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### Topic: absolute molecular mass  (Read 6889 times)

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#### mandy9008

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##### absolute molecular mass
« on: May 08, 2011, 09:46:32 PM »
The average molecular weight of a polypeptide is 110. Calculate the absolute molecular mass of a protein consisting of 682 amino acid residues. (1 Dalton = 1 amu = 1g/mole)

I thought that you would just divide the residues by the molecular weight:
682 / 110 = 6.2 Daltons

This, however, is wrong.

#### Borek

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##### Re: absolute molecular mass
« Reply #1 on: May 09, 2011, 03:47:36 AM »
Is it a complete question? It doesn't make sense to me.
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#### rjb

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##### Re: absolute molecular mass
« Reply #2 on: May 09, 2011, 11:03:02 AM »
Mandy,

I think that this is supposed to read...

"The average molecular weight of an amino acid residue is 110. Calculate the absolute molecular mass of a protein consisting of 682 amino acid residues. (1 Dalton = 1 amu = 1g/mole)"

What its asking you is what is the absolute molecular mass of the entire protein given that on average each of 682 aa residues has an amu of 110, so its a multiplication basically... Its always worth having a think about what kind of answer that you're expecting before you do that calculation... may be worth thinking about what size an typical protein might be (normally in the KDa range), just 100 aa's produce a protein of (11,000) 11 KDa.

Hope this helps

R