Molecular "light switch" [Ru(phen)2dppzidzo](2+) monitoring the aggregation of tau.

Monitoring the aggregation of the tau protein is a key protocol for elucidating the pathogenic mechanism of Alzheimer's disease. In the present article, Ru(phen)2dppzidzo, a "light switch" ruthenium(ii) complex, was presented as a new monitoring probe for the aggregation of a tau R3 peptide, the third repeat unit of the tau microtubule-binding domain. Having little impact on the aggregation process, large fixed Stokes shift and small background luminescence made the complex a better probe for monitoring the aggregation process and quantitatively detecting tau filaments compared to thioflavin S, a commonly used fluorescent dye for staining neurofibrillary tangles and monitoring tau aggregation. Furthermore, a long luminescence lifetime of this complex could also expand its potential usage in the detection of tau filaments in the presence of short-lived fluorescent backgrounds.