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Hydrothermal Conversion of One-Photon-Fluorescent Poly-(4-vinylpyridine) into Two-Photon-Fluorescent Carbon Nanodots.
Katherine Lawrence, Fengjie Xia, Rory L Arrowsmith, Haobo Ge, Geoffrey W Nelson, John S Foord, Monica Felipe-Sotelo, Nick D M Evans, John M Mitchels, Stephen E Flower, Stanley W Botchway, Daniel Wolverson, Gazi N Aliev, Tony D James, Sofia Pascu, Frank Marken Langmuir 2014
A novel two-photon-fluorescent N,O-heteroatom-rich carbon nanomaterial has been synthesized and characterized. The new carbon nanoparticles were produced by hydro-thermal conversion from a one-photon-fluorescent poly-(4-vinylpyridine) precursor (P4VP). The carbonized particles (cP4VP-dots) with non-uniform particle diameter (ranging from sub-6 nm to 20 nm with some aggregates up to 200 nm) exhibit strong fluorescent properties in different solvents and have also been investigated for applications in cell culture media. The cP4VP-dots retain their intrinsic fluorescence in a cellular environment and exhibit an average excited state lifetime of 2.0 ± 0.9 ns in cell. The cP4VP-dots enter HeLa cells and do not cause significant damage to outer cell membranes. They provide one-photon or two-photon fluorescent synthetic scaffolds for imaging applications and/or drug delivery.
Colorimetric enantioselective recognition of chiral secondary alcohols via hydrogen bonding to a chiral metallocene containing chemosensor.
Su-Ying Xu, Bin Hu, Stephen E Flower, Yun-Bao Jiang, John S Fossey, Wei-Ping Deng, Tony D James Chemical Communications 2013
An operationally simple colorimetric method for enantioselective detection of chiral secondary alcohols via hydrogen bonding interactions using a chiral ferrocene derivative is reported.
"Integrated" and "insulated" boronate-based fluorescent probes for the detection of hydrogen peroxide.
Xiaolong Sun, Su-Ying Xu, Stephen E Flower, John S Fossey, Xuhong Qian, Tony D James Chemical Communications 2013 49, 8311-8313.
Integrated and insulated boronate-based fluorescent probes have been evaluated for the detection of hydrogen peroxide in the presence of saccharides.
Analysis of protein glycation using fluorescent phenylboronate gel electrophoresis.
Marta P Pereira Morais, Dominic Marshall, Stephen E Flower, Christopher J Caunt, Tony D James, Robert J Williams, Nicholas R Waterfield, Jean M H van den Elsen Scientific Reports 03/2013; 3:1437.
Glycated proteins are important biomarkers for age-related disorders, however their analysis is challenging because of the complexity of the protein-carbohydrate adducts. Here we report a method that enables the detection and identification of individual glycated proteins in complex samples using fluorescent boronic acids in gel electrophoresis. Using this method we identified glycated proteins in human serum, insect hemolymph and mouse brain homogenates, confirming this technique as a powerful proteomics tool that can be used for the identification of potential disease biomarkers.
A simple and effective colorimetric technique for the detection of boronic acids and their derivatives
Katherine Lawrence, Stephen E Flower, Gabriele Kociok-Kohn, Christopher G Frost, Tony D James
Analytical methods 2012; 4(8):2215-2217.
A rapid and facile TLC staining method is reported for the qualitative analysis of boronic acids and related boron-containing derivatives. A red colouration is observed when boron is present due to the formation of a boron–curcumin complex. The structure of the phenylboronic acid–curcumin complex was confirmed using single crystal X-ray diffraction data.
Biotinylated boronic acid fluorophore conjugates: Quencher elimination strategy for imaging and saccharide detection
F. D'Hooge, S. A. Elfeky, S. E. Flower, S.I. Pascu, A. T. A. Jenkins, J. M. van den Elsen, T. D. James, J.S. Fossey
RSC Advances 2012; 2: 3274-3280.
A biotinylated boronic acid fluorophore conjugate bound to a diol-quencher via a boronic ester linkage demonstrated a fluorescence increase upon exposure to model saccharides. The sensing motif was attached to SuperAvidin microspheres where the sensing regime was imaged by fluorescence microscopy.
"Field-effect saccharide sensing using AlGaN/GaN heterostructures and boronic acid based chemical receptors"
Tim A. Schuller, Martin Kuball, Stephen E. Flower, Tony D. James, John S. Fossey, Denis Marcon, Jo Das, Stefan Degroot, Marianne Germain, Andrei Sarua Sensors and Actuators B Chemical 2011; 160:1078-1081.
We demonstrate a novel field-effect saccharide sensor device using an AlGaN/GaN heterostructure functionalized with a chemical receptor, featuring a thiol group, alkane chain linker and a simple boronic acid. Fabricated devices were demonstrated to electronically detect buffered saccharide solutions (fructose, galactose and glucose) of varying concentrations. These results provide proof-of-concept for the development AlGaN/GaN-based sensor devices incorporating boronic acid receptor chemistry.
"Boronic acid based photoinduced electron transfer (PET) fluorescence sensors for saccharides"
Joseph D. Larkin, Karine A. Frimat, Thomas M. Fyles, Stephen E. Flower and Tony D. James, New Journal of Chemistry, 2010, 34(12), 2922-2931.
