Graham Hungerford

HORIBA, Kioto, Kyōto, Japan

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Publications (76)155.26 Total impact

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    ABSTRACT: Monitoring the interaction of biomolecules is important and the use of energy transfer is a principal technique in elucidating nanoscale interactions. Lanthanide compounds are promising luminescent probes for biological samples as their emission is longer-lived than any native autofluorescence. Polyoxometalates (POMs) are interesting structural motifs to incorporate lanthanides, offering low toxicity and a size pertinent for biological applications. Here we employ iso-structured POMs containing either terbium or europium and assess their interaction with serum albumin by sensitisation of a fluorescent tag on the protein via LRET (luminescence resonance energy transfer) by exciting the lanthanide. Time-resolved measurements showed energy transfer with an efficiency of over 90% for the POM-protein systems. The Tb-POM results were relatively straightforward, while those with the iso-structured Eu-POM were complicated by the effect of protein shielding from the aqueous environment.
    No preview · Article · Dec 2015 · ChemPhysChem
  • Francesca Bot · Monica Anese · M Adília Lemos · Graham Hungerford
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    ABSTRACT: Compounds exhibiting antioxidant activity have received much interest in the food industry because of their potential health benefits. Carotenoids such as lycopene, which in the human diet mainly derives from tomatoes (Solanum lycopersicum), have attracted much attention in this aspect and the study of their extraction, processing and storage procedures is of importance. Optical techniques potentially offer advantageous non-invasive and specific methods to monitor them. To obtain both fluorescence and Raman information to ascertain if ultrasound assisted extraction from tomato pulp has a detrimental effect on lycopene. Use of time-resolved fluorescence spectroscopy to monitor carotenoids in a hexane extract obtained from tomato pulp with application of ultrasound treatment (583 kHz). The resultant spectra were a combination of scattering and fluorescence. Because of their different timescales, decay associated spectra could be used to separate fluorescence and Raman information. This simultaneous acquisition of two complementary techniques was coupled with a very high time-resolution fluorescence lifetime measurement of the lycopene. Spectroscopic data showed the presence of phytofluene and chlorophyll in addition to lycopene in the tomato extract. The time-resolved spectral measurement containing both fluorescence and Raman data, coupled with high resolution time-resolved measurements, where a lifetime of ~5 ps was attributed to lycopene, indicated lycopene appeared unaltered by ultrasound treatment. Detrimental changes were, however, observed in both chlorophyll and phytofluene contributions. Extracted lycopene appeared unaffected by ultrasound treatment, while other constituents (chlorophyll and phytofluene) were degraded. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.
    No preview · Article · Aug 2015 · Phytochemical Analysis
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    ABSTRACT: A new benzocoumarin bearing an amino group is proposed as a photocleavable protecting group for carboxylic acids. The novel heterocycle, 6-amino-4-chloromethyl-2-oxo-2H-naphtho[1,2-b]pyran was used in the preparation of ester conjugates of butyric acid, and of the corresponding mono- and dimethylated or ethylated derivatives. The photolability of the ester conjugates was studied by irradiation at selected wavelengths in methanol/HEPES buffer (80:20) solutions, and the release of butyric acid was followed with HPLC/UV and 1H NMR monitoring. Release of the carboxylic acid was faster for the monoalkylated derivatives (approximately within 20 min), at the longer wavelengths of irradiation (350 and 419 nm). The photophysics of the heterocyclic conjugates was also evaluated by both steady state and time-resolved methods.
    No preview · Article · Aug 2015 · European Journal of Organic Chemistry
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    ABSTRACT: The evaluation of the photorelease of a carboxylic acid drug, using butyric acid as a representative model, was carried out by using 7-amino-4-chloromethyl-2-oxo-2H-naphtho[1,2-b] pyran, an aminobenzocoumarin, and its mono- and di-methylated or ethylated derivatives. This study was intended to improve the release of butyric acid from benzocoumarins by the addition of an amino group to the heterocycle by applying the knowledge of second-generation coumarinylmethyl-based photoremovable protecting groups. Photolysis studies were performed on the resultant ester cages by irradiation in a photochemical reactor at 254, 300, 350 and 419 nm, using methanol/HEPES buffer 80:20 solutions as solvent. The data obtained showed that these new fluorescent aminobenzocoumarins are superior to all the previously tested benzocoumarins with the same or different ring fusions. As well as the photolysis, the photophysics of the compounds were characterised by both steady state and time-resolved methods.
