If you are new to this area, the only thing you need to appreciate is that the molecular weight (regardless of what it is) followed by the g symbol = 1 mole of substance.

i.e., 427.2 grams of ADP = 1 mole

It follows that 427.2 grams PER LITER = 1 mole per liter = 1 M (molar)

In your case, 427.2 MILLIGRAMS per liter = 1 mM, which might be a more convenient starting position.

This would allow you to make solutions of between 5 and 100uM easily. For example, a 1/10 dilution gives you 100 uM, 1/50 gives 50uM, and so on.

Or you might add 42.72 mg in 100ml, or even 4.272 mg/10ml to make smaller volumes of the 1mM stock (In the last case, you must have a very accurate balance).

I can only give the above general advice as I do not know your exact volume requirements.

Once you have good understanding of the underlying principles, you can just use a simple formula to switch between absolute amounts and concentrations and work with any mass and volume.

Nick Gee Please look at my calculations and tell me if I have done them correctly.

MW: 427.2 , pack size of ADP from sigma is 100 mg.

Target is 50 uM to create stock solution

100mg/ml X M

X= 100/427.2

X= 0.23408 M ( this is times 1000)

X=234.08 mM

234.08 / 5 ml ( PBS)= 46.816 mM (45.82 mM)

1000/46.82 mM= 21.36 ul. ( then to make aliquot solution I add 21.36 ul plus 978.64 ul )

Mathematically it is correct down to the penultimate line but if the aim is to make a 50uM stock (line 3 above) then you actually have a final conc of 1mM. It is a perfectly reasonable stock to make, however. You should also try to avoid awkward volumes e.g., 21.36ul and 978.64ul, since no pipettors can deliver those volumes accurately. The most straightforward route is perhaps something like this:

4.272 mg/ml = 10mM.

Thus, 42.72mg/10ml = 10mM (I'm not sure how much of your ADP you want to make up, you could double the mass and vol again and still have enough solid).

Freeze some 1ml aliquots.

Take 1 aliquot and add it to 9ml buffer = 1mM (the same end position as above)

If you really want 50uM, you just need a further 1/20 dilution of the 1mM stock e.g., 1ml +19ml buffer.

To make up the entire 100mg is more complicated because of the volumes needed. Let me know if you must do this, but it is very common to weigh out an amount that makes the preparation of the solution easier and more accurate.

I hope this helps.

Nick Gee Thank you very much, its clear to me now.

Much appreciated

Hi Aleksandar,

You may use the web tool to calculate

https://www.alfa-chemistry.com/mass-molarity-calculator.htm