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1

Perturbation analyses of intermolecular interactions.  

Science.gov (United States)

Conformational fluctuations of a protein molecule are important to its function, and it is known that environmental molecules, such as water molecules, ions, and ligand molecules, significantly affect the function by changing the conformational fluctuations. However, it is difficult to systematically understand the role of environmental molecules because intermolecular interactions related to the conformational fluctuations are complicated. To identify important intermolecular interactions with regard to the conformational fluctuations, we develop herein (i) distance-independent and (ii) distance-dependent perturbation analyses of the intermolecular interactions. We show that these perturbation analyses can be realized by performing (i) a principal component analysis using conditional expectations of truncated and shifted intermolecular potential energy terms and (ii) a functional principal component analysis using products of intermolecular forces and conditional cumulative densities. We refer to these analyses as intermolecular perturbation analysis (IPA) and distance-dependent intermolecular perturbation analysis (DIPA), respectively. For comparison of the IPA and the DIPA, we apply them to the alanine dipeptide isomerization in explicit water. Although the first IPA principal components discriminate two states (the ? state and PPII (polyproline II) + ? states) for larger cutoff length, the separation between the PPII state and the ? state is unclear in the second IPA principal components. On the other hand, in the large cutoff value, DIPA eigenvalues converge faster than that for IPA and the top two DIPA principal components clearly identify the three states. By using the DIPA biplot, the contributions of the dipeptide-water interactions to each state are analyzed systematically. Since the DIPA improves the state identification and the convergence rate with retaining distance information, we conclude that the DIPA is a more practical method compared with the IPA. To test the feasibility of the DIPA for larger molecules, we apply the DIPA to the ten-residue chignolin folding in explicit water. The top three principal components identify the four states (native state, two misfolded states, and unfolded state) and their corresponding eigenfunctions identify important chignolin-water interactions to each state. Thus, the DIPA provides the practical method to identify conformational states and their corresponding important intermolecular interactions with distance information. PMID:21929141

Koyama, Yohei M; Kobayashi, Tetsuya J; Ueda, Hiroki R

2011-08-12

2

Intermolecular interaction in water hexamer.  

UK PubMed Central (United Kingdom)

The origin of the intermolecular interaction, especially the many-body interaction, in eight low-lying water hexamer structures (prism, cage, book-1, book-2, cyclic-chair, bag, cyclic-boat-1, and cyclic-boat-2) is unraveled using the localized molecular orbital energy decomposition analysis (LMO-EDA) method at the second-order Møller-Plesset perturbation (MP2) level of theory with a large basis set. It is found that the relative stabilities of these hexamer structures are determined by delicate balances between different types of interaction. According to LMO-EDA, electrostatic and exchange interactions are strictly pairwise additive. Dispersion interaction in these water hexamer structures is almost pairwise additive, with many-body effects varying from -0.13 to +0.05 kcal/mol. Repulsion interaction is roughly pairwise additive, with many-body effects varying from -0.84 to -0.62 kcal/mol. Polarization interaction is not pairwise additive, with many-body effects varying from -13.10 to -8.85 kcal/mol.

Chen Y; Li H

2010-11-01

3

Explicitly correlated intermolecular distances and interaction energies of hydrogen bonded complexes  

DEFF Research Database (Denmark)

We have optimized the lowest energy structures and calculated interaction energies for the H(2)O-H(2)O, H(2)O-H(2)S, H(2)O-NH(3), and H(2)O-PH(3) dimers with the recently developed explicitly correlated CCSD(T)-F12 methods and the associated VXZ-F12 (where X = D,T,Q) basis sets. For a given cardinal number, we find that the results obtained with the CCSD(T)-F12 methods are much closer to the CCSD(T) complete basis set limit than the conventional CCSD(T) results. In general we find that CCSD(T)-F12 results obtained with the VTZ-F12 basis set are better than the conventional CCSD(T) results obtained with an aug-cc-pV5Z basis set. We also investigate two ways to reduce the effects of basis set superposition error with conventional CCSD(T), namely, the popular counterpoise correction and limiting diffuse basis functions to the heavy atoms only. We find that for a given cardinal number, these selectively augmented correlation consistent basis sets yield results that are closer to the complete basis set limit than the corresponding fully augmented basis sets. Furthermore, we find that the difference between standard and counterpoise corrected interaction energies and intermolecular distances is reduced with the selectively augmented basis sets.

Lane, Joseph R; Kjærgaard, Henrik G

2009-01-01

4

Intermolecular interactions during ultrafiltration of pegylated proteins.  

UK PubMed Central (United Kingdom)

Recent studies have demonstrated the feasibility of using membrane ultrafiltration for the purification of pegylated proteins; however, the separations have all been performed at relatively low protein concentrations where intermolecular interactions are unimportant. The objective of this study was to examine the behavior at higher PEG concentrations and to develop an appropriate theoretical framework to describe the effects of intermolecular interactions. Ultrafiltration experiments were performed using pegylated ?-lactalbumin as a model protein with both neutral and charged composite regenerated cellulose membranes. The transmission of the pegylated ?-lactalbumin, PEG, and ?-lactalbumin all increase with increasing PEG concentration due to the increase in the solute partition coefficient arising from unfavorable intermolecular interactions in the bulk solution. The experimental results were in good agreement with a simple model that accounts for the change in Gibbs free energy associated with these intermolecular interactions, including the effects of concentration polarization on the local solute concentrations upstream of the membrane. These intermolecular interactions are shown to cause a greater than expected loss of pegylated product in a batch ultrafiltration system, and they alter the yield and purification factor that can be achieved during a diafiltration process to remove unreacted PEG.

Ruanjaikaen K; Zydney AL

2013-05-01

5

An Efficient Method to Evaluate Intermolecular Interaction Energies in Large Systems Using Overlapping Multicenter ONIOM and the Fragment Molecular Orbital Method.  

UK PubMed Central (United Kingdom)

We propose an approach based on the overlapping multicenter ONIOM to evaluate intermolecular interaction energies in large systems and demonstrate its accuracy on several representative systems in the complete basis set limit at the MP2 and CCSD(T) level of theory. In the application to the intermolecular interaction energy between insulin dimer and 4'-hydroxyacetanilide at the MP2/CBS level, we use the fragment molecular orbital method for the calculation of the entire complex assigned to the lowest layer in three-layer ONIOM. The developed method is shown to be efficient and accurate in the evaluation of the protein-ligand interaction energies.

Asada N; Fedorov DG; Kitaura K; Nakanishi I; Merz KM Jr

2012-09-01

6

Energy partitioning on intermolecular interactions: ab initio Monte Carlo study of water dimer  

Directory of Open Access Journals (Sweden)

Full Text Available Ab initio Monte Carlo computations were carried out on H2O dimer system. By introducing the energy partitioning scheme that we have developed recently, ab initio calculated H2O-H2O interaction can be analyzed from the viewpoint of atom-atom interaction. The electronic polarization caused by the interaction and its temperature dependence are also discussed. To our best knowledge, this is the first report on the thermal distribution of electronic distortion energy assigned to a molecule.

T.Amano; H.Sato; S.Sakaki

2007-01-01

7

Hyperspherical representation of potential energy surfaces: intermolecular interactions in tetra-atomic and penta-atomic systems  

International Nuclear Information System (INIS)

In this paper, we discuss the applications of spherical and hyperspherical harmonics expansions for potential energy surfaces for intermolecular interactions, focusing on four- and five-body problems. Case studies include diatomic-molecule-diatomic-molecule systems, floppy-molecule-rare-gas-atom cases, atom-triatomic, and nonlinear-molecule-linear-molecule systems. Among these systems, the important ones regarding water interaction with atoms and diatomic molecules are presented here to illustrate the use of spherical and hyperspherical coordinates and harmonics for weakly interacting systems. The interaction potential representation involves the distance between the centers of mass of the two molecules and a set of angles that defines the mutual orientation of the molecules, whose geometries are assumed to be either 'frozen' in their equilibrium configurations or to vary according to specific large-amplitude modes. The potential energy surfaces in the given examples of water-hydrogen, nitrogen and oxygen interactions are generated at the CCSD(T)/aug-cc-pVTZ level. Comparisons to the theoretical and experimental results of recent works for these and similar systems are presented.

2011-08-01

8

A retarded coupling approach to intermolecular interactions  

International Nuclear Information System (INIS)

[en] A wide range of physical phenomena such as optical binding and resonance energy transfer involve electronic coupling between adjacent molecules. A quantum electrodynamical description of these intermolecular interactions reveals the presence of retardation effects. The clarity of the procedure associated with the construction of the quantum amplitudes and the precision of the ensuing results for observable energies and rates are widely acknowledged. However, the length and complexity of the derivations involved in such quantum electrodynamical descriptions increase rapidly with the order of the process under study. Whether through the use of time-ordering approaches, or the more expedient state-sequence method, time-consuming calculations cannot usually be bypassed. A simple and succinct method is now presented, which provides for a direct and still entirely rigorous determination of the quantum electrodynamical amplitudes for processes of arbitrarily high order. Using the approach, new results for optical binding in two- and three-particle systems are secured and discussed.

2009-04-28

9

Perturbation theory approach to intermolecular interactions  

Energy Technology Data Exchange (ETDEWEB)

A general perturbation theory approach to intermolecular interactions is described. Various symmetry adapted perturbation theories can be shown to represent specific cases of this general approach and to differ in the degree of symmetry forcing on the unperturbed wavefunction. Numerical results for the He... He interaction are presented and discussed.

Jeziorski, B.; Kolos, W. (Warsaw Univ. (Poland))

1981-10-01

10

Intermolecular interactions for hydrocarbons on Wyodak coal  

Energy Technology Data Exchange (ETDEWEB)

Low rank coals are abundant in the U.S. Although their calorific values, mineral matter contents, and coking properties make them less desirable than higher rank coals in some industrial applications, low rank coals are used as feedstocks in coal liquefaction and are coprocessed with higher rank coals for other applications. The desire to use these coal resources more effectively would be aided by an understanding of the intermolecular and surface interactions at mineral-organic and organic-organic coal interfaces. Inverse gas chromatography has been used to quantify the intermolecular forces of Wyodak subbituminous coal.

Glass, A.S.; Stevenson, D.S. [Univ. of Dayton, OH (United States)

1996-12-31

11

Intermolecular interactions for hydrocarbons on Wyodak coal  

Energy Technology Data Exchange (ETDEWEB)

Adsorption enthalpies have been measured for hydrocarbons interacting with Wyodak coal surfaces. A different dependence of adsorption enthalpy on electronic polarizability has been found for saturated and for unsaturated hydrocarbons. Adsorption enthalpies for all 1-alkenes studied decreased by the same amount ({approximately}1.2 kcal/mol) when the coal was heated to 200{degrees}C, independent of the alkene`s size. This value (1.2 kcal/mol) represents the strength of the specific interaction between an alkene double bond and a carboxylate or ion-exchange site on the coal. Plots of adsorption enthalpy vs. electronic polarizability are steeper for unsaturated hydrocarbons (alkenes and benzene) than for saturated hydrocarbons (alkanes), demonstrating that alkenes and aromatics experience stronger nonspecific van der Waals forces than those experienced by alkanes. A dispersive surface energy of {approximately}20 mJ/m{sup 2} has been measured for Wyodak coal. This quantity depends on interactions with alkanes only. In contrast, data for unsaturated hydrocarbons demonstrate that components of the Wyodak surface produce complex intermolecular forces on this coal.

Glass, A.S.; Stevenson, D.S. [Univ. of Dayton, OH (United States)

1996-10-01

12

A CSOV study of the difference between HF and DFT intermolecular interaction energy values: the importance of the charge transfer contribution.  

UK PubMed Central (United Kingdom)

Intermolecular interaction energy decompositions using the Constrained Space Orbital Variation (CSOV) method are carried out at the Hartree-Fock level on the one hand and using DFT with usual GGA functionals on the other for a number of model complexes to analyze the role of electron correlation in the intermolecular stabilization energy. In addition to the overall stabilization, the results provide information on the variation, with respect to the computational level, of the different contributions to the interaction energy. The complexes studied are the water linear dimer, the N-methylformamide dimer, the nucleic acid base pairs, the benzene-methane and benzene-N2 van der Waals complexes, [Cu+ -(ImH)3]2, where "ImH" stands for the Imidazole ligand, and ImH-Zn++. The variation of the frozen core energy (the sum of the intermolecular electrostatic energy and the Pauli repulsion energy) calculated from the unperturbed orbitals of the interacting entities indicates that the intramolecular correlation contributions can be stabilizing as well as destabilizing, and that general trends can be derived from the results obtained using usual density functionals. The most important difference between the values obtained from HF and DFT computations concerns the charge transfer contribution, which, in most cases, undergoes the largest increase. The physical meaning of these results is discussed. The present work gives reference calculations that might be used to parametrize new correlated molecular mechanics potentials.

Piquemal JP; Marquez A; Parisel O; Giessner-Prettre C

2005-07-01

13

A CSOV study of the difference between HF and DFT intermolecular interaction energy values: the importance of the charge transfer contribution.  

Science.gov (United States)

Intermolecular interaction energy decompositions using the Constrained Space Orbital Variation (CSOV) method are carried out at the Hartree-Fock level on the one hand and using DFT with usual GGA functionals on the other for a number of model complexes to analyze the role of electron correlation in the intermolecular stabilization energy. In addition to the overall stabilization, the results provide information on the variation, with respect to the computational level, of the different contributions to the interaction energy. The complexes studied are the water linear dimer, the N-methylformamide dimer, the nucleic acid base pairs, the benzene-methane and benzene-N2 van der Waals complexes, [Cu+ -(ImH)3]2, where "ImH" stands for the Imidazole ligand, and ImH-Zn++. The variation of the frozen core energy (the sum of the intermolecular electrostatic energy and the Pauli repulsion energy) calculated from the unperturbed orbitals of the interacting entities indicates that the intramolecular correlation contributions can be stabilizing as well as destabilizing, and that general trends can be derived from the results obtained using usual density functionals. The most important difference between the values obtained from HF and DFT computations concerns the charge transfer contribution, which, in most cases, undergoes the largest increase. The physical meaning of these results is discussed. The present work gives reference calculations that might be used to parametrize new correlated molecular mechanics potentials. PMID:15898112

Piquemal, Jean-Philip; Marquez, Antonio; Parisel, Olivier; Giessner-Prettre, Claude

2005-07-30

14

The Nature of Intermolecular Interactions Between Aromatic Amino Acid Residues  

Energy Technology Data Exchange (ETDEWEB)

The nature of intermolecular interactions between aromatic amino acid residues has been investigated by a combination of molecular dynamics and ab initio methods. The potential energy surface of various interacting pairs, including tryptophan, phenilalanine, and tyrosine, was scanned for determining all the relevant local minima by a combined molecular dynamics and conjugate gradient methodology with the AMBER force field. For each of these minima, single-point correlated ab initio calculations of the binding energy were performed. The agreement between empirical force field and ab initio binding energies of the minimum energy structures is excellent. Aromatic-aromatic interactions can be rationalized on the basis of electrostatic and van der Waals interactions, whereas charge transfer or polarization phenomena are small for all intermolecular complexes and, particularly, for stacked structures.

Gervasio, Francesco; Chelli, Riccardo; Procacci, Piero; Schettino, Vincenzo

2002-05-01

15

Effects of Aromatic Trifluoromethylation, Fluorination, and Methylation on Intermolecular ?-? Interactions.  

Science.gov (United States)

Marcus theory states that the rate of charge transfer is directly proportional to the amount of intermolecular orbital overlap. Theoretically optimizing the electronic coupling through the orientation and distance which both can increase the frontier orbital overlap between molecules is an attractive route to potentially provide theoretical insight for discovering new high performance semiconductor materials. To investigate how these parameters qualitatively affect charge transfer of model systems, unconstrained dimer optimizations with MP2 and dispersion-corrected DFT methods were used to probe the ?-? interactions of methylated, fluorinated, and trifluoromethylated benzene, pyridine, and bipyridine dimers. These systems can serve as simplified models representing weak noncovalent interactions in organic semiconductor materials. Enhanced intermolecular interaction energies, reduced ?-? distances, and more favorable cofacial orientations were found with the trifluoromethylated dimers compared to fluorinated and methylated dimers studied. Similar effects were found with donor-acceptor pairs that represent organic p-n heterojunction systems. These enhanced ?-? interactions are likely caused by increased molecular quadrupole moment and dispersion interaction associated with trifluoromethylation. This computational study illustrates the strong potential of trifluoromethylation and, possibly perfluoroalkylation of acenes and heteroacenes, leading qualitatively to enhanced electron transfer through better ?-? stacked structures, making them viable candidates for use as n-type organic semiconductor materials. The findings also provide insight for fundamental interactions between drug molecules that include fluorinated and trimethylfluorinated aromatics binding to protein receptors. PMID:23906416

Mottishaw, Jeffery D; Sun, Haoran

2013-08-02

16

Effects of Aromatic Trifluoromethylation, Fluorination, and Methylation on Intermolecular ?-? Interactions.  

UK PubMed Central (United Kingdom)

Marcus theory states that the rate of charge transfer is directly proportional to the amount of intermolecular orbital overlap. Theoretically optimizing the electronic coupling through the orientation and distance which both can increase the frontier orbital overlap between molecules is an attractive route to potentially provide theoretical insight for discovering new high performance semiconductor materials. To investigate how these parameters qualitatively affect charge transfer of model systems, unconstrained dimer optimizations with MP2 and dispersion-corrected DFT methods were used to probe the ?-? interactions of methylated, fluorinated, and trifluoromethylated benzene, pyridine, and bipyridine dimers. These systems can serve as simplified models representing weak noncovalent interactions in organic semiconductor materials. Enhanced intermolecular interaction energies, reduced ?-? distances, and more favorable cofacial orientations were found with the trifluoromethylated dimers compared to fluorinated and methylated dimers studied. Similar effects were found with donor-acceptor pairs that represent organic p-n heterojunction systems. These enhanced ?-? interactions are likely caused by increased molecular quadrupole moment and dispersion interaction associated with trifluoromethylation. This computational study illustrates the strong potential of trifluoromethylation and, possibly perfluoroalkylation of acenes and heteroacenes, leading qualitatively to enhanced electron transfer through better ?-? stacked structures, making them viable candidates for use as n-type organic semiconductor materials. The findings also provide insight for fundamental interactions between drug molecules that include fluorinated and trimethylfluorinated aromatics binding to protein receptors.

Mottishaw JD; Sun H

2013-08-01

17

Accurate Intermolecular Interactions at Dramatically Reduced Cost and a Many-Body Energy Decomposition Scheme for XPol+SAPT  

Science.gov (United States)

An efficient, monomer-based electronic structure method is introduced for computing non-covalent interactions in molecular and ionic clusters. It builds upon our ``explicit polarization" (XPol) with pairwise-additive symmetry-adapted perturbation theory (SAPT) using the Kohn-Sham (KS) version of SAPT, but replaces the problematic and expensive sum-over-states dispersion terms with empirical potentials. This modification reduces the scaling from {O}(N^5) to {O}(N^3) and also facilitates the use of Kohn-Sham density functional theory (KS-DFT) as a low-cost means to capture intramolecular electron correlation. Accurate binding energies are obtained for benchmark databases of dimer binding energies, and potential energy curves are also captured accurately, for a variety of challenging systems. As compared to traditional DFT-SAPT or SAPT(DFT) methods, it removes the limitation to dimers and extends SAPT-based methodology to many-body systems. For many-body systems such as water clusters and halide-water cluster anions, the new method is superior to established density-functional methods for non-covalent interactions. We suggest that using different asymptotic corrections for different monomers is necessary to get good binding energies in general, as DFT-SAPT or SAPT(DFT), especially for hydrogen-bonded complexes. We also introduce a decomposition scheme for the interaction energy that extends traditional SAPT energy decomposition analysis to systems containing more than two monomers, and we find that the various energy components (electrostatic, exchange, induction, and dispersion) are in very good agreement with high-level SAPT benchmarks for dimers. For (H_2O)_6, the many-body contribution to the interaction energy agrees well with that obtained from traditional Kitaura-Morokuma energy decomposition analysis.

Lao, Ka Un; Herbert, John M.

2013-06-01

18

Intermolecular interactions and the thermodynamic properties of supercritical fluids  

Science.gov (United States)

The role of different contributions to intermolecular interactions on the thermodynamic properties of supercritical fluids is investigated. Molecular dynamics simulation results are reported for the energy, pressure, thermal pressure coefficient, thermal expansion coefficient, isothermal and adiabatic compressibilities, isobaric and isochoric heat capacities, Joule-Thomson coefficient, and speed of sound of fluids interacting via both the Lennard-Jones and Weeks-Chandler-Andersen potentials. These properties were obtained for a wide range of temperatures, pressures, and densities. For each thermodynamic property, an excess value is determined to distinguish between attraction and repulsion. It is found that the contributions of intermolecular interactions have varying effects depending on the thermodynamic property. The maxima exhibited by the isochoric and isobaric heat capacities, isothermal compressibilities, and thermal expansion coefficient are attributed to interactions in the Lennard-Jones well. Repulsion is required to obtain physically realistic speeds of sound and both repulsion and attraction are necessary to observe a Joule-Thomson inversion curve. Significantly, both maxima and minima are observed for the isobaric and isochoric heat capacities of the supercritical Lennard-Jones fluid. It is postulated that the loci of these maxima and minima converge to a common point via the same power law relationship as the phase coexistence curve with an exponent of ? = 0.32. This provides an explanation for the terminal isobaric heat capacity maximum in supercritical fluids.

Yigzawe, Tesfaye M.; Sadus, Richard J.

2013-05-01

19

Intermolecular interactions and the thermodynamic properties of supercritical fluids.  

UK PubMed Central (United Kingdom)

The role of different contributions to intermolecular interactions on the thermodynamic properties of supercritical fluids is investigated. Molecular dynamics simulation results are reported for the energy, pressure, thermal pressure coefficient, thermal expansion coefficient, isothermal and adiabatic compressibilities, isobaric and isochoric heat capacities, Joule-Thomson coefficient, and speed of sound of fluids interacting via both the Lennard-Jones and Weeks-Chandler-Andersen potentials. These properties were obtained for a wide range of temperatures, pressures, and densities. For each thermodynamic property, an excess value is determined to distinguish between attraction and repulsion. It is found that the contributions of intermolecular interactions have varying effects depending on the thermodynamic property. The maxima exhibited by the isochoric and isobaric heat capacities, isothermal compressibilities, and thermal expansion coefficient are attributed to interactions in the Lennard-Jones well. Repulsion is required to obtain physically realistic speeds of sound and both repulsion and attraction are necessary to observe a Joule-Thomson inversion curve. Significantly, both maxima and minima are observed for the isobaric and isochoric heat capacities of the supercritical Lennard-Jones fluid. It is postulated that the loci of these maxima and minima converge to a common point via the same power law relationship as the phase coexistence curve with an exponent of ? = 0.32. This provides an explanation for the terminal isobaric heat capacity maximum in supercritical fluids.

Yigzawe TM; Sadus RJ

2013-05-01

20

Accurate calculations of intermolecular interaction energies using explicitly correlated coupled cluster wave functions and a dispersion-weighted MP2 method.  

UK PubMed Central (United Kingdom)

Explicitly correlated coupled-cluster calculations of intermolecular interaction energies for the S22 benchmark set of Jurecka, Sponer, Cerny, and Hobza (Chem. Phys. Phys. Chem. 2006, 8, 1985) are presented. Results obtained with the recently proposed CCSD(T)-F12a method and augmented double-zeta basis sets are found to be in very close agreement with basis set extrapolated conventional CCSD(T) results. Furthermore, we propose a dispersion-weighted MP2 (DW-MP2) approximation that combines the good accuracy of MP2 for complexes with predominately electrostatic bonding and SCS-MP2 for dispersion-dominated ones. The MP2-F12 and SCS-MP2-F12 correlation energies are weighted by a switching function that depends on the relative HF and correlation contributions to the interaction energy. For the S22 set, this yields a mean absolute deviation of 0.2 kcal/mol from the CCSD(T)-F12a results. The method, which allows obtaining accurate results at low cost, is also tested for a number of dimers that are not in the training set.

Marchetti O; Werner HJ

2009-10-01

 
 
 
 
21

Accurate Calculations of Intermolecular Interaction Energies Using Explicitly Correlated Coupled Cluster Wave Functions and a Dispersion-Weighted MP2 Method  

Science.gov (United States)

Explicitly correlated coupled-cluster calculations of intermolecular interaction energies for the S22 benchmark set of Jure?ka, \\vsponer, ?erný, and Hobza (Chem. Phys. Phys. Chem. 2006, 8, 1985) are presented. Results obtained with the recently proposed CCSD(T)-F12a method and augmented double-? basis sets are found to be in very close agreement with basis set extrapolated conventional CCSD(T) results. Furthermore, we propose a dispersion-weighted MP2 (DW-MP2) approximation that combines the good accuracy of MP2 for complexes with predominately electrostatic bonding and SCS-MP2 for dispersion-dominated ones. The MP2-F12 and SCS-MP2-F12 correlation energies are weighted by a switching function that depends on the relative HF and correlation contributions to the interaction energy. For the S22 set, this yields a mean absolute deviation of 0.2 kcal/mol from the CCSD(T)-F12a results. The method, which allows obtaining accurate results at low cost, is also tested for a number of dimers that are not in the training set.

Marchetti, Oliver; Werner, Hans-Joachim

2009-10-01

22

Intermolecular interactions and unexpected isostructurality in the crystal structures of the dichlorobenzaldehyde isomers  

DEFF Research Database (Denmark)

The crystal structures of the six dichlorobenzaldehyde isomers, four of them newly determined, are analyzed in terms of the geometry and energies of their intermolecular interactions, quantified using the semi-classical density sums (SCDS-PIXEL) method. A consistent feature in all six structures is molecular stacks propagating along a short crystallographic axis of ca 3.8?Å. The stacks have a closely comparable geometry in each isomer, but the interaction energies between stacked molecules are variable on account of the differing relative positions of the Cl substituents. In the majority of the isomers the stacking interactions are the most stabilizing in the structure. Exceptions are the 2,4- and 3,5-isomers, where more stabilizing interactions are made between stacks. In general, the most stabilizing non-stacking intermolecular interactions in the structures are those involving C-H...O contacts. Observed motifs based on Cl...Cl interactions appear to be largely imposed by the constraints of other more stabilizing intermolecular interactions. The isomeric series displays the following noteworthy features: (i) the 2,3- and 2,6-isomers are isostructural despite having different orientations of the Cl and aldehyde functionalities; (ii) the 2,5-isomer exhibits whole-molecule disorder; (iii) the 2,5- and 3,5-isomers have more than one molecule in the crystallographic asymmetric unit (Z' > 1). These features in particular are considered on the basis of the intermolecular interaction energies.

Solanko, Katarzyna; Bond, Andrew D

2011-01-01

23

Computing free energy hypersurfaces for anisotropic intermolecular associations.  

UK PubMed Central (United Kingdom)

We previously used an adaptive reaction coordinate force biasing method for calculating the free energy of conformation (Naidoo and Brady, J Am Chem Soc 1999, 121, 2244) and chemical reactions (Rajamani et al., J Comput Chem 2003, 24, 1775) amongst others. Here, we describe a generalized version able to produce free energies in multiple dimensions, descriptively named the free energies from adaptive reaction coordinate forces method. To illustrate it, we describe how we calculate a multidimensional intermolecular orientational free energy, which can be used to investigate complex systems such as protein conformation and liquids. This multidimensional intermolecular free energy W(r, theta(1), theta(2), phi) provides a measure of orientationally dependent interactions that are appropriate for applications in systems that inherently have molecular anisotropic features. It is a highly informative free energy volume, which can be used to parameterize key terms such as the Gay-Berne intermolecular potential in coarse grain simulations. To demonstrate the value of the information gained from the W(r, theta(1), theta(2), phi) hypersurfaces we calculated them for TIP3P, TIP4P, and TIP5P dimer water models in vacuum. A comparison with a commonly used one-dimensional distance free energy profile is made to illustrate the significant increase in configurational information. The W(r) plots show little difference between the three models while the W(r, theta(1), theta(2), phi) hypersurfaces reveal the underlying energetic reasons why these potentials reproduce tetrahedrality in the condensed phase so differently from each.

Strümpfer J; Naidoo KJ

2010-01-01

24

Intermolecular interactions of reduced nicotinamide adenine dinucleotide (NADH) in solution  

Science.gov (United States)

Nicotinamide adenine dinucleotide (NAD^+/NADH) is a coenzyme involved in cellular respiration as an electron transporter. In aqueous solution, the molecule exhibits a folding transition characterized by the stacking of its aromatic moieties. A transition to an unfolded conformation is possible using chemical denaturants like methanol. Because the reduced NADH form is fluorescent, the folding transition can be monitored using fluorescence spectroscopy, e.g., via a blue-shift in the UV-excited emission peak upon methanol unfolding. Here we present evidence of interactions between NADH molecules in solution. We measure the excited-state emission from NADH at various concentrations (1-100 ?M in MOPS buffer, pH 7.5; 337-nm wavelength excitation). Unlike for the folded form, the emission peak wavelength of the unfolded form is concentration dependent, exhibiting a red-shift with higher NADH concentration, suggesting the presence of intermolecular interactions. An understanding of NADH spectra in solution would assist in interpreting intercellular NADH measurements used for the in vivo monitoring cellular energy metabolism.

Jasensky, Joshua; Junaid Farooqi, M.; Urayama, Paul

2008-10-01

25

Tuning intermolecular non-covalent interactions for nanowires of organic semiconductors  

Science.gov (United States)

Anthracene and its derivatives are used to demonstrate a simple way to cast assemble nanowires of organic semiconductors with tuning of intermolecular non-covalent interactions by molecular design. The tuning of intermolecular interactions could be achieved by (i) decreasing intermolecular hydrophobic interactions by linking hydrophilic side chains to anthracene rings, (ii) increasing intermolecular interaction for self-assembly with the assistance of hydrogen bonds, and (iii) enhancing molecular ?-? interaction by increasing the conjugated dimension of the compounds.

Jiang, Lang; Gao, Jianhua; Fu, Yanyan; Dong, Huanli; Zhao, Huaping; Li, Hongxiang; Tang, Qingxin; Chen, Keqiu; Hu, Wenping

2010-12-01

26

Strong intermolecular interactions shaping a small piano-stool complex.  

Science.gov (United States)

The smallest piano stool [CpNa(NH3 )3 ] is not a stand-alone unit in the solid state but is largely shaped by strong intermolecular N?H???? interactions. Small but important structural features, such as the bending of the C?H bonds inwards to the sodium atom that was confirmed by experimental charge density investigations, could only be reproduced by quantum mechanical calculations that included a lattice of more than 300 units. PMID:23929586

Hey, Jakob; Andrada, Diego M; Michel, Reent; Mata, Ricardo A; Stalke, Dietmar

2013-08-08

27

Cation-? Interactions: Accurate Intermolecular Potential from Symmetry-Adapted Perturbation Theory.  

UK PubMed Central (United Kingdom)

Symmetry-adapted perturbation theory (SAPT) is used to decompose the total intermolecular interaction energy between the ammonium cation and a benzene molecule into four physically motivated individual contributions: electrostatics, exchange, dispersion, and induction. Based on this rigorous decomposition, it is shown unambiguously that both the electrostatic and the induction energy components contribute almost equally to the attractive forces stabilizing the dimer with a nonnegligible contribution coming from the dispersion term. A polarizable potential model for the interaction of ammonium cation with benzene is parametrized by fitting these four energy components separately using the functional forms of the AMOEBA force field augmented with the missing charge penetration energy term calculated as a sum over pairwise electrostatic energies between spherical atoms. It is shown that the proposed model is able to produce accurate intermolecular interaction energies as compared to ab initio results, thus avoiding error compensation to a large extent.

Ansorg K; Tafipolsky M; Engels B

2013-09-01

28

Intermolecular forces and nonbonded interactions: Superoperator nonlinear time-dependent density-functional-theory response approach  

International Nuclear Information System (INIS)

Electrostatic and dispersive interactions of polarizable molecules are expressed in terms of generalized (nonretarded) charge-density response functions of the isolated molecules, which in turn are expanded using the collective electronic oscillator (CEO) eigenmodes of linearized time-dependent density-functional theory. Closed expressions for the intermolecular energy are derived to sixth order in charge fluctuation amplitudes.

2004-01-01

29

He-, Ne-, and Ar-Phosgene Intermolecular Potential Energy Surfaces.  

UK PubMed Central (United Kingdom)

Using the CCSD(T) model, we evaluated the intermolecular potential energy surfaces of the He-, Ne-, and Ar-phosgene complexes. We considered a representative number of intermolecular geometries for which we calculated the corresponding interaction energies with the augmented (He complex) and double augmented (Ne and Ar complexes) correlation-consistent polarized valence triple-? basis sets extended with a set of 3s3p2d1f1g midbond functions. These basis sets were selected after systematic basis set studies carried out at geometries close to those of the surface minima. The He-, Ne-, and Ar-phosgene surfaces were found to have absolute minima of -72.1, -140.4, and -326.6 cm(-1) at distances between the rare-gas atom and the phosgene center of mass of 3.184, 3.254, and 3.516 Å, respectively. The potentials were further used in the evaluation of rovibrational states and the rotational constants of the complexes, providing valuable results for future experimental investigations. Comparing our results to those previously available for other phosgene complexes, we suggest that the results for Cl2-phosgene should be revised.

Munteanu CR; Henriksen C; Felker PM; Fernández B

2013-04-01

30

Morphology development in polymer blends exhibiting strong intermolecular interactions  

Energy Technology Data Exchange (ETDEWEB)

He et al. measured the spinodal decomposition (SD) kinetics of a blend of poly(butyl methacrylate) with a polystyrene modified with 1.5 mol% of a hydroxy-containing comonomer that exhibited intermolecular hydrogen bonding, who studied blends. For small excursions into the spinodal region, multiple structures developed in the blend, which suggested that multiple mechanisms may be involved in the phase separation process. For most cases, however, the kinetics of phase separation followed Cahn-Hilliard theory in the early stage of spinodal decomposition and a self-similar mechanism in the later stages, similar to non-associating polymer blends such as PS/PVME. The failure to observe an effect of a specific intermolecular interaction on SD kinetics may be a consequence of the low concentration of hydroxyl groups on the polystyrene, ca. five per chain, and the weakening of the hydrogen bond at the elevated temperatures used to study phase separation where the crosslink effect of hydrogen bonding may not be significant. At elevated temperatures, the association-dissociation equilibrium shifts towards non-associated hydroxyl and ester groups. An objective of the present study was to use a polymer blend having a relatively higher degree of intermolecular association at the phase separation temperature and to investigate how physical crosslinks affect the phase separation kinetics accompanying spinodal decomposition.

Weiss, R.A.; Feng, Y. [Univ. of Conneticut, Storrs, CT (United States); Han, C.C.; Karim, A. [National Institute of Standards and Technology, Gaithersburg, MD (United States)

1996-12-31

31

Weak intermolecular interactions in gas-phase NMR  

CERN Document Server

Gas-phase NMR spectra demonstrating the effect of weak intermolecular forces on the NMR shielding constants of the interacting species are reported. We analyse the interaction of the molecular hydrogen isotopomers with He, Ne, and Ar, and the interaction in the He-CO_2 dimer. The same effects are studied for all these systems in the ab initio calculations. The comparison of the experimental and computed shielding constants is shown to depend strongly on the treatment of the bulk susceptibility effects, which determine in practice the pressure dependence of the experimental values. Best agreement of the results is obtained when the bulk susceptibility correction in rare gas solvents is evaluated from the analysis of the He-rare gas interactions, and when the shielding of deuterium in D_2-rare gas systems is considered.

Garbacz, Piotr; Jackowski, Karol; Moszynski, Robert; Jaszunski, Michal

2011-01-01

32

Weak intermolecular interactions in gas-phase nuclear magnetic resonance.  

Science.gov (United States)

Gas-phase nuclear magnetic resonance (NMR) spectra demonstrating the effect of weak intermolecular forces on the NMR shielding constants of the interacting species are reported. We analyse the interaction of the molecular hydrogen isotopomers with He, Ne, and Ar, and the interaction in the He-CO(2) dimer. The same effects are studied for all these systems in the ab initio calculations. The comparison of the experimental and computed shielding constants is shown to depend strongly on the treatment of the bulk susceptibility effects, which determine in practice the pressure dependence of the experimental values. Best agreement of the results is obtained when the bulk susceptibility correction in rare gas solvents is evaluated from the analysis of the He-rare gas interactions, and when the shielding of deuterium in D(2)-rare gas systems is considered. PMID:21895188

Garbacz, Piotr; Piszczatowski, Konrad; Jackowski, Karol; Moszynski, Robert; Jaszu?ski, Micha?

