problem with isoelectric focussing on beta lactamases

[karen_bush at INTERNETMAIL.PR.CYANAMID.COM]

Beta-lactamase activity as detected with nitrocefin is a much more sensitive 
assay for the presence of beta-lactamases than protein staining.  You can detect  
much lower amounts of active enzyme with nitrocefin than with either Coomassie 
or silver stain.  

However, it is also possible that the silver staining was not optimized.  The 
best results (at least on the prepared gels from LKB) are obtained by first 
staining wiht Coomassie, and THEN staining with silver stain.
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Subject: problem with isoelectric focussing on beta lactamases
From:    93462028 at comet.np.ac.sg (Poon Wai Mun) at INTERNETMAIL
Date:    1/31/96  8:56 AM

dear netters,

we are doing a project on Beta-lactamases. Currently, we are using comassie
blue to stain for protein bands after isoelectric foccusing. However, there
were no protein bands shown but an activity stain showed bands for the
various samples we used. The same senario happened when we did a silver
stain. Can anybody please help us out. Thanks a zillions.

Regards 
Wai Mun

PS: the gel we use has a pI ranging from 3 to 9. The gel we use is obtained
from Pharmacia Biotech. The markers for IEF were clearly shown after
coomassie and silver staining.