Peptide δ-turn: Literature survey and recent progress

Abstract

Among the various types of α-peptide folding motifs, δ-turn, which requires a central cis-amide disposition, has been one of the least extensively investigated. In particular, this main-chain reversal topology has been studied in-depth neither in linear/cyclic peptides nor in proteins. This Minireview article assembles and critically analyzes relevant data from a literature survey on the δ-turn conformation in those compounds. Unpublished results from recent conformational energy calculations and a preliminary solution-state analysis on a small model peptide, currently ongoing in our laboratories, are also briefly outlined.C.C. is grateful to Ministerio de Economía yCompetitividad (grant CTQ2013-40855-R) and Gobierno de Aragón-FSE (research group E40), and C.A. acknowledges support from MICINN-FEDER funds (MAT2012-34498) and CESCA.Peer Reviewe