scholarly journals Encapsulation of Tricopper Cluster in a Protein-like Cavitand Enables Facile Redox Processes from CuICuICuI to CuIICuIICuII States

Author(s):  
Shiyu Zhang ◽  
Weiyao Zhang ◽  
Curtis Moore

One-pot reaction of tris(2-aminoethyl)amine (TREN), [CuI (MeCN)4]PF6, and paraformaldehyde affords a mixedvalent [TREN4CuIICuICuI (3-OH)](PF6)3 complex. The macrocyclic azacryptand TREN4 contains four TREN motifs, three of which provide a bowl-shape binding pocket for the [Cu3(3-OH)]3+ core. The fourth TREN caps on top of the tricopper cluster to form a cavitand, imposing conformational constraints and preventing solvent interaction. Contrasting the limited redox capability of synthetic tricopper complexes reported so far, [TREN4CuIICuICuI (3-OH)](PF6)3 exhibits several reversible single-electron redox events. The distinct electrochemical behaviors of [TREN4CuIICuICuI (3-OH)](PF6)3 and its solvent-exposed analog [TREN3CuIICuIICuII (3-O)](PF6)4 suggest that isolation of tricopper core in a protein-like cavitand enables facile electron transfer, allowing potential application of synthetic tricopper complexes as redox catalysts. Indeed, the fully reduced [TREN4CuICuICuI (3- OH)](PF6)2 can reduce O2 under acidic conditions. The geometric constraints provided by the cavitand are reminiscent of Nature’s multicopper oxidases (MCOs). For the first time, a synthetic tricopper cluster was isolated and fully characterized at CuICuICuI (4a), CuIICuICuI (4b), and CuIICuIICuI (4c) state, providing structural and spectroscopic models for many intermediates in MCOs. Fast electron transfer rates (105 - 106 M −1 s −1 ) were observed for both CuICuICuI /CuIICuICuI and CuIICuICuI /CuIICuIICuI redox couples, approaching the rapid electron transfer rates of copper sites in MCO.

2020 ◽  
Author(s):  
Shiyu Zhang ◽  
Weiyao Zhang ◽  
Curtis Moore

One-pot reaction of tris(2-aminoethyl)amine (TREN), [CuI (MeCN)4]PF6, and paraformaldehyde affords a mixedvalent [TREN4CuIICuICuI (3-OH)](PF6)3 complex. The macrocyclic azacryptand TREN4 contains four TREN motifs, three of which provide a bowl-shape binding pocket for the [Cu3(3-OH)]3+ core. The fourth TREN caps on top of the tricopper cluster to form a cavitand, imposing conformational constraints and preventing solvent interaction. Contrasting the limited redox capability of synthetic tricopper complexes reported so far, [TREN4CuIICuICuI (3-OH)](PF6)3 exhibits several reversible single-electron redox events. The distinct electrochemical behaviors of [TREN4CuIICuICuI (3-OH)](PF6)3 and its solvent-exposed analog [TREN3CuIICuIICuII (3-O)](PF6)4 suggest that isolation of tricopper core in a protein-like cavitand enables facile electron transfer, allowing potential application of synthetic tricopper complexes as redox catalysts. Indeed, the fully reduced [TREN4CuICuICuI (3- OH)](PF6)2 can reduce O2 under acidic conditions. The geometric constraints provided by the cavitand are reminiscent of Nature’s multicopper oxidases (MCOs). For the first time, a synthetic tricopper cluster was isolated and fully characterized at CuICuICuI (4a), CuIICuICuI (4b), and CuIICuIICuI (4c) state, providing structural and spectroscopic models for many intermediates in MCOs. Fast electron transfer rates (105 - 106 M −1 s −1 ) were observed for both CuICuICuI /CuIICuICuI and CuIICuICuI /CuIICuIICuI redox couples, approaching the rapid electron transfer rates of copper sites in MCO.


Synthesis ◽  
2021 ◽  
Author(s):  
Pengkai Wang ◽  
yan xu cao ◽  
Songlin Zhang

The utilities of ytterbium(II) reagent, both as nucleophilic reagent and single electron transfer reagent in the reaction of isatin derivatives with ytterbium(II) reagent are reported for the first time in this paper. From a synthetic point of view, a general, efficient, and experimentally simple one-pot method for preparation of 3-substituted-2-oxindoles was developed.


2011 ◽  
Vol 286 (22) ◽  
pp. 19693-19701 ◽  
Author(s):  
Elia Zomot ◽  
Ivet Bahar

Virulent enteric pathogens have developed several systems that maintain intracellular pH to survive extreme acidic conditions. One such mechanism is the exchange of arginine (Arg+) from the extracellular region with its intracellular decarboxylated form, agmatine (Agm2+). The net result of this process is the export of a virtual proton from the cytoplasm per antiport cycle. Crystal structures of the arginine/agmatine antiporter from Escherichia coli, AdiC, have been recently resolved in both the apo and Arg+-bound outward-facing conformations, which permit us to assess for the first time the time-resolved mechanisms of interactions that enable the specific antiporter functionality of AdiC. Using data from ∼1 μs of molecular dynamics simulations, we show that the protonation of Glu-208 selectively causes the dissociation and release of Agm2+, but not Arg+, to the cell exterior. The impact of Glu-208 protonation is transmitted to the substrate binding pocket via the reorientation of Ile-205 carbonyl group at the irregular portion of transmembrane (TM) helix 6. This effect, which takes place only in the subunits where Agm2+ is released, invites attention to the functional role of the unwound portion of TM helices (TM6 Trp-202–Glu-208 in AdiC) in facilitating substrate translocation, reminiscent of the behavior observed in structurally similar Na+-coupled transporters.


