Two-dimensional infrared spectroscopy of the alanine dipeptide in aqueous solution

The linear-infrared and two-dimensional infrared (2D IR) spectra in the amide-I' region of the alanine dipeptide and its (super 13)C isotopomers in aqueous solution (D2O) are reported. The experimental results and simulations are consistent with a PP(sub II)-like conformation for the alanine dipeptide in aqueous solution, in which two amide-I' modes are highly localized and whose frequency distributions are uncorrelated.