Reaction Patterns Revealed In 3-D

A research team at Brandeis University has observed three-dimensional reaction-diffusion patterns, known as Turing patterns, in a model chemical system for the first time (Science, DOI: 10.1126/science. 1200815). The Turing model, developed in the 1950s, describes how diffusing, interacting species create specific spatial cell patterns during processes such as embryonic development. Until now, only 2-D patterns have been measured for chemical and biological systems. Using absorption tomography, Irving R. Epstein and coworkers visualized 3-D patterns in a microemulsion-based Belousov-Zhabotinsky oscillating redox reaction. The researchers mixed aqueous malonic acid, sodium bromate, sulfuric acid, and the iron redox indicator ferroin with a surfactant and cyclooctane in a capillary to create the microemulsion. During the redox reaction, fast-diffusing nonpolar intermediates communicate between the slow-diffusing droplets containing ferroin, which is detected by absorption imaging. By controlling the initial concentrations of the reactants, the team created cylindrical, labyrinthine, and other motifs that demonstrate the importance of dimensionality and starting conditions on pattern formation. Although 3-D Turing patterns have yet to be reported for biological systems, the researchers suggest it could happen soon for lab studies on processes such as skeletal formation.