The spontaneous lipid transfer (SLT) rates are studied and found to be strongly related to the heterogeneity of the distribution of species on the bilayer. We obtained consistent SLT rates between vesicles (liposomes) and bicelles (nanodiscs, spontaneously forming in a long- and short- chain lipid mixture), respectively, using a variety of techniques differential scanning calorimetry, small angle neutron scattering and fluorescence cross spectroscopy. The obtained SLT rate between bicelles is at least two orders of magnitude faster than that of the same species between vesicles. This enhanced rate cannot be not completely explained by the slow flip-flop process that only occurs in vesicles and is most likely attributed to the reduction of the activation energy for the transfer process, taking place at the intermediate domains between the gel long-chain lipid phases. The SLT rate also increases with decreased long- to short- chain ratios, implying larger intermediate domains are forming in mixtures at higher short-chain compositions. Moreover, we have found that SLT rate does not directly correspond to the stability of the nanoparticles.

Spontaneous lipid transfer and its implication of membrane lateral organization and structural stability

251st National Meeting (2016)

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