Effect of conformation on spin-lattice relaxation in azide methemoglobin

Abstract

Spin-lattice relaxation of Fe 3+ has been measured as a function of temperature in azide methemoglobin in natural and heat denaturated condition. Of the two spin states present ( S= 1 2 , and S= 5 2 ) the high spin state always follows on Orbach mechanism of relaxation with a characteristic energy dependent on the protein conformation. In the absence of thermal equilibrium of the two spin states, the S= 1 2 state follows a Raman relaxation process whose exponent, n, is related to the conformation of the protein.