Expanding the Genetic Code of Escherichia coli

@article{Wang2001ExpandingTG,
  title={Expanding the Genetic Code of Escherichia coli},
  author={Lei Wang and Ansgar Brock and Brad Herberich and Peter G. Schultz},
  journal={Science},
  year={2001},
  volume={292},
  pages={498 - 500}
}
A unique transfer RNA (tRNA)/aminoacyl-tRNA synthetase pair has been generated that expands the number of genetically encoded amino acids in Escherichia coli. When introduced into E. coli, this pair leads to the in vivo incorporation of the synthetic amino acid O-methyl-l-tyrosine into protein in response to an amber nonsense codon. The fidelity of translation is greater than 99%, as determined by analysis of dihydrofolate reductase containing the unnatural amino acid. This approach should… 
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The genetic code is established by the aminoacylation of transfer RNA, reactions in which each amino acid is linked to its cognate tRNA that, in turn, harbors the nucleotide triplet (anticodon)
Expanding the genetic code.
TLDR
Using this strategy, the genetic code of Escherichia coli has been expanded to incorporate unnatural amino acids with a fidelity rivaling that of natural amino acids.
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