Graham Hungerford

Glasgow Caledonian University, Glasgow, Scotland, United Kingdom

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Publications (69)139.57 Total impact

  • M Adília Lemos, Maryam M Aliyu, Graham Hungerford
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    ABSTRACT: Tubers rich in phytochemicals can exhibit a potential health benefit. This work aims at studying the relative effect of different domestic cooking techniques by monitoring the level of total phenolic compounds (TP), total anthocyanins (TA) and anti-oxidant activity (AOA) on a variety of pigmented potatoes. Raw purple potatoes are a good source of anthocyanins (219mg/kgFW) and the level of these compounds increased using different cooking techniques, with the exception of baking. However, the levels of phenolic compounds (originally 209mgGAE/100gFW) decreased in the cooked potatoes. Although potatoes contain different antioxidants in this work the antioxidant activity seems to be related to the levels of phenolic compounds present in the pigmented potato. The fact that some of the compounds present fluoresce enabled both steady state and time-resolved fluorescence techniques to be assessed as a non destructive means of monitoring. This elucidated the presence of different components (via spectral deconvolution and time-resolved emission spectra). Their relative contribution to the fluorescence emission was found to be affected by the different cooking process, with a longer wavelength emission appearing to relate to reflect the presence of anthocyanins. Copyright © 2014 Elsevier Ltd. All rights reserved.
    Food Chemistry 04/2015; 173:462-7. DOI:10.1016/j.foodchem.2014.10.064 · 3.26 Impact Factor
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    ABSTRACT: ng at the improvement of the photorelease of butyric acid – a model carboxylic acid drug, a set of heteroaromatic compounds based on acridine, naphtho[2,1-b]pyran, 3H-benzopyran fused julolidine and thioxo-naphtho[2,1-b]pyran were evaluated as benzyl-type phototriggers, in comparison with the well-known o-nitrobenzyl group. The corresponding ester cages were irradiated in a photochemical reactor at 254, 300, 350 and 419 nm, in two solvent systems (methanol or acetonitrile in 80:20 mixtures with HEPES buffer). Photolysis studies showed that, for some of the cages, the release of the active molecule occurred with short irradiation times using 419 nm. Time-resolved fluorescence was used to elucidate their photophysical properties and determine the decay kinetics. Studies were also carried out to assess the suitability of using two-photon excitation to address these compounds, which is advantageous if their use in biological systems is to be considered.
    Journal of Photochemistry and Photobiology A Chemistry 10/2014; DOI:10.1016/j.jphotochem.2014.10.016 · 2.29 Impact Factor
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    ABSTRACT: The investigation of protein dynamics has long been of interest, since protein interactions and functions can be determined by their structure and changes in conformation. Although fluorescence, occurring on the nanosecond timescale, from intrinsic fluorescent amino acids has been extensively used, in order to fully access conformational changes longer timescales are required. Phosphorescence enables processes on the microsecond to second timescale to be accessed. However, at room temperature this emission can be weak and non trivial to measure. It requires the removal of oxygen - a common triplet state quencher and appropriate instrumentation. In this work we make use of a chemical deoxygenator to study room temperature phosphorescence from tryptophan in human serum albumin excited using a pulsed UV light emitting diode. This is extended to monitor the phosphorescence emission upon increasing temperature, allowing pre-denaturing transitions to be observed. Time-resolved data are analysed, both as the sum of exponential decays and using a distribution analysis based on non extensive decay kinetics. These results are compared to a fluorescence study and both the average lifetime and contribution of the different emitting components were found to give more dramatic changes on the phosphorescence timescale.
    Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 01/2014; 124C:611-617. DOI:10.1016/j.saa.2014.01.073 · 2.13 Impact Factor
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    ABSTRACT: The photoinduced release of several neurotransmitter amino acids (glycine, alanine, glutamic acid, β-alanine and γ-aminobutyric acid) was accomplished from ester cages based on a new photoremovable protecting group consisting of a coumarin built on the julolidine nucleus, namely a (11-oxo-2,3,5,6,7,11-hexahydro-1H-pyrano[2,3-f]pyrido[3,2,1-ij]quinolin-9-yl)methyl group. Photolysis and steady-state sensitization studies revealed that release of the active molecule occurred in short irradiation times at long wavelengths, with a very promising performance at 419 nm. Given the interest in the development of novel protecting groups that are cleavable with UV A or even visible radiation, it was found that a structural modification in the coumarin ring by assembly of a fused julolidine leads to a promising photolabile protecting group for organic synthesis and also for bioapplications.
    European Journal of Organic Chemistry 12/2013; 2013(34). DOI:10.1002/ejoc.201300730 · 3.15 Impact Factor
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    ABSTRACT: The viability of Saccharomyces cerevisiae in biocompatible polymers under different growth conditions and studied using time-resolved fluorescence techniques is presented. Two fluorophores, the viscosity sensitive probe 4-(4-(dimethylamino)styryl)-N-methyl-pyridiniumiodine (DASPMI) and the yeast viability stain 2-chloro-4-(2,3-dihydro-3-methyl-(benzo-1,3-thiazol-2-yl)-methylidene)-1-phenylquinolinium iodide (FUN-1) are used to elucidate information on the incorporated yeast cell viability. Variations in cell viscosity, which are indicative of the cell state, were obtained using DASPMI. Prior to observing FUN-1 in yeast cells using fluorescence lifetime imaging, its photophysics in solution and heterogeneous media were investigated. Time-resolved emission spectra were measured and analysed to associate lifetimes to the spectral emission. Preliminary results show that monitoring the fluorescence lifetime of FUN-1 may give a useful insight into cellular metabolism. The results indicate that both fluorophores may be used to monitor the entrapped yeast cell viability, which is important for in vitro studies and applications, such as that in the biofuel industry, where Saccharomyces cerevisiae are required to remain active in high ethanol environments.
    Photochemical and Photobiological Sciences 10/2013; DOI:10.1039/c3pp50202c · 2.94 Impact Factor
  • M Adília Lemos, Graham Hungerford
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    ABSTRACT: Turmeric (Curcuma Longa L) is obtained from the rhizome of the Zingberaceae family and has a long history as an ingredient in cooking. It has been used as a dye and recently research has concentrated on its possible health benefits, specifically because of its antioxidant activity. The principal compound that is responsible for this activity is curcumin, which is present with the other curcuminoids; demethoxycurcumin and bisdemethoxycurcumin. Curcumin exhibits fluorescence and its photophysics are markedly affected by the polarity, hydrogen bonding and pH. This provides a means to examine its interaction with proteins, which is important if its potential health role is to be fully investigated. In this work we monitor the binding kinetics using time-resolved fluorescence measurements, enabled by the use of low dead time electronics coupled with a high repetition rate excitation source, and time-resolved emission spectra of the extracted curcuminoids upon interaction with bovine serum albumin. From these measurements the decay associated spectra of the different lifetime components were obtained, which is consistent with reports of more than one binding site. Monitoring changes in these spectra with increasing temperature also allows for the denaturing of the serum albumin to be inferred. This article is protected by copyright. All rights reserved.
    Photochemistry and Photobiology 07/2013; 89(5). DOI:10.1111/php.12129 · 2.68 Impact Factor
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  • M. Adília Lemos, Graham Hungerford
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    ABSTRACT: Turmeric (Curcuma longa L.) is obtained from the rhizome of the Zingberaceae family and has a long history as an ingredient in cooking. It has been used as a dye and recently research has concentrated on its possible health benefits, specifically because of its antioxidant activity. The principal compound that is responsible for this activity is curcumin, which is present with the other curcuminoids; demethoxycurcumin and bisdemethoxycurcumin. Curcumin exhibits fluorescence and its photophysics are markedly affected by the polarity, hydrogen bonding and pH. This provides a means to examine its interaction with proteins, which is important if its potential health role is to be fully investigated. In this work, we monitor the binding kinetics using time‐resolved fluorescence measurements, enabled by the use of low dead time electronics coupled with a high repetition rate excitation source and time‐resolved emission spectra of the extracted curcuminoids upon interaction with bovine serum albumin. From these measurements the decay‐associated spectra of the different lifetime components were obtained, which is consistent with reports of more than one binding site. Monitoring changes in these spectra with increasing temperature also allows for the denaturing of the serum albumin to be inferred.
