Incorporation of 2,3‐Diaminopropionic Acid into Linear Cationic Amphipathic Peptides Produces pH‐Sensitive Vectors
- 7 June 2010
- journal article
- research article
- Published by Wiley in ChemBioChem
- Vol. 11 (9), 1266-1272
- https://doi.org/10.1002/cbic.201000073
Abstract
Nonviral vectors that harness the change in pH in endosomes, are increasingly being used to deliver cargoes, including nucleic acids, into mammalian cells. Here we present evidence that the pKa of the β‐NH2 in 2,3‐diaminopropionic acid (Dap) is sufficiently lowered, when Dap is incorporated into peptides, that its protonation state is sensitive to the pH changes that occur during endosomal acidification. The lowered pKa of around 6.3 is stabilized by the increased electron‐withdrawing effect of the peptide bonds, by intermolecular hydrogen bonding and from contributions arising from the peptide conformation. These include mixed polar/apolar environments, Coulombic interactions and intermolecular hydrogen bonding. Changes in the charged state are therefore expected between pH 5 and 7, and large‐scale conformational changes are observed in Dap‐rich peptides, in contrast to analogues containing lysine or ornithine, when the pH is altered through this range. These physical properties confer a robust gene‐delivery capability on designed cationic amphipathic peptides that incorporate Dap.Keywords
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