Protected decapeptide ortho-nitrophenylsulphenyl–( L -leucyl– L -alanyl) 5 –ethyl ester [nps–( L -leu– L -ala) 5 –OEt]. Shortest critical peptide size for development of the α-helix in the solid state

Conformational studies of a series of oligopeptides having the sequence of alternate L-leucyl and L-alanyl residues in the solid state have revealed that the α-helical conformation begins forming at the decapeptide level, which may be considered as the shortest critical peptide chain length for development of the α-helical conformation in the solid state.