Relevant bibliographies by topics / Photocyclo addition

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Academic literature on the topic 'Photocyclo addition'

Author: Grafiati
Published: 4 June 2021
Last updated: 17 February 2022

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Journal articles on the topic "Photocyclo addition"

1

Hart, Jaynee E., Stuart Sullivan, Paweł Hermanowicz, Jan Petersen, L. Aranzazú Diaz-Ramos, David J. Hoey, Justyna Łabuz, and John M. Christie. "Engineering the phototropin photocycle improves photoreceptor performance and plant biomass production." Proceedings of the National Academy of Sciences 116, no. 25 (June 3, 2019): 12550–57. http://dx.doi.org/10.1073/pnas.1902915116.

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The ability to enhance photosynthetic capacity remains a recognized bottleneck to improving plant productivity. Phototropin blue light receptors (phot1 and phot2) optimize photosynthetic efficiency in Arabidopsis thaliana by coordinating multiple light-capturing processes. In this study, we explore the potential of using protein engineering to improve photoreceptor performance and thereby plant growth. We demonstrate that targeted mutagenesis can decrease or increase the photocycle lifetime of Arabidopsis phototropins in vitro and show that these variants can be used to reduce or extend the duration of photoreceptor activation in planta. Our findings show that slowing the phototropin photocycle enhanced several light-capturing responses, while accelerating it reduced phototropin’s sensitivity for chloroplast accumulation movement. Moreover, plants engineered to have a slow-photocycling variant of phot1 or phot2 displayed increased biomass production under low-light conditions as a consequence of their improved sensitivity. Together, these findings demonstrate the feasibility of engineering photoreceptors to manipulate plant growth and offer additional opportunities to enhance photosynthetic competence, particularly under suboptimal light regimes.
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Bose, Salil, Anup K. Mukhopadyay, Swetlana Dracheva, and Richard W. Hendler. "Role of Salt in Reconstituting Photocycle Behavior in Triton-Damaged Purple Membranes by Addition of Native Lipids." Journal of Physical Chemistry B 101, no. 49 (December 1997): 10584–87. http://dx.doi.org/10.1021/jp972260h.

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3

Shigemura, Shunta, Shoko Hososhima, Hideki Kandori, and Satoshi P. Tsunoda. "Ion Channel Properties of a Cation Channelrhodopsin, Gt_CCR4." Applied Sciences 9, no. 17 (August 21, 2019): 3440. http://dx.doi.org/10.3390/app9173440.

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We previously reported a cation channelrhodopsin, Gt_CCR4, which is one of the 44 types of microbial rhodopsins from a cryptophyte flagellate, Guillardia theta. Due to the modest homology of amino acid sequences with a chlorophyte channelrhodopsin such as Cr_ChR2 from Chlamydomonas reinhardtii, it has been proposed that a family of cryptophyte channelrhodopsin, including Gt_CCR4, has a distinct molecular mechanism for channel gating and ion permeation. In this study, we compared the photocurrent properties, cation selectivity and kinetics between well-known Cr_ChR2 and Gt_CCR4 by a conventional path clamp method. Large and stable light-induced cation conduction by Gt_CCR4 at the maximum absorbing wavelength (530 nm) was observed with only small inactivation (15%), whereas the photocurrent of Cr_ChR2 exhibited significant inactivation (50%) and desensitization. The light sensitivity of Gt_CCR4 was higher (EC50 = 0.13 mW/mm2) than that of Cr_ChR2 (EC50 = 0.80 mW/mm2) while the channel open life time (photocycle speed) was in the same range as that of Cr_ChR2 (25~30 ms for Gt_CCR4 and 10~15 ms for Cr_ChR2). This observation implies that Gt_CCR4 enables optical neuronal spiking with weak light in high temporal resolution when applied in neuroscience. Furthermore, we demonstrated high Na+ selectivity of Gt_CCR4 in which the selectivity ratio for Na+ was 37-fold larger than that for Cr_ChR2, which primarily conducts H+. On the other hand, Gt_CCR4 conducted almost no H+ and no Ca2+ under physiological conditions. These results suggest that ion selectivity in Gt_CCR4 is distinct from that in Cr_ChR2. In addition, a unique red-absorbing and stable intermediate in the photocycle was observed, indicating a photochromic property of Gt_CCR4.
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Schmidt, Marius, Tim Graber, Robert Henning, and Vukica Srajer. "Five-dimensional crystallography." Acta Crystallographica Section A Foundations of Crystallography 66, no. 2 (February 18, 2010): 198–206. http://dx.doi.org/10.1107/s0108767309054166.

