Simulation of intramolecular hydrogen bond dynamics in manzamine A as a sensitive test for charge distribution quality.

Subtle balance of inter- and intramolecular hydrogen bond strength in aqueous solutions often governs the structure and dynamics of molecular species used as potential drugs and in supramolecular applications. In silico molecular dynamics study of water solution of manzamine A has been performed with different atomic charges in order to investigate the influence of charge distribution choice on predicting qualitative and quantitative features of the simulated systems. Various well known charge schemes (MK-ESP, RESP, Mulliken, AMI-BCC, Gasteiger-Hückel, Gasteiger-Marsili, MMFF94, and Dynamic Electronegativity Relaxation - DENR) led to qualitatively different pictures of dynamic behavior of the intramolecular hydrogen bond. The reported calculation framework represents a relatively rare case where differences in charge distributions lead to noticeable differences in simulated properties, thus providing a useful test case for force field and charge distribution development, provided high quality experiments are conducted to use as references.