Structure and stability of β-pleated sheets

Beside α‐helices, β‐sheets are the most common secondary structure elements of proteins. In this article, the question of structure and stability of parallel and antiparallel sheets of various lengths is addressed. All data obtained are compared to a selected set of protein structures. In antiparallel β‐sheets, one of the two possible H‐bonded structures (containing 14 atoms in the H‐bonded pseudoring) is energetically more favored and also more abundant in proteins than the other one (with 10 atoms involved in the pseudoring). Parallel β‐sheets and their subunits are energetically less stable and indeed found to occur more rarely in proteins. Antiparallel hairpins are disfavored compared to β‐sheets formed by sequentially separated strands. Agreement between theory and experimental data indicates that characterization of structural building blocks at an appropriately accurate level of theory is a useful tool to get insight into fundamentals of protein structure. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 1155–1168, 2005