UDC 525. 235;538.958 Denaturation of serum albumin under the influence of temperature and ionic detergent sodium dodecylsulfate (SDS) is investigated by laser correlation spectroscopy of scattered light. It is shown that thermal denaturation is stronger at pH values of the buffer solution of protein that are close to the isoelectric point of the given protein. Coupling of the micelles of SDS with albumin follows the principle of positive cooperativity. The concentration of protein saturation with the surfactant is determined, upon the attainment of which further protein denaturation was not observed. It is shown that the interaction of SDS with albumin is of an electrostatic nature.Introduction. The laser spectroscopy of scattered light is one of the most universal methods of studying the properties and structure of biological macromolecules. Correlation spectroscopy of a quasi-elastically scattered light (method of dynamic light scattering) now holds a firm place as a standard procedure of measuring the dimensions and shape of scattering particles [1], including proteins [2].In the present work, by the method of laser correlation spectroscopy we investigated the dependences of the dimensions and shape of the molecules of serum albumin of the human blood plasma on the concentration of the detergent sodium dodecylsulfate (SDS), which denatures proteins at different values of the pH of buffer solutions, and thermal denaturation of protein at different pH.The choice of the serum albumin of the human blood plasma as a model protein was conditioned by the important part it plays in the blood plasma. This protein, first, ensures osmotic blood pressure, on which the exchange by water and by the substance dissolved in it between the blood and the tissue liquid depends to a great extent; second, together with other proteins of the blood it regulates the pH of the blood due to the buffer properties, third, influences the viscosity of the blood, and, fourth, serves as a carrier of hormones, lipids, mineral substances, and medicinal preparations [3].Many biological and pharmaceutical systems contain proteins and surfactants (detergents). Moreover, in analytical biochemistry, electrophoresis in polyacrylamide gel with SDS is a frequently employed procedure used to estimate the molecular weight of proteins [4]. Proteins are treated by SDS (by an anionic detergent) in order that the protein mobility in the field could be determined only by its mass. Because of the electrostatic repulsion of the negatively charged residues of sulfuric acid, which are closely located on the protein globule and enter into the composition of the detergent micelles, the protein chain is straightened, and the protein is denatured in the presence of SDS. The denaturation changes that lead to the loss of biological (enzymatic) activity of protein molecules also occurs in the region of extreme values of temperature.As is known, the structure of the majority of proteins is stabilized by two classes of strong bonds (peptide and disulfide ones) and by t...

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