TRFS-green 

TRFS-green is a highly selective off−on fluorescent probe for imaging selenoprotein thioredoxin reductase (TrxR) in living cells. TRFS-green has the maximum absorbance at around 373 nm. After it is activated by TrxR, the maximum absorbance shifts to around 440 nm^[1].

TRFS-green displays a green fluorescence off−on change induced by TrxR-mediated disulfide cleavage and subsequent intramolecular cyclization to liberate the masked naphthalimide fluorophore^[1].
TRFS-green gives a signal at ~480 nm when excited at 377 nm. Pretreatment of living cells with TrxR inhibitors in a dose-dependent manner can inhibit the fluorescence signal of TRFS-green in living cells, thereby facilitating the development of living cell-based screening assays for TrxR inhibitors^[1].
TRFS-green shows no response to GSH or Cys, the predominant thiols in cells, or the endogenous reducing agents, such as vitamin C and NADPH^[1].

Measure TrxR activity in crude cell extracts^[1]: Incubate cell lysates with TRFS-green for an appropriate time (usually 1-2 hours), and measure fluorescence intensity by fluorimeter (Em= 540 nm, Ex=440 nm). It is also possible to monitor the time-dependent increase in fluorescence (Em=540 nm, Ex=440 nm) over a given period of time.
Cells treated with TRFS-green (10 μM; 2-4 h) can be observed through the green fluorescent channel of the microscope^[1].
Note: In order to obtain a clear fluorescence image, it is recommended to wash the cells with PBS or fresh medium immediately before taking pictures to remove residual TRFS-green.

TRFS-green is the first fluorescent probe of TrxR with a green emission. However, the response rate of TRFS-green to the enzyme is slow, and it takes more than 2 h to reach the maximal fluorescence signal even using tris(2-carboxyethyl)phosphine (TCEP) as a reducing agent^[2].

MedChemExpress (MCE) has not independently confirmed the accuracy of these methods. They are for reference only.

416.51

C₂₀H₂₀N₂O₄S₂

1513848-14-0

Solid

White to off-white

O=C(OC1CSSC1)NC2=CC=C(C3=C4C=CC=C32)C(N(CCCC)C4=O)=O

Room temperature in continental US; may vary elsewhere.

* Please refer to the solubility information to select the appropriate solvent. Once prepared, please aliquot and store the solution to prevent product inactivation from repeated freeze-thaw cycles.
Storage method and period of stock solution: -80°C, 6 months; -20°C, 1 month. When stored at -80°C, please use it within 6 months. When stored at -20°C, please use it within 1 month.

• [1]. Liangwei Zhang, et al. Highly selective off-on fluorescent probe for imaging thioredoxin reductase in living cells. J Am Chem Soc. 2014 Jan 8;136(1):226-33.  [Content Brief]

  [2]. Xinming Li, et al. A fast and specific fluorescent probe for thioredoxin reductase that works via disulphide bond cleavage. Nat Commun. 2019 Jun 21;10(1):2745.  [Content Brief]