102505 - BE.342/442 Tuesday, October 25, 2005 Topic:...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
BE.342/442 Tuesday, October 25, 2005 Topic: Biomineralization: Bones and Teeth Bones Bones and teeth can be mineralized and fossilized. The insoluble calcium and bones and teeth is held together with proteins, the crystal structure of which is not entirely known. Read “The Material Bone: Stucture-Mechanical Function Relations” by S. Weiner and H. D. Wagner, on the course website. This article discusses the structures found within bone proteins. The mineralized collagen fibrils of bone have highly complex structures described in terms of up to 7 hierarchical levels of organization. The materials have evolved to fulfill a variety of mechanical functions. The article discusses structure-mechanical relations at each of the hierarchical levels, and discusses gaps in present knowledge and potential for novel discoveries. The Young’s modulus of bone increases with calcium content – so calcium content is important for strength, but the structure is mediated by proteins in the extracellular matrix of bone. The 7 hierarchical levels span from the components of collagen fibrils to the whole bone. Level 1: Components, including proline and hydroxyproline. Level 2: Mineralized collagen. Level 3: Arrays of fibers. Level 4: Fiber array patterns, e.g., spirals that may remind you of alpha-helical structures! Level 5: Osteons: cylindrical motifs in bone structure Level 6: Spongy vs. compact bone Level 7: Whole bone Comparison of human, baboon, cow, and rat bones have been studied by means of SEM micrographs of lamellar fracture surfaces. These do not highlight the differences very clearly: clearly the hierarchical varies are quite complex and span a wide range of length scales. A closer view of the scaffold in a bone reveals porous fibers. On the scale of a few hundred nanometers, bones can be observed and analyzed using x-ray diffraction. The diffraction rings at this resolution can reveal the distance between collagen bundles, but little other information. Collagen bundles can organize into parallel groups, interwoven fiber structures, plywood-like
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 4

102505 - BE.342/442 Tuesday, October 25, 2005 Topic:...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online