A DESIGNED BETA-HAIRPIN PEPTIDE IN CRYSTALS

beta-hairpin structures have been crystallographically characterized o nly in very short acyclic peptides, in contrast to helices, The struct ure of the designed beta-hairpin, toxycarbonyl-Leu-Val-Val-D-Pro-Gly-L eu-Val-Val-OMe in crystals is described, The two independent molecules of the octapeptide fold into almost ideal beta-hairpin conformations with the central D-Pro-Gly segment adopting a Type II' beta-turn confo rmation. The definitive characterization of a beta-hairpin has implica tions for de novo peptide and protein design, particularly for the dev elopment of three- and four-stranded beta-sheets.