2017 ◽  
Vol 1 (4) ◽  
pp. 725-736 ◽  
Author(s):  
Abhijeet P. Borole ◽  
Alex J. Lewis

Proton transfer in microbial electrochemical cells is as important as electron transfer. This study quantifies proton transfer rates in MEC for the first time. Control of flow rate and loading rate allows improvement in proton transfer rates enabling hydrogen productivities >10 L per L per day.


2020 ◽  
Vol 23 (23) ◽  
pp. 2626-2634
Author(s):  
Saiedeh Kamalifar ◽  
Hamzeh Kiyani

: An efficient and facial one-pot synthesis of 4-aryl-3,4-dihydrobenzo[g]quinoline- 2,5,10(1H)-triones was developed for the first time. The process proceeded via the three-component cyclocondensation of 2-amino-1,4-naphthoquinone with Meldrum’s acid and substituted benzaldehydes under green conditions. The fused 3,4-dihydropyridin-2(1H)- one-ring naphthoquinones have been synthesized with good to high yields in refluxing ethanol as a green reaction medium. This protocol is simple and effective as well as does not involve the assistance of the catalyst, additive, or hazardous solvents.


Author(s):  
Sundarababu Baskaran ◽  
Kirana D V ◽  
Kanak Kanti Das

A one-pot catalytic method has been developed for the stereoselective synthesis of cyclopropane-fused cyclic amidines using CuBr2/K2S2O8 as an efficient single electron transfer (SET) oxidative system. The generality of this...


2021 ◽  
Vol 45 (12) ◽  
pp. 5576-5588
Author(s):  
C. Sabarinathan ◽  
M. Karthikeyan ◽  
R. M. Murugappan ◽  
Savarimuthu Philip Anthony ◽  
Bhaskaran Shankar ◽  
...  

One-pot synthesis of POM-salt ([Himi]4[SiMo12O40] (1)) was achieved by mixing silicomolybdic acid and imidazole in acidic conditions and characterized by FTIR, TGA, SEM, EDX, ICP-OES and XPS.


Molecules ◽  
2021 ◽  
Vol 26 (14) ◽  
pp. 4265
Author(s):  
Victor Carramiñana ◽  
Ana M. Ochoa de Ochoa de Retana ◽  
Francisco Palacios ◽  
Jesús M. de los de los Santos

Several phosphorus-substituted N-acylated cyanoaziridines 2 and N-carbamoylated cyanoziridines 5 were prepared in good to high yields. N-Acylated cyanoaziridines 2 were used, after ring expansion, in an efficient synthesis of oxazoline derivative 3a and in a completely regio-controlled reaction in the presence of NaI. Conversely, N-carbamoyl cyanoaziridines 5 reacted with NaI to obtain a regioisomeric mixture of 2-aminocyanooxazolines 7. Mild acidic conditions can be used for the isomerization of N-thiocarbamoyl cyanoaziridine 6a into a 2-aminocyanothiazoline derivative 8a by using BF3·OEt2 as a Lewis acid. Likewise, a one pot reaction of NH-cyanoaziridines 1 with isocyanates obtained 2-iminocyanooxazolidines 9 regioselectively. This synthetic methodology involves the addition of isocyanates to starting cyanoaziridines to obtain N-carbamoyl cyanoaziridines 5, which after the ring opening, reacts with a second equivalent of isocyanate to give the final 2-imino cyanooxazolidines 9. In addition, the cytotoxic effect on the cell lines derived from human lung adenocarcinoma (A549) was also screened. 2-Iminooxazolidines 9 exhibited moderate activity against the A549 cell line in vitro. Furthermore, a selectivity towards cancer cells (A549) over non-malignant cells (MCR-5) was detected.


2019 ◽  
Vol 43 (5) ◽  
pp. 2269-2273 ◽  
Author(s):  
Guojie Meng ◽  
Shengguang Gao ◽  
Ying Liu ◽  
Li Zhang ◽  
Chunmei Song ◽  
...  
Keyword(s):  
One Pot ◽  

The synthesis of amino- and sulfo-bifunctionalized hyper-crosslinked organic nanotube frameworks for one-pot cascade reactions was reported for the first time.


Antioxidants ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1106
Author(s):  
Marko R. Antonijević ◽  
Dušica M. Simijonović ◽  
Edina H. Avdović ◽  
Andrija Ćirić ◽  
Zorica D. Petrović ◽  
...  

Compounds from the plant world that possess antioxidant abilities are of special importance for the food and pharmaceutical industry. Coumarins are a large, widely distributed group of natural compounds, usually found in plants, often with good antioxidant capacity. The coumarin-hydroxybenzohydrazide derivatives were synthesized using a green, one-pot protocol. This procedure includes the use of an environmentally benign mixture (vinegar and ethanol) as a catalyst and solvent, as well as very easy isolation of the desired products. The obtained compounds were structurally characterized by IR and NMR spectroscopy. The purity of all compounds was determined by HPLC and by elemental microanalysis. In addition, these compounds were evaluated for their in vitro antioxidant activity. Mechanisms of antioxidative activity were theoretically investigated by the density functional theory approach and the calculated values of various thermodynamic parameters, such as bond dissociation enthalpy, proton affinity, frontier molecular orbitals, and ionization potential. In silico calculations indicated that hydrogen atom transfer and sequential proton loss–electron transfer reaction mechanisms are probable, in non-polar and polar solvents respectively. Additionally, it was found that the single-electron transfer followed by proton transfer was not an operative mechanism in either solvent. The conducted tests indicate the excellent antioxidant activity, as well as the low potential toxicity, of the investigated compounds, which makes them good candidates for potential use in food chemistry.


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