Some contaminants have reared up their ugly heads in my MALDI samples
recently. I have been doing tryptic digests followed by fingerprinting on
spots cut out from 2d gels.
I have talked to other people in the lab who have seen the same
contaminants. I was wondering if anyone here has seen these before. More
importantly, does anyone know where they come from and how to get rid of
them? It seems to be an intermittent problem (i.e. not all the samples
have them and they don't appear all the time). Actually, for me, this is
the first time they have become such a bad headache.
The most prominent contaminant peaks are:
1133.3
1207.4
1283.4
2780.1
All are monoisotopic values. The 2780 seems to be a doubly charged 5560.
I have checked in the databases but they don't seem to be keratin or any
other common contaminating protein either.
Thanks in advance for all the help.
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Regards,
M.