H-1-NMR STUDIES OF 1-METHYLIMIDAZOLE COMPLEX OF CYTOCHROME-C

Some hyperfine shifted H-1 resonances of 1-methylimidazole complex of horse ferricytochrome c (1-Melm.cyt c) have been assigned for the first time using 1D saturation transfer and 2D EXSY exchange correlated spectroscopy) experiments. Kinetic and equilibrium data for 1-Melm binding to cyt c at a temperature range of 303-319 K have been determined at pH 7.0 by using the NMR method. The observed thermodynamic parameters for 1-Melm binding are Delta H degrees = 39.5 kJ.mol(-1), Delta S degrees = 154 J.mol(-1) K-1, and Ea = 142 kJ.mol(-1). The source of the asymmetric spin density distribution in heme groups of 1-Melm.cyt c and the reason of low affinity of cytochrome c for 1-Melm are also discussed.