2011-08-28

33

Weak intermolecular interactions in gas-phase nuclear magnetic resonance.  

UK PubMed Central (United Kingdom)

Gas-phase nuclear magnetic resonance (NMR) spectra demonstrating the effect of weak intermolecular forces on the NMR shielding constants of the interacting species are reported. We analyse the interaction of the molecular hydrogen isotopomers with He, Ne, and Ar, and the interaction in the He-CO(2) dimer. The same effects are studied for all these systems in the ab initio calculations. The comparison of the experimental and computed shielding constants is shown to depend strongly on the treatment of the bulk susceptibility effects, which determine in practice the pressure dependence of the experimental values. Best agreement of the results is obtained when the bulk susceptibility correction in rare gas solvents is evaluated from the analysis of the He-rare gas interactions, and when the shielding of deuterium in D(2)-rare gas systems is considered.

Garbacz P; Piszczatowski K; Jackowski K; Moszynski R; Jaszu?ski M

2011-08-01

34

Towards the biaxial nematic phase via specific intermolecular interactions  

CERN Document Server

The work described in this thesis has been focussed on the search of an elusive liquid crystal phase, known as the biaxial nematic phase. Indeed, despite nearly thirty years of intense research, no-one has been able to characterise unambiguously a biaxial nematic phase in a low-molar-mass thermotropic system. Our research is based on the concept of molecular biaxiality as distinct from shape biaxiality. Thus, we are seeking to design palladium complexes where specific intermolecular interactions could exist. Therefore, a few original synthetic strategies were developed to tackle the challenge of discovering the biaxial nematic phase

Omnes, L

2001-01-01

35

Atom-atom partitioning of intramolecular and intermolecular Coulomb energy  

Science.gov (United States)

An atom-atom partitioning of the (super)molecular Coulomb energy is proposed on the basis of the topological partitioning of the electron density. Atom-atom contributions to the molecular intra- and intermolecular Coulomb energy are computed exactly, i.e., via a double integration over atomic basins, and by means of the spherical tensor multipole expansion, up to rank L=lA+lB+1=5. The convergence of the multipole expansion is able to reproduce the exact interaction energy with an accuracy of 0.1-2.3 kJ/mol at L=5 for atom pairs, each atom belonging to a different molecule constituting a van der Waals complex, and for nonbonded atom-atom interactions in single molecules. The atom-atom contributions do not show a significant basis set dependence (3%) provided electron correlation and polarization basis functions are included. The proposed atom-atom Coulomb interaction energy can be used both with post-Hartree-Fock wave functions and experimental charge densities in principle. The Coulomb interaction energy between two molecules in a van der Waals complex can be computed by summing the additive atom-atom contributions between the molecules. Our method is able to extract from the supermolecule wave function an estimate of the molecular interaction energy in a complex, without invoking the reference state of free noninteracting molecules. We provide computational details of this method and apply it to (C2H2)2; (HF)2; (H2O)2; butane; 1,3,5-hexatriene; acrolein and urocanic acid, thereby covering a cross section of hydrogen bonds, and covalent bonds with and without charge transfer.

Popelier, P. L. A.; Kosov, D. S.

2001-04-01

36

Infrared absorption by H2-Ar collisional complexes and the anisotropy of the intermolecular interaction potential  

International Nuclear Information System (INIS)

H2-Ar scattering processes in the presence of a weak photon field are considered. Calculations are based on an accurate ab initio interaction-induced electric dipole surface and an anisotropic intermolecular potential energy surface. The close-coupled scheme of integrating the Schroedinger equation is employed to calculate the rototranslational absorption spectrum of H2-Ar pairs in the far-infrared region of the electromagnetic spectrum. The results are compared with previous work where the weak anisotropy of the intermolecular interaction potential was suppressed. Under the conditions considered, accounting for the anisotropy modifies the rototranslational absorption spectrum discernibly, but only at some frequency bands where the corrections are negative, typically below 10%.

2006-01-01

37

The water-nitric oxide intermolecular potential-energy surface revisited.  

UK PubMed Central (United Kingdom)

The two lowest energy intermolecular potential-energy surfaces (IPESs) of the water-nitric oxide complex are evaluated using the spin-restricted coupled-cluster R-CCSD(T) model and the augmented correlation-consistent polarized-valence triple-zeta basis set extended with a set of the 3s3p2d1f1g midbond functions. A detailed characterization of the IPESs for both the (2)A(') and (2)A(") electronic states in the C(s)-symmetry configurations of the complex is performed. The global minimum for the (2)A(') state represented by the lowest energy of -461.8 cm(-1) is deeper than the global minimum in the (2)A(") state with an energy of -435.2 cm(-1). To explore the physics of the interaction an open-shell implementation of the symmetry-adapted perturbation theory is employed and the results are analyzed as a function of the intermolecular parameters. The electrostatic term shows the strongest geometric anisotropy, while the exchange, induction, and dispersion contributions mostly depend on the intermolecular distance. The energy separation between the (2)A(') and (2)A(") states is largely dominated by electrostatic contribution for long intermolecular distances. In the region of short intermolecular distances the exchange part is as important as the electrostatic one and the induction and dispersion effects are also substantial.

Cybulski H; Zuchowski PS; Fernández B; Sadlej J

2009-03-01

38

Intermolecular diatomic energies of a hydrogen dimer with non-Born-Oppenheimer nuclear and electron wave packets  

Science.gov (United States)

We have developed an efficient theoretical framework of a non-Born-Oppenheimer (non-BO) nuclear and electron wave packet (NWP and EWP) method and applied it to intra- and intermolecular energies of a hydrogen dimer. The energy surface functions were derived at low computational cost. In contrast with the ordinary BO nuclear quantization on a given energy surface that reduces the effective barrier, non-trivial non-BO interactions between the EWPs and NWPs resulted in increases of intermolecular rotational and translational barriers. A direct comparison demonstrated that the non-BO effect on the intermolecular energy is significant.

Hyeon-Deuk, Kim; Ando, Koji

2012-04-01

39

The p-difluorobenzene-argon S1 excited state intermolecular potential energy surface.  

UK PubMed Central (United Kingdom)

The first excited state (S1) intermolecular potential energy surface for the p-difluorobenzene-Ar van der Waals complex is evaluated using the coupled-cluster method and the augmented correlation consistent polarized valence double-zeta basis set extended with a set of 3s3p2d1f1g midbond functions. In order to calculate the S1 interaction energies we use the ground state surface evaluated with the same basis set and the coupled-cluster singles and doubles [CCSD] including connected triple excitations [CCSD(T)] model, and interaction and excitation energies evaluated at the CCSD level. The surface minima are characterized by the Ar atom located above and below the p-difluorobenzene center of mass at a distance of 3.4736 A. The corresponding interaction energy is -435.233 cm-1. The surface is used in the evaluation of the intermolecular level structure of the complex.

Fajín JL; Fernandez B; Felker PM

2006-12-01

40

New bases for the evaluation of interaction energies: An ab initio study of the CO-Ne van der Waals complex intermolecular potential and ro-vibrational spectrum  

International Nuclear Information System (INIS)

Graphical abstract: CO-Ne IPES. Highlights: ? From the LPol, MLPol, and aug-pc-2 bases we obtained new bases for the evaluation of CO-Ne interaction energies. ? We checked the bases on the evaluation of the rovibrational spectrum. ? The results were satisfactory, being the new bases more efficient than those previously available. - Abstract: Recently we have derived new efficient basis sets for the evaluation of interaction energies in the X-Y (X, Y = He, Ne, Ar) van der Waals complexes. Here we extend the study to the CO-Ne complex. For this, we start with a systematic basis set study, where the LPol, MLPol and Jensen's aug-pc-2 basis sets are considered as starting point (for the Ne atom LPol bases are developed). As reference we take interaction energy results obtained with Dunning's augmented correlation consistent polarized valence basis sets. In all cases we test extensions with different sets of midbond functions. With the selected bases we evaluate CCSD(T) interaction potentials, and to check the potentials further, we obtain the ro-vibrational spectrum of the complex. The results are compared to the available experimental data.

2011-07-28

 
 
 
 
41

p-Difluorobenzene-argon ground state intermolecular potential energy surface.  

UK PubMed Central (United Kingdom)

The ground state intermolecular potential energy surface for the p-difluorobenzene-Ar van der Waals complex is evaluated using the coupled cluster singles and doubles including connected triple excitations [CCSD(T)] model and the augmented correlation consistent polarized valence double-zeta basis set extended with a set of 3s3p2d1f1g midbond functions. The surface minima are characterized by the Ar atom located above and below the difluorobenzene center of mass at a distance of 3.5290 A. The corresponding binding energy is -398.856 cm(-1). The surface is used in the evaluation of the intermolecular level structure of the complex. The results clearly improve previously available data and show the importance of using a good correlation method and basis set when dealing with van der Waals complexes.

Cagide Fajín JL; Fernández B; Felker PM

2005-12-01

42

Symmetry-adapted double-perturbation analysis of intramolecular correlation effects in week intermolecular interactions  

International Nuclear Information System (INIS)

A general symmetry-adapted double-perturbation procedure for treating intramolecular or intra-atomic correlation in the theory of intermolecular forces is developed. The method was applied to the interaction of two helium atoms. The calculations were made employing the Moeller-Plesset partition of atomic hamiltonians and using a large basis set of explicitly correlated gaussian wave functions. At the van der Waals minimum the total intra-atomic correlation contribution to the interaction energy amounts to - 2.9 K and is mainly due to the change of the dispersion energy. The total interaction energy is equal to -10.3 K being in agreement with the latest experimental result of Burgmans, Farrar and Lee. (author)

1979-01-01

43

Solar energy storage with intermolecular addition compounds: Final report  

Energy Technology Data Exchange (ETDEWEB)

The objective of the research has been to search for intermolecular addition compounds which may serve as energy storage systems, and to characterize (especially with respect to energy changes) any system that showed promise for use in solar energy storage. Inasmuch as water is cheap, non-toxic, non-inflammable, and has desirable thermal properties, it is a natural choice for one component of a storage system, and was used as a common component in all the systems studied. A wide variety of substances have been tried as the second component including alcohols, amines, carboxylic acids, ethers, and esthers.

Goates, J.R.; Ott, J.B.

1982-03-18

44

The role of long-range intermolecular interactions in discovery of new drugs.  

UK PubMed Central (United Kingdom)

Introduction: Long-range intermolecular interactions (interactions at distances between 100 and 1000 Å) play an important role in the interaction between drugs and therapeutic targets, and design techniques based on this concept could significantly improve and accelerate new drug discovery. Understanding these long-range intermolecular interactions will also help further our understanding of the molecular mechanisms and the underlying basic biological processes. Areas covered: This article looks at the physical bases of long-range intermolecular interactions in biological systems with a brief review of the literature data to support this concept. The article also gives some examples of techniques used in drug discovery that were based on the long-range intermolecular interaction concept. Expert opinion: The electron-ion interaction potential (EIIP) and average quasivalence number (AQVN) concepts shed new light on the role of long-range intermolecular interactions in biological systems. Further research of physicochemical mechanisms underlying long-range interactions between biological molecules is necessary for a better understanding of the basic biological processes. The addition of the computer-aided design techniques based on the EIIP/AQVN concept to the research and development will lead not only to a significant reduction in cost but also to an acceleration in the development of new drugs.

Veljkovic N; Glisic S; Perovic V; Veljkovic V

2011-12-01

45

MODELS OF AMPHOTERICIN MEMBRANE CHANNEL BASED ON CONCERTED INTERMOLECULAR =C-H…O INTERACTIONS  

Directory of Open Access Journals (Sweden)

Full Text Available To study the possibility for amphotericin to form membrane channel via intermolecular interactions mimicing the association mode of polyene macrolides in crystal structures we have built two channel models in vacuo: amphotericin B octamer and hexamer. The octamer model does not reproduce the concerted weak =C-H…O intermolecular interactions within the whole aggregate structure and has too large pore diameter. For hexamer model, the pore diameter is within experimental estimates. The hexamer model rather well reproduces characteristic features of a channel with such concerted weak interactions: association mode, H-bonding pattern within the whole assembly and accessibility of polyene hydroxyl groups for hydrophyllic interactions in the pore.

Lisnyak Yu. V

2012-01-01

46

Reversible electron-induced cis-trans isomerization mediated by intermolecular interactions  

International Nuclear Information System (INIS)

Reversible isomerization processes are rarely found when organic molecular switches are adsorbed on metal surfaces. One obstacle is the large energy difference of the isomeric forms, since usually the most planar conformer has the largest adsorption energy. In the example of an imine derivative, we show a strategy for also stabilizing the non-planar isomer by intermolecular bonding to its neighbors. Tunneling electrons from the tip of a scanning tunneling microscope can then be used to induce reversible switching between the trans and cis-like state. Supported by model force-field calculations, we illustrate that the most probable cause of the enhanced stability of the three-dimensional cis state at specific adsorption sites is the electrostatic interaction with N sites of the neighboring molecule.

2012-10-03

47

The fluorobenzene-argon S(1) excited-state intermolecular potential energy surface.  

UK PubMed Central (United Kingdom)

We evaluate the first excited-state (S1) intermolecular potential energy surface for the fluorobenzene-Ar van der Waals complex using the coupled cluster method and the augmented correlation-consistent polarized valence double-zeta basis set extended with a set of 3s3p2d1f1g midbond functions. To calculate the S(1) interaction energies, we use ground-state interaction energies evaluated with the same basis set and the coupled cluster singles and doubles (CCSD) including connected triple excitations [CCSD(T)] model and interaction and excitation energies evaluated at the CCSD level. The surface minima are characterized by the Ar atom located above and below the fluorobenzene ring at a distance of 3.5060 A with respect to the fluorobenzene center of mass and at an angle of 5.89 degrees with respect to the axis perpendicular to the fluorobenzene plane. The corresponding interaction energy is -425.226 cm(-1). The surface is used in the evaluation of the intermolecular level structure of the complex, and the results are compared to the experimental data available and to those found in previous theoretical papers on ground-state potentials for similar complexes.

Fajín JL; Capelo SB; Fernandez B; Felker PM

2007-08-01

48

Determination of stepsize parameters for intermolecular vibrational energy transfer  

Energy Technology Data Exchange (ETDEWEB)

Intermolecular energy transfer of highly excited polyatomic molecules plays an important role in many complex chemical systems: combustion, high temperature and atmospheric chemistry. By monitoring the relaxation of internal energy we have observed trends in the collisional efficiency ({beta}) for energy transfer as a function of the substrate's excitation energy and the complexities of substrate and deactivator. For a given substrate {beta} increases as the deactivator's mass increase to {approximately}30 amu and then exhibits a nearly constant value; this is due to a mass mismatch between the atoms of the colliders. In a homologous series of substrate molecules (C{sub 3}{minus}C{sub 8}) {beta} decreases as the number of atoms in the substrate increases; replacing F with H increases {beta}. All substrates, except for CF{sub 2}Cl{sub 2} and CF{sub 2}HCl below 10,000 cm{sup {minus}1}, exhibited that {beta} is independent of energy, i.e. <{Delta}E>{sub all} is linear with energy. The results are interpreted with a simple model which considers that {beta} is a function of the ocillators energy and its vibrational frequency. Limitations of current approximations used in high temperature unimolecular reactions were evaluated and better approximations were developed. The importance of energy transfer in product yields was observed for the photoactivation of perfluorocyclopropene and the photoproduction of difluoroethyne. 3 refs., 18 figs., 4 tabs.

Tardy, D.C.

1992-03-01

49

MODELLING INTERMOLECULAR FORCES IN BIOMOLECULES: FROM PROTEIN-PROTEIN INTERACTIONS TO HALOGEN BONDS.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The accurate description and evaluation of the intermolecular interactions has a great importance in the molecular modelling of biological systems. Protein-protein interactions, in particular, being involved in virtually every cellular process, are nowadays the object of thorough studies aimed at t...

RENDINE, STEFANO

50

Intermolecular interactions of aromatic hydrocarbons in carbonaceous materials - a molecular and quantum mechanics  

Energy Technology Data Exchange (ETDEWEB)

Aromatic hydrocarbons (PAHs and oligomers) that are models of carbonaceous materials components were studied using MM + All Atom Force Field and the semi-empirical methods (MINDO3 and ZINDO1) of quantum chemistry. The following intermolecular interactions were studied through potential energy function: (1) Among PAH molecules; (2) among oligomeric molecules; and (3) among oligomer and PAH molecules. It was found: (1) The potential energy minimized stacks of PAHs showed interlayer distances which correspond to the experimentally measured distances in carbonaceous materials. (2) Interactions among oligomers, in general, resulted in aggregates that showed random space orientation of aromatic units. Only few aromatic units of separate oligomers were parallel to each other. (3) Interactions among the oligomer and PAH molecules resulted in parallel orientation of PAH molecules relative to aromatic units of the oligomer. Common orbitals were found in stacks of parallel oriented aromatic planes,no matter whether the planes belonged to individual molecules forming PAH crystallites, oligomeric aggregates, or PAH/oligomer aggregates. Conclusions refer to the chemical structure of the optical isotropy phase occurring in carbonaceous materials, electrical conductivity of the materials, and X-ray measurements of the average size of the aromatic units (La).

Marzec, A. [Polish Academy of Science, Gliwice (Poland). Inst. of Coal Chemistry

2000-07-01

51

Intermolecular interactions of the malate synthase of Paracoccidioides spp.  

UK PubMed Central (United Kingdom)

BACKGROUND: The fungus Paracoccidioides spp is the agent of paracoccidioidomycosis (PCM), a pulmonary mycosis acquired by the inhalation of fungal propagules. Paracoccidioides malate synthase (PbMLS) is important in the infectious process of Paracoccidioides spp because the transcript is up-regulated during the transition from mycelium to yeast and in yeast cells during phagocytosis by murine macrophages. In addition, PbMLS acts as an adhesin in Paracoccidioides spp. The evidence for the multifunctionality of PbMLS indicates that it could interact with other proteins from the fungus and host. The objective of this study was to identify and analyze proteins that possibly bind to PbMLS (PbMLS-interacting proteins) because protein interactions are intrinsic to cell processes, and it might be possible to infer the function of a protein through the identification of its ligands. RESULTS: The search for interactions was performed using an in vivo assay with a two-hybrid library constructed in S. cerevisiae; the transcripts were sequenced and identified. In addition, an in vitro assay using pull-down GST methodology with different protein extracts (yeast, mycelium, yeast-secreted proteins and macrophage) was performed, and the resulting interactions were identified by mass spectrometry (MS). Some of the protein interactions were confirmed by Far-Western blotting using specific antibodies, and the interaction of PbMLS with macrophages was validated by indirect immunofluorescence and confocal microscopy. In silico analysis using molecular modeling, dynamics and docking identified the amino acids that were involved in the interactions between PbMLS and PbMLS-interacting proteins. Finally, the interactions were visualized graphically using Osprey software. CONCLUSION: These observations indicate that PbMLS interacts with proteins that are in different functional categories, such as cellular transport, protein biosynthesis, modification and degradation of proteins and signal transduction. These data suggest that PbMLS could play different roles in the fungal cell.

de Oliveira KM; da Silva Neto BR; Parente JA; da Silva RA; Quintino GO; Voltan AR; Mendes-Giannini MJ; de Almeida Soares CM; Pereira M

2013-01-01

52

Ab initio ground state phenylacetylene-argon intermolecular potential energy surface and rovibrational spectrum  

DEFF Research Database (Denmark)

We evaluate the phenylacetylene-argon intermolecular potential energy surface by fitting a representative number of ab initio interaction energies to an analytic function. These energies are calculated at a grid of intermolecular geometries, using the CCSD(T) method and the aug-cc-pVDZ basis set extended with a series of 3s3p2d1flg midbond functions. The potential is characterized by two equivalent global minima where the Ar atom is located above and below the phenylacetylene plane at a distance of 3.5781 angstrom from the molecular center of mass and at an angle of 9.08 degrees with respect to the axis perpendicular to the phenylacetylene plane and containing the center of mass. The calculated interaction energy is -418.9 cm(-1). To check further the potential, we obtain the rovibrational spectrum of the complex and the results are compared to the available experimental data. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4742153

Cybulski, Hubert; Fernandez, Berta

2012-01-01

53

Intermolecular interactions between natural polysaccharides and silk fibroin protein.  

UK PubMed Central (United Kingdom)

Fabricating novel functional and structural materials from natural renewable and degradable materials has attracted much attention. Natural polysaccharides and proteins are the right natural candidates due to their unique structures and properties. The polysaccharide-protein composites or blends were widely investigated, however, there are few systematical studies on the interactions between natural polysaccharides and silk fibroin protein at the molecular level. Among various interactions, hydrogen bonding, electrostatic interactions and covalent bonding play important roles in the structure and properties of the corresponding materials. Therefore, the focus is placed on the three interactions types in this review. A future challenge is to create polysaccharide and protein composites or blends with tailored structure and properties for the wide applications.

Shang S; Zhu L; Fan J

2013-04-01

54

Intermolecular interaction of prednisolone with bovine serum albumin: spectroscopic and molecular docking methods.  

UK PubMed Central (United Kingdom)

The intermolecular interaction of prednisolone with bovine serum albumin (BSA) was studied using fluorescence, circular dichroism (CD) and molecular docking methods. The experimental results showed that the fluorescence quenching of the BSA at 338 nm by prednisolone resulted from the formation of prednisolone-BSA complex. The number of binding sites (n) for prednisolone binding on BSA was approximately equal to 1. Base on the sign and magnitude of the enthalpy and entropy changes (?H(0)=-149.6 kJ mol(-1) and ?S(0)=-370.7 J mol(-1)K(-1)) and the results of molecular docking, it could be suggested that the interaction forces were mainly Van der Waals and hydrogen bonding interactions. Moreover, in the binding process of BSA with prednisolone, prednisolone molecule can be inserted into the hydrophobic cavity of subdomain IIIA (site II) of BSA. The distance between prednisolone and Trp residue of BSA was calculated as 2.264 nm according to Forster's non-radiative energy transfer theory.

Shi JH; Zhu YY; Wang J; Chen J; Shen YJ

2013-02-01

55

The Study of Intermolecular Interactions Using Optical Biosensors Operating on the Effect of Surface Plasmon Resonance  

Directory of Open Access Journals (Sweden)

Full Text Available Present knowledge of the technology of optical biosensors based on the effect of surface plasmon resonance (SPR) is presented. SPR enables to register almost all molecular interactions in real time without any labels or associated processes. There are considered the main technical characteristics of SPR biosensors and the principles of analysis of kinetic, equilibrium and thermodynamic parameters of intermolecular interactions.There are presented a number of examples of Biacore biosensors (GE Healthcare, USA) application in post-genomic researches carried out in the Institute of Biomedical Chemistry (Moscow, Russia): SPR technology has been used in the analysis of intermolecular interactions, like protein-protein, protein-low-molecular-weight compounds, protein-DNA; in the analysis of protein oligomerization and the search of dimerization inhibitors; in the search of drug prototype compounds interacting with a target protein; and in biosensor analysis of disease biomarkers.The technology of optical biosensors operating on the effect of surface ?lasmon resonance is getting one of the approaches in researching various intermolecular interactions. It is of universal character and enables to record the interactions between almost any molecular objects in a wide range of concentrations. SPR-biosensors have very high accuracy, capability of reproducing and sensitivity; due to these characteristics their application is growing both in fundamental and applied researches.

?.S. Ivanov

2012-01-01

56

Atom depth analysis delineates mechanisms of protein intermolecular interactions.  

UK PubMed Central (United Kingdom)

The systematic analysis of amino acid distribution, performed inside a large set of resolved protein structures, sheds light on possible mechanisms driving non random protein-protein approaches. Protein Data Bank entries have been selected using as filters a series of restrictions ensuring that the shape of protein surface is not modified by interactions with large or small ligands. 3D atom depth has been evaluated for all the atoms of the 2,410 selected structures. The amino acid relative population in each of the structural layers formed by grouping atoms on the basis of their calculated depths, has been evaluated. We have identified seven structural layers, the inner ones reproducing the core of proteins and the outer one incorporating their most protruding moieties. Quantitative analysis of amino acid contents of structural layers identified, as expected, different behaviors. Atoms of Q, R, K, N, D residues are increasingly more abundant in going from core to surfaces. An opposite trend is observed for V, I, L, A, C, and G. An intermediate behavior is exhibited by P, S, T, M, W, H, F and Y. The outer structural layer hosts predominantly E and K residues whose charged moieties, protruding from outer regions of the protein surface, reorient free from steric hindrances, determining specific electrodynamics maps. This feature may represent a protein signature for long distance effects, driving the formation of encounter complexes and the eventual short distance approaches that are required for protein-protein functional interactions.

Alocci D; Bernini A; Niccolai N

2013-07-01

57

The Experimental Charge-Density Approach in the Evaluation of Intermolecular Interactions. Application of a New Module of the XD Programming Package to Several Solids Including a Pentapeptide  

Energy Technology Data Exchange (ETDEWEB)

A new module interfaced to the XD programming package has been used in the evaluation of intermolecular interactions and lattice energies of the crystals of p-nitroaniline, l-asparagine monohydrate and the pentapeptide Boc-Gln- d-Iva-Hyp-Ala-Phol (Boc = butoxycarbonyl, Iva = isovaline = ethylalanine, Phol = phenylalaninol).

Abramov, Yu A.; Volkov, Anatoliy; Wu, G; Coppens, P

2000-11-01

58

Magnitude and orientation dependence of intermolecular interaction of perfluoropropane dimer studied by high-level ab initio calculations: Comparison with propane dimer  

Science.gov (United States)

Intermolecular interaction energies of 12 orientations of C3F8 dimers were calculated with electron correlation correction by the second-order Møller-Plesset perturbation method. The antiparallel C2h dimer has the largest interaction energy (-1.45 kcal/mol). Electron correlation correction increases the attraction considerably. Electrostatic energy is not large. Dispersion is mainly responsible for the attraction. Orientation dependence of the interaction energy of the C3F8 dimer is substantially smaller than that of the C3H8 dimer. The calculated interaction energy of the C3F8 dimer at the potential minimum is 78% of that of the C3H8 dimer (-1.85 kcal/mol), whereas the interaction energies of the CF4 and C2F6 dimers are larger than those of the CH4 and C2H6 dimers. The intermolecular separation in the C3F8 dimer at the potential minimum is substantially larger than that in the C3H8 dimer. The larger intermolecular separation due to the steric repulsion between fluorine atoms is the cause of the smaller interaction energy of the C3F8 dimer at the potential minimum. The calculated intermolecular interaction energy potentials of the C3F8 dimers using an all atom model OPLS-AA (OPLS all atom model) force field and a united atom model force field were compared with the ab initio calculations. Although the two force fields well reproduces the experimental vapor and liquid properties of perfluoroalkenes, the comparison shows that the united atom model underestimates the potential depth and orientation dependence of the interaction energy. The potentials obtained by the OPLS-AA force field are close to those obtained by the ab initio calculations.

Tsuzuki, Seiji; Uchimaru, Tadafumi; Mikami, Masuhiro; Urata, Shingo

2004-11-01

59

Studies of interdiffusion, chemical bonding, and intermolecular interactions in fiber-matrix adhesion  

Energy Technology Data Exchange (ETDEWEB)

A study of the key factors involved in adhesion was conducted to determine a quantitative relation between the underlying physicochemical mechanisms of adhesion and the adhesive performance at the fiber-matrix interface. Aramid fiber was modified by attaching pendent chains to its surface to change the nature of its interaction with matrix materials. The relative importance of the three fundamental factors of adhesion (interdiffusion, intermolecular interactions, and chemical bonding) was studied by evaluating the fiber-matrix adhesive performance of these modified fiber-matrix systems.

Chou, Chiate.

1990-01-01

60

Intermolecular interactions and electrostatic properties of the ?-hydroquinone apohost: implications for supramolecular chemistry.  

UK PubMed Central (United Kingdom)

The crystal structure of the ?-polymorph of hydroquinone (?-HQ), the apohost of a large family of clathrates, is reported with a specific focus on intermolecular interactions and the electrostatic nature of its cavity. Hirshfeld surface analysis reveals subtle close contacts between two interconnecting HQ networks, and the local packing and related close contacts were examined by breakdown of the fingerprint plot. An experimental multipole model containing anisotropic thermal parameters for hydrogen atoms has been successfully refined against 15(2) K single microcrystal synchrotron X-ray diffraction data. The experimental electron density model has been compared with a theoretical electron density calculated with the molecule embedded in its own crystal field. Hirshfeld charges, interaction energies and the electrostatic potential calculated for both models are qualitatively in good agreement, but small differences in the electrostatic potential persist due to charge transfer from all hydrogen atoms to the oxygen atoms in the theoretical model. The electrostatic potential in the center of the cavity is positive, very shallow and highly symmetric, suggesting that the inclusion of polar molecules in the void will involve a balance between opposing effects. The electric field is by symmetry zero in the center of the cavity, increasing to a value of 0.0185 e/Å(2) (0.27 V/Å) 1 Å along the 3-fold axis and 0.0105 e/Å(2) (0.15 V/Å) 1 Å along the perpendicular direction. While these values are substantial in a macroscopic context, they are quite small for a molecular cavity and are not expected to strongly polarize a guest molecule.

Clausen HF; Chen YS; Jayatilaka D; Overgaard J; Koutsantonis GA; Spackman MA; Iversen BB

2011-11-01

 
 
 
 
61

Intermolecular interactions between imidazole derivatives intercalated in layered solids. Substituent group effect  

Science.gov (United States)

This study sheds light on the intermolecular interactions between imidazole derive molecules (2-methyl-imidazole, 2-ethyl-imidazole and benzimidazole) intercalated in T[Ni(CN)4] layers to form a solid of formula unit T(ImD)2[Ni(CN)4]. These hybrid inorganic–organic solids were prepared by soft chemical routes and their crystal structures solved and refined from X-ray powder diffraction data. The involved imidazole derivative molecules were found coordinated through the pyridinic N atom to the axial positions for the metal T in the T[Ni(CN)4] layer. In the interlayers region ligand molecules from neighboring layers remain stacked in a face-to-face configuration through dipole–dipole and quadrupole–quadrupole interactions. These intermolecular interactions show a pronounced dependence on the substituent group and are responsible for an ImD-pillaring concatenation of adjacent layers. This is supported by the structural information and the recorded magnetic data in the 2–300 K temperature range. The samples containing Co and Ni are characterized by presence of spin–orbit coupling and pronounced temperature dependence for the effective magnetic moment except for 2-ethyl-imidazole related to the local distortion for the metal coordination environment. For this last one ligand a weak ferromagnetic ordering ascribed to a super-exchange interaction between T metals from neighboring layers through the ligands ?–? interaction was detected.

González, M.; Lemus-Santana, A. A.; Rodríguez-Hernández, J.; Aguirre-Velez, C. I.; Knobel, M.; Reguera, E.

2013-08-01

62

A Model DMMP/TiO2 (110) Intermolecular Potential Energy Function Developed from ab Initio Calculations  

Energy Technology Data Exchange (ETDEWEB)

A hierarchy of electronic structure calculations, scalings, and fittings were used to develop an analytic intermolecular potential for dimethyl methylphosphonate (DMMP) interacting with the TiO2 rutile (110) surface. The MP2/aug-cc-pVDZ (6-311+G** for Ti) level of theory, with basis set superposition error (BSSE) corrections, was used to calculate multiple intermolecular potential curves between TiO5H6 as a model for the Ti and O atoms of the TiO2 surface, and CH3OH and O=P(CH3)(OH)2 as models for different types of atoms comprising DMMP. Each intermolecular potential energy emphasized a particular atom-atom interaction, and the curves were fit simultaneously by a sum of two-body potentials between the atoms of the two interacting molecules. The resulting analytic intermolecular potential gives DMMP/TiO5H6 potential curves in excellent agreement with those calculated using MP2/aug-cc-pVDZ (6-311+G** for Ti) theory. MP2 theory with the smaller basis set, 6-31++G** (6-31G** for Ti), gives DMMP/TiO5H6 potential energy curves similar to those found using MP2/aug-cc-pVDZ (6-311+G** for Ti), suggesting the smaller basis set may be used to describe DMMP interactions with larger cluster models of the TiO2 surface. The TiO5H6 cluster does not model either the 6-fold coordinated Ti-atoms or the bridging O-atoms of the TiO2 (110) surface and to also model these atoms MP2/6-31++G** (6-31G** for Ti) theory was used to calculate potential energy curves for DMMP interacting with the larger Ti3O13H14 cluster and much large cluster Ti11O40H36 cluster. The two-body potential energy curves for DMMP/TiO5H6 were scaled to fit both the DMMP/Ti3O13H14 and DMMP/Ti11O40H36 potential energy curves. The resulting parameters for the 5- and 6-fold coordinated Ti-atoms and bridging and bulk O-atoms were used to develop an analytic intermolecular potential for DMMP interacting with rutile TiO2 (110).

Yang, Li; Taylor, Ramona; De Jong, Wibe A.; Hase, William L.

2011-06-30

63

Drug-polymer intermolecular interactions in hot-melt extruded solid dispersions.  

UK PubMed Central (United Kingdom)

The purpose of the study was to investigate and identify the interactions within solid dispersions of cationic drugs and anionic polymers processed by hot-melt extrusion (HME) technique. Propranolol HCl (PRP) and diphenhydramine HCl (DPD) were used as model cationic active substances while pH sensitive anionic methacrylic acid based methyl methacrylate copolymers Eudragit L100 (L100) and ethyl acrylate copolymer Eudragit L100-55 (Acryl EZE) (L100-55) were used as polymeric carriers. The extrudates were further characterised using various physicochemical characterisation techniques to determine the morphology, the drug state within the polymer matrices and the type of drug-polymer interactions. Molecular modelling predicted the existence of two possible H-bonding types while the X-ray photon spectroscopy (XPS) advanced surface analysis of the extrudates revealed intermolecular ionic interactions between the API amino functional groups and the polymer carboxylic groups through the formation of hydrogen bonding. The magnitude of the intermolecular interactions varied according to the drug-polymer miscibility.

Maniruzzaman M; Morgan DJ; Mendham AP; Pang J; Snowden MJ; Douroumis D

2013-02-01

64

Drug-polymer intermolecular interactions in hot-melt extruded solid dispersions.  

Science.gov (United States)

The purpose of the study was to investigate and identify the interactions within solid dispersions of cationic drugs and anionic polymers processed by hot-melt extrusion (HME) technique. Propranolol HCl (PRP) and diphenhydramine HCl (DPD) were used as model cationic active substances while pH sensitive anionic methacrylic acid based methyl methacrylate copolymers Eudragit L100 (L100) and ethyl acrylate copolymer Eudragit L100-55 (Acryl EZE) (L100-55) were used as polymeric carriers. The extrudates were further characterised using various physicochemical characterisation techniques to determine the morphology, the drug state within the polymer matrices and the type of drug-polymer interactions. Molecular modelling predicted the existence of two possible H-bonding types while the X-ray photon spectroscopy (XPS) advanced surface analysis of the extrudates revealed intermolecular ionic interactions between the API amino functional groups and the polymer carboxylic groups through the formation of hydrogen bonding. The magnitude of the intermolecular interactions varied according to the drug-polymer miscibility. PMID:23262428

Maniruzzaman, Mohammed; Morgan, David J; Mendham, Andrew P; Pang, Jiayun; Snowden, Martin J; Douroumis, Dennis

2012-12-20

65

Direction-dependent intermolecular interactions: catechol on TiO2(110)-1×1  

Science.gov (United States)

The adsorption of a submonolayer of catechol (C6H6O2) on the rutile TiO2(110)-1×1 surface has been investigated by Scanning Tunneling Microscopy (STM). The catechol molecules are preferentially adsorbed on the surface 5-fold coordinated Ti4+ sites, and occupy two neighboring lattice Ti sites. No preference for adsorption at surface step edges is observed at room temperature. A statistical analysis of intermolecular distances demonstrates that the interaction between the molecules strongly depends on the surface crystallographic direction: catechol molecules exhibit attractive interaction along [1-1 0], while they repel each other along the [001] direction. The attractive interaction is proposed to be caused by the coupling of ? bonding electrons and the repulsive interaction is possibly mediated by substrate.

Li, Shao-Chun; Diebold, Ulrike

2009-08-01

66

A look at molecular nanosized magnets from the aspect of inter-molecular interactions.  

Science.gov (United States)

Nanosized molecular magnetic materials such as single-molecule magnets and single-chain magnets are recent attractive research targets in the fields of materials chemistry and physics, not only because of their fundamental fascination, but also because of their potential applications as ultimate memory devices or in quantum computations. In this paper, we give our personal perspectives on these materials. In particular "magnetic assemblies of single-molecule magnets", in which inter-molecular interaction is an essential factor in determining their properties, will be focused on together with related compounds reported recently. PMID:17213922

Miyasaka, Hitoshi; Yamashita, Masahiro

2006-11-29

67

A look at molecular nanosized magnets from the aspect of inter-molecular interactions.  

UK PubMed Central (United Kingdom)

Nanosized molecular magnetic materials such as single-molecule magnets and single-chain magnets are recent attractive research targets in the fields of materials chemistry and physics, not only because of their fundamental fascination, but also because of their potential applications as ultimate memory devices or in quantum computations. In this paper, we give our personal perspectives on these materials. In particular "magnetic assemblies of single-molecule magnets", in which inter-molecular interaction is an essential factor in determining their properties, will be focused on together with related compounds reported recently.

Miyasaka H; Yamashita M

2007-01-01

68

Intermolecular interactions in staphylokinase-plasmin(ogen) bimolecular complex: function of His43 and Tyr44.  

UK PubMed Central (United Kingdom)

Staphylokinase (SAK) forms a 1:1 stoichiometric complex with human plasmin (Pm) and switches its substrate specificity to generate a plasminogen (Pg) activator complex. Site-directed mutagenesis of SAKHis43 and SAKTyr44 demonstrated the crucial requirement of a positively charged and an aromatic residue, respectively, at these positions for optimal functioning of SAK-Pm activator complex. Molecular modeling studies further revealed the role of these residues in making cation-pi and pi-pi interactions with Trp215 of Pm and thus establishing the crucial intermolecular contacts within the active site cleft of the activator complex for the cofactor activity of SAK.

Dahiya M; Singh S; Rajamohan G; Sethi D; Ashish; Dikshit KL

2011-06-01

69

Intermolecular interactions in staphylokinase-plasmin(ogen) bimolecular complex: function of His43 and Tyr44.  

Science.gov (United States)

Staphylokinase (SAK) forms a 1:1 stoichiometric complex with human plasmin (Pm) and switches its substrate specificity to generate a plasminogen (Pg) activator complex. Site-directed mutagenesis of SAKHis43 and SAKTyr44 demonstrated the crucial requirement of a positively charged and an aromatic residue, respectively, at these positions for optimal functioning of SAK-Pm activator complex. Molecular modeling studies further revealed the role of these residues in making cation-pi and pi-pi interactions with Trp215 of Pm and thus establishing the crucial intermolecular contacts within the active site cleft of the activator complex for the cofactor activity of SAK. PMID:21510941

Dahiya, Monika; Singh, Satish; Rajamohan, Govindan; Sethi, Deepti; Ashish; Dikshit, Kanak L

2011-04-16

70

Characterizing and circumventing intermolecular electrostatic interactions in highly electro-optic polymers  

Energy Technology Data Exchange (ETDEWEB)

In general, polymers possessing non-resonant electro-optic activities exceeding 20 pm/V require chromophores with strong electron withdrawing groups (cyanovinyls, carbon acid moieties, etc.) as well as highly polarizable bridges. Although much progress has been made on designing and preparing materials with molecular electro-optic activities, their incorporation into polymers to show comparable large bulk electro-optic activities has been met with little success. The authors report here the nature of the difficulty of the translation of microscopic to macroscopic electro-optic activity. The optimization of molecular activity increases intermolecular electrostatic interactions between chromophores, and these interactions impede induction of polar ascentric order in the polymers. Theoretical analysis of the problem is presented, as well as one example of a material that is designed to circumvent these interactions. The resulting material possesses electro-optic coefficients as high as 29 pm/V and optical losses as low as 1.5 dB/cm.

Harper, A.W.; Zhu, J.; He, M.; Dalton, L.R.; Garner, S.M.; Steier, W.H.

1998-07-01

71

Effect of the electronic structure of quinoline and its derivatives on the capacity for intermolecular interactions  

Energy Technology Data Exchange (ETDEWEB)

Calculations of the ground and excited states of quinoline and its 20H-, 70H-, 7NH2-, 7N(CH3)2-, and 7N(C2H5)2- substituted derivatives were undertaken by the INDO method, and the effect of intramolecular proton transfer (IPT) on their electronic structure was studied. The proton-accepting capacity of the compounds for intermolecular interactions was estimated by the molecular electrostatic potential method. It was shown that the proton-accepting capacity with respect to intermolecular interactions increases during the tautomeric transformation of the enolic form of 2-OH-quinoline to its keto form. The change in the basicity of the two forms of the molecules is affected by the orbital nature, and the multiplicity of the state is also important for the keto form. Substitution by electron-donating groups leads to increase in the proton-accepting capacity of both forms of the compounds in the S0, S/sub */, and T/sub */ states.

Privalova, N.Yu.; Sokolova, I.V.

1985-05-01

72

Regions of the herpes simplex virus scaffolding protein that are important for intermolecular self-interaction.  

Science.gov (United States)

The herpes simplex virus type 1 (HSV-1) scaffolding protein encoded by gene UL26.5 promotes the formation of the icosahedral capsid shell through its association with the major capsid protein VP5 and through intermolecular interactions with itself. Inside the capsid shell, the UL26.5 product together with the maturational protease, a minor protein, form a spherical structure which is broken down and released from the capsid during packaging of the viral genome. Selected residues from four internal regions of the HSV-1 scaffolding protein that have significant conservation of amino acids within the scaffolding proteins of alphaherpesviruses were mutated, and the properties of the proteins were examined. Only the HSV-1 scaffolding protein with mutations in the conserved N-terminal domain showed reduced interaction with the varicella-zoster virus homologue in a cell-based immunofluorescence assay, providing the first evidence that this domain in the HSV-1 protein is likely to be involved in intermolecular self-interaction. Scaffolding protein with mutations in this domain or in either of two other domains failed to assemble into scaffold-like particles but retained the ability to self-interact, although the aggregates were significant smaller than most of the aggregates formed by the wild-type protein. These results suggest that there are multiple domains involved in the intermolecular self-association of the HSV-1 scaffolding protein that can act independently of one another. This conclusion was supported by the observation that none of the mutant proteins with lesions in an individual domain, including a protein with mutations in a central region previously implicated in self-interaction (A. Pelletier, F. Dô, J. J. Brisebois, L. Lagacé, and M. G. Cordingley, J. Virol. 71:5197-5208, 1997), interfered with capsid assembly in a baculovirus expression system. A protein mutated in the central region and another conserved domain, both of which had been predicted to form coiled coils, was impaired for capsid formation but still retained the capacity to interact with VP5. PMID:11752158

Preston, Valerie G; McDougall, Iris M

2002-01-01

73

Regions of the herpes simplex virus scaffolding protein that are important for intermolecular self-interaction.  

UK PubMed Central (United Kingdom)

The herpes simplex virus type 1 (HSV-1) scaffolding protein encoded by gene UL26.5 promotes the formation of the icosahedral capsid shell through its association with the major capsid protein VP5 and through intermolecular interactions with itself. Inside the capsid shell, the UL26.5 product together with the maturational protease, a minor protein, form a spherical structure which is broken down and released from the capsid during packaging of the viral genome. Selected residues from four internal regions of the HSV-1 scaffolding protein that have significant conservation of amino acids within the scaffolding proteins of alphaherpesviruses were mutated, and the properties of the proteins were examined. Only the HSV-1 scaffolding protein with mutations in the conserved N-terminal domain showed reduced interaction with the varicella-zoster virus homologue in a cell-based immunofluorescence assay, providing the first evidence that this domain in the HSV-1 protein is likely to be involved in intermolecular self-interaction. Scaffolding protein with mutations in this domain or in either of two other domains failed to assemble into scaffold-like particles but retained the ability to self-interact, although the aggregates were significant smaller than most of the aggregates formed by the wild-type protein. These results suggest that there are multiple domains involved in the intermolecular self-association of the HSV-1 scaffolding protein that can act independently of one another. This conclusion was supported by the observation that none of the mutant proteins with lesions in an individual domain, including a protein with mutations in a central region previously implicated in self-interaction (A. Pelletier, F. Dô, J. J. Brisebois, L. Lagacé, and M. G. Cordingley, J. Virol. 71:5197-5208, 1997), interfered with capsid assembly in a baculovirus expression system. A protein mutated in the central region and another conserved domain, both of which had been predicted to form coiled coils, was impaired for capsid formation but still retained the capacity to interact with VP5.

Preston VG; McDougall IM

2002-01-01

74

Relativistic effects in the intermolecular interaction-induced nuclear magnetic resonance parameters of xenon dimer  

DEFF Research Database (Denmark)

Relativistic effects on the 129Xe nuclear magnetic resonance shielding and 131Xe nuclear quadrupole coupling (NQC) tensors are examined in the weakly bound Xe2 system at different levels of theory including the relativistic four-component Dirac-Hartree-Fock (DHF) method. The intermolecular interaction-induced binary chemical shift d, the anisotropy of the shielding tensor ?s, and the NQC constant along the internuclear axis ?ll are calculated as a function of the internuclear distance. DHF shielding calculations are carried out using gauge-including atomic orbitals. For comparison, the full leading-order one-electron Breit-Pauli perturbation theory (BPPT) is applied using a common gauge origin. Electron correlation effects are studied at the nonrelativistic (NR) coupled-cluster singles and doubles with perturbational triples [CCSD(T)] level of theory. The fully relativistic second-order Møller-Plesset many-body perturbation (DMP2) theory is used to examine the cross coupling between correlation and relativityon NQC. The same is investigated for d and ?s by BPPT with a density functional theory model. A semiquantitative agreement between the BPPT and DHF binary property curves is obtained for d and ?s in Xe2. For these properties, the currently most complete theoretical description is obtained by a piecewise approximation where the uncorrelated relativistic DHF results obtained close to the basis-set limit are corrected, on the one hand, for NR correlation effects and, on the other hand, for the BPPT-based cross coupling of relativity and correlation. For ?ll, the fully relativistic DMP2 results obtain a correction for NR correlation effects beyond MP2. The computed temperature dependence of the second virial coefficient of the 129Xe nuclear shielding is compared to experiment in Xe gas. Our best results, obtained with the piecewise approximation for the binary chemical shift combined with the previously published state of the art theoretical potential energy curve for Xe2, are in excellent agreement with the experiment for the first time. © 2007 American Institute of Physics. [DOI: 10.1063/1.2777143

Hanni, Matti; Lantto, Perttu

2007-01-01

75

Ab initio intermolecular potential energy surfaces of the water-rare gas atom complexes.  

Science.gov (United States)

Highly accurate analytical intermolecular potential energy surfaces (PESs) of the complexes composed of the water molecule and the rare gas (Rg) atom are presented for Rg=He, Ne, Ar, and Kr. These PESs were scanned using the supermolecule coupled cluster singles and doubles including connected triples method [CCSD(T)]. Efficient basis sets including the bond functions (3s3p2d1f1g) enabled the calculation of more than 430 single-point interaction energies for each complex. These energies were utilized to construct the analytical many-body representations of the PESs. They were refined using the interaction energies evaluated at the complete basis set limit in the PES stationary points. In addition, the corrections from the core correlation were calculated for the complexes including He, Ne, and Ar. The many-body PES of XeH(2)O was built using the ab initio energy values reported by Wen and Jager [J. Phys. Chem. A 110, 7560 (2006)]. The clear regularities of the equilibrium structure and the potential barriers were found in the RgH(2)O series. A comparison of the ab initio and experimental PESs of ArH(2)O [R. C. Cohen and R. J. Saykally, J. Chem. Phys. 98, 6007 (1993)] reveals their close similarity, except for the potential barriers corresponding to the planar saddle points. Their energetic order is different in both PESs. This suggests that an alternative PES with the reversed barriers, consistent with the ab initio ones, could be derived from the experimental data. PMID:19045406

Makarewicz, Jan

2008-11-14

76

A structural study of the intermolecular interactions of tyramine in the solid state and in solution  

Science.gov (United States)

The nature of the interactions between tyramine units was investigated in the solid state and in solution. Crystals of tyramine in its free base form were analyzed by Fourier transform infrared (FT-IR) spectroscopy and single-crystal X-ray diffraction (XRD). The crystal structure shows a linear molecular organization held together by "head-to-tail" intermolecular hydrogen bonds between the amino groups and the phenolic hydroxyl groups. These chains are arranged in double layers that can geometrically favor the formation of templates in solution, which may facilitate macrocyclization reactions to form azacyclophane-type compounds. Computational calculations using the PM6-DH+ method and electrospray ionization mass spectrometry (ESI-HRMS) reveal that the formation of a hydrogen-bonded tyramine dimer is favored in solution.

Quevedo, Rodolfo; Nuñez-Dallos, Nelson; Wurst, Klaus; Duarte-Ruiz, Álvaro

2012-12-01

77

Intermolecular interaction between a branching ribozyme and associated homing endonuclease mRNA  

DEFF Research Database (Denmark)

Abstract RNA tertiary interactions involving docking of GNRA (N; any base; R; purine) hairpin loops into helical stem structures on other regions of the same RNA are one of the most common RNA tertiary interactions. In this study, we investigated a tertiary association between a GAAA hairpin tetraloop in a small branching ribozyme (DiGIR1) and a receptor motif (HEG P1 motif) present in a hairpin structure on a separate mRNA molecule. DiGIR1 generates a 2', 5' lariat cap at the 5' end of its downstream homing endonuclease mRNA by catalysing a self-cleavage branching reaction at an internal processing site. Upon release, the 5' end of the mRNA forms a distinct hairpin structure termed HEG P1. Our biochemical data, in concert with molecular 3D modelling, provide experimental support for an intermolecular tetraloop receptor interaction between the L9 GAAA in DiGIR1 and a GNRA tetraloop receptor-like motif (UCUAAG-CAAGA) found within the HEG P1. The biological role of this interaction appears to be linked to the homing endonuclease expression by promoting post-cleavage release of the lariat capped mRNA. These findings add to our understanding of how protein-coding genes embedded in nuclear ribosomal DNA are expressed in eukaryotes and controlled by ribozymes.

Birgisdottir, Asa B; Nielsen, Henrik

2011-01-01

78

Description of cross peaks induced by intermolecular vibrational energy transfer in two-dimensional infrared spectroscopy  

CERN Document Server

In the present work, the analytical description of an intermolecular vibrational energy transfer, analyzed by two dimensional infrared spectroscopy, is established. The energy transfer process takes place between the dark combination states of low frequency modes pertaining to different molecules. The appearance of the cross peaks results from coherent transfer between these combination states and an optically active state of the acceptor molecule. Such a process has recently been observed experimentally between the nitrile groups of acetonitrile-d3 and benzonitrile molecules. This molecular system will be used as a model for the simulations of their two-dimensional infrared spectra. The dependence of the cross-peak growth, which is a signature of the intermolecular energy transfer, will be discussed in detail as a function of the molecular dynamical constants.

Villaeys, Albert A

2013-01-01

79

Effects of Weak Intermolecular Interactions on the Molecular Isomerism of Tricobalt Metal Chains  

Energy Technology Data Exchange (ETDEWEB)

Depending on the number of interstitial solvent molecules, n, crystals of the linear chain compound Co3(dipyridylamide)4Cl2{center_dot}nCH2Cl2 adopt either symmetrical or unsymmetrical metal chain structures. We explore here the possible reasons for such behavior using Hirshfeld surface analysis of intermolecular interactions as well as the charge density determined from 100(1) K X-ray diffraction data on the unsymmetrical complex Co3(dipyridylamide)4Cl2{center_dot}2.11CH2Cl2, u-1, and crystal structures of u-1 determined from single crystal synchrotron X-ray diffraction data at 20, 150, and 300 K. The new crystal structures are compared with previous structural results on a crystal with slightly different solvent content. This change in solvent content only affects the bond distances to atom Co(3), which are also strongly affected by temperature changes due to a spin crossover transition. Large differences in intermolecular interactions are revealed by the Hirshfeld surface analysis between symmetrical (s-1) and unsymmetrical (u-1) crystal solvates, suggesting that the molecular isomerism is strongly influenced by crystal packing effects. Topological analysis of the static electron density of u-1 suggests that there is direct metal-metal bonding for both the shorter Co(1)-Co(2) and the longer Co(2)-Co(3) contact. The approximate description of the system as a (Co2)2+-dimer and an isolated Co2+-ion is reflected in the character of the metal-ligand interactions, which are more ionic for the isolated Co(3) atom, and the topological charges Co(1)+0.50, Co(2)+0.77, and Co(3)+1.36. The two termini of u-1 are found to be very different, both in terms of structural surroundings as well as topology. The central Co(2) atom is similar to a cobalt atom in a tetragonally distorted octahedral environment resulting in preferred occupancy in the t2g orbitals. The Co(1) atom has significant deformation in the xz and yz planes (z along the chain axis, x and y toward ligands) reflecting covalent interactions with the terminal chlorine atom Cl(1). The Co(3) atom has a relatively high occupancy of the dx2-y2 orbital and a relatively low occupancy of the dxy orbital confirming that these orbitals are involved in the spin crossover process and predominantly responsible for the observed variation in bond lengths with temperature.

Poulsen, R.; Overgaard, J; Schulman, A; Østergaard, C; Murillo, C; Spackman, M; Iversen, B

2009-01-01

80

Structural changes of CFTR R region upon phosphorylation: a plastic platform for intramolecular and intermolecular interactions.  

Science.gov (United States)

Chloride channel gating and trafficking of the cystic fibrosis transmembrane conductance regulator (CFTR) are regulated by phosphorylation. Intrinsically disordered segments of the protein are responsible for phospho-regulation, particularly the regulatory (R) region that is a target for several kinases and phosphatases. The R region remains disordered following phosphorylation, with different phosphorylation states sampling various conformations. Recent studies have demonstrated the crucial role that intramolecular and intermolecular interactions of the R region play in CFTR regulation. Different partners compete for the same binding segment, with the R region containing multiple overlapping binding elements. The non-phosphorylated R region interacts with the nucleotide binding domains and inhibits channel activity by blocking heterodimerization. Phosphorylation shifts the equilibrium such that the R region is excluded from the dimer interface, facilitating gating and processing by stimulating R region interactions with other domains and proteins. The dynamic conformational sampling and transient binding of the R region to multiple partners enables complex control of CFTR channel activity and trafficking. PMID:23826884

Bozoky, Zoltan; Krzeminski, Mickael; Chong, P Andrew; Forman-Kay, Julie D

2013-07-25

 
 
 
 
81

Modeling intermolecular interactions of physisorbed organic molecules using pair potential calculations  

International Nuclear Information System (INIS)

The understanding and control of epitaxial growth of organic thin films is of crucial importance in order to optimize the performance of future electronic devices. In particular, the start of the submonolayer growth plays an important role since it often determines the structure of the first layer and subsequently of the entire molecular film. We have investigated the structure formation of 3,4,9,10-perylene-tetracarboxylic dianhydride and copper-phthalocyanine molecules on Au(111) using pair-potential calculations based on van der Waals and electrostatic intermolecular interactions. The results are compared with the fundamental lateral structures known from experiment and an excellent agreement was found for these weakly interacting systems. Furthermore, the calculations are even suitable for chemisorptive adsorption as demonstrated for copper-phthalocyanine/Cu(111), if the influence of charge transfer between substrate and molecules is known and the corresponding charge redistribution in the molecules can be estimated. The calculations are of general applicability for molecular adsorbate systems which are dominated by electrostatic and van der Waals interaction.

2011-12-21

82

Molecular evidence for the intermolecular S···S interaction in the surface molecular packing motifs of a fused thiophene derivative.  

UK PubMed Central (United Kingdom)

A microscopic investigation of the molecular packing structures of a fused thiophene derivative reveals the important role of intermolecular S···S interaction in directing the 2D self-assembly. Thermal annealing of the assembly results in the irreversible phase transition to a new structure with different molecular trimeric packing motifs.

Wang XY; Jiang W; Chen T; Yan HJ; Wang ZH; Wan LJ; Wang D

2013-03-01

83

Pentacene on ag(111): correlation of bonding distance with intermolecular interaction and order.  

Science.gov (United States)

We report coverage and temperature dependent bonding distances of vacuum-sublimed pentacene (PEN) submonolayers on Ag(111) obtained by the X-ray standing wave technique. The average vertical bonding distance of 2.98 Å at room temperature for 0.50 monolayer (ML) coverage increases to 3.12 Å for 0.75 ML due to competing intermolecular and adsorbate-substrate interactions. In contrast, decreasing the temperature from 295 to 145 K does not impact the bonding distance despite the concomitant transition from a "liquidlike" to an ordered molecular arrangement. In combination with X-ray photoelectron spectroscopy results, we could identify "soft chemisorption" with a subtle balance of molecule-molecule and substrate-molecule interactions as being responsible for this special adsorption behavior. Thus our study sheds light not only on the interface between PEN and Ag(111), but also on fundamental adsorption processes of organic adsorbates on metals in the context of chemi- and physisorption. PMID:24016756

Duhm, Steffen; Bürker, Christoph; Niederhausen, Jens; Salzmann, Ingo; Hosokai, Takuya; Duvernay, Julien; Kera, Satoshi; Schreiber, Frank; Koch, Norbert; Ueno, Nobuo; Gerlach, Alexander

2013-09-24

84

Probing intermolecular interactions in water/ionic liquid mixtures by far-infrared spectroscopy.  

Science.gov (United States)

Far-infrared spectra in the range from 600 to 20 cm-1 of two hydrophilic (1-ethyl-3-methylimidazolium tetrafluoroborate and 1-butyl-3-methylimidazolium tetrafluoroborate) and one hydrophobic (1-butyl-3-methylimidazolium hexafluorophosphate) ionic liquids and their mixtures with water at different concentrations are reported. Shifts of the librational water bands depending on the nature of the anion are found to be related to the strength of the interaction between the water molecules and the anions. For both hydrophilic ionic liquids, the librational band is centered around 460 cm-1, whereas for the hydrophobic ionic liquid, it is shifted to 388 cm-1, indicating less hindered rotation of single water molecules. Multivariate curve resolution, paying special attention to the spectral range from 50 to 350 cm-1, was used to investigate the presence of different species with increasing water concentration. For both hydrophilic ionic liquids, a band located at 153 cm-1 was resolved into two different contributions. A small contribution at 202 cm-1 can be attributed to intermolecular interactions between water molecules forming dimers. The major contribution (centered at 148 cm-1) corresponds to water molecules that do not bond to each other via H-bonding. It is therefore assigned to a hindered translation arising from the stretching of the hydrogen bond between BF4- anions and water molecules. Formation of water dimers in the hydrophobic ionic liquid does not occur. Furthermore, the spectral contribution of the stretching of H-bonds between water molecules and PF6- cannot be unambiguously detected, which indicates an extremely weak interaction between water molecules and this anion. PMID:17408256

Dominguez-Vidal, Ana; Kaun, Nina; Ayora-Cañada, Maria Jose; Lendl, Bernhard

2007-04-05

85

Probing intermolecular interactions in water/ionic liquid mixtures by far-infrared spectroscopy.  

UK PubMed Central (United Kingdom)

Far-infrared spectra in the range from 600 to 20 cm-1 of two hydrophilic (1-ethyl-3-methylimidazolium tetrafluoroborate and 1-butyl-3-methylimidazolium tetrafluoroborate) and one hydrophobic (1-butyl-3-methylimidazolium hexafluorophosphate) ionic liquids and their mixtures with water at different concentrations are reported. Shifts of the librational water bands depending on the nature of the anion are found to be related to the strength of the interaction between the water molecules and the anions. For both hydrophilic ionic liquids, the librational band is centered around 460 cm-1, whereas for the hydrophobic ionic liquid, it is shifted to 388 cm-1, indicating less hindered rotation of single water molecules. Multivariate curve resolution, paying special attention to the spectral range from 50 to 350 cm-1, was used to investigate the presence of different species with increasing water concentration. For both hydrophilic ionic liquids, a band located at 153 cm-1 was resolved into two different contributions. A small contribution at 202 cm-1 can be attributed to intermolecular interactions between water molecules forming dimers. The major contribution (centered at 148 cm-1) corresponds to water molecules that do not bond to each other via H-bonding. It is therefore assigned to a hindered translation arising from the stretching of the hydrogen bond between BF4- anions and water molecules. Formation of water dimers in the hydrophobic ionic liquid does not occur. Furthermore, the spectral contribution of the stretching of H-bonds between water molecules and PF6- cannot be unambiguously detected, which indicates an extremely weak interaction between water molecules and this anion.

Dominguez-Vidal A; Kaun N; Ayora-Cañada MJ; Lendl B

2007-05-01

86

A combined experimental and quantum chemical studies on molecular structure, spectral properties, intra and intermolecular interactions and first hyperpolarizability of 4-(benzyloxy)benzaldehyde thiosemicarbazone and its dimer  

Science.gov (United States)

In the present work, a detailed spectroscopic analysis of 4-(benzyloxy)benzaldehyde thiosemicarbazone (3) has been carried out using 1H NMR, 13C NMR, UV-Visible and FT-IR spectroscopic techniques. The quantum chemical calculations have been carried out using DFT level of theory, B3LYP functional and 6-31G(d,p) basis set. The calculated thermodynamic parameters show that the formation of 3 is an exothermic and spontaneous reaction at 25 °C. The vibrational analysis indicates the formation of dimer in the solid state by intermolecular hydrogen bonding (NH⋯SC) and the binding energy of dimer is calculated to be 11.2 kcal/mol, using DFT calculation. NBO analysis is carried out to investigate the charge transfer in various intra and intermolecular interactions involved in dimer. Topological parameters at bond critical points (BCPs) are calculated to analyze the strength and nature of various intra and intermolecular interactions in dimer by Bader's 'Atoms in molecules' AIM theory in detail. The local reactivity descriptors such as Fukui functions (fk+,fk-), local softnesses (sk+,sk-) and electrophilicity indices (?k+,?k-) analysis are performed to determine the reactive sites within molecule. Non linear optical (NLO) behavior of title compound is investigated by the computed value of first hyperpolarizability (?0).

Kumar, Amit; Rawat, Poonam; Baboo, Vikas; Verma, Divya; Singh, R. N.; Saxena, Deepti; Gauniyal, H. M.; Pandey, Anoop Kumar; Pal, Harish

2013-02-01

87

Competition between intermolecular interaction and configuration entropy as the structure-determining factor for inclusion compounds  

Energy Technology Data Exchange (ETDEWEB)

This paper presented a newly developed method to accurately predict the thermodynamic properties of clathrate hydrates, particularly their structural phase transitions under pressure. The method is based on the theory of Van-der-Waals and Platteeuw with some modifications that include the influence of guest molecules on the host lattice. The model was used to explain the exception from the established rule that small guest molecules form structure s1 and large molecules form structure s2 hydrates. In this study, the thermodynamic properties of argon (Ar) hydrate and methane hydrate, each in both cubic structure s1 and s2 were modelled. The model showed that two competing factors play a role in the formation of inclusions, notably the intermolecular interaction of guest molecules with water molecules, and the configuration entropy. Competition of these 2 factors determines the structure of hydrate formed at different pressures. The model provides an accurate description of the thermodynamic properties of gas hydrates and how they behave under pressure. For the argon hydrates, the structural phase transition from structure s2 to s1 at high pressure was predicted, while methane hydrates were predicted to be metastable in the s2 structure. The model can be used for other inclusion compounds with the same type of composition such as clathrate silicon, zeolites, and inclusion compounds of semiconductor elements. 17 refs., 5 figs.

Subbotin, O.; Belosludov, V.; Adamova, T. [Russian Academy of Science, Novosibirsk (Russian Federation). Nikolaev Inst. of Inorganic Chemistry; Belosludov, R.; Kawazoe, Y. [Tohoku Univ., Aoba-ku, Sendai (Japan). Inst. for Materials Research; Kudoh, J.I. [Tohoku Univ., Aoba-ku, Sendai (Japan). Center for Northeast Asia Studies

2008-07-01

88

Intermolecular Interactions and Aggregation of fac-Tris(2-phenylpyridinato-C(2),N)iridium(III) in Nonpolar Solvents.  

Science.gov (United States)

The intermolecular interaction and aggregation of the neutral complex fac-tris(2-phenylpyridinato-C(2),N)iridium(III) (fac-Ir(ppy)3) in solution was investigated. Intermolecular interactions were found to effectively decrease the luminescence lifetime via self-quenching with increasing fac-Ir(ppy)3 concentrations. A Stern-Volmer plot for quenching in acetonitrile was linear, due to bimolecular self-quenching, but curved in toluene as the result of excimer formation. (1)H NMR spectra demonstrated a monomer-aggregate equilibrium which resulted in spectral shifts depending on solvent polarity. X-ray crystallography provided structural information concerning the aggregate, which is based on a tetramer consisting of two ?-fac-Ir(ppy)3-?-fac-Ir(ppy)3 pairs. Offset ?-? stacking of ppy ligands and electrostatic dipole-dipole interactions between complex molecules play an important role in the formation of these molecular pairs. PMID:23865453

Takayasu, Satoshi; Suzuki, Takayoshi; Shinozaki, Kazuteru

2013-08-05

89

Intermolecular Interactions and Aggregation of fac-Tris(2-phenylpyridinato-C(2),N)iridium(III) in Nonpolar Solvents.  

UK PubMed Central (United Kingdom)

The intermolecular interaction and aggregation of the neutral complex fac-tris(2-phenylpyridinato-C(2),N)iridium(III) (fac-Ir(ppy)3) in solution was investigated. Intermolecular interactions were found to effectively decrease the luminescence lifetime via self-quenching with increasing fac-Ir(ppy)3 concentrations. A Stern-Volmer plot for quenching in acetonitrile was linear, due to bimolecular self-quenching, but curved in toluene as the result of excimer formation. (1)H NMR spectra demonstrated a monomer-aggregate equilibrium which resulted in spectral shifts depending on solvent polarity. X-ray crystallography provided structural information concerning the aggregate, which is based on a tetramer consisting of two ?-fac-Ir(ppy)3-?-fac-Ir(ppy)3 pairs. Offset ?-? stacking of ppy ligands and electrostatic dipole-dipole interactions between complex molecules play an important role in the formation of these molecular pairs.

Takayasu S; Suzuki T; Shinozaki K

2013-08-01

90

Intermolecular Interactions in Ternary Glycerol–Sample–H2O : Towards Understanding the Hofmeister Series (V)  

DEFF Research Database (Denmark)

We studied the intermolecular interactions in ternary glycerol (Gly)–sample (S)–H2O systems at 25?°C. By measuring the excess partial molar enthalpy of Gly, HGlyEHEGly, we evaluated the Gly–Gly enthalpic interaction, HGly-GlyEHEGly--Gly, in the presence of various samples (S). For S, tert-butanol (TBA), 1-propanol (1P), urea (UR), NaF, NaCl, NaBr, NaI, and NaSCN were used. It was found that hydrophobes (TBA and 1P) reduce the values of HGly-GlyEHEGly--Gly considerably, but a hydrophile (UR) had very little effect on HGly-GlyEHEGly--Gly. The results with Na salts indicated that there have very little effect on HGly-GlyEHEGly--Gly. This contrasts with our earlier studies on 1P–S–H2O in that Na+, F? and Cl? are found as hydration centers from the induced changes on HIP-IPEHEIP--IP in the presence of S, while Br?, I?, and SCN? are found to act as hydrophiles. In comparison with the Hofmeister ranking of these ions, the kosmotropes are hydration centers and the more kosmotropic the higher the hydration number, consistent with the original Hofmeister’s concept of “H2O withdrawing power.” Br?, I? and SCN?, on the other hand, acted as hydrophiles and the more chaotropic they are the more hydrophilic. These observations hint that whatever effect each individual ion has on H2O, it is sensitive only to hydrophobes (such as 1P) but not to hydrophiles (such as Gly). This may have an important bearing towards understanding the Hofmeister series, since biopolymers are amphiphilic and their surfaces are covered by hydrophobic as well as hydrophilic parts.

Westh, Peter; Rasmussen, Erik Lumby

2011-01-01

91

Production of low kinetic energy electrons and energetic ion pairs by Intermolecular Coulombic Decay.  

UK PubMed Central (United Kingdom)

PURPOSE: The paper gives an introduction into Interatomic and Intermolecular Coulombic Decay (ICD). ICD is an autoionization process, which contrary to Auger decay involves neighbouring sites of the initial vacancy as an integral part of the decay transition. As a result of ICD, slow electrons are produced which generally are known to be active in radiation damage. The author summarizes the properties of ICD and reviews a number of important experiments performed in recent years. MATERIALS AND METHODS: Intermolecular Coulombic Decay can generally take place in weakly bonded aggregates in the presence of ionizing particles or ionizing radiation. Examples collected here mostly use soft X-rays produced by synchrotron radiation to ionize, and use rare-gas clusters, water clusters or solutes in a liquid jet to observe ICD after irradiation. RESULTS: Intermolecular Coulombic Decay is initiated by single ionization into an excited state. The subsequent relaxation proceeds via an ultra-fast energy transfer to a neighbouring site, where a second ionization occurs. Secondary electrons from ICD have clearly been identified in numerous systems. ICD can take place after primary ionization, as the second step of a decay cascade which also involves Auger decay, or after resonant excitation with an energy which exceeds the ionization potential of the system. CONCLUSIONS: ICD is expected to play a role whenever particles or radiation with photon energies above the ionization energies for inner valence electrons are present in weakly bonded matter, e.g., biological tissue. The process produces at the same time a slow electron and two charged atomic or molecular fragments, which will lead to structural changes around the ionized site.

Hergenhahn U

2012-12-01

92

Programmable display of DNA-protein chimeras for controlling cell-hydrogel interactions via reversible intermolecular hybridization.  

UK PubMed Central (United Kingdom)

Extensive studies have been recently carried out to achieve dynamic control of cell-material interactions primarily through physicochemical stimulation. The purpose of this study was to apply reversible intermolecular hybridization to program cell-hydrogel interactions in physiological conditions based on DNA-antibody chimeras and complementary oligonucleotides. The results showed that DNA oligonucleotides could be captured to and released from the immobilizing DNA-functionalized hydrogels with high specificity via DNA hybridization. Accordingly, DNA-antibody chimeras were captured to the hydrogels, successfully inducing specific cell attachment. The cell attachment to the hydrogels reached the plateau at approximately half an hour after the functionalized hydrogels and the cells were incubated together. The attached cells were rapidly released from the bound hydrogels when triggering complementary oligonucleotides were introduced to the system. However, the capability of the triggering complementary oligonucleotides in releasing cells was affected by the length of intermolecular hybridization. The length needed to be at least more than 20 base pairs in the current experimental setting. Notably, because the procedure of intermolecular hybridization did not involve any harsh condition, the released cells maintained the same viability as that of the cultured cells. The functionalized hydrogels also exhibited the potential to catch and release cells repeatedly. Therefore, this study demonstrates that it is promising to regulate cell-material interactions dynamically through the DNA-programmed display of DNA-protein chimeras.

Zhang Z; Li S; Chen N; Yang C; Wang Y

2013-04-01

93

Iodinated ortho-carboranes as versatile building blocks to design intermolecular interactions in crystal lattices.  

UK PubMed Central (United Kingdom)

The crystal structures of numerous iodinated ortho-carboranes have been studied, which has revealed the diversity of intermolecular interactions that these substances can adopt in the solid state. The nature-mostly as it relates to hydrogen and/or halogen bonds-and relative strength of such interactions can be adjusted by selectively introducing substituents onto the cluster, thus enabling the rational design of crystal lattices. In this work we present the newly determined crystal structures of the following iodinated ortho-carboranes: 9-I-1,2-closo-C(2)B(10)H(11), 4,5,7,8,9,10,11,12-I(8)-1,2-closo-C(2)B(10)H(4), 3,4,5,6,7,8,9,10,11,12-I(10)-1,2-closo-C(2)B(10)H(2), 1-Me-8,9,10,12-I(4)-1,2-closo-C(2)B(10)H(7), 1,2-Me(2)-8,9,10,12-I(4)-1,2-closo-C(2)B(10)H(6), and 1,2-Ph(2)-8,9,10,12-I(4)-1,2-closo-C(2)B(10)H(6). Their 3D supramolecular organization has been thoroughly investigated and compared to similar previously published crystal structures. Such a systematic survey has allowed us to draw some general trends. C(c)-HI--B hydrogen bonds (C(c)= cluster carbon atoms) appear to be significant in the growth of the crystal lattices of these compounds, given the acidity of hydrogen atoms bonded to C(c), and the polarization of B-I bonds. These hydrogen bonds can be disrupted by selectively blocking the positions next to C(c), that is, B(3) and B(6), with bulky substituents that prevent iodine atoms from approaching as hydrogen acceptors. Halogen bonds of the type B-II-B are frequently observed in most cases, thus suggesting that these interactions could be attractive in boron clusters. In addition, different substituents can be grafted onto the ortho-carborane surface, thereby providing further possibilities for homomeric or heteromeric molecular assembly.

