How to convert µg/ml in µM?

Question

Hey guys

I performed some cytotoxity assays using cisplatin recently and defined the IC50 in µg/ml (e.g. for one cell line I got 5.4 µg/ml). Now I would like to compare these values with ones mentioned in some papers but most of them use µM as a unit (e.g. 1.2 µM in one). As I do not come from the chemistry field, hated math and my time in school has been some 500 years ago, I have no clue how to convert the µg/ml in µM or the other way around. I googled a little and found out that I need to use the molecular weight (301,1 g/mol for cisplatin) somehow...but I just don't know what I need to do with that exactly and everytime I tried converting them by dividing it through the molecular weight or anything I got quite unrealistic results :-D.

Could anyone of you help me please?

Thank you very much!

Answer 1

You have 5.4 ug / ml and want uM.

uM is defined as umoles / liter, so we need to convert 5.4 ug to umoles and ml to liters.

The molecular weight is 301 g/mol which is the same as 301 ug / umole

5.4 ug x 1 umol / 301 ug = 0.0179 umoles

1 ml = 0.001 liters

So, you have 0.0179 umoles / 0.001 liters = 17.9 uM (almost 18 uM)

This would make your IC50 about 15 times greater than that reported in the literature. This could be because different cell lines were used, or it could be due to something else. In vitro IC50 values (or related values) may be unrelated to in vivo values for obvious reasons.

Answer 2

Dimensional analysis!

5.4ug x 1000 mL x 1 g x 1 mol x 1 x 10⁶ umol = which is 17 umol/L

mL 1L 1x10⁶ ug 301g 1 mol