Normalized derivative functions of CPM profiles obtained from CPM assay of MOR solubilized in DDM (a), OGNG (b), LMNG (c), MTG-E11 (d), MTG-E12 (e), or MTG-E13 (f). DDM-purified receptor solubilized in the individual detergents thermally denatured in the presence of CPM dye by increasing the temperature from 15 to 70 °C. The value in parenthesis represents average receptor Tm ± SEM (n = 3–5). Tm of OGNG-solubilized MOR could not be obtained due to the inconsistency of the data.