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The energy transfer dynamics of the biohybrid photosynthetic antenna complexes were investigated by transient absorption. The mechanism of energy transfer was discussed in terms of the higher-lying exciton state of bacteriochlorophyll aggregates.

A functional linkage between light-harvesting and photocatalytic components is a pivotal issue for using solar energy in chemical conversions; however, this concept is far from being practically re...

The two-dimensional molecular assembly was accomplished of bacteriochlorophyll

Photosynthetic light-harvesting (LH) systems consist of photosynthetic pigments, which are non-covalently self-assembled with protein scaffolds in many phototrophs and attain highly efficient excitation energy transfer via ultrafast dynamics. In this study, we constructed a biohybrid LH system composed of an LH complex (LH2) from Rhodoblastus acidophilus strain 10050 and a hydrophobic fluorophore ATTO647N (ATTO) as an extrinsic antenna in the lipid bilayer. Through the addition of ATTOs into a solution of LH2-reconstituted lipid vesicles, ATTOs were incorporated into the hydrophobic interior of the lipid bilayer to configure the non-covalently self-assembled biohybrid LH. Steady-state fluorescence spectroscopy clearly showed efficient energy transfer from ATTO to B850 bacteriochlorophylls in LH2. Femtosecond transient absorption spectroscopy revealed that the energy transfer took place in the time range of 3–13 ps, comparable to that of the covalently linked LH2-ATTO that we previously reported. In addition, the biohybrid LH system exhibited a much higher antenna effect than the LH2-ATTO system because of the higher loading level of ATTO in the membrane. These findings suggest that the facile self-assembled biohybrid LH system is a promising system for constructing LH for solar-energy conversion.

We report strong dissymmetry between left- and right-handed circularly polarized photoluminescence (PL) enhancement induced by 2D chiral gold nanostructures, which can be utilized to provide a circularly polarized luminescence source. Lightning-bolt-like (composed of two displaced rectangles) chiral plasmonic gold nanostructures were fabricated on a glass substrate and were adopted as materials to induce dissymmetry in PL enhancement. We employed achiral IR125 dye as an achiral molecular PL emitter with luminescence that was enhanced by near-field interaction between the chiral plasmon and the molecule. PL decay measurements confirmed that the PL enhancement arose from the plasmonic effect. Large PL enhancement dissymmetry factors g > 0.1 were obtained in the wavelength region near 800 nm. The dissymmetry of PL enhancement showed maximum amplitudes at 800–850 nm, which approximately correspond to the wavelength providing maximal extinction dissymmetry (∼800 nm), and is resonant with a chiral multipolar pl...

The heterostructures fabricated with a combination of 2-D materials and conventional semiconductors are of great interest owing to their unique optoelectronic properties. Here, we demonstrate the fabrication of a germanium (Ge)/MoS2 heterostructure and observation of a photovoltaic action with broadband photoresponsivity. A thin interface was formed in-between the thermally evaporated Ge and chemical vapor deposited MoS2 layers, considering the atomically smooth surface of MoS2. The current density-voltage ( ${J}$ – ${V}$ ) measurement showed a diode like characteristic and photoresponsivity under light illumination. The Ge/MoS2 heterojunction showed an open circuit voltage ( ${V}_{\text {oc}}$ ) of 0.185 V and short circuit current density ( ${J}_{\text {sc}}$ ) of 0.028 mA/cm2 under illumination of light (wavelength 350–1100 nm). The transient photoresponse characteristics of the Ge-MoS2 heterojunction device showed significant photoresponsivity for ultraviolet, visible, and near-infrared light at different bias voltages. The interfacial charge transfer at the Ge-MoS2 heterojunction is the critical aspect to create an effective build in field for the broadband photoresponsive device. The demonstrated ultrathin heterojunction of Ge and MoS2 layers can be significant for developing self-powered broadband photodetectors.

With the aim of understanding the excitation energy transfer mechanism in natural photosynthetic membranes, light-harvesting (LH)2 and LH1-reaction center, which are pigment-protein complexes separated from Rhodobacter sphaeroides, were aligned on a planar electrode surface in stripe patterns at 5 urn intervals. Observation of the absorption spectrum and fluorescence microphotographs revealed selective immobilization and conservation of the pigments. Photocurrent signals were obtained when the electrode was illuminated at either 880 or 800 nm. The fabricated structure was confirmed to function as a natural photosynthetic membrane with the highest photocurrent signal being obtained when using a co-immobilized substrate under excitation at 800 nm.

The photosynthetic light-harvesting–reaction center core complex (LH1-RC) is a natural excitonic and photovoltaic device embedded in a lipid membrane. In order to apply LH1-RCs as a biohybrid energy-producing material, some important issues must be addressed, including how to make LH1-RCs function as efficiently as possible. In addition, they should be characterized to evaluate how many active LH1-RCs efficiently work in artificial systems. We report here that an anionic phospholipid, phosphatidylglycerol (PG), stabilizes the charge-separated state (a photooxidized electron donor and reduced quinone pair, P+QB–) of LH1-RC (from Rhodopseudomonas palustris) and enhances its activity in photocurrent generation. Steady-state fluorometric analysis demonstrated that PG enhances the formation of the P+QB– state at lower irradiances. The photocurrent generation activity was analyzed via Michaelis–Menten kinetics, revealing that 38% of LH1-RCs reconstituted into the PG membrane generated photocurrent at a turnover...

