>Manfred-
>I know this is well documented either in STMS or ABRF archives (it is a
>recurrent topic) I couldn't figure a search pattern to pull it up however
>(44 does not cut it).
>
>I know you said that the "other spots look fine" but here are my thoughts.
>
>So the short answer is... some polymer with an ethoxy group monomer. The
>ethoxy is 44 (C2H4O) - typical ones are pegs and maybe detergents. They
can
>exhibit multiple charging and the +2 and +1 groups can even overlap. This
>really messes up the normal mass range. They may have been introduced in
>sample handling (container surfaces or solvents) or more likely as part of
>the sample prep stream.
>
>The only thing neat about them is the way that the different chain length
>species elute off a reverse phase HPLC at different times. First one m/z
>peak goes up than down, then another 44amu away increases then decreases
and
>so forth. Looks cool on 3-D plots. Really quiz the submitter hard - it is
>probably not you if you never saw this before. As they are UV transparent
>at normal lamda the submitter may claim not to see them on HPLC...duh.
Also
>the quality control for solvents is by HPLC-UV (among others) and so the
>vendor of your water may have shipped you a bad batch (say if the prot was
>HPLC fraction collected and concentrated) but this rarely happens (2x I
have
>suspected it). Another reason to worry about lot numbers and so forth.
>Maybe the polymer moved in the gel to a spot right by the protein you
>isolated (if that is the procedure)....?
>
>Matt Sweeney
>mattsweeney@earthlink.net
>Mass Spec Consulting
>Training/Operations/Consulting/Method Development
>LC/MS Pharmacokinetics, Peptides, Proteins, Metabolism,
>Maintenance Classes, Specialist in Finnigan Equipment and Software
>
>-----Original Message-----
>From: mraida@gmx.de <mraida@gmx.de>
>To: Recipients of ABRF List <abrf@aecom.yu.edu>
>Date: Wednesday, May 24, 2000 8:54 AM
>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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