Fig. 2. (a) Cage-mediated cytosolic delivery: the peptide–cage vector recognizes pyranine, promotes its membrane translocation, and releases the cargo into the cytosol of cells. In the cage/probe complex bipyridine has been substituted with a red line for clarity. The pH dependent excitation maxima can be used to track the intracellular pH (i.e. endosome). (b) Structure of the peptide cage hybrids. (c) Titration of pyranine (8.4 nM) with increasing concentrations of peptide–cage AcR4C, showing the decrease of fluorescence of the former with increasing amounts of the peptide–cage hybrid. Fitting of the fluorescence titration to a Hill model (KD = 189 nM).
