The rate of interconversion between the two unfolded forms of ribonuclease A does not depend on guanidinium chloride concentration.

The interconversion between the fast-folding and slow-folding forms of ribonuclease A is unaffected by the protein denaturant guanidinium chloride, between 2.8 m and 7.0 m, at 10 °C. Thus the rate of this reaction is insensitive to denaturants, in contrast to the model proposed by Kanehisa &; Tsong (1979). This result is consistent with other evidence that the interconversion reaction is proline isomerization.