Green Light Irradiation Research Articles

PHOTOCATALYTIC ACTIVITY OF NITROGEN AND FLUORINE CO-DOPED TITANIUM DIOXIDE PREPARED USING OF VARIOUS PH SOLUTIONS

Introducing different atoms into TiO 2 crystal lattice is a famous method to improve photocatalytic activity of TiO 2 under visible-light irradiation. In this paper, Nitrogen ( N ) and fluorine ( F ) co -doped TiO 2 powders were prepared by mixing TiCl 3 solutions with ammonium fluoride ( NH 4 F ). In preparation, we used NH 3- H 2 O solution for adjustment of pH values (pH 2, 7, and 9) of mixed solution. X-ray diffraction (XRD) indicated N , F - TiO 2 powders prepared at pH7 and pH9 contained only anatase phase, but the powders prepared at pH2 contained both anatase and rutile phase. The result of XRD also indicated N , F - TiO 2 powders prepared at pH7 had the smallest crystallite size. We measured photocatalytic activity of prepared N , F - TiO 2 powders by the decomposition of methylene blue. N , F - TiO 2 powder prepared at pH7 and pH9 showed same high photocatalytic activity under ultraviolet light irradiation (peak wave length = 352 nm). Furthermore, under green light LED irradiation (wave length = 525 nm), a sample prepared at pH7 decomposed methylene blue more quickly than any other samples. As the result, N , F - TiO 2 prepared at pH7 had the best catalytic activity under both UV-light and visible light in the all of N , F - TiO 2 prepared and reference TiO 2 photocatalyst (ST-01 produced by Ishihara Co. Ltd).

Structural studies on serum albumins under green light irradiation

This paper presents two new experimental results: the protective effect of green light (GL) on ultraviolet (UV) denaturation of proteins, and the effect of GL on protein macromolecular structures. The protective effect of GL was revealed on two serum albumins, bovine (BSA) and human (HSA), and recorded by electrophoresis, absorption, and circular dichroism spectra. The effect of GL irradiation on protein structure was recorded by using fluorescence spectroscopy and electrophoresis. These new effects were modeled by quantum-chemistry computation using Gaussian 03 W, leading to good fit between theoretical and experimental absorption and circular dichroism spectra. A mechanism for these phenomena is suggested, based on a double-photon absorption process. This nonlinear effect may lead to generation of long-lived Rydberg macromolecular systems, capable of long-range interactions. These newly suggested systems, with macroscopic quantum coherence behaviors, may block the UV denaturation processes.

Identification of the amino acid residues responsible for the reversible photoconversion of the monomeric red fluorescent protein TagRFP

The site-directed mutagenesis of the monomeric red fluorescent protein TagRFP and its variants was performed with the goal of generating reversibly photoactivatable fluorescent proteins. Amino acids at positions 69, 148, 165, 179, and 181 (enumeration according to the green fluorescent protein GFP) were shown to play a key role in the manifestation of the photoactivatable properties. A reversibly photoactivatable red fluorescent protein KFP-HC with excitation and emission maxima at 585 and 615 nm, respectively, was generated. The KFP-HC fluorescent intensity was decreased by 5-10 times under green light (530-560 nm) irradiation (due to the fall of the fluorescence quantum yield) and restored under irradiation with blue light (450-490 nm) or after incubation in the dark (time of half reconstruction of 30 min).

Green-light photocatalytic reduction using dye-sensitized TiO2and transition metal nanoparticles

Nitrobenzenes are cleanly reduced to anilines using Ru-sensitized TiO2 photocatalysts and green light irradiation, if very small amounts of transitions metal salts are added, which form metal nanoparticles of narrow size distribution under the experimental conditions. The catalyst system is prepared by simple mixing of the components and is therefore easy to apply in organic synthesis. As light sources, commercial high power LEDs or sunlight are used. We report the optimization of the reaction conditions, the effect of trace amounts of added metal salts and demonstrate the use of green light photoreduction in the conversion of several nitrobenzene derivatives.

