scholarly journals Probing the heterogeneous structure of eumelanin using ultrafast vibrational fingerprinting

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Christopher Grieco ◽  
Forrest R. Kohl ◽  
Alex T. Hanes ◽  
Bern Kohler
Keyword(s):  
Active Material ◽  
Radical Scavenging ◽  
Visible Spectrum ◽  
Heterogeneous Structure ◽  
Chemical Structures ◽  
Redox Active ◽  
Bond Stretching ◽  
Energy Conversion And Storage ◽  
Uv Visible ◽  
And Storage

Abstract Eumelanin is a brown-black biological pigment with sunscreen and radical scavenging functions important to numerous organisms. Eumelanin is also a promising redox-active material for energy conversion and storage, but the chemical structures present in this heterogeneous pigment remain unknown, limiting understanding of the properties of its light-responsive subunits. Here, we introduce an ultrafast vibrational fingerprinting approach for probing the structure and interactions of chromophores in heterogeneous materials like eumelanin. Specifically, transient vibrational spectra in the double-bond stretching region are recorded for subsets of electronic chromophores photoselected by an ultrafast excitation pulse tuned through the UV-visible spectrum. All subsets show a common vibrational fingerprint, indicating that the diverse electronic absorbers in eumelanin, regardless of transition energy, contain the same distribution of IR-active functional groups. Aggregation of chromophores diverse in oxidation state is the key structural property underlying the universal, ultrafast deactivation behavior of eumelanin in response to photoexcitation with any wavelength.

Photo-assisted Charge/discharge Li-organic Battery with a Charge-separated and Redox-active C60@Porous Organic Cage Cathode

2022 ◽  
Author(s):  
Xiang Zhang ◽  
Kongzhao Su ◽  
Aya Mohamed ◽  
Caiping Liu ◽  
Qing-Fu Sun ◽  
...  
Keyword(s):  
Solar Energy ◽  
Energy Conversion ◽  
High Efficiency ◽  
Solar Energy Conversion ◽  
Redox Active ◽  
Energy Conversion And Storage ◽  
Organic Batteries ◽  
A Charge ◽  
And Storage ◽  
Charge Discharge

Photo-assisted Li-organic batteries provide an attractive approach for solar energy conversion and storage, while the challenge lies in the design of high-efficiency organic cathodes. Herein, a charge-separated and redox-active C60@porous...

Protein–coenzyme interactions in adenosylcobalamin-dependent glutamate mutase

2001 ◽  
Vol 355 (1) ◽  
pp. 131-137 ◽  
Author(s):  
Marja S. HUHTA ◽  
Hao-Ping CHEN ◽  
Craig HEMANN ◽  
C. Russ HILLE ◽  
E. Neil G. MARSH
Keyword(s):  
Gel Filtration ◽  
Visible Spectrum ◽  
Titration Calorimetry ◽  
Coenzyme B12 ◽  
Glutamate Mutase ◽  
Carbon Bond ◽  
Coenzyme Binding ◽  
Radical Intermediates ◽  
Bond Stretching ◽  
Uv Visible

Glutamate mutase catalyses an unusual isomerization involving free-radical intermediates that are generated by homolysis of the cobalt–carbon bond of the coenzyme adenosylcobalamin (coenzyme B12). A variety of techniques have been used to examine the interaction between the protein and adenosylcobalamin, and between the protein and the products of coenzyme homolysis, cob(II)alamin and 5′-deoxyadenosine. These include equilibrium gel filtration, isothermal titration calorimetry, and resonance Raman, UV-visible and EPR spectroscopies. The thermodynamics of adenosylcobalamin binding to the protein have been examined and appear to be entirely entropy-driven, with ∆S = 109 Jċmol-1ċK-1. The cobalt–carbon bond stretching frequency is unchanged upon coenzyme binding to the protein, arguing against a ground-state destabilization of the cobalt–carbon bond of adenosylcobalamin by the protein. However, reconstitution of the enzyme with cob(II)alamin and 5′-deoxyadenosine, the two stable intermediates formed subsequent to homolysis, results in the blue-shifting of two of the bands comprising the UV-visible spectrum of the corrin ring. The most plausible interpretation of this result is that an interaction between the protein, 5′-deoxyadenosine and cob(II)alamin introduces a distortion into the ring corrin that perturbs its electronic properties.

