Bio21 - Research Publications
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ItemNo Preview AvailableFingerprints of Chalcogen Bonding Revealed Through 77Se-NMR.(Wiley, 2024-03-20)77Se-NMR is used to characterise several chalcogen bonded complexes of derivatives of the organoselenium drug ebselen, exploring a range of electron demand. NMR titration experiments support the intuitive understanding that chalcogen bond donors bearing more electron withdrawing substituents give rise stronger chalcogen bonds. The chemical shift of the selenium nucleus is also shown to move upfield as it participates in a chalcogen bond. Solid-state NMR is used to explore chalcogen bonding in co-crystals. Due to the lack of molecular reorientation on the NMR timescale in the solid state, the shape of the chemical shift tensor can be determined using this technique. A range of co-crystals are shown to have extremely large chemical shift anisotropy, which suggests a strongly anisotropic electron density distribution around the selenium atom. A single crystal NMR experiment was conducted using one of the co-crystals, affording the absolute orientation of the chemical shift tensor within the crystal. This showed that the selenium nucleus is strongly shielded in the direction of the chalcogen bond (due to the approach of the lone pair of the Lewis base), and strongly deshielded in the perpendicular direction. The orientation of the deshielded axis is consistent with the presence of a second σ-hole which is not participating in a chalcogen bond, showing the profound effect of electron density anisotropy on the chemical shift.
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ItemNo Preview AvailableComparative structure activity and target exploration of 1,2-diphenylethynes in Haemonchus contortus and Caenorhabditis elegans.(Elsevier BV, 2024-03-19)Infections and diseases caused by parasitic nematodes have a major adverse impact on the health and productivity of animals and humans worldwide. The control of these parasites often relies heavily on the treatment with commercially available chemical compounds (anthelmintics). However, the excessive or uncontrolled use of these compounds in livestock animals has led to major challenges linked to drug resistance in nematodes. Therefore, there is a need to develop new anthelmintics with novel mechanism(s) of action. Recently, we identified a small molecule, designated UMW-9729, with nematocidal activity against the free-living model organism Caenorhabditis elegans. Here, we evaluated UMW-9729's potential as an anthelmintic in a structure-activity relationship (SAR) study in C. elegans and the highly pathogenic, blood-feeding Haemonchus contortus (barber's pole worm), and explored the compound-target relationship using thermal proteome profiling (TPP). First, we synthesised and tested 25 analogues of UMW-9729 for their nematocidal activity in both H. contortus (larvae and adults) and C. elegans (young adults), establishing a preliminary nematocidal pharmacophore for both species. We identified several compounds with marked activity against either H. contortus or C. elegans which had greater efficacy than UMW-9729, and found a significant divergence in compound bioactivity between these two nematode species. We also identified a UMW-9729 analogue, designated 25, that moderately inhibited the motility of adult female H. contortus in vitro. Subsequently, we inferred three H. contortus proteins (HCON_00134350, HCON_00021470 and HCON_00099760) and five C. elegans proteins (F30A10.9, F15B9.8, B0361.6, DNC-4 and UNC-11) that interacted directly with UMW-9729; however, no conserved protein target was shared between the two nematode species. Future work aims to extend the SAR investigation in these and other parasitic nematode species, and validate individual proteins identified here as possible targets of UMW-9729. Overall, the present study evaluates this anthelmintic candidate and highlights some challenges associated with early anthelmintic investigation.
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ItemSpectroscopic study of L-DOPA and dopamine binding on novel gold nanoparticles towards more efficient drug-delivery system for Parkinson's disease(PERGAMON-ELSEVIER SCIENCE LTD, 2022-03-05)Nano-drug delivery systems may potentially overcome current challenges in the treatment of Parkinson's disease (PD) by enabling targeted delivery and more efficient blood-brain penetration ability. This study investigates novel gold nanoparticles (AuNPs) to be used as delivery systems for L-DOPA and dopamine by considering their binding capabilities in the presence and absence of a model protein, bovine serum albumin (BSA). Four different AuNPs were prepared by surface functionalization with polyethylene glycol (PEG), 1-adamantylamine (Ad), 1-adamantylglycine (AdGly), and peptidoglycan monomer (PGM). Fluorescence and UV-Vis measurements demonstrated the strongest binding affinity and L-DOPA/dopamine loading efficiency for PGM-functionalized AuNPs with negligible impact of the serum protein presence. Thermodynamic analysis revealed a spontaneous binding process between L-DOPA or dopamine and AuNPs that predominantly occurred through van der Waals interactions/hydrogen bonds or electrostatic interactions. These results represent PGM-functionalized AuNPs as the most efficient at L-DOPA and dopamine binding with a potential to become a drug-delivery system for neurodegenerative diseases. Detailed investigation of L-DOPA/dopamine interactions with different AuNPs was described here for the first time. Moreover, this study highlights a cost- and time-effective methodology for evaluating drug binding to nanomaterials.
