Chemistry - A European Journal最新文献

Molecular recognition is a crucial process in multiple areas, including separation, storage, and catalysis etc. Covalent organic cages (COCs), owing to their preorganized 3D cavities, customizable binding sites, and outstanding chemical stability, have been widely used for molecular recognition. Among the components of COCs, the covalent linkers play a crucial role in molecular recognition by shaping cavities and providing noncovalent interactions. In this concept, we exemplified recent progress in COC-based host-guest recognition, briefly summarized the bonding strategies (both dynamic and irreversible) used in covalent linkers for COC construction, and discussed how these linkers influence guest encapsulation by adjusting size, shape, and binding sites of their cavities. These insights are expected to provide a reference for the design of novel COCs for molecular recognition.

The mechanism of O-O bond formation in PSII is still debated. Although it is generally accepted to occur during the S₃ → [S₄] → S₀ transition, some studies suggest it may already begin in the S₃ state. Notably, the 2017 XFEL study by Suga et al. supports this hypothesis by reporting structural features consistent with a peroxide intermediate formed from the S₃ state. Here, we present DFT calculations showing that, in the high oxidation state (HOS) model, O-O coupling starting from the S₃ state with the hydroxo-oxo configuration is kinetically feasible, forming a peroxide intermediate via a modest activation energy of 19.5 kcal/mol. However, in the HOS model, the resulting peroxide would be readily converted to O₂ with ΔG^‡ = 11 kcal mol^-1, inconsistent with experimental observations that O₂ release proceeds only after reaching the [S₄] state. In contrast, we show that if peroxide forms from the S₃ state, its persistence is more plausibly explained by the low oxidation state (LOS) model, where further conversion to superoxide or O₂ is energetically unfavorable. This distinction between these two models stems from the greater oxidizing power of Mn(IV) in the HOS paradigm relative to Mn(III) in the LOS paradigm in promoting peroxide-to-O₂ conversion.

Leishmaniasis and trypanosomiasis are severe parasitic infections with significant impacts on veterinary and public health, particularly affecting the poorest populations. The therapeutic arsenal against these neglected tropical diseases is limited, and the emergence of resistance to available medicines complicates treatment. These kinetoplastid parasites share a unique DNA modification, that is β-d-glucosyl-5-hydroxymethyluracil (base J), which appears to play an essential role in parasite development and survival through an original epigenetic mechanism, allowing adaptation to environmental changes. To date, the regulatory pathway of this unique nucleobase has not been explored as a potential therapeutic target. In this work, we report the synthesis of several families of base J analogues and assess their potential against different kinetoplastid species. Some compounds have shown antiparasitic activity and no toxicity toward human primary fibroblasts, revealing promising new strategies for antiparasitic therapy.

Cu^II-catalyzed oxidative coupling reactions based on Chan-Lam (CL) protocol have established themselves as one of most reliable and practical synthetic tools for the efficient formation of carbon-nitrogen/heteroatom bonds. Since decades this methodology has witnessed considerable development in its application scope, industrial uptake and fundamental mechanistic knowledge. Despite its successful application and popularity, the underlying mechanistic understanding remains underdeveloped and unexplored. Current theoretical investigation underpins the mechanism of CL-based amination reaction under base-free conditions employing the transmetalation by-product B(OH)₃ as promoter. The rate-determining transmetalation involves an energy span of 26.4 kcal mol^-1 with subsequent overall disproportionation and reductive elimination barrier of 25.4 kcal mol^-1, accompanying stable intermediates in comparison to the base-mediated CL amination. The aryl migration involves a unique six-membered transition state unlike similar transition-metal catalyzed transmetalation event. The Cu^I→Cu^II oxidative regeneration is facile in the presence of B(OH)₃ coordinated intermediates. The calculated results are in line with experimental kinetic studies and for the first time elucidates the mechanistic effect of inverting the organoboron: amine stoichiometry. Furthermore, Hammett studies involving substituted aryl boronic acid substrates reveals electron-rich substitution to entail lower transmetalation barrier. Overall, the boric acid stabilized copper intermediates are thermodynamically stable, allowing the amination to occur at improved time frame.

