Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: scientizscht on 13/10/2019 21:02:25

Title: How to convert kDa to molecular weight?
Post by: scientizscht on 13/10/2019 21:02:25
Hello!

How can I find the molecular weight of a protein in grams/mol if I know that it's 150kDa?

I read that 1Da = 1g/mol but this is means that 1mol of that protein will weigh 150,000grams or 150kg!

Also, I read that LDL is 3million daltons which means that 1mol of LDL will weigh 3 million grams or 3 tonnes!

But this result says only 386.654 g/mol.
https://www.google.com/search?q=molecular+weight+of+ldl

What is wrong?

Thanks!
Title: Re: How to convert kDa to molecular weight?
Post by: evan_au on 13/10/2019 21:54:51
Quote from: OP
1mol of that protein will weigh 150,000grams or 150kg!
Fortunately, your body doesn't need 1 mole of that protein...
Title: Re: How to convert kDa to molecular weight?
Post by: chiralSPO on 13/10/2019 22:37:27
They are both right. Cholesterol is a small molecule with a molecular mass of 387 g/mol (or387 Da). And many proteins have molecular weights of hundreds of kg/mol (KDa)

Title: Re: How to convert kDa to molecular weight?
Post by: scientizscht on 13/10/2019 22:45:27
LDL is 3,000kDa which is 3,000kg/mol. In familial hypercholesterolemia, it reaches 10mmol/L which is 10mmol x 5L = 0,050mol in the whole blood. This is 0.050 x 3,000kg = 150kg!

(https://www.researchgate.net/profile/Luis_Salazar8/publication/12275334/figure/tbl1/AS:601606697533454@1520445622334/Clinical-details-of-Brazilian-heterozygous-familial-hypercholesterolemia-FH-patients.png)
Title: Re: How to convert kDa to molecular weight?
Post by: Bored chemist on 14/10/2019 19:32:02
I suspect that it's LDL measured as the cholesterol contained / combined in the protein.