X-Ray Diffraction Patterns from Reprecipitated Connective Tissue

For a number of years 1 it has been known that tendon gives excellent crystalline reflections. Recently 2 large spacings have been observed which provide strong evidence for the view that collagenous structures may be fibrous arrays of true crystals composed of very large molecules.

Most forms of tendon from adult animals cannot be put into solution without obvious chemical disintegration. The work of Nageotte and of others 3 has, however, demonstrated that optically active fibrous precipitates can be obtained from weakly acid solutions made from the tail tendon of adult rats and from many connective tissues of foetal animals. The optical appearance of these precipitates suggests that they are at least similar to the tissue from which they were dissolved. We have carried out a series of experiments to determine: (a) whether reprecipitated tendon is really crystalline and (b) whether its X-ray diffraction pattern is like that of the original tissue.

Reprecipitated connective tissue was obtained according to the procedures outlined by Nageotte. Pieces of freshly excised tail tendon from adult rats were placed in dilute (1 to 25,000) acetic acid. In such acid the tendon swells and a portion of it dissolves to form a clear but highly viscous solution. The reprecipitated tissue is obtained from this solution by salting out with 5% NaCl. Series of X-ray diffraction studies have been made of a number of these preparations. Some of these diffraction photographs were made with the usual short crystal-to-film distances; others were made with very small slit systems and with the large camera radii needed to record spacings of the order of 100 A.