The SnAvi-tag is a novel in-vivo fluorescent tag combining several features to allow for tandem-purification, western blotting and in-vivo subcellular localization of proteins fused to it. It has been shown to work in expression systems as diverse as C. elegans, E. Coli and vertebrate cells. For further information see Schäffer et al., Nucleic Acids Res. 2010 Jan 4: SnAvi–a new tandem tag for high-affinity protein-complex purification (PMID: 20047968)