X-Ray Scattering of Biomaterials

Abstract

Molecular structures of biomaterials have close relation to their functions. We are interested in how biological building blocks assemble into the structures of native biomaterials and the hierarchy of those structures. We tackled the problem mainly with X-ray diffraction experiments and developed a thorough analysis technique to assign the X-ray signals to protein secondary structures and chitin. Three different types of biomaterials were examined: vimentin fibres, squid pens, and human hair. In vimentin fibres, we found that the secondary protein structures play an important role in the strength of the fibres. In native squid pens, we found a self-similar, hierarchical structure from millimetres down to nanometres. In human hair, we compared the signals corresponding to keratin proteins, intermediate filaments, and lipids between different subjects, and found small deviations. The structures of these three biomaterials, which encompass different orders of length scales, were described both quantitatively and graphically. We hope that this work will eventually allow us to understand how and why nature builds biomaterials this way.