Figure 3

pH titration: (a) Fluorescence intensity line scans across channels containing bilayers composed of 0.5 mol% ortho -rhodamine B POPE (oRB) in POPC with and without 5 mol% biotin-PE. (b) Titration curves for each membrane composition. The y-axis values were obtained by dividing the intensity of the fluorescence line scan at each pH value by the maximum fluorescence intensity line scan at pH 4.5. The solid circles represent individual fluorescence measurements and the solid lines are sigmoidal fits to the data.