The Professor of Zhejiang University found the Molecular Switch of Shell Molt
2009-12-08 |
As we all know, the cicada leaves its dry shell behind. Actually many animals have the ability to come out of their shells. The research group led by Prof. Ruikang Tang from Department of Chemistry, Zhejiang University, who is Appointed Professor of Chang Jiang Scholars Program, discovered that the process of shell molt was determined by switch signals. The mineral conserved in the body was prepared for the new shell under the switch-off signal; on the switch-on signal occurring, the new shell generated rapidly. This discover provided a sample for further research on bionic control function to make the biomaterial production controllable.
On December 7th, the related thesis < Magnesium-aspartate-based Crystallization Switch Inspired from Shell Molt of Crustacean > was published on the Proceedings of the National Academy of Sciences.
The group selected the Armadillidium vulgare, one kind of common crustacean, as the living model. The Armadillidium vulgare molts its shell for several times during its whole life. The previous studies revealed that calcium carbonates prepared for the new were in amorphous state before the shell molt; with the help of the magnesian ions, these unstable calcium carbonates were kept in metastable condition, which could be conserved in the organism, to generate the new shell rapidly. The whole preparation lasted for 2 weeks. However, it was still a secret for the scientists how the animals activated the shell molt precisely to turn the mineral from metastable condition to crystallization in a short time.
The group found the switch signal. Through studying on the Armadillidium vulgare in the shell molt, they found that the protein rich in acidicamino acid such as aspartate was another key signal. It played an important role in activating the shell molt to turn the mineral into crystallization so that the new shell could be created in only a few hours under natural conditions.
“In fact both the magnesian ions and the acidic protein acted as the switches.” Prof. Ruikang Tang explained, “The shell molt was a kind of crystallization. The mineral went through the non-steady state, the metastable condition and the stable state. As a switch-off signal, the magnesian ions stopped the crystallization to prolong the non-crystalline state temporarily; while the acidic protein as the switch-on signal terminated the non-crystalline state to stimulate the crystallization.” The group successfully demonstrated the switches of the magnesian ions and the acidic amino acid in the laboratory and proved that the principle also existed in calcium phosphate, which applied universally.
Ruikang Tang said that this discover inspired people to create a bionic switch so that the synthesis of the biomaterial could be more controllable and the biomaterial with various structures, shapes and functions could be more easily produced. The switch principle could be further used in the mineralization control of human body such as the formation of the bone or teeth, and pathologic formation like calculus or angiosteosis.
Prof. Ruikang Tang has been devoted to bio-mineralization research for a long time and has invented a method to dress a cell. In 2008 he successfully put a shell on a yeast cell. The recent research found a way to dress prettier. The bio-mineralization is the process by which living organisms produce minerals. The model of bio-mineralization in human body includes the formation of bones and teeth. The common biogenic minerals have coral, shell, pearl, etc.
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