Power distribution companies must establish an optimal maintenance schedule that balances the reliability and efficiency of a number of widely scattered facilities. Accordingly, we have developed an optimization method for inspection scheduling by which optimal inspection schedules are planned using 1) a method to predict the inspection priority for each facility and 2) a method to establish an inspection schedule that minimizes the inspection cost. In this study, for step 1, a practical method using both inspection history and facility attributes is proposed. The method consists of two approaches: a relation analysis and a defect prediction. In the relation analysis, relations between facility defect and other maintenance data are analyzed using a multiple correlation analysis method on the basis of chi-square testing. And then, facility defect is predicted using the data items that correlated with the facility defect obtained from the relation analysis. A modified quantification method type II introducing biased posterior probability is proposed for the prediction. Furthermore, proposed method is demonstrated by utilizing maintenance data accumulated by a certain Japanese power utility company. Evaluation results show that inspection cost can be reduced by 36–58% compared with the conventional twice-every-two-years inspection while retaining reliability.

Photosynthesis in natural systems is one of the typical examples where the interaction between multiple photons and multiple chromophores leads to the synergetic responses in three-dimensionally arranged molecular aggregates. Accordingly, the investigation of primary events in the excited state could provide important information on the progress in the artificial photosynergetic systems. Along with this line, we have prepared biohybrid light-harvesting complexes to study ultrafast dynamics of excitation energy transfer in the present project. Light-harvesting 2 complex (LH2) from photosynthetic purple bacteria is a molecular assembly, in which multiple photosynthetic chromophores are well organized. To expand high-harvesting activity of LH2, we attached a fluorophore, Alexa647, to lysine residues on the LH2 polypeptide so as to cover broad solar spectrum. Ultrafast energy transfer from Alexa 647 to the intrinsic chromophores B800 and B850 in LH2 was observed using femtosecond transient absorption spectroscopy. Detailed analysis revealed two possible energy transfer pathways. In addition, we made a LH2 mutant bearing reactive Cys residue on the N-terminal region of LH2β polypeptide. The engineered LH2 allows us to provide the defined position of Alexa647. Together with the system in which LH2 was dissolved in micellar solution, a lipid bilayer system in which the bioengineered LH2 was incorporated was applied to control the location of the external fluorophore.

Enhancing the light-harvesting potential of antenna components in a system of solar energy conversion is an important topic in the field of artificial photosynthesis. We constructed a biohybrid light-harvesting complex 2 (LH2) engineered from Rhodobacter sphaeroides IL106 strain. An artificial fluorophore Alexa Fluor 647 maleimide (A647) was attached to the LH2 bearing cysteine residue at the N-terminal region (LH2-NC) near B800 bacteriochlorophyll a (BChl) assembly. The A647-attached LH2-NC conjugate (LH2-NC-A647) preserved the integrity of the intrinsic chromophores, B800- and B850-BChls, and carotenoids. Femtosecond transient absorption spectroscopy revealed that the sequential energy transfer A647 → B800 → B850 occurs at time scale of 9–10 ps with monoexponential dynamics in micellar and lipid bilayer systems. A B800-removed conjugate (LH2-NC[B800(−)]-A647) exhibited a significant decrease in energy transfer efficiency in the micellar system; however, surprisingly, direct energy transfer from A647 to B850 was observed at a rate comparable to that for LH2-NC-A647. This result implies that the energy transfer pathway is modified after B800 removal. The results obtained suggested that a LH2 complex is a potential platform for construction of biohybrid light-harvesting materials with simple energy transfer dynamics through the site-selective attachment of the external antennae and the modifiable energy-funnelling pathway.

To develop efficient systems for light-energy conversion, monomeric and dimeric zinc chlorin derivatives were synthesized. These derivatives act as photosensitizers for light-induced hydrogen production with methylviologen as the electron mediator and Pt nanoparticles as the hydrogen-evolution catalyst. The monomeric derivative exhibited ~1.5-times higher activity than the dimeric derivative. The photocurrent-generating activity of the Zn chlorin derivatives assembled on a chemically modified indium tin oxide electrode was investigated; the dimeric derivative exhibited significant activity compared to the monomeric derivative. The photosensitizing activity of the derivatives in dye-sensitized solar cells was also investigated. The dimeric derivative exhibited two-fold higher performance than the monomeric derivative. The dimerization effect on the photosensitizing activities is briefly discussed in terms of stacking conformations based on the results of absorption and fluorescence spectroscopies.

