There is a recurrent theme on this list of +44 ion series (in both MALDI and
ESI) coming from polymers with an ethoxy monomer, e.g. PEG and some
non-ionic detergents that are polyoxyethylenes. (For example, we have seen
it in MALDI spectra after lysing cells in buffer containing 0.05% Tween-20,
although at higher masses than you are seeing (900-1200)).
Could it be a detergent used in your sample prep?
For more details on this, see for example:
http://www.abrf.org/archives/hmail/0011/0043.html
or
http://www.abrf.org/archives/hmail/0011/0045.html
Bruce Stanley
-- Bruce A. Stanley, Ph.D. Director, Scientific Programs Section of Technology Development and Research Resources H093 Penn State College of Medicine> Dear Colleagues, > > we are trying to measure ceramides in yeasts. After initial fractionation, > we end up with a crude preparation of ceramides in chloroform-methanol 9:1. > When spraying this ceramide preparation we measure abundant singly charged > ions in positive mode with mass to charge ratios of 507, 551, 595, 640, > 684, 728, and 772 Da. The mass difference of these ions is 44 Da. Does > somebody have an idea what 44 Da means with respect to ceramide lipids? > > Thanks for your input. > > Regards > > Paul > > Paul Jenoe, PhD > Department of Biochemistry > Biozentrum of the University of Basel > Klingelbergstrasse 70 > CH-4056 Basel > Switzerland > > Tel. +41 61 267 21 57 > Fax. +41 61 267 21 48 > e-mail Paul.Jenoe@unibas.ch > > >
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