Autoclaved MOPS: is it supposed to be yellow?

David L. Haviland, PhD dhavilan at IMM2.IMM.UTH.TMC.EDU
Sat Feb 28 09:04:12 EST 1998

On Sat, 28 Feb 1998, Brett Burkholder wrote:

> Date: Sat, 28 Feb 1998 02:58:30 +0000
> From: Brett Burkholder <bburkho at>
> To: methods at
> Subject: Autoclaved MOPS: is it supposed to be yellow?
> I'm trying to set up an RNA gel for a Northern blot.
> The protocol I'm using, Current Protocols in Molecular Biology 4.9.1
> -4.9.8, gives the recipe for MOPS buffer (10X: 0.4 M MOPS, 0.1 M Sodium
> Acetate, 0.01 M EDTA).
> I made the solution, added DEPC to treat for remaining RNases, then
> autoclaved it.  Now my MOPS buffer is yellow, so I'm wondering if
> something is wrong.
> Is this the correct way to make the buffer, or should I be making it
> with water which has previously been treated with DEPC and autoclaved?


In a word: Backwards...

Add mili-Q water to baked flask, add DEPC, stir with stirbar to mix.
DEPC won't go into the water but the idea is to expose as much of the
water to DEPC as you can.  I usually let it stir for about 20-30 mins.

Autoclave water.  Cool to RT.

Then make your MOPS solution per the recipe you have.  Filter, we use
either 0.2 um or 0.45 um.

I would be dubious of the yellow MOPS.  In fact, that is usually a sign to
discard it.

Hope this helps,

David L. Haviland, PhD
Assistant Professor, Immunology
University of Texas, HSC - Houston
Institute of Molecular Medicine
2121 W. Holcombe Blvd.
Houston, TX  77030

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