Urea-containing buffers: How long can I store them?

[Bob Steinberg]

Viraj Master wrote:
> 
> Hello all,
> 
> I am using the Qiagen pQE series of vectors to express proteins.  There
> are two buffers which I use a lot, Buffer B and Buffer C.
> 
> These contain:
> 8M urea
> 0.1M NaH2PO4
> 0.01M Tris
> 
> Buffer B is at pH=8
> Buffer C is at pH=6.3
> 
> I have been told that I must make these buffers up **fresh** each time
> prior to use.  I would like to be able to prepare batches of these
> buffers and store them.  Does anybody know whether this can be done and
> not affect the protein prep?  If so, are they stored in the cold, or at
> room temp?  For how long can they be stored?
> 
> Many thanks,
> 
> Viraj
> 
> Viraj Master PhD
> Dept of Organismal Biology
> University of Chicago

I assume the the problem is the urea, which can decompose forming
isocyanate-- this, in turn, will react with your proteins. Although I
would not recommend storing urea-containing buffers for extended
periods, you can alleviate the isocyanate problem by including a high
concentration of a scavenger (e.g., L-lysine) in your buffers.