摘要:

Abstract—Site‐selection fluorescence spectra of chlorophyllbin membranes of lecithin vesicles and in the solvents ethanol,n‐butanol,n‐butyl acetate, 2‐methyl tetrahydrofuran and toluene are presented. The spectra in vesicles display zero‐phonon lines as pronounced as those in the best organic glasses. The characteristics of the distributions of O—O transition energies and of the electron‐phonon couplings allow to infer the position of the chlorophyll molecule in the membrane of vesicles. It is thus found that the chromophore of chlorophyllbis situated in the layer formed by the ester moieties of the lecithins, i. e. close to the surface of the membrane but not in direct contact with th

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03356.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—Marmesin was isolated from the medicinal plant,Afraegle paniculata.Its cytotoxicity and mutagenicity in Chinese hamster V79 cells when sensitized to near ultraviolet (NUV) and long wavelength ultraviolet light or black light (BL) were assayed.Marmesin was extremely cytotoxic in the dark. This cytotoxicity was photoenhanced in NUV and BL; the photoenhanced lethality being higher in NUV than in BL. The LD50of marmesin under NUV and BL photosensitization were 0.002 μMand (0.012 μM), respectively. In the absence of NUV and BL, marmesin's LD50was 0.013 μM. NUV and BL without marmesin were not significantly cytotoxic at the fluence rates of 0.29 W/m2and 4.2 W/m2, respectively, for up to 20 min. In contrast to the observed high cytotoxicity of marmesin, its mutagenicity at the HGPRT locus (AzGr) was weak. The implication of this result in the high incidence of skin cancer in Nigeria in whichA. paniculatais used as a medicinal plant is discu

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03357.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—The furocoumarin 8‐methoxypsoralen (8‐MOP) is not detected as a mutagen in the standard Ames test either in the presence or absence of S9‐mix and/or ultraviolet light‐A (320–400 nm). The Ames strains have recently been shown to harbor bacteriophages that are inducible by carcinogens and mutagens. Psoralen (8‐MOP) plus UVA (PUVA) was found to be a potent prophage inducing treatment. Induction was observed in TA1535, TA1538, TA98, TA100, TA1978 and TA1975 with 0.1 μg/ml of 8‐MOP and 2.5 kJ/m2of UVA. PUVA is a potent bactericidal treatment at concentrations of 8‐MOP above 0.5 μg/ml and 2.5 kJ/m2in tester strains TA1535, TA1538, TA98, and TA100. PUVA is known to be bactericidal, but the cytotoxicity observed in this study was unique in that the frameshift tester strains (TA1538 and TA98) were more sensitive to the lethal effects of PUVA than the base pair tester strains (TA1535 and TA100). The differential cytotoxicity in such closely related strains led to the examination of some of the strains from which the Ames strains were derived. The data suggest mutations introduced into the Ames strains to make them more sensitive to carcinogens and mutagens (ΛuvrB) have resulted in an altered response to PUVA. It is postulated that TA1535 retains a DNA repair function that is lost by TA1538 during the selection foruvrBdeficient strains.PUVA is also unique in that plasmid pKM101 does not confer enhanced survival of TA100 compared to TA1535 in contrast to many other carcinogens and mutagens. In conclusion, these data show that PUVA induces a pathway leading to prophage induction and demonstrates the potential use of prophage induction assays to detect mutagens and carcinogens that may otherwise be lethal to the

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03358.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—Delayed photohemolysis has been shown to vary with the composition of the reaction vessel. Human erythrocytes were illuminated in the presence of sensitizer for 1 h and examined 23 h later for percent hemolysis. Four sensitizers, two cationic and two anionic, and three types of reaction vessel were studied. The cationic sensitizers were much more effective in tissue culture treated plastic than in neutral plastic or glass. All were somewhat more effective in neutral plastic than glass. Sorption of sensitizers to reaction vessels without cells present was also studied. In some cases sorption leads to virtually complete removal of sensitizer from the reaction medium. In other cases no sorption is detectable. For the highest sorbing sensitizer total replacement of the reaction medium with sensitizer‐free solution did not decrease effectiveness, demonstrating that sorbed sensitizer is available to sensitize. The results suggest that photooxidation of the cell membrane occurs in two zones, one at the interface between vessel surface and cell surface, and the other where the membrane faces the bulk reaction medium. The relative importance of the interface may depend on the strength of sorption and the affinity of sensitizer for the cell membr

