Paraquat (Methylviologen): Its Interference with Primary Photochemical Reactions

1993 ◽  
Vol 48 (3-4) ◽  
pp. 374-378 ◽  
Author(s):  
Tetsuo Hiyama ◽  
Akira Ohinata ◽  
Shin-ichi Kobayashi
Keyword(s):  
Reaction Center ◽  
Electron Donor ◽  
Photosystem I ◽  
Photochemical Reaction ◽  
Photochemical Reactions ◽  
The Other ◽  
Primary Photochemical Reaction

Paraquat(methylviologen), a widely used nonspecific herbicide, is ptoreduced in the primary photochemical reaction of photosystemI. Using two types of the photosystem I reaction center preparations, i.e. one with FeSA/FeSB and the other without, the immediate electron donor to methylviologen was determined to be FeSx (P430) rather than FeSA/FeSB.

scholarly journals Sunscreen-Assisted Selective Photochemical Transformations

Molecules ◽  
2020 ◽  
Vol 25 (9) ◽  
pp. 2125
Author(s):  
Or Eivgi ◽  
N. Gabriel Lemcoff
Keyword(s):  
Photochemical Reaction ◽  
Reaction Pathway ◽  
General Procedure ◽  
Molar Absorptivity ◽  
Photochemical Reactions ◽  
The Other ◽  
Protecting Group ◽  
Selective Reaction ◽  
Photochemical Transformations ◽  
Photolabile Protecting Group

In this review, we describe a simple and general procedure to accomplish selective photochemical reaction sequences for two chromophores that are responsive to similar light frequencies. The essence of the method is based on the exploitation of differences in the molar absorptivity at certain wavelengths of the photosensitive groups, which is enhanced by utilizing light-absorbing auxiliary filter molecules, or “sunscreens”. Thus, the filter molecule hinders the reaction pathway of the least absorbing molecule or group, allowing for the selective reaction of the other. The method was applied to various photochemical reactions, from photolabile protecting group removal to catalytic photoinduced olefin metathesis in different wavelengths and using different sunscreen molecules. Additionally, the sunscreens were shown to be effective also when applied externally to the reaction mixture, avoiding any potential chemical interactions between sunscreen and substrates and circumventing the need to remove the light-filtering molecules from the reaction mixture, adding to the simplicity and generality of the method.

scholarly journals Laser-Induced Photochemical Reaction of Maleic Acid Solutions in the Presence of Hydrogen Peroxide

1997 ◽  
Vol 17 (2) ◽  
pp. 97-108 ◽  
Author(s):  
Yuichi Shimizu ◽  
Shun'ichi Sugimoto ◽  
Shunichi Kawanishi ◽  
Nobutake Suzuki
Keyword(s):  
Hydrogen Peroxide ◽  
Maleic Acid ◽  
Photochemical Reaction ◽  
Room Temperature ◽  
Direct Synthesis ◽  
Reaction Scheme ◽  
Photochemical Reactions ◽  
The Other ◽  
Acid Solutions ◽  
Selective Formation

Targeting the selective and direct synthesis of tartaric acid (TA), the photochemical reactions of maleic acid (MA) solutions containing H2O2. in various solvents have been investigated using four wavelengths in the UV region between 193 and 351 nm, with high intensity from an excimer laser. All the laser irradiations in H2O resulted in the direct synthesis of TA with lower selectivity and it was found that, with XeF-laser (351 nm) irradiation in 1,4-dioxane, TA is selectively and directly synthesized from MA containing H2O2 of lower concentration at room temperature. On the other hand, none of the irradiations in methanol, N,N-dimethylformamide, acetonitrile, and tetrahydrofuran gave the selective formation of TA. On the basis of these results, the reaction scheme for the selective formation of TA is discussed.

Photochemical reactions of bacteriorhodopsin in Triton X-100 solution studied by low temperature spectrophotometry

1985 ◽  
Vol 63 (7) ◽  
pp. 1891-1898 ◽  
Author(s):  
Tatsuo Iwasa ◽  
Fumio Tokunaga ◽  
Tỏru Yoshizawa
Keyword(s):  
Low Temperature ◽  
Thermal Equilibrium ◽  
Photochemical Reaction ◽  
Membrane Structure ◽  
Purple Membrane ◽  
Photochemical Reactions ◽  
The Other ◽  
Other Hand ◽  
Triton X

The photochemical reaction of purple membrane solubilized with Triton X-100 (T-BR) was investigated by low temperature spectrophotometry. The batho- and meta-intermediates of T-BR were observed to resemble bacteriorhodopsin in native purple membrane. Two photoproducts characteristic of the T-BR system were found, which were named the "490-nm complex" and the "380-nm complex". The 490-nm complex was in thermal equilibrium with T-BR in the dark. Cooling T-BR to low temperature favoured the 490-nm complex, which was photoinsensitive. On the other hand, the 380-nm complex was produced by warming the batho-intermediate and reverted to the original T-BR. The meta-intermediate of T-BR may possibly be in thermal equilibrium with the 380-nm complex. On the basis of the above results, the possible role of the membrane structure was discussed

In vivo Participation of a High Potential Iron-Sulfur Protein as Electron Donor to the Photochemical Reaction Center of Rubrivivax gelatinosus

Biochemistry ◽  
1995 ◽  
Vol 34 (37) ◽  
pp. 11736-11742 ◽  
Author(s):  
Barbara Schoepp ◽  
Pierre Parot ◽  
Laure Menin ◽  
Jacques Gaillard ◽  
Pierre Richaud ◽  
...  
Keyword(s):  
Reaction Center ◽  
Electron Donor ◽  
Photochemical Reaction ◽  
High Potential ◽  
Iron Sulfur ◽  
Sulfur Protein ◽  
Iron Sulfur Protein ◽  
Rubrivivax Gelatinosus

Functional Characterization of Four Thylakoid Membrane Polypeptides with Apparent Molecular Weights between 40 000 and 48 000

1978 ◽  
Vol 33 (3-4) ◽  
pp. 280-289 ◽  
Author(s):  
Wilhelm Menke ◽  
Friederike Koenig ◽  
Georg H. Schmid ◽  
Alfons Radunz
Keyword(s):  
Electron Donor ◽  
Photosystem I ◽  
Thylakoid Membrane ◽  
Functional Characterization ◽  
Sodium Dodecyl ◽  
Gel Filtration ◽  
Fluorescence Yield ◽  
Exchange Chromatography ◽  
The Other ◽  
Molecular Weights

Four polypeptides which exhibited apparent molecular weights from 40 000 to 48 000 were isolated from the thylakoid membrane. The isolation was achieved by gel filtration of polypeptides, solubilized by means of sodium dodecyl sulfate and, after removal of detergent by anion exchange chromatography in ethanolic solution. The polypeptide of the molecular weight 40000 was iden­tified as the y-component of the coupling factor of photophosphorylation via the effect of its antiserum and by its serological cross reactions. The antiserum not only inhibits photophosphory­lation reactions by 90% but also to the same extent the photoreduction of anthraquinone-2-sulfonate with tetramethyl benzidine as the electron donor, provided ADP, Pi and Mg2+ are present in the assay. The inhibition of electron transport is accompanied by a corresponding increase in the fluorescence yield. The other three antisera inhibit photosystem I reactions. In addition, the antiserum designated 45 000 PSI-1 inhibits phenazine methosulfate-mediated cyclic photophos­phorylation. This antiserum as well as the two other sera do not contain any detectable anti­coupling factor activity. Antiserum 45 000 PSI-4, in contrast to 45 000 PSI-1, does not inhibit cyclic photophosphorylation. Moreover, it is the only one of the four antisera which does not affect the ratio of the fluorescence yields measured at 735 and 685 nm (F 735/F 685) at 77 °K. Hence, the antigen 45 000 PSI-4 probably plays a role on the acceptor side of photosystem I. On the other hand, the antiserum 48 000 PSI-3 seems to exert its effect on the donor side of photosystem I, because it inhibits the photoreduction of anthraquinone-2-sulfonate with low con­centrations of the electron donor dichlorophenol indophenol. The prominent property of this anti­serum is that the photophosphorylation with fcrricyanide as the electron acceptor is stimulated more than two fold. This, however, it not accompanied by an apparent change of the electron flux between water and ferricyanide. The antiserum causes a decrease of fluorescence yield which is probably due to an increased energy spill-over. All antisera exert their activity only after an il­lumination of the chloroplast preparations for several minutes. The dosis-effect curve is hyperbolic for the antiserum 48 000 PSI-3 and is sigmoidal with the other three antisera.

