A chlorin‐carotenoid dyad Dyad‐COOH possessing a C32‐carboxylic acid group and a carotenoid moiet... more A chlorin‐carotenoid dyad Dyad‐COOH possessing a C32‐carboxylic acid group and a carotenoid moiety at the terminal end of C17‐substituent is synthesized from naturally occurring chlorophyll‐a as a new sensitizer for photocatalytic hydrogen evolution (PHE). Under the same experimental conditions, a maximum turnover number (TON) of PHE based on Dyad‐COOH/Pt/TiO2 is much higher than those of Pt/TiO2‐based photocatalysts sensitized by the corresponding chlorin carboxylic acid (Chl‐COOH) without carotenoid side chain, sole carotenoic acid (Car‐COOH), or their 1:1 (mol/mol) mixture. By co‐adsorbing different types of carboxylic acid, the TON of Chl‐COOH is found to be increased probably due to the suppression of chlorin aggregates on the TiO2 surface. The Dyad‐COOH/Pt/TiO2 exhibits excellent photocatalytic performance with the hydrogen evolution of 9147 µmol g−1 h−1 with TON of 425 when 43 µmol g−1 of dye is loaded on the Pt/TiO2 catalyst, while a better TON of 556 is achieved by preparing the photocatalyst with 10 µmol g−1 of Dyad‐COOH. This study provides new ideas for utilizing traditional photosynthetic dyes to a low‐cost and highly‐efficient photosensitizer for PHE.
Development of efficient photocatalysts with a wide spectral range for the photocatalytic hydroge... more Development of efficient photocatalysts with a wide spectral range for the photocatalytic hydrogen evolution reaction (HER) is a promising way to address the current energy and environmental crises.
The siphonaxanthin-siphonein-Chl-a/b-protein (SCP) is the light-harvesting complex of the marine ... more The siphonaxanthin-siphonein-Chl-a/b-protein (SCP) is the light-harvesting complex of the marine alga Codium fragile. Its structure resembles that of the major light-harvesting complexes of higher plants, LHC II, yet it features a reversed Chl a:Chl b ratio and it accommodates other variants of carotenoids. We have recorded the fluorescence emission spectra and fluorescence lifetimes from ensembles and single SCP complexes for three different scenarios of handling the samples. While the data obtained from ensembles of SCP complexes yield equivalent results, those obtained from single SCP complexes featured significant differences as a function of the sample history. We ascribe this discrepancy to the different excitation intensities that have been used for ensemble and single complex spectroscopy, and conclude that the SCP complexes undergo an aging process during storage. This process is manifested as a lowering of energetic barriers within the protein, enabling thermal activation ...
The LH1 antenna complex and a native form of the LH2 complex were isolated from the carotenoidles... more The LH1 antenna complex and a native form of the LH2 complex were isolated from the carotenoidless R26 and R26.1 mutants of Rhodobacter sphaeroides by the use of a new detergent, sucrose monocholate. One-color, pump-and-probe transient Raman spectroscopy of these complexes using 351 nm, approximately 50 ps pulses showed the generation of the triplet state of bacteriochlorophyll a (BChl a), whereas measurements using 355 nm, approximately 12 ns pulses showed the generation of BChl a cation radical. Subpicosecond to nanosecond time-resolved absorption spectroscopy using 388 nm, 200 fs pulses for excitation showed rapid (<1 ps) generation of the triplet state and fast decay (<10 ps) of the singlet state of BChl a. Microsecond absorption spectroscopy confirmed the generation of BChl a cation radical. EPR spectroscopy using 532 nm, approximately 5 ns pulses for excitation established the generation of BChl a cation radical. The EPR line width suggested that the unpaired electron is shared by two BChl a molecules. In LH1, the yield of BChl a cation radical per complex was estimated to be about 80% of that in the reaction center, and in LH2 about 50%. Thus, rapid generation of the triplet state, and its subsequent transformation into the cation-radical state of BChl a have been shown to be intrinsic properties of B870 and B850 BChl a assembly in the carotenoidless LH1 and LH2 antenna complexes. In the case of the carotenoid-containing LH2 complex, the triplet states of BChl a and carotenoid (spheroidene) were generated immediately after excitation, but the triplet-state BChl a was quenched efficiently by the carotenoid so that no BChl a cation radical was generated. Thus, the photoprotective function of the carotenoid in this antenna complex is shown.
