Turbidity measurements in an analytical ultracentrifuge. Determinations of mass per length for filamentous viruses fd, Xf, and Pf3.

An analytical ultracentrifuge has been used to measure light-scattering intensities by the transmittance method. The technique, which is applicable to particles of many sizes and shapes, has the principal advantage that samples can be kept free of dust during the measurements. Also, sample volumes are small, and the scanner and interference optics can be used simultaneously to obtain, for a given sedimenting boundary, turbidity steps at different wavelengths and the concentration step. In the present application the data yield mass per length estimates for three filamentous viruses, 19 100 daltons/nm for fd, 19 600 daltons/nm for Pf3, and 19 100 daltons/nm for Xf.