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Journal articleBradford T, Summers PA, Majid A, et al., 2024,
Imaging G-Quadruplex Nucleic Acids in Live Cells Using Thioflavin T and Fluorescence Lifetime Imaging Microscopy.
, Anal ChemVisualization of guanine-rich oligonucleotides that fold into G-quadruplex (G4) helical structures is of great interest in cell biology. There is a large body of evidence that suggests that these noncanonical structures form in vivo and play important biological roles. A promising recent development highlighted fluorescence lifetime imaging microscopy (FLIM) as a robust technique for the direct and quantitative imaging of G4s in live cells. However, this method requires specialized, bespoke synthetic dyes that are not widely available. Herein, we demonstrate that the fluorescence lifetime of commercially available environmentally sensitive dyes Thioflavin T (ThT) and Thiazole Orange (TO) is strongly dependent on the type of DNA topology they bind to, with G4s showing long and distinctive decay times that should allow G4 detection in the biological environment. We applied this observation to visualize G4s in live U2OS cells using FLIM of ThT, upon alteration in G4 levels due to competitive binding or nuclease treatment of cells.
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Journal articleBartlett M, Burke J, Sherin P, et al., 2024,
Platinum(II)-Salphen complexes as DNA binders and photosensitisers
, Chemistry: A European Journal, Vol: 30, ISSN: 0947-6539Current anticancer therapies suffer from issues such as off-target side effects and the emergence of drug resistance; therefore, the discovery of alternative therapeutic approaches is vital. These can include the development of drugs with different modes of action, and the exploration of new biomolecular targets. For the former, there has been increasing interest in drugs that are activated by an external stimulus to generate cytotoxic species. For the latter, significant efforts are being directed to explore non-canonical DNA and RNA structures (e.g. guanine-quadruplexes), as alternative biomolecular targets. Herein we report the synthesis of a library of 21 new platinum(II)-Salphen complexes, investigation of their photophysical and photochemical properties, their interactions with duplex and quadruplex DNA, and their cytotoxicity against HeLa cancer cells in the dark and upon light irradiation. Thanks to the intrinsic phosphorescence of the platinum(II) complexes, confocal microscopy was used for six of the complexes to determine their cellular permeability and localisation in two cancer cell lines. These studies have allowed us to identify two lead platinum(II) complexes with high guanine-quadruplex DNA affinity and selectivity, good cell permeability and nuclear localisation, and high cytotoxicity against HeLa cancer cells upon irradiation with no detected cytotoxicity in the dark.
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Journal articleKench T, Rahardjo A, Terrones GG, et al., 2024,
A semi-automated, high-throughput approach for the synthesis and identification of highly photo-cytotoxic iridium complexes
, Angewandte Chemie International Edition, Vol: 63, ISSN: 1433-7851The discovery of new compounds with pharmacological properties is usually a lengthy, laborious and expensive process. Thus, there is increasing interest in developing workflows that allow for the rapid synthesis and evaluation of libraries of compounds with the aim of identifying leads for further drug development. Herein, we apply combinatorial synthesis to build a library of 90 iridium(III) complexes (81 of which are new) over two synthesise-and-test cycles, with the aim of identifying potential agents for photodynamic therapy. We demonstrate the power of this approach by identifying highly active complexes that are well-tolerated in the dark but display very low nM phototoxicity against cancer cells. To build a detailed structure-activity relationship for this class of compounds we have used density functional theory (DFT) calculations to determine some key electronic parameters and study correlations with the experimental data. Finally, we present an optimised semi-automated synthesise-and-test protocol to obtain multiplex data within 72 hours.