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A method for determining a comprehensive chemical kinetic mechanism in macromolecular reactions is presented. The method is based on five-dimensional crystallography, where, in addition to space and time, temperature is also taken into consideration and an analysis based on singular value decomposition is applied. First results of such a time-resolved crystallographic study are presented. Temperature-dependent time-resolved X-ray diffraction measurements were conducted on the newly upgraded BioCARS 14-ID-B beamline at the Advanced Photon Source and aimed at elucidating a comprehensive kinetic mechanism of the photoactive yellow protein photocycle. Extensive time series of crystallographic data were collected at two temperatures, 293 K and 303 K. Relaxation times of the reaction extracted from these time series exhibit measurable differences for the two temperatures, hence demonstrating that five-dimensional crystallography is feasible.
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5

Goings, Joshua J., Pengfei Li, Qiwen Zhu, and Sharon Hammes-Schiffer. "Formation of an unusual glutamine tautomer in a blue light using flavin photocycle characterizes the light-adapted state." Proceedings of the National Academy of Sciences 117, no. 43 (October 9, 2020): 26626–32. http://dx.doi.org/10.1073/pnas.2016719117.

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Blue light using flavin (BLUF) photoreceptor proteins are critical for many light-activated biological processes and are promising candidates for optogenetics because of their modular nature and long-range signaling capabilities. Although the photocycle of the Slr1694 BLUF domain has been characterized experimentally, the identity of the light-adapted state following photoexcitation of the bound flavin remains elusive. Herein hybrid quantum mechanical/molecular mechanical (QM/MM) molecular dynamics simulations of this photocycle provide a nonequilibrium dynamical picture of a possible mechanism for the formation of the light-adapted state. Photoexcitation of the flavin induces a forward proton-coupled electron transfer (PCET) process that leads to the formation of an imidic acid tautomer of Gln50. The calculations herein show that the subsequent rotation of Gln50 allows a reverse PCET process that retains this tautomeric form. In the resulting purported light-adapted state, the glutamine tautomer forms a hydrogen bond with the flavin carbonyl group. Additional ensemble-averaged QM/MM calculations of the dark-adapted and purported light-adapted states demonstrate that the light-adapted state with the imidic acid glutamine tautomer reproduces the experimentally observed spectroscopic signatures. Specifically, the calculations reproduce the red shifts in the flavin electronic absorption and carbonyl stretch infrared spectra in the light-adapted state. Further hydrogen-bonding analyses suggest the formation of hydrogen-bonding interactions between the flavin and Arg65 in the light-adapted state, providing a plausible explanation for the experimental observation of faster photoinduced PCET in this state. These characteristics of the light-adapted state may also be essential for the long-range signaling capabilities of this photoreceptor protein.
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Xu, Qian-Zhao, Pavlo Bielytskyi, James Otis, Christina Lang, Jon Hughes, Kai-Hong Zhao, Aba Losi, Wolfgang Gärtner, and Chen Song. "MAS NMR on a Red/Far-Red Photochromic Cyanobacteriochrome All2699 from Nostoc." International Journal of Molecular Sciences 20, no. 15 (July 26, 2019): 3656. http://dx.doi.org/10.3390/ijms20153656.

