problems in purification of small DNA fragments

Klaus Salger salger at
Wed Nov 30 23:42:50 EST 1994

carver cathy (CCARVER at UGA.CC.UGA.EDU) wrote:
: We have been having some problems in isolating smaller DNA (120bp)
: fragments from agarose gels. We have tried QIAEX columns,
: electroelution but with little sucess. The former did not elute any
: DNA whereas the latter gave a very poor yield - about 10ng per microlitre.

I recommend Jim Graham's protocol which is on Paul Hengen's FAQ-list:
run fragment on low melting agarose
cut it out
melt the gel slice
freezing it (e.g. in N2)
thaw it
centrifuge (minimum 5min 14000rpm)
DNA is in the supernatant

This works with normal agarose, too (leave out the melting) but gives
lower yields.
Hope this helps

Klaus Salger                phone : ++49 (0)89 5902 -502
Zoologisches Institut       FAX   :                 -450
AG MacWilliams              e-mail: salger at
Luisenstr. 14
80333 Muenchen

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