Fig. 1. Effects of insertion of different molecules into lipid bilayer on efficiency of FRET between probes located in lipid headgroup and between probes in lipid hydrocarbon tail regions.
a Increasing bulk concentrations of either dioleoyl phosphatidylcholine, DOPC (from 1 µM to 10 µM), or lysophosphatidylcholine, LPC (from 10 µM to 100 µM) or sMyomerger26-84 (from 50 nM to 0.5 µM) were added to 2.5 µM liposomes containing fluorescence resonance energy transfer (FRET) pair with both probes located in the lipid headgroup region or with both probes located in the lipid hydrocarbon tail region. Dependence of FRET efficiency characterized as change in quantum efficiency of donor emission due to the presence of acceptors (see Methods section) for probes in headgroup region E(FRET) in Heads vs E(FRET) in Tails for probes in hydrocarbon tails from a representative experiment is shown. For all three reagents and for probes both in the headgroup region and in hydrocarbon tails, E(FRET) monotonously decreased as the bulk concentration of the reagent increased. Individual points correspond to a single bulk concentration of the added molecules, the line shows linear fit of the data and error bands are centered on the linear fit values and show 0.95 confidence interval of the linear regression. b Slopes of the E(FRET) in Heads vs E(FFET) in Tails are different for DOPC, LPC, and sMyomerger26-84 with DOPC < LPC < sMyomerger26-84. Individual dot points represent a slope estimate obtained as shown in a from an independent experiment (n = 14, 9, and 8 for LPC, sMyomerger26-84, and DOPC, respectively), diamond points and error bars represent slope means with 95% confidence interval.