JACS Au最新文献

Although the triazole skeleton is significant in biochemistry as a click reaction candidate, as well as in material chemistry due to its excellent absorption of UV light, the preparation of these compounds relies on multinitrogen reagents such as diazo and azido compounds. In this work, o-nitroazobenzenes are first used in a series of neat, fast, green, and efficient reactions for the synthesis of 2-aryl-2H-benzotriazoles under visible light, without RN₃ and metals. It is the visible light-induced boron radical that initiates the reaction by reducing the nitro group into a nitroso group, followed by a barrierless N-N coupling and a facile further deoxygenation by diboron ester to yield benzotriazoles as potential UV absorbers in excellent yields.

Designing dynamic polymer networks that resist creep while remaining reprocessable is a central challenge in sustainable polymeric materials development. Here, we report charge-neutral diblock copolymers (i.e., ionomers) with 18 mol % ammonium chloride that combine high creep resistance and recoverability (>90% recovery after five creep cycles) with thermal processability (compression moldable at 80 °C), outperforming conventional statistical ionomers that soften at elevated temperatures due to ion dissociation. Unlike the 1-3 nm ionic clusters formed in statistical ionomers, these diblock ionomers self-assemble into an inverse hexagonal (iHEX) morphology where glassy ionic domains form the continuous matrix and rubbery neutral domains form the cylinders. The rigid ionic scaffold and large interdomain spacing (>30 nm) substantially extend chain pull-out times and interdomain diffusion, imparting elasticity, while the unentangled flexible blocks within the rubbery cylinders enable processability. By demonstrating that precise control over ion distribution can convert a thermoplastic-like ionomer into a reprocessable elastomer, this work establishes a general design principle for creating nanostructured dynamic polymers with enhanced mechanical integrity, recoverability, and sustainability.

Nucleic acid structures are stabilized by both base pairing and base stacking. While energetics of base pairing interactions are relatively well established, our understanding of the energetic contributions of base stacking remain incomplete. Here, we use a combination of single-molecule and computational biophysics approaches to investigate the effect of strand polarity on base-stacking energetics. We designed pairs of DNA constructs with reversed stacking polarities at nick sites, along with corresponding no-stack controls to isolate stacking contributions. Performing single-molecule force-clamp assays with a Centrifuge Force Microscope (CFM), we observed polarity-dependent differences in stacking energetics. These differences were most pronounced in purine-purine and certain purine-pyrimidine interactions. Notably, a 5' purine stacked on a 3' pyrimidine was generally more stable than the reverse polarity. We employed molecular dynamics (MD) simulations to observe stacking interfaces in the DNA constructs. The simulations were qualitatively consistent with our experiments, and showed positional differences between opposite polarity stacking pairs, giving some insight into the origin of these polarity differences. Overall, these results demonstrate that base polarity can modulate stacking stability and should be considered when designing short duplex regions such as overhangs in molecular biology and biotechnology applications.

To date, a variety of covalent cysteine-reactive chemical probes have been reported. The most common ones include maleimide for bioconjugation and iodoacetamide alkyne (IAA) for chemoproteomics analyses. Their applicability, however, is limited due to, e.g., the hydrolytic lability of maleimide adducts and the slow reaction kinetics as well as the inability to record the entirety of the cysteinome with IAA. This is compounded by the missing potential to fine-tune their reactivity tailored to advanced applications. To generate a high-reactivity, cysteine-selective chemical probe with broad utility, we have performed an in-depth investigation into the acrylophenone scaffold. The aryl group connected to the vinyl ketone chemotype can be readily substituted, which provides the potential to fine-tune the reactivity and install a bioorthogonal handle. We took advantage of this feature by modifying acrylophenone-alkyne (APA) with two ortho chlorine groups to generate ortho-dichloroacrylophenone-alkyne (CAPA), which increased the stability of the probe and the yield of its cysteine adducts. To showcase the reactivity, we performed reaction rate analyses with model reagents. The selectivity was demonstrated by specifically labeling cysteine residues within two peptides under physiological conditions. To investigate its utility toward bioconjugation reactions, we performed the stoichiometric labeling of two proteins. Remarkably, CAPA was successfully implemented as a high-reactivity cysteine-selective chemical probe into activity-based protein profiling (ABPP) experiments using both in-gel fluorescence (in-gel ABPP) and mass spectrometry analyses. The chemoproteomics workflow, named isoDTB-ABPP, allowed us to highlight that CAPA provides a complementary approach to IAA in expanding the coverage of the cysteinome.

