摘要:

AbstractThe water soluble carotenoid crocetin has been studied as a singlet molecular oxygen monitor in D2O solution, pD 8.4. Crocetin reacts chemically with singlet molecular oxygen with a rate constant of 4 x 108M‐1s‐1. The rate constant for total quenching, chemical and physical, is 2.5 x 109M‐1s‐1. Crocetin shows evidence for a reversible reaction with singlet molecular oxygen, as demonstrated by a fairly rapid absorption recovery after bl

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb04331.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractThe photoionization of 3,4‐dihydroxyphenylalanine (dopa) and catechol has been studied by electron spin resonance spectroscopy using the free radical scavenger 5,5‐dimethyI‐1‐pyrroline‐1 ‐oxide as a spin trap for hydrated electrons and hydrogen atoms. The photochemistry of these materials is shown to resemble tyrosine in that both photoionization and photohomolysis (to give H) occur, with photoionization predominating (by a factor of 2.6 for dopa). Ionization of one of the phenolic hydroxyl groups increases the yield of radicals by a factor of 2. Action spectra and quantum yields for radical production a

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb04332.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractThe molecule (1,l'‐dipyrenyl)‐methyl ether (dipyme) was used for monitoring the bilayer fluidity of surfactant and sonicated phospholipid vesicles. In the latter systems, the observed transition temperatures (Tc) are identical with those found by different methods. Surfactant vesicles prepared from dioctadecyldimethylammonium bromide (DODAB) and dihexadecylphosphate (DHP) molecules manifest a similar fluidity of their bilayers as those of sonicated phospholipid vesicles below theirTc.However, unlike in phospholipid vesicles, there was no significant change of the bilayer structure aboveTcobserved in surfactant vesicles. DHP vesicles formed in pure water provide a different solubilization site for dipyme than those prepared in a buffer solution. Such sites are characterized by a relatively high local concentration of the probe and the appearance of the blue shifted spectrum of the exci

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb04333.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractTriplet indole‐3‐aldehyde generated by the peroxidase catalyzed aerobic oxidation of indole‐3‐acetic acid adds to t‐RNAphewith an efficiency which can reach 20% of the theoretical value based upon the substrate. The reaction occurs with uridine groups and is of the Paterno‐Büchi type. Magnesium ions reduced addition and increased the sensitized emission from the 4‐thiouridine group. Our results, coupled with available biological data obtained with selectively labeled indole‐3‐acetic acid, support the hypothesis that formation of triplet indole‐3‐aldehyde is at the root of the biological effects o

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb04334.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractFurocoumarins with linear (psoralen, 8‐methylpsoralen, 8‐methoxypsoralen and 3‐carbethox‐ypsoralen) and angular molecular structures (angelicin and 4,5'‐dimethylangelicin) were found to inactivate enzymes to different extents through UV‐A irradiation. Moreover, enzymes with different structures (glutamate dehydrogenase, lysozyme, 6‐phosphogluconate dehydrogenase, enolase, thermoly‐sine and ribonuclease) are inactivated to different extents by the same furocoumarin. UV‐A irradiation produces both covalent incorporation of the furocoumarins into the protein molecule and photodegra‐dation of amino acid residues; the latter phenomenon seems to be mainly responsible for the photoinactivation process. A close correlation was found between the capacity of the furocoumarins to photoinactivate enzymes and their capacity to modify free amino acids.A study of the effects of quenchers of various forms of activated oxygen on the photoinactivation of glutamate dehydrogenase, used as a model enzyme, and psoralen and 8‐methylpsoralen as a reference for furocoumarins, showed that singlet oxygen is the species most involved in the phot

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb04335.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractOptical spectroscopy and proton nuclear magnetic resonance spectroscopy have been used to investigate the non‐covalent and covalent binding of 8‐azidoethidium (8‐azido‐3‐amino‐5‐ethyl‐6‐phe‐nyl‐phenanthridium) with transfer RNA (tRNA) molecules. The nuclear magnetic resonance measurements demonstrate that ethidium and ethidium monoazide bind to the same unique binding site on tRNA molecules. However, the optical studies demonstrate that the photochemical reaction between ethidium monoazide and tRNA generates at least three different photoproducts. One of the covalent photoproducts has fluorescence properties which mimic those of intercalated, non‐covalently bound ethidium, but it is produced only in about 10% yield. The major photoproduct(s) is(are) virtually non‐fluorescent. The ethidium monoazide photochemistry with tRNA molecules is obviously complex and this may complicate its use as a phot

