Artículos de revistas: "Monomeric antennae"

1

Crepin, Aurélie, Erica Belgio, Barbora Šedivá, Eliška Kuthanová Trsková, Edel Cunill-Semanat y Radek Kaňa. "Size and Fluorescence Properties of Algal Photosynthetic Antenna Proteins Estimated by Microscopy". International Journal of Molecular Sciences 23, n.º 2 (11 de enero de 2022): 778. http://dx.doi.org/10.3390/ijms23020778.

Texto completo

Resumen

Antenna proteins play a major role in the regulation of light-harvesting in photosynthesis. However, less is known about a possible link between their sizes (oligomerization state) and fluorescence intensity (number of photons emitted). Here, we used a microscopy-based method, Fluorescence Correlation Spectroscopy (FCS), to analyze different antenna proteins at the particle level. The direct comparison indicated that Chromera Light Harvesting (CLH) antenna particles (isolated from Chromera velia) behaved as the monomeric Light Harvesting Complex II (LHCII) (from higher plants), in terms of their radius (based on the diffusion time) and fluorescence yields. FCS data thus indicated a monomeric oligomerization state of algal CLH antenna (at our experimental conditions) that was later confirmed also by biochemical experiments. Additionally, our data provide a proof of concept that the FCS method is well suited to measure proteins sizes (oligomerization state) and fluorescence intensities (photon counts) of antenna proteins per single particle (monomers and oligomers). We proved that antenna monomers (CLH and LHCIIm) are more “quenched” than the corresponding trimers. The FCS measurement thus represents a useful experimental approach that allows studying the role of antenna oligomerization in the mechanism of photoprotection.

Los estilos APA, Harvard, Vancouver, ISO, etc.

2

Wang, Quan y W. E. Moerner. "Dissecting pigment architecture of individual photosynthetic antenna complexes in solution". Proceedings of the National Academy of Sciences 112, n.º 45 (5 de octubre de 2015): 13880–85. http://dx.doi.org/10.1073/pnas.1514027112.

Texto completo

Resumen

Oligomerization plays a critical role in shaping the light-harvesting properties of many photosynthetic pigment−protein complexes, but a detailed understanding of this process at the level of individual pigments is still lacking. To study the effects of oligomerization, we designed a single-molecule approach to probe the photophysical properties of individual pigment sites as a function of protein assembly state. Our method, based on the principles of anti-Brownian electrokinetic trapping of single fluorescent proteins, step-wise photobleaching, and multiparameter spectroscopy, allows pigment-specific spectroscopic information on single multipigment antennae to be recorded in a nonperturbative aqueous environment with unprecedented detail. We focus on the monomer-to-trimer transformation of allophycocyanin (APC), an important antenna protein in cyanobacteria. Our data reveal that the two chemically identical pigments in APC have different roles. One (α) is the functional pigment that red-shifts its spectral properties upon trimer formation, whereas the other (β) is a “protective” pigment that persistently quenches the excited state of α in the prefunctional, monomer state of the protein. These results show how subtleties in pigment organization give rise to functionally important aspects of energy transfer and photoprotection in antenna complexes. The method developed here should find immediate application in understanding the emergent properties of other natural and artificial light-harvesting systems.

Los estilos APA, Harvard, Vancouver, ISO, etc.

3

Wang, Zhimo, Bingbing Suo, Shiwei Yin y Wenli Zou. "Quantum Chemical Simulation of the Qy Absorption Spectrum of Zn Chlorin Aggregates for Artificial Photosynthesis". Molecules 26, n.º 4 (19 de febrero de 2021): 1086. http://dx.doi.org/10.3390/molecules26041086.

Texto completo

Resumen

Zn chlorin (Znchl) is easy to synthesize and has similar optical properties to those of bacteriochlorophyll c in the nature, which is expected to be used as a light-harvesting antenna system in artificial photosynthesis. In order to further explore the optical characteristics of Znchl, various sizes of a parallel layered Znchl-aggregate model and the THF-Znchl explicit solvent monomer model were constructed in this study, and their Qy excited state properties were simulated by using time-dependent density functional theory (TDDFT) and exciton theory. For the Znchl monomer, with a combination of the explicit solvent model and the implicit solvation model based on density (SMD), the calculated Qy excitation energy agreed very well with the experimental one. The Znchl aggregates may be simplified to a Zn36 model to reproduce the experimental Qy absorption spectrum by the Förster coupling theory. The proposed Znchl aggregate model provides a good foundation for the future exploration of other properties of Znchl and simulations of artificial light-harvesting antennas. The results also indicate that J-aggregrates along z-direction, due to intermolecular coordination bonds, are the dominant factor in extending the Qy band of Znchl into the near infrared region.

Los estilos APA, Harvard, Vancouver, ISO, etc.

4

Miloslavina, Yuliya, Silvia de Bianchi, Luca Dall'Osto, Roberto Bassi y Alfred R. Holzwarth. "Quenching in Arabidopsis thaliana Mutants Lacking Monomeric Antenna Proteins of Photosystem II". Journal of Biological Chemistry 286, n.º 42 (15 de agosto de 2011): 36830–40. http://dx.doi.org/10.1074/jbc.m111.273227.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

5

Pishchalnikov, Roman, Vladimir Shubin y Andrei Razjivin. "Single Molecule Fluorescence Spectroscopy of PSI Trimers from Arthrospira platensis: A Computational Approach". Molecules 24, n.º 4 (25 de febrero de 2019): 822. http://dx.doi.org/10.3390/molecules24040822.

Texto completo

Resumen

Based on single molecule spectroscopy analysis and our preliminary theoretical studies, the linear and fluorescence spectra of the PSI trimer from Arthrospira platensis with different realizations of the static disorder were modeled at cryogenic temperature. Considering the previously calculated spectral density of chlorophyll, an exciton model for the PSI monomer and trimer including the red antenna states was developed taking into account the supposed similarity of PSI antenna structures from Thermosynechococcus e., Synechocystis sp. PCC6803, and Arthrospira platensis. The red Chls in the PSI monomer were assumed to be in the nearest proximity of the reaction center. The PSI trimer model allowed the simulation of experimentally measured zero phonon line distribution of the red states considering a weak electron-phonon coupling for the antenna exciton states. However, the broad absorption and fluorescence spectra of an individual emitter at 760 nm were calculated by adjusting the Huang-Rhys factors of the chlorophyll lower phonon modes assuming strong electron-phonon coupling.

Los estilos APA, Harvard, Vancouver, ISO, etc.

6

Ballottari, Matteo, Milena Mozzo, Julien Girardon, Rainer Hienerwadel y Roberto Bassi. "Chlorophyll Triplet Quenching and Photoprotection in the Higher Plant Monomeric Antenna Protein Lhcb5". Journal of Physical Chemistry B 117, n.º 38 (8 de julio de 2013): 11337–48. http://dx.doi.org/10.1021/jp402977y.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

7

KUREISHI, YASUHIKO y HITOSHI TAMIAKI. "Synthesis and Self-aggregation of Zinc 20-Halogenochlorins as a Model for Bacteriochlorophylls c/d". Journal of Porphyrins and Phthalocyanines 02, n.º 02 (marzo de 1998): 159–69. http://dx.doi.org/10.1002/(sici)1099-1409(199803/04)2:2<159::aid-jpp62>3.0.co;2-q.

Texto completo

Resumen

Zinc 20-halogenochlorins 2(20- F ), 3(20- Cl ) and 4(20- Br ) were synthesized by halogenation of a chlorophyll a derivative at the 20-position as a model for bacteriochlorophyll ( BChl )c, which possesses a methyl group at the 20-position and 20-unsubstituted BChl d. Visible spectra in a polar tetrahydrofuran ( THF ) solution showed that 2-4 were monomeric and the planarity of the chlorin ring, was distorted with increasing bulkiness of the 20-substituent. Visible, circular dichroism and IR spectra revealed that 2-4 self-aggregated to form oligomers similarly with 20-unsubstituted 1 and BChls c/d in the heterogeneous thin film as well as in homogeneous non-polar solvents (1% (v/v) THF-hexane). Therefore, the in vitro self-aggregates of 2-4 are good structural models for in vivo BChls c/d self-aggregates, the main antenna components of photosynthetic green bacteria. Fluorescence spectra showed that monomeric 3 and 4 were less emissive than 1 and 2 due to the heavy atom effect which could not be observed in the oligomeric species, indicating that the in vitro aggregates should be promising as functional (light-harvesting) models.

