We propose to continue our XPS studies of the core-level spectra of porphyrins in the gas phase and to extend our studies of porphyrin valence levels. In particular, we wish to examine valence levels using Zr M radiation in order to change atomic cross sections because this allows a better analysis of the valence level electronic structure. In conjunction with our valence level studies, we propose to perform CNDO calculations of the valence electronic structures of metalloporphyrins and to examine the core binding energies using CNDO calculations and including electronic rearrangement. Finally, we propose to study various heme proteins immobilized on suitable substrates and of various species prepared by binding porphyrins to specially-treated glass surfaces.