Fig. 3.

X-band EPR spectra of T7R1 in POPC (A) and with E3R added (B). The arrows indicate the positions of the narrower lineshape component that appears in several spectra in the presence of POPC. This component represents a minor population of the Ton box that is present in an undocked configuration in these POPC membranes. The fraction of undocked Ton box varies with the position of the R1 substitution and with the lipid composition. Spectra were acquired with an incident microwave power of 2 mW, a 1-G modulation amplitude, and a 100-G scan width.