Intracrystalline Protein Repeat Sequences: Structure and Function

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9901356EvansThe focus of this project is on an emerging area of biomolecular-based materials referred to as biomineralization, an organism-directed process which lead to the formation of composites - i.e., polymers in association with inorganic material. An interesting model system in biomineralization are sea urchins and sponges: in their embryonic stage, both organisms produce a calcium carbonate-based mineral structure known as the spicule. In sea urchins, the spicule begins as single crystal calcite, but develops an amorphous calcium carbonate phase which envelopes the calcitic phase. The amorphous phase then transforms into calcite as development proceeds. In sponges, the story is slightly different: some spicules are either entirely comprised of amorphous calcium carbonate, or, have a calcitic core which is surrounded by the amorphous phase. In both organisms, the inorganic matrix contains a protein-based, self-assembled matrix which runs parallel to the mineral phase. The proteins which comprise this matrix contains a protein-based, self-assembled matrix which runs parallel to the mineral phase, and are believed to stabilize the amorphous phase and/or manifest fracture-resistant or elastic properties. To understand how these proteins perform their functions, NMR and molecular modeling studies will be undertaken to determine the structure of sea urchin spicule matrix protein sequences, and, how these particular domains may either associate with each other, with the mineral environment, or, behave under force extension. The data obtained from these studies will not only help to understanding how biological self-assembly, inorganic phase stability, and fracture resistance occur within spicules, but will also lead to the development of a molecular blueprint for novel and versatile biomimetic-based materials. Educational goals within this project will include the development of multidisciplinary training programs for graduate and undergraduate students, as well as involvement of high school students in research projects which draw from the areas of biology, chemistry, and physics.In a quest for better materials that can be used in medicine, aerospace and manufacturing, scientists are now turning to Nature, where simple organisms, such as sea urchins and sponges, have developed way to generate structures that protect them from their environment. These structures involve naturally-occurring polymers that associate with inorganic-based materials like calcium carbonate. Our plan is to study these structures tat the molecular level. From these studies, new strategies will emerge for material processing, creating environmentally-friendly materials, and improving material properties such as fracture resistance or material stability.