Cloudy DNA

Dave tranmaster at hotmail.com
Tue Aug 24 08:27:28 EST 2004


I recently did some work with CT DNA and found the Sigma CT-DNA fine
when suspended in aqueous NaCl and Buffer (i used HEPES).  It was easy
to rehydrate and solutions were not at all cloudy, with the UV-vis
profile also looking fine.

aaron.engelhart at gmail.com (Aaron Engelhart) wrote in message news:<afd496b4.0408230123.33877bd6 at posting.google.com>...
> We do some work with calf thymus DNA at high concentrations (3-7
> millimolar) in milliliter quantities for spectrophotometry/transient
> absorption spectroscopy purposes. One problem is that it seems to be
> fairly cloudy above the millimolar level. This is the cheapest source
> of DNA, so I like to use it for obvious reasons before doing
> experiments on synthetic oligos or polyG-polyC, etc, but the
> cloudiness is a problem. I have done some work with phenol extraction,
> which seems to help a bit, but with significant product loss. Every
> time I do a phenol extraction, there is a bit of whitish gunk at the
> interface. I don't understand the mechanics of this completely, or
> exactly what it is. There's some obvious product loss from leaving a
> bit of the supernatant behind to avoid taking up the impurity, but my
> understanding is that the dsDNA stays in the aqeuous phase and the
> proteins go into the organic phase. A260/280 ratio looks fine (and
> unchanged!) before and after extraction. Does anyone have a good way
> to clear up CTDNA/know what this is? TIA,
> Aaron

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