Hong Li,
The recovery of phosphopeptide from Ziptips is sequence dependent. Some
peptides are captured and eluted as per the millipore instructions whereas
other peptides are not efficiently captured. I also have the same experience
with the THAP matrix vs alphaCHCA, namely better signal intensities with the
alphaCHCA. Also note that phosphopeptides produce lower intensities relative
to the nonphosphorylated peptides (about half the intensity is typical).
--------------------------------------------------------
Gordon Alton, Ph.D.
Analytical/Protein Chemistry and Mass Spectrometry
Signal Pharmaceuticals Inc.
5555 Oberlin Drive
San Diego, CA 92121
Email: galton@signalpharm.com
Phone: 858-558-7500 x8252
Fax: 858-623-0870
WWW: http://www.signalpharm.com
-------------------------------------------------
-----Original Message-----
From: Hong Li [mailto:liho2@umdnj.edu]
Sent: Monday, September 11, 2000 7:55 PM
To: Recipients of ABRF List
Subject: IMAC Ziptip Question
Hi All:
We are evaluating IMAC ZipTip for the purpose of phosphopeptide isolation
for MALDI analysis. We seem to have difficulty with SDS-PAGE separated
proteins, even with around 10 pmol of a/b casein and ovalbumin. Per ealier
ABRF discussion, SDS might have a negative effect on IMAC performance. Can
anyone give some feedback on their experice w/ IMAC ziptip? Also Millipore
suggests that THAP is the preferred matrix for phosphorpeptide analysis
by MALDI, but in our hands, the calibration peptide signal is at least 10x
less than using alpha-cyano. Any comment on this observation?
Thank you,
Hong Li
New Jersey Medical School
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