The fibrous matrix of connective tissue collagen when acting as a support is reinforced and stabilized in many ways, including aldehyde-derived cross-links, mineralization, and bonding to non-collagenous matrix material. Disturbances of this reinforcement are extremely common and lead to serious pathology. Treatments for these collagen diseases are hampered by a lack of understanding of these stabilization mechanisms, which in turn is partly caused by the anatomical and biochemical complexity of mammalian tissue. We will study some relatively primitive connective tissues that appear to have unusual ways of stabilizing themselves to provide a rigid structure, and will serve as valuable models for the more familiar stabilization chemistry. This will be a multidisciplinary project combining X-ray diffraction, electron microscopy, and biochemistry. We will study shark fin elastoidin which is a complex of collagen and a proteinaceous tyrosine rich component (TRC). We will characterize the collagen chains and their cross-linking pattern, and the TRC structure. The nature of the collagen-TRC interaction and its relationship to mineralization and other forms of stabilization will be investigated. We will investigate the skeletal structures of several families of coral. One of these (gorgonian) contains a collagen of unusual spacing (360 A). We will develop models to explain this spacing. The other family (antipatheria) consists of chitin complexed with an unusual matrix which may be a pre-collagen. The matrix protein system, because of its high histidine content, may bear relevance to the structure of dental enamel. The interaction of the poly N acetyl glucosamine (chitin) with the protein matrix will be investigated. Results obtained throughout this project will be applied to appropriate mammalian systems.