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ELSEVIER Chemical Physics 212 (1996) 207-219 A temperature-dependent effective potential explains CO binding
 

Summary: Chemical
Physics
ELSEVIER Chemical Physics 212 (1996) 207-219
A temperature-dependent effective potential explains CO binding
to myoglobin
Noam Agmon, G. Madhavi Sastry
Department of Physical Chemistry and the Fritz Haber Research Center, The Hebrew University; Jerusalem 91904, Israel
Received 9 February 1996
Abstract
Up to the onset of ligand escape from the heme pocket, CO binding to myoglobin can be explained by stochastic motion
of the protein subject to an effective, temperature-dependent potential. Two "temperature-models" for the effective potential
are investigated. The quantitative solution of the transient Smoluchowski equation for these models shows inhomogeneous
kinetics at short times and protein relaxation at intermediate times. Additional two phases of ligand binding, ligand escape
and bimolecular recombination, can be identified. Both models agree that the protein "diffusion coefficient" increases in an
Arrhenius fashion through the solvent glass transition, indicating that protein relaxation occurs mainly in the interior of the
protein. In contrast, the effective potential "collapses" above the glass transition temperature, indicating that it is determined
also by interactions at the surface of the protein. In one of the models the parameters of the potential vary linearly with
temperature, resembling the situation for rubber elasticity.
1. Introduction
Heine proteins play a central role in oxygen trans-

  

Source: Agmon, Noam - Institute of Chemistry, Hebrew University of Jerusalem

 

Collections: Chemistry