Los estilos APA, Harvard, Vancouver, ISO, etc.

8

Meador, Michael A., Mary Ann Meador, Daniel S. Tyson y Faysal Ilhan. "Use of Diels-Alder Cyclopolymerizations in the Photocuring of Polymers". High Performance Polymers 19, n.º 5-6 (octubre de 2007): 665–83. http://dx.doi.org/10.1177/0954008307081210.

Texto completo

Resumen

Radiation curable polymers are needed for use in space rigidizable inflatable structures (antenna supports, habitats, rovers) for future NASA missions. One approach developed at NASA Glenn utilizes the Diels-Alder trapping of bisdienes (o-xylylenols) generated by the photolysis of o-methylphenyl ketones with bisdienophiles (bismaleimides and bisacrylates). A variety of polyimides and polyesters have been prepared with this chemistry and their properties evaluated. The glass transition temperatures of these resins varied from –27 to over 300°C depending upon monomer structures. Onsets of decomposition, measured by thermogravimetric analysis in air, were in the neighborhood of 300°C and did not vary much with monomer structure. Some monomer systems are liquids at room temperature and have the potential for use in solvent-free UV-cured coatings.

Los estilos APA, Harvard, Vancouver, ISO, etc.

9

Squires, Allison H. y W. E. Moerner. "Direct single-molecule measurements of phycocyanobilin photophysics in monomeric C-phycocyanin". Proceedings of the National Academy of Sciences 114, n.º 37 (28 de agosto de 2017): 9779–84. http://dx.doi.org/10.1073/pnas.1705435114.

Texto completo

Resumen

Phycobilisomes are highly organized pigment–protein antenna complexes found in the photosynthetic apparatus of cyanobacteria and rhodophyta that harvest solar energy and transport it to the reaction center. A detailed bottom-up model of pigment organization and energy transfer in phycobilisomes is essential to understanding photosynthesis in these organisms and informing rational design of artificial light-harvesting systems. In particular, heterogeneous photophysical behaviors of these proteins, which cannot be predicted de novo, may play an essential role in rapid light adaptation and photoprotection. Furthermore, the delicate architecture of these pigment–protein scaffolds sensitizes them to external perturbations, for example, surface attachment, which can be avoided by study in free solution or in vivo. Here, we present single-molecule characterization of C-phycocyanin (C-PC), a three-pigment biliprotein that self-assembles to form the midantenna rods of cyanobacterial phycobilisomes. Using the Anti-Brownian Electrokinetic (ABEL) trap to counteract Brownian motion of single particles in real time, we directly monitor the changing photophysical states of individual C-PC monomers from Spirulina platensis in free solution by simultaneous readout of their brightness, fluorescence anisotropy, fluorescence lifetime, and emission spectra. These include single-chromophore emission states for each of the three covalently bound phycocyanobilins, providing direct measurements of the spectra and photophysics of these chemically identical molecules in their native protein environment. We further show that a simple Förster resonant energy transfer (FRET) network model accurately predicts the observed photophysical states of C-PC and suggests highly variable quenching behavior of one of the chromophores, which should inform future studies of higher-order complexes.

Los estilos APA, Harvard, Vancouver, ISO, etc.

10

Pi, Xiong, Songhao Zhao, Wenda Wang, Desheng Liu, Caizhe Xu, Guangye Han, Tingyun Kuang, Sen-Fang Sui y Jian-Ren Shen. "The pigment-protein network of a diatom photosystem II–light-harvesting antenna supercomplex". Science 365, n.º 6452 (1 de agosto de 2019): eaax4406. http://dx.doi.org/10.1126/science.aax4406.

Texto completo

Resumen

Diatoms play important roles in global primary productivity and biogeochemical cycling of carbon, in part owing to the ability of their photosynthetic apparatus to adapt to rapidly changing light intensity. We report a cryo–electron microscopy structure of the photosystem II (PSII)–fucoxanthin (Fx) chlorophyll (Chl) a/c binding protein (FCPII) supercomplex from the centric diatom Chaetoceros gracilis. The supercomplex comprises two protomers, each with two tetrameric and three monomeric FCPIIs around a PSII core that contains five extrinsic oxygen-evolving proteins at the lumenal surface. The structure reveals the arrangement of a huge pigment network that contributes to efficient light energy harvesting, transfer, and dissipation processes in the diatoms.

Los estilos APA, Harvard, Vancouver, ISO, etc.

11

Hofmann, E., T. Schulte, S. P. Sharples y R. G. Hiller. "High-salt peridinin-chlorophyll-protein fromA. carterae: the structure of the monomeric antenna protein complex". Acta Crystallographica Section A Foundations of Crystallography 62, a1 (6 de agosto de 2006): s137. http://dx.doi.org/10.1107/s0108767306097261.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

12

Mascoli, Vincenzo, Vladimir Novoderezhkin, Nicoletta Liguori, Pengqi Xu y Roberta Croce. "Design principles of solar light harvesting in plants: Functional architecture of the monomeric antenna CP29". Biochimica et Biophysica Acta (BBA) - Bioenergetics 1861, n.º 3 (marzo de 2020): 148156. http://dx.doi.org/10.1016/j.bbabio.2020.148156.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

13

Yin, Lianhua. "Preparation of High-barrier Polyethylene Terephthalate bottle by Microwave Plasma Enhanced Chemical Vapor Deposition". MATEC Web of Conferences 358 (2022): 01002. http://dx.doi.org/10.1051/matecconf/202235801002.

Texto completo

Resumen

In this work, we reported the investigation of diamond-like carbon (DLC) coating on the inner surface of polyethylene terephthalate (PET) bottles by Microwave Plasma Enhanced Chemical Vapor Deposition to improve their barrier properties. We used 2.45 GHz microwave to generate plasma, acetylene (C2H2) and argon (Ar) were used as monomer gas and diluted gas. The effects of plasma process parameters on deposition uniformity and barrier properties of thin films were studied in detail. In addition, we designed a new antenna shape to improve the uniformity of film deposition. We analyzed the microstructure and morphology of the DLC coating by atom force microscope (AFM). Fourier transform infrared spectroscope (FTIR) and Raman spectroscope were employed to investigate chemical composition and bonding structure. The deposition rate was obtained by Step Profiler. For the barrier properties, we measured the oxygen transmission rate (OTR) of the PET bottle coated with DLC film. It is noted that the uniformity of film deposition is affected by the process parameters and antenna shape, after optimizing the process parameters and antenna shape, the barrier property of PET bottles is improved obviously.

Los estilos APA, Harvard, Vancouver, ISO, etc.

14

Gruszecki, Wieslaw I. "Light-driven regulatory mechanisms in the photosynthetic antenna complex LHCII". Biochemical Society Transactions 38, n.º 2 (22 de marzo de 2010): 702–4. http://dx.doi.org/10.1042/bst0380702.

Texto completo

Resumen

Protection against strong-light-induced photodamage of the photosynthetic apparatus and entire organisms is a vital activity in plants and is also realized at the molecular level of the antenna complexes. Reported recently, the regulatory mechanisms which operate in the largest plant antenna complex, LHCII (light-harvesting complex II), based on light-driven processes, are briefly reviewed and discussed. Among those processes are the light-induced twisting of the configuration of the LHCII-bound neoxanthin, the light-induced configurational transition of the LHCII-bound violaxanthin, the light-induced trimer–monomer transition in LHCII and the blue-light-induced excitation quenching in LHCII. The physiological importance of the processes reviewed is also discussed with emphasis on the photoprotective excitation quenching and on possible involvement in the regulation of the xanthophyll cycle.

Los estilos APA, Harvard, Vancouver, ISO, etc.

