The visualization of individual collagen molecules and aggregates in collagen solution: The effect of preparation and sampling techniques

The use of electron microscopic observations to characterize the state of aggregation of collagen molecules in solution has been examined from the point of view that the observed structures must be compatible with the physical chemical properties of the solution. The common procedure of addition of droplets of a collagen solution to a grid followed by negative staining produces aggregates on the grid which could not have represented the aggregation state in solution. Closer representation of fibril diameters can be achieved by freeze cleave-etch methods. The best representation of the state of aggregation in collagen solutions can be achieved by use of a careful drop-washing procedure. This procedure, described in detail, permits correlation between intrinsic viscosity and electron microscopic observations.