24 results on '"MOLECULAR core binding energy"'
Search Results
2. Structural flexibility of intrinsically disordered proteins induces stepwise target recognition.
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Shirai, Nobu C. and Kikuchi, Macoto
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PHYSICS research , *PROTEIN research , *MATHEMATICAL transformations , *BINDING energy , *MOLECULAR core binding energy - Abstract
An intrinsically disordered protein (IDP) lacks a stable three-dimensional structure, while it folds into a specific structure when it binds to a target molecule. In some IDP-target complexes, not all target binding surfaces are exposed on the outside, and intermediate states are observed in their binding processes. We consider that stepwise target recognition via intermediate states is a characteristic of IDP binding to targets with 'hidden' binding sites. To investigate IDP binding to hidden target binding sites, we constructed an IDP lattice model based on the HP model. In our model, the IDP is modeled as a chain and the target is modeled as a highly coarse-grained object. We introduced motion and internal interactions to the target to hide its binding sites. In the case of unhidden binding sites, a two-state transition between the free states and a bound state is observed, and we consider that this represents coupled folding and binding. Introducing hidden binding sites, we found an intermediate bound state in which the IDP forms various structures to temporarily stabilize the complex. The intermediate state provides a scaffold for the IDP to access the hidden binding site. We call this process multiform binding. We conclude that structural flexibility of IDPs enables them to access hidden binding sites and this is a functional advantage of IDPs. [ABSTRACT FROM AUTHOR]
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- 2013
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3. Binding energy and photoionization cross-section of hydrogen-like donor impurity in strongly oblate ellipsoidal quantum dot.
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Hayrapetyan, D.B., Ohanyan, G.L., Baghdasaryan, D.A., Sarkisyan, H.A., Baskoutas, S., and Kazaryan, E.M.
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LAME'S functions , *QUANTUM dots , *BINDING energy , *MOLECULAR core binding energy , *NUCLEAR forces (Physics) - Abstract
Hydrogen-like donor impurity states in strongly oblate ellipsoidal quantum dot have been studied. The hydrogen-like donor impurity states are investigated within the framework of variational method. The trial wave function constructed on the base of wave functions of the system without impurity. The dependence of the energy and binding energy for the ground and first excited states on the geometrical parameters of the ellipsoidal quantum dot and on the impurity position have been calculated. The behavior of the oscillator strength for different angles of incident light and geometrical parameters have been revealed. Photoionization cross-section of the electron transitions from the impurity ground state to the size-quantized ground and first excited states have been studied. The effects of impurity position and the geometrical parameters of the ellipsoidal quantum dot on the photoionization cross section dependence on the photon energy have been considered. [ABSTRACT FROM AUTHOR]
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- 2018
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4. Divacancy Binding Energy, Formation Energy And Surface Energy of BCC Transition Metals Using MEAM Potentials.
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Uniyal, Shweta, Chand, Manesh, Joshi, Subodh, and Semalty, P. D.
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BINDING energy , *MOLECULAR core binding energy , *TRANSITION metals , *SURFACE energy , *BODY-centered cubic metals - Abstract
The modified embedded atom method (MEAM) potential parameters have been employed to calculate the unrelaxed divacancy formation energy, binding energy and surface energies for low index planes in bcc transition metals. The calculated results of divacancy binding energy and vacancy formation energy compare well with experimental and other available calculated results. [ABSTRACT FROM AUTHOR]
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- 2016
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5. Molecular simulation of interfacial reaction between TiAl alloy melts and different coatings.
