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Crown ethers as artificial decoys: A supramolecular strategy to block SARS-CoV-2 entry via host-guest interactions.

Coronavirus disease (COVID-19) remains a major global health challenge, highlighting the need for antiviral strategies that act at the earliest stages of infection. Given that viral entry and spike-receptor interaction are critical steps in the coronavirus life cycle, targeting these processes represents a powerful strategy to block infection at its earliest stage. Inspired by the glycan-recognition and extracellular viral-trapping functions of pulmonary surfactant collectins (SP-A and SP-D), this work integrates supramolecular chemistry, pulmonary surfactant biology, and antiviral research to establish a biomimetic supramolecular molecular-decoy framework based on crown ethers, cyclodextrins, and related macrocyclic architectures. Through host-guest molecular recognition, these macrocyclic scaffolds can be engineered to mimic sialylated host receptors and multivalent glycan motifs, enabling competitive binding to viral spike proteins, virion capture, and sequestration away from epithelial surfaces. By redirecting viruses toward artificial host-mimetic structures, supramolecular decoys could intercept SARS-CoV-2 and other enveloped respiratory viruses before host-cell attachment, membrane fusion, or genome release. Acting upstream of intracellular replication, this strategy may prevent initiation of the viral replication cycle and subsequent hijacking of the host protein synthesis machinery, while potentially minimizing interference with host metabolic pathways and reducing the likelihood of resistance development. Furthermore, it can be translated into inhalation nanoformulations for pulmonary delivery and localized formulations targeting the upper respiratory tract. Overall, by integrating the biological principles of pulmonary surfactant immunity with supramolecular host-guest chemistry, this work provides a conceptual foundation for biomimetic molecular-decoy antivirals and highlights a promising direction for next-generation broad-spectrum antiviral design against emerging respiratory viruses.

Antiviral Agents

Substrate-Dependent Crosslinking by the Cytochrome P450 From Aminopyruvatide Biosynthesis.

Cytochrome P450s catalyze an array of reactions including crosslinking of aromatic side chains in the biosynthesis of ribosomally synthesized and post-translationally modified peptides (RiPPs). ApyO is a cytochrome P450 that forms a C─C bond between two tyrosines in a YLY motif in the substrate ApyA, the precursor peptide of the RiPP aminopyruvatide. We utilized cell-free translation to generate ApyA variants and probe the substrate tolerance of ApyO. Through AlphaFold-based modelling and in vitro assays, we show that ApyO accepts the 10 C-terminal residues of ApyA and requires a conserved Arg/Lys in the substrate. Inspired by substrate sequences in orthologous biosynthetic gene clusters, we substituted one of the tyrosine residues with a tryptophan and observed that ApyO catalyzed formation of an N─C bond between the indole of Trp and Cε2 of Tyr. ApyO unexpectedly catalyzed formation of a C─O bond between the two tyrosine residues when we substituted the leucine residue in the YLY motif with tyrosine or tryptophan. A peptide containing a biaryl linkage and C-terminal aminopyruvate displayed sub-nanomolar inhibition of select proteases, with the aminopyruvate group critical for activity. Overall, this study demonstrates plasticity in the manner of macrocyclization catalyzed by the P450 ApyO.

biosynthesis

Macrocyclization of Broad-Spectrum Kinase Inhibitor Bosutinib Leads to Potent and Selective Quinoline-Based HIPK4 Inhibitor AZ137.

Homeodomain-interacting protein kinase 4 (HIPK4) remains an understudied member of the dark kinome. While genetic knockout studies suggest its involvement in spermiogenesis and cutaneous squamous cell carcinoma, whether these cellular functions can be recapitulated by pharmacological inhibition remains to be determined. These investigations are currently hampered by a lack of high-quality chemical tools. To address this, we employed a rational design strategy utilizing macrocyclization of a bosutinib-based scaffold. Systematic optimization led to the discovery of AZ137 (28e), a potent and selective HIPK4 inhibitor (IC50: 11 nM; cellular EC50: 76 nM). AZ137 exhibits exceptional selectivity across three comprehensive orthogonal panels, high solubility, and no detectable cytotoxicity. Its cellular activity was confirmed in cell-based assays of HIPK4-dependent F-actin remodeling. Together with a negative control compound, this probe set provides a foundational framework for validating HIPK4 as a therapeutic target and a high-quality resource to elucidate its roles in normal physiology and disease.

Quinolines

Macrocyclization of Broad-Spectrum Kinase Inhibitor Bosutinib leads to Potent and Selective Quinoline-based HIPK4 Inhibitor AZ137.

Homeodomain-interacting protein kinase 4 (HIPK4) remains an understudied member of the dark kinome. While genetic knockout studies suggest roles for HIPK4 in spermiogenesis and cutaneous squamous cell carcinoma, whether these cellular functions can be recapitulated by pharmacological inhibition remains to be determined. However, such investigations have been hampered by a lack of high-quality chemical tools. To address this, we employed a rational design strategy utilizing macrocyclization of a bosutinib-based scaffold. Systematic optimization led to the discovery of AZ137 (28e), a potent and selective HIPK4 inhibitor (IC50 = 11 nM; cellular EC50 = 76 nM). AZ137 exhibits exceptional selectivity across three comprehensive orthogonal panels, high solubility, and no detectable cytotoxicity. Its cellular activity was confirmed in cell-based assays of HIPK4-dependent F-actin remodeling. Together with a negative control compound, this probe set provides a foundational framework for the validating HIPK4 as a therapeutic target and a high-quality resource to elucidate its roles in normal physiology and disease.

Journal Article

Recent advances in supramolecular macrocycle-based artificial light-harvesting systems.

Artificial light-harvesting systems (ALHSs) inspired by the antenna function of natural photosynthesis provide molecular platforms for collecting excitation energy and directing it to emissive or reactive acceptors. In many supramolecular ALHSs, however, practical performance is limited by poorly defined donor-acceptor orientation, aggregation-caused quenching (ACQ), interfacial defects, and limited stability in aqueous or complex media. Supramolecular macrocycles-particularly pillar[n]arenes (PAs), cucurbit[n]urils (CBs), calixarenes (CAs), cyclodextrins (CDs), and supramolecular coordination complexes (SCCs)-offer a useful design space because their cavities, pre-organized scaffolds, and reversible non-covalent interactions can confine chromophores, tune local donor/acceptor ratios, and modulate Förster resonance energy transfer (FRET). This Review systematically examines the unique structural advantages and assembly mechanisms of the five macrocyclic families, with an emphasis on their use in constructing ALHSs-from single-step to cascaded FRET-and in advancing aqueous photocatalysis, near-infrared bioimaging, panchromatic fluorescence modulation, and singlet oxygen generation. The resulting structure-property-application framework is intended to guide the rational design of macrocycle-assisted photofunctional materials while avoiding overextension of the photosynthesis analogy.

Journal Article