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Journal articlePriessner M, Gaboriau DCA, Sheridan A, et al., 2024,
Content-aware frame interpolation (CAFI): deep learning-based temporal super-resolution for fast bioimaging
, NATURE METHODS, Vol: 21, ISSN: 1548-7091 -
Journal articleRobinson J, Stenspil SG, Maleckaite K, et al., 2024,
Cellular visualization of G-quadruplex RNA via fluorescence- lifetime imaging microscopy
, Journal of the American Chemical Society, Vol: 146, Pages: 1009-1018, ISSN: 0002-7863Over the past decade, appreciation of the roles of G-quadruplex (G4) structures in cellular regulation and maintenance has rapidly grown, making the establishment of robust methods to visualize G4s increasingly important. Fluorescent probes are commonly used for G4 detection in vitro; however, achieving sufficient selectivity to detect G4s in a dense and structurally diverse cellular environment is challenging. The use of fluorescent probes for G4 detection is further complicated by variations of probe uptake into cells, which may affect fluorescence intensity independently of G4 abundance. In this work, we report an alternative small-molecule approach to visualize G4s that does not rely on fluorescence intensity switch-on and, thus, does not require the use of molecules with exclusive G4 binding selectivity. Specifically, we have developed a novel thiazole orange derivative, TOR-G4, that exhibits a unique fluorescence lifetime when bound to G4s compared to other structures, allowing G4 binding to be sensitively distinguished from non-G4 binding, independent of the local probe concentration. Furthermore, TOR-G4 primarily colocalizes with RNA in the cytoplasm and nucleoli of cells, making it the first lifetime-based probe validated for exploring the emerging roles of RNA G4s in cellulo.
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Journal articleReyes JB, Sherin PS, Sarkar A, et al., 2023,
Platinum(II)-based optical probes for imaging quadruplex DNA structures via phosphorescence lifetime imaging microscopy
, Angewandte Chemie International Edition, Vol: 62, ISSN: 1433-7851G-quadruplex DNA is a non-canonical structure that forms in guanine-rich regions of the genome. There is increasing evidence showing that G-quadruplexes have important biological functions, and therefore molecular tools to visualise these structures are important. Herein we report on a series of new cyclometallated platinum(II) complexes which, upon binding to G-quadruplex DNA, display an increase in their phosphorescence, acting as switch-on probes. More importantly, upon binding to G-quadruplexes they display a selective and distinct lengthening of their emission lifetime. We show that this effect can be used to selectively visualise these structures in cells using Phosphorescence Lifetime Imaging Microscopy (PLIM).
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Journal articleBerrones Reyes J, Sherin PS, Sarkar A, et al., 2023,
Platinum(II)-based optical probes for imaging quadruplex DNA structures via phosphorescence lifetime imaging microscopy
, Angewandte Chemie, Vol: 135, Pages: e202310402-e202310402, ISSN: 0044-8249G-quadruplex DNA is a non-canonical structure that forms in guanine-rich regions of the genome. There is increasing evidence showing that G-quadruplexes have important biological functions, and therefore molecular tools to visualise these structures are important. Herein we report on a series of new cyclometallated platinum(II) complexes which, upon binding to G-quadruplex DNA, display an increase in their phosphorescence, acting as switch-on probes. More importantly, upon binding to G-quadruplexes they display a selective and distinct lengthening of their emission lifetime. We show that this effect can be used to selectively visualise these structures in cells using Phosphorescence Lifetime Imaging Microscopy (PLIM).
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Journal articleIannace V, Sabate F, Bartlett M, et al., 2023,
Syntheses, Characterization, and DNA Binding Studies of a Series of Copper(II), Nickel(II), Platinum(II) and Zinc(II) Complexes Derived from Schiff Base Ligands
, EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, ISSN: 1434-1948 -
Journal articleKench T, Rakers V, Bouzada D, et al., 2023,
Dimeric metal-salphen complexes which target multimeric G-quadruplex DNA
, Bioconjugate Chemistry, Vol: 34, Pages: 911-921, ISSN: 1043-1802G-Quadruplex DNA structures have attracted increasing attention due to their biological roles and potential as targets for the development of new drugs. While most guanine-rich sequences in the genome have the potential to form monomeric G-quadruplexes, certain sequences have enough guanine-tracks to give rise to multimeric quadruplexes. One of these sequences is the human telomere where tandem repeats of TTAGGG can lead to the formation of two or more adjacent G-quadruplexes. Herein we report on the modular synthesis via click chemistry of dimeric metal-salphen complexes (with NiII and PtII) bridged by either polyether or peptide linkers. We show by circular dichroism (CD) spectroscopy that they generally have higher selectivity for dimeric vs monomeric G-quadruplexes. The emissive properties of the PtII-salphen dimeric complexes have been used to study their interactions with monomeric and dimeric G-quadruplexes in vitro as well as to study their cellular uptake and localization.
