LIGHT AND pH INDUCED CHANGES IN THE SURFACE PRESSURE-AREA ISOTHERMS OF BACTERIORHODOPSIN

Abstract— Pressure-area isotherms of monolayers of purple membrane fragments were measured at an air-water interface. The pH of the aqueous phase was varied from 2 to 10. Over the pH range 5 to 9 the area/molecule of bacteriorhodopsin was constant and illumination of the film had no effect on the isotherms.
At pH's more acid than 5 and more alkaline than 9, there were large decreases in area/molecule. Under these conditions of extreme pH the monolayer was very sensitive to light. Illumination resulted in irreversible increases in area/molecule.     

THE EFFECT OF LEVULINIC ACID ON THE LIGHT INDUCED DEVELOPMENT OF PHOTOSYSTEM I AND II ACTIVITIES IN GREENING MAIZE LEAVES*

Photosystem I and Photosystem II activities were measured in chloroplasts isolated after 0–20 h illumination from etiolated maize leaves in which chlorophyll synthesis was specifically inhibited by levulinic acid. In control leaves not treated with levulinic acid, Photosystem I activity/chlorophyll developed rapidly during the first 2h in light, then fell off, and reached a constant level after 6h of illumination. In levulinic acid treated leaves, in which chlorophyll accumulation was inhibited up to 60%, a similar initial rise in Photosystem I activity was observed. However, the decrease in activity was much slower and continued for at least 20 h. The development of Photosystem I activity calculated on a leaf fresh weight basis was similar for control leaves or leaves treated with levulinic acid. This indicates that development of Photosystem I activity may not be related to chlorophyll accumulation during greening. Photosystem II activity/chlorophyll in leaves treated with or without levulinic acid increased similarly during the first 6h and then remained constant. Activity of Photosystem II per leaf fresh weight increased linearly, after the first h, for 20 h in the control leaves; in levulinic acid treated leaves this development was reduced by about 60%. Thus, development of Photosystem II activity can be related to chlorophyll accumulation. SDS gel electrophoresis of plastid membranes from control leaves illuminated for 12 h showed the presence of chlorophyll-protein complex I as well as Chl-protein 11; in the case of levulinic acid treated leaves only Chl-protein complex I was detectable, while Chl-protein complex II was markedly reduced.     

BLUE LIGHT INDUCED PHOTOTRANSFORMATION OF PHYTOCHROME IN THE PRESENCE OF FLAVIN*

Abstract— Irradiation of the P_r form of phytochrome in the presence of flavin mononucleotide (FMN) which absorbs the actinic blue light yields P_fr at a rate greater than that in the absence of FMN. The actinic blue light absorbed by FMN enhances the phototransformation of P_r via the energy transfer from the former to the latter. On the other hand, the photoreversion of P_fr was inhibited by the presence of FMN when illuminated with blue light. The lack of photo-enhancement of the reversion of P_r, by blue light suggests that the P_fr chromophore (acceptor) transition dipole is virtually perpendicular to the FMN transition dipole, as the result of a chromophore reorientation in the P_r→P_fr phototransformation. The fact that blue light absorbed by flavin preferentially enhances the forward phototransformation of phytochrome while inhibiting the reversion may have an important implication in the high irradiance responses in plants in terms of a preferential accumulation of P_fr by blue light excitation.     

COMPARISON OF PHOTOTRAP COMPLEXES FROM CHROMATOPHORES OF RHODOSPIRILLUM RUBRUM, RHODOPSEUDOMONAS SPHEROIDES, AND THE R-26 MUTANT OF RHODOPSEUDOMONAS SPHEROIDES*

