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Biomedical subjects

V I Gorbach

Publications and source records attributed to V I Gorbach.

17 recordsLinked to original sources
PubMed2006

Determination of binding constants of lipopolysaccharides of different structure with chitosan.

The interaction of endotoxins--lipopolysaccharides (LPS) different in degree of the O-specific chain polymerization--with 20- and 130-kD chitosan was studied using the competitive binding of LPS with the complex of chitosan-anionic dye (tropaeolin 000-2) and the direct binding of (125)I-labeled LPS with chitosan immobilized on Sepharose 4B. The interaction of 20-kD chitosan with LPS was non-cooperative, and immobilization of the polycation on Sepharose resulted in its binding to (125)I-labeled LPS with a positive cooperativity. The interaction of LPS possessing a long O-specific chain with 130-kD chitosan was characterized by negative cooperativity. Binding constants of LPS with the polycation and the number of binding sites per amino group of chitosan were determined. The interaction affinity and stoichiometry of the LPS-chitosan complexes significantly depend on the LPS structure and concentration in the reaction mixture. The increase in the length of carbohydrate chains of LPS results in increase in the binding constants and decrease in the bound endotoxin amount.

Azo Compounds↗
PubMed2003

Applications of electron-ion dissociation reactions for analysis of polycationic chitooligosaccharides in Fourier transform mass spectrometry.

Singly protonated, doubly protonated, and sodiated pentaglucosamide (GlcNAc)(5), oligoglucosamines (GlcN)(m)(), and (GlcN)(3)GlcN(3OH14:0) were analyzed in an FTICR mass spectrometer by electron-ion dissociation reactions and compared to collision activation. The general fragmentation mode was found as the asymmetrical sequence fragments (B(n)() and minor C(n)() ion series) with full sequence coverage. Molecular mass information of each glucosamide or glucosamine residue can be readily obtained from the ion series. Fragmentation by electron capture dissociation revealed additional fragmentation of the N-acetyl moiety compared to sustained off-resonance irradiation collision-activated dissociation (SORI-CAD) and electron-induced dissociation (EID). Sodiated GlcNAc(5) molecular adduct ions were analyzed by EID and compared to CAD. Both techniques provided full sequence coverage. EID was more effective, but CAD resulted in the cross-ring ion products (0,2)A(n)() and (2,4)A(n)() for all relevant glucosamide residues.

Journal Article↗
PubMed2001

Effect of ionic carbohydrate-containing biopolymers on complement activation.

We studied in vitro effects of charged polysaccharides on the classic and alternative pathways of complement activation. The complement system was affected by substances having different charges. Our findings suggest that the conformation of polysaccharide molecules, but not their charge, plays a primary role in the interaction with C1 and C3 complement components followed by initiation of cascade enzymatic reactions.

Biopolymers↗
PubMed2000

Interaction of bacterial endotoxins with chitosan. Effect of endotoxin structure, chitosan molecular mass, and ionic strength of the solution on the formation of the complex.

The interaction of endotoxins of different structure (lipopolysaccharides (LPS) and lipopolysaccharide-protein complexes (LPPC)) with chitosan has been studied. It was shown that the mechanism of interaction is rather complicated and depends on the macromolecular organization of endotoxin as well as on the degree of polymerization of the chitosan. Chitosan with molecular mass of 20 kD reveals higher affinity to LPS than chitosan with molecular mass of 140 kD. Endotoxins with long O-specific chains can bind completely with chitosan with the formation of LPS-chitosan and LPPC-chitosan complexes with weight ratios between the original components of 1:1 and 1:5. When endotoxins with higher degree of hydrophobicity and short O-specific chains were mixed with chitosan, a part of the LPS remained unbound. The stability of the complexes formed depends on ionic strength. It was shown that, in addition to electrostatic forces, other types of forces take part in the formation of the complexes. A decrease in acute toxicity of various LPSs is observed on their binding with chitosans.

