Abstract
The binding of a colloidal gold-Concanavalin A (ConA) complex to the plasmalemma of tobacco leaf protoplasts has been investigated using scanning electron microscopy. At 5° C the particles of gold-ConA appear to be randomly distributed over the surface of the protoplast. If the temperature is raised, the particles associate into clusters. Saturation of the membrane with particles can only occur when the weight of ConA in solution exceeds 1 μg/104 protoplasts in suspension, and when its concentration exceeds 15 μg/ml. These results are discussed in terms of the properties of the ConA binding site and the mobility of such sites within the membrane surface.