Membrane-Embedded
Nanoparticles Induce Lipid Rearrangements
Similar to Those Exhibited by Biological Membrane Proteins
- Publication date
- Publisher
Abstract
Amphiphilic
monolayer-protected gold nanoparticles (NPs) have recently
been shown to spontaneously fuse with lipid bilayers under typical
physiological conditions. The final configuration of these NPs after
fusion is proposed to be a bilayer-spanning configuration resembling
transmembrane proteins. In this work, we use atomistic molecular dynamics
simulations to explore the rearrangement of the surrounding lipid
bilayer after NP insertion as a function of particle size and monolayer
composition. All NPs studied induce local bilayer thinning and a commensurate
decrease in local lipid tail order. Bilayer thickness changes of similar
magnitude have been shown to drive protein aggregation, implying that
NPs may also experience a membrane-mediated attraction. Unlike most
membrane proteins, the exposed surface of the NP has a high charge
density that causes electrostatic interactions to condense and reorient
nearby lipid head groups. The decrease in tail order also leads to
an increased likelihood of lipid tails spontaneously protruding toward
solvent, a behavior related to the kinetic pathway for both NP insertion
and vesicle–vesicle fusion. Finally, our results show that
NPs can even extract lipids from the surrounding bilayer to preferentially
intercalate within the exposed monolayer. These drastic lipid rearrangements
are similar to the lipid mixing encouraged by fusion peptides, potentially
allowing these NPs to be tuned to perform a similar biological function.
This work complements previous studies on the NP–bilayer fusion
mechanism by detailing the response of the bilayer to an embedded
NP and suggests guidelines for the design of nanoparticles that induce
controllable lipid rearrangements