Beyond the Active Site: The Impact of the Outer Coordination Sphere on Electrocatalysts for Hydrogen Production and Oxidation

2014 ◽  
Vol 47 (8) ◽  
pp. 2621-2630 ◽  
Author(s):  
Bojana Ginovska-Pangovska ◽  
Arnab Dutta ◽  
Matthew L. Reback ◽  
John C. Linehan ◽  
Wendy J. Shaw
Keyword(s):  
Hydrogen Production ◽  
Coordination Sphere ◽  
Active Site ◽  
Outer Coordination Sphere ◽  
The Impact

Incorporating Peptides in the Outer-Coordination Sphere of Bioinspired Electrocatalysts for Hydrogen Production

2011 ◽  
Vol 50 (9) ◽  
pp. 4073-4085 ◽  
Author(s):  
Avijita Jain ◽  
Sheri Lense ◽  
John C. Linehan ◽  
Simone Raugei ◽  
Herman Cho ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Coordination Sphere ◽  
Outer Coordination Sphere

Enrichment of hydrogen production from fruit waste biomass using ozonation assisted with citric acid

2021 ◽  
pp. 0734242X2110103
Author(s):  
Anbazhagan Sethupathy ◽  
Pushkar Kumar Pathak ◽  
Palani Sivashanmugam ◽  
Chelliah Arun ◽  
Jayakumar Rajesh banu ◽  
...  
Keyword(s):  
Citric Acid ◽  
Hydrogen Production ◽  
Suspended Solid ◽  
Net Energy ◽  
Waste Biomass ◽  
Acid Pretreatment ◽  
Disintegration Time ◽  
Fruit Waste ◽  
The Impact ◽  
Acid Dosage

In this study, the impact of ozonation abetted with the citric acid pretreatment (OZCAP) method on fruit waste was investigated for ameliorating hydrogen production. Initially, the ozonation pretreatment (OZP) method was performed by varying ozone (O3) dosage and disintegration time. At optimized conditions (O3 dosage (0.04 g/g suspended solid; SS) and disintegration time (40 minutes)), 17.6% of liquefied organics emancipate rate (LER) and 13.5% of SS reduction were perceived. Further augmenting LER of fruit waste, OZCAP method was proceeded by varying citric acid dosage and disintegration time at an optimized OZP dosage (0.04 g/g SS). A higher LER (24.4%) and SS reduction (19%) were described at an optimal citric acid dosage (0.03 g/g SS) and disintegration time (20 minutes). Then, the hydrogen production potential of OZCAP, OZP and raw fruit waste were evaluated in which OZCAP method exhibited a higher cumulative hydrogen production (30 mL/g volatile solids). Energy valuation reveals that OZCAP method exhibited a net energy of 3.7 kWh/kg of fruit waste.

Phenol Reduces Nitrite to NO at Copper(II): Role of a Proton-Responsive Outer Coordination Sphere in Phenol Oxidation

2020 ◽  
Vol 142 (4) ◽  
pp. 1726-1730 ◽  
Author(s):  
Aditesh Mondal ◽  
Kiran P. Reddy ◽  
Jeffery A. Bertke ◽  
Subrata Kundu
Keyword(s):  
Coordination Sphere ◽  
Phenol Oxidation ◽  
Outer Coordination Sphere

scholarly journals Enhanced hydrogen production of Rhodobacter sphaeroides promoted by extracellular H+ of Halobacterium salinarum

2021 ◽  
Vol 71 (1) ◽  
Author(s):  
Jiang-Yu Ye ◽  
Yue Pan ◽  
Yong Wang ◽  
Yi-Chao Wang
Keyword(s):  
Hydrogen Production ◽  
Production Rate ◽  
Rhodobacter Sphaeroides ◽  
Coupled System ◽  
Purple Membrane ◽  
Halobacterium Salinarum ◽  
Control Group ◽  
Hydrogen Production Rate ◽  
Production Of Hydrogen ◽  
The Impact

Abstract Purpose This study utilized the principle that the bacteriorhodopsin (BR) produced by Halobacterium salinarum could increase the hydrogen production of Rhodobacter sphaeroides. H. salinarum are co-cultured with R. sphaeroides to determine the impact of purple membrane fragments (PM) on R. sphaeroides and improve its hydrogen production capacity. Methods In this study, low-salinity in 14 % NaCl domesticates H salinarum. Then, 0–160 nmol of different concentration gradient groups of bacteriorhodopsin (BR) and R. sphaeroides was co-cultivated, and the hydrogen production and pH are measured; then, R. sphaeroides and immobilized BR of different concentrations are used to produce hydrogen to detect the amount of hydrogen. Two-chamber microbial hydrogen production system with proton exchange membrane-assisted proton flow was established, and the system was operated. As additional electricity added under 0.3 V, the hydrogen production rate increased with voltages in the coupled system. Results H salinarum can still grow well after low salt in 14% NaCl domestication. When the BR concentration is 80 nmol, the highest hydrogen production reached 217 mL per hour. Both immobilized PC (packed cells) and immobilized PM (purple membrane) of H. salinarum could promote hydrogen production of R. sphaeroides to some extent. The highest production of hydrogen was obtained by the coupled system with 40 nmol BR of immobilized PC, which increased from 127 to 232 mL, and the maximum H2 production rate was 18.2 mL−1 h−1 L culture. In the 192 h experiment time, when the potential is 0.3 V, the hydrogen production amount can reach 920 mL, which is 50.3% higher than the control group. Conclusions The stability of the system greatly improved after PC was immobilized, and the time for hydrogen production of R. sphaeroides significantly extended on same condition. As additional electricity added under 0.3 V, the hydrogen production rate increased with voltages in the coupled system. These results are helpful to build a hydrogen production-coupled system by nitrogenase of R. sphaeroides and proton pump of H. salinarum. Graphical abstract

