Biomedical subjects

V T Ivanov

Publications and source records attributed to V T Ivanov.

At least 73 records · Page 4Linked to original sources

PubMed1993

[Search for T-epitopes of the hepatitis A virus using synthetic peptides].

Computer search for probable T-epitopes of the hepatitis A virus capsid proteins was performed using developed integrated set of programmes. The following peptides were chosen and synthesised by solid phase technique: 75-92 VP1, 115-139 VP1, 209-221 VP1, 69-99 VP2, 80-99 VP2, 45-57 VP3, 137-150 VP3 and 1-23 VP4. Peptides 1-17 VP1, 10-33 VP1, 11-25 VP1, 75-85 VP1 and 276-298 VP1 previously examined as probable B-epitopes were used as well. All the peptides were tested for their ability to stimulate proliferation of lymph node T-cells primed with synthetic peptides. Almost all the predicted T-epitopes did affected the T-cell proliferation. 10-33 VP1 and 276-298 VP1 stimulated lymph node proliferation of all tested mouse strains. 107-126 VP1 and 115-126 VP1 did not influence proliferation of lymphocytes of mice primed with these peptides but stimulated proliferation of T-cells of F1 (CBA x C57Bl6) mice primed with 115-139 VP1.

Animals↗

PubMed1993

[Synthesis and biological properties of delta-sleep peptide analogs. 2. Antimetastatic effect].

With the aim to investigate structure-functional relations of DSIP, 11 DSIP analogues were tested on antimetastatic activity, among them five new analogues, differing in positions 2 and 6 of the DSIP amino acid sequence were synthesized by the solid-phase method using Fmoc-approach. Experiments on C57B1 mice with metastatic Lewis lung carcinoma showed some analogues to be more efficient as antimetastatic agents then DSIP after i.v. (50 micrograms/kg) administration. Normalization of neuroendocrine status and activity of peritoneal, alveolar and spleen macrophages after the DSIP and some analogues injections in mice with metastatic Lewis lung carcinoma took place. Antimetastatic action of DSIP derivatives is considerably affected by structural changes, especially in the N-terminal part. Conformational factors rather than enhanced enzymatic resistance are essential for antimetastatic response.

Amino Acid Sequence↗

PubMed1993

[Neuroactive complexed zinc compounds from bovine brain].

The fraction obtained from acidic extract of bovine brain homogenate after several steps of chromatographic purification provokes spontaneous aggressive encounters in rats upon intracerebroventricular injection. The simultaneous long-term raising of electric shock-induced aggression with the suppressing of muricidal and intraspecies aggressive behaviour has been observed. Intravenous and intraperitoneal injections of this fraction induce no behavioural changes in rats. It has been determined that the fraction consists of complex compounds of zinc with various aliphatic amines. A similar or higher behavioural activity has been discovered in series of synthetic complexes of zinc with different ligands, that are suggested for use in modelling any nervous and psychiatric disorders connected with an increased aggression level.

Aggression↗

PubMed1993

[Synthesis and biological properties of new analogs of delta-sleep peptide. I. Antiepileptic effect].

To study structure-functional relationship in the series of DSIP, eleven DSIP analogues varying in positions 1, 2 and 6 were synthesized by the solid-phase method using both Boc- and Fmoc-approaches. The antiepileptic action of these analogues was compared with that of DSIP. The seizure activity was induced by the corazol or picrotoxin i. p. injection. Some analogues proved more efficient as antiepileptic agents than DSIP after their central (50 micrograms/kg in rats) and peripheral (1.0 mg/kg in mice) administration.

Amino Acid Sequence↗

PubMed1993

[2D-1H-NMR-study of the conformation of transmembrane segments of C, E, and G bacteriorhodopsin].

Conformations of synthetic peptides, analogues of the membrane spanning segments C (residues 67-106), E (128-162) and G (190-233) of bacteriorhodopsin Halobacterium halobium were studied by two-dimensional 1H-NMR spectroscopy. Peptides were solubilized in the mixture chloroform-methanol (1:1), 0.1 M LiC1O4. The spectrum resonances were assigned by means of phase-sensitive DQF-COSY, TOCSY and NOESY techniques. Interproton nuclear Overhauser effects were derived from NOESY spectra. Amide protons with slow deuterium exchange rates were determined. Analysis of the obtained data showed that segments C, E and G form right-handed alpha-helices including residues 77-101, 131-159 and 198-227, respectively.

