Chemical Waves and Pattern Formation in the 1,2- Palmitoyl-sn-glycero-3-phosphocholine/Water Lamellar System

The Belousov Zhabotinsky (BZ) reaction-diffusion system is the most famous example of oscillating chemical reactions. Recently, compartmentalization within microemulsion droplets showed that peculiar patterns, as striped standing waves and Turing structures can be generated by the coherent coupling of independent oscillator. In this work we studied a BZ reaction, carried out in the 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)/water system, which presents layered aqueous domains separated by lipid bilayers. Phosphatidylcholines are the major components of biological membranes, and are generally used as models for cell plasma membranes. The structural properties of our system were investigated by small-angle X-ray scattering, showing that a lamellar structure was maintained in the presence of the BZ reactants. The obtained chemical waves were found to depend on the DPPC content. In particular, a variety of interesting patterns such as stationary Turing-like labyrinthine structure were observed in the range [DPPC] = 10-25%. For lower DPPC content only traveling waves and pacemaker structures were obtained, whereas at lipid concentrations higher than 30% w/w no waves were observed. In all the investigated systems patterns started at the edge of the Petri dish used as reactor.