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ItemGrowth of Gold Nanorods: A SAXS Study(AMER CHEMICAL SOC, 2021-09-16)Using simultaneous, in situ optical spectroscopy and time-resolved, small-angle X-ray scattering (SAXS), we have directly monitored the seeded growth of nearly monodisperse gold nanorods using hydroquinone as the reductant. Growth of the rods is much slower than with the ascorbate ion, allowing the rate of growth along both the longitudinal and transverse directions to be independently determined. The thickness of the stabilizing CTAB layer (3.2 ± 0.3 nm) has also been extracted. We find that increasing the hydrogen tetrachloroaurate(III) concentration produces longer rods, while conversely, increasing the hydroquinone concentration reduces the final aspect ratio. The final number of gold rods is smaller than the initial number of seed particles and decreases in the presence of larger concentrations of HAuCl4. The SAXS data reveal an early transition from a spherical morphology to an ellipsoidal one and then to spherically capped cylinders. The growth curve exhibits at least three distinct regimes: an initial phase comprising spherical seed growth, followed by symmetry breaking and slow elongation. A third phase is marked by rapid rod growth and increases in the aspect ratio. This process is temporally well resolved from the initial symmetry breaking but typically occurs when the rods are around 6 nm in diameter using hydroquinone as the reductant. The results provide qualitative support for the “popcorn model” proposed by Edgar et al. [ Formation of Gold Nanorods by a Stochastic “Popcorn” Mechanism. ACS Nano 2012, 6, 1116 1125 ].
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ItemInsights into dynamic properties of water in lipidic cubic phases by 2D nuclear Overhauser effect (NOE) NMR spectroscopy.(Elsevier BV, 2024-07-15)Two-dimensional NOE (nuclear Overhauser effect) NMR spectroscopy was employed to investigate the dynamic properties of water within lyotropic bicontinuous lipidic cubic phases (LCPs) formed by monoolein (MO). Experiments observed categorically different effective residence times of water molecules: (i) in proximity to the glycerol moiety of MO, and (ii) adjacent to the hydrophobic chain towards the hydrocarbon tail of MO, as evidenced by the opposite signs of intermolecular NOE cross peaks between protons of water and those of MO in 2D 1H-1H NOESY spectra. Spectroscopic data delineating the different effective residence times of water molecules within both the gyroid (QIIG) and diamond (QIID) phase groups corresponding to hydration levels of 35 and 40 wt%, respectively, are presented. Additionally, an increase in effective residence time of water molecules in proximity to the glycerol moiety of MO in LCPs was observed upon storage at ambient temperature and in the presence of an additive lipid, cholesterol. Atom-specific NOE build-up curves for protons of water and those of MO are also given. The results presented herein provide new insight into the physicochemical properties and behaviour of water in LCPs, and demonstrate an additional avenue for experimental study of water-lipid interactions and hydration dynamics in model membranes and nanomaterials using 2D NOE NMR spectroscopy.
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ItemUnravelling the mechanism of neurotensin recognition by neurotensin receptor 1(NATURE PORTFOLIO, 2023-12-09)The conformational ensembles of G protein-coupled receptors (GPCRs) include inactive and active states. Spectroscopy techniques, including NMR, show that agonists, antagonists and other ligands shift the ensemble toward specific states depending on the pharmacological efficacy of the ligand. How receptors recognize ligands and the kinetic mechanism underlying this population shift is poorly understood. Here, we investigate the kinetic mechanism of neurotensin recognition by neurotensin receptor 1 (NTS1) using 19F-NMR, hydrogen-deuterium exchange mass spectrometry and stopped-flow fluorescence spectroscopy. Our results indicate slow-exchanging conformational heterogeneity on the extracellular surface of ligand-bound NTS1. Numerical analysis of the kinetic data of neurotensin binding to NTS1 shows that ligand recognition follows an induced-fit mechanism, in which conformational changes occur after neurotensin binding. This approach is applicable to other GPCRs to provide insight into the kinetic regulation of ligand recognition by GPCRs.