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Unlike canonical phytochromes, the GAF domain of cyanobacteriochromes (CBCRs) can bind bilins autonomously and is sufficient for functional photocycles. Despite the astonishing spectral diversity of CBCRs, the GAF1 domain of the three-GAF-domain photoreceptor all2699 from the cyanobacterium Nostoc 7120 is the only CBCR-GAF known that converts from a red-absorbing (Pr) dark state to a far-red-absorbing (Pfr) photoproduct, analogous to the more conservative phytochromes. Here we report a solid-state NMR spectroscopic study of all2699g1 in its Pr state. Conclusive NMR evidence unveils a particular stereochemical heterogeneity at the tetrahedral C31 atom, whereas the crystal structure shows exclusively the R-stereochemistry at this chiral center. Additional NMR experiments were performed on a construct comprising the GAF1 and GAF2 domains of all2699, showing a greater precision in the chromophore–protein interactions in the GAF1-2 construct. A 3D Pr structural model of the all2699g1-2 construct predicts a tongue-like region extending from the GAF2 domain (akin to canonical phytochromes) in the direction of the chromophore, shielding it from the solvent. In addition, this stabilizing element allows exclusively the R-stereochemistry for the chromophore-protein linkage. Site-directed mutagenesis performed on three conserved motifs in the hairpin-like tip confirms the interaction of the tongue region with the GAF1-bound chromophore.
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Griesbeck, Axel G., Manabu Abe, and Samir Bondock. "Selectivity Control in Electron Spin Inversion Processes: Regio- and Stereochemistry of Paternò−Büchi Photocyclo- additions as a Powerful Tool for Mapping Intersystem Crossing Processes." Accounts of Chemical Research 37, no. 12 (December 2004): 919–28. http://dx.doi.org/10.1021/ar040081u.

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8

Mueller, Maria. "Light-induced Helix Movements in Channelrhodopsin-2." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C1067. http://dx.doi.org/10.1107/s2053273314089323.

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Electron crystallography has the unique advantage of visualizing membrane proteins in a native-like lipid environment, which likely favors the native conformation. In addition, it allows for the protein to undergo conformational changes in response to their activating signals. We used 2D crystals of channelrhodopsin-2, a cation-selective light-gated channel from Chlamydomonas reinhardtii (Nagel et al., 2003) to study light-induced conformational changes of this intriguing channel, which is currently a powerful tool in optogenetics. Therefore, 2D crystals of the slow photocycling C128T ChR2 mutant were exposed to 473 nm light and rapidly frozen to trap the open state. Projection difference maps at 6 Å resolution show the location, extent and direction of light-induced conformational changes in ChR2 during the transition from the closed state to the ion-conducting open state. Difference peaks indicate that transmembrane helices (TMHs) 2, 6, and 7 reorient or rearrange during the photocycle. No major differences were found near TMH3 and 4 at the dimer interface. While conformational changes in TMH6 and 7 are known from other microbial-type rhodopsins, our results indicate that TMH2 has a key role in light-induced channel opening and closing in ChR2.
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9

Froehlich, Allan C., Bosl Noh, Richard D. Vierstra, Jennifer Loros, and Jay C. Dunlap. "Genetic and Molecular Analysis of Phytochromes from the Filamentous Fungus Neurospora crassa." Eukaryotic Cell 4, no. 12 (December 2005): 2140–52. http://dx.doi.org/10.1128/ec.4.12.2140-2152.2005.

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ABSTRACT Phytochromes (Phys) comprise a superfamily of red-/far-red-light-sensing proteins. Whereas higher-plant Phys that control numerous growth and developmental processes have been well described, the biochemical characteristics and functions of the microbial forms are largely unknown. Here, we describe analyses of the expression, regulation, and activities of two Phys in the filamentous fungus Neurospora crassa. In addition to containing the signature N-terminal domain predicted to covalently associate with a bilin chromophore, PHY-1 and PHY-2 contain C-terminal histidine kinase and response regulator motifs, implying that they function as hybrid two-component sensor kinases activated by light. A bacterially expressed N-terminal fragment of PHY-2 covalently bound either biliverdin or phycocyanobilin in vitro, with the resulting holoprotein displaying red-/far-red-light photochromic absorption spectra and a photocycle in vitro. cDNA analysis of phy-1 and phy-2 revealed two splice isoforms for each gene. The levels of the phy transcripts are not regulated by light, but the abundance of the phy-1 mRNAs is under the control of the circadian clock. Phosphorylated and unphosphorylated forms of PHY-1 were detected; both species were found exclusively in the cytoplasm, with their relative abundances unaffected by light. Strains containing deletions of phy-1 and phy-2, either singly or in tandem, were not compromised in any known photoresponses in Neurospora, leaving their function(s) unclear.
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10

