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. Author manuscript; available in PMC: 2014 Jan 1.
Published in final edited form as: Wiley Interdiscip Rev Nanomed Nanobiotechnol. 2012 Sep 13;5(1):31–48. doi: 10.1002/wnan.1197

Figure 7.

Figure 7

Cellular uptake of a transportan-derived CPP was controlled by the pH-triggered ionization of histidine residues. Peptides whose cationic lysine residues were replaced with histidine residues (TH) exhibited low levels of cellular uptake, as measured by flow cytometry, in HeLa cervical cancer cells at pH 7.4 due to the neutral charge of the histidines at this pH. At pH 6.0 the ionization of the histidine residues conferred positive charge to the CPP and increased cellular uptake. This pH-triggered cellular uptake was in contrast to the original lysine-containing peptide (TK), which demonstrated equivalent cellular uptake at both pH 7.4 and 6.0. Reprinted with permission from Ref 85. Copyright 2011 American Chemical Society.