Vibronic effects in spectroscopy of heme proteins

摘要

It is obtained that, in deoxyheme proteins, the pseudo Jahn-Teller effect leads to the weak anharmonic coupling between the displacement of the iron out of the heme plane and the iron - histidine vibration. This anharmonic coupling and the effect of the glass - liquid phase transition cause a notable temperature dependence of the iron-histidine resonance Raman band. It is shown that the strong temperature and pressure dependence of the optical absorption band III stem from the anharmonic coupling, strong dependence of the band's dipole transition moment on the iron - porphyrin distance, and glass - liquid phase transition. It follows from the theoretical study of this temperature dependence that the band III position (and not only width) must be very sensitive to the protein structure and dynamics. Consequently, this band can be used as a probe of the protein dynamics in different conditions.