Abstract
Peptides containing selenocysteine moieties are susceptible to non‐catalytic reactions of diselenide bonds metathesis induced by visible light. In contrast to previously reported radical metathesis of disulfide bridges in cysteine derivatives, this newly developed reaction is fast and clean, and proceeds without decomposition of peptides and without formation of side products. The diselenide bond in peptides was reported in literature to be more stable than the disulfide one and also less susceptible to metathesis induced by thiols and reducing reagents. We demonstrated that visible light induces fast metathesis of Se−Se bonds in peptides. This reaction is important for the folding of peptides containing selenocysteine residues and may find application in designing dynamic combinatorial libraries of peptides responsive to external influence.
Highlights
UV irradiation induced disulfide metathesis is based on homolytic cleavage of the disulfide bond and the subsequent cross-reaction between resulting radicals, the visible light turned out to be sufficient for a diselenide exchange because of relatively low energy of Se Se bond.[14]
The metathesis reaction in diselenide based systems is useful in designing self-healing polymers[15,16] as well as in selective surface modification e. g. for bioconjugation purposes.[17]
We found that prolongation of the irradiation up to 24 h resulted in a higher yield of the exchange synthesis of peptide libraries based on diselenide bridges
Summary
We confirmed the previous literature reports that application of similar conditions enables the exchange reaction between two low-molecular-weight compounds.[21] The reactions were monitored by NMR and the final results are presented in the Supplementary section (see Figures S13–14). The metathesis reaction for low-molecular-weight systems was confirmed by TLC (data not presented). The exchange processes did not proceed in the absence of light. This observation is consistent with the literature data and, in our opinion, decisively proves the proposed free radical mechanism.[21a] the aforementioned mechanism We showed for the first time the visible light induced diselenides exchange in peptides
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