The secondary chemical shift experienced by the 1H-NMR resonances of the α C-H protons in proteins can be correlated with their backbone torsional angles ψ, which dictate the orientation of the α C-H proton to the adjacent carbonyl group. It is shown that α C-H protons present in β-sheet regions experience downfield secondary shifts, whereas those in α-helix regions experience upfield secondary shifts. The predictive use of this correlation in assignment studies is illustrated for the calcium-binding protein paravalbumin, for which a crystal structure is available, and troponin C, for which no crystallographic data are available.

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