ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb09838.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—The photobleaching of excited tris(2,2′‐bipyridyl)‐ruthenium(II), *Ru(bpy)32+, by peroxydis‐ulfate in the presence of DNA and a series of polynucleotides, mononucleosides (uridine, cytidine, adenosine, guanosine), and purine or pyrimidine bases was studied in deoxygenated aqueous solution at room temperature. A reaction scheme is proposed which is confirmed by data obtained from mixing experiments with Ru(III) and bleaching measurements of Ru(II) using either continuous visible light or a nanosecond laser pulse (353 nm). The primary photobleaching step is the formation of Ru(bpy)32+and the SO4‐radical anion. In the presence of nucleic acids the two oxidizing species are formed in close proximity to the strand, since we used conditions where the Ru(bpy)32+ion is bound to the strand. Concerning the secondary reactions two clear cases (and several more complex cases) can be distinguished. On addition of uracil to the Ru(bpy)32+/S2O82‐system the quantum yield for photobleaching is not significantly changed (φrel⋍ 0.95), whereas it drops to virtually zero for guanosine‐containing substrates, including DNA. The former result is explained by a reaction of SO4‐with uracil leading to theN–1 radical which oxidizes Ru(II) to Ru(IIl). In contrast, the guanine moiety reacts with Ru(III) converting it into Ru(II). Therefore, in the presence of S2O82‐and a substrate carrying a guanine moiety, Ru(bpy32

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02691.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—We used frequency‐domain fluorescence spectroscopy to measure rotational diffusion and time‐resolved emission spectra of indole in methanol on the picosecond timescale. The indole emission was quenched by acrylamide to allow measurements to the instrumental limit of 2 GHz and to eliminate emission from the longer‐lived indole molecules, which can no longer provide information on the picosecond (ps) processes. The resolution was adequate to measure rotational correlation times as short as 8 ps at 80†C, and spectral relaxation times as short as 16

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02692.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Flash photolysis at 450 nm has been used to study the quenching of the excited triplet state of lumiflavin and the transient species formed in subsequent reactions in deaerated phosphate buffer (pH 6.9).The effect of the presence of ferricyanide on the life time of triplet lumiflavin has been studied. The results suggest an energy transfer reaction without concurrent electron transfer reactions. The rate constant for the process was 2.8 times 109M‐1s‐1. The analogous reaction with ferrocyanide could not be observed because of the efficient electron transfer reaction (δG = ‐20.6 kcal mol‐1) leading to the formation of the semireduced lumiflavin and ferricyanide. The rate constant for this reaction was 3.3 times 109M‐1s‐1. The semireduced lumiflavin radical was found to disappear in a second order reaction with a rate constant of 1.7 times 109M‐1s‐1. It was found to react with ferricyanide with a rate constant of 0.7 times 109M‐1s‐1.A model for the various photochemical and photophysical processes involved in the decay and quenching of the lumiflavin triplet state is s

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02693.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—A new method is proposed for expressing the data obtained fromin vivostudies of drug‐induced photosensitivity. It is shown that consideration of the underlying normal photobiological responses that occur in the absence of the photosensitising drug can yield much closer agreement between thein vitroabsorption spectrum of the drug and the action spectrum obtained in photosensitised skin than is apparent from many published repo

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02694.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Phenylheptatriyne (PHT) plus near‐ultraviolet light(320–400 nm; NUV) hemolyzed human erythrocytes in an oxygen dependent manner. When the phototoxicity of PHT plus NUV was tested with a series ofEscherichia colistrains carrying all four possible combinations of genes controlling excision proficiency (uvrA6 vs uvrA+) and catalase activity (HPII,katF vs katF*), the membrane was found to be an important lethal target. Consistent with this observation. PHT plus NUV did not induce histidine independent (his‐4+) mutations in the four tester strains (RT7h‐RT10h). Using tester strain RT10h, it was shown that there was no inactivation by PHT plus NUV in nitrogen. Results of experiments with anE. colifatty acid auxotroph (K1060) treated with PHT plus NUV are also consistent with membrane proteins being the chief targets for attack. Radicals were formed during the photolysis of PHT plus NUV in aqueous solutions, both in the presence of air and under nitrogen. Since PHT plus NUV did not hemolyze erythrocytes or inactivateE. colicells under nitrogen, these radicals are not

