Conformational Study of Amino Acid Type Molecules in Solution Using Raman Optical Activity

Abstract

Raman and Raman optical activity (ROA) spectroscopy are a set of especially effective spectroscopic practices for measuring the vibrational transitions of molecules in solution. They are particularly well suited for measurements of aqueous solutions because of the relatively little Raman scattering produced by water. This is useful for biologically relevant molecules, as such systems exist by and large in aqueous environments. Through the use of quantum mechanical calculations, Raman and ROA spectra can be determined for given molecules, and even molecules solvated explicitly. This explicit solvation is key in understanding the conformational changes a molecule undergoes when dissolved in a solvent. Certain solute-solvent complexes form and it is proposed that the lifetimes of some are longer than others. These longer-lived complexes likely contribute more to the observed experimental Raman and ROA spectral features. The following chapters detail work to determine what the solute-solvent complexes are for the amino acid type molecules N-acetyl-L-cysteine and serine through combined theoretical and experimental method. Sets of solute-solvent complexes are constructed and their respective spectra are fit and compared to those produced experimentally. In this way, the conformational changes and interactions between the solvent molecules and target molecule can be determined in the hope of better understanding how the molecules behave in solution.