. Author manuscript; available in PMC: 2010 Sep 30.

Published in final edited form as: Adv Drug Deliv Rev. 2009 Jul 20;61(11):940–952. doi: 10.1016/j.addr.2009.07.002

Table 3.

pH-responsive peptides.

Peptides	^*Motif trend	Properties	References
Leucine zippers	[abcdefg]_n a-g ≠ P. a = hydrophobic d = L e,g = charged n = 5,6	Acidic groups at ‘e’ and ‘g’ induce the formation of a rigid coiled coil structure at pH 4.5; but on increasing the pH (7–11) the structure disassembles.	[89,91,132,154]
Carboxymethyl poly(l-histidine)	[HOOCH₂C-His]_n	Cationic peptide polymer contains an imidazole ring and carboxymethyl group, which helps in conferring dual functionality to the polypeptide.	[137,138]
GALA peptide	WEAALAEALAE ALAEHLAEALAE ALEALAA	Changes conformation from a random coil to an amphipathic α-helix when pH is lowered from 7 to 5.	[91,134,135]
KALA peptide	WEAKLAKALAK ALAKHLAKALAK ALKACEA	Changes conformation from a random coil to an amphipathic α-helix when pH is increased from 5 to 7.5.	[136]

A=Alanine, E=Glutamic acid, H=Histidine, K= Lysine, L=Leucine, P=Proline, W=Tryptophan.