I do not have the original message,but your message reminds me of the
behavior of hCG,
a dissimilar subunits chain dimer,held together non- covalently.In my early
days,when I placed the dimer on an HPLC column,and ran it with TFA,pH=2 ion
pairings,I was getting three peaks,the dimer,as well as the alpha and beta
subunits.So,I have to work at pH 5-7 to
preserve the dimer.Of course with the post-translational modifications,it
is hopeless to
study hCG or subunits by MALDI.But,this mystery protein could be run at pH
2,to see what
is its mass.If the mass is lower,it must be held together non-
covalently,if it remains
the same,the interaction would have to be covalent.
"Amina S. Woods" <awoods@jhmi.edu>@aecom.yu.edu> on 04/15/2000 11:16:13 AM
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Subject: RE: MALDI: Protein dimmer
I do a lot of work at pH of 5-7Ýto study non-covalent interaction by MALDI
(Enzyme-Substrate complexes, DNA-peptide etc...).Ý So I have to use
matrices with pH in the range of 5-7.Ý 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together.ÝI have also unpublished data using basic matrices showing 5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.ÝI think the best paper to read is Terry
Farmar's review in the Journal of Mass Spectrometry.Ý I think it was
published in 1998.Ý 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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