Molar ratios

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Apr 25, 2017

Hi all,

I obviously have problem with molarity. I need help with understanding this, I need 1:1 molar ratio and 1:5 molar ratio of protein and dye.
I have 9.2mM dye and 40uM protein sample. Once someone told me to get 1:1 ratio I need to use 2ul of this dye to this sample of protein and (of course) if I want 1:5 ratio then I would use 10ul of this dye. I do not understand the calculation behind this, seems wrong to me. Can someone please explain this to me? If it is possible please use example.


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mdfenko 10 months ago

the amount of dye required depends on the volume of the protein sample. 40uM is a concentration, not an amount.

however, 1:1 molar ratio means you want 1 mole of dye per mole of protein and 1:5 means you want 5 moles of dye per mole of protein.

the volume of the protein solution will allow you to calculate the number of moles of protein. then you determine the volume of dye required to give you the same and 5 times the moles of dye.

the problem with these types of calculations is that people get caught up in terminology and don't realize that it's simple arithmetic to determine the answer.

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nekameneka 10 months ago

I know what means 1:1 and 1:5, I still have a little bit of brain haha, but thanks I think I got it, it's pretty easy, correct me if I am wrong but if I have 40uM protein concentration that means I have 0.04 nmol in one microliter and in one microliter of 9.2mM dye I have 9.2nmol. That means I need 230ul of this protein sample and 1ul of this dye to make 1:1 molar ratio, am I right? I think it is simple as that...maybe
Thank you!!

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mdfenko 10 months ago

you are correct