Дисертації з теми "Photochemical studies"
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1
Baker, James R. "Photochemical studies towards stemoamide." Thesis, University of Bristol, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414177.
2
Brookman, Jennifer. "Photochemical studies on selected biomolecules." Thesis, University of the West of Scotland, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398322.
3
Buckland, S. J. "Photochemical studies in organophosphorus chemistry." Thesis, City University London, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.482525.
4
Marsh, R. R. "Studies of some photochemical pericyclic reactions." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375284.
5
Cantrell, Ann. "Photochemical studies of organic UVA sunscreens." Thesis, Keele University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323702.
6
Gulácsy, Christina Elizabeth. "Photochemical and spectroscopic studies of ketoaziridines." Thesis, University of Bath, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.698993.
Анотація:
While alcohols have successfully undergone kinetic resolutions, amines pose a challenge due to their nucleophilic nature. Aziridines were identified as potential substrates as a result of their synthetic utility and reduced nucleophilicity. Using a helical aminopyridine catalyst, the kinetic resolutions of ketoaziridines were explored. Initial attempts revealed anomalous kinetic behaviour [slow conversion and non-first order]. Non-buffered noncatalytic control reactions demonstrated unexpected reaction dynamics, as gauged by HPLC and 1H NMR. Stopped-flow spectroscopy revealed photochemical sensitivity of the aziridine. As a result of this new information, the project evolved into a study of the photochemical behaviour of ketoaziridines and their spectroscopic properties. UV-vis absorbance and fluorescence spectroscopy were used to probe the photochemical reactivity of ketoaziridines. These studies suggested a two-step mechanism where an azomethine ylide formed a reactive intermediate, ultimately to form 2,5-diphenyloxazole. Kinetic analysis revealed the mechanism was autocatalytic with respect to oxazole formation. TD-DFT calculations suggested the mechanism proceeded via a diradical species upon irradiation. This mechanistic route was studied by investigating the presence of a magnetic field effect on the kinetics of absorption and emission changes, in collaboration with the Manchester Institute of Biotechnology. Further studies demonstrated a radical species, derived from the irradiation of aziridine, may be used as a photoinitiator in the polymerization of methyl methacrylate. This work also involved development of a synthetic platform to diphenyloxazoles, where functionality may be installed in the initial steps. Use of this strategy allowed for the synthesis of a natural product, texaline.
7
Vaidyalingam, Anand S. "Photochemical studies of zeolite-based systems /." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486401895208909.
8
Georgopoulos, Panagiotis Gerasimou Seinfeld John H. Seinfeld John H. "Mathematical studies of photochemical air pollution /." Diss., Pasadena, Calif. : California Institute of Technology, 1986. http://resolver.caltech.edu/CaltechETD:etd-02012007-092322.
9
Grosser, E. "Photochemical oxidant air pollution : peroxyacetyl nitrate (PAN) as an indicator of photochemical activity." Master's thesis, University of Cape Town, 1990. http://hdl.handle.net/11427/8282.
Анотація:
Bibliography: leaves 75-84.Photochemical smog is formed by the interaction of sunlight with nitrogen oxides and hydrocarbons. These precursors are principally emitted by anthropogenic sources. As the major component of the photochemical oxidants is ozone, it is used as the indicator of photochemical smog and air quality standards today are therefore based on ozone. Another important photochemical oxidant is peroxyacetyl nitrate (PAN). Many authors believe that PAN is a better indicator of photochemical activity than ozone, because PAN has, unlike ozone, no large natural sources. Thus, the occurrence of high PAN concentrations is unequivocally related to anthropogenic pollution. The objectives of this work are to summarise the current research on the formation of photochemical smog with emphasis on PAN and to investigate the photochemical smog situation in South Africa using PAN as an indicator.
10
Vanover, Eric. "Photochemical Oxidation Studies of Porphyrin Ruthenium Complexes." TopSCHOLAR®, 2012. http://digitalcommons.wku.edu/theses/1201.
Анотація:
In nature, transition metal containing enzymes display many biologically important, attractive and efficient catalytic oxidation reactions. Many transition metal catalysts have been designed to mimic the predominant oxidation catalysts in nature, namely, the cytochrome P450 enzymes. Ruthenium porphyrin complexes have been the center of this research and have successfully been utilized, as catalysts, in major oxidation reactions, such as the hydroxylation of alkanes. The present work focuses on photocatalytic studies of aerobic oxidation reactions with well characterized ruthenium porphyrin complexes.
The photocatalytic studies of aerobic oxidation reactions of hydrocarbons The photocatalytic studies of aerobic oxidation reactions of hydrocarbons catalyzed by a bis-porphyrin-ruthenium(IV) μ-oxo dimer using atmospheric oxygen as the oxygen source in the absence of co-reductants were investigated. The ruthenium(IV) μ-oxo bisporphyrin (3a-d) was found to catalyze aerobic oxidation of a variety of organic substrates efficiently. By comparison, 3d was found to be a more efficient photocatalyst than the well-known 3a under identical conditions. A KIE at 298K was found to be larger than those observed in autoxidation processes, suggesting a nonradical mechanism that involved the intermediacy of ruthenium(V)-oxo species as postulated. The reactivity order in the series of ruthenium(IV) μ-oxo bisporphyrin complexes follows TPFPP>4- CF3TPP>TPP, and is consistent with expectations based on the electrophilic nature of the ruthenium(IV) μ-oxo bisporphyrin species.
The trans-dioxoruthenium(VI) porphyrins have been among the best characterized metal-oxo intermediates and their involvement as the active oxidant in the hydrocarbon oxidation have been extensively studied. In addition to the well-known chemical methods, we developed a novel approach for generation of trans-dioxoruthenium( VI) porphyrins with visible light by extension of the known photoinduced ligand cleavage reactions. A series of trans-dioxoruthenium(VI) porphyrin complexes (6a-d) were photochemically synthesized and spectroscopically characterized by UV-vis, and 1H-NMR.
11
Wang, Jian. "Photochemical and photobiological studies of benzydamine hydrochloride." Thesis, The University of Sydney, 1995. https://hdl.handle.net/2123/26813.
Анотація:
Benzydamine hydrochloride [l-benzyl-3-(3-dimethylaminopropoxy)-1Hindazole hydrochloride] is a unique non-steroidal anti-inflammatory drug with local anaesthetic properties. Its photochemistry, photophysics, and photosensitization characteristics have been studied intensively to determine the basis of the adverse photosensitivity reactions associated with the use of its different formulations.
Benzydamine absorbs strongly in the UVB region at 308 nm. The excited state properties of benzydamine were established by fluorescence and phosphorescence measurement. In water, benzydamine gives a strong fluorescence at 345 nm with a quantum yield of 0.17 at pH 7 and 0.10 at pH 11. It also shows a strong phosphorescence emission at 422, 457, 490 nm implying a relatively high population of the triplet state when irradiated.
The photodegradation of benzydamine in acetonitrile, methanol and water solutions, was examined using reverse phase HPLC. The decomposition occurs readily in acetonitrile solution under a nitrogen atmosphere with the formation of 3-dimethylaminopropoxy-lH-indazole as the main primary product. Under aerobic conditions, benzaldehyde is an additional product presumed to result from oxidation of the benzyl radical dissociated from benzydamine. The photodecomposition of benzydamine in methanol and water under aerobic conditions is slower than that in acetonitrile with the formation of the above products plus 1-benzy1-3-(3—methylaminopropoxy)-lH-indazole from N—demethylation and 3-benzyl-lH-indazole as primary main products. The identification of the products was based on data from UV, Cl and EI Mass spectra, and H and C NMR spectra.
The photostability of benzydamine in three commercially available formulations (Difflam cream, gel and mouthwash) has been tested. Photodegradation occurs upon exposure to direct sunlight or artificial UV radiation. The principal reaction in the formulations is the photodegradation of benzydamine, yielding the same photoproducts as found in benzydamine water solution under the UV arc source.
The ability of benzydamine to act as a photosensitizer was examined in terms of its capacity to initiate free radical reactions and generate singlet oxygen in aqueous solution and micellar solutions by measuring the oxygen uptake rate of benzydamine in the presence of singlet oxygen acceptors. The capacity to act as a generator of singlet oxygen species is dependent on pH and the cation form is more efficient than the neutral form. The ability of benzydamine to act as a Type I (fiee radical) photosensitizer on irradiation was tested by the initiation of photopolymerization of acrylamide. The neutral form of benzydamine is more involved in free radical generation than the cationic form.
The involvement of an electron transfer mechanism in benzydamine photosensitization was tested under aerobic and anaerobic conditions by several methods (i) reduction of nitro blue tetrazolium (ii) reduction of cytochrome c (iii) reduction of Cu (11) and formation of copper (1) complex with BCDS in phosphate buffer solutions (iv) the oxidation of tetramethylphenylenediamine to generate TMPD cation radical, in acetonitrile, methanol and water solutions. Benzydamine was active in all these systems, showing the ability to act as both an electron donor and acceptor when irradiated.
Additionally, benzydamine photosensitized the peroxidation of linoleic acid, as monitored by the spectrophotometric detection of dienic hydroperoxide formation. While this photodynamic action was found to be strictly oxygen dependent, the reaction was suppressed completely when the free radical scavengers, reduced glutathione or butylated hydroxyanisole was added before irradiation, but was only partially inhibited by the singlet oxygen quenchers, sodium azide or 1,4-diazabicyclo[2,2,2]octane, suggesting that the free radical pathway is predominant.
Studies have also been performed to elucidate the phototoxic potential of benzydamine and its photoproducts towards biological membranes using human erythrocytes as a model system both under oxygen and nitrogen atmosphere. At a much higher concentration employed compared to that used in the lipid peroxidation experiment, benzydamine photosensitized hemolysis of human erythrocytes. A free radical mechanism was suggested since GSH inhibited the hemolysis under anaerobic conditions. Under aerobic conditions, the hemolysis was inhibited totally by GSH and partially by NaNs, but not by superoxide dismutase (SOD). The hemolysis was completely suppressed by copper(II) with bathocuproinedisulphonic acid (Cu/BCDS) which is a complex with SOD-like activity. The photohemolysis was enhanced when D20 replaced H20 in the buffer solution suggesting singlet oxygen involvement. Preirradiated benzydamine induced hemolysis in the dark indicating that one or more of the photoproducts is toxic.
In summary, benzydamine has been shown to be relatively active in a photochemical sense with free radical mechanisms playing a major role. The results imply that there is a definite risk of phototoxicity when long time sunlight exposure is combined with topical application of a benzydamine formulation.
12
Sutton, Paul David. "Studies in infrared multiple photon excitations." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291598.
13
Lejeune, Guillaume. "Photochemical studies toward the synthesis of natural products." Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/314573.
Анотація:
Els derivats de ciclobutà son uns compostos remarcables no nomes com productes naturals, com el en camp de les feromones on moltes estructures contenen un ciclobutà, però també alguns ciclobutans juguen un paper molt important en l’àrea farmacèutica, com en el cas de molts anàlegs de nucleòsid que tenen una gran activitat contra la replicació d’alguns virus (Herpès o VIH).
La fotoquímica en síntesi orgànica ha proporcionat un mètode extremadament potent per la conversió de substrats senzills a productes més complexos. Diverses dificultats van associar amb l'actuació de les fotoreaccions en l'escala gran ha estat percebuda per ser un problema seriós per ser solucionat abans de la seva aplicació rutinària.
Aquesta tesi ha estat enfocada en l'estudi del potencial de diferent 2(5H)-furanones substituïdes com precursors de pirà a través de la formació de compostos bicíclic que podrien donar accés a una família d'específic tetrahidropirans trisubstituïts Hem desenvolupat una ruta fotoquímica per accedir a THP estereocontrollats des de una furanone en dues passos de síntesi.