Abstract— After dissolution of the membrane structure of chromatophores from Rhodospirillum rubrum, Rhodopseudomonas spheroides , and the R-26 mutant of Rhodopseudomonas spheroides , active phototrap complexes from each have been purified by a column electrophoresis procedure. Phospholipids and transition metals were well separated from the phototrap complex in all three systems. The purified R. rubrum phototrap complex retained a full complement of antenna bacteriochlorophyll and carotenoid pigments which had nearly the same absorbance spectra as in the intact cell, and which delivered absorbed light energy to the phototrap with just as high efficiency as in the intact cell. Sodium dodecyl sulfate (SDS) disc gel electrophoresis using Tris buffer showed that these preparations often contained only two prominent polypeptides of 30,000 ± 2000 and 12,000 ± 4000 mol. wt., and a lesser amount of a third polypeptide of 21,000 ± 2000 mol. wt.
The phototrap complexes prepared from the wild type and the R-26 mutant of R. spheroides were similar, in that a partial separation from antenna pigments occurred during column electrophoresis. Both complexes had prominent polypeptides of 24,000 ± 2000 and 21,000 ± 2000 mol. wt., but no polypeptide of 30,000 mol. wt remained after electrophoresis. A third major polypeptide occurred with a mol. wt. of about 12,000 but seemed identifiable with an incompletely separated antenna pigment fraction. The phototrap complex prepared from the R-26 mutant had a typical reaction center spectrum.
In the case of wild type R. spheroides purification, two distinct protein-pigment complexes separated. Although the absorbance of the bacteriochlorophyll and carotenoid pigments were little changed from those of the in vivo system, different polypeptides in the two fractions were observed by SDS disc gel electrophoresis; only one fraction seemed to be intimately related with the phototrap complex.     

INFLUENCE OF LIGHT ON THE EPR-DETECTABLE, ELECTRON TRANSPORT COMPONENTS IN WHOLE CELL RHODOSPIRILLUM RUBRUM

Abstract —The influence of light upon the electron paramagnetic resonance (EPR)-active components of R. rubrum , both in whole cells and in subcellular particle preparations, is presented. In the whole cells, 16 EPR signals can be detected, 11 of which are influenced by illumination of the bacteria. Four of these are also affected by illumination at 77 K. The effects of K₃Fe(CN)₆, Na₂S₂O₄ and heating upon the signals observed in the whole cells are also presented. The whole cells contain several photoinfluenced, EPR-active components that are missing in the subcellular particle preparations. The kinetics of most of the signals in the whole cells are complex, whereas in the subcellular particles the kinetics are generally monotonic. For comparison, some of the EPR signals detected in whole-cell Chromatium D are also presented. The signals observed in these two strains of bacteria differ considerably. A discussion of the possible identities of the R. rubrum signals and speculation as to the role of some of them in the photosynthetic electron transport system are also included.     

A COMPARISON OF DECAY KINETICS OF PHOTO-PRODUCED ABSORBANCE,EPR, AND LUMINESCENCE CHANGES IN CHROMATOPHORES OF RHODOSPIRRILLUM RUBRUM*

–Quantitative comparison of the decay rate for absorbance photochanges in chromatophores of R. rubrum at the major wavelengths of peaks and troughs (280, 365, 385, 433, 605, 763, 790, 810, 850, 865, 890 nm) reveal no major differences under a variety of sample conditions. In addition, the decay kinetics of EPR phtochange at the two environmental potentials used in this study are identical with the absorbance ph;otochange decay. Decay curves for fresh chromatophores, aged chromatophores, and fresh chromatophores at high ionic strength display a variety of half times and curve shapes. All of these data however, may be fit (within 10 per cent) by the equation x=αe^8.2t+βe^0.18t by merely varying the values of α and β. This is interpreted as meaning that any single trapping site may exist in one of two major forms each of which decays following a first order or pseudo-first order reaction. Although the change in decay pattern upon aging is not reversible, that due to high ionic strength is. The time dependencies for two light emission phenomena have been measured as well as their response to the oxidation state of molecules at the trapping site. A major component of long-lived luminescence follows pseudo-second order kinetics with a half time of 38 msec. A very long lived luminescence shows an increse with time which is nearly proportional to the decay of absorbance photochanges.     

EFFECTS OF SHORT PULSES OF BLUE LIGHT ON THE ALKALINIZATION ASSOCIATED WITH THE UPTAKE OF NO3− AND CL− BY THE GREEN ALGA MONORAPHIDIUM BRAUNII AND RELATED ACTION SPECTRA

In Monoraphidium braunii, uptake of NO₃^?, NO₂^? and Cl^? is associated with proton transport and triggered by blue light (BL). Only 10 s after cells able to reduce NO₃^? to NH₄⁺ were irradiated with continuous, low-fluence BL in the presence of NO₃^?, an alkalinization of the medium began and only became interrupted by switching off the BL with a 60–90 s time lag. With 30 s BL pulses, the NO₃^?-dependent alkalinization lasted 3–5 min until it stopped. When the cells were exposed to continuous BL in the presence of Cl^?, the alkalinization also started within 10 s but lasted only 3 min. After that, the pH remained constant and decreased when the BL was switched off. With 30 s BL pulses, the Cl^?-dependent alkalinization lasted 3 min and then decreased to its initial value. The NO₃^?-dependent alkalinization shown by cells unable to reduce NO₃^? to NH₄⁺ was similar to that observed in the presence of Cl^?. These alkalinization rates fit the Bunsen-Roscoe reciprocity law. With 2 s pulses of high-fluence BL, the delay time of the NO₃ - or Cl^?-dependent alkalinizations was only 2 s, one of the fastest BL responses reported so far. The action spectra for Cl^? and NO₃^? uptakes proved to be very similar and matched the absorption spectra of flavins, including the 267 nm peak.     