Acylsilanes represent a unique class of organosilicon compounds with distinctive photochemical reactivities, including hydrogen atom transfer (HAT) and silyl shift pathways. Recently, a new photolabile protecting group (PPG) benzoyldiisopropylsilane (BDIPS) featuring an acylsilane functionality was introduced for alcohol protection. While the photomediated deprotection of aliphatic silyl ethers in methanol provided the free alcohols, BDIPS-protected benzyl or allyl alcohols resulted in rearranged ketones upon photoexcitation in acetonitrile. In this work, we systematically investigate the photochemical behavior of different BDIPS-ethers, focusing on the mechanistic divergence leading to either alcohol release as PPG or rearranging ketone formation. Through a combined approach of femtosecond transient absorption spectroscopy and density functional theory calculations, we elucidate the competing reaction pathways for model compounds 1a, 1b, and 1c. Our results reveal that the presence of an α-hydrogen adjacent to an olefinic moiety kinetically favors the HAT pathway, yielding rearranged ketone products, while its absence promotes a silyl shift mechanism that results in efficient alcohol photodeprotection. Furthermore, solvent-dependent studies demonstrate distinct photoreaction behaviors for 1c in methanol and acetonitrile, underscoring the role of the local chemical environment in steering reaction outcomes. This study provides fundamental insights into the structure-reactivity relationships of acylsilane-based PPGs and offers a strategic basis for the rational design of photoresponsive systems with programmable release properties.

Methanol-to-propylene (MTP) is one of the important propylene production technologies that is commonly achieved by the use of zeolite catalysts. However, effectively regulating the selectivity toward propylene remains challenging due to the insufficient understanding of the principles behind selectivity control. In this study, we proposed an interpretable function to assess the propylene/ethylene (P/E) selectivity based on a thorough investigation of the MTP selectivity control mechanism and implemented a machine learning (ML) method for high-throughput screening of zeolite frameworks for MTP. Density functional theory and grand canonical Monte Carlo simulations have been used to build the ML model. The P/E selectivity predictions are supported by the reported and our own experiments. We chose Mobil Five (MFI) (rank 374) and Deca-dodecasil 3R (DDR) (rank 5869) for experimental validation. Experimental results showed that the Ga-MFI catalyst achieved a P/E ratio of 12.3 and a remarkably longer operational lifespan of 121.3 h in the MTP process, surpassing previously reported values. Additionally, the marked superiority of Ga-MFI over Ga-DDR, especially in terms of P/E ratios and lifespans, further underscores the effectiveness of our zeolite screening strategy.

RNA molecules fold into intricate three-dimensional tertiary structures that are central to their biological functions. Yet reliably discovering new motifs that form true tertiary interactions remains a major challenge. Here we show that RNA tertiary folding occasionally generates electronegative motifs that react selectively with the small, positively charged probe trimethyloxonium (TMO). Sites with enhanced reactivity to TMO, compared with the neutral reagent dimethyl sulfate (DMS), are indicative of tertiary structure and define T-sites. These positions share a structural signature in which a reactive nucleobase is adjacent to nonbridging phosphate oxygens, creating a localized region of negative charge. T-sites consistently map to the cores of higher-order structural interactions and functional centers across diverse RNAs, including distinct states in conformational ensembles. In the 10,723-nt dengue virus genome, three strong T-sites were detected, each within a complex structure required for viral replication. Cation-based covalent chemistry enables high-confidence discovery and analysis of functional RNA tertiary motifs across long and complex RNAs, opening new opportunities for transcriptome-wide structural analysis.

