Graduation Year

2010

Document Type

Thesis

Degree

M.S.

Degree Granting Department

Chemistry

Major Professor

Randy W. Larsen, Ph.D.

Keywords

Myoglobin, Thermodynamics, Heme proteins, Calixarenes, Photoacoustic calorimetry

Abstract

Small ligand diffusion in heme proteins is not fully understood. To help better understand CO diffusion, three systems were investigated: L29H/F43H site-directed sperm whale myoglobin, horse heart myoglobin in a heavy water buffer, and calix[4]resorcinarene. Binding of copper to calix[4]resorcinarene was photophysically characterized to unravel transient binding of small molecules in heme-copper proteins. Copper binding was found to have a low dissociation constant of approximately 8.6 micrometers.. Reaction profiles using photoacoustic calorimetry were constructed for the myoglobin systems. In deuterium oxide, ligand escape is not rate limited by water entry. Large enthalpy differences arise from the thermodynamic properties of deuterium oxide and the extensive hydrogen bonding network in myoglobin. In the mutant, CO rebinds primarily to the heme and is exothermic with a large volume contraction because of altered electrostatics within the binding pocket and higher water occupancy.

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