Thermal Denaturation Properties of Deoxyribonucleic Acid and Chromatin during the Life Cycle of Spirogyra

Abstract

Half melting temperature (Tm) of DNA prepared from the nuclear fraction of vegetatively growing cells of Spirogyra was 86°C in the standard saline‐citrate solution and 68°C in the dilute saline‐citrate solution, and the major Tm values of soluble chromatin were 68°C and 78–80°C in the dilute saline‐citrate solution. The Tm value of DNA prepared from the nuclear fractions of conjugating and zygote cells was 88°C in the standard saline‐citrate solution and 70°C in the dilute saline‐citrate solution, and the major Tm values of soluble chromatin were 72°C, 78–80°C, and 84°C in the dilute saline‐citrate solution. The Tm values of DNA prepared from cells arrested at different stages of the life cycle of Spirogyra were raised by combining with different fractions of histones. The results agreed with an altered structure of the nucleoprotein complex during the life cycle of Spirogyra.