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03359.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—Benoxaprofen [2‐(4‐chlorophenyl)‐α‐methyl‐5‐benzoxazoleacetic acid] is a phototoxic non‐steroidal anti‐inflammatory agent. Irradiation of human erythrocytes in the presence of benoxaprofen (8 μM) and oxygen resulted in rapid cell lysis which began after 10 min and was complete within 30 min. While photohemolysis was also observed under anerobic conditions, its onset was delayed for more than 20 min and it took nearly 100 min for complete lysis to occur. Photohemolysis was also delayed by butylated hydroxyanisole but was unaffected by reduced glutathione. 1,4‐diazabicyclo[2.2.2]octane, D2O. β‐carotene, or superoxide dismutase. The main photoproduct of benoxaprofen, 2‐(4‐chlorophenyl)‐5‐ethylbenzoxazole, was almost as effective in causing photohemolysis as benoxaprofen itself. In the presence of UV irradiation, benoxaprofen (10 (μM) caused the degranulation of rat peritoneal mast cells and the release of histamine. The release of mast cell histamine may provide a reasonable explanation for the urticarial response to benoxaprofen and i

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03360.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—InHalobacrerium hnlobium.retinal is the chromophore of the light‐energy converting pigments bacteriorhodopsin (BR) and halorhodopsin (HR) and of the sensory photosystems. PS 370 and PS 565. In both photosystems as well as in BR and HR. retinal was substituted by retinal analogues.Retinal2(3,4‐dehydro‐retinal).shifts the main sensitivity maximum of PS 370 and of PS 565 by about 1.5 nm to longer wavelengths. The absorption maxima of BR and HR are both shifted in the same direction, but by 37 nm.13‐Ethylretinaland13‐propylretirnalshift the main sensitivity maximum of each sensory photosystem to shorter wavclengths; the absorption maxima of BR and HR are shifted in the same direction but to a smaller extent. Both sensory photosystems are equally active with retinal and with each of the three analogues as the chromophore. After substitution of retinal by the analogues, the action spectra of PS 565 of the BR‐containing strain R1L3show a secondary bensitivity peak in addition to the main peak. This secondary peak matches the absorption maximum of the corresponding BR. In the action spectra of the BR‐deficient strainET–15 this secondary peak is missing. Action spectra of PS 565 of the BR‐deficient strainL–33, which synthesizes increased amounts of HR. with all retinals show a secondary peak which matches the absorption maximum of the corresponding HR.The results show that the analogues can substitute retinal in both sensory pigments as well as in BR and HR. Moreover, the data support the previous assumption that both BRand HR, although not required for photosensory activity can contribute to photos

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03361.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—Trifluoperazine is a commonly used agent for the treatment of psychiatric disorders. Perfusion of corneal endothelial cells with trifluoperazine‐HCI concurrent with 3 min of exposure to long wavelength ultraviolet light resulted in a corneal swelling rate which was greater than that found in corneas where endothelial cells were perfused with trifluoperazine‐HCI and not exposed to ultraviolet light. Exposure of endothelial cells to 25 W incandescent light for 5 min during perfusion with trifluoperazine‐HCI did not result in a corneal swelling rate in excess of that found during perfusion with trifluoperazine in the dark. The increased corneal swelling rate could be produced by pre‐exposure of the trifluoperazine‐HCI perfusing solution to ultraviolet light suggesting the production of toxic photo‐products during exposure of trifluoperazine HCI to ultraviolet light. Perfusion of corneal endothelial cells with non‐ultraviolet illuminated trifluoperazine HCI had no effect on endothelial cell membranes or ultra‐structure. This is in contrast to cells perfused with trifluoperazine HCI that had been exposed to ultraviolet light in which there was an alteration of mitochondria and a loss of cytoplasmic homogeneity. The data imply that the trifluoperazine HCI photoproduct had an adverse effect on cellular transport mechanisms. The study also further demonstrates that value of the corneal endothelial cell model for identifying the physiological and anatomical changes occurring in photo‐indu

