What you are given
- Vector mass (ng): 50
- Vector length (bp): 5000
- Insert length (bp): 1000
- Insert : vector ratio: 3
Formula: ng insert = ratio x ng vector x (insert bp / vector bp)
Molecular biology
How do you calculate ligation ratio?
Insert mass for a target insert:vector molar ratio. The relationship used is ng insert = ratio x ng vector x (insert bp / vector bp).
Worked example
Every number below is computed by the calculator, not typed in
The working
- Length ratio:
insertBp / vectorBp=0.2 - Substitute:
3 · 50 ng · (1000 / 5000)=30 ng
Use 30 ng of insert with 50 ng of vector (3:1).
What each symbol means
- mᵢ: Insert mass to add (ng)
- R: Insert to vector molar ratio
- mᵥ: Vector mass (ng)
- Lᵢ: Insert length (bp)
- Lᵥ: Vector length (bp)
A printable one-page version is on the formula sheet.
Try it yourself
Two problems, with the working revealed
Problem 1 Ligation ratio
Work out the result for ligation ratio.
- Vector mass (ng): 20
- Vector length (bp): 7500
- Insert length (bp): 1000
- Insert : vector ratio: 3
Show the answer and the working
Use 8 ng of insert with 20 ng of vector (3:1).
- Length ratio:
insertBp / vectorBp=0.1333 - Substitute:
3 · 20 ng · (1000 / 7500)=8 ng
Open this in the calculator to change the numbers.
Problem 2 Ligation ratio
Work out the result for ligation ratio.
- Vector mass (ng): 10
- Vector length (bp): 5000
- Insert length (bp): 3000
- Insert : vector ratio: 6
Show the answer and the working
Use 36 ng of insert with 10 ng of vector (6:1).
- Length ratio:
insertBp / vectorBp=0.6 - Substitute:
6 · 10 ng · (3000 / 5000)=36 ng
Open this in the calculator to change the numbers.
Do it with your own numbers.
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