Structural modeling and spectroscopic investigation of isolated and hydrochloride tyramine neurotransmitter

Abstract

We have reported optimized molecular structure and vibrational spectra of an important biomolecule named tyramine in ten different conformers. The FTIR and FTRaman spectra were recorded in the spectral region 400–4000 cm−1 and 50–4000 cm−1 respectively. The first principles Density Functional Theory (DFT) and Hartree-Fock (HF) calculations were employed to carry out theoretical computations. In DFT, the exchange correlation functional B3LYP was included. Potential energy scanning was performed to find out the possible numbers of tyramine conformers which confirms ten minimum energy structures of tyramine. Vibrational frequencies of all the ten conformers were computed after optimization. Normal coordinate analysis was also treated to scale the DFT and HF calculated frequencies and to calculate potential energy distributions of the normal modes. We also reported the effect of N..H hydrogen bond in geometrical parameters and vibrational frequencies in tyramine hydrochloride. NBO analyses of tyramine conformers were also performed. HOMO-LUMO energy gap is 5.62eV for the most stable conformer of tyramine.