Chris,
I assume you have read Carr SA, Huddleston MJ, Annan RS, Anal Biochem 1996
Aug 1;239(2):180-92 describing precursor ion scanning on a triple quad? It
really works.
Regards....Ken
-- Ken Mitchelhill Ph.D. Principal Instrumentation Scientist Vision Instruments Ltd. Private Bag 18/495 Blackburn Road, Mount Waverley ,Victoria 3149, Australia. E-Mail: ken.mitchelhill@visioninst.com Ph: +61 3 9211 7428 Fax: +61 3 9211 7401> -----Original Message----- > From: Christoph W. Turck [SMTP:turck@itsa.ucsf.edu] > Sent: Sunday, December 10, 2000 7:29 AM > To: Recipients of ABRF List > Subject: phosphopeptides/mass spec > > > Like many of you we are trying to map protein phosphorylation sites by > > mass spectrometry. Everybody in the field knows how tricky this can be and > > I wanted to find out if there are any tricks on the mass spec end of the > analysis that one can use to get to these sites. Since the stoichiometry > of > phosphorylation is often low one encounters the scenario where there is a > relatively high amount of unphosphorylated peptides next to a small amount > > of phosphopeptides. This leads to ion suppression and weak signals for the > > phosphopeptides. One possible solution to this problem is enrichment of > phosphopeptides by metal chelating resins, a method that apparently > doesn't > always work that well due to phosphopeptide loss during the procedure. > Also, the fractionation of peptides during LC/MS/MS can help in finding > the > phosphopeptides. > > Although the above methods can improve the chances of finding the > phosphopeptides I think there is still a good chance that one will miss > certain sites. The question I have is if one can optimize the mass spec in > > a way that favors the ionization and detection of low amounts of > phosphopeptides in a more or less complex mixture with other more abundant > > non-phosphopeptides? How about using different buffer systems, > positive/negative ion mode, ionization voltages, etc. to selectively > increase the signal for the phosphopeptides over non-phosphopeptides? > > > Chris (turck@itsa.ucsf.edu)
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