Amino Acid Sequence↗

PubMed1993

[Solid-phase synthesis of peptides modelling the transmembrane segment of bacteriorhodopsin].

Peptides modelling transmembrane segments C, D, E and G of bacteriorhodopsin were obtained by solid phase method using the conventional Boc strategy. Protected peptides were assembled on PAM polystyrene support. Side chain protecting groups were: Tos for Arg, Bzl for Thr and Ser, cHx for Asp and Glu, Bzl(Cl2) for Tyr, For for Trp, Z(Cl) for Lys. Syntheses were performed on a modernized Beckman 990 synthesizer in the automatic mode. Double couplings by a preformed hydroxybenzotriazole ester were used for all residues. Qualitative and quantitative ninhydrine tests were used to monitor coupling efficiency. Removal of protecting groups and peptide cleavage were achieved by hydrogen fluoride, containing p-cresol and p-thiocresol as scavengers. Preparative reverse phase HPLC was used for purification. Peptide structure and homogeneity were confirmed by amino acid analysis, 1H-NMR and analytical HPLC.

Amino Acid Sequence↗

PubMed1992

Effective method for synthetic peptide immobilization that increases the sensitivity and specificity of ELISA procedures.

A procedure is described for the immobilization of synthetic peptide antigens on a plastic solid phase for performing ELISA. The use of a streptavidin-biotinylated peptide system for coating microplates with peptide antigen markedly increased both the sensitivity and the specificity compared to a standard ELISA based on synthetic peptides. The procedure was used for the detection of HIV-1-specific antibodies.

Amino Acid Sequence↗

PubMed1992

Molecular structure of cyclo[-(D-Val-L-Hyi-L-Val-D-Hyi)2-] revealed by x-ray analysis.

The crystal structure of a synthetic analogue of valinomycin, cyclo[-(D-Val-L-Hyi-L-Val-D-Hyi)2-] (octa-meso-valinomycin) (I) (C40H68N4O12.1.5.C4H8O2, M(r) = 937.01 + 88.10), has been determined. Crystals grown from dioxane are monoclinic, space group P2(1)/a, with cell parameters a = 21.487 (8), b = 16.836 (5), c = 16.089 (4) A, beta = 111.70 (4), and Z = 4. The atomic coordinates for nonhydrogen atoms were refined in the anisotropic thermal motion approximation. H atom positions were included in the structure factor calculations at their geometrically expected positions. Values of the standard and weighted R factors after refinement are 0.11 and 0.13, respectively. The conformation of the depsipeptide crystallized from dioxane is different from that crystallized from chloroform (II). The molecule adopts a rectangular shape with two type IV beta-turns containing a hydrogen bond and possesses pseudorotational symmetry. The side chains are located on the molecular periphery. The orientation of the carbonyl groups of the molecule is not conducive for efficient metal-ion coordination and in the observed conformation cannot behave as an ionophore. In the crystal the molecules form infinite chains parallel to the c axis, and are stabilized by two intermolecular hydrogen bonds that are shorter and have better geometry than the intramolecular hydrogen bonds. A phi/psi plot for dodecadepsipeptides with a (DLLD)3 sequence has well-defined areas for Val and Hyi residues only in cases when the crystals have been grown from nonpolar or medium-polar solvents. The phi/psi plot for octadepsipeptides crystallized from chloroform (II) shows this behavior also.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1992

Crystal and molecular structure of the depsipeptide ionophore hexadecaisoleucinomycin, cyclo-[(D-Ile-L-Lac-L-Ile-D-Hyi)4-] (C80H136N8O24).

