Figure 2. Strong peak broadening due to the PRE effect was observed in cTnC residues in the vicinity of each cTnI spin label.

The glycine-containing region of the paramagnetic (red) and diamagnetic (blue) ¹H-¹⁵N-TROSY spectrum of each spin-labeled binary cTnC-cTnI construct. The MTSL spin label is attached to cTnI residues (A) I57, (B) I143, (C) I151 and, (D) I159. Spectra are shown for +Ca²⁺ (left panels) and −Ca²⁺ conditions (right panels). The superimposed paramagnetic spectrum is offset by 0.5 ppm in the ¹⁵N dimension for clarity.