[Notgoodatcalculations]

Hi,

How can I go from mg/mL to moles? Is this possible.
For example, I have streptavidin which is 55,000 g/mol (55,000 daltons). The concentration of the streptavidin is 2mg/mL.

Is the following correct:
2 mg/ml x 1 g/1,000 mg x 1 mole/55,000 gram x 1,000 ml/1 L x 1,000 millimole/1 mole = 0.0364 millimole/ml = 0.0364mM

[jeffmoonchop]

yep

[chenbeier]

0.0364 millimole/ml = 0.0364mM

This is wrong.

1 mmol/ml = 1 mol/l = 1 M

2 mg/ml = 2 g/l  = 2 g/l/(55 g/mol) = 0,0364 mol/l = 0,0364 M

1 mM would be 1 mmol/l

[Notgoodatcalculations]

Ok so I have 0.0364M.

To go from Moles to molecules multiply by avagadro's number?

0.0364M x 6.022x10^23=2.19 x10^22

[chenbeier]

Yes but this is then molecules per liter.

It is a difference  0,0364 mol between 0,0364 M

[AWK]

0.0364 millimole/ml = 0.0364mM

This is wrong.

1 mmol/ml = 1 mol/l = 1 M

2 mg/ml = 2 g/l  = 2 g/l/(55 g/mol) = 0,0364 mol/l = 0,0364 M

1 mM would be 1 mmol/l

MM is 55 kD

[chenbeier]

Ok.
Komma in USA and dot in Europe and vise versa. For me was 55,000 g/mol 55 g/mol  and not 55000 g/mol.

What is MM and kD.   I know m for milli = 10^{^-3} and M for molar.  But no MM.

It is the atomic mass unit u and used in USA in Dalton, so it is misunderstanding with different  or equal abrevations.

[AWK]

Ok.
Komma in USA and dot in Europe and vise versa. For me was 55,000 g/mol 55 g/mol  and not 55000 g/mol.

What is MM and kD.   I know m for milli = 10^{^-3} and M for molar.  But no MM.

It is the atomic mass unit u and used in USA in Dalton, so it is misunderstanding with different  or equal abrevations.

I have streptavidin which is 55,000 g/mol (55,000 daltons)

In the above quote from the Notgoodatcalculations post, there are two pieces of information that allow you to correctly identify numbers.
1. Streptavidin is rather a large molecule. If it was a small molecule, it would probably be given a systematic name.
No atom or particle has a mass of 55.000. The closest mass shows the manganese atom - 54.938.
2. Giving the mass with such high accuracy of 50.000 makes no sense because three zeros after the comma or dot can be written only for the C-12 carbon isotope.

55,000 daltons must therefore refer to 55000 daltons (55 kD).