In recent years, a number of light-induced hydrogen production systems composed of photosystem I (PSI) and hydrogen production catalysts (e.g. hydrogenases and Pt nanoparticles) have been reported. However, the utility of these systems under aerobic conditions is limited due to their poor stability in the presence of oxygen. The development of light-induced hydrogen production systems that work under aerobic conditions is, therefore, of great importance to establish artificial photosynthetic devices. Ideally, these systems should utilise water as an electron source, via water splitting by photosystem II (PSII). We report the construction of a novel light-induced hydrogen production system composed of PSI-platinum nanoparticle conjugates and cytochrome c 6 (cyt c 6) immobilised in nanoporous glass plates (PGP50, 50-nm pore diameter). PSI trimer (PSIt) from Thermosynechococcus elongatus and Pt nanoparticles (PtNPs) were conjugated via electrostatic interactions (PSIt-PtNP). PSIt-PtNP and cyt c 6 were spontaneously absorbed in nanopores of PGP50 without denaturation. Upon irradiation in the presence of ascorbate as a sacrificial electron donor, catalytic H2 evolution was observed for PSIt-PtNP immobilised in the pores of PGP50 (PSIt-PtNP/PGP50) under both anaerobic and aerobic conditions, indicating that an effective photoinduced electron transfer system had been established. PSIt-PtNP/PGP50 was found to exhibit improved oxygen resistivity over the homogeneous solution system consisting of PSIt-PtNP, cyt c 6, and ascorbate, suggesting that the PSIt-PtNP/PGP50 system could be a potential candidate for artificial photosynthetic systems. The distribution of the components, PSIt-PtNP and cyt c 6, in PGP50 was characterised to discuss the efficiency of light-induced hydrogen production.

Light-harvesting complex of photosystem II (LHCII) is the most abundant membrane protein-chlorophyll complex in chloroplasts. Here, we evaluated the photocatalytic activity of the native trimer and the enzymatically treated monomer forms of LHCII. Upon white light irradiation using a solar simulator, photocatalytic reduction of methylviologen revealed that the activity of monomeric LHCII was higher than that of the trimer form. Fluorescence of the monomeric LHCII was more significantly quenched by methylviologen than that of the trimer form. In the presence of Pt nanoparticles in a catalytic solution system, photoinduced hydrogen production was observed for the LHCII monomer. The difference in photocatalytic activities of LHCII trimer and monomer are briefly discussed in terms of an interaction between LHCII and methylviologen.

A light harvesting system that effectively drives photocatalytic component is essential for converting solar light into chemical energy. Here we addressed the extension of light harvesting activity and presented a quantitative analysis of the functional linkage between light harvesting and a photocatalytic reaction of biohybrid light-harvesting 1–reaction center core complex (LH1-RC from Rhodopseudomonas palustris). Light harvesting wavelengths were extended by a series of fluorophores (Alexa647, 680, 750, and ATTO647N), which were covalently attached to LH1-RC (LH1-RC-Fluors). Femtosecond transient absorption spectroscopy revealed ultrafast excitation energy transfer (EET) from the fluorophores to bacteriochlorophyll a pigments in LH1 (B875), followed by charge separation in RC. The rate of EET increased with increase in the spectral overlap between the emission bands of the fluorophores and the absorption band of B875. The attachment of the external light harvesting fluorophores boosted the maximum yield of charge separation and photocurrent generation activity. We discussed the effects of the number of fluorophores attached to LH1-RC and location of the fluorophores in a lipid bilayer environment on light harvesting activity.

We report a controlled chain-growth polymerization of methyl 3-octylaminobenzoate having a bithiophene chromophore at the 5-position of the benzene ring with the improved polymerization activity, which gives poly(N-octyl-m-benzamide)s with the better solubility. The introduction of a terthiophene chromophore at the propagating end is also described. From spectroscopic data and theoretical investigations, it was found that neighboring bithiophene chromophores have the π–π interaction and the excited energy can migrate along the polymer chain.

Fused π-conjugated imidazolium compounds bearing two or three long alkoxy chains and various counter anions were systematically prepared following our reported synthetic route. On the basis of DSC measurements and POM observations, the combination of three alkoxy chains longer than the dodecyl group and moderately coordinating anions was important to obtain an enantiotropic mesophase. VT-XRD measurements coupled with a single crystal X-ray structure of a model compound revealed a hexagonal columnar structure supported by ionic interactions. The regularity of the self-organized nanostructure was governed by the alkoxy chain length and the coordinating ability of the counter anion. In the solution state, UV-vis and fluorescence peak maxima were influenced by the number of alkoxy chains and independent of the chain length and anion character. On the contrary, the alkoxy chain length and the coordinating ability of the counter anion had a large impact on the fluorescence spectra in the solid state. A longer wavelength emission at around 560 nm was observed for compounds with the highly regular hexagonal columnar structure. From the result of fluorescence lifetime measurements, the interaction between fused π-conjugated imidazolium cations was suggested.

Zinc chlorophyll a derivatives were synthesised for use as photosensitizers. Herein, we report a system for photoinduced hydrogen production with colloidal platinum via photoreduction of methylviologen (MV2+) using the photosensitization of a Zn pyropheophorbide a (ZnPyOH) dimer connected by lysine (ZnPy-K(ZnPy)OH) as a special pair model in the photosynthetic reaction centre in the presence of NADPH as an electron donor.

