Synthesis and characterization of a ruthenium(II)-based redox conjugate for reagentless biosensing

Synthesis of a novel sulfhydryl-specific, tetraammine Ru(II)polypyridyl com plex, [Ru(II)(NH3)(4)(1,10-phenanthroline-5-maleimide)](PF6)(2), which exhi bits environment-sensitive electrochemical properties is described. When co njugated to an allosteric site in a genetically engineered mutant of maltos e binding protein, the formal potential of the conjugated redox probe is sh ifted to higher potential upon maltose binding. The magnitude of this poten tial shift was used to measure maltose affinity of the protein-redox conjug ate complex and to monitor maltose concentration in solution. These results are presented in context of reagentless biosensing.