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.     

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.     

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

Abstract— In the presence of methylene blue, red light causes the reduction of a h-type cytochrome in particulate fractions from corn coleoptiles. Two types of difference spectra for the cytochromes in these fractions are presented: (a) red light-minus-dark in the presence of methylene blue, and (b) dithionite-reduced-minus-oxidized. Comparison of these spectra shows that photoexcited methylene blue selectively reduces a b-type cytochrome which constitutes at most only 30% of the total dithionite-reducible cytochrome present in the most active fractions. The photoreducible cytochrome has an alpha band at room temperature near 557 nm. Bleaching of methylene blue precedes cytochrome reduction under appropriate conditions, suggesting that the photoreduced dye is donating an electron to the cytochrome. This electron transfer does not involve a flavin, at least as judged by the absence of light-induced spectral changes attributable to flavins. Preliminary kinetic studies suggest that EDTA provides the pool of electrons for the reaction. The cytochrome cannot be assigned exclusively either to mitochondria or to endoplasmic reticulum, as judged by its sedimentation properties. These results and the current literature are discussed in the context of the hypothesis that this b-type cytochrome may be involved in the photoreception mechanism for blue and uv light in vivo.     

ANALYSIS OF LIGHT-CONTROLLED ANTHOCYANIN FORMATION IN COLEOPTILES OF Zea mays L.: THE ROLE OF UV-B, BLUE, RED AND FAR-RED LIGHT

Abstract— Light-induced anthocyanin formation in Zea mays L. coleoptiles was investigated in seven different varieties of this species. Under the test conditions, four varieties showed practically no response to any waveband used (UV, continuous red and continuous far-red), two responded strongly to both UV and far-red, and one showed a strong response only to far-red. The radiation-sensitive varieties showed, however, only a very weak response to continuous red light. In those varieties sensitive to far-red light, a pretreatment with continuous red light led to a greatly enhanced response to UV or in one case the manifestation of a response to UV that was previously lacking. Further investigations in one radiation-sensitive variety (INRA) showed that the UV response was to UV-B radiation below 350 nm. The UV response, as well as the far-red and blue responses in this variety, showed fluence-rate dependency. Red light was almost ineffective and showed only a very weak fluence-rate dependency.     

STUDIES ON LYSOZYME: EFFECT OF VISIBLE LIGHT ON THE CONFORMATION OF THE ENZYME IN THE PRESENCE OF METHYLENE BLUE

Abstract— Lysozyme undergoes conformational changes when exposed to visible light in the presence of methylene blue. Ultracentrifugation, gel filtration and end group analysis showed that no peptide bond was cleaved. About 30 per cent of the tryptophan residues were, however, modified. The enzymic activity decreased by 50 per cent. The sedimentation coefficient and helical content decreased; the extinction in the u.v. region between 185 to 210 nm increased. The photooxidized enzyme was more susceptible to trypsinolysis than the native enzyme.     

THE BLUE LIGHT GRADIENT IN UNILATERALLY IRRADIATED MAIZE COLEOPTILES: MEASUREMENT WITH A FIBER OPTIC PROBE

Abstract— The blue light (450 nm) gradient was measured with a fiber optic microsensor in etiolated maize coleoptiles that were irradiated unilaterally. Patterns of transmitted and scattered light across the shoot were related to the morphology of the coleoptile and varied greatly between the coleoptile base, mid-region and tip. In the coleoptile base, light was scattered equatorially around the coleoptile sheath so that there was more light on the shaded side of the sheath than in the shaded side of the primary leaves. In the hollow mid-region there were strong reflecting boundaries at the air-coleoptile interfaces, which resulted in step like transitions in the light gradient. In the coleoptile tip, there was a steep, near-linear gradient of blue light, with the greatest amount of light on the irradiated side. There was no evidence that the coleoptile tip acts as a lens or that there are anomalies that result in more light on the shaded than irradiated side. Immediately beneath the irradiated surface, the space irradiance was about twice the fluence rate of the light beam. The magnitude of the light gradient was 4:1 between the irradiated and shaded side of the mid-region and tip and 8:1 for the coleoptile base.     

