Yellow MOPS - why?

csc un691cs at
Thu Mar 23 03:50:31 EST 2000

On 21 Mar 2000, Wolfgang Schechinger wrote:

-Hi all, 
-I'd appreciate any explanation why our MOPS buffer  (pH 7, compsition 
-below) got yellow after autoclaving. Is this commonly observed? 
-(It's not the first time we make this buffer, but the first time it 
-got yellow. Maybe it was heated up a bit too long?) May we still 
-using it for northerns? The bottles used had aluminium screw caps. 
-Does this fact eventually matter? (Although I'd not assume that Al 
-is affected at this pH)

The yellow color is of no importance, but why on earth would you want to
autoclave it ? RNAses remain fully active after autoclaving. And adding
DEPC won't help either, because the RNAses in the autoclave (for instance
from LB) may well diffuse into your bottle.
Best way to make MOPS: buy a fresh bottle of all the reagents, use a
sterile spoon, add all the contencts to a new plastic disposable vial, add
water directly form the Millipore machine. Autoclaving is only

Kind regards, 

Clemens Suter-Crazzolara, PhD
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