pH -Dependent Chirality of L-Proline studied by Raman Optical Acticity and DFT calculation

The characteristic pyrrolidine ring structure of Proline (Pro) and its conformational flexibility are important to the biological function in peptides and proteins. Raman Optical Activity (ROA) spectroscopy is used to carefully study the chirality of L-Pro in aqueous solution with different pH values. Raman shifts and ROA intensities are found to be directly correlated with the acidic or basic environment. The dramatic changes of the distributions and the dispersion of the ROA intensities indicate that an acidic or basic environment not only leads to the simple abstraction or addition of a proton but also changes the electron delocalization throughout the molecule. These results will be useful for interpreting the ROA spectra of proline-rich peptides.