Is it obligatory to precipitate DNA from ligation before transformed into E.coli - (Apr/18/2006 )

I added DNA from ligation reaction without ethanol precipitation with competent cells of E.coli, but got no colonies. I found some articles on the internet suggusting to do the ethanol precipitation before transformation into E.coli because of the ion strength in the ligation buffer. Is that obligatory to do so?
Hope anyone give me some suggestions.

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I have succesfully transformed directly from the ligation mixture, so it works. I don't know if precipitation would make it more succesfull, maybe it does make a difference for electroporation?

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hi
the risk is to add too much salts for electroporation. My boss do 1µl ligation with 50*µl electrocompetent bacterias with great results.

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if you don't remove the salts before electroporation (ie. clean up your ligation) you will get a loud pop and destroy your cells!
before heatshock there is no real reason to clean up your ligation....

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I didn't destroy the cells since the electroporation machine showed the voltage is normal.

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hi I never did precipitation of my ligation. never heard aqbout this before.
I heat shock them ar 42C for 1m30s.

never add a problem
if you don't get clolony I don't think it's a transformation problem.
you ligation maybe wrong.

ulujm

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if you are electroporating and want to remove excess salts (the other ligation components shouldn't really hurt anything, I think) then drop-dialysis against sterile dH2O is much faster than ethanol precipitation and allows for probably a higher percentage of recovery..it only takes about 5-10 minutes and will remove salts quite readily

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Thanks to eveybody here.
I also think there is some problem with my ligation because my positive control got many colonies. I will try to do the ligation again. I hope I will get what I expect in a few days.
Thanks again to vairus, fred_33, aussieuk, ulujm, and aimikins

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