Puga AV; Teixidor F; Sillanpää R; Kivekäs R; Viñas C

2009-09-01

94

The effect of intermolecular interaction on the output of carbon in carbonization processes. Vliyaniye mezhmolekulyarnogo vzaimodeystviya na vykhod ugleroda v protsessakh karbonizatsii  

Energy Technology Data Exchange (ETDEWEB)

The work uses a kinetic approach to analyze the processes of carbonization in organic systems of petroleum and coal tars and petroleum residues polydispersed in mass and composition. The relationship between the caking and plastic properties of tars, which are characterized by cokability and softening point, is theoretically justified and experimentally tested in accordance with concepts about the theory of petroleum dispersed systems about the presence of micellar structures in petroleum and coal systems. The linear relationship between the cokability and the energy of intermolecular interaction acquired from rheological measurements is established. The established relationships have a nature universal for polydispersed systems. The following stages of the process are noted: a rapid stage of carbonization inside the micellium and a slow diffusion stage of impregnation of the micellii by low molecular components of the medium. A classification is proposed of the cokability of the tars based on the energies of intermolecular interaction in a viscous flow state. For tars with a cokability of 10, 50 and 100 percent these energies are 24, 130 and 265 kilojoules per mole and are close to the energy of hydrogen, donor acceptor and covalent chemical bonds.

Dolmatov, M.Yu.; Akhmetov, S.A.; Dolmatov, L.V.

1984-01-01

95

Detection of short-lived transient protein-protein interactions by intermolecular nuclear paramagnetic relaxation: plastocyanin from Anabaena variabilis.  

Science.gov (United States)

An NMR approach is presented that provides detailed information about short-lived, transient interactions between protein molecules in solution. The approach is based on the longitudinal paramagnetic relaxation rates of the protein nuclei and requires that at least one of the interacting molecules is paramagnetic. The specific interactions are monitored by the intermolecular paramagnetic contribution to the relaxation of protons at or close to the interaction surface. By applying the approach to plastocyanin from Anabaena variabilis, specific regions of interaction that may be involved in the electron self-exchange process of this plastocyanin were identified. This is in accord with recent 15N NMR relaxation studies of the backbone dynamics of Anabaena variabilis plastocyanin, with site-directed mutagenesis studies of the functional importance of the corresponding regions in Phormidium laminosum plastocyanin and with the crystal packing surface of P. laminosum plastocyanin. PMID:12783525

Hansen, D Flemming; Hass, Mathias A S; Christensen, Hans M; Ulstrup, Jens; Led, Jens J

2003-06-11

96

Single walled carbon nanotubes functionalized with hydrides as potential hydrogen storage media: A survey of intermolecular interactions  

Energy Technology Data Exchange (ETDEWEB)

In this paper, we have analyzed the intermolecular interactions between H{sub 2} and single walled carbon nanotube (SWCNT)-hydride complexes and project their capability as a practicable hydrogen storage medium (HSM). In this respect, we have investigated the type of interactions namely van der Waals, electrostatic, and orbital interactions to understand the molecular hydrogen binding affinity of various systems. We found that the charge transfer effects coupled with induced electrostatic interactions are responsible for synergetic action of SWCNT and hydrides on adsorption of H{sub 2} molecules at ambient conditions. Also we have calculated the thermodynamically usable capacity of hydrogen in all the systems. This study enables one to identify and design potential hydrogen storage materials. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Surya, V.J.; Iyakutti, K. [School of Physics, Madurai Kamaraj University, Madurai, Tamil Nadu (India); Venkataramanan, N.S.; Mizuseki, H.; Kawazoe, Y. [Institute for Materials Research, Tohoku University, Katahira Aoba-ku, Sendai (Japan)

2011-09-15

97

Closed-shell ring coupled cluster doubles theory with range separation applied on weak intermolecular interactions  

CERN Multimedia

We explore different variants of the random phase approximation (RPA) to the correlation energy derived from closed-shell ring-diagram approximations to coupled cluster doubles theory. We implement these variants in range-separated density-functional theory, i.e. by combining the long-range random phase approximations with short-range density-functional approximations. We perform tests on the rare-gas dimers He_2, Ne_2, and Ar_2, and on the weakly interacting molecular complexes of the S22 set of Jurecka et al. [Phys. Chem. Chem. Phys. 8, 1985 (2006)]. The two best variants correspond to the ones originally proposed by Szabo and Ostlund [J. Chem. Phys. 67, 4351 (1977)]. With range separation, they reach mean absolute errors on the equilibrium interaction energies of the S22 set of about 0.4 kcal/mol, corresponding to mean absolute percentage errors of about 4 %, with the aug-cc-pVDZ basis set.

Toulouse, Julien; Savin, Andreas; Jansen, Georg; Angyán, János G

2011-01-01

98

Proper correction for the basis set superposition error in SCF calculations of intermolecular interactions  

Science.gov (United States)

The effects of basis set extension to the space of the partner monomer in supermolecular SCF and perturbation calculations have been analysed for the model He2 and HeLi+ systems. In contrast to the suggestions of many authors it is demonstrated that the correction for the basis set superposition error should be calculated with the full basis set of the dimer without removing the occupied orbitals of the partner monomer. In fact, the enlargement of the monomer basis set by the partner occupied orbitals effectively improves the first-order exchange interaction energy. For the first-order electrostatic interaction energy any enlargement of a poor or medium size basis set of the monomer by the partner orbitals worsens its value.

Gutowski, Maciej; van Duijneveldt, Frans B.; Cha?asi?ski, Grzegorz; Piela, Lucjan

99

Lack of evidence for intermolecular epistatic interactions between adiponectin and resistin gene polymorphisms in Malaysian male subjects  

Scientific Electronic Library Online (English)

Full Text Available Abstract in english Epistasis (gene-gene interaction) is a ubiquitous component of the genetic architecture of complex traits such as susceptibility to common human diseases. Given the strong negative correlation between circulating adiponectin and resistin levels, the potential intermolecular epistatic interactions between ADIPOQ (SNP+45T > G, SNP+276G > T, SNP+639T > C and SNP+1212A > G) and RETN (SNP-420C > G and SNP+299G > A) gene polymorphisms in the genetic risk underlying type 2 diabe (more) tes (T2DM) and metabolic syndrome (MS) were assessed. The potential mutual influence of the ADIPOQ and RETN genes on their adipokine levels was also examined. The rare homozygous genotype (risk alleles) of SNP-420C > G at the RETN locus tended to be co-inherited together with the common homozygous genotypes (protective alleles) of SNP+639T > C and SNP+1212A > G at the ADIPOQ locus. Despite the close structural relationship between the ADIPOQ and RETN genes, there was no evidence of an intermolecular epistatic interaction between these genes. There was also no reciprocal effect of the ADIPOQ and RETN genes on their adipokine levels, i.e., ADIPOQ did not affect resistin levels nor did RETN affect adiponectin levels. The possible influence of the ADIPOQ gene on RETN expression warrants further investigation.

Lau, Cia-Hin; Muniandy, Sekaran

2012-01-01

100

Lack of evidence for intermolecular epistatic interactions between adiponectin and resistin gene polymorphisms in Malaysian male subjects  

Directory of Open Access Journals (Sweden)

Full Text Available Epistasis (gene-gene interaction) is a ubiquitous component of the genetic architecture of complex traits such as susceptibility to common human diseases. Given the strong negative correlation between circulating adiponectin and resistin levels, the potential intermolecular epistatic interactions between ADIPOQ (SNP+45T > G, SNP+276G > T, SNP+639T > C and SNP+1212A > G) and RETN (SNP-420C > G and SNP+299G > A) gene polymorphisms in the genetic risk underlying type 2 diabetes (T2DM) and metabolic syndrome (MS) were assessed. The potential mutual influence of the ADIPOQ and RETN genes on their adipokine levels was also examined. The rare homozygous genotype (risk alleles) of SNP-420C > G at the RETN locus tended to be co-inherited together with the common homozygous genotypes (protective alleles) of SNP+639T > C and SNP+1212A > G at the ADIPOQ locus. Despite the close structural relationship between the ADIPOQ and RETN genes, there was no evidence of an intermolecular epistatic interaction between these genes. There was also no reciprocal effect of the ADIPOQ and RETN genes on their adipokine levels, i.e., ADIPOQ did not affect resistin levels nor did RETN affect adiponectin levels. The possible influence of the ADIPOQ gene on RETN expression warrants further investigation.

Cia-Hin Lau; Sekaran Muniandy

2012-01-01

 
 
 
 
101

Circular dichroism studies on intermolecular interactions of amphotericin B in ionic liquid-rich environments.  

UK PubMed Central (United Kingdom)

Aggregation of amphotericin B (AmB) in an ionic liquid-rich environment was investigated using circular dichroism (CD) spectroscopy. It was found that nature of the ionic liquids' anion had a strong impact not only on the aggregation of AmB, but more importantly on the nature of AmB aggregates, as observed in the asymmetry of the exciton couplet of the aggregate in CD spectra. Unique CD signals for AmB aggregates were observed in three different 1-butyl-3-methylimidazolium ionic liquid solutions: [C4 -mim]Br favored the formation of AmB aggregates that were similar to those found in water, whereas [C4 -mim]BF4 and [C4 -mim]NO3 produced AmB aggregates that were different from each other and those found in water. The obtained results suggest that the designer solvent ability of ionic liquids could be expanded to address numerous intermolecular processes.

Jameson LP; Dzyuba SV

2013-07-01

102

Structure and intermolecular interactions in selected binary solutions studied by X-ray methods  

Science.gov (United States)

The results of X-ray structural studies of liquid chloroanisole C6H4OCH3Cl and 10% solutions of chloroanisole in 1,4-dimethylbenzene C8H10 are presented. It is the first paper on an X-ray diffraction study of the liquid solutions of chloroanisole. The X-ray measurements were made at 293 K for the scattering angle range 2? varying from 6° to 120°. Averaged scattered X-ray angular distributions I¯(S) were determined. The angular distributions of the intensity of X-ray scattered by 10% solutions of chloroanisole in 1,4-dimethylbenzene were compared to the angular distributions obtained for liquid ortho-, meta- and para-chloroanisole. The differential radial distribution functions of electron density 4?r?j,knK[?k(r)??0] were numerically found using the Fourier analysis from a modified Warren, Krutter and Morningstar equation. To the maxima of DRDFs, interatomic and intermolecular distances were assigned. The use of short-wave radiation from an X-ray tube with a molybdenum anode permitted determination of the spheres of intermolecular ordering in the studied liquids and their solutions. The experimental results were used to plot models of the most highly probable mutual disposition of the molecules in liquid chloroanisole and their solutions. The benzene rings of two molecules are situated in parallel plane what results in antiparallel setting of the dipole moments of the chloroanisole molecules. X-ray structural analysis was applied to determine the packing coefficients of chloroanisole molecules. The results obtained in this paper confirm the specific structural properties of the solutions studied.

Drozdowski, Henryk; Romaniuk, Anna; B?aszczak, Zdzis?aw

2013-12-01

103

Identification of molecular crystals capable of undergoing an acyl-transfer reaction based on intermolecular interactions in the crystal lattice.  

UK PubMed Central (United Kingdom)

Investigation of the intermolecular acyl-transfer reactivity in molecular crystals of myo-inositol orthoester derivatives and its correlation with crystal structures enabled us to identify the essential parameters to support efficient acyl-transfer reactions in crystals: 1)?the favorable geometry of the nucleophile (?OH) and the electrophile (C?O) and 2)?the molecular assembly, reinforced by C?H???? interactions, which supports a domino-type reaction in crystals. These parameters were used to identify another reactive crystal through a data-mining study of the Cambridge Structural Database. A 2:1 co-crystal of 2,3-naphthalene diol and its di-p-methylbenzoate was selected as a potentially reactive crystal and its reactivity was tested by heating the co-crystals in the presence of solid sodium carbonate. A facile intermolecular p-toluoyl group transfer was observed as predicted. The successful identification of reactive crystals opens up a new method for the detection of molecular crystals capable of exhibiting acyl-transfer reactivity.

Tamboli MI; Krishnaswamy S; Gonnade RG; Shashidhar MS

2013-09-01

104

Natural states of interacting systems and their use for the calculation of intermolecular forces. II  

International Nuclear Information System (INIS)

The asymptotic natural states i.e. the natural states of the subsystems in the various terms of the asymptotic expansion of the primitive wavefunction of the supersystem are defined. Intergro-differential equations are derived that allow the direct calculation of these asymptotic natural states and from them, the terms C6, C8 etc. in the asymptotic 1/R expansion of the interaction energy. A pictorial interpretation of these states is given and the rapid convergence of the expansion in natural states is explained. The transferability of certain matrix elements is demonstrated and a virtually exact combination rule for the calculation of the Csub(k) coefficients between different atoms from those for like atoms is obtained. The effects of intra-atomic electron correlation of the Csub(k) as well as the justification of a core-valence separation are discussed. (Auth.)

1978-08-15

105

Relação entre transferência de carga e as interações intermoleculares em complexos de hidrogênio heterocíclicos Relationship between charge transfer and intermolecular interactions in heterocyclic hydrogen-bonded complexes  

Directory of Open Access Journals (Sweden)

Full Text Available Hydrogen-bonded complexes formed by the interaction of the heterocyclic molecules C2H4O and C2H5N with HF, HCN, HNC and C2H2 have been studied using density functional theory. The hydrogen bond strength has been analyzed through electron density charge transfer from the proton acceptor to the proton donor. The density charge transfer has been estimated using different methods such as Mulliken population analysis, CHELPG, GAPT and AIM. It has been shown that AIM-estimated charge transfer correlates very well with the hydrogen bond energy and the infrared bathochromic effect of the proton donor stretching frequencies.

Boaz G. Oliveira; Regiane C. M. U. de Araújo

2007-01-01

106

Transport properties in mixtures involving carbon dioxide at low and moderate density: test of several intermolecular potential energies and comparison with experiment  

Energy Technology Data Exchange (ETDEWEB)

It is the purpose of this paper to extract unlike intermolecular potential energies of five carbon dioxide-based binary gas mixtures including CO{sub 2}-He, CO{sub 2}-Ne, CO{sub 2}-Ar, CO{sub 2}-Kr, and CO{sub 2}-Xe from viscosity data and compare the calculated potentials with other models potential energy reported in literature. Then, dilute transport properties consisting of viscosity, diffusion coefficient, thermal diffusion factor, and thermal conductivity of aforementioned mixtures are calculated from the calculated potential energies and compared with literature data. Rather accurate correlations for the viscosity coefficient of afore-cited mixtures embracing the temperature range 200 Kintermolecular potentials energy. Our estimated accuracies for the viscosity are to within {+-}2%. In addition, the calculated potential energies are used to present smooth correlations for other transport properties. The accuracies of the binary diffusion coefficients are of the order of {+-}3%. Finally, the unlike interaction energy and the calculated low density viscosity have been employed to calculate high density viscosities using Vesovic-Wakeham method. (orig.)

Moghadasi, Jalil; Yousefi, Fakhri [Shiraz University, Department of Chemistry, Shiraz (Iran); Papari, Mohammad Mehdi; Faghihi, Mohammad Ali [Shiraz University of Technology, Department of Chemistry, Shiraz (Iran); Mohsenipour, Ali Asghar [University of Waterloo, Department of Chemical Engineering, Waterloo (Canada)

2009-09-15

107

Intermolecular interactions and thermodynamic properties of 3,6-diamino-1,2,4,5-tetrazine-1,4-dioxide dimers: A density functional theoretical study  

Scientific Electronic Library Online (English)

Full Text Available Abstract in english Three fully optimized structures of 3,6-diamino-1,2,4,5-tetrazine-1,4-dioxide (LAX-112) dimers have been obtained with the density functional theory (DFT) method at the B3LYP/6-311++G level. Vibrational frequency calculations were carried out to ascertain that each structure is a minimum (no imaginary frequencies). The intermolecular interaction energy is calculated with the basis set superposition error (BSSE) correction and zero point energy (ZPE) correction. The greate (more) st corrected binding energy among the three dimers is -42.38 kJ mol-1. The charge redistribution mainly occurs on the adjacent O(N)......H atoms between submolecules and the charge transfer between two subsystems is very small. Natural bond orbital (NBO) analysis was performed to reveal the origin of the interaction. Based on the vibrational analysis, the standard thermodynamic functions (heat capacities (cºp), entropies (S°m) and enthalpies (H°m)) and the changes of thermodynamic properties from the monomer to dimer with the temperature ranging from 200.00 K to 800.00 K have been obtained using statistical thermodynamics. The results show that the strong hydrogen bonds dominantly contribute to the dimers, while the bonding energies are not only determined by the hydrogen bonding. The dimerization process of dimer II can occur spontaneously at room temperature.

Zhao, Ning Ning; Zhao, Ya Ling; Hu, Yin; Ma, Hai Xia; Zhao, Feng Qi; Song, Ji Rong

2013-08-01

108

Study of intermolecular interactions in binary mixtures of 2'-chloro-4-methoxy-3-nitro benzil in various solvents and at different concentrations by the measurement of acoustic properties.  

UK PubMed Central (United Kingdom)

Density (?), ultrasonic velocity (u), adiabatic compressibility (?), apparent molar volume (Ø), acoustic impedance (Z), intermolecular free length (L(f)), relative association (RA) of binary mixtures of 2'-chloro-4-methoxy-3-nitro benzil (abbreviated as 2CBe) in ethanol, acetonitrile, chloroform, dioxane and benzene were measured at different concentrations at 298 K. Several useful parameters such as excess density, excess ultrasonic velocity, excess adiabatic compressibility, excess apparent molar volume, excess acoustic impedance and excess intermolecular free length have been calculated. These parameters are used to explain the nature of intermolecular interactions taking place in the binary mixture. The above study is useful in understanding the solute--solvent interactions occurring in different concentrations at room temperature.

Nithya G; Thanuja B; Kanagam CC

2013-01-01

109

Relação entre transferência de carga e as interações intermoleculares em complexos de hidrogênio heterocíclicos/ Relationship between charge transfer and intermolecular interactions in heterocyclic hydrogen-bonded complexes  

Scientific Electronic Library Online (English)

Full Text Available Abstract in english Hydrogen-bonded complexes formed by the interaction of the heterocyclic molecules C2H4O and C2H5N with HF, HCN, HNC and C2H2 have been studied using density functional theory. The hydrogen bond strength has been analyzed through electron density charge transfer from the proton acceptor to the proton donor. The density charge transfer has been estimated using different methods such as Mulliken population analysis, CHELPG, GAPT and AIM. It has been shown that AIM-estimated (more) charge transfer correlates very well with the hydrogen bond energy and the infrared bathochromic effect of the proton donor stretching frequencies.

Oliveira, Boaz G.; Araújo, Regiane C. M. U. de

2007-08-01

110

Intermolecular forces - hybrid calculations  

International Nuclear Information System (INIS)

The available theoretical methods for the calculation of molecular interactions can be divided into three categories: 1) 'a priori' methods, 2) semi-empirical methods and 3) hybrid methods. The author presents the modification of a previously introduced hybrid method which is useful to predict intermolecular forces with precision comparable to that obtained from experimental information

1980-02-15

111

Multibody effects in intermolecular interactions and reaction pathways for catalytic processes. Part II the contributions of Sidonio Castillo  

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish Aquí continuaremos la revisión del trabajo de Octavio Novaro y sus colaboradores en los importantes campos de la no aditividad de las interacciones intermoleculares y de la catálisis, enfatizando las contribuciones de Sidonio Castillo que resultaron altamente útiles en este esfuerzo conjunto, antes de su prematuro fallecimiento. Sus primeros trabajos, con reconocidos científico polacos en los trímeros de metáno y amoniaco y con coautores ingleses en trimeros y tetr (more) ameros de fósforo y nitrógeno, serán presentados primero, seguidos de sus estudiós sobre la activación catalítica de moléculas de metáno, silano y germano (de alto potencial en aplicaciónes valiosas). Sus primeros trabajos en catálisis formaron parte de su tesis doctoral dirigida por O. Novaro y los últimos fueron consecuencia de las tesis doctorales que el Dr. Castillo dirigió a los otros dos coautores de esta revisión. Esta labor fue desgraciadamente interrumpida por la muerte de Sidonio. Así concluyó su corta pero brillante carrera. Abstract in english We here continue the review on the work of Octavio Novaro and collaborators in the important field of nonadditivity of intermolecular interactions and catalysis, with special interest in the work that Sidonio Castillo contributed to this effort before his demise. His early work with Polish coauthors on methane and ammonia trimers and with British coauthors on N3, P3, N4 and P4 are highlighted. Then our focus will shift mainly to his work on the activation of methane, sila (more) ne and germane starting with his Ph.D. thesis under O. Novaro and ending in his last papers with the present authors which marked the end of his short but brilliant career.

Novaro, O.; Pacheco-Sánchez, J.H.; Luna, H.

2009-10-01

112

Natural states of interacting systems and their use for the calculation of intermolecular forces. I  

International Nuclear Information System (INIS)

The theory of the primitive function of a supersystem consisting of interacting subsystems is concisely reviewed and the subsystem density matrices and the natural states of the interacting subsystems are defined. Integro-differential equations for the natural states are derived and the physical meaning of these states - which differ basically from spectroscopic states - is discussed. (Auth.)

1978-08-15

113

The theory of intermolecular forces  

CERN Document Server

The theory of intermolecular forces has advanced very greatly in recent years. It has become possible to carry out accurate calculations of intermolecular forces for molecules of useful size, and to apply the results to important practical applications such as understanding protein structure and function, and predicting the structures of molecular crystals. The Theory of Intermolecular Forces sets out the mathematical techniques that are needed to describe and calculate intermolecular interactions and to handle the more elaborate mathematical models. It describes the methods that are used to calculate them, including recent developments in the use of density functional theory and symmetry-adapted perturbation theory. The use of higher-rank multipole moments to describe electrostatic interactions is explained in both Cartesian and spherical tensor formalism, and methods that avoid the multipole expansion are also discussed. Modern ab initio perturbation theory methods for the calculation of intermolecular inte...

Stone, Anthony J

2013-01-01

114

Polymer materials for electro-optic and optoelectronic applications: maximizing device performances by creating desirable intermolecular electrostatic interactions  

Science.gov (United States)

In EO polymer materials, the second-order nonlinear optic chromophores must be oriented in one direction in order to be electro-optically active. Interchromophore electrostatic interactions, which encourages the formation of non-active and light-scattering crystalline domains through the antiparallel stacking of dipoles, have long been an obstacle to the translation of large molecular optical nonlinearity into corresponding bulk nonlinearity. Great progresses have been made in the design and synthesis of chormophores with reduced electrostatic interactions. New effort toward the complete elimination of the destructive effect of the electrostatic forces is on the way. On the contrary, strong intermolecular electrostatic interaction (e.g. the force responsible for ?-? stacking of conjugated systems) is often desired in LED, transistor and photovoltaic (PV) devices since high mobilities of the charge carriers are the key to their high performances and often come from ordered stacking of pi-conjugated systems. For PV applications, bi-continuous "bulk heterojunction" of electron donor (D) and acceptor (A) is ideal for efficient charge carrier generation, transport and collection. Differential electrostatic interactions between D and A is the key to the formation of such morphology. We have synthesized a novel type of block copolymer having a basic unit of D-B-A (B is a non-conjugate bridge) for solar cell application. D and A can be designed in such a way that D-D and A-A interactions are stronger than the D-A interaction, and therefore, have a strong tendency to phase separate.

Zhang, Cheng; Sun, Sam-Shajing; Bonner, Carl E.; Kim, Songku; Fetterman, Harold R.; Dalton, Larry R.

2005-12-01

115

12C/13C and H/D vapor pressure isotope effects of fluoroform: intermolecular interactions in liquid fluoroform  

International Nuclear Information System (INIS)

A precision cryostat of the Bigeleisen-Brooks-Ribnikar-Ishida (BBIR) type with associated vacuum systems has been constructed and the appropriate temperature/pressure measurement and control systems designed and implemented. Various improvements in the cryostat design were incorporated in order to facilitate the assembly and repair processes. A major design change involved the incorporation of a digital stand alone computer to control cryostat operations. This apparatus was used to measure the 12C/13C and H/D Vapor Pressure Isotope Effects of Fluoroform. Analysis of the measured VPIE results, in light of existing experimental data and theories, has demonstrated the need of a temperature dependent liquid force field, specifically a temperature-dependent interaction force constant between the C-H stretching motion and translational motion in the direction of the figure axis of CHF3. This result is consistent with the observed spectroscopic data and vibrational and configurational models of fluoroform dimers. The intermolecular interaction is believed to be a weak hydrogen-bond in nature.

1981-01-01

116

Intermolecular interaction effects on the ultrafast depolarization of the optical emission from conjugated polymers.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We have investigated the effect of interchain interactions on the ultrafast depolarization of the photoluminescence from solid films of a conjugated polymer. Accurate control was exercised over the interchain separation by threading of the conjugated chains with insulating macrocycles or complexatio...

Chang, MH; Frampton, MJ; Anderson, HL; Herz, LM

117

Interaction of red blood cells with a polarized electrode: evidence of long-range intermolecular forces.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We have investigated the electrostatic interaction of glutaraldehyde-fixed human red cells with a polarizable electrode carrying a defined surface charge density which can be varied continuously through a wide range. Cells in a dilute salt solution are unable to adhere to the electrode at high negat...

Gingell, D; Fornes, J A

118

Impact of molecular structure on intermolecular interactions and organic luminescence in supramolecular systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Supramolecular chemistry provides a versatile approach to tune organic solid state luminescence by controlling the molecular organization through weak interactions. In this study, we have successfully tuned the solid state luminescence of 2-cyano-3(4-(diphenylamino)phenyl)acrylic ac...

119

Synthesis, crystal structures and intermolecular interactions of two Mn(II) complexes with 4,4?-bipy and methyl benzoates  

Science.gov (United States)

Two manganese complexes containing 4,4?-bipyridine and methyl benzoate as ligands have been prepared and crystallized by solvent evaporation method in DMF. The single crystal X-ray crystallographic analyses reveal that the complexes crystallize in monoclinic system. Crystal of 1 [Mn2(4,4?-bipy)2 (o-MBA)4]n has space group of P21/c with unit cell parameters of a = 17.508 (Å), b = 11.6229 (Å), c = 27.983 (Å), ? = 128.123°, V = 4.4797 nm3, empirical formula: C52H44Mn2N4O8, Mr = 962.79, Z = 4, Dc = 1.428 g/cm3, ? = 0.625 mm-1, and F(000) = 1992. The crystal of 2 [Mn (4,4?-bipy)(m-MBA)2]n belongs to space group C2/c with a = 16.079 (Å), b = 11.652 (Å), c = 24.887 (Å), ? = 92.02°, V = 4.660 nm3, empirical formula: C26H22MnN2O4, Mr = 481.40, Z = 8, Dc = 1.372 g/cm3, ? = 1.179 mm-1, F(000) = 1992. The weak interactions in structures are observed from the X-ray crystallographic data. These include the CH\\ctdot O hydrogen bonds, ?-? stacking and CH\\ctdot ? interactions found in 1. The different strength of intermolecular interaction in the structures is reflected on their different thermal stability of the two complexes measured by thermal gravimetric analysis and the 2D-IR correlation spectroscopy. The study of weak interactions is meaningful to provide supporting data for potential application in molecular biology.

Xin-Jian, Wu; Yi-Ping, Chen; Ze-Min, Xia; Su-Zhi, Ge; Feng, Chai; Ling-Yan, Zhao; Jian-Zhong, Chen

2013-03-01

120

Redetermined structure of diphenylphosphonimidotriphenylphosphorane: location of the hydrogen atoms and analysis of the intermolecular interactions  

Directory of Open Access Journals (Sweden)

Full Text Available The title compound, C30H25NOP2, is a bulky phosphazene derivative. Its previous crystal structure [Cameron et al. (1979). Acta Cryst. B35, 1373–1377] is confirmed and its H atoms have been located in the present study. The formal P=N double bond is about 0.05?Å shorter than the P—N single bond and the large P=N—P bond angle reflects the steric strain in the molecule. An intramolecular C—H...O interaction occurs. In the crystal, short C—H...O contacts connect the molecules into chains propagating in [011], which are cross-linked via C—H...? interactions, generating a three-dimensional network. Aromatic ?–? stacking also occurs [shortest centroid–centroid separation = 3.6012?(11)?Å].

Richard Betz; Thomas Gerber; Eric Hosten; Henk Schalekamp

2011-01-01

 
 
 
 
121

Prediction of polymer mixture compatibility by Monte Carlo simulation of intermolecular binary interactions  

CERN Multimedia

We have evaluated conformational and orientational averages of binary interaction integrals for pairs of chains constituting atomistic representations of short polymer molecules. By considering A-A, B-B and A-B pairs, we relate these results with the Flory-Huggins parameter for the A-B mixtures. This parameter is commonly accepted as a good indicator of compatibility. Since the method ignores the simultaneous interactions with other molecules in the mixture, the local environment is approximately described by introducing an effective medium dielectric constant whose value is conveniently parameterized. The results for four different real systems are compared with data obtained from experimental neutron scattering data. The method qualitatively predicts the sign and variation with temperature in the four different cases, also showing a reasonable quantitative agreement in some of the cases. Its performance is discussed in comparison with a standard method that evaluates the Flory-Huggins parameter by calculati...

Ahmadi, Amirhossein

2009-01-01

122

The molecular structure and intermolecular interactions of 1,3:2,4-dibenzylidene-D-sorbitol  

Science.gov (United States)

The 1,3(R):2,4(S)-dibenzylidene-D-sorbitol (DBS) molecule is a low molar mass organic gelator (LMOG) that is capable of hydrogen-bonding with itself. As a consequence, DBS molecules self-organize into nanofibrillar networks at relatively low concentrations in a wide variety of organic solvents and polymers. In this work, molecular mechanics and molecular dynamics simulations were conducted to elucidate the equilibrium structure of DBS and the molecular interactions that govern DBS self-assembly. Molecular mechanics calculations performed on single DBS molecules with Cerius2 and InsightII software reveal that the phenyl rings tend to adopt an equatorial position and that the pendant hydroxyl group prefers to form an intramolecular hydrogen bond with an acetal oxygen, in contrast to the terminal hydroxyl group. Molecular mechanics and molecular dynamics on DBS dimers reveal that they are capable of forming hydrogen bonds and participating in ? interactions, suggesting that the mechanism of nanofibrillar network formation may be complex, involving more than one type of physical interaction.

Wilder, Elizabeth A.; Spontak, Richard J.; Hall, Carol K.

123

Mass analyzed threshold ionization spectra of phenol...Ar2: ionization energy and cation intermolecular vibrational frequencies.  

Science.gov (United States)

The phenol(+)...Ar(2) complex has been characterized in a supersonic jet by mass analyzed threshold ionization (MATI) spectroscopy via different intermediate intermolecular vibrational states of the first electronically excited state (S(1)). From the spectra recorded via the S(1)0(0) origin and the S(1)?(x) intermolecular vibrational state, the ionization energy (IE) has been determined as 68,288 ± 5 cm(-1), displaying a red shift of 340 cm(-1) from the IE of the phenol(+) monomer. Well-resolved, nearly harmonic vibrational progressions with a fundamental frequency of 10 cm(-1) have been observed in the ion ground state (D(0)) and assigned to the symmetric van der Waals (vdW) bending mode, ?(x), along the x axis containing the C-O bond. MATI spectra recorded via the S(1) state involving other higher-lying intermolecular vibrational states (?(s)(1), ?(x)(3), ?(s)(1)?(x)(1), ?(s)(1)?(x)(2)) are characterized by unresolved broad structures. PMID:21063583

Armentano, Antonio; Tong, Xin; Riese, Mikko; Pimblott, Simon M; Müller-Dethlefs, K; Fujii, Masaaki; Dopfer, Otto

2010-11-09

124

Co-amorphous simvastatin and glipizide combinations show improved physical stability without evidence of intermolecular interactions  

DEFF Research Database (Denmark)

The objective of this study was to prepare a co-amorphous drug/drug combination between two BCS class II drugs, simvastatin (SVS) and glipizide (GPZ). This pharmacologically relevant combination of two drugs could produce a promising candidate for formulations intended for combination therapy of metabolic disorders. The co-amorphous SVS-GPZ mixtures (molar ratios 2:1, 1:1 and 1:2) were prepared by mechanical activation (ball milling or cryomilling) and characterized with respect to their thermal properties, possible molecular interactions, dissolution properties and physical stability, and compared to the behaviour of pure amorphous forms and their physical mixtures. It was found that even though a molecular mixture was achieved with all SVS-GPZ mixture ratios, no molecular interactions between the drugs could be detected. By formation of co-amorphous single-phase mixtures, only the dissolution rate of GPZ could be improved. The co-amorphous mixtures showed improved stability compared to the pure amorphous forms and the amorphous physical mixtures. It was concluded that this was attributable to the molecular level mixing of SVS with GPZ upon milling, and GPZ is acting as an anti-plasticizer in these mixtures.

Löbmann, Korbinian; Strachan, Clare

2012-01-01

125

Intermolecular Interaction Between Cry2Aa and Cyt1Aa and Its Effect on Larvicidal Activity Against Culex quinquefasciatus.  

Science.gov (United States)

The Cyt1Aa protein of Bacillus thuringiensis susbp. israelensis elaborates demonstrable toxicity to mosquito larvae, but more importantly, it enhances the larvicidal activity of this species Cry proteins (Cry11Aa, Cry4Aa, and Cry4Ba) and delays the phenotypic expression of resistance to these that has evolved in Culex quinquefasciatus. It is also known that Cyt1Aa, which is highly lipophilic, synergizes Cry11Aa by functioning as a surrogate membrane-bound receptor for the latter protein. Little is known, however, about whether Cyt1Aa can interact similarly with other Cry proteins not primarily mosquitocidal; for example, Cry2Aa, which is active against lepidopteran larvae, but essentially inactive or has very low toxicity to mosquito larvae. Here we demonstrate by ligand binding and enzyme-linked immunosorbent assays that Cyt1Aa and Cry2Aa form intermolecular complexes in vitro, and in addition show that Cyt1Aa facilitates binding of Cry2Aa throughout the midgut of C. quinquefasciatus larvae. As Cry2Aa and Cry11Aa share structural similarity in domain II, the interaction between Cyt1Aa and Cry2Aa could be a result of a similar mechanism previously proposed for Cry11Aa and Cyt1Aa. Finally, despite the observed interaction between Cry2Aa and Cyt1Aa, only a 2-fold enhancement in toxicity resulted against C. quinquefasciatus. Regardless, our results suggest that Cry2Aa could be a useful component of mosquitocidal endotoxin complements being developed for recombinant strains of B. thuringiensis subsp. israelensis and B. sphaericus aimed at improving the efficacy of commercial products and avoiding resistance. PMID:23727800

Bideshi, Dennis K; Waldrop, Greer; Fernandez-Luna, Maria Teresa; Diaz-Mendoza, Mercedes; Wirth, Margaret C; Johnson, Jeffrey J; Park, Hyun-Woo; Federici, Brian A

2013-08-28

126

Intermolecular Interaction Between Cry2Aa and Cyt1Aa and Its Effect on Larvicidal Activity Against Culex quinquefasciatus.  

