摘要:

Abstract—The rate constants for the reactions of all‐transretinol and retinal with singlet oxygen were measured in a variety of solvents of different polarities. The rate constants increased with increasing solvent dielectric constant, which suggests that a charge transfer mechanism plays a part in the reaction. Further, the rate constant of reaction of singlet oxygen with retinal is greater than that with retinol. Since retinal has a lower ionization potential than retinol, these relative rates also support the hypothesis of charge transfer involvement in the react

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03851.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—A study of the photooxidation of magnesium tetraphenylporphyrin by oxygen in methanol with methyl viologen present has been carried out. The reaction was normally followed by the decrease of Soret band absorbance with time. The influences of air, methyl viologen, light wavelength and intensity, presence of ß‐carotene, pH, and MgTPP concentration were investigated. From bulk photolysis experiments, three products have been separated and partially characterized. A mechanism based on superoxide as the dominant oxidant is prop

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03852.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—Riboflavin 5'‐phosphate (FMN)‐sensitized photodynamic modifications of multisubunit alcohol dchydrogenase, bacterial luciferase. L‐glutamate dehydrogenase, and catalase all lead to significant formation of crosslinked species. On the contrary, irradiation of monomeric lysozyme, trypsin inhibitor, trypsin, and bovine serum albumin in the presence of FMN yields either no or only trace amounts of polymerized molecules. Photodynamic modifications thus appear to be much more efficient in crosslinking proteins with quaternary structures in their native forms. While no photodegradations of other proteins were found, FMN‐sensitized modifications of the nonidentical dimeric (αß) bacterial luciferase resulted in the formation of two degraded fragments as well as two polymerized species. Singlet oxygen is shown to be involved in the photopolymerization of luciferase but it is unclear whether singlet oxygen is the sole species active in initiating the crosslinking reaction(s). FMN also sensitizes effective inactivations of luciferase which can be attributed to actions of singlet oxygen, triplet FMN, H2O2. and superoxide anion. Photodynamic inactivation of luciferase proceeds faster than photopolymerization; these processes are thus

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03853.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—When sensitized by riboflavin, the reduction of NBT2+(nitro blue tetrazolium ion) takes place in both aerated and degassed aqueous solution. Laser photolysis experiments revealed that the triplet riboflavin reduces NBT2+to nitro blue tetrazolinyl radical, NBT2+. and it disappears according to pseudo‐first order kinetics, with a bimolecular rate constant of (4.2 ± 0.2) X 108M‐1s‐1. It is shown that NBT2+is not always a good detecting reagent for the superoxide anion, when the formation of the anion is mediated by ri

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03854.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—Triplet‐and singlet‐related photoprocesses of pyrene‐1‐aldehyde (PA) in various solvents have been investigated in detail using 337.1 and 355 nm laser flash photolysis in conjunction with time‐correlated determination of fluorescence lifetimes (τF) and steady‐state photochemical and absorption‐emission spectral measurements. In benzene, the lowest triplet of PA (43

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03855.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—Transient absorption spectra produced by laser flash‐photolysis of an aqueous solution of ephedrine have been measured under a variety of conditions. Ephedrine was found to photoionise via a biphotonic process. The apparent yield of photoionisation increases with lowering of pH, a value of 8.8 being found for the pKaassociated with this change. The cation radical absorption spectrum has been determined using the techniques of both pulse radiolysis and laser flash photolysis. The extinction coefficient of the cation at 295 nm was determined to be 1.37 × 104dm3mol‐1cm‐1and 1.2 × 104dm3mol‐1cm‐1by the two techniques, respectively, at pH 11. It is also shown that the rate constant for electron abstraction by the azide radical to form the ephedrine cation is controlled by protonation of the amine group in the side chain. The ephedrine anion radical spectrum and its extinction coefficient at 305 nm were also determined. The excited states responsible for photoionisation and photodegradation

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03856.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—The variation with temperature, pH and light of the ESR signal of hydrated melanin powders from Japanese black hair has been studied. An explanation of the results is proposed on the basis of quinhydrone type complexes and of acid‐base equilibria of melanin and its semiquinone radicals. During exposure to light of wavelengths 254–600 nm, both stable and unstable radicals have been observed. The action spectrum for the formation of stable melanin radicals has been deter

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03857.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—The photochemical reaction in aqueous solutions of several phenothiazines with an N‐alkylamine chain, and their salts, is studied by means of Chemically Induced Dynamic Nuclear Polarization (CIDNP)¶. The particular behaviour of chlorpromazine hydrochloride is outlined and evidence is shown for the existence of a substitution product with the solvent at the α‐carbon atom of the side‐chain, and an aldehydic derivative resulting in the cleavage of that one. Radical‐ions pairs of CPZ are involved in bot

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03858.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—This study demonstrates that photobiological effects by exogenous molecules are notper serestricted to the skin. As an example the photopharmacology of chlordiazepoxide (e.g. LibriumR) was studied. Rats being exposed to UV‐A after administration of14C2labeled chlordiazepoxide (CDZ) showed a marked change in the pattern of urinary metabolites; the quantity of metabolites without N4‐oxide function increased, whereas that of compounds with N4‐oxide function decreased. Covalent binding to organ tissue of especially liver and skin of the irradiated rats was found. This would mean that in the irradiated rats oxaziridines which may also react with tissue of the inner organs are formed from CDZ and its N4‐oxymetabolites.Further, the combination of light and CDZ leads to a 30% decrease in weight of the liver, indicating liver damage. This is also supported by the percentage of conjugated urinary metabolites being 1.5–2.5 times lower than in the non‐irradiated CDZ‐treated rats, possibly caused by a decrease of enzymatic activity.The administration of CDZ‐oxaziridine to non‐irradiated rats provoked the same effects, such as a decrease of the weight of the liver comparable to that of irradiated CDZ‐treated rats. On the other hand the combination of light and treatment with N4‐desoxy CDZ did not have

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03859.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—Repair of photodynamic damage induced by acriflavine and visible light has been examined in three strains ofVibrio choleraediffering in their capabilities to repair ultraviolet (UV) light induced DN A damage. Excision repair deficient wild type cells of strain 154 are more sensitive to photodynamic treatment compared to repair proficient cells of strain 569B. However, no difference in their capabilities to repair of damage following photodynamic treatment can be detected. No single‐strand breaks in the irradiated cell DNA are observed when the cell survival is more than 10%. Single‐strand breaks observed at cell survival less than 5% are not dark repairable even in excision repair proficient wild type cells. Repair of membrane damage can partially account for the recovery observed at low doses. In contrast, radiation‐sensitive mutant 569Bscells which lack both excision and medium‐dependent dark repair for UV‐lesions are most efficient in repairing damage induced by photodynami

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03860.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY