Calculation of the conjugation energy and anisotropy of the diamagnetic susceptibility of conjugated molecules with weakly bound fragments

1975 ◽  
Vol 9 (6) ◽  
pp. 581-585
Author(s):  
L. I. Egorova ◽  
L. A. Borovinskii
Keyword(s):  
Diamagnetic Susceptibility ◽  
Weakly Bound ◽  
Conjugated Molecules ◽  
Conjugation Energy

Existence of ring currents in cyclic conjugated molecules and their contribution to the diamagnetic susceptibility

1971 ◽  
Vol 12 (3) ◽  
pp. 507-508 ◽  
Author(s):  
M. D. Kumanova ◽  
T. K. Rebane
Keyword(s):  
Diamagnetic Susceptibility ◽  
Conjugated Molecules ◽  
Ring Currents

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.

Spectral characteristics of the weakly bound electron species in methanol as determined from a hybrid solvation model

1996 ◽  
Vol 93 ◽  
pp. 182-187 ◽  
Author(s):  
C Pépin ◽  
T Goulet ◽  
D Houde ◽  
JP Jay-Gerin
Keyword(s):  
Spectral Characteristics ◽  
Solvation Model ◽  
Weakly Bound ◽  
Bound Electron

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.

Visualization and Manipulation of Molecular Motion in Solid State through Photo-Induced Clusteroluminescence

2019 ◽  
Author(s):  
Haoke Zhang ◽  
Lili Du ◽  
Lin Wang ◽  
Junkai Liu ◽  
Qing Wan ◽  
...  
Keyword(s):  
Quantum Mechanics ◽  
Excited State ◽  
Solid State ◽  
Light Source ◽  
Molecular Motion ◽  
Molecular Machine ◽  
Conjugated Molecules ◽  
Time Resolved ◽  
Packing Structure ◽  
New Strategy

<p>Building molecular machine has long been a dream of scientists as it is expected to revolutionize many aspects of technology and medicine. Implementing the solid-state molecular motion is the prerequisite for a practical molecular machine. However, few works on solid-state molecular motion have been reported and it is almost impossible to “see” the motion even if it happens. Here the light-driven molecular motion in solid state is discovered in two non-conjugated molecules <i>s</i>-DPE and <i>s</i>-DPE-TM, resulting in the formation of excited-state though-space complex (ESTSC). Meanwhile, the newly formed ESTSC generates an abnormal visible emission which is termed as clusteroluminescence. Notably, the original packing structure can recover from ESTSC when the light source is removed. These processes have been confirmed by time-resolved spectroscopy and quantum mechanics calculation. This work provides a new strategy to manipulate and “see” solid-state molecular motion and gains new insights into the mechanistic picture of clusteroluminescence.<br></p>

Ab initio Hartree-Fock Investigation of π-Conjugated Compounds Presenting Large βv/βe Ratio: Merocyanines

1998 ◽  
Vol 63 (9) ◽  
pp. 1295-1308 ◽  
Author(s):  
Benoît Champagne ◽  
Thierry Legrand ◽  
Eric A. Perpete ◽  
Olivier Quinet ◽  
Jean-Marie André
Keyword(s):  
Ab Initio ◽  
First Hyperpolarizability ◽  
Conjugated Molecules ◽  
Hartree Fock ◽  
Experimental Discovery ◽  
Conjugated Compounds ◽  
Molecular Frame

CHF/6-311G* calculations of the first electronic and vibrational hyperpolarizabilities reveal that merocyanines present a substantial βv/βe ratio under their quinonoid nonpolar form. It originates from a large vibrational first hyperpolarizability whereas its electronic counterpart is small for this class of push-pull π-conjugated molecules. The transition from the quinonoid to the aromatic configuration is accompanied by an increase of βe and a decrease of the βv/βe ratio as well as by a ≈ 180° rotation in the plane of the molecule of βe and βv with respect to the molecular frame. Our results support the recent experimental discovery that antiparallel aggregation of aromatic and quinonoid forms of merocyanine is energetically favoured and that their first hyperpolarizabilities, which combine constructively, present both electronic and non purely electronic origins.

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.

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