The photo-induced commensurate modulated structure in site-selective spin crossover complex trans-[Fe(abpt)2(NCS)2

The photo-induced superstructure of polymorph C of trans-[Fe(abpt)(2)(NCS)(2)] (abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole) is discovered as a commensurate modulated structure by single-crystal X-ray diffraction under irradiation. The crystal structure at 25 K before the photo-irradiation composed of two crystallographically independent iron molecules, one of which exhibits high spin (HS) state and the other at low spin (LS) state. Under green laser light (λ = 532 nm) irradiation, the LS molecule (Fe1) is found to be excited to a metastable HS state and gives rise to a commensurate tripled superstructure along the c axis. In addition, it is confirmed that this modulation persists until the HS → LS relaxation temperature beyond 52 K. Our structural findings suggest that the structural modulation and the site-selective LS → HS excitation are highly correlated.

The light-induced spin transition of tetranuclear spin crossover complex [Fe4(CN)4(bpy)4(tpa)2](PF6)4

We report on the light induced spin transition in the tetranuclear spin crossover complex [Fe4(CN)4(bpy)4(tpa)2](PF6)4. The photo-conversion occurs at the specific site (Fe2) of four FeII ions. The red light irradiation (1.79 eV) gives rise to full conversion of Fe2 into the high spin state from the low spin state. The green light irradiation (2.33 eV) can convert only the half of Fe2 into the high spin state, though the photo-conversion rate in the beginning is much higher than that with the red light. We present a simple model in which the photo-conversion kinetics is controlled by a large background absorption due to remaining three FeII ions (Fe1, Fe3 and Fe4).

1P-275 蛍光性BODIPYケージド化合物を用いた生体分子の時空間光制御(バイオエンジニアリング,第47回日本生物物理学会年会)

1P-275 蛍光性BODIPYケージド化合物を用いた生体分子の時空間光制御(バイオエンジニアリング,第47回日本生物物理学会年会)

低溫及LED光質處理對阿魏菇(Pleurotus eryngii var. ferulae)原基誘導之影響

Mycelia of Pleurotus eryngii var. ferulae cultured on PDA with 25℃ dark condition, then moved to 15℃ with red, yellow, blue, green, and white light irradiation (12 hr light/12 hr dark). After two months, no primordia appeared under constant dark, red and yellow light; primordia appearance of blue and white light treatment were 83.3% and 75%, respectively. Low mycelial growth temperature had significant effects on indeces such as days of primordia appearance, days of 90% primordia appearance, days of major primordia appearance, percentage of plate with primordia appearance, and number of primordia per plate. The mechanical treatment increased the number of primordia per plate. The optimal conditions for inducing primordia of P. eryngii var. ferulae were that mycelia cultured at 25℃ without mechanical treatment and then incubated at 15℃, the next was mechanical treated 30℃ incubated mycelia cultured incubated at 15℃. Among low temperature treatments, the primordia were poorly or not induced at temperature higher than 20℃. The dual temperature treatment decreased the percentage of plate with primordia appearance and was not able to reduce the days of primordia appearance.

Distinct Responses of Chloroplasts to Blue and Green Laser Microbeam Irradiations in the Centric Diatom Pleurosira laevis

The centric diatom Pleurosira laevis is a large unicellular alga, in which ca 200 chloroplasts migrate toward the nuclear cytoplasm through the transvacuolar cytoplasmic strands in response to blue-light irradiation and, on the contrary, toward the cortical cytoplasm in response to green-light irradiation. We analyzed these light-induced chloroplast migrations using a scanning laser microbeam provided by a confocal microscope for intracellular irradiation. Spot irradiation of a blue laser microbeam induced rapid assemblage of chroloplasts into the nuclear cytoplasm regardless of the spot position and spot number. On the other hand, one or two spots of green laser microbeam induced chloroplast accumulation at the spots, although increasing spot numbers suppressed chloroplast accumulation at each spot. In our experimental condition, ca 1 min of blue-light irradiation was sufficient to stimulate movement, whereas green-light irradiation required uninterrupted and longer irradiation time (ca 15 min). Chloroplast assemblage induced by blue-light required extracellular Ca2+, and was inhibited by Ca2+ channel antagonists. Furthermore, higher efficiencies of chloroplast migration were obtained when a single beam spot was fragmented and scattered over wider area of plasma membrane. These observations suggested that blue-light induced a response at the plasma membrane, which subsequently activated Ca2+ permeable channels. This sequence of physiological events is identical to what was previously observed with chloroplast movement in response to mechanical stimulation. Furthermore, experiments with the cytoskeleton-disrupting agents, colchicine and cytochalasin D, indicated that blue-light-induced chloroplast movement required microtubules whereas the green-light-induced response to beam spot required actin filaments.

