scholarly journals Cryo-EM structure of a functional monomeric Photosystem I from Thermosynechococcus elongatus reveals red chlorophyll cluster

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Orkun Çoruh ◽  
Anna Frank ◽  
Hideaki Tanaka ◽  
Akihiro Kawamoto ◽  
Eithar El-Mohsnawy ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Photosystem I ◽  
Excitation Energy Transfer ◽  
Spectroscopic Characterization ◽  
High Resolution Structure ◽  
Induced Changes ◽  
Surrounding Membrane ◽  
Resolution Structure

AbstractA high-resolution structure of trimeric cyanobacterial Photosystem I (PSI) from Thermosynechococcus elongatus was reported as the first atomic model of PSI almost 20 years ago. However, the monomeric PSI structure has not yet been reported despite long-standing interest in its structure and extensive spectroscopic characterization of the loss of red chlorophylls upon monomerization. Here, we describe the structure of monomeric PSI from Thermosynechococcus elongatus BP-1. Comparison with the trimer structure gave detailed insights into monomerization-induced changes in both the central trimerization domain and the peripheral regions of the complex. Monomerization-induced loss of red chlorophylls is assigned to a cluster of chlorophylls adjacent to PsaX. Based on our findings, we propose a role of PsaX in the stabilization of red chlorophylls and that lipids of the surrounding membrane present a major source of thermal energy for uphill excitation energy transfer from red chlorophylls to P700.

Spectroscopic Characterization of the Excitation Energy Transfer in the Fucoxanthin–Chlorophyll Protein of Diatoms

2005 ◽  
Vol 86 (1-2) ◽  
pp. 241-250 ◽  
Author(s):  
Emmanouil Papagiannakis ◽  
Ivo H.M. van Stokkum ◽  
Holger Fey ◽  
Claudia Büchel ◽  
Rienk van Grondelle
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Excitation Energy Transfer ◽  
Spectroscopic Characterization ◽  
Chlorophyll Protein

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

scholarly journals Appearance of efficient luminescence energy transfer in doped orthovanadate nanocrystals

2017 ◽  
Vol 50 (3) ◽  
pp. 787-794 ◽  
Author(s):  
Swati Bishnoi ◽  
G. Swati ◽  
Paramjeet Singh ◽  
V. V. Jaiswal ◽  
Mukesh K. Sahu ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Band Gap ◽  
Photoluminescence Intensity ◽  
X Ray Diffraction ◽  
Synthesis Mechanism ◽  
Enhanced Photoluminescence ◽  
Nir Absorption ◽  
Decay Parameters

This paper reports the detailed synthesis mechanism and the structural, morphological and optical characterization of ultraviolet (∼311 nm) excitable samarium doped gadolinium yttrium orthovanadate, (Gd,Y)VO4:Sm3+, nanocrystals. X-ray diffraction and Rietveld refinement studies confirmed that the synthesized samples crystallize in a tetragonal structure withI41/amdspace group. The enhanced photoluminescence intensity of (Gd,Y)VO4:Sm3+compared with the existing YVO4:Sm3+phosphor clearly indicates the significant role of Gd3+ions. This has been attributed to the sensitization of the6PJenergy level of Gd3+ions by energy transfer from orthovanadate (VO43−) ions and subsequent energy trapping by Sm3+ions. The energy transfer from VO43−to Sm3+viaGd3+ions as intermediates and concentration quenching of Gd3+luminescence are discussed in detail. The optical band gap of the as-prepared nanocrystals has been estimated using UV–vis–NIR absorption spectroscopy, which reveals a slightly higher band gap (3.75 eV) for YVO4as compared to GdYVO4(3.50 eV). Furthermore, confocal microcopy, decay parameters and Commission Internationale de l'Eclairage chromatic coordinates have supplemented these studies, which established the suitability of these nanophosphors for achieving spectral conversion in silicon solar cells.

pH-Induced Regulation of Excitation Energy Transfer in the Cyanobacterial Photosystem I Tetramer

2020 ◽  
Vol 124 (10) ◽  
pp. 1949-1954 ◽  
Author(s):  
Ryo Nagao ◽  
Makio Yokono ◽  
Yoshifumi Ueno ◽  
Tian-Yi Jiang ◽  
Jian-Ren Shen ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Photosystem I ◽  
Excitation Energy Transfer

scholarly journals Structure of a cyanobacterial photosystem I surrounded by octadecameric IsiA antenna proteins

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Fusamichi Akita ◽  
Ryo Nagao ◽  
Koji Kato ◽  
Yoshiki Nakajima ◽  
Makio Yokono ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Photosystem I ◽  
Fluorescence Spectra ◽  
Protein A ◽  
Excitation Energy Transfer ◽  
Electron Microscopic ◽  
Time Resolved ◽  
Closed Ring ◽  
Membrane Spanning

AbstractIron-stress induced protein A (IsiA) is a chlorophyll-binding membrane-spanning protein in photosynthetic prokaryote cyanobacteria, and is associated with photosystem I (PSI) trimer cores, but its structural and functional significance in light harvesting remains unclear. Here we report a 2.7-Å resolution cryo-electron microscopic structure of a supercomplex between PSI core trimer and IsiA from a thermophilic cyanobacterium Thermosynechococcus vulcanus. The structure showed that 18 IsiA subunits form a closed ring surrounding a PSI trimer core. Detailed arrangement of pigments within the supercomplex, as well as molecular interactions between PSI and IsiA and among IsiAs, were resolved. Time-resolved fluorescence spectra of the PSI–IsiA supercomplex showed clear excitation-energy transfer from IsiA to PSI, strongly indicating that IsiA functions as an energy donor, but not an energy quencher, in the supercomplex. These structural and spectroscopic findings provide important insights into the excitation-energy-transfer and subunit assembly mechanisms in the PSI–IsiA supercomplex.

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