Chemical hydrolysis of DOTAP and DOPE in a liposomal environment

In this study the hydrolysis kinetics of 1,2-dipalmitoyl- sn-glycero-3-phosphocholine (DPPC), 1,2-dioleoyl- sn-glycero-3-phosphoethanolamine (DOPE) and 1,2-dioleoyltrimethylammoniumpropane (DOTAP) in net neutral DPPC–DOPE (3:1, mol/mol) and cationic DOTAP–DOPE (1:1, mol/mol) liposomes are described. The log k obs–pH profile for DOTAP–DOPE liposomes differs markedly from earlier observed hydrolysis profiles: the slope approaches zero in the acidic region and +1 in the alkaline region. The concept of amine-influenced hydrolysis is introduced to explain the lack of pH dependency in the acidic region of the log k obs–pH profiles.