IMPROVED VISUALIZATION OF FOLDED COLLAGEN ALPHA-CHAINS BY ULTRA-RAPIDFREEZING

Transmission electron microscopy techniques are commonly employed to e xamine the folded polymer structure of collagen polypeptides. These te chniques include deposition of a sample by spraying, slow freeze-fixat ion, air drying and vacuum drying the specimen at room temperature, an d using additives such as glycerol in the collagen preparation. Here w e report preliminary observations of type I collagen alpha-chains, fol ded in water, at a concentration of 35 mug ml-1 and 10 mug ml-1, visua lized 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 vo lumes 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 carbohydrate s).