Model systems for β-hairpins and β-sheets

β-Sheets and α-helices are the two principal secondary structures in proteins. However, our understanding of β-sheet structure lags behind that of α-helices, largely because, until recently, there was no model system to study the β-sheet secondary structure in isolation. With the development of well-folded β-hairpins, this is changing rapidly. Recent advances include: increased understanding of the relative contributions of turn, strand and sidechain interactions to β-hairpin and β-sheet stability, with the role of aromatic residues as a common subtheme; experimental and theoretical kinetic and thermodynamic studies of β-hairpin and β-sheet folding; de novo protein design, including all-β structures, mixed α/β motifs and switchable systems; and the creation of functional β-hairpins.