També hem investigat el potencial de diferent maleimides substituïdes com a precursor de derivats d'aminoàcid amb conformació restringida i a azepà gracies a la formació de compostos tricíclic per una reacció de fotoquímica. Hem sintetitzat diferents precursors d’anàleg d'aminoàcid. No vam acomplir la síntesi de derivats d’azepà, però els derivats d’amino àcid sintetitzat des dels derivats de ciclobutè i de ciclobutà, poden tenir una activitat biològica en contra algunes tumor d’esser humà.
Finalment, les femelles del poll blanc, és una plaga mundial, principalment trobat en les zones tropicals i subtropical, que causa un debilitament general de l'arbre i deterioració severa de la fruita. L'ús de la seva feromona sexual per interferir en la comunicació entre el mascle i la femella controlarà la població en l'àrea infectada. Per aconseguir aquest control, és de primera importància de ser capaç de sintetitzar el compost actiu de la feromona sexual. Aquesta feromona presenta les característiques estructurals comunes a (+)-grandisol, molècula sintetitzada en el nostre grup de recerca, com per exemple dos de les cadenes acícliques van enllaçar al ciclobutà la configuració del centre estereogenic. Aquestes semblances ens van suggerir la possibilitat d'adaptar la ruta sintètica anteriorment dissenyat per (+)-grandisol a la feromona sexual d’Aspidiotus nerii. La modificació principal de la síntesi anterior del grandisol serà la introducció del cadena terpènica en l’anell de ciclobutà. Hem sintetitzat dos intermedis avançats cap a la síntesi de la feromona sexual.Cyclobutane derivatives are remarkable compounds not only as attractive natural products, as in the pheromone field where several structures bearing a cyclobutane ring are known, but also some cyclobutanes play a crucial role in the pharmaceutical field, as it is the case of several nucleoside analogues that present a strong activity against the replication of some viruses (eg Herpes or HIV). Synthetic organic photochemistry has provided an extremely powerful method for the conversion of simple substrates into more complex products. Several difficulties associated with the performance of preparative photoreactions on large scale have been perceived to be a serious problem to be solved before their routine application. The present thesis has been focused on the study of the potential of different substituted 2(5H)-furanones as precursors of pyran through the formation of bicyclic compounds which could give access to a family of specific trisubsituted tetrahydropyrans. We have developed a photochemical route to access stereocontrolled 2,3,5-trisubstituted THP’s from furanone in a two step synthesis. Also we have investigated the potential of different substituted maleimides as precursor of conformationally restricted amino acid derivatives and azepane throught the formation of tricyclic compounds by photochemistry. We have synthesized different precursors of amino acid analogues from substituted maleimide, we did not accomplished the synthesis of azepane derivatives, but the amino acid derivatives, synthesized from tricyclic cyclobutene and cyclobutane derivatives, can have a biological activity against panel of human tumour cell lines. Finally, Oleander scales’ females, is a cosmopolitan pest, mainly found in tropical and subtropical areas, that causes a general weakening of the tree, dicoloration of leaves, and severe deterioration of the fruit. The use of its sexual pheromone to interfere the communication between the male and female will control the population in the infected area. To achieve this control, it is of first importance to be able to synthesize the sexual pheromone active compound. This pheromone presents structural characteristics common to (+)-grandisol, synthesized in our research group, such as two of the acyclic chains linked to the cyclobutane and the configuration of the stereogenic centres. These similarities suggested us the possibility of adapting the synthetic pathway previously designed for (+)-grandisol to the sexual pheromone of Aspidiotus nerii. The principal modification of the former synthesis of grandisol will be the introduction of the terpenic chain in the cyclobutane ring. We have synthesized two advanced intermediates toward the synthesis of the sexual pheromone.
14
Soomro, Shahid A. "Design, synthesis and photochemical studies of stilbenoid dendrimers." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975958569.
15
Deng, Lingquan. "Photochemical Surface Functionalization : Synthesis, Nanochemistry and Glycobiological Studies." Doctoral thesis, KTH, Organisk kemi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-41973.
Анотація:
This thesis mainly deals with the development of photochemical approaches to immobilize carbohydrates on surfaces for glycobiological studies. These approaches have been incorporated into a number of state-of-the-art nanobio-platforms, including carbohydrate microarrays, surface plasmon resonance (SPR), quartz crystal microbalance (QCM), atomic force microscopy (AFM), and glyconanomaterials. All the surfaces have displayed good binding capabilities and selectivities after functionalization with carbohydrates, and a range of important data have been obtained concerning surface characteristics and carbohydrate-protein interactions, based on the platforms established. Besides, a variety of non-carbohydrate and carbohydrate-based molecules have been synthesized, during which process the mutarotation of 1-glycosyl thiols and the stereocontrol in 1-S-glycosylation reactions have been thoroughly studied.QC 20111004
16
Foley, Sarah. "Photochemical and photobiological studies of photosensitisers and phytochemicals." Thesis, Keele University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389604.
17
Monteiro, Diana Canelhas Freitas. "New photochemical tools for time-resolved structural studies." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/10637/.
Анотація:
The current bottleneck preventing the wider application of time-resolved structural techniques is the ability to quickly and accurately trigger protein function across an ensemble of molecules either in solution or in crystallo. The fastest and most accurate approach to achieve protein function synchronisation is by using protein photo caging approaches. During this project, a new class of protein photo cleavable crosslinking reagents was designed and synthesised. This novel crosslinking scaffold carries two α-bromoacetate groups, which were shown to react with protein surface cysteines efficiently and cleanly. The crosslinker is released from the protein by UV irradiation, by photolysis of ortho-nitrobenzyl groups, cleaving the surface “staple” from the cysteine residues, leaving only a small methyl carboxylate group on the cysteine side chains. The cysteine “anchors” can be easily introduced by site-directed mutagenesis. This new set of reagents were developed as a new approach to protein photocaging which decouples the protein activation step from the protein chemistry being investigated. The photocage does not target residues directly involved in function but rather aims to restrict the conformational space explored by the protein, limiting essential dynamics and preventing function. This approach opens avenues for more widely applicable protein triggering methodology, potentially allowing for time resolved experiments to be performed in wider variety of protein classes than those investigated to date. To test these reagents, aspartate α-decarboxylase (ADC) was chosen as a model system. This enzyme catalyses the conversion of aspartate to β-alanine, a precursor of coenzyme A. ADC is expressed as an inactive zymogen which cleaves post-translationally, yielding a catalytic pyruvoyl group. The cleavage requires an additional activating partner, PanZ. Protein homogeneity is an essential requirement for a successful time resolved experiment and, therefore, the mechanism by which PanZ activates ADC was investigated. The crystal structure of the ADC-PanZ protein-protein complex was determined at high-resolution, as well as those of several ADC mutants. With the aid of complementary techniques (SAXS, ITC, MS, NMR, in cellulo studies) the molecular mechanism by which this protein-protein interaction promotes ADC activation was elucidated. The protein complex formation causes the formation of a strained, activation-competent conformation of the ADC peptide backbone at the site of cleavage. Furthermore, a novel negative feedback mechanism for pantothenate and CoA biosynthesis regulation in bacteria was discovered and proposed.
