X-Ray Diffraction as a Tool for Studying Collagen Structure
This chapter reviews the areas of collagen structure which have been analyzed by X-ray diffraction and to examine questions at various levels of connective tissue organization that may be resolved by X-ray studies. X-ray diffraction is a tool capable of determining structure from the molecular level to the tissue level in the hydrated state, but the usefulness of X-ray studies depends critically on the nature of the specimen. Collagen molecules and fibrils have far less order than a single crystal, and, as a result, diffraction studies on connective tissue are used to suggest and refine structural models, rather than for direct calculation of molecular structure. Derivation of structural data from X-ray diffraction patterns of connective tissues requires considerable analysis. This analysis is often complemented with the direct visual observation of collagen fibrils using electron microscopy and with structural information from other sources, such as nuclear magnetic resonance spectroscopy and energy calculations.