The Signaling State of Arabidopsis Cryptochrome 2 Contains Flavin Semiquinone

Cryptochrome (Cry) photoreceptors share high sequence and structural similarity with DNA repair enzyme DNA-photolyase and carry the same flavin cofactor. Accordingly, DNA-photolyase was considered a model system for the light activation process of cryptochromes. In line with this view were recent spectroscopic studies on cryptochromes of the CryDASH subfamily that showed photoreduction of the flavin adenine dinucleotide (FAD) cofactor to its fully reduced form. However, CryDASH members were recently shown to have photolyase activity for cyclobutane pyrimidine dimers in single-stranded DNA, which is absent for other members of the cryptochrome/photolyase family. Thus, CryDASH may have functions different from cryptochromes. The photocycle of other members of the cryptochrome family, such as Arabidopsis Cry1 and Cry2, which lack DNA repair activity but control photomorphogenesis and flowering time, remained elusive. Here we have shown that Arabidopsis Cry2 undergoes a photocycle in which semireduced flavin (FADH(.)) accumulates upon blue light irradiation. Green light irradiation of Cry2 causes a change in the equilibrium of flavin oxidation states and attenuates Cry2-controlled responses such as flowering. These results demonstrate that the active form of Cry2 contains FADH(.) (whereas catalytically active photolyase requires fully reduced flavin (FADH(-))) and suggest that cryptochromes could represent photoreceptors using flavin redox states for signaling differently from DNA-photolyase for photorepair.

Synthesis, structure and magnetic properties of an iron(II) complex with nitronyl nitroxides

An iron(II) complex with nitronyl nitroxides, [Fe II(dppNN) 2](BF 4) 2 · CH 3COCH 3 ( 1) (dppNN = 2,6-di(pyrazol-1-yl)-4-(4,4,5,5-tetramethyl-1-oxido-3-ylooxy-4,5-dihydro-3H-imidazol-2′-yl)pyridine) was synthesized. In 1 the central iron(II) ion was coordinated by two tridentate ligands with nitronyl nitroxides. Magnetic susceptibility measurements showed that χ m T values below 130 K was almost temperature independent, while upon increasing temperature χ m T values showed gradual increase, suggesting an occurrence of a spin transition from low to high spin state. Green light irradiation on powder sample at 5 K resulted in spin conversion (LIESST).

Complexes based on ethylene- and propylene-bridged-pentadentate-Fe(III)-units allow interplay between magnetic centers and multistability investigated by Mössbauer spectroscopy

The propylene-based 53,3-L=[N,N′-Bis(1-hydroxy-2-benzylidene)-1,7-diamino-4-azaheptane] and ethylene-based pentadentate ligand 52,2-L=[N,N′-Bis(1-hydroxy-2-benzylidene)-1,5-diamino-3-azapentane] has been prepared. Complexation with Fe(III) yields high-spin (S=5/2) complexes of [FeIII(52,2-L)Cl] and [FeIII 53,3-L)Cl]. Such precursors were combined with [M(CN) x ] y− (M=W(IV), Mo(IV), Ru(II), Co(III)) and heptanuclear and nonanuclear clusters of [M(CN-FeIII(52,2-L) x ]Cl y and [M(CN-FeIII(53,3-L) x ]Cl y resulted. Such starshaped hepta- and nonanuclear compounds are high-spin systems at room temperature. On cooling to 20 K in all presented ethylene compounds the iron(III) centers switch to a second high-spin state as proven by Mossbauer spectra with a yield of about 30%, i.e., multiple electronic transitions. The propylene compounds, however, perform a high-spin to low-spin transition. Mossbauer spectra taken during green light irradiation indicate changes in the population of the different electronic states, i.e. concerted inorganic reaction.

