Improved visualization of folded collagen alpha-chains by ultra-rapid freezing

Transmission electron microscopy techniques are commonly employed to examine the folded polymer structure of collagen polypeptides. These techniques include deposition of a sample by spraying, slow freeze-fixation, air drying and vacuum drying the specimen at room temperature, and using additives such as glycerol in the collagen preparation. Here we report preliminary observations of type I collagen alpha-chains, folded in water, at a concentration of 35 micrograms ml-1 and 10 micrograms ml-1, visualized by an ultra-rapid, freeze-fixation technique designed to minimize structural deformation caused by spraying, additives and poor freeze-fixation. The technique also allows the use of submicrolitre sample volumes of known concentrations with negligible loss and shearing, while at the same time providing excellent contrast to the collagen polymer for electron microscopy. This technique can be employed to study the structure of a wide range of macromolecules (proteins and carbohydrates).