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Yan-wei Sui, Cheng Cheng, Kun Feng, Ji-qiu Qi, Ye-zeng He, Fu-xiang Wei, Qing-kun Meng, and Zhi Sun
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MOLECULAR dynamics , *INTERFACIAL reactions , *BINDING energy , *MOLECULAR core binding energy , *NUCLEAR forces (Physics) , *MOLECULAR interactions - Abstract
The effect of coatings (Y2O3, ZrO2 and Al2O3) on the interfacial reaction of TiAl alloys was studied with molecular dynamics. The binding energy of coatings and the diffusion process of oxygen in the melt were simulated, and then the simulation results were compared with the experimental results. The simulation results indicate that for each of the three simulated coatings, inordinate interfacial reactions have occurred between the coating and the melt. The binding energy results show that Y2O3 has the best stability and is the most difficult to break down. ZrO2 has the greatest decomposition energy and is the easiest to break down in the melt. Besides, the molecular dynamics indicate that the diffusion coefficient of the oxygen atom in Al2O3 is larger than that in the other two coatings, indicating that oxygen diffusion in Al2O3 is the fastest at a given temperature. The experimental results show that the oxygen concentration of the melt with Al2O3 coating is the highest, and the oxygen diffusion is of similar magnitude to the simulation values, from which the conclusion can be obtained that the oxygen concentration is significantly influenced by the coating materials. [ABSTRACT FROM AUTHOR]
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- 2017
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6. Rb ultralong-range Rydberg molecules in magnetic and electric fields.
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Gaj, Anita
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MOLECULAR interactions , *RYDBERG states , *ELECTRON-molecule scattering , *ELECTRON-atom collisions , *MOLECULAR core binding energy , *ULTRACOLD molecules - Abstract
We review the field of ultralong-range Rydberg molecules with a focus on recent developments. We briefly revisit the binding mechanism of Rydberg molecules based on electron-atom scattering and give an overview of experimental realizations in different ultracold atomic systems. However the main focus of the manuscript is on Rb Rydberg molecules. We discuss different angular momenta of the excited Rydberg states ( S and D) and the interaction of the molecules with external electric and magnetic fields. Furthermore, we cover the transition from low atomic densities, where only a single atom is bound by a Rydberg electron, to high densities, where polyatomic bound states can be observed. [ABSTRACT FROM AUTHOR]
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- 2016
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7. Lactic acid derivatives with terphenyl molecular core.
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Novotná, Vladimíra, Hamplová, Věra, Sasnouski, Genadz, and Salamon, Peter
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LACTIC acid , *POLYCHLORINATED terphenyls , *MOLECULAR core binding energy , *MICROSCOPY , *POLARIZATION (Electricity) - Abstract
New lactic acid derivatives, based on terphenyl molecular core laterally substituted by chlorine atom, have been synthesised and their liquid crystalline properties studied. We varied the molecular structure by prolonging the non-chiral chain and analysed the mesogenic properties with respect to its length. We found that all new compounds reveal the SmA*–SmC* phase sequence in an extremely broad temperature interval. The experimental techniques, namely the polarising optical microscopy, differential scanning calorimetry, x-ray diffraction and helical pitch measurements, have been applied to establish the physical properties. Studied compounds exhibit very high values of the spontaneous polarisation and the tilt angle grows continuously on cooling up to 42°. The pitch values drop down when prolonging the molecular non-chiral chain. [ABSTRACT FROM AUTHOR]
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- 2016
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8. A self-assembled octanuclear complex bearing the uncommon close-packed {Fe4Mn4(μ4-O)4(μ-O)4} molecular core.
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Nesterova, Oksana V., Chygorin, Eduard N., Kokozay, Vladimir N., Omelchenko, Irina V., Shishkin, Oleg V., Boča, Roman, and Pombeiro, Armando J. L.
