Converting from micrograms (µg) to nanomoles (nmol) to picomoles (pmol) to nanomolar to milimolar can be confusing. The goal of this short tutorial is to show you a way to easily inter-convert these values while standing in front of your mass spectrometer talking to a client.

Remember: M > mM > µM > nM > pM > fM

1.) Quantities: An easy method to convert nmols to µgs

Easy trick number one.

1 nmol of a compound is equal to the kDa mass of the compound converted to µgs.

For example 1 nmol of a 50 kDA protein is 50 µg.

The Proof:

1 mole of a 50 kDa protein is

50,000 g

1 millimole is

50 g or 50,000,000 µg

1 micromole is

50,000 µg

1 nanomole is

50 µg

2.) Concentrations: An easy method to convert molar concentration to absolute quantities. (because as LC/MS people we always want to know the absolute amount going on to the HPLC column.)

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Easy trick number two.

A 1 millimolar solution of a compound is equal to the kDa mass of the compound converted to µgs/µl.

For example a 1 millimolar solution of a 50 kDa protein is 50 µg/µl.

The Proof:

A 1 molar solution of a 50 kDa protein is

50,000 g/L

A 1 millimolar solution of a 50 kDa protein is

50 g/L

or

50 ug/ul

Q: For example if someone says, "I have 10 µLs of a 10 mM solution of a 50 kDa protein", how many µgs does he have?

A: A one mM solution would be 50 µg/µl therefore a 10 mM solution is 10 X 50 µg/µl = 500 µg/µl and then 10 µl of such a solution is 10 X 500 µg/µl = 5000 µg

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In Summary

1.) 1 nmol of a 50 kDa compound is 50 µg

2.) A 1 mM solution of a 50 kDa compound is at a concentration of 50 µg/µl