Vibrational circular dichroism of polypeptides. IV. Film studies of L‐alanine homo‐oligopeptides

Vibrational CD (VCD) and ir absorption data are reported for a series of films of Boc‐( L ‐Ala) n ‐OMe homo‐oligopeptides ( n = 3–7) in the amide I and A regions. The data evidenced a sharp change between n = 3 and n = 4, which parallels the onset of β‐structure formation, and another between n = 5 and n = 6, which parallels the full development of β‐structure. This represents the first report of the application of VCD to oligopeptide conformation. The data resembled earlier reported film VCD studies of higher‐molecular‐weight polypeptides of known β‐structure.