A new fluorescence-based, hydrophobic photolabeling technique for analyzing membrane-associated proteins

We introduce a new, fluorescent and photoactivatable fatty acid derivative (SANU) for hydrophobic labelling of membrane-bound proteins. The technique allows fast and highly sensitive screening of hydrophobically inserting proteins analyzed by SDS-PAGE with a detection limit below 0.1 pmol. A reliable calculation of labelling efficiencies is achieved by simultaneous densitometry of fluorescence and protein staining. We have applied the new technique on the membrane inserting protein talin, G-actin, and, as a negative control, on RNase, which only binds electrostatically to negatively charged lipid interfaces. In several ways superior to radiolabelling, we can recommend this technique for all laboratories under any circumstances.