Photon-, Electron-, and Proton-Induced Isomerization Behavior of Ferrocenylazobenzenes

3-, 4-, and 2-ferrocenylazobenzenes, 1, 2, and 3, respectively, and several derivatives of 1 were synthesized, and their photoisomerization behaviors were examined. The molecular structures of 1 and its derivatives, 2-chloro-5-ferrocenylazobenzene (5) and 3-ferrocenyl-4'-hydroxylazobenzene (11), were determined by X-ray diffraction analysis. 3-Ferrocenyl compound 1 undergoes reversible trans-to-cis isomerization with a single green light source and the Fe(III)/Fe(II) redox change. 4- and 2-Ferrocenyl compounds, 2 and 3, also respond to green light in addition to UV light, exciting the pi-pi* transition, but the cis molar ratio in the photostationary state (PSS) is lower than that of 1. The response to green light in 2 and 3 is caused by the MLCT (from Fe d orbital to azo pi* orbital) band excitation, while the character of the MLCT band, as estimated by time-dependent density functional theory calculations, differs between 1 and 2. The oxidized form of 2 undergoes facile cis-to-trans thermal isomerization. Both 1 and 2 undergo facile protonation and show proton-catalyzed cis-to-trans isomerization. Among the derivatives of 1, 2-chloro-5-ferrocenylazobenzene (5) exhibits the highest cis molar ratio (47%) in the PSS of green light irradiation.

A 2D Layered Spin Crossover Complex Constructed by NH···Cl-Hydrogen Bonds: [FeIIH3LMe]Cl·I3(H3LMe= Tris[2-(((2-methylimidazoyl-4-yl)methylidene)amino)ethyl]amine

A 2D layered spin crossover complex, [FeIIH3L(Me)]Cl.I3, has been synthesized from the reaction of FeIIICl3, a tripod ligand (H3LMe = tris[2-(((2-methylimidazoyl-4-yl)methylidene)amino)ethyl]amine), and NaI in methanol. The compound showed an abrupt spin transition between the HS (S = 2) and LS (S = 0) states at T(1/2) = 110 K without hysteresis. The crystal structures of the HS and LS states were determined at 180 and 90 K. A 2D layered structure is composed of NH...Cl- hydrogen bonds between the Cl- ion and three neighboring imidazole groups of [FeIIH3LMe]2+. The green light irradiation at 5 K induced the LIESST effect, and the thermal relaxation process from the HS to LS state showed a sigmoid curve at T > 55 K.

The effect of green laser light irradiation on whole blood platelets

Background Laser light irradiation is assumed to have biostimulating effect in various cell types. However, there is still a lack of information concerning response of blood platelets to laser light irradiation. Methods In our study we used flow cytometry to monitor the effect of a green Nd-YAG laser (532 nm, 30 mW) irradiation on platelet activation and the expression of activated GPIIbIIIa glycoprotein complex (fibrinogen receptor) of whole blood platelets stained with fluorolabelled monoclonal antibody PAC-1. Also the formation of platelet microparticles and aggregates in a population of whole blood platelets following such irradiation was evaluated. Results Effects of laser light on platelet activation and reactivity were significant over a wide range of applied energies ( p < 0.01). While low and medium laser light energies (18 and 54 J) increased platelet activation, the irradiation with a high-energy laser light (108 J) resulted in depressed platelet reactivity and attenuated platelet response to activators. In addition, laser light irradiation had significant influence on the formation of platelet microparticles in either resting ( p < 0.05) or ADP-activated ( p < 0.05) platelets, while no significant effect was observed in collagen-activated platelets. On the other hand, laser light irradiation significantly increased the formation of platelet aggregates both in resting ( p < 0.01) and agonists-activated ( p < 0.05) platelets. Conclusions Our results clearly point that the laser light irradiation of blood platelets can trigger signal transduction, leading to platelet activation, as well as the gradual loss of natural platelet reactivity and platelets’ ability to respond to activating agents.

