la6b02099_si_001.pdf (1.29 MB)
Morphology-Induced Defects Enhance Lipid Transfer Rates
journal contribution
posted on 2016-08-25, 00:00 authored by Yan Xia, Kamil Charubin, Drew Marquardt, Frederick
A. Heberle, John Katsaras, Jianhui Tian, Xiaolin Cheng, Ying Liu, Mu-Ping NiehMolecular
transfer between nanoparticles has been considered to
have important implications regarding nanoparticle stability. Recently,
the interparticle spontaneous lipid transfer rate constant for discoidal
bicelles was found to be very different from spherical, unilamellar
vesicles (ULVs). Here, we investigate the mechanism responsible for
this discrepancy. Analysis of the data indicates that lipid transfer
is entropically favorable, but enthalpically unfavorable with an activation
energy that is independent of bicelle size and long- to short-chain
lipid molar ratio. Moreover, molecular dynamics simulations reveal
a lower lipid dissociation energy cost in the vicinity of interfaces
(“defects”) induced by the segregation of the long-
and short-chain lipids in bicelles; these defects are not present
in ULVs. Taken together, these results suggest that the enhanced lipid
transfer observed in bicelles arises from interfacial defects as a
result of the hydrophobic mismatch between the long- and short-chain
lipid species. Finally, the observed lipid transfer rate is found
to be independent of nanoparticle stability.