Re: MALDI-TOF vs ESI-MS
Gary Hathaway (hathaway@its.caltech.edu)
Thu, 25 Feb 1999 14:42:49 -0700
At 8:33 AM -0700 2/25/99, Jim.Bloom.B@bayer.com wrote:
. So, to put
>my young whippersnapper colleague in place, could someone tell me that, yes
>indeed, the MALDI has produced an artifact and maybe tell us what most likely
>the artifact is (has the MALDI knocked off an -OH??) and perhaps most
>importantly, how to prevent the machine from producing said artifacts!! I
>would be most grateful!!
>
>PS: In case it is important, the MALDI-TOF was run in positive ion reflector
>mode with delayed extraction.
>
Jim,
Sorry Jim I'm no guru, but it seems to me the MALDI hasn't really produced
an artifact. It merely produced a metastable ion which lost, most likely,
NH3. Had your colleague elected to run the sample in linear DE, the -17
would either magically disappear (metastables not seen) or still been there
in which case you really would have a modified peptide. With experience,
one quickly becomes accustomed to the adducts and metastable losses
associated with MALDI-TOF. Also, remember that metastables can be quite
valuable in providing structural information. I don't know which matrix was
used for these peptides, but I have found that the larger peptides work
much better with sinapic acid while alphacyanocinnamic is better with less
than 4 kDa peptides. Nevertheless, I wouldn't consul that you retire your
ESI/quad any time soon. We have one too.
best regards,
Gary Hathaway