Some properties of neutral-salt-soluble collagen. 2

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Abstract
Fibers formed from concentrated solutions of fraction B of neutral-salt-soluble collagen by salting-out had the typical striated appearance of collagen fibers in the electron microscope. No fibers were formed on warming enriched solutions of fraction B in 0.067 [image]-phosphate buffer, pH 7.4, although the collagen concentration was several times as great as concentrations at which fraction A forms fibers under these conditions. Solubility properties of fraction A varied considerably with temperature in the range 27-37[degree], and were not those of a single Phase-Rule component. At pH 3.7 the specific optical rotation of fraction B varied with temperature (0 37[degree]) whereas those of fractions A and C did not. The polarimetric behaviour of solutions of neutral and acid-soluble collagen were identical on varying the temperature at pH 3.7. Conversion into gelatin was rapid at 39.5[degree]. The glycine of fractions A, B and C had identical specific radioactivities in samples isolated from guinea pigs 6 hr. after injection of [C14] glycine. The rate of precipitation of neutral-salt-soluble collagen varied directly with pH in the range pH 6.5-7.4. The activation energy was about 80 kcal./mole/degree at pH 6.8. The temperature-dependent-solubility behavior of neutral-salt-soluble collagen and the nature of fractions A, B and C are discussed.