摘要:

Abstract—Octaethylporphinato‐magnesium (MgOEP) has been photooxygenated in quantitative yield to a brown compound with its main absorption peaks at 825 and 408 nm. The product has been isolated and evidence suggests that it is 4‐formyl‐5‐oxa‐octaethylporphinato‐magnesiumII. IIis very labile to hydrolysis, the main isolated decomposition product being 1, γ‐dioxo‐8‘‐formyl‐octaethyl violinIII.The absorption, i.r.,PMRand mass spectra ofIIandIIIare reported and possible paths to their

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1971.tb06140.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Abstract—A pyrimidine adduct, 6‐4‘‐[pyrimidine‐2’‐one] thymine (PO‐T)‡, observed in DNA hydrolysates of 254‐nm ultraviolet (u.v.) irradiated conidia ofStreptomyces coelicolor, increases linearly with u.v. dose up to 2 × 105ergs/mm2. Yields of thymine dimer (T○) and uracil‐thymine dimer (U○) level off at much lower doses. Initial relative rates of formation of these u.v. photoproducts are: 1:1.3:4.8 for PO‐T, T○ and U○, respectively. Similar results were obtained with aStreptomyces griseusmutant, PHR‐1.An equation is derived to estimate the ratio of the amount of PO‐T to the total amount of thymine‐derived photoproducts at low (biological) u.v. doses. The observed PO‐T fractions compare well with the calculated values.Rapid photolysis of the precursor of PO‐T was observed by post‐u. v. treatment at 313 nm of conidia ofS. coelicolorand ofS. griseusPHR‐1. The photolysis was much slower at 365 nm and did not occur at all at 405 nm. Pyrimidine dimers were not appreciably affected by post‐u. v. treatment at the above wavelengths in theseStreptomycesstrains. Both of these strains are phenotypically photoreactivation‐deficient, and the present results indicate that they do not possess active photoreactivating enzyme.In earlier papers[3,4,5], the pyrimidine adduct found in acid hydrolysates of DNA was loosely referred to as “uracil‐thymine adduct (U‐T adduct)”. Such terminology is not strictly correct. The pyrimidine adduct in acid hydrolysates is PO‐T (sometimes called P2B), which could theoretically result from removal of ammonia from

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1971.tb06141.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Abstract—An investigation of the methylene blue sensitized oxidation of isolated nucleotides has been carried out, based on the behaviour of the excited dye molecule in long‐term irradiation and flash photolysis experiments. It was necessary first to establish the effect of the phosphate buffer upon the triplet excited state of the dye and the consequent effect upon its photo‐fading. The buffer has a salt effect which accelerates the protonation of the dye triplet, and also the photoreduction of the dye which takes place through the resulting protonated triplet. Xanthosine monophosphate (XMP), which is the nucleotide most sensitive to the photodynamic action of methylene blue, is also effective in reducing the triplet of the dye, while other nucleotides which are resistant to photooxidation do not act as reducing agents. The quantum yield of the sensitized oxidation of XMP was found to correspond to that of the anaerobic photo‐reduction of methylene blue in its presence, which leads to the conclusion that the primary step of the photooxidation is electron or hydrogen abstraction from the nucleotide by the triplet excited methylene blue m

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1971.tb06142.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Abstract—The oxidation of purpurogalline (PPG) by alkaline solution of H2O2pH 9–11 at 298°K is accompanied by chemiluminescence (CL) in the spectral range 400–600 nm with the maximum at 500 nm and quantum yield about 10‐6. The optimal concentrations of reactants with respect to maximal intensity are: 2 × 10‐4MPPG, 10‐2MNaOH, 1MH2O2. Activation energy calculated from the maximum intensity of CL is 8.1×0.4 kcal/mole. Light emission occurs only when OH‐groups of the phenolic ring of PPG undergo oxidation and the blue anion ofo‐PPG‐quinone is formed. The rate that determines step in the reaction associated with luminescence is the nucleophilic attack of OOH‐ion on the blue anion ofo‐PPG‐quinone. In this exergonic step (‐ΔH = 63 to 230kcal/mole) theo‐ and/orp‐quinone ring is opened and carbonyl derivatives of α‐tropolone are produced. They display fluorescence in the region 400–600 nm. The fluorescence spectrum of the reaction mixture after oxidation of PPG is very close to that of CL. It is likely that carbonyl derivat

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1971.tb06143.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Abstract—When rhodopsin is associated with membrane particles, phospholipid may be involved in maintaining a preferred conformation of the opsin and the asymmetric structure of the chromophore of rhodopsi

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1971.tb06144.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

Abstract—The Uranyl acetate sensitized killing ofEscherichia coliK‐12 by a light source approximating sunlight in both intensity and wavelength distribution is demonstrated to occur at a concentration of 5.0 × 10O‐4Muranyl acetate (pH 7.0). The photosensitized killing was evident after 150 min and almost complete within 320 min. Auxotrophic mutants were isolated from cultures incubated in both light and dark for 160 min at this concentration of uranyl acetate. Binding of UO22+toE. coliis shown to occur with 82% of the UO22+ions in a 5 × 10‐4Msolution (pH 7.0) being bound to the cell wall. In the dark as well as at other pH values the extent of binding was much less. Most of the binding occurred in a time less than 30 min. The observation of rapid binding but delayed photosensitization is attributed to the necessity for penetration of uranyl ions into the cells' interior to effect photosens

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1971.tb06145.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1971.tb06146.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1971.tb06147.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1971.tb06148.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1971.tb06149.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY