Fig. 2. Carrier activity obtained from the HPTS/DPX assay.
a, Schematic representation of the transport of otherwise impermeable analytes facilitated by superchaotropic cluster anions with encapsulated HPTS/DPX probe/quencher pair used for signalling. In the presence of suitable carriers, cargo is carried into the vesicles and the cationic quencher DPX is transported from the endoliposomal phase to the bulk, resulting in increased fluorescence of HPTS as the optical signal of successful cargo transport. b, Changes in HPTS emission (I) (λex = 413 nm, λem = 511 nm) in EYPC⊃HPTS/DPX vesicles as a function of time during the addition of the membrane carriers B12Br122− and B12Cl122−, the established activator pyrenebutyrate (1), as well as the inactive parent B12H122−, as negative control; clusters (150 µM) added at t = 50 s, WR7 at t = 100 s and TX-100 at t = 600 s, for calibration. c, Dependence of fractional activity Y for WR7 transport on the concentration of different clusters, and the corresponding Hill curve fits in comparison to reference compound 1. d, Transport efficiency of B12Br122− towards selected impermeable analytes of biological/medicinal relevance; values obtained by non-linear regression analysis (Hill equation), see Extended Data Table 1. e, Comparable transport of WR7 (circles) and WK7 (triangles or squares) activated by B12Br122− (red, solid lines) versus exclusive transport of WR7 activated by 1 (black, dashed lines). f, Successful transport of membrane-impermeable analytes (100 µM) affected by B12Br122− (red, solid line) in the HPTS/DPX assay and transport failure for the established amphiphilic activator pyrenebutyrate (1, black, dashed lines). g, ‘Conventional’ (dashed line) versus reverse addition (solid line), demonstrating that the sequence of addition does not markedly affect transport efficiency. h, Transport efficiency in anionic DMPE/DPPG/CHOL⊃HPTS/DPX vesicles as a function of B12Br122− (red, solid line) versus pyrenebutyrate (1, black, dashed line) concentration at constant cargo concentration (WR7). Concentrations of carrier and cargo, when fixed, were 40 and 20 µM, respectively, unless explicitly stated.