Okadaic Acid Time-Resolved Absorption and Resonance FT-IR and Raman Biospectroscopy and Density Functional Theory (DFT) Investigation of Vibronic-Mode Coupling Structure in Vibrational Spectra Analysis

Okadaic acid, C₄₄H₆₈O₁₃, is a toxin produced by several species of dinoflagellates, and is known to accumulate in both marine sponges and shellfish. One of the primary causes of diarrhetic shellfish poisoning, Okadaic acid is a potent inhibitor of specific protein phosphatases and is known to have a variety of negative effects on cells. A polyketide, polyether derivative of a C38 fatty acid, Okadaic acid and other members of its family have shined light upon many biological processes both with respect to dinoflagellate polyketide synthesis as well as the role of protein phosphatases in cell growth. Parameters such as FT-IR and Raman vibrational wavelengths and intensities for single crystal Okadaic Acid are calculated using density functional theory and were compared with empirical results. The investigation about vibrational spectrum of cycle dimers in crystal with carboxyl groups from each molecule of acid was shown that it leads to create Hydrogen bonds for adjacent molecules. The current study aimed to investigate the possibility of simulating the empirical values. Analysis of vibrational spectrum of Okadaic Acid is performed based on theoretical simulation and FT-IR empirical spectrum and Raman empirical spectrum using density functional theory in levels of HF/6-31G^*, HF/6-31++G^**, MP2/6-31G, MP2/6-31++G^**, BLYP/6-31G, BLYP/6-31++G^**, B3LYP/6-31G and B3LYP6-31-HEG^**. Vibration modes of methylene, carboxyl acid and phenyl cycle are separately investigated. The obtained values confirm high accuracy and validity of results obtained from calculations.