ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1963.tb08122.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1963.tb08123.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

Abstract—Observations of the two light induced EPR resonances in intact cells ofChlamy domonas reinhardiare presented. An action spectrum for the amplitude of the narrow, rapidly‐decayingRsignal made with dilute suspensions has a peak at 680mµ, lending support to the theory that this signal is due to chlorophylla. The decay mechanism for these spins apparently involves the oxygen‐producing system, since factors attenuating this activity enhance theRsignal, and in some cases decrease or abolish the broad, slowly‐decaying S signal. It is pro posed that this latter resonance can be attributed to the seniiquinone of plastoquinone which may be maintained in n paramagnetic state by means of light energy absorbed by priiiiary or accessory

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1963.tb08124.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

Abstract—Suspensioris of aerobic and anaerobic yeast were subjected to ultraviolet radiation (principally 254mµ) under closely comparable experimental conditions, and changes in the level and in the temperature dependence of their catalase activity were determined. Qualita tively, the effects of U.V. on the enzyme of the anaerobic cells were similar to those on that of the aerobic cells. The effect of U.V. on the anaerobic catalase differed from that on the aerobic enzyme in the following respects: I, a considerably greater dose of U.V. was necessary in order to attain the maximum activity and the minimum activation energy of the enzyme‐substrate system; 2, a far greater dose was required before appreciable photoinactivation of the maxi mally active enzyme occurred; 3, photoinactivation proceeded at less than one‐half the rate; 4, the u.v.‐induced increase in the catalase activity of the suspension was virtually complete before appreciable reduction in activation energy occured. The first three of these differences were interpreted in terms of a model, which pictures the anaerohic catalase as being tightly bound to an intracellular chromopho

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1963.tb08125.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

Abstract—The role of carotenoids in protecting a photochromogenic Mycobacterium has been investigated. Bacteria previously induced to synthesize carotenoids by low intensity white light are not killed by high intensity white light while uninduced (carotenoid‐free bacteria) are. If high intensity irradiation with white light is carried out at O°, carotenoids still protect these organisms although at a reduced level. This finding is taken to mean that carotenoids can protect these organisnis from photodynamic death by shading photosensitizing pigm

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1963.tb08126.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

Abstract—>The inactivation of the enzymes chymotrypsin, lysozyme, ribonuclease, and trypsin by ultraviolet light can be accounted for quantitatively by summing the products of (1) the probability that light is absorbed by a given amino acid residue, the molecular extinc tion coefficient, and (2) the probability that absorbed light induces a chemical change in the residue, the quantum yield for the residue. The principal residues involved are cystyl and tryptophanyl. Peptide bond rupture is not important. Energy transfer among chromophores within molecules of enzymes need not be invoked in order to account for photochemical inactivation.Quantum yields for the destruction of a number of amino acids at 2537 A have been measure

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1963.tb08127.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

Abstract—The isolation of a mutant, strain PM‐9, ofRhodopseudonionus spheroideswith an abnormal complement of carotenoid pigments is described.PM‐9 accumulates phytoene, phytofluene, ζ‐carotene and neurosporene. Semi‐aerobic cultures form more ζ‐carotene and neurosporene relative to total carotenoids than do photo‐synthetic cultures.PM‐9 is killed on exposure to light and oxygen.By making use of the effect of oxygen on the nature of the carotenoids in PM‐9, we have shown that these pigments do not directly influence thein vivospectrum of bacteriochlorophyll.Diphenylamine inhibits the synthesis of coloured carotenoids inRhodopseudonionos gelatinosabut does not change the bacterioc

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1963.tb08128.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

Abstract—Ultraviolet irradiation (2537 Å) of 2,6‐dimethyl‐4‐aminopyrimidine (I) results in an intramolecular rearrangement with the formation, either in aqueous or anyhdrous medium, of only one photoproduct, 2‐amino‐3‐cyanopent‐2‐enemine (II), in quantitative yield. The quantum yield for this reaction is 0.043 einsteins/mole.Deamination of II gives, quantitatively, 2‐amino‐3‐cyanopent‐2‐en‐4‐one (III) and this, in turn, may be deaminated to give, quantitatively, 3‐cyanopent‐2‐en‐2‐01‐4‐0ne (cyanoacetyl‐acetone, IV). Identification of II was achieved initially through isolation of III and IV. Some of the chemical and physico‐chemical properties of these compounds are reported, as well as methods for obtaining all of them on a preparative scale.The mono‐protonated form of I also gives II on irradiation, but in lower quantum yield, 7.3times108einsteins/mole. Irradiation of the doubly protonated form of I in strongly acid medium leads directly to the formation of a mixture of II, III and IV, with approxi mately the same quantum yield.The possible mechanisms for the foregoing photochemical reactions are discussed and their significance related to the photochemistry of 4‐aminopyrimidines in general

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1963.tb08129.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

Abstract—The sensitivity ofHemophilus influenzaetransforming DNA to monochromatic ultraviolet radiation has been determined with and without maximum photoreactivation. The fraction of ultraviolet damage which is photoreactivable (the photoreactivable sector) is large and varies with the wavelengths of the inactivating radiation, decreasing at the extremes of the ultraviolet spectrum. Equating photoreactivable damage with thymine dimer damage, we may interpret the wavelength dependence of photoreactivability and the spectrum for non‐photo‐reactivable damage in terms of the absorption spectra of thymidine and cytosine deoxyriboside. The data suggest that cytosine deoxyriboside alteration is important in non‐photoreactivable biological

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1963.tb08130.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY

摘要:

Abstract—The effect of wave‐length of light on leaf expansion inTropaeolum majus‘Double Orange Gleam’ andPisurn sativum‘Meteor’ has been studied. In both species leaf growth is strongly promoted by light.Increasing the daily duration of exposure to light increased leaf expansion inTropueolumin both blue and red wave‐bands over a range of light intensities. InPisuma similar effect of ail increase in duration of irradiation was found over the whole range of intensities used for blue light but only at the highest intensity for red light: at the two lower intensities in red an increase in duration of the light treatment beyond 1 hr did not increase leaf expansion.In both species a period of 4 hr of blue followed by 4 hr of red promoted leaf growth more than 4 hr of red followed by 4 hr of blue. The effect of a 4 hr period of red light was largely prevented when it was followed by far‐red; the effect of 4 hr of blue light, on the other hand, was not affected by subsequent exposure to far‐red.It is concluded that leaf growth inPisumandTropaeolumis dependent not only on the ‘low‐energy’ red/far‐red reversible reaction but also on one or more ‘h

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1963.tb08131.x

出版商:Blackwell Publishing Ltd    

年代:1963

数据来源: WILEY