Incorporation of 2,3-diaminopropionic acid into linear cationic amphipathic peptides produces pH-sensitive vectors.
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 pK(a) of the beta-NH(2) 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 pK(a) 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.
Lan
Yun
Y
King's College London, Pharmaceutical Science Division, 150 Stamford Street, London, SE1 9NH, UK.
Langlet-Bertin
Bérangère
B
Abbate
Vincenzo
V
Vermeer
Louic S
LS
Kong
Xiaole
X
Sullivan
Kelly E
KE
Leborgne
Christian
C
Scherman
Daniel
D
Hider
Robert C
RC
Drake
Alex F
AF
Bansal
Sukhvinder S
SS
Kichler
Antoine
A
Mason
A James
AJ
D000595:Amino Acid Sequence; D002460:Cell Line; D002942:Circular Dichroism; D011992:Endosomes / Q000378:metabolism; D018014:Gene Transfer Techniques; D006801:Humans; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry*; D015091:beta-Alanine / Q000031:analogs & derivatives* / Q000737:chemistry
D010455:Peptides; D015091:beta-Alanine; C011757:2,3-diaminopropionic acid