Ligation Calculator
A ligation joins a piece of DNA, the insert, into a vector, the plasmid it goes into. This works out how much insert to add, by mass, for the molar ratio you choose. Change any number and the answer follows.
- Free
- Works offline after your first visit
- Saves on this device
- No sign-up
- Updated
How it works
Insert mass equals the vector mass times the insert length divided by the vector length, then times the molar ratio. A longer insert weighs more for the same number of molecules, so the size comparison matters.
A molar ratio of 3 to 1 is a common starting point, but many protocols suggest testing a few ratios. Your enzyme kit's instructions have the final word for your reaction.
Worked example
A 3,000 bp vector with 100 ng of DNA and a 1,000 bp insert, at a 3 molar ratio, needs 100 ng of insert.
Questions
What is a molar ratio?
It is how many insert molecules you add for each vector molecule. A 3 to 1 ratio means three insert molecules for every vector molecule.
Why does the mass change with insert size?
Mass depends on size as well as count. A longer insert weighs more, so the same number of molecules needs more nanograms.
Can I use this for any kit?
It uses the standard insert and vector math. Some kits recommend their own amounts, so check your kit's protocol too.
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