title: Thermodynamics of the binding of calcium and strontium to bovine alpha-lactalbumin.
abstract: Microcalorimetry and equilibrium gel filtration were used to determine the thermodynamic functions delta H degrees, delta G degrees and delta S degrees guiding the interaction of Ca2+ and Sr2+ with bovine alpha-lactalbumin. Two methods of nearly complete metal removal from the protein gave identical results. The single Ca- and Sr-binding site, which has moderate affinity for these ions (KCa = 2.5 X 10(6) M-1 and KSr = 5.1 X 10(5) M-1), displays unusually large enthalpy changes of -118 kJ X mol-1 for Ca2+ and -75 kJ X mol-1 for Sr2+. The concomitant reaction entropies equal -273 and -142 J X K-1 X mol-1, respectively.
mesh_terms: D000818:Animals; D002118:Calcium / Q000032:analysis*; D002151:Calorimetry / Q000379:methods; D002417:Cattle; D002850:Chromatography, Gel; D007768:Lactalbumin / Q000032:analysis*; D011485:Protein Binding; D013324:Strontium / Q000032:analysis*; D013816:Thermodynamics
chemical_list: D007768:Lactalbumin; D002118:Calcium; D013324:Strontium