CALIBRATION OF RING-CURRENT MODELS FOR THE HEME RING

Abstract

Three ring-current models for the heme ring system have been calibrated using data from cytochrome c, cytochrome c551, cytochrome b5, and pyridine and picoline complexes of zinc porphyrin. Excellent agreement between observed and calculated shifts was obtained, even for protons in close proximity to the heme ring. Best agreement was obtained with the eight-loop Johnson-Bovey and five-loop Haigh-Mallion models. Data was fitted less well when a Johnson-Bovey five-loop model was used. The new calibrations provide a basis for conformational studies of diamagnetic heme proteins. © 1985.