Light microscopy, electron microscopy, and X-ray diffraction analysis of glycerinated collagen fibers

Light microscopy, transmission electron microscopy (freeze-fracture replicas and thin sections), and X-ray diffraction techniques were used to investigate the structure of rat tail tendon collagen fibers subjected to one of the following treatments: water, phosphate buffer, glutaraldehyde, glutaraldehyde followed by glycerol, glycerol, and glycerol followed by phosphate buffer. As seen by light microscopy, only treatment with glycerol induces a remarkable swelling of the native (untreated) collagen specimens. Replicas and thin sections show that this swelling is due to an expansion of the interfibrillar space, and to a dissociation of the collagen fibrils into microfibrils. X-Ray diffraction analysis reveals great disorder in the glycerol-swollen collagen fibers. However, this does not appreciably involve the microfibrillar and molecular structure. Light and electron microscopy as well as X-ray diffraction techniques show that the collagen fiber swelling induced by glycerol is an almost completely reversible process.