Quantification of Electric Field inside the Protein Active Sites and Fullerenes

2021 ◽  
Author(s):  
Ambuj Dhakad ◽  
Subhrakant Jena ◽  
Dipak Kumar Sahoo ◽  
Himansu S. Biswal
Keyword(s):  
Electric Field ◽  
Electrostatic Field ◽  
Electrostatic Interactions ◽  
Active Sites ◽  
Biological Functions ◽  
Simple Method ◽  
Protein Active Sites

While electrostatic interactions are exceedingly accountable for biological functions, no simple method exists to directly estimate or measure the electrostatic field in the protein active sites. The electrostatic field inside...

Transient Response of Electrostatic Field due to Collision ESD between Spherical Electrodes by using Bare-chip Optical Electric Field Sensor

2020 ◽  
Vol 140 (12) ◽  
pp. 599-600
Author(s):  
Kento Kato ◽  
Ken Kawamata ◽  
Shinobu Ishigami ◽  
Ryuji Osawa ◽  
Takeshi Ishida ◽  
...  
Keyword(s):  
Electric Field ◽  
Transient Response ◽  
Electrostatic Field ◽  
Electric Field Sensor ◽  
Field Sensor

Field Effect Modulation of Electrocatalytic Hydrogen Evolution at Back-Gated Two-Dimensional MoS2 Electrodes

2019 ◽  
Author(s):  
Yan Wang ◽  
Sagar Udyavara ◽  
Matthew Neurock ◽  
C. Daniel Frisbie
Keyword(s):  
Electric Field ◽  
Hydrogen Evolution ◽  
Active Sites ◽  
Density Functional ◽  
Electrode Materials ◽  
Density Functional Theory Calculations ◽  
Electronic Charge ◽  
Back Side ◽  
Gate Electrode ◽  
Conventional Manner

<div> <div> <div> <p> </p><div> <div> <div> <p>Electrocatalytic activity for hydrogen evolution at monolayer MoS2 electrodes can be enhanced by the application of an electric field normal to the electrode plane. The electric field is produced by a gate electrode lying underneath the MoS2 and separated from it by a dielectric. Application of a voltage to the back-side gate electrode while sweeping the MoS2 electrochemical potential in a conventional manner in 0.5 M H2SO4 results in up to a 140-mV reduction in overpotential for hydrogen evolution at current densities of 50 mA/cm2. Tafel analysis indicates that the exchange current density is correspondingly improved by a factor of 4 to 0.1 mA/cm2 as gate voltage is increased. Density functional theory calculations support a mechanism in which the higher hydrogen evolution activity is caused by gate-induced electronic charge on Mo metal centers adjacent the S vacancies (the active sites), leading to enhanced Mo-H bond strengths. Overall, our findings indicate that the back-gated working electrode architecture is a convenient and versatile platform for investigating the connection between tunable electronic charge at active sites and overpotential for electrocatalytic processes on ultrathin electrode materials.</p></div></div></div><br><p></p></div></div></div>

scholarly journals Addressing a lattice of rotatable molecular dipoles with the electric field of an STM tip

2021 ◽  
Vol 23 (8) ◽  
pp. 4874-4881
Author(s):  
Timo Frauhammer ◽  
Lukas Gerhard ◽  
Kevin Edelmann ◽  
Marcin Lindner ◽  
Michal Valášek ◽  
...  
Keyword(s):  
Electric Field ◽  
Electrostatic Interactions ◽  
Head Groups

Electrostatic interactions within a lattice of freestanding rotatable head groups mounted on tripodal molecular platforms.

Effects of Space Charge on ESEM Gas Amplification

1997 ◽  
Vol 3 (S2) ◽  
pp. 609-610 ◽  
Author(s):  
B.L. Thiel ◽  
M.R. Hussein-Ismail ◽  
A.M. Donald
Keyword(s):  
Electric Field ◽  
Electrostatic Field ◽  
Secondary Electron ◽  
Sample Surface ◽  
Cascade Process ◽  
Secondary Electrons ◽  
Positive Ions ◽  
Space Charges ◽  
Cascade Amplification ◽  
Environmental Sem

We have performed a theoretical investigation of the effects of space charges in the Environmental SEM (ESEM). The ElectroScan ESEM uses an electrostatic field to cause gas cascade amplification of secondary electron signals. Previous theoretical descriptions of the gas cascade process in the ESEM have assumed that distortion of the electric field due to space charges can be neglected. This assumption has now been tested and shown to be valid.In the ElectroScan ESEM, a positively biased detector is located above the sample, creating an electric field on the order of 105 V/m between the detector and sample surface. Secondary electrons leaving the sample are cascaded though the gas, amplifying the signal and creating positive ions. Because the electrons move very quickly through the gas, they do not accumulate in the specimen-to-detector gap. However, the velocity of the positive ions is limited by diffusion.

scholarly journals Insight into Inhibitor Binding in the Eukaryotic Proteasome: Computations of the 20S CP

2018 ◽  
Vol 19 (12) ◽  
pp. 3858
Author(s):  
Milan Hodošček ◽  
Nadia Elghobashi-Meinhardt
Keyword(s):  
Electrostatic Interactions ◽  
Active Sites ◽  
Sampling Period ◽  
Md Simulations ◽  
Structural Features ◽  
Relaxation Dynamics ◽  
Inhibitor Binding ◽  
Computational Analyses ◽  
Insight Into ◽  
Proteolytic Chamber