Ischemic brain injury provokes complex, time-dependent downstream pathways that ultimately lead t... more Ischemic brain injury provokes complex, time-dependent downstream pathways that ultimately lead to cell death. We aimed to demonstrate the levels of a wide range of metabolites in brain lysates and their on-tissue distribution following neonatal stroke and cell therapies. Postnatal day 12 mice underwent middle cerebral artery occlusion (MCAO) and were administered 1 × 105 cells after 48 h. Metabolomic analysis of the injured hemisphere demonstrated that a variety of amino acids were significantly increased and that tricarboxylic acid cycle intermediates and some related amino acids, such as glutamate, were decreased. With the exception of the changes in citric acid, neither mesenchymal stem/stromal cells nor CD34+ cells ameliorated these changes. On-tissue visualization with matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) imaging revealed that the signal intensity of glutamate was significantly decreased in the infarct area, consistent with the metabolomic a...
The 17-propionate ester group of chlorophyll(Chl)-a in some oxygenic phototrophs was investigated... more The 17-propionate ester group of chlorophyll(Chl)-a in some oxygenic phototrophs was investigated using HPLC. Chls-a esterified with partially dehydrogenated forms of a phytyl group were found in fully grown cells of a diatom, Chaetoceros calcitrans: geranylgeranyl (GG), dihydrogeranylgeranyl (DHGG), and tetrahydrogeranylgeranyl (THGG). Chls-a bearing such esterifying groups were reported to be found only in greening processes of higher plants, and thus these Chls-a have been thought to be biosynthetic precursors for phytylated Chl-a. Their molecular structures were unambiguously determined using H and C NMR spectroscopy and mass spectrometry. In particular, the positions of C═C double bonds in DHGG were identified at C2═C3, C6═C7, and C14═C15, and those in THGG were determined to be at C2═C3 and C14═C15. Notably, the present DHGG was different from the previously determined DHGG of bacteriochlorophyll-a in purple bacteria (C2═C3, C10═C11, and C14═C15). Moreover, thylakoid membranes...
Abstract The composition of carotenoid pigments from the fruit of the Pandanus plant, Pandanus co... more Abstract The composition of carotenoid pigments from the fruit of the Pandanus plant, Pandanus conoideus Lam. monocot or locally named as red fruit, indigenous to the Papua Islands, was investigated. By chromatographic and spectrometric analyses using RP-HPLC with C18 and C30 columns and gradient elution, NMR, MS/MS and FT-IR, eight κ-end group carotenoids, 5,6-diepicapsokarpoxanthin, capsorubin, capsanthin, cryptocapsin, 13-cis capsorubin, and three capsanthin epoxides were identified. Additionally, β-cryptoxanthin 5,6-epoxide, α- and β-cryptoxanthin, α- and β-carotene, and other carotenoid-type compounds were found. The κ-end group carotenoids in red fruit comprised 92 % in relative contents and was much higher than that in red chili pepper, Capsicum annuum L., at 64 %. These findings indicate that red fruit has similar carotenoids to those of red chili pepper, not only in composition but also in the content. Xanthophyll cycle carotenoids antheraxanthin and violaxanthin are the precursors of capsanthin and capsorubin, respectively. However, these precursors, as well as the precursors of zeaxanthin, were not detected in the chromatographic separation and identification in the extracts of red fruit, although they were detected in red chili pepper under the same analytical conditions used. Therefore, in red fruit, those precursors are likely not responsible for the biosynthesis of κ-end group carotenoids.
