engleski

Molecular Dynamics Study of the Interaction of Guanidinium and Ammonium Cations with Zwitterionic and Anionic Lipid Bilayers

The mechanism of passage of cationic cell-penetrating peptides through phospholipid membranes is widely researched, but still unresolved question in biochemistry [1]. Arginine (Arg) -based peptides can pass through cellular membranes, while lysine (Lys) -based peptides cannot, though both amino acids possess the same +1 charge [2]. In order to provide molecular-level insight into the differing interactions of Arg and Lys with zwitterionic and anionic membranes, the model system was created using guanidinium (Gdm+) and ammonium (NH4+) cations (Arg and Lys building blocks). Lipid bilayers consisting of 128 molecules of zwitterionic dipalmitoyl-phosphatidylcholine (DPPC) or anionic dipalmitoyl-phosphatidylserine (DPPS) were simulated in GROMACS, alone and with the addition of either NH4+ or Gdm+ (0.1 M), NaCl as neutralizing salt, and 12800 water molecules. CHARMM36m force field was applied and the simulations were run for a total of 100 ns at two temperatures (above and below phase transition temperature of either lipid). The changes in membrane packing were evaluated by calculating properties such as area per lipid, membrane thickness and deuterium order parameters, while the interaction of cations was monitored through partial density profiles, radial distribution functions and quantification of cations adsorbed to the membrane. NH4+ and Gdm+ both readily adsorb to the membranes and are located among the lipid headgroups, however Gdm+ adsorbs in significantly higher amounts (50% more to DPPS and 100% more to DPPC), suggesting stronger physico-chemical interactions. Obtained results will be used to compare with experimental findings, in order to elucidate the different behavior of NH4+ and Gdm+ with differently charged membrane systems.

guanidinium ; ammonium ; lipid bilayers ; molecular dynamics

nije evidentirano