Spectral Broadening in Biomolecules

Abstract

We have studied the optical line shapes of deoxy myoglobin (Mb) and its ligand-bound form (MbCO). Simulations of the observed line shapes using "transform" and time-correlator techniques show the presence of strong coupling to low-frequency modes in MbCO and substantial non-Gaussian inhomogeneous broadening in Mb. The iron-porphyrin disorder parameter in Mb is found to be $\sigma =0.25\mathrm{}$ Å, and the quadratic dependence of the $\pi -{\pi }^{*}$ electronic excitation energy on the iron coordinates is also determined.