Molecular-level insight into the binding of arginine to a zwitterionic Langmuir monolayer

KLUG, JOAQUÍN; MASONE, DIEGO; DEL PÓPOLO, MARIO G.

RSC Adv.

The Royal Society of Chemistry

Lugar: Londres; Año: 2017 vol. 7 p. 30862 - 30869

Solutions of the cationic amino-acid arginine (Arg + ) in contact with a phospholipidmonolayer are investigated by molecular dynamics simulations. The results show that Arg + bindsstrongly to the lipid/water interface, with adsorption free-energiesranging from -43.8 to -22.2 kJ 1/mol , depending on the amino-acidsconcentration. The large binding energies are attributed to hydrogenbonding between the charged moieties Arg + and the phosphate andcarbonyl groups of the phospholipids, that compensate for changes inthe levels of hydration upon adsorption. We show that a concentratedlayer of Arg + , tightly bound to the interface, has little effect onthe compression isotherm and the lateral mechanical properties of themonolayer, while having a substantial impact on the interfacialelectrostatic potential and the lateral mobility of the lipids. Theseeffects are readily explained in terms of the arrangement that theamino-acids adopt when bound to the monolayer.