¹ H NMR Shows Slow Phospholipid Flip-Flop in Gel and Fluid Bilayers

Journal Article · Fri Feb 03 00:00:00 EST 2017 · Langmuir

DOI:https://doi.org/10.1021/acs.langmuir.6b04485· OSTI ID:1342412

Marquardt, Drew ; Heberle, Frederick A.; Miti, Tatiana; Eicher, Barbara; London, Erwin; Katsaras, John; Pabst, Georg

We measured the transbilayer diffusion of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) in large unilamellar vesicles, in both the gel (L_β') and fluid (L_α) phases. The choline resonance of headgroup-protiated DPPC exchanged into the outer leaflet of headgroup-deuterated DPPC-d13 vesicles was monitored using ¹H NMR spectroscopy, coupled with the addition of a paramagnetic shift reagent. This allowed us to distinguish between the inner and outer bilayer leaflet of DPPC, to determine the flip-flop rate as a function of temperature. Flip-flop of fluid-phase DPPC exhibited Arrhenius kinetics, from which we determined an activation energy of 122 kJ mol^–1. In gel-phase DPPC vesicles, flip-flop was not observed over the course of 250 h. Our findings are in contrast to previous studies of solid-supported bilayers, where the reported DPPC translocation rates are at least several orders of magnitude faster than those in vesicles at corresponding temperatures. We reconcile these differences by proposing a defect-mediated acceleration of lipid translocation in supported bilayers, where long-lived, submicron-sized holes resulting from incomplete surface coverage are the sites of rapid transbilayer movement.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)
• Sponsoring Organization: Austrian Science Fund (FWF); National Science Foundation (NSF); USDOE Office of Science (SC)
• Grant/Contract Number: 7394; AC05-00OR22725
• OSTI ID: 1342412
• Alternate ID(s): OSTI ID: 1352553; OSTI ID: 1362240
• Journal Information: Langmuir, Journal Name: Langmuir Vol. 33 Journal Issue: 15; ISSN 0743-7463
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

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