Enthalpy of Interaction between some Globular Proteins and Sodium n-Dodecyl Sulphate in Aqueous Solution

Abstract

The enthalpy of binding of sodium n-dodecyl sulphate (SDS) to scrum albumin, ovalbumin and ribonuclease A has been measured by microcalorimetry over the temperature range 18.5 to 32.0 C. The amount of SDS bound to the proteins has been measured over a wide range of SDS concentration by equilibrium dialysis. Changes in protein conformation have been monitored by viscometry. The results are consistent with a mechanism in which SDS binds initially to ionic sites on the protein molecules and initiates chain unfolding. At high binding levels the interaction is predominantly of a hydrophobic nature.