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1. Sm( iii )[12-MC _Ga(III)shi -4] as a luminescent probe for G-quadruplex structures

   https://doi.org/10.1039/C7MT00232G  

   Rajczak, Ewa; Pecoraro, Vincent L.; Juskowiak, Bernard (January 2017, Metallomics)

   G-quadruplexes (GQs), spatial assemblies of guanine-rich DNA strands, play an important role in the regulation of gene expression and chromosome stabilization. These structures are recognized to be useful in cancer therapies as the presence of multiple G-quadruplexes in a telomeric strand stops cancer cell proliferation. Metallacrowns of the type 12-MC-4 form planar structures that have remarkable similarity to G-tetrads in terms of dimension, shape and the ability to bind alkali metal and lanthanide cations in a central cavity. The interaction between the Sm( iii )[12-MC Ga(III)shi -4] (SmMC) metallacrown (MC) and human telomeric G-quadruplex structures was examined using several methods including CD titrations, CD melting temperatures, fluorescence titration of SmMC with GQ/Na + , fluorescence intercalator displacement (FID) assays and methods measuring the MC quenching effect on the Tb 3+ /GQ luminescence. It was proven that the studied metallacrown acted as a sensing probe and interacted with quadruplex DNA. The Stern–Volmer quenching constant ( K as ) of Tb 3+ /GQ luminescence was calculated to be 3.9 × 10 5 M −1 . The binding constant using the indirect FID method gave the result of 1.3 × 10 5 M −1 . CD melting temperature experiments reveal the following pattern – the higher the concentration of the complex the lower the registered T m for quadruplex DNA, which indicates a destabilizing effect of SmMC at higher GQ : MC ratios. These data implicate a shape and size selective interaction between MCs and GQs that may be exploited for telomere detection. 

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2. G-quadruplexes catalyze protein folding by reshaping the energetic landscape

   https://doi.org/10.1073/pnas.2414045122  

   Huang, Zijue; Ghosh, Kingshuk; Stull, Frederick; Horowitz, Scott (February 2025, Proceedings of the National Academy of Sciences)

   Many proteins have slow folding times in vitro that are physiologically untenable. To combat this challenge, ATP-dependent chaperonins are thought to possess the unique ability to catalyze protein folding. Performing quantitative model selection using protein folding and unfolding data, we here show that short nucleic acids containing G-quadruplex (G4) structure can also catalyze protein folding. Performing the experiments as a function of temperature demonstrates that the G4 reshapes the underlying driving forces of protein folding. As short nucleic acids can catalyze protein folding without the input of ATP, the ability of the cell to fold proteins is far higher than previously anticipated. 

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3. Reversed Cation Selectivity of G ₈ ‐Octamer and G ₁₆ ‐Hexadecamer towards Monovalent and Divalent Cations

   https://doi.org/10.1002/asia.202000016  

   He, Ying; Zhang, Yanbin; Wojtas, Lukasz; Akhmedov, Novruz G.; Pan, Qinhe; Guo, Hao; Shi, Xiaodong (March 2020, Chemistry – An Asian Journal)

   Abstract A reverse‐binding‐selectivity between monovalent and divalent cations was observed for two different self‐assembly G₁₆‐hexadecamer and G₈‐octamer systems. The dissociation constant between G₄‐quadruplex and monomer was calculated via VT‐¹H NMR experiments. Quantitative energy profiles revealed entropy as the key factor for the weaker binding toward Ba²⁺compared with K⁺in the G₈‐octamer system despite stronger ion‐dipole interactions. This study is the first direct comparison of the G₄‐quartet binding affinity between mono and divalent cations and will benefit future applications of G‐quadruplex‐related research. Further competition experiments between the G₈‐octamer and 18‐crown‐6 with K⁺demonstrated the potential of this G₈system as a new potassium receptor. 

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4. Use of neomycin as a structured amino‐containing side chain motif for phenanthroline‐based G‐quadruplex ligands and telomerase inhibitors

   https://doi.org/10.1111/cbdd.13741  

   Singh, Mandeep; Wang, Siwen; Joo, Hyun; Ye, Zhihan; Christison, Krege M.; Hekman, Ryan; Vierra, Craig; Xue, Liang (July 2020, Chemical Biology & Drug Design)

   Abstract In this paper, we report the synthesis of a phenanthroline and neomycin conjugate (7). Compound7binds to a human telomeric G‐quadruplex (G1) with a higher affinity compared with its parent compounds (phenanthroline and neomycin), which is determined by several biophysical studies. Compound7shows good selectivity for G‐quadruplex (G4) DNA over duplex DNA. The binding of7withG1is predominantly enthalpy‐driven, and the binding stoichiometry of7withG1is one for the tight‐binding event as determined by ESI mass spectrometry. A plausible binding mode is a synergistic effect of end‐stacking and groove interactions, as indicated by docking studies. Compound7can inhibit human telomerase activity at low micromolar concentrations, which is more potent than previously reported 5‐substituted phenanthroline derivatives. 

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5. Selective Catalytic Combustion of Hydrogen under Aerobic Conditions on Na ₂ WO ₄ /SiO ₂

   https://doi.org/10.1002/anie.202412932  

   Kipp, Elijah R; Garcia‐Barriocanal, Javier; Bhan, Aditya (December 2024, Angewandte Chemie International Edition)

   Abstract Na₂WO₄/SiO₂, a material known to catalyze alkane selective oxidation including the oxidative coupling of methane (OCM), is demonstrated to catalyze selective hydrogen combustion (SHC) with >97 % selectivity in mixtures with several hydrocarbons (CH₄, C₂H₆, C₂H₄, C₃H₆, C₆H₆) in the presence of gas‐phase dioxygen at 883–983 K. Hydrogen combustion rates exhibit a near‐first‐order dependence on H₂partial pressure and are zero‐order in H₂O and O₂partial pressures. Mechanistic studies at 923 K using isotopically‐labeled reagents demonstrate the kinetic relevance of H−H dissociation and absence of O‐atom recombination. In situ X‐ray diffraction (XRD) and W L_III‐edge X‐ray absorption spectroscopy (XAS) studies demonstrate, respectively, a loss of Na₂WO₄crystallinity and lack of second‐shell coordination with respect to W⁶⁺cations below 923 K; benchmark experiments show that alkali cations must be present for the material to be selective for hydrogen combustion, but that materials containing Na alone have much lower combustion rates (per gram Na) than those containing Na and W. These data suggest a synergy between Na and W in a disordered phase at temperatures below the bulk melting point of Na₂WO₄(971 K) during SHC catalysis. The Na₂WO₄/SiO₂SHC catalyst maintains stable combustion rates at temperatures ca. 100 K higher than redox‐active SHC catalysts and could potentially enable enhanced olefin yields in tandem operation of reactors combining alkane dehydrogenation with SHC processes. 

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