15

Kroh, Pavel, Jakub Pšenčík, TomÁŠ Polívka, David Engst y Jan Hála. "Laser Induced Hole Filling of Bacteriochlorophyll d Monomers of Green Sulfur Photosynthetic Bacteria Antennae". Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals 291, n.º 1 (diciembre de 1996): 201–7. http://dx.doi.org/10.1080/10587259608042748.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

16

Caffarri, Stefano, Francesca Passarini, Roberto Bassi y Roberta Croce. "A specific binding site for neoxanthin in the monomeric antenna proteins CP26 and CP29 of Photosystem II". FEBS Letters 581, n.º 24 (4 de septiembre de 2007): 4704–10. http://dx.doi.org/10.1016/j.febslet.2007.08.066.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

17

Kell, Adam, Anton Yu Khmelnitskiy, Tonu Reinot y Ryszard Jankowiak. "On uncorrelated inter-monomer Förster energy transfer in Fenna–Matthews–Olson complexes". Journal of The Royal Society Interface 16, n.º 151 (febrero de 2019): 20180882. http://dx.doi.org/10.1098/rsif.2018.0882.

Texto completo

Resumen

The Fenna–Matthews–Olson (FMO) light-harvesting antenna protein of green sulfur bacteria is a long-studied pigment–protein complex which funnels energy from the chlorosome to the reaction centre where photochemistry takes place. The structure of the FMO protein from Chlorobaculum tepidum is known as a homotrimeric complex containing eight bacteriochlorophyll a per monomer. Owing to this structure FMO has strong intra-monomer and weak inter-monomer electronic coupling constants. While long-lived (sub-picosecond) coherences within a monomer have been a prevalent topic of study over the past decade, various experimental evidence supports the presence of subsequent inter-monomer energy transfer on a picosecond time scale. The latter has been neglected by most authors in recent years by considering only sub-picosecond time scales or assuming that the inter-monomer coupling between low-energy states is too weak to warrant consideration of the entire trimer. However, Förster theory predicts that energy transfer of the order of picoseconds is possible even for very weak (less than 5 cm –1 ) electronic coupling between chromophores. This work reviews experimental data (with a focus on emission and hole-burned spectra) and simulations of exciton dynamics which demonstrate inter-monomer energy transfer. It is shown that the lowest energy 825 nm absorbance band cannot be properly described by a single excitonic state. The energy transfer through FMO is modelled by generalized Förster theory using a non-Markovian, reduced density matrix approach to describe the electronic structure. The disorder-averaged inter-monomer transfer time across the 825 nm band is about 27 ps. While only isolated FMO proteins are presented, the presence of inter-monomer energy transfer in the context of the overall photosystem is also briefly discussed.

Los estilos APA, Harvard, Vancouver, ISO, etc.

18

Ballottari, Matteo, Julien Girardon, Nico Betterle, Tomas Morosinotto y Roberto Bassi. "Identification of the Chromophores Involved in Aggregation-dependent Energy Quenching of the Monomeric Photosystem II Antenna Protein Lhcb5". Journal of Biological Chemistry 285, n.º 36 (28 de junio de 2010): 28309–21. http://dx.doi.org/10.1074/jbc.m110.124115.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

19

Betterle, Nico, Matteo Ballottari, Rainer Hienerwadel, Luca Dall’Osto y Roberto Bassi. "Dynamics of zeaxanthin binding to the photosystem II monomeric antenna protein Lhcb6 (CP24) and modulation of its photoprotection properties". Archives of Biochemistry and Biophysics 504, n.º 1 (diciembre de 2010): 67–77. http://dx.doi.org/10.1016/j.abb.2010.05.016.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

20

Sumaoka, Jun, Hiroki Akiba y Makoto Komiyama. "Selective Sensing of Tyrosine Phosphorylation in Peptides Using Terbium(III) Complexes". International Journal of Analytical Chemistry 2016 (2016): 1–14. http://dx.doi.org/10.1155/2016/3216523.

Texto completo

Resumen

Phosphorylation of tyrosine residues in proteins, as well as their dephosphorylation, is closely related to various diseases. However, this phosphorylation is usually accompanied by more abundant phosphorylation of serine and threonine residues in the proteins and covers only 0.05% of the total phosphorylation. Accordingly, highly selective detection of phosphorylated tyrosine in proteins is an urgent subject. In this review, recent developments in this field are described. Monomeric and binuclearTbIIIcomplexes, which emit notable luminescence only in the presence of phosphotyrosine (pTyr), have been developed. There, the benzene ring of pTyr functions as an antenna and transfers its photoexcitation energy to theTbIIIion as the emission center. Even in the coexistence of phosphoserine (pSer) and phosphothreonine (pThr), pTyr can be efficintly detected with high selectivity. Simply by adding theseTbIIIcomplexes to the solutions, phosphorylation of tyrosine in peptides by protein tyrosine kinases and dephosphorylation by protein tyrosine phosphatases can be successfully visualized in a real-time fashion. Furthermore, the activities of various inhibitors on these enzymes are quantitatively evaluated, indicating a strong potential of the method for efficient screening of eminent inhibitors from a number of candidates.

Los estilos APA, Harvard, Vancouver, ISO, etc.

21

Haldosén, L. A., G. Andersson y J. A. Gustafsson. "Characterization of hepatic lactogen receptor. Subcellular distribution and characterization of N-linked carbohydrate chains". Biochemical Journal 263, n.º 1 (1 de octubre de 1989): 33–40. http://dx.doi.org/10.1042/bj2630033.

Texto completo

Resumen

The types of carbohydrate chains present in a rat liver lactogenic hormone-binding receptor species with an Mr of 82,000, and in its hormone-binding subunits with Mr values of 40,000 and 35,000, were characterized using carbohydrate-chain-cleaving enzymes and affinity cross-linking. The subcellular distribution of lactogenic hormone-binding species was studied in organelle-enriched fractions. The monomeric Mr-40,000 and Mr-35,000 species contain N-linked tri- or tetra-antennary complex and high-mannose chains respectively. The Mr-82,000 species exists in two forms, where the Mr-40,000 and Mr-35,000 subunits are each combined with unglycosylated and, with the technique used, unlabelled subunit(s). Studies with organelle-enriched fractions revealed that the Mr-35,000 species was found in an endoplasmic reticulum-enriched fraction. The Mr-40,000 species was the predominant monomeric binding species in Golgi/endosome- and plasma membrane-enriched fractions. It is suggested that the Mr-35,000 species is a precursor to the Mr-40,000 species. In lysosome/endosome- or lysosome-enriched fractions, a broad distribution in Mr (35,000-40,000) was characteristic of the hormone-binding species. The Mr-82,000 species was only found in a Golgi/endosome-enriched fraction. Labelling of endosome lactogen receptor by injection of 125I-labelled ovine prolactin in vivo and cross-linking yielded only the Mr-40,000 species. Thus, the Mr-40,000 and Mr-35,000 lactogenic hormone-binding species each appear to be combined with the unglycosylated receptor subunit(s) in the Golgi complex to form Mr-82,000 heterodimeric complexes.

Los estilos APA, Harvard, Vancouver, ISO, etc.

22

Kobuke, Yoshiaki. "Porphyrin supramolecules by complementary coordination for units constructing photosynthetic systems". Journal of Porphyrins and Phthalocyanines 08, n.º 02 (febrero de 2004): 156–74. http://dx.doi.org/10.1142/s1088424604000155.