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IRON chlorides , *HYDROXYLAMINE hydrochloride , *IRON-manganese alloys , *MOLECULAR core binding energy , *X-rays , *SINGLE crystals - Abstract
A one-pot open-air reaction of manganese powder with iron(ii) chloride in DMF solution of the Schiff base (H2L) formed in situ from salicylaldehyde and hydroxylamine hydrochloride yields the heterometallic complex [Fe4(μ4-O)4Mn4(L)8(DMF)4]·2DMF (1). Single crystal X-ray analysis shows that its molecular structure is based on the octanuclear core {Fe4Mn4(μ4-O)4(μ-O)4} with a quite rare molecular structure type {M8(μ4-X)4(μ-X)4}, where the central cube-like iron motif is modified with four terminal manganese fragments, the whole core being presented as the {Fe4(μ4-O)4} + 4{Mn(μ-O)} combination. Using the data from the Cambridge Structural Database (CSD), an analysis of the octanuclear structures with similar central {M4(μ4-X)4} fragments was performed. The hierarchical order of molecular structure types with the general formula M8Xn for such compounds was proposed and the topological features as well as the factors that influence the molecular type formation are discussed. Variable-temperature (1.8–300 K) magnetic susceptibility measurements reveal an antiferromagnetic coupling among the magnetic centres in 1. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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9. Resolving the chemical substructure of Orion-KL.
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Feng, S., Beuther, H., Henning, Th., Semenov, D., Palau, A., and Mills, E. A. C.
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CHEMICAL structure , *ORION (Constellation) , *STAR formation , *MOLECULAR core binding energy , *VELOCITY - Abstract
Context. The Kleinmann-Low nebula in Orion (Orion-KL) is the nearest example of a high-mass star-forming environment. Studying the resolved chemical substructures of this complex region provides important insight into the chemistry of high-mass star-forming regions (HMSFRs), as it relates to their evolutionary states. Aims. The goal of this work is to resolve the molecular line emission from individual substructures of Orion-KL at high spectral and spatial resolution and to infer the chemical properties of the associated gas. Methods. We present a line survey of Orion-KL obtained from combined Submillimeter Array (SMA) interferometric and IRAM 30 m single-dish observations. Covering a 4 GHz bandwidth in total, this survey contains over 160 emission lines from 20 species (25 isotopologues), including 11 complex organic molecules (COMs). Spectra are extracted from individual substructures and the intensity-integrated distribution map for each species is provided. We then estimate the rotation temperature for each substructure, along with their molecular column densities and abundances. Results. For the first time, we complement 1.3 mm interferometric data with single-dish observations of the Orion-KL region and study small-scale chemical variations in this region. (1) We resolve continuum substructures on ~3" angular scale. (2) We identify lines from the low-abundance COMs CH3COCH3 and CH3CH2OH, as well as tentatively detect CH3CHO and long carbon-chain molecules C6H and HC7N. (3) We find that while most COMs are segregated by type, peaking either towards the hotcore (e.g., nitrogenbearing species) or the compact ridge (e.g., oxygen-bearing species like HCOOCH3 and CH3OCH3), the distributions of others do not follow this segregated structure (e.g., CH3CH2OH, CH3OH, CH3COCH3). (4) We find a second velocity component of HNCO, SO2, 34SO2, and SO lines, which may be associated with a strong shock event in the low-velocity outflow. (5) Temperatures and molecular abundances show large gradients between central condensations and the outflow regions, illustrating a transition between hot molecular core and shock-chemistry dominated regimes. Conclusions. Our observations of spatially resolved abundance variations in Orion-KL provide the nearest reference source for hot molecular core and outflow chemistry, which will be an important example for interpreting the chemistry of more distant HMSFRs. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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10. Technical Note: Improvements in geant4 energy-loss model and the effect on low-energy electron transport in liquid water.
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Kyriakou, I., Incerti, S., and Francis, Z.
