Amide I vibrational circular dichroism of dipeptide: Conformation dependence and fragment analysis

The amide I vibrational circular dichroic response of alanine dipeptide analog (ADA) was investigated using fragment analysis technique. The local and normal mode frequencies were calculated by varying two dihedral angles determining the three-dimensional ADA conformation. The vibrational circular spectra were calculated using both the density functional theory calculation and fragment analysis method. It was found that the most of the quantities were reproduced by the fragment approximation theory.