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Cellular proteins are dynamically regulated in response to environmental stimuli. Conventional proteomics compares the entire proteome in different cellular states to identify differentially expressed proteins, which suffers from limited sensitivity for analyzing acute and subtle changes. To address this challenge, nascent proteomics has been developed, which selectively analyzes the newly synthesized proteins, thus offering a more sensitive and timely insight into the dynamic changes of the proteome. In this Minireview, we discuss recent advancements in nascent proteomics, with an emphasis on methodological developments. Also, we delve into the current challenges and provide an outlook on the future prospects of this exciting field. [ABSTRACT FROM AUTHOR]

Chiral nanographenes with both high fluorescence quantum yields (ΦF) and large dissymmetry factors (glum) are essential to the development of circularly polarized luminescence (CPL) materials. However, most studies have been focused on the improvement of glum, whereas how to design highly emissive chiral nanographenes is still unclear. In this work, we propose a new design strategy to achieve chiral nanographenes with high ΦF by helical π‐extension of strongly luminescent chromophores while maintaining the frontier molecular orbital (FMO) distribution pattern. Chiral nanographene with perylene as the core and two dibenzo[6]helicene fragments as the wings has been synthesized, which exhibits a record high ΦF of 93 % among the reported chiral nanographenes and excellent CPL brightness (BCPL) of 32 M−1 cm−1. [ABSTRACT FROM AUTHOR]

Synthesis of bicyclic scaffolds has gained significant attention in drug discovery due to their potential to mimic benzene bioisosteres. Here, we present a mild and scalable Sc(OTf)3‐catalyzed [3+2] cycloaddition of bicyclo[1.1.0]butanes (BCBs) with ynamides, yielding a diverse array of polysubstituted 2‐amino‐bicyclo[2.1.1]hexenes in good to excellent yields. These products offer valuable starting materials for the construction of novel functionalized bicyclo[1.1.0]butanes. Preliminary mechanistic studies indicate that the reaction involves a nucleophilic addition of ynamides to bicyclo[1.1.0]butanes, followed by an intramolecular cyclization of in situ generated enolate and keteniminium ion. We expect that these findings will encourage utilization of complex bioisosteres and foster further investigation into BCB‐based cycloaddition chemistry. [ABSTRACT FROM AUTHOR]

Despite the remarkable synthetic accomplishments in creating diverse polycyclic aromatic hydrocarbons with B−N bonds (BN‐PAHs), their optoelectronic applications have been less exploited. Herein, we report the achievement of high‐mobility organic semiconductors based on existing BN‐PAHs through a "periphery engineering" strategy. Tetraphenyl‐ and diphenyl‐substituted BN‐anthracenes (TPBNA and DPBNA, respectively) are designed and synthesized. DPBNA exhibits the highest hole mobility of 1.3 cm2 V−1 s−1 in organic field‐effect transistors, significantly outperforming TPBNA and all the reported BN‐PAHs. Remarkably, this is the first BN‐PAH with mobility over 1 cm2 V−1 s−1, which is a benchmark value for practical applications as compared with amorphous silicon. Furthermore, high‐performance phototransistors based on DPBNA are also demonstrated, implying the high potential of BN‐PAHs for optoelectronic applications when the "periphery engineering" strategy is implemented. [ABSTRACT FROM AUTHOR]

Proteins are ubiquitously modified with glycans of varied chemical structures through distinct glycosidic linkages, making the landscape of protein glycosylation challenging to map. Profiling of intact glycopeptides with mass spectrometry (MS) has recently emerged as a powerful tool for revealing matched information of the glycosylation sites and attached glycans (i.e. intact glycosites), but is largely limited to individual glycosylation types. Herein, we describe Click‐iG, which integrates metabolic labeling of glycans with clickable unnatural sugars, an optimized MS method, and a tailored version of pGlyco3 software to enable simultaneous enrichment and profiling of three types of intact glycopeptides: N‐linked, mucin‐type O‐linked, and O‐GlcNAcylated glycopeptides. We demonstrate the utility of Click‐iG by the identification of thousands of intact glycosites in cell lines and living mice. From the mouse lung, heart, and spleen, a total of 2053 intact N‐glycosites, 262 intact O‐GalNAc glycosites, and 1947 O‐GlcNAcylation sites were identified. Click‐iG‐enabled comprehensive coverage of the protein glycosylation landscape lays the foundation for interrogating crosstalk between different glycosylation pathways. [ABSTRACT FROM AUTHOR]

