Modulating the sensory response of a conjugated polymer by proteins: an agglutination assay for mercury ions in water.

The complexes of a carboxylate-substituted poly(para-phenyleneethynylene) (PPE) with histone, bovine serum albumin, and papain were investigated. At higher concentrations, the proteins have a significant effect on the emission characteristics of the PPE. The electrostatic complexes formed from the PPE, and the proteins are agglutinated by different metal cations. The observed selectivities and sensitivities of these simple systems are most unusual; combination of the carboxylate-PPE and commercially available papain forms an electrostatic complex that is precipitated by mercury ions at concentrations above 10-5 mol L-1.