Time-resolved absorption and fluorescence spectroscopy are used to study the dynamics of protein structural changes subsequent to rapid mixing or excitation with short laser pulses. Molecular models for the protein dynamics are used to fit and interpret the measured data. A. We have succeeded in implementing two new techniques which can be used to study the kinetics of a wide variety of processes, a rapid mixing technique which, in principle, is capable of initiating reactions within 10 microseconds and a laser temperature jump experiment in which water is heated by an infrared laser pulse. B. The dynamics of short-lived states on the folding pathway of cytochrome c have been investigated using continuous-flow mixing and fluorescence quenching to monitor the tryptophan-heme distance. The most rapid phase observed occurs at about 100 microseconds, followed by a decay in fluorescence intensity which includes at least 4 additional exponential relaxations.