Animals↗
PubMed1999

The effect of temperature on the interaction of Yersinia pseudotuberculosis lipopolysaccharide with chitosan.

The mechanism of binding of lipopolysaccharide (LPS) from Yersinia pseudotuberculosis to low-molecular-weight chitosan was investigated using sedimentation analysis, centrifugation in glycerol and percoll density gradients, and isopicnic centrifugation in cesium chloride. The LPS interaction with chitosan was shown to be a multistage process that depended on time and reaction temperature. A stable LPS-chitosan complex could be formed only after preliminary incubation of the initial components at an elevated temperature (37 degrees C). This temperature caused the LPS dissociation and promoted its binding to chitosan. The LPS binding to chitosan results in further dissociation of the endotoxin and formation of the complex with a molecular weight that is tens of times less than the initial molecular weight of LPS. The obtained complex remained stable in solutions of high ionic strength.

Anti-Bacterial Agents↗
PubMed1994

New glycolipids (chitooligosaccharide derivatives) possessing immunostimulating and antitumor activities.

New glycolipids, derived from chitooligosaccharides of dp 2-4 and containing both free and acylated amino groups, were synthesized. The structure of the key compounds (di-, tri-, and tetra-saccharides acylated with different fatty acids) were elucidated by 13C NMR spectroscopy. Only the amino group of the reducing end of the chitooligosaccharides was found to be acylated when equimolecular amounts of reagents were used. The compounds obtained were shown to possess a low toxicity and certain immunostimulatory and antitumor activities. An induction of interleukin-1 and tumor necrosis factor by the immunocompetent cells and an augmentation by 140-180% of the mean life of mice with the Erlich carcinoma were observed.

Adjuvants, Immunologic↗
PubMed1993

[Interaction of the outer membrane pore-forming protein of Yersinia pseudotuberculosis with lipid A and its synthetic analogs].

Interaction of the major outer membrane protein form Yersinia pseudotuberculosis with lipid A was investigated by intrinsic fluorescence, CD spectroscopy and CsCl gradient centrifugation methods. The protein was shown to have two independent binding sites with an association constant 6.1 x 10(4) M-1. The interaction depends on both the type of the glycoside bond and hydrophilic--hydrophobic balance of the glycolipid molecule.

Bacterial Outer Membrane Proteins↗
PubMed1988

[Synthesis of lipid A analogs: achievements and perspective].

Data on the synthesis of analogues of lipid A, a biologically active fragment of gram-negative bacteria's lipopolysaccharides, are summarized. Main types of the compounds obtained are systematized, and problems of the synthesis of various parts of the molecule considered. The results of studying biological activity of lipid A analogues are discussed, which led to some conclusions on the structure-function relation. Perspectives of further studies are briefly outlived.

Chemical Phenomena↗
PubMed1987

[Synthesis of lipid A analogs. Preparation of serologically active glycolipids on the basis of beta-1,4-glucosaminobiose (chitobiose)].

Synthesis of beta-1,4-glucosaminobiose (chitobiose) 4'-phosphates N,N'-diacylated with (R)-3-hydroxymyristic acid is described, the structure being corroborated by 13C-NMR spectra. It was shown that activity of the components in various reactions with antibodies to lipid A from Yersinia pseudotuberculosis is similar to the lipid A activity.

Chemical Phenomena↗
PubMed1985

[Synthesis of lipid A analogs. Obtaining conjugates of 6-phosphate 2-desoxy-2-(3-hydroxymyristoyl)amino-D-glucose with polymer carriers and their immunological properties].

The derivatives of 2-acylamino-6-O-(2-aminoethyl) phosphono-3-deoxy-D-glucose acylated with acetic or D,L-3-hydroxytetradecanoic acid were obtained, and their 31P-and 13C-NMR spectra investigated. These haptens were bound with a polysaccharide (Ficoll) or proteins (albumins, bovine gamma-globulin). The protein conjugates were immunogenic in rabbits, specific antibodies against the hapten being revealed by two immunochemical methods. As shown by the enzyme-linked immunoadsorbent assay, the specific rabbit antiserum reacted with lipid A from Yersinia pseudotuberculosis.

