Solubilization of collagen from bovine articular with pepsin requires the preliminary extraction of proteoglycans from the ground substance. Biochemical and physiochemical properties of this pepsin-solubilized collagen are independent of the pretreatment (extraction with 1.5M-CaCl2, 5M-guanidinium chloride or 0.2M-NaOH) and of the age range (2-4-year-old and 2-month-old animals). Characterization of the de-natured components, of the CNBr peptides and of the amino acid and cross-link composition shows that the collagen of the hyaline cartilage is all type II. Electrical birefringence measurements showed the presence of tropocollagen molecules (length 280nm) and molecules whose length is slightly less than twice that of the tropocollagen molecules. This latter molecule may be a dimer composed of two monomers linked by intermolecular head-to-tail bonds and whose theoretical length (530nm), according to the quarter-stagger theory, is in good agreement with our measured values (510-530nm). We have verified that the beta-components of this collagen are formed of two alpha-chains linked by the stable intermolecular bond, dehydrodihydroxylysinonorleucine. These dimeric molecules are absent from solutions of skin collagen whose beta-components possess only aldol-type intramolecular cross-links. Although reconstituted fibres from solutions of skin and cartilage collagen are similar, the segment-long spacing crystallites formed with pepsin-solubilized cartilage collagen present a symmetrical and dimeric form corresponding to the lateral aggregation of two monomers with an overlap (90nm) of the C-terminal ends.
