Biomedical subjects

V S Ivanov

Publications and source records attributed to V S Ivanov.

At least 19 recordsLinked to original sources

PubMed2006

The K2 2(3)Pi(g) state: new observations and analysis.

Totally 3045 transitions into the 2(3)Pi(g) v = 0-42, J = 0-103, Omega = 0, 1, 2 rovibrational levels have been observed by infrared-infrared double resonance fluorescence excitation and two-photon spectroscopy. Molecular constants including the spin-orbit interaction parameters are obtained. Although the K2 2(3)Pi(g) state dissociates to the 4s + 3d atomic limit, it is strongly mixed with the 3P ionic states in the range of the potential well. This mixing results in a relatively large equilibrium internuclear distance Re = 5.254 A and a larger spin-orbit constant A0 approximately 14.17 cm(-1) than that of the atomic limit -2.33 cm(-1). Strong perturbations of the 2(3)Pi(g) levels observed are attributed to the spin-orbit coupling with the 4(1)Sigma(g)+ state.

Journal Article↗

PubMed2005

Experimental study of the 39K2 2 3Pi(g) state by perturbation facilitated infrared-infrared double resonance and two-photon excitation spectroscopy.

The 39K2 2 3Pi(g) state has been observed by perturbation facilitated infrared-infrared double resonance and two-photon excitations. The vibrational numbering of the 2 3Pi(g) levels was determined by resolved fluorescence into the bound levels as well as to the continuum of the a 3Sigma(u)+ state. The rotational assignment of the 2 3Pi(g) levels excited by two-photon transitions was determined from excitation frequencies and resolved fluorescence into the bound levels of the a 3Sigma(u) + and b 3Pi(u) states. Molecular constants obtained from these observed levels agree with theoretical constants.

Journal Article↗

PubMed1997

Tumor cell cytolysis mediated by valorphin, an opioid-like fragment of hemoglobin beta-chain.

Valorphin, an endogenous opioid-like hemoglobin fragment, is cytotoxic for L929 and K562 tumor cells in 10(-7)-10(-13) M concentration range. Because cytolytic effects induced by valorphin in K562 cells are inhibited by naloxone, opioid receptors should be involved in induction of valorphin-mediated tumor cell death. Three distinct cytolytic processes, differing in the onset time and the development time, take place with K562 cells within 10-18 h of incubation with valorphin. All three processes are not associated with apoptotic mechanism of cell death.

Adamantane↗

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

Peptides of a major histocompatibility complex class I (Kb) molecule cause prolongation of skin graft survival and induce specific down-regulatory T cells demonstrable in the mixed lymphocyte reaction.

Six individual peptides of the major histocompatibility complex (MHC) class I molecule H-2Kb were synthesized. Intravenous injection of peptide 6 into mice prolonged the survival of Kb (BL/6 or B10.MBR) skin grafts on allogeneic R101 and B10.AKM mice, respectively. This was specific, as control skin grafts from Kk (B10.BR) or Kd (DBA/2) donors, respectively, were rejected at the same time in both control and peptide-treated mice. The optimal doses for peptide 6, which is from the alpha 2 domain, were defined. The test system was the inhibition of proliferation in vitro of naive lymph node cells by syngeneic mitomycin c-treated spleen cells from R101 mice preimmunized with irradiated stimulator splenocytes of Kb (BL/6) origin. Down-regulation was specific, as proliferation in response to third-party allogeneic stimulator Kk (B10.BR) splenocytes was not inhibited. Of the six peptides of H-2Kb tested, potent down-regulatory cells were induced by peptides 2 (alpha 1 domain) and 5 and 6 (alpha 2 domain). The greatest down-regulatory activity was obtained by giving peptide 2 to mice that had already been immunized against H-2Kb by injecting EL4 cells. Under the same conditions, injecting peptide 2 did not induce any cytotoxic T cells. In contrast, specific cytotoxic lymphocytes (CTL) were induced when cells from primed mice were incubated for 4 days with heated stimulator cells from BL/6 mice. The data suggest that peptides from MHC class I molecules activate precursors of down-regulatory T cells, but not of CTL, and this may explain their ability to prolong skin allograft survival.

