摘要:

Abstract—The photodynamic action of proflavine on the amino acids cystine, rnethionine, tyrosine, histidine, tryptophan and related peptides was tested in anhydrous formic and acetic acids. Only rnethionine and tryptophan were found to be photooxidized: the former, whether free or bound in a polypeptide chain, is quantitatively converted to methioninesulphoxide; the latter, when free, is fragmented to several compounds, which may be divided into two main classes: melanines and kynurenine derivatives.Whereas masking the carboxyl group of tryptophan has no effect on the photooxidation products, N‐substituted derivatives of tryptophan are converted in high yields to the corre‐sponding kynurenine compounds. The possible applications of the method to biologically active polypeptides are disc

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb09650.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Abstract—When glycylphenylalanine and phenylalanylglycine were irradiated on thin layers of silica gel G, peptide bond fission, diketopiperazine formation and deamination occured. The products were identified by thin‐layer chromatogrpahy on thesameplate, procedure which enables very small quantities of material to be irradia

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb09651.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Abstract—The ocellar pigment ofSpirocodon saltatrixextractable with phosphate buffer and acidified methanol was considered to be a substance closely related to or identical with xanthommatin, from its behaviour on paper and thin‐layer chromatography and from the position of the absorption maxima in the ultra‐violet and visible ranges of the spectrum in various solvents. The infra‐red spectrum also supported this view. The pigment extracted with cetyltrimethylammonium bromide was gel‐filtered through a column of Sephadex G 100. The pigment was eluted fairly quickly and the elution pattern was narrow, indicating that the eluted pigment is large as well as homogeneous in its molecular size. The gel‐filtered pigments from medusan ocelli and fly ommatidia underwent an almost indentical photoreduction under anaerobic

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb09652.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Abstract—The Emerson effect is demonstrated in the ferricyanide Hill reaction when the rates of steady‐state oxygen evolution are measured in spinach chlorplast fragments exposed to red (650 nm) and far‐red (700 nm) light of high but not saturating intensity. However, at very low light intensity, the Emerson effect could not be observed. These experiments suggest that ferricyanide can be reduced at two sites. At low light intensity, the rate at one site predominates and at this site one photochemical system is active. At high light intensity, however, the action at a site that is dependent on the cooperation of two photochemical systems predominates.The action spectra of the ferricyanide Hill reaction measured in the presence of an excess of 650 nm or in the excess of 700 nm light show two peaks: one at 650 nm due to chlorophyllband the other around 675 nm due to chlorophylla. The ratio of chlorophyllato chlorophyllbpeaks is about 1.4 when 650 nm background light is used; the same ratio is about 0.7 with 700 nm background light. The two pigment systems seem to contain both chlorophyllaand chlorophyllbbut in different propor

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb09653.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Abstract—Several flavoproteins are known to undergo photoactivated reduction by EDTA. However, the effects of visible light on the non‐heme iron containing flavoproteins have not been characterized previously. Dihydroorotate dehydrogenase was studied as an example of this class of enzymes. Interaction with visible light was found to be complex.Under low intensity photoirradiation of long duration the anaerobic enzyme was partially reduced to a form having increased absorbance at 630 nm. Similar absorbance changes have been correlated with semiquinone species. However, the irradiated enzyme exhibited irreversible changes in catalytic function. Activity with NADH was greatly reduced and a portion of the flavin coenzyme content was labilized. Fluorescence intensity of the enzyme was markedly increased by exposure to light, confirming partial degradation of a catalytic site.Isothermal irradiation with light of high intensity in the range 330–600 nm caused the enzyme to be reduced rapidly. Spectroscopic changes were observed which persisted after reoxidation of flavins. Intense new absorbance maxima between 310 and 330 nm together with a large decrase in absorbance at 450 nm were noted. Under controlled conditions approximately half of the total flavin and practically all of the bound FAD were labilized. NADH oxidase activity and NADH linked reduction of orotate were selectively lost. The correlation between FAD labilization and loss of activity strengthens the hypothesis that FAD represents the site of activity with NADH. Activity with NADH was partially restored by incubation of the irradiated enzyme with FAD o

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb09654.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Abstract—Kinetics and quantum yields of light‐induced oxidation of P700 and thef‐type cytochrome were measured in marine red algae from absorbance changes in the region 420, 435 and 705 nm. The quantum yield for cytochrome oxidation inIridaea splendensandSchizymenia pacificawas 0.5‐0.65 in far‐red light, at 20d̀ and at 0d̀C.Oxidation rates of P700 measured when varying amounts of cytochrome were in the oxidized state indicated that a reaction center of system 1 inIridaeacontains 1 P700 and 4 cytochrome molecules. Oxidized P700 only accumulates when all 4 cytochromes are oxidized. The rate of photochemistry of system 1, measured as the sum of the rates of P700 and cytochrome oxidation, was independent of the oxidation level of cytochrome, but decreased with accumulation of oxidized P700. This decrease was less than proportional to the fraction of P700 that was in the oxidized state, which suggested transfer of excitation energy between reaction centers.The quantum yield for cytochrome oxidation after dark periods of 1 min or more was only about 0.2. This effect was tentatively ascribed to a dark reduction of the cytochrome coupled to phos

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb09655.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Abstract—Changes in light absorption in the region 450–540 nm were observed upon illumination of the red algaeIridaea splendens, Schizymenia pacificaandPorphyra perforataand the brown algaPheostrophion irregulare. The difference spectra of these changes inIridaeaandSchizymeniashowed maxima and minima at about 465, 480, 495, 515 nm. The spectra were similar to difference spectra earlier observed in photosynthetic bacteria, and the location of the maxima and minima suggested a shift towards longer wavelength of a compound with absorption maxima at about 440, 470, and 500 nm, probably a carotenoid. Similar, but more distorted difference spectra were observed in the other algae. Time courses and size of the signals induced by light of different wavelengths suggest that excitation of both photosynthetic pigment systems causes a shift in carotenoid absorption, with kinetics which appear to be similar to those of the well‐known change at 515 nm in green p

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb09656.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

摘要:

Abstract—Brief high temperature treatments, applied early in the pregerminative period to radiation‐requiring seeds of lettuce, inhibited both dark and radiation‐induced germination. The inhibition increased with increasing incubation temperature. There was little difference in the germination percentage whether the inductive irradiation was applied before or after the high temperature treatment. When the high temperature treatment preceded induction, there was an increase in the radiation dosage required for maximum germination. These findings are interpreted in terms of lability of physiologically active phytochrome to higher tempera

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb09657.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb09658.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1967.tb09659.x

出版商:Blackwell Publishing Ltd    

年代:1967

数据来源: WILEY