scholarly journals Rotational predissociation of extremely weakly bound atom-molecule complexes produced by Feshbach resonance association

2011 ◽  
Vol 135 (12) ◽  
pp. 124313 ◽  
Author(s):  
Alisdair O. G. Wallis ◽  
Roman V. Krems
Keyword(s):  
Feshbach Resonance ◽  
Weakly Bound

Cross section for photoionization of the positronium negative ion at the lowest Feshbach resonance

2013 ◽  
Vol 91 (9) ◽  
pp. 751-755 ◽  
Author(s):  
Allen Paine Mills
Keyword(s):  
Lower Limit ◽  
Cross Section ◽  
Line Width ◽  
Feshbach Resonance ◽  
Photoionization Cross Section ◽  
Negative Ion ◽  
Broad Line ◽  
Outer Electron ◽  
Weakly Bound ◽  
Three Body

The photoionization cross section for the positronium (Ps) negative ion, Ps−, at the lowest n = 2 Feshbach resonance, estimated by neglecting the influences of the weakly bound outer electron, is σF = 1.4 × 10−12 cm2, about 3 × 103 times the existing lower limit calculated by Igarashi and co-workers (New J. Phys. 2, 17 (2000)). Although the estimated cross section is 200 times smaller than the analogous cross section for photoexcitation of the Ps Lyman-α transition, including the effect of the broad line width of the resonance shows it will be feasible to observe this resonance to obtain precision information about the three body Ps− system.

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.

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.

Tuning of Electronic Properties in Conducting Polymers

2001 ◽  
Vol 66 (8) ◽  
pp. 1208-1218 ◽  
Author(s):  
Guofeng Li ◽  
Mira Josowicz ◽  
Jiří Janata
Keyword(s):  
Hydrogen Bonding ◽  
Binding Site ◽  
Binding Sites ◽  
Polymer Chains ◽  
Electronic Transitions ◽  
Weakly Bound ◽  
Ordered Structures ◽  
Doped Polymer ◽  
Positively Charged ◽  
Repeated Cycling

Structural and electronic transitions in poly(thiophenyleneiminophenylene), usually referred to as poly(phenylenesulfidephenyleneamine) (PPSA) upon electrochemical doping with LiClO4 have been investigated. The unusual electrochemical behavior of PPSA indicates that the dopant anions are bound in two energetically different sites. In the so-called "binding site", the ClO4- anion is Coulombically attracted to the positively charged S or N sites on one chain and simultaneously hydrogen-bonded with the N-H group on a neighboring polymer chain. This strong interaction causes a re-organization of the polymer chains, resulting in the formation of a networked structure linked together by these ClO4- Coulombic/hydrogen bonding "bridges". However, in the "non-binding site", the ClO4- anion is very weakly bound, involves only the electrostatic interaction and can be reversibly exchanged when the doped polymer is reduced. In the repeated cycling, the continuous and alternating influx and expulsion of ClO4- ions serves as a self-organizing process for such networked structures, giving rise to a diminishing number of available "non-binding" sites. The occurrence of these ordered structures has a major impact on the electrochemical activity and the morphology of the doped polymer. Also due to stabilization of the dopant ions, the doped polymer can be kept in a stable and desirable oxidation state, thus both work function and conductivity of the polymer can be electrochemically controlled.

scholarly journals Real-time observation of ultrafast molecular rotation in weakly bound dimers

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Jiaqi Zhou ◽  
Chaoxiong He ◽  
Ming-Ming Liu ◽  
Enliang Wang ◽  
Shaokui Jia ◽  
...  
Keyword(s):  
Real Time ◽  
Molecular Rotation ◽  
Weakly Bound ◽  
Time Observation ◽  
Real Time Observation

Weakly bound halo breakup of neutron- Li7 and nucleon- Be7 on a lead target

2020 ◽  
Vol 102 (6) ◽  
Author(s):  
B. Mukeru ◽  
T. Frederico ◽  
Lauro Tomio
Keyword(s):  
Lead Target ◽  
Weakly Bound
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