Abstract
We have investigated low temperature-induced structural reversibility of ribonuclease A (RNase A) in aqueous choline dihydrogen phoshpahte ([Chol][dhp]) solutions (X(mol%D_2O)=100〜70) by the uses of FTIR and Raman spectroscopies. From the IR spectral analyses, we found that the structural stability of RNase A remains unchanged in the concentration of [Chol][dhp] region from X=97 to 85. Moreover the secondary and tertiary structures of RNase A showed good reversibility upon cooling (77 K) in the same concentration region. On the other hand, Raman OD stretching spectra showed that the aqueous [Chol][dhp]-RNase A solutions take into the glassy state at 77 K in the region from X=90 to 70. On the basis of these results, in the concentration region from X=90 to 85, the aqueous [Chol][dhp]-RNase A solutions have a possibility of good cryoprospectant for aqueous protein solutions.