Texto completo

Resumen

Among unique structural arrangements provided by nature, special pair and macroring antenna complexes in bacterial photosynthetic systems have been mimicked by simple organization of choromophores. The special pair was mimicked by imidazolyl-substituted porphyrinatozinc which gave a complementary coordination dimer of slipped cofacial orientation with an extremely large stability constant of 1010 M-1 in CHCl 3. When two imidazolylporphyrinatozinc units were linked directly at the meso positions, linear and continuous growth of the complementary coordination lead to porphyrin arrays of a few hundreds nanometer scale, corresponding to molecular weights of a few 105. At the same time, the porphyrin array could be dissociated into the monomeric unit by competitive coordination of solvents. This provided a way of terminating or initiating the oligomeric porphyrin array with appropriate chain terminals/initiators. Two imidazolylporphyrinatozinc complexes were then linked by a m-phenylene unit with an angle of 120°. The linear and macrocyclic oligomer mixtures initially obtained were converged smoothly by reorganization equilibrium into a mixture of hexameric and pentameric macrocycles under high-dilution conditions. The ring mimicked the structure and function of the light harvesting complexes of bacterial photosynthetic systems. The covalent linking of coordination organized porphyrins was also developed to maintain the structure even in highly coordinating solvents such as pyridine. The linear array formation and the facile introduction of specific terminal/initiator groups by complementary coordination were then applied to introduce antenna function onto solar cell. Through thiolate attachment on a gold surface, imidazolylporphyrinatozinc initiated the growth of meso-meso linked porphyrin arrays by successive complementary coordination. This methodology improved the efficiency of absorption of incident photon and increased significantly the total photocurrent generation efficiency.

Los estilos APA, Harvard, Vancouver, ISO, etc.

23

Sola-Llano, Rebeca, Yasuhiko Fujita, Luis Gómez-Hortigüela, Almudena Alfayate, Hiroshi Uji-i, Eduard Fron, Shuichi Toyouchi, Joaquín Pérez-Pariente, Iñigo López-Arbeloa y Virginia Martínez-Martínez. "One-Directional Antenna Systems: Energy Transfer from Monomers to J-Aggregates within 1D Nanoporous Aluminophosphates". ACS Photonics 5, n.º 1 (19 de octubre de 2017): 151–57. http://dx.doi.org/10.1021/acsphotonics.7b00553.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

24

Tang, Gaoyan y Keith P. Mintz. "Glycosylation of the Collagen Adhesin EmaA of Aggregatibacter actinomycetemcomitans Is Dependent upon the Lipopolysaccharide Biosynthetic Pathway". Journal of Bacteriology 192, n.º 5 (8 de enero de 2010): 1395–404. http://dx.doi.org/10.1128/jb.01453-09.

Texto completo

Resumen

ABSTRACT The human oropharyngeal pathogen Aggregatibacter actinomycetemcomitans synthesizes multiple adhesins, including the nonfimbrial extracellular matrix protein adhesin A (EmaA). EmaA monomers trimerize to form antennae-like structures on the surface of the bacterium, which are required for collagen binding. Two forms of the protein have been identified, which are suggested to be linked with the type of O-polysaccharide (O-PS) of the lipopolysaccharide (LPS) synthesized (G. Tang et al., Microbiology 153:2447-2457, 2007). This association was investigated by generating individual mutants for a rhamnose sugar biosynthetic enzyme (rmlC; TDP-4-keto-6-deoxy-d-glucose 3,5-epimerase), the ATP binding cassette (ABC) sugar transport protein (wzt), and the O-antigen ligase (waaL). All three mutants produced reduced amounts of O-PS, and the EmaA monomers in these mutants displayed a change in their electrophoretic mobility and aggregation state, as observed in sodium dodecyl sulfate (SDS)-polyacrylamide gels. The modification of EmaA with O-PS sugars was suggested by lectin blots, using the fucose-specific Lens culinaris agglutinin (LCA). Fucose is one of the glycan components of serotype b O-PS. The rmlC mutant strain expressing the modified EmaA protein demonstrated reduced collagen adhesion using an in vitro rabbit heart valve model, suggesting a role for the glycoconjugant in collagen binding. These data provide experimental evidence for the glycosylation of an oligomeric, coiled-coil adhesin and for the dependence of the posttranslational modification of EmaA on the LPS biosynthetic machinery in A. actinomycetemcomitans.

Los estilos APA, Harvard, Vancouver, ISO, etc.

25

Dannenbauer, Nicole, Ana Kuzmanoski, Claus Feldmann y Klaus Müller-Buschbaum. "1,3-Thiazole as Suitable Antenna Ligand for Lanthanide Photoluminescence in [LnCl3(thz)4]·0.5thz, Ln = Sm, Eu, Gd, Tb, Dy". Zeitschrift für Naturforschung B 69, n.º 2 (1 de febrero de 2014): 255–62. http://dx.doi.org/10.5560/znb.2014-3292.

Texto completo

Resumen

The series of luminescent monomeric lanthanide thiazole complexes [LnCl3(thz)4]⋅0.5thz (Ln = Sm, Eu, Gd, Tb, Dy; thz=1,3-thiazole) has been synthesised and characterised by powder and singlecrystal X-ray diffraction, IR and photoluminescence spectroscopy, DTA/TG as well as elemental analysis. The colourless compounds exhibit photoluminescence in the visible region with varying quantum efficiencies up to QY = 48% for [TbCl3(thz)4]⋅0.5thz. Both, the lanthanide ions as well as the thiazole ligand contribute to the luminescence. Excitation can be achieved via intra-4 f transitions and by exciting the ligand, emission is observed mainly from the lanthanide ions again by 4 f transitions. Thiazole can transfer energy to the lanthanide ions, which further feeds the lanthanide emission by an efficient antenna effect even at room temperature. The lanthanide ions show pentagonalbipyramidal coordination by three chloride anions and four N atoms of 1,3-thiazole, which leads to a strong 5D0 →7F4 transition for europium. Significant differences arise as compared to thiophene complexes because no sulphur atom is involved in the metal coordination, as the thiazole ligand is solely coordinated via its nitrogen function.

Los estilos APA, Harvard, Vancouver, ISO, etc.

26

Tahersima, Mohammad H., M. Danang Birowosuto, Zhizhen Ma, William C. Coley, Michael D. Valentin, Sahar Naghibi Alvillar, I.-Hsi Lu et al. "Testbeds for Transition Metal Dichalcogenide Photonics: Efficacy of Light Emission Enhancement in Monomer vs Dimer Nanoscale Antennae". ACS Photonics 4, n.º 7 (22 de junio de 2017): 1713–21. http://dx.doi.org/10.1021/acsphotonics.7b00208.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

27

Fang, C., Yan Xiang Wang, Z. G. Su y Zhao Xian Xiong. "Gelcasting of BaO-Nd₂O₃-TiO₂ Microwave Ceramics". Key Engineering Materials 280-283 (febrero de 2007): 747–50. http://dx.doi.org/10.4028/www.scientific.net/kem.280-283.747.

Texto completo

Resumen

Gelcasting is a novel ceramic forming process for fabricating products of complex-shaped ceramics. In this contribution, the gelcasting process is applied to manufacture green body of microwave ceramic components for resonators, oscillators and antennas. Calcined powders, dispersant and organic monomers are mixed together by ball-milling to acquire high solid loading slurry with low viscosity. After addition of initiator and catalyst, the slurry is cast into a non-pours mold and then polymerized. The slurry is thus solidified in situ and the green bodies with the desired shapes are obtained. The dried body is rather strong and can be machined so as to get more precise or complex-shaped components. Then the green bodies are sintered at high temperature. The microwave properties (εr, Q, τf) and microstructures of the ceramics prepared by gelcasting are compared with those of die-pressed ones.

Los estilos APA, Harvard, Vancouver, ISO, etc.

28

Skandary, Sepideh, Alexander Konrad, Martin Hussels, Alfred J. Meixner y Marc Brecht. "Orientations between Red Antenna States of Photosystem I Monomers from Thermosynechococcus elongatus Revealed by Single-Molecule Spectroscopy". Journal of Physical Chemistry B 119, n.º 43 (14 de agosto de 2015): 13888–96. http://dx.doi.org/10.1021/acs.jpcb.5b04483.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

29

Piskarev, V. E., J. Navrátil, H. Karásková, K. Bezouska y J. Kocourek. "Interaction of egg-white glycoproteins and their oligosaccharides with the monomer and the hexamer of chicken liver lectin. A multivalent oligosaccharide-combining site exists within the carbohydrate-recognition domain". Biochemical Journal 270, n.º 3 (15 de septiembre de 1990): 755–60. http://dx.doi.org/10.1042/bj2700755.

