Sensing of heavy metal ions by intrinsic TMV coat protein fluorescence

We propose the use of a cysteine mutant of TMV coat protein as a signal transducer for the selective sensing and quantification of the heavy metal ions, Cd²⁺, Pb²⁺, Zn²⁺ and Ni²⁺ based on intrinsic tryptophan quenching. TMV coat protein is inexpensive, can be mass-produced since it is expressed and extracted from E-coli. It also displays several different functional groups, enabling a wide repertoire of bioconjugation chemistries; thus it can be easily integrated into functional devices. In addition, TMV-ion interactions have been widely reported and utilized for metallization to generate organic-inorganic hybrid composite novel materials. Building on these previous observations, we herein determine, for the first time, the TMV-ion binding constants assuming the static fluorescence quenching model. We also show that by comparing TMV-ion interactions between native and denatured coat protein, we can distinguish between chemically similar heavy metal ions such as cadmium and zinc ions.