Nicotinamide and picolinamide in phospholipid monolayers

Abstract

Molecular dynamics simulations have been performed to investigate the interactions between nicotinamide (NA) and picolinamide (PA) with Langmuir monolayers of zwitterionic lipids: dimyristoylphosphatidylcholine (DMPC) and di- myristoylphosphatidylethanolamine (DMPE). Our results for the DMPC monolayers show that both NA and PA molecules are essentially found at the lipid/water interface and present orientational disorder of the molecules. In the case of DMPE monolayers, the pyridine nitrogen seems to be located deeper inside the monolayer than the amide group, for both isomers, being the effect higher for PA. We have computed electrostatic surface potentials and found qualitatively goodagreement with experimental results. The different orientationand specific interactions of each molecule determine changesin the head orientation of the phospholipids, as the case of PAin DMPE monolayers, or in the orientation of the waterdipoles, as it is the case of PA in DMPC monolayers. Throughthese analyses, we were able to capture the maincontributions to the electrostatic potential in each system.