Intermediate oxiranes in the base-catalyzed depolymerisation of lignin

2016 ◽  
Vol 18 (6) ◽  
pp. 1590-1596 ◽  
Author(s):  
Timm Lankau ◽  
Chin-Hui Yu
Keyword(s):  
Quantum Calculations ◽  
Alkoxide Route

Quantum calculations show that βO4′ links break in two ways; the carbanion route yields monomers, the alkoxide route facilitates repolymerisation.

Quantum calculations of inelastic scattering of HCN and HNC by Ar

1996 ◽  
Vol 88 (1) ◽  
pp. 21-32 ◽  
Author(s):  
JOEL BOWMAN ◽  
D.ANNAPURNA PADMAVATHI
Keyword(s):  
Inelastic Scattering ◽  
Quantum Calculations

Quantum Calculation of Proton and Other Charge Transfer Steps in Voltage Sensing in the Kv1.2 Channel

2019 ◽  
Author(s):  
Alisher M Kariev ◽  
Michael Green
Keyword(s):  
Charge Transfer ◽  
Energy Charge ◽  
Quantum Calculation ◽  
Quantum Calculations ◽  
Gating Current ◽  
Transmembrane Segment ◽  
Voltage Sensing ◽  
Standard Models ◽  
Charge Displacement ◽  
Voltage Sensing Domain

Quantum calculations on 976 atoms of the voltage sensing domain of the K<sub>v</sub>1.2 channel, with protons in several positions, give energy, charge transfer, and other properties. Motion of the S4 transmembrane segment that accounts for gating current in standard models is shown not to occur; there is H<sup>+ </sup>transfer instead. The potential at which two proton positions cross in energy approximately corresponds to the gating potential for the channel. The charge displacement seems approximately correct for the gating current. Two mutations are accounted for (Y266F, R300cit, cit =citrulline). The primary conclusion is that voltage sensing depends on H<sup>+</sup> transfer, not motion of arginine charges.

scholarly journals Quantum Calculations on Ion Channels: Why Are They More Useful Than Classical Calculations, and for Which Processes Are They Essential?

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 655
Author(s):  
Alisher M. Kariev ◽  
Michael E. Green
Keyword(s):  
Charge Transfer ◽  
Ion Channels ◽  
Correlation Energy ◽  
Force Fields ◽  
Critical Role ◽  
Atomic Scale ◽  
Quantum Calculations ◽  
Interatomic Distances ◽  
Classical Analogue ◽  
Exchange And Correlation

There are reasons to consider quantum calculations to be necessary for ion channels, for two types of reasons. The calculations must account for charge transfer, and the possible switching of hydrogen bonds, which are very difficult with classical force fields. Without understanding charge transfer and hydrogen bonding in detail, the channel cannot be understood. Thus, although classical approximations to the correct force fields are possible, they are unable to reproduce at least some details of the behavior of a system that has atomic scale. However, there is a second class of effects that is essentially quantum mechanical. There are two types of such phenomena: exchange and correlation energies, which have no classical analogues, and tunneling. Tunneling, an intrinsically quantum phenomenon, may well play a critical role in initiating a proton cascade critical to gating. As there is no classical analogue of tunneling, this cannot be approximated classically. Finally, there are energy terms, exchange and correlation energy, whose values can be approximated classically, but these approximations must be subsumed within classical terms, and as a result, will not have the correct dependence on interatomic distances. Charge transfer, and tunneling, require quantum calculations for ion channels. Some results of quantum calculations are shown.

Quantum calculations of the photoelectron spectra of the OH−·NH3 anion: implications for OH + NH3 → H2O + NH2 reaction dynamics

2021 ◽  
Vol 23 (11) ◽  
pp. 6950-6958
Author(s):  
Kohei Saito ◽  
Yutaro Sugiura ◽  
Takaaki Miyazaki ◽  
Yukinobu Takahashi ◽  
Toshiyuki Takayanagi
Keyword(s):  
Quantum Dynamics ◽  
Photoelectron Spectrum ◽  
Reaction Dynamics ◽  
Photoelectron Spectra ◽  
Quantum Calculations ◽  
Anion Complex

Quantum dynamics calculations were performed to analyze the experimentally measured photoelectron spectrum of the OH−·NH3 anion complex.

scholarly journals Helium Isotopes Quantum Sieving through Graphtriyne Membranes

Nanomaterials ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 73
Author(s):  
Marta I. Hernández ◽  
Massimiliano Bartolomei ◽  
José Campos-Martínez
Keyword(s):  
Low Temperatures ◽  
Quantum Tunneling ◽  
Transition State Theory ◽  
Selective Adsorption ◽  
State Theory ◽  
Helium Isotopes ◽  
Quantum Calculations ◽  
Approximate Methods ◽  
Helium Atoms ◽  
Quantum Behavior

We report accurate quantum calculations of the sieving of Helium atoms by two-dimensional (2D) graphtriyne layers with a new interaction potential. Thermal rate constants and permeances in an ample temperature range are computed and compared for both Helium isotopes. With a pore larger than graphdiyne, the most common member of the γ-graphyne family, it could be expected that the appearance of quantum effects were more limited. We find, however, a strong quantum behavior that can be attributed to the presence of selective adsorption resonances, with a pronounced effect in the low temperature regime. This effect leads to the appearance of some selectivity at very low temperatures and the possibility for the heavier isotope to cross the membrane more efficiently than the lighter, contrarily to what happened with graphdiyne membranes, where the sieving at low energy is predominantly ruled by quantum tunneling. The use of more approximate methods could be not advisable in these situations and prototypical transition state theory treatments might lead to large errors.

Introducing the ELF Topological Analysis in the Field of Quasirelativistic Quantum Calculations

2012 ◽  
Vol 8 (9) ◽  
pp. 2985-2990 ◽  
Author(s):  
Julien Pilmé ◽  
Eric Renault ◽  
Tahra Ayed ◽  
Gilles Montavon ◽  
Nicolas Galland
Keyword(s):  
Topological Analysis ◽  
Quantum Calculations
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