A chlorin‐carotenoid dyad Dyad‐COOH possessing a C32‐carboxylic acid group and a carotenoid moiet... more A chlorin‐carotenoid dyad Dyad‐COOH possessing a C32‐carboxylic acid group and a carotenoid moiety at the terminal end of C17‐substituent is synthesized from naturally occurring chlorophyll‐a as a new sensitizer for photocatalytic hydrogen evolution (PHE). Under the same experimental conditions, a maximum turnover number (TON) of PHE based on Dyad‐COOH/Pt/TiO2 is much higher than those of Pt/TiO2‐based photocatalysts sensitized by the corresponding chlorin carboxylic acid (Chl‐COOH) without carotenoid side chain, sole carotenoic acid (Car‐COOH), or their 1:1 (mol/mol) mixture. By co‐adsorbing different types of carboxylic acid, the TON of Chl‐COOH is found to be increased probably due to the suppression of chlorin aggregates on the TiO2 surface. The Dyad‐COOH/Pt/TiO2 exhibits excellent photocatalytic performance with the hydrogen evolution of 9147 µmol g−1 h−1 with TON of 425 when 43 µmol g−1 of dye is loaded on the Pt/TiO2 catalyst, while a better TON of 556 is achieved by preparing the photocatalyst with 10 µmol g−1 of Dyad‐COOH. This study provides new ideas for utilizing traditional photosynthetic dyes to a low‐cost and highly‐efficient photosensitizer for PHE.
Development of efficient photocatalysts with a wide spectral range for the photocatalytic hydroge... more Development of efficient photocatalysts with a wide spectral range for the photocatalytic hydrogen evolution reaction (HER) is a promising way to address the current energy and environmental crises.
The siphonaxanthin-siphonein-Chl-a/b-protein (SCP) is the light-harvesting complex of the marine ... more The siphonaxanthin-siphonein-Chl-a/b-protein (SCP) is the light-harvesting complex of the marine alga Codium fragile. Its structure resembles that of the major light-harvesting complexes of higher plants, LHC II, yet it features a reversed Chl a:Chl b ratio and it accommodates other variants of carotenoids. We have recorded the fluorescence emission spectra and fluorescence lifetimes from ensembles and single SCP complexes for three different scenarios of handling the samples. While the data obtained from ensembles of SCP complexes yield equivalent results, those obtained from single SCP complexes featured significant differences as a function of the sample history. We ascribe this discrepancy to the different excitation intensities that have been used for ensemble and single complex spectroscopy, and conclude that the SCP complexes undergo an aging process during storage. This process is manifested as a lowering of energetic barriers within the protein, enabling thermal activation ...
The LH1 antenna complex and a native form of the LH2 complex were isolated from the carotenoidles... more The LH1 antenna complex and a native form of the LH2 complex were isolated from the carotenoidless R26 and R26.1 mutants of Rhodobacter sphaeroides by the use of a new detergent, sucrose monocholate. One-color, pump-and-probe transient Raman spectroscopy of these complexes using 351 nm, approximately 50 ps pulses showed the generation of the triplet state of bacteriochlorophyll a (BChl a), whereas measurements using 355 nm, approximately 12 ns pulses showed the generation of BChl a cation radical. Subpicosecond to nanosecond time-resolved absorption spectroscopy using 388 nm, 200 fs pulses for excitation showed rapid (<1 ps) generation of the triplet state and fast decay (<10 ps) of the singlet state of BChl a. Microsecond absorption spectroscopy confirmed the generation of BChl a cation radical. EPR spectroscopy using 532 nm, approximately 5 ns pulses for excitation established the generation of BChl a cation radical. The EPR line width suggested that the unpaired electron is shared by two BChl a molecules. In LH1, the yield of BChl a cation radical per complex was estimated to be about 80% of that in the reaction center, and in LH2 about 50%. Thus, rapid generation of the triplet state, and its subsequent transformation into the cation-radical state of BChl a have been shown to be intrinsic properties of B870 and B850 BChl a assembly in the carotenoidless LH1 and LH2 antenna complexes. In the case of the carotenoid-containing LH2 complex, the triplet states of BChl a and carotenoid (spheroidene) were generated immediately after excitation, but the triplet-state BChl a was quenched efficiently by the carotenoid so that no BChl a cation radical was generated. Thus, the photoprotective function of the carotenoid in this antenna complex is shown.
