Multi-molecule reaction of serum albumin can occur through thiol-yne coupling

Abstract

The free-radical hydrothiolation of alkynes (thiol-yne coupling, TYC) unites two thiol fragments across the carbon-carbon triple bond to give a dithioether derivative with exclusive 1,2-addition; this reaction can be used for modification of peptides and proteins allowing glycoconjugation and fluorescent labeling. These results have implications not only as a flexible strategy for attaching two modifications at a single site in proteins but also for unanticipated side-reactions of reagents (such as cycloalkynes) used in other protein coupling reactions.

Synthesis of Heterobifunctional Protein Fusions Using Copper‐Free Click Chemistry and the Aldehyde Tag

“…One concern was the possible side reactivity of DIBAC reagents with free thiols, which has been noted with other reactive cyclooctynes. [40,41] Our experiments with MBP could not address this issue, as the protein has no free cysteine residues. Thus, we performed a similar reaction with aldehyde-tagged human serum albumin (HSA), which contains a natural free cysteine residue.…”

Selective chemical protein modification

“…This has subsequently been exploited at both genetically encoded alkenes 169,183 and native cysteine residues 184 to generate glycoprotein mimics 169,184 , and for surface immobilisation of proteins 172 . A related reaction, the thiol-yne reaction with alkynes, has also been reported 100,185 . Photocrosslinking residues in proteins that exploit the chemistry of photogenerated reactive intermediates have also seen a resurgence.…”

“…The site-specific incorporation of cyclooctynes 97 and biscyclononynes 98 into proteins by amberstop codon suppression has also recently been reported. However, limitations remain, such as occasional difficulty in the synthesis and handling of strained and unstable compounds, while crucially a degree of incompatibility towards cysteine has been reported 99,100 . In addition, these reactions remain relatively slow (Fig.…”

Reactivity of Persulfides Toward Strained Bicyclo[6.1.0]nonyne Derivatives: Relevance to Chemical Tagging of Proteins

“…8 , 5, 6 Moreover, strained alkynes demonstrate interesting bioorthogonal selectivity towards some cysteine PTMs as they are inert towards disulfide, sulfinic acids, S-nitrosothiols or thiols, although this last point needs further clarification. 9,10,11 Another cysteine oxidative modification recently emerged and is related to hydrogen sulfide (H 2 S)-mediated redox signaling. H 2 S is the third gaseous transmitter in mammals, along with nitrogen and carbon monoxides, and part of its signaling activity is mediated by the formation of proteins 12,13,14,15,16,17 and low molecular weight persulfides (= hydrodisulfides).…”