Msr-blue is a first turn-on fluorescent probe for methionine sulfoxide reductase with a more than 100-fold fluorescence increment. Msr-blue is used for monitoring the enzyme activity in live cells (Λex=340 nm, Λem=440 nm)[1].

Msr-blue is emited blue fluorescence after activation by methionine sulfoxide reductase A (Msr A). Msr-blue responded to Msr A in both a time- and dose-dependent manner, and more than a 100-fold increase in the emission is observed. Msr-blue is converted to its corresponding sulfide (15′) under catalysis by either the purified Msr A or a cell lysate[1]. The 6-OHDA-treated PC12 cells as a cellular model of Parkinson's disease (PD) is employed and applied Msr-blue to probe the function of Msrs in the cells. With the aid of Msr-blue, a decline of the Msr activity in a PD model was disclosed for the first time[1].

[1]. Liangwei Zhang, et al. A specific fluorescent probe reveals compromised activity of methionine sulfoxide reductases in Parkinson's disease. Chem Sci. 2017 Apr 1;8(4):2966-2972.