Zeta potential of human X‐ and Y‐bearing sperm

The zeta potential of human X- and Y-bearing sperm was measured by two different methods: (i) using an electrophoretic light scattering spectrophotometer, and (ii) using a laser-rotating prism. The X- and Y-bearing sperm were separated by free-flow electrophoresis, and their purities were determined by staining for the F-body using quinacrine mustard. The zeta potential of the sperm in the fraction containing more than 80% Y-bearing sperm was approximately -16 mV, whereas that of sperm in the fraction containing more than 95% X-bearing sperm was approximately -20 mV. In other words, the net negative-charge on the cell surface of human X-bearing sperm is higher than that of Y-bearing sperm.