Ion-Mediated Electron Transfer in a Supramolecular Donor-Acceptor Ensemble

Science ◽  
2010 ◽  
Vol 329 (5997) ◽  
pp. 1324-1327 ◽  
Author(s):  
Jung Su Park ◽  
Elizabeth Karnas ◽  
Kei Ohkubo ◽  
Ping Chen ◽  
Karl M. Kadish ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Ion Binding ◽  
Acceptor Pair ◽  
Initial Oxidation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Back Electron Transfer ◽  
Donor And Acceptor ◽  
Mediated Electron Transfer ◽  
Donor Acceptor

Ion binding often mediates electron transfer in biological systems as a cofactor strategy, either as a promoter or as an inhibitor. However, it has rarely, if ever, been exploited for that purpose in synthetic host-guest assemblies. We report here that strong binding of specific anions (chloride, bromide, and methylsulfate but not tetrafluoroborate or hexafluorophosphate) to a tetrathiafulvalene calix[4]pyrrole (TTF-C4P) donor enforces a host conformation that favors electron transfer to a bisimidazolium quinone (BIQ2+) guest acceptor. In contrast, the addition of a tetraethylammonium cation, which binds more effectively than the BIQ2+ guest in the TTF-C4P cavity, leads to back electron transfer, restoring the initial oxidation states of the donor and acceptor pair. The products of these processes were characterized via spectroscopy and x-ray crystallography.

scholarly journals Structural and functional properties of a magnesium transporter of the SLC11/NRAMP family

eLife ◽  
2022 ◽  
Vol 11 ◽  
Author(s):  
Karthik Ramanadane ◽  
Monique S Straub ◽  
Raimund Dutzler ◽  
Cristina Manatschal
Keyword(s):  
Hydration Shell ◽  
Transition Metal Ions ◽  
Ion Binding ◽  
X Ray ◽  
X Ray Crystallography ◽  
Protein Architecture ◽  
Large Pool ◽  
Structural And Functional Properties ◽  
The Family ◽  
Magnesium Transporter

Members of the ubiquitous SLC11/NRAMP family catalyze the uptake of divalent transition metal ions into cells. They have evolved to efficiently select these trace elements from a large pool of Ca2+ and Mg2+, which are both orders of magnitude more abundant, and to concentrate them in the cytoplasm aided by the cotransport of H+ serving as energy source. In the present study, we have characterized a member of a distant clade of the family found in prokaryotes, termed NRMTs, that were proposed to function as transporters of Mg2+. The protein transports Mg2+ and Mn2+ but not Ca2+ by a mechanism that is not coupled to H+. Structures determined by cryo-EM and X-ray crystallography revealed a generally similar protein architecture compared to classical NRAMPs, with a restructured ion binding site whose increased volume provides suitable interactions with ions that likely have retained much of their hydration shell.

Fluorescent P-Type 4H-SiC Grown by PVT Method

2016 ◽  
Vol 858 ◽  
pp. 326-330
Author(s):  
Shi Yi Zhuo ◽  
Xi Liu ◽  
Pao Gao ◽  
Wei Huang ◽  
Cheng Feng Yan ◽  
...  
Keyword(s):  
Visible Light ◽  
Room Temperature ◽  
Light Emission ◽  
Green Fluorescence ◽  
Acceptor Pair ◽  
Aluminum Doping ◽  
Visible Light Range ◽  
Donor And Acceptor ◽  
Donor Acceptor ◽  
P Type

Fluorescent SiC, which contains donor and acceptor impurities with optimum concentrations, can work as a phosphor for visible light emission by donor-acceptor-pair (DAP) recombination. In this work, 3 inch N-B-Al co-doped fluorescent 4H-SiC crystals are prepared by PVT method. The p-type fluorescent 4H-SiC with low aluminum doping concentration can show intensive yellow-green fluorescence at room temperature. N-B DAP peak wavelength shifts from 578nm to 525nm and weak N-Al DAP emission occurred 403/420 nm quenches, when the temperature increases from 4K to 298K. The aluminum doping induces higher defect concentration in the fluorescent crystal and decreases optical transmissivity of the crystal in the visible light range. It triggers more non-radiative recombination and light absorption losses in the crystal.

