Interactions between collagen chains and fiber formation.

Abstract

The temperature-dependent dissociation of neutral salt-soluble collagen into its component chains was measured in 0.6-1.6 M urea solutions at pH 7.3. The temperature-dependent association of the same radioactively labeled collagen into fibers was measured in 0-0.4 M urea solutions, pH 7.3. The effect of urea on the temperature, Tm(G), for half dissociation into chains was small, and the value extrapolated to zero urea concentration was 39 degrees C. In contrast, the effect of urea on the temperature, Tm(F), for half association into fibers was large, and the value at zero urea concentration was 30 degrees C. We conclude that while body temperature provides excellent conditions for the matching of collagen chains to form molecules, the conditions are not optimal for the formation of highly ordered fibers. The large effects of 0.1 M urea suggest that other factors in vivo may help to destabilize mismatched molecular association during fiber growth. Alternately this might be facilitated by parts of the extension peptides of procollagen.