Assembly of Collagen Fibrils on Mica
Collagen is the most abundant protein found in humans and other animals. It assembles in vivo into hierarchical structures found in numerous tissues. In addition, it is widely used to create substrates and 3D scaffolds in vitro for cell and tissue culture. Hence, understanding the mechanism of collagen self-assembly has both fundamental and practical importance.
The results shown here were obtained on a Cypher VRS video-rate AFM. Briefly, the movie begins with images of bare mica in buffer obtained in tapping mode at a line rate of 400 Hz with 512×256 pixels for a frame rate of 1.5 frames/second (fps). The movie here is played back at 15 fps, i.e. 10× the acquisition rate. A dilute solution of collagen molecules is added. The three steps of assembly are captured:
- Adsorption of highly mobile collagen molecules on mica within several seconds after injection
- Nucleation of poorly ordered structures through the spatial fluctuations, interaction and aggregation of adsorbed collagen molecules
- Growth of fibrils exhibiting the D-band structure by attachment of collagen monomers as well as merging of small nucleated collagen aggregates
Samples provided courtesy of Jinhui Tao and Jim De Yoreo, Pacific Northwest National Laboratory.
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Run Time - 1:59