Oligo stability in water at -20 C

Hiranya Roychowdhury hroychow at NMSU.EDU
Tue Aug 11 10:34:26 EST 1998


At 01:31 AM 8/11/98 GMT, Michael T. MacDonell wrote:
>Dear Hiranya:
>
>Maybe.
>I just have not observed it to be significant, and I have been
>observing for about 15 years.  Anyway, I wonder how much spontaneous
>degradation is actually attributable to nucleases.  How are can you be
>sure you are not seeing nuclease degradation and believing that it to
>be autocatalysis?
>
>Best Regards,
>Mike MacDonell, Ph.D.
>Chief Scientific Officer
>Ransom Hill Bioscience
>

Dear Mike,
        While nuclease may not be totally discounted in any situation,
autocatalysis of nucleic acid is a fact. The reason I'm sure about this is
that I had performed a simple expt a couple of years back. I made up two
tubes of a working conc. of a DNA size markers: one in plain water
(nuclease-free) and the other in TE. they were both stored at 4 C in the
walk-in cooler. I checked the markers periodically. After about six weeks,
the markers stored in plain water started showing diffused pattern, and, by
about another four weeks, only a smear on the gel used to be visible. The
markers stored in TE continued to show sharp bands till the tube was empty. 
        The reason for this demonstration was a grad student's show of
disbelief at the suggestion of NA autocatalysis. She had made up aliquotes
of the DNA markers in plain water (about 40 of them), and they were of no
use after some time. The degradation is minimal at -70 C. At -20 C, unless
undergoing repeated thawings, it proceeds but very slowly. Degradation due
to nucleases at 4 C, or even at -20 C, does not take very long.
with regards,
Hiranya


Dr. Hiranya Sankar Roychowdhury
Plant Genetic Engineering Lab.
New Mexico State University
Las Cruces, NM 88003
Ph. (505) 646-5785
hroychow at nmsu.edu




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