摘要:

AbstractPorphycene and a tetra‐n‐propyl derivative remained unaltered on irradiation in toluene at room temperature. Quantum yields of fluorescence, S T intersystem crossing, and singlet molecular oxygen sensitization, as well as lifetimes of the singlet and triplet excited states were measured. In view of their structural relationship to porphyrin, their high absorption above 620 nm, their stability towards photooxidation, and their high quantum yields of fluorescence and singlet oxygen sensitization, these compounds qualify as potential agents for tumor marking and photodynamic ther

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04708.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractBoth the UVB (290‐320 nm) and UVA (320‐380 nm) regions of sunlight damage human skin cells but, particularly at the longer wavelengths, information is scant concerning the mechanism(s) of damage induction and the roles of cellular defense mechanisms. Following extensive glutathione depletion of cultured human skin fibroblasts, the cells become strongly sensitized to the cytotoxic action of near‐visible (405 nm), UVA (334 nm, 365 nm) and UVB (313 nm) but not UVC (254 nm) radiations. In the critical UVB region, the magnitude of the protection afforded by endogenous glutathione approaches that of the protection provided by excision repair. The results suggest that a significant fraction of even UVB damage can be mediated by free radical attack and that a major role of glutathione in human skin cells is to protect them from the cytotoxic action of sun

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04709.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe Bunsen‐Roscoe law, also known as the reciprocity law (E=f(F)withF=I t) has only limited validity for monophotonic reactions of nucleic acids. Especially at low fluence rates, the extent ofin vitroandin vivophotoreactions of nucleic acids in the far‐UV and near‐UV range is a function of the fluence and of the fluence rate (E=f(F;I)).In vitroexperiments with poly(dA)poly(dT) clearly show that the far‐UV (254 nm) response, indicated by the changes of the ellipticity at 315 nm, does not obey the Bunsen‐Roscoe law at low fluence rates in the range between 1 W m‐2and 20 W m‐2.In vivoexperiments withEscherichia colirevealed very similar anomalies. Studying the growth delay after irradiation with far‐UV light at 280 nm or near‐UV light at 334 nm, we have confirmed the lack of reciprocity in both spectral ranges. The failure of the Bunsen‐Roscoe law for the 280 nm and 334 nm UV irradiation effect at low fluence rates was in the range O

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04710.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractUnusual behaviour of harmaline and harmalol by excited state proton transfer has been studied and the acidity constants for the different prototropic equilibria in the ground and excited singlet states have been reported.

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04711.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractDeactivation of excited pyrene incorporated to cationic (cetyltrimethylammonium chloride), anionic (sodium dodecyl sulfate) and neutral (Triton X‐100) micelles by tryptophan has been investigated over a wide pH range. Data obtained allow an estimation of the tryptophan association to the micelles, of the tryptophan apparent pKin the micellar solutions, and of the dynamics of tryptophan incorporation to the micellar pseudophase. In particular, the data obtained at pH 7 allow an estimation of the effect of the micellar charge upon the binding capacity of the tryptophan zwitterio

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04712.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe interaction of a series of water‐soluble mono‐ and bis‐psoralenamines with calf thymus DNA has been studied with flow UV linear dichroism (LD), circular dichroism (CD) and equilibrium techniques. The positive charge of a protonated amino group strongly enhances the DNA affinity compared to that of the parent compound, 8‐methoxypsoralen. The orientation of the psoralen when bound to DNA, depends on the position of the amino substituent. With amino substituents in the 5‐position (on the‘hydrophobic edge’of psoralen) psoralenamines tend to bind with a considerable tilt relative to the average orientation of the DNA base‐pairs. The tilt generally increases with an increased psoralen: base‐pair ratio, indicating a more random, nonintercalated binding. With the amino substituents in the 8‐position the psoralen binds with its plane parallel to that of the DNA bases as expected for intercalation. The DNA CD supports that these psoralenamines induce a considerable perturbation of the DNA structure, and the CD induced in the psoralen chromophore is in qualitative agreement with intercalation. The study also includes a theoretical and an experimental determination of the UV transition moments of the p

