Conformational changes in heat-denatured nucleoprotein complex of human lymphocytes during subsequent cooling

Abstract

To study the kinetics of conformational changes in the nucleoprotein complex (NPC) of human peripheral blood lymphocytes a microfluorometric method of analysis was used, whereby the state of the chromatin could be assessed quantitatively from binding of the dye acridine orange. Extraction of the F₁-fraction of histones with 0.01N HCl, pH 2.0, essentially modified (delayed) conformational changes in NPC. Extraction of F₁−, F₂−, and F₃-fractions of histones with 0.25N HCl, pH 0.6, led to more marked delay of the kinetics of the conformational changes. The kinetics of conformational changes of NPC also was delayed when the process was carried out in a more viscous medium (in 70% glycerol solution). In this case the NPC has low values of intensity of fluorescence at 530 nm (F₅₃₀) and of the ratio I₆₄₀/I₅₃₀; this evidently points to irreversibility of denaturation of NPC.