Myoglobin ligand binding

That the environment could play a major role in determining ligand binding to iron in heme models and, probably, in myoglobin also, is in agreement with the conclusions of site-directed... 

Ostermann, A., Waschipky, R., Parak, R G., Nienhaus, G. U. 2000. Ligand binding and conformational motions in myoglobin. Nature 404 205-8. 

Effects of solvent mixtures can be seen in biochemical systems. Ligand binding to myoglobin in aqueous solution involves two kinetic components, one extramolecular and one intramolecular, which have been interpreted in terms of two sequential kinetic barriers. In mixed solvents and subzero temperatures, the outer barrier increases and the inner barrier splits into several components, giving rise to fast intramolecular recombination. Measurements of the corresponding solvent structural relaxation rates by frequency resolved calorimetry allows the discrimination between solvent composition and viscosity-related effects. The inner barrier and its coupling to structural relaxation appear to be independent of viscosity but change with solvent composition (Kleinert et al., 1998). 

As is the case with myoglobin, ligands other than oxygen can bind to hemoglobin. An important example is carbon monoxide, which binds to hemoglobin about 250 times better than does oxygen. Human exposure to CO can have tragic consequences (Box 5-1). 

Olson, J.S. Phillips, G.N., Jr. (1996) Kinetic pathways and barriers for ligand binding to myoglobin. J. Biol. Chem. 271,... 

Austin RH, Beeson KW, Eisenstein L, Frauenfelder H, Gunsalus IC. Dynamics of ligand binding to myoglobin. Biochemistry 1975 14 5355-5373. 

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