Determination of the direction of preferred orientation and the orientation distribution function of collagen fibrils in connective tissues from high-angle X-ray diffraction patterns

A quantitative technique is described for determining the direction of preferred orientation and the orientation distribution function of collagen fibrils in connective tissues from high-angle X-ray diffraction patterns. In principle, the direction of preferred orientation is parallel to the orientation of the meridian on the diffraction pattern; in practice, the orientation of the equator, which is perpendicular to the meridian and is more clearly defined, is used to deduce this direction. The angular dependence of the equatorial intensity distribution is measured at a convenient radius on a pattern. The same measurements are made on a pattern from elastoidin spicules, which consist of effectively perfectly oriented collagen molecules. Deconvolution of the former by the latter yields the orientation distribution function. This deconvolution is achieved in Fourier-transform space where the equivalent operation is simply division; inverse transformation yields the required result. Measurements and analysis were performed with a program written for the Joyce Loebl Magiscan Image Analysis System.