One-electron photooxidation of N-ethylcarbazole in the presence of carbon tetrachloride. Products and mechanism of the photochemical reaction

1985 ◽  
Vol 63 (7) ◽  
pp. 1654-1665 ◽  
Author(s):  
Bogumil Zelent ◽  
Gilles Durocher
Keyword(s):  
Carbon Tetrachloride ◽  
Photochemical Reaction ◽  
Reaction Medium ◽  
Chloride Ion ◽  
Photochemical Reactions ◽  
The Other ◽  
Main Process ◽  
Reaction Products ◽  
Solvent Cage ◽  
Ct Complex

The mechanism of the photodecomposition of N-ethylcarbazole (NEC) in the presence of carbon tetrachloride has been discussed on the basis of the photoproducts identified. The photodissociation of the N-ethyl bond and the electron transfer in the transiently formed ex-CT complex, [Formula: see text], have been proposed as the primary photochemical processes involved irr the singlet excited NEC molecule. The latter, treated as the main process, leads to the radical cation of NEC, chloride ion, and trichloromethyl radical in the solvent cage, [NEC+•Cl−ĊCl3]. The other reactions in the system studied are analysed following the decomposition of NEC+• in the presence of Cl− and ĊCl3, which can occur by the N-ethyl group and (or) by the aromatic ring. The formation of intermediate products such as[Formula: see text]in the solvent cage gives rise to secondary photochemical reactions in the system studied. The polarity and chemical activity of the reaction media used strongly influence the nature of the secondary photochemical transformations both in and outside the solvent cage. The formation mechanism of the photochemical reaction products in CCl4 when ammonia was used, after and during irradiation, has been explained mainly by the transformations of the radical αr and cation αk as well as by the carbazyl radical β, which is also formed in the reaction medium. On the other hand, reaction of the cation [Formula: see text] explains the formation of the photoproducts in the irradiated solution of NEC with CCl4 in ethanol. These photochemical results have been compared to the photochemical reactions involved in the carbazole–CCl4 system.

scholarly journals Structure of the far-red light utilizing photosystem I of Acaryochloris marina

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tasuku Hamaguchi ◽  
Keisuke Kawakami ◽  
Kyoko Shinzawa-Itoh ◽  
Natsuko Inoue-Kashino ◽  
Shigeru Itoh ◽  
...  
Keyword(s):  
Reaction Center ◽  
Photosystem I ◽  
Red Light ◽  
Primary Electron ◽  
Photochemical Reactions ◽  
Oxygenic Photosynthesis ◽  
Energy Yield ◽  
Type I ◽  
Cyanobacterial Species ◽  
Acaryochloris Marina

AbstractAcaryochloris marina is one of the cyanobacterial species that can use far-red light to drive photochemical reactions for oxygenic photosynthesis. Here, we report the structure of A. marina photosystem I (PSI) reaction center, determined by cryo-electron microscopy at 2.58 Å resolution. The structure reveals an arrangement of electron carriers and light-harvesting pigments distinct from other type I reaction centers. The paired chlorophyll, or special pair (also referred to as P740 in this case), is a dimer of chlorophyll d and its epimer chlorophyll d′. The primary electron acceptor is pheophytin a, a metal-less chlorin. We show the architecture of this PSI reaction center is composed of 11 subunits and we identify key components that help explain how the low energy yield from far-red light is efficiently utilized for driving oxygenic photosynthesis.

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