摘要:

AbstractThe chemiluminescent autoxidation of over fifty indoles has been measured in dimethyl sulfoxide (DMSO). The 3‐alkylindole derivatives represent the brightest and most efficient members of this group.The chemiluminescence yield (per mole) of skatole is (1·5 ± 0·6) × 10‐3. The chemiluminescence spectrum of skatole is identical with the fluorescence spectrum of o‐formamidoacetophenone in the same environment Similar results for 2,3‐dimethylindole lead to the identification of the acylamide anion as the emitter in indole chemiluminescence. A peroxide ring cleavage excitation mechanism

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb07403.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractEvidence for the existence of a reactive triplet excited state of lumiflavin has been obtained by the flash‐photolysis technique. The triplet state is formed in high yield on the irradiation of flavin solutions in water or chloroform by visible light, and it has been demonstrated that it can transfer its energy to a second molecular species. The flavin‐sensitised oxidation of two purine nucleotides, adenylic and guanylic acids, has been studied by flash‐photolysis and by long‐term irradiation, and the results suggest a triplet‐triplet mechanism for the transfer of energy from the excited flavin to the nucleotide.Approximate absorption spectra of the triplet state and of a semiquinone of the flavin have been calculated from the complex transient absorption curves observed on flashing the flavin solution. The triplet decays by a first‐order process wherek1= 1·1 × 10‐3. The chemiluminescence spectrum of skatole is identical with the fluorescence spectrum of o‐formamidoacetophenone in the same environment Similar results for 2,3‐dimethylindole lead to the identification of the acylamide anion as the emitter in indole chemiluminescence. A peroxide ring cleavage excitation mechanism is proposed. 104sec‐1and the semiquinone by a second‐order process wherek2= 0·75 × 1091.m‐1sec‐1. The rate constants and extinction coefficients obtained enable decay curves to be calculated which fit satisfactorily those measured wit

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb07404.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractThe known inverse square lawS= 1/(1+CD)2, relating survival of transforming activitySto ultraviolet (u.v.) doseD, Cbeing a constant, fails for two linked‐double genetic markers inH. influenzae.For these double markers the law isS= 1/(1+CD)4, both for u.v. and nitrous acid inactivation. A theoretical model which predicts the inverse square law for singles also predicts the inverse fourth power law for linked doubles, if the possibility of an even number (>0) of genetic recombinations between the markers is allowed for. However, it can be shown rather generally that other models, not specified in exact detail, can lead to the same inverse square law for single markers, and thus to the inverse fourth power law for sufficiently separated linked‐doubles. Ability to predict these laws is not, therefore, strong evidence for the validity of any one model. For all these models, the mean number of damaging lesions per unit length of DNA is directly proportional to dose, making (√(1/S)–1) for single markers and (√(1/S)–1) for loosely linked‐doubles a reasonable biological measure of inactivating dama

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb07405.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractIn mixed monolayers with purified chloroplast glycolipids and other colorless lipids, chlorophyllafluorescence exhibits a decrease in quantum efficiency with increasing chlorophyll concentration. The fluorescence, which is strongly polarized in dilute films, becomes progressively depolarized as the area fraction of chlorophyll increases, and it is completely depolarized in a pure chlorophyllamonolayer. The observed behavior is consistent with an inductive resonance mechanism of energy transfer among the chlorophyll molecules with a critical transfer distance of 20–90 Å, depending on the model chosen for the energy transfer mechanism.The purified glycolipids–mono‐and digalactosyl diglycerides and sulfoquinovodiglyceride–separately form stable, compressible monolayers of the liquid‐expanded type on an aqueous subphase and in an atompshere of nitrogen. At maximum compression the three glycolipids occupy areas of 55, 80 and 47 A2‐molecule‐1, respectively, in the monolayer. Mixed monolayers of chlorophyllawith, separately, the monogalactolipid and the sulfolipid behave upon compression as two‐dimensional solutions. The fluorescence polarization at high chlorophyll concentrations in mixed monolayers indicates that several of the lipid diluents facilitate local ordering of the p

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb07406.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractThe dye (F)*sensitized photooxidation ofp‐diaminotoluene (RH2) was examined by flash‐spectroscopy and the mechanism was elucidated. The first chemical reaction is the generation of two free radicals from the triplet dye and the hydrogen donor. These radicals may react in several ways without oxygen:or additionally with oxygen:The connection of this mechanism with photodynamic action is discus

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb07407.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractThe action of ultra violet rays of 260 nm on aqueous solutions of bases, nucleosides and nucleotides of DNA at 77°K is studied by electron spin resonance. It is shown that the free radicals observed are similar, with a few noteworthy exceptions to those induced by X‐rays, under the same conditions of temperature, in the solid state. Contrary to what might be excepted on the basis of the results obtained by X‐rays, the variation in the yield in paramagnetic centres in each sequence studied does not seem to be impor

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb07408.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractA study has been made of the emission spectra at 77°K from polyA, polyU, polyC, their complexes, and from native and heat‐denatured DNA in buffered aqueous solutions containing 0·25 per cent glucose: no emission was observed from these polynucleotides at room temperature. The spectra differed from those obtained in the polyalcoholic glasses used by other workers. The principal differences between the emission spectra of polyAand adenosine at pH 7 in a water‐glucose mixture were: (a) a decrease in bothP/Fand the overall intensity in polyA; (b) absence of the structure normally found in adenosine phosphorescence; and (c) appearance of a new short‐lived component in the phosphorescence decay. Further changes in the emission characteristics (e.g. the increase ofP/F, the proportional increase of the short‐lived component in the phosphorescence decay) from polyAwere observed at pH 5. These can not be explained solely by protonization of adenosine residues, but rather appear to depend upon exciton interactions of the most intense π–π* transition in double‐stranded polyA.and perturbation of the lowest‐lying emitting band. When polyAor polyCis complexed with polyUor polyIthe luminescence intensity decreases in two‐strand complexes and is completely quenched in poly (A + 2U), poly (A+2I) and poly (C++I); no emission was observed from either, single‐strand polyIor polyU.Identical emission patterns were obtained from native and heat‐denatured samples of DNA. The comparison of polynucleotide emission spectra in the water‐glucose medium with those obtained from polyalcoholic glasses leads to the conclusion that the emission spectra depend most critically upon the relative proportions of base‐solvent and base‐base interactions in each environment: the possible importance of proton tunneling and/or triplet‐triplet transfer

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb07409.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb07410.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb07411.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1968.tb07412.x

出版商:Blackwell Publishing Ltd    

年代:1968

数据来源: WILEY