C-13(alpha) and C-13(beta) chemical shifts as a tool to delineate beta-hairpin structures in peptides

Unravelling the factors that contribute to the formation and the stability of beta -sheet structure in peptides is a subject of great current interest . A beta -hairpin, the smallest beta -sheet motif, consists of two antipara llel hydrogen-bonded beta -strands linked by a loop region. We have perform ed a statistical analysis on protein beta -hairpins showing that the most a bundant types of beta -hairpins, 2:2, 3:5 and 4:4, have characteristic patt erns of C-13(alpha) and C-13(beta) conformational shifts, as expected on th e basis of their phi and psi angles. This fact strongly supports the potent ial value of C-13(alpha) and C-13(beta) conformational shifts as a means to identify beta -hairpin motifs in peptides. Their usefulness was confirmed by analysing the patterns of C-13(alpha) and C-13(beta) conformational shif ts in 13 short peptides, 10-15 residues long, that adopt beta -hairpin stru ctures in aqueous solution. Furthermore, we have investigated their potenti al as a method to quantify beta -hairpin populations in peptides.