The crystal structure of a synthetic depsipeptide ionophore hexadecaisoleucinomycin, cyclo [-(D-Ile-L-Lac-L-Ile-D-Hyi)4-] (C80H136N8O24), has been determined by single crystal x-ray diffraction techniques. The crystals are orthorhombic, space group P2(1)2(1)2(1), number of molecules per unit cell z = 4, and cell parameters a = 11,195, b = 17.853, c = 54.835 A. The values of the standard (R) and weighted (Rw) discrepancy factors after refinement are 0.122 and 0.135, respectively. The structure is characterized by an elongated bracelet form with a twofold axis of pseudosymmetry. It is stabilized by eight intramolecular 4----1 hydrogen bonds between the amide C = O and N - H groups. The ester carbonyls are directed toward the inside of the molecule, their oxygen atoms forming an ellipsoidal internal cavity. The side chains are located on the molecular periphery. The conformational states of hexadecaisoleucinomycin in solution are discussed in the light of the data obtained.

Amino Acid Sequence↗

PubMed1992

[Study of the antigenic structure of human immunodeficiency virus using synthetic peptides].

In a search for synthetic peptide antigens fit to detect anti-HIV antibodies, a set of algorithms were used to predict the probable antigenic determinants of gag, pol, env and nef proteins of HIV-1 and HIV-2. Over forty peptides were synthesized by the solid-phase method. The reactivity of the peptide antigens was evaluated in ELISA on panels of HIV-1/2-positive sera. Application of the synthetic peptides for the early HIV diagnostics was examined.

Amino Acid Sequence↗

PubMed1992

[Structure of macrocyclic K+, Rb+-complexon of meso-valinomycin monohydrate, cyclo[-(D-Val-Hyi-Val-D-Hyi)3-].H2O, in a crystalline complex with dioxane by x-ray structural data].

The crystal structure of a valinomycin analogue, cyclo[-(D-Val-Hyi-Val-D-Hyi)3-]x(C60H102N6O18) crystallized with dioxane and water molecules, has been solved by X-ray direct methods. The conformation found is analogous to one established for free meso-valinomycin crystallized from other organic solvents. It is characterized by a centrosymmetric bracelet form, stabilized by six intramolecular 4----1 type hydrogen bonds between amide N-H and C = O groups. One water molecule is fixed asymmetrically by hydrogen bonds in the internal negatively charged cavity of the complexon. The meso-valinomycin molecule "bracelets" in the crystal form stacks alternatively with dioxane molecules.

Cations, Monovalent↗

PubMed1992

[An increase in the immunogenicity of bacterial antigens under the influence of one of the derivatives of muramyl dipeptide].

As revealed in animal experiments, glucosaminylmuramyl dipeptide (GMDP), the synthetic analog of muramyl dipeptide, when introduced intraperitoneally in a single injection or orally, exhibits adjuvant activity with respect to Citrobacter 0-antigens, Shigella flexneri and enhances the protective properties of dysentery and pertussis vaccines. The stimulating properties of GMDP depend on its dose, the route of its administration, the time elapsed after its administration, its ratio to the concomitant doses of bacterial antigens and to the dose of the virulent culture used for challenge.

Acetylmuramyl-Alanyl-Isoglutamine↗

PubMed1991

Muramyl peptide-binding sites are located inside target cells.

Using flow cytometry and fluorescence polarization analysis, specific muramyl peptide-binding sites were shown to be located inside T-lymphocytes, macrophages and neuroblastoma cells, but not inside B-cells. No binding sites were found on the cell surface. The number of binding sites for each cell type was determined. Two types of binding sites were observed for myelomonocytic WEHI-3 cells with Kd values of 21 and 540 nM. Inhibition analysis demonstrated that for effective binding, an intact glycopeptide molecule and D-configuration of isoglutamine residue are important.

Animals↗

PubMed1991

Molecular conformation of a D,L stereoisomeric analogue of valinomycin, cyclo[-(L-Val-L-Hyi-L-Val-D-Hyi)2-(D-Val-L-Hyi-L-Val-D-Hyi)-].

