Ligation/Transformation problem - (Nov/24/2005 )

The ligatoin was transformed sucessfully into XLI-Blue competent cell and about 100 colonies were obtained.
AFter one month, I used the same ligation product stored at 4 oC to trnasform the same type of competent cell and did not get any colony growing. Meanwhile, the positive control did show expected colonies growing.

I am wondering did something happen to this ligation product during 1 month storage at 4 oC?
Any comment is welcome.
Thanks

I prefer to keep ligation product in -20. I have no experience to keep it at 4 degree.

Plasmid DNA is generally stored at -20C. Still your plasmid kept at 4C for one month should be fine. Check other possibilities like comp cells.

I've never had good luck with a ligation reaction that's been sitting for more than a day, even in the fridge. Not sure why, I assume trace nuclease or just something in the reaction mixture that interferes (I believe NEB ligase buffer, possibly others, have DTT in them, which does tend to take on unwanted properties if left to sit for too long).

I guess I don't know what causes it, but I never attempt to transform any ligation over a day old.

i agree i would keep the ligation product at -20......you never know...