18
Sexton, Catherine Jane. "Photochemical studies on a series of pentamethylcyclopentadienyl rhodium complexes." Thesis, University of York, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489204.
Анотація:
This thesis describes the study of a range of rhodium cyclopentadienyl alkene complexes by NMR spectroscopic techniques. Photochemical reactions of these complexes at low temperatures with a range of substituents were investigated, with the reaction products similarly characterised using NMR.
19
Pathak, P. "Photophysical and photochemical studies of cyanobiphenyl based liquid crystals." Thesis, University of Salford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360437.
20
Baldwin, P. J. "Some studies of thermal and photochemical gas phase reactions." Thesis, University of Reading, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.353460.
21
Magero, Denis. "Electrochemical and photochemical studies of some remarkable ruthenium complexes." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAV071/document.
Анотація:
Cette thèse fait partie d’un projet franco-keyan dénommé ELEPHOX (ELEctrochemical and PHOto Properties of Some Remarkable Ruthenium and Iron CompleXes). En particulier, notre focus est la continuation du travail de C. Muhavini Wawire, Damien Jouvenot, Fréd erique Loiseau, Pablo Baudin, Sébastien Liatard, Lydia Njenga, Geoffrey Kamau, et Mark E. Casida, “Density-Functional Study of Lumininescence in Polypyridine Ruthenium Complexes,” J. Photochem. and Photobiol. A 276, 8 (2014). Cet article a proposé une indice orbitalaire de temps de luminescence pour les complexesde ruthénium. Cependant cet article n’était limité qu’à quelques mnolecules. Afin d’avoir une théorie plus fiable et donc potentiellement plus utile, il faudra tester l’indice de luminescence sur beaucoup plus de molécules. Ayant établi le protocol, il était “évident” mais toujours un défi de le tester sur encore une centaine de molécules pour démonter ou infirmer l’indice proposée. Pour ce faire, j’ai examainé les 98 pages de la Table I de A. Juris, V. Balzani, F. Bargelleti, S. Campagna, P. Belser, et A.V. Zelewsky, “Ru(II) polypyridine complexes: Photophysics, photochemistry, electrochemistry, and chemiluminescence,” Chem. Rev. 84, 85 (1988) et j’ai extrait un nombre important de données susceptibles à comparaison avec les résultats des calculs de la théorie de la fonctionelle de la densité (DFT) et la DFT dépendante du temps (TD-DFT). Comme les résultats étaient suffisament encourageant, le modèle DFT était examiné de plus près avec la méthode d’une théorie de champs de ligands (LFT) à la base de la densité des états partielle (PDOS). Ainsi j’ai pu tester l’indice de luminescence proposée précédement par laméthode PDOS-LFT et j’ai trouvé des difficultés avec l’indice initialement proposée. Par contre, nous avons pu proposer une nouvelle indice de luminescence qui, à quelques exceptions près, a une corrélation linéaire avec une barrière énergétique moyenne pour l’état triplet excité dérivée à partir des données experimentales. À l’avenir nous pouvons proposer une investigation plus directe de la barrière sur la surface triplet excité pour remplacer la valeur approximative déduite de l’expérience. Puis nous voulons voir sinotre indice de luminescence s’appliquent aux cas des complexes d’iridiumThis thesis is part of the Franco-Kenyan project ELEPHOX (ELEctrochemicaland PHOto Properties of Some Remarkable Ruthenium and Iron CompleXes)project. In particular, it focused on the continuation of the work ofC. Muhavini Wawire, Damien Jouvenot, Fréd erique Loiseau, Pablo Baudin,Sébastien Liatard, Lydia Njenga, Geoffrey Kamau, and Mark E. Casida,“Density-Functional Study of Lumininescence in Polypyridine RutheniumComplexes,” J. Photochem. and Photobiol. A 276, 8 (2014). That paperproposed a luminescence index for estimating whether a ruthenium complexwill luminesce or not. However that paper only tested the theory ona few molecules. In order for the theory to have a significant impact, itmust be tested on many more molecules. Now that the protocol has beenworked out, it was a straightforward but still quite challenging matter todo another 100 or so molecules to prove or disprove the theory. In order todo so, I went through the 98 pages of Table I of A. Juris, V. Balzani, F.Bargelleti, S. Campagna, P. Belser, and A.V. Zelewsky, “Ru(II) polypyridinecomplexes: Photophysics, photochemistry, electrochemistry, and chemiluminescence,”Chem. Rev. 84, 85 (1988) and extracted data suitable for comparingagainst density-functional theory (DFT) and time-dependent (TD-)DFT.Since the results were sufficiently encouraging, the DFT model was examinedin the light of partial density of states ligand field theory (PDOS-LFT) andthe previously proposed luminescence indices were tested. In fact, the originallyproposed indices were not found to be very reliable but we were able topropose a new luminescence index based upon much more data and in analogywith frontier-molecular orbital ideas. Except for a few compounds, this index provides a luminescence index with a good linear correlation with anexperimentally-derived average excited-state activation energy barrier. Futurework should be aimed at both explicit theoretical calculations of thisbarrier for ruthenium complexes and extension of the luminescence indexidea to iridium complexes
22
Mitchell, Ellen Margaret. "Photochemical Studies of Dinuclear Methylene-Bridged Transition- Metal Complexes /." The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487930304688889.