TEMPERATURE AND MYCOCHROME SYSTEM IN NEAR-UV LIGHT INDUCIBLE AND BLUE LIGHT REVERSIBLE PHOTOINDUCTION OF CONIDIATION IN Alternaria tomato*

Abstract— When dark-grown colonies were exposed to near-UV light, conidiophore formation was induced, and conidia developed during a subsequent dark period. Simultaneous exposure to near-UV and blue light inhibited induction of conidiation. The inductive effect of near-UV light irradiation was greatly enhanced by treating colonies with low temperatures for 4 h during the 2nd-6th hour of incubation in the dark following inductive irradiation: the enhancement was greatest at 21^°C. The extent of inhibition by blue light increased with the temperature between 10 and 28^°C. This diminution by low temperature was greatest when colonies previously kept at a low temperature were exposed to inductive irradiation: the longer the duration between inductive irradiation and temperature treatment, the lower the diminution. Higher fluences of blue light were required to suppress conidial induction at lower temperature. Thus, it is evident that the inductive effect of near-UV light irradiation on conidiation and the suppressive effect of blue light irradiation are each responsive to different temperatures applied at different times.     

可见光光解H2S产H2的研究——Rh2O3/CdS悬浮体系中硫化物水溶液的光解

在半导体粉末悬浮体系光解水研究中,最常用的半导体粉末是CdS和TiO₂。前者光谱响应好,可见光即可激发,但易于光腐蚀;后者稳定性好,但禁带宽,仅紫外光可激发。从不同角度改善这二者的性能,一直为人们所关注。在CdS上沉积RuO₂,并选择适宜的反应以抑制CdS的光腐蚀^[1];应用掺杂的方法,使TiO₂的光谱响应扩展至可见区,已取得进展。     

BLUE and NEAR ULTRAVIOLET REVERSIBLE PHOTOREACTION IN THE INDUCTION OF FUNGAL CONIDIATION

Abstract— The effects of blue light and near UV light on the induction of conidiation in the fungus, Aliernuriu tomato, were investigated. Induction of conidiation was repeatedly controlled by alternating doses of near UV light and blue light. When the final light was near UV, conidiation was induced and conidia developed in the following darkness; when it was blue, the induction of conidiation was suppressed. When conidiation was induced by irradiation with a light mixed with near UV and blue, not only the time lag for inducing conidiation but also the amount of conidia formed were regulated by the fluence rates of both those lights.
Thus, 'mycochrome' is considered to function as a photoreceptor system in the induction of conidiation of this fungus.     

BINDING OF ANTHRACENE TO CELLULAR MACROMOLECULES IN THE PRESENCE OF LIGHT

Ultraviolet radiation (δ > 295 nm) induced covalent binding of anthracene to DNA which increased with time and was not affected by oxygen. Irradiation in the presence of anthracene induced nicking of Col E, circular DNA and decreased the thermal denaturation temperature of calf thymus DNA. These effects were oxygen dependent, and were decreased by GMP. Irradiation of anthracene and human serum albumin resulted in covalent binding of the hydrocarbon to the protein accompanied by crosslinking of the protein. Protein crosslinking decreased under anaerobic conditions. Irradiation of anthracene bound to liposomes induced lipid peroxidation which was not affected by superoxide dismutase or catalase.     

OXIDATION OF RIBOSE MOIETY OF ADENOSINE INDUCED BY IRRADIATION OF NEAR-UV LIGHT IN THE PRESENCE OF IRON(III) CHLORIDE

Abstract— Irradiation of near-UV light in the presence of FeCl₃ caused oxidation of adenosine with concomitant reduction of Fe(III) under either aerobic or anaerobic atmosphere. Major photoproducts were adenine and adenosine-5'-aldehyde, showing that oxidation took place mostly at the ribose moiety of adenosine. Detailed study showed that the reaction proceeded by the light absorption due to Fe(III) at 300-350 nm.     

STUDIES ON FLAVINS IN ORGANIC SOLVENTS—II*. PHOTODECOMPOSITION OF RIBOFLAVIN IN THE PRESENCE OF OXYGEN

Abstract— The photodegradation of riboflavin by 436 mμ monochromatic light and of lumichrome by white nonfiltered light was studied in a set of organic solvents including ethanol, acetone, dioxane, pyridine and acetic acid. For comparison, water was used as a solvent. Photolysis was carried out in the presence of atmospheric oxygen. Riboflavin and lumichrome were found to be effectively stabilized towards the action of light by hydrogen bonds with solvent molecules, and consequently are most light-stable in water solutions. The overall scheme of riboflavin photolysis in organic solvents seems to be the same as in aqueous solutions. Lumichrome has been found as the main product of riboflavin photolysis in the organic solvents tested.     

