The Precipitation of Segmented-Long-Spacing Collagen by Inorganic Triphosphate and Perdisulphate Ions

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Abstract
Triphosphoric acid and perdisulphuric acid are both effective in inducing the formation of segmented-long-spacing (SLS) collagen (in which tropocollagen macromolecules occur in parallel non-staggered array). The conditions under which large, well-formed segments can be obtained have been characterised. The segments so obtained are identical in all observable features to one another and they are also identical to segments formed when ATP is used as the inducing agent. It is concluded that the staining pattern (after exposure to heavy metal ions) reflects the distribution of polar groups in a tropocollagen macromolecule and is not significantly influenced by the inducing agent. The greater stability of triphosphoric acid makes it a more convenient reagent than ATP. Segments form more slowly in perdisulphuric acid. The conditions to be satisfied by the inducing agent appear to be a central backbone of positive charge surrounded by an elongated cloud of strongly negative charge, capable of linking like positively charged features of adjacent macromolecules in accurate transverse register.