Slide this way

When cells of the slime mold Dictyostelium sense cAMP, they get the urge to merge, steering toward the source of the chemical and fusing into a slimy blob. By observing labeled cAMP receptors on traveling slime mold cells, Masahiro Ueda (Osaka University, Osaka, Japan) and coworkers were able to document differences in receptor activity between the “front” and “back” ends. The paper marks one of the first uses of a new technique for resolving and monitoring individual molecules.

To label the individual cAMP receptors, the authors fused cAMP molecules to an orange fluorescent dye called Cy3 and thenexposed the slime mold cells to the compound. Using a total internal reflection fluorescence microscope, they could track and count the receptors on the cell surface that had bound to the glowing cAMP. “This technique can reveal the...