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ENERGY dissipation , *ELECTRON transport , *WATER , *NUCLEAR cross sections , *IONIZATION (Atomic physics) , *RADIATION dosimetry - Abstract
Purpose: The GEANT4-DNA physics models are upgraded by a more accurate set of electron cross sections for ionization and excitation in liquid water. The impact of the new developments on lowenergy electron transport simulations by the GEANT4 Monte Carlo toolkit is examined for improving its performance in dosimetry applications at the subcellular and nanometer level. Methods: The authors provide an algorithm for an improved implementation of the Emfietzoglou model dielectric response function of liquid water used in the GEANT4-DNA existing model. The algorithm redistributes the imaginary part of the dielectric function to ensure a physically motivated behavior at the binding energies, while retaining all the advantages of the original formulation, e.g., the analytic properties and the fulfillment of the f -sum-rule. In addition, refinements in the exchange and perturbation corrections to the Born approximation used in the GEANT4-DNA existing model are also made. Results: The new ionization and excitation cross sections are significantly different from those of the GEANT4-DNA existing model. In particular, excitations are strongly enhanced relative to ionizations, resulting in higher W-values and less diffusive dose-point-kernels at sub-keV electron energies. Conclusions: An improved energy-loss model for the excitation and ionization of liquid water by low-energy electrons has been implemented in GEANT4-DNA. The suspiciously low W-values and the unphysical long tail in the dose-point-kernel have been corrected owing to a different partitioning of the dielectric function. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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11. A new study of an old sink of sulphur in hot molecular cores: the sulphur residue.
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Woods, Paul M., Occhiogrosso, A., Viti, S., Kaňuchová, Z., Palumbo, M. E., and Price, S. D.
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STAR formation , *ASTRONOMICAL observations , *MOLECULAR structure , *MOLECULAR core binding energy , *SOLID-phase analysis , *SULFUR - Abstract
Sulphur appears to be depleted by an order of magnitude or more from its elemental abundance in star-forming regions. In the last few years, numerous observations and experiments have been performed in order to understand the reasons behind this depletion without providing a satisfactory explanation of the sulphur chemistry towards high-mass star-forming cores. Several sulphur-bearing molecules have been observed in these regions, and yet none are abundant enough to make up the gas-phase deficit. Where, then, does this hidden sulphur reside? This paper represents a step forward in our understanding of the interactions among the various S-bearing species. We have incorporated recent experimental and theoretical data into a chemical model of a hot molecular core in order to see whether they give any indication of the identity of the sulphur sink in these dense regions. Despite our model producing reasonable agreement with both solid-phase and gas-phase abundances of many sulphur-bearing species, we find that the sulphur residue detected in recent experiments takes up only ~ 6 per cent of the available sulphur in our simulations, rather than dominating the sulphur budget. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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12. Anisotropic exciton Stark shift in black phosphorus.
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Chaves, A., Low, Tony, Avouris, P., Çakır, D., and Peeters, F. M.
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ANISOTROPIC crystals , *HAMILTONIAN mechanics , *QUANTUM confined Stark effect , *MOLECULAR core binding energy , *IONIZATION energy - Abstract
We calculate the excitonic spectrum of few-layer black phosphorus by direct diagonalization of the effective mass Hamiltonian in the presence of an applied in-plane electric field. The strong attractive interaction between electrons and holes in this system allows one to investigate the Stark effect up to very high ionizing fields, including also the excited states. Our results show that the band anisotropy in black phosphorus becomes evident in the direction-dependent field-induced polarizability of the exciton. [ABSTRACT FROM AUTHOR]
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- 2015
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13. Large Chern-number topological superfluids in a coupled-layer system.
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Beibing Huang, Chun Fai Chan, and Ming Gong
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MOLECULAR core binding energy , *SUPERFLUIDITY , *BAND gaps , *PFAFFIAN systems , *CHERN classes - Abstract
Large Chern-number topological phase is always an important topic in modern physics. Here we investigate the topological superfluids in a coupled-layer system, in which transitions between different topological superfluids can be realized by controlling the binding energy, interlayer tunneling, and layer asymmetry, etc. These topological transitions are characterized by energy gap closing and reopening at the critical points at zero momentum, where the Chern number and sign of Pfaffian undergo a discontinuous change. Topological protected edge modes at the boundaries are ensured by the bulk-edge correspondence. In a trapped potential the edge modes are spatially localized at the interfaces between distinct topological superfluids, where the number of edge modes is equal to the Chern-number difference between the left and right superfluids. These topological transitions can be detected by spin texture at or near zero momentum, which changes discretely across the critical points due to band inversion. The model can be generalized to a multilayer system in which the Chern number can be equal to any positive integer. These large Chern-number topological superfluids provide fertile grounds for exploring exotic quantum matters in the context of ultracold atoms. [ABSTRACT FROM AUTHOR]
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- 2015
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14. Reduction of False Positives in Structure-Based Virtual Screening When Receptor Plasticity Is Considered.
