Fig. 8.

A backbone amide that is in close vicinity to the CMTSL spin-label of Q48C^CMTSL apoflavodoxin in 3.4 M GuHCl can give rise to two cross peaks in the corresponding ¹H–¹⁵N HSQC spectrum. Blue contour levels highlight cross peaks arising from diamagnetic Q48C^CMTSL apoflavodoxin, red contour levels highlight cross peaks arising from paramagnetic Q48C^CMTSL apoflavodoxin, and green contour levels highlight cross peaks arising from Q48C apoflavodoxin with no spin-label attached to it. A set of two cross peaks is shown for a Ser-40 and Glu-42, b Leu-78, c Ala-41 and for d Gly-53