Date of Award
Chemistry and Biochemistry
Serotonin, or 5-hydroxytryptamine, is a neurotransmitter and metabolite vital to the normal function of the cardiovascular, gastrointestinal, and nervous systems. Although it might be colloquially known as the ‘happiness drug,’ malfunctions in serotoninergic pathways can result in mental health disorders, heart disease, irritable bowel syndrome, and even collateral death. Without a current method to directly measure, or even detect, serotonin in the human body, these diseases, along with many others, pose a threat of developing without proper warning. Raman spectroscopy presents a unique method to vibrationally characterize molecules based upon the inelastic scattering of light. Serotonin’s unique, amphipathic structure presents 69 vibrational modes that are observable under vibrational spectroscopy. Using B3LYP method and 6-311++G** basis set, the optimized structures of serotonin and various intramolecular structures were determined, and the results were Raman simulated. These spectra were compared to experiment collected for the crystalline solid, using a Horiba LabRAM spectrometer, 633nm excitation source, and over the 5-4000cm-1range. The comparison lead to greater peak matchup than ever previously published of the Raman spectrum of serotonin. Because of its amphipathic nature, it is also interesting to consider interactions amongst serotonin with various solvents. Using the same level of theory, Raman systems were modeled for serotonin and solvents water, methanol, and ethanol. Theoretical results were studied to predict red and blue peak shifts that would be observed in experiment. Experimental data was collected with a custom Raman setup that vaporizes the solvent and assists its constant flow through the system by vacuum. The same spectrometer was used with a 532nm excitation source and collected over the 200-4000cm-1 range. The comparison of theory with experiment, although cut short due to the COVID-19 outbreak, lead to the successful observation of the solvent effects that methanol has on serotonin, as visible under Raman spectroscopy.
Loe, Mallory, "A Raman Spectroscopic and Quantum Chemical Investigation of Serotonin, It's Intramolecular Interactions, and the Solvent Effects of Methanol, Ethanol, and Water" (2020). Honors Theses. 1531.