23
Archer, Marsi E. "Photochemical and ligand reactivity studies of dinuclear organoiron complexes /." The Ohio State University, 1998. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487951214939753.
24
Perry, M. C. "Studies of factors influencing the photochemical cleavage of water." Thesis, Aston University, 1986. http://publications.aston.ac.uk/14243/.
25
Gadde, Suresh :. D'Souza Francis. "Supramolecular porphyrin-fullerene conjugates design, synthesis, electrochemical and photochemical studies /." Diss., Click here for available full-text of this dissertation, 2006. http://library.wichita.edu/digitallibrary/etd/2006/d008.pdf.
Анотація:
Thesis (Ph.D.)--Wichita State University, Dept. of Chemistry."May 2006." Title from PDF title page (viewed on September 29, 2006). Thesis adviser: Francis D'Souza. Includes bibliographic references (leaves 189-199).
26
Chen, Xing. "Theoretical Studies on Magnetic and Photochemical Properties of Organic Molecules." Doctoral thesis, KTH, Teoretisk kemi och biologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-52818.
Анотація:
The present thesis is concerned with the theoretical studies on magnetic and photochemical properties of organic molecules. The ab initio and first principles theories were employed to investigate the vibrational effects on the isotropic hyperfine coupling constant (HFCC) known as the critical parameter in electron paramagnetic resonance spectrum, the theoretical simulations of the vibronically resolved molecular spectra, the photo-induced reaction mechanism of α-santonin and the spin-forbidden reaction of triplet-state dioxygen with cofactor-free enzyme. The theoretical predictions shed light on the interpretation of experimental observations, the understanding of reaction mechanism, and importantly the guideline and perspective in respect of the popularized applications. We focused on the vibrational corrections to the isotropic HFCCs of hydrogen and carbon atoms in organic radicals. The calculations indicate that the vibrational contributions induce or enhance the effect of spin polarization. A set of rules were stated to guide experimentalist and theoretician in identification of the contributions from the molecular vibrations to HFCCs. And the coupling of spin density with vibrational modes in the backbone is significant and provides the insight into the spin density transfer mechanism in organic π radicals. The spectral characters of the intermediates in solid-state photoarrangement of α-santonin were investigated in order to well understand the underlying experimental spectra. The molecular spectra simulated with Franck-Condon principle show that the positions of the absorption and emission bands of photosantonic acid well match with the experimental observations and the absorption spectrum has a vibrationally resolved character. α-Santonin is the first found organic molecule that has the photoreaction activities. The photorearrangement mechanism is theoretically predicted that the low-lying excited state 1(nπ*) undergoing an intersystem crossing process decays to 3(ππ*) state in the Franck-Condon region. A pathway which is favored in the solid-state reaction requires less space and dynamic advantage on the excited-state potential energy surface (PES). And the other pathway is predominant in the weak polar solvent due to the thermodynamical and dynamical preferences. Lumisantonin is a critical intermediate derived from α-santonin photoreaction. The 3(ππ*) state plays a key role in lumisantonin photolysis. The photolytic pathway is in advantage of dynamics and thermodynamics on the triplet-state PES. In contrast, the other reaction pathway is facile for pyrolysis ascribed to a stable intermediate formed on the ground-state PES. The mechanism of the oxidation reaction involving cofactor-free enzyme and triplet-state dioxygen were studied. The theoretical calculations show that the charge-transfer mechanism is not a sole way to make a spin-forbidden oxidation allowed. It is more likely to take place in the reactant consisting of a non-conjugated substrate. The other mechanism involving the surface hopping between the triplet- and singlet-state PESs via a minimum energy crossing point (MECP) without a significant charge migration. The electronic state of MECP exhibits a mixed characteristic of the singlet and triplet states. The enhanced conjugation of the substrate slows down the spin-flip rate, and this step can in fact control the rate of the reaction that a dioxygen attaches to a substrate.QC 20111220
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Norberg, Oscar. "Photochemical Ligation Techniques for Carbohydrate Biosensors and Protein Interaction Studies." Doctoral thesis, KTH, Organisk kemi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-90956.
Анотація:
This thesis concerns the development of surface ligation techniques for the preparation of carbohydrate biosensors. Several methodologies were developed based on efficient photochemical insertion reactions which quickly functionalize polymeric materials, with either carbohydrates or functional groups such as alkynes or alkenes. The alkyne/alkene surfaces were then treated with carbohydrate azides or thiols and reacted under chemoselective Cu-catalyzed azide-alkyne cycloaddition (CuAAC) or photo-radical thiol-ene/yne click chemistry, thus creating a range of carbohydrate biosensor surfaces under ambient conditions. The methodologies were evaluated by quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) flow through instrumentations with recurring injections of a range of lectins, allowing for real-time analysis of the surface interactions. The developed methods were proven robust and versatile, and the generated carbohydrate biosensors showed high specificities and good capacities for lectin binding. The methods were then used to investigate how varying the glycan linker length and/or a sulfur-linkage affect the subsequent protein binding. The survey was further explored by investigating the impact of sulfur in glycosidic linkages on protein binding, through competition assays with various O/S-linked disaccharides in solution interactions with lectins.QC 20120309
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Chretien, Michelle N. "Photochemical, photophysical, and photobiological studies of zeolite guest-host complexes." Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/29205.
Анотація:
This thesis focuses on the photochemistry and photophysics of a variety of zeolite complexes, from catalysts to sunscreens. The first chapter describes the preparation and photophysical and photochemical characterization of two new photocatalytic materials. The catalysts are based on a multi-component zeolite, host-guest complex and the interaction between components was probed using time-resolved spectroscopic techniques. The catalytic efficiency, in terms of the ability to photodegrade biological contaminants, was also investigated. These studies were performed with the aim of developing efficient catalysts for wastewater remediation which can be used with solar (visible) radiation.
