Secondary Structure Elements for Catalytic Systems

Here we present de novo designed peptides that contains structural elements qualified for both stable helical folding as well as sheet formations as competing subunits. In order to obtain soluble, flexible, dimeric or trimeric structures we have synthetized and observed hetero-oligopeptides (i.e. composed of two or more types of monomer) with different length and compositions that can potentially assume a ?-sheet helical conformation. The balance between hydrogen bonds and hydrophobic interactions permit us to provide the conformational stability of the predicted structure(s). Interesting, norleucine oligopeptides form molecular aggregate that are unsoluble in organic solvents[2], whereas short sequences of L-isoleucine form soluble molecular aggregates in which the peptide chain assume the ?-conformation [3]. In this work we report about synthesis and conformational analysis of oligonorleucine peptides containing some leucine/isoleucine residues, with n=8-18 residues, having Boc-N- and -COOMe protected terminals. The result are discusses on the basis of steric and hydrophobic properties of the three side chain. References [1] Navarro E., Fenude E., Celda B., Biopolymers (2004) 73, 229-241 [2] Fenude Schoch E., Römer U.D., Lorenzi G.P., Int. J. Peptide Protein Res.(1994) 44, 10-18 [3] Lorenzi G.P., Paganetti T., J. Am. Chem. Soc.(1977) 104, 1282-83 [4] Saviano M. J. Am. Chem. Soc. (1995) 117, 8651-8658