Facile de novo sequencing of tetrazine-cyclized peptides through UV-induced ring-opening and cleavage from solid phase.

While most FDA-approved peptide drugs are cyclic, robust cyclization chemistry of peptides and the deconvolution of the cyclic peptide sequences using tandem mass spectrometry render cyclic peptide drug discovery difficult. Here we present a successful design of cyclic peptides on solid phase that addresses both these problems. We demonstrate that this peptide cyclization method using dichloros-tetrazine on solid-phase allows successful cyclization of a panel of random peptide sequences with varying charges and hydrophobicity. The cyclic peptides can be linearized and cleaved from the solid phase by simple UV light irradiation, and we demonstrate that accurate sequence information can be obtained for the UV-cleaved linearized peptides using tandem mass spectrometry. The tetrazine linker used in the cyclic peptides can further be explored for inverse electron-demand Diels Alder (IEDDA) reactions for screening or bioconjugation applications in the future.