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Yaw Awuni and Yuguang Mu
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FALSE positive error , *MOLECULAR docking , *MOLECULAR core binding energy , *ANTIVIRAL agents ,ALTERNATIVE treatment for influenza - Abstract
Structure-based virtual screening for selecting potential drug candidates is usually challenged by how numerous false positives in a molecule library are excluded when receptor plasticity is considered. In this study, based on the binding energy landscape theory, a hypothesis that a true inhibitor can bind to different conformations of the binding site favorably was put forth, and related strategies to defeat this challenge were devised; reducing false positives when receptor plasticity is considered. The receptor in the study is the influenza A nucleoprotein, whose oligomerization is a requirement for RNA binding. The structural flexibility of influenza A nucleoprotein was explored by molecular dynamics simulations. The resultant distinctive structures and the crystal structure were used as receptor models in docking exercises in which two binding sites, the tail-loop binding pocket and the RNA binding site, were targeted with the Otava PrimScreen1 diversity-molecule library using the GOLD software. The intersection ligands that were listed in the top-ranked molecules from all receptor models were selected. Such selection strategy successfully distinguished high-affinity and low-affinity control molecules added to the molecule library. This work provides an applicable approach for reducing false positives and selecting true ligands from molecule libraries. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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15. Fragmentation and kinematics of dense molecular cores in the filamentary infrared-dark cloud G011.11-0.12.
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Ragan, Sarah E., Henning, Thomas, Beuther, Henrik, Linz, Hendrik, and Zahorecz, Sarolta
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INFRARED astronomy , *NUCLEAR fragmentation , *KINEMATICS , *MOLECULAR core binding energy , *STELLAR evolution , *INTERFEROMETERS - Abstract
We present new Plateau de Bure Interferometer observations of a region in the filamentary infrared-dark cloud (IRDC) G011.11-0.12 containing young, star-forming cores. In addition to the 3.2 mm continuum emission from cold dust, we map this region in the N2H+(1-0) line to trace the core kinematics with an angular resolution of 200 and velocity resolution of 0.2 km s-1. These data are presented in concert with recent Herschel results, single-dish N2H+(1-0) data, SABOCA 350 μm continuum data, and maps of the C18O (2-1) transition obtained with the IRAM 30 m telescope. We recover the star-forming cores at 3.2 mm continuum, while in N2H+ they appear at the peaks of extended structures. The mean projected spacing between N2H+ emission peaks is 0.18 pc, consistent with simple isothermal Jeans fragmentation. The 0.1 pc-sized cores have low virial parameters on the criticality borderline, while on the scale of the whole region, we infer that it is undergoing large-scale collapse. The N2H+ linewidth increases with evolutionary stage, while CO isotopologues show no linewidth variation with core evolution. Centroid velocities of all tracers are in excellent agreement, except in the starless region where two N2H+ velocity components are detected, one of which has no counterpart in C18O. We suggest that gas along this line of sight may be falling into the quiescent core, giving rise to the second velocity component, possibly connected to the global collapse of the region. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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16. Dual-inhibitors of STAT5 and STAT3: studies from molecular docking and molecular dynamics simulations.
