Fig. 2.

Two-dimensional ¹³C-¹³C DARR-MAS spectra of ¹³C, ¹⁵N reverse-labeled CrgA. (A and B) DARR spectra of CrgA with all but Thr, Ile, Phe, Ser, and Trp labeled, using mixing times of 1,000 ms (red), 700 ms (green), and 300 ms (blue). Cross peaks corresponding to three interhelical distance restraints are indicated. (C) Superimposed DARR spectra of CrgA with unlabeled Ile, Leu, Phe, Tyr, and Ser at 100-ms mixing time (blue) and ¹³C, ¹⁵N uniform-labeled CrgA at 50-ms mixing time (red). The Gly39–Thr84 cross peak represents an interhelical distance restraint. All spectra were collected at 600 MHz proton frequency in liquid–crystalline POPC/POPG liposomes at 13 °C and 12-kHz spinning rate.