Rapid selection of aminoacyl-tRNAs based on biotinylation of alpha-NH2 group of charged amino acids.

A rapid selection procedure to separate low amounts of aminoacylated tRNAs from large pools of inactive variants is described. The procedure involves a three-step protocol. After initial aminoacylation of a tRNA pool, N-hydroxysuccinimide ester chemistry is applied to biotinylate the alpha-NH2 group of the amino acid bound to the 3'-end of a tRNA. The biotin tag is used to capture the derivatized tRNAs on streptavidin-conjugated magnetic beads. Variants bound to the solid phase can be amplified by RT-PCR and transcription, providing tRNAs for subsequent selection rounds.