Uncertainty studies on hydrogen source term with MAAP5 code

Kerntechnik ◽  
2021 ◽  
Vol 86 (2) ◽  
pp. 152-163
Author(s):  
T.-C. Wang ◽  
M. Lee
Keyword(s):  
Hydrogen Production ◽  
Nuclear Power ◽  
Hydrogen Generation ◽  
Pearson Correlation ◽  
Latin Hypercube Sampling ◽  
Severe Accident ◽  
Model Parameters ◽  
Power Company ◽  
Sensitivity Studies ◽  
The Impact

Abstract In the present study, a methodology is developed to quantify the uncertainties of special model parameters of the integral severe accident analysis code MAAP5. Here, the in-vessel hydrogen production during a core melt accident for Lungmen Nuclear Power Station of Taiwan Power Company, an advanced boiling water reactor, is analyzed. Sensitivity studies are performed to identify those parameters with an impact on the output parameter. For this, multiple calculations of MAAP5 are performed with input combinations generated from Latin Hypercube Sampling (LHS). The results are analyzed to determine the 95th percentile with 95% confidence level value of the amount of in-vessel hydrogen production. The calculations show that the default model options for IOXIDE and FGBYPA are recommended. The Pearson Correlation Coefficient (PCC) was used to determine the impact of model parameters on the target output parameters and showed that the three parameters TCLMAX, FCO, FOXBJ are highly influencing the in-vessel hydrogen generation. Suggestions of values of these three parameters are given.

Macromolecular Engineering of the Outer Coordination Sphere of [2Fe-2S] Metallopolymers to Enhance Catalytic Activity for H2 Production

2018 ◽  
Vol 7 (11) ◽  
pp. 1383-1387 ◽  
Author(s):  
William P. Brezinski ◽  
Metin Karayilan ◽  
Kayla E. Clary ◽  
Keelee C. McCleary-Petersen ◽  
Liye Fu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Coordination Sphere ◽  
H2 Production ◽  
Outer Coordination Sphere

scholarly journals Exploiting correlated molecular-dynamics networks to counteract enzyme activity–stability trade-off

2018 ◽  
Vol 115 (52) ◽  
pp. E12192-E12200 ◽  
Author(s):  
Haoran Yu ◽  
Paul A. Dalby
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Active Site ◽  
Dynamic Networks ◽  
Aromatic Aldehydes ◽  
Active Site Residues ◽  
Trade Off ◽  
Highly Correlated ◽  
Dynamics Simulations ◽  
The Impact

The directed evolution of enzymes for improved activity or substrate specificity commonly leads to a trade-off in stability. We have identified an activity–stability trade-off and a loss in unfolding cooperativity for a variant (3M) of Escherichia coli transketolase (TK) engineered to accept aromatic substrates. Molecular dynamics simulations of 3M revealed increased flexibility in several interconnected active-site regions that also form part of the dimer interface. Mutating the newly flexible active-site residues to regain stability risked losing the new activity. We hypothesized that stabilizing mutations could be targeted to residues outside of the active site, whose dynamics were correlated with the newly flexible active-site residues. We previously stabilized WT TK by targeting mutations to highly flexible regions. These regions were much less flexible in 3M and would not have been selected a priori as targets using the same strategy based on flexibility alone. However, their dynamics were highly correlated with the newly flexible active-site regions of 3M. Introducing the previous mutations into 3M reestablished the WT level of stability and unfolding cooperativity, giving a 10.8-fold improved half-life at 55 °C, and increased midpoint and aggregation onset temperatures by 3 °C and 4.3 °C, respectively. Even the activity toward aromatic aldehydes increased up to threefold. Molecular dynamics simulations confirmed that the mutations rigidified the active-site via the correlated network. This work provides insights into the impact of rigidifying mutations within highly correlated dynamic networks that could also be useful for developing improved computational protein engineering strategies.

scholarly journals High-throughput quantum-mechanics/molecular-mechanics (ONIOM) macromolecular crystallographic refinement withPHENIX/DivCon: the impact of mixed Hamiltonian methods on ligand and protein structure

