One fusion protein, many labels: promega and covalys create multifunctional tagging systems.(Tools & Tech)

Have you ever needed a red fluorescent version of a protein, but only green was available? Promega (www.promega.com) of Madison, Wis., and Swiss company Covalys Biosciences (www.covalys.com), have developed methods to tag proteins with a wide range of fluorescent dyes (and other ligands) by first fusing a protein of interest to a generic, nonfiuorescent protein "handle." The handle binds covalently to an adapter on the ligand, linking the protein to the tag.

"You do only one cloning to get the fusion protein and then you expose the cell to different [ligands]," explains Covalys spokesperson Tom Gibbs, "whereas you have to reclone to get a different fusion protein for …