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Journal articleCodina AS, Huerta AT, Heiba HF, et al., 2023,
Functionalised polymeric materials for the removal of arsenate from contaminated water
, Environmental Science: Water Research & Technology, Vol: 9, Pages: 772-780, ISSN: 2053-1419Inorganic arsenic is a carcinogen and, in some regions, one of the biggest contaminants in drinking water. The World Health Organisation (WHO) has indicated that over 140 million people worldwide are drinking water with levels of arsenic above the recommended guideline value of 10 μg L−1. Therefore, there is a pressing need to find low-cost technologies for the removal of inorganic arsenic from water. As part of our efforts to tackle this problem, we previously developed an efficient sorbent material (ImpAs) based on a polymeric support (HypoGel) functionalised with a selective chemical receptor for arsenate (i.e. arsenic(V)). With the aim to lower the production cost of this material and improve its arsenate removal capacity, we have studied other polymeric materials as solid supports. Herein, we report the synthesis of new inexpensive sorbent materials by covalently attaching our previously reported arsenate receptor onto Merrifield and Purolite C106 polymer beads. We carried out batch and flow-through experiments with the new polymeric materials demonstrating that they have up to 60% higher arsenate removal capacities than the original functionalised HypoGel material. Furthermore, the new polymeric materials operate very well under flow-through conditions, removing over 99% of arsenate present in solutions containing low (15 μg L−1) and high (300 μg L−1) levels of arsenate. We also report on the lower production cost of the new Purolite-based material as compared to the original functionalised HypoGel polymer beads.
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Journal articleVilar Compte R, Evans L, Kotar A, et al., 2023,
Identification and characterisation of G-quadruplex DNA-forming sequences in the Pseudomonas aeruginosa genome
, RSC Chemical Biology, Vol: 4, Pages: 94-100, ISSN: 2633-0679A number of Gram-negative bacteria such as Pseudomonas aeruginosa are becoming resistant to front-line antibiotics. Consequently, there is a pressing need to find alternative bio-molecular targets for the development of new drugs. Since non-canonical DNA structures such as guanine-quadruplexes (G4s) have been implicated in regulating transcription, we were interested in determining whether there are putative quadruplex-forming sequences (PQS) in the genome of Pseudomonas aeruginosa. Using bioinformatic tools, we screened 36 genes potentially relevant to drug resistance for the presence of PQS and 10 of these were selected for biophysical characterisation (i.e. circular dichroism and thermal difference UV/Vis spectroscopy). These studies showed that three of these G-rich sequences (linked to murE, ftsB and mexC genes) form stable guanine-quadruplexes which were studied by NMR spectroscopy; detailed analysis of one of the sequences (mexC) confirmed that it adopts a two-quartet antiparallel quadruplex structure in the presence of K+ ions. We also show by FRET melting assays that small molecules can stabilise these three new G4 DNA structures under physiological conditions. These initial results could be of future interest in the development of new antibiotics with alternative bio-molecular targets which in turn would help tackle antimicrobial resistance.
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Journal articleLo R, Majid A, Fruhwirth GO, et al., 2022,
Radiolabelling Pt-based quadruplex DNA binders via click chemistry.
, Bioorganic and Medicinal Chemistry, Vol: 76, Pages: 1-9, ISSN: 0968-0896Guanine-rich sequences of DNA and RNA can fold into intramolecular tetra-helical assemblies known as G-quadruplexes (G4). Their formation in vivo has been associated to a range of biological functions and therefore they have been identified as potential drug targets. Consequently, a broad range of small molecules have been developed to target G4s. Amongst those are metal complexes with Schiff base ligands. Herein, we report the functionalisation of one of these well-established G4 DNA binders (based on a square planar platinum(II)-salphen complex) with two different radiolabelled complexes. An 111In-conjugate was successfully used to assess its in vivo distribution in a mouse tumour model using single-photon emission computed tomography (SPECT) imaging. These studies highlighted the accumulation of this Pt-salphen-111In conjugate in the tumour.
