Hi Trudy,
We have frequently seen this loss in MALDI-MS of nitro-compounds,
but
not by ESI-MS. Laser desorption MS of a drug molecule (it flew without
matrix as
well as with, at 337 nm irradiation) also showed this loss.
Rachel
Rachel Ogorzalek Loo
Discovery Technologies Department
Biological Mass Spectrometry Center
28/G013E
Pfizer Global R&D
2800 Plymouth Road
Ann Arbor, MI 48105
(734) 622-1507
(734) 622-2716 fax
rachel.loo@pfizer.com
-----Original Message-----
From: Mehrnoosh Sadeghi [mailto:msadeghi@thinksrs.com]
Sent: Thursday, February 22, 2001 5:05 PM
To: Recipients of ABRF List
Subject: Re: PepSyn: Y(NO2)
Hi Trudy,
If the observed peaks are a result of the acidic conditions of sample
preparation in MALDI, you can probably avoid that by using a
neutral matrix such as trihydroxyacetophenone (THAP). What
solvents are you using for the peptide and the matrix? You may
also be able to use dithranol or 3-indoleacrylic acid, depending on
your sample? I would give it a try...
Good luck,
Mehrnoosh
________________________________________
From: "Holyst, Trudy" <tholyst@bcsew.edu>
Subject: PepSyn: Y(NO2)
Date sent: Thu, 22 Feb 2001 10:10:32 -0600
To: Recipients of ABRF List <abrf@aecom.yu.edu>
Hi All,
I have just synthesized two peptides with Fmoc-Y(3-NO2).
The syntheses
seemed to go fine and the HPLC tracings showed one
strong peak but the
MALDI TOF mass spec of the purified peak showed the
expected mass plus
minus 16 and minus 32. Is this an artifact of the mass
spec? Is the
nitrate group acid sensitive? I am purifying using RP
HPLC at pH 2.
Thanks is advance for your thoughts on this.
Trudy Holyst
Blood Research Institute
Peptide Core Laboratory
Blood Center of SE WI
Milwaukee WI 53201
_____________________
Mehrnoosh Sadeghi, Ph.D.
Stanford Research Systems
Sunnyvale, CA 94089
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