The photosynthetic light-harvesting-reaction center core complex (LH1-RC) is a natural excitonic and photovoltaic device embedded in a lipid membrane. In order to apply LH1-RCs as a biohybrid energy-producing material, some important issues must be addressed, including how to make LH1-RCs function as efficiently as possible. In addition, they should be characterized to evaluate how many active LH1-RCs efficiently work in artificial systems. We report here that an anionic phospholipid, phosphatidylglycerol (PG), stabilizes the charge-separated state (a photooxidized electron donor and reduced quinone pair, P

Photosystem II (PSII) has attracted a lot of attention for use in the construction of artificial photosynthetic materials due to its high activity of oxidation of water molecules. However, the robustness of PSII needs to be improved for in vitro application. In this study, we incorporated PSII (Thermosynechococcus vulcanus) into various phospholipid membranes to examine the activity and durability of oxygen evolution. PSII was incorporated into anionic 1,2-dioleoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (PSII-DOPG), zwitterionic 1,2-dioleoyl-sn-glycero-3-phosphocholine (PSII-DOPC), and cationic 1,2-dioleoyl-sn-glycero-3-ethylphosphocholine (PSII-EDOPC). Structural integrity of PSII was examined by absorption and fluorescence spectroscopy. Compared with PSII dissolved in a micellar solution of n-dodecyl-β-d-maltoside (PSII-micelle), durability of PSII-DOPC and PSII-DOPG were enhanced by 1.3- and 1.5-fold, respectively. The activity and durability of PSII-EDOPC was significantly low. Lipid-dependent activity and durability were discussed in terms of kinetic parameters of V max and K m, and inhibition of the electron acceptor, phenyl-p-benzoquinone.

Photosystems, PSI and PSII isolated from Thermosynechococcus elongatus were successfully immobilized on a TiO2 nanostructured film for use in dye-sensitized biosolar cells (DSBCs). The photosystem complexes were also immobilized on an ITO electrode modified with 3-aminopropyltriethoxysilane by utilizing the interactions between the electrode and the surface of the PSI or PSII polypeptide. Illumination of the PSI and PSII complexes immobilized on the ITO electrode resulted in action spectra in the presence of methyl viologen, which corresponded to the absorption spectra of the complexes. Compared with the ITO electrode, PSI or PSII complexes assembled on the TiO2 electrode had much higher energy-conversion efficiency in the presence of an iodide/triiodide redox system of an ionic-liquid-based electrolyte. This could have interesting applications in the development of DSBCs.

A light-harvesting complex of photosystem II (LHCII), isolated from spinach, was immobilized onto a gold electrode modified with self-assembled monolayers (SAMs) of alkanethiols, NH2–(CH2) n –SH, n = 2, 6, 8, 11; HOOC–(CH2)7–SH; and CH3–(CH2)7–SH; and a bare electrode. The extent of LHCII complex adsorption according to surface treatment decreased in the order amino groups > carboxylic acid groups > methyl groups and increased with the methylene chain length in NH2–(CH2) n –SH. Interestingly, the photocurrent density depended on the terminal group and the methylene chain length in NH2–(CH2) n –SH and decreased in the order amino groups > methyl groups > carboxylic acid groups. An efficient photocurrent response of the LHCII complex on SAMs of NH2–(CH2) n –SH, n = 8 was observed upon illumination at 680 nm. These results indicated that the LHCII complexes were well organized on the cationic surfaces of the gold electrodes modified with amino alkanethiols. The quantum yield depended on the methylene chain length (n), where the maximum photocurrent response was observed at n = 8, which corresponded to a distance of 1.7 nm between the terminal amino group in NH2–(CH2)8–SH and the gold surface.

Hydrogenases are powerful catalysts for light-driven H2 production using a combination of photosensitizers. However, except oxygen-tolerant hydrogenases, they are immediately deactivated under aerobic conditions. We report a light-driven H2 evolution system that works stably even under aerobic conditions. A [NiFe]-hydrogenase from Desulfovibrio vulgaris Miyazaki F was immobilized inside nanoporous glass plates (PGPs) with a pore diameter of 50 nm together with a ruthenium complex and methyl viologen as a photosensitizer and an electron mediator, respectively. After immersion of PGP into the medium containing the catalytic components, an anaerobic environment automatically established inside the nanopores even under aerobic external conditions upon irradiation with solar-simulated light; this system constantly evolved H2 with an efficiency of 3.7 μmol H2 m(-2) s(-1). The PGP system proposed in this work represents a promising first step toward the development of an O2-tolerant solar energy conversion system.