In subsequent chapters, zeolite materials have been used as matrices for the stabilization of various transient or reactive species. In the case of ZSM-5-type zeolite, the dibenzotropylium cation was rendered indefinitely persistent allowing the examination of its excited-state behaviour. The geometric restriction within the cavities also permits the observation of electron transfer chemistry in the absence of a nucleophilic addition reaction with the electron donor. In a second example, ketoprofen (a non-steroidal anti-inflammatory drug) was found to undergo intrazeolite photodecarboxylation to generate a benzylic carbanion. The lifetime of the zeolite-encapsulated carbanion was found to be fifty times longer than in solution. The enhanced lifetime allows intermolecular nucleophilic addition chemistry to compete with protonation, effectively, a photo-initiated Grignard-type reaction is observed.
In Chapter 6, fluorescence is used as tool to probe both intra- and interzeolite interactions. In the first part, a zeolite-entrapped radical probe was prepared by ship-in-a-bottle synthesis for the investigation of radical percolation in the zeolite matrix. The probe is a molecular dyad containing a persistent free-radical and a quenched fluorophore. When the probe radical couples with a carbon-centered radical, the probe fluorescence is restored and in this way free-radical species in heterogeneous systems can be conveniently examined. In the second section, zeolite particles were irreversibly labeled with a biologically-compatible fluorophore (also by ship-in-a-bottle synthesis).
The last part of this thesis deals with a project relating to supramolecular sunscreens. (Abstract shortened by UMI.)
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Lary, David John. "Photochemical studies with a three-dimensional model of the atmosphere." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386150.
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Wang, T. W. "Studies of photochemical internalisation : mechanisms and strategies in cancer therapeutics." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/19572/.
Анотація:
Photochemical internalisation (PCI) is a technique which enhances targeted drug delivery using light in combination with a photosensitiser. It is a modification of photodynamic therapy (PDT) which involves sub-lethal photodynamic treatment to modify the intracellular distribution of co-administered drugs and other agents which are sequestered in lyso/endosomes. In this study, PDT and PCI using a sulfonated chlorin, AmphinexTM (TPCS2a), in combination with two anti-cancer drugs, saporin or bleomycin, have been investigated both in vitro and in vivo. In vitro experiments initially examined the cell uptake, photostability and cellular localisation of Amphinex using A431 human epidermoid carcinoma cells and HN5 human head and neck squamous cells. The cell killing effect after PDT and PCI in the presence of saporin and bleomycin were assessed. The bioavailability and therapeutic efficacy were also compared with another two PCI photosensitisers, TPPS2a and AlPcS2a. The results indicate that PCI is able to induce the relocalisation of bleomycin and saporin inside cells and thereby enhance cell death. A new porphyrin-peptide bioconjugate of a cell penetrating peptide (CPP) and tetraphenylporphine was investigated for PDT and PCI. It was found that CPP peptide conjugation renders efficient cellular delivery of the tetraphenylporphine for use as a PDT and PCI sensitiser. The pharmacokinetics of Amphinex in normal and tumour-bearing rats was studied using quantitative fluorescence microscopy and chemical extraction. In vivo Amphinex PCI effects and the comparison with PDT were investigated in normal rat liver, colon and a syngeneic rat fibrosarcoma tumour models. Amphinex PCI showed a significant enhancement in inducing damage to normal tissues and tumour. The involvement of apoptosis was also established using the TUNEL assay. This thesis has demonstrated that Amphinex has favourable properties for PDT and PCI. The consistent results from both in vitro and in vivo experiments indicate that Amphinex has the potential for further clinical utilization.
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Ogunsipe, Abimbola Olukayode. "Photophysical and photochemical studies of non-transition metal phthalocyanine derivatives." Thesis, Rhodes University, 2005. http://hdl.handle.net/10962/d1007721.
Анотація:
A detailed photophysicochemical study of some non-transition metal (AI, Zn, Si, Ge, and Sn) metallophthalocyanine (MPc) derivatives is presented. The effects of substituents, central metal ions and solvents on the photophysical and photochemical properties are investigated and rationalized accordingly. The presence of peripheral substituents on the macrocycle enhances the yield of the triplet state. Near infra-red absorptions of the solvents reveal that solvents which absorb around 1100 nm and around 1270 nm, quench the triplet state of the MPc derivative and singlet oxygen, respectively. Although water has a high singlet oxygen quenching effect, the singlet oxygen quantum yield (Φ∆) value for sulphonated zinc phthalocyanine in water is still reasonably high at 0.48, which may provide an explanation for the efficient photosensitization by this molecule in photodynamic studies. The lowering of Φ∆ following protonation of the MPc macrocycle is attributed to the lowering of triplet energy to the level where energy transfer to ground state oxygen is no longer favourable. MPc inclusion complexes with cyclodextrins showed larger Φ∆ values when compared to the complexes before inclusion. Job's plots show that 2:1 and 4:1 (CD:MPc) complexes may be formed. Fluorescence quenching by electron donors and acceptors were analysed by StemVolmer relationship and the results used in determining fluorescence lifetimes of the complexes. Qualitative and quantitative interpretations of the interaction of sulphonated MPcs with bovine serum albumin (BSA) are provided in this thesis. 1:1 adducts were formed with BSA, but the binding feasibilities varied markedly. Spectral, photophysical and photochemical properties of the complexes are altered in the presence of BSA.
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Lee, Hyunjung. "DESIGN AND PHOTOCHEMICAL STUDIES OF ZEOLITE-BASED ARTIFICIAL PHOTOSYNTHETIC SYSTEMS." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1039117753.
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Gudimetla, Vittal Babu. "Conjugated Low Coordinate Organophosphorus Materials: Synthesis, Characterization and Photochemical Studies." Cleveland, Ohio : Case Western Reserve University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1260565401.
34
Dalvi, P. V. "Strategies towards stereocontrolled medium cyclic rings and related photochemical studies." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 1992. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/3016.
