Factors Affecting the Interactions of Collagen Molecules as Observed by in Vitro Fibril Formation

Abstract

The interaction between acid-soluble collagen and pepsin-treated collagen during the course of fibril formation in vitro was examined. The apparent rates of fibril formation from acid-soluble collagen and pepsin-treated collagen increased as the initial concentration of collagen was raised. However, when the total collagen concentration was increased by the addition of pepsin-treated collagen to a solution of acid-soluble collagen whose concentration was kept constant, the rate of fibril formation was reduced in 0.15 m phosphate buffer (pH 6.8). It was thus suggested that the added pepsin-treated collagen interacted with the acid-soluble collagen as a “competitive” inhibitor of fibril formation under the conditions employed. Based on these and other observations, the following model was suggested for the process of collagen fibril formation. Collagen molecules in solution interact with one another to produce a loosely bound aggregate which is then transformed gradually to another aggregate (nucleus). The nucleus thus produced is capable of binding other collagen molecules to complete the fibril formation. This model is consistent with that proposed by Wood in that the rate of fibril formation is controlled by the incorporation of a collagen molecule to a growing fibril but not by the diffusion of a collagen molecule onto the surface of the fibril.