Increased Positive Electrostatic Potential inp-Hydroxybenzoate Hydroxylase Accelerates Hydroxylation but Slows Turnover†

Biochemistry ◽  
2004 ◽  
Vol 43 (6) ◽  
pp. 1569-1579 ◽  
Author(s):  
Mariliz Ortiz-Maldonado ◽  
Lindsay J. Cole ◽  
Sara M. Dumas ◽  
Barrie Entsch ◽  
David P. Ballou
Keyword(s):  
Electrostatic Potential ◽  
Hydroxybenzoate Hydroxylase ◽  
Positive Electrostatic Potential

Halogen bonds as a tool in the design of high energetic materials: evidence from crystal structures and quantum chemical calculations

CrystEngComm ◽  
2021 ◽  
Author(s):  
Aleksandra B. Đunović ◽  
Dušan Ž Veljković
Keyword(s):  
Crystal Structures ◽  
Quantum Chemical Calculations ◽  
Electrostatic Potential ◽  
Energetic Materials ◽  
Quantum Chemical ◽  
Central Area ◽  
Molecular Surface ◽  
Halogen Bonds ◽  
Positive Electrostatic Potential

Positive electrostatic potential over the central area of the molecular surface is one of the main characteristics of high energetic materials (HEM) that determines their sensitivity towards detonation. The influence...

scholarly journals σ-Holes vs. Buildups of Electronic Density on the Extensions of Bonds to Halogen Atoms

Inorganics ◽  
2019 ◽  
Vol 7 (6) ◽  
pp. 71 ◽  
Author(s):  
Peter Politzer ◽  
Jane S. Murray
Keyword(s):  
Electrostatic Potential ◽  
Local Minimum ◽  
Halogen Atom ◽  
Local Maximum ◽  
Outer Side ◽  
Electronic Density ◽  
Halogen Atoms ◽  
Positive Electrostatic Potential

Our discussion focuses upon three possible features that a bonded halogen atom may exhibit on its outer side, on the extension of the bond. These are (1) a region of lower electronic density (a σ-hole) accompanied by a positive electrostatic potential with a local maximum, (2) a region of lower electronic density (a σ-hole) accompanied by a negative electrostatic potential that also has a local maximum, and (3) a buildup of electronic density accompanied by a negative electrostatic potential that has a local minimum. In the last case, there is no σ-hole. We show that for diatomic halides and halogen-substituted hydrides, the signs and magnitudes of these maxima and minima can be expressed quite well in terms of the differences in the electronegativities of the halogen atoms and their bonding partners, and the polarizabilities of both. We suggest that the buildup of electronic density and absence of a σ-hole on the extension of the bond to the halogen may be an operational indication of ionicity.

Caractérisation physicochimique et électronique de la structure Pt–a-Si: H–c-Si(n)

1991 ◽  
Vol 69 (3-4) ◽  
pp. 357-360 ◽  
Author(s):  
S. Belkouch ◽  
L. Paquin ◽  
A. Deneuville ◽  
E. Gheeraert
Keyword(s):  
Infrared Absorption ◽  
Electrostatic Potential ◽  
Potential Drop ◽  
Localized States ◽  
Electrical Measurements ◽  
Potential Barriers ◽  
Infrared Absorption Spectra ◽  
Hydrogenated Amorphous ◽  
Positive Electrostatic Potential ◽  
Absorption Measurements

Infrared absorption spectra, and electrical measurements I(V, T) and C(V) at 100 Hz of the Pt–a-Si:H–c-Si structure are presented. The thickness, d, of the hydrogenated amorphous silicium, a-Si:H, varies between 4800 and 180 Å(1 Å = 10−10 m). Infrared absorption measurements on a-Si:H show that with the decrease in d there is an increase in the number of defects and the hydrogen concentration on Si-H sites. The electrical results I(V, T) show a Schottky-like structure whose ideality factor increases with decreasing T, but remains limited even for small values of d (1.4 at 300 K for d = 180 Å). Two potential barriers are also deduced: at high temperature [Formula: see text] and is independent of d. This barrier is attributed to the Pt–a-Si:H interface. At low temperature, [Formula: see text] increases from 0.23 to 0.5 eV as d decreases from 2400 to 180 Å. This barrier is attributed to the a-Si = H–c-Si, interface, the transport in a-Si:H taking place by tunnelling between localized states. The C(V) measurements allow the separation between the c-Si and the a-Si:H responses. Above 100 kHz, there is no response from a-Si:H, which behaves then as a dielectric. The electrostatic potential drop in c-Si is deduced as a function of the applied voltage V for each value of d. A positive electrostatic potential is found when V = 0 for d ≤ 500 Å.[Journal translation]

scholarly journals How aromatic system size affects the sensitivities of highly energetic molecules?

