Dealkenylative Ni-Catalyzed Cross-Coupling Enabled by Tetrazine and Photoexcitation.

A new and general method to functionalize the C(sp3)-C(sp2) bond of alkyl and alkene linkages has been developed, leading to the dealkenylative generation of carbon-centered radicals that can be intercepted to undergo Ni-catalyzed C(sp3)-C(sp2) cross-coupling. This one-pot protocol leverages the easily procured alkene feedstocks for organic synthesis with excellent functional group compatibility without the need for a photoredox catalyst.

Total Synthesis of (+)-Haperforin G.

A concise chemical synthesis of (+)-haperforin G in 20 steps from commercially available starting materials is achieved with the integration of the Co-catalyzed intramolecular Pauson-Khand reaction for the stereoselective construction of cyclopentanone bearing an all-carbon quaternary stereogenic center at the bridge-head position and the light-initiated photocatalysis for convergent and asymmetric cross-coupling of the unstabilized C(sp3)-radical with an enone. The developed chemistry paves the way to synthesizing structurally diverse analogs of haperforin G (6).

A Dimethyl-Labeling-Based Strategy for Site-Specifically Quantitative Chemical Proteomics.

Activity-based protein profiling (ABPP) has emerged as a powerful functional chemoproteomic strategy which enables global profiling of proteome reactivity toward bioactive small molecules in complex biological and/or pathological processes. To quantify the degree of reactivity in a site-specific manner, an isotopic tandem orthogonal proteolysis (isoTOP)-ABPP strategy has been developed; however, the high cost and long workflow associated with the synthesis of isotopically labeled cleavable tags limit its wide use. Herein, we combined reductive dimethyl labeling with TOP-ABPP to develop a fast, affordable, and efficient method, termed "rdTOP-ABPP", for quantitative chemical proteomics with site-specific precision and triplex quantification. The rdTOP-ABPP method shows high accuracy and precision, good reproducibility, and better capacity for site identification and quantification and is highly compatible with many commercially available cleavable tags. We demonstrated the power of rdTOP-ABPP by profiling the target of (1 S,3 R)-RSL3, a canonical inducer for cell ferroptosis, and provided the first global portrait of its proteome reactivity in a quantitative and site-specific manner.

Selenium-Encoded Isotopic Signature Targeted Profiling.

Selenium (Se), as an essential trace element, plays crucial roles in many organisms including humans. The biological functions of selenium are mainly mediated by selenoproteins, a unique class of selenium-containing proteins in which selenium is inserted in the form of selenocysteine. Due to their low abundance and uneven tissue distribution, detection of selenoproteins within proteomes is very challenging, and therefore functional studies of these proteins are limited. In this study, we developed a computational method, named as selenium-encoded isotopic signature targeted profiling (SESTAR), which utilizes the distinct natural isotopic distribution of selenium to assist detection of trace selenium-containing signals from shotgun-proteomic data. SESTAR can detect femtomole quantities of synthetic selenopeptides in a benchmark test and dramatically improved detection of native selenoproteins from tissue proteomes in a targeted profiling mode. By applying SESTAR to screen publicly available datasets from Human Proteome Map, we provide a comprehensive picture of selenoprotein distributions in human primary hematopoietic cells and tissues. We further demonstrated that SESTAR can aid chemical-proteomic strategies to identify additional selenoprotein targets of RSL3, a canonical inducer of cell ferroptosis. We believe SESTAR not only serves as a powerful tool for global profiling of native selenoproteomes, but can also work seamlessly with chemical-proteomic profiling strategies to enhance identification of target proteins, post-translational modifications, or protein-protein interactions.