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  • Estimate DNA concentration of restricted fragments. Aim for a 3:1 insert:vector molar ratio (660 g/mole/base pair).
    • Where x is the desired concentration of insert, y is the desired concentration of vector, and n is the current ratio of their concentrations, a 3:1 ratio implies the relationship 3/n*y = x .
    • Additionally, the volumes of the substances is governed by the equation total volume = volX + volY + buffer. Usually the total volume we use for ligations is 40μL.


  1. for 20 μL reaction volume, to eppendorf add:
Stuff Volume (uL)
insert x
vector y
dH2O z
10X T4 ligase buffer 2
T4 ligase 0.5
Total 20

where x is usually 5-15 uL, y=[1,5] uL.

Also, always remember to do a negative control, which will be like the reaction above, but w/ no insert. Your transformation plates will then be an measure of any vector re-ligation/uncut background.

  • For overnight ligation, store at 16C (15 hr)