Hi everybody,
I have a question concerning the Bacterial Test Standard (BTS) used in whole cell identification by MALDI-TOF MS (Biotyper Bruker). This Quality Control based on E.coli extract seems extremely subject to variation. Briefly, some peaks selected for the calibration move by +8 or +16 Da, which would correspond to an oxidation process of proteins. This observation is not systematic and I don’t find a cause. Anybody have an idea ?
Thanks,
RC
Hi Romain,
The only thing that spring to my mind by your description some oxidation event happens between the preparation of BTS and analysis. My hypothesis is that the variable wait time from the preparation of the extract and when it's actually analysed and the environmental conditions (room temperature, humidity, etc) could influence the oxidation with a casual pattern.
Thanks Manlio for your response.
We have effectively suspected unfavorable environmental conditions for the preparation of BTS. However, temperature and pressure of our lab is well controlled. Relative hygrometry can fluctuate from 50% to 80%. Do you think it could be a reason of oxidation ?
From another angle, we use bleach for cleaning lab benches near to the place of preparation for MALDI-TOF analysis. Residues of bleach could be an other source of the oxidation process of proteins ?
Thanks,
Romain
Hi Romain, we also observed oxidation of ribosomal proteins which are mostly detected by MALDI-TOF MS, see Fig.2 of the paper attached. It appears that oxidation is often caused by traces of substances used for inactivation/sterilization purposes like sodium hypochloride, peracetic acid, or hydrogene superoxide. So the answer is Yes: residues of bleaches could be the source of the oxidation process. Best regards, -Peter
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