Animals↗
PubMed1982

The application of 13C-NMR spectroscopy to study lipid A from Yersinia pseudotuberculosis lipopolysaccharide.

The use of 13C-NMR spectroscopy in the establishment of lipid A backbone structure from lipopolysaccharide of Yersinia pseudotuberculosis has been described. The 13C-NMR spectra of degraded lipid A and its N-acetate were obtained. The assignment of signals was made by comparison with the chemical shifts for 13C-NMR spectra of glucosaminitol, N-acetyl-glucosaminitol and their beta-1,4 and beta-1,6 disaccharides. It was shown that lipid A backbone of the lipopolysaccharide in question consists of beta-1,6-linked glucosamine disaccharide.

Lipid A↗
PubMed1979

Structural studies on the immunodominant group of lipid A from lipopolysaccharide of Yersinia pseudotuberculosis.

Lipid A isolated from lipopolysaccharide of Yersinia pseudotuberculosis was used for immunization of rabbits to afford antisera to lipid A with titers of 1:640 in the passive hemolysis test. Exhaustion of immune serume with sheep erythrocytes decreased antibody titers up to 1:160. Authentic samples of 2-(DL-3-hydroxytetradecanoyl)amino-2-deoxy-D-glucose 6-phosphate, 2-tetradecanoylamino-2-deoxy-D-glucose 6-phosphate and 2-acetamido-2-deoxy-D-glucose 6-phosphate have been synthesized in order to carry out a comparative study of inhibitory activity of these compounds and lipid A using a system of lipid A and antiserum to lipid A. As a result, the immunodominant moiety of the lipid A of Y. pseudotuberculosis proved to contain a D-glucosamine residue acylated with 3-hydroxytetradecanoic acid at the amino group. The nature of the fatty acid acylating the amino group of glucosamine does not play an important role in the structure of immunodominant moiety of lipid A.

Animals↗
PubMed1978

Studies on lipid A from Yersinia pseudotuberculosis lipopolysaccharide. Isolation and general characterization.

Lipid A was isolated from lipopolysaccharide of Yersinia pseudotuberculosis S form (strain 341, subtype IB) using mild hydrolysis with acetic acid. The purified material (yield about 25%, molecular weight about 2900) contained D-glucosamine (11%), fatty acids (54%), protein concomitant (9.7%) and phosphorus (approximately 2%). Dodecanoic and 3-hydroxy-tetradecanoic acids in a molar ratio of 1 : 3.6 were detected as major fatty acid constituents. The hydroxyl groups of D-glucosamine were acylated with the residues of both fatty acids, while the amino groups were substituted with the residue of 3-hydroxy-tetradecanoic acid. Such a simple fatty acid composition is reminiscent of that found in lipid A in Y. pestis.

Chromatography, Gas↗
PubMedDate not supplied

[Comparative study of the physico-chemical properties of chitosans with varying degree of polymerization in neutral aqueous solutions].

The physicochemical properties of chitosan samples with high (130 kD) and low (30 kD) molecular masses in neutral aqueous solutions (pH 6.0) were studied by the methods of high-speed and equilibrium sedimentation, viscosimetry, and NMR and UV spectroscopies. Differences in the hydrodynamic characteristics of the samples were revealed. It was found that low-molecular-weight chitosan represents flexible linear macromolecules which undergo conformational changes upon temperature increase. The high-molecular-weight chitosan forms more rigid asymmetric structures whose conformation does not vary significantly with temperature increase. It was found that the high-molecular-weight chitosan has a higher constant of binding to the anionic dye tropeoline 000-II, which can be explained by different conformations of their macromolecules in solution.

Chitin↗