Stabilization of beta-ribbon structures in peptides using disulfide bonds.

The effect of a disulfide crosslink between two peptide chains on the stability of beta-ribbon secondary structures formed by these peptides has been investigated. Based on structural principles, we hypothesized that introduction of an unstrained disulfide crosslink at appropriate locations on two peptide chains should have a stabilizing effect on the beta-ribbon structure formed by these two peptide chains. To test this hypothesis, we designed and synthesized two sets of 9-residue peptides incorporating cysteine in one and (S)-alpha-amino-epsilon-mercaptohexanoic acid in the other. Comparison of the CD data clearly show that the dimer containing a disulfide bond between the longer sidechains of (S)-alpha-amino-epsilon-mercaptohexanoic acid shows dramatically higher beta-ribbon character as compared to the dimer with cystine disulfide bond, thus validating our structural hypothesis.