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Leone, Joseph A. Flagan Richard C. "Studies in photochemical smog chemistry : I. Atmospheric chemistry of toluene. II. Analysis of chemical reaction mechanisms for photochemical smog /." Diss., Pasadena, Calif. : California Institute of Technology, 1985. http://resolver.caltech.edu/CaltechETD:etd-12042006-093443.
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Rice, James H. "Spectroscopic studies of porphyrins in model bio-molecular environments : photophysical, photochemical and electrochemical studies." Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388177.
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Morris, Leigh John. "Photochemical studies of some heavy transition metal compounds with catalytic potential." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343436.
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Baglo, Yan. "Preclinical studies of photodynamic therapy and photochemical internalization in bladder cancer." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for kreftforskning og molekylær medisin, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-24802.
Анотація:
Prekliniske studier av fotodynamisk terapi og fotokjemisk internalisering ved urinblærekreft Urinblærekreft er en av de hyppigste kreftformene i verden med høy frekvens av tilbakefall og progresjon. Omtrent 70-80 % av diagnostiserte tilfeller av urinblærekreft er ikke-muskel-invasiv blærekreft (NMIBC). Denne kreftformen er potensielt godt egnet for behandlingsformer som fotodynamisk terapi (PDT) eller fotokjemisk internalisering (PCI). Denne avhandlingen beskriver bruken av både PDT og PCI i fire prekliniske studier på urinblærekreft. I studien av PDT-effekt på proteinuttrykk og post-translasjonelle modifikasjoner (PTM) ble hexyl 5-aminolevulinate (HAL) brukt til å mediere PDT i en kreftcellelinje fra rotteblære (AY-27). Målet var å utvide vår forståelse av PDT-mekanismen. Ved å kombinere todimensjonal gel-elektroforese (2D-DIGE), immunopresipitering og massepektrometri identifiserte vi 40 proteiner som ble kartlagt for endringer knyttet til PDT, og identifiserte dessuten 10 proteiner med endret karbonylering. Det ble vist at PDT påvirket proteinuttrykk og induserte proteinmodifikasjoner. Dette tyder på at PDT utløser en kompleks cellulær respons som involverer flere biologiske prosesser, slik som transport, stressrespons, DNA-reparasjon, overlevelse og celledød. I den neste studien så vi på transportmekanismer for 5-aminolevulinate (ALA) og metyl aminolevulinate (MAL) via GABA-transportør (GAT) i forbindelse med PDT. Vi modellerte fire humane GAT-er ved molekylmodellering (ICM). Etter kvalitetssikring av modellene ble GABA, ALA og MAL dokket til bindingssetet i hver modell, og elektrostatiske potensialer (ESPs) i porene for translokasjon i modellene ble beregnet. Resultatene tyder på at ALA kan være substrat for alle GAT-ene, mens MAL er substrat for GAT-2, GAT-3 og BGT-1. I tillegg kan forskjeller i ESP mellom transportørene bli utnyttet i utviklingen av selektive inhibitorer, for eksempel for å redusere smerte i PDT ved bruk av ALA eller MAL. For å forbedre effekten av bleomycin som cytostatika ved blærekreft ble PCI kombinert med bleomycin i tre cellelinjer (T24, AY-27, A431), ved hjelp av en ny amfifil fotosensitizer tetrafenyl klorin disulfonat (TPCS2a). To nye strategier for å forsterke PCI-bleomycin effekten ble studert; et nytt peptid-basert medikament ATX -101, som kan svekke DNA- reparasjon, og en proteaseinhibitor E-64, som kan inaktivere bleomycin hydrolase. Våre resultater viser at PCI øker bleomycin-effekten, og at denne effekten blir ytterligere forsterket av ATX-101. Vi viser også at PCI øker DNA-skadenivået (studert med comet assay), noe som tyder på at den observerte effekten skyldes økt cellulær internalisering av bleomycin. For å etablere en protokoll for PCI-bleomycin i dyreforsøk med TPCS2a fotosensitizer ble kinetikk og lokaliseringen av TPCS2a studert i en etablert dyremodell for blærekreft i rotte, ved bruk av histologi og ex vivo fluorescensmålinger. Dette viser at TPCS2a har et overfladisk distribusjonsmønster i tumorvevet i rotteblæren, og at det er nesten fullstendig eliminert fra tumorvevet etter 72 timer. En optimal protokoll for TPCS2a ble utviklet for dyremodellen, inkludert et 24 timers TPCS2a-til-lys-intervall med en dose på 3 mg/ml TPCS2a.
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Krodel, David James 1978. "Photochemical and time-resolved spectroscopic studies of dirhodium hydrogen-generating species." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/16910.
Анотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2003.Vita.
Includes bibliographical references (leaf 29).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Photochemical and time-resolved spectroscopic studies of di- and mono-rhodium inorganic complexes were undertaken to elucidate the mechanism of photocatalytic hydrogen generation from hydrohalic acid solutions ...
by David James Krodel.
S.M.
40
Rahman, Mohammad Saifur. "SYNTHESIS AND PHOTOCHEMICAL STUDIES OF NEW PHOTOACTIVATABLE NITROXYL (HNO)-RELEASING COMPOUNDS." Kent State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=kent1574853859162083.
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Sakai, Wataru. "Studies on Photochemical Reactions via Two-Photon Ionization in Polymer Solids." Kyoto University, 1997. http://hdl.handle.net/2433/202321.
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McMoneagle, Andrew. "Antioxidant behaviour in photo-oxidation studies of model lipid compounds." Thesis, University of the West of Scotland, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311777.
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Grenfell, John Lee. "Southern hemisphere studies with a photochemical 3-dimensional model of the atmosphere." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388367.
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Clark, Charlotte Ann. "Time-resolved studies of excited states and photochemical reduction of carbon dioxide." Thesis, University of Nottingham, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.663259.
