RESUMEN
Gel filtration of type I collagen has been of limited use, because at low pH where the protein is not associated it binds to agarose gels, and at neutrality collagen has a tendency to form fibrils. The more porous polyacrylamide-based gels do not interact with collagen but cannot be used at very high flow rates because they are compressible. It was found that these difficulties are surmounted by use of Fractogel TSK HW-65F, a spherical gel made from a weakly hydrophilic vinyl polymer, and use of the buffer system 0.5 M urea, 0.117 M Tris-HCl, pH 7.3, which prevents fibril formation. The solvent has only a slight effect on the thermal stability of collagen, as determined by circular dichroism measurements. The recovery of native collagen, at 25 degrees C, was at least 88% and that of partially unfolded collagen, at 35 degrees C where it is about one-third unfolded, was 98%. The Fractogel TSK gels and the urea, Tris solvent system should be useful for both preparative work and for studies involving interaction of unaggregated type I collagen with smaller molecules at physiological pH.
