the incorporation of click reaction partners into systems in and ex vivo contribute to the scope of possible reactions. The development of unnatural amino acid incorporation by ribosomes has allowed for the incorporation of click reaction partners as unnatural side groups on these unnatural amino acids. For example, an UAA with an azide side group provides convenient access for cycloalkynes to proteins tagged with this "AHA" unnatural amino acid. In another example, "CpK" has a side group including a cyclopropane alpha to an amide bond that serves as a reaction partner to tetrazine in an inverse diels-alder reaction. The synthesis of luciferin exemplifies another strategy of isolating reaction partners, which is to take advantage of rarely-occurring, natural groups such as the 1,2-aminothiol, which appears only when a cysteine is the final N' amino acid in a protein. Their natural selectivity and relative bioorthogonality is thus valuable in developing probes specific for these tags. The above reaction occurs between a 1,2-aminothiol and a 2-cyanobenzothiazole to make luciferin, which is fluorescent. This luciferin fluorescence can be then quantified by spectrometry following a wash, and used to determine the relative presence of the molecule bearing the 1,2-aminothiol. If the quantification of non-1,2-aminothiol-bearing protein is desired, the protein of interest can be cleaved to yield a fragment with a N' Cys that is vulnerable to the 2-CBT. Additional applications include: two-dimensional gel electrophoresis separation preparative organic synthesis of 1,4-substituted triazoles modification of peptide function with triazoles modification of natural products and pharmaceuticals natural product discovery drug discovery macrocyclizations using Cu(I) catalyzed triazole couplings modification of DNA and nucleotides by triazole ligation supramolecular chemistry: calixarenes, rotaxanes, and catenanes dendrimer design carbohydrate clusters and carbohydrate conjugation by Cu(1) catalyzed triazole ligation reactions polymers and biopolymers surfaces material science nanotechnology, bioconjugation, for example, azidocoumarin, and biomaterials In combination with combinatorial chemistry, high-throughput screening, and building chemical libraries, click chemistry has hastened new drug discoveries by making each reaction in a multistep synthesis fast, efficient, and predictable. Technology license The Scripps Research Institute has a portfolio of click-chemistry patents. Licensees include Invitrogen, Allozyne, Aileron, Integrated Diagnostics, and the biotech company baseclick, a BASF spin-off created to sell products made using click chemistry. Moreover, baseclick holds a worldwide exclusive license for the research and diagnostic market for the nucleic acid field. Fluorescent azides and alkynes are also produced by companies such as Cyandye. References External links Click Chemistry: Short