The integral membrane protein diacylglycerol kinase (DGK) from E. Coli unfolds reversibly upon varying the molar ratio of n-decyl-b-D-maltoside (DM) and sodium dodecylsulfate (SDS) in a protein-detergent-mixed micelle system. Two distinct denaturation phases are observed, the first corresponding to unfolding of the cytoplasmic domain and the second to unfolding of the membrane embedded portion of the protein. Differential scanning calorimetric (DSC) studies are currently in progress to investigate the thermal stability of DGK in the absence and presence of SDS. Preliminary measurements indicate that the DSC profile of DM-solubilized protein (without SDS) is characterized by a single cooperative endotherm at high temperature (Tm = 90 C). Additional DSC experiments conducted at various molar ratios of DM and SDS will enable us to compare the denaturant- and temperature-induced unfolding of DGK.