Biomedical subjects

V T Ivanov

Publications and source records attributed to V T Ivanov.

At least 19 recordsLinked to original sources

PubMed1995

Localization of a sequential B-epitope in the VP2 protein of hepatitis A virus.

A set of synthetic peptides derived from the capsid protein of hepatitis A virus was used to search for B-epitopes. Peptides from the 115-139 region of the VP1 protein, from the 69-99 region of the VP2 protein and peptide 137-150 from the VP3 protein were found to react with monoclonal and polyclonal anti-HAV antibodies. MAPs based on 64-80 and 66-80 fragments of VP3 were reactive as well. Peptides, their conjugates with protein carriers and MAPs were used for antipeptide antibody production. Only free peptide 69-99 from the VP2 protein caused formation of HAV binding antibodies.

Amino Acid Sequence↗

PubMed1995

Crystal and molecular structure of the centrosymmetric meso-valinomycin analogue--cyclo (D-Val-D-Hyi-D-Val-L-Hyi-L-Val-D-Hyi-L-Val-L-Hyi-L-Val-D-Hyi-D-Val-L-Hy i) (C60H102N6O18).

The crystal structure of cyclo (D-Val-D-Hyi-D-Val-L-Hyi-L-Val-D-Hyi-L-Val-L-Hyi -L-Val-D-Hyi-D-Val-L-Hyi).2H2O has been solved by x-ray direct methods. The crystals (grown from a mixture of octane/CH2Cl2) are an orthorhombic, centrosymmetric space group Pbca, cell parameters a = 11.458 (2), b = 25.613 (3), c = 23.691 (3) A, Z = 4; therefore the molecule lies on a center of inversion in the cell. The atomic coordinates for the C, N, and O atoms were refined in the anisotropic thermal motion approximation (allowing for H-atom contribution to Fcal) to a standard R-factor value of 0.081. In contrast to meso-valinomycin, the analogue under study does not adopt an octahedral cage bracelet conformation. It has an unusual centrosymmetric elongated form with two type II terminal beta-bends formed by N-H ... C=O 4-->1 type intramolecular H bonds. Two symmetry-related water molecules reside in the elongated molecular cavity of the centrosymmetric depsipeptide ring.

Crystallization↗

PubMed1995

Proteolytic degradation of hemoglobin in erythrocytes leads to biologically active peptides.

A number of hemoglobin-derived homogeneous peptides were isolated from erythrocyte lysate. The amino acid sequences of nine peptides were determined. Seven out of nine peptides were relatively long, 30-32 membered peptides covering the N- or C-terminal sequences of globin chains. The remaining two were the pentapeptide neo-kyotorphin and its tetrapeptide derivative.

Adult↗

PubMed1995

Synthesis and immunological evaluation of the conjugates composed from a muramyl peptide GMDP and tuftsin.

The conjugates of a muramyl dipeptide analog GMDP (N-acetylglucosaminyl beta 1-->4 N-acetylmuramyl-L-alanyl-D-isoglutamine) and tuftsin (Thr-Lys-Pro-Arg) were synthesized from unprotected GMDP by mixed anhydride procedure. The identity of the conjugates was confirmed by high resolution NMR and their immunomodulating properties were determined in various tests. It was found that the conjugate in which the GMDP carboxyl group forms an amide bond with the epsilon-amino group of tuftsin lysyl residue exceeds GMDP in all the activities determined. Synergism of GMDP and tuftsin was found in phagocytosis stimulation assay.

Acetylmuramyl-Alanyl-Isoglutamine↗

PubMed1994

Isolation of endogenous hemorphin-related hemoglobin fragments from bovine brain.

Six short-chain peptides were isolated from an acidic extract of bovine brain in the course of total peptide screening. Their primary structures determined by Edman degradation were LVVYP, LVVYPWT, LVVYPWTQ, LVVYPWTQRF, VVYPWTQ and VVYPWTQRF, which respectively corresponded to the fragments 31-35, 31-37,31- 38, 31-40, 32-38 and 32-40 of bovine hemoglobin beta-chain. All these peptides contained sequences of opioid peptides - hemorphins. For two of these peptides, viz. 32-38 and 31-40, isolated from other sources, an opioid activity was demonstrated formerly.

Amino Acid Sequence↗

PubMed1994

Synthetic peptides in the determination of hepatitis A virus T-cell epitopes.