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb04336.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractChromosomal abnormality due to the ultraviolet (UV) irradiation of sperm and its modification by photoreactivation (PR) were studied in the sea urchin,Hemicentrotus pulcherrimus.When sperm was UV‐irradiated and allowed to fertilize unirradiated eggs, the effect of UV was manifested as an abnormal separation of chromosomes at the anaphase of the first mitosis. The frequency of abnormal anaphase increased with UV fluence. In the UV fluence of larger than 20J/m2, more than 90% of eggs showed chromosomal abnormality. The UV‐induced chromosomal abnormality was prevented by photoreactivation when the fertilized eggs were illuminated with visible light. The PR sector for the PR of chromosomal abnormality, which was comparable to the PR sector for morphological abnormality, was higher than that of cleavage delay. The UV sensitivity expressed in terms of chromosomal abnormality was significantly higher than the sensitivity expressed in terms of morphological abnormality. Photo‐reactivation illumination sufficed to effect a nearly complete PR when applied up to 20 min after fertilization, while the PR effectiveness declined thereafter. Illumination after 40 min had little effect f

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb04337.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractChinese hamster ovary cells in exponential growth were incubated with various concentrations of hematoporphyrin derivative (HpD). Cellular porphyrin content was determined after 2 h incubation at 37°C using [3H]‐hematoporphyrin derivative. Photoactivation of cell‐bound HpD by red light resulted in a family of survival curves with terminal slopes proportional to cellular HpD concentration. The degree of cellular lysis, assayed 1 h after illumination using a chromium‐51 labeling technique, was also found to be related to cellular HpD concentration. The amount of 51Cr released increased with post‐irradiation incubation to a level parallel to cell lethality as measured by colony formation. These data suggest that lysis of the cell membrane may be largely responsible for cellular inactivation following HpD photoirr

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb04338.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractVisible irradiation of DNA‐daunomycin solutions resulted in a decrease of viscosity of the DNA and an increase of the rate of denaturation of DNA in formaldehyde. These changes are consistent with the induction of single‐strand breaks in the DNA, some of which pair to cause fragmentation of the DNA. The DNA damage increases with drug: nucleotide ratio up to 0.2 and is diminished beyond that range. The damage also increases with ionic strength up to 0.6Mand is diminished above that value. These results suggest that the non‐intercalated form of the drug is involved in the photosensitization process. Radicals that are produced accompanying the degradation have been trapped by 5,5‐dimeth‐yl‐l‐pyrroline‐1‐oxide and identified as hydroxyl radicals from their ESR spectrum. The DNA photosensitized damage is completely inhibited when hydroxyl radicals are removed by the spin‐trap, suggesting a direct role for the hydroxyl radicals in the DNA photosensitized degradation process. The implications of the photosensitized DNA damage and the production of hydroxyl radicals in this process are discussed with respect to the medical uses and chemotherapeutic

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb04339.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractBenoxaprofen (2‐[4‐chlorophenyl]‐α‐methyl‐5‐benzoxazole acetic acid), a non‐steroidal antiinflammatory drug, was found to provoke phototoxicity reactions in humans. Exposure of the skin of benoxaprofen‐treated subjects to either solar simulating radiation or a broad UV‐A wavelength band produced intense itching and burning sensations, followed by the development of a classical wheal and flare response within 2‐4 min. Phototoxicity was related to both the UV radiation fluence and the dose of orally administered benoxaprofen. Wavelengths between 320 and 340nm were active in provoking urticaria.In vitrostudies demonstrated that benoxaprofen and UV irradiation produced a dose‐dependent lysis of sheep erythrocytes which did not appear to be dependent on the presence of oxygen. Red cells were not lysed by pre‐irradiated benoxaprofen arguing against the production of stable lytic photoproducts. Human neutrophils were lysed by benoxaprofen and UV light which resulted in the liberation of both cytoplasmic and lysosomal enzymes. Benoxaprofen failed to induce photolysis of human platelets and photoactivation of complement in human serum. It is suggested that phototoxic urticaria provoked by benoxaprofen may be due to a direct photolytic effect on

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1982.tb04340.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY