has a maximal positive deviation from the mean statistical value, is shown to correspond in most cases to the code of the amino acid codon roots. It reveals particularly amino acid pairs in n and n+5 positions of polypeptide chains. Amino acids belonging to A/U family contribute mostly to the folding of peptide chains.

Amino Acids↗
PubMed1992

[Antagonistic properties of tetra-substituted analog of vasopressin with selective antidiuretic effects].

Biological properties of a novel vasopressin analogue were investigated. It was found that this analogue has no vasopressor and oxytocic activities but it exhibits a selective antidiuretic effect which is weaker than that of adiuretin (DDAVP). Novel analogue inhibits vasopressor, oxytocic and antidiuretic effects caused by arginine--vasopressin. The usefulness of novel compound as a pharmacological tool--vasopressin antagonist is suggested.

Animals↗
PubMed1991

[Code of codon roots of amino acids and idiotypic networks].

Novel models of idiotype nets of antibodies have been developed to study the code responsible for the amino acid interaction and complex formation of proteins. It is shown that the interaction of protein active centres in idiotype nets can be interpreted and predicted basing on the structure of code of codon roots of amino acids and polarity principle. "Internal images" of the sequence antigen determinants of proteins in immunoglobulin molecules are built mainly from the amino acid groups having common codon roots, which is in agreement with the conception of the structure of the root code.

Amino Acid Sequence↗
PubMed1991

[Hidden symmetry of the genetic code and laws of amino acid interaction].

Natural amino acids having common antiamino acids are divided into families and groups according to the algorithm of the genetic code (a-n-n-a, amino acid-codon-anticodon-antiamino acid). Members of these groups are placed symmetrically in the structure of the genetic code. In the course of evolution, those point mutations are predominantly accepted retained. In homologous proteins of phylogenetically related organisms which lend to amino acids belonging to one family or group and having common antiamino acids. This assumption is in agreement with L. B. Mekler's theory (1969) of the amino acid interaction code a-a.

Amino Acid Sequence↗
PubMed1991

[Interaction code for polar and nonpolar amino acids: "ice-breaker" model].

A novel model for the study of recognition and interaction code of amino acids in peptides, proteins and their complexes has been proposed. The model is designed on the modern notions on the structure and properties of water and hydrophobic bonds. It is assumed that the polar side chains of amino acids during the formation of the hydrophobic bonds act as "ice-breaker", thus destroying the organized structure of water (clusters or "icebergs") around the hydrophobic radicals of amino acids.

Amino Acid Sequence↗
PubMed1991

[Code of codon roots, determining the intra- and intermolecular interaction of amino acids in peptide chains].

To study the recognition processes and interaction of peptides and proteins, a model has been suggested according to which the first steps of complex formation of molecules are defined by G/C and A/U complementarity of codon roots of amino acid forming the molecules contact sites or surfaces. In contrast to amino acid--antiamino acid interaction code (L. B. Mekler, 1969), the code of codon roots involves the interaction of amino acids independently of the base structures in nucleotide triplets in positions 1 and 3. The analysis of the spectra of point mutations homologous proteins confirms the possible role of the root code.

Amino Acid Sequence↗
PubMed1990

[General principles of mast cell activation by cyclic analogs of basic vasoactive peptides].

The histamine-releasing activity of some linear and cyclic analogues of bradykinin (BK) and kallidin (K) was studied on rat peritoneal mast cells and compared with that of angiotensin (AT) cycloanalogues assayed earlier. Peptide cyclization, irrespective of the main pharmacological effect of the linear precursors (hypotensive for BK and K, hypertensive for AT), considerably enhanced their histamine-releasing activity. The activity of the tested compounds was found to depend on their amphiphilicity and cycle size. Linear AT and BK and their cycloanalogues bind to different receptor structures on rat mast cells. These findings suggest that BK, K and AT cycloanalogues belong to the same group of nonimmunological mast cell activators whose specific mechanism of action is based on the common structural features resulting from cyclization.

Amino Acid Sequence↗
PubMed1990

Binding selectivity of short [D-Arg2,Leu5]enkephalin analogues to mu- and delta-subclasses of opiate receptors.

[D-Arg2,Leu5]enkephalin and its analogues, shortened from the C-terminus, were studied in a rat brain membrane fraction with the aid of radioreceptor analysis. The interaction between these compounds and the peripheral opiate receptors of isolated organs (guinea pig ileum and mouse vas deferens) was also investigated. The ethyl ester of the [D-Arg2]tripeptide retains approximately 10% of the mu-receptor activity of leucine-enkephalin. This implies that for interaction with the mu-subclass of opiate receptors there is no requirement for a second aromatic ring in addition to the tyramine group in the minimal active moiety of the enkephalin molecule.

