I would like to calculate the concentration of T7 polymerase in the enzyme from NEB. Can anyone tell me how I can do this?
Thanks in advance.
Hi there,
from NEB leaflet, T7 RNA polymerase is 50 000 U/mL and specific activity is 1 200 000 U/mg therefore mass concentration is 50 000/1 200 000 = 41,7 µg/mL. As T7 RNA polymerase MW is 99kDa, molar concentration of NEB sample is 0.0417 / 99 000 = 0.42 µM.
https://www.neb.com/-/media/catalog/datacards-or-manuals/m0251datasheet-lot0091203.pdf
Thank you very much for your explanation, much appreciated!!
Subramaniyam
But, be careful,
manufacturers typically state the minimum specific activity, so you might actually have somewhat less protein, if the purity of your lot of enzyme is especially high, and, correspondingly, also the specific activity is thus higher.
I had also asked the same question to NEB and got this reply:
> T7 Polymerase is about 99kD. At 50,000U/ml, it is ~0.1mg/ml. > > So the molar concentration is about ~1uM.
I asked them how this calculation was done. This was the reply.
This is based on the Molecular weight and the concentration values. C= m/v X 1/MW
C= molar concentration in mol/L. m = mass (i.e., weight) of solute in grams . v = volume of solution in liters (L) MW = Molecular weight in g/mol
Maybe my specific activity is actually lesser?
Thanks,
Subramaniyam
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