The sea urchin's crystal secret ------------------------------------------------------------------------ -------- Judy Siegel-Itzkovich, THE JERUSALEM POST Nov. 28, 2004 ------------------------------------------------------------------------ -------- The sea urchin has a lowly name, but its tough, brittle spines are an engineering wonder. Composed of a single crystal from base to needle-sharp tip, they grow back within a few days after being broken off. Now a team of scientists at the Weizmann Institute in Rehovot has an explanation for how they do it. While many crystals grow from component atoms or molecules that are dissolved in liquid - sugar and salt being the most familiar examples - professors Lia Addadi and Steve Weiner of the institute's structural biology department found that the sea urchin uses another strategy: The material that comprises the spines is first amassed in a non-crystalline form, called amorphous calcium carbonate (ACC). Packets of ACC are shoveled out of the cells surrounding the base of a broken spine and up to the growing end. Within hours of arriving in place, the amorphous material, which is composed of densely packed but disorganized molecules, turns to calcite crystal in which the molecules line up evenly in lattice formations. In addition to increasing scientific understanding of these species, the idea of growing single crystals by first creating the material in an amorphous phase might prove useful to material scientists and engineers wanting to produce and shape sophisticated synthetic materials that have the properties of crystals. Working with graduate students Yael Politi and Eugenia Klein, and Talmon Arad of the chemical research support unit, they used four different methods of investigation, including two kinds of electron microscopy, to look for the ACC as it was being deposited and turning to crystal. "The question," says Weiner "is why it is so difficult to observe a process that seems to be so basic. Scientists have been studying it for over a 100 years. In fact, because the ACC is a transient phase, we had to develop new methods to catch it while it exists." The captured images show microscopic needles that first grow straight out from the stump of the spine, and then branch out to form a lacy structure that is hard but light. The crystalline structure of the old spine provides the template for the alignment of the molecules, and thus controls the intricate yet precise growth pattern. Though previous studies by the Weizmann group have shown that the same strategy is used by immature sea urchins and mollusks in the larval stage to build internal skeletons, this is the first time the process was observed in adult marine animals. It is far from obvious that larvae and adult creatures would use the same methods; their lifestyles are very different, and this can translate into differences in biological processes. For instance, the tiny sea urchin larva is transparent and swims around, while the round, spiky adult lives on the sea floor. Because it works for both, Addadi and Weiner believe this method is probably a basic strategy used by not only close relatives of the sea urchin such as sea stars, but by a wide variety of spiny and shelled sea creatures like mollusks and corals. FRANCO-ISRAELI RESEARCH A cooperation agreement between the Hebrew University of Jerusalem and the French National Scientific Research Organization (Le Centre National de la Recherche Scientifique, or CNRS) has been signed via a video conference linking Jerusalem and Paris. The agreement will establish a joint lab for research in neurophysiology and neurophysics. The agreement represents a further effort by the governments and scientific communities of France and Israel to promote scientific cooperation. CNRS is a large basic research organization operating throughout France. Over 1,200 CNRS units are functioning in conjunction or association with institutes of higher education and other French research bodies. Sitting in the Mount Scopus campus, HU president Prof. Menachem Magidor was a signatory, while in Paris, the agreement was signed by CNRS director-general Dr. Bernard Larrouturou, president of the University of Bordeaux, Prof. Bernard Begaud and University of Paris president Prof. Jean-Francoise Dhainaut. ------------------------------------------------------------------------ -------- ------------------------------------------------------------------------ -------- This article can also be read at http://www.jpost.com/servlet/Satellite?pagename=JPost/JPArticle/ShowFull &cid=1101615858962&p=1091072353995 [ Back to the Article ] ------------------------------------------------------------------------ -------- Copyright 1995-2004 The Jerusalem Post - http://www.jpost.com/