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04713.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe efficiency of several porphyrins at 10 μMand 83 μMas sensitizers of the photooxidation of 0.1 mMtryptophan and histidineviaa singlet oxygen‐mechanism was studied in pH 7.4‐buffered aqueous solutions and in aqueous dispersions of Triton X‐100 micelles. The porphyrins were either solubilized in the bulk aqueous medium or associated with the micellar phase, whereas the amino acids were always located in the aqueous phase. With those porphyrins, such as uroporphyrin I, meso‐tetra (4‐sulfonatophenyl)porphine, meso‐tetra(4‐carboxyphenyl)porphine andmeso‐tetra)N,N,N‐trimethylanilinium)porphine, which are>98% monomeric in both media, the efficiency of histidine photooxidation was independent of the site of O2(1Δg) generation, as shown by the closely similar values for the photooxidation rate constant and oxygen‐consumption quantum yield in the presence and absence of Triton micelles; the same indications were provided by photokinetic experiments with tryptophan. Actually, laser flash photolysis studies showed that the micelle‐incorporation of the above mentioned porphyrins brought about only minor changes in their photophysical properties, including the relative yield of O2(1Δg) generation. On the other hand, hematoporphyrin IX, its Zn2+‐complex, and coproporphyrin III are largely aggregated in homogeneous aqueous solution; their incorporation into Triton micelles caused an increase of the triplet quantum yield and an enhancement of the oxygen‐consumption quantum yield and photooxidation rate constant for both histidine and tryptophan. The lower photosensitizing efficiency of aggregated porphyrin species in comparison with the corresponding monomeric porphyrin was confirmed by measuring the initial rate and quantum yield of oxygen consumption upon irradiation of 1 mMhistidine and tryptophan in the presence of different hematoporphyrin concentrati

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04714.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractA series of phage with different genomes (both single‐stranded and double‐stranded RNA and DNA) was inactivated with hydrogen peroxide (H2O2) in various combinations with far‐ultraviolet (FUV) and near‐ultraviolet (NUV) radiations. In every case but one (a lipid‐coated phage), a sublethal H2O2concentration greatly enhanced killing by NUV but not FUV. Moreover, this NUV/H2O2synergism was oxygen independent and there was little if any host cell reactivation upon NUV plus H2O2inactivation. These results suggest that these phage are inactivated by a common mechanism irrespective of nucleic acid composition, but that some phage genomes may be more vulnerable to NUV/H2O2inactivation th

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04715.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe wavelength dependence for the induction of a lambda‐lacZfusion phage ofE. coliby photo‐activated gilvocarcin V was determined using a spot test or a quantitative assay for thelacZgene product. Suspensions of bacteria and chemical were exposed to radiation of different wavelengths in the region 313‐546 nm, using a double grating monochromator. The prophage induction profiles generated were similar to the absorption spectrum of gilvocarcin V in this region, with a peak near 400 nm. The radiation fluence and chemical concentration required for threshold levels of prophage induction exhibited a nearly reciprocal relationship. These results have implications for the therapeutic use of gilvocarcins as antitumor a

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04716.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractA simple model of phototherapy (PT) for neonatal jaundice is presented. Two coupled systems are considered: the “skin” (upper skin layers and vascular network where phototherapy light may penetrate) and the “body” (i.e. the “dark” ensemble of blood vessels and organs where circulation and metabolization of biliribin (BR) and its photoisomers occur).The mathematics necessary to analyze the PT process is presented together with an appropriate optical model of skin based on a multilayered system to which the theory of radiation transfer in isotropically scattering and absorbing media is applied. A simple matrix formalism is introduced to determine analytically the light distribution in the multilayer skin. The results are. then, used to analyze the initial transient of PT, i.e. configurational isomerization up to photoequilibrium in the superficial skin layers under blue (450 nm) and green (500 nm) light irradiation within a time interval sufficiently short to neglect diffusion of pigments and formation of structural isomers of BR.Strong coupling among the various BR layers due to the time variation of diffuse transmittance and reflectance is found, resulting in complicated time patterns with initial and final single‐exponential behavior. The initial decay constant of BR concentration depends sensibly on the depth of the layer, while the final one is independent of it. As expected the amount of BR conversion at photoequilibrium is larger with blue than with green light. However, at sufficiently larger depths green light is more efficient than blue light to produce the initial conversion ofZZtoZEisomers of BR.The present analysis has some relevance for the understanding of the different efficiencies of coloured fluorescent lamps in clinical PT. The application of the complete model (“skin”+“body”) requires the knowledge of the diffusion constants and absorption coefficients of pigments and of the optical parameters of d

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1986.tb04717.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY