摘要:

Abstract—The physical units most commonly used in photometry have limited value outside the field of illumination engineering. They tend also to conceal rather than display the physical concept of radiation as understood at present.Only by making the concepts of quantum theory accessible by a fundamental change of units, can those concepts make their full contribution to photobiology.The paper suggests adoption of the quantum as the unit of intensity and the electron volt as the specification of spectral quality, thus bringing the nomenclature of photometry into line with other branches of radiation physics. A start is made with definition of some of the essential derived units, source intensity, irradiation, and flu

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb08774.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Abstract—Zinc porphin is photoreduced to zinc chlorin through an intermediate dihydroporphin (PH2) by ascorbic acid in ethanol containing 1% to 10% (v/v) piperidine. Under the same conditions zinc chlorin is more slowly photoreduced to zinc tetrahydroporphin. The reactions leading to chlorin are photosensitized by the product chlorin and so are autocatalytic in red light. Quantum yields for these reactions range up to 0.05.Other aliphatic amines catalyze these reactions, but at rates peculiar to the amine. The immediate product of reduction of zinc porphin, PH2, is distinguished by an intense band at 437 nm; it reverts to porphin in the dark in the presence of oxygen or dehydroascorbic acid. Its conversion to chlorin is effected by light absorbed by porphin or chlorin, but not by light absorbed by PH2itself. A suggested structure for PH2, compatible with the observed reactions, has added hydrogens on one bridge carbon and one β‐pyrrole carbon. The possibility of an analogy between these reactions and the biochemical conversion of protochlorophyll to chlorophyll is discu

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb08775.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Abstract—In an aqueous buffered solution of TpC monochromatic ultraviolet light lowers the absorption peak to approximately half its value, characterized by a photostationary state. The quantum yield for this photochemical decomposition is independent of the wavelength between 2400 and 3000 Å.At pH 7 the quantum yield amounts to 0.006, at pH 2 to 0.002, respectively. At neutral pH about 85 per cent of the photochemical transformation produced are reversible in the dark, at pH 2 only 40 per cent. Three photoproducts, being non‐reversible in the dark, were isolated electrophoretically and characterized by their absorption spectra. These three compounds have an absorption peak around 2680 Å, one compound has a second absorption maximum at 3120 Å

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb08776.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Abstract—The triplet state of flavin derivatives and d‐amino acid oxidase was observed by electron paramagnetic resonance at 77°K.Flavin triplets (Δm=± 2) originate from the isoalloxazine ring and are resonant at 1560 guass.The half‐life of the FMN triplet in 1NHCl is 15 nisec.This life‐time is prolonged indirectly by the presence of paramagnetic species, such as oxygen or free radicals.The flavin triplet state is pH dependent.In neutral solution the nlaximum triplet yield is obtained and the longest life‐time is observed.The triplet state is affected by intra‐and inter‐molecular complex formation, FAD is partially quenched by indirectly substituted adenine.Tryptophan quenches completely the FMN triplet.The FAD triplet of d‐amino acid oxidase is enhanced but the life‐time is shortened relative to

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb08777.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Abstract—The triplet states of proteins, bovine serum albumin, ovalbumin and d‐amino acid oxidase, were observed by electron paramagnetic resonance at 77°K.The triplet state of aromatic amino acids, tryptophan, tyrosine and phenylalanine was also detected.The protein triplet originates from the tryptophan residues of these proteins.It is suggested that an energy transfer takes place between tyrosine and trypto

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb08778.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Abstract—Quantum yields for dimethylbiacridylium ion chemiluminescence based on the amount of methyl acridone formed by treatment with either H2O2or with xanthine oxidasehypoxanthine in 0.01MNa2CO3at pH 10.4 and at 25°C were found to lie between 0.011 and 0.020 with an average of about 0.016.In mixed solvents containing pyridine and water or alcohol and water the emission spectrum of chemiluminescence of dimethylbiacridylium ions as well as those of diniethylbiacridene and its oxide were found to be identical with or very similar to the fluorescence of methyl acridone in the same solvent.A mechanism involving two successive two equivalent reductions of the diniethylbiacridylium ion to dimethylbiacridan followed by a radical attack and auto‐oxidation leading to a compound which can undergo a reverse aldol type reaction to yield one (or two) molecule of methylacridone and one of a somewhat more reduced form is suggested.The kinetic equation relating maximum intensity of chemiluminescence to dimethylbiacridylium ion, hypoxanthine, xanthine oxidase, H+and O2concentrations was derived from the scheme suggested and found to fit satisfactorily the data obtained from a series of experiments in which the quantum yield was also obta

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb08779.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Abstract—Treatment of etiolated pea seedlings with a short exposure to red light caused a stimulation of growth (size and dry wt production) and carotenoid synthesis during the following 48 hr compared with seedlings kept entirely in darkness.The effect is nullified by a following dose of far red light and thus the phenomenon is probably phytochrome‐controlled.Similar treatment with red light one hour before continuous illumination with white light tended to reduce the lag period for chlorophyll synthesis.Again a following dose of far red light reversed this respo

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb08780.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Abstract—A semiclassical calculation of the ionisation potential of solid polyethylene yields a value of 4.5 eV.A dissolution technique is employed to study the absorption spectrum in the near U.V.The absorption contains both structural and impurity components but there is no edge near 4.5 eV.Neither absorption component is correlated with the carrier trap distribution suggested for the material.It is inferred that the photoconductivity is extrinsi

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb08781.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

摘要:

Abstract—The therrnochemiluminescence of the chloroplasts from normal lettuce seedlings is enhanced by the addition of β carotene but not by chlorophylla.The thermochemiluminescence of chloroplasts from etiolated seedlings is enhanced by neither β carotene nor chlorophylla.A variety of electron donors were substituted for β carotene in the mixtures with chlorophylla.The most active were squalene, β carotene, vitamin A, and nerolidol.The isoprene structure (‐CH2‐CCH3=CH‐CH2‐) appears to be a necessary but not sufficient requirement for energy transfer during thermochemiluminescence.Changes in the absorption spectra indicate that both chlorophyll and carotene are destroyed during thermochem

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb08782.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1964.tb08783.x

出版商:Blackwell Publishing Ltd    

年代:1964

数据来源: WILEY