| 1. |
- Akpe, Victor, et al.
(författare)
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Understanding the Photochemical Pathway of In Vitro Target Delivery of Aluminium Phthalocyanine : A Mechanistic Approach Using Radical Reaction Chemistry
- 2014
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Ingår i: ChemPlusChem. - : Wiley. - 2192-6506. ; 79:5, s. 671-679
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Tidskriftsartikel (refereegranskat)abstract
- A classical dye, aluminium phthalocyanine (AlPc), is used to study the photochemical processes involved in the chromophore-assisted laser inactivation technique. Both cell-free and cell-based systems are investigated by novel methods and radical reaction chemistry. Findings on the photochemical pathways in two models representing cell-free and a cell-based systems are reported. In the cell-free system, the unsubstituted, free, fluorescence-active photosensitiser AlPc recovers its fluorescence signal by means of phosphorescence through a reversible photobleaching process. In the cell-based system, photoactivation of substituted AlPc conjugated to an antibody results in the loss of fluorescence signal at the area examined. Reinjection of the AlPc-conjugated antibodies restores the fluorescence signal.
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| 2. |
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| 3. |
- Karlsson, Erik A., et al.
(författare)
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Synthesis and Electron-Transfer Processes in a New Family of Ligands for Coupled Ru-Mn2 Complexes
- 2014
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Ingår i: ChemPlusChem. - : Wiley. - 2192-6506. ; 79:7, s. 936-950
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Tidskriftsartikel (refereegranskat)abstract
- A series of [Ru(bpy)(3)](2+)-type (bpy= 2,2'-bipyridine) photosensitisers have been coupled to a ligand for Mn, which is expected to give a dinuclear complex that is active as a water oxidation catalyst. Unexpectedly, photophysical studies showed that the assemblies had very short lived excited states and that the decay patterns were complex and strongly dependent on pH. One dyad was prepared that was capable of catalysing chemical water oxidation by using [Ru(bpy)(3)](3+) as an oxidant. However, photochemical water oxidation in the presence of an external electron acceptor failed, presumably because the short excited-state lifetime precluded initial electron transfer to the added acceptor. The photophysical behaviour could be explained by the presence of an intricate excited-state manifold, as also suggested by time-dependent DFT calculations.
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| 4. |
- Liang, Yu, et al.
(författare)
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Ultrafast Dynamics of meso-Tetraphenylmetalloporphyrins : The Role of Dark States
- 2013
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Ingår i: ChemPlusChem. - : Wiley. - 2192-6506. ; 78:10, s. 1244-1251
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Tidskriftsartikel (refereegranskat)abstract
- Studying the relaxation pathways of porphyrins and related structures upon light absorption is crucial to understand the fundamental processes of light harvesting in biosystems and many applications. Herein, we show by means of transient absorption studies, following Q- and Soret-band excitation, and abinitio calculations on meso-tetraphenylporphyrinato magnesium(II) (MgTPP) and meso-tetraphenylporphyrinato cadmium(II) (CdTPP) that electronic relaxation following Soret-band excitation of porphyrins with a heavy central atom is mediated by a hitherto disregarded dark state. This accounts for an increased rate of internal conversion. The dark state originates from an orbital localized at the central nitrogen atoms and its energy continuously decreases along the series from magnesium to zinc to cadmium to below 2.75eV for CdTPP dissolved in tetrahydrofuran. Furthermore, we are able to directly trace fast intersystem crossing in the cadmium derivative, which takes place within (110 +/- 20)ps.
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| 5. |
- Rönnholm, Petra, 1969, et al.
(författare)
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Aggregation and Solvation of Chiral N,P-Amide Ligands in Coordinating Solvents: A Computational and NMR Spectroscopic Study
- 2012
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Ingår i: Chempluschem. - : Wiley. - 2192-6506. ; 77:9, s. 799-806
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Tidskriftsartikel (refereegranskat)abstract
- The lithium amides of a series of chiral N,P ligands were studied in solution. This ligand class had been shown previously to give good selectivities in asymmetric alkylation of benzaldehyde. These lithium amides were found to aggregate into dimers with surprisingly strong coordination of phosphorus to lithium. The equilibrium between dimeric forms was found to depend strongly on non-bonded interactions within the solute and between solute and solvent. Only if dispersion and free-energy contributions were scaled to approximately 20?% of the gas-phase values was it possible to reproduce the experimentally observed aggregation preferences. NMR spectroscopic shieldings were calculated and found to correlate well with the experimentally observed shifts. Calculated Li,P couplings were shown to be a sensitive measure of the Li?P distance.
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| 6. |
- Serra, Immacolata, et al.
(författare)
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Developing a Collection of Immobilized Nucleoside Phosphorylases for the Preparation of Nucleoside Analogues: Enzymatic Synthesis of Arabinosyladenine and 2,3-Dideoxyinosine
- 2013
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Ingår i: Collection of Czechoslovak Chemical Communications. - : Wiley. - 2192-6506. ; 78:2, s. 157-165
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Tidskriftsartikel (refereegranskat)abstract
- The use of nucleoside phosphorylases (NPs; EC 2.4.2.n) represents a convenient alternative to the chemical route for the synthesis of natural and modified nucleosides. We purified four recombinantly expressed nucleoside phosphorylases from the bacterial pathogens Citrobacter koseri, Clostridium perfringens, and Streptococcus pyogenes (CkPNPI, CkPNPII, CpUP, SpUP) and their substrate specificity was investigated towards either natural pyrimidine or purine nucleosides and some analogues, namely, arabinosyladenine (araA) and 2,3-dideoxyinosine (ddI). A 23% activity towards these latter compounds (compared to the natural substrates) was observed. Enzyme activities were compared to the specificities obtained for the enzymes pyrimidine nucleoside phosphorylase from Bacillus subtilis (BsPyNP) and purine nucleoside phosphorylase from Aeromonas hydrophila (AhPNPII) previously reported by some of the authors. The enzymes displaying the suitable specificity for the synthesis of araA and ddI were immobilized on aldehydeagarose. The immobilized preparations were highly stable at alkaline pH and in the presence of methanol or acetonitrile as cosolvent. They were used in the synthesis of araA and ddI by a one-pot, bienzymatic transglycosylation achieving 74 and 44% conversion, respectively.
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