European biophysics journal with biophysics letters vol:20 issue:5 pages:263-268
By means of reaction calorimetry we measured the apparent enthalpy change, DELTA-H(app), of the binding of Mn2+-ions to goat alpha-lactalbumin as a function of temperature. The observed DELTA-H(app) can be written as the sum of contributions resulting from a conformational and a binding process. In combination with the thermal unfolding curve of goat alpha-lactalbumin, we succeeded in separating the complete set of thermodynamic parameters (DELTA-H, DELTA-G, DELTA-S, DELTA-C(p)) into the binding and conformational contributions. By circular dichroism we showed that NH4+-ions, upon binding to bovine alpha-lactalbumin, induce the same conformational change as do Na+ and K+: the binding constant K(app)NH4+ equals 98 +/- 9 M-1.