Human X- and Y-bearing sperm differ in cell surface sialic acid content.

Analysis of cell surface charge of human sperm by means of free-flow electrophoresis revealed that the electrophoretic mobility of X-bearing sperm was faster than that of Y-bearing sperm, indicating that X-bearing sperm have a higher net negative charge on the cell surface than do Y-bearing sperm. Sialidase treatment of X- and Y-bearing sperm caused an obvious and progressive reduction in the electrophoretic mobilities of the two types of cells, until they finally merged into a single peak. This observation suggests that the difference in net negative charge between X- and Y-bearing sperm is due mainly to sialic acid content on the cell surface.