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Shao, Shengjuan, Yu, Rilei, Yu, Yanqing, and Li, Yanni
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MOLECULAR docking , *MOLECULAR dynamics , *DRUG therapy , *IMATINIB , *TREATMENT of chronic myeloid leukemia , *MOLECULAR core binding energy - Abstract
Although molecularly targeted therapy with imatinib has improved treatments of chronic myeloid leukemia (CML), clinical resistance gradually develops in patients with accelerated or blast phase CML. The inability of imatinib to cure CML suggests that inactivation of BCR-ABL kinase activity alone is not sufficient to control the disease. Aberrant STAT signaling and constitutive STAT5 or STAT3 activation are frequently found in both acute and chronic leukemia. Constitutive activation of STAT5 and STAT3 are associated with imatinib resistance on leukemia cells. Development of drugs targeting SH2 domains of STAT5 and STAT3 provides a novel strategy for the treatment of the imatinib-resistant CML. Here, molecular docking and molecular dynamics simulations were used to investigate the interactions of the drugs targeting STAT3 and STAT5 receptors at molecular level. The calculated binding free energies are consistent with the ranking of the experimental affinities and our simulations also explained their differences in binding energy. Then virtual screening based on molecular docking and molecular dynamics was applied to screen a set of ~1500 compounds for dual inhibitors of the SH2 domains of STAT5 and STAT3. Three top score compounds obtained in virtual screening were compound 660, 304, and 561. Results show that the three predicted dual-inhibitors are well fitted within the two binding domains and are predicted to present improved STAT5 and STAT3 SH2 inhibitory activity. [ABSTRACT FROM AUTHOR]
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- 2014
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17. Non-jellium scaling of metal cluster ionization energies and electron affinities.
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Svanqvist, M. and Hansen, K.
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IONIZATION (Atomic physics) , *SCISSION (Chemistry) , *ELECTROSTATICS , *ONTOLOGY , *MICROCLUSTERS - Abstract
Experimental literature data on ionization energies and electron affinities of metal clusters are reviewed and analyzed in terms of an expansion in the inverse cluster radius. The coefficient of the finite size correction for ionization energies decreases with increasing bulk work function whereas the corresponding coefficient for electron affinities increases. This sharply contrasts the predictions based both on density functional theory of spherical jellium clusters and on classical electrostatics. A scaling of the coefficient for the ionization potentials with the atomic radius yields a linear behavior which extrapolates to zero around 6 eV. [ABSTRACT FROM AUTHOR]
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- 2010
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18. Selective binding of hydrogen chloride and its trapping through supramolecular gelation.
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Basak, Shibaji, Nandi, Nibedita, and Banerjee, Arindam
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HYDROGEN chloride , *MOLECULAR core binding energy , *SUPRAMOLECULES , *GELATION , *HYDROCHLORIC acid - Abstract
A pyridine containing amino acid based gelator forms gel in aqueous media in the presence of hydrochloric acid and the chloride ion is found to be very selective for gelation. The gelator is successfully applied for the detection and trapping of hydrogen chloride gas and this indicates its probable application for removing hazardous HCl gas from the environment. [ABSTRACT FROM AUTHOR]
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- 2014
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19. Pillararene‐Based Two‐Component Thixotropic Supramolecular Organogels: Complementarity and Multivalency as Prominent Motifs.
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Zafrani, Yossi, Kaizerman, Dana, Hadar, Maya, Bigan, Nitzan, Granot, Eran, Ghosh, Moumita, Adler‐Abramovich, Lihi, Patolsky, Fernando, and Cohen, Yoram
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THIXOTROPY , *SUPRAMOLECULAR chemistry , *MOLECULAR core binding energy , *TOXICOLOGICAL interactions , *CATALYTIC activity - Abstract
Invited for the cover of this issue is the group of Yossi Zafrani and Yoram Cohen at the Tel Aviv University. The image depicts an artistic rendition of the supramolecular organogel with nanotubular molecular core structure. Read the full text of the article at 10.1002/chem.201801418. "The present study describes a rationally designed thixotropic two‐component supramolecular organogels based on multiple chemical interactions between percarboxylato‐ and peramino‐pillar[5]arenes." Read more about the story behind the cover in the Cover Profile and about the research itself on page 15750 ff. (DOI: 10.1002/chem.201801418). [ABSTRACT FROM AUTHOR]
- Published
- 2018
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20. High-mass Star Formation through Filamentary Collapse and Clump-fed Accretion in G22.
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Jinghua Yuan, Jin-Zeng Li, Yuefang Wu, Simon P. Ellingsen, Christian Henkel, Ke Wang, Tie Liu, Hong-Li Liu, Annie Zavagno, Zhiyuan Ren, and Ya-Fang Huang
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STAR formation , *STELLAR dynamics , *ACCRETION (Astrophysics) , *MOLECULAR core binding energy , *PARTICLE kinematics - Abstract
How mass is accumulated from cloud-scale down to individual stars is a key open question in understanding high-mass star formation. Here, we present the mass accumulation process in a hub-filament cloud G22 that is composed of four supercritical filaments. Velocity gradients detected along three filaments indicate that they are collapsing with a total mass infall rate of about 440 M⊙ Myr−1, suggesting the hub mass would be doubled in six free-fall times, adding up to ∼2 Myr. A fraction of the masses in the central clumps C1 and C2 can be accounted for through large-scale filamentary collapse. Ubiquitous blue profiles in HCO+ (3–2) and 13CO (3–2) spectra suggest a clump-scale collapse scenario in the most massive and densest clump C1. The estimated infall velocity and mass infall rate are 0.31 km s−1 and 7.2 × 10−4M⊙ yr−1, respectively. In clump C1, a hot molecular core (SMA1) is revealed by the Submillimeter Array observations and an outflow-driving high-mass protostar is located at the center of SMA1. The mass of the protostar is estimated to be 11–15 M⊙ and it is still growing with an accretion rate of 7 × 10−5M⊙ yr−1. The coexistent infall in filaments, clump C1, and the central hot core in G22 suggests that pre-assembled mass reservoirs (i.e., high-mass starless cores) may not be required to form high-mass stars. In the course of high-mass star formation, the central protostar, the core, and the clump can simultaneously grow in mass via core-fed/disk accretion, clump-fed accretion, and filamentary/cloud collapse. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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21. ALMA Observations of the Archetypal “Hot Core” That Is Not: Orion-KL.
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M. T. Orozco-Aguilera, Luis A. Zapata, Tomoya Hirota, Sheng-Li Qin, and Josep M Masqué
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PROTOSTARS , *STAR clusters , *INTERSTELLAR molecules , *ARCHETYPES , *MOLECULAR core binding energy - Abstract
We present sensitive high angular resolution (∼0.″1–0.″3) continuum Atacama Large Millimeter/Submillimeter Array (ALMA) observations of the archetypal hot core located in the Orion Kleinmann-Low (KL) region. The observations were made in five different spectral bands (bands 3, 6, 7, 8, and 9) covering a very broad range of frequencies (149–658 GHz). Apart from the well-known millimeter emitting objects located in this region (Orion Source I and BN), we report the first submillimeter detection of three compact continuum sources (ALMA1–3) in the vicinities of the Orion-KL hot molecular core. These three continuum objects have spectral indices between 1.47 and 1.56, and brightness temperatures between 100 and 200 K at 658 GHz, suggesting that we are seeing moderate, optically thick dust emission with possible grain growth. However, as these objects are not associated with warm molecular gas, and some of them are farther out from the molecular core, we thus conclude that they cannot heat the molecular core. This result favors the hypothesis that the hot molecular core in Orion-KL core is heated externally. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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22. Core-level electron spectroscopy on the sodium dimer Na 2p level
- Author
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Rander, Torbjörn, Schulz, Joachim, Huttula, Marko, Mäkinen, Ari, Tchaplyguine, Maxim, Svensson, Svante, Öhrwall, Gunnar, Björneholm, Olle, Aksela, Seppo, Aksela, Helena, Rander, Torbjörn, Schulz, Joachim, Huttula, Marko, Mäkinen, Ari, Tchaplyguine, Maxim, Svensson, Svante, Öhrwall, Gunnar, Björneholm, Olle, Aksela, Seppo, and Aksela, Helena
- Abstract
The lifetime broadening and molecular field splitting of the sodium dimer 2p core level is studied by x-ray photoelectron spectroscopy and by Auger electron spectroscopy. The lifetime of the Na 2p core hole has been determined to be 15±8fs , much shorter than what has previously been reported for solid sodium. The molecular field splitting of this core level has been determined to be 42±10meV . The Auger measurements have experimentally confirmed that the sodium dimer is a good example of when the Coulomb explosion mechanism determines the spectral shape.
