Biotechniques. 2002 Dec;33(6):1256-60

Wang QS, Unrau PJ.

Purification of histidine-tagged T4 RNA ligase from E. coli.

De-adenylation of T4 RNA ligase is required prior using adenylated substrates. Incubating with pyrophosphate during some purification steps does the job. Commercial T4 usually contains mostly de-adenylated enzyme. Mesuring reaction efficiency without ATP gives adenylation levels.