Terminal Deoxynucleotidyl Transferase, Recombinant (rTdT) is a DNA polymerase that catalyzes the addition of deoxynucleotides to the 3fi hydroxyl terminus of DNA. A TdT Technical Bulletin is available.

Applications: Homopolymer tailing of vector and insert for cloning. Labeling oligonucleotides with biotin (1,2), ³²P- or ³⁵S-label (3), or in apoptosis (TUNEL) (4,5).

Source: Purified from E. coli clone of calf thymus TdT.

Performance and Quality Testing: Endonuclease, 3´ and 5´ exodeoxyribonuclease, and levels of incorporation tested.

Unit Definition: One unit incorporates 1 nmol dATP into acid-precipitable material in 1 h at 37°C, using d(pA)₅₀ as a primer.

Hazard Warning: Toxic; potassium cacodylate contained in reaction buffer. Also contains cobalt chloride, a highly toxic chemical.
See MSDS.

Unit Reaction Conditions: 0.2 M potassium cacodylate (pH 7.2), 10 mM MgO₄ C₄ H₆ , 1 mM 2-mercaptoethanol, 0.5 mg/ml BSA,
100 flM d(pA)₅₀, 1 mM [³H]dATP, and enzyme in 0.15 ml for 1 h at 37°C.