A combination of molecular dynamics (MD) simulations and computational analyses uncovers structural features that may influence substrate passage and exposure to the active sites within the proteolytic chamber of the 20S proteasome core particle (CP). MD simulations of the CP reveal relaxation dynamics in which the CP slowly contracts over the 54 ns sampling period. MD simulations of the SyringolinA (SylA) inhibitor within the proteolytic B 1 ring chamber of the CP indicate that favorable van der Waals and electrostatic interactions account for the predominant association of the inhibitor with the walls of the proteolytic chamber. The time scale required for the inhibitor to travel from the center of the proteolytic chamber to the chamber wall is on the order of 4 ns, accompanied by an average energetic stabilization of approximately −20 kcal/mol.

scholarly journals Heterogeneous Catalytic Synthesis of 2-Methylbenzimidazole from 2-Nitroaniline and Ethanol Over Mg Modified Cu-Pd/γ-Al2O3

Catalysts ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 8 ◽  
Author(s):  
Feng Feng ◽  
Yaqin Deng ◽  
Zheng Cheng ◽  
Xiaoliang Xu ◽  
Qunfeng Zhang ◽  
...  
Keyword(s):  
Active Sites ◽  
Hydrogen Transfer ◽  
High Efficiency ◽  
Simple Procedure ◽  
Direct Synthesis ◽  
Reaction System ◽  
Simple Method ◽  
Heterogeneous Catalytic ◽  
Coupled Reaction ◽  
Al2o3 Catalyst

The direct synthesis of benzimidazoles from 2-nitroaniline and ethanol over Cu-Pd/γ-Al2O3 catalysts has the advantages of requiring easily available starting materials, having high efficiency, and a simple procedure. The modification by Mg of the Cu-Pd/γ-Al2O3 catalyst could improve the catalytic activity significantly. The addition of Mg to the Cu-Pd/γ-Al2O3 catalyst could maintain and promote the formation of CuPd alloy active sites. Meanwhile, the basicity of the support was enhanced appropriately by Mg, which generated more basic sites (Al-Oδ−) to accelerate the dehydrogenation of alcohol and increased the rate of the whole coupled reaction. The 2-nitroaniline was completely converted over Cu-Pd/(Mg)γ-Al2O3 after reacting for six hours, and the yield of 2-methylbenzimidazole was 98.8%. The results of this work provide a simple method to develop a more efficient catalyst for the “alcohol-dehydrogenation, hydrogen transfer and hydrogenation” coupled reaction system.

scholarly journals Adsorption of Lysozyme Into a Charged Confining Pore

2021 ◽  
Author(s):  
Sidney Carvalho ◽  
Ralf Metzler ◽  
Andrey Cherstvy ◽  
Daniel Caetano
Keyword(s):  
Electrostatic Interactions ◽  
Active Sites ◽  
Coarse Grained ◽  
Pore Surface ◽  
Solution Ph ◽  
Coarse Grained Model ◽  
Egg White Lysozyme ◽  
Constant Ph ◽  
Pka Shift ◽  
Effects Of Ph

Several applications arise from the confinement of proteins on surfaces since their stability and biological activity are enhanced. It is also known that the way a protein adsorbs on the surface is important for its biological function since its active sites should not be obstructed. In this study, the adsorption properties of hen egg-white Lysozyme, HEWL, into a negatively charged silica pore is examined employing a coarse-grained model and constant-pH Monte Carlo simulations. The role of electrostatic interactions is taken into account when including the Debye-Hueckel potentials into the Ca structure-based model. We evaluate the effects of pH, salt concentration, and pore radius on the protein preferential orientation and spatial distribution of its residues regarding the pore surface. By mapping the residues that stay closer to the pore surface, we find the increase of pH leads to orientational changes of the adsorbed protein when the solution pH gets closer to the HEWL isoelectric point. At these conditions, the pKa shift of these important residues caused by the adsorption into the charged confining surface results in a HEWL charge distribution that stabilizes the adsorption in the observed protein orientation. We compare our observations to the results of pKa shift for HEWL available in the literature and to some experimental data.

scholarly journals The Role of Electrostatics in Enzymes: Do Biomolecular Force Fields Reflect Protein Electric Fields?

2020 ◽  
Author(s):  
Richard T Bradshaw ◽  
Jacek Dziedzic ◽  
Chris-Kriton Skylaris ◽  
Jonathan W. Essex
Keyword(s):  
Electric Fields ◽  
Active Sites ◽  
Catalytic Mechanism ◽  
Force Fields ◽  
Prolyl Isomerase ◽  
Peptidyl Prolyl Isomerase ◽  
Polarizable Force Field ◽  
Polarizable Force Fields ◽  
Protein Active Sites ◽  
Dynamics Simulations

<div><div><div><p>Preorganization of large, directionally oriented, electric fields inside protein active sites has been proposed as a crucial contributor to catalytic mechanism in many enzymes, and may be efficiently investigated at the atomistic level with molecular dynamics simulations. Here we evaluate the ability of the AMOEBA polarizable force field, as well as the additive Amber ff14SB and Charmm C36m models, to describe the electric fields present inside the active site of the peptidyl-prolyl isomerase cyclophilin A. We compare the molecular mechanical electric fields to those calculated with a fully first principles quantum mechanical (QM) representation of the protein, solvent, and ions, and find that AMOEBA consistently shows far greater correlation with the QM electric fields than either of the additive force fields tested. Catalytically-relevant fields calculated with AMOEBA were typically smaller than those observed with additive potentials, but were generally consistent with an electrostatically-driven mechanism for catalysis. Our results highlight the accuracy and the potential advantages of using polarizable force fields in systems where accurate electrostatics may be crucial for providing mechanistic insights.</p></div></div></div>

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