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03362.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—The incorporation of relatively small amounts (≤ 20 mol%) of a negatively charged surfactant into otherwise electrically neutral phosphatidylcholine vesicles containing chlorophyll in the presence of benzoquinone has been shown to produce large effects on radical formation and decay as measured by laser flash photolysis. When salt ions are present in the aqueous phase, increasing the level of negative surfactant leads to a small increase in radical yield, followed by a larger decrease in radical yield. When the salt concentration is low, increasing the negative surfactant concentration leads to a suppression of the fast radical recombination process, an increase in slow radical decay and, at the highest surfactant concentration, an approximately 35% increase in total radical yield. An analysis of these effects is given in terms of the influence of a negative electrostatic field on radical pair stabilization and recombination, radical pair separation and expulsion of the acceptor radical anion from the vesicle.The incorporation of relatively small amounts (≤ 20 mol%) of a positively charged surfactant into egg phosphatidylcholine (EPC) vesicles containing chlorophyll and benzoquinone also produces large effects on radical formation and decay. When the electrolyte concentration in the suspending aqueous medium is high, radical yields are decreased as the surfactant concentration is increased, without any appreciable effect on decay kinetics. When deionized water is used, the slow recombination component of the decay is specifically suppressed by the presence of the positive surfactant, whereas the fast decay component decreased and then increased in amount as the surfactant concentration is increased. In all cases, however, the total radical yield is less than in pure EPC vesicles. These results can be understood in terms of the influence of a positive electrostatic field on radical pair separation and acceptor radical anion mobility. When equimolar amounts of both positively and negatively charged surfactants are incorporated into EPC vesicles, the radical yields and decay kinetics are relatively unaffected, but a large effect is observed on the radical difference spectrum. This may be a consequence of clustering of oppositely charged molecules within the bilayer su

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03363.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—The characterization and kinetic analysis by laser Rash photolysis of an improved model system for observing chlorophyllaphotosensitized electron transfer across a lipid bilayer membrane is described. In this system, the electron acceptor is a water‐soluble naphthoquinone, S‐(2‐methyl‐l,4‐naphthoquinonyl‐3)‐glutathione (MGNQ) which is dissolved in the inner aqueous compartments of phospholipid bilayer vesicles, and the electron donor is glutathione (GSH) which is dissolved in the outer aqueous phase. Chlorophyll (Chl) is dissolved in the membrane. Oxidative quenching of the triplet state of Chl by the quinone at the inner surface of the vesicle produces the Chl+and MGNQ‐radicals. Chi+is reduced by GSH at the outer surface of the vesicle (k= 2.6 × 106M‐1s‐1) in competition with the recombination between Chl+. and MGNO‐(k= 2.5 × 103S‐1). It is shown that a kinetic mechanism involving competition between recombination, electron transfer across the bilayer, and reduction by donor at the opposite surface can quantitatively account for the decay of Chl+. Electron transport across the bilayer is postulated to occur by a two‐step mechanism involving electron exchange between Chl and Chl+within the lipid monolayer (k= 3.2 × 106M‐1s‐1) and across the bilayer. The rate constant for the latter exchange process approaches 104s‐1as the concentration of Chl in the bilayer increases. Under appropriate conditions, approximately 20% of all photons absorbed by the vesicle system result in electron transfer

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03364.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract—The temperature dependencies of the primary donor triplet state spectra are presented for the phorosynthetic bacteriaRhodopseudomonas sphaeroideswild type. GIC and R26. The data suggest that energy transfer from the primary donor triplet state to the reaction center carotenoid is dependent on the type of carotenoid present, reversible in the case of strain GIC, and best understood by a model depicting the kinetic processes that can occur between two potential energy surfaces; one representing the state3BChl2*Car and the other representing BChl23Car*. Furthermore, it is shown that the onset of spin lattice relaxation in the primary donor triplet is most likely coupled to the same energy vibrational mode as that which promotes triplet state energy transfer from the primary donor to the reaction center caroteno

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1983.tb03365.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY