¹H NMR Studies of 1-Ethylimidazole Binding to Cytochrome C

Abstract

Kinetic and equilibrium data for 1-EtIm binding to cyt c at temperature range of 303–319K have been determined at pH 7.0 by using ¹HNMR method. Thermodynamic values (ΔH°=39.5 kJ mol⁻¹, ΔS° = 154 J mol⁻¹K⁻¹ and Ea = 142 kJ mol⁻¹) are obtained from Van't Hoff and Arrhenius's relations. Some hyperfine shifted resonances of l-EtIm cyt c have been assigned for the first time using 1D saturation transfer experiments. The origin of the asymmetric spin density distribution in heme groups of 1-EtIm cyt c and the reason of low affinity of cytochrome c for 1-EtIm are also discussed move toward upfield from original position. However, Te-2, 4 substituents in cyt c are more electron withdrawing than the propionic acid side chains, which lead to the 5-methyl group going toward downfield.

Key Words:

• Cytochrome c
• 1-Ethylimidazole
• Thermodynamic parameter
• Assignment and ¹H NMR