Anti-Stokes fluorescence from chlorophyll a molecules dispersed in diethyl ether has been observed. From the excitation power dependence of the fluorescence spectrum, it is concluded that the anti-Stokes fluorescence appears via the linear optical process. To consider the relationship between the observed spectral shape and vibrational modes, the model spectral density has been determined based on the Raman spectrum and real-time coherent vibrational oscillation signals. The absorption spectrum observed in the experiment was well reproduced by the calculation, indicating the validity of the model spectral density. The involvement of the low-frequency vibrational modes in the anti-Stokes fluorescence process is discussed.

Here, we demonstrate the formation of silver nanoparticles (Ag-NPs) on chemical vapor deposited graphene by dissolving base Ag foil, and their integration for Schottky junction photodetector fabrication. Ag-NPs of the size 20–100 nm were directly obtained by dissolving the Ag foil of the as-synthesized graphene in a diluted HNO3 solution. A Schottky junction is fabricated by transferring the Ag-NPs incorporated graphene onto a Si substrate. In the fabricated device, a significant photoresponse is observed with illumination of 3.6, 5.1 and 2.1 mW cm−2 of near-infrared (1000 nm), visible (550 nm) and near ultraviolet (350 nm) light, respectively. The graphene–Si Schottky junction shows photoresponses of 122, 98 and 78 mA W−1 at 550, 350 and 1000 nm, respectively. The strong photoresponse can be attributed to light interaction with the plasmonic Ag-NPs and effective graphene–Si Schottky junction. Our finding shows that enhancing the light absorption with plasmonic nanoparticles the weakest of incident light can be detected for a broad-wavelength range.

LH1-α and -β polypeptides, which make up the light-harvesting 1 (LH1) complex of purple photosynthetic bacteria, along with bacteriochlorophylls, have unique binding properties even for various porphyrin analogs. Herein, we used the porphyrin analogs, Zn-Chlorin and the Zn-Chlorin dimer, and examined their binding behaviors to the LH1-α variant, which has a His-tag at the C-terminus (MBP-rubα-YH). Zn-Chlorin and the Zn-Chlorin dimer could bind to MBP-rubα-YH and form a subunit-type assembly, similar to that from the native LH1 complex. These complexes could be immobilized onto Ni-nitrilotriacetic acid-modified Au electrodes, and the cathodic photocurrent was successfully observed by photoirradiation. Since Zn-Chlorins in this complex are too far for direct electron transfer from the electrode, a contribution of polypeptide backbone for efficient electron transfer was implied. These findings not only show interesting properties of LH1-α polypeptides but also suggest a clue to construct artificial photosynthesis systems using these peptide materials.

Transcription activator-like effector (TALE) nuclease (TALEN) is widely used as a tool in genome editing. The DNA binding part of TALEN consists of a tandem array of TAL-repeats that form a right-handed superhelix. Each TAL-repeat recognises a specific base by the repeat variable diresidue (RVD) at positions 12 and 13. TALEN comprising the TAL-repeats with periodic mutations to residues at positions 4 and 32 (non-RVD sites) in each repeat (VT-TALE) exhibits increased efficacy in genome editing compared with a counterpart without the mutations (CT-TALE). The molecular basis for the elevated efficacy is unknown. In this report, comparison of the physicochemical properties between CT- and VT-TALEs revealed that VT-TALE has a larger amplitude motion along the superhelical axis (superhelical motion) compared with CT-TALE. The greater superhelical motion in VT-TALE enabled more TAL-repeats to engage in the target sequence recognition compared with CT-TALE. The extended sequence recognition by the TAL-repeats improves site specificity with limiting the spatial distribution of FokI domains to facilitate their dimerization at the desired site. Molecular dynamics simulations revealed that the non-RVD mutations alter inter-repeat hydrogen bonding to amplify the superhelical motion of VT-TALE. The TALEN activity is associated with the inter-repeat hydrogen bonding among the TAL repeats.

A light-harvesting (LH) antenna complex II, LHCII, isolated from spinach was immobilized onto an indium tin oxide (ITO) electrode with dot patterning of 3-aminopropyltriethoxysilane (APS) by utilizing electrostatic interactions between the cationic surface of the electrode and the anionic surface of stromal side of the LHCII polypeptide. Interestingly, the illumination of LHCII assembled onto the ITO electrode produced a photocurrent response that depends on the wavelength of the excitation light. Further, LHCII was immobilized onto a TiO2 nanostructured film to extend for the development of a dye-sensitized biosolar cell system. The photocurrent measured in the iodide/tri-iodide redox system of an ionic liquid based electrolyte on the TiO2 system showed remarkable enhancement of the conversion efficiency, as compared to that on the ITO electrode.

The two-dimensional molecular assembly was accomplished of bacteriochlorophyll a (BChl a) and zinc-substituted BChl a (Zn-BChl a) together with synthetic poly(ethylene glycol)(PEG)-linked light-harvesting (LH) model polypeptides on a gold Au(111) electrode modified with supported lipid bilayers. Model polypeptides for LH1-α from Rhodospirillum (Rs.) rubrum were successfully synthesized and stably assembled with Zn-BChl a in 1,2-dioleoyl-sn-glycero-3-[phospho-rac-(1′-glycerol)] (DOPG) lipid bilayers on an electrode at room temperature, as well as in liposomal solution, in which the Zn-BChl a complex unlike BChl a, was stably assembled. The PEG moiety of the model polypeptide assisted the stable assembly with an α-helical conformation of the LH1-α model peptides together with these pigments onto the gold electrode with defined orientation. The photocurrent response depended on the combinations of the pigments and synthetic LH model polypeptides. The results presented herein will be useful for the self-assem...

