High-efficiency fluorescence quenching of conjugated polymers by proteins

The fluorescence of the water-soluble anionic conjugated polymer, poly[lithium 5-methoxy-2-(4-sulfobutoxy)-1,4-phenylenevinylene] (MBL-PPV), is quenched in dilute aqueous solution by cytochrome c, a small, naturally occurring electron-transfer protein. The large value obtained for the Stern-Volmer constant (K(sv) = 3.2 x 10(8) at pH 7.4, and approximately 10(9) in acidic solutions) is attributed to a combination of two factors: (1) facile ET between the luminescent semiconducting polymer and the protein and (2) the Columb attraction between the oppositely charged polyelectrolytes. This system shows significant potential for biosensor applications.