    Photochemistry and Photobiology 01/2013; 89(5). · 2.68 Impact Factor
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    ABSTRACT: This paper reports the preparation and structural studies of praseodymium and samarium (0.5, 2 and 4 mol%) oxide doped lithium boro tellurite glasses. These materials were prepared by the quenching technique in a ceramic crucible at 950 °C. Structural characterization was performed by Raman spectroscopy, Scanning Electron Microscopy and Energy Dispersive X-ray spectroscopy techniques. Results from Raman analysis are in good agreement with those reported in the literature, revealing a normal glass structure for the host material. Understanding on how the glasses internal structure changed when the doping concentration increases was also assessed.
    Materials Research Bulletin 11/2012; 47(11):3489–3494. DOI:10.1016/j.materresbull.2012.06.071 · 2.29 Impact Factor
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    ABSTRACT: An investigation of the use of an azaheterocycle, acridine, as an alternative photochemically removable protecting group for the carboxylic function of neurotransmitter amino acids was carried out. 9-Bromomethylacridine was used in the reaction with glycine, alanine, glutamic acid, β-alanine and γ-aminobutyric acid, to obtain model ester derivatives, which were irradiated at different wavelengths in a photochemical reactor. The process was followed by HPLC/UV, resulting in the release of the active molecule in short irradiation times. The results obtained using 419 nm irradiation show promise (35-98 min) for practical purposes. The compounds were further characterised via time-resolved fluorescence to elucidate their photophysical properties and determine the decay kinetics.
    Photochemical and Photobiological Sciences 10/2012; 12(2). DOI:10.1039/c2pp25261a · 2.94 Impact Factor
  • M. Adília Lemos, Maryam M. Aliyu, Graham Hungerford
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    ABSTRACT: Anthocyanins are water soluble phenolic compounds present in fruit and vegetables which are responsible for the bright red, blue and purple colours of these food products. They are also responsible for the characteristic autumn leaf colouration in some trees. These are versatile compounds, as well as having application in the food industry, they have also found usage to sensitise titanium dioxide in research related to dye sensitised solar cells. This has prompted investigation into their photophysical properties in order to elucidate their charge transfer mediation behaviour. Recently anthocyanins are becoming of high interest both from a health point of view and because of their potential usage as food colouring agents. However, anthocyanins are very unstable compounds and their stability can be affected by several factors such as temperature, pH, oxygen and light. Here we show the effect of the microwave process (which is a promising method for anthocyanin extraction) on the location and form of anthocyanin in Purple Majesty potato (novel variety of purple potato rich in anthocyanins, the major one of which is petanin), when compared with the raw potato using time-resolved fluorescence techniques, both on extracted anthocyanin and in-situ on potato slices using fluorescence lifetime imaging.Industrial relevanceAnthocyanins can be extracted from plant based food and have potential application in Food Industry because of their anti-microbial and anti-oxidant properties. This group of compounds also present strong (principally) red and purple colourations in plant matter, which make them interesting to use as food colorants by the Food Industry. However, anthocyanins can have different structures (forms) which are dependent of the environmental conditions (mainly pH/complexation/concentration) which can affect their properties.Considering that these compounds can be extracted from plants it is important to easily observe their location in the cell and to elucidate their properties. Because of this requirement we show, in this paper, that it is possible to use time-resolved fluorescence, using microscopy and time-resolved emission spectra, which we believe add novelty to obtain pertinent information from extracted (unpurified) anthocyanin and in-situ within the potato tuber cells. This shows the potential of these techniques in elucidating data in this study and with future application in food industry.