Green light stimulates early stem elongation, antagonizing light-mediated growth inhibition.

During the transition from darkness to light, the rate of hypocotyl elongation is determined from the integration of light signals sensed through the phototropin, cryptochrome, and phytochrome signaling pathways. In all light conditions studied, from UV to far-red, early hypocotyl growth is rapidly and robustly suppressed within minutes of illumination in a manner dependent upon light quality and quantity. In this study, it is shown that green light (GL) irradiation leads to a rapid increase in the growth rate of etiolated Arabidopsis seedlings. GL-mediated growth promotion was detected in response to constant irradiation or a short, single pulse of light with a similar time course. The response has a threshold between 10(-1) and 10(0) micromol m(-2), is saturated before 10(2) micromol m(-2) and obeys reciprocity. Genetic analyses indicate that the cryptochrome or phototropin photoreceptors do not participate in the response. The major phytochrome receptors influence the normal amplitude and timing of the GL response, yet the GL response is normal in seedlings grown for hours under constant dim-red light. Therefore, phytochrome activation enhances, but is not required for, the GL response. Seedlings grown under green, red, and blue light together are longer than those grown under red and blue alone. These data indicate that a novel GL-activated light sensor promotes early stem elongation that antagonizes growth inhibition.

Multi-Mode Molecular Switching Properties and Functions of Azo-Conjugated Metal Complexes

Abstract Recent studies on the azo-group-combined photochromic metal complexes are reviewed. These studies show unique trans–cis isomerization behaviors that have not been observed in regular organic azobenzenes. In the case of azobenzene-bound bis(terpyridine) complexes of transition metals, photoisomerization behavior depends strongly on the central metals, counterions, and solvents. Rh and Co complexes undergo photoisomerization smoothly, but the isomerization of Ru and Fe complexes is substantially retarded due to the energy transfer from the π–π* excited state to the MLCT transition. The photoluminescence property of an azobenzene-attached Pt complex is switched by photoisomerization of the azo moiety. Tris(azobenzene-bound bipyridine)cobalt undergoes reversible trans–cis isomerization using a combination of the CoIII/CoII redox change and a single UV light source exciting the π–π* transition. The trans–cis conversion yield is higher for the meta isomer (with respect to the position of the azo group against the pyridyl group) than for the para isomer. The trans–cis photoisomerization behavior of a 6,6′-dimethyl-substituted azobenzene-bipyridine ligand is synchronized with coordination of the bipyridine moiety to copper, and the trans/cis isomerization can be controlled reversibly through CuII/CuI redox and a single UV light irradiation. Photoreaction of azoferrocene occurs not only by UV-light irradiation but also by green light irradiation that excites the MLCT transition. 3-Ferrocenylazobenzene undergoes reversible trans–cis isomerization using a single green light source and the FeIII/FeII redox change. Azo-conjugated metalladithiolenes of NiII, PdII, and PtII with diphenylphosphinoethane as a co-ligand show facile photoisomerization. The energy of the reversible trans-to-cis photoisomerization is considerably lower than that of azobenzene. The thermal stability of the cis form is, however, much higher than that of the organic azobenzene derivatives showing similar low-energy trans-to-cis photoisomerization. A novel proton response of the azo group occurs, and the combination of photoisomerization and protonation leads to a novel proton-catalyzed cis-to-trans isomerization. These results indicate that several kinds of multi-photo-functionalities can be realized for the azo-conjugated transition metal complexes by tuning the interaction between the azo moiety and the metal complex unit.

