Quantification of Intramolecular Hydrogen Bond in Neurotransmitter Dopamine

Abstract

Dopamine is a catecholamine chemically, 3, 4-dihydroxyphenyethylamine. It has intramolecular H-bond (IHB) between the two hydroxyl groups. The energy of intramolecular H-bond might contribute energy in binding of the neurotransmitter with the receptors. Here the IHB in Dopamine is calculated in different levels of theories. The energetics of intramolecular hydrogen bonds is of fundamental importance in biochemistry. In contrast with intermolecular H-bonds, whose enthalpy can be determined by a supermolecular approach, there is no general accepted procedure to determine the enthalpy of an intramolecular H-bond. In this work, different ways for assessing the energetics of intramolecular H-bonds of selected aromatic systems were applied and compared. They include the widely used conformational analysis approach (cis-trans method), a recently proposed isodesmic reaction method, and a new procedure that is designated as the ortho-para method.