PHYS 390 |
| In this report, the results of photoacoustic calorimetry (PAC) studies involving CO photodissociation from Horseradish Peroxidase (HRP) and Soybean Peroxidase (SBP) are discussed. HRP and SBP, contain a heme active site which can oxidize a large diversity of organic and inorganic compounds. The heme group of both HRP and SBP is 5 coordinate, high spin, where His 170 and His 169 are the HRP and SBP proximal ligands, respectively. It also has been demonstrated that HRP has a direct exit channel from the heme active site to the solvent. In addition, SBP can bind a Tris molecule in the distal pocket near the heme group that could potentially regulate ligand binding. Results of PAC indicate a monophasic relaxation for both HRP and SBP subsequent to CO photolysis in phosphate and Tris buffers and with varying concentrations of Tris. The molar volume/enthalpy changes associated with the monophasic decay are similar for both HRP and SBP: ~7mL/15kcal/mol. The results suggest that for both HRP and SBP, the volume change was due to the displacement of CO to the bulk solvent and the enthalpy change was due to the breaking Fe-CO bond. The results also suggest that the binding of a Tris molecule to SBP doesn't affect the energetics of diffusional CO exit from the SBP active site. |
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PHYS Poster Session - General Experiment
7:30 PM-10:00 PM, Wednesday, April 9, 2008 Morial Convention Center -- Hall A, Poster
Division of Physical Chemistry |