MALDI-TOF for quantification of related proteins

[Paul S. Brookes.]

You're actually asking two separate questions......
1) Can those Mw fragments be resolved using MALDI - basically, yes.  The 
resolution in the range 2000 or so is reasonably good for differences of a 
few mass units, so you should have relatively few problems detecting 4 
peaks in your trypsinized mixture.
2) Can you quantify proteins on MALDI - not really.  When your sample gets 
dried onto the plate with the matrix it crystallizes, and therefore you get 
localized domains containing different amounts of protein.  Depending on 
where the operator points the laser beam, they may hit a rich deposit, or 
an area with none at all.  Therefore, while it is "possible" to quantify 
things approximately, I would take any values obtained this way with a 
pinch of salt.

- You could try cutting with a different enzyme to give more/less fragments?
- HPLC might resolve them?

Paul

_________________________________________
Dr. Paul S. Brookes.            (brookes at uab.edu)
UAB Department of Pathology,   G004 Volker Hall
1670 University Blvd., Birmingham AL 35294 USA
Tel (001) 205 934 1915     Fax (001) 205 934 1775
http://peir.path.uab.edu/brookes

The quality of e-mails can go down as well as up
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