Electron structure calculations are used to explore stabilization effects of disulfide bridges in a (Ala-Cys-Ala-Cys-Ala)(2) beta-sheet model both in the parallel and the anti-parallel (10(3) 14(2) and 14(3) 10(2)) arrangements. Stabilities were calculated using a redox reaction involving a weak oxidizing agent (1,4-benzoquinone). The results show that both inter-and intra-strand disulfide SS-bridges stabilize the beta-sheet backbone fold. However, inter-strand SS-bridges give more stability than their intra-strand counterparts. For both single and double disulfide linked conformations, stabilization was larger for the parallel than for the anti-parallel beta-sheet arrangements. (C) 2013 Elsevier B.V. All rights reserved.