Denaturation of Carp Actomyosin by Freezing in Phosphates Buffer

Abstract

The denaturation of actomyosin due to freezing in buffer phosphates was investigated by means of measurement of its solubility, ATPase activity, and viscosity, and was compared with the case in chlorides.
1) In both the buffer of K_2^- and Na₁ phosphates and the buffer of K_2^- and K₁ phosphates, actomyosin was not entirely denatured when it was frozen. It was only slightly denatured in Na_2^- and K₁ phosphates buffer, whereas it was denatured markeldy in Na_2^- and Na₁ phosphates, NaCl, and KCl. The particular denaturation in the buffer of Na_2^- and Na₁ salts was attributed to the acidification of the solution resulting from the eutectic crystallization of the Na₂ salt. 2) Actomyosin in KCl was more unstable when it was frozen in a solution of relatively high ionic strength, while that in K_2^- and Na₁ phosphates was quite stable, irrespective of ionic strength. 3) The stability of the protein to freezing in the mixture of phosphate and KCl was affected by the relative concentrations of both salts.