UNCORRECTED PROOF 1 2 Anisotropic lattice distortions in biogenic calcite induced by 3 intra-crystalline organic molecules 4 Boaz Pokroy a, * , Andrew N. Fitch c , Frederic Marin d , Moshe Kapon b , Noam Adir b , 5 Emil Zolotoyabko a 6 a Department of Materials Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel 7 b Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 32000, Israel 8 c European Synchrotron Radiation Facility, BP 220, 38043 Grenoble Cedex, France 9 d Laboratoire de Bioge ´osciences, UMR CNRS 5561, Universite ´ de Bourgogne, 6 Bd. Gabriel, 21000 Dijon, France 10 Received 27 January 2006; received in revised form 16 March 2006; accepted 17 March 2006 11 12 Abstract 13 We have performed precise structural measurements on five different calcitic seashells by high-resolution X-ray powder diffraction on 14 a synchrotron beam line and by laboratory single crystal X-ray diffraction. The unit cell parameters a and c of biogenic calcite were found 15 to be systematically larger than those measured in the non-biogenic calcite. The maximum lattice distortion (about 2 Æ 10 3 ) was detected 16 along the c-axis. Under heat treatment above 200 °C, a pronounced lattice relaxation was observed, which allowed us to conclude that 17 anisotropic lattice swelling in biogenic calcite is induced by organic macromolecules incorporated within the single crystal calcitic prisms 18 during biomineralization. This conclusion is supported by the results of crystallization experiments in the presence of specific protein 19 extracted from one of the shells. 20 Ó 2006 Published by Elsevier Inc. 21 Keywords: Biomineralization; Biogenic crystals; Calcite; X-ray diffraction; Synchrotron radiation; Crystal growth and nucleation; Intra-crystalline 22 organic molecules 23 24 1. Introduction 25 Organisms produce a large number of minerals in the 26 course of biomineralization (Lowenstam and Weiner, 27 1989; Mann, 2001; Meldrum, 2003; Weiner and Addadi, 28 1997). These biogenic minerals have been extensively stud- 29 ied because of their fascinating mechanical (Currey, 1976; 30 Kamat et al., 2000; Mayer, 2005; Pokroy and Zolo- 31 toyabko, 2003), optical (Aizenberg et al., 2001) and mag- 32 netic (Sparks et al., 1990) characteristics and due to the 33 capability of living organisms to effectively control the 34 polymorph selection (Falini et al., 1996; Gotliv et al., 35 2003) and crystal morphology (Aizenberg et al., 1995a, 36 1996; Albeck et al., 1993, 1996b; DeOliveira and Laursen, 37 1997; Heywood et al., 1990). Calcium carbonate, CaCO 3 , 38 is by far the most abundant biogenic mineral (Lowenstam 39 and Weiner, 1989; Mann, 2001; Weiner and Addadi, 1997), 40 which exists in different structural forms (listed in the order 41 of descending thermodynamic stability at normal condi- 42 tions): calcite, aragonite, vaterite, and amorphous calcium 43 carbonate. 44 Calcite, which is stable at room temperature and atmo- 45 spheric pressure, is deposited by various organisms such as 46 echinoderms, molluscs, brachiopods, octocorals, sponges, 47 foraminifera, and coccolithophorid algae (Weiner and 48 Addadi, 1997). It has been shown, that biogenic calcite is, 49 in fact, a nano-composite, containing intra-crystalline mac- 50 romolecules within single crystals (Towe and Thompson, 51 1972). This conclusion is deduced from growth experiments 52 in which macromolecules extracted from single crystals of 1047-8477/$ - see front matter Ó 2006 Published by Elsevier Inc. doi:10.1016/j.jsb.2006.03.008 * Corresponding author. Fax: +972 4 8295677. E-mail address: bpokroy@tx.technion.ac.il (B. Pokroy). www.elsevier.com/locate/yjsbi Journal of Structural Biology xxx (2006) xxx–xxx Journal of Structural Biology YJSBI 5040 No. of Pages 8; 4c: 5; Model 5+ 20 April 2006 Disk Used Anand (CE) / Gnanasekar (TE) ARTICLE IN PRESS