Applicability of agarose gel electrophoresis to the physical characterization of clathrin-coated vesicles

Agarose gel electrophoresis was found to be applicable to the physical characterization of clathrin-coated vesicles from bovine brain and rat liver. The vesicles from brain are smaller and, at pH 6.4, more highly charged than those from liver. Using a standard curve for spherical viruses, the mean radii of the brain vesicles averaged 40 +/- 3 nm for two preparations, and those of liver vesicles 53 +/- 5 nm. When the comparison between the two species is made within the same experiment, the size difference between rat liver-derived and bovine brain-derived clathrin-coated vesicles is significant at the 95% confidence level. The sizes are compatible with electron microscopy measurements. The mobilities (uncorrected for electroendosmosis), extrapolated to 0% agarose on the Ferguson plot, mu'0 (cm2/sec/V), were 0.76 +/- 0.04 for brain vesicles and 0.61 +/- 0.09 for liver vesicles. These are measures of the average surface net charge of the vesicles. The higher net charge of brain vesicles, compared to liver vesicles, is significant at the 95% confidence level whether the two species are compared intra- or interexperimentally. Charge differences between two different preparations from the same organ were significant at the 95% confidence level, while size differences were not.