Fig. 7.

PRE of amide protons of WT^CMTSL and Q48C^CMTSL apoflavodoxin unfolded in GuHCl at 25°C. The ratio of the intensities of HSQC cross peak maxima (I _para/I _dia) of backbone amides was determined as described in the legend of Fig. 6. Shown are I _para/I _dia of a WT^MTSL and b Q48C^MTSL apoflavodoxin, both in 6.0 M GuHCl, and I _para/I _dia of c WT^MTSL and d Q48C^MTSL, both in 3.4 M GuHCl. Green dots highlight the positions of the CMTSL spin-label. Residues Ser-40, Ala-41, Glu-42, Gln-46, Phe-49, Leu-50, Leu-52, Gly-53, Thr-54, and Leu-78 of Q48C^CMTSL apoflavodoxin in 3.4 M GuHCl each give rise to two backbone amide cross peaks (a few examples are shown in Fig. 8) and are indicated with red bars in (d)