T4 RNA Ligase 1 is an ATP-dependent enzyme that catalyzes the formation of phosphodiester bonds between the 5'-P and 3'-OH ends of single-stranded RNA, single-stranded DNA, or single nucleotides, either intermolecular or intramolecular. It is suitable for the connection of single-stranded RNA molecules and the 5' end junction constructed by miRNA libraries in NGS. Labeled with RNA 3 'terminal; Cyclization of oligonucleotides; tRNA modification; In 5'-RACE （Rapid Amplification of cDNA Ends） assay, it is used for oligonucleotides to bind to single-stranded cDNA; and the introduction of unnatural amino acids into proteins.