T4 DNA Ligase

T4 DNA ligase is supplied at either 500 U/µL or 2500 U/µL along with 10X buffer. 1U is a cohesive end joining unit (CELU). 250 CELUs is approximately 1 Weiss unit so 500 CELUs/µL is equivalent to ~2 Weiss units/µL (TDL1, TDL2) or 10 Weiss units/µL (TDL3C)

1 CELU is defined as the amount of enzyme to give 50% of HindIII fragments of λ DNA (5´ DNA termini concentration of 0.12 µM, 300- µg/mL) in a total reaction volume of 20 μL in 30 minutes at 16°C in 1X T4 DNA Ligase Assay Buffer.

Enzyme Storage Buffer:

10 mM Tris.HCl (pH 7.5); 50 mM KCl, 1 mM DTT,  0.1 mM EDTA, 50% Glycerol

*Enzyme storage buffer also available with TCEP instead of DTT

T4 DNA Ligase Assay Buffer

50 mM Tris.HCl (pH 7.5), 10mM MgCl2, 10 mM DTT, and 1mM ATP,  (Supplied as 10X). 

Alternative T4 DNA Ligase Storage Buffer 

50 mM Tris (pH7.5), 100 mM NaCl, 0.1 mM EDTA, 2mM TCEP, 50% Glycerol, 0.1% (v/v) Triton X-100*

* can be supplied with Tween-20 or without detergent.