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protein size determining methods


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#1 maharith

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Posted 13 May 2012 - 02:16 AM

Hi colleagues
I would like to greet all, I am new member.
I have simple questions regarding protein size determining, I checked one method and it was the division of the number of bases by 3 (is 3 represent amino acid?) then multiply the result by 110 (mean MW of AA) and you get the size? (right or Im mistaken) for example, I have gene sequence encoding for protein and the number of bases is 100
so 1000/3 = 333
333 * 110 = 36, 630 D
= 36 kD

is there any alternative method for determining the size?


thanks with regards

#2 doxorubicin

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Posted 14 May 2012 - 02:43 AM

This is a good approximation of theoretical molecular weight. For more precise calulation use a tool like this one: http://web.expasy.org/compute_pi/

If you want to know the apparent molecular weight by western blot, even the precise calculation can be very far off because of differential SDS binding, post-translational modifications, etc.
If the protein has an alternative name that starts with a "p", then the number after the "p" will likely be the apparent molecular weight by SDS page. One exception is PTEN (ha ha).
One good method to find the apparent molecular weight by SDS-PAGE is to do a google search for "kDa [protein name]" in quotes. You will often find many results where people refer to, for example, "...the 470kDa DNA-PK..."




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