Electron Donor-Acceptor Compounds. Synthesis and Structure of 5-(1,4-Benzoquinone-2-yl)-10,15,20-trialkylporphyrins

1998 ◽  
Vol 53 (9) ◽  
pp. 1021-1030 ◽  
Author(s):  
Steffen Runge ◽  
Mathias O. Senge
Keyword(s):  
Crystal Structure ◽  
Structure Analysis ◽  
Supramolecular Structure ◽  
Crystal Structure Analysis ◽  
Free Base ◽  
X Ray ◽  
X Ray Crystallography ◽  
New Methods ◽  
Polymeric Chains ◽  
Donor Acceptor

Abstract A series of 5-(benzoquinone)-10,15,20-trialkylporphyrins was synthesized via cross condensation of the respective aldehydes, 2,5-dimethoxybenzaldehyde and pyrrole followed by demethylation with BBr3 and oxidation with PbO2. This method worked reasonably well for compounds bearing the benzoquinone substituent and butyl, isopropyl, 1 -methylpropyl and 2-ethylpropyl residues (2a-d). The free base porphyrin quinones were converted into the zinc(II) complexes (3a-d) all of which showed remarkable stability for porphyrin quinones. The zinc(II) complex 3c bearing isopropyl residues was investigated by X-ray crystallography and showed a supramolecular structure consisting of polymeric chains facilitated by coordina­tion of a benzoquinone oxygen to a neighboring zinc(II) center. Attempts to synthesize a 5-(benzoquinone)-10,15,20-tris(terr-butylporphyrin) resulted in the formation of a yellow porphomethene (4), which could not be oxidized further. A crystal structure analysis of 4, the first for a free base porphomethene, shows an extremely twisted conformation with syn-orientation of the three tert-butyl groups. The results indicate that new methods will have to be developed for the synthesis of nonplanar porphyrin quinones.

97 Study on electron transfer through RNA/DNA duplex using pyrene and 5-bromouracil as an electron donor and acceptor pair

2013 ◽  
Vol 31 (sup1) ◽  
pp. 61-62
Author(s):  
Tadao Takada ◽  
Kenji Maie ◽  
Yumiko Otsuka ◽  
Tomohiro Saeki ◽  
Yuta Takamatsu ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electron Donor ◽  
Dna Duplex ◽  
Acceptor Pair ◽  
Donor And Acceptor ◽  
Electron Donor And Acceptor

scholarly journals Electron transfer across a thermal gradient

2016 ◽  
Vol 113 (34) ◽  
pp. 9421-9429 ◽  
Author(s):  
Galen T. Craven ◽  
Abraham Nitzan
Keyword(s):  
Electron Transfer ◽  
Heat Transport ◽  
Single Point ◽  
State Theory ◽  
Free Energy Surface ◽  
Donor And Acceptor ◽  
Transfer Channel ◽  
Different Temperatures ◽  
Donor Acceptor ◽  
Open Electron

Charge transfer is a fundamental process that underlies a multitude of phenomena in chemistry and biology. Recent advances in observing and manipulating charge and heat transport at the nanoscale, and recently developed techniques for monitoring temperature at high temporal and spatial resolution, imply the need for considering electron transfer across thermal gradients. Here, a theory is developed for the rate of electron transfer and the associated heat transport between donor–acceptor pairs located at sites of different temperatures. To this end, through application of a generalized multidimensional transition state theory, the traditional Arrhenius picture of activation energy as a single point on a free energy surface is replaced with a bithermal property that is derived from statistical weighting over all configurations where the reactant and product states are equienergetic. The flow of energy associated with the electron transfer process is also examined, leading to relations between the rate of heat exchange among the donor and acceptor sites as functions of the temperature difference and the electronic driving bias. In particular, we find that an open electron transfer channel contributes to enhanced heat transport between sites even when they are in electronic equilibrium. The presented results provide a unified theory for charge transport and the associated heat conduction between sites at different temperatures.

The Preparation and Crystal Structures of a Series of Urea Adducts: with Fumaric Acid (2 : 1), with Itaconic Acid (1 : 1) and with Cyanuric Acid (1 : 1)

1997 ◽  
Vol 50 (10) ◽  
pp. 1021 ◽  
Author(s):  
Graham Smith ◽  
Colin H. L. Kennard ◽  
Karl A. Byriel
Keyword(s):  
Hydrogen Bonding ◽  
Crystal Structures ◽  
Itaconic Acid ◽  
Fumaric Acid ◽  
Cyanuric Acid ◽  
X Ray ◽  
X Ray Crystallography ◽  
Donor And Acceptor ◽  
Bonding Systems ◽  
Urea Adducts

The adducts of a series of compounds with urea (ur) have been prepared and their crystal structures determined by X-ray crystallography. These are the adducts with the unsaturated aliphatic acids fumaric acid [(fumaric acid)(ur)2] (1) and itaconic acid [(itaconic acid)(ur)] (2), and with cyanuric acid [(cyanuric acid)(ur)] (3). All structures have extensive hydrogen-bonding systems in which most of the urea donor and acceptor sites are involved.

