The present proposal is part of a project to formulate a quantitative synergy between experiment and theory, complimenting the results the applicants have already established in the literature on weakly polar interactions in short peptide systems. We aim to characterise the conformational preferences and intra-molecular interactions of N- and C-protected amino acid diamides ('mono-peptides') and dipeptides in terms of their vibrational spectra, towards describing their influence on the bioactivity of larger oligo-peptides. Specifically N-Acetyl-Phenylalanine-N-Methylamide, its Proline-analogue, and their dipeptides shall be investigated. Data on the low energy motions, such as rotations and librations, will complement works on high-energy vibrations established by the applicants. Of particular interest is the impact of sequence identity (FP vs. PF) on the proline phenyl ring libration