FIG. 2.

Electron microscopic image of recombinant B19-lacZ particles. The recombinant virions were purified on CsCl gradients, as described in Materials and Methods. Samples were negatively stained with 3% phosphotungstic acid (pH 6.5), and the particles were visualized at a magnification of ×80,000 with a Philips 400 electron microscope (bar = 80 nm).