UK PubMed Central (United Kingdom)

The Cyt1Aa protein of Bacillus thuringiensis susbp. israelensis elaborates demonstrable toxicity to mosquito larvae, but more importantly, it enhances the larvicidal activity of this species Cry proteins (Cry11Aa, Cry4Aa, and Cry4Ba) and delays the phenotypic expression of resistance to these that has evolved in Culex quinquefasciatus. It is also known that Cyt1Aa, which is highly lipophilic, synergizes Cry11Aa by functioning as a surrogate membrane-bound receptor for the latter protein. Little is known, however, about whether Cyt1Aa can interact similarly with other Cry proteins not primarily mosquitocidal; for example, Cry2Aa, which is active against lepidopteran larvae, but essentially inactive or has very low toxicity to mosquito larvae. Here we demonstrate by ligand binding and enzyme-linked immunosorbent assays that Cyt1Aa and Cry2Aa form intermolecular complexes in vitro, and in addition show that Cyt1Aa facilitates binding of Cry2Aa throughout the midgut of C. quinquefasciatus larvae. As Cry2Aa and Cry11Aa share structural similarity in domain II, the interaction between Cyt1Aa and Cry2Aa could be a result of a similar mechanism previously proposed for Cry11Aa and Cyt1Aa. Finally, despite the observed interaction between Cry2Aa and Cyt1Aa, only a 2-fold enhancement in toxicity resulted against C. quinquefasciatus. Regardless, our results suggest that Cry2Aa could be a useful component of mosquitocidal endotoxin complements being developed for recombinant strains of B. thuringiensis subsp. israelensis and B. sphaericus aimed at improving the efficacy of commercial products and avoiding resistance.

Bideshi DK; Waldrop G; Fernandez-Luna MT; Diaz-Mendoza M; Wirth MC; Johnson JJ; Park HW; Federici BA

2013-08-01

127

Protein rotation study of cytochrome P-450 in submitochondrial particles: effect of KCl and intermolecular interactions with redox partners.  

Science.gov (United States)

The rotational diffusion of cytochrome P-450 in submitochondrial particles (SMP) of bovine adrenocortical mitochondria was measured by detecting the decay of absorption anisotropy, r(t), after photolysis of the heme.CO complex by a vertically polarized laser flash. Analysis of r(t) was based on a "rotation-about-membrane normal" model. The measurements were used to investigate the effect of KCl on intermolecular interactions involving cytochrome P-450 and to investigate the interactions of cytochrome P-450 with other redox partners. The rotational diffusion of cytochrome P-450 was significantly dependent on KCl concentration. When the KCl concentration was increased from 0 to 1,000 mM, the mobile population of cytochrome P-450 was increased from 33 to 82%. After removing the KCl, the mobile population of cytochrome P-450 returned to the original 33%. These results suggest that nonspecific protein aggregates are dissociated by the presence of KCl, possibly due to the change in electrostatic interactions, resulting in mobilization of cytochrome P-450. SMP were observed to be nearly free from adrenodoxin and adrenodoxin reductase. The addition of adrenodoxin to SMP increased the mobile population of cytochrome P-450 from 35 to 54%. Further addition of adrenodoxin reductase to SMP containing adrenodoxin immobilized cytochrome P-450 by 6%. The addition of only adrenodoxin reductase to SMP, however, did not immobilize cytochrome P-450. The present results are consistent with our previous observations [Ohta, Y., Mitani, F., Ishimura, Y., Yanagibashi, K., Kawamura, M., & Kawato, S. (1990) J. Biochem. 107, 97-104] that cholesterol-bearing P-450SCC forms a transient ternary association with adrenodoxin and adrenodoxin reductase. PMID:1869512

Ohta, Y; Yanagibashi, K; Hara, T; Kawamura, M; Kawato, S

1991-04-01

128

Protein rotation study of cytochrome P-450 in submitochondrial particles: effect of KCl and intermolecular interactions with redox partners.  

UK PubMed Central (United Kingdom)

The rotational diffusion of cytochrome P-450 in submitochondrial particles (SMP) of bovine adrenocortical mitochondria was measured by detecting the decay of absorption anisotropy, r(t), after photolysis of the heme.CO complex by a vertically polarized laser flash. Analysis of r(t) was based on a "rotation-about-membrane normal" model. The measurements were used to investigate the effect of KCl on intermolecular interactions involving cytochrome P-450 and to investigate the interactions of cytochrome P-450 with other redox partners. The rotational diffusion of cytochrome P-450 was significantly dependent on KCl concentration. When the KCl concentration was increased from 0 to 1,000 mM, the mobile population of cytochrome P-450 was increased from 33 to 82%. After removing the KCl, the mobile population of cytochrome P-450 returned to the original 33%. These results suggest that nonspecific protein aggregates are dissociated by the presence of KCl, possibly due to the change in electrostatic interactions, resulting in mobilization of cytochrome P-450. SMP were observed to be nearly free from adrenodoxin and adrenodoxin reductase. The addition of adrenodoxin to SMP increased the mobile population of cytochrome P-450 from 35 to 54%. Further addition of adrenodoxin reductase to SMP containing adrenodoxin immobilized cytochrome P-450 by 6%. The addition of only adrenodoxin reductase to SMP, however, did not immobilize cytochrome P-450. The present results are consistent with our previous observations [Ohta, Y., Mitani, F., Ishimura, Y., Yanagibashi, K., Kawamura, M., & Kawato, S. (1990) J. Biochem. 107, 97-104] that cholesterol-bearing P-450SCC forms a transient ternary association with adrenodoxin and adrenodoxin reductase.

Ohta Y; Yanagibashi K; Hara T; Kawamura M; Kawato S

1991-04-01

129

Hexacyanometalate Molecular Chemistry Trinuclear CrNi2 Complexes; MicroSQUID Magnetisation Studies of Intermolecular Interactions  

CERN Multimedia

Three different CrNi2 complexes were synthesized. They differ from each other by the nature of the terminal ligand and of the counter anion : [Cr(CN)4[CN-Ni(tetren)]2]Cl, that crystallizes in two different crystallographic systems and [Cr(CN)4[CN-Ni(dienpy2)]2](ClO4). The ground state spin value is 7/2 for the three systems (ferromagnetic interaction between chromium(III) and nickel(II) ions). The magnetisation of the three CrNi2 complexes was measured using an array of micro-SQUIDs in a temperature range between 0.04 K and 7 K, under a magnetic field up to 1 T. The three samples present a three dimensional magnetic ordering. The correlation between the structure and the intermolecular coupling is analysed in terms of steric hindrances of the terminal ligand, orientation of the molecules in the unit cell (canted structure) and crystal symmetry.

Tiron, R; Tuyeras, F; Scuiller, A; Marvaud, V; Verdaguer, M; Tiron, Raluca; Wernsdorfer, Wolfgang; Tuyeras, Fabien; Scuiller, Ariane; Marvaud, Valerie; Verdaguer, Michel

2003-01-01

130

Solid-State [2+2] Photodimerization and Photopolymerization of ?,?-Diarylpolyene Monomers: Effective Utilization of Noncovalent Intermolecular Interactions in Crystals  

Directory of Open Access Journals (Sweden)

Full Text Available [2+2] Photocycloaddition of olefins is a very useful reaction in synthetic organic chemistry to obtain cyclobutane-containing molecules, which are almost inaccessible by other methods. The reaction, when performed in the crystalline state, occurs more efficiently and selectively than in homogeneous solution due to tight and regular molecular arrangement in the crystal state. Despite numerous examples for the solid-state [2+2] photodimerization of monoenes, however, it is still a challenge to prepare not only dimers but also higher oligomers and polymers from conjugated polyenes, which have multiple reactive double bonds in a molecule. In our recent studies of the solid-state photoreactions of ?,?-diarylpolyenes, noncovalent intermolecular interactions in crystals were effectively utilized to prealign molecules in stacking arrangements, suitable for the [2+2] reaction. With appropriate ring-substituents, [2+2] photodimerization and photopolymerization of the polyenes took place, although the degree of polymerization was relatively low. This review will describe the details of these reactions.

Yoriko Sonoda

2010-01-01

131

Study of Intermolecular Interactions of Acetophenone and Benzene at 303.15, 313.15 and 323.15 K  

Directory of Open Access Journals (Sweden)

Full Text Available The behaviour of mixture of acetophenone  and  benzene  as a function of temperature and composition  has been investigated by measuring sound velocity in conjunction with density at 303.15, 313.15and 323.15 K. Derived parameters computed from density (?) and sound velocity (U) have been used to determine excess molar volumes (VME), excess isentropic compressibilities (KSE) and excess inter molecular free length (LfE).The excess functions have been discussed in terms of intermolecular interactions between the components of binary mixture. The validity of various theoretical approaches of liquids has been tested for the system by comparing theoretical sound speeds with those experimentally determined over the entire composition range in the temperature range 303.15-323.15K. The computed results have been fitted to the Redlich-Kister polynomial equation to estimate the smoothening coefficients and standard deviations for this system. The validity of various theoretical approaches of liquids has been tested for the system by comparing theoretical sound speeds with those experimentally determined over the entire composition range in the temperature303.15-323.15K.

K. Saravanakumar; R. Baskaran; T. R. Kubendran

2010-01-01

132

Carbon Dioxide Clathrate Hydrates: Selective Role of Intermolecular Interactions and Action of the SDS Catalyst.  

UK PubMed Central (United Kingdom)

The ability of a single sodium dodecyl sulfate (SDS) molecule to promote the formation of CO2 clathrate hydrates in water (as it does for methane) has been investigated at the microscopic level. For this purpose, the components of the related force field were carefully formulated and assembled following the procedure previously adopted for methane. The properties of the whole system (as well as those of its components) were analyzed by carrying out extended molecular dynamics calculations. Contrary to what happens for methane, the calculations singled out the propensity of CO2 (pure) water clusters to form clathrate hydrate-like structures and the disappearance of such propensity when a single SDS molecule is added to the clusters. This feature was found to be due to the strong interaction of carbon dioxide with the additive that makes the SDS molecule lose its shape together with its ability to drive water molecules to form a suitable cage.

Albertí M; Pirani F; Laganà A

2013-08-01

133

Intermolecular interactions between the neurotensin and the third extracellular loop of human neurotensin 1 receptor.  

UK PubMed Central (United Kingdom)

Neurotensin (NT) is a tridecapeptide hormone in the periphery and neurotransmitter in the brain that principally activates three receptor subtypes, named NTS1, NTS2, and NTS3. Since little is known about its structure in the presence of its principal receptor NTS1, we determined it using the key domain of the receptor, i.e. the third extracellular loop. We conclude the following: (i) for the receptor fragment, NT binding modifies its central part, underlying the great flexibility and adaptability of this region; (ii) for bound NT, the extended conformation of its C-terminus is confirmed for the first time in experimental conditions and in the presence of a part of the receptor; and (iii) despite some substitutions, the human receptor residues that are involved in the interaction with NT could be similar to those of the rat receptor which play an important role in NT binding.

Da Costa G; Bondon A; Coutant J; Curmi P; Monti JP

2012-11-01

134

Fabrication and Intermolecular Interactions of Silk Fibroin/Hydroxybutyl Chitosan Blended Nanofibers  

Directory of Open Access Journals (Sweden)

Full Text Available The native extracellular matrix (ECM) is composed of a cross-linked porous network of multifibril collagens and glycosaminoglycans. Nanofibrous scaffolds of silk fibroin (SF) and hydroxybutyl chitosan (HBC) blends were fabricated using 1,1,1,3,3,3-hexa?uoro-2-propanol (HFIP) and trifluoroacetic acid (TFA) as solvents to biomimic the native ECM via electrospinning. Scanning electronic microscope (SEM) showed that relatively uniform nanofibers could be obtained when 12% SF was blended with 6% HBC at the weight ratio of 50:50. Meanwhile, the average nano?brous diameter increased when the content of HBC in SF/HBC blends was raised from 20% to 100%. Fourier transform infrared spectra (FTIR) and 13C nuclear magnetic resonance (NMR) showed SF and HBC molecules existed in hydrogen bonding interactions but HBC did not induce conformation of SF transforming from random coil form to ?-sheet structure. X-ray diffraction (XRD) confirmed the different structure of SF/HBC blended nanofibers from both SF and HBC. Thermogravimetry-Differential thermogravimetry (TG-DTG) results demonstrated that the thermal stability of SF/HBC blend nanofibrous scaffolds was improved. The results indicated that the rearrangement of HBC and SF molecular chain formed a new structure due to stronger hydrogen bonding between SF and HBC. These electrospun SF/HBC blended nanofibers may provide an ideal tissue engineering scaffold and wound dressing.

Kui-Hua Zhang; Qiao-Zhen Yu; Xiu-Mei Mo

2011-01-01

135

Fabrication and intermolecular interactions of silk fibroin/hydroxybutyl chitosan blended nanofibers.  

Science.gov (United States)

The native extracellular matrix (ECM) is composed of a cross-linked porous network of multifibril collagens and glycosaminoglycans. Nanofibrous scaffolds of silk fibroin (SF) and hydroxybutyl chitosan (HBC) blends were fabricated using 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) and trifluoroacetic acid (TFA) as solvents to biomimic the native ECM via electrospinning. Scanning electronic microscope (SEM) showed that relatively uniform nanofibers could be obtained when 12% SF was blended with 6% HBC at the weight ratio of 50:50. Meanwhile, the average nanofibrous diameter increased when the content of HBC in SF/HBC blends was raised from 20% to 100%. Fourier transform infrared spectra (FTIR) and (13)C nuclear magnetic resonance (NMR) showed SF and HBC molecules existed in hydrogen bonding interactions but HBC did not induce conformation of SF transforming from random coil form to ?-sheet structure. X-ray diffraction (XRD) confirmed the different structure of SF/HBC blended nanofibers from both SF and HBC. Thermogravimetry-Differential thermogravimetry (TG-DTG) results demonstrated that the thermal stability of SF/HBC blend nanofibrous scaffolds was improved. The results indicated that the rearrangement of HBC and SF molecular chain formed a new structure due to stronger hydrogen bonding between SF and HBC. These electrospun SF/HBC blended nanofibers may provide an ideal tissue engineering scaffold and wound dressing. PMID:21731435

Zhang, Kui-Hua; Yu, Qiao-Zhen; Mo, Xiu-Mei

2011-03-30

136

Fabrication and intermolecular interactions of silk fibroin/hydroxybutyl chitosan blended nanofibers.  

UK PubMed Central (United Kingdom)

The native extracellular matrix (ECM) is composed of a cross-linked porous network of multifibril collagens and glycosaminoglycans. Nanofibrous scaffolds of silk fibroin (SF) and hydroxybutyl chitosan (HBC) blends were fabricated using 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) and trifluoroacetic acid (TFA) as solvents to biomimic the native ECM via electrospinning. Scanning electronic microscope (SEM) showed that relatively uniform nanofibers could be obtained when 12% SF was blended with 6% HBC at the weight ratio of 50:50. Meanwhile, the average nanofibrous diameter increased when the content of HBC in SF/HBC blends was raised from 20% to 100%. Fourier transform infrared spectra (FTIR) and (13)C nuclear magnetic resonance (NMR) showed SF and HBC molecules existed in hydrogen bonding interactions but HBC did not induce conformation of SF transforming from random coil form to ?-sheet structure. X-ray diffraction (XRD) confirmed the different structure of SF/HBC blended nanofibers from both SF and HBC. Thermogravimetry-Differential thermogravimetry (TG-DTG) results demonstrated that the thermal stability of SF/HBC blend nanofibrous scaffolds was improved. The results indicated that the rearrangement of HBC and SF molecular chain formed a new structure due to stronger hydrogen bonding between SF and HBC. These electrospun SF/HBC blended nanofibers may provide an ideal tissue engineering scaffold and wound dressing.

Zhang KH; Yu QZ; Mo XM

2011-01-01

137

Influence of intermolecular interaction on kinetics of conformational transitions in poly-m-phenyleneisopthalamide  

Energy Technology Data Exchange (ETDEWEB)

The authors study the kinetics of conformational transitions during crystallization from a glasslike state and they compare the results obtained with the character of the conformational transitions in other polymers with a lower IMI energy. As the initial samples the authors used amorphous nonoriented PPIA films obtained from a polymer solution at a concentration of 1-20% in dimethylacetamide (DMA). The individual regions of the IR spectrum in which the difference between the amorphous and crystalline states of the polymer is most pronounced is shown. The authors found that IMI appreciably influences conformational transitions in polymers. Increase in IMI leads to an increase in /SUP E/ conf and, consequently, to a decrease in the kinetic flexibility of the molecule and an increase in the phase transition temperatures.

Pakhomov, P.M.; Korsvkov, V.E.; Novak, I.I.; Shablygin, M.V.

1986-02-01

138

Intermolecular forces and their evaluation by perturbation theory  

Energy Technology Data Exchange (ETDEWEB)

The aim of these notes is to offer a modern picture of the perturbative approach to the calculation of intermolecular forces. The point of view taken is that a perturbative series truncated at a low order can provide a valuable way for evaluating interaction energies, especially if one limits oneself to the case of intermediate- and long-range distances between the interacting partners.

Arrighini, P.

1981-01-01

139

A Theoretical Study of Intermolecular Interaction and Hydrogen Bond for Furan with HCl and CH4-nCln (n = 0-3)  

Directory of Open Access Journals (Sweden)

Full Text Available Furan has both the oxygen lone pair electrons and an aromatic ?-electron. The study of the interaction between furan as a proton acceptor and a proton donor is important to understand the properties of furan and the related hydrogen bond. The geometries, intermolecular energies and vibrational properties of the furan-HCl and furan-CH4-nCln (n = 0-3) complexes have been performed using the second order Moller-Plesset perturbation theory. The NBO analysis of the optimized geometries has also been performed. The optimized geometries of furan-HCl and furan-CH4-nCln (n = 0-3) show both the C(Cl)-H...O and C(Cl)-H...? interactions. In all of the optimized geometries of furan-CH4-nCln (n = 0-3), C-H bond lengths are shorten and vibrational frequencies are blue-shifted, while for the furan-HCl complex, C-H bond length is lengthened and vibrational frequencies are red-shifted. The NBO analysis shows that, for the furan-CH4-nCln (n = 0-3) complexes, the charge transfer from the lone pairs of the O atom to both ?*(CH) antibonding MO and lone pairs of Cl atom, which is the important feature for blue-shifted hydrogen bond. Both lone pairs and ? electrons of furan can be acted as a proton acceptor interacting with a proton donor. Cl-H...O(?) is a conventional hydrogen bond , while C-H...O(?) is a blue-shifted hydrogen bond.

Daiqian Xie; Jiang Li

2003-01-01

140

On the theory of the proton free induction decay and Hahn echo in polymer systems: The role of intermolecular magnetic dipole-dipole interactions and the modified Anderson-Weiss approximation  

Science.gov (United States)

The influence of the intermolecular magnetic dipole-dipole interaction on the free induction decay (FID) as well as on the Hahn-echo of proton spins in polymer melts is investigated. It is shown that for isotropic models of polymer dynamics, when polymer segment displacements do not correlate with an initial chain conformation, the influence of the intermolecular magnetic dipole-dipole interactions to the FID and Hahn echo is increasing more rapidly with evolution time than the corresponding influence of the intramolecular magnetic dipole-dipole interactions. On the other hand, the situation is inverted for the tube-reptation model: here the influence of the intramolecular magnetic dipole-dipole interactions to the FID and Hahn echo is increasing faster with time than the contribution from intermolecular interactions. A simple expression for the relative mean squared displacements of polymer segments from different chains is obtained from the intermolecular contribution to the FID. A modified Anderson-Weiss approximation, taking into account flip-flop transitions between different spins, is proposed and on that basis, the conditions for extracting the relative intermolecular mean squared displacements of polymer segments from the intermolecular contribution to the proton FID is established. Systematic investigations of intermolecular contributions, which were considered as an unimportant factor for FID and Hahn echo in polymer systems by most previous works, actually cannot be considered as negligible and opens a new dimension for obtaining information about polymer dynamics in the millisecond regime.

Fatkullin, N.; Gubaidullin, A.; Mattea, C.; Stapf, S.

2012-12-01

 
 
 
 
141

The different biological effects of telomestatin and TMPyP4 can be attributed to their selectivity for interaction with intramolecular or intermolecular G-quadruplex structures.  

Science.gov (United States)

Demonstration of the existence of G-quadruplex structures in telomeres of Stylonychia macronuclei and in the promoter of c-myc in human cells has validated these secondary DNA structures as potential targets for drug design. The next important issue is the selectivity of G-quadruplex-interactive agents for the different types of G-quadruplex structures. In this study, we have taken an important step in associating specific biological effects of these drugs with selective interaction with either intermolecular or intramolecular G-quadruplex structures formed in telomeres. Telomestatin is a natural product isolated from Streptomyces anulatus 3533-SV4 and has been shown to be a very potent telomerase inhibitor through its G-quadruplex interaction. We have demonstrated that telomestatin interacts preferentially with intramolecular versus intermolecular G-quadruplex structures and also has a 70-fold selectivity for intramolecular G-quadruplex structures over duplex DNA. Telomestatin is able to stabilize G-quadruplex structures that are formed from duplex human telomeric DNA as well as from single-stranded DNA. Importantly, telomestatin stabilizes these G-quadruplex structures in the absence of monovalent cations, which is a unique characteristic among G-quadruplex-interactive compounds. At noncytotoxic concentrations, telomestatin suppresses the proliferation of telomerase-positive cells within several weeks. In contrast, TMPyP4, a compound that preferentially facilitates the formation of intermolecular G-quadruplex structures, suppresses the proliferation of alternative lengthening of telomeres (ALT)-positive cells as well as telomerase-positive cells. We have also demonstrated that TMPyP4 induces anaphase bridges in sea urchin embryos, whereas telomestatin did not have this effect, leading us to conclude that the selectivity of telomestatin for intramolecular G-quadruplex structures and TMPyP4 for intermolecular G-quadruplex structures is important in mediating different biological effects: stabilization of intramolecular G-quadruplex structures produces telomerase inhibition and accelerated telomere shortening, whereas facilitation of the formation of intermolecular G-quadruplex structures induces the formation of anaphase bridges. PMID:12810655

Kim, Mu-Yong; Gleason-Guzman, Mary; Izbicka, Elzbieta; Nishioka, David; Hurley, Laurence H

2003-06-15

142

Pro42 and Val45 of staphylokinase modulate intermolecular interactions of His43-Tyr44 pair and specificity of staphylokinase-plasmin activator complex.  

UK PubMed Central (United Kingdom)

Staphylokinase (SAK) forms a 1:1 stoichiometric complex with plasmin (Pm) and changes its substrate specificity to create a plasminogen (Pg) activator complex. The His(43)-Tyr(44) pair of SAK resides within the active site cleft of the partner Pm and generates intermolecular contacts to confer Pg activator ability to the SAK-Pm bimolecular complex. Site-directed mutagenesis and molecular modeling studies unravelled that mutation at 42nd or 45th positions of SAK specifically disrupts cation-pi interaction of His(43) with Trp(215) of partner Pm within the active site, whereas pi-pi interaction of Tyr(44) with Trp(215) remain energetically favoured.

Singh S; Ashish; Dikshit KL

2012-03-01

143

Pro42 and Val45 of staphylokinase modulate intermolecular interactions of His43-Tyr44 pair and specificity of staphylokinase-plasmin activator complex.  

Science.gov (United States)

Staphylokinase (SAK) forms a 1:1 stoichiometric complex with plasmin (Pm) and changes its substrate specificity to create a plasminogen (Pg) activator complex. The His(43)-Tyr(44) pair of SAK resides within the active site cleft of the partner Pm and generates intermolecular contacts to confer Pg activator ability to the SAK-Pm bimolecular complex. Site-directed mutagenesis and molecular modeling studies unravelled that mutation at 42nd or 45th positions of SAK specifically disrupts cation-pi interaction of His(43) with Trp(215) of partner Pm within the active site, whereas pi-pi interaction of Tyr(44) with Trp(215) remain energetically favoured. PMID:22321644

Singh, Satish; Ashish; Dikshit, Kanak L

2012-02-02

144

Determination of stepsize parameters for intermolecular vibrational energy transfer. Final report, May 1, 1987--December 31, 1991  

Energy Technology Data Exchange (ETDEWEB)

Intermolecular energy transfer of highly excited polyatomic molecules plays an important role in many complex chemical systems: combustion, high temperature and atmospheric chemistry. By monitoring the relaxation of internal energy we have observed trends in the collisional efficiency ({beta}) for energy transfer as a function of the substrate`s excitation energy and the complexities of substrate and deactivator. For a given substrate {beta} increases as the deactivator`s mass increase to {approximately}30 amu and then exhibits a nearly constant value; this is due to a mass mismatch between the atoms of the colliders. In a homologous series of substrate molecules (C{sub 3}{minus}C{sub 8}) {beta} decreases as the number of atoms in the substrate increases; replacing F with H increases {beta}. All substrates, except for CF{sub 2}Cl{sub 2} and CF{sub 2}HCl below 10,000 cm{sup {minus}1}, exhibited that {beta} is independent of energy, i.e. <{Delta}E>{sub all} is linear with energy. The results are interpreted with a simple model which considers that {beta} is a function of the ocillators energy and its vibrational frequency. Limitations of current approximations used in high temperature unimolecular reactions were evaluated and better approximations were developed. The importance of energy transfer in product yields was observed for the photoactivation of perfluorocyclopropene and the photoproduction of difluoroethyne. 3 refs., 18 figs., 4 tabs.

Tardy, D.C.

1992-03-01

145

Intermolecular forces in organic clusters  

Energy Technology Data Exchange (ETDEWEB)

The effects of alkyl groups on the binding energies of cluster ions were investigated. The data were obtained by variable-temperature pulsed high-pressure mass spectrometric equilibrium measurements on protonated clusters A{sub n}H{sup +} (A = MeOH, n-PrOH, n-AmOH, MeCOOH, MeNH{sub 2}, n-PrNH{sub 2}, and Me{sub 2}NH). Inner shell binding energies are not affected by alkylation, suggesting pure hydrogen-bonding interactions with the core ions. Shell-filling effects are also not affected. Thus, going to the second shell causes an equal drop of 17 {plus_minus} 4 kJ/mol (4 {plus_minus} 1 kcal/mol) in all the observed clusters, despite the variation in the number of hydrogen-bonding sites and charge densities at the core ions. This suggests opposing effects of intramolecular and intermolecular solvation at the shell-filling step. However, the alkyl groups do affect the outer shells. The bonding energies in the outer shells of the alcohol clusters approach the respective bulk condensation energies within {plus_minus} 6 kJ/mol ({plus_minus}1.5 kcal/mol.) This suggests liquidlike hydrophobic alkyl-alkyl interactions in the outer shells which may contribute 12-25 kJ/mol (3-6 kcal/mol) to the bonding energies. 70 refs., 12 figs., 2 tabs.

Meot-Ner, M. [National Inst. of Standards and Technology, Gaithersburg, MD (United States)

1992-04-22

146

Far-infrared vibration--rotation-tunneling spectroscopy of Ar--NH3: Intermolecular vibrations and effective angular potential energy surface  

International Nuclear Information System (INIS)

[en] Two new intermolecular vibration--rotation-tunneling (VRT) bands of Ar--NH3 have been measured using tunable far infrared laser spectroscopy. We have unambiguously assigned these and a previously measured FIR band [Gwo et al., Mol. Phys. 71, 453 (1990)] as ?(10, n=0)left-arrow ?(00, n=0), ?(10, n=0)left-arrow ?(00, n=0), and ?(00, n=1)left-arrow ?(00, n=0). The three upper states of these are found to be strongly mixed by anisotropy and Coriolis effects. A simultaneous least squares fit of all transitions has yielded vibrational frequencies, rotational and centrifugal distortion constants, and a Coriolis parameter as well as quadrupole hyperfine coupling constants for the upper states. An effective angular potential energy surface for Ar--NH3 in its lowest stretching state has been determined from these data, after explicitly accounting for the effects of bend stretch interactions. Features of the surface include a global minimum at the near T-shaped configuration (?=90 degree), a 30 cm-1 to 60 cm-1 barrier to rotation at ?=180 degree (or 0 degree), and a very low barrier or possibly a secondary minimum at ?=0 degree (or 180 degree). Both attractive and repulsive interactions are shown to contribute significantly to the anisotropic forces in the complex. Comparison with ab initio calculations are presented

1991-07-01

147

A B3LYP and MP2(full) theoretical investigation into the strength of the C-NO(2) bond upon the formation of the intermolecular hydrogen-bonding interaction between HF and the nitro group of nitrotriazole or its methyl derivatives.  

UK PubMed Central (United Kingdom)

The changes of bond dissociation energy (BDE) in the C-NO(2) bond and nitro group charge upon the formation of the intermolecular hydrogen-bonding interaction between HF and the nitro group of 14 kinds of nitrotriazoles or methyl derivatives were investigated using the B3LYP and MP2(full) methods with the 6-311++G**, 6-311++G(2df,2p) and aug-cc-pVTZ basis sets. The strength of the C-NO(2) bond was enhanced and the charge of nitro group turned more negative in complex in comparison with those in isolated nitrotriazole molecule. The increment of the C-NO(2) bond dissociation energies correlated well with the intermolecular H-bonding interaction energies. Electron density shifts analyses showed that the electron density shifted toward the C-NO(2) bond upon complex formation, leading to the strengthened C-NO(2) bond and the possibly reduced explosive sensitivity.

Li BH; Shi WJ; Ren FD; Wang Y

2013-02-01

148

Intermolecular potential energy surface and rovibrational spectra of the He-N2O complex from ab initio calculations  

International Nuclear Information System (INIS)

[en] We report an ab initio intermolecular potential energy surface calculation on the He-N2O complex with N2O at its ground state using a supermolecular approach. The calculation was performed at the coupled-cluster [CCSD(T)] level, with the full counterpoise correction for the basis set superposition error and a large basis set including midpoint bond functions. The CCSD(T) potential is found to have two minima corresponding to the T-shaped and linear He-ONN structures. The T-shaped minimum is the global minimum. The two-dimensional discrete variable representation method was employed to calculate the rovibrational energy levels for 4He-N2O and 3He-N2O with N2O at its ground and ?3 excited states. The results indicate that the CCSD(T) potential supports five and four vibrational bound states for the 4He-N2O and 3He-N2O, respectively. Moreover, the calculations on the line intensities of the rotational transitions in the ?3 region of N2O for the ground vibrational state shows that the 3He-N2O spectrum is dominated by a-type transitions (?Ka=0), while the 4He-N2O spectrum is contributed by both the a-type and b-type (?Ka=±1) transitions. The calculated transition frequencies and the intensities are in good agreement with the observed results

2004-05-08

149

Interacting agegraphic dark energy  

Energy Technology Data Exchange (ETDEWEB)

A new dark energy model, named ''agegraphic dark energy'', has been proposed recently, based on the so-called Karolyhazy uncertainty relation, which arises from quantum mechanics together with general relativity. In this note, we extend the original agegraphic dark energy model by including the interaction between agegraphic dark energy and pressureless (dark) matter. In the interacting agegraphic dark energy model, there are many interesting features different from the original agegraphic dark energy model and holographic dark energy model. The similarity and difference between agegraphic dark energy and holographic dark energy are also discussed. (orig.)

Wei, Hao [Beijing Institute of Technology, Department of Physics, Beijing (China); Tsinghua University, Department of Physics and Tsinghua Center for Astrophysics, Beijing (China); Cai, Rong-Gen [Chinese Academy of Sciences, Institute of Theoretical Physics, Beijing (China)

2009-01-15

150

Energy component analysis of ? interactions.  

UK PubMed Central (United Kingdom)

Fundamental features of biomolecules, such as their structure, solvation, and crystal packing and even the docking of drugs, rely on noncovalent interactions. Theory can help elucidate the nature of these interactions, and energy component analysis reveals the contributions from the various intermolecular forces: electrostatics, London dispersion terms, induction (polarization), and short-range exchange-repulsion. Symmetry-adapted perturbation theory (SAPT) provides one method for this type of analysis. In this Account, we show several examples of how SAPT provides insight into the nature of noncovalent ?-interactions. In cation-? interactions, the cation strongly polarizes electrons in ?-orbitals, leading to substantially attractive induction terms. This polarization is so important that a cation and a benzene attract each other when placed in the same plane, even though a consideration of the electrostatic interactions alone would suggest otherwise. SAPT analysis can also support an understanding of substituent effects in ?-? interactions. Trends in face-to-face sandwich benzene dimers cannot be understood solely in terms of electrostatic effects, especially for multiply substituted dimers, but SAPT analysis demonstrates the importance of London dispersion forces. Moreover, detailed SAPT studies also reveal the critical importance of charge penetration effects in ?-stacking interactions. These effects arise in cases with substantial orbital overlap, such as in ?-stacking in DNA or in crystal structures of ?-conjugated materials. These charge penetration effects lead to attractive electrostatic terms where a simpler analysis based on atom-centered charges, electrostatic potential plots, or even distributed multipole analysis would incorrectly predict repulsive electrostatics. SAPT analysis of sandwich benzene, benzene-pyridine, and pyridine dimers indicates that dipole/induced-dipole terms present in benzene-pyridine but not in benzene dimer are relatively unimportant. In general, a nitrogen heteroatom contracts the electron density, reducing the magnitude of both the London dispersion and the exchange-repulsion terms, but with an overall net increase in attraction. Finally, using recent advances in SAPT algorithms, researchers can now perform SAPT computations on systems with 200 atoms or more. We discuss a recent study of the intercalation complex of proflavine with a trinucleotide duplex of DNA. Here, London dispersion forces are the strongest contributors to binding, as is typical for ?-? interactions. However, the electrostatic terms are larger than usual on a fractional basis, which likely results from the positive charge on the intercalator and its location between two electron-rich base pairs. These cation-? interactions also increase the induction term beyond those of typical noncovalent ?-interactions.

Sherrill CD

2013-04-01

151

Intermolecular Forces: Solids and Liquids  

Science.gov (United States)

General chemistry WebCT exam/quiz questions. The Intermolecular Forces: Solids and Liquids topic covers the forces that exist between atoms and molecules in solids and liquids, and how these affect properties such as boiling point, conductivity, and lattice energy.

2007-09-07

152

A structural basis for the regulation of the LIM-homeodomain protein islet 1 (Isl1) by intra- and intermolecular interactions.  

UK PubMed Central (United Kingdom)

Islet 1 (Isl1) is a transcription factor of the LIM-homeodomain (LIM-HD) protein family and is essential for many developmental processes. LIM-HD proteins all contain two protein-interacting LIM domains, a DNA-binding homeodomain (HD), and a C-terminal region. In Isl1, the C-terminal region also contains the LIM homeobox 3 (Lhx3)-binding domain (LBD), which interacts with the LIM domains of Lhx3. The LIM domains of Isl1 have been implicated in inhibition of DNA binding potentially through an intramolecular interaction with or close to the HD. Here we investigate the LBD as a candidate intramolecular interaction domain. Competitive yeast-two hybrid experiments indicate that the LIM domains and LBD from Isl1 can interact with apparently low affinity, consistent with no detection of an intermolecular interaction in the same system. Nuclear magnetic resonance studies show that the interaction is specific, whereas substitution of the LBD with peptides of the same amino acid composition but different sequence is not specific. We solved the crystal structure of a similar but higher affinity complex between the LIM domains of Isl1 and the LIM interaction domain from the LIM-HD cofactor protein LIM domain-binding protein 1 (Ldb1) and used these coordinates to generate a homology model of the intramolecular interaction that indicates poorer complementarity for the weak intramolecular interaction. The intramolecular interaction in Isl1 may provide protection against aggregation, minimize unproductive DNA binding, and facilitate cofactor exchange within the cell.

Gadd MS; Jacques DA; Nisevic I; Craig VJ; Kwan AH; Guss JM; Matthews JM

2013-07-01

153

Studies on tolfenamic acid-chitosan intermolecular interactions: effect of pH, polymer concentration and molecular weight.  

