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N F Sepetov

Publications and source records attributed to N F Sepetov.

At least 19 recordsLinked to original sources
PubMed1996

Enzyme-mediated spatial segregation on individual polymeric support beads: application to generation and screening of encoded combinatorial libraries.

Proteolysis of short N alpha-protected peptide substrates bound to polyoxyethylene-polystyrene beads releases selectively free amino sites in the enzyme-accessible "surface" area. The substantial majority of functional sites in the "interior" of the polymeric support are not reached by the enzyme and remain uncleaved (protected). Subsequent synthesis with two classes of orthogonal protecting groups-N alpha-tert-butyloxycarbonyl (Boc) and N alpha-9-fluorenylmethyloxy-carbonyl (Fmoc)-allows generation of two structures on the same bead. The surface structure is available for receptor interactions, whereas the corresponding interior structure is used for coding. Coding structures are usually readily sequenceable peptides. This "shaving" methodology was illustrated by the preparation of a peptide-encoded model peptide combinatorial library containing 1.0 x 10(5) members at approximately 6-fold degeneracy. From this single library, good ligands were selected for three different receptors: anti-beta-endorphin anti-body, streptavidin, and thrombin, and the binding structures were deduced correctly by sequencing the coding peptides present on the same beads.

Amino Acid Sequence↗
PubMed1995

Library of libraries: approach to synthetic combinatorial library design and screening of "pharmacophore" motifs.

Construction of synthetic combinatorial libraries is described that allows for the generation of a library of motifs rather than a library of compounds. Peptide libraries based on this strategy were synthesized and screened with model targets streptavidin and anti-beta-endorphin antibody. The screens resulted in observation of expected motifs providing evidence of the effectiveness of the suggested approach.

Amino Acid Sequence↗
PubMed1995

One-bead-one-structure combinatorial libraries.

Combinatorial libraries employing the one-bead-one-compound technique are reviewed. Two distinguishing features characterize this technique. First, each compound is identified with a unique solid support, enabling facile segregation of active compounds. Second, the identity of a compound on a positively reacting bead is elucidated only after its biological relevance is established. Direct methods of structure identification (Edman degradation and mass spectroscopy) as well as indirect "coding" methods facilitating the synthesis and screening of nonpeptide libraries are discussed. Nonpeptide and "scaffold" libraries, together with a new approach for the discovery of a peptide binding motif using a "library of libraries," are also discussed. In addition, the ability to use combinatorial libraries to optimize initially discovered leads is illustrated with examples using peptide libraries.

Amino Acid Sequence↗
PubMed1994

Sequence-dependent modification of Trp by the Pmc protecting group of Arg during TFA deprotection.

The extent of transfer of the Pmc protecting group from the guanidino group of arginine to the side chain of tryptophan depends on the spacial distance of these side chains. When these two amino acids are separated by one amino acid, the transfer of the Pmc protecting group is the most pronounced, and it cannot be completely prevented by the use of currently utilized scavenger mixtures. The extent of this side reaction also depends on the amino acid separating the arginine and tryptophan residues and position of tryptophan within the peptide chain as well as on the type of the solid-phase carrier.

Amino Acid Sequence↗
PubMed1993

The use of hydrogen-deuterium exchange to facilitate peptide sequencing by electrospray tandem mass spectrometry.

The utility of hydrogen-deuterium exchange for sequencing peptides by mass spectrometry is demonstrated. The number of exchangeable hydrogens in a peptide is readily obtained by electrospray analysis of the peptide dissolved in deuterated solvents. This information can be used, in conjunction with published computer algorithms for interpreting peptide mass spectra, to reduce significantly the number of candidate sequences that fit the experimental data. This information, when combined with fragment-ion information in the mass spectrum, greatly increases the reliability of sequence determination.

Amino Acid Sequence↗
PubMed1993

Spontaneous chemical degradation of substance P in the solid phase and in solution.

The instability of the undecapeptide substance P (SP), a neuropeptide implicated in several physiological processes, was occasionally observed when the peptide was stored in the solid state or in solution. The aim of the present study was to identify the decomposition products of SP stored as lyophilized peptide or in aqueous neutral solution. The main pathway of the decomposition of SP acetate consists of the subsequent release of N-terminal dipeptides via their diketopiperazines, cyclo(Arg-Pro) and cyclo(Lys-Pro). In contrast to the decomposition of the acetate of SP, the hydrochloride and trifluoroacetate salts were found to be considerably more stable. Under the studied conditions the release of N-terminal dipeptides dominates over other possible routes of spontaneous modifications, such as S-oxidation and deamidation.

Amino Acid Sequence↗
PubMed1991

[Atrial natriuretic peptides. IV. Synthesis and study of shortened analogs].

