Figure 4.

Long-term stability of β₂AR in the different detergents (a), SEC profiles of individual detergent-purified β₂AR after detergent exchange (b), and of β₂AR solubilized and purified in DDM (c) or PSE-C11 (d). For long-term stability measurement, 0.1% DDM-purified β₂AR was diluted into individual detergent solutions and the receptor activity was monitored at regular intervals over a 4-day incubation. Antagonist [³H]-dihydroalprenolol (DHA) was used to measure the receptor activity via radioligand binding assay. The protein samples were incubated on ice for the first two days and increased to room temperature in the next two days. For SEC analysis, the DDM-purified receptor was applied for a superdex-200 GL column after detergent exchange. Alternatively, β₂AR solubilized in 1% DDM or PSE-C11 was purified in 20×CMC DDM and PSE-C11, respectively, and was then applied to the SEC column which had been equilibrated with detergent-containing or detergent-free buffer. The chromatogram of each agent-purified receptor was obtained from UV absorbance at 280 nm or the intrinsic tryptophan emission at 345 nm.