Vibrational Dephasing of Carbonmonoxy Myoglobin

Abstract

The autocorrelation function of vibrational frequency fluctuations of the CO ligand in carbonmonoxy myoglobin, Cδδ(t), is computed from molecular dynamics simulations. Electrostatic interactions are assumed to dominate the modulation of the CO vibrational frequency. The simulated Cδδ(t) is consistent with linear and nonlinear infrared spectroscopic measurements. The short-time decay of Cδδ is dominated by dynamics of the distal histidine, and of a water molecule that can occupy the heme pocket. Correlated protein and solvent dynamics induce spectral diffusion of the CO frequency on longer time scales.