Amino Acid Sequence↗

PubMed1995

[Use of histocompatibility class I molecule peptides for in vivo induction of specific T-suppressors in allogenic systems and prolongation of mouse skin graft life].

Six synthetic peptides were selected for the individual molecule H-2Kb of the major histocompatibility complex class 1. Optimum conditions were elaborated for the induction of specific suppressor T cells in vivo by peptide 6 (alpha 2 domain) in an intravenous dose of 33 micrograms to the tail vein or 100 micrograms to the orbital sinus, followed by testing the suppressor activity in inhibiting in vitro proliferation in the three-cell MLC in response to irradiated cells of the stimulator Kb (BL/6) in the absence of suppressed response to the foreign stimulator Kk (B10.BR). Out of 6 different peptides of the same molecule H-2Kb, suppressor T cells were induced effectively by peptides 2 (alpha 2-domain), 5 and 6 (alpha 2-domain), while the high efficiency of suppressors is realized by memory cells along with peptides 2. Under the same conditions, in vivo peptide immunization did not induce cytotoxic T lymphocytes at all. In contrast, CTL were specific in their high efficiency where memory cells were in vitro pretreated with stimulators of warmed BL/6 cells. Intravenous administration of peptide 6 to mice gave rise to prolongation of Kb (BL/6 or B10.MBR)-induced skin transplantation during the transfer from allogenic murine R101 and B10.AKM, respectively, but without the terms of skin prolongation at all with the stranger donors Kk (B10.BR) or Kd (DBA/2).

Amino Acid Sequence↗

PubMed1995

[Identification of immunoreactive epitopes in proteins coded by gag, env, and pol genes of the type I human T-lymphotropic virus (HTLV-I) using synthetic peptides].

Reactivity of 26 synthetic peptides that comprise 12 to 26 amino acid residues corresponding to segments of the gag p19, env gp46, and pol proteins of human T-lymphotropic virus type I toward 31 positive sera was studied using enzyme-linked immunosorbent assay. Specific reactivity with high titers of antibodies (presented in reciprocal dilution values) was detected for the synthetic peptides corresponding to fragments 110-130 and 100-130 (titers up to 4050) of p19, 174-197 (up to 800), 186-201 (up to 4050), 191-215 (up to 1350), 242-257 (up to 800), and 272-292 (up to 450) of gp46. Immunoreactivity of seven peptides, fragments of pol-proteins, was weak. New linear epitopes in the regions 145-158, 272-277, and 292-300 of gp46 were detected. In addition, location of the known linear epitopes in p19 and gp46 was refined on the basis of comparative study of overlapping peptides from these proteins.

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

[Modeling antigenic determinants of the hepatitis A virus using synthetic peptides].

Monoclonal and polyclonal anti-hepatitis A (HAV) antibodies were used to search for peptides mimicking the antigenic determinants of HAV. Synthetic peptides VP1 115-139, VP1 117-139, VP1 126-139, VP2 69-99, VP2 80-99, VP3 45-57, VP3 137-150, were shown to bind the anti-HAV antibodies in ELISA. Peptides VP1 115-139, VP1 117-139, VP2 69-99 were utilized to produce the antipeptide antibodies. Mice were immunized with the free peptides or with their conjugates with ovalbumin. Only the free VP2 69-99 caused formation of HAV binding antibodies.

Amino Acid Sequence↗

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↗

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

[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↗

PubMed1991

The synthetic peptide from HIV increases functional activity of granulocytes in healthy subjects.