A new energy conversion and storage device of cobalt oxide nanosheets

2018 ◽  
Vol 6 (1) ◽  
pp. 36-40 ◽  
Author(s):  
Saran Kalasina ◽  
Nutthaphon Phattharasupakun ◽  
Montree Sawangphruk
Keyword(s):  
Energy Conversion ◽  
Cobalt Oxide ◽  
Visible Spectrum ◽  
Storage Device ◽  
Light Illumination ◽  
White Led ◽  
Hybrid Energy ◽  
Energy Conversion And Storage ◽  
New Energy ◽  
And Storage

A new design of a single hybrid energy conversion and storage cell of cobalt oxide (Co3O4) nanosheets, which can absorb the whole visible spectrum, exhibits the highest volumetric capacitance of 80.8 F cm−3 under light illumination (white LED), which is 2.2-fold higher than that under dark conditions at 1.5 A cm−3.

Redox-active metal–organic frameworks for energy conversion and storage

2019 ◽  
Vol 7 (28) ◽  
pp. 16571-16597 ◽  
Author(s):  
Joaquín Calbo ◽  
Matthias J. Golomb ◽  
Aron Walsh
Keyword(s):  
Energy Conversion ◽  
Metal Organic Frameworks ◽  
Mixed Valence ◽  
Redox Activity ◽  
Redox Active ◽  
Active Metal ◽  
Energy Conversion And Storage ◽  
Metal Organic ◽  
And Storage ◽  
Redox Active Metal

We review progress in the study of electroactive MOFs with redox activity for energy conversion and storage. Recent advances in mixed-valence MOFs are highlighted, which have led to record conductivities towards metallic porous materials.

Liquid-liquid extraction of succinate using a dicopper cryptate

2020 ◽  
Author(s):  
Riccardo Mobili ◽  
Sonia La Cognata ◽  
Francesca Merlo ◽  
Andrea Speltini ◽  
Massimo Boiocchi ◽  
...  
Keyword(s):  
Aqueous Phase ◽  
Visible Spectrum ◽  
Tca Cycle ◽  
Residual Concentration ◽  
Waste Products ◽  
Liquid Liquid Extraction ◽  
The Tca Cycle ◽  
Quantitative Extraction ◽  
Uv Visible

<div> <p>The extraction of the succinate dianion from a neutral aqueous solution into dichloromethane is obtained using a lipophilic cage-like dicopper(II) complex as the extractant. The quantitative extraction exploits the high affinity of the succinate anion for the cavity of the azacryptate. The anion is effectively transferred from the aqueous phase, buffered at pH 7 with HEPES, into dichloromethane. A 1:1 extractant:anion adduct is obtained. Extraction can be easily monitored by following changes in the UV-visible spectrum of the dicopper complex in dichloromethane, and by measuring the residual concentration of succinate in the aqueous phase by HPLC−UV. Considering i) the relevance of polycarboxylates in biochemistry, as e.g. normal intermediates of the TCA cycle, ii) the relevance of dicarboxylates in the environmental field, as e.g. waste products of industrial processes, and iii) the recently discovered role of succinate and other dicarboxylates in pathophysiological processes including cancer, our results open new perspectives for research in all contexts where selective recognition, trapping and extraction of polycarboxylates is required. </p> </div>

Theoretical Exploration of 2,2’-Bipyridines as Electro-Active Compounds in Flow Batteries

2019 ◽  
Author(s):  
Mariano Sánchez-Castellanos ◽  
Martha M. Flores-Leonar ◽  
Zaahel Mata-Pinzón ◽  
Humberto G. Laguna ◽  
Karl García-Ruiz ◽  
...  
Keyword(s):  
Redox Potential ◽  
Active Material ◽  
Chemical Properties ◽  
Small Subset ◽  
Solubility In Water ◽  
Protonation Reaction ◽  
Redox Active ◽  
Physico Chemical ◽  
Pka Value ◽  
Flow Batteries

Compounds from the 2,2’-bipyridine molecular family were investigated for use as redox-active materials in organic flow batteries. For 156 2,2’-bipyridine derivatives reported in the academic literature, we calculated the redox potential, the pKa for the first protonation reaction, and the solubility in aqueous solutions. Using experimental data on a small subset of derivatives, we were able to calibrate our calculations. We find that functionalization with electron-withdrawing groups leads to an increase of the redox potential and to an increase of the molecular acidity (as expressed in a reduction of the pKa value for the first protonation step). Furthermore, calculations of solubility in water indicate that some of the studied derivatives have adequate solubility for flow battery applications. Based on an analysis of the physico-chemical properties of the 156 studied compounds, we down-select five molecules with carbonyl- and nitro-based functional groups, whose parameters are especially promising for potential application as negative redox-active material inorganic flow batteries.

