Antibody-Stilbene Interactions Illuminated

When the antibody EP2-19G2 hooks up with the molecule trans-stilbene, the resulting complex produces a bright blue luminescence, a feature that has been exploited to create biosensors. Scientists had attributed the complex's blue light to stilbene fluorescence. A team led by Richard A. Lerner of the Scripps Research Institute has now shown that the blue emission comes from a charge-transfer-excited complex of an anionic stilbene and a cationic, parallel π-stacked tryptophan residue (Science 2008, 319, 1232). By mutating specific residues on the antibody, Lerner's team found that a tyrosine plays an essential role in forming this complex by pressing the stilbene against the tryptophan. They also found that the stilbene penetrates deeply into the antibody's ligand-binding pocket. This is in contrast to other, shallower binding antibody-stilbene complexes, which produce green or purple light from fluorescence. The researchers suggest that programming charge-recombination-induced luminescence into other antibody-chromophore complexes could lead to further biosensing applications.