Paul - Your m/z values, if you are looking for standard ceramides,
don't make much sense. Refer to "Ceramide profiling of complex lipid
mixtures by electrospray ionization mass spectrometry", Analyt.
Biochem. 244 (1997) 347-356 by Gu et al.
Some fungi do make unusual sphingosine bases. Refer to John Weete's
book on fungal lipid biochemistry for references to the older
literature. Eliana Bergter and others have published more recently
in this area.
Have you tried precursor ion scanning to look for sphingosine,
dihydrophsingosine or other headgroups to confirm that you are
looking at ceramides?
We have found that 1-10% chloroform reduces sensitivity and/or
completely inhibits analysis of numerous lipid classes using
electrospray introduction into triple quadrupole/ion trap/FTICR mass
spectrometers. The degree of inhibition depends upon the lipid
class. For ceramides using a TSQ 7000, we found stock solutions of
ceramide extracts in CHCl3 dissolved in MeOH (5/95, v/v) work well.
Regards -
Jim Kerwin
Mass Spectrometry Facility
Cornell University
Ithaca, NY 14853
>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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