1-Methoxy PES is an electron mediator which has higher stability of solutions than 1-Methoxy PMS(M003). The stability in neutral to alkali conditions has been extremely improved with 1-Methoxy PES. 1-Methoxy PES is a stable small-molecular compound and it has an equal or higher thermal stability than diaphorase. The 1-Methoxy PES solution can be stored long term.
Characteristics of Each Electron Mediator
Stable in Wide Range of pH – Comparison with 1-Methox PMS
The residual activity of electron mediator was determined by colorimetric measurement after mixing WST-8 and NADH to the electron mediator solution that was stored for 30 days at 30 oC.
The stability of 1-Methoxy PMS solution dropped drastically at pH6 and above, on the other hand, 1-Methoxy PES solution was stable until pH8.
Solution Stability Compared to Diaphorase
50 mmol/l HEPES buffer (pH7.0)
1% Triton X-100
1-Methoxy PES (final concentration of 2 umol/l) or diaphorase (final concentration of 0.05 U/ml) was mixed with the working solution. 100 ul of 200 umol/l NADH (50 mmol/l HEPES buffer pH7.0) was added to 100 ul of each electron mediator solution. After 20 minutes at 37 oC, an absorbance of WST formazan was read (450nm). The freshly prepared solution and the solution stored for 45 days at 5oC were utilized for residual activity comparison.
There was 20% drop in the residual activity of diaphorase after 45 days of storage, on the other hand, 1-Methoxy PES showed similar residual activity as a freshly prepared solution.