Manuals And Inserts
Specific Protocol
PNPP Assay for Shp-2 (BML-SE273)
Assay Buffer: 25mM Tris, pH 7.0, 50mM NaCl, 2mM EDTA, 5mM DTT, 0.01% Brij35, 1mg/ml BSA. Store on ice bath.
p-nitrophenylphosphate (pNPP) stock solution: 100mM pNPP (sodium salt) dissolved in assay buffer [PROTECT FROM LIGHT!] Store at RT.
Shp-2 (BML-SE273): Dilute ten-fold in Assay Buffer to 0.1mg/ml and store on ice.
ASSAY IN 96-WELL ½-VOLUME MICROPLATE
1. Add 45μl assay buffer to the desired number of wells of the microplate and warm to 30°C.
2. Add 5μl Shp-2 (0.1mg/ml; stored on ice) to the 45μl of Assay Buffer.
3. Start reaction by adding 50μl pNPP stock solution, prewarmed to 30°C. Mix thoroughly. Final pNPP concentration=50mM.
4. Follow A405nm in a plate-reading visible spectrophotometer. Monitor for 5-20 min., recording, for example, A405nm at 1 min. intervals.
DATA ANALYSIS
1. Plot A405nm versus time. Determine slope (OD/min.) in linear part of curve.
2. At the pH of the assay (7.0) the extinction coefficient (ε) for p-nitrophenol is ~18,000 OD M-1 cm-1. The optical pathlength for 100μl in a ½-volume 96-well microplate is 0.5cm. The rate of phosphate release in pmol/min would be:
Rate of hydrolysis (pmol/min.)
= Slope (OD/min.) x (100 x 10-6 L x 1012 pmol/mol)/(18,000 OD L mol-1 cm-1 x 0.5 cm)
= Slope (OD/min.) x 24,000 pmol/OD
Specific Activity
= x pmol/min ÷ total amount of protein