Science.gov (United States)

Solid-state properties of tolfenamic acid (TA) and its complexes with chitosan (CT) have been studied. Effect of medium pH, molecular weight of polymer and its different concentrations on these TA-CT complexes were studied in detail. Low and medium molecular weight CT have been used in different ratios at pH ranging from 4 to 6 and freeze-drying technique has been employed to modify the appearance of crystalline TA. Physical properties of the formed complexes have been studied by employing X-ray diffraction, differential scanning calorimetry and scanning electron microscopy; chemical structure has been studied using Fourier transform infrared spectroscopy. The results showed that both forms of the polymer exhibited complete conversion in 1:8 ratio at pH 4, 1:4 at pH 5 and 1:1 at pH 6 indicating a marked effect of pH on drug-polymer complexation. The percent crystallinity calculations indicated low molecular weight CT slightly more effective than the other form. No changes in the complexes have been observed during the 12 week storage under controlled conditions. Both forms of CT at different pH values indicated retardation of recrystallization in TA during cooling of the melt from 1:1 ratios exhibiting formation of strong intermolecular hydrogen bonding between the drug and the polymer. PMID:23620261

Ahmed, Sofia; Sheraz, Muhammad Ali; Rehman, Ihtesham Ur

2013-04-27

154

Structural Analysis of Intermolecular Interactions in the Kinesin Adaptor Complex Fasciculation and Elongation Protein Zeta 1/ Short Coiled-Coil Protein (FEZ1/SCOCO)  

Science.gov (United States)

Cytoskeleton and protein trafficking processes, including vesicle transport to synapses, are key processes in neuronal differentiation and axon outgrowth. The human protein FEZ1 (fasciculation and elongation protein zeta 1 / UNC-76, in C. elegans), SCOCO (short coiled-coil protein / UNC-69) and kinesins (e.g. kinesin heavy chain / UNC116) are involved in these processes. Exploiting the feature of FEZ1 protein as a bivalent adapter of transport mediated by kinesins and FEZ1 protein interaction with SCOCO (proteins involved in the same path of axonal growth), we investigated the structural aspects of intermolecular interactions involved in this complex formation by NMR (Nuclear Magnetic Resonance), cross-linking coupled with mass spectrometry (MS), SAXS (Small Angle X-ray Scattering) and molecular modelling. The topology of homodimerization was accessed through NMR (Nuclear Magnetic Resonance) studies of the region involved in this process, corresponding to FEZ1 (92-194). Through studies involving the protein in its monomeric configuration (reduced) and dimeric state, we propose that homodimerization occurs with FEZ1 chains oriented in an anti-parallel topology. We demonstrate that the interaction interface of FEZ1 and SCOCO defined by MS and computational modelling is in accordance with that previously demonstrated for UNC-76 and UNC-69. SAXS and literature data support a heterotetrameric complex model. These data provide details about the interaction interfaces probably involved in the transport machinery assembly and open perspectives to understand and interfere in this assembly and its involvement in neuronal differentiation and axon outgrowth.

da Silva, Julio Cesar; Sforca, Mauricio Luis; Honorato, Rodrigo Vargas; Granato, Daniela Campos; dos Santos Migueleti, Deivid Lucas; Neves, Jorge L.; de Oliveira, Paulo Sergio Lopes; Paes-Leme, Adriana Franco; Zeri, Ana Carolina de Mattos; de Torriani, Iris Concepcion Linares; Kobarg, Jorg

2013-01-01

155

Ab initio calculations of the Ar-ethane intermolecular potential energy surface using bond function basis sets.  

UK PubMed Central (United Kingdom)

The intermolecular potential energy surface (PES) of argon with ethane has been studied by ab initio calculations at the levels of second-order Møller-Plesset perturbation (MP2) theory and coupled-cluster theory with single, double, and noniterative triple configurations (CCSD(T)) using a series of augmented correlation-consistent basis sets. Two sets of bond functions, bf1 (3s3p2d) and bf2 (6s6p4d2f), have been added to the basis sets to show a dramatic and systematic improvement in the convergence of the entire PES. The PES of Ar-ethane is characterized by a global minimum at a near T-shaped configuration with a well depth of 0.611 kcal mol(-1), a second minimum at a collinear configuration with a well depth of 0.456 kcal mol(-1), and a saddle point connecting the two minima. It is shown that an augmented correlation-consistent basis set with a set of bond functions, either bf1 or bf2, can effectively produce results equivalent to the next larger augmented correlation-consistent basis set, that is, aug-cc-pVDZ-bf1 ? aug-cc-pVTZ, aug-cc-pVTZ-bf1 ? aug-cc-pVQZ. Very importantly, the use of bond functions improves the PES globally, resulting accurate potential anisotropy. Finally, MP2 method is inadequate for accurate calculations, because it gives a potentially overestimated well depth and, more seriously, a poor potential anisotropy.

Zhang JD; Li SJ; Tao FM

2013-03-01

156

Mechanism of intermolecular interactions of microsomal cytochrome P450s CYP17 and CYP21 involved in steroid hormone biosynthesis.  

UK PubMed Central (United Kingdom)

Protein-protein interactions play a significant role in regulation of functional activity of cytochrome P450s. The aim of the present study was to elucidate the molecular interactions between steroidogenic enzymes CYP17 and CYP21 localized in endoplasmic reticulum membranes of adrenal cortex and involved in biosynthesis of corticosteroid hormones. In the present work, we demonstrate for the first time the direct interaction at molecular level between highly purified human recombinant cytochrome P450s in a mixed reconstituted system. The dependence of the interaction between CYP17 and CYP21 on concentration of the redox-partner - NADPH-cytochrome P450 reductase - is demonstrated, and it is shown that electrostatic interactions play a crucial role in the interaction between CYP17 and CYP21.

Sushko TA; Gilep AA; Usanov SA

2012-06-01

157

Mechanism of intermolecular interactions of microsomal cytochrome P450s CYP17 and CYP21 involved in steroid hormone biosynthesis.  

Science.gov (United States)

Protein-protein interactions play a significant role in regulation of functional activity of cytochrome P450s. The aim of the present study was to elucidate the molecular interactions between steroidogenic enzymes CYP17 and CYP21 localized in endoplasmic reticulum membranes of adrenal cortex and involved in biosynthesis of corticosteroid hormones. In the present work, we demonstrate for the first time the direct interaction at molecular level between highly purified human recombinant cytochrome P450s in a mixed reconstituted system. The dependence of the interaction between CYP17 and CYP21 on concentration of the redox-partner - NADPH-cytochrome P450 reductase - is demonstrated, and it is shown that electrostatic interactions play a crucial role in the interaction between CYP17 and CYP21. PMID:22817457

Sushko, T A; Gilep, A A; Usanov, S A

2012-06-01

158

Intermolecular inter-ligand interaction in mixed ligand complexes of lanthanides(III) involving histidine and some amino acids  

International Nuclear Information System (INIS)

[en] The formation constant studies on binary and mixed ligand complexes of Pr (III) and Nd (III) involving histidine (hist) as primary ligand and ?-alanine (?-ala), valine (val) or leucine (leu) as secondary ligands have been undertaken to evaluate the extra-stabilization in the mixed ligand complexes due to possible occurrence of intramolecular inter-ligand interaction. Stability quantifying parameters (? log k and ?? log k) indicate significant inter-ligand interaction. (author)

2003-01-01

159

Electronic transitions and intermolecular forces  

International Nuclear Information System (INIS)

[en] This thesis describes two different subjects - electronic transitions and intermolecular forces - that are related mainly by the following observation: The wavenumber at which an electronic transition in an atom or molecule occurs, depends on the environment of that atom or molecule. This implies, for instance, that when a molecule becomes solvated its absorption spectrum may be shifted either to the blue or to the red side of the original gasphase spectrum. In part I attention is paid to the experimental aspects of VUV spectroscopy, both in the gasphase and in the condensed phase. In part II a series of papers are presented, dealing with the calculation of intermolecular forces (and some related topics) both for the ground state and for the excited state interactions, using different non-empirical methods. The calculations provide, among other results, a semiquantitative interpretation of the spectral blue shifts encountered in our experiments. (Auth.)

1981-01-01

160

Intermolecular interactions in albumin-sulfoxide-water systems at low temperatures, investigated by means of fluorescence quenching  

Science.gov (United States)

The effect of low temperatures on the interaction in human serum albumin (HSA)-diethyl sulfoxife (DESO)-dipropyl sulfoxide (DPSO)-water systems is investigated by means of fluorescence spectroscopy (intrinsic protein fluorescence, three-dimensional excitation/emission matrix (3D EEM)). The Stern-Volmer constants of HSA quenching are calculated for these systems. The structural changes occurring in these systems are characterized using 3D EEM profiles of HSA. It is shown that the HSA structural changes depend not only on the direct interaction of protein with sulfoxides but on structural changes in the solvent as well.

Grigoryan, K. R.; Shilajyan, H. A.

2013-05-01

 
 
 
 
161

The effect of intermolecular interaction on the plastic properties of tars. Vliyaniye mezhmolekulyarnogo vzaimodeystviya na plasticheskiye svoystva pekov  

Energy Technology Data Exchange (ETDEWEB)

In light of the theory of dispersed petroleum systems and the kinetic theory of liquids, the association between the plastic characteristics of tars of varying origin and softening point and the effective energy of activation of viscous flow which correlates with the cohesive energy is studied. The mutually unambiguous linear correspondence between this energy and the softening point and the concentration of the malthene gamma fraction, which is the tar softener, is established. The molecular energetics of the processes of softening are studied. A classification of tars based on the cohesive energy in the region of a viscofluid state is proposed. For impregnating and binding tars and tars for the production of carbon fibers, these energies are 96 to 123 kilojoules per mole, 23 to 190 kilojoules per mole and 190 to 197 kilojoules per mole, respectively.

Dolmatov, L.V.; Akhmetov, S.A.; Dolmatov, M.Yu.

1984-01-01

162

Columnar self-assembly of rhomboid macrocyclic molecules via step-like intermolecular interaction. Crystal formation and gelation.  

UK PubMed Central (United Kingdom)

Two macrocyclic compounds with a rhomboid molecular shape, composed of a ?-conjugated framework and an imine or amine functionality, were synthesized. The amine-containing macrocycle crystallizes with step-like interaction of each molecule, forming a columnar arrangement, although dispersion of the imine gelates upon ultrasonification.

Ide T; Takeuchi D; Osakada K

2012-01-01

163

Intermolecular Forces (Netorials)  

Science.gov (United States)

Intermolecular Forces: this is a resource in the collection "Netorials". In this resource there is a review of Lewis structures, molecular geometry, electronegativity, or molecular polarity. After that, you can learn about the forces of attraction that exist between molecules. This module explores London forces and dipole-dipole forces (including hydrogen bonds). The Netorials cover selected topics in first-year chemistry including: Chemical Reactions, Stoichiometry, Thermodynamics, Intermolecular Forces, Acids & Bases, Biomolecules, and Electrochemistry.

164

All-atom Molecular Dynamic Simulations and NMR Spectra Study on Intermolecular Interactions of N,N-dimethylacetamide-Water System  

Science.gov (United States)

N,N-dimethylacetamide (DMA) has been investigated extensively in studying models of peptide bonds. An all-atom MD simulation and the NMR spectra were performed to investigate the interactions in the DMA-water system. The radial distribution functions (RDFs) and the hydrogen-bonding network were used in MD simulations. There are strong hydrogen bonds and weak C-H...O contacts in the mixtures, as shown by the analysis of the RDFs. The insight structures in the DMA-water mixtures can be classified into different regions by the analysis of the hydrogen-bonding network. Chemical shifts of the hydrogen atom of water molecule with concentration and temperatures are adopted to study the interactions in the mixtures. The results of NMR spectra show good agreement with the statistical results of hydrogen bonds in MD simulations.

Zhang, Rong; Tan, Zai-you; Luo, San-lai

2008-06-01

165

Weak intermolecular interactions of chromium, molybdenum and vanadium bis-arene complexes with CH- and OH-acids  

International Nuclear Information System (INIS)

[en] Using the method of IR spectroscopy coordination interactions of molybdenum and vanadium organometallic compounds (OMC) (bis-ethyl benzene molybdenum, bisethyl benzene vanadium) with hydroperoxides of ternary butyl and cumyl, as well as with ternary butanol and phenol are investigated. Possible types of OMC coordination with CH- and OH-acids are considered. The role of coordination complexes in the oxidation mechanism of bis-arene derivatives of transition metals by hydroperoxides is discussed

1988-01-01

166

Intra and inter-molecular interactions dictate the aggregation state of irinotecan co-encapsulated with floxuridine inside liposomes  

DEFF Research Database (Denmark)

PURPOSE: The inter/intramolecular interactions between drugs (floxuridine, irinotecan) and excipients (copper gluconate, triethanolamine) in the dual-drug liposomal formulation CPX-1 were elucidated in order to identify the physicochemical properties that allow coordinated release of irinotecan and floxuridine and maintenance of the two agents at a fixed, synergistic 1:1 molar ratio. METHODS: Release of irinotecan and floxuridine from the liposomes was assessed using an in vitro-release assay. Fluorescence, Nuclear Magnetic Resonance spectroscopy (NMR) and UV-Vis were used to characterize the aggregation state of the drugs within the liposomes. RESULTS: Coordinated release of the drugs from liposomes was disrupted by removing copper gluconate. Approximately 45% of the total irinotecan was detectable in the copper-containing CPX-1 formulation by NMR, which decreased to 19% without copper present in the liposomal interior. Formation of higher order, NMR-silent aggregates was associated with slower and uncoordinated irinotecan release relative to floxuridine and loss of the synergistic drug/drug ratio. Solution spectroscopy and calorimetry revealed that while all formulation components were required to achieve the highest solubility of irinotecan, direct drug-excipient binding interactions were absent. CONCLUSIONS: Long-range interactions between irinotecan, floxuridine and excipients modulate the aggregation state of irinotecan, allowing for simultaneous release of both drugs from the liposomes.

Dicko, Awa; Frazier, April A

2008-01-01

167

Local Conformation and Intermolecular Interaction of Rigid Ring Polymers Are Not Always the Same as the Linear Analogue: Cyclic Amylose Tris(phenylcarbamate) in ? Solvents.  

UK PubMed Central (United Kingdom)

Small-angle X-ray scattering and static and dynamic light scattering measurements were made for cyclic amylose tris(phenylcarbamate) (cATPC) of which weight-average molar mass Mw ranges from 1.3 × 10(4) to 1.5 × 10(5) to determine their z-average mean square radius of gyration ?S(2)?z, particle scattering function P(q), hydrodynamic radius RH, and second virial coefficient A2 in methyl acetate (MEA), ethyl acetate (EA), and 4-methyl-2-pentanone (MIBK). The obtained ?S(2)?z, P(q), and RH data were analyzed in terms of the wormlike ring to estimate the helix pitch per residue h and the Kuhn segment length ?(-1) (the stiffness parameter, twice the persistence length). Both h and ?(-1) for cATPC in MEA, EA, and MIBK are smaller than those for linear amylose tris(phenylcarbamate) (ATPC) in the corresponding solvent and the discrepancy becomes more significant with increasing the molar volume of the solvent. This indicates that not every rigid ring has the same local helical structure and chain stiffness as that for the linear polymer in the Mw range investigated while infinitely long ring chains should have the same local conformation. This conformational difference also affects A2. In actuality, negative A2 was observed for cATPC in MIBK at the ? temperature of linear ATPC whereas intermolecular topological interaction of ring polymers increases A2.

Asano N; Kitamura S; Terao K

2013-08-01

168

Solid-State [2+2] Photodimerization and Photopolymerization of a,w-Diarylpolyene Monomers: Effective Utilization of Noncovalent Intermolecular Interactions in Crystals  

Directory of Open Access Journals (Sweden)

Full Text Available [2+2] Photocycloaddition of olefins is a very useful reaction in synthetic organic chemistry to obtain cyclobutane-containing molecules, which are almost inaccessible by other methods. The reaction, when performed in the crystalline state, occurs more efficiently and selectively than in homogeneous solution due to tight and regular molecular arrangement in the crystal state. Despite numerous examples for the solid-state [2+2] photodimerization of monoenes, however, it is still a challenge to prepare not only dimers but also higher oligomers and polymers from conjugated polyenes, which have multiple reactive double bonds in a molecule. In our recent studies of the solid-state photoreactions of a,w-diarylpolyenes, noncovalent intermolecular interactions in crystals were effectively utilized to prealign molecules in stacking arrangements, suitable for the [2+2] reaction. With appropriate ring-substituents, [2+2] photodimerization and photopolymerization of the polyenes took place, although the degree of polymerization was relatively low. This review will describe the details of these reactions.

Yoriko Sonoda

2010-01-01

169

Networks of intermolecular interactions involving nitro groups in the crystals of three polymorphs of 9-aminoacridinium 2,4-dinitrobenzoate ? 2,4-dinitrobenzoic acid  

Science.gov (United States)

We report on the crystal structures of three polymorphs of 9-aminoacridinium 2,4-dinitrobenzoate ? 2,4-dinitrobenzoic acid (I, II and III). Single-crystal X-ray diffraction measurements show that the title compound forms three polymorphs with the space groups P21/n (I) and P1¯ (II and III). The asymmetric units of all the polymorphs consist of 9-aminoacridinium cation, the 2,4-dinitrobenzoate anion and the 2,4-dinitrobenzoic acid molecule. The neutral and ionic forms of 2,4-dinitrobenzoic acid are linked via O–H⋯O hydrogen bonds with a D graph-set motif, forming monoanionic dimers. The amine and carboxylic acid moieties are linked via N–H⋯O, O–H⋯O and C–H⋯O hydrogen bonds. The acridinium skeletons in the crystal packing form ?-stacked columns, whereas the monoanionic dimers of 2,4-dinitrobenzoic acid are linked by different types of intermolecular interactions, especially those involving nitro groups. To the best of our knowledge, the crystal structure of 9-aminoacridinium 2,4-dinitrobenzoate ? 2,4-dinitrobenzoic acid is the first in which the appearance of monoanionic dimers of 2,4-dinitrobenzoic acid has been documented.

Sikorski, Artur; Trzybi?ski, Damian

2013-10-01

170

13C/15N-19F intermolecular REDOR NMR study of the interaction of TAR RNA with Tat peptides.  

UK PubMed Central (United Kingdom)

The complex of the HIV TAR RNA with the viral regulatory protein Tat is of considerable interest, but the plasticity of this interaction has made it impossible so far to establish the structure of that complex. In order to explore a new approach to obtain structural information on protein-RNA complexes, we performed (13)C/(15)N-(19)F REDOR NMR experiments in the solid state on TAR bound to a peptide comprising the RNA-binding section of Tat. A critical arginine in the peptide was uniformly (13)C and (15)N labeled, and 5-fluorouridine was incorporated at the U23 position of TAR. REDOR irradiation resulted in dephasing of the (13)C and (15)N resonances, indicating the proximity of the U23(5F)-C and U23(5F)-N spin pairs. Best fits to the REDOR data show the U23(5F)-C distances and the U23(5F)-N distances are in good agreement with the distances obtained from solution NMR structures of partial complexes of Tat with TAR. These results demonstrate that it is possible to study protein-RNA complexes using solid-state REDOR NMR measurements, adding to a growing list of solid state techniques for studying protein-nucleic acid complexes.

Huang W; Varani G; Drobny GP

2010-12-01

171

13C/15N-19F intermolecular REDOR NMR study of the interaction of TAR RNA with Tat peptides.  

Science.gov (United States)

The complex of the HIV TAR RNA with the viral regulatory protein Tat is of considerable interest, but the plasticity of this interaction has made it impossible so far to establish the structure of that complex. In order to explore a new approach to obtain structural information on protein-RNA complexes, we performed (13)C/(15)N-(19)F REDOR NMR experiments in the solid state on TAR bound to a peptide comprising the RNA-binding section of Tat. A critical arginine in the peptide was uniformly (13)C and (15)N labeled, and 5-fluorouridine was incorporated at the U23 position of TAR. REDOR irradiation resulted in dephasing of the (13)C and (15)N resonances, indicating the proximity of the U23(5F)-C and U23(5F)-N spin pairs. Best fits to the REDOR data show the U23(5F)-C distances and the U23(5F)-N distances are in good agreement with the distances obtained from solution NMR structures of partial complexes of Tat with TAR. These results demonstrate that it is possible to study protein-RNA complexes using solid-state REDOR NMR measurements, adding to a growing list of solid state techniques for studying protein-nucleic acid complexes. PMID:21105680

Huang, Wei; Varani, Gabriele; Drobny, Gary P

2010-11-24

172

Intermolecular and surface forces  

CERN Document Server

This reference describes the role of various intermolecular and interparticle forces in determining the properties of simple systems such as gases, liquids and solids, with a special focus on more complex colloidal, polymeric and biological systems. The book provides a thorough foundation in theories and concepts of intermolecular forces, allowing researchers and students to recognize which forces are important in any particular system, as well as how to control these forces. This third edition is expanded into three sections and contains five new chapters over the previous edition.· starts fr

Israelachvili, Jacob N

2011-01-01

173

Theoretical study of intermolecular energy transfer involving electronically excited molecules: He(1S) + H2(B 1?/sub u/+)  

International Nuclear Information System (INIS)

To further understanding of gas phase collision dynamics involving electronically-excited molecules, a fully quantum mechanical study of He + H2(B 1?/sub u/+) was undertaken. Iterative natural orbital configuration interaction (CI) calculations were performed to obtain the interaction potential between He and H2(B 1?/sub u/+). The potential energy surface (PES) is highly anisotropic and has a van der Waals well of about 0.03 eV for C/sub 2v/ approach. Avoided PES crossings occur with He + H2(E,F 1?/sub g/+) and with He + H2(X 1?/sub g/+) and cause a local maximum and a deep minimum in the He + H2(B 1?/sub u/+) PES, respectively. The crossing with He + H2(X 1?/sub g/+) provides a mechanism for fluorescence quenching. The computed CI energies were combined with previous multi-reference double excitation CI calculations and fit with analytic functions for convenience in scattering calculations. Accurate dipole polarizabilities and quadrupole moment of H2(B 1?/sub u/+) were computed for use in the multipole expansion, which is the analytic form of the long-range PES. 129 refs., 28 figs., 35 tabs.

1986-01-01

174

New Type of Dual Solid-State Thermochromism: Modulation of Intramolecular Charge Transfer by Intermolecular ?-? Interactions, Kinetic Trapping of the Aci-Nitro Group, and Reversible Molecular Locking  

Science.gov (United States)

When heated above room temperature, some crystalline polymorphs of the 1,3-bis(hydroxyalkylamino)-4,6-dinitrobenzenes (BDBn, n = 2-5), bis(hydroxyalkyl) analogues of the intramolecular charge-transfer molecule 1,3-diamino-4,6-dinitrobenzene, exhibit "dual" thermochromism: gradual color change from yellow to orange at lower temperatures, and sharp color change from orange to red at higher temperatures. These two thermochromic changes are related to different solid-state processes. When allowed to cool to room temperature, the yellow color of the thermochromic molecules with different alkyl length (n) is recovered with unexpectedly different kinetics, the order of the respective rate constants ranging from 10-7-10-6 s-1 for BDB2 to about 0.1 s-1 in the case of BDB3. The thermochromic mechanism and the reasons behind the different kinetics were clarified on the basis of detailed crystallographic characterization, kinetic thermoanalysis, and spectroscopic study of eight crystalline forms (seven polymorphs and one solvate). It was found that the polymorphism is due to the possibility of "locking" and "unlocking" of the alkyl arms by formation of a strong intramolecular hydrogen bond between the hydroxyl groups at their hydroxyl termini. The locking of BDB2, with shortest alkyl arms, is reversible and it can be controlled thermally; either of the two conformations can be obtained in the solid state by proper thermal treatment. By use of high temperature in situ single crystal X-ray diffraction analysis of BDB3, direct evidence was obtained that the gradual thermochromic change is related to increased distance and weakened ?-? interactions between the stacked benzene rings: the lattice expands preferably in the stacking direction, causing enhanced oscillator strength and red shift of the absorption edge of the intramolecular charge transfer transition. The second, sharp thermochromic change had been assigned previously to solid-solid phase transition triggered by intramolecular proton transfer of one amino proton to the nitro group, whereupon an aci-nitro form is thermally populated. Contrary to the numerous examples of solid thermochromic molecules based on either pericyclic reactions or keto-enol tautomerism, this system appears to be the first organic thermochromic family where the thermochromic change appears as an effect of intermolecular ?-? interactions and thermal intramolecular proton transfer to aromatic nitro group.

Naumov, Pan?e; Lee, Sang Cheol; Ishizawa, Nobuo; Jeong, Young Gyu; Chung, Ihn Hee; Fukuzumi, Shunichi

2009-09-01

175

Intermolecular forces for hydrogen, nitrogen and acetylene  

International Nuclear Information System (INIS)

Orientation-dependent intermolecular potentials for H2, N2, and C2H2 have been determined on the basis of electron charge density contours, octopolar induction in the dispersion force, electrostatic quadrupolar interaction, and the observed second virial coefficients. The recently settled structure of low-temperature solid acetylene has been discussed. (Auth.)

1977-05-01

176

Terahertz laser spectroscopy of the water dimer intermolecular vibrations. I. (D2O)2  

International Nuclear Information System (INIS)

Terahertz laser VRT spectra of the water dimer consisting of 731 transitions measured with an average precision of 2 MHz and involving four (D2O)2 intermolecular vibrations (one previously published) have been measured between 65 and 104 cm-1. The precisely determined energy level patterns differ both qualitatively and quantitatively from the predictions of several dimer potentials tested, and reveal an ordering of the intermolecular vibrations which differs dramatically from that predicted by standard normal mode analysis. Strong coupling is indicated between the low barrier tunneling motions and the intermolecular vibrations as well as among different vibrations. Particularly, the 83 cm-1 (acceptor wag) and 90 cm-1 (D2O)2 (acceptor twist) vibrations interact through a Coriolis perturbation. These spectra provide the basis for our recent determination of the water pair potential. The corresponding data set for (H2O)2 is presented in an accompanying paper. (c) 2000 American Institute of Physics.

2000-06-15

177

Symmetry in the polarization expansion for intermolecular forces  

Energy Technology Data Exchange (ETDEWEB)

In the usual polarization expansion for intermolecular forces, exchange effects that determine the separations of energy levels within the manifold of interacting states are ignored. Previous low order calculations on simple physical systems have indicated that these exchange terms can be described reasonably well by an appropriate ad hoc symmetrization of the polarization wave function (the SYM-P method). But theoretical considerations suggest that the SYM-P method should be good for only one of the interacting states and not for the others in the manifold. Here this long standing apparent conflict between theoretical expectations and actual results is explained by consideration of a simple model system in which the relevant equations can be solved exactly. It is concluded that while the SYM-P method is potentially exact for only one of the interacting states, it may provide good approximations to the other states of the manifold in the case of large separations of the interacting subsystems.

Chipman, D.M.; Hirschfelder, J.O.

1980-11-15

178

Symmetry in the polarization expansion for intermolecular forces  

International Nuclear Information System (INIS)

In the usual polarization expansion for intermolecular forces, exchange effects that determine the separations of energy levels within the manifold of interacting states are ignored. Previous low order calculations on simple physical systems have indicated that these exchange terms can be described reasonably well by an appropriate ad hoc symmetrization of the polarization wave function (the SYM-P method). But theoretical considerations suggest that the SYM-P method should be good for only one of the interacting states and not for the others in the manifold. Here this long standing apparent conflict between theoretical expectations and actual results is explained by consideration of a simple model system in which the relevant equations can be solved exactly. It is concluded that while the SYM-P method is potentially exact for only one of the interacting states, it may provide good approximations to the other states of the manifold in the case of large separations of the interacting subsystems

1980-11-15

179

Self-assembled trimer structures highlight the competitive roles of intermolecular and adsorbate-substrate interactions: PVBA trimer on Pd(111).  

UK PubMed Central (United Kingdom)

We observed the orientation of 4-trans-2-(pyrid-4-yl-vinyl)benzoic acid (PVBA) trimers on Pd(111) using scanning tunneling microscopy (STM) under ultrahigh vacuum (UHV). The image showed three different types of trimers, one of which does not follow predicted dimer orientations. This type of trimer displays 10° rotations of each molecule in clockwise or counterclockwise directions. Calculations of adsorbate-substrate energy and hydrogen bonding energy revealed that the rotations are a result of competition between adsorbate-adsorbate and adsorbate-substrate interactions.

Kim BI; Kim S

2012-05-01

180

Intermolecular interactions in Li+-glyme and Li+-glyme-TFSA- complexes: relationship with physicochemical properties of [Li(glyme)][TFSA] ionic liquids.  

UK PubMed Central (United Kingdom)

The stabilization energies (?E(form)) calculated for the formation of the Li(+) complexes with mono-, di- tri- and tetra-glyme (G1, G2, G3 and G4) at the MP2/6-311G** level were -61.0, -79.5, -95.6 and -107.7 kcal? mol(-1), respectively. The electrostatic and induction interactions are the major sources of the attraction in the complexes. Although the ?E(form) increases by the increase of the number of the O???Li contact, the ?E(form) per oxygen atom decreases. The negative charge on the oxygen atom that has contact with the Li(+) weakens the attractive electrostatic and induction interactions of other oxygen atoms with the Li(+). The binding energies calculated for the [Li(glyme)](+) complexes with TFSA(-) anion (glyme = G1, G2, G3, and G4) were -106.5, -93.7, -82.8, and -70.0 kcal?mol(-1), respectively. The binding energies for the complexes are significantly smaller than that for the Li(+) with the TFSA(-) anion. The binding energy decreases by the increase of the glyme chain length. The weak attraction between the [Li(glyme)](+) complex (glyme = G3 and G4) and TFSA(-) anion is one of the causes of the fast diffusion of the [Li(glyme)](+) complex in the mixture of the glyme and the Li salt in spite of the large size of the [Li(glyme)](+) complex. The HOMO energy level of glyme in the [Li(glyme)](+) complex is significantly lower than that of isolated glyme, which shows that the interaction of the Li(+) with the oxygen atoms of glyme increases the oxidative stability of the glyme.

Tsuzuki S; Shinoda W; Seki S; Umebayashi Y; Yoshida K; Dokko K; Watanabe M

2013-06-01

 
 
 
 
181

Theoretical studies of the CO2-N2O van der Waals complex: ab initio potential energy surface, intermolecular vibrations, and rotational transition frequencies.  

UK PubMed Central (United Kingdom)

Theoretical studies of the potential energy surface and bound states were performed for the CO(2)-N(2)O van der Waals complex. A four-dimensional intermolecular potential energy surface (PES) was constructed from 11,466 ab initio data points which were calculated at the coupled-cluster single double (triple) level with aug-cc-pVTZ basis set supplemented with bond functions. Three co-planar local minima were found on this surface. They correspond to two equivalent isomers with a slipped parallel structure in which the O atom in N(2)O is near the C atom in CO(2) and a T-shaped isomer in which the terminal N atom in N(2)O is closest to the C atom in CO(2). The two slipped parallel isomers are energetically more stable than the T-shaped isomer by 178 cm(-1). Four fundamental vibrational excited states for the slipped parallel isomers and two fundamental vibrational excited states (torsion and disrotation) for the T-shaped isomer were assigned via bound states calculations based on this PES. The theoretical vibrational frequencies are in good agreement with the available experimental values for the slipped parallel isomers. Rotational excitations (J = 0-6) for the ground vibrational state of the slipped parallel structure were calculated and the accuracy of the PES in the vicinity of minima is validated by the good agreement between the theoretical and experimental transition frequencies and spectroscopic parameters.

Zheng L; Lee SY; Lu Y; Yang M

2013-01-01

182

Desensitization of metastable intermolecular composites  

Energy Technology Data Exchange (ETDEWEB)

A method to substantially desensitize a metastable intermolecular composite material to electrostatic discharge and friction comprising mixing the composite material with an organic diluent and removing enough organic diluent from the mixture to form a mixture with a substantially putty-like consistency, as well as a concomitant method of recovering the metastable intermolecular composite material.

Busse, James R. (South Fork, CO); Dye, Robert C. (Los Alamos, NM); Foley, Timothy J. (Los Alamos, NM); Higa, Kelvin T. (Ridgecrest, CA); Jorgensen, Betty S. (Jemez Springs, NM); Sanders, Victor E. (White Rock, NM); Son, Steven F. (Los Alamos, NM)

2011-04-26

183

Effect of surface-plasmon polaritons on spontaneous emission and intermolecular energy-transfer rates in multilayered geometries  

International Nuclear Information System (INIS)

We use a Green's tensor method to investigate the spontaneous emission rate of a molecule and the energy-transfer rate between molecules placed in two types of layered geometries: a slab geometry and a planar waveguide. We focus especially on the role played by surface-plasmon polaritons in modifying the spontaneous emission and energy-transfer rates as compared to free space. In the presence of more than one interface, the surface-plasmon polariton modes split into several branches, and each branch can contribute significantly to modifying the electromagnetic properties of atoms and molecules. Enhancements of several orders of magnitude both in the spontaneous emission rate of a molecule and the energy-transfer rate between molecules are obtained and, by tuning the parameters of the geometry, one has the ability to control the range and magnitude of these enhancements. For the energy-transfer rate interference effects between contributions of different plasmon-polariton branches are observed as oscillations in the distance dependence of this rate.

2011-01-01

184

Effect of surface-plasmon polaritons on spontaneous emission and intermolecular energy-transfer rates in multilayered geometries  

Energy Technology Data Exchange (ETDEWEB)

We use a Green's tensor method to investigate the spontaneous emission rate of a molecule and the energy-transfer rate between molecules placed in two types of layered geometries: a slab geometry and a planar waveguide. We focus especially on the role played by surface-plasmon polaritons in modifying the spontaneous emission and energy-transfer rates as compared to free space. In the presence of more than one interface, the surface-plasmon polariton modes split into several branches, and each branch can contribute significantly to modifying the electromagnetic properties of atoms and molecules. Enhancements of several orders of magnitude both in the spontaneous emission rate of a molecule and the energy-transfer rate between molecules are obtained and, by tuning the parameters of the geometry, one has the ability to control the range and magnitude of these enhancements. For the energy-transfer rate interference effects between contributions of different plasmon-polariton branches are observed as oscillations in the distance dependence of this rate.

Marocico, C. A.; Knoester, J. [Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, NL-9747 AG Groningen (Netherlands)

2011-11-15

185

Electronic Mechanisms of Intra and Intermolecular J Couplings in Systems with C-H···O Interactions  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract: Correlation effects on the change of 1J(CH) couplings in model systems I:NCH...H2O and II:CH4...H2O as a function of the H...O distance are discussed. RPA and SOPPA results follow a similar trend in system II. In system I RPA values decrease monotonously as the H...O distance decreases, while SOPPA ones exhibit flat maximum near equilibrium. Such different behavior is ascribed to the π-transmitted component. Intermolecular couplings at the equilibrium geometry of I are analyzed by means of the CLOPPA approach. The larger absolute value of 2hJ(CO) compared to 1hJ(HO) is found to arise from contributions involving a vacant LMO localized in the C-H...O moiety.

Claudia G. Giribet; Martin C. Ruiz de Azua; Celia V. Vizioli; Claudio N. Cavasotto

2003-01-01

186

Intermolecular vibrational spectra of C3v CXY3 Molecular Liquids, CHCl3, CHBr3, CFBr3, and CBrCl3.  

Science.gov (United States)

We report the quality anisotropic intermolecular vibrational spectra within the frequency range 0.5-800 cm(-1) of four C(3v) CXY(3) molecular liquids, CHCl(3), CHBr(3), CFBr(3), and CBrCl(3), by means of femtosecond optical-heterodyne-detected Raman-induced Kerr effect spectroscopy. The results show that the first moment of the intermolecular vibrational spectrum is proportional to the square root of the value of the surface tension divided by the liquid density. This implies that the intermolecular vibrational spectrum reflects the bulk properties of the liquids. To understand the molecular-level aspects of the intermolecular vibrational spectra of the liquids, the spectra are compared with the molecular properties such as molecular weight, rotational constants, and bimolecular interaction energy. Overall, the first moment of the spectrum moderately correlates to the inverse square roots of both the molecular weight and the fast rotational constant. Therefore, the molecular properties are responsible for the intermolecular vibrational spectrum. Plots of the first moment of the intermolecular vibrational spectrum vs the square root of the value of the simple bimolecular interaction energy divided by the molecular surface area and the molecular weight show a linear correlation in the case of the oblate symmetric top molecular liquids, CHCl(3), CHBr(3), and CFBr(3). However, CBrCl(3), which is a prolate symmetric top molecular liquid, does not show the same correlation for the oblate molecular liquids. PMID:21749053

Shirota, Hideaki; Kato, Tatsuya

2011-07-25

187

Intermolecular vibrational spectra of C3v CXY3 Molecular Liquids, CHCl3, CHBr3, CFBr3, and CBrCl3.  

UK PubMed Central (United Kingdom)

We report the quality anisotropic intermolecular vibrational spectra within the frequency range 0.5-800 cm(-1) of four C(3v) CXY(3) molecular liquids, CHCl(3), CHBr(3), CFBr(3), and CBrCl(3), by means of femtosecond optical-heterodyne-detected Raman-induced Kerr effect spectroscopy. The results show that the first moment of the intermolecular vibrational spectrum is proportional to the square root of the value of the surface tension divided by the liquid density. This implies that the intermolecular vibrational spectrum reflects the bulk properties of the liquids. To understand the molecular-level aspects of the intermolecular vibrational spectra of the liquids, the spectra are compared with the molecular properties such as molecular weight, rotational constants, and bimolecular interaction energy. Overall, the first moment of the spectrum moderately correlates to the inverse square roots of both the molecular weight and the fast rotational constant. Therefore, the molecular properties are responsible for the intermolecular vibrational spectrum. Plots of the first moment of the intermolecular vibrational spectrum vs the square root of the value of the simple bimolecular interaction energy divided by the molecular surface area and the molecular weight show a linear correlation in the case of the oblate symmetric top molecular liquids, CHCl(3), CHBr(3), and CFBr(3). However, CBrCl(3), which is a prolate symmetric top molecular liquid, does not show the same correlation for the oblate molecular liquids.