Theoretical Exploration of 2,2’-Bipyridines as Electro-Active Compounds in Flow Batteries

2019 ◽  
Author(s):  
Mariano Sánchez-Castellanos ◽  
Martha M. Flores-Leonar ◽  
Zaahel Mata-Pinzón ◽  
Humberto G. Laguna ◽  
Karl García-Ruiz ◽  
...  
Keyword(s):  
Redox Potential ◽  
Active Material ◽  
Chemical Properties ◽  
Small Subset ◽  
Solubility In Water ◽  
Protonation Reaction ◽  
Redox Active ◽  
Physico Chemical ◽  
Pka Value ◽  
Flow Batteries

Compounds from the 2,2’-bipyridine molecular family were investigated for use as redox-active materials in organic flow batteries. For 156 2,2’-bipyridine derivatives reported in the academic literature, we calculated the redox potential, the pKa for the first protonation reaction, and the solubility in aqueous solutions. Using experimental data on a small subset of derivatives, we were able to calibrate our calculations. We find that functionalization with electron-withdrawing groups leads to an increase of the redox potential and to an increase of the molecular acidity (as expressed in a reduction of the pKa value for the first protonation step). Furthermore, calculations of solubility in water indicate that some of the studied derivatives have adequate solubility for flow battery applications. Based on an analysis of the physico-chemical properties of the 156 studied compounds, we down-select five molecules with carbonyl- and nitro-based functional groups, whose parameters are especially promising for potential application as negative redox-active material inorganic flow batteries.

Synthesis, Characterization and Thermal Degradation of Some New 3,5-dimethyl Pyrazole Derivatives

2017 ◽  
Vol 68 (2) ◽  
pp. 317-322
Author(s):  
Anca Mihaela Mocanu ◽  
Constantin Luca ◽  
Alina Costina Luca
Keyword(s):  
Thermal Degradation ◽  
Degradation Mechanism ◽  
New Products ◽  
Analysis Data ◽  
Biological Properties ◽  
Elemental Analysis Data ◽  
Ftir Analysis ◽  
Spectral Measurements ◽  
Chemical Structures ◽  
And Storage

The purpose of this research is to synthetize, characterize and thermal degradation of new heterolytic derivates with potential biological properties. The derivates synthesis was done by obtaining new molecules with pyralozone structure which combine two pharmacophore entities: the amidosulfonyl-R1,R2 phenoxyacetil with the 3,5-dimethyl pyrazole which can have potential biological properties. The synthesis stages of the new products are presented as well as the elemental analysis data and IR, 1H-NMR spectral measurements made for elucidating the chemical structures and thermostability study which makes evident the temperature range proper for their use and storage. The obtained results were indicative of a good correlation of the structure with the thermal stability as estimated by means of the initial degradation temperatures as well as with the degradation mechanism by means of the TG-FTIR analysis.

Synthesis, Characterization, Antimicrobial and Antioxidant Potential of Diazenyl Chalcones

2018 ◽  
Vol 18 (10) ◽  
pp. 844-856 ◽  
Author(s):  
Harmeet Kaur ◽  
Balasubramanian Narasimhan
Keyword(s):  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Antioxidant Potential ◽  
Dilution Method ◽  
Dpph Assay ◽  
Antimicrobial Potential ◽  
Structural Conformation ◽  
Uv Visible ◽  
Tube Dilution Method

A series of diazenyl chalcones was prepared by base catalyzed Claisen-Schmidt condensation of synthesized hydroxy substituted acetophenone azo dye with various substituted aromatic/ heteroaromatic aldehydes. The structural conformation of synthesized chalcones was done by a number of physicochemical and spectral means like FTIR, UV-visible, mass, NMR spectroscopy and CHNS/O analysis. These diazenyl chalcones were assessed for their in vitro antimicrobial potential against several Gram-negative, Gram-positive bacterial and fungal strains by serial tube dilution method. The fluconazole and cefadroxil were used as standard drugs. The target compounds were also evaluated for their antioxidant potential by DPPH assay. (2E)-3-(2,4-Dichlorophenyl)-1-(4-((2,6- dihydroxyphenyl)diazenyl)phenyl)prop-2-en-1-one (C-7) had shown very good antimicrobial potential with MIC ranges from 3.79 to 15.76 μg/ml against most of the tested microorganisms. Most of the synthesized diazenyl chalcones were found to be active against B. subtilis. The (2E)-1-(5-((2-Chloro- 4-nitrophenyl)diazenyl)-2-hydroxyphenyl)-3-(2-hydroxynaphthalen-1-yl)prop-2-en-1-one (C-10) had shown high free radical-scavenging activity when compared with the ascorbic acid as the reference antioxidant.

scholarly journals Energy Conversion and Storage in Solid-state Photogalvanic Cells

1981 ◽  
Vol 54 (6) ◽  
pp. 1640-1644 ◽  
Author(s):  
Hiroshi Hada ◽  
Kazuchiyo Takaoka ◽  
Masahiko Saikawa ◽  
Yoshiro Yonezawa
Keyword(s):  
Solid State ◽  
Energy Conversion ◽  
Energy Conversion And Storage ◽  
And Storage
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