Blunt end ligation

Morris F. Manolson mm6y+ at
Thu Feb 25 15:41:35 EST 1993

>  Can someone please send me a copy of their protocol for blunt end 
>ligation of DNA fragments.  Notes on pitfalls would be most appreciated.

I do my blunt end ligations almost the same way I do my sticky
end ligations except for 

1) I phosphatase the vector at 50 C (instead of 37 C) and use twice the
units of Calf Alkaline Phosphatase. 

2) I do the ligation at Rm. Temp (instead of 12 C).

3) I up the ratio of insert to vector from about 2:1 to 4:1

If I am having a real hard time, I will first do the ligation
in 10 ul for a couple of hours at Rm. Temp. (or untill I am ready to go home)
bring the volume up to 19 ul with buffer, add another ul of
ligase and let it sit o/n at 12 C.

Apparently Calf Alk Phos has alot harder time getting the
5' phosphate off a blunt end rather than a 5' sticky end.
If you have lots of vector religation, this may be your problem.
hope this helps,  Morrie

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