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Journal articleBullen JC, Lapinee C, Miller LA, et al., 2022,
Spectroscopic (XAS, FTIR) investigations into arsenic adsorption onto TiO2/Fe2O3 composites: evaluation of the surface complexes, speciation and precipitation predicted by modelling
, Results in Surfaces and Interfaces, Vol: 9, ISSN: 2666-8459Over 50 million people in South Asia are exposed to groundwater contaminated with carcinogenic arsenic(III). Photocatalyst-adsorbent composite materials are popularly developed for removing arsenic in a single-step water treatment. Here, As(III) is oxidised to As(V), which is subsequently removed via adsorption. We previously developed a component additive surface complexation model (CA-SCM) to predict the speciation of arsenic adsorbed onto TiO2/Fe2O3 under different environmental conditions, using surface complexes taken from studies of single-phase minerals. In this work, we critically evaluate this approach, using experimental observations of the surface structures of arsenic adsorbed onto TiO2/Fe2O3. Extended X-ray absorption fine structure spectroscopy (EXAFS) indicates significant As(III) surface precipitation, and the possible formation of tridentate 3C complexes. EXAFS was unable to identify As binding modes for TiO2 and Fe2O3 surface complexes simultaneously, highlighting the challenge of analysing composite surfaces. FTIR and zeta potential analysis indicate that As(III)-Fe2O3 surface complexes are protonated at neutral pH, whilst As(III)-TiO2, As(V)-Fe2O3 and As(V)-TiO2 surface complexes are negatively charged. Our study confirms the speciation predicted by CA-SCM, particularly As(III) surface precipitation, but also introduces the possibility of tridentate As(III) at acidic pH. This study highlights how experiment and modelling can be combined to assess surface complexation on composite surfaces.
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Journal articleNorthover G, Mao Y, Blasco S, et al., 2022,
Synergistic use of siderophores and weak organic ligands during zinc transport in the rhizosphere controlled by pH and ion strength gradients
, Scientific Reports, Vol: 12, ISSN: 2045-2322Citrate (Cit) and Deferoxamine B (DFOB) are two important organic ligands coexisting in soils with distinct different affinities for metal ions. It has been theorized that siderophores and weak organic ligands play a synergistic role during the transport of micronutrients in the rhizosphere, but the geochemical controls of this process remain unknown. Here we test the hypothesis that gradients in pH and ion strength regulate and enable the cooperation. To this end, first we use potentiometric titrations to identify the dominant Zn(II)–Cit and Zn(II)–DFOB complexes and to determine their ionic strength dependent stability constants between 0 and 1 mol dm−3. We parametrise the Extended Debye-Hückel (EDH) equation and determine accurate intrinsic association constants (logβ0) for the formation of the complexes present. The speciation model developed confirms the presence of [Zn(Cit)]−, [Zn(HCit)], [Zn2(Cit)2(OH)2]4−, and [Zn(Cit)2]4−, with [Zn(Cit)]− and [Zn2(Cit)2(OH)2]4− the dominant species in the pH range relevant to rhizosphere. We propose the existence of a new [Zn(Cit)(OH)3]4− complex above pH 10. We also verify the existence of two hexadentate Zn(II)–DFOB species, i.e., [Zn(DFOB)]− and [Zn(HDFOB)], and of one tetradentate species [Zn(H2DFOB)]+. Second, we identify the pH and ionic strength dependent ligand exchange points (LEP) of Zn with citrate and DFOB and the stability windows for Zn(II)–Cit and Zn(II)–DFOB complexes in NaCl and rice soil solutions. We find that the LEPs fall within the pH and ionic strength gradients expected in rhizospheres and that the stability windows for Zn(II)–citrate and Zn(II)–DFOB, i.e., low and high affinity ligands, can be distinctly set off. This suggests that pH and ion strength gradients allow for Zn(II) complexes with citrate and DFOB to dominate in different parts of the rhizosphere and this explains why mixtures of low and h
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Journal articleSummers PA, Thomas AP, Kench T, et al., 2021,
