Thermostability of MelBSt solubilized in DDM or a novel amphiphile (PSA-C11, PSE-C9, PSE-C11, or PSE-C13). Membranes containing MelBSt were treated with the indicated detergent at 0°C or an elevated temperature (45°C, 55°C, or 65°C). (a) Western blot: the proteins solubilized by detergent treatment were analysed by SDS-15% PAGE and Western blotting as described in the materials the methods. The untreated membrane sample (Memb) represents the total amount of MelBSt protein. (b) Histogram: the amount of soluble MelBSt in a detergent (DDM, PSA-C11, PSE-C9, PSE-C11, or PSE-C13) detected in panel (a) is expressed as a percentage of band density relative to the untreated membrane sample. Error bars, SEM, n = 3. (c) Melibiose reversal of Trp to dansyl-2-galactoside (D2G) FRET. The right-side-out (RSO) membranes containing MelBSt or MelBEc were extracted with DDM or PSE-C11. After ultracentrifugation, the supernatant was directly used for the measurements as described in the Methods.