How to convert 1.0mg/ml of TNFa (17.5kDa) to 1,10,100µM via serial dilution?

[stephanie]

Please help me understand the formula.

Ideally, I would like to dilute it in dH2O first and then further into cell culture medium at the 1, 10, 100µM

Thank you

[gubment_cheez]

To dilute your starting solution of 1.0 mg/ml of TNFa (17.5 kDa) in dH2O first and then further into cell culture medium to achieve final concentrations of 1 µM, 10 µM or 100 µM, you can follow these steps:
1.Calculate the molarity of your starting solution in mol/L using this formula:

molarity = mass (g) / (molecular weight (g/mol) * volume (L))
For TNFa with a molecular weight of 17.5 kDa (17500 g/mol) and a starting concentration of 1.0 mg/ml (1.0 g/L), the molarity is:
molarity = 1.0 g / (17500 g/mol * 1 L) = 5.71e-5 mol/L
2. Determine the dilution factor DF for each desired final concentration using this formula:

DF = Y / X


where Y is the molarity of the starting solution in mol/L and X is the desired final concentration in mol/L.

For example, to achieve a final concentration of 1 µM from a starting solution with molarity 5.71e-5 mol/L, determine the dilution factor DF using this formula:

DF = Y / X = 5.71e-5 / (1e-6) = 57


So you need to take one volume unit of the starting solution and add it to 56 volume units of dH2O.

Similarly to achieve final concentrations of 10µM or 100µM, then their respective Dilution Factors would be: DF(10µM)=Y/X=5.71e-5/(10e-6)=5.71 DF(100µM)=Y/X=5.71e-5/(100e-6)=0.571

3. Perform the first dilution by taking one volume unit of the starting solution and adding it to DF - 1 volume units of dH2O.

4. Take one volume unit from each diluted sample prepared in step 3 and add it to an appropriate amount of cell culture medium to achieve the desired final concentrations.

It’s important to note that when performing serial dilutions, it’s essential to mix each diluted sample thoroughly before taking a sample for further dilution.

[JohnS]

a starting solution with molarity 5.71e-5 mol/L, determine the dilution factor DF using this formula:

It is worth noting that this value is 57.1 µmol/L, and is already more dilute that 100 µmol/L. It will be necessary to find a stronger stock concentration to make this value.