Xu, Xiuling, Astrid Höppner, Christian Wiebeler, Kai-Hong Zhao, Igor Schapiro, and Wolfgang Gärtner. "Structural elements regulating the photochromicity in a cyanobacteriochrome." Proceedings of the National Academy of Sciences 117, no. 5 (January 21, 2020): 2432–40. http://dx.doi.org/10.1073/pnas.1910208117.

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The three-dimensional (3D) crystal structures of the GAF3 domain of cyanobacteriochrome Slr1393 (Synechocystis PCC6803) carrying a phycocyanobilin chromophore could be solved in both 15-Z dark-adapted state, Pr, λmax = 649 nm, and 15-E photoproduct, Pg, λmax = 536 nm (resolution, 1.6 and 1.86 Å, respectively). The structural data allowed identifying the large spectral shift of the Pr-to-Pg conversion as resulting from an out-of-plane rotation of the chromophore’s peripheral rings and an outward movement of a short helix formed from a formerly unstructured loop. In addition, a third structure (2.1-Å resolution) starting from the photoproduct crystals allowed identification of elements that regulate the absorption maxima. In this peculiar form, generated during X-ray exposition, protein and chromophore conformation still resemble the photoproduct state, except for the D-ring already in 15-Z configuration and tilted out of plane akin the dark state. Due to its formation from the photoproduct, it might be considered an early conformational change initiating the parental state-recovering photocycle. The high quality and the distinct features of the three forms allowed for applying quantum-chemical calculations in the framework of multiscale modeling to rationalize the absorption maxima changes. A systematic analysis of the PCB chromophore in the presence and absence of the protein environment showed that the direct electrostatic effect is negligible on the spectral tuning. However, the protein forces the outer pyrrole rings of the chromophore to deviate from coplanarity, which is identified as the dominating factor for the color regulation.
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Dissertations / Theses on the topic "Photocyclo addition"

1

Bouillot, Anne. "Contribution à la synthèse de la Colchicine par voie photochimique." Paris 11, 1987. http://www.theses.fr/1987PA112150.

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L'objectif de cette thèse est de mettre au point une nouvelle possibilité de synthèse du squelette de la Colchicine, alcaloïde possédant des activités biologiques intéressantes. En préliminaire, quelques généralités sur les réactions de photocycloaddition [2 + 2] sont exposées après avoir brièvement présenté les synthèses de la Colchicine ainsi que ses activités. Dans la première partie de ce travail, nous avons tenté, par différentes voies, la synthèse du bicyclo [5. 5. 0] dodécane, constituant les cycles B et C de la Colchicine, par une réaction de photocycloaddition [2 + 2]. La possibilité d'utiliser le dioxène-1,4, précurseur du cycle C, dans une réaction de photocycloaddition sur les cycles A et B préformés, est étudiée dans la deuxième partie. Il a été montré que la cycloaddition photochimique du dioxène sur un modèle tel que le méthyl-3 cyclohexèn-2 one conduit à quatre stéréoisomères dont la structure a été déterminée par diffraction des rayons X, R. M. N. 13c et méthode des champs de force. Le réarrangement acido-catalysé de ces adduits a abouti à trois produits inattendus dont les structures ont été déterminées par diffraction des rayons X et R. M. N. 13c. La formation de ces composés a supposé le passage par un intermédiaire cationique commun, stabilisé par le cycle du dioxanne Enfin, la troisième partie se résume à étudier la photocycloaddition du carbonate de vinylène, précurseur du cycle C de la Colchicine sur la benzo-4,5 cycloheptadièn-2,4 one, dont une nouvelle synthèse a été mise au point. Au cours de ce travail, nous avons pu montrer la complexité des réactions de photocycloaddition [2 + 2] appliquées à des systèmes possédant des cycles à sept chainons.
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