Membrane vesicles of cellular dimensions fit in two geometric series.

Preparations of basal-lateral plasma membranes from rat intestinal epithelial cells were analyzed with the analytical centrifuge. In these preparations a number of well-defined membrane fractions were observed. The particle weights of these fractions appear to fit in two geometric series. Until now only relatively small vesicles up to a diameter of about 1 micron were observed. In our preparation we have observed vesicles up to a diameter of 7.5 microns. Therefore, even vesicles with the same size as the plasma membranes of intact cells fit in the two geometric series.