Natural cell membranes grow during cell replication. Researchers have been able to make artificial membranes with similar capabilities by embedding a catalyst that promotes the synthesis of phospholipids in the bilayer structure of the membrane. As the membrane grows, though, the concentration of the catalyst decreases and the membrane loses the ability to grow further. Now, Neal Devaraj and colleagues at the University of California in San Diego have designed a catalyst that can self-synthesize, as well as catalyse the formation of phospholipids.
The researchers use a tertiary amine attached to three alkyl triazole arms. This compound can coordinate Cu+ ions. Once it does so, it becomes a dual purpose catalyst. On the one hand, it promotes self-catalysis from three alkyl azides and a tripropargylamine precursor. On the other hand, it can catalyse the formation of new phospholipids from an alkyl azide and a lipid precursor containing an alkyne linking group. Both reactions are catalysed through click chemistry, azide–alkyne reactions facilitated by the presence of the chelated Cu+ in the structure of the catalyst. Using this method, Devaraj and colleagues achieve sustained growth of their artificial membrane and observe new vesicle formation once a critical surface area is reached.