Osteogenesis imperfecta: An x ray fibre diffraction study

The use of x ray fibre diffraction to study the molecular architecture of healthy and diseased human tendon is described. The three dimensional structure of human (finger) tendon is derived to high resolution and is shown to be very similar to that reported for rat tail tendon. In particular the presence of a 38 Å row line in the diffraction pattern suggests that a high degree of lateral order within the collagen fibrils is a more widespread feature of tendon tissue than was formerly realised. Axially projected electron density maps of the 670 Å unit repeat of the collagen fibrils of this tissue, and of tendon tissue from three cases of osteogenesis imperfecta (OI), are calculated and compared. The results are in agreement with recent biochemical studies in suggesting that type I (Sillence) OI is principally a quantitative, rather than a qualitative, defect of type I collagen biosynthesis. The features by which a molecular lesion may be recognised and characterised from diffraction data are discussed.