Two types of photosynthetic membrane proteins, the peripheral antenna complex (LH2) and the core antenna/reaction center complex (LH1-RC), play an essential role in the primary process of purple bacterial photosynthesis, that is, capturing light energy, transferring it to the RC where it is used in subsequent charge separation. Establishment of experimental platforms is required to understand the function of the supramolecular assembly of LH2 and LH1-RC molecules into arrays. In this study, we assembled LH2 and LH1-RC arrays into domain-structured planar lipid bilayers placed on a coverglass using stepwise combinations of vesicle-to-planar membrane formation and vesicle fusion methods. First, it was shown that assembly of LH2 and LH1-RC in planar lipid bilayers, through vesicle-to-planar membrane formation, could be confirmed by absorption spectroscopy and high resolution atomic force microscopy (AFM). Second, formation of a planar membrane incorporating LH2 molecules made by the vesicle fusion method was corroborated by AFM together with quantitative analysis by surface plasmon resonance (SPR). By combining planar membrane formation and vesicle fusion, in a stepwise manner, LH2 and LH1-RC were successfully organized in the domain-structured planar lipid membrane. This methodology for construction of LH2/LH1-RC assemblies will be a useful experimental platform with which to investigate energy transfer from LH2 to LH1-RC where the relative arrangement of these two complexes can be controlled.

In purple photosynthetic bacteria, light-harvesting complex 2 (LH2) and the light harvesting-reaction center complex (LH1-RC) play the key roles of capturing and transferring light energy and subsequent charge separation. These photosynthetic apparatuses form a molecular assembly; however, how the assembly influences the efficiency of energy conversion is not yet clear. To address this issue, direct observation of the assembly at the molecular level is necessary to analyze its function. In this study, we reconstituted photosynthetic membrane proteins into artificial lipid bilayers and directly observed their assembly by AFM. The absorption spectra of the reconstituted proteins showed characteristic Qy bands of bacteriochlorophyll a that were identical to those of intact proteins. AFM observation of the reconstituted membranes revealed that LH2 and LH1-RC were successfully assembled into the lipid bilayer, and their observed structures were in good agreement with corresponding crystallographic structures. Specifically, binary proteins, i.e., LH2/LH1-RC and LH2/LH1, which form a densely packed molecular assembly, could be clearly identified at the molecular level by this method of observation. Energy transfer from LH2 to LH1-RC in a reconstituted lipid bilayer was observed by steady-state fluorescence spectroscopy. Enhanced energy transfer was confirmed in the membrane phase compared to that in a homogeneous micellar solution. Such reconstituted molecular assemblies are useful experimental platforms to investigate the relationship between supramolecular arrays and function. [DOI: 10.1380/ejssnt.2011.15]

Molecular assembly of Zn-porphyrin pigments on a gold electrode using synthetic 1α-helix hydrophobic polypeptides which have similar amino acid sequences to the hydrophobic core in the native photosynthetic light-harvesting (LH) 1-β polypeptide from Rhodobacter sphaeroides has been achieved. This method is clearly successful in allowing assembly of porphyrins together with LH1 type functional complexes with a defined distance and orientation on the electrode. In this case, the photocurrent direction and the distance of electron transfer of pigments could be controlled by these synthetic LH1 model polypeptides. This method will be useful for the self-assembly of these pigment and protein complexes in order to study the energy transfer and electron transfer reactions between individual pigments in the supramolecular complexes on the electrode, as well as to provide insight into the effect of the distance and orientation of pigments and the effect of the structure of 1α-helix hydrophobic polypeptide on the energy transfer and electron transfer reactions.

光合成膜中では，光エネルギー変換機能をもつタンパク質超分子複合体に含まれる色素分子が，タンパク質と相互作用をしてその機能を発揮している．本報では，光合成のアンテナ系タンパク質超分子複合体(LH1 複合体)中のカロテノイド色素分子の構造と機能の関係を調べるために，共役二重結合鎖長の異なるカロテノイドを用いて LH1 複合体の再構成を行った．そして，得られた再構成 LH1 複合体の Stark スペクトル測定を行い，カロテノイドおよびバクテリオクロロフィル a(BChl a)周辺の静電場環境を評価した．さらに，カロテノイド分子の半経験的分子軌道計算を行って，LH1 複合体中のカロテノイド分子の立体構造を解析した．その結果，このカロテノイド分子は，結晶構造が報告されている LH2 複合体中のカロテノイドと同様に，全トランス体のねじれ構造でタンパク質との結合部位に組織化されていると考えられた．

A persulfated molecular umbrella derived from one spermine, four lysine, and eight deoxycholic acid molecules was found to exhibit ionophoric activity, as shown by pH discharge and Na(+) and Cl(-) transport experiments. In sharp contrast, a moderately more hydrophilic analogue derived from cholic acid showed no such ionophoric activity. Both molecular umbrellas crossed liposomal membranes by passive transport with experimental rates that were similar. These findings show how the interactions between such amphomorphic molecules and phospholipid bilayers are a sensitive function of the umbrella's hydrophilic/lipophilic balance (HLB). They also raise the possibility of exploiting molecular umbrellas in fundamentally new ways.

