Gramicidin Peptides Alter Global Lipid Compositions and Bilayer Thicknesses of Coexisting Liquid-Ordered and Liquid-Disordered Membrane Domains

Ebrahim Hassan-Zadeh, Abul Hussain, Juyang Huang

Research output: Contribution to journalArticle

Abstract

© 2017 American Chemical Society. Effects of adding 1 mol % of gramicidin-A on the biochemical properties of coexisting liquid-ordered and liquid-disordered (L o + L d ) membrane domains were investigated. Quaternary giant unilamellar vesicles (GUV) of di18:1PC(DOPC)/di18:0PC(DSPC)/cholesterol/gramicidin-A were prepared using our recently developed damp-film method. The phase boundary of L o + L d coexisting region was determined using video fluorescence microscopy. Through fitting Nile Red fluorescence emission spectra, the thermodynamic tie-lines in the L o + L d two-phase region were determined. We found that at 1 mol % (i.e., ∼7% of membrane area), gramicidin peptides alter the phase boundary and thermodynamic tie-lines. Gramicidin abolishes the coexisting phases at some lipid compositions but induces phase separation at others. Previous studies of gramicidin emphasize the local perturbation of bilayer thickness adjacent to the protein through the interaction of “hydrophobic
Original languageEnglish
Pages (from-to)3324-3332
JournalLangmuir
StatePublished - Apr 4 2017

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