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. Author manuscript; available in PMC: 2013 Feb 22.
Published in final edited form as: J Am Chem Soc. 2012 Feb 10;134(7):3387–3395. doi: 10.1021/ja208640t

Figure 6.

Figure 6

Effects of different cations in SP-FRET on LUVs. (A) Concentration-dependent SP-FRET of BODIPY-FL and BODIPY-TMR PIP2 are measured with physiological divalent cations. Arrow indicates the concentration at which insoluble Zn(OH)2 forms. Fluorescence intensity changes are shown for titration with (B) Ca2+ and (C) Mg2+. (D) Reversibility is tested by titrating with EDTA4- with pre-existing 100 μM Ca2+. (E) The same experiment was repeated using polyamines with charges ranging from +2 to +4; (inset) normalized surface pressure responses of 25 mol% PIP2 monolayers as 1 mM multivalent cations are added. LUVs were excited at 470 nm with overall lipid concentration and PIP2 mole fraction held constant at 5 mol%, including 0.3 mol% each fluorescent PIP2 analog. PIP2/DChol/SOPC = 5/15/80 for all PIP2-containing LUVs. Buffer: 10mM HEPES, 5mM DTT, 1 μM EDTA, pH 7.4.