Cationic helicenes as selective G4 DNA binders and optical probes for cellular imaging
, CHEMICAL SCIENCE, Vol: 12, Pages: 14624-14634, ISSN: 2041-6520- Author Web Link
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- Citations: 8
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Journal articlePriessner M, Gaboriau DCA, Sheridan A, et al., 2021,
Content-aware frame interpolation (CAFI): Deep Learning-based temporal super-resolution for fast bioimaging
<jats:p>The development of high-resolution microscopes has made it possible to investigate cellular processes in 4D (3D over time). However, observing fast cellular dynamics remains challenging as a consequence of photobleaching and phototoxicity. These issues become increasingly problematic with the depth of the volume acquired and the speed of the biological events of interest. Here, we report the implementation of two content-aware frame interpolation (CAFI) deep learning networks, Zooming SlowMo (ZS) and Depth-Aware Video Frame Interpolation (DAIN), based on combinations of recurrent neural networks, that are highly suited for accurately predicting images in between image pairs, therefore improving the temporal resolution of image series as a post-acquisition analysis step. We show that CAFI predictions are capable of understanding the motion context of biological structures to perform better than standard interpolation methods. We benchmark CAFI’s performance on six different datasets, obtained from three different microscopy modalities (point-scanning confocal, spinning-disk confocal and confocal brightfield microscopy). We demonstrate its capabilities for single-particle tracking methods applied to the study of lysosome trafficking. CAFI therefore allows for reduced light exposure and phototoxicity on the sample and extends the possibility of long-term live-cell imaging. Both DAIN and ZS as well as the training and testing data are made available for use by the wider community via the ZeroCostDL4Mic platform.</jats:p>
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Journal articlePriessner M, Summers PA, Lewis BW, et al., 2021,
Selective Detection of Cu<sup>+</sup> Ions in Live Cells via Fluorescence Lifetime Imaging Microscopy
, Angewandte Chemie, Vol: 133, Pages: 23332-23337, ISSN: 0044-8249<jats:title>Abstract</jats:title><jats:p>Copper is an essential trace element in living organisms with its levels and localisation being carefully managed by the cellular machinery. However, if misregulated, deficiency or excess of copper ions can lead to several diseases. Therefore, it is important to have reliable methods to detect, monitor and visualise this metal in cells. Herein we report a new optical probe based on BODIPY, which shows a switch‐on in its fluorescence intensity upon binding to copper(I), but not in the presence of high concentration of other physiologically relevant metal ions. More interestingly, binding to copper(I) leads to significant changes in the fluorescence lifetime of the new probe, which can be used to visualize copper(I) pools in lysosomes of live cells via fluorescence lifetime imaging microscopy (FLIM).</jats:p>
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Journal articleVilar R, Priessner M, Summers PA, et al., 2021,
Selective detection of Cu+ ions in live cells via fluorescence lifetime imaging microscopy.
, Angewandte Chemie International Edition, Vol: 60, Pages: 23148-23153, ISSN: 1433-7851Copper is an essential trace element in living organisms with its levels and localisation being carefully managed by the cellular machinery. However, if misregulated, deficiency or excess of copper ions can lead to several diseases. Therefore, it is important to have reliable methods to detect, monitor and visualise this metal in cells. Herein we report a new optical probe based on BODIPY, which shows a switch-on in its fluorescence intensity upon binding to copper(I), but not in the presence of high concentration of other physiologically relevant metal ions. More interestingly, binding to copper(I) leads to significant changes in the fluorescence lifetime of the new probe, which can be used to visualize copper(I) pools in lysosomes of live cells via fluorescence lifetime imaging microscopy (FLIM).