Texto completo

Resumen

Binding of egg-white glycoproteins and their oligosaccharides to hexameric solubilized form of the chicken hepatic lectin and the monomeric soluble fragment containing the carbohydrate-recognition domain has been investigated by several techniques. Ligand blotting revealed significant differences in binding to two forms of the lectin only for glycoproteins bearing multiple N-linked oligosaccharide moieties in their molecule (riboflavin-binding glycoprotein, avidin or ovomucoid). Inhibition studies indicated that inhibitory potency in a series of linear and branched N-acetyl-D-glucosamine-terminated oligosaccharides is critically dependent on the number and spatial arrangement of the terminal monosaccharide residues for both forms of the lectin. Direct binding of 4-hydroxyphenyl-derivatized radioiodinated oligosaccharides measured by equilibrium dialysis and frontal affinity chromatography points to the existence of two N-acetyl-D-glucosamine-combining sites per one subunit of the lectin, as has been recently reported for the rabbit and rat liver lectin [Lee & Lee (1988) Biochem. Biophys. Res. Commun. 155, 1444-1452]. Highly branch (penta-antennary) oligosaccharides interact with more than one subunit of the hexameric form of the lectin and thus resemble the more complex interaction of the whole glycoprotein.

Los estilos APA, Harvard, Vancouver, ISO, etc.

30

Zurdo, J., R. M. Lozano, C. Fernandez-Cabrera y J. M. Ramirez. "Dimeric carotenoid interaction in the light-harvesting antenna of purple phototrophic bacteria". Biochemical Journal 274, n.º 3 (15 de marzo de 1991): 881–84. http://dx.doi.org/10.1042/bj2740881.

Texto completo

Resumen

The carotenoid content of intracytoplasmic membrane vesicles isolated from purple phototrophic bacteria was reduced to a variable extent by mild extraction with light petroleum. Using preparations obtained from Rhodobacter capsulatus strains that contained the Light Harvesting System I (LHI) complex as the only major photosynthetic holochrome, it was shown that the visible circular dichroism of the carotenoids increased with the square of the membrane carotenoid content, as expected from being caused by dimeric exciton interaction. No chirality resulting from twists of the individual planar chromophore was detected. Therefore the contribution to carotenoid optical activity of non-degenerate interactions with bacteriochlorophyll or the apoprotein does not appear to be significant. The broadening of the absorption band of the bound pigment, caused by the splitting of the monomer transition, was demonstrated in membrane vesicles of both Rb, capsulatus and Rhodospirillum rubrum as a decrease of the fine structure of the band. Furthermore, the dimeric organization of the carotenoid pigments in the bacterial LHI complex accounted for the observed quantitative relationship between the fine structure of the band and the carotenoid content of the membrane.

Los estilos APA, Harvard, Vancouver, ISO, etc.

31

Ashley, Steven. "Electric Plastics". Mechanical Engineering 120, n.º 04 (1 de abril de 1998): 62–64. http://dx.doi.org/10.1115/1.1998-apr-3.

Texto completo

Resumen

This article reviews the importance of conductive polymer. The big chemical company is marketing the polythiophene under the trade name Baytron. The material could also be used to make plastics paintable by adding the conductive agent first, or in the electrodes of small, high-performance tantalum capacitors found in telecommunications, computer, and automotive products. Probably the most significant commercialization of conductive polymers was for flexible, long-lived batteries that were produced in quantity by Bridgestone Corp. and Seiko Co. in Japan and by BASF/Varta in Germany. Conductive polymers are long, carbon-based chains composed of simple repeating units called monomers. The list of potential applications for conductive polymers remains a long one, and includes antiradiation coatings, batteries, catalysts, deicer panels, electrochromic windows, electromechanical actuators, embedded-array antennas, fuel cells, lithographic resists, nonlinear optics, radar dishes, and wave guides. However, how big an impact the materials will make in these markets remains unclear.

Los estilos APA, Harvard, Vancouver, ISO, etc.

32

Gradinaru, Claudiu C., Sevgi Özdemir, Demet Gülen, Ivo H. M. van Stokkum, Rienk van Grondelle y Herbert van Amerongen. "The Flow of Excitation Energy in LHCII Monomers: Implications for the Structural Model of the Major Plant Antenna". Biophysical Journal 75, n.º 6 (diciembre de 1998): 3064–77. http://dx.doi.org/10.1016/s0006-3495(98)77747-1.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

33

Garab, Győző, Zoltán Cseh, László Kovács, Subramanyam Rajagopal, Zsuzsanna Várkonyi, Mark Wentworth, László Mustárdy et al. "Light-Induced Trimer to Monomer Transition in the Main Light-Harvesting Antenna Complex of Plants: Thermo-Optic Mechanism†". Biochemistry 41, n.º 51 (diciembre de 2002): 15121–29. http://dx.doi.org/10.1021/bi026157g.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

34

Das, Suresh y Prashant V. Kamat. "Can H-Aggregates Serve as Light-Harvesting Antennae? Triplet−Triplet Energy Transfer between Excited Aggregates and Monomer Thionine in Aersol-OT Solutions". Journal of Physical Chemistry B 103, n.º 1 (enero de 1999): 209–15. http://dx.doi.org/10.1021/jp983816j.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

35

Tang, Kun, Wen-Long Ding, Astrid Höppner, Cheng Zhao, Lun Zhang, Yusaku Hontani, John T. M. Kennis et al. "The terminal phycobilisome emitter, LCM: A light-harvesting pigment with a phytochrome chromophore". Proceedings of the National Academy of Sciences 112, n.º 52 (15 de diciembre de 2015): 15880–85. http://dx.doi.org/10.1073/pnas.1519177113.

Texto completo

Resumen

Photosynthesis relies on energy transfer from light-harvesting complexes to reaction centers. Phycobilisomes, the light-harvesting antennas in cyanobacteria and red algae, attach to the membrane via the multidomain core-membrane linker, LCM. The chromophore domain of LCM forms a bottleneck for funneling the harvested energy either productively to reaction centers or, in case of light overload, to quenchers like orange carotenoid protein (OCP) that prevent photodamage. The crystal structure of the solubly modified chromophore domain from Nostoc sp. PCC7120 was resolved at 2.2 Å. Although its protein fold is similar to the protein folds of phycobiliproteins, the phycocyanobilin (PCB) chromophore adopts ZZZssa geometry, which is unknown among phycobiliproteins but characteristic for sensory photoreceptors (phytochromes and cyanobacteriochromes). However, chromophore photoisomerization is inhibited in LCM by tight packing. The ZZZssa geometry of the chromophore and π-π stacking with a neighboring Trp account for the functionally relevant extreme spectral red shift of LCM. Exciton coupling is excluded by the large distance between two PCBs in a homodimer and by preservation of the spectral features in monomers. The structure also indicates a distinct flexibility that could be involved in quenching. The conclusions from the crystal structure are supported by femtosecond transient absorption spectra in solution.

Los estilos APA, Harvard, Vancouver, ISO, etc.

36

Milanesio, M. Elisa, Miguel Gervaldo, Luis A. Otero, Leonides Sereno, Juana J. Silber y Edgardo N. Durantini. "Synthesis of a diporphyrin dyad bearing electron-donor and electron-withdrawing substituents with potential use in the spectral sensitization of semiconductor solar cells". Journal of Porphyrins and Phthalocyanines 07, n.º 01 (enero de 2003): 42–51. http://dx.doi.org/10.1142/s1088424603000070.

