Chain-length dependence for secondary structure formation of homo-oligopep tides fromε-tert.-butyloxycarbonyl-L-lysine with a lipophilic C-terminal group

A solid-state and solution analysis of the homo-oligopeptides from ε-tert.-butyloxycarbonyl-L-lysine with p-oxymethylbenzylcholestan-3β-yl succinate as C-terminal group, using infrared absorption and circular dichroism, is described. The occurrence of intermolecular β-structure is seen in the solid state and in solvents of low polarity, e.g. methylene chloride, for peptides of intermediate size (from pentamer to decamer). Conversely, the eicosapeptide exhibits a high percentage of α-helical structure both in the solid state and in 2, 2, 2-trifluoroethanol. The influence of the C-terminal group on the conformational preferences of the ε-blocked homo-oligolysines in the solid state and in organic solvents appears negligible.