Looking for a robust, synthetic, fully-extended (2.05-Helical) Peptide Structure - Effect of Terminal Groups

The incorporation of α-amino acids with a quaternary α-carbon atom into a peptide provides a tool to effectively restrict the available range of its backbone conformations. Specifically, under favorable conditions, Cα,α-diethylglycine (Deg) homopeptides are known to preferentially adopt the fullyextended (2.05-helical) structure, which is characterized by the longest possible separation between two adjacent α- amino acid Cα atoms. We have investigated the influence of the nature of the N- and/or C-terminal protecting (or blocking) groups on the relative stabilities of the fully-extended conformation vs. the competing, shorter 310-helical structure in a synthetic Deg homopeptide series.