Assembly and disassembly of tubular spherulites

Abstract

We report a higher-order assembly of lithocholic acid (LCA) into spherulites composed of a large number of well-defined tubules in aqueous solution at physiological pH of 7.5. Under a polarizing optical microscope, the tubular spherulites show a Maltese-cross extinction pattern. The disassembly of tubular spherulites by brief sonication leads to the formation of a large quantity of well-dispersed straight tubules with a crystalline wall and a narrow diameter distribution. We find that the tubules, which are organized in spherulites and dispersed in solution, show a pH-switchable shape transition.