scholarly journals Complete ligand loss in electron ionization of the weakly bound organometallic tungsten hexacarbonyl dimer

2016 ◽  
Vol 18 (15) ◽  
pp. 9893-9896 ◽  
Author(s):  
Michael Neustetter ◽  
Andreas Mauracher ◽  
Paulo Limão-Vieira ◽  
Stephan Denifl
Keyword(s):  
Valence Bond ◽  
Electron Ionization ◽  
Intermolecular Bond ◽  
Weakly Bound ◽  
Tungsten Hexacarbonyl

Electron ionization of the weakly bound tungsten hexacarbonyl dimer leads to a transformation of the weak intermolecular bond into a strong valence bond.

Infrared spectra of carbocations and CH4+ in helium

2021 ◽  
Author(s):  
Julia Ann Davies ◽  
Shengfu Yang ◽  
Andrew M Ellis
Keyword(s):  
Ir Spectra ◽  
Infrared Spectra ◽  
Electron Ionization ◽  
Weakly Bound ◽  
Cation Complexes

Infrared (IR) spectra of several hydrocarbon cations are reported, namely CH3+, CH4+, CH5+, CH5+(CH4) and C2H5+. The spectra were generated from weakly-bound helium-cation complexes formed by electron ionization of helium...

scholarly journals Fragmentation pathways of tungsten hexacarbonyl clusters upon electron ionization

2016 ◽  
Vol 145 (5) ◽  
pp. 054301 ◽  
Author(s):  
M. Neustetter ◽  
E. Jabbour Al Maalouf ◽  
P. Limão-Vieira ◽  
S. Denifl
Keyword(s):  
Electron Ionization ◽  
Tungsten Hexacarbonyl ◽  
Fragmentation Pathways

CRYO-Electron Microscopy of the Acto-Myosin-ATP Complex

1990 ◽  
Vol 48 (1) ◽  
pp. 248-249
Author(s):  
John Trinickt ◽  
Howard White
Keyword(s):  
Electron Microscopy ◽  
Atp Hydrolysis ◽  
Myosin Head ◽  
Bound State ◽  
Cross Linking ◽  
Weakly Bound ◽  
Cryo Electron Microscopy ◽  
Myosin Subfragment 1 ◽  
Attached State ◽  
High Fraction

The primary force of muscle contraction is thought to involve a change in the myosin head whilst attached to actin, the energy coming from ATP hydrolysis. This change in attached state could either be a conformational change in the head or an alteration in the binding angle made with actin. A considerable amount is known about one bound state, the so-called strongly attached state, which occurs in the presence of ADP or in the absence of nucleotide. In this state, which probably corresponds to the last attached state of the force-producing cycle, the angle between the long axis myosin head and the actin filament is roughly 45°. Details of other attached states before and during power production have been difficult to obtain because, even at very high protein concentration, the complex is almost completely dissociated by ATP. Electron micrographs of the complex in the presence of ATP have therefore been obtained only after chemically cross-linking myosin subfragment-1 (S1) to actin filaments to prevent dissociation. But it is unclear then whether the variability in attachment angle observed is due merely to the cross-link acting as a hinge.We have recently found low ionic-strength conditions under which, without resorting to cross-linking, a high fraction of S1 is bound to actin during steady state ATP hydrolysis. The structure of this complex is being studied by cryo-electron microscopy of hydrated specimens. Most advantages of frozen specimens over ambient temperature methods such as negative staining have already been documented. These include improved preservation and fixation rates and the ability to observe protein directly rather than a surrounding stain envelope. In the present experiments, hydrated specimens have the additional benefit that it is feasible to use protein concentrations roughly two orders of magnitude higher than in conventional specimens, thereby reducing dissociation of weakly bound complexes.

Resolving the Quadruple Bonding Conundrum in C2 Using Insights Derived from Excited State Potential Energy Surfaces: A Molecular Orbital Perspective

2019 ◽  
Author(s):  
Ishita Bhattacharjee ◽  
Debashree Ghosh ◽  
Ankan Paul
Keyword(s):  
Excited State ◽  
Potential Energy ◽  
Molecular Orbital ◽  
High Spin ◽  
Potential Energy Surfaces ◽  
Valence Bond ◽  
Deep Minimum ◽  
State Potential ◽  
Energy Surfaces ◽  
Mo Theory

The question of quadruple bonding in C<sub>2</sub> has emerged as a hot button issue, with opinions sharply divided between the practitioners of Valence Bond (VB) and Molecular Orbital (MO) theory. Here, we have systematically studied the Potential Energy Curves (PECs) of low lying high spin sigma states of C<sub>2</sub>, N<sub>2</sub> and Be<sub>2</sub> and HC≡CH using several MO based techniques such as CASSCF, RASSCF and MRCI. The analyses of the PECs for the<sup> 2S+1</sup>Σ<sub>g/u</sub> (with 2S+1=1,3,5,7,9) states of C<sub>2</sub> and comparisons with those of relevant dimers and the respective wavefunctions were conducted. We contend that unlike in the case of N<sub>2</sub> and HC≡CH, the presence of a deep minimum in the <sup>7</sup>Σ state of C<sub>2</sub> and CN<sup>+</sup> suggest a latent quadruple bonding nature in these two dimers. Hence, we have struck a reconciliatory note between the MO and VB approaches. The evidence provided by us can be experimentally verified, thus providing the window so that the narrative can move beyond theoretical conjectures.

Optimal Duration of the Preincubation Phase in Enzyme Inhibition Experiments

2020 ◽  
Author(s):  
Petr Kuzmic
Keyword(s):  
Enzyme Inhibition ◽  
Dose Response ◽  
Enzyme Inhibitor ◽  
Single Point ◽  
Association Rate ◽  
Weakly Bound ◽  
Inhibitor Complex ◽  
Dissociation Equilibrium ◽  
Optimal Duration ◽  
Algebraic Formula

This report describes an algebraic formula to calculate the optimal duration of the pre-incubation phase in enzyme-inhibition experiments, based on the assumed range of expected values for the dissociation equilibrium constant of the enzyme–inhibitor complex and for the bimolecular association rate constant. Three typical experimental scenarios are treated, namely, (1) single-point primary screening at relatively high inhibitor concentrations; (2) dose-response secondary screening of relatively weakly bound inhibitors; (3) dose-response screening of tightly-bound inhibitors.

Reduction Reactions in the Ion Source in Electron Ionization Mass Spectrometry

2020 ◽  
Vol 75 (13) ◽  
pp. 1685-1692
Author(s):  
D. M. Mazur ◽  
M. E. Zimens ◽  
Th. B. Latkin ◽  
N. V. Ul’yanovskii ◽  
V. B. Artaev ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Ion Source ◽  
Electron Ionization ◽  
Electron Ionization Mass Spectrometry ◽  
Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Reduction Reactions

Kekulé index for valence bond structures of conjugated systems containing cyclobutadiene

1978 ◽  
Vol 43 (5) ◽  
pp. 1375-1392 ◽  
Author(s):  
Ante Graovac ◽  
Ivan Gutman ◽  
Milan Randić ◽  
Nenad Trinajstić
Keyword(s):  
Valence Bond ◽  
Conjugated Systems
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