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Journal articleLo R, Fruhwirth G, Vilar R, 2021,
A quadruplex-DNA binder functionalised with a SPECT probe for in vivo imaging
<jats:p>Guanine-rich sequences of DNA can fold into intramolecular tetra-helical assemblies known as G-quadruplexes (G4). Their formation in vivo has been associated to a range of biological functions and therefore they have been identified as potential drug targets. Consequently, a broad range of small molecules have been developed to target quadruplexes. However, to date, there is very limited information of the biodistribution of quadruplex binders in whole organisms. Here, we report the functionalisation of a well-established G4 DNA binder (based on a square planar platinum(II)-salphen complex) with two different radiolabelled complexes. An 111In-conjugate was successfully used to assess its in vivo distribution in a mouse tumour model using single-photon emission computed tomography (SPECT) imaging. These studies have shown the overall biodistribution of the G4 DNA binder highlighting its accumulation in the tumour.</jats:p>
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Journal articleLo R, Fruhwirth G, Vilar R, 2021,
A quadruplex-DNA binder functionalised with a SPECT probe for in vivo imaging
<jats:p>Guanine-rich sequences of DNA can fold into intramolecular tetra-helical assemblies known as G-quadruplexes (G4). Their formation in vivo has been associated to a range of biological functions and therefore they have been identified as potential drug targets. Consequently, a broad range of small molecules have been developed to target quadruplexes. However, to date, there is very limited information of the biodistribution of quadruplex binders in whole organisms. Here, we report the functionalisation of a well-established G4 DNA binder (based on a square planar platinum(II)-salphen complex) with two different radiolabelled complexes. An 111In-conjugate was successfully used to assess its in vivo distribution in a mouse tumour model using single-photon emission computed tomography (SPECT) imaging. These studies have shown the overall biodistribution of the G4 DNA binder highlighting its accumulation in the tumour.</jats:p>
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Journal articleWeiss D, Northover G, Hanif M, et al., 2021,
Isotope fractionation of zinc in the paddy rice soil-water environment and the role of 2’deoxymugineic acid (DMA) as zincophore under Zn limiting conditions
, Chemical Geology, Vol: 577, Pages: 1-21, ISSN: 0009-2541Non-traditional stable isotope systems are increasingly used to study micronutrient cycling and acquisition in terrestrial ecosystems. We previously proposed for zinc (Zn) a conceptual model linking observed isotope signatures and fractionations to biogeochemical processes occurring in the rice soil environment and we suggested that 2’deoxymugineic acid (DMA) could play an important role for rice during the acquisition of Zn when grown under Zn limiting conditions. This proposition was sustained by the extent and direction of isotope fractionation observed during the complexation of Zn with DMA synthesised in our laboratory. Here we report a new set of experimental data from field and laboratory studies designed to further elucidate the mechanisms controlling Zn isotope fractionation in the rice rhizosphere and the role of DMA. First, we present acidity (pKa) and complexation (logK) constants for DMA with H+ and Zn2+, respectively, using synthetic 2’deoxymugineic acid and show that they are significantly different from previously published data using isolates from plants. Our new set of thermodynamic data allows for a more accurate calculation of the formation of ZnDMA complexes over pH ranges typically found in the rhizosphere of flooded lowland rice soils and in rice plant compartments (xylem, phloem). We show that at pH > 6.5, Zn is fully complexed by DMA and at pH <4.5 fully dissociated. This has important implications, i.e. that in alkaline paddy soils, DMA can strip Zn from soil solids (organic and inorganic) and that ZnDMA complexes are stable at the root interface if the pH is alkaline and in the phloem and xylem of the rice shoot. Second, we present a new set of Zn isotope data in rice grown in alkaline soils with low Zn availability with and without Zn addition. We used two genotypes not tested to date, i.e. A69–1, tolerant to low Zn supply, and IR26, sensitive to low Zn supply. We confirm previous findings that, in contrast to obse
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Journal articleNorthover G, Mao Y, Ahmed H, et al., 2021,
Effect of salinity on the zinc(II) binding efficiency of siderophore functional groups and implications for salinity tolerance mechanisms in barley
, Scientific Reports, Vol: 11, Pages: 1-12, ISSN: 2045-2322Bacteria, fungi and grasses use siderophores to access micronutrients. Hence, the metal binding efficiency of siderophores is directly related to ecosystem productivity. Salinization of natural solutions, linked to climate change induced sea level rise and changing precipitation patterns, is a serious ecological threat. In this study, we investigate the impact of salinization on the zinc(II) binding efficiency of the major siderophore functional groups, namely the catecholate (for bacterial siderophores), α-hydroxycarboxylate (for plant siderophores; phytosiderophores) and hydroxamate (for fungal siderophores) bidentate motifs. Our analysis suggests that the order of increasing susceptibility of siderophore classes to salinity in terms of their zinc(II) chelating ability is: hydroxamate < catecholate < α-hydroxycarboxylate. Based on this ordering, we predict that plant productivity is more sensitive to salinization than either bacterial or fungal productivity. Finally, we show that previously observed increases in phytosiderophore release by barley plants grown under salt stress in a medium without initial micronutrient deficiencies (i.e., no micronutrient limitations prior to salinization), are in line with the reduced zinc(II) binding efficiency of the α-hydroxycarboxylate ligand and hence important for the salinity tolerance of whole-plant zinc(II) status.