    Innovative Food Science & Emerging Technologies 10/2012; 16:61-68. DOI:10.1016/j.ifset.2012.04.008 · 2.25 Impact Factor
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    ABSTRACT: In order to develop butyric acid photoactive prodrugs, new heteroaromatic conjugates based on oxygen and nitrogen were synthesised and evaluated under irradiation at 254, 300, 350 and 419 nm. Light-triggered uncaging of butyric acid from the corresponding heterocyclic cages was achieved with complete release of the drug in short times. Naphtho[2,3-d]oxazole, naphtho[1,2-d]oxazole, 3-oxo-3H-benzo[f]benzopyran, 2-oxo-2H-benzo[h]benzopyran and 6-oxo-6H-benzopyrano[6,7-d]oxazole conjugates were readily photolysed, and the best results were obtained for naphtho-oxazoles at 254 and 300 nm and for 3-oxo-3H-benzo[f]benzopyran, 2-oxo-2H-benzo[h]benzopyran and 2-methyl-6-oxo-6H-benzopyrano[6,7-d]oxazole at 350 nm. 3-Oxo-3H-benzo[f]benzopyran also afforded good results at 419 nm. The photophysical processes involved were further elucidated by the use of time-resolved fluorescence techniques.
    European Journal of Organic Chemistry 02/2012; 2012(5). DOI:10.1002/ejoc.201101392 · 3.15 Impact Factor
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    ABSTRACT: The efficiency of Förster resonance energy transfer (FRET) can be enhanced in the presence of a metal. Herein, we demonstrate the increased efficiency for a novel model sensor system where FRET is shown to occur between Rhodamine 6G in the bulk sol-gel matrix and Texas Red, which is held a fixed distance away by covalent attachment onto a silane spacer. Silver colloids are formed using light to initiate the reduction of a silver salt, which can be achieved at controlled locations within the film. Both the fluorescence intensity and lifetime maps and analysis indicate that an enhanced FRET efficiency has been achieved in the presence of silver nanoparticles. An increase in efficiency of 1.2-1.5 times is demonstrated depending on the spacer used. The novelty of our approach lies in the method of silver-nanoparticle formation, which allows for the accurate positioning of the silver nanoparticles and hence selective fluorescence enhancement within a biocompatible host material. Our work gives a practical demonstration of metal-enhanced FRET and demonstrates the ability of such systems to be developed for molecular-recognition applications that could find use in lab-on-a-chip technologies.
    ChemPhysChem 02/2012; 13(2):535-41. DOI:10.1002/cphc.201100734 · 3.36 Impact Factor
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    ABSTRACT: Time-resolved stimulated emission spectroscopy was employed to probe the local environment of DASPMI (4-(4-(dimethylamino)styryl)-N-methyl-pyridinium iodide) in binary solvents of different viscosity and in a sol-gel matrix. DASPMI is one of the molecules of choice to probe local environments, and the dependence of its fluorescence emission decay on viscosity has been previously used for this purpose in biological samples, solid matrices as well as in solution. The results presented in this paper show that time-resolved stimulated emission of DASPMI is a suitable means to probe the viscosity of local environments. Having the advantage of a higher time resolution, stimulated emission can provide information that is complementary to that obtained from fluorescence decay measurements, making it feasible to probe systems with lower viscosity.
    International Journal of Spectroscopy 01/2012; 2012. DOI:10.1155/2012/271435
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    ABSTRACT: Simple to manufacture polysaccharide films containing a silver salt, from which silvernanostructures can be produced in situ by light irradiation, were investigated for possible biosensing applications. The silvernanostructures were patterned in situ within a film and cast from a liquid solution of gellan gum, using a compact time-resolved fluorescence microscope. The position and time of irradiation, made using a semiconductor laser in CW mode, were computer controlled. Evidence for their formation was obtained via UV-vis spectroscopy, AFM and SEM-EDAX. On drying the polysaccharide film exhibited a viscosity increase of several orders of magnitude, which was elucidated by changes in the fluorescence lifetime of a probe molecule (DASPMI). To demonstrate the potential for biocompatible sensing applications the influence of the presence of areas of silvernanostructures on the fluorescence of a protein (bovine serum albumin) labelled with fluorescein isothiocyanate was monitored via fluorescence lifetime imaging and the photophysical behaviour found to be consistent with a metal induced increase in the radiative decay rate.
