Effects of Amino Acid φ,ψ Propensities and Secondary Structure Interactions in Modulating Hα Chemical Shifts in Peptide and Protein β-Sheet

Hα chemical shifts are often used as indicators of secondary structure formation in protein structural analysis and peptide folding studies. On the basis of NMR analysis of model β-sheet and α-helical peptides, together with a statistical analysis of protein structures for which NMR data are available, we show that although the gross pattern of Hα chemical shifts reflects backbone torsion angles, longer range effects from distant amino acids are the dominant factor determining experimental chemical shifts in β-sheets of peptides and proteins. These show context-dependent variations that aid structural assignment and highlight anomalous shifts that may be of structural significance and provide insights into β-sheet stability.