RSC Advances ◽  
2021 ◽  
Vol 11 (51) ◽  
pp. 31933-31940
Author(s):  
Ivana S. Veljković ◽  
Jelena I. Radovanović ◽  
Dušan Ž. Veljković
Keyword(s):  
Dft Calculations ◽  
Electrostatic Potential ◽  
System Size ◽  
Aromatic System ◽  
Positive Electrostatic Potential

DFT calculations showed that with the increase of the aromatic system size, values of positive electrostatic potential above the central areas of energetic molecules decrease, leading to the decrease in the sensitivities towards detonation.

scholarly journals The σ-hole revisited

2017 ◽  
Vol 19 (48) ◽  
pp. 32166-32178 ◽  
Author(s):  
Peter Politzer ◽  
Jane S. Murray ◽  
Timothy Clark ◽  
Giuseppe Resnati
Keyword(s):  
Electrostatic Potential ◽  
Electronic Density ◽  
Covalently Bonded ◽  
Positive Electrostatic Potential

A covalently-bonded atom typically has a region of lower electronic density, a “σ-hole,” on the side of the atom opposite to the bond, approximately along its extension. There is often a positive electrostatic potential (strongest shown in red) associated with a σ-hole, although it may deviate from the extension of the bond.

scholarly journals Can the sensitivity of energetic materials be tuned by using hydrogen bonds? Another look at the role of hydrogen bonding in the design of high energetic compounds.

2021 ◽  
Author(s):  
Danijela S. Kretić ◽  
Jelena I. Radovanović ◽  
Dušan Ž Veljković
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Electrostatic Potential ◽  
Energetic Materials ◽  
Energetic Compounds ◽  
Positive Electrostatic Potential

Strongly positive electrostatic potential in the central areas of molecules of the energetic materials is one of the most important factors that determine the sensitivity of these molecules towards detonation....

scholarly journals CFTR: A Cysteine at Position 338 in TM6 Senses a Positive Electrostatic Potential in the Pore

2004 ◽  
Vol 87 (6) ◽  
pp. 3826-3841 ◽  
Author(s):  
Xuehong Liu ◽  
Zhi-Ren Zhang ◽  
Matthew D. Fuller ◽  
Joshua Billingsley ◽  
Nael A. McCarty ◽  
...  
Keyword(s):  
Electrostatic Potential ◽  
Positive Electrostatic Potential

Specific Recognition of Methanol Using a Symmetric Tetramethylcucurbit[6]uril-Based Porous Supramolecular Assembly Incorporating Adsorbed Dyes

2020 ◽  
Vol 73 (11) ◽  
pp. 1065 ◽  
Author(s):  
Fei Yang Tian ◽  
Rui Xue Cheng ◽  
Yun Qian Zhang ◽  
Zhu Tao ◽  
Qian Jiang Zhu
Keyword(s):  
Electrostatic Potential ◽  
Outer Surface ◽  
Supramolecular Assembly ◽  
Dipole Interaction ◽  
Carbonyl Oxygen ◽  
Polycyclic Compounds ◽  
Dipole Interactions ◽  
Fluorescence Characteristics ◽  
Volatile Organic ◽  
Positive Electrostatic Potential

A symmetric tetramethylcucurbit[6]uril-based porous supramolecular assembly was prepared in an aqueous H2SO4 solution (5M). The driving force for the formation of this assembly is mainly the outer surface interaction of Q[n], which includes the ion-dipole interaction of SO42− anions and the positive electrostatic potential of the outer surface of the symmetric tetramethylcucurbit[6]uril (TMeQ[6]), the dipole-dipole interactions between the positive electrostatic potential of the outer surface of TMeQ[6] and portal carbonyl oxygens of TMeQ[6], and the hydrogen bonding between lattice water molecules and portal carbonyl oxygen atoms in TMeQ[6]. The TMeQ[6]-based porous supramolecular assembly exhibits the characteristics of absorbed fluorophore guests (FGs), such as dyes and polycyclic compounds with different fluorescence characteristics. Moreover, the resulting luminescent assemblies (FG@As) can respond to certain volatile organic compounds; in particular, the luminescent assemblies of rhodamine B or pyrene display a unique fluorescence enhancement in response to methanol.

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