Ischemic brain injury provokes complex, time-dependent downstream pathways that ultimately lead t... more Ischemic brain injury provokes complex, time-dependent downstream pathways that ultimately lead to cell death. We aimed to demonstrate the levels of a wide range of metabolites in brain lysates and their on-tissue distribution following neonatal stroke and cell therapies. Postnatal day 12 mice underwent middle cerebral artery occlusion (MCAO) and were administered 1 × 105 cells after 48 h. Metabolomic analysis of the injured hemisphere demonstrated that a variety of amino acids were significantly increased and that tricarboxylic acid cycle intermediates and some related amino acids, such as glutamate, were decreased. With the exception of the changes in citric acid, neither mesenchymal stem/stromal cells nor CD34+ cells ameliorated these changes. On-tissue visualization with matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) imaging revealed that the signal intensity of glutamate was significantly decreased in the infarct area, consistent with the metabolomic a...
The 17-propionate ester group of chlorophyll(Chl)-a in some oxygenic phototrophs was investigated... more The 17-propionate ester group of chlorophyll(Chl)-a in some oxygenic phototrophs was investigated using HPLC. Chls-a esterified with partially dehydrogenated forms of a phytyl group were found in fully grown cells of a diatom, Chaetoceros calcitrans: geranylgeranyl (GG), dihydrogeranylgeranyl (DHGG), and tetrahydrogeranylgeranyl (THGG). Chls-a bearing such esterifying groups were reported to be found only in greening processes of higher plants, and thus these Chls-a have been thought to be biosynthetic precursors for phytylated Chl-a. Their molecular structures were unambiguously determined using H and C NMR spectroscopy and mass spectrometry. In particular, the positions of C═C double bonds in DHGG were identified at C2═C3, C6═C7, and C14═C15, and those in THGG were determined to be at C2═C3 and C14═C15. Notably, the present DHGG was different from the previously determined DHGG of bacteriochlorophyll-a in purple bacteria (C2═C3, C10═C11, and C14═C15). Moreover, thylakoid membranes...
Abstract The composition of carotenoid pigments from the fruit of the Pandanus plant, Pandanus co... more Abstract The composition of carotenoid pigments from the fruit of the Pandanus plant, Pandanus conoideus Lam. monocot or locally named as red fruit, indigenous to the Papua Islands, was investigated. By chromatographic and spectrometric analyses using RP-HPLC with C18 and C30 columns and gradient elution, NMR, MS/MS and FT-IR, eight κ-end group carotenoids, 5,6-diepicapsokarpoxanthin, capsorubin, capsanthin, cryptocapsin, 13-cis capsorubin, and three capsanthin epoxides were identified. Additionally, β-cryptoxanthin 5,6-epoxide, α- and β-cryptoxanthin, α- and β-carotene, and other carotenoid-type compounds were found. The κ-end group carotenoids in red fruit comprised 92 % in relative contents and was much higher than that in red chili pepper, Capsicum annuum L., at 64 %. These findings indicate that red fruit has similar carotenoids to those of red chili pepper, not only in composition but also in the content. Xanthophyll cycle carotenoids antheraxanthin and violaxanthin are the precursors of capsanthin and capsorubin, respectively. However, these precursors, as well as the precursors of zeaxanthin, were not detected in the chromatographic separation and identification in the extracts of red fruit, although they were detected in red chili pepper under the same analytical conditions used. Therefore, in red fruit, those precursors are likely not responsible for the biosynthesis of κ-end group carotenoids.
Uploads
Papers by Ritsuko Fujii