ON INDUCED PHOTOCHROMISM OF THE C-PHYCOCYANIN CHROMOPHORE: THE ZINC COMPLEX IN MICELLES*

Abstract— Absorption spectra of the chromophore of C-phycocyanin, in its free base form and as its zinc complex, were measured after denaturation with 8 M urea and with a cationic detergent. An acidic and an alkaline form of the zinc complex are distinguished. The acidic form shows photoreversible photochrom-ism, but only when it is embedded in detergent micelles. The photochromism is tentatively ascribed to a direct photoisomerization of the chromophore.     

EFFECT OF UVA AND BLUE LIGHT ON PORPHYRIN BIOSYNTHESIS IN EPIDERMAL CELLS*

Abstract— To study porphyrin biosynthesis in normal human keratinocytes and A431 cells derived from human epidermoid carcinoma, cultured cells were incubated with delta-aminolevulinic acid (ALA), the precursor of porphyrin synthesis, and accumulation of porphyrins was measured spectrofluorometrically. Both human keratinocytes and A431 cells accumulated porphyrins in a time-dependent and a dose-dependent fashion. Protoporphyrin was the predominant porphyrin accumulated by both cell types. Porphyrin accumulation was enhanced by Ca Mg ethylene-diaminetetraacetic acid, a ferrochelatase inhibitor, and the enhancement was reversed by the addition of iron, suggesting the utilization of iron by ferrochelatase. The effect of light on porphyrin accumulation was evaluated by exposing the ALA-loaded A431 cells to ultraviolet-A (UVA) and blue light radiation, followed by continued incubation with ALA for 2–48 h. There was an enhancement of porphyrin accumulation 2–48 h after the radiation as compared with nonirradiated controls. Consistent with this finding, ferrochelatase activity decreased in these cells at 24 h and 48 h. These data demonstrate that human keratinocytes and A431 cells are capable of porphyrin biosynthesis, and that exposure of porphyrin-containing A431 cells to light, which includes the Soret band spectrum, decreases the ferrochelatase activity, which is responsible, at least in part, for the further increase in porphyrin level.     

FLASH PHOTOLYSIS OF SEVERAL AROMATICS BY ULTRAVIOLET LIGHT AND VISIBLE LIGHT IN THE PRESENCE OF EOSIN Y*

Abstract— A flash photolysis investigation was made of the photo-oxidation of aqueous aniline, resorcinol, βnaphthol, p-sulfanilic acid, and p-bromophenol induced by ultraviolet and visible light irradiation in the presence of eosin Y. The transient spectra show that u.v. irradiation generates the hydrated electron (except in p-bromophenol) and the radical products of one-electron oxidation. The initial products of the eosin-sensitized oxidations are the dye semi-quinone and aromatic radicals which coincide with the u.v. photolysis products in at least several cases. The investigation of the reaction kinetics by rapid spectrophotometry with analog computer analysis shows that the aromatics quench the triplet state of eosin and also react with it in a slower electron-transfer process, in competition with ‘dye-dye’ quenching and electron-transfer reactions. The u.v. and dye-sensitized oxidations are discussed in terms of their energetics.     

THE EFFECT OF INHIBITORS AND UNCOUPLERS OF PHOTOSYNTHETIC PHOSPHORYLATION ON THE DELAYED LIGHT EMISSION OF CHLOROPLASTS*

Abstract— Measurements were made of the 3.7 msec delayed light emission of chloroplasts treated with a variety of agents which affect the rate of electron transport (Hill reaction) or photosynthetic phosphorylation. The presence of the electron acceptors ferricyanide or pyocyanine increased delayed light emission. Inhibitors of electron transport (3-(3,4-dichlorophenyl)-1, -1-dimethylurea or 1,10(ortho)-penanthroline) inhibited delayed light emission. The addition of a phosphate acceptor system inhibited delayed light emission. This inhibition was reversed by inhibitors of the phosphorylation reaction, e.g. Dio-9 or phlorizin. From these results it was concluded that the 3.7 msec delayed light emission probably occurs as a result of back reactions of intermediates in the coupled electron transport and photosynthetic phosphorylation systems.     

