Precise determination of the helical repeat of tobacco mosaic virus.

ABSTRACT

Tobacco mosaic virus (TMV) is widely used as a distance standard in electron microscopy, fiber diffraction, and other imaging techniques. The dimension used as a reference is the pitch of the viral helix, 23 A. This distance, however, has never been measured with any great degree of precision. The helical pitch of TMV has been determined to be 22.92+/-0.03 A by X-ray fiber diffraction methods using highly collimated synchrotron radiation.