Application of femtosecond coherence spectroscopy to the observation of nuclear motions in heme proteins and transparent solutions

Abstract

The technique of femtosecond coherence spectroscopy (FCS) was applied to simple transparent organic fluids (chloroform and fenchone) and light-absorbing heme proteins (myoglobin derivatives). This study demonstrates that time-domain coherence measurements are in good agreement with standard frequency-domain Raman and resonance Raman scattering experiments. The unique capability of FCS to detect the low-wavenumber nuclear motions driven by the pumping fields and by the electronic state changes associated with photoinduced chemical reactions is also demonstrated. The latter response cannot be probed using traditional Raman spectroscopy. In all studies of myoglobin derivatives a low-wavenumber mode was observed near 40 cm−1. A sequence of low-wavenumber modes was also observed near 80, 120 and 160 cm−1 that could be an indication of an overtone sequence. Copyright © 2000 John Wiley & Sons, Ltd.