THE EFFECT OF PROLONGED LIGHT EXPOSURE ON THE EFFECTIVENESS OF PHYTOCHROME IN ANTHOCYANIN SYNTHESIS IN TOMATO SEEDLINGS*

Abstract— The hypocotyl of the tomato ( Lycopersicon esculentum ) seedling synthesizes large amounts of anthocyanin if exposed to prolonged light. Single light pulses are totally ineffective. The involvement of phytochrome can be shown by light pulse treatments following a prolonged light exposure. It is predominantly the action of blue/UV light which leads to a high responsiveness of anthocyanin synthesis towards phytochrome. Moreover, the data suggest a phytochrome-independent action of blue/UV light, in particular of UV-B, on anthocyanin synthesis.     

CYTOTOXIC AND MUTAGENIC EFFECTS OF THE PHOTODYNAMIC ACTION OF CHLOROALUMINUM PHTHALOCYANINE AND VISIBLE LIGHT IN L5178Y CELLS

Abstract The cytotoxic and mutagenic effects of chloroaluminum phthalocyanine (CAPC) plus red light have been measured in strains of L5178Y mouse lymphoma cells which differ in their DNA repair capacities. Strain LY-R, deficient in the excision repair of UV-induced dimers, was found to be relatively more sensitive to the cytotoxic effects of CAPC plus light, whereas strain LY-S, deficienl in the repair of DNA double-strand breaks, was more sensitive than strain LY-R to the mutagenic effects of the treatment. Mutation frequencies were measured in LY-S and LY-R sub-strains which were heterozygous or hemizygous at the thymidine kinase (tk) locus. The mutation frequency at the tk locus induced in the heterozygous strain LY-SI by CAPC plus light was lower than that induced by an equitoxic dose of ionizing radiation but similar to that induced by an equitoxic dose of UVC radiation: The mutation frequency at the F., dose of CAPC plus light was approximately 1100 per 10⁶ surviving cells. The induced frequency in strain LY-S1 was much higher than in either tk+l-heterozygous or ik+10 hemizygous strains of LY-R. The rate and extent of incorporation of CAPC by the LY-R strains was somewhat greater than for strain LY-S1 at early times after CAPC addition, but by the time the cells were irradiated (18 h after CAPC addition) the difference was not great enough to account for the difference in cytotoxicity. It is possible that the cytotoxic and mutagenic lesions differ and that either the quantities of the respective lesions induced or the efficiencies of repair of the respective lesions differ inversely in the two strains. light have been measured in strains of L5178Y mouse lymphoma cells which differ in their DNA repair capacities. Strain LY-R, deficient in the excision repair of UV-induced dimers, was found to be relatively more sensitive to the cytotoxic effects of CAPC plus light, whereas strain LY-S, deficienl in the repair of DNA double-strand breaks, was more sensitive than strain LY-R to the mutagenic effects of the treatment. Mutation frequencies were measured in LY-S and LY-R sub-strains which were heterozygous or hemizygous at the thymidine kinase (tk) locus. The mutation frequency at the tk locus induced in the heterozygous strain LY-SI by CAPC plus light was lower than that induced by an equitoxic dose of ionizing radiation but similar to that induced by an equitoxic dose of UVC radiation: The mutation frequency at the F., dose of CAPC plus light was approximately 1100 per 10⁶ surviving cells. The induced frequency in strain LY-S1 was much higher than in either tk+l-heterozygous or ik+10 hemizygous strains of LY-R. The rate and extent of incorporation of CAPC by the LY-R strains was somewhat greater than for strain LY-S1 at early times after CAPC addition, but by the time the cells were irradiated (18 h after CAPC addition) the difference was not great enough to account for the difference in cytotoxicity. It is possible that the cytotoxic and mutagenic lesions differ and that either the quantities of the respective lesions induced or the efficiencies of repair of the respective lesions differ inversely in the two strains.     

