Abstract
Recent work has demonstrated that charged gold nanoparticles (AuNPs) protected by an amphiphilic organic monolayer can spontaneously insert into the core of lipid bilayers to minimize the exposure of hydrophobic surface area to water. However, the kinetic pathway to reach the thermodynamically stable transmembrane configuration is unknown. Here, we use unbiased atomistic simulations to show the pathway by which AuNPs spontaneously insert into bilayers and confirm the results experimentally on supported lipid bilayers. The critical step during this process is hydrophobic-hydrophobic contact between the core of the bilayer and the monolayer of the AuNP that requires the stochastic protrusion of an aliphatic lipid tail into solution. This last phenomenon is enhanced in the presence of high bilayer curvature and closely resembles the putative pre-stalk transition state for vesicle fusion. To the best of our knowledge, this work provides the first demonstration of vesicle fusion-like behaviour in an amphiphilic nanoparticle system.
Highlights
Recent work has demonstrated that charged gold nanoparticles (AuNPs) protected by an amphiphilic organic monolayer can spontaneously insert into the core of lipid bilayers to minimize the exposure of hydrophobic surface area to water
We use a combination of atomistic molecular dynamics simulations and experiments to gain insight into the kinetic barriers that may affect the insertion of amphiphilic AuNPs into bilayers
This process must involve the contact between hydrophobic material in the monolayer and the hydrophobic core of the bilayer as in similar situations reported in the literature: for example, recent studies on peripheral protein binding have suggested that hydrophobic residues may contact the hydrophobic core of the bilayer through ‘hydrophobic defects’[33], while the pathway of vesicle–vesicle fusion involves the contact of lipid tails via stochastic protrusions into solvent[34,35,36,37,38]
Summary
Recent work has demonstrated that charged gold nanoparticles (AuNPs) protected by an amphiphilic organic monolayer can spontaneously insert into the core of lipid bilayers to minimize the exposure of hydrophobic surface area to water. We use a combination of atomistic molecular dynamics simulations and experiments to gain insight into the kinetic barriers that may affect the insertion of amphiphilic AuNPs into bilayers This process must involve the contact between hydrophobic material in the monolayer and the hydrophobic core of the bilayer as in similar situations reported in the literature: for example, recent studies on peripheral protein binding have suggested that hydrophobic residues may contact the hydrophobic core of the bilayer through ‘hydrophobic defects’[33], while the pathway of vesicle–vesicle fusion involves the contact of lipid tails via stochastic protrusions into solvent[34,35,36,37,38]. Using unbiased atomistic simulation methods that accurately capture the physicochemical forces acting at this nano–bio interface, we demonstrate a lipid tail protrusionmediated pathway for the spontaneous fusion of soluble charged AuNPs with a bilayer
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