Direct air capture (DAC) of CO₂ is a critical technology to combat climate change, offering a scalable approach to mitigate atmospheric CO₂ accumulation. Despite advancements in adsorbent materials, the performance of DAC systems remains highly sensitive to environmental conditions, such as temperature and humidity. Poly-(ethylenimine) (PEI)-functionalized silica has emerged as a promising sorbent due to its high CO₂ capacity and tunable properties. However, optimizing its performance across diverse climatic conditions requires a deeper understanding of how the PEI loading impacts the adsorption capacity and kinetics under varying temperatures and humidities. This study reports the CO₂ and H₂O adsorption kinetics and capacities, desorption behavior, and speciation of adsorbed CO₂ using silica/PEI adsorbents supported within expanded poly-(tetrafluoroethylene) (ePTFE) sheets across a wide range of temperatures and humidities, representing the diversity of climates found across the United States. With the obtained data, guidelines for selecting and optimizing PEI-loaded silica-based sorbents for DAC applications are developed. These findings provide a framework for tailoring sorbents to specific climatic scenarios, ensuring a reliable and efficient DAC performance.

Magnetic properties of lanthanide endohedral metallofullerenes are strongly modulated by intramolecular metal-metal interactions, which suppress the quantum tunneling of magnetization (QTM) in Dy₂ScN@C₈₀, but lead to magnetic frustration with pronounced QTM in Dy₃N@C₈₀. In this work, we explore how exohedral chemical modification of Dy₂ScN@C₈₀ and Dy₃N@C₈₀ by photochemical addition of adamantylidene (Ad) affects Dy···Dy interactions and influences their single-molecule magnetism. For each fullerene, the photochemical reaction with adamantane aziridine produced two isomers of Ad monoadduct, minor [5,6]-open and major [6,6]-open. By virtue of the high sensitivity of the ¹H nuclear spin probe in the Ad moiety to the position of Dy ions, paramagnetic NMR helped to establish Sc-Ad coordination in the [5,6] isomer and predominant Dy-Ad coordination in the [6,6] isomer of Dy₂ScN@C₈₀(Ad). SQUID magnetometry and relaxation measurements demonstrated that Ad addition has almost no effect on the strength of the Dy···Dy coupling in the [6,6] isomer of Dy₂ScN@C₈₀(Ad), but it does increase the coupling in the [5,6] counterpart by 20%. The blocking temperature of magnetization and the coercivity are both softened by adamantylidene addition, irrespective of the isomeric structure of Dy₂ScN@C₈₀(Ad). For Dy₃N@C₈₀(Ad), Ad addition substantially increased Dy···Dy coupling constants and the energy spread of exchange-coupled states in comparison to that of Dy₃N@C₈₀ and lifted geometric frustration. As a result, both Dy₃N@C₈₀(Ad) isomers exhibit open hysteresis without pronounced QTM signatures and have a higher blocking temperature of magnetization than the pristine Dy₃N@C₈₀. Our work demonstrates that chemical derivatization can have profound influence on the metal-metal coupling and relaxation of magnetization in metallofullerene molecular magnets.

The design of flow reactors for heterogeneous photocatalysis is key to enhancing the control, efficiency, and scalability of chemical reactions. However, conventional designs such as slurry reactors and fixed bed reactors often suffer from poor light penetration, challenging catalyst attachment to the support, and difficult separations. We report an efficient and robust methodology for the functionalization of perfluoroalkoxy (PFA) coil reactors with different fluorinated photocatalysts [a perylene diimide (F-PDI) and poly-(p-phenylene ethynylene) polymers (PPEST and POLPDI)] through fluorophilic interactions. We have evaluated the efficiency of photocatalyst-functionalized coil reactors in continuous flow experiments through the [2 + 2] photocycloaddition of 9-vinylcarbazole (VCZ) using blue and green light (440 and 525 nm). The conversion of VCZ to the product 1,2-trans-dicarbazylcyclobutane ( t -DCZCB) was continuously monitored by in-line nuclear magnetic resonance (NMR) spectroscopy, and we found that PPEST was the most robust photocatalyst coating of those studied, leading to high conversions with different lamp powers and residence times. Further experiments proved that PPEST-functionalized coil reactors were stable and efficient after 18 h of continuous flow with conversions from around 50 to 75%.