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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↗
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↗
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↗
PubMed1977

[Antigenic activity of angiotensin II and its fragments].

The antigenic activity of angiotensin and its seven fragments has been studied in cross-reaction with specific antibodies, elicited to angiotensin and its fragments: C-terminal hexapeptide and middle tetrapeptide. It has been found that all the fragments studied possess certain affinity for antibodies elicited to angiotensin, C-terminal hexapeptide and middle tetrapeptide. The middle tetrapeptide was identified to be the immunologically active centre of the angiotensin molecule.

Angiotensin II↗
PubMed1976

[Potentiation of ACTH action by a fragment of it: a decrease in the rat adrenal ascorbic acid concentration in vivo].

The effect of tripeptide NH2CO-Arg-Pro-Val-NH2, the analogue of common fragments of some peptide hormones and kinins, on the content of ascorbic acid in rat adrenal glands in vivo is studied. It is shown that the peptide (5 divided by 3000 mkg/100 g body weight) produces no effect on the content of ascorbic acid in adrenal glands, but its injection half an hour before the administration of native ACTH canses a significant increase in the ACTH activity. The peptide possesses the myotropic activity; it exerts sinergism and potentiation of the ACTH action on rat ascending colon.

Adrenal Glands↗
PubMed1976

[Potentiation of in vitro lipolytic effect of ACTH by its fragment].

The influence of fragment ACTH 11-14 analogues with amino acid sequences H-Lys-Pro-Val-Gly-OH (fragment I) and H-Lys-Pro-Val-Gly-NH2 (fragment II), possessing structural elements, similar for certain groups of peptide hormones and kinins, on lipolytic effect of ACTH in adipose tissue and isolated epydidymal fat cells of rat, was studied. Both fragments have no effect on the lipolysis; they potentiate the ACTH-induced lipolysis 1,5--2,0 fold, but do not alter the maximal effect at concentrations 0,1--1,0 mkg/ml in tissue and fragment I--at concentrations from 0,01 to 0,1 mkg/ml in isolated fat cell system. The role of "common" fragments in hormone-receptor interactions as well as mechanism of their potentiating effect is discussed. It is assumed that the "common" fragment of ACTH--ACTH11-14--is a second, non-specific active site of hormone directly involved in secondary signal formation.

Adipose Tissue↗
PubMed1976

[Use of specific angiotensin inhibitors in the study of hormone-receptor interaction].

The specificity of receptors participating in the interaction with angiotensin II (AT 1--8) fragments, e. g. N-terminal tri-(AT 1--3), C-terminal penta-(AT 4--8), and middle tetrapeptide (at 3--6), was studied in experiments on rat ascending colon which were performed to investigate the influence of a specific angiotensin antagonist, /1-hydantoic acid, 5-valine, 8-alanine/-angiotensin (HAAT 1--8), on myotropic effects of these fragments as well as the influence of the fragments on the myotropic activity of the whole hormone molecule. Competitive antagonism was found between HAAT 1--8 and AT 4--8 and AT 3--6 and between these fragments and AT 1--8. No antagonisma was revealed between AT 1--3 and HAAT 1--8, and between AT 1--3 and AT 1--8. It is assumed that the fragments AT 4--8 and AT 3--6 interact at the level of angiotensin receptors, and that of AT 1--3 at the level of non-specific receptors. A new model for the structural and functional organization of angiotensin is proposed.

Angiotensin II↗
PubMedDate not supplied

[A model of intra- and intermolecular interactions of peptide chains].

Results of attempts to determine the code of interaction of amino acids in peptide chains proceeding from their coding nucleotide sequences have been summarized. According to the model suggested the G/C and A/U complementarity of codon roots determines the mutual binding of coded amino acid residues. Structures of analogs of the immunoactive peptide, a fragment of IgG1 (336-370) EPQVY have been constructed on the basis of the model.

Amino Acid Sequence↗
PubMedDate not supplied

[Changes in the complex conditioned reflex activity of rat pups under the influence of penta-peptide].

Influence of YFRKD, modified fragment of interferon-alpha, on the formation of two-links system of feed-procuring conditioned reflexes was studied in rats in ontogenesis. The experiments have shown that YFRKD impedes both current learning and use of previous experience. The process of synthesis of two reflexes in united complicated functional complex is disturbed.

Animals↗