Phospholipid-linked naphthoquinones separated by spacer methylene groups (C n ), PE-C n -NQ ( n = 0, 5, 11), were synthesized to investigate the quinone-mediated electron transfers on a glassy carbon (GC) electrode covered with phospholipids membrane. The PE-C n -NQ could be incorporated in lipid bilayer composed of phosphatidylcholine and exhibited characteristic absorption spectral change corresponding to their redox state, quinone/hydroquinone. The cyclic voltammogram of PE-C n -NQ-containing lipid bilayer modified on a GC electrode indicated a set of waves corresponding to the consecutive two-electron and two-proton transfer reduction of the quinone moiety. The peak currents of PE-C n -NQ as a function of temperature showed a sharp break point in the current–temperature behavior, reflecting the gel-fluid phase transition. The shape of the cyclic voltammograms changed with the pH of the buffer solution. Below pH 6 the first step of the reduction of quinone was a monoprotonation of quinone, whereas above pH 10 the first step of the oxidation was a monodeprotonation of hydroquinone. This indicates that reaction sequences of quinone/hydroquinone were different with the change of the pH. These results showed that the PE-C n -NQ exhibited electron transfer associated with proton transfer in the lipid membranes, depending on the diffusivity of the redox species in the membrane and pH. Interestingly, less effect of the number of methylene of the spacer group on the peak currents was observed. Comparison of manganese porphyrin-mediated electron transfer that depends on the spacer methylene lengths [M. Nango, T. Hikita, T. Nakano, T. Yamada, M. Nagata, Y. Kurono, T. Ohtsuka, Langmuir 14 (1998) 407] is made.

Photosynthetic light-harvesting polypeptide/pigment complexes (LH ) play an essential role in the primary process of an efficient solar energy-transduction in photosynthetic membrane. In our research, we aim to use the LH complex and control its direction and orientation on electrodes for the development of nanobiodevices from solar to fuel. Specifically, we focus on the construction of an array of the LH on electrodes using a modified photosynthetic protein complex prepared from modern biosynthetic manufacturing methods and in lipid membranes.

We reported here that polyethylene glycol (PEG)-linked manganese pyrochlorophyllide a (PEG-MnPChlide a) possesses remarkable catalytic activity comparable to horseradish peroxidase (HRP). The PEG-MnPChlide a catalyzed the oxidation decoloration reaction of C.I. Acid Orange 7 by hydrogen peroxide under a mild aqueous condition, pH 8.0 at 25 degrees C. The manganese pyrochlorophyride a methylester (MnPChlide a ME) dissolved in a Triton X-100 micellar solution also exhibited the catalytic activity, indicating the micellar environment plays an important role in the catalytic reaction. The reaction rate was accelerated by addition of imidazole. The catalytic reactions were analyzed by Michaelis-Menten kinetics, revealing that the higher reactivity of catalyst-substrate complex is responsible for the present catalytic reaction system.

Laminar-Turbulent transition of a boundary layer induced by a single roughness element in the inlet region of a circular pipe was experimentally investigated. Mean and fluctuating velocity components in the axial direction were measured by a hot-wire anemometer. The Reynolds number based on the pipe diameter and the bulk velocity was 20 000. A stationary turbulent region was formed downstream of the roughness element. The contour lines of the turbulent region were wedge-shaped once they unfolded onto a flat plane. The virtual origin of the turbulent region equaled the roughness position. The contour lines of intermittency, which were initially staight, then curved to the outside. This condition is similar to that of the turbulence wedge on a flat plate. The fluctuating velocity was as its maximum not at the center of the region but at an interface region between the turbulent region and surrounding laminar region. The fluctuation within the interface region was large.

To reveal the structure-function relationship of membrane proteins, a membrane environment is often used to establish a suitable platform for assembly, functioning, and measurements. The control of the orientation of membrane proteins is the main challenge. In this study, the electron conductivity and photocurrent of a light-harvesting/reaction center core complex (LH1-RC) embedded in a lipid membrane were measured using conductive atomic force microscopy (C-AFM) and photoelectrochemical analysis. AFM topographs showed that LH1-RC molecules were well-orientated, with their H-subunits toward the membrane surface. Rectified conductivity was observed in LH1-RC under precise control of the applied force on the probe electrode (