Shirota H; Kato T

2011-08-01

188

High energy neutrino interactions  

Energy Technology Data Exchange (ETDEWEB)

The article reviews the experimental techniques of neutrino physics, traces the main developments, summarises the present status of the field and give some hints on future activities. It concentrates on those fields of physics where neutrino experiments have made unique contributions, namely the structure of the charged and neutral weak currents, the verification of the quark parton model and the determination of the quark and gluon distributions in the nucleon including their scaling violations, and the study of new particle production in neutrino interactions.

Eisele, F.

1986-03-01

189

Transport properties and intermolecular forces (1) viscosity  

International Nuclear Information System (INIS)

A semi-empirical procedure is introduced by means of which the like and unlike interaction parameters of an intermolecular potential of the form L.J. (n-6) can be obtained from the temperature dependence of the viscosity of pure gases and their binary mixtures. The potentials with n=7 to 90 are considered. The procedure is tested and proved successful for the Ar - Kr system. It is found that the best potential representing the interaction of this system is the L.J. (11.5-6). It reproduces the experimental results satisfactorily to within 4%

1985-01-01

190

Energy or Mass and Interaction  

CERN Multimedia

A review. Problems: 1-Many empirical parameters and large dimension number; 2-Gravitation and Electrodynamics are challenged by dark matter and energy. Energy and nonlinear electrodynamics are fundamental in a unified nonlinear interaction. Nuclear energy appears as nonlinear SU(2) magnetic energy. Gravitation and electromagnetism are unified giving Einstein's equation and a geometric energy momentum tensor. A solution energy in the newtonian limit gives the gravitational constant G. Outside of this limit G is variable. May be interpreted as dark matter or energy. In vacuum, known gravitational solutions are obtained. Electromagnetism is an SU(2) subgroup. A U(1) limit gives Maxwell's equations. Geometric fields determine a generalized Dirac equation and are the germ of quantum physics. Planck's h and of Einstein's c are given by the potential and the metric. Excitations have quanta of charge, flux and spin determining the FQHE. There are only three stable 1/2 spin fermions. Mass is a form of energy. The rest...

Gonzalez-Martin, Gustavo R

2010-01-01

191

Multiplicities in high energy interactions  

Energy Technology Data Exchange (ETDEWEB)

This paper reviews the data on multiplicities in high energy interactions. Results from e/sup +/e/sup -/ annihilation, from neutrino interactions, and from hadronic collisions, both diffractive and nondiffractive, are compared and contrasted. The energy dependence of the mean charged multiplicity, , as well as the rapidity density at Y = 0 are presented. For hadronic collisions, the data on neutral pion production shows a strong correlation with . The heavy particle fractions increase with ..sqrt..s up to the highest energies. The charged particle multiplicity distributions for each type of reaction show a scaling behavior when expressed in terms of the mean. Attempts to understand this behavior, which was first predicted by Koba, Nielsen, and Olesen, are discussed. The multiplicity correlations and the energy variation of the shape of the KNO scaling distribution provide important constraints on models. Some extrapolations to the energies of the Superconducting Super Collider are made. 51 refs., 27 figs.

Derrick, M.

1985-05-13

192

Multiplicities in high energy interactions  

International Nuclear Information System (INIS)

This paper reviews the data on multiplicities in high energy interactions. Results from e+e- annihilation, from neutrino interactions, and from hadronic collisions, both diffractive and nondiffractive, are compared and contrasted. The energy dependence of the mean charged multiplicity, , as well as the rapidity density at Y = 0 are presented. For hadronic collisions, the data on neutral pion production shows a strong correlation with . The heavy particle fractions increase with ?s up to the highest energies. The charged particle multiplicity distributions for each type of reaction show a scaling behavior when expressed in terms of the mean. Attempts to understand this behavior, which was first predicted by Koba, Nielsen, and Olesen, are discussed. The multiplicity correlations and the energy variation of the shape of the KNO scaling distribution provide important constraints on models. Some extrapolations to the energies of the Superconducting Super Collider are made. 51 refs., 27 figs

1985-01-01

193

Impact of protein/protein interactions on global intermolecular translocation rates of the transcription factors Sox2 and Oct1 between DNA cognate sites analyzed by z-exchange NMR spectroscopy.  

Science.gov (United States)

Oct1 and Sox2 synergistically regulate developmental genes by binding to adjacent sites within promoters. We have investigated the kinetics of global intermolecular translocation of Sox2 and Oct1 between cognate sites located on different DNA molecules by z-exchange NMR spectroscopy. In the Hoxb1 promoter, the Sox2 and Oct1 sites are immediately adjacent to one another, and the intermolecular translocation rates are too slow to be measured by z-exchange spectroscopy. By introducing a 3-bp insertion between the Sox2 and Oct1 sites to mimic the spacing in the FGF4 enhancer, the interprotein contact surface is reduced, and the translocation rates are increased. Interaction between Sox2 and the POU-specific domain (POU(S)) of Oct1 does not affect the translocation mechanism but modulates the rates. Translocation involves only jumping (dissociation and reassociation) for Sox2, but both jumping and direct intersegment transfer (no dissociation into free solution) for Oct1. The dissociation (k(off) ?1.5 s(-1)) and association (k(on) ?5.1 × 10(9) m(-1)s(-1)) rate constants for Sox2 are reduced 4-fold and increased 5-fold, respectively, in the presence of Oct1. k(off) (?3.5 s(-1)) for Oct1 is unaffected by Sox2, whereas k(on) (?1.3 × 10(9) m(-1)s(-1)) is increased ?13-fold. The direct intermolecular translocation rate (k(inter) ?1.8 × 10(4) m(-1)s(-1)) for the POU(S) domain of Oct1 is reduced 2-fold by Sox2, whereas that for the POU homeodomain (POU(HD)) of Oct1 (k(inter) ? 1.7 × 10(4) m(-1)s(-1)) remains unaltered, consistent with the absence of contacts between Sox2 and POU(HD). The data suggest a model for the sequence of binding events involved in synergistic gene regulation by Sox2 and Oct1. PMID:22718759

Takayama, Yuki; Clore, G Marius

2012-06-20

194

Impact of protein/protein interactions on global intermolecular translocation rates of the transcription factors Sox2 and Oct1 between DNA cognate sites analyzed by z-exchange NMR spectroscopy.  

UK PubMed Central (United Kingdom)

Oct1 and Sox2 synergistically regulate developmental genes by binding to adjacent sites within promoters. We have investigated the kinetics of global intermolecular translocation of Sox2 and Oct1 between cognate sites located on different DNA molecules by z-exchange NMR spectroscopy. In the Hoxb1 promoter, the Sox2 and Oct1 sites are immediately adjacent to one another, and the intermolecular translocation rates are too slow to be measured by z-exchange spectroscopy. By introducing a 3-bp insertion between the Sox2 and Oct1 sites to mimic the spacing in the FGF4 enhancer, the interprotein contact surface is reduced, and the translocation rates are increased. Interaction between Sox2 and the POU-specific domain (POU(S)) of Oct1 does not affect the translocation mechanism but modulates the rates. Translocation involves only jumping (dissociation and reassociation) for Sox2, but both jumping and direct intersegment transfer (no dissociation into free solution) for Oct1. The dissociation (k(off) ?1.5 s(-1)) and association (k(on) ?5.1 × 10(9) m(-1)s(-1)) rate constants for Sox2 are reduced 4-fold and increased 5-fold, respectively, in the presence of Oct1. k(off) (?3.5 s(-1)) for Oct1 is unaffected by Sox2, whereas k(on) (?1.3 × 10(9) m(-1)s(-1)) is increased ?13-fold. The direct intermolecular translocation rate (k(inter) ?1.8 × 10(4) m(-1)s(-1)) for the POU(S) domain of Oct1 is reduced 2-fold by Sox2, whereas that for the POU homeodomain (POU(HD)) of Oct1 (k(inter) ? 1.7 × 10(4) m(-1)s(-1)) remains unaltered, consistent with the absence of contacts between Sox2 and POU(HD). The data suggest a model for the sequence of binding events involved in synergistic gene regulation by Sox2 and Oct1.

Takayama Y; Clore GM

2012-08-01

195

A study for the cause of ferulic acid-induced quenching of tyrosine fluorescence and whether it is a reliable marker of intermolecular interactions or not.  

UK PubMed Central (United Kingdom)

Intrinsic fluorescence of peptides and proteins is extensively used to monitor their specific interactions with several natural and synthetic molecules known to have wide-ranging beneficial or detrimental effects on health. A consequence of these interactions would be a significant decrease of the fluorescence emission intensity of Tyrosine (Tyr) and/or Tryptophan (Trp) residues in the protein due to structural rearrangements of proteic microenvironment. However fluorescence quenching can be also caused by "trivial" artefacts. In this study we examined the effect of Ferulic acid (FA) on Tyr fluorescence. FA is a natural anti-oxidant suggested to bind to and to modify the structural properties of several proteins thus altering their biological activities. Fluorescence spectroscopy experiments on Tyr and on proteins containing Tyr and no Trp like beta amyloid peptides and Insulin were performed. Our results suggest that Tyr fluorescence loss can mainly result from an inner filter effect rather than from specific interactions with FA.

Sgarbossa A; Lenci F

2013-05-01

196

Dynamics of interacting dark energy  

CERN Document Server

Dark energy and dark matter are only indirectly measured via their gravitational effects. It is possible that there is an exchange of energy within the dark sector, and this offers an interesting alternative approach to the coincidence problem. We consider two broad classes of interacting models where the energy exchange is a linear combination of the dark sector densities. The first class has been previously investigated, but we define new variables and find a new exact solution, which allows for a more direct, transparent and comprehensive analysis. The second class has not been investigated in general form before. We give general conditions on the parameters in both classes to avoid unphysical behavior (such as negative energy densities).

Caldera-Cabral, Gabriela; Urena-Lopez, L Arturo

2008-01-01

197

Influence both of radiation and peroxide cross-linking on inter-chain interaction for polyethylene  

International Nuclear Information System (INIS)

The activation energy values of thermal oxidative destruction obtained in a temperature range corresponding to initiation of polymer oxidation have been proposed to be used in calculation of intermolecular interaction energy in polyethylene.

2000-01-01

198

Theoretical investigation of the ethylene dimer: interaction energy and dipole moment.  

UK PubMed Central (United Kingdom)

The interaction potential energy and the interaction-induced dipole moment surfaces of the van der Waals C(2)H(4)-C(2)H(4) complex has been calculated for a broad range of intermolecular separations and configurations in the approximation of rigid interacting molecules. The calculations have been carried out using high-level ab initio theory with the aug-cc-pVTZ basis set and within the framework of the analytical description of long-range interactions between ethylene molecules. Binding energy for the most stable configuration of the C(2)H(4)-C(2)H(4) complex was calculated at the CCSD(T)/CBS level of theory. The harmonic fundamental vibrational frequencies for this complex were calculated at the MP2 level of theory.

Kalugina YN; Cherepanov VN; Buldakov MA; Zvereva-Loëte N; Boudon V

2012-01-01

199

Shaping interactions between polar molecules with far-off-resonant light  

CERN Multimedia

We show that dressing polar molecules with a far-off-resonant optical field leads to new types of intermolecular potentials, which undergo a crossover from the inverse-power to oscillating behavior depending on the intermolecular distance, and whose parameters can be tuned by varying the laser intensity and wavelength. We present analytic expressions for the potential energy surfaces, thereby providing direct access to the parameters of an optical field required to design intermolecular interactions experimentally.

Lemeshko, Mikhail

2011-01-01

200

Intermolecular forces involving the water molecules in lithium sulfate monohydrate  

International Nuclear Information System (INIS)

A study of the low-temperature infrared spectra of varyingly deuterated mulls of lithium sulfate monohydrate has afforded information as to the nature of vibrations of water molecules causing infrared absorptions. Using intra- and intermolecular force constants, obtained from the data of doublet spectra, spectra of intermolecularly coupled species were predicted and compared with experiment. The agreement between calculated and observed spectra is good, but not perfect. This indicates that nonneighbor interactions are weak but significant in determining the nature of the stretching modes involving water molecules in Li2SO4xH2O. Furthermore, it is shown that the intermolecular interactions involving water molecules are mostly dipolar in origin

1976-05-15

 
 
 
 
201

Failure of lamin A/C to functionally assemble in R482L mutated familial partial lipodystrophy fibroblasts: altered intermolecular interaction with emerin and implications for gene transcription.  

Science.gov (United States)

Familial partial lipodystrophy is an autosomal dominant disease caused by mutations of the LMNA gene encoding alternatively spliced lamins A and C. Abnormal distribution of body fat and insulin resistance characterize the clinical phenotype. In this study, we analyzed primary fibroblast cultures from a patient carrying an R482L lamin A/C mutation by a morphological and biochemical approach. Abnormalities were observed consisting of nuclear lamin A/C aggregates mostly localized close to the nuclear lamina. These aggregates were not bound to either DNA-containing structures or RNA splicing intranuclear compartments. In addition, emerin did not colocalize with nuclear lamin A/C aggregates. Interestingly, emerin failed to interact with lamin A in R482L mutated fibroblasts in vivo, while the interaction with lamin C was preserved in vitro, as determined by coimmunoprecipitation experiments. The presence of lamin A/C nuclear aggregates was restricted to actively transcribing cells, and it was increased in insulin-treated fibroblasts. In fibroblasts carrying lamin A/C nuclear aggregates, a reduced incorporation of bromouridine was observed, demonstrating that mutated lamin A/C in FPLD cells interferes with RNA transcription. PMID:14597414

Capanni, Cristina; Cenni, Vittoria; Mattioli, Elisabetta; Sabatelli, Patrizia; Ognibene, Andrea; Columbaro, Marta; Parnaik, Veena K; Wehnert, Manfred; Maraldi, Nadir M; Squarzoni, Stefano; Lattanzi, Giovanna

2003-11-15

202

Metal-Arene Complexes with Indolo[3,2-c]-quinolines: Effects of Ruthenium vs Osmium and Modifications of the Lactam Unit on Intermolecular Interactions, Anticancer Activity, Cell Cycle, and Cellular Accumulation.  

UK PubMed Central (United Kingdom)

Six novel ruthenium(II)- and osmium(II)-arene complexes with three modified indolo[3,2-c]quinolines have been synthesized in situ starting from 2-aminoindoloquinolines and 2-pyridinecarboxaldehyde in the presence of [M(p-cymene)Cl(2)](2) (M = Ru, Os) in ethanol. All complexes have been characterized by elemental analysis, spectroscopic techniques ((1)H, (13)C NMR, IR, UV-vis), and ESI mass spectrometry, while four complexes were investigated by X-ray diffraction. The complexes have been tested for antiproliferative activity in vitro in A549 (non-small cell lung), SW480 (colon), and CH1 (ovarian) human cancer cell lines and showed IC(50) values between 1.3 and >80 ?M. The effects of Ru vs Os and modifications of the lactam unit on intermolecular interactions, antiproliferative activity, and cell cycle are reported. One ruthenium complex and its osmium analogue have been studied for anticancer activity in vivo applied both intraperitoneally and orally against the murine colon carcinoma model CT-26. Interestingly, the osmium(II) complex displayed significant growth-inhibitory activity in contrast to its ruthenium counterpart, providing stimuli for further investigation of this class of compounds as potential antitumor drugs.

Filak LK; Göschl S; Heffeter P; Ghannadzadeh Samper K; Egger AE; Jakupec MA; Keppler BK; Berger W; Arion VB

2013-02-01

203

Metal-Arene Complexes with Indolo[3,2-c]-quinolines: Effects of Ruthenium vs Osmium and Modifications of the Lactam Unit on Intermolecular Interactions, Anticancer Activity, Cell Cycle, and Cellular Accumulation.  

Science.gov (United States)

Six novel ruthenium(II)- and osmium(II)-arene complexes with three modified indolo[3,2-c]quinolines have been synthesized in situ starting from 2-aminoindoloquinolines and 2-pyridinecarboxaldehyde in the presence of [M(p-cymene)Cl(2)](2) (M = Ru, Os) in ethanol. All complexes have been characterized by elemental analysis, spectroscopic techniques ((1)H, (13)C NMR, IR, UV-vis), and ESI mass spectrometry, while four complexes were investigated by X-ray diffraction. The complexes have been tested for antiproliferative activity in vitro in A549 (non-small cell lung), SW480 (colon), and CH1 (ovarian) human cancer cell lines and showed IC(50) values between 1.3 and >80 ?M. The effects of Ru vs Os and modifications of the lactam unit on intermolecular interactions, antiproliferative activity, and cell cycle are reported. One ruthenium complex and its osmium analogue have been studied for anticancer activity in vivo applied both intraperitoneally and orally against the murine colon carcinoma model CT-26. Interestingly, the osmium(II) complex displayed significant growth-inhibitory activity in contrast to its ruthenium counterpart, providing stimuli for further investigation of this class of compounds as potential antitumor drugs. PMID:23431223

Filak, Lukas K; Göschl, Simone; Heffeter, Petra; Ghannadzadeh Samper, Katia; Egger, Alexander E; Jakupec, Michael A; Keppler, Bernhard K; Berger, Walter; Arion, Vladimir B

2013-01-17

204

Copper-catalyzed intermolecular aminocyanation and diamination of alkenes.  

Science.gov (United States)

'N' front and center: The facile construction of C-N bonds by the generation of nitrogen-centred radicals from N-fluorobenzenesulfonimide results in the aminative difuctionalization of alkenes. The first copper-catalyzed intermolecular aminocyanation of alkenes and diamination of styrenes were realized. Si-F and B-F interactions play a significant role in the reaction. PMID:23355412

Zhang, Hongwei; Pu, Weiya; Xiong, Tao; Li, Yan; Zhou, Xue; Sun, Kai; Liu, Qun; Zhang, Qian

2013-01-25

205

Role of long-range intermolecular forces in the formation of inorganic nanoparticle clusters.  

UK PubMed Central (United Kingdom)

An understanding of the role played by intermolecular forces in terms of the electron density distribution is fundamental to the understanding of the self-assembly of molecules in the formation of a molecular crystal. Using ab initio methods capable of describing both short-range intramolecular interactions and long-range London dispersion interactions arising from electron correlation, analyses of inorganic dimers of As(4)S(4) and As(4)O(6) molecules cut from the structures of realgar and arsenolite, respectively, reveal that the molecules adopt a configuration that closely matches that observed for the crystal. Decomposition of the interaction energies using symmetry-adapted perturbation theory reveals that both model dimers feature significant stabilization from electrostatic forces as anticipated by a Lewis acid/Lewis base picture of the interaction. London dispersion forces also contribute significantly to the interaction, although they play a greater role in the realgar structure near equilibrium than in arsenolite.

Gibbs GV; Crawford TD; Wallace AF; Cox DF; Parrish RM; Hohenstein EG; Sherrill CD

2011-11-01

206

Role of long-range intermolecular forces in the formation of inorganic nanoparticle clusters.  

Science.gov (United States)

An understanding of the role played by intermolecular forces in terms of the electron density distribution is fundamental to the understanding of the self-assembly of molecules in the formation of a molecular crystal. Using ab initio methods capable of describing both short-range intramolecular interactions and long-range London dispersion interactions arising from electron correlation, analyses of inorganic dimers of As(4)S(4) and As(4)O(6) molecules cut from the structures of realgar and arsenolite, respectively, reveal that the molecules adopt a configuration that closely matches that observed for the crystal. Decomposition of the interaction energies using symmetry-adapted perturbation theory reveals that both model dimers feature significant stabilization from electrostatic forces as anticipated by a Lewis acid/Lewis base picture of the interaction. London dispersion forces also contribute significantly to the interaction, although they play a greater role in the realgar structure near equilibrium than in arsenolite. PMID:21939256

Gibbs, G V; Crawford, T D; Wallace, A F; Cox, D F; Parrish, R M; Hohenstein, E G; Sherrill, C D

2011-09-22

207

Neutral CH3Cl and CH3Br clusters studied by X-ray photoelectron spectroscopy and modeling: Insight to intermolecular interactions and structure  

International Nuclear Information System (INIS)

Single-component clusters of methyl chloride and methyl bromide have been produced by adiabatic expansion and their C 1s, Cl 2p and Br 3d photoelectron spectra recorded using synchrotron radiation and a high-resolution electron analyzer. The experimentally observed cluster-to-monomer shifts in core-level ionization energies are interpreted in terms of theoretical models based on molecular dynamics (MD) in conjunction with polarizable force fields developed and validated in the course of this work. MD simulations have also been used to explore the global and local structure of the clusters, providing evidence for a predominance of anti-parallel, head-to-tail arrangement of neighboring molecules. Whereas the cluster-to-monomer shifts are strongly dominated by polarization effects, the polarization contribution is very similar for ionization of carbon and the halogen, respectively. The difference in cluster shifts between the two ionization sites within the same molecule, C vs. Cl or C vs. Br, is thus determined by permanent electrostatic moments, i.e. the magnitude and direction of the permanent dipole moment and the local alignment of dipoles.

2008-01-01

208

High-Energy Neutrino Interactions  

CERN Document Server

This experiment studies neutrino interactions in iron at the highest available energies using the narrow-band neutrino beam N3 and the wide-band neutrino beam N1. The basis of the detector is a massive target-calorimeter in which the energy deposited by a neutrino (or antineutrino) is measured by electronic techniques and the momentum of outgoing muons is determined by magnetic deflection. The detector is constructed in the form of a 20 m long iron-cored toroidal magnet, composed of modules of length 70~cm and 90~cm, and of 3.75~m diameter. Drift chambers placed in between each module measure the trajectory of muons from the neutrino interactions. The modules are of three types. The first ten modules are constructed of 2.5~cm iron plates with 20~scintillator planes inserted between the plates. The next five modules are constructed of 5~cm plates with 15~planes of scintillator and the last six modules are constructed of 15~cm plates with 5~planes of scintillators. The total mass of the detector is @=~1400 tons...

2002-01-01

209

Quantitative tomographic imaging of intermolecular FRET in small animals.  

Science.gov (United States)

Forster resonance energy transfer (FRET) is a nonradiative transfer of energy between two fluorescent molecules (a donor and an acceptor) in nanometer range proximity. FRET imaging methods have been applied to proteomic studies and drug discovery applications based on intermolecular FRET efficiency measurements and stoichiometric measurements of FRET interaction as quantitative parameters of interest. Importantly, FRET provides information about biomolecular interactions at a molecular level, well beyond the diffraction limits of standard microscopy techniques. The application of FRET to small animal imaging will allow biomedical researchers to investigate physiological processes occurring at nanometer range in vivo as well as in situ. In this work a new method for the quantitative reconstruction of FRET measurements in small animals, incorporating a full-field tomographic acquisition system with a Monte Carlo based hierarchical reconstruction scheme, is described and validated in murine models. Our main objective is to estimate the relative concentration of two forms of donor species, i.e., a donor molecule involved in FRETing to an acceptor close by and a nonFRETing donor molecule. PMID:23243567

Venugopal, Vivek; Chen, Jin; Barroso, Margarida; Intes, Xavier

2012-11-08

210

Topological characterisation of intermolecular lithium bonding  

International Nuclear Information System (INIS)

Bader's atoms in molecules topological theory was employed to analyse the B3LYP/6-311++G(3d2f,3p2d) electron distributions of several adducts that contain LiF. The results indicate significant differences between lithium bonding (LB) and hydrogen bonding (HB): (i) in spite of their larger stability, the charge density at the intermolecular critical points of LB complexes is about half of its value in the corresponding HB complexes, suggesting a dominant role of electrostatic interactions in the former; (ii) the Li atom in LB compounds is more shared between the base atom and the attached fluorine than hydrogen in HB complexes; and (iii) the Li atom gains electron charge from the hydrogens in all the complexes here studied, undergoing energetic stabilisation.

2006-08-01

211

Ab Initio and Analytic Intermolecular Potentials for Ar-CF?  

Energy Technology Data Exchange (ETDEWEB)

Ab initio calculations at the CCSD(T) level of theory are performed to characterize the Ar ? CF ? intermolecular potential. Extensive calculations, with and without a correction for basis set superposition error (BSSE), are performed with the cc-pVTZ basis set. Additional calculations are performed with other correlation consistent (cc) basis sets to extrapolate the Ar---CF?potential energy minimum to the complete basis set (CBS) limit. Both the size of the basis set and BSSE have substantial effects on the Ar + CF? potential. Calculations with the cc-pVTZ basis set and without a BSSE correction, appear to give a good representation of the potential at the CBS limit and with a BSSE correction. In addition, MP2 theory is found to give potential energies in very good agreement with those determined by the much higher level CCSD(T) theory. Two analytic potential energy functions were determined for Ar ? CF?by fitting the cc-pVTZ calculations both with and without a BSSE correction. These analytic functions were written as a sum of two body potentials and excellent fits to the ab initio potentials were obtained by representing each two body interaction as a Buckingham potential.

Vayner, Grigoriy; Alexeev, Yuri; Wang, Jiangping; Windus, Theresa L.; Hase, William L.

2006-03-09

212

Interacting dark energy models in fractal cosmology  

CERN Document Server

We investigate interacting dark energy models in the framework of fractal cosmology. We discuss a fractal FRW universe filled with the dark energy and dark matter which interact with each other. We obtain the equation for the relative density of dark matter and dark energy and the deceleration parameter. This model demonstrates new types of evolution, which are not common to cosmological models with this type of interaction.

Lemets, O A

2012-01-01

213

Development of a polarizable intermolecular potential function (PIPF) for liquid amides and alkanes.  

Science.gov (United States)

A polarizable intermolecular potential function (PIPF) employing the Thole interacting dipole (TID) polarization model has been developed for liquid alkanes and amides. In connection with the internal bonding terms of the CHARMM22 force field, the present PIPF-CHARMM potential provides an adequate description of structural and thermodynamic properties for liquid alkanes and for liquid amides through molecular dynamics simulations. The computed heats of vaporization and liquid density are within 1.4% of experimental values. Polarization effects play a major role in liquid amides, which are reflected by an increase of 1.5 to 1.8 D in molecular dipole moment for primary and secondary amides. Furthermore, the computed polarization energies contribute to the total intermolecular interaction energy by 6 to 24%. The ability of the PIPF-CHARMM force field to treat protein backbone structures is tested by examining the potential energy surface of the amide bond rotation in N-methylacetamide and the Ramachandran surface for alanine dipeptide. The agreement with ab initio MP2 results and with the original CHARMM22 force field is encouraging, suggesting the PIPF-CHARMM potential can be used as a starting point to construct a complete polarizable force field for proteins. PMID:18958290

Xie, Wangshen; Pu, Jingzhi; Mackerell, Alexander D; Gao, Jiali

2007-01-01

214

New type of dual solid-state thermochromism: modulation of intramolecular charge transfer by intermolecular pi-pi interactions, kinetic trapping of the aci-nitro group, and reversible molecular locking.  

Science.gov (United States)

When heated above room temperature, some crystalline polymorphs of the 1,3-bis(hydroxyalkylamino)-4,6-dinitrobenzenes (BDBn, n = 2-5), bis(hydroxyalkyl) analogues of the intramolecular charge-transfer molecule 1,3-diamino-4,6-dinitrobenzene, exhibit "dual" thermochromism: gradual color change from yellow to orange at lower temperatures, and sharp color change from orange to red at higher temperatures. These two thermochromic changes are related to different solid-state processes. When allowed to cool to room temperature, the yellow color of the thermochromic molecules with different alkyl length (n) is recovered with unexpectedly different kinetics, the order of the respective rate constants ranging from 10(-7)-10(-6) s(-1) for BDB2 to about 0.1 s(-1) in the case of BDB3. The thermochromic mechanism and the reasons behind the different kinetics were clarified on the basis of detailed crystallographic characterization, kinetic thermoanalysis, and spectroscopic study of eight crystalline forms (seven polymorphs and one solvate). It was found that the polymorphism is due to the possibility of "locking" and "unlocking" of the alkyl arms by formation of a strong intramolecular hydrogen bond between the hydroxyl groups at their hydroxyl termini. The locking of BDB2, with shortest alkyl arms, is reversible and it can be controlled thermally; either of the two conformations can be obtained in the solid state by proper thermal treatment. By use of high temperature in situ single crystal X-ray diffraction analysis of BDB3, direct evidence was obtained that the gradual thermochromic change is related to increased distance and weakened pi-pi interactions between the stacked benzene rings: the lattice expands preferably in the stacking direction, causing enhanced oscillator strength and red shift of the absorption edge of the intramolecular charge transfer transition. The second, sharp thermochromic change had been assigned previously to solid-solid phase transition triggered by intramolecular proton transfer of one amino proton to the nitro group, whereupon an aci-nitro form is thermally populated. Contrary to the numerous examples of solid thermochromic molecules based on either pericyclic reactions or keto-enol tautomerism, this system appears to be the first organic thermochromic family where the thermochromic change appears as an effect of intermolecular pi-pi interactions and thermal intramolecular proton transfer to aromatic nitro group. PMID:19780605

Naumov, Pance; Lee, Sang Cheol; Ishizawa, Nobuo; Jeong, Young Gyu; Chung, Ihn Hee; Fukuzumi, Shunichi

2009-10-22

215

New type of dual solid-state thermochromism: modulation of intramolecular charge transfer by intermolecular pi-pi interactions, kinetic trapping of the aci-nitro group, and reversible molecular locking.  

UK PubMed Central (United Kingdom)

When heated above room temperature, some crystalline polymorphs of the 1,3-bis(hydroxyalkylamino)-4,6-dinitrobenzenes (BDBn, n = 2-5), bis(hydroxyalkyl) analogues of the intramolecular charge-transfer molecule 1,3-diamino-4,6-dinitrobenzene, exhibit "dual" thermochromism: gradual color change from yellow to orange at lower temperatures, and sharp color change from orange to red at higher temperatures. These two thermochromic changes are related to different solid-state processes. When allowed to cool to room temperature, the yellow color of the thermochromic molecules with different alkyl length (n) is recovered with unexpectedly different kinetics, the order of the respective rate constants ranging from 10(-7)-10(-6) s(-1) for BDB2 to about 0.1 s(-1) in the case of BDB3. The thermochromic mechanism and the reasons behind the different kinetics were clarified on the basis of detailed crystallographic characterization, kinetic thermoanalysis, and spectroscopic study of eight crystalline forms (seven polymorphs and one solvate). It was found that the polymorphism is due to the possibility of "locking" and "unlocking" of the alkyl arms by formation of a strong intramolecular hydrogen bond between the hydroxyl groups at their hydroxyl termini. The locking of BDB2, with shortest alkyl arms, is reversible and it can be controlled thermally; either of the two conformations can be obtained in the solid state by proper thermal treatment. By use of high temperature in situ single crystal X-ray diffraction analysis of BDB3, direct evidence was obtained that the gradual thermochromic change is related to increased distance and weakened pi-pi interactions between the stacked benzene rings: the lattice expands preferably in the stacking direction, causing enhanced oscillator strength and red shift of the absorption edge of the intramolecular charge transfer transition. The second, sharp thermochromic change had been assigned previously to solid-solid phase transition triggered by intramolecular proton transfer of one amino proton to the nitro group, whereupon an aci-nitro form is thermally populated. Contrary to the numerous examples of solid thermochromic molecules based on either pericyclic reactions or keto-enol tautomerism, this system appears to be the first organic thermochromic family where the thermochromic change appears as an effect of intermolecular pi-pi interactions and thermal intramolecular proton transfer to aromatic nitro group.

Naumov P; Lee SC; Ishizawa N; Jeong YG; Chung IH; Fukuzumi S

2009-10-01

216

Inelastic scattering calculations in polyatomic systems using an ab initio intermolecular potential energy surface: The CO2* (0,0,1,0)+H2(D2) ?CO2(0,0,0,0)+H2(D2) systems  

International Nuclear Information System (INIS)

[en] An ab initio computation of the energy transfer dynamics in the (CO2,H2) and (CO2,D2) systems has been carried out. The intermolecular potential energy hypersurface has been obtained from the results of ab initio SCF computations using extended Gaussian basis sets. The potential energy has been computed for 1053 different geometries. Previously formulated cubic spline fitting procedures are employed to effect surface interpolation and to extract surface gradients. At small CO2--H2 center-of-mass separations, the potential energy is repulsive and nearly exponential in form. At larger separations, small attractive wells are found. At a given separation, the most stable conformation is a planar, parallel structure of C2/sub v/ symmetry. Vibrational deexcitation probabilities, energy transfer mechanisms, and isotope ratios for the relaxation of the first excited state of the doubly degenerate bending mode of CO2 have been computed as a function of temperature by quasiclassical trajectories. In the temperature range below 600 K, the computed deexcitation probabilities are in fair to good agreement with the experimental shock tube data. At higher temperatures up to 1500 K, the computed results are too large by a factor of 3 or less. This error is interpreted to result at least partly from the assumption of classical motion. Computed isotope ratios are in fair accord with experiment over a 1000 K temperature range. The major relaxation mechanism is found to be V?R energy transfer for T

217

A simple non-empirical procedure for spin-component-scaled MP2 methods applied to the calculation of the dissociation energy curve of noncovalently-interacting systems.  

UK PubMed Central (United Kingdom)

We present a simple and non-empirical method to determine optimal scaling coefficients, within the (spin-component)-scaled MP2 approach, for calculating intermolecular potential energies of noncovalently-interacting systems. The method is based on an observed proportionality between (spin-component) MP2 and CCSD(T) energies for a wide range of intermolecular distances and allows us to compute with high accuracy a large portion of the dissociation curve at the cost of a single CCSD(T) calculation. The accuracy of the present procedure is assessed for a series of noncovalently-interacting test systems: the obtained results reproduce CCSD(T) quality in all cases and definitely outperform conventional MP2, CCSD and SCS-MP2 results. The difficult case of the beryllium dimer is also considered.

Grabowski I; Fabiano E; Della Sala F

2013-10-01

218

Simple non-empirical procedure for spin-component-scaled MP2 methods applied to the calculation of dissociation energy curve of noncovalently-interacting systems  

CERN Multimedia

We present a simple and non-empirical method to determine optimal scaling coefficients, within the (spin-component)-scaled MP2 approach, for calculating intermolecular potential energies of noncovalently-interacting systems. The method is based on an observed proportionality between (spin-component) MP2 and CCSD(T) energies for a wide range of intermolecular distances and allows to compute with high accuracy a large portion of the dissociation curve at the cost of a single CCSD(T) calculation. The accuracy of the present procedure is assessed for a series of noncovalently-interacting test systems: the obtained results reproduce CCSD(T) quality in all cases and definitely outperform conventional MP2, CCSD and SCS-MP2 results. The difficult case of the Beryllium dimer is also considered.

Grabowski, I; Della Sala, F

2013-01-01

219

Far-infrared laser spectroscopy of van der Waals bonds: A powerful new probe of intermolecular forces  

Energy Technology Data Exchange (ETDEWEB)

Our objective in these studies is to provide a detailed characterization of the structures and internal dynamics of weakly bound complexes as the requisite first step toward the ultimate goal: obtaining details three-dimensional intermolecular potential-energy surfaces for molecular weak interactions. The current state of the art limits us to studies of binary systems, but several groups are currently seeking to extend both the theory and experiments to address ternary and quaternary complexes. This will afford a detailed examination of the many-body effects (e.g., Axelrod -Teller triple dipole dispersion interaction), which becomes of potential importance in models of the chemistry of liquids.

Saykally, R.J. (Lawrence Berkeley Lab., CA (USA))

1989-09-01

220

Study of Coulomb interactions at VECC energies  

CERN Document Server

we study the effect of Coulomb interactions on balance energy for various colliding nuclei in terms of mass asymmetry. This study shows that the balance energy is affected by the Coulomb interactions as well as different nuclear equations of state. The preliminary results calculated theoretically will be of great use for scientists at VECC. This study is further in progress.

Kaur, Varinderjit; Puri, Rajeev K; Bhattacharya, S

2011-01-01

 
 
 
 
221

Desensitization and recovery of metastable intermolecular composites  

Energy Technology Data Exchange (ETDEWEB)

A method to substantially desensitize a metastable intermolecular composite material to electrostatic discharge and friction comprising mixing the composite material with an organic diluent and removing enough organic diluent from the mixture to form a mixture with a substantially putty-like consistency, as well as a concomitant method of recovering the metastable intermolecular composite material.

