Manfred,
You most likely have a polyethylene glycol contaminant, with a repeating
unit of CH2CH2O (44 Da). It is not unusual to observe clusters of PEG
oligomers in the lower mass region of MALDI mass spectra. Not sure about
MALDI, but in electrospray you can observe the PEG oligomers either
protonated, sodiated or ammoniated depending on the solution cations.
Roger Mercer - rsmercer@ucdavis.edu (http://carbon.ucdavis.edu)
Mass Spec Specialist UC Davis Molecular Structure Facility
====
When asked why he had left the Northeast and moved to California,
the scientist replied, "When I was 20, I wanted to be a lover. When
I was 30, I wanted to be rich. Now I just want to be warm."
-----Original Message-----
From: Association of Biomolecular Resource Facilities
[mailto:abrf-request@aecom.yu.edu]On Behalf Of mraida@gmx.de
Sent: Wednesday, May 24, 2000 5:35 AM
To: Recipients of ABRF List
Subject: Mass difference of 44
Hi all,
we observe a number of peaks in MALDI-MS having a 44 mass difference, but
only up appr. MW 1400, the rest looks good and we could identify the
protein. Other spots are also fine. Has anybody seen the same and knows what
this
is.
Thanks a lot in advance
Manfred Raida
APB Proteomics
-- Dr. Manfred Raida European Proteomics Lab Amersham Pharmacia Biotech Munzingerstrasse 9 D-79111 Freiburg Germany Email: Manfred.Raida@eu.apbiotech.com
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