Deuterium- and tritium-labeled pharmaceutical compounds are pivotal diagnostic tools in drug discovery research, providing vital information about the biological fate of drugs and drug metabolites. Herein we demonstrate that a photoredox-mediated hydrogen atom transfer protocol can efficiently and selectively install deuterium (D) and tritium (T) at α-amino sp3 carbon-hydrogen bonds in a single step, using isotopically labeled water (D2O or T2O) as the source of hydrogen isotope. In this context, we also report a convenient synthesis of T2O from T2, providing access to high-specific-activity T2O. This protocol has been successfully applied to the high incorporation of deuterium and tritium in 18 drug molecules, which meet the requirements for use in ligand-binding assays and absorption, distribution, metabolism, and excretion studies.

Myotube formation by fusion of myoblasts and subsequent elongation of the syncytia is essential for skeletal muscle formation. However, molecules that regulate myotube formation remain elusive. Here we identify PIEZO1, a mechanosensitive Ca2+ channel, as a key regulator of myotube formation. During myotube formation, phosphatidylserine, a phospholipid that resides in the inner leaflet of the plasma membrane, is transiently exposed to cell surface and promotes myoblast fusion. We show that cell surface phosphatidylserine inhibits PIEZO1 and that the inward translocation of phosphatidylserine, which is driven by the phospholipid flippase complex of ATP11A and CDC50A, is required for PIEZO1 activation. PIEZO1-mediated Ca2+ influx promotes RhoA/ROCK-mediated actomyosin assemblies at the lateral cortex of myotubes, thus preventing uncontrolled fusion of myotubes and leading to polarized elongation during myotube formation. These results suggest that cell surface flip-flop of phosphatidylserine acts as a molecular switch for PIEZO1 activation that governs proper morphogenesis during myotube formation.

We found that N-heterocyclic carbene catalysis promoted the unprecedented decarboxylative coupling of aryl aldehydes and tertiary or secondary alkyl carboxylic acid-derived redox-active esters to produce aryl alkyl ketones. The mild and transition-metal-free reaction conditions are attractive features of this method. The power of this protocol was demonstrated by the functionalization of pharmaceutical drugs and natural product. A reaction pathway involving single electron transfer from an enolate form of Breslow intermediate to a redox ester followed by recombination of the resultant radical pair to form a carbon–carbon bond is proposed.

Lipids play crucial roles as the structural elements, signalling molecules, and material transporters in cells. However, the functions and dynamics of lipids within cells remain unclear because of a lack of methods to selectively label lipids in specific organelles and trace their movement by live-cell imaging. We describe here a technology for the selective labelling and fluorescence micro/nanoscopic imaging of phosphatidylcholines in target organelles. The approach involves the metabolic incorporation of azido-choline followed by a spatially limited bioorthogonal reaction, which enables the visualization and quantitative analysis of interorganelle lipid transport in live cells. Most importantly, with live-cell imaging, we obtained direct evidence that the autophagosome membrane originates from the endoplasmic reticulum. This method is simple and robust, and thus powerful for real-time tracing of interorganelle lipid trafficking.

Ceramide phosphoethanolamine (CPE), a sphingomyelin analog, is a major sphingolipid in invertebrates and parasites, whereas only trace amounts are present in mammalian cells. In this study, mushroom-derived proteins of the aegerolysin family—pleurotolysin A2 (PlyA2; K(D) = 12 nM), ostreolysin (Oly; K(D) = 1.3 nM), and erylysin A (EryA; K(D) = 1.3 nM)—strongly associated with CPE/cholesterol (Chol)-containing membranes, whereas their low affinity to sphingomyelin/Chol precluded establishment of the binding kinetics. Binding specificity was determined by multilamellar liposome binding assays, supported bilayer assays, and solid-phase studies against a series of neutral and negatively charged lipid classes mixed 1:1 with Chol or phosphatidylcholine. No cross-reactivity was detected with phosphatidylethanolamine. Only PlyA2 also associated with CPE, independent of Chol content (K(D) = 41 μM), rendering it a suitable tool for visualizing CPE in lipid-blotting experiments and biologic samples from sterol auxotrophic organisms. Visualization of CPE enrichment in the CNS of Drosophila larvae (by PlyA2) and in the bloodstream form of the parasite Trypanosoma brucei (by EryA) by fluorescence imaging demonstrated the versatility of aegerolysin family proteins as efficient tools for detecting and visualizing CPE.