    No preview · Article · Jul 2015 · New Journal of Chemistry
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    ABSTRACT: The study of compounds that exhibit antioxidant activity has recently received much interest in the food industry because of their potential health benefits. Most of these compounds are plant based, such as polyphenolics and carotenoids, and there is a need to monitor them from the field through processing and into the body. Ideally, a monitoring technique should be non-invasive with the potential for remote capabilities. The application of the phenomenon of fluorescence has proved to be well suited, as many plant associated compounds exhibit fluorescence. The photophysical behaviour of fluorescent molecules is also highly dependent on their microenvironment, making them suitable probes to monitor changes in pH, viscosity and polarity, for example. Time-resolved fluorescence techniques have recently come to the fore, as they offer the ability to obtain more information, coupled with the fact that the fluorescence lifetime is an absolute measure, while steady state just provides relative and average information. In this work, we will present illustrative time-resolved measurements, rather than a comprehensive review, to show the potential of time-resolved fluorescence applied to the study of bioactive substances. The aim is to help assess if any changes occur in their form, going from extraction via storage and cooking to the interaction with serum albumin, a principal blood transport protein.
    Preview · Article · Jun 2015
  • 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.
    No preview · Article · Apr 2015 · Food Chemistry
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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.
    Full-text · Article · Oct 2014 · Journal of Photochemistry and Photobiology A Chemistry
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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.
    No preview · Article · Jan 2014 · Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy
  • João Coelho · Graham Hungerford · N. Sooraj Hussain
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    ABSTRACT: The paper reports the visible-NIR luminescence and time-resolved emission spectral profiles of Nd3+, and Er3+ doped silver zinc borate glasses. Steady state luminescence (SSL) and time-resolved emission spectroscopy (TRES) were used to evaluate how the randomness of the network can influence the emission from rare earth ions in the visible region. As expected the composition of the glasses strongly influences the emission bands of the dopant ions. The lack of homogeneity in the glass network results in distorted and broad luminescence spectra. Moreover, time-resolved techniques allowed the visualization of the time dependence of the spectra. The luminescence was also characterized using steady state techniques and the strongest NIR emission peaks were 4F3/2 → 4I11/2 for Nd 3+ and 4I13/2 → 4I15/2 for Er 3+ ions respectively.
    No preview · Article · Jan 2014 · Solid State Phenomena
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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.
    No preview · Article · Dec 2013 · European Journal of Organic Chemistry
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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.
    No preview · Article · Oct 2013 · Photochemical and Photobiological Sciences
  • 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.
    No preview · Article · Jul 2013 · Photochemistry and Photobiology
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    Dataset: Chapter 8

    Full-text · Dataset · Apr 2013
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    Dataset: Chapter 8

    Full-text · Dataset · Apr 2013
  • 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.
    No preview · Article · Jan 2013 · Photochemistry and Photobiology
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    Full-text · Dataset · Nov 2012
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    Pedro Damas · João Coelho · Graham Hungerford · N. Sooraj Hussain
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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.
    Full-text · Article · Nov 2012 · Materials Research Bulletin
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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.
    Preview · Article · Oct 2012 · Photochemical and Photobiological Sciences
  • 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.
    No preview · Article · Oct 2012 · Innovative Food Science & Emerging Technologies
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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.
    No preview · Article · Feb 2012 · European Journal of Organic Chemistry

Publication Stats

830 Citations
155.26 Total Impact Points

Institutions

  • 2010
    • HORIBA
      Kioto, Kyōto, Japan
  • 2009
    • Imperial College London
      • Department of Chemistry
      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