The influence of HIV lysate and eight synthetic peptides which are fragments of HIV proteins on the functional activity of polymorphonuclear neutrophils (PMN) was tested in 12 healthy subjects. PMN activity in nitroblue tetrazolium reduction (NBT test) and PMN chemiluminescence (CL) was studied. Only one peptide was found to result in a significant increase in NBT test on the whole blood. This was the oligopeptide (G-97) from the CD4-binding site of HIV-1 gp120. The increase of CL response of PMN in the presence of G-97 was revealed after only 15 min preincubation. The same effect in the presence of sera from healthy or infected patients at the persistent generalized lymphadenopathy stage was achieved by increasing the time of preincubation to 30 min. G-97 did not influence the proliferative activity of lymphocytes.

Adult↗

PubMed1991

Influence of HIV antigens on functional activity of neutrophilic granulocytes in.

The effect of nine HIV antigens, including eight synthetic peptides, on the functional activity of granulocytes was studied using the reduction of nitroblue tetrazolium test (NBT test). Some peptides partly suppressed the functional activity of granulocytes. The most pronounced suppression was caused by ImVL (HIV-1 lysate immobilized on plates for ELISA) and SP-7 (a synthetic peptide from the gp41 protein of HIV-1). The degrees to which the functional activity of granulocytes was suppressed by ImVL and SP-7 was in inverse proportion to the specific antibody concentrations. No correlation was found between the reduction in the NBT test value and the amount of CD4+, CD8+ cells on CD4/8 ratio.

Adult↗

PubMed1991

[Synthesis and immunochemical properties of oligopeptides--fragments of capsid proteins of the hepatitis A virus].

The hepatitis A virus (HAV) capsid protein VP1, VP2 and VP3 are exposed at the virion surface and should therefore contain antigenic determinants. Algorithms for hydrophilicity, antigenicity and flexibility were used to predict probable antigenic sites. Synthesis of 7- to 23-membered overlapping peptides from seven sites, viz., 1-11, 1-17, 2-33, 11-25, 73-82, 76-86, 98-109, 98-112, 102-107, 102-108, 108-127, 113-123, 118-140, 276-298 from VP1, 42-62 from VP2, 76-85 from VP3, and 1-23 from VP4, was performed by various solid-phase methods. Free peptides and their conjugates with different carriers were used for immunization and study of antigenicity. The peptides did not interact with antibodies to the hepatitis A virus, whereas their conjugates did not induce the formation of anti-HAV-antibodies.

Amino Acid Sequence↗

PubMed1990

On searching for the active sites in proteins and peptide hormones.

An essential part of structure-functional studies of proteins is the search for sites responsible for specific functional activity. The information theory can be of much help in such a search. According to this theory, rarely occurring oligomers contain more information and thus are more likely to take part in forming the active site. We used frequencies of occurrences of amino acids (mean and for each polypeptide) to search for clusters of highly informative amino acids by the moving window smoothing method. In 16 out of 19 peptide hormones such sequences were active sites known from literature.

Amino Acids↗

PubMed1990

[Lymphotropic chemotherapy of patients with tuberculosis of the lymph nodes, skin and abdominal organs].

Experience gained as a result of indirect endolymphatic chemotherapy of patients with tuberculosis of the skin, peripheral and mesenteric lymph nodes is presented. The above treatment is tolerated well by the patients and causes no local or general complications. The clinical effect is achieved 1-3 months earlier than with a traditional therapy which provides a significant drop in the inpatient period and the drug load. Incidence of exacerbations also becomes less. It is worthwhile to include lymphotropic chemotherapy into a complex of therapeutic measures both at the beginning of the treatment and in a torpid course of the disease.

Adult↗

PubMed1989

[A method of searching for amphipathic structures in protein sequences].

A simple method for searching amphipathic helices based on estimation of correlation between hydrophobicity distribution and periodic function is proposed. The method was examined in a series of proteins with known T-cell epitopes, which are mostly amphipathic helices. The predictive power of the method is discussed.

Algorithms↗