The crystal structure of a synthetic analogue of valinomycin, cyclo[-(L-Val-L-Hyi-L-Val-D-Hyi)2-(D-Val-L-Hyi-L-Val-D -Hyi)-] ([L-Val1, L-Val5]meso-valinomycin), C60H102N6O18, has been determined. Crystals grown from petroleum ether are orthorhombic, space group P2(1)2(1)2(1), with cell parameters a = 16.41(1), b = 18.76(1), c = 25.86(1) A, and Z = 4. The atomic coordinates for nonhydrogen atoms, except those of terminal carbons on one side chain, were refined in the anisotropic thermal motion approximation. The coordinate parameters of the H atoms were incorporated into the structure factor calculations at geometrically expected positions. Values of the standard and weighted R factors after refinement are 0.074 and 0.083, respectively. The crystal structure of the molecule is asymmetric and adopts a conformation with four 4----1 type and one 6----1 type intramolecular hydrogen bonds between amide nitrogens and carbonyl oxygens. Valinomycin binds potassium more than 100 times strongly than the D,L stereoisomeric analogue, as a result of a different spatial orientation of potentially interacting carbonyl groups.

Amino Acid Sequence↗

PubMed1991

Two-dimensional NMR study of the conformation of (34-65)bacterioopsin polypeptide in SDS micelles.

The conformation of the synthetic 32-residue polypeptide, an analog of the membrane spanning segment B (residues 34-65) of Halobacterium halobium bacterioopsin, incorporated into perdeuterated sodium dodecyl sulfate micelles in the presence of trifluoroethanol was investigated by 1H NMR spectroscopy. The spectrum resonances were assigned by means of phase-sensitive DQF-COSY, TOCSY and NOESY techniques. Interproton nuclear Overhauser effects and deuterium exchange rates of individual NH groups were derived from two-dimensional NMR spectra. Analysis of the obtained data showed that segment B has a right-handed alpha-helical stretch from Lys41 to Leu62 with a kink at Pro50. The alpha-helix in the C-terminal part is terminated at Gly63, which adopts a conformation typical of amino acid residues in a left-handed helix. The N-terminal part (residues 34-40) has no ordered conformation. NMR data are provided for comparison of the segment B conformation in the isotropic system of an organic solvent, in SDS micelles and in the purple membrane bacterioopsin. Factors affecting the conformation of membrane spanning segment B in various milieus are discussed.

Amino Acid Sequence↗

PubMed1991

[Peptide synthesis--protein fragments from Plasmodium falciparum and their conjugates with protein and synthetic carriers].

To study coat proteins of Plasmodium falciparum, seven putative antigenic-determinants of PMMSA, SHARP, GBP and four known determinants of CSP, CRA and RESA were synthesized. Computerized methods for predicting protein antigenic determinants were employed to select the peptides. For immunochemical studies the peptides were conjugated to proteins and synthetic carriers by means of nonspecific and regiospecific heterobifunctional reagents.

Amino Acid Sequence↗

PubMed1991

[Identification of a protective epitope--a fragment of Lassa virus nucleoprotein].

Several peptides from Lassa virus glyco- and nucleoproteins were predicted as probable T-cell epitopes. Their synthesis was performed by solid phase method. The study of possible protective effect in vivo with Lassa-sensitive CBA mice revealed protective epitope within the 277-303 nucleoprotein region. Further studies reduced the protective epitope structure to the 287-300 nucleoprotein fragment.

Amino Acid Sequence↗

PubMed1991

[Antigenic structure of the foot-and-mouth virus. VI. Functional segments of the immunodominant region of the VP1 protein of foot-and-mouth virus strains O1K and A22].

B- and T-epitopes have been localized within the protective fragments of VP1 protein, viz., 136-152 of the O1K strain and 135-159 of the A22 strain of the foot-and-mouth disease virus (FMDV). Antibodies eliciting after immunization of various animals with the 135-159 A22 peptide are directed to different sites of the peptide. Immunogenicity of fragments of the 135-159 A22 peptide on mice correlates with their activity on T-cells of the same animals and protective activity on guinea pigs. The investigations were carried out using synthetic fragments of the 136-152-O1K and 135-159-A22 peptides.

Amino Acid Sequence↗