Collagen - Imaging of large rod-like molecules with Atomic Force Microscopy
Collagen for medical use is commonly produced by digestion of bovine skin. This soluble collagen consists of individual "monomers", longer chains (dimers and higher oligomers) and fragments. In the US, Federal regulators require that the consistency of this mix be documented and controlled. One medical use of purified collagen monomers is to plump up the skin (remove wrinkles).
One way to characterize materials such as collagen is by using Atomic Force Microscopy (AFM). Individual molecules can be seen and measured and whether the molecule is a fragment, monomer, dimer, or higher oligomer can be determined from the length and geometry. Monomers are nominally 280 nm long. Fragments will be shorter. Dimers and higher oligomers may be linear, branched or looped. By using AFM to take images of batches of collagen molecules and measure the molecules within them, one can provide an independent check on other quality assurance techniques, ensure compliance with Federal regulations, and produce better quality materials.
|
Individual collagen molecules deposited on freshly cleaved mica from an aqueous suspension form wormlike patterns. 2 micron scan. |
The collagen molecules, or "monomers", shown here are composed of
three polypeptide chains which are arranged in a triple helix. In the
body, collagen monomers aggregate in a staggered manner with a longitudinal
offset of ca. 67 nm to form fibrils and fibers. These structures are the
predominant matrix in tissues such as skin, tendon and bones. To read more
about Collagen, a good place to start is:
Karl A. Piez, "Collagen" in "Encyclopedia of Polymer Science and
Engineering", John Wiley, New York, 1985
updated 04/09/2007