Naph-EA-mal (Thiol-green 1) is a highly efficient and quick-responding thiol fluorescence probe specifically designed for protein labeling and bioimaging applications. This compound offers a rapid detection method and exhibits ultrafast turn-on fluorescence upon interaction with thiols. Naph-EA-mal (Thiol-green 1) enables the detection of thiols in live cells, facilitates the labeling of protein thiols, enables quantification of total thiol concentration in cell lysate, and allows for the determination of reversible protein thiol oxidation in fixed cells. It possesses an excitation wavelength of 488 nM and an emission wavelength of 540 nM.

Imaging thiols in living cells[1]Hep G2 cells incubated with Naph-EA-mal (Thiol-green 1) (1 μM;5 mins), and strong green fluorescence can be observed. When cells are preincubated the cells to block the intracellular thiols with NEM (a thiol block reagent; 100 μM), a weaker fluorescence is observed in cells[1].Monitoring thiol-disulfide levels in fixed cellsDue to the majority of cellular thiols are present in the reduced form, Naph-EA-mal (Thiol-green 1) (10 μM) induces strong fluorescence in Hep G2 cells. After diamide treatment, fluorescent signal sharp dimed is observed[1].The Hep G2 cells, oxidized by diamide (200 μM; 30 min), are fixed by 70% EtOH and the remaining free thiols are blocked by NEM (100 μM). then The cells are further treated with TCEP (5 mM) followed by addition of the Naph-EA-mal (Thiol-green 1) (10 μM). The green fluorescent signal is detected again[1]