The disclosure provides compounds of formula II with warheads and their use in treating medical diseases or disorders, such as viral infections. Pharmaceutical compositions and methods of making various compounds with warheads are provided. The compounds are contemplated to inhibit proteases, such as the 3C, CL- or 3CL-like protease.

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The invention relates to genetic incorporation of 2,3-diamino propionic acid (DAP) into polypeptides, to unnatural amino acids comprising DAP, to a tRNA synthetase for charging tRNA with unnatural amino acids comprising DAP, and to methods of using the resulting polypeptides, for example in capturing substrates and/or intermediates in enzymatic reactions. The invention also relates to compounds of formula (I) or (II): or salts, solvates, tautomers, isomers or mixtures thereof.

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The present disclosure provides a biosensor for the detection of protease activity. The detection of protease activity can be used for the detection of viral infection, in particular coronavirus infection. The biosensor described herein can be used to detect SARS-CoV-2. The present disclosure also provides vectors expressing the biosensor and methods for using the same.

A method of identifying compounds that reduce main protease (Mpro) activity of a coronavirus is described, which comprises identifying compounds that bind to and stabilize a modified Mpro in an oxidized conformation with a disulfide bond formed between Cys145 (C145) and Cys117 (C117) of Mpro, reducing the catalytic activity of the modified Mpro. The modified Mpro may comprise substitution of a residue at one or both sites of His163 (H163), and/or Phe140 (F140). A modified Mpro enzyme structure (and its in vitro synthesized form) is described, together with a system for screening or designing compounds useful in treatment or prophylaxis of coronavirus infection such as infection from SARS-CoV-2.

The invention relates to genetic incorporation of 2,3-diamino propionic acid (DAP) into polypeptides, to unnatural amino acids comprising DAP, to a tRNA synthetase for charging tRNA with unnatural amino acids comprising DAP, and to methods of using the resulting polypeptides, for example in capturing substrates and/or intermediates in enzymatic reactions. The invention also relates to compounds of formula (I) or (II): ##STR00001##
or salts, solvates, tautomers, isomers or mixtures thereof.

The invention relates to genetic incorporation of 2,3-diamino propionic acid (DAP) into polypeptides, to unnatural amino acids comprising DAP, to a tRNA synthetase for charging tRNA with unnatural amino acids comprising DAP, and to methods of using the resulting polypeptides, for example in capturing substrates and/or intermediates in enzymatic reactions. The invention also relates to compounds of formula (I) or (II):

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or salts, solvates, tautomers, isomers or mixtures thereof.