Simulation of amide I′ band profiles of trans polyproline based on an excitonic coupling model

We measured the amide I′ band profile of the IR, isotropic Raman, anisotropic Raman, and Vibrational Circular Dichroism spectrum of poly-l-proline in D2O. The band shapes were modeled by using an algorithm that exploits the delocalized character of the excited vibrational states [R. Schweitzer-Stenner, J. Phys. Chem. B. 108 (2004) 16965]. The band shapes could be quantitatively reproduced by invoking the polyproline II or 31-helix conformation for all peptide residues. This corroborates the notion that the combined use of the above spectroscopies is an ideal tool to discriminate different conformations associated with the so-called random coil state of peptides.