| Abstract: | To study the contribution of disulfide bonds to protein stablity, a derivative of ribonuclease T1 (RNase T1) with both cystine residues reduced and methylated has been prepared using an improved procedure adapted from that of Heinrikson [Heinrikson, R.L. (1971) J. Biol. Chern. 246, 4090]. Characterization using urea and thermal denaturation show that the reduced, methylated ribonuclease T1 is about 8 kcal/mol less stable than RNase T1, but is .5 and 1 kcal/mol more stable than reduced carboxyamidomethylated and reduced carboxymethylated RNase T1, respectively. It is suggested that this difference in stability arises from the increase in conformational entropy of the unfolded state and the size and hydrophobicity of the blocking group. |
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