New approach to the study of hormone-protein interaction using the microcalorimetric method

Binding enthalpies of various hormones to bovine serum albumin (BSA) and human serum albumin (HSA) in 50 mM phosphate buffer, pH 7.4, at 37 degrees C have been determined by direct microcalorimetry. The observed enthalpies of binding of progesterone, testosterone, dihydrotestosterone, corticosterone and estriol to BSA were found to be -13.24 plus or minus 0.11 -10.31 plus or minus 0.02, -2.37 plus or minus 0.46, -17.64 plus or minus 0.32 and -17.14 plus or minus 0.36 kcal/mol of hormone, respectively. under the same experimental conditions the enthalpies of binding of progesterone, testosterone, dihydrotestosterone, corticosterone and estriol to HSA were found to be -23.94 plus or minus 0.32, -18.88 plus or minus 0.49, -11.14 plus or minus 0.02, -9.88 plus or minus 0.14 and -20.85 plus or minus 0.39 kcal/mol of hormone, respectively.