ABSTRACT
The native collagen fractionation schemes described which separate the various interstitial collagen types are relatively independent of the methods of solubilization. The solubilities of the various collagens are sufficiently different from each other that effective procedures have been devised which accomplish relatively rapid fractionation from bulk solutions. The preferential solubilization of precipitated collagens by solutions of varying ionic strengths has been adapted by Ehrlich for rapid separation of collagen mixtures. Denatured collagen fractions recovered from either molecular sieve or ion exchange chromatography will renature upon dialysis at low temperature and can be precipitated at low ionic strengths. Chromatography of native collagens on ion exchange resins has been used to separate procollagens, especially pro-Type I from pro-Type III and pepsin-solu-bilized Types IV and V. In general, native collagen molecules at 4°C are soluble below pH 5 only if the ionic strength of the solvent is low, whereas above pH 5, a moderate ionic strength is necessary.
