Skip to content


You currently have no items in your basket.

Total (excl. vat) £0.000
View basket & checkout


Non-natural amino acid-charged tRNAs for site directed protein functionalization.


CloverDirect™ is a line of products from Protein Express that permit targeted incorporation of non-natural amino acids into proteins expressed in cell-free coupled transcription/translation systems based on cell lysates or purified components. Each product comprises an aminoacyl tRNA (either UAG [amber] or CGGG) charged with a specific unnatural amino acid. To introduce unnatural amino acids at user-defined positions, templates are designed with appropriately placed UAG (amber) and/or CGGG codons. User-designed templates can be either mRNA, linear PCR products or expression plasmids.


Protein Express also offers linear template-generating PCR kits and expression vectors that encode a specialized N-terminal peptide (ProX tag) designed for large unnatural amino acids whose efficient incorporation requires precise N-terminal positioning (codon 9) and a specific codon context (flanked by AAC and TCT) (1). Originally developed for the 4 base CGGG codon, the ProX tag can also function to promote N-terminal incorporation of unnatural amino acids using the amber codon (2).



CloverDirect™ offers off-the-shelf UAG or CGGG aminoacyl tRNAs charged with non-natural amino acids that permit:

  1. Fluorescent-labeling
  2. Biotin-labeling
  3. PEGylation
  4. Chemical crosslinking
  5. Photo-regulation of a variety of biological processes, including enzyme, receptor, and ion channel activity