Theoretical DFT study on spectroscopic signature and molecular dynamics of neurotransmitter and effect of hydrogen removal

Structural and vibrational investigations of a neurotransmitter molecule: Serotonin (5-hydroxy tryptamine)

“…in agreement with the work of Mukherjee and Yadav [42]. The frequency 249 cm À1 is assigned to the torsional mode in the present case.…”

“…In the present case no frequency observed in the IR and Raman spectra correspond to the r(NH 2 ) mode. This mode (n 37 ) is computed to be (unscaled) frequency The u(NH 2 )(n 26 ) and t(NH 2 )(n 7 ) modes for serotonin have been assigned at 814 and 237 cm À1 by Mukherjee and Yadav [42]. In the present case we observed the frequencies 827 and 822 cm À1 in the IR and Raman spectra and correlate to the u(NH 2 ) mode.…”

Spectroscopic signatures and structural motifs in isolated and hydrated serotonin: a computational study

“…The hydride stretching modes can be divided into three groups: the heterocyclic system of the indole ring (aromatic CH and indole NH stretches), the ethylamine side chain (alkyl CH and amine NH stretches), and hydroxyl group (OH stretch). The asymmetric amino NH stretching band is predicted at the higher frequency than the corresponding symmetric mode which is in agreement to the assignment of LeGreve et al 5 Therefore the assignment of conventional IR band observed at 3438 cm À1 as a symmetric NH 2 stretching mode by Mukherjee et al 18 seems to be ambiguous. It is evident from theoretical and experimental IR spectra that the frequency (predicted at 3530/ 3531 cm À1 ) and intensity of indole NH stretching mode in the all conformers of serotonin are almost unchanged from one conformer to other, as they were found in tryptamine.…”

“…5 Computed vibrational fundamentals are found only slightly larger than the experimental values, excluding the hydroxyl (OH) stretching mode. Surprisingly Mukherjee et al 18 have assigned the conventional IR bands observed at 3438 and 3397 cm À1 as symmetric and asymmetric NH 2 stretching mode respectively. As we have mentioned in the earlier section that the scaling factor of 0.977 and 0.988 for the OH and the NH/CH stretch fundamentals respectively are used to scale down the vibrational mode frequencies of the monomer, however there is no scaling used for the alkyl CH stretching and bending fundamentals.…”

“…1) can exist in various forms, differing from each other by the arrangements of the ethylamine side chain and hydroxyl group. 11 Bayari et al 16 and few other researchers [17][18][19] presented FT-IR spectra of serotonin in KBr lms as well as in aqueous solution. 1) of the ethylamine side chain, is expected to be highly relevant for the drug-receptor interaction and molecular recognition.…”