On the thermodynamics and kinetics of the spin transition in aquomethemoglobin

Abstract

Summary The temperature-induced transition in aquo-methemoglobin, which is attributed to the spin transition on the basis of the kinetic difference spectrums is investigated from −20 to +20°C by temperature-jump experiments. Reaction and activation enthalpies of the transition are determined. The equilibrium is almost fully on one side, suggesting that two kinds of spin-equilibria exist in this temperature range. The presence of inorganic ions (Cl − ) should be avoided since these ions exhibit additional effects.