Texto completo

Resumen

A new dyad 9( ZnP - P ) has been synthesized linking 5,15-bis(4-carboxyphenyl)-10,20-bis(4-nitrophenyl) porphyrin 4( P ) and Zn(II) 5-(4-aminophenyl)-10,15,20-tris(4-methoxylphenyl) porphyrin 8 (ZnP) by an amide bond. The structural moieties of dyad 9( ZnP-P ) present both different singlet state energy and redox properties. Dyad 9 was designed to improve the intramolecular electron transfer capacity. The ZnP moiety bears electron-donating methoxy groups and a zinc ion, while the other porphyrin structure, P , is substituted by electron-withdrawing nitro groups. On the other hand, structure P bears a carboxylic acid group, which is able to benefit from the orientation of dyad 9 adsorbed on the SnO 2 electrode. Absorption spectroscopic studies indicated only a very weak interaction between the chromophores in the ground state. The fluorescence analysis shows that both porphyrin moieties in dyad 9 are strongly quenched and that the quenching increases in a polar solvent. The ZnP moiety acts like an antenna for porphyrin P , but, singlet-singlet energy transfer is not complete. Thermodynamically, dyad 9 presents a high capacity to form the photoinduced charge-separated state, ZnP ·+- P ·-. Dyad 9 sensitizes the SnO 2 electrode and the photocurrent action spectrum closely matches the absorption spectrum, which confirms that light absorption by dyad is the initial step in the charge transfer mechanism. The photocurrent efficiency of dyad 9 is considerably higher than those of porphyrin monomers used as models of ZnP and P structures. Two processes may be contributing to enhance the charge injection efficiency in dyad 9; one involves an antenna effect that produces energy transfer from ZnP to P and the other includes electron transfer from the ZnP moiety to the photooxidizable free-base P . This dyad design, with P in direct contact with the substrate through the free carboxylic acid group, is a promising architecture of organic material for spectral sensitization of semiconductor solar cells.

Los estilos APA, Harvard, Vancouver, ISO, etc.

37

Tseghai, Granch Berhe, Desalegn Alemu Mengistie, Benny Malengier, Kinde Anlay Fante y Lieva Van Langenhove. "PEDOT:PSS-Based Conductive Textiles and Their Applications". Sensors 20, n.º 7 (28 de marzo de 2020): 1881. http://dx.doi.org/10.3390/s20071881.

Texto completo

Resumen

The conductive polymer complex poly (3,4-ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS) is the most explored conductive polymer for conductive textiles applications. Since PEDOT:PSS is readily available in water dispersion form, it is convenient for roll-to-roll processing which is compatible with the current textile processing applications. In this work, we have made a comprehensive review on the PEDOT:PSS-based conductive textiles, methods of application onto textiles and their applications. The conductivity of PEDOT:PSS can be enhanced by several orders of magnitude using processing agents. However, neat PEDOT:PSS lacks flexibility and strechability for wearable electronics applications. One way to improve the mechanical flexibility of conductive polymers is making a composite with commodity polymers such as polyurethane which have high flexibility and stretchability. The conductive polymer composites also increase attachment of the conductive polymer to the textile, thereby increasing durability to washing and mechanical actions. Pure PEDOT:PSS conductive fibers have been produced by solution spinning or electrospinning methods. Application of PEDOT:PSS can be carried out by polymerization of the monomer on the fabric, coating/dyeing and printing methods. PEDOT:PSS-based conductive textiles have been used for the development of sensors, actuators, antenna, interconnections, energy harvesting, and storage devices. In this review, the application methods of PEDOT:SS-based conductive polymers in/on to a textile substrate structure and their application thereof are discussed.

Los estilos APA, Harvard, Vancouver, ISO, etc.

38

Kataoka, Yumiko, Yutaka Shibata y Hitoshi Tamiaki. "Supramolecular energy transfer from photoexcited chlorosomal zinc porphyrin self-aggregates to a chlorin or bacteriochlorin monomer as models of main light-harvesting antenna systems in green photosynthetic bacteria". Bioorganic & Medicinal Chemistry Letters 22, n.º 16 (agosto de 2012): 5218–21. http://dx.doi.org/10.1016/j.bmcl.2012.06.066.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

39

Hull, S. R., Z. Sheng, O. Vanderpuye, C. David y K. L. Carraway. "Isolation and partial characterization of ascites sialoglycoprotein-2 of the cell surface sialomucin complex of 13762 rat mammary adenocarcinoma cells". Biochemical Journal 265, n.º 1 (1 de enero de 1990): 121–29. http://dx.doi.org/10.1042/bj2650121.

Texto completo

Resumen

Sialomucins are the dominant components of the cell surfaces of some carcinoma ascites cells and have been postulated to inhibit recognition of tumours by the immune system. The sialomucin ASGP-1 (ascites sialoglycoprotein-1) of the 13762 rat mammary adenocarcinoma is associated with the cell surface as a complex with a concanavalin-A-binding glycoprotein called ASGP-2. This sialomucin complex has been purified from ascites cell microvilli by extraction with Triton X-100 and CsCl density-gradient centrifugation. ASGP-1 (which has been purified previously) and ASGP-2 were dissociated in 6 M-guanidine hydrochloride and separated by gel filtration. The molecular mass of the undenatured detergent complex of ASGP-2, estimated by gel filtration and velocity sedimentation in Triton X-100, was 148 kDa. Since the apparent molecular mass by SDS/polyacrylamide-gel electrophoresis was about 120 kDa, ASGP-2 must be a monomer as extracted from the membrane. Studies of its chemical composition indicate that it contains about 45% carbohydrate by weight, including both mannose and galactosamine. Alkaline borohydride treatment of ASGP-2 converted approx. half of the N-acetylgalactosamine to N-acetylgalactosaminitol, demonstrating the presence of O-linked oligosaccharides. Analyses of mannose-labelled Pronase glycopeptides from ASGP-2 by lectin-affinity chromatography on concanavalin A and leucocyte-agglutinating phytohaemagglutinin suggested that 40% of the label was present in high-mannose/hybrid oligosaccharides, 20% in triantennary oligosaccharides substituted on the C-2 and C-4 mannose positions and 40% in tri- or tetra-antennary oligosaccharides substituted on C-2 and C-6. The presence of polylactosamine sequences on these oligosaccharides was suggested by lectin blots and by precipitation from detergent extracts with tomato lectin. From chemical analyses and lectin-affinity studies, we estimate that ASGP-2 contains four high-mannose and 13 complex N-glycosylated oligosaccharides, plus small amounts of polylactosamine and O-linked oligosaccharides. The presence of four different classes of oligosaccharides on this glycoprotein suggests that it will be an interesting model system for biosynthetic comparisons of the different glycosylation pathways.

Los estilos APA, Harvard, Vancouver, ISO, etc.

40

Tang-Siegel, Gaoyan G., David R. Danforth, Jake Tristano, Teresa Ruiz y Keith P. Mintz. "The serotype a-EmaA adhesin of Aggregatibacter actinomycetemcomitans does not require O-PS synthesis for collagen binding activity". Microbiology 168, n.º 5 (12 de mayo de 2022). http://dx.doi.org/10.1099/mic.0.001191.

Texto completo

Resumen

Aggregatibacter actinomycetemcomitans , a causative agent of periodontitis and non-oral diseases, synthesizes a trimeric extracellular matrix protein adhesin A (EmaA) that mediates collagen binding and biofilm formation. EmaA is found as two molecular forms, which correlate with the serotype of the bacterium. The canonical protein (b-EmaA), associated with serotypes b and c, has a monomeric molecular mass of 202 kDa. The collagen binding activity of b-EmaA is dependent on the presence of O-polysaccharide (O-PS), whereas biofilm activity is independent of O-PS synthesis. The EmaA associated with serotype a strains (a-EmaA) has a monomeric molecular mass of 173 kDa and differs in the amino acid sequence of the functional domain of the protein. In this study, a-emaA was confirmed to encode a protein that forms antenna-like appendages on the surface of the bacterium, which were found to be important for both collagen binding and biofilm formation. In an O-PS-deficient talose biosynthetic (tld) mutant strain, the electrophoretic mobility of the a-EmaA monomers was altered and the amount of membrane-associated EmaA was decreased when compared to the parent strain. The mass of biofilm formed remained unchanged. Interestingly, the collagen binding activity of the mutant strain was similar to the activity associated with the parent strain, which differs from that observed with the canonical b-EmaA isoform. These data suggest that the properties of the a-EmaA isoform are like those of b-EmaA, with the exception that collagen binding activity is independent of the presence or absence of the O-PS.

Los estilos APA, Harvard, Vancouver, ISO, etc.

