Yellow MOPS - why?

Nick Theodorakis nicholas_theodorakis at
Thu Mar 23 14:12:29 EST 2000

In article <pathos-2303000854500001 at>,
pathos at (pathos) wrote:


> Water directly from the millipore machine is not and should not be
> considered RNase free. It is very likely that it will be but the chance
> of contamination is still to great for my taste. I always make my RNase
> free solutions from DEPC treated water.
> --
> Peter Pediaditakis
> University of Pittsburgh
> Dept. of Pathology

Well, it seems everybody wants to get their $0.02 in, so here is my turn.

In my experience, the "good" water (e.g., millipore or equivalent -- the
18 megaohm, low TOC stuff) is RNAse-free. I have used it for RNA (even
resuspending the RNA in ultrapure water directly from the tap) without
any further treatment for years without any problem -- no DEPC, no
autoclaving, no 'nuttin. I think if your water has RNAse activity, you
need to get better water, because it probably has other stuff in it, too,
and RNase is not the only thing that can go wrong in the lab.

As for MOPS, I used to autoclave it, and it turned yellow, but it still
worked. Then I stopped autoclaving it, because the yellow did make me a
little nervous, and it still worked. But lately, I've been buying 10X
MOPS (non-yellow) from Quality Biologicals, because I did the price
calculation and it really wasn't that cost-effective to make it from
powder. And I'm one of those crotchety guys who like to make everything
from scratch, too ("What?! You _buy_ TE? Aren't you ashamed?").

Finally, I don't think that RNAse is going to be active in the presence
of formaldehyde in the gel during electrophoresis even if it was there.


Nick Theodorakis
nicholas_theodorakis at

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