Ortho-aminophenol-N,N,O-triacetate (APTRA) has been widely adopted for binding and sensing Mg²⁺, although it binds Ca²⁺ more strongly. This contribution investigates APTRA derivatives that incorporate an aryl-alkynyl fluorophore, addressing how the binding affinities for Mg²⁺ and Ca²⁺ are modulated by a substituent R in the aryl ring of the fluorophore. Six such derivatives have been synthesized via their tris-ethyl esters. They feature X ═ CN, CF₃, or OMe, as a mesomerically electron-withdrawing, inductively electron-withdrawing, or electron-donating substituent, respectively, with the alkyne either para or meta to the APTRA nitrogen. Study of the absorption and fluorescence properties of the esters reveals the importance of intramolecular charge transfer (ICT) states for X ═ CN and CF₃, but not OMe. The corresponding carboxylate ligands are less emissive in water, and the fluorescence is not strongly modulated by metal ions. However, the absorption spectra change markedly, allowing dissociation constants K_d to be evaluated. The key conclusions are that (i) electron-withdrawing substituents attenuate the affinity for Ca²⁺ more than Mg²⁺, leading to a net improvement in selectivity for Mg²⁺, and (ii) the effect is larger when the APTRA nitrogen (as opposed to phenolic oxygen) is para to-and hence directly conjugated with-the alkyne.

The widespread use of tetracycline (TC) has resulted in severe water pollution, highlighting the urgent need for efficient degradation technologies. In this study, a Bi-BTC/BiYO₃/CA photocatalyst was synthesized using cellulose acetate (CA) as a carrier via a solvothermal process combined with nonsolvent-induced phase separation, and its photocatalytic performance in TC degradation was systematically evaluated. Under optimal conditions, a degradation efficiency of 95.06% was achieved. Both experimental and theoretical analyses revealed that the formation of the Bi-BTC/BiYO₃ heterojunction enhances the separation of photogenerated charge carriers and improves visible-light absorption, whereas the incorporation of CA significantly boosts the material's recyclability. Various characterization methods confirmed the successful synthesis of Bi-BTC/BiYO₃/CA. Additionally, the efficient carrier separation and expansion of the light absorption range achieved by the Bi-BTC/BiYO₃ heterojunction were demonstrated. Notably, the photocatalyst retained 91% of its initial degradation efficiency after four recycling cycles, underscoring the potential of the CA-based composite catalyst for application in simulated wastewater treatment. This synergistic integration of a heterojunction and carrier provides a promising strategy for the effective degradation of environmental pollutants.

Self-assembling peptides have attracted increasing attention as building blocks for developing functional materials. Among them, collagen-mimetic peptides (CMPs) represent a class of self-assembling systems. However, although short-chain CMPs spontaneously fold into thermodynamically stable triple-helical trimers, they fail to further undergo supramolecular assembly to form hydrogels. We report a new strategy for supramolecular hydrogel formation based on CMPs. The designed peptide, termed kinkCMP, features a kinked backbone introduced at the center of the sequence via adjacent disulfide bonds. The kinkCMP forms a gel, and its gel denaturation temperature can be tuned by varying the peptide chain length. Moreover, the hydrogel can be used as a cell culture scaffold. These results provide a versatile approach for constructing supramolecular hydrogels based on CMPs, expanding the design strategies for peptide-based functional materials.

Photothermal therapy (PTT) is a promising tumor treatment strategy. However, developing organic photothermal agents (PTAs) with both high photothermal conversion efficiency (PCE) and simple synthesis remains a major challenge. Herein, we developed the charge-transfer complex nanoparticles (termed PER-TCQ), via supramolecular assembly of perylene (PER) as the electron donor and tetrachloro-1,4-benzoquinone (TCQ) as the electron acceptor. The strong charge-transfer interaction between PER and TCQ confers PER-TCQ nanoparticles with pronounced near-infrared (NIR) absorption. Upon 808 nm laser irradiation, PER-TCQ achieved a high PCE of 66.1%. Its effective antitumor efficacy was consistently validated by in vitro and in vivo experiments, demonstrating the great promise of such programmable complexes as high-performance organic PTAs.

Inducible protein expression is a cornerstone of many aspects of industrial and molecular biotechnological processes. However, limited availability of inducible transcription factors can reduce our ability to control expression at a population level. The design and synthesis of a powerful inducer containing a fucose is demonstrated to induce protein expression through the lac operon only in cells with the ability to selectively de-fucosylate them. Batch and automated continuous-flow processes are reported for the syntheses of both 2'-fucosyl isopropyl-β-D-thiogalactopyranose (2'F-IPTG) and isobutyl-C-galactoside (2'F-IBCG) mimics. Fucosylation of the inducer allowed for fucosidase-dependent expression of a reporter protein, providing an additional layer of control over inducible gene expression.

Scandium triflate-catalyzed tandem reaction of electron-rich phenols and 2-cinnamoylpyridine 1-oxides is realized. This protocol enables the highly diastereoselective construction of 2,3-dihydrobenzopyrans (chromanes) via a domino Michael addition (Friedel-Crafts alkylation) and hemiketalization process under mild conditions. Using 2-cinnamoylpyridine 1-oxides as Michael acceptors, electron-rich phenols can be extended to methylphenols. The diastereoselectivity is mainly decided by the stability of diastereomeric products, but is impacted by steric and electronic effects. The current study expands the synthetic toolbox for benzopyran derivatives.