PHOTO-OXIDATION OF LYSOZYME IN THE PRESENCE OF METHYLENE BLUE: A PROBABLE MECHANISM

Abstract— In order to elucidate the mechanism of the photo-oxidation of lysozyme sensitized by methylene blue this enzyme was oxidized by singlet oxygen generated by a high–frequency discharge in gaseous oxygen. The action of singlet oxygen on lysozyme gives products identical with those obtained upon dye-sensitized oxidation with respect to their affinity to chitin, their amino acid content, their UV spectra and their enzymic activity. It is concluded that photo-oxidation of lysozyme in the presence of methylene blue proceeds according to the singlet-oxygen mechanism.     

MICROWAVE INDUCED SYNTHESIS OF COUMARINS FROM IN SITU GENERATED STABILIZED PHOSPHORUS YLIDES IN THE PRESENCE OF SILICA GEL POWDER IN SOLVENT-FREE CONDITIONS

Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates, by phenols (1-hydroxynaphthalene, 2-hydroxynaphthalene and 4-bromophenol) leads to vinyltriphenylphosphonium salts, which undergo aromatic electrophilic substitution reaction with conjugate base to produce corresponding stabilized phosphorus ylides. Microwave was found to catalyze conversion of the stabilized phosphorus ylides to corresponding coumarins in the presence of silica gel powder in solvent-free conditions.     

FLAVIN COMPOUNDS AS AGENTS FOR THE OXIDATION OF PLASTOCYANIN IN BLUE LIGHT

Abstract—Flavins, flavin nucleotides and selected flavoproteins have been compared in a reaction using blue light. in which plastocyanin is oxidized as the flavin is photoreduced. Per unit of light absorbed. flavin mononucleotide is more effective than flavin adenine dinucleotide, ribotlavin or lumiflavin. Of the flavoproteins tested, diaphorase from Clostridium kluyveri was most effective, but was less active than free flavin mononucleotide. The oxidation of plastocyanin requires aerobic conditions. and appears to be mediated by the production of singlet oxygen when the flavin is irradiated.     

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.     

EFFECTS OF HEMATOPORPHYRIN DERIVATIVE ON THE CELLULAR ENERGY METABOLISM IN THE ABSENCE AND PRESENCE OF LIGHT

Effects of Photofrin II on energy metabolism and metabolic viability were studied in a mammalian transformed cell line (BHK-21) in dark and after photo-irradiation with visible light. Cells were allowed to accumulate Photofrin by incubating for 4 h in buffer containing Photofrin (5-60 micrograms/ml). The results show that Photofrin significantly affects the cellular energy metabolism even in the absence of light; activity of cytochrome c oxidase is decreased and glucose utilization and lactate production (glycolysis) are increased. Irradiation with light resulted in a significant decrease in the activity of cytochrome c oxidase, glycolysis, ATP content, energy charge, ratios of adenine nucleotides like ATP/ADP, ATP/AMP and cell viability (dye exclusion test). Presence of inhibitors of energy metabolism, potassium cyanide (respiration) and 2-deoxyglucose (glycolysis), further enhanced the cytotoxic effects induced by hematoporphyrin derivative and light.     

PHOTOELECTRIC EFFECTS IN A BIMOLECULAR LIPID MEMBRANE IN THE PRESENCE OF LIGHT SENSITIVE INORGANIC IONS

Abstract— A new membrane photoeffect of high quantum efficiency is reported. The presence of a number of inorganic ions in the bathing solution of a bimolecular lipid film of oxidized cholesterol causes a change in the measured e.m.f. from -100 to -40 mV (photo e.m.f. effect) and increase in the conductivity by a factor of 100–200 (photoconductive effect) when the ions are excited by light. A model system, based upon the classical Becquerel Effect phenomenon of electronic charge injection into the membrane from electronically excited ions, is suggested and experiments verifying this model are reported. An extension of this model is used to suggest a new mechanism of the visual receptor process in biological photoreceptor structures.     

PHYSIOLOGICAL STUDIES ON PEA TENDRILS—X. CHARACTERIZATION OF THE LIGHT ACTIVATION EFFECT ON CONTACT COILING AS A BLUE LIGHT TRIGGER*

Abstract— Tendrils of the Alaska pea lose their capacity to coil in response to a mechanical stimulus between 24 and 48 h after being placed in the dark. Light is thereafter necessary for the motor response to proceed once the mechanical stimulus has becn sensed by dark-adapted tendrils. An action spectrum for this light activation effect showed that the most effective region of the visible spectrum was a narrow band in the blue region. Tendrils excised from their petiole and leaflets coiled more than any other preparation used. A linear relationship was found between the duration of post-stimulated white light treatment and the amount of coiling.