Open AccessDynamics of the Spin Transition in Camphor‐Bound Ferric Cytochrome P‐450 versus Temperature, Pressure and Viscosity
Author(s) -
MARDEN Michael C.,
Hui bon hoa Gaston
Publication year - 1982
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1982.tb07028.x
Subject(s) - chemistry , ferric , solvent , viscosity , thermodynamics , activation energy , volume (thermodynamics) , kinetics , spin (aerodynamics) , spin transition , analytical chemistry (journal) , crystallography , inorganic chemistry , chromatography , organic chemistry , physics , quantum mechanics
The kinetics and equilibrium of the low‐spin (LS) to high‐spin (HS) transition in camphor‐bound ferric cytochrome P‐450 have been measured versus temperature, pressure and visocsity at selected pH and KCl concentration. The results cannot be described by a single set of Δ E °, Δ V ° and Δ S , since these parameters change with the solvent conditions. A three‐state model can explain a large bulk of the data but it is clear that other substates are involved. The activation energy and volume are practically zero for the high to low spin transition, while the low to high spin transition parameters vary from 20 kJ/mol to 80 kJ/mol for Δ E Ψ and from 5 cm 3 /mol to 80 cm 3 mol for Δ V Ψ. The observed relaxation time could be varied from about 10 ms to more than 1000 s by changing temperature, pressure and viscosity. Both K LH and K HL rate coefficients scale roughly as l/η, indicating that the slow spin change involves protein motions which are influenced by the solvent viscous forces.