Computer search for probable T-epitopes of hepatitis A virus capsid proteins was performed using an integrated set of programs. Eight segments of the VP1, VP2, VP3 and VP4 proteins were chosen and synthesised. Five peptides 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 predicted T-epitopes affected the T-cell proliferation. None of the peptides had mitogenic activity. We demonstrated that regions 17-33 and 276-298 of VP1 are possible immunodominant promiscuous sites activating lymphocytes of all mouse haplotypes.

Amino Acid Sequence↗

PubMed1994

Dituftsin and polytuftsin induce an anti-peptide IgG response to non-immunogenic peptides in mice.

The effect of covalently attaching multiple forms of the immunomodulating tetrapeptide tuftsin to normally non-immunogenic peptides was studied in BALB/c and C57Bl/6 mice. The peptides: (NANP)3 from the Plasmodium falciparum circumsporozoite protein and peptides 136-152 and 205-213 derived from the capsid protein of foot-and-mouth disease virus were coupled to polytuftsin or dituftsin. Anti-peptide IgG titers were determined after two immunizations. All of these three non-immunogenic peptides coupled to polytuftsin or dituftsin induced anti-peptide antibody production in mice while peptides alone did not elicit IgG. In addition, a conjugate of (NANP)3 and polytuftsin with built-in glycopeptide adjuvant elicited an anti-peptide response comparable in magnitude with that of a peptide-KLH conjugate. The data suggest that when non-immunogenic peptides are synthesized in tandem with dituftsin or conjugated to polytuftsin a significant immune response to the peptides may be elicited. This approach may be employed in synthetic vaccine design.

Amino Acid Sequence↗

PubMed1994

Comparative study of immunomodulatory properties of muramyl peptides on immune system cells of young and old mice.

The immunomodulatory effects of two synthetic muramyl peptides (MP): muramyl dipeptide and glucosaminyl- muramyl dipeptide have been compared. It was shown, that MP effects on immune response are a consequence of the alteration in T lymphocyte regulators balance. MP action on old mice immune response and lymphocyte function was stimulating only: increasing of T helper precursors frequency and IL-1 production by macrophages. In the latter both MPs acted as correctors, recovering the decreased IL-1 production by old mice macrophages to young control level.

Acetylmuramyl-Alanyl-Isoglutamine↗

PubMed1993

New virus-specific T-helper epitopes of foot-and-mouth disease viral VP1 protein.

Immunogenicity studies of synthetic peptides from different regions of VP1 protein of foot-and-mouth disease virus strain A22 revealed the following active fragments: 39-61, 50-69, 135-159, 175-189, 170-189 and 197-213. Testing of virus neutralizing antibody production in rabbits primed by peptides and then inoculated by the virus showed that only peptides 135-159 and 170-189 were able to induce the functional T-cell helper activity. Localization of virus-specific T-cell recognition sites in sequences 135-159 and 170-189 was confirmed in in vitro recognition experiments of the virus by peptide activated mice lymphocytes.

Amino Acid Sequence↗

PubMed1993

The double pi pi 5.6 helix of gramicidin A predominates in unsaturated lipid membranes.

The structure of the channel-forming polypeptide gramicidin A (GA) incorporated into phosphatidyl-choline (PC) liposomes has been studied as a function of the degree of unsaturation of the acyl chains of PC. The initial conformational state of GA in reconstituted bilayers is determined by the solvent in which the peptide and the lipid are initially co-dissolved, whereas the equilibrium conformational state (after heat incubation) is affected by the lipid structure rather than by the nature of the solvent. The conformational equilibrium of GA has been studied in liposomes prepared from PC having a variable number of double bonds in the fatty acid moiety, by circular dichroism and Fourier transform infrared. Liposomes were prepared from trifluoroethanol or ethanol solutions and incubated at 68 degrees C. GA was shown to retain the conformation of the right-handed pi-->6.3 pi<--6.3 helix in PC with saturated acyl chains and with one double bond, whereas in dilinoleoyl-PC, having two double bond in each chain, the thermodynamically preferred structures are left-handed antiparallel and parallel double pi pi 5.6 helices. Natural soybean PC also favours left-handed pi pi 5.6 helical structures of GA (approximately 75%). This finding is discussed in terms of the role of PC unsaturation in the dynamic properties of the lipid matrix. Differences between observed FTIR spectra of the increases decreases pi pi 5.6 helix in solution (and to a larger extent in the membrane) and the calculated IR spectra can be interpreted as resulting from deviation of the real structure from the theoretically derived ideal helix. The data obtained provide grounds for better understanding of a GA channel functioning in lipids of variable degrees of unsaturation.

Cesium↗

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↗

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↗