13C(alpha) and 13C(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 antiparallel hydrogen-bonded beta-strands linked by a loop region. We have performed a statistical analysis on protein beta-hairpins showing that the most abundant types of beta-hairpins, 2:2, 3:5 and 4:4, have characteristic patterns of 13C(alpha) and 13C(beta) conformational shifts, as expected on the basis of their phi and psi angles. This fact strongly supports the potential value of 13C(alpha) and 13C(beta) conformational shifts as a means to identify beta-hairpin motifs in peptides. Their usefulness was confirmed by analysing the patterns of 13C(alpha) and 13C(beta) conformational shifts in 13 short peptides, 10-15 residues long, that adopt beta-hairpin structures in aqueous solution. Furthermore, we have investigated their potential as a method to quantify beta-hairpin populations in peptides.