ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1965.tb05731.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

Abstract—The thermoluminescence of polycrystalline L‐tyrosine kept at 77°K during irradiation by U.V. light has been investigated. On the basis of action spectra, emission spectra, and decay kinetics, a phenomenological model is proposed in which the final radiative transition is from the lowest triplet to the ground singlet state of the molecule. The role of metal ions in trace amounts, various gases in contact with the sample and a bleaching effect by white light were also stu

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1965.tb05732.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1965.tb05733.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

Abstract—The paper presents ideas according to which the primary photochemical reaction of chlorophyll and its analogs can be either photooxidation or photoreduction of the pigment sensitizer depending on the reaction conditions. The factors determining the course of the process of photosensitization comprise the nature and state of the pigment and participating reagents, the nature and reaction of the medium, concentration of the oxidant and reductant, their ability to form complexes with the pigment, etc.The paper presents the results of simple kinetic investigations in which, by means of changing pH of the medium, conditions were created favouring either the primary photo‐oxidation or the primary photoreduction of the pigment‐sensitizer. These results, as well as the data of experiments on the changes in reagents' concentration show the reality of the above mentioned concepts.Considerations are presented on the possibility of photochemical interaction of two chlorophyll molecules in vivo during the photosensitization of photosynt

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1965.tb05734.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

Abstract—Chlorophyllain aqueous hexane solutions has two fluorescence peaks, two fluorescence excitation peaks in the blue, and two fluorescence excitation peaks in the red. One of these set of peaks (excitation 2.34μ‐1and 1.52μ‐1, fluorescence 1–50μ‐1) is identical with those found in methanol solutions of chlorophyllaand is assigned to an unaggregated species, while the other set of peaks (excitation 2.44μ‐1 and 1.475μ‐l, fluorescence 1.48μ‐l) is assigned to a species aggregated in the presence of water. The spectral shifts occurring in the aggregate follow the selection rules obtained by McRae and Kasha for a linear stack of parallel dye molecules. The sharply increased overlap of absorption and fluorescence leads to resonance fluorescence in the aggregate. The resonance fluorescence is demons

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1965.tb05735.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

Abstract—A new method of using hydroxylamine as the reagent was developed to determine the concentrations of chlorophylls a andbin plant extracts accurately and sensitively. The method is based on the principle that hydroxylamine reacts in a short time with the aldehyde group of chlorophyllbin 95 per cent methanol at pH 5.8 to afford a derivative having a red band similar in position to the red band of chlorophylla, while the spectrum of chlorophyllais unaffected by the treatment with hydroxylamine. The method includes the measurements of absorbanlce for the mixture of a plant extract with hydroxylamine and for the reagent blank at a single wavelength, 666 mμ, and the concentrations of chlorophylls a andbare calculated from the absorbance value for the reagent blank and the increment of absorbance due to the reaction. By measuring this increment directly by difference photometry, one can determine a low concentration of chlorophyllbrelative to chlorophylla. The contents of chlorophylls in matured and etiolated leaves were determined by the method, and the errors included in this method were shown to be smaller than those in a commonly used technique including the measurements at two different wavelengt

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1965.tb05736.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

Abstract—The action spectrum for inactivation of aRhizobiurnbacteriophage by U.V. radiation follows the shape of the absorption spectrum of DNA between the wave‐lengths of 240 and 290 mμ (where inactivation probably reflects damage to the nucleic acid only), and deviates sharply upwards at wave‐lengths shorter than 240 mμ (where inactivation may depend on damage to both the nucleic acid, and protein of the phage). The rate of inactivation follows first order kinetics approximately at all wave‐lengths tested. Infectivity of the phage is halved when each mg of the phage nucleic acid has absorbed about 0 08 J of radiation energy at any wave‐length between 240 and 290 mμ.The bacteriopharge can be photoreactivated after inactivation at any wave‐length between 230 and 290 mμ, but less so after inactivation at 230 mμ than at any wave‐length above 240 mμ. No evidence was found to suggest that dimerization of thymine residues of the phage‐DNA plays any part in the mechanism of inactivation of the bacterioph

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1965.tb05737.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

Abstract—Atrainof tobacco necrosis virus (TNV) and infective nucleic acid isolated from it (TNV‐RNA) are equally susceptible to inactivation by U.V. radiation at all wave‐lengths tested (230‐290 mμ) and can be photoreactivated to the same extent by exposing inoculated host plants to daylight. The shape of the action spectrum for inactivation by U.V. of TNV and of TNV‐RNA follows that of the absorption spectrum of TNV‐RNA. Thus, unlike the RNA of tobacco mosaic virus, the RNA of TNV behaves in all these respects in the same way irrespective of whether it is inside or outside the virus particle. To inactivate TNV or TNV‐RNA to 50 per cent of their original infectivities, each mg of RNA must absorb about 0.27 joules of radiation energy of any wave‐length between 230 and 290 mp, which corresponds to a quantum yield of about 0.6

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1965.tb05738.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

Abstract—An attemlpt was made to localize the site of photoinhibition of photosynthesis by measuring the decay of various chloroplast reactions after exposure to very strong light. A11 substrate reductions coupled to oxygen evolution as well as photophosphorylation mediated by PMS, proved equally sensitive to photoinhibition. Reactions involving only the long wave photosystem, such as TPN reduction with ascorbate as electron donor and photooxidation of cytochromec by detergent‐treated chloroplasts were sensitive to a lower degree.Photoinhibition irreversibly annihilated the ‘variable’ fraction of fluorescence emission —it decreased the steady state yield 2‐3 fold and abolished the slow rise of the emission at the onset of illurnination.It is concluded that the primary site of light inactivation is in, or close to, the trapping centers of the oxygen evolving step of photosynthesis. Pre‐illumination leaves these traps in a state capable of draining light from sensitizing pigments but unable to perform useful p

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1965.tb05739.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY

摘要:

Abstract—Kinetic data are reported for the thermal decay of colored transients formed by U.V. irradiation of aqueous solutions of 2‐nitrotoluene. The transients display an acid‐base equilibrium with a pK value of 3.7. The decay is catalyzed by acids and the following rate constants in liter sec‐lmole‐1were evaluated for the base form of the transient reacting with an acid at 30.0°C: 3.5 × 10‐3(H2O), 2.6×103(CH3COOH), 4.7×104(+NH3CH2COOH)

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1965.tb05740.x

出版商:Blackwell Publishing Ltd    

年代:1965

数据来源: WILEY