Zeptoscale cell metabolism

A new assay allows scientists to analyze the metabolism of glycosphingolipids in single cells. The method could help biologists examine cell-to-cell diversity and metabolic regulation of these cell-surface molecules. Glycosphingolipids are molecules consisting of a saccharide head and a split lipid tail containing a sphingosine chain and a fatty acid side chain. One type of these molecules, called gangliosides, has up to four sialic acid groups attached to the head. Gangliosides make up a large fraction of the outer membrane of neurons. Tay-Sachs disease and other disorders are associated with problems in ganglioside metabolism. By replacing gangliosides' fatty-acid side chain with the fluorescent dye tetramethylrhodamine, a team led by Norman J. Dovichi of the University of Washington analyzed ganglioside metabolism in 54 individual cultured pituitary tumor cells, using capillary electrophoresis and laser-induced fluorescence (Anal. Chem., DOI: 10.1021/ac070716d). The team can detect at the low zeptomole (10^-21) level all metabolites that retain the dye.