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1.
Formation and reactivity of free radicals in 5-hydroxymethyl-2-furaldehyde--the effect on isoprenaline photostability 总被引:1,自引:0,他引:1
Brustugun J Tønnesen HH Edge R Navaratnam S 《Journal of photochemistry and photobiology. B, Biology》2005,79(2):109-119
Solutions of glucose are used as diluents for drugs in various drug infusions. When sterilized by heat small amounts of the substance 5-hydroxymethyl-2-furaldehyde (5-HMF) is produced from glucose. At a hospital ward such infusions may be exposed to irradiation; including UV-light. The photoreactivity of the furaldehyde is investigated. It is shown to photodestabilize the catecholamine isoprenaline. It is shown to be a producer, but also a consumer, of singlet oxygen. The excited triplet, cation and anion radical have been produced by pulse radiolysis and flash photolysis and their absorbance characteristics have been determined. The triplet absorption spectrum showed absorption bands at 320 and 430 nm with molar absorption coefficients of 4700 and 2600 M-1 cm-1, respectively. The anion radical showed absorption bands at 330 and 420 nm with molar absorption coefficients of 2000 and 300 M-1 cm-1, respectively. The cation radical had an absorption band at 320 nm with a molar absorption coefficient of 5000 M-1 cm-1. The quantum yield for the production of singlet oxygen, sensitized by the 5-HMF triplet, was determined to be 0.6, whilst the quantum yield for the triplet formation was 1.0. Aqueous solutions of 5-HMF were found to photoionize to yield the hydrated electron and the cation radical of 5-HMF in a biphotonic process. The influences of pH, buffer and glucose on the formation of transients were evaluated. The reactions between 5-HMF and the solvated electron, the hydroxyl radical and the superoxide were also studied. 相似文献
2.
S. K. Olsen C. Tr holt A. Kü hle M. D umling O. T nnesen 《Physica C: Superconductivity and its Applications》1998,310(1-4):267-271
A high temperature superconducting cable may be based on a centrally located cylindrical support, a so-called former. If electrically conductive, the former can contribute to the AC losses through eddy current losses caused by unbalanced axial and tangential magnetic fields. With these measurements we aim at investigating the eddy current losses of commonly used former materials. A one layer cable conductor was wound on a glass fibre reinforced polymer (GFRP) former. By inserting a variety of materials into this, it was possible to measure the eddy current losses of each of the former candidates separately; for example copper tubes, stainless steel braid, copper braid, corrugated stainless steel tubes, etc. The measured data are compared with the predictions of a theoretical model. Our results show that in most cases, the losses induced by eddy currents in the former are negligible. However, for materials with a low resistivity the eddy current losses may become significant, e.g., for high purity Cu or Al. 相似文献
3.
Nardo L Andreoni A Bondani M Másson M Haukvik T Tønnesen HH 《Journal of fluorescence》2012,22(2):597-608
The steady-state absorption and fluorescence, as well as the time-resolved fluorescence properties of dimethoxycurcumin and
bis-dehydroxycurcumin dissolved in several solvents differing in polarity and H-bonding capability are presented. The singlet
oxygen generation efficiency of the two compounds relative to curcumin is estimated. The photodegradation quantum yield of
the former compound in acetonitrile and methanol is determined. The dimethoxycurcumin and bis-dehydroxycurcumin decay mechanisms
from the S
1 state are discussed and compared with those of curcumin, dicinnamoylmethane and bis-demethoxycurcumin. 相似文献
4.
Solid-phase extraction and high-performance liquid chromatographic determination of flumequine and oxolinic acid in salmon plasma 总被引:1,自引:0,他引:1
K E Rasmussen F T?nnesen H H Thanh A Rogstad A Aanesrud 《Journal of chromatography. A》1989,496(2):355-364
Two methods for determination of oxolinic acid and flumequine in salmon plasma are described. The first method applies sample pretreatment on C2 disposable solid-phase extraction columns. The second method is based on direct plasma injection and on-line sample clean-up on a polystyrene-divinylbenzene precolumn. After column-switching, the analytes are separated on a polystyrene-divinylbenzene analytical column and detected with a fluorescence detector. Validation of the methods showed good sensitivity, precision and reproducibility. Both methods are well suited for determination of plasma levels of the drugs in pharmacokinetic studies in Atlantic salmon. 相似文献
5.
Ch. Sannié W. G. Brown H. Flood Ch. Lapp K. Erali H. Brockmann Hella Schodder H. H. Strain P. Ruggli P. Jensen E. Waldschmitt-Leitz P. Fisher-Jørgensen M. Tønnesen G. Schramm J. Primosigh G. -M. Schwab K. Dockers G. Siewert H. Jungnickel Gretl Dattler A. N. Ghosh M. Venturello N. Agliardi H. Dahn H. Erlenmeyer W. Schoenauer und J. N. Wison 《Fresenius' Journal of Analytical Chemistry》1943,126(3):101-117
Ohne Zusammenfassung 相似文献
6.
