Adjust the protein concentration about 0.1 to 1 mg / mL and the thiol concentration to 100 μmol / mL or less.
 Please refer to the following protocol for a quantification example of thiol concentration (for 96 well plate) using DTNB (product code: D029).
1. Reagent and solution preparation
 Required material: Reaction buffer (100 mmol / L sodium phosphate, pH 8.0, 1 mmol / L EDTA)
A) 400 μmol / L DTNB solution
 (1) Weigh 4 mg DTNB [5,5′-Dithiobis (2-nitrobenzoic acid), Code: D029] and dissolve in 1 mL of reaction buffer. (10 mmol / L) solution (a)
 (2) Dilute the solution (a) 25 times with reaction buffer. Final concentration: 400 μmol / L
* Prepare 0.1 mL of solution for each well. (ex. if you use 9 wells, please prepare about 1mL.)
B) L-Cysteine standard solution
 (1) Dissolve 2.42 mg of L-Cysteine in 5 mL of reaction buffer to make 4 mmol / L of L-Cysteine solution. Solution (b)
 (2) Dilute 100 μL of Solution (b) with 900 μL of reaction buffer to make a 400 μmol / L of L-Cysteine solution. Dilute this solution twice in order to make L-Cysteine standard solution (200, 100, 50, 25, 12.5, 0 μmol / L).
C) Measurement sample
 Prepare several samples (cell lysate, protein solution, etc.) diluted with reaction buffer. (To measure at N = 3, prepare 350 μL or more.)
2. Procedure
 (1) Add 100 μL of the measurement sample and L-Cysteine standard solution to each well of a 96-well microplate (Figure 1).
 (2) Add 100 μL of 400 μmol / L DTNB solution and mix by pipetting.
 (3) After incubating at room temperature for 15 minutes, measure the absorbance at 412 nm with a microplate reader.
 (4) Calculate the thiol concentration in the measurement sample from the L-Cysteine calibration curve (Figure 2).
*Calculate the thiol concentration in the sample from the sample dilution ratio.