[Effect of Ca2+ ions on thermal denaturation of chromatin in an aqueous medium]

Thermal denaturation of chromatin has been investigated in the presence of Ca2+ ions by adiabatic scanning microcalorimetryc and thermomechanical methods. In contrast to EDTA treated chromatin with two melting bands (74 degrees C and 82,5 degrees C) on differential melting curve, the only denaturation peak (82 degrees C) was observed in the presence of a very low Ca2+ level (0,1 mM). Chromatin melting temperature has been shown to decrease with Ca2+ concentration and in the region of 65-67 degrees C a heatless transition due to chromatin repacking in a more compact form occurred.