From Heit Lab Wiki
- Determine the amount of plasmid and insert to be used through the equation X ng plasmid/[(1 M) X bp] = X ng insert/[(X M) X bp]. It is best to have a pasmid to insert ratio between 1:4 and 1:10. Note: a useful website for this calculation is http://www.insilico.uni-duesseldorf.de/Lig_Input.html. Also, using 150 ng of vector is a good starting point.
- Add the following volumes to a round-lidded PCR tube:
X of insert
X of plasmid
|5x T4 DNA ligase buffer
|T4 DNA ligase
||up to 20 μL
Note: Larger total volumes can be used; however, it is best to keep the total volume as small as possible, without going below 20 μL.
- Gently mix by tapping the side of the tube.
- Centrifuge the tube for 5 seconds at 4,500 xg
- Leave tube at room temperature overnight.