2018 ◽  
Vol 74 (11) ◽  
pp. 1063-1077 ◽  
Author(s):  
Oleg Borbulevych ◽  
Roger I. Martin ◽  
Lance M. Westerhoff
Keyword(s):  
Quantum Mechanics ◽  
Molecular Mechanics ◽  
High Throughput ◽  
Active Site ◽  
Binding Modes ◽  
Acta Cryst ◽  
Structure Based Drug Design ◽  
Energy Functionals ◽  
Conventional Methods ◽  
The Impact

Conventional macromolecular crystallographic refinement relies on often dubious stereochemical restraints, the preparation of which often requires human validation for unusual species, and on rudimentary energy functionals that are devoid of nonbonding effects owing to electrostatics, polarization, charge transfer or even hydrogen bonding. While this approach has served the crystallographic community for decades, as structure-based drug design/discovery (SBDD) has grown in prominence it has become clear that these conventional methods are less rigorous than they need to be in order to produce properly predictive protein–ligand models, and that the human intervention that is required to successfully treat ligands and other unusual chemistries found in SBDD often precludes high-throughput, automated refinement. Recently, plugins to thePython-based Hierarchical ENvironment for Integrated Xtallography(PHENIX) crystallographic platform have been developed to augment conventional methods with thein situuse of quantum mechanics (QM) applied to ligand(s) along with the surrounding active site(s) at each step of refinement [Borbulevychet al.(2014),Acta CrystD70, 1233–1247]. This method (Region-QM) significantly increases the accuracy of the X-ray refinement process, and this approach is now used, coupled with experimental density, to accurately determine protonation states, binding modes, ring-flip states, water positions and so on. In the present work, this approach is expanded to include a more rigorous treatment of the entire structure, including the ligand(s), the associated active site(s) and the entire protein, using a fully automated, mixed quantum-mechanics/molecular-mechanics (QM/MM) Hamiltonian recently implemented in theDivConpackage. This approach was validated through the automatic treatment of a population of 80 protein–ligand structures chosen from the Astex Diverse Set. Across the entire population, this method results in an average 3.5-fold reduction in ligand strain and a 4.5-fold improvement inMolProbityclashscore, as well as improvements in Ramachandran and rotamer outlier analyses. Overall, these results demonstrate that the use of a structure-wide QM/MM Hamiltonian exhibits improvements in the local structural chemistry of the ligand similar to Region-QM refinement but with significant improvements in the overall structure beyond the active site.

scholarly journals Active Site Elucidation and Optimization in Pt Co-catalysts for Photocatalytic Hydrogen Production over Titania

ChemCatChem ◽  
2017 ◽  
Vol 9 (22) ◽  
pp. 4268-4274 ◽  
Author(s):  
Zhi Jiang ◽  
Mark A. Isaacs ◽  
Zheng Wen Huang ◽  
Wenfeng Shangguan ◽  
Yifeng Deng ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Active Site ◽  
Photocatalytic Hydrogen Production ◽  
Co Catalysts

Exploration of Umbelliferone Based Derivatives as Potent MAO Inhibitors: Dry vs. Wet Lab Evaluation

2019 ◽  
Vol 18 (21) ◽  
pp. 1857-1871 ◽  
Author(s):  
Priyanka Dhiman ◽  
Neelam Malik ◽  
Anurag Khatkar
Keyword(s):  
Active Site ◽  
Docking Simulation ◽  
Selectivity Index ◽  
Drug Candidates ◽  
Ic50 Value ◽  
Spectrophotometric Titrations ◽  
Wet Lab ◽  
Inhibitory Potential ◽  
Anxiety Depression ◽  
The Impact

Background: Monoamine oxidase inhibitors are potential drug candidates within therapeutics of different neuropsychological and neurodegenerative disorders including anxiety, depression and Parkinson’s disease. Objective: We investigated the MAO inhibitory effects of the umbelliferone based derivatives for the treatment of neurological disorders. The potential antioxidant effects of the derivatives were evaluated by DPPH and H2O2 scavenging methods. Method: A series of different umbelliferone derivatives was designed and synthesized, and the derivatives were screened for hMAO-A and hMAO-B inhibition. Moreover, the mechanistic insight for enzyme- compound infractions was achieved by docking simulation. The antioxidant potential was dually assessed by two spectrophotometric titrations methods. Results: Compound 5 with bromo 5-bromo-isatin exhibited a remarkable hMAO-A inhibitory potential (7.473±0.035 µM and the selectivity index of 0.14) revealing the impact of hybrid coumarin and 5- bromo-2-oxoindolin-3-yl ring with hydrazine linker on the hMAO-A active site. Compound 13 exhibited significant hMAO-B inhibition with an IC50 value of 10.32±0.044µM with an exceptional selectivity index of 8.55. Incorporation of 2-hydroxy-2-phenylacetate moiety on 2-oxo-2H-chromen ring led the important binding infractions within the hMAO active site. Conclusion: Our findings revealed a good correlation between experimental MAO inhibition and docking score by computational studies. Notably, the compounds with remarkable MAO inhibitory potential were also observed as potential antioxidants.

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