    Soft Matter 12/2011; 8(3):653-659. DOI:10.1039/C1SM06813J · 4.15 Impact Factor
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    ABSTRACT: (6-Methoxy-2-oxo-2H-naphtho[1,2-b]pyran-4-yl)methyl esters of valine or phenylalanine as model bifunctional molecules were synthesised to assess its applicability as a photocleavable protecting group for solution phase organic synthesis and in caging applications at longer wavelengths. The behaviour of the corresponding derivatives towards photolysis was evaluated by irradiation at 350 and 419 nm in a mixture of HEPES buffer and acetonitrile or methanol in a photochemical reactor, followed by HPLC/UV monitoring. Time-resolved fluorescence measurements were used to elucidate the dynamics.
    European Journal of Organic Chemistry 10/2011; 2011(28). DOI:10.1002/ejoc.201100391 · 3.15 Impact Factor
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    João Coelho, Graham Hungerford, N. Sooraj Hussain
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    ABSTRACT: The structural properties of Er3+: silver lead borate glass is assessed by means of SEM, X-ray mapping, EDS and Raman analysis. In order to verify the time dependency of emission spectra, steady-state luminescence spectroscopy (SSLS) and time-resolved emission spectroscopy (TRES) studies have been performed. The stimulated emission cross-sections for the NIR emission transition 4I13/2→4I15/2 (1535nm) at 970nm excitation are reported. The decay times were obtained by fitting one (τm=0.301ms) and two (τm1=0.141ms, τm2=0.368ms) distributions for the NIR transition. Furthermore, by making use of TRES measurements the decay associated spectra were obtained allowing the time dependency for the different emission bands to be elucidated.
    Chemical Physics Letters 08/2011; 512(1):70-75. DOI:10.1016/j.cplett.2011.07.019 · 1.99 Impact Factor
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    ABSTRACT: Erbium oxide (0.5–4 mol%) doped lithium boro tellurite (LBT) glasses have been prepared and the NIR emission band at 1.5 μm characterized. By pumping with LED excitation sources at 495 nm and 970 nm, a broader NIR emission transition (4I13/2 → 4Il5/2) was observed. The Judd–Ofelt intensity parameters (Ω2 = 7.36 × 10−20 cm2; Ω4 = 2.79 × 10−20 cm2 and Ω6 = 2.32 × 10−20 cm2) were derived for the 1 mol% Er3+-doped LBT glass and compared with other tellurite host glasses. The full width at half the maximum (FWHM), stimulated emission cross-sections (σPE) and lifetimes (τmea) for NIR luminescence transitions 4I13/2 → 4I15/2 are reported. For both excitation wavelengths, overall the decay times were found to decrease with increasing erbium content. The present study describes the excitation dependent luminescence properties for this NIR transition.
    Optical Materials 06/2011; 33(8):1167-1173. DOI:10.1016/j.optmat.2011.02.003 · 2.08 Impact Factor

Publication Stats

590 Citations
139.57 Total Impact Points

Institutions

  • 2013
    • Glasgow Caledonian University
      • School of Engineering and Built Environment
      Glasgow, Scotland, United Kingdom
  • 2009
    • ICL
      Londinium, England, United Kingdom
  • 1999–2009
    • University of Minho
      • Departamento de Física (DF)
      Bracara Augusta, Braga, Portugal
  • 2008
    • King's College London
      • Department of Physics
      Londinium, England, United Kingdom