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Journal articleChan TG, Ruehl CL, Morse SV, et al., 2021,
Modulation of amyloid-beta aggregation by metal complexes with a dual binding mode and their delivery across the blood-brain barrier using focused ultrasound
, Chemical Science, Vol: 12, Pages: 9485-9493, ISSN: 2041-6520One of the key hallmarks of Alzheimer's disease is the aggregation of the amyloid-β peptide to form fibrils. Consequently, there has been great interest in studying molecules that can disrupt amyloid-β aggregation. While a handful of molecules have been shown to inhibit amyloid-β aggregation in vitro, there remains a lack of in vivo data reported due to their inability to cross the blood–brain barrier. Here, we investigate a series of new metal complexes for their ability to inhibit amyloid-β aggregation in vitro. We demonstrate that octahedral cobalt complexes with polyaromatic ligands have high inhibitory activity thanks to their dual binding mode involving π–π stacking and metal coordination to amyloid-β (confirmed via a range of spectroscopic and biophysical techniques). In addition to their high activity, these complexes are not cytotoxic to human neuroblastoma cells. Finally, we report for the first time that these metal complexes can be safely delivered across the blood–brain barrier to specific locations in the brains of mice using focused ultrasound.
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Journal articleKench T, Summers PA, Kuimova MK, et al., 2021,
Rotaxanes as Cages to Control DNA Binding, Cytotoxicity, and Cellular Uptake of a Small Molecule**
, Angewandte Chemie, Vol: 133, Pages: 11023-11029, ISSN: 0044-8249<jats:title>Abstract</jats:title><jats:p>The efficacy of many drugs can be limited by undesirable properties, such as poor aqueous solubility, low bioavailability, and “off‐target” interactions. To combat this, various drug carriers have been investigated to enhance the pharmacological profile of therapeutic agents. In this work, we demonstrate the use of mechanical protection to “cage” a DNA‐targeting metallodrug within a photodegradable rotaxane. More specifically, we report the synthesis of rotaxanes incorporating as a stoppering unit a known G‐quadruplex DNA binder, namely a Pt<jats:sup>II</jats:sup>‐salphen complex. This compound cannot interact with DNA when it is part of the mechanically interlocked assembly. The second rotaxane stopper can be cleaved by either light or an esterase, releasing the Pt<jats:sup>II</jats:sup>‐salphen complex. This system shows enhanced cell permeability and limited cytotoxicity within osteosarcoma cells compared to the free drug. Light activation leads to a dramatic increase in cytotoxicity, arising from the translocation of Pt<jats:sup>II</jats:sup>‐salphen to the nucleus and its binding to DNA.</jats:p>
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Journal articleReyes JB, Kuimova MK, Vilar R, 2021,
Metal complexes as optical probes for DNA sensing and imaging
, CURRENT OPINION IN CHEMICAL BIOLOGY, Vol: 61, Pages: 179-190, ISSN: 1367-5931- Author Web Link
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- Citations: 21
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Journal articleCasini A, Vilar R, 2021,
Editorial overview: Bioinorganic chemistry
, CURRENT OPINION IN CHEMICAL BIOLOGY, Vol: 61, Pages: A4-A5, ISSN: 1367-5931 -
Journal articleKench T, Summers PA, Kuimova MK, et al., 2021,
Rotaxanes as cages to control DNA binding, cytotoxicity, and cellular uptake of a small molecule
, Angewandte Chemie International Edition, Vol: 60, Pages: 1-1, ISSN: 1433-7851The efficacy of many drugs can be limited by undesirable properties, such as poor aqueous solubility, low bioavailability, and “off‐target” interactions. To combat this, various drug carriers have been investigated to enhance the pharmacological profile of therapeutic agents. In this work, we demonstrate the use of mechanical protection to “cage” a DNA‐targeting metallodrug within a photodegradable rotaxane. More specifically, we report the synthesis of rotaxanes incorporating as a stoppering unit a known G‐quadruplex DNA binder, namely a PtII‐salphen complex. This compound cannot interact with DNA when it is part of the mechanically interlocked assembly. The second rotaxane stopper can be cleaved by either light or an esterase, releasing the PtII‐salphen complex. This system shows enhanced cell permeability and limited cytotoxicity within osteosarcoma cells compared to the free drug. Light activation leads to a dramatic increase in cytotoxicity, arising from the translocation of PtII‐salphen to the nucleus and its binding to DNA.
