Would PPG specifically target a cysteine? How would that be covalently
linked? Scott mentioned that the MS/MS data showed that the 58 amu was
associated with the cysteine. That would suggest a covalent modification
right? If this was a nickel contamination, as suggested, wouldn't it be
impossible to see with MS/MS?? (non-covalent interaction). I guess the
final question is: What does the Edman sequencing data look like? Could it
really be CM cys because someone upstream was using iodoacetic acid to
inhibit proteases? I know we had some trouble for a while because Pefabloc
was being added to the purification scheme and we ended up with a percentage
of + 183 containing proteins.
Gary Lange
gary.w.lange@monsanto.com
-----Original Message-----
From: Ricardo Bastos Cunha [mailto:rbcunha@unb.br]
Sent: Tuesday, August 08, 2000 4:18 PM
To: Recipients of ABRF List
Subject: Re: +58amu?
Dear Scott,
If you use polypropylene glycol (PPG) for calibration, the +58 ion series
may be coming from there. It may also be due to extracted polymer from
plastic ware or silicon coatings. Shot detergent containing samples also
explain the +58 ion series.
Best regards,
---------------------------------------------------------
Prof. Ricardo B. Cunha
Brazilian Center for Protein Research and Services - CBSP
Laboratory of Protein Chemistry and Biochemistry
Institute of Chemistry
University of Brasilia
Brasilia - DF Brazil
ZIP CODE: 70910-900
Tel: 55-21-61-307-2142
Fax: 55-21-61-272-4548
mailto:rbcunha@unb.br
http://www.geocities.com/Athens/Acropolis/5221
http://www.unb.br/cbsp
--------------------------------------------------------
----- Original Message -----
From: Scott Chamberlain <Scott_Chamberlain@cc.chiron.com>
To: Recipients of ABRF List <abrf@aecom.yu.edu>
Sent: Monday, August 07, 2000 5:31 PM
Subject: +58amu?
Hi folks,
We've seen a +58 species several times when dealing with recombinant
proteins (not carboxymethylated!). Does anyone have any ideas as to
what this could be?
Thanks in advance...
Scott Chamberlain
Protein Structure Analysis
Chiron Corp.
510-923-2839
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