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ItemStructures of the interleukin 11 signalling complex reveal gp130 dynamics and the inhibitory mechanism of a cytokine variant(NATURE PORTFOLIO, 2023-11-20)Interleukin (IL-)11, an IL-6 family cytokine, has pivotal roles in autoimmune diseases, fibrotic complications, and solid cancers. Despite intense therapeutic targeting efforts, structural understanding of IL-11 signalling and mechanistic insights into current inhibitors are lacking. Here we present cryo-EM and crystal structures of the human IL-11 signalling complex, including the complex containing the complete extracellular domains of the shared IL-6 family β-receptor, gp130. We show that complex formation requires conformational reorganisation of IL-11 and that the membrane-proximal domains of gp130 are dynamic. We demonstrate that the cytokine mutant, IL-11 Mutein, competitively inhibits signalling in human cell lines. Structural shifts in IL-11 Mutein underlie inhibition by altering cytokine binding interactions at all three receptor-engaging sites and abrogating the final gp130 binding step. Our results reveal the structural basis of IL-11 signalling, define the molecular mechanisms of an inhibitor, and advance understanding of gp130-containing receptor complexes, with potential applications in therapeutic development.
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ItemNo Preview AvailablePharmacologic hyperstabilisation of the HIV-1 capsid lattice induces capsid failure(eLIFE SCIENCES PUBL LTD, 2024-02-13)The HIV-1 capsid has emerged as a tractable target for antiretroviral therapy. Lenacapavir, developed by Gilead Sciences, is the first capsid-targeting drug approved for medical use. Here, we investigate the effect of lenacapavir on HIV capsid stability and uncoating. We employ a single particle approach that simultaneously measures capsid content release and lattice persistence. We demonstrate that lenacapavir's potent antiviral activity is predominantly due to lethal hyperstabilisation of the capsid lattice and resultant loss of compartmentalisation. This study highlights that disrupting capsid metastability is a powerful strategy for the development of novel antivirals.
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ItemNo Preview AvailableStructure-activity relationship and target investigation of 2-aryl quinolines with nematocidal activity(ELSEVIER SCI LTD, 2024-04)Within the context of our anthelmintic discovery program, we recently identified and evaluated a quinoline derivative, called ABX464 or obefazimod, as a nematocidal candidate; synthesised a series of analogues which were assessed for activity against the free-living nematode Caenorhabditis elegans; and predicted compound-target relationships by thermal proteome profiling (TPP) and in silico docking. Here, we logically extended this work and critically evaluated the anthelmintic activity of ABX464 analogues on Haemonchus contortus (barber's pole worm) - a highly pathogenic nematode of ruminant livestock. First, we tested a series of 44 analogues on H. contortus (larvae and adults) to investigate the nematocidal pharmacophore of ABX464, and identified one compound with greater potency than the parent compound and showed moderate activity against a select number of other parasitic nematodes (including Ancylostoma, Heligmosomoides and Strongyloides species). Using TPP and in silico modelling studies, we predicted protein HCON_00074590 (a predicted aldo-keto reductase) as a target candidate for ABX464 in H. contortus. Future work aims to optimise this compound as a nematocidal candidate and investigate its pharmacokinetic properties. Overall, this study presents a first step toward the development of a new nematocide.
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ItemNo Preview AvailableFree drug percentage of moxidectin declines with increasing concentrations in the serum of marsupials(ELSEVIER, 2024-04)Moxidectin (MOX) is a macrocyclic lactone used to eliminate endo and ectoparasites in many mammalian species. It is notably the active ingredient of the anti-parasitic drug Cydectin®, manufactured by Virbac, and is frequently used to treat sarcoptic mange in Australian wildlife. Protein binding plays a significant role in the efficacy of a drug, as the unbound/free drug in plasma ultimately reflects the pharmacologically relevant concentration. This study aimed to investigate the free drug percentage of Moxidectin after in vitro spiking into the sera of four sarcoptic mange-susceptible Australian wildlife species; the koala (Phascolarctos cinereus), the bare-nosed wombat (Vombatus ursinus), the eastern grey kangaroo (Macropus giganteus), and the mountain brushtail possum (Trichosurus cunninghami). Three concentration points of MOX were tested for each individual: 20 pg/μL, 100 pg/μL and 500 pg/μL. Serum from five individuals of each species underwent an equilibrium dialysis followed by liquid chromatography tandem mass spectrometry (LC-MS/MS). The results showed an atypical concentration dependent binding across all species, where free drug percentage decreased as MOX concentration increased. In addition, wombats showed significantly lower free drug levels. These findings call for further research into the mechanisms of moxidectin protein binding to help understand MOX pharmacokinetics in marsupials.