The observed monoexponential fluorescence decay of N-acetyl-beta-homo-
tyrosine methylamide (Ac-beta Hty-NHMe) (I) and N-acetyl-(O-methyl)-be
ta-homo-tyrosine methylamide (Ac-beta Hty(OMe)-NHMe) (II) is supportin
g the rotamer population theory, according to which rotamers are respo
nsible for heterogeneity of the fluorescence decay of N-acetyl-tyrosin
e amide or tyrosine incorporated within a peptide chain, in general.