41

Li, Meijing, Jianfei Ma, Xueming Li y Sen-Fang Sui. "In situ cryo-ET structure of phycobilisome–photosystem II supercomplex from red alga". eLife 10 (13 de septiembre de 2021). http://dx.doi.org/10.7554/elife.69635.

Texto completo

Resumen

Phycobilisome (PBS) is the main light-harvesting antenna in cyanobacteria and red algae. How PBS transfers the light energy to photosystem II (PSII) remains to be elucidated. Here we report the in situ structure of the PBS–PSII supercomplex from Porphyridium purpureum UTEX 2757 using cryo-electron tomography and subtomogram averaging. Our work reveals the organized network of hemiellipsoidal PBS with PSII on the thylakoid membrane in the native cellular environment. In the PBS–PSII supercomplex, each PBS interacts with six PSII monomers, of which four directly bind to the PBS, and two bind indirectly. Additional three ‘connector’ proteins also contribute to the connections between PBS and PSIIs. Two PsbO subunits from adjacent PSII dimers bind with each other, which may promote stabilization of the PBS–PSII supercomplex. By analyzing the interaction interface between PBS and PSII, we reveal that αLCM and ApcD connect with CP43 of PSII monomer and that αLCM also interacts with CP47' of the neighboring PSII monomer, suggesting the multiple light energy delivery pathways. The in situ structures illustrate the coupling pattern of PBS and PSII and the arrangement of the PBS–PSII supercomplex on the thylakoid, providing the near-native 3D structural information of the various energy transfer from PBS to PSII.

Los estilos APA, Harvard, Vancouver, ISO, etc.

42

Gerotto, Caterina, Andrea Trotta, Azfar Ali Bajwa, Tomas Morosinotto y Eva-Mari Aro. "Role of Serine/Threonine Protein Kinase Stn7 in the Formation of Two Distinct Photosystem I Supercomplexes in Physcomitrium patens". Plant Physiology, 23 de junio de 2022. http://dx.doi.org/10.1093/plphys/kiac294.

Texto completo

Resumen

Abstract Reversible thylakoid protein phosphorylation provides most flowering plants with dynamic acclimation to short-term changes in environmental light conditions. Here, through generating Serine/Threonine protein kinase 7 (STN7)-depleted mutants in the moss Physcomitrella (Physcomitrium patens), we identified phosphorylation targets of STN7 kinase and their roles in short- and long-term acclimation of the moss to changing light conditions. Biochemical and mass spectrometry analyses revealed STN7-dependent phosphorylation of N-terminal Thr in specific Light Harvesting Complex II (LHCII) trimer subunits (LHCBM2 and LHCBM4/8) and provided evidence that phospho-LHCBM accumulation is responsible for the assembly of two distinct Photosystem I (PSI) supercomplexes, both of which are largely absent in STN7-depleted mutants. Besides the canonical state transition complex (PSI-LHCI-LHCII), we isolated the larger moss-specific PSI-Large (PSI-LHCI-LHCB9-LHCII) from stroma-exposed thylakoids. Unlike PSI-LHCI-LHCII, PSI-Large did not demonstrate short-term dynamics for balancing the distribution of excitation energy between PSII and PSI. Instead, PSI-Large contributed to a more stable increase in PSI antenna size in Physcomitrella, except under prolonged high irradiance. Additionally, the STN7-depleted mutants revealed altered light-dependent phosphorylation of a monomeric antenna protein, LHCB6, whose phosphorylation displayed a complex regulation by multiple kinases. Collectively, the unique phosphorylation plasticity and dynamics of Physcomitrella monomeric LHCB6 and trimeric LHCBM isoforms, together with the presence of PSI supercomplexes with different antenna size and responsiveness to light changes, reflect the evolutionary position of mosses between green algae and vascular plants, yet with clear moss-specific features emphasizing their adaptation to terrestrial low-light environments.

Los estilos APA, Harvard, Vancouver, ISO, etc.

43

Akhtar, Parveen, Avratanu Biswas, Fanny Balog-Vig, Ildikó Domonkos, László Kovács y Petar H. Lambrev. "Trimeric photosystem I facilitates energy transfer from phycobilisomes in Synechocystis sp. PCC 6803". Plant Physiology, 18 de marzo de 2022. http://dx.doi.org/10.1093/plphys/kiac130.

Texto completo

Resumen

Abstract In cyanobacteria, phycobilisomes (PBS) serve as peripheral light-harvesting complexes of the two photosystems, extending their antenna size and the wavelength range of photons available for photosynthesis. The abundance of PBS, the number of phycobiliproteins they contain, and their light-harvesting function are dynamically adjusted in response to the physiological conditions. PBS are also thought to be involved in state transitions that maintain the excitation balance between the two photosystems. Unlike its eukaryotic counterpart, PSI is trimeric in many cyanobacterial species and the physiological significance of this is not well understood. Here, we compared the composition and light-harvesting function of PBS in cells of Synechocystis sp. PCC 6803, which has primarily trimeric PSI, and the ΔpsaL mutant, which lacks the PsaL subunit of PSI and is unable to form trimers. We also investigated a mutant additionally lacking the PsaJ and PsaF subunits of PSI. Both strains with monomeric PSI accumulated significantly more allophycocyanin per chlorophyll, indicating higher abundance of PBS. On the other hand, a higher phycocyanin:allophycocyanin ratio in the wild type suggests larger PBS or the presence of APC-less PBS (CpcL-type) that are not assembled in cells with monomeric PSI. Steady-state and time-resolved fluorescence spectroscopy at room temperature and 77 K revealed that PSII receives more energy from the PBS at the expense of PSI in cells with monomeric PSI, regardless of the presence of PsaF. Taken together, these results show that the oligomeric state of PSI impacts the excitation energy flow in Synechocystis.

Los estilos APA, Harvard, Vancouver, ISO, etc.

44

Mahato, Kapil Dev y Uday Kumar. "A Review of Organic Dye Based Nanoparticles: Preparation, Properties, and Engineering/Technical Applications". Mini-Reviews in Organic Chemistry 19 (29 de junio de 2022). http://dx.doi.org/10.2174/1570193x19666220629103920.

Texto completo

Resumen

Abstract: Organic dye-based nanoparticles (ODNPs) are fabricated with desired morphologies using laser ablation, reprecipitation, ion association, and self-assembly methods. Primitively, this review introduces the theory of the molecular origins of dye aggregation, manifestations of the formations of monomer to J-dimer, H-dimer, and oblique dimer (mixed J and H dimer) in ODNPs. Although, organic dye nanoparticles have better basic properties than their monomer counterparts. These nanoparticles are suitable candidates for many engineering and technical applications. Furthermore, we have discussed OLEDs, optoelectronics, sensing, environmental, light-harvesting antennas, cryptography, and biomedical imaging applications. The conclusion made from the critical review analysis opens up a new horizon for the future development of ODNPs applications.

Los estilos APA, Harvard, Vancouver, ISO, etc.

45

Mazor, Yuval, Daniel Nataf, Hila Toporik y Nathan Nelson. "Crystal structures of virus-like photosystem I complexes from the mesophilic cyanobacterium Synechocystis PCC 6803". eLife 3 (28 de enero de 2014). http://dx.doi.org/10.7554/elife.01496.

Texto completo

Resumen

Oxygenic photosynthesis supports virtually all life forms on earth. Light energy is converted by two photosystems—photosystem I (PSI) and photosystem II (PSII). Globally, nearly 50% of photosynthesis takes place in the Ocean, where single cell cyanobacteria and algae reside together with their viruses. An operon encoding PSI was identified in cyanobacterial marine viruses. We generated a PSI that mimics the salient features of the viral complex, named PSIPsaJF. PSIPsaJF is promiscuous for its electron donors and can accept electrons from respiratory cytochromes. We solved the structure of PSIPsaJF and a monomeric PSI, with subunit composition similar to the viral PSI, providing for the first time a detailed description of the reaction center and antenna system from mesophilic cyanobacteria, including red chlorophylls and cofactors of the electron transport chain. Our finding extends the understanding of PSI structure, function and evolution and suggests a unique function for the viral PSI.

