PARAMAGNETIC INVERSION OF THE SIGN OF THE INTERFERENCE CONTRIBUTION TO THE TRANSVERSE RELAXATION OF THE IMIDO PROTONS OF THE COORDINATED IMIDAZOLES IN THE UNIFORMLY N-15-LABELED CYTOCHROME C(3)

In the spectrum of uniformly N-15-labeled cytochrome c(3), the relativ e linewidths of the doublet peaks of the N-15-coupled imido proton of the coordinated imidazole group were reversed on oxidation. This inver sion was explained by the interference relaxation process between the electron-proton dipolar and N-15-H-1 dipolar interactions. The inversi on can be used to assign the imido protons of the coordinated imidazol e groups in heme proteins. (C) 1998 Academic Press.