I have been asked to analyze (for QC purposes) some MAPS peptides by MS. I
have both MALDI and ESI-triple quad MS available. The expected MW of them
is around 25kDa.
I seem to recall from the dark recesses of my memory that there are some
unique difficulties with this class of peptide. Could anyone with specific
experience with mass spectrometry of MAPS peptides share their experience
with me?
Regards...Ken
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Ken I. Mitchelhill
The John Holt Protein Structure Laboratory
St. Vincent's Institute of Medical Research
41 Victoria Parade
Fitzroy 3065 Victoria
AUSTRALIA
Hallo Ken,
we spent some time in the analysis of MAPS by ESI-MS and also (but very
short time) by MALDI-MS. I had a poster on the Chicago ASMS, directly
beside another poster about the same question and we had similar
experiences. Some MAPS work like linear peptides, a substance-P MAP looked
very nice, other show only broad peaks with no clear visible mass while
other didnot show anything, in ESI-MS. The same for MALDI-MS. We sequenced
the MAPS and could not see any mistakes in sequences, in most cases I could
reach the starting Ala. As far as one could say from the sequence analysis
all MAPS were fine. We discussed the reasons for the mass spectra and could
not find a final answer. I had the idea that due to the structure some MAPS
may carry water with them and do not loose the water in the spray and this
causes the broad peaks. So we thought about the SCIEX turbo-ion spray, but
we didnot have this and, as time goes by, we forgot to do it. We donot
longer analyze MAPS by MS (neitehr ESI, nor MALDI) if we are in doubt we
sequence them. Also in CZE the peaks look very bad, broad with long
tailing.
This is our special experience and as far as I remeber I have not seen any
new results from anyone.
Yours
Manfred
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Manfred Raida
Niedersaechsisches Institut fuer Peptid-Forschung
(IPF)
Dep. of Analytical Peptide-Chemistry
Feodor-Lynen Strasse 31
D-30625 Hannover
Germany
E-Mail Manfred_Raida@compuserve.com
Tel.: +49 511 5466 210
Fax: +49 511 5466 102
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