First-principles approach to vibrational spectroscopy of biomolecules

Vibrational spectroscopy of biomolecules like enzymes, nucleic acids, carbohydrates, lipids, and their components, is in most cases the vibrational spectroscopy of large molecules in aqueous solution or in vivo. Since large molecules in solution are likely to yield conventional infrared (IR) and Raman spectra with many close-lying peaks, spectroscopic techniques which filter out information selectively are of special interest in this field. Because of the large size of the investigated molecules and the lack of reliable rules of thumb for many special techniques, accurate first-principles calculations are an important means of interpreting the resulting spectra. First-principle calculations on biomolecules in solution have to cope with the challenges arising from the size of the systems under study, which make selective computational techniques an essential tool in order to be able to investigate biomolecular systems of reasonable size with sufficient computational accuracy. This is why the focus of this work is on the selective first-principles calculation of vibrational spectra of biomolecules obtained by special techniques such as difference IR and Raman, Vibrational Circular Dichroism, Raman Optical Activity, resonance Raman, and also Coherent Anti-Stokes Raman Spectroscopy, two-dimensional IR and Nuclear Resonance Vibrational Spectroscopy. For each of these techniques, a short introduction of their relevance for studies on biomolecules is given. Theoretical as well as practical aspects of calculating the corresponding intensities are discussed and complemented by references to original work on these topics.