Solution structure of dehydropeptides: A CD investigation

Abstract

A CD investigation of eleven dehydropeptides is reported. The compounds investigated include tri-, tetra-, hepta-, and octapeptides and contain one, two, or three dehydro-phenylalanine (deltaPhe) residues. The peptides showed different CD profiles depending on chain length, position, and number of dehydro residues. The CD data very much complemented that provided by nmr studies, confirming the conformational preference for beta-bend structures in small peptides (tripeptides), and 3(10)-helical or alpha-helical structures in longer peptides. The secondary structures were stable in chloroform solution and were denatured by addition of trifluoroacetic acid. Solvent titration experiments performed by measuring CD as a function of solvent composition provided evidence that the order < or > disorder conformational changes occurred as cooperative transitions.