Measurement of the resonantly enhanced quasielastic light scattering cross sections of heme proteins

Abstract

We have measured the absolute cross sections for resonantly enhanced quasielastic light scattering in the heme proteins: cytochrome-c and metmyoglobin. Measurements of the scattered intensity were made as a function of protein concentration using the Brillouin scattering of the solvent as an internal standard. Our choice of scattering standard permits the measurement of absolute cross sections without employing correction factors for the reabsorption of scattered light. Incident laser excitation was on the red edge of the ‘‘Soret’’ absorption band of these proteins (21 839–23 529 cm−1). Scattering cross sections are nearly a factor of 3 larger than predicted with the Kramers–Kronig transform for both cytochrome-c and metmyoglobin.