Polarized XAS on vectorially oriented single monolayers of cytochrome c

Polarized x-ray absorption measurements have been performed in fluorescence mode under total reflection conditions on a frozen hydrated monolayer of yeast cytochrome c (YCC). The protein molecules were oriented by tethering their naturally occurring and unique surface cysteine residues to the isolated sulfhydryl endgroups of an organic self-assembled monolayer, itself covalently attached to an ultra-pure silicon wafer. The experimental spectra will be compared with theoretically generated output from FEFF7 using both crystallographic data and results from molecular dynamics simulations as input parameters. Accurate structural information on the prosthetic groups of such fully-functional protein monolayers is important in understanding the role of the protein-membrane interaction in the structure-function relationship of membrane proteins.