I do a lot of work at pH of 5-7 to study non-covalent interaction by MALDI
(Enzyme-Substrate complexes, DNA-peptide etc...). So I have to use matrices
with pH in the range of 5-7. In those cases I do see more dimmer formation
than usual even at low concentrations of compound deposited. Usually if I
look at the same sample using matrices at pH less than 2.0 these dimmers are
absent.
I do believe that these dimmers are usually two molecules trapped together.
I have also unpublished data using basic matrices showing 5 isomers (MH+) as
well as the MH2+.
If you are interested in non-covalent interaction I'll refer you to my
papers and others on the subject. I think the best paper to read is Terry
Farmar's review in the Journal of Mass Spectrometry. I think it was
published in 1998. Akos Vertes and John Callahan published in 1995, and
Louis Pannell also published in 1995 on non-covalent interaction seen by
MALDI
Amina S. Woods, Ph.D.
NIDA Intramural Program, NIH
5500 Nathan Schock Drive
Baltimore, MD 21224
Tel: 410-550-1507(office)
Tel:410-550-5168 (lab)
Fax: 410-550-2971
e-mail: awoods@intra.nida.nih.gov
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