Self‐renewal and differentiation of embryonic stem cells (ESCs) are influenced by protein O‐linked β‐N‐acetylglucosamine (O‐GlcNAc) modification, but the underlying mechanism remains incompletely understood. Herein, we report the identification of 979 O‐GlcNAcylated proteins and 1340 modification sites in mouse ESCs (mESCs) by using a chemoproteomics method. In addition to OCT4 and SOX2, the third core pluripotency transcription factor (PTF) NANOG was found to be modified and functionally regulated by O‐GlcNAc. Upon differentiation along the neuronal lineage, the O‐GlcNAc stoichiometry at 123 sites of 83 proteins—several of which were PTFs—was found to decline. Transcriptomic profiling reveals 2456 differentially expressed genes responsive to OGT inhibition during differentiation, of which 901 are target genes of core PTFs. By acting on the core PTF network, suppression of O‐GlcNAcylation upregulates neuron‐related genes, thus contributing to mESC fate determination. [ABSTRACT FROM AUTHOR]

A stable nanohoop radical (OR3) combining the structures of cycloparaphenylene and an olympicenyl radical is synthesized and isolated in the crystalline state. X‐ray crystallographic analysis reveals that OR3 forms a unique head‐to‐tail dimer that further aggregates into a one‐dimensional chain in the solid state. Variable‐temperature NMR and concentration‐dependent absorption measurements indicate that the π‐dimer is not formed in solution. An energy decomposition analysis indicates that van der Waals interactions are the driving force for the self‐association process, in contrast with other olympicenyl derivatives that favor π‐dimerization. The physical properties in solution phase have been studied, and the stable cationic species obtained by one‐electron chemical oxidation. This study offers a new molecular design to modulate the self‐association of organic radicals for overcoming the spin‐Peierls transition, and to prepare novel nanohoop compounds with spin‐related properties. [ABSTRACT FROM AUTHOR]

Metabolic labeling with clickable noncanonical amino acids has enabled nascent proteome profiling, which can be performed in a cell‐type‐specific manner. However, nascent proteomics in an intercellular communication‐dependent manner remains challenging. Here we develop communication‐activated profiling of protein expression (CAPPEX), which integrates the LuxI/LuxR quorum sensing circuit with the cell‐type‐specific nascent proteomics method to enable selective click‐labeling of newly synthesized proteins in a specific bacterium upon receiving chemical signals from another reporter bacterium. CAPPEX reveals that E. coli competes with Salmonella for tryptophan as the precursor for indole, and the resulting indole suppressed the expression of virulence factors in Salmonella. This tryptophan‐indole axis confers attenuation of Salmonella invasion in host cells and living mice. The CAPPEX strategy should be widely applicable for investigating various interbacterial communication processes. [ABSTRACT FROM AUTHOR]

Molecular imaging of glycans has been actively pursued in animal systems for the past decades. However, visualization of plant glycans remains underdeveloped, despite that glycosylation is essential for the life cycle of plants. Metabolic glycan labeling in Arabidopsis thaliana by using N-azidoacetylglucosamine (GlcNAz) as the chemical reporter is reported. GlcNAz is metabolized through the salvage pathway of N-acetylglucosamine (GlcNAc) and incorporated into N-linked glycans, and possibly intracellular O-GlcNAc. Click-labeling with fluorescent probes enables visualization of newly synthesized N-linked glycans. N-glycosylation in the root tissue was discovered to possess distinct distribution patterns in different developmental zones, suggesting that N-glycosylation is regulated in a developmental stage-dependent manner. This work shows the utility of metabolic glycan labeling in elucidating the function of N-linked glycosylation in plants. [ABSTRACT FROM AUTHOR]

We report here the development of clickable and highly near‐infrared (NIR) fluorescent lanthanide (Ln) complexes for bioorthogonal labeling of biomolecules. These azide‐ or alkyne‐functionalized Ln complexes are hydrophilic and fluorogenic, exhibiting a strong increase of NIR fluorescence upon conjugation with biomolecules. Metabolic labeling of biomolecules with azide or alkyne, followed by click labeling with the Ln complexes, enables NIR fluorescence (NIRF) imaging of DNA, RNA, proteins, and glycans in cells. Furthermore, multicolor imaging is performed by combining click‐labeling with the Ln complexes and immunostaining. In addition, the Ln complexes is compatible with click‐expansion microscopy (click‐ExM), which enables high‐resolution NIRF imaging of cellular glycoproteins. Finally, the Ln complexes can be used for time‐of‐flight secondary‐ion mass spectrometry (ToF‐SIMS) imaging, thus achieving the first example of dual‐modal imaging combining NIRF and SIMS microscopies. [ABSTRACT FROM AUTHOR]

