# 0,2uM is 100ng of a 18-mer primer - (Jul/18/2006 )

I wonder how they can calculate that 100ng of a 18-mer primer is about 0,2uM. Do they use any tools or how do they know it?

Thanks.

Thanks.

it seems there is a little mistake here. you have forgotten /mL I guess.

if you know the average molecular weight of a mer (I don't), you can calculate the molarity of a 18-mer if you know the concentration (ng/mL)

I wonder how they can calculate that 100ng of a 18-mer primer is about 0,2uM. Do they use any tools or how do they know it?

Thanks.

it seems there is a little mistake here. you have forgotten /mL I guess.

if you know the average molecular weight of a mer (I don't), you can calculate the molarity of a 18-mer if you know the concentration (ng/mL)

Dear Missele,

Thanks for replying. Yes, it should be 100ng/ul. A DNA base weights approx. 300-330 daltons. Can you show me how i can calculate the molarity of a 18-mer? This is quite hard for me. I do not know how to make daltons into molarity.

Thanks again!

I wonder how they can calculate that 100ng of a 18-mer primer is about 0,2uM. Do they use any tools or how do they know it?

Thanks.

it seems there is a little mistake here. you have forgotten /mL I guess.

if you know the average molecular weight of a mer (I don't), you can calculate the molarity of a 18-mer if you know the concentration (ng/mL)

Dear Missele,

Thanks for replying. Yes, it should be 100ng/ul. A DNA base weights approx. 300-330 daltons. Can you show me how i can calculate the molarity of a 18-mer? This is quite hard for me. I do not know how to make daltons into molarity.

Thanks again!

1 dalton is 1 g/mol

hmm, I have a head ache, and I can't find the right result !

1 base is 330 dalton, it means 330g/mol. from 330g you get 1 mol

For a 18-mer, it's quite 18 times : 1 mole is 330*18=**5940**g

you have 100 ng/µL

100 g is 100/**5940**=0.016 mol

100 **n**g is 0.016 **n**mol

100 ng**/µL** is 0.016 nmol**/µL**, or 0.016mmol/L (id est 0.016 mM)

Where is my mistake?

1 base is 330 dalton, it means 330g/mol. from 330g you get 1 mol

For a 18-mer, it's quite 18 times : 1 mole is 330*18=

**5940**g

you have 100 ng/µL

100 g is 100/

**5940**=0.016 mol

100

**n**g is 0.016

**n**mol

100 ng

**/µL**is 0.016 nmol

**/µL**, or 0.016mmol/L (id est 0.016 mM)

Where is my mistake?

I do not know. does anyone has any suggestions? 0.016mM is the same as 16uM. It should be 0.2uM.

I completely agree with Missele. That's the right way of calculating the molarity.

I would say it's 0,2 µM:

(100 E-9 g/µl) / 5940 g/mol = 0,17 E-12 mol/µl = 0,17 E-6 mol/l = 0,17 µM ~ 0,2 µM

sorry if it's too crowded...

U can find the use this formula to calculate.

From IDT's website: Milligrams = Molecular Weight * Nanomoles * 10-6