Luca Nardo Alessandra Andreoni Maria Bondani Mr Msson Hanne Hjorth Tnnesen 《Journal of photochemistry and photobiology. B, Biology》2009,97(2):77-86
Curcumin is the main constituent of curry. In its ground state it shows chemo-preventive, chemo-therapeutic, anti-inflammatory and immune stimulating effects, and it is considered as a drug or drug model in the treatment of AIDS and cystic fibrosis. Further biological activity is induced in curcumin by light exposure: cytotoxicity is enhanced and photosensitized antibacterial effects are achieved. For the curcumin cis enol conformer, the fastest deactivation mechanism of the first excited singlet state is an excited-state intra-molecular proton transfer, which brings curcumin back to the ground state. This mechanism, as well as reketonization, interaction with the solvent and photodegradation, compete with the phototherapeutic action. The native compound curcumin carries phenolic hydroxyl and methoxy groups that influence the molecular charge distribution and hence the excited-state intra-molecular proton transfer rate in an unpredictable way. In this work we study static and time-resolved spectroscopic properties of a non-substituted curcuminoid that lacks both the phenolic hydroxyl and the phenolic methoxy groups. The photophysical properties of this compound are compared to those of native curcumin, in order to provide a rationale to the design of curcuminoids with molecular structures optimized for a photosensitizer. 相似文献
7.
8.
A sensitive and selective method for the detection of pholcodine and its metabolite morphine in urine using high-performance liquid chromatography is described. It involves on-line clean-up of urine on a trace enrichment column packed with a polymeric strong cation-exchange material. Pholcodine and its metabolites were separated on two analytical columns with different selectivities. Pholcodine was detected by a fluorescence detector and morphine was detected electrochemically. One system, based on reversed-phase chromatography, applied a polystyrene-divinylbenzene column and gradient elution. The other system was based on normal-phase chromatography with a silica column and isocratic elution. Morphine was confirmed to be a metabolite of pholcodine by reversed-phase chromatography and electrochemical detection. Two unidentified metabolites of pholcodine were separated from pholcodine by normal-phase chromatography and detected by fluorescence detection. 相似文献
9.
Solveig Kristensen Ruth Edge Hanne Hjorth Tønnesen Roger Hugh Bisby Suppiah Navaratnam 《Journal of photochemistry and photobiology. B, Biology》2009,94(3):147-157
The formation and reactivity of excited states and free radicals from primaquine, a drug used in the treatment of malaria, was studied in order to evaluate the primary photochemical reaction mechanisms. The excited primaquine triplet was not detected, but is likely to be formed with a short lifetime (<50 ns) and with a triplet energy <250 kJ/mol as the drug is an efficient quencher of the fenbufen triplet and the biphenyl triplet, and forms by laser flash photolysis . Primaquine (PQ) exists as the monocation in aqueous solution at physiological pH. photoionises by a biphotonic process and also forms the monoprotonated cation radical by one electron oxidation by (kq = 6.6 × 109 M?1 s?1) and (kq = 4.7 × 109 M?1 s?1) at physiological pH, detected as a long-lived transient decaying essentially by a second order process (k2 = 7.4 × 108 M?1 s?1). is scavenged by O2, although at a limited rate (kq = 1.0 × 106 M?1 s?1). The reduction potential (E°) of is < +1015 mV, as measured versus tryptophan (). Primaquine also forms at pH 2.4, by one electron oxidation by and proton loss (kq = 2.7 × 109 M?1 s?1). The non-protonated cation radical () is formed during one electron oxidation with at alkaline conditions (kq = 4.2 × 109 M?1 s?1 at pH 10.8). The estimated pKa-value of is pKa ~ 7–8. Primaquine is not a scavenger of at physiological pH. Thus self-sensitization by is eliminated as a degradation pathway in the photochemical reactions. Impurities in the raw material and photochemical degradation products initiate photosensitized degradation of primaquine in deuterium oxide, prevented by addition of the quencher sodium azide. Photosensitized degradation by formation of is thus important for the initial photochemical decomposition of primaquine, which also proceeds by free radical reactions. Formation of is expected to play an essential part in the photochemical degradation process in a neutral, aqueous medium. 相似文献
10.
Ch. Sannié W. G. Brown H. Flood Ch. Lapp K. Erali H. Brockmann Hella Schodder H. H. Strain P. Ruggli P. Jensen E. Waldschmitt-Leitz P. Fisher-J?rgensen M. T?nnesen G. Schramm J. Primosigh G. -M. Schwab K. Dockers G. Siewert H. Jungnickel Gretl Dattler A. N. Ghosh M. Venturello N. Agliardi H. Dahn H. Erlenmeyer W. Schoenauer J. N. Wison 《Analytical and bioanalytical chemistry》1943,126(3):101-117