Boron‐embedded heteroacenes (boraacenes) have attracted enormous interest in organic chemistry and materials science. However, extending the skeleton of boraacenes to higher acenes (N≥6) is synthetically challenging because of their limited stability under ambient conditions. Herein, we report the synthesis of boron‐embedded heptacene (DBH) and nonacene (DBN) as the hitherto longest boraacenes. The former is highly stable (even after 240 h in tetrahydrofuran), while the latter is air‐sensitive with the half‐life (t1/2) of 11.8 min. The structures of both compounds are verified by single‐crystal X‐ray diffraction, revealing a linear backbone with an antiaromatic C4B2 core. Photophysical characterizations associated with theoretical calculations indicate that both compounds exhibit highly efficient anti‐Kasha emissions. Remarkably, the air‐stable DBH manifests an ultrahigh photoluminescence quantum yield (PLQY) of 98±2 % and can be chemically reduced to its radical anion and dianion states, implying the value of boron‐doped higher acenes as novel functional materials. [ABSTRACT FROM AUTHOR]

Single‐cell RNA sequencing (scRNA‐seq) has emerged as a powerful tool for profiling gene expression of distinct cell populations at the single‐cell level. However, the information of the positions of cells within the multicellular samples is missing in scRNA‐seq datasets. To overcome this limitation, we herein develop OpTAG (optical cell tagging) as a new chemical platform for attaching functional tags onto cell surfaces in a spatially resolved manner. With OpTAG, we establish OpTAG‐seq, which enables spatially resolved scRNA‐seq. We apply OpTAG‐seq to investigate the spatially defined transcriptional program in migrating cancer cells and identified a list of genes that are potential regulators for cancer cell migration and invasion. OpTAG‐seq provides a convenient method for mapping cellular heterogeneity with spatial information within multicellular biological systems. [ABSTRACT FROM AUTHOR]

Protein lipoylation is a post‐translational modification of emerging importance in both prokaryotes and eukaryotes. However, labeling and large‐scale profiling of protein lipoylation remain challenging. Here, we report the development of iLCL (iodoacetamide‐assisted lipoate‐cyclooctyne ligation), a chemoselective reaction that enables chemical tagging of protein lipoylation. We demonstrate that the cyclic disulfide of lipoamide but not linear disulfides can selectively react with iodoacetamide to produce sulfenic acid, which can be conjugated with cyclooctyne probes. iLCL enables tagging of lipoylated proteins for gel‐based detection and cellular imaging. Furthermore, we apply iLCL for proteomic profiling of lipoylated proteins in both bacteria and mammalian cells. In addition to all of the eight known lipoylated proteins, we identified seven candidates for novel lipoylated proteins. The iLCL strategy should facilitate uncovering the biological function of protein lipoylation. [ABSTRACT FROM AUTHOR]

CD22, a member of Siglec family of sialic acid binding proteins, has restricted expression on B cells. Antibody‐based agents targeting CD22 or CD20 on B lymphoma and leukemia cells exhibit clinical efficacy for treating these malignancies, but also attack normal B cells leading to immune deficiency. Here, we report a chemoenzymatic glycocalyx editing strategy to introduce high‐affinity and specific CD22 ligands onto NK‐92MI and cytokine‐induced natural killer cells to achieve tumor‐specific CD22 targeting. These CD22‐ligand modified cells exhibited significantly enhanced tumor cell binding and killing in vitro without harming healthy B cells. For effective lymphoma cell killing in vivo, we further functionalized CD22 ligand‐modified NK‐92MI cells with the E‐selectin ligand sialyl Lewis X to promote trafficking to bone marrow. The dual‐functionalized cells resulted in the efficient suppression of B lymphoma in a xenograft model. Our results suggest that natural killer cells modified with glycan ligands to CD22 and selectins promote both targeted killing of B lymphoma cells and improved trafficking to sites where the cancer cells reside, respectively. [ABSTRACT FROM AUTHOR]

Rational design of hollow micro‐ and/or nano‐structured cathodes as sulfur hosts has potential for high‐performance lithium‐sulfur batteries. However, their further commercial application is hindered because infusing sulfur into hollow hosts is hard to control and the interactions between high loading sulfur and electrolyte are poor. Herein, we designed hierarchical porous hollow carbon nanospheres with radially inwardly aligned supporting ribs to mitigate these problems. Such a structure could aid the sulfur infusion and maximize sulfur utilization owing to the well‐ordered pore channels. This highly organized internal carbon skeleton can also enhance the electronic conductivity. The hollow carbon nanospheres with further nitrogen‐doping as the sulfur host material exhibit good capacity and excellent cycling performance (0.044 % capacity degradation per each cycle for 1000 cycles). [ABSTRACT FROM AUTHOR]