Ligandensubstitution an cis-Mo(CO)2(PPh3)2(MeCN)(η2-SO2), Kristall- und Molekülstruktur von cis-Mo(CO)2(PMe3)3(η2-SO2) / Ligand Substitution at cis-Mo(CO)2(PPh3)2(MeCN)(η2-SO2), Crystal and Molecular Structure of cis-Mo(CO)2(PMe3)3(η2-SO2)

1986 ◽  
Vol 41 (10) ◽  
pp. 1211-1218 ◽  
Author(s):  
Franz-Erich Baumann ◽  
Christian Burschka ◽  
Wolfdieter A . Schenk
Keyword(s):  
Molecular Structure ◽  
Crystal And Molecular Structure ◽  
Ligand Substitution ◽  
X Ray ◽  
X Ray Crystallography ◽  
Donor And Acceptor ◽  
The Relationship ◽  
Bonding Mode

Abstract Mo(CO)2(PPh3)2(MeCN)(η2-SO2), reacts with a number of unidentate or tridentate phosphines with displacement of both MeCN and PPh3. Mixtures of up to three different isomers are obtained the structures of which are assigned by IR , 1H, 13C, and 31PNMR , and in one case by X-ray crystallography. The results support earlier observations concerning the relationship between the disposition of donor and acceptor ligands around the metal and the bonding mode of SO2 .

scholarly journals Cyan-emitting and orange-emitting fluorescent proteins as a donor/acceptor pair for fluorescence resonance energy transfer

2004 ◽  
Vol 381 (1) ◽  
pp. 307-312 ◽  
Author(s):  
Satoshi KARASAWA ◽  
Toshio ARAKI ◽  
Takeharu NAGAI ◽  
Hideaki MIZUNO ◽  
Atsushi MIYAWAKI
Keyword(s):  
Energy Transfer ◽  
Fluorescence Resonance Energy Transfer ◽  
Fluorescent Proteins ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Acceptor Pair ◽  
Donor And Acceptor ◽  
Donor Acceptor ◽  
Donor Acceptor Pair ◽  
Fluorescence Resonance

GFP (green fluorescent protein)-based FRET (fluorescence resonance energy transfer) technology has facilitated the exploration of the spatio-temporal patterns of cellular signalling. While most studies have used cyan- and yellow-emitting FPs (fluorescent proteins) as FRET donors and acceptors respectively, this pair of proteins suffers from problems of pH-sensitivity and bleeding between channels. In the present paper, we demonstrate the use of an alternative additional donor/acceptor pair. We have cloned two genes encoding FPs from stony corals. We isolated a cyan-emitting FP from Acropara sp., whose tentacles exhibit cyan coloration. Similar to GFP from Renilla reniformis, the cyan FP forms a tight dimeric complex. We also discovered an orange-emitting FP from Fungia concinna. As the orange FP exists in a complex oligomeric structure, we converted this protein into a monomeric form through the introduction of three amino acid substitutions, recently reported to be effective for converting DsRed into a monomer (Clontech). We used the cyan FP and monomeric orange FP as a donor/acceptor pair to monitor the activity of caspase 3 during apoptosis. Due to the close spectral overlap of the donor emission and acceptor absorption (a large Förster distance), substantial pH-resistance of the donor fluorescence quantum yield and the acceptor absorbance, as well as good separation of the donor and acceptor signals, the new pair can be used for more effective quantitative FRET imaging.

scholarly journals Overcoming Back Electron Transfer Facilitates the Implementation of Electron Donor-Acceptor Complexes in Catalysis

2020 ◽  
Author(s):  
Edward McClain ◽  
Timothy Monos ◽  
Mayuko Mori ◽  
Joel Beatty ◽  
Corey Stephenson
Keyword(s):  
Electron Transfer ◽  
Electron Donor ◽  
Mild Conditions ◽  
Back Electron Transfer ◽  
Synthetic Utility ◽  
Visible Light Driven ◽  
Donor Acceptor ◽  
Alkylation Reactions ◽  
Donor Species ◽  
Ethyl Isonicotinate

Electron donor-acceptor (EDA) complexes can controllably generate radicals under mild conditions through selective photoexcitation events. However, unproductive reactivity from fast deactivation of the photoexcited complexes through back electron transfer has slowed the development of EDA complexes in synthetic methodology. Here, we disclose the study of EDA complexes derived from 2-methoxynaphthalene donor and acylated ethyl isonicotinate <i>N</i>-oxide acceptor that undergo a fast N–O bond fragmentation event upon photoexcitation. This reaction design not only overcomes the limitations of back electron transfer but also enables the regeneration of the donor species, representing a rare example EDA photochemistry in a catalytic regime. The synthetic utility is demonstrated through visible light-driven radical trifluoromethylation and Minisci alkylation reactions. The scalability of the EDA complex promoted reaction evidenced by the successful multigram-scale trifluoromethylation of methyl N-Boc pyrrole-2-carboxylate in a continuous flow manifold.

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