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02695.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—The absorption and fluorescence properties of porphyrinc(Pc), the porphyrin chromophore present in cytochromec, have been determined in several solvents and micellar environments. In aqueous buffer solutions at pH 7.5 Pc may exist in both a fluorescent monomeric form with quantum yield of fluorescence, (Φf,) ∼ 0.03, and fluorescence lifetime, (τf) ∼ 8 ns, and as a non‐fluorescent aggregate. The proportion of monomeric form is higher in organic solvents and micelles but is reduced with increasing porphyrin concentrations in aqueous solutions. Porphyrincreadily complexes with Zn2+to produce a fluorescent chelate (Zn‐Pc) with Φf, ∼ 0.02 and τf, ∼ 2 ns at pH 7.5. The yields of singlet excited oxygen formation from Pc and the Zn‐Pccomplex are higher than observed for hematoporphyrin derivative (HpD). Both Pcand Zn‐Pcare effective agents in tumor phototherapy and do not induce the prolonged cutaneous photosensitivity observe

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02696.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—Upon e‐‐pulse irradiation in nonprotic solvents, all‐transretinol (ROH) and retinylmethyl ether (ROMe) form transient species (τ= 0.5–7μs, λmax=575–590 nm) identifiable as radical anions. Similar species are also formed upon laser pulse photoexcitation of these retinyl derivatives in the presence of N,N‐dimethylaniline in acetonitrile. In contrast, electron transfer or attachment to all‐transretinyl acetate (ROAc) and palmitate (ROPa) results in ‘instantaneous’ loss of carboxylate anions from electron adducts giving the retinylmethyl radical (R‐, λmax= 395 nm, τk>100 μ,s); the radical anions in these cases are too short‐lived to be detected by nanosecond pulse radiolysis. The lifetimes of radical anions of ROH and ROMe are very sensitive to water and alcohols (e.g.kq= 107M‐1s‐1with methanol as quencher for ROH‐in tetrahydrofuran). Based on these findings, the spectral dissimilarity of the one‐electron reduction products from ROH and ROAc in alcohols and aqueous micelles becomes explainable in terms of fast formation of protonated radical anions (RH(OH), τ1/2,>100 μs, λmax=370–375 nm) in the case of ROH and of retinylmethyl radicalvialoss of AcO‐from radical anion in the case of ROAc. In tetrahydrofuran, the complexation of ROH‐with cations such as Na+and Bu4N+affects the relative importance of its major decay modes, namely, protonation and dehydroxylation, the latter process being

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02697.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—The absorption maximum of bacteriorhodopsin is shifted from 568 nm to 480 nm when halogenated volatile anesthetics (enflurane; halothane) are added to purple membranes. Analysis of the rate of formation of this new species upon addition of the anesthetic and of the back‐formation of native bacteriorhodopsin upon its removal indicate that in purple membranes, the dark‐adapted chromophore is much less reactive than its light‐adapted counterpart. Lipid‐soluble molecules thus have a lower accessibility to the dark‐adapted chromophore.In addition, activity of the 480 nm bacteriorhodopsin was investigated. Flash and steady‐state photolysis experiments reveal that this blue shifted chromophore has full photochemical activity. It has a meta‐intermediate absorbing maximally at 380 nm. The photocycle ofBR–480 is mainly characterized by a slow decay of the “O” intermediate, enabling the direct observation of the branching reaction between the “M” intermediate and

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02698.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Abstract—June yellows (J‐y) of strawberry (Fragaria) is an inheritable condition for which no causal pathogen has been demonstrated. Spectroscopic analysis of intact leaf lamina was applied to strawberry leaves with J‐y. The spectra were analyzed by fourth derivative technique. Differences were found between asymptomatic and affected leaves with respect to chlorophyll‐protein complexes. Affected leaves show spectra consistent with loss of certain chlorophyll‐a‐proteins (Ca). Distinct types of effects are found. In one type Ca684 decreases, in another Ca693 is diminished. Studies of strawberry clone pedigree suggest that Ca684 losses are observed in clones with Howard 17 parentage, and Ca693 losses in clones with Aberdeen parentage. One clone with both Howard 17 and Aberdeen parentage had a spectra consistent with diminished Ca684 and Ca693. The simplest explanation of the data is that J‐y results from several different types of genetic lesions on different Ca. Some viral infection effects on Caspectra are a

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1988.tb02699.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY