Questions about DNA recovery by silica binding

Wilson netson at
Sat Oct 18 02:29:37 EST 1997

Dear all,
	Thanks for all netters who answer my questions.  I have a few
questions about the procedure of silica binding.  I have made the silica
and resuspended in guanidium thiocyanate.  After adding the silica to
solution which contain dissolved agarose, DNA and guanidium thiocyanate
salt,  I tap the solution to mix them.  Then should I incubate the mixture
in ice or at room temp?  Which temperature can give better DNA recovery?
Should I use 50% ethanol with 100mM NaCl, Tris-HCl and EDTA or only 70%
ethanol as the washing solution?  Finally,  which incubation temperature
45, 55 or 65oC can elute the DNA more effective?
	One more question is about the safety of guanidium thiocyanate. I
would like to use silica binding to recovery the DNA in mini-prep.  I know
that guanidium thiocyanate can release very toxic gas in acidic solution.
Is it possible that toxic gas released  in the procedure (e.g solution
III) of miniprep?   

Thanks a lot


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