Hi there,

2.5U is the total amount of polymerase needed in 50µL so pipet 0.5µL of the stock solution into your PCR mixture.

If you are taking 2.5 U Taq Polymerase for 50 uL total reaction mixture then you have to  take 0.5 uL from the stock enzyme having concentration of 5 u/uL

Good luck....

Hi all, how to calculate that? I believe 2.5 U is not enzyme concentration, it is enzyme unit activity. I cannot get the value based on C1V1=C2V2

Hi again,

You don't need to get into the C1V1=C2V2 stuff as the recipe you have states on the total amount of polymerase required for the reaction. You need to introduce 2.5U into your 50µL reaction mix. Knowing that the polymerase stock solution contains 5U/µL, 0.5µL of this stock will contain the 2.5U required.

If you absolutely want to get into C1V1=C2V2; you will first have to calculate the actual concentration of polymerase in the reaction mix (2.5U/50µL) and then consider the volume of the reaction (50µL) and the concentration of the polymerase stock solution (5U/µL) and make the calculation... And find that the required pipetting is 0.5µL.

This systematic approach (ie using C1V1=C2V2) is actually much more complicated in most cases and is in my experience a source of calculation errors for the students.

It is easy to solve this issue logically. Applying equation in this situations will make the situation more complicated. but both approaches are good .

Hi Ridwan, by simple unitary method (basic maths) you can solve it in the following way; Your stock is 5 U / uL hence;

If 5 U in 1 uL 

so 2.5 U in = 2.5 x 1 / 5 = 0.5 uL, So just add 0.5 uL from stock and add in 49.5 uL. Really no need to enter in C1V1 equation. Hope it will help. Many regards..

Thank you very much for your explanation. I now understand based on what you all did describe it. I am very grateful and appreciate everyone's help. It is very easy actually.