Amino Acid Sequence↗
PubMed1990

[The effect of synthetic thyroliberin on lactation in cows].

Synthetic thyroliberine increased the thyroxin concentration in the blood of lactating cows. Thyroliberine administration twice a day during 15 days (5 micrograms per kg) in cows on the 4th, 6th and 8th months of lactation increased the milk productivity for 17 days by 9.2, 14.9 and 8.3 per cent, resp. The milk protein and lipid content did not essentially change.

Animals↗
PubMed1979

Theoretical conformational analysis of oxytocin molecule.

The total semi-empirical conformational analysis of the oxytocin molecule has been carried out. It has been revealed the two main types of stable structures of cyclic moiety backbone and the great lability of the tail. The optimal spacing of cyclic moiety side chains has been found for every backbone structure. The calculation results are in good agreement with the data of physico-chemical investigations. Among the set of stable molecule structures reported in the present study are structures with beta-turn conformation of the cyclic moiety backbone and without closer spacing of the cyclic moiety and the tail, as well as structures with closely spaced N- and C-terminal parts which, however, lack beta-turn in the cyclic moiety.

Hydrogen Bonding↗
PubMed1978

[The antigen activity and structure of analogues and fragments of angiotensin, which contain enantiomeric forms of amino acids and aza-alpha'-homoamino acids].

The antigen activity of angiotensin, its fragments and analogues, which contain enantiomeric forms of amino acids and aza-alpha'-homoamino acids is studied by cross reactions with specific antibodies, obtained for angiotensin and its central tetrapeptide. It is found that the inclusion of additional NH-group between alpha carbon and carboxyl group of peptide chain, although in few cases radically changes spatial structure of compounds, does not deprivate their antigen activity. The replacement of NH-group to the C-end of the angiotensin molecule by affection the antigen determinant considerably decreases the antigen activity of the analogues. The important role in the determination of the antigen activity play the tyrosine residue and its specific orientation with respect to the antigen molecule. Low molecular weight fragments and analogues of the central part of angiotensin molecule, which have less "rigid" spatial structures, are capable to reorganize their spatial structure during interaction with antibodies.

Amino Acids↗
PubMed1977

[Structurally functional organization of corticotropin: lipolytic and steroidogenic activity of some of its fragments].

The influence of ACTH fragments, possessing structural elements, common for certain groups of peptide hormones and kinins--"common" fragments and cluster of basic amino-acids--(Lys 17,18-ACTH 11-18-NH2--I; ACTH 11-13-NH2--II; NH2CO-ACTH18-20-NH2--III) on lipolytic effect of ACTH in rat isolated fat cells and on the steroidogenic effect of ACTH in isolated rat adrenal cells was studied. Fragment I exerts a steroidogenic effect (alpha=0,84) at concentrations of 1--100 microng/ml. At low concentrations (10(-8)--10(-3) microng/ml) fragment I potentiates ACTH-induced steroidogenesis. Fragment I has no effect on the lipolysis;however, it potentiates ACTH-induced lipolysis at concentrations of 10--100 microng/ml. The results obtained support our previous supposition that "common" fragments are essential secondary non-specific active sites of hormones.

Adipose Tissue↗
PubMed1977

[Comparison of structural and functional organization of adrenocorticotropic hormone and wasp kinin].

A comparative study of structural and functional organization of the polypeptides -- ACTH and wasp kinin was made. The effects of fragments Lys 17, 18-ACTH11(-18)-NH2--(I) and WK4(-12)--(II), possessing "common" fragments and a cluster of basic amino-acids, on the lipolytic and steroidogenic effects of ACTH and myotropic effects of bradykinin were studied. Both fragments I and II potentiate ACTH-induced lipolysis and steroidogenesis in isolated rat fat and adrenal cells but suppress the myotropic effect of bradykinin on guinea pig ileum. The similarity of biological effects of ACTH and WK fragments support our supposition on the similarity in structurally functional organization of these peptides.

Adipose Tissue↗
PubMed1977

[Radioimmunoassay for the determination of angiotensin II and its fragments].

A radioimmunoassay procedure for the determination of angiotensin and its fragments: C-terminal hexapeptide and middle tetrapeptide has been developed. The sensitivity of the method reaches up to 5 ng/ml. The accuracy calculated from the standard deviation, for angiotensin and of its fragments presents the average +/- 1,5%; reproducibility (n = 10) is +/- 0,51% for angiotensin, +/- 2,12% for C-terminal hexapeptide and +/- 6,93% for the middle tetrapeptide. Using the Ouchterlony test with the cross-reactions showed that antibodies elicited to angiotensin interact with its fragments--middle tetrapeptide and C-terminal hexapeptide.

Angiotensin II↗