scholarly journals Chlorophyll–carotenoid excitation energy transfer and charge transfer in Nannochloropsis oceanica for the regulation of photosynthesis

2019 ◽  
Vol 116 (9) ◽  
pp. 3385-3390 ◽  
Author(s):  
Soomin Park ◽  
Collin J. Steen ◽  
Dagmar Lyska ◽  
Alexandra L. Fischer ◽  
Benjamin Endelman ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Charge Transfer ◽  
Excitation Energy ◽  
Transient Absorption ◽  
Excitation Energy Transfer ◽  
Excited State Absorption ◽  
Thermal Dissipation ◽  
Live Cells ◽  
Nannochloropsis Oceanica

Nonphotochemical quenching (NPQ) is a proxy for photoprotective thermal dissipation processes that regulate photosynthetic light harvesting. The identification of NPQ mechanisms and their molecular or physiological triggering factors under in vivo conditions is a matter of controversy. Here, to investigate chlorophyll (Chl)–zeaxanthin (Zea) excitation energy transfer (EET) and charge transfer (CT) as possible NPQ mechanisms, we performed transient absorption (TA) spectroscopy on live cells of the microalga Nannochloropsis oceanica. We obtained evidence for the operation of both EET and CT quenching by observing spectral features associated with the Zea S1 and Zea●+ excited-state absorption (ESA) signals, respectively, after Chl excitation. Knockout mutants for genes encoding either violaxanthin de-epoxidase or LHCX1 proteins exhibited strongly inhibited NPQ capabilities and lacked detectable Zea S1 and Zea●+ ESA signals in vivo, which strongly suggests that the accumulation of Zea and active LHCX1 is essential for both EET and CT quenching in N. oceanica.

Charge transfer-induced assembly of a gold nanocomposite mediated by N-methylfulleropyrrolidine: excitation energy transfer from Rhodamine B

2017 ◽  
Vol 41 (6) ◽  
pp. 2401-2408 ◽  
Author(s):  
Sanjeeb Sutradhar ◽  
Archita Patnaik
Keyword(s):  
Energy Transfer ◽  
Charge Transfer ◽  
Excitation Energy ◽  
Rhodamine B ◽  
Excitation Energy Transfer ◽  
Aurophilic Interactions ◽  
Composite Self ◽  
Energy Acceptor ◽  
Ph Controlled

A pH controlled functionalized fullerene-C60-gold NP composite self-assembles via electrostatic as well as aurophilic interactions and acts as an excitation energy acceptor from fluorescent Rhodamine B (3.79 × 6.5 inch).

scholarly journals De novo synthetic biliprotein design, assembly and excitation energy transfer

2018 ◽  
Vol 15 (141) ◽  
pp. 20180021 ◽  
Author(s):  
Joshua A. Mancini ◽  
Molly Sheehan ◽  
Goutham Kodali ◽  
Brian Y. Chow ◽  
Donald A. Bryant ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
De Novo ◽  
Excitation Energy Transfer ◽  
Fluorescence Yield ◽  
Conformational Restriction ◽  
Wide Range ◽  
Α Helix

Bilins are linear tetrapyrrole chromophores with a wide range of visible and near-visible light absorption and emission properties. These properties are tuned upon binding to natural proteins and exploited in photosynthetic light-harvesting and non-photosynthetic light-sensitive signalling. These pigmented proteins are now being manipulated to develop fluorescent experimental tools. To engineer the optical properties of bound bilins for specific applications more flexibly, we have used first principles of protein folding to design novel, stable and highly adaptable bilin-binding four-α-helix bundle protein frames, called maquettes, and explored the minimal requirements underlying covalent bilin ligation and conformational restriction responsible for the strong and variable absorption, fluorescence and excitation energy transfer of these proteins. Biliverdin, phycocyanobilin and phycoerythrobilin bind covalently to maquette Cys in vitro . A blue-shifted tripyrrole formed from maquette-bound phycocyanobilin displays a quantum yield of 26%. Although unrelated in fold and sequence to natural phycobiliproteins, bilin lyases nevertheless interact with maquettes during co-expression in Escherichia coli to improve the efficiency of bilin binding and influence bilin structure. Bilins bind in vitro and in vivo to Cys residues placed in loops, towards the amino end or in the middle of helices but bind poorly at the carboxyl end of helices. Bilin-binding efficiency and fluorescence yield are improved by Arg and Asp residues adjacent to the ligating Cys on the same helix and by His residues on adjacent helices.

scholarly journals Beads on a Chain (BoC) Fluorescent Oligomeric Materials: Interactions of Conjugated Organic Cross-Linkers with Silsesquioxane Cages

2021 ◽  
Author(s):  
Shahrea Mahbub ◽  
Sukanya Saha ◽  
Ramakrishna Guda ◽  
Joseph Furgal
Keyword(s):  
Energy Transfer ◽  
Excitation Energy ◽  
Transient Absorption ◽  
Electronic Materials ◽  
Field Effect Transistors ◽  
Single Photon ◽  
Photophysical Properties ◽  
Excitation Energy Transfer ◽  
Transient Absorption Spectroscopy ◽  
Gravimetric Analysis

<div> <div> <div> <p>Organic electronic materials have advantages over inorganics in terms of versatility, cost and processability. Recent advancements in organic materials for light emitting diodes (OLED), field effect transistors (OFET), and photovoltaics have engendered extensive innovation potential on this field. In this research, we focus on synthesizing SQ (silsesquioxane) based oligomers cross- linked by di-bromo-aromatic linkers and explore how the cross-linker and oligomer length influence their photophysical properties. Bis-tri-alkoxy silyl (linker) model compounds were synthesized to compare non-cage photophysical properties with the oligomers. Several techniques such as UV/Vis, fluorescence, FTIR, thermal gravimetric analysis (TGA) have been used to characterize the systems. Time-resolved fluorescence and femtosecond transient absorption spectroscopy are used to understand the excited state dynamics of these materials. Studies are carried out to understand the differences between monomers and oligomers and potential energy transfer and charge transfer between the cages and cross-linking chromophores. Transient absorption showed lower energy absorption from the excited states, suggesting short range communication between moieties. Single photon counting studies have shown distinct lifetime differences between most linkers and cages showing possible excitation energy transfer through these materials. Transient absorption anisotropy measurements have shown signatures for excitation energy transfer between linker chromophores for oligomeric compounds. The silsesquioxane (SQ) backbone of the oligomers gives substantial thermal stability as well as solution processability, giving better flexibility for achieving energy transfer between linking chromophores. </p> </div> </div> </div>

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