The kinetics of protein response and of CO recombination after photolysis of the Fe-CO bond in carbonmonoxymyoglobin have been monitored via time-resolved step-scan FT-IR absorption difference spectroscopy in D<sub>2</sub>O solution. Although the initial photodissociation is too fast to observe with currently available FT-IR instrumentation, we have been able to correlate the CO recombination kinetics with protein secondary structural changes via changes in the amide I band of the polypeptide chain with microsecond time resolution. The spectral and kinetic data corroborate and confirm previously published single-frequency infrared studies. This is the first application of time-resolved step-scan FT-IR spectroscopy in the absorbance difference mode to study the photodynamics of an aqueous protein solution at room temperature. This work also demonstrates the potential of the technique for the sub-microsecond kinetic analysis of other biological molecules of interest.
Susan E. Plunkett, James L. Chao, Thomas J. Tague, and Richard A. Palmer, "Time-Resolved Step-Scan FT-IR Spectroscopy of the Photodynamics of Carbonmonoxymyoglobin," Appl. Spectrosc. 49, 702-708 (1995)