New analogues of atrial peptides of rat were synthesized by classical methods of peptide chemistry in solution. They contain a D-amino acid residue in the C-terminal part and a residue of mercaptopropionic acid in the N-terminal part of the molecule. Biological activity of the new analogues was studied.

Amino Acid Sequence↗
PubMed1991

[Structure of the carbohydrate chain of riboflavin-binding glycoprotein from hen egg white. Neutral oligosaccharides of the hybrid type].

Reductive cleavage of the riboflavin-binding glycoprotein from hen egg white with LiBH4/tert-BuOH followed by NaBH4 treatment gave rise to oligosaccharide alditols. After fractionation by HPLC two individual oligosaccharide alditols of a hybrid type were isolated. Their structures were proved by 1H NMR 500 MHz spectroscopy and methylation analysis. One of the oligosaccharides has earlier been found in ovalbumin, whereas the other is identified in glycoproteins for the first time.

Animals↗
PubMed1990

[The structure of carbohydrate chains of riboflavin-binding glycoprotein from chicken egg protein. III. 1H-NMR spectroscopy (500 MHz) of neutral fucosylated oligosaccharides].

Using LiBH4/ButOH treatment, oligosaccharides were cleaved off the hen egg white riboflavin-binding glycoprotein. HPLC led to the isolation of four fucose-containing oligosaccharide alditols, whose structure was elucidated by means of 1H NMR 500 MHz spectroscopy. The main fucosylated oligosaccharide, also present in hen ovomucoid, was found to be a biantennary carbohydrate chain of N-acetyllactosamine type.

Animals↗
PubMed1989

The flexible region of protein L12 from bacterial ribosomes studied by proton nuclear magnetic resonance.

The dimeric protein L7/L12 from bacterial ribosomes has a highly elongated and flexible structure. We have, using 1H NMR methods, analyzed the extent of the flexible region and also the size of the organized structures of the molecule. A number of mutants of the protein as well as monomeric and dimeric forms of the protein and a COOH-terminal fragment have been used for the identification of certain resonances. Thus, residues 37-50 were found to be highly mobile whereas the amino-terminal and COOH-terminal regions are organized into folded domains. The flexibility between the domains and its relation to functional properties of the protein are discussed.

Acetylation↗
PubMed1989

[Structure of carbohydrate chains of the riboflavin-binding glycoprotein of chicken egg protein. II. 1H-NMR (500 MHz) spectroscopy of the major neutral oligosaccharides].

Reductive cleavage of riboflavin-binding glycoprotein from hen egg white (RF-GPw) with LiBH4/tert-BuOH followed by NaBH4/NaOH treatment gave rise to oligosaccharide alditols, fractionated by a successive HPLC on muBondapak C18 and Zorbax NH2 columns. Seven main individual oligosaccharide alditols were isolated and their structure was investigated by 1H NMR 500-MHz spectroscopy. The structure and relative content of the main oligosaccharide chains were proved to be identical in RF-GPw and ovomucoid. Structure of polypeptide chains and their molecular weight, number of glycosylation sites and their structure had little or no effect on the glycosylation pattern in both glycoproteins. HPLC of the oligosaccharide alditols from another egg white glycoprotein, ovotransferrin, also revealed its high microheterogeneity and close resemblance to those of ovomucoid and RF-GPw.

Animals↗
PubMed1989

[A study of enzymatic hydrolysis of splenopentin and its analogs in human serum].

Degradation of immunoactive peptide splenopentin and its analogue N-acetylsplenopentin in human serum has been investigated by 1H NMR spectroscopy. It is shown that degradation of splenopentin occurs due to hydrolysis of peptide bonds in its N-terminal part, whereas in N-acetylsplenopentin peptide bonds in C-terminal part of the molecule are cleaved. Degradation pathways and life times of these peptides in human serum are established.

Humans↗
PubMed1987

[The use of 1H-NMR-spectroscopy for the study of peptide degradation by angiotensin-converting enzyme].

A new method for continuous registration of enzymatic hydrolysis of peptides involving 1H-NMR spectroscopy was developed. The advantages of the method were demonstrated, using dalargin (Tyr-D-Ala-Gly-Phe-Leu-Arg) hydrolysis catalyzed by human kidney angiotensin-converting enzyme as an example. It was shown that the maximal activity of the enzyme towards dalargin is observed at pH 7.8; Km is 0.35 mM. The enzyme is inhibited by the substrate (Kd = 0.55 mM). Cl- do not influence the catalytic activity of the enzyme with respect to dalargin. The stereospecificity of the angiotensin-converting enzyme towards dalargin diasteriomers was studied.

Enkephalin, Leucine↗
PubMed1987

[Synthesis of endorphins].

alpha-, beta-, gamma- and (des-Tyr1)-gamma-endorphins were synthesised by classical methods of peptide chemistry. Optical purity of these peptides was controlled by GLC and NMR. Data on the opioid activity of the peptides synthesised are presented.

Amino Acids↗