Slow-scan-rate differential scanning calorimetry of enzymes can detect conformational changes which are under kinetic control and not observable at standard scan rates. This method detected a nondenaturational conformational change of bovine &agr;-chymotrypsin at 286 K. This temperature occurs between bovine physiological temperature of 312 K and x-ray crystallography temperature, typically 277 K. This suggests that there are two conformers of &agr;-chymotrypsin, a low temperature conformation and a physiological temperature conformation. The low-temperature to physiological-temperature conformational change has a high activation energy and thus is temperature dependent. The equilibrium thermodynamic changes suggest a reordering of the enzyme structure to give more favorable inter-residue interactions accompanied by an ordering of the structure but one in which there is no change in associated water molecules. The transition state thermodynamics suggest a very strained transition state but one where, again, no change in water interactions is detectable.
|Advisor:||Britt, Billy M.|
|Commitee:||Britt, Billy M., Omary, Manal, Sheardy, Richard|
|School:||Texas Woman's University|
|School Location:||United States -- Texas|
|Source:||MAI 52/04M(E), Masters Abstracts International|
|Keywords:||Differential scanning calorimetry, Nondenaturational conformational change|
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