Abstract: Membrane voltage is an important biophysical signal that underlies intercellular electrical communications. A fluorescent voltage indicator is presented that enables the investigation of electrical signaling at high spatial resolution. The method is built upon the site‐specific modification of microbial rhodopsin proteins with organic fluorophores, resulting in a hybrid indicator scaffold that is one of the most sensitive and fastest orange‐colored voltage indicators developed to date. We applied this technique to optically map electrical connectivity in cultured cells, which revealed gap junction‐mediated long‐range coupling that spanned over hundreds of micrometers. [ABSTRACT FROM AUTHOR]

Abstract: The unexpected, non‐enzymatic S‐glycosylation of cysteine residues in various proteins by per‐O‐acetylated monosaccharides is described. This artificial S‐glycosylation greatly compromises the specificity and validity of metabolic glycan labeling in living cells by per‐O‐acetylated azido and alkynyl sugars, which has been overlooked in the field for decades. It is demonstrated that the use of unacetylated unnatural sugars can avoid the artifact formation and a corrected list of O‐GlcNAcylated proteins and O‐GlcNAc sites in HeLa cells has been assembled by using N‐azidoacetylgalactosamine (GalNAz). [ABSTRACT FROM AUTHOR]

We herein report a chemical decaging strategy for the in situ generation of neuramic acid (Neu), a unique type of sialic acid, on live cells by the use of a palladium-mediated bioorthogonal elimination reaction. Palladium nanoparticles (Pd NPs) were found to be a highly efficient and biocompatible depropargylation catalyst for the direct conversion of metabolically incorporated N-(propargyloxycarbonyl)neuramic acid (Neu5Proc) into Neu on cell-surface glycans. This conversion chemically mimics the enzymatic de-N-acetylation of N-acetylneuramic acid (Neu5Ac), a proposed mechanism for the natural occurrence of Neu on cell-surface glycans. The bioorthogonal elimination was also exploited for the manipulation of cell-surface charge by unmasking the free amine at C5 to neutralize the negatively charged carboxyl group at C1 of sialic acids. [ABSTRACT FROM AUTHOR]

Although it has been well known that dynamic changes in glycosylation are associated with tumor progression, it remains challenging to selectively visualize the cancer glycome in vivo. Herein, a strategy for the targeted imaging of tumor-associated glycans by using ligand-targeted liposomes encapsulating azidosugars is described. The intravenously injected liposomal nanoparticles selectively bound to the cancer-cell-specific receptors and installed azides into the melanoma glycans in a xenograft mouse model in a tissue-specific manner. Subsequently, a copper-free click reaction was performed in vivo to chemoselectively conjugate the azides with a near-infrared fluorescent dye. The glycosylation dynamics during tumor growth were monitored by in vivo fluorescence imaging. Furthermore, the newly synthesized sialylated glycoproteins were enriched during tumor growth and identified by glycoproteomics. Compared with the labeling methods using free azidosugars, this method offers improved labeling efficiency and high specificity and should facilitate the elucidation of the functional role of glycans in cancer biology. [ABSTRACT FROM AUTHOR]

Alkynes can be metabolically incorporated into biomolecules including nucleic acids, proteins, lipids, and glycans. In addition to the clickable chemical reactivity, alkynes possess a unique Raman scattering within the Raman-silent region of a cell. Coupling this spectroscopic signature with Raman microscopy yields a new imaging modality beyond fluorescence and label-free microscopies. The bioorthogonal Raman imaging of various biomolecules tagged with an alkyne by a state-of-the-art Raman imaging technique, stimulated Raman scattering (SRS) microscopy, is reported. This imaging method affords non-invasiveness, high sensitivity, and molecular specificity and therefore should find broad applications in live-cell imaging. [ABSTRACT FROM AUTHOR]

Direct detection of glycans on live cells using surface‐enhanced Raman scattering (SERS) has been shown. A bioorthogonal Raman reporter was directly installed onto the monosaccharide analogs. Once metabolically incorporated into cell surface glycans, the Raman reporter was detected using SERS (see picture). [ABSTRACT FROM AUTHOR]

Raman detection of glycans on surfaces of live cells has been achieved, as described in the Communication by Z.‐Q. Tian, X. Chen, and co‐workers on page 7266 ff. A bioorthogonal Raman reporter (for alkyne, azide, and nitrile groups, or carbon–deuterium bonds) was installed onto the monosaccharide analogues, which were metabolically incorporated into cell surface glycans. The Raman reporter is detected using surface‐enhanced Raman scattering with the aid of gold nanoparticles. [ABSTRACT FROM AUTHOR]