Los estilos APA, Harvard, Vancouver, ISO, etc.

46

Xu, Caizhe, Xiong Pi, Yawen Huang, Guangye Han, Xiaobo Chen, Xiaochun Qin, Guoqiang Huang et al. "Structural basis for energy transfer in a huge diatom PSI-FCPI supercomplex". Nature Communications 11, n.º 1 (8 de octubre de 2020). http://dx.doi.org/10.1038/s41467-020-18867-x.

Texto completo

Resumen

Abstract Diatom is an important group of marine algae and contributes to around 20% of the global photosynthetic carbon fixation. Photosystem I (PSI) of diatoms is associated with a large number of fucoxanthin-chlorophyll a/c proteins (FCPIs). We report the structure of PSI-FCPI from a diatom Chaetoceros gracilis at 2.38 Å resolution by single-particle cryo-electron microscopy. PSI-FCPI is a monomeric supercomplex consisting of 12 core and 24 antenna subunits (FCPIs), and 326 chlorophylls a, 34 chlorophylls c, 102 fucoxanthins, 35 diadinoxanthins, 18 β-carotenes and some electron transfer cofactors. Two subunits designated PsaR and PsaS were found in the core, whereas several subunits were lost. The large number of pigments constitute a unique and huge network ensuring efficient energy harvesting, transfer and dissipation. These results provide a firm structural basis for unraveling the mechanisms of light-energy harvesting, transfer and quenching in the diatom PSI-FCPI, and also important clues to evolutionary changes of PSI-LHCI.

Los estilos APA, Harvard, Vancouver, ISO, etc.

47

"Zeolite Microcrystals as Hosts for Supramolecular Organization of Dye Molecules". CHIMIA 52, n.º 10 (28 de octubre de 1998): 525. http://dx.doi.org/10.2533/chimia.1998.525.

Texto completo

Resumen

Zeolite microcrystals can act as host for supramolecular organization of molecules, complexes, clusters, and quantum-size particles. They allow the design of precise and reversible functionalities. Techniques for arranging zeolite microcrystals of good quality and narrow size distribution as dense monograin layers on different substrates can be used to realize specific properties. The chemical reactivity between the intercalated molecules offers possibilities for in situ synthesis of molecular chains, clusters, and quantum-size particles, which might not be accessible otherwise. In some cases, guest-host reactivity must be considered. The reactivity of intercalated compounds with (small) molecules penetrating from the outside is an option for changing the composition of a material, i.e., molecules intercalated as monomers in a first step can be linked to form chains. New electronic structures are accessible either by specific geometrical arrangements made possible by the structure of the host and/or by explicitly involving its electronic properties. Some systems meet the conditions necessary for the occurrence of intrazeolite charge transport (ionic and electronic), realized by the guests in their ground state and in electronically excited states under high-vacuum conditions or in the presence of a solvent, depending on the composition and the structure of the material. In this article, we focus on organic dye molecules in the one-dimensional channels of zeolites with a hexagonal framework. This system consists of supramolecularly organized dye molecules. It is shown to provide fascinating possibilities for building an artificial antenna device which consists of highly concentrated monomeric dye molecules of up to 0.4M with a large Förster energy-transfer radius and a high luminescence quantum yield in an ideal geometrical arrangement of optimal size. Extremely fast electronic excitation-energy transport has been demonstrated by us in oxonine- and pyronine-dye-loaded zeolite L microcrystals. Many other highly organized dye-zeolite materials can be prepared, and they are expected to show a wide variety of challenging properties. We report on methods to distinguish between dye molecules which are inside of a microcrystal and those adsorbed on its outer surface, and we explain a demonstration experiment illustrating the intercalation of thionine into zeolite L and the thus resulting improved chemical stability of this dye.

Los estilos APA, Harvard, Vancouver, ISO, etc.

48

Caoa, Youfu, Jeffrey S. Moore y Raoul Kopelman. "Studies of Temperature-Dependent Excimer-Monomer Conversion in Dendrimeric Antenna Supermolecules by Fluorescence Spectroscopy". MRS Proceedings 651 (2000). http://dx.doi.org/10.1557/proc-651-t7.27.1.

Texto completo

Resumen

AbstractPhenylacetylene (PA) dendrimer labeled with perylene (See Fig 1) is discovered to exhibit temperature-dependent emission spectra in certain organic solvents over the temperature range of 20-65°C. The monomer signal is increasing rapidly when temperature increases, while the excimer signal decreases slowly. Models of excimer formation and weakly associated pairs (M+M) dissociation dynamics are included, and the equilibrium constants at different temperatures are calculated. This behavior suggests potential applications in fluorescence-based thermometry.

Los estilos APA, Harvard, Vancouver, ISO, etc.

49

Bourne-Worster, Susannah, Oliver Feighan y Frederick R. Manby. "Charge transfer as a mechanism for chlorophyll fluorescence concentration quenching". Proceedings of the National Academy of Sciences 120, n.º 5 (23 de enero de 2023). http://dx.doi.org/10.1073/pnas.2210811120.

Texto completo

Resumen

Highly concentrated solutions of chlorophyll display rapid fluorescence quenching. The same devastating energy loss is not seen in photosynthetic light-harvesting antenna complexes, despite the need for chromophores to be in close proximity to facilitate energy transfer. A promising, though unconfirmed mechanism for the observed quenching is energy transfer from an excited chlorophyll monomer to a closely associated chlorophyll pair that subsequently undergoes rapid nonradiative decay to the ground state via a short-lived intermediate charge-transfer state. In this work, we make use of newly emerging fast methods in quantum chemistry to assess the feasibility of this proposed mechanism. We calculate rate constants for the initial charge separation, based on Marcus free-energy surfaces extracted from molecular dynamics simulations of solvated chlorophyll pairs, demonstrating that this pathway will compete with fluorescence (i.e., drive quenching) at experimentally measured quenching concentrations. We show that the rate of charge separation is highly sensitive to interchlorophyll distance and the relative orientations of chromophores within a quenching pair. We discuss possible solvent effects on the rate of charge separation (and consequently the degree of quenching), using the light-harvesting complex II (LH2) protein from rps. acidophila as a specific example of how this process might be controlled in a protein environment. Crucially, we reveal that the LH2 antenna protein prevents quenching, even at the high chlorophyll concentrations required for efficient energy transfer, by restricting the range of orientations that neighboring chlorophyll pairs can adopt.

Los estilos APA, Harvard, Vancouver, ISO, etc.

50

Karki, Akchheta, Yu Yamashita, Shangzhi Chen, Tadanori Kurosawa, Jun Takeya, Vallery Stanishev, Vanya Darakchieva, Shun Watanabe y Magnus P. Jonsson. "Doped semiconducting polymer nanoantennas for tunable organic plasmonics". Communications Materials 3, n.º 1 (14 de julio de 2022). http://dx.doi.org/10.1038/s43246-022-00268-w.

Texto completo

Resumen

AbstractOptical nanoantennas are often based on plasmonic resonances in metal nanostructures, but their dynamic tunability is limited due to the fixed permittivity of conventional metals. Recently, we introduced PEDOT-based conducting polymers as an alternative materials platform for dynamic plasmonics and metasurfaces. Here, we expand dynamic organic plasmonic systems to a wider class of doped polythiophene-based semiconducting polymers. We present nanodisks of PBTTT semiconducting polymer doped with a dicationic salt, enabling a high doping level of around 0.8 charges per monomer, and demonstrate that they can be used as nanooptical antennas via redox-tunable plasmonic resonances. The resonances arise from the polymer being optically metallic in its doped state and dielectric in its non-conducting undoped state. The plasmonic resonances are controllable over a 1000 nm wavelength range by changing the dimensions of the nanodisks. Furthermore, the optical response of the nanoantennas can be reversibly tuned by modulating the doping level of the polymer. Simulations corroborate the experimental results and reveal the possibility to also modulate the optical nearfield response of the nanoantennas.

Los estilos APA, Harvard, Vancouver, ISO, etc.

Artículos de revistas sobre el tema "Monomeric antennae"

Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros