B-factor of wild-type and mutant RNase A. Loops 1, 2, 3, and 4 correspond to those in Fig. 1 ▶. Atoms of the side-chain at 120 are omitted from the plots. (Inset) An enlargement of the C-terminal regions. Wild-type, F120A, F120G, and F120W RNase A are drawn with black, red, green, and blue, respectively.