CALCIUM-CARBONATE FILMS AND HELICES GROWN IN SOLUTIONS OF POLY(ASPARTATE)

Addition of charged polypeptides, in particular poly(aspartate), to su persaturated solutions of calcium carbonate (CaCO3) leads to unusual m orphologies in the inorganic phase. The polymer causes deposition of C aCO3 films, which appear to act as membranous substrates that mediate the growth of CaCO3 crystals. Spherulitic vaterite aggregates with hel ical extensions, and distorted calcite crystals that contain spiral pi ts, have been produced. A correlation has been noted between the struc tures of the crystalline films and those of the crystal aggregates ass ociated with them: i.e. films of spherulitic texture yield electron di ffraction patterns characteristic of vaterite and support the growth o f spherulitic vaterite aggregates whereas calcitic single-crystal mosa ic films carry rhombohedral calicite crystals. These films and aggrega tes exhibit features reminiscent of the morphologies observed in bioge nic minerals. (C) 1998 Elsevier Science B.V. All rights reserved.