Atomic force microscopy of phase separation on ruptured, giant unilamellar vesicles, and a mechanical pathway for the co-existence of lipid gel phases

Yanfei Jiang, Kenneth M. Pryse, Srikanth Singamaneni, Guy M. Genin, Elliot L. Elson

Research output: Contribution to journalArticlepeer-review

Abstract

Phase separation of lipid species is believed to underlie formation of lipid rafts that enable the concentration of certain surface receptors. However, the dynamics and stabilization of the resulting surface domains are unclear. We developed a methodology for collapsing giant unilamellar vesicles (GUVs) into supported bilayers in a way that keeps membrane nanodomains stable and enables their imaging. We used a combination of fluorescence and atomic force microscopy (AFM) of this system to uncover how a surprising phase separation occurs on lipid vesicles, in which two different gel phases of the same lipid co-exist. This unusual phase behavior was evident in binary GUVs containing 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) and either 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC). The approach showed that one of the phases is stabilized by lipid patches that become ejected from the membrane, thereby enabling the stabilization of what would otherwise be a thermodynamically impossible coexistence. These results show the utility of AFM on collapsed GUVs, and suggest a possible mechanical mechanism for stabilization of lipid domains.

Original languageEnglish
Article number071003
JournalJournal of Biomechanical Engineering
Volume141
Issue number7
DOIs
StatePublished - Jul 1 2019

Keywords

  • GUV rupture
  • atomic force microscopy
  • fluorescence microscopy
  • giant unilamellar vesicles
  • lipid domains
  • lipid rafts
  • supported lipid bilayers

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