Figure 1.

A, Photograph of a nonaqueous (heptane:tetrachloroethylene) gradient of lyophilized particles from soybean nodules. The approximate location of each of the 10 fractions is shown to the right of the photograph. The red color is due to Lb. B, The approximate density of the liquid associated with each fraction of the gradient that is shown in A. The gradient was poured onto a 4-mL cushion of tetrachloroethylene having a density of 1.64 g mL⁻¹, and the sample was loaded in a heptane:tetrachloroethylene mixture having a density of 1.23 g mL⁻¹.