A simple three step synthesis was developed to provide six novel modular sensors, consisting of three para sensors, and three meta sensors with naphthalene, anthracene and pyrene fluorophores. The interaction of the six sensors with the saccharides: D-glucose, D-fructose, D-galactose, and D-mannose, were evaluated. All sensors displayed increasing fluorescence intensity upon the addition of these saccharides, with all of the sensors showing enhanced selectivity for D-glucose over D-galactose, D-fructose and D-mannose. High affinity (Kobs) was also observed for the meta sensors with respect to the para sensors. The naphthalene and anthracene meta sensors showed particularly high affinity (Kobs) for D-galactose. Circular dichroism spectroscopy was used to probe the structures of the complexes formed. Cyclic complexes were formed between all six sensors and D-glucose. Whilst naphthalene and anthracene meta sensors which displayed high affinity for D-galactose also formed cyclic complexes with that saccharide.
"Microwave-electrochemical formation of colloidal zinc oxide at fluorine doped tin oxide electrodes"
Liza Rassaei, Robben Jaber, Stephen E. Flower, Karen J. Edler, Richard G. Compton, Tony D. James and Frank Marken, Electrochemistry Acta, 2010, 55(27), 7909-7915.
Colloidal ZnO is obtained during microwave-enhanced electrochemical deposition experiments from an aqueous solution containing 0.1 M Zn(NO3)2 and 0.02 M H2O2 via repetitive negative going potential cycles from 0.3 to -0.8 V vs. SCE. The effects of temperature and temperature gradients on ZnO electro-formation at fluorine doped tin oxide (FTO) electrodes are investigated with both a conventional thermostated bath system (isothermal) and an in situ microwave electrochemistry system (non-isothermal). Mainly electrodeposition of ZnO is observed in uniformly heated stagnant solution and predominantly the electro-formation of ZnO colloid is observed in the presence of microwave-induced temperature gradients in a flowing solution. For the ZnO colloid prepared via microwave activation, SAXS data suggests an average particle radius of ca. 18 nm. The increase of ZnO nanoparticle concentration during repetitive potential scans is followed by photoluminescence spectroscopy. A possible mechanism for ZnO colloid formation during electrochemical reduction of H2O2 is suggested.
"Diol Appended Quenchers for Fluorescein Boronic Acid"
Souad A. Elfeky,Stephen E. Flower,Naoko Masumoto, François D'Hooge, Ludivine Labarthe, Wenbo Chen, Christophe Len, Tony D. James, John S. Fossey, Chemistry - An Asian Journal, 5, 3, 581-588.
Fluorescein isothiocyanate is treated with 3-aminophenylboronic acid to provide a fluorescently tagged boronic acid derivative which is used to assess Förster resonance energy transfer (FRET) quenching upon boronate ester formation with a series of bespoke diol appended quenchers. Fluorescence spectroscopy comparison of quenching efficiency between treatment of fluorescein and its boronic acid appended congener with quencher appended diol reveals boronate ester formation (covalently linked) to be the more efficient regime and from the panel of quenchers which also included nucleosides.
"An electrochemical gene detection assay utilising T7 exonuclease activity on complementary probe–target oligonucleotide sequences"
Hillier SC, Flower SE, Frost CG, Jenkins ATA*, Keay RW, Braven HT, Clarkson JM, Electrochemistry Communications, 6 (2004) 1227–1232.
This communication describes the synthesis of an electrochemically active oligonucleotide probe and its application in sensing complementary oligonucleotides sequences using a T7 exonuclease enzyme. Target oligonucleotides are detected by hybridisation with a ferrocene labelled probe oligonucleotide followed by addition of T7 exonuclease. The T7 enzyme is a double strand specific exonuclease that removes the terminal 50 nucleotide of the probe sequence. The 50 nucleotide is attached to a ferrocene label, which is subsequently detected at an electrode using differential pulse voltammetry. Time and temperature resolved measurements were performed and an associated study using dual labelled fluorophore–quencher labelled probes was performed to confirm the validity of the electrochemical assay.
"An electrochemical study of enzymatic oligonucleotide digestion"
Hillier SC, Frost CG, Jenkins ATA, Braven HT, Keay RW, Flower SE, Clarkson JM, Bioelectrochemistry 63 (1-2): 307-310 JUN 2004.
This paper describes the synthesis and application of a novel ferrocene (Fc) label that can be efficiently attached to oligonucleotides. We demonstrate how pulse electrochemical methods can be used to measure very low concentrations of ferrocene label and, importantly, show good electroanalytical discrimination between a labelled oligonucleotide and an enzyme digested labelled oligonucleotide, in which the ferrocene label nucleotide conjugate has been released. Real time in situ analysis gives a much greater understanding of the process. Potential applications include the detection of specific nucleic acid sequences and measurement of nuclease activity.
"One-Pot Synthesis of Perhydrofuro[2,3- b]pyran Derivatives”
M. C. Willis and S. E. Flower, Synlett 2003, 1491-1493.
Abstract: TiCl4 mediated addition of 3,4-dihydro-2H-pyran to (2- trimethylsilyl)ethyl pyruvate results in a one-pot addition-cyclisation sequence to deliver a functionalised perhydrofuro[2,3-b]pyran derivative in good yield.
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