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.