ThioD is a protein linker with a hydrophobic thioester[1].
References
[1] Nicholas Holloran, et al. Site-Specific Synthesis of Cysteine-Bridged Glycoproteins via Expressed Protein Glycoligation. Bioconjug Chem. 2020 Oct 21;31(10):2362-2366. DOI:10.1021/acs.bioconjchem.0c00437