Translocation of protons from the outside to the inside vesicles resulted in a more acidic pH inside the LUVs. When illumination was discontinued, the measured pH outside the LUVs decreased, indicating that protons leaked out again across the membrane and reached an equilibrium (Figure 4). As shown in this figure, the Camptothecin cell line proton pumping process can be repeated with the same sample. Figure 4 pH changes outside the BR-reconstituted vesicle as a function of illumination time. Conditions: 20mM potassium phosphate buffer and 100mMKCl, pH 7.2 inside the 20% negatively charged LUVs, 120mM KCl outside the LUVs, … We have Inhibitors,research,lifescience,medical repeated the experiment in the absence of BR to investigate whether

this effect observed is due to the proton pumping of BR or some other effects. No changes in pH were observed upon illumination of LUVs in the absence of BR which Inhibitors,research,lifescience,medical indicates that light-induced pH changes are indeed due to the proton pumping of BR (data not shown). The change in pH (ΔpH) outside the vesicles can be used to calculate the corresponding ΔpH inside the vesicles based on proton concentration and the estimated inner volume of all vesicles in the solution. Inhibitors,research,lifescience,medical A ΔpH outside the vesicles of +0.2 after 25min corresponds to almost −2 pH units inside the vesicles under the conditions used here. We also evaluated the effect of the pH gradient on the translocation

abilities of the fluorescein-labeled CPP penetratin. BR with the Inhibitors,research,lifescience,medical inside-out orientation was reconstituted into LUVs. Upon illumination, BR pumps protons into the LUVs creating a pH gradient over the membrane. Fluorescein-labeled penetratin together with KI as a quencher was enclosed in the BR-reconstituted LUVs. Figure 5 shows the fluorescence intensity changes of the sample containing BR-reconstituted LUVs and fluorescein-labeled penetratin together with fluorescence quencher KI inside the LUVs. Figure 5 Fluorescence changes of the sample containing BR-LUVs with fluorescein-labeled penetratin and Inhibitors,research,lifescience,medical fluorescence quencher KI inside the vesicles. Changes in fluorescence intensity between 505 and 550nm (excitation wavelength 494nm) were recorded …

In the dark, we observed no changes in the fluorescence intensity, indicating insignificant leakage of the peptide out of the LUVs. The peptides are not able to translocate across the membrane without any promoting proton gradient (Figure Oxymatrine 5(a)). Efficient peptide escape was observed in the presence of the light. A significant increase in the fluorescence intensity was observed when the sample was illuminated. This result indicates that a pH gradient across the membrane enhances the vesicular escape for the examined fluorescein-labeled CPP (Figure 5(b)). Longer period of illumination leads to more leakage of the CPP. However, after around 100min, it reaches an almost stable condition, corresponding to the transport of around 30% of the fluorescein-labeled penetratin out of the LUVs (data not shown).