As I know, we calculate the mass concentration of nucleic acids by spectrometre which gives it as ng/ul. To determine the molarity of deoxyribonucleotides, you should divide this concentration by 327.0 ( average MW of deoxyribonucleotide monophosphates).

For example, if we have a 850 ng/ul (=850 mg/l) of DNA, then the molarity of nucleotides equal:

850/327=2.6 mM (10^-3 molar)

To determine the molarity of DNA molecules, dived the deoxyribonucleotides' molarity by [size of the DNA molecule (in bp) * 2].

For example, if the size of DNA molecule in the previous example is 50bp, the molarity of DNA molecules equal:

2.6/(50*2)=0.026 mM

The method for determination of DNA molecules' molarity is applicable for conditions where all of the DNA molecules in the sample have a single size. If not, you need to know the size of DNA molecules and their mass concentration.

Be successful;

As I know, we calculate the mass concentration of nucleic acids by spectrometre which gives it as ng/ul. To determine the molarity of deoxyribonucleotides, you should divide this concentration by 327.0 ( average MW of deoxyribonucleotide monophosphates).

For example, if we have a 850 ng/ul (=850 mg/l) of DNA, then the molarity of nucleotides equal:

850/327=2.6 mM (10^-3 molar)

To determine the molarity of DNA molecules, dived the deoxyribonucleotides' molarity by [size of the DNA molecule (in bp) * 2].

For example, if the size of DNA molecule in the previous example is 50bp, the molarity of DNA molecules equal:

2.6/(50*2)=0.026 mM

The method for determination of DNA molecules' molarity is applicable for conditions where all of the DNA molecules in the sample have a single size. If not, you need to know the size of DNA molecules and their mass concentration.

Be successful;

Hi, Sayed. Thank you for answering, but I'm still a little bit confused. =/

Let me use an example of my lab routine. I have a ssDNA of 5386 bp at 400 ng/uL.

So, the MW of this DNA would be 1761222 Da (5386*327). This is correct? Let's continue with my doubts:

According to a colleague that gave me the DNA, this ssDNA at 400 ng/uL it's equal to 1.2 mM and not 1.2 nM, according to the calculations you've taught. She also told me that the dsDNA version of this DNA would have the same molar concentration both in numbers of nucleotides and molecules but I can't understand why.

Could you explain me with how this would be?

Once, again. Thank you very much.

Dear Daniel,

I made a mistake. I edited my previous answer.

You're right. The MW of the ssDNA and the molar concentration of nucleotides of the sample equals 1761222 Da and 1.2 mM, respectively.

Let me tell more:

We would have 1.2 mM of nucleotides if we completely degrade the ssDNA to its monomers. By definition, one mole of a substance contains 6.022×10^23 elementary entities of the substance. Every molecule of the ssDNA consists of 5386 nucleotides. We can write an equation:

5386 nucleotide ---> 1 ssDNA + 5385 H2O

So, the molarity of the ssDNA would be:

1.2/5386=2.2 uM

As the numbers of DNA molecules would be constant if the ssDNA becomes double-stranded (because a complementary strand which consists of 5386 nucleotides binds to this ssDNA by hydrogen bonds), the molarity of the dsDNA equals the molarity of the ssDNA which equals 2.2 uM.

1 ssDNA + 1 complementary ssDNA ---> 1 dsDNA

But the molar concentration of the nucleotides of the dsDNA would be double of the molar concentration of the ssDNA:

1.2*2=2.4 mM

Best wishes;

Use this :)

http://www.endmemo.com/bio/dnamolarity.php

Presumably you are getting the amount via UV absorbance. Then you need the extinction coefficient of the DNA to get the molar concentration of the DNA. OR you use an average nucleotide extinction coefficient (around 10000 L/(cm mol)) to get the molar concentration.

NOTE: the absorbance extinction coefficient) depends on solvent pH, Temp, and structure of the DNA). To get more accurate measurements you need to denature the DNA and calculate the extinction coefficient from the base composition.

e.g. A20 is quite different from T20 and if you mix them (and they form a duplex) the absorbance is lower

Hi, you can use this online tool:

http://www.molbiotools.com/dnacalculator.html