Effects of low concentrations of synthetic antioxidant phenosan potassium salt on the thermoinduced structural transitions in the protein component of plasma membranes.

Abstract

An important problem of modern science is to elu� cidate the mechanisms of the effect of ultraweak chemical and physical effects on biological systems of different complexity. We have previously found that a number of biologically active substances (BASs), including antioxidants of natural and synthetic origin used in ultralow concentrations ( <10 -11 M) able to sig� nificantly modify the structure of the lipid compo� nents of biological membranes in experiments in vitro (1-3). Dose dependences of biological effects have a nonlinear multimodal pattern with several peaks sepa� rated by intervals of concentrations when the effect is drastically reduced or absent, the socalled "dead zones." A characteristic feature of the activity of these agents on the biological membranes and liposomes prepared from the total lipid extracts of biomembranes is not only the effect on the microviscosity of deep� surface layers of lipids and their rigidity but also the changes in the position, width, and number of ther� mally induced structural transitions in these lipid regions (1-3). In particular, the synthetic antioxidant potassium salt of β�(4 �hydroxy�3,5�ditertbutylphe� nyl)propionate (phenosan potassium, PP) in ultralow doses (10 -14 M, 10 -18 M) at a temperature of 293 K increases the microviscosity and degree of ordering of phospholipids and lead to the appearance of an addi� tional thermally induced structural transition in the range of physiological temperatures 307-315 K (34- 42°С) (3). The phase state of membrane lipids affects the activity of membranebound enzymes, because it affects their conformation, mobility, degree of hydra� tion, etc. (4). The structural state of globular proteins, in turn, is directly associated with the thermodynamic characteristics of melting and denaturation of these molecules (4, 5). Therefore, to establish how PP at dif� ferent concentrations affects the protein fraction of the plasma membrane (PM), it is necessary to perform experiments on studying the changes in their thermo� dynamic characteristics under the influence of PP, which was the aim of this work.