Inhibitory effects of total flavones of Hippophae Rhamnoides L on thrombosis in mouse femoral artery and in vitro platelet aggregation

Total flavones of Hippophae Rhamnoides L (TFH) are extracted from Sea buckthorn, a Chinese herbal medicine. Sea buckthorn has antioxidant, anti-ulcerogenic and hepato-protective actions, and its berry oil is reported to suppress platelet aggregation. Though it is frequently used for patients with thrombosis, the likely mechanism(s) and effects of TFH on thrombogenesis remain unclear. Thus, we have investigated the effect in-vivo of TFH on thrombogenesis and in vitro on platelet aggregation, comparing them to those of aspirin. We measured thrombotic occlusion time in a mouse femoral artery thrombosis model by the photochemical reaction between intravenously injected rose bengal and green light irradiation. In vitro platelet aggregation in whole blood was measured by single platelet counting. Thrombotic occlusion time was 8.5 ± 0.6 min in the control group. TFH at a dose of 300 μg/kg, intravenously administered 15 min before the rose bengal injection, significantly prolonged it to 11.6 ± 1.0 min ( P < 0.05), a similar effect on in-vivo thrombogenesis to that of aspirin. TFH at a concentration of 3.0 μg/ml significantly ( P < 0.01) inhibited in vitro platelet aggregation induced by collagen (2 μg/ml) in a concentration dependent manner, in contrast TFH did not affect aggregation induced by arachidonic acid (80 μM) and ADP (0.3 μM). The results of the present study, in which TFH prevented in-vivo thrombogenesis, probably due to inhibition of platelet aggregation, suggest a possible clinical approach for the prevention of thrombosis.

Chromophore Environment Provides Clue to “Kindling Fluorescent Protein” Riddle

asCP, the unique green fluorescent protein-like nonfluorescent chromoprotein from the sea anemone Anemonia sulcata, becomes fluorescent ("kindles") upon green light irradiation, with maximum emission at 595 nm. The kindled protein then relaxes to a nonfluorescent state or can be "quenched" instantly by blue light irradiation. In this work, we used asCP mutants to investigate the mechanism underlying kindling. Using site-directed mutagenesis we showed that amino acids spatially surrounding Tyr(66) in the chromophore are crucial for kindling. We propose a model of the kindling mechanism, in which the key event is chromophore turning or cis-trans isomerization. Using site-directed mutagenesis we also managed to transfer the kindling property to the two other coral chromoproteins. Remarkably, most kindling mutants were capable of both reversible and irreversible kindling. Also, we obtained novel variants that kindled upon blue light irradiation. The diversity of photoactivated fluorescent proteins that can be developed by site-directed mutagenesis is promising for biotechnological needs.

Redox-Conjugated Reversible Isomerization of Ferrocenylazobenzene with a Single Green Light

A new reversible isomerization cycle for meta-ferrocenylazobenzene accomplished by combination of a single green light (546 nm) and redox change between Fe(II) and Fe(III) was discovered. In the Fe(II) state, trans-to-cis isomerization proceeded upon the green light irradiation exciting the metal-to-ligand charge transfer (MLCT) in a high quantum yield (Phit-->c = 0.51) which exceeds that of azobenzene (Phit-->c = 0.12 (313 nm excitation)). The cis molar ratio reached 35% in the photostationary state. The oxidation to the Fe(III) state followed by irradiation with the same green light led to the cis-to-trans back-reaction to recover almost all of the trans-form. The "on-off switching" of the MLCT character played an important role in the redox-dependent response to the green light for the isomerization. The photoisomerization behavior of ferrocenylazobenzenes was strongly dependent on the substitution position of the ferrocenyl moiety on the benzene ring. The MLCT excitation was not effective for the trans-to-cis conversion in para-ferrocenylazobenzene. Time-dependent density functional theory (TD-DFT) calculations for meta- and para-ferrcenylazobenzene showed that the origin of the visible band (MLCT band) is different. The initial orbital for the MLCT in meta-ferrocenylazobenzene is delocalized over Fe and the Cp ring, while that in para-ferrocenylazobenzene is localized on the iron.