Disulfide-linked manganese mesoporphyrin derivatives with spacer methylene-chain groups (Cn), (MnMP–Cn–S)2 [n=2, 6, 12] and one fluorinated mesoporphyrin derivative, (MnMPF4–C12–S)2 (Scheme 1) were synthesized and assembled on a gold electrode to study the nature of their electron transfer with respect to catalytic activity. The electron transfer of the mesoporphyrins from and to the self-assembled monolayers (SAMs) was measured in aqueous solution as well as in dimethyl sulfoxide (DMSO) using cyclic voltammetry and potential modulation reflectance, i.e., electroreflectance. Redox reaction of the mesoporphyrins on the electrode occurred between Mn(III) and Mn(II) occluded in the porphyrin ring. The rate constants of the electron transfer from and to the manganese mesoporphyrins on gold electrodes, estimated from the ER vs. modulation frequency relation, increased with the decreasing chain lengths but decreased due to fluorination of the porphyrin ring, which is in agreement with the rates for tetraphenyl porphyrins and its halogenated derivatives. Interestingly, the rate constants for the manganese mesoporphyrins in DMSO were greater than the rates for the tetraphenyl porphyrins and were enhanced by additional insertion of alkanethiols into the SAMs in aqueous solution.

In this study, TiN thin film was deposited onto a glass substrate by the inclined opposite target type DC magnetron sputtering method with the good electric characteristics. The coating of TiN thin film was carried out onto substrate at the temperature of 303 K. The effects of nitrogen gas flow and film thickness on transparency, electric resistivity and electromagnetic wave shielding effectiveness of TiN thin films were discussed. The experimental results obtained were summarized as follows: (1) The TiN thin film deposited at the room temperature showed very low electric resistivity of 8.8×10-5Ω.cm. The TiN film showed the crystal structure when the depositing time was over 20 min. (2) When the film thickness of TiN was very thin, the TiN thin film was transparent for the visible light. The electric resistivity decreased with increasing the deposition time. (3) The electric resistivity and the transparency of TiN thin film depended greatly on the nitrogen gas flow.

Peptide-based gemini surfactants, called PG-surfactants, consisting of a tri- or tetra-Asp peptide core and acetylated dodecylamine-conjugated Cys residues at both the N- and C-terminal ends (D3C12...

The In2O3-SnO2, ITO, thin film is a transparent conductive film. Then, the ITO film is one of the materials for widely practical use. Because the ITO film has high transparency in the area of the visible ray and low resistivity, it should show excellent electromagnetic wave shielding effectiveness. In the present study, the ITO film was produced onto glass substrate at room temperature by the inclined opposite target type DC magnetron sputtering equipment, in which pure In and Sn metal targets were used. The effects of oxygen partial pressure and work voltage on the specific resistivity and transparency of the ITO film were discussed. For low resistivity of the ITO film, the electromagnetic wave shielding effectiveness was studied. The results obtained were summarized as follows: (1) The ITO film produced at room temperature had amorphous structure with very smooth surface. (2) The resistivity of ITO film deposited at room temperature showed minimum value at the oxygen partial pressure of 2.73×10-2Pa. (3) The resistivity of ITO film deposited at room temperature depended on the work voltage and showed the minimum value in the work voltage of -30V. (4) When the optimum coating conditions were selected, the resistivity of 3.5×10-4Ω.cm was obtained. (5) When the work voltage was -30V, the ITO film deposited at room temperature showed the most effective electromagnetic wave shielding performance. Also, the electromagnetic wave shielding performance was increased by laminating the film.

The electromagnetic interference (EMI) may cause disruptions in robots, personal computers, cellular phones, medical appliance and other electronic instruments. It is therefore important to develop the materials where shield the electromagnetic wave in the environment from the EMI generated by electronic devices. This study was performed to obtain an instruction for the development of smart materials having shielding effectiveness for electromagnetic wave. In the plastic composites used, fine copper wires were oriented with various angles and separations. The fundamental characteristics of shielding effectiveness for electromagnetic wave investigated for the basic plastic composite and carbon fiber reinforced composite. The shielding effectiveness was measured using a copper shielding box located in an electromagnetic shielding room. It was found out that the shielding effectiveness for electromagnetic wave depends on the oriented angle of copper wire. The shielding effectiveness decreased with increasing the wire separation. For carbon fiber reinforced composites, the shielding effectiveness was improved by the contact of carbon fiber each other.

We simulated a temperature change in thin phase-change optical discs that have various substrate thicknesses in order to evaluate the thermal tolerance of a polycarbonate substrate during DC sheet beam initialization. We simulated the temperature change by applying a finite difference method to the partial differential equation for heat conduction. In discs with substrates on both sides, the difference between the sums of the given heat while the temperature of each substrate is more than or equal to glass transition temperature for a disc with a 100-µm-thick substrate on both sides and a disc with a 5-µm-thick substrate on one or both sides, was within 5%. The sum of the given heat to the substrate for a disc with a substrate on one side, was about 1.5 times larger than that for a disc with substrates on both sides. These results showed that the initialization margin needed to obtain a good-quality initialization state with no thermal damage to the substrate is smaller for a disc with a substrate on one side than for that with substrates on both sides.