Properties of the organic matrix of bone as well as its function in the microstructure could be the key to the remarkable mechanical properties of bone. Previously, it was found that on the molecular level, calcium-mediated sacrificial bonds increased stiffness and enhanced energy dissipation in bone constituent molecules. Here we present evidence for how this sacrificial bond and hidden length mechanism contributes to the mechanical properties of the bone composite, by investigating the nanoscale arrangement of the bone constituents and their interactions. We find evidence that bone consists of mineralized collagen fibrils and a non-fibrillar organic matrix, which acts as a 'glue' that holds the mineralized fibrils together. We believe that this glue may resist the separation of mineralized collagen fibrils. As in the case of the sacrificial bonds in single molecules, the effectiveness of this mechanism increases with the presence of Ca2+ ions.

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With the development of atomic force microscopes that allow higher scan speeds, the need for data acquisition systems ͑DAQ͒ that are capable of handling the increased amounts of data in real time arises. We have developed a low cost data acquisition and scan control system around a commercially available DAQ board in a WINDOWS environment. By minimizing the involvement of the processor in the data transfer using direct memory access, and generation of the scan signals synchronously with the data acquisition, we were able to record 30 frames per second with a pixel resolution of 150ϫ 150 pixels and 14 bit per channel.

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