Busse, James R. (South Fork, CO); Dye, Robert C. (Los Alamos, NM); Foley, Timothy J. (Los Alamos, NM); Higa, Kelvin T. (Ridgecrest, CA); Jorgensen, Betty S. (Jemez Springs, NM); Sanders, Victor E. (White Rock, NM); Son, Steven F. (Los Alamos, NM)

2010-09-07

222

High-energy cosmic ray interactions  

International Nuclear Information System (INIS)

Research into hadronic interactions and high-energy cosmic rays are closely related. On one hand--due to the indirect observation of cosmic rays through air showers--the understanding of hadronic multiparticle production is needed for deriving the flux and composition of cosmic rays at high energy. On the other hand the highest energy particles from the universe allow us to study the characteristics of hadronic interactions at energies far beyond the reach of terrestrial accelerators. This is the summary of three introductory lectures on our current understanding of hadronic interactions of cosmic rays.

2009-04-30

223

Propagation studies of metastable intermolecular composites (MIC).  

Energy Technology Data Exchange (ETDEWEB)

Thermite materials are attractive energetic materials because the reactions are highly exothermic, have high energy densities, and high temperatures of combustion. However, the application of thermite materials has been limited because of the relative slow release of energy compared to other energetic materials. Engineered nano-scale composite energetic materials, such as Al/MoO{sub 3}, show promise for additional energetic material applications because they can react very rapidly. The composite material studied in this work consists of tailored, ultra-fine grain (30-200 nm diameter) aluminum particles that dramatically increase energy release rates of these thermite materials. These reactant clusters of fuel and oxidizer particles are in nearly atomic scale proximity to each other but are constrained from reaction until triggered. Despite the growing importance of nano-scale energetic materials, even the most basic combustion characteristics of these materials have not been thoroughly studied. This paper reports initial studies of the ignition and combustion of metastable intermolecular composites (MIC) materials. The goals were lo obtain an improved understanding of flame propagation mechanisms and combustion behaviors associated with nano-structured energetic materials. Information on issues such as reaction rate and behavior as a function of composition (mixture ratio), initial static charge, and particle size are essential and will allow scientists to design applications incorporating the benefits of these compounds. The materials have been characterized, specifically focusing on particle size, shape, distribution and morphology.

Son, S. F. (Steven F.); Busse, J. R. (James R.); Asay, B. W. (Blaine W.); Peterson, P. D. (Paul D.); Mang, J. T. (Joseph T.); Bockmon, B. (Bryan); Pantoya, M. (Michelle)

2002-01-01

224

The effect of intermolecular hydrogen bonding on the planarity of amides.  

UK PubMed Central (United Kingdom)

Ab initio and density functional theory (DFT) calculations on some model systems are presented to assess the extent to which intermolecular hydrogen bonding can affect the planarity of amide groups. Formamide and urea are examined as archetypes of planar and non-planar amides, respectively. DFT optimisations suggest that appropriately disposed hydrogen-bond donor or acceptor molecules can induce non-planarity in formamide, with OCNH dihedral angles deviating by up to ca. 20° from planarity. Ab initio energy calculations demonstrate that the energy required to deform an amide molecule from the preferred geometry of the isolated molecule is more than compensated by the stabilisation due to hydrogen bonding. Similarly, the NH(2) group in urea can be made effectively planar by the presence of appropriately positioned hydrogen-bond acceptors, whereas hydrogen-bond donors increase the non-planarity of the NH(2) group. Small clusters (a dimer, two trimers and a pentamer) extracted from the crystal structure of urea indicate that the crystal field acts to force planarity of the urea molecule; however, the interaction with nearest neighbours alone is insufficient to induce the molecule to become completely planar, and longer-range effects are required. Finally, the potential for intermolecular hydrogen bonding to induce non-planarity in a model of a peptide is explored. Inter alia, the insights obtained in the present work on the extent to which the geometry of amide groups may be deformed under the influence of intermolecular hydrogen bonding provide structural guidelines that can assist the interpretation of the geometries of such groups in structure determination from powder X-ray diffraction data.

Platts JA; Maarof H; Harris KD; Lim GK; Willock DJ

2012-09-01

225

Thz Spectroscopy and DFT Modeling of Intermolecular Vibrations in Hydrophobic Amino Acids  

Science.gov (United States)

Vibrations that involve intermolecular displacements occur in molecular crystals at frequencies in the 0.5-5 THz range (˜15-165 cm^{-1}), and these motions are direct indicators of the interaction potential between the molecules. The intermolecular potential energy surface of crystalline hydrophobic amino acids is inherently interesting simply because of the wide variety of forces (electrostatic, dipole-dipole, hydrogen-bonding, van der Waals) that are present. Furthermore, an understanding of these particular interactions is immediately relevant to important topics like protein conformation and pharmaceutical polymorphism. We measured the low-frequency absorption spectra of several polycrystalline hydrophobic amino acids using THz time-domain spectroscopy, and in addition we carried out DFT calculations using periodic boundary conditions and an exchange-correlation functional that accounts for van der Waals dispersion forces. We chose to investigate a series of similar amino acids with closely analogous unit cells (leucine, isoleucine, and allo-isoleucine, in racemic or pseudo-racemic mixtures). This allows us to consider trends in the vibrational spectra as a function of small changes in molecular arrangement and/or crystal geometry. In this way, we gain confidence that peak assignments are not based on serendipitous similarities between calculated and observed features.

Williams, michael R. C.; Aschaffenburg, Daniel J.; Schmuttenmaer, Charles A.

2013-06-01

226

Low energy K-P interactions  

International Nuclear Information System (INIS)

[en] The author discusses the lack of information about low energy K-p interactions and its reasons. Furthermore he describes the use of a time-projection chamber for the study of this reaction. (HSI)

1982-06-25

227

Interacting Ricci-like holographic dark energy  

CERN Multimedia

In a flat Friedmann-Lema\\^itre-Robertson-Walker background, a scheme of dark matter-dark energy interaction is studied considering a holographic Ricci-like model for the dark energy. Without giving a priori some specific model for the interaction function, we show that this function can experience a change of sign during the cosmic evolution. The parameters involved in the holographic model are adjusted with Supernova data and we obtained results compatible with the observable universe.

Arevalo, F; Lepe, S; Peña, F

2013-01-01

228

Intermolecular vibrations in hydrophobic amino Acid crystals: experiments and calculations.  

UK PubMed Central (United Kingdom)

Intermolecular vibrations of amino acid crystals occur in the THz, or far-infrared, region of the electromagnetic spectrum. We have measured the THz and Raman spectra of dl-leucine as well as two polymorphs of dl-valine, the spectroscopic properties of which have not previously been compared. Theoretical modeling of intermolecular vibrations in hydrophobic amino acids is challenging because the van der Waals interactions between molecules are not accounted for in standard density functional theory. Therefore, to calculate the vibrational modes, we used a recently developed approach that includes these nonlocal electron correlation forces. We discuss methods for comparing results from different theoretical models using metrics other than calculated vibrational frequency and intensity, and we also report a new approach enabling concise comparison of vibrational modes that involve complicated mixtures of inter- and intramolecular displacements.

Williams MR; Aschaffenburg DJ; Ofori-Okai BK; Schmuttenmaer CA

2013-09-01

229

Intermolecular vibrations in hydrophobic amino Acid crystals: experiments and calculations.  

Science.gov (United States)

Intermolecular vibrations of amino acid crystals occur in the THz, or far-infrared, region of the electromagnetic spectrum. We have measured the THz and Raman spectra of dl-leucine as well as two polymorphs of dl-valine, the spectroscopic properties of which have not previously been compared. Theoretical modeling of intermolecular vibrations in hydrophobic amino acids is challenging because the van der Waals interactions between molecules are not accounted for in standard density functional theory. Therefore, to calculate the vibrational modes, we used a recently developed approach that includes these nonlocal electron correlation forces. We discuss methods for comparing results from different theoretical models using metrics other than calculated vibrational frequency and intensity, and we also report a new approach enabling concise comparison of vibrational modes that involve complicated mixtures of inter- and intramolecular displacements. PMID:23931283

Williams, Michael R C; Aschaffenburg, Daniel J; Ofori-Okai, Benjamin K; Schmuttenmaer, Charles A

2013-08-28

230

Intermolecular Vibrations in Hydrophobic Amino Acid Crystals: Experiments and Calculations.  

UK PubMed Central (United Kingdom)

Intermolecular vibrations of amino acid crystals occur in the THz, or far-infrared, region of the electromagnetic spectrum. We have measured the THz and Raman spectra of DL-leucine as well as two polymorphs of DL-valine, the spectroscopic properties of which have not previously been compared. Theoretical modeling of intermolecular vibrations in hydrophobic amino acids is challenging because the van der Waals interactions between the molecules are not accounted for in standard density functional theory. Therefore, to calculate the vibrational modes, we used a recently developed approach that includes these non-local electron correlation forces. We discuss methods for comparing results of different theoretical models using metrics other than calculated vibrational frequency and intensity, and we also report a new approach for concise comparison of vibrational modes that involve complicated mixtures of inter- and intramolecular displacements.

Williams MR; Aschaffenburg DJ; Ofori-Okai B; Schmuttenmaer CA

2013-08-01

231

The inclusion of electron correlation in intermolecular potentials: Applications to the formamide dimer and liquid formamide  

DEFF Research Database (Denmark)

A test of the quality of the electrostatic properties and polarizabilities used in the nonempirical molecular orbital (NEMO) potential is carried out for formamide by calculating the molecular dipole moment and polarizability at the second-order Moller-Plesset (MP2) level of theory. The molecular dipole moment is 11% lower at the MP2 level than at the Hartree-Fock (HF) level, whereas the isotropic part of the polarizability is increased by 36% by adding electron correlation and using a considerably larger basis set. The atomic charges, dipole moments and polarizabilities obtained at the HF level are rescaled to get the correct molecular properties at the MP2 level. The potential minimum for the cyclic dimer of formamide is -17.50 kcal/mol with the MP2-scaled properties and is significantly lower than other potentials give. Two intermolecular potentials are constructed and used in subsequent molecular dynamics simulations: one with the regular NEMO potential and the other with the rescaled MP2 properties. A damping of the electrostatic field at short intermolecular distances is included in the present NEMO model. The average energies for liquid formamide are lower for the MP2-scaled model and are in good agreement with experimental results. The lowering of the simulation energy for the MP2-scaled potential indicates the strong dispersive interactions in liquid formamide.

Brdarski, S.; Åstrand, P.-O.

2000-01-01

232

JACEE results on very high energy interactions  

Energy Technology Data Exchange (ETDEWEB)

Direct observations of cosmic ray interactions in emulsion chambers of the JACEE experiment at energies above 1 TeV/nucleon are presented. An analysis of two decay of short lived particles produced in cosmic ray interactions is described. The known decay modes of bottom and charged particles do not account satisfactorily for the observations. This could possibly indicate a new decay channel of a heavy particle. The JACEE results support the hypothesis of existence of a long-flying component in cosmic ray showers. An interaction event was observed which may be the first direct observation of (mini)anticentauro interaction. (author) 13 refs, 12 figs, 1 tab

Wilczynski, H. [The H. Niewodniczanski Inst. of Nuclear Physics, Cracow (Poland); JACEE Collaboration

1996-12-31

233

Dark energy interacting with two fluids  

Energy Technology Data Exchange (ETDEWEB)

A cosmological model of dark energy interacting with dark matter and another general component of the universe is investigated. We found general constraints on these models imposing an accelerated expansion. The same is also studied in the case for holographic dark energy.

Cruz, Norman [Departamento de Fisica, Facultad de Ciencia, Universidad de Santiago, Casilla 307, Santiago (Chile)], E-mail: ncruz@lauca.usach.cl; Lepe, Samuel [Instituto de Fisica, Facultad de Ciencias Basicas y Matematicas, Universidad Catolica de Valparaiso, Avenida Brasil 2950, Valparaiso (Chile)], E-mail: slepe@ucv.cl; Pena, Francisco [Departamento de Ciencias Fisicas, Facultad de Ingenieria, Ciencias y Administracion, Universidad de La Frontera, Avda. Francisco Salazar 01145, Casilla 54-D Temuco (Chile)], E-mail: fcampos@ufro.cl

2008-05-29

234

Expectations for ultra-high energy interactions  

International Nuclear Information System (INIS)

Strong interactions at ultra-high energies are discussed with emphasis on the hadrons produced in high energy collisions. Evidence is considered that quantum chromodynamics might be the right theory, and also some estimates are given of quantum chromodynamics asymptotic-freedom phenomena, the work under discussion being very preliminary. 6 references.

1978-03-31

235

Nonadditive intermolecular forces from the spectroscopy of van der Waals trimers: A theoretical study of Ar2-HF  

International Nuclear Information System (INIS)

[en] Calculations of vibrational energies and rotational constants are carried out for the van der Waals trimer Ar2-HF. The calculations include all five intermolecular degrees of freedom. The different intramolecular vibrational states v of the HF molecule are separated out adiabatically, so that the calculations are carried out on effective intermolecular potentials for each HF vibrational state separately. Calculations are performed both on pairwise-additive potentials, derived from the well-known Ar-Ar and Ar-HF potentials, and on nonadditive potentials, incorporating various different contributions to the three-body forces. The results are compared with experimental results from high-resolution spectroscopy, and provide detailed information on the anisotropy of the nonadditive intermolecular forces. As in previous work on Ar2-HCl, it is found that a very important nonadditive term arises from the interaction between the permanent multipoles of the HF molecule and the exchange quadrupole caused by distortion of the two Ar atoms as they overlap. An improved model of this term is described

1995-01-01

236

Nonadditive intermolecular forces from the spectroscopy of van der Waals trimers: A theoretical study of Ar[sub 2]-HF  

Energy Technology Data Exchange (ETDEWEB)

Calculations of vibrational energies and rotational constants are carried out for the van der Waals trimer Ar[sub 2]-HF. The calculations include all five intermolecular degrees of freedom. The different intramolecular vibrational states [ital v] of the HF molecule are separated out adiabatically, so that the calculations are carried out on effective intermolecular potentials for each HF vibrational state separately. Calculations are performed both on pairwise-additive potentials, derived from the well-known Ar-Ar and Ar-HF potentials, and on nonadditive potentials, incorporating various different contributions to the three-body forces. The results are compared with experimental results from high-resolution spectroscopy, and provide detailed information on the anisotropy of the nonadditive intermolecular forces. As in previous work on Ar[sub 2]-HCl, it is found that a very important nonadditive term arises from the interaction between the permanent multipoles of the HF molecule and the exchange quadrupole caused by distortion of the two Ar atoms as they overlap. An improved model of this term is described.

Ernesti, A.; Hutson, J.M. (Department of Chemistry, University of Durham, South Road, Durham, DH13LE (United Kingdom))

1995-01-01

237

Imaging Erg and Jun transcription factor interaction in living cells using fluorescence resonance energy transfer analyses  

International Nuclear Information System (INIS)

[en] Physical interactions between transcription factors play important roles in modulating gene expression. Previous in vitro studies have shown a transcriptional synergy between Erg protein, an Ets family member, and Jun/Fos heterodimer, members of the bZip family, which requires direct Erg-Jun protein interactions. Visualization of protein interactions in living cells is a new challenge in biology. For this purpose, we generated fusion proteins of Erg, Fos, and Jun with yellow and cyan fluorescent proteins, YFP and CFP, respectively. After transient expression in HeLa cells, interactions of the resulting fusion proteins were explored by fluorescence resonance energy transfer microscopy (FRET) in fixed and living cells. FRET between YFP-Erg and CFP-Jun was monitored by using photobleaching FRET and fluorescence lifetime imaging microscopy. Both techniques revealed the occurrence of intermolecular FRET between YFP-Erg and CFP-Jun. This is stressed by loss of FRET with an YFP-Erg version carrying a point mutation in its ETS domain. These results provide evidence for the interaction of Erg and Jun proteins in living cells as a critical prerequisite of their transcriptional synergy, but also for the essential role of the Y371 residue, conserved in most Ets proteins, in this interaction

2005-07-15

238

Energy and entropy of interacting dislocations  

International Nuclear Information System (INIS)

[en] The energy and entropy of interacting edge dislocations have been calculated by atomistic simulations, with the use of piecewise-linear forces in a two-dimensional triangular lattice. We conclude that the interaction energy between small groups of dislocations is well described by continuum mechanics for separations greater than a few lattice spacings. Our calculations enable us to make a precise determination of the core energy, which is an essential parameter in determining dislocation multiplication rates. We find also that continuum mechanics gives an accurate representation of the interaction of a dislocation pair with a homogeneous elastic stress field. The vibrational contribution to the entropy of such a pair is small, about 0.3k

1982-11-15

239

Tetrads in low-energy weak interactions  

CERN Document Server

Tetrads are introduced in order to study the relationship between gravity and particle interactions, specially in weak processes at low energy. Through several examples like inverse Muon decay, elastic Neutrino-Electron scattering, it is explicitly shown how to assign to each vertex of the corresponding low-order Feynman diagram in a weak interaction, a particular set of tetrad vectors. The relationship between the tetrads associated to different vertices is exhibited explicitly to be generated by a SU(2) local gauge transformation.

Garat, A

2006-01-01

240

Antiproton-nucleus interaction at low energy  

International Nuclear Information System (INIS)

[en] On the basis of the Brueckner-Hartree-Fock theory, the self-energy of an antiproton in nuclear matter is evaluated with the static Bryan-Phillips potential, and the density-dependent effective anti NN interaction is estimated with this selfenergy. Using the anti p-nucleus optical potential constructed by folding this effective anti NN interaction, one can predict the complex level shift of anti p-atoms. (orig.)

1983-06-02

 
 
 
 
241

Intermolecular and intramolecular contributions to the relaxation process in sorbitol and maltitol  

Science.gov (United States)

Molecular mobility in sorbitol and maltitol is studied with spectroscopic techniques and molecular dynamics simulations in order to evaluate the relative contributions of the intermolecular and intramolecular interactions involved in the relaxation processes. The results of the molecular dynamics simulations performed on the polyols in the bulk or in vacuum compares well with the results of the analysis of the relaxation diagrams in the framework of the Perez et al . model. They both imply that the difference in the relative contributions of the intermolecular and intramolecular interactions associated with the different chemical architectures of the two polyols must be taken into account. The intermolecular interactions cannot be neglected and they are stronger in sorbitol than in maltitol in relation with the linear structure of this polyol. The intramolecular barrier, higher in the maltitol molecule with a more complex structure, could be at the origin of the higher junction temperature between the ?and ?relaxation processes.

Sixou, B.; Faivre, A.; David, L.; Vigier, G.

242

Polynomial identities for ternary intermolecular recombination  

CERN Multimedia

The operation of binary intermolecular recombination, originating in the theory of DNA computing, permits a natural generalization to n-ary operations which perform simultaneous recombination of n molecules. In the case n = 3, we use computer algebra to determine the polynomial identities of degree <= 9 satisfied by this trilinear nonassociative operation. Our approach requires computing a basis for the nullspace of a large integer matrix, and for this we compare two methods: (i) the row canonical form, and (ii) the Hermite normal form with lattice basis reduction. In the conclusion, we formulate some conjectures for the general case of n-ary intermolecular recombination.

Bremner, Murray R

2010-01-01

243

Transport properties and intermolecular forces  

International Nuclear Information System (INIS)

The semi-empirical procedure, previously introduced by the authors for the determination of like and unlike interaction parameters from viscosity data, is extended to be applied to ordinary diffusion data. The L.J. (n-6) potentials, with n ranging from 7 to 90, are considered. The procedure is tested and proved successful for Ne, Ar, Xe, and their binary mixtures. The best values of n representing the interaction of these systems are found to be 11.8 (for Ne), 12.1 (for Ar), 11.6 (for Xe), 11.9 (for Ne-Ar), 12 (for Ne-Xe), and 12 (for Ar-Xe). These potentials are found to reproduce the experimental results satisfactorily to within 8%

1986-01-01

244

Low-energy Antiproton Interaction with Helium  

CERN Document Server

An ab initio potential for the interaction of the neutral helium atom with antiprotons and protons is calculated using the Born-Oppenheimer approximation. Using this potential, the annihilation cross section for antiprotons in the energy range 0.01 microvolt to 1 eV is calculated.

Gibbs, W R

1997-01-01

245

Halo events in superhigh energy nuclear interactions  

International Nuclear Information System (INIS)

[en] Gamma family events with visible energies higher than 1015 eV usually form halos in the emulsion chambers, which bring up some problems for further investigating the characteristics of superhigh energy nuclear interactions. At present, only a few gross quantities are used for describing the halo events. On the other hand, there are some fine structures inside the halo, which can give us more information. We have measured all the showers one by one in the superhigh energy family events and compared the results with those obtained by the method of halo measurements. Analyses and discussions are made for some special events

1996-01-01

246

Department of High Energy Nuclear Interactions - Overview  

International Nuclear Information System (INIS)

Full text: In 1998 the research activities of the Department concentrated on investigations of heavy ion interactions and the study of the primary cosmic rays. In the field of heavy ion physics the EMU13 experiment supplied us with the data on Pb collisions with different targets at the energy of 158 GeV/nucleon. High multiplicity Pb-Ag/Br collisions were studied on event by event basis. It is believed that the investigation of individual high multiplicity events should reveal the onset of new phenomena such as e.g., creation of a quark gluon plasma. The fragmentation process of lead projectiles in Pb-Pb interactions recorded in emulsion chambers specially designed for this purpose was also studied. The measured cross section indicated the important role of electromagnetic processes in the high energy Pb-Pb interactions. We also continued the investigations of Au collisions with the components of nuclear emulsion at 10.6 GeV/nucleon (experiment BNL868). The results on the particle production were compared with predictions of the RQMD model. The fragmentation of the Au projectile as well as the target nuclei were analyzed. PHOBOS experiment at the Relativistic Heavy Ion Collider at BNL will investigate Au-Au interactions at a center of mass energy 200 GeV/nucleon. Such interactions will produce the highest energy density ever reached in a laboratory. It is expected that under these conditions the quark gluon plasma will be discovered. The preparation for PHOBOS experiment have entered the final stage with the first physical run at the accelerator planned for November 1999. The physicists from our Department and the engineers from the High Energy Physics Detector Construction Group have been involved in computer simulations of various physical processes as well as designing, testing and constructing the elements of the PHOBOS detector. In the field of cosmic ray research our Department has started participating in the Pierre Auger Project. The aim of this broad-based international effort is to study cosmic rays at the highest energies (E > 1019 eV) in order to obtain information on the sources and acceleration mechanisms of these high energy particles. I would like to take this opportunity to acknowledge the great effort of all the members of the Department of High Energy Nuclear Interactions in obtaining the significant scientific results in the past year. (author)

1999-01-01

247

Evaluation of intermolecular attractive forces in coal-derived liquids  

Energy Technology Data Exchange (ETDEWEB)

The effect of structural features (hence types of intermolecular interactions) on the physical properties of coal-derived preasphaltenes was studied by comparing (1) the solubility of several model compounds of known structure with the dissolvability of preasphaltene samples as a function of solvent parameters and (2) intrinsic viscosities of model compounds of known structure with viscosities of preasphaltene samples. The quantitative dissolvabilities of nine model compounds and nine preasphaltene samples isolated from different liquefaction runs in 12 solvents were measured. The dissolvabilities were correlated with five solvent parameters: Hidebrand solubility parameter ({delta}), net hydrogen-bonding index ({theta}), donor number (DN), donor number minus acceptor number (DN-AN), and donor number divided by acceptor number (DN/AN). The intrinsic viscosities of 66 model compounds and 38 size-separated preasphaltene samples were determined in THF solution. The model compounds were divided into three subsets: (1) models which were primarily hydrocarbon, with dispersion and {pi}--{pi} interactions as the dominant intermolecular forces, (2) models which contained polar groups, such as etheral oxygen and heterocyclic amine, but which exhibited the same general types of interactions as group 1, and (3) models which contained hydrogen-bond donor functionalities. The preasphaltene samples were isolated from different liquefaction runs and were separated into narrow molecular weight fractions by preparative gel permeation chromatography.

Jones, M.B.

1989-08-01

248

Constraining dark energy interacting models with WMAP  

CERN Multimedia

We determine the range of parameter space of an interacting quintessence (IQ) model that best fits the luminosity distance of type Ia supernovae data and the recent WMAP measurements of Cosmic Microwave Background temperature anisotropies. Models in which quintessence decays into dark matter provide a clean explanation for the coincidence problem. We focus on cosmological models of zero spatial curvature. We show that if the dark energy (DE) decays into cold dark matter (CDM) at a rate that brings the ratio of matter to dark energy constant at late times, the supernovae data are not sufficient to constrain the interaction parameter. On the contrary, WMAP data constrain it to be smaller than $c^2 < 10^{-2}$ at the $3\\sigma$ level. Accurate measurements of the Hubble constant and the dark energy density, independent of the CMB data, would support/disprove this set of models.

Olivares, G; Pavón, D; Olivares, German; Atrio-Barandela, Fernando; Pavon, Diego

2006-01-01

249

Experimental and theoretical study on the intermolecular complex formation between trehalose and benzene compounds in aqueous solution.  

UK PubMed Central (United Kingdom)

The uniqueness of trehalose as a stress protectant may exist in its potential amphiphilic character capable of interacting with both hydrophilic and hydrophobic partners in aqueous solution. To address this issue, we here investigated the interaction between trehalose and aromatic compounds. NMR measurements, including (1)H-(1)H NOESY spectra, provide direct evidence for the formation of stable intermolecular complexes of trehalose with benzene (or p-cresol) in aqueous solution. In addition, corresponding theoretical evidence is provided by calculating the potential mean force as a function of the distance between trehalose and benzene. In the energy minimum structure, the benzene molecule is located only around the hydrophobic side of trehalose where the first hydration shell is not formed. Therefore, it can be concluded that benzene binds to trehalose in a fashion in which dehydration penalty is minimized. Finally, we discuss the possible biological roles of the trehalose-benzene interaction discovered here.

Sakakura K; Okabe A; Oku K; Sakurai M

2011-08-01

250

Interactions between dark energy and dark matter  

International Nuclear Information System (INIS)

We have investigated interacting dark energy cosmologies both concerning their impact on the background evolution of the Universe and their effects on cosmological structure growth. For the former aspect, we have developed a cosmological model featuring a matter species consisting of particles with a mass that increases with time. In such model the appearance of a Growing Matter component, which is negligible in early cosmology, dramatically slows down the evolution of the dark energy scalar field at a redshift around six, and triggers the onset of the accelerated expansion of the Universe, therefore addressing the Coincidence Problem. We propose to identify this Growing Matter component with cosmic neutrinos, in which case the present dark energy density can be related to the measured average mass of neutrinos. For the latter aspect, we have implemented the new physical features of interacting dark energy models into the cosmological N-body code GADGET-2, and we present the results of a series of high-resolution simulations for a simple realization of dark energy interaction. As a consequence of the new physics, cold dark matter and baryon distributions evolve differently both in the linear and in the non-linear regime of structure formation. Already on large scales, a linear bias develops between these two components, which is further enhanced by the non-linear evolution. We also find, in contrast with previous work, that the density profiles of cold dark matter halos are less concentrated in coupled dark energy cosmologies compared with ?CDM. Also, the baryon fraction in halos in the coupled models is significantly reduced below the universal baryon fraction. These features alleviate tensions between observations and the ?CDM model on small scales. Our methodology is ideally suited to explore the predictions of coupled dark energy models in the fully non-linear regime, which can provide powerful constraints for the viable parameter space of such scenarios. (orig.)

2009-01-01

251

Interactions between dark energy and dark matter  

Energy Technology Data Exchange (ETDEWEB)

We have investigated interacting dark energy cosmologies both concerning their impact on the background evolution of the Universe and their effects on cosmological structure growth. For the former aspect, we have developed a cosmological model featuring a matter species consisting of particles with a mass that increases with time. In such model the appearance of a Growing Matter component, which is negligible in early cosmology, dramatically slows down the evolution of the dark energy scalar field at a redshift around six, and triggers the onset of the accelerated expansion of the Universe, therefore addressing the Coincidence Problem. We propose to identify this Growing Matter component with cosmic neutrinos, in which case the present dark energy density can be related to the measured average mass of neutrinos. For the latter aspect, we have implemented the new physical features of interacting dark energy models into the cosmological N-body code GADGET-2, and we present the results of a series of high-resolution simulations for a simple realization of dark energy interaction. As a consequence of the new physics, cold dark matter and baryon distributions evolve differently both in the linear and in the non-linear regime of structure formation. Already on large scales, a linear bias develops between these two components, which is further enhanced by the non-linear evolution. We also find, in contrast with previous work, that the density profiles of cold dark matter halos are less concentrated in coupled dark energy cosmologies compared with {lambda}{sub CDM}. Also, the baryon fraction in halos in the coupled models is significantly reduced below the universal baryon fraction. These features alleviate tensions between observations and the {lambda}{sub CDM} model on small scales. Our methodology is ideally suited to explore the predictions of coupled dark energy models in the fully non-linear regime, which can provide powerful constraints for the viable parameter space of such scenarios. (orig.)

Baldi, Marco

2009-03-20

252

Förster Resonance Energy Transfer (FRET) as a Tool for Dissecting the Molecular Mechanisms for Maturation of the Shigella Type III Secretion Needle Tip Complex  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Förster resonance energy transfer (FRET) provides a powerful tool for monitoring intermolecular interactions and a sensitive technique for studying Å-level protein conformational changes. One system that has particularly benefited from the sensitivity and diversity of FRET measurements is ...

Nicholas E. Dickenson; William D. Picking

253

Holographic dark energy interacting with dark matter  

CERN Multimedia

We investigate a spatially flat Friedmann-Robertson-Walker (FRW) cosmological model with cold dark matter coupled to a dark energy which is given by the modified holographic Ricci cutoff. The interaction used is linear in both dark energy densities, the total energy density and its derivative. Using the statistical method of $\\chi^2$-function for the Hubble data, we obtain $H_0=73.6km/sMpc$, $\\omega_s=\\gamma_s -1=-0.842$ for the asymptotic equation of state and $ z_{acc}= 0.89 $. The estimated values of $\\Omega_{c0}$ which fulfill the current observational bounds corresponds to a dark energy density varying in the range $0.25R < \\ro_x < 0.27R$.

Forte, Mónica I

2012-01-01

254

Intermolecular forces and molecular dynamics simulation of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) using symmetry adapted perturbation theory.  

UK PubMed Central (United Kingdom)

The dimer potential energy surface (PES) of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) has been explored using symmetry adapted perturbation theory based on a Kohn-Sham density functional theory description of the monomers [SAPT(DFT)]. An intermolecular potential energy function was parametrized using a grid of 880 ab initio SAPT(DFT) dimer interaction energies, and the function was used to identify stationary points on the SAPT(DFT) dimer PES. It is shown that there exists a variety of minima with a range of bonding configurations and ab initio analyses of the interaction energy components, along with radial cross sections of the PES near each minimum, are presented. Results of isothermal-isostress molecular dynamics simulations are reported, and the simulated structure, thermal expansion, sublimation enthalpy, and bulk modulus of the TATB crystal, based on the SAPT(DFT) interaction potential, are in good agreement with experiment.

Taylor DE

2013-04-01

255

Intermolecular forces and molecular dynamics simulation of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) using symmetry adapted perturbation theory.  

Science.gov (United States)

The dimer potential energy surface (PES) of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) has been explored using symmetry adapted perturbation theory based on a Kohn-Sham density functional theory description of the monomers [SAPT(DFT)]. An intermolecular potential energy function was parametrized using a grid of 880 ab initio SAPT(DFT) dimer interaction energies, and the function was used to identify stationary points on the SAPT(DFT) dimer PES. It is shown that there exists a variety of minima with a range of bonding configurations and ab initio analyses of the interaction energy components, along with radial cross sections of the PES near each minimum, are presented. Results of isothermal-isostress molecular dynamics simulations are reported, and the simulated structure, thermal expansion, sublimation enthalpy, and bulk modulus of the TATB crystal, based on the SAPT(DFT) interaction potential, are in good agreement with experiment. PMID:23565605

Taylor, DeCarlos E

2013-04-16

256

Protein-Protein Interaction Analysis by Docking  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Based on a protein-protein docking approach we have developed a procedure to verify or falsify protein-protein interactions that were proposed by other methods such as yeast-2-hybrid assays. Our method currently utilizes intermolecular energies but can be expanded to incorporate additional terms suc...

Florian Fink; Stephan Ederer; Wolfram Gronwald

257

Department of High Energy Nuclear Interactions - Overview  

International Nuclear Information System (INIS)

Full text: In 1999 the research activities of the Department concentrated on the investigations of heavy ion interactions, cosmic ray interactions and astrophysical aspects of the study of primary cosmic rays. In the field of relativistic heavy ion physics, high multiplicity interactions of 158 GeV/nucleon Pb ions on Pb targets were investigated (Experiment EMU13). It was shown that the shape of pseudorapidity distributions of particles produced in Pb+Pb interactions does not depend on the centrality of the collision. A new method was developed to study the distributions of participating and spectator protons. Emulsion chambers used in the EMU13 Experiment were designed to study also the fragmentation of the Pb projectile in collisions with different target nuclei. Such study was completed for a minimum bias sample of Pb+Pb interactions. In 1999 a group of physicists from our Department started to measure Pb collisions with light nuclear targets. The analysis of this data should enable the separation of the electromagnetic and nuclear processes for the samples of Pb interactions with heavy and light nuclei. The physics program of the PHOBOS experiment at the Relativistic Heavy Ion Collider (RHIC) at the Brookhaven National Laboratory is aimed to investigate Au+Au interactions at the center of mass energy of 200 GeV/nucleon. Such interactions will produce the highest energy density ever reached in laboratory conditions. It is expected that under these conditions a quark-gluon plasma will be formed. The main goal of the PHOBOS project is to discover this new phase of matter. At the end of 1999 the PHOBOS detector construction was completed and the assembly and installation of the apparatus entered the final stage. The detector will be ready for the first physics run in spring 2000. The software infrastructure for data acquisition and analysis has been developed and is ready for data taking. In the field of cosmic ray research our Department participated in the preparation of Pierre Auger Project. The aim of this project is to study the cosmic rays at the highest energies (E>1019 GeV) in order to obtain information on the sources and acceleration mechanisms of these high energy particles. The physicists from our Department and engineers from the Division of Mechanical Construction have been involved in computer simulations of various processes as well as in the design of the elements of the Auger detector. Computer simulations of the distribution of the fluorescent light emitted by extensive air showers were performed. These results will be used to define appropriate trigger conditions for the Auger detector. The analysis of multiple electron pairs recorded in high energy cosmic ray interactions has been carried out on the basis of the data obtained from the JACEE experiment. A comparison of our results with recently published compilation of the low energy nuclear data indicates possible production of a new neutral boson decaying into electron pairs. Some details on the research activity of the Department are presented in the following pages. (author)

2000-01-01

258

Correlated ab initio investigations on the intermolecular and intramolecular potential energy surfaces in the ground electronic state of the O2(-)(X2?g)-HF(X1?+) complex.  

Science.gov (United States)

This work reports the first highly correlated ab initio study of the intermolecular and intramolecular potential energy surfaces in the ground electronic state of the O(2)(-)(X(2)?(g))-HF(X(1)?(+)) complex. Accurate electronic structure calculations were performed using the coupled cluster method including single and double excitations with addition of the perturbative triples correction [CCSD(T)] with the Dunning's correlation consistent basis sets aug-cc-pVnZ, n = 2-5. Also, the explicitly correlated CCSD(T)-F12a level of theory was employed with the AVnZ basis as well as the Peterson and co-workers VnZ-F12 basis sets with n = 2 and 3. Results of all levels of calculations predicted two equivalent minimum energy structures of planar geometry and C(s) symmetry along the A" surface of the complex, whereas the A' surface is repulsive. Values of the geometrical parameters and the counterpoise corrected dissociation energies (Cp-D(e)) that were calculated using the CCSD(T)-F12a/VnZ-F12 level of theory are in excellent agreement with those obtained from the CCSD(T)/aug-cc-pV5Z calculations. The minimum energy structure is characterized by a very short hydrogen bond of length of 1.328 Å, with elongation of the HF bond distance in the complex by 0.133 Å, and D(e) value of 32.313 Kcal/mol. Mulliken atomic charges showed that 65% of the negative charge is localized on the hydrogen bonded end of the superoxide radical and the HF unit becomes considerably polarized in the complex. These results suggest that the hydrogