A Photoacoustic Calorimetric Study of the Protein Dynamics of Myoglobin

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Dr. Peters proposed to study how protein structure controls the dynamics of the enthalpy and volume changes associated with the dissociation of carbon monoxide from myoglobin. The method of analysis is time-resolved photoacoustic calorimetry. Time-resolved photoacoustic calorimetry measures the dynamics of the enthalpy and volume changes for reactions that are initiated by light. The resolution of the experiment is such that for reactions which occur in less than 100 nanoseconds, the sum of the enthalpy and volume changes are measured. For reactions occurring between 100 nanoseconds and 20 microseconds the dynamics of enthalpy and volume changes can be obtained. For the past three years Dr. Peters has been examining the dynamics of enthalpy and volume changes associated with the photodissociation of carbon monoxide from sperm-whale, horse and human myoglobins. He has found evidence for a new intermediate in sperm-whale myoglobin that is formed upon the dissociation of carbon monoxide which involves the breaking of a salt bridge and re- organization of the protein structure. Following these initial observations Dr. Peters would like to investigate the nature of this protein structural change. He will examine mutants of sperm-whale and human myoglobin, engineered by site directed mutagenesis, to determine the origin of the barrier to the formation of this intermediate. Also, using combinations of buffers he will examine pH titration curves for the energetics and dynamics of the myoglobins in order to ascertain if structural changes are occurring within the protein that may effect the acidity of some amino acids.