Intramolecular Reorientational Motion in Trypsinogen Studied by Perturbed Angular Correlation ofHg199mLabels

Time-differential perturbed angular correlation measurements of the nuclear quadrupole interaction of ${}_{}{}^{199m}{}_{}{}^{}\mathrm{Hg}$ labels introduced into the disulfide bridge of the activation domain of bovine trypsinogen reveal intramolecular reorientational motion over a wide angular range with a correlation time ${\tau }_c={11}_{-3\mathrm{}}^{+6\mathrm{}}$ nsec. No dynamics in this time range was observed in the trypsinlike complex formed with pancreatic trypsin inhibitor, where the activation domain is rigid.