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Journal articleVilar R, Lewis BW, Bisballe N, et al., 2021,
Assessing the key photophysical properties of triangulenium dyes for DNA binding by alteration of the fluorescent core
, Chemistry: A European Journal, Vol: 27, Pages: 2523-2536, ISSN: 0947-6539Four-stranded G-quadruplex (G4) DNA is a non-canonical DNA topology that has been proposed to form in cells and play key roles in how the genome is read and used by the cellular machinery. Previously, a fluorescent triangulenium probe (DAOTA-M2) was used to visualise G4s in cellulo, thanks to its distinct fluorescence lifetimes when bound to different DNA topologies. Herein, we expand the library of available triangulenium probes to explore how modifications to the fluorescent core of the molecule affect its photophysical characteristics, interaction with DNA and cellular localisation. The benzo-bridged and isopropyl-bridged diazatriangulenium dyes, BDATA-M2 and CDATA-M2 respectively, featuring ethyl-morpholino substituents, were synthesised and characterised. The interactions of these molecules with different DNA topologies were studied to determine their binding affinity, fluorescence enhancement and fluorescence lifetime response. Finally, the cellular uptake and localisation of these optical probes were investigated. Whilst structural modifications to the triangulenium core only slightly alter the binding affinity to DNA, BDATA-M2 and CDATA-M2 cannot distinguish between DNA topologies through their fluorescence lifetime. This work presents valuable new evidence into the critical role of PET quenching when using the fluorescence lifetime of triangulenium dyes to discriminate G4 DNA from duplex DNA, highlighting the importance of fine tuning redox and spectral properties when developing new triangulenium-based G4 probes.
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Journal articleVilar Compte R, Summers P, Lewis B, et al., 2021,
Visualising G-quadruplex DNA dynamics in live cells by fluorescence lifetime imaging microscopy
, Nature Communications, Vol: 12, ISSN: 2041-1723Guanine rich regions of oligonucleotides fold into quadruple-stranded structures called G-quadruplexes (G4s). Increasing evidence suggests that these G4 structures form in vivo and play a crucial role in cellular processes. However, their direct observation in live cells remains a challenge. Here we demonstrate that a fluorescent probe (DAOTA-M2) in conjunction with fluorescence lifetime imaging microscopy (FLIM) can identify G4s within nuclei of live and fixed cells. We present a FLIM-based cellular assay to study the interaction of non-fluorescent small molecules with G4s and apply it to a wide range of drug candidates. We also demonstrate that DAOTA-M2 can be used to study G4 stability in live cells. Reduction of FancJ and RTEL1 expression in mammalian cells increases the DAOTA-M2 lifetime and therefore suggests an increased number of G4s in these cells, implying that FancJ and RTEL1 play a role in resolving G4 structures in cellulo.
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Journal articleKench T, Summers PA, Kuimova MK, et al., 2020,
Rotaxanes as Cages to Control DNA Binding, Cytotoxicity and Cellular Uptake of a Small Molecule
<jats:p>In this paper we report a unique approach to control the DNA interactions, cellular uptake and cellular localisation of a small molecule. We have designed rotaxanes that include a luminescent DNA binder, a macrocycle that modulates the DNA binding and a stopper that can be cleaved by either light or the activity of an enzyme.</jats:p>
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