Questions about DNA recovery by silica binding

Paul R. Rohde P.Rohde at
Tue Oct 14 02:34:15 EST 1997

Wilson <netson at> writes: > Dear all,
> 	I would like to use homemake silica to recover DNA from agarose
> gel.  I know that DNA can bind to the silica under high salt
> concentration.  Almost all protocol are suggested that high concentration
> of NaI is used to dissolve agarose gel and provide the high salt condition
> for the DNA binding.  Is it possible to use other salt such as NaCl, KCl
> etc to substitute NaI (if my DNA is in agarose gel or in TE)?  Is there
> any advantage of using NaI rather than other salt? 
> Thank you very much
> Wilson

I can't comment about the other salts, but a 4 M solution of 
Guanidinium thiocyanate or  7 M Guanidinium HCl should do the trick.
These will dissolve the agarose, and allow DNA to bind to silica, plus
they inhibit nucleases.  Sombody who does RNA work may have these salts.
Before eluting the DNA off the silica, wash a couple of times in 70% EtOH.

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