Fig. 1.

SMFS of β₂AR reconstituted into liposomes composed of either phospholipids (DOPC) or phospholipids and cholesterol (DOPC/CHS). (A) Pressing the AFM stylus onto the proteoliposomes promotes the unspecific attachment of a single β₂AR polypeptide to the stylus. Withdrawal of the AFM cantilever stretches the polypeptide and induces the sequential unfolding of β₂AR. (B and C) Selection of F-D curves recorded on N-terminal unfolding of β₂AR reconstituted into DOPC (B, Upper) and DOPC/CHS (C, Upper) liposomes. Density plots of superimposed F-D curves (B, Lower and C, Lower) highlight their common features. Number of superimposed F-D curves: n = 100 (B) and n = 100 (C). Red numbers on top of each WLC curve (red dashed lines) indicate the average contour lengths (in amino acids) revealed from fitting each force peak of each superimposed F-D curve. Gray scale bars allow evaluation of how frequently individual force peaks were populated.