SIMPLE PHYSICAL MODEL OF COLLAGEN FIBRILLOGENESIS BASED ON DIFFUSION-LIMITED AGGREGATION

Type I collagen is a rod-like protein which self-assembles in a regula r array to form elongated fibrils. The process of fibril formation, te rmed fibrillogenesis, is driven by the increase in entropy associated with loss of water from the bound monomers. A model based on diffusion limited aggregation (DLA) was used to investigate same of the mechani sms involved in this process. The aggregates created in the model disp layed several features in common with collagen fibrils including an el ongated morphology and a preference for tip growth. Analysis of these aggregates revealed a linear relationship between mass and distance fr om the tip, consistent with experimental observations. Intrafibrillar fluidity was introduced into the model by using a surface diffusion te rm. This led to the formation of aggregates with more compact morpholo gies. These results strongly implicate the role of diffusion limited g rowth in collagen fibril formation.