Fig. 5: One-pot furan-thiol-amine (FuTine) multicomponent reaction (MCR) for chemoselective modification of proteins.

a Optimization of the selective modification of lysine on protein myoglobin by varying equivalents of both oxidized furan (1–15 equiv.) and thiol (1–15 equiv.) reagents. The full conversion was observed by using 5 equiv. of thiol and furan indicating high robustness and efficiency of the thiol-amine reaction. b MS/MS analysis of modified myoglobin (treated with 1 equiv. each of thiol and furan) showed the modification of K79 and K63 in a 3:1 ratio. c pyrrole-modified myoglobin (pyr-Myo) under the optimized conditions (treatment with 5 equiv. of thiol and furan) demonstrates a similar ability to oxidize o-phenylenediamine as compared to unmodified myoglobin. This data supports the hypothesis that the 3D structure of the myoglobin remained intact after the modification, which was further verified by circular dichroism analysis.