Анотація:
Chapter 1 - Introduction In this Chapter brief introductions to both excited states and time-resolved spectroscopy are provided. The majority of the work described in this Thesis has utilised time-resolved infrared (TRIR) spectroscopy on an ultrafast time-scale, and as such, the details of this approach are described. Chapter 2 - Utilising TRIR spectroscopy to probe the photophysics of Re and Ru dppz complexes The photophysics of several Re and Ru complexes containing the diimine ligand dppz have been investigated using ps and ns TRIR, in the v(CO) and 1600-1300 cm-I spectral regions. From the spectra in the < 1600 cm-I region it has been possible to differentiate between the types of excited states formed following photolysis for both previously assigned and novel complexes.
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Campen, Andrew Kenneth. "Photochemical and photophysical studies of transition metal species in low temperature media." Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236338.
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Castagnola, Norma B. "Spectroscopic studies and photochemical charge separation in Zeolite encapsulated donor-acceptor systems /." The Ohio State University, 1999. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488190595942664.
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Clark, Johnathan Lee. "NMR studies of the thermal and photochemical reactions of cyclopentadienyl ruthenium complexes." Thesis, University of York, 2011. http://etheses.whiterose.ac.uk/2116/.
Анотація:
The research reported in this thesis primarily focuses on the thermal and photochemical reactions of half-sandwich ruthenium complexes. The photochemical reactions employ the use of ex situ and in situ UV irradiation of the complexes. The latter of these techniques allows for samples to be irradiated within an NMR spectrometer, the principal method used to monitor reactions when highly unstable products result. The reactivity of [CpRu(PPh3)2Cl] towards a range of substrates is first described, where the thermal and photochemical reactions (applying the ex situ method) are contrasted. Replacement of PPh3 by a range of 2-electron donors, including CO, PEt3, ethene and tBuNC was achieved. Similar treatment is given to the complex, [CpRu(PPh3)2H]. However, this hydride complex proved to be slow to react and only minimal conversion to products was achieved, even using photochemical methods. The reactivity of CpRu(PPh3)2Me toward a range of 2 electron donors was considered in greater detail, particularly its ability to activate Si-H, H-H and C-H adducts under photochemical conditions. Low temperature photochemical techniques, using the in situ method, were employed to determine that both Si-H and C-H bond activation is undertaken by the fragment [CpRu(κ2-2-C6H4PPh2)]. This fragment was shown to activate the C-H bonds of solvent molecules, and form Ru(IV) complexes [CpRu(PPh3)(sol)(SiEt3)H] (where sol = C-H activated solvent, e.g. THF), which were stable at room temperature. The substitution of PPh3 occurs in an analogous fashion to that of the chloride derivative. However, the rate of conversion was increased but no evidence for migration of either CO or ethene into the RuMe bond was observed. The η3-coordinated complexes, [CpRu(PPh3)(η3-Si(Me2)-CH=CH2)], [CpRu(PPh3)(η3-CH2C2H3)], [CpRu(PPh3)(η3-CH2C6H5)] and [CpRu(PPh3)(η3-CH2C10H7)] were synthesised. In the cases of [CpRu(PPh3)(η3-CH2C2H3)] and [CpRu(PPh3)(η3-CH2C6H5)], thermal and photochemical reaction was initiated with substrates to generate the corresponding η1 substituted derivatives. These products were characterised by NMR techniques. Finally, the ability of the fragment, [CpRh(NR3)], to C-H activate benzene was considered. NMR data were collected for the low stability products of the photochemical reaction which strongly indicated that this auxiliary is capable of C-H bond activation. Due to working at low temperatures (233 K) and the large amounts of amine required to generate [CpRh(NR3)], full characterisation by NMR of these species was not attained.
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Liao, Chen. "Photochemical electron transfer (ET) reaction studies (1) photooxidations of sulfides; (2) development of new ET sensitizers /." Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1594481351&sid=3&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Dong, Jian. "Photochemical and Photophysical Studies of Synthetic Derivatives of the Green Fluorescent Protein Chromophore." Diss., Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24655.
Анотація:
We have synthesized dimethyl derivatives of the GFP chromophore (p-HOBDI) and several of its derivatives, and their photochemistry and photophysics were investigated using various steady-state and time-resolved techniques as follows.
We first consider the effect of the £]-barrel on the optical properties of the GFP chromophore (p-HOBDI) experimentally by selective variation of the protonation state of chromophores and different solvents. Each of these forms shows a complex solvatochromic behavior and is governed by both polar and acid/base properties of the solvents. In contrast to their solution behavior, some O-alkyl GFP chromophore (alkoxy-BDI) derivatives exhibit large fluorescent enhancement in the solid state. The color of the crystalline BDI is tuned by substituent-mediated crystal packing, showing the potential applications in optoelectronic devices.
Using femtosecond polarization-sensitive infrared (IR) spectrosceopy of the C=O stretching mode of the HOBDI, we have then discovered a near complete twisting around the ethylenic bridge between the phenolate and imidazolidinone groups upon electronic excitation. Cis/trans isomerization induced by the rotation around the bridge is thought to be responsible for the behavior of blinking in fluorescent protein; however, the mechanism of the thermal reverse isomerization is more problematic. Thus we synthesized BDI derivatives with decreasing para-donating ability, HO, CH3O, CH3, H, and Cl, and used a Hammett plot for the rate study. With a positive â value, we conceived, for the first time, a novel nucleophilic addition/elimination mechanism.
Finally, the GFP chromophore falls into the general category of hydroxyarene photoacids, which exhibit high excited-state acidities but neutral ground states. A hydroxyl substituent at the meta position shows enhanced charge transfer and greater acidity in the excited state. As a result, we have demonstrated that the fast quenching of the excited state by internal conversion to the ground state is much slower in meta- than in para-HOBDI derivatives. This allows studies of this ultrafast intermolecular ESPT that competes with isomerization. The photoinduced dynamics of the meta isomer of GFP chromophore was further investigated using femtosecond transient absorption and fluorescence upconversion spectroscopies.
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Matsuda, Shigeo. "Studies on the Photochemical Ligation of DNA and the Synthesis of Functionalized Oligonucleotides." 京都大学 (Kyoto University), 2001. http://hdl.handle.net/2433/150702.