CHARACTERIZATION OF THE RED LIGHT INDUCED REDUCTION OF A PARTICLE ASSOCIATED b-TYPE CYTOCHROME FROM CORN IN THE PRESENCE OF METHYLENE BLUE*

Methylene blue transfers electrons to a membrane-associated b-type cytochrome in particulate fractions from corn coleoptiles. The K_m for methylene blue is less than 1 µM under optimal conditions. This reaction is destroyed by boiling, but not by 7 M urea. Kinetic analyses of the influence of light intensity on cytochrome reduction suggest that a first order photochemical reaction is limiting. Free EDTA may serve as an electron donor in this system at least at high methylene blue and protein concentrations. The photoactivity does not coincide either with mitochondrial or endoplasmic reticulum markers, and may be localized in plasma membrane. There is an estimated 5 times 10^-10 mol photoreducible cytochrome per g coleoptile tissue. Studies on the effect of pH on the reaction in the presence of methylene blue or thionine indicate that dye photoreduction itself is not rate-limiting. Wavelength dependence studies suggest that it is methylene blue monomer and not dimer which mediates the reaction. Although oxygen is apparently required for the reaction, neither superoxide nor excited singlet oxygen appear to be involved. The reaction mechanism is still unknown.     

GENETIC VARIATIONS AND LINOLENIC ACID INDUCED CHANGES IN THE ORIENTATION PATTERN OF CHLOROPHYLL a IN THYLAKOID MEMBRANES

Abstract Orientation pattern of the Q_y absorption and emission dipoles of chlorophyll a were studied in wild type Scenedesmus obliquus and in mutants deficient in chlorophyll b and carotenoids. Fluorescence polarization ratio at –140°C and linear dichroism at 25°C were measured in whole cells and thylakoids aligned in polyacrylamide gel. Unlike normal thylakoids, mutants displayed fluorescence polarization ratios significantly lower than 1.0 and showed a negative LD signal around 672 nm, indicating the tendency of the Q_y dipoles to tilt out from the membrane plane. Such an orientation pattern can also be artificially induced by treating normal thylakoids with linolenic acid.     

THE INFLUENCE OF LIGHT ON THE NON-DIAPAUSE RELATED ASPECTS OF DEVELOPMENT AND REPRODUCTION IN INSECTS

A literature review was undertaken to evaluate the effects of light on larval development and adult reproduction excluding diapause. Shortening or lengthening of larval developmental time, adult emergence, gametogenesis, fecundity and oviposition are all affected by both photoperiod and light quality.     

INDUCTION OF DNA-PROTEIN CROSS-LINKS IN CHINESE HAMSTER CELLS BY THE PHOTODYNAMIC ACTION OF CHLOROALUMINUM PHTHALOCYANINE AND VISIBLE LIGHT

Abstract— Chloroaluminum phthalocyanine (CAPC) is an efficient photosensitizer for the inactivation of Chinese hamster V79 cells. In order to investigate possible molecular mechanisms in the photo-dynamic action of CAPC and visible light, the induction and repair rate of two classes of DNA lesions have been determined, i.e. DNA single-strand breaks and DNA-protein cross-links. In cells pretreated with 1 μ.M CAPC, a fluence of 12 kJ/m² of red light (>600 nm) kills approximately 50% of the cells and induces 3 to 3.5 Gy-equivalents of single-strand breaks. The repair of these breaks was slower than the repair of single-strand breaks induced by -irradiation. The photodynamic action of CAPC also induces a large number of DNA-protein cross-links which, in contrast to -radiation-induced DNA-protein cross-links, do not appear to be repaired during 4 h of post-treatment incubation in fresh medium. These studies suggest that DNA may be an important target for the cytotoxicity of CAPC + red light.     

甲苯基重氮盐及其与冠醚络合物光解活泼自由基的ESR研究

本文以2,3,5,6-四甲基亚硝基苯(ND)和苯亚甲基叔丁基氮氧化物(PBN)作自由基捕捉剂研究了甲苯基重氮盐及共冠醚络合物光解的自由基历程。ESR结果表明光解可产生相应的甲苯基自由基,并能被ND或PBN所捕获。由共ESR谱可得到甲基取代苯环上的甲基质子通过超共轭作用产生的超精细裂分,共裂分值与苯环上相同位置质子与未偶电子间极化偶合作用引起的裂分值相近。即:α_(p-)~H≈α_(P-)~(CH):α_(o-)~H≈α_(o-)~(CH)3;α_(m-)~H≈α_(m-)~(CH)3.同时还存在下列关系式:α_(p-)~H≈α_(o-)~H>α_(m-)~H.