title: X-ray diffraction effects related to superstructure in rat tail tendon collagen.
abstract: A number of unusual X-ray diffraction effects concerning the meridional low angle reflections of collagen are presented which are due to structural inhomogeneities in the 100 micron range within the tendon such as are expected to be associated with the planar crimp structure of tendon units. These newly observed effects provide diffraction confirmation for such a crimped morphology. The effects consist of splitting of the reflections both azimuthally and radially. Azimuthal split varied with rotation of the tendon unit around its own axis and is directly related to the existence of the crimp, its angle and planarity. Radial splitting is a consequence of the limited sampling of the micro-structure by the collimator, which provides further support for the crimp morphology and conveys added information about the crimp form. It is shown that this limited sampling can provide a kind of "micro-X-ray topography" technique for the study of micro-textures on the appropriate dimensional level, while ti could be the source of misrepresentation if its origin remains unrecognized. The effect of stretching is examined and interpreted in terms of crimp straightening. Simultaneous examination of medium angle equatorial reflections, when combined with some electron micrographs point to further issues concerning the relation between the large scale and fibril substructure. It is believed that the present findings have general implications for structure research on collagen.
mesh_terms: D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D003094:Collagen; D008854:Microscopy, Electron; D010772:Phosphotungstic Acid; D051381:Rats; D013623:Tail; D013710:Tendons / Q000648:ultrastructure; D014501:Uranium; D014961:X-Ray Diffraction / Q000379:methods
chemical_list: D010772:Phosphotungstic Acid; D014501:Uranium; D003094:Collagen