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Does PTMs interfere with protein/peptide quantification using AAAs?

Posted: Thu Nov 21, 2013 4:33 am
by m/z
I know this forum is about MS but have been asked a couple of questions I cannot answer:

1) Can PTMs interfere with quantification of (native) proteins using amino acid analyzers (AAA)?
From what I remember AAAs quantify all amino acids of the purified protein and from this calculate the exact amount of protein (when taking into consideration that some amino acids are present more or less frequent in the already known protein sequence). But what if there is PTMs? Couldn't this in principle interfere with the quantification?

2) The same question, but for absolute quantification using MS? Here it is obvious that you can have a problem right? For example if you need to set up a clinical ELISA you would like to know if the quantification using MS and antibodies can be compared?

Posted: Thu Nov 21, 2013 11:14 pm
by Biomarker
Hey,

I don't have any idea about your first question. But this http://www.mcponline.org/content/early/2013/06/10/mcp.E113.031658.full.pdf+html link will partly address your second question. This paper from Ruedi Aebersold group nicely explained about western blotting vs SRM MS.

cheers..

Posted: Fri Nov 22, 2013 5:37 am
by m/z
Thank you.