Help! DNA insoluble in water

Ian A. York york at mbcrr.dfci.harvard.edu
Mon Oct 17 18:14:02 EST 1994


In article <37ugi1$iab at nermal.cs.uoguelph.ca> nxu at uoguelph.ca (Nanfel Xu) writes:

>	It drives me crazy that my DNA won't dissolve in water!  I put 60 
[ . . . ]
>P.S.  I tried precipitating the same DNA without digestion.  It dissolved 
>in water perfectly no matter how it was dried or precipitated.
>

	I occasionally run into DNA that doesn't want to resuspend, but 
usually persistence (or setting it aside and forgetting about it for a 
while) gets it into solution.  I haven't found any one procedure that 
consistently causes insoluble DNA.  
	You have probably already tried these, but (1) try air-drying
rather than speedvac (the books say that speed-vacc'ed DNA is hard to
dissolve); (2) perhaps your water is a little on the acidic side, and/or
you are carrying over some acidic stuff from previous steps: be sure to
give the DNA a wash with 70% EtOH after the EtOH precip, and try
resuspending in TE pH 7.5 rather than water; (3) try resuspending in
warm/hot water (50oC or higher); (4) try using one of the DNA cleanup 
kits, rather than phenol, to purify out the enzyme.
	Good luck.

Ian

-- 
Ian York   (york at mbcrr.harvard.edu)
Dana-Farber Cancer Institute, 44 Binney St., Boston MA 02115
Phone (617)-632-4328     Fax  (617)-632-2627




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