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Molecular weight of protein

Discussion of all aspects of biological molecules, biochemical processes and laboratory procedures in the field.

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Molecular weight of protein

Postby khushi » Fri Oct 24, 2008 3:04 pm

This is my assignment.

A pure protein was subjected to N-terminal analysis using c14-phenyl isothiocyanate,specific activity 120ci/mole.Reaction of the reagent with 2.3microgram of protein produced 12,300 cpm PTH-met and 8200 cpm PTH-val with a 90% counting efficiency.Calculate molecular weight of protein and subunit composition?

I got an answer(1.40x10e6)

I have no idea if this is rite answer.let me know if anyone can help me with this
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Re: Molecular weight of protein

Postby blcr11 » Mon Oct 27, 2008 3:13 pm

That's not what I get. How did you come up with 1.4E6 and what do you think the subunit composition is?

From the specific activity of PTH you can calculate the number of moles of protein that must be equivalent to 2.3 ug of total protein. (You need to adjust your cpm before calculating the molar yields of PTH-amino acids to account for the fact that you're only seeing 90% of the counts that are actually there.) The simplest subunit composition is evident from the PTH amino acid analysis.
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