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1. Quantifying the Antioxidant Capacity of Inorganic Nanoparticles: Challenges and Analytical Solutions

   https://doi.org/10.3390/antiox14101254  

   Hu, Yue; Zhang, Qingbo; Xiao, Zhen; Guo, Xiaoting; Ling, Vivian; Bi, Yidan; Colvin, Vicki L (October 2025, Antioxidants)

   Antioxidant properties of inorganic nanoparticles in aqueous media are attracting growing interest due to their high surface reactivity. Materials such as cerium oxide, iron oxide, silver, and gold exhibit distinct radical-scavenging behaviors at the nanoscale, but reliable quantification remains challenging. Conventional assays developed for molecular antioxidants cannot be directly applied because probes such as 2,2-diphenyl-1-picrylhydrazyl (DPPH) require methanol–water mixtures and are unstable in aqueous nanoparticle suspensions, while other assays are affected by nanoparticle-induced absorption or fluorescence changes. Here we demonstrate strategies to correct these interferences by independently measuring nanoparticle optical properties after oxidation and customizing assay conditions to account for the dilute, per-particle concentrations of nanomaterials. Using a high-throughput 96-well format, four adapted assays revealed that silver, ceria, and iron oxide nanoparticles possess substantially higher antioxidant capacities than Trolox, while gold showed negligible activity. This optimized approach enables reproducible comparison of nanoparticle antioxidants and provides a platform for tailoring nanostructures with enhanced radical-scavenging properties. 

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2. Characterization of Terpenoids from the Ambrosia Beetle Symbiont and Laurel Wilt Pathogen Harringtonia lauricola

   https://doi.org/10.3390/jof9121175  

   Zhu, Zhiqiang; Yang, Chenjie; Keyhani, Nemat O.; Liu, Sen; Pu, Huili; Jia, Peisong; Wu, Dongmei; Stevenson, Philip C.; Fernández-Grandon, G. Mandela; Pan, Jieming; et al (December 2023, Journal of Fungi)

   Little is known concerning terpenoids produced by members of the fungal order Ophiostomales, with the member Harringtonia lauricola having the unique lifestyle of being a beetle symbiont but potentially devastating tree pathogen. Nine known terpenoids, including six labdane diterpenoids (1–6) and three hopane triterpenes (7–9), were isolated from H. lauricola ethyl acetate (EtOAc) extracts for the first time. All compounds were tested for various in vitro bioactivities. Six compounds, 2, 4, 5, 6, 7, and 9, are described functionally. Compounds 2, 4, 5, and 9 expressed potent antiproliferative activity against the MCF-7, HepG2 and A549 cancer cell lines, with half-maximal inhibitory concentrations (IC50s) ~12.54–26.06 μM. Antimicrobial activity bioassays revealed that compounds 4, 5, and 9 exhibited substantial effects against Gram-negative bacteria (Escherichia coli and Ralstonia solanacearum) with minimum inhibitory concentration (MIC) values between 3.13 and 12.50 μg/mL. Little activity was seen towards Gram-positive bacteria for any of the compounds, whereas compounds 2, 4, 7, and 9 expressed antifungal activities (Fusarium oxysporum) with MIC values ranging from 6.25 to 25.00 μg/mL. Compounds 4, 5, and 9 also displayed free radical scavenging abilities towards 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide (O2−), with IC50 values of compounds 2, 4, and 6 ~3.45–14.04 μg/mL and 22.87–53.31 μg/mL towards DPPH and O2−, respectively. These data provide an insight into the biopharmaceutical potential of terpenoids from this group of fungal insect symbionts and plant pathogens. 

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3. Recent Advances in the Application of Selectfluor as a “Fluorine‐free” Functional Reagent in Organic Synthesis

   https://doi.org/10.1002/asia.202000011  

   Yang, Ke; Song, Mengjie; Ali, Ahmed_I_M; Mudassir, Syed_M; Ge, Haibo (March 2020, Chemistry – An Asian Journal)

   Abstract Selectfluor, [1‐chloromethyl‐4‐fluoro‐1,4‐diazoniabicyclo‐[2.2.2]octane bis(tetrafluoroborate)], is not only an important electrophilic fluorinating agent but also a facile and efficient “fluorine‐free” functional reagent in other organic reactions. In this Minireview, we will present a brief history of Selectfluor as a transition metal oxidant, fluorine cation and radical initiator in “fluorine‐free” functionalizations over the last five years. 

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4. Enantioselective decarboxylative alkylation using synergistic photoenzymatic catalysis

   https://doi.org/10.1038/s41929-023-01065-5  

   Sun, Shang-Zheng; Nicholls, Bryce T.; Bain, David; Qiao, Tianzhang; Page, Claire G.; Musser, Andrew J.; Hyster, Todd K. (January 2024, Nature Catalysis)

   Photoenzymatic catalysts are attractive for stereoselective radical reactions because the transformation occurs within tunable enzyme active sites. When using flavoproteins for non-natural photoenzymatic reactions, reductive mechanisms are often used for radical initiation. Oxidative mechanisms for radical formation would enable abundant functional groups, such as amines and carboxylic acids, to serve as radical precursors. However, excited state flavin is short-lived in many proteins because of rapid quenching by the protein scaffold. Here we report that adding an exogenous Ru(bpy)3 2+ cofactor to flavin-dependent ‘ene’-reductases enables the redox-neutral decarboxylative coupling of amino acids with vinylpyridines with high yield and enantioselectivity. Additionally, stereo-complementary enzymes are found to provide access to both enantiomers of the product. Mechanistic studies indicate that Ru(bpy)3 2+ binds to the protein, helping to localize radical formation to the enzyme’s active site. This work expands the types of transformation that can be rendered asymmetric using photoenzymatic catalysis and provides an intriguing mechanism of radical initiation. 

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5. The C‐Terminal Domain of α‐Synuclein Confers Steric Stabilization on Synaptic Vesicle‐Like Surfaces

   https://doi.org/10.1002/admi.201902151  

   Chung, Peter_J; Hwang, Hyeondo_Luke; Slaw, Benjamin_R; Leong, Alessandra; Adams, Erin_J; Lee, Ka_Yee_C (May 2020, Advanced Materials Interfaces)

   Abstract While α‐synuclein, an intrinsically disordered protein linked to Parkinson's disease, has been shown to associate with membrane organelles, its overall cellular function remains nebulous. α‐Synuclein binds to membranes through its amino‐terminal domain (first ≈100 residues), but there is no consensus on the biophysical function of the carboxyl‐terminal domain (last ≈40 residues) due, in part, to its lack of strong interaction partners and persisting intrinsic disorder even when membrane bound. Here, by directly applying force on α‐synuclein bound to spherical nanoparticle‐supported lipid bilayers (SSLBs) and tracking higher‐order structural changes through small‐angle X‐ray scattering, strong evidence is presented that α‐synuclein sterically stabilizes membrane surfaces through its carboxyl‐terminal domain. Full‐length α‐synuclein dramatically increases the critical osmotic pressure at which SSLBs cluster (P_C≈ 1.3 × 10⁵Pa) compared to α‐synuclein without the carboxyl‐terminal domain (P_C≈ 1.9 × 10⁴Pa) at physiological salt and temperature conditions. This clustering of α‐synuclein‐bound SSLBs is shown to be reversible and sensitive to monovalent/divalent salt, both features of grafted polyelectrolyte‐mediated steric stabilization. In elucidating the biophysical function of α‐synuclein in the framework of polymer science, it is demonstrated that the carboxyl‐terminal domain can potentially utilize its persisting intrinsic disorder to functionalize membrane surfaces. 

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