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. 2018 Jul 27;10(8):830. doi: 10.3390/polym10080830

Figure 2.

Figure 2

Design of pH-controllable cell-penetrating polypeptides (PCCPs), and proposed mechanism of pH-controllable helicity and selective cellular penetration. (a) Proposed mechanism of PCCP possessing a pH-activated cell-penetrating property exclusively at the tumor extracellular matrix. 2° and 3° indicate “secondary” and “tertiary”, respectively. (b) Schematic illustration of the PCCP undergoing pH-dependent conformational transition induced by the charge balances of two opposite ions. Reprinted permission from [11]. Copyright 2017, Elsevier.