- Published
- 2007
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23. OUTFLOW DETECTION IN A 70 μm DARK HIGH-MASS CORE.
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Siyi Feng, Henrik Beuther, Qizhou Zhang, Hauyu Baobab Liu, Zhiyu Zhang, Ke Wang, and Keping Qiu
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MOLECULAR core binding energy , *EMISSION control , *CLEAN development mechanism (Emission control) , *TELESCOPES , *CORE & periphery (Economic theory) - Abstract
We present observations toward a high-mass (), low-luminosity () dark molecular core G28.34 S-A at 3.4 mm, using the IRAM 30 m telescope and the NOEMA interferometer. We report the detection of line emission, which is spatially resolved in this source at a linear resolution of ∼0.1 pc, while the 3.4 mm continuum image does not resolve any internal sub-structures. The SiO emission exhibits two W–E oriented lobes centering on the continuum peak. Corresponding to the redshifted and blueshifted gas with velocities up to relative to the quiescent cloud, these lobes clearly indicate the presence of a strong bipolar outflow from this dark core, a source previously considered as one of the best candidates of “starless” core. Our SiO detection is consistent with ALMA archival data of , whose high-velocity blueshifted gas reveals a more compact lobe spatially closer to the dust center. This outflow indicates that the central source may be in an early evolutionary stage of forming a high-mass protostar. We also find that the low-velocity components (in the range of ) have an extended, NW–SE oriented distribution. Discussing the possible accretion scenarios of the outflow-powering young stellar object, we argue that molecular line emission and the molecular outflows may provide a better indication of the accretion history of the forming young stellar object, than snapshot observations of the present bolometric luminosity. This is particularly significant for cases of episodic accretion, which may occur during the collapse of the parent molecular core. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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24. ICE CHEMISTRY IN STARLESS MOLECULAR CORES.
- Author
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J. Kalvāns
- Subjects
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MOLECULAR core binding energy , *BINDING energy , *INTERSTELLAR medium , *PHOTODESORPTION , *GAS phase reactions - Abstract
Starless molecular cores are natural laboratories for interstellar molecular chemistry research. The chemistry of ices in such objects was investigated with a three-phase (gas, surface, and mantle) model. We considered the center part of five starless cores, with their physical conditions derived from observations. The ice chemistry of oxygen, nitrogen, sulfur, and complex organic molecules (COMs) was analyzed. We found that an ice-depth dimension, measured, e.g., in monolayers, is essential for modeling of chemistry in interstellar ices. Particularly, the H2O:CO:CO2:N2:NH3 ice abundance ratio regulates the production and destruction of minor species. It is suggested that photodesorption during the core-collapse period is responsible for the high abundance of interstellar H2O2 and O2H and other species synthesized on the surface. The calculated abundances of COMs in ice were compared to observed gas-phase values. Smaller activation barriers for CO and H2CO hydrogenation may help explain the production of a number of COMs. The observed abundance of methyl formate HCOOCH3 could be reproduced with a 1 kyr, 20 K temperature spike. Possible desorption mechanisms, relevant for COMs, are gas turbulence (ice exposure to interstellar photons) or a weak shock within the cloud core (grain collisions). To reproduce the observed COM abundances with the present 0D model, 1%–10% of ice mass needs to be sublimated. We estimate that the lifetime for starless cores likely does not exceed 1 Myr. Taurus cores are likely to be younger than their counterparts in most other clouds. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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