The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform
Tanai Cardona - One of the best experts on this subject based on the ideXlab platform.
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evolution of Photochemical Reaction centres more twists
Trends in Plant Science, 2019Co-Authors: Tanai Cardona, William A RutherfordAbstract:One of the earliest events in the molecular evolution of photosynthesis is the structural and functional specialisation of type I (ferredoxin-reducing) and type II (quinone-reducing) Reaction centres. In this opinion article we point out that the homodimeric type I Reaction centre of heliobacteria has a calcium-binding site with striking structural similarities to the Mn4CaO5 cluster of photosystem II. These similarities indicate that most of the structural elements required to evolve water oxidation chemistry were present in the earliest Reaction centres. We suggest that the divergence of type I and type II Reaction centres was made possible by a drastic structural shift linked to a change in redox properties that coincided with or facilitated the origin of photosynthetic water oxidation.
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evolution of Photochemical Reaction centres more twists
bioRxiv, 2018Co-Authors: Tanai Cardona, William A RutherfordAbstract:The earliest event recorded in the molecular evolution of photosynthesis is the structural and functional specialisation of Type I (ferredoxin-reducing) and Type II (quinone-reducing) Reaction centres. Here we point out that the homodimeric Type I Reaction centre of Heliobacteria has a Ca2+-binding site with a number of striking parallels to the Mn4CaO5 cluster of cyanobacterial Photosystem II. This structural parallels indicate that water oxidation chemistry originated at the divergence of Type I and Type II Reaction centres. We suggests that this divergence was triggered by a structural rearrangement of a core transmembrane helix resulting in a shift of the redox potential of the electron donor side and electron acceptor side at the same time and in the same redox direction.
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a fresh look at the evolution and diversification of Photochemical Reaction centers
Photosynthesis Research, 2015Co-Authors: Tanai CardonaAbstract:In this review, I reexamine the origin and diversification of Photochemical Reaction centers based on the known phylogenetic relations of the core subunits, and with the aid of sequence and structural alignments. I show, for example, that the protein folds at the C-terminus of the D1 and D2 subunits of Photosystem II, which are essential for the coordination of the water-oxidizing complex, were already in place in the most ancestral Type II Reaction center subunit. I then evaluate the evolution of Reaction centers in the context of the rise and expansion of the different groups of bacteria based on recent large-scale phylogenetic analyses. I find that the Heliobacteriaceae family of Firmicutes appears to be the earliest branching of the known groups of phototrophic bacteria; however, the origin of Photochemical Reaction centers and chlorophyll synthesis cannot be placed in this group. Moreover, it becomes evident that the Acidobacteria and the Proteobacteria shared a more recent common phototrophic ancestor, and this is also likely for the Chloroflexi and the Cyanobacteria. Finally, I argue that the discrepancies among the phylogenies of the Reaction center proteins, chlorophyll synthesis enzymes, and the species tree of bacteria are best explained if both types of Photochemical Reaction centers evolved before the diversification of the known phyla of phototrophic bacteria. The primordial phototrophic ancestor must have had both Type I and Type II Reaction centers.
Jong Liang Lin - One of the best experts on this subject based on the ideXlab platform.
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Comparison of the Thermal and Photochemical Reaction Pathways of Melamine on TiO2
The Journal of Physical Chemistry C, 2015Co-Authors: Yu Chen Lin, Tzu En Chien, Jong Liang LinAbstract:Fourier transform infrared spectroscopy was employed to study the thermal and Photochemical Reactions of melamine ((H2N)3(C3N3)) on TiO2. Also tested was the adsorption of urea, cyanamide (H2N–C≡N), dicyandiamide ((H2N)2C═N–C≡N), and cyanuric acid ((OH)3(C3N3)) for identifying possible Reaction intermediates. It was found that the thermal decomposition of melamine starts with N–H bond scission, possibly forming intermediates such as (H2N)2(C3N3)NH– and (H2N)(C3N3)(NH)2–. Further loss of hydrogen atoms and ring-opening from these intermediates lead to the formation of −NCO (isocyanate) and −N3 (azide) on the surface. The TiO2-mediated Photochemical Reaction of melamine proceeds via a different mechanism, forming dicyandiamide. These thermal and Photochemical Reaction pathways of melamine on TiO2 are reported for the first time. They are different from previous studies showing the processes of polymerization, and substitution of NH2 by OH to form cyanuric acid and urea.
