DNA Ligation Calculator
Determine the exact mass of insert DNA required for an optimized ligation reaction. Ensures correct stoichiometric ratios to maximize cloning efficiency.
Reaction Parameters
Specify vector size, vector mass, insert size, and molar ratio.
Required Insert Mass
* Stoichiometric amount for optimal sticky-end or blunt-end cloning.
Sticky vs. Blunt Ends
Use 3:1 for cohesive overhangs. Increase to 5:1 or 10:1 for blunt-end ligations.
Recommended Ligation Conditions Reference Matrix
| Ligation Type | Recommended Molar Ratio (Insert:Vector) | Incubation Temp & Duration | Dephosphorylation Needed? |
|---|---|---|---|
| Sticky Ends (Dual Cut) | 3 : 1 | 16°C overnight OR 25°C for 10 min | No (Incompatible ends) |
| Sticky Ends (Single Cut) | 3 : 1 or 5 : 1 | 16°C overnight | Yes (CIP / rSAP recommended) |
| Blunt Ends (EcoRV, SmaI, etc.) | 5 : 1 or 10 : 1 | 16°C overnight OR 20°C for 2 hours | Yes (High self-ligation risk) |
| TA Cloning (PCR Products) | 3 : 1 | 14–16°C overnight | No (T-overhang vector) |
Calculation Methodology & Equations
Ligation Mass Equation
Maintains stoichiometric equivalence based on base pair length.
Total DNA Load
Ensures total reaction DNA is kept under 200 ng per 20 μL reaction for optimal competent cell transformation efficiency.
Frequently Asked Questions
What molar ratio of insert-to-vector should I use? ▼
A 3:1 molar ratio (insert to vector) is standard for cohesive (sticky-end) ligations. For blunt-end cloning or difficult inserts, increase the molar ratio to 5:1 or 10:1.
How is insert mass calculated for ligation? ▼
Insert Mass (ng) = Vector Mass (ng) × [Insert Size (kb) / Vector Size (kb)] × Molar Ratio (Insert:Vector).
Why should vector DNA be dephosphorylated? ▼
Removing 5' phosphate groups from linearized vector DNA using alkaline phosphatase (CIP/rSAP) prevents self-ligation without an insert, reducing background transformants.
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