“…The rotational disorder, characteristic of the trifluoroacetamido group (Barone, Bavoso, Benedetti, Di Blasio, Grimaldi, Lelj, Pavone, Pedone, Bonora, Toniolo, Lingham & Hardy, 1984;Kalyanaraman, Kispert & Atwood, 1978), unless rigidly bound in the active site of an enzyme (Hughes et al, 1982), is found also in FsAc-Aib-OH.…”