Isao Komasawa - One of the best experts on this subject based on the ideXlab platform.
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a deep desulfurization process for light oil by Photochemical Reaction in an organic two phase liquid liquid extraction system
Industrial & Engineering Chemistry Research, 1998Co-Authors: Yasuhiro Shiraishi, Takayuki Hirai And, Isao KomasawaAbstract:A novel deep desulfurization process of light oil, effected by a combination of Photochemical Reaction and organic two-phase liquid−liquid extraction, has been investigated. The process is comprised of two stages. The first consists of the transfer of the sulfur-containing compounds from the light oil to an aqueous-soluble polar solvent. This is then followed by the photooxidation and photodecomposition of the sulfur-containing compounds in the solvent by UV irradiation, using a high-pressure mercury lamp. The operations are carried out under conditions of room temperature and atmospheric pressure. Acetonitrile was found to be the most suitable polar solvent for the process. In acetonitrile, dibenzothiophene (DBT) is converted to DBT 5-monoxide and then to DBT 5,5-dioxide, dibenz[c,e][1,2]oxathiin 6-oxide, and aromatic sulfonate or sulfinate anion by the UV irradiation. These products are highly polarized and are therefore not distributed into the nonpolar light oil phase. An adverse effect of naphthalene...
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effect of photosensitizer and hydrogen peroxide on desulfurization of light oil by Photochemical Reaction and liquid liquid extraction
Industrial & Engineering Chemistry Research, 1997Co-Authors: Takayuki Hirai, Yasuhiro Shiraishi, Ken Ogawa, Isao KomasawaAbstract:A desulfurization process for dibenzothiophene (DBT) by a combination of Photochemical Reaction and liquid-liquid extraction has been investigated. The DBT dissolved in tetradecane was photodecomposed by the use of a high-pressure mercury lamp and removed into the water phase at conditions of room temperature and atmospheric pressure. The addition of benzophenone (BZP), a triplet photosensitizer, enhanced the removal of DBT from tetradecane. This Reaction, however, hardly proceeded in the presence of naphthalene (NP), probably because of triplet energy transfer from photoexcited DBT or BZP to ground-state NP. The addition of hydrogen peroxide enhanced the desulfurization of commercial light oil as well as the removal of DBT from tetradecane, since H{sub 2}O{sub 2} acted as a weak oxidizing agent for photoexcited DBT and interrupted the energy transfer from excited DBT to NP to some extent. In the case using a 30% H{sub 2}O{sub 2} solution, the desulfurization yield of commercial light oil was 75% following 24 h of photoirradiation and the sulfur content in the light oil was reduced from 0.2 wt % to less than 0.05 wt %.
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desulfurization process for dibenzothiophenes from light oil by Photochemical Reaction and liquid liquid extraction
Industrial & Engineering Chemistry Research, 1996Co-Authors: Takayuki Hirai, Ken Ogawa, Isao KomasawaAbstract:A desulfurization process for dibenzothiophene (DBT) and its derivatives such as 4-methyldibenzothiophene (4-MDBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) by combination of Photochemical Reaction and liquid−liquid extraction has been investigated. In this, the DBTs dissolved in tetradecane were quantitatively photodecomposed by the use of a high-pressure mercury lamp and were removed to the water phase as SO42- at conditions of room temperature and atmospheric pressure. The order of reactivity for the DBTs was DBT < 4-MDBT < 4,6-DMDBT, thus indicating a different tendency from that reported for the hydrodesulfurization method. The desulfurization yield of commercial light oil, however, by the proposed method was only 22% following 30 h irradiation and was caused mainly by the depression of the photoReaction of DBT by the presence of aromatic compounds in the light oil.
J. Philip Thornber - One of the best experts on this subject based on the ideXlab platform.
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Thirty years of fun with antenna pigment-proteins and Photochemical Reaction centers: A tribute to the people who have influenced my career
Photosynthesis Research, 1995Co-Authors: J. Philip ThornberAbstract:The author summarizes the research contributions to photosynthesis made by him, his graduate and postdoctoral students, visiting scientists and by his collaboration with other photosynthesis workers during 1964–1994. The development of isolation procedures and biochemical/biophysical characterization of antenna pigment-proteins and Photochemical Reaction centers are described together with the author's education and experiences as a scientific researcher. Some anecdotes hopefully add insight into what it was like to be in this area of science during the period.
Takehiko Kitamori - One of the best experts on this subject based on the ideXlab platform.
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single cell attachment and culture method using a Photochemical Reaction in a closed microfluidic system
Biomicrofluidics, 2010Co-Authors: Kihoon Jang, Yo Tanaka, Kae Sato, Kazuma Mawatari, Tomohiro Konno, Kazuhiko Ishihara, Takehiko KitamoriAbstract:Recently, interest in single cell analysis has increased because of its potential for improving our understanding of cellular processes. Single cell operation and attachment is indispensable to realize this task. In this paper, we employed a simple and direct method for single-cell attachment and culture in a closed microchannel. The microchannel surface was modified by applying a nonbiofouling polymer, 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer, and a nitrobenzyl photocleavable linker. Using ultraviolet (UV) light irradiation, the MPC polymer was selectively removed by a Photochemical Reaction that adjusted the cell adherence inside the microchannel. To obtain the desired single endothelial cell patterning in the microchannel, cell-adhesive regions were controlled by use of round photomasks with diameters of 10, 20, 30, or 50 μm. Single-cell adherence patterns were formed after 12 h of incubation, only when 20 and 30 μm photomasks were used, and the proportions of adherent and nonadherent cel...
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an efficient surface modification using 2 methacryloyloxyethyl phosphorylcholine to control cell attachment via Photochemical Reaction in a microchannel
Lab on a Chip, 2010Co-Authors: Kihoon Jang, Yo Tanaka, Kae Sato, Kazuma Mawatari, Tomohiro Konno, Kazuhiko Ishihara, Moritoshi Sato, Takahiro Nakajima, Takehiko KitamoriAbstract:This report describes a direct approach for cell micropatterning in a closed glass microchannel. To control the cell adhesiveness inside the microchannel, the application of an external stimulus such as ultraviolet (UV) was indispensible. This technique focused on the use of a modified 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer, which is known to be a non-biofouling compound that is a photocleavable linker (PL), to localize cells via connection to an amino-terminated silanized surface. Using UV light illumination, the MPC polymer was selectively eliminated by Photochemical Reaction that controlled the cell attachment inside the microchannel. For suitable cell micropatterning in a microchannel, the optimal UV illumination time and concentration for cell suspension were investigated. After selective removal of the MPC polymer through the photomask, MC-3T3 E1 cells and vascular endothelial cells (ECs) were localized only to the UV-exposed area. In addition, the stability of patterned ECs was also confirmed by culturing for 2 weeks in a microchannel under flow conditions. Furthermore, we employed two different types of cells inside the same microchannel through multiple removal of the MPC polymer. ECs and Piccells were localized in both the upper and down streams of the microchannel, respectively. When the ECs were stimulated by adenosine triphosphate (ATP), NO was secreted from the ECs and could be detected by fluorescence resonance energy transfer (FRET) in Piccells, which is a cell-based NO indicator. This technique can be a powerful tool for analyzing cell interaction research.
