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. Author manuscript; available in PMC: 2019 Feb 1.
Published in final edited form as: Biochim Biophys Acta. 2017 Nov 11;1860(2):534–543. doi: 10.1016/j.bbamem.2017.11.006

FIGURE 3. Membrane partitioning free energy of pHLIP-WT and P20G.

FIGURE 3

Partitioning of pHLIP to membranes was measured in duplicate by FRET between both Trp in pHLIP (donor) and 2% Dansyl-PE in LUV as acceptors (Fig. S4). The measured data was fit as explained in the methods section, and the interfacial partitioning coefficient (Kx), defined as the [Lipid] required for maximum intensity was used to calculate the partitioning free energy ΔGIF. Data is shown as the relative decrease in intensity of the Trp band as a function of lipid (acceptor) concentration for both pHLIP variants; errors were calculated by support plane analysis and indicated as a range in brackets (Fig. S5–6). (a) pHLIP-WT ΔGIF: POPC = −6.5 [−6.3; −6.7] kcal/mol (I∞ = 0.7)), 25POPE:75POPC = −6.2 [−6.1; −6.3] kcal/mol (I∞ = 0.4), 25POPS:75POPC = −6.3 [−6.1; −6.4] kcal/mol (I∞ = 0.6). (b) pHLIP-P20G ΔGIF: POPC = −6.8 [−6.7; −6.9] kcal/mol (I∞ = 0.5), 25POPE:75POPC = −6.3 [−6.2; −6.4] kcal/mol (I∞ = 0.5), 25POPS:75POPC = −6.8 [−6.8;−6.9] kcal/mol (I∞ = 0.7).