[Determination of blood lipoprotein dimensions by optical methods].
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Humans↗
Biomedical subjects
G E Dobretsov
Publications and source records attributed to G E Dobretsov.
[Localization of the tryptophan residues of influenza virus matrix protein in reconstructed proteoliposomes: a fluorescent analysis].
Influenza virus matrix protein (M-protein) interaction with model phospholipid membranes, liposomes, was studied. Measuring of the effectiveness of energy transfer from M-protein triptophan residues to a fluorescent zond pyren included into the lipid phase of proteoliposomes was employed to assess the steric organization of the proteoliposome protein-lipid complex. A steric model is proposed in which M-protein molecules are located on the surface of lipid bilayer forming trimers. Analysis of pyren fluorescence proper demonstrated a strong influence of M-protein on the lipid bilayer structure: the viscosity of the lipid phase in the presence of M-protein was increased 2.3-fold.
Energy Transfer↗
[Effect of anthelmintic preparations on phospholipase A2 activity].
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Animals↗
[Changes in the structure of atherogenic lipoproteins in experimental atherosclerosis].
Lipoproteins were isolated, using preparative ultracentrifugation, from blood plasma of rabbits with alimentary hypercholesterolemia. Alterations in the lipoprotein structure were studied by means of light-dispersion, intrinsic fluorescence of the protein component in lipoproteins and by fluorescence of probes--I-aniline naphthalene-8-sulfonate and pyrene. The structural alterations consisted in an increase of size of the lipoproteins of very low density, elevated viscosity of the lipid phase of lipoproteins of low and very low density as well as in occurrence of additional positively charged groups on the surface of these particles. Potential importance of the impairments observed in structure of atherogenic lipoproteins from blood plasma in atherogenesis is discussed.
Animals↗
[Changes in the surface charge of lipoproteins isolated from the plasma of persons with hyperalphalipoproteinemia].
In patients with hyperalphalipoproteinemia amount of positively charged groups was increased on the surface of high density lipoproteins and decreased on the surface of low density lipoproteins as shown by fluorescent probe with 1-aniline naphthalene 8-sulphonate. The alteration of the lipoprotein charges observed in blood plasma of the patients appears to serve as a protective mechanism against the heart ischemic disease in hyperalphalipoproteinemia.
Adult↗
[Molecular bases of the fluorescence method in the determination of binding capacity of serum albumin].
A fluorescent method for assessment of albumin capacity to bind low-molecular metabolites, toxins, or drugs in blood serum, making use of fluorescent probe K-35, was recently suggested. The paper presents results of investigation of molecular basis of the method and of principles of interaction between fluorescent test molecules with albumin molecules in the blood serum. Molecules of fluorescent probe K-35 in blood serum plasma or serum are binding to albumin centers transporting low-molecular ligands (metabolites, toxins, drugs, etc.). Virtually the total intensity of K-35 fluorescence is due to the very molecules of the probe which are situated in these albumin centers. K-35 occupies two types of albumin centers, both of them equally contributing to total fluorescence intensity. Appearance of metabolites filling albumin centers and competing with K-35 probe results in reduction of the probe fluorescence. It is observed both in simulation experiments and in disease. It is possible that, besides the competitive mechanism, other mechanisms of blocking albumin centers in disease exist, to which K-35 is similarly sensitive. K-35 probe may be also used to measure effective albumin concentration.
Binding, Competitive↗
[Fluorescent method of determining mass concentration of human serum albumin].
Fluorescent method for measuring mass (total) albumin concentration in human blood serum is suggested. Fluorophore K-35 previously suggested for measuring the effective concentration of albumin is recommended. Total albumin concentration is measured in acid pH range in the presence of nonionic detergent. Conditions under which the effects of factors impeding albumin assay virtually do not manifest were found. The resultant values of total albumin concentration coincide with the values determined by the bromocresol purple method.
Bromcresol Purple↗
[Method for determining concentration of fluorescent probes binding to biological structures].
Fluorescent probes are used to study the structure and functions of proteins, biological membranes, lipoproteins, nucleic acids, nucleoproteins etc. The binding centers of these biological objects that interact with probes are usually rather heterogeneous. It is often impossible to describe the interaction of the probe with these centers in terms of simple Langmuir isotherms. Moreover, these centers can affect each other; as they are occupied with probe molecules, the properties of both free and probe-occupied centers change. The fluorescence quantum yield of the probe in different centers is not the same and can change due to their reciprocal influences. As a result, It is often impossible to determine even the number of probe molecules bound to these centers. In this paper we describe a method for determining the number of probe molecules bound to a biological object without regard to object heterogeneity and mutual influence of the centers. We abandoned the earlier accepted practice of calculating the number of bound molecules of the probe from the intensity of its fluorescence. Instead, the fluorescence of the probe is used only to compare solutions with different concentrations of probes and centers to achieve an equal occupancy of the centers with probe molecules. This makes it possible to measure the amount of the bound probe irrespective of the heterogeneity of the binding centers even in the presence of mutual influence of the centers.
Chemistry Techniques, Analytical↗
[Influence of the physical structure of phospholipid membranes on peroxidation induced by Fe2+ ions].
Kinetics of free radical lipid peroxidation, induced by Fe2+ in presence of ascorbic acid, was studied in phospholipid membranes. The maximal rate of peroxidative oxidation was observed at 2.5 muM concentration of Fe2+, in this case a half of the maximal amount of peroxidative oxidation products was formed within 20-30 min at 20 degrees and at 200 muM concentration of ascorbic acid. The rate of peroxidative oxidation depended on addition of substances modifying the membrane structure (linoleic acid, cetyl trimethylammonium, Tween-60, derivatives of phenothiazol). Charge of the membrane surface was shown to have a distinct effect on the peroxidative oxidation. Loosening of membranes by non-ion detergent (Tween-60) increased the rate of the process, whereas the increase of the membranes rigidity by cholesterol did not cause any effect. Uneffectiveness of cholesterol is discussed with relation to diffusion of radicals, participating in peroxidative oxidation, from depth of the membrane to its surface and in the opposite direction.
Ascorbic Acid↗
[Relation between fluorescence and circular dichroism of the complex of the fluorescence probe 4-dimethylaminochalcone with serum albumin].
The fluorescence probe(4-dimethylaminochalcone; DMH) was noncovalently linked to human serum albumin (HSA). The variation of pH was due to serum albumin structural changes, which was determined in terms of DMH and HSA fluorescence and CD spectra. Considerable changes of fluorescence and CD spectra were observed at pH 8 and 10, where there is ionization of two more recently titrated tyrosin residues. It is assumed that these two tyrosine residues are in binding region and quench the fluorescence of DMH between pH 4 to 8. Quenching disappears if these residues are ionized (pH greater than 8) or if the protein undergoes the N -F transition (pH less than 4).
Chalcone↗
[Distribution of small hydrophobic molecules in membranes. II. Heterogeneity of binding centers on a phospholipid bilayer surface].
4-dimethylaminochalcone (DMC), a hydrophobic uncharged fluorescent probe, was bound to a phospholipid bilayer surface and was distributed in different binding sites. Sites whose polar groups of phospholipid and hydration shell molecules were the least mobile had the greatest affinity to DMC. The increase DMC/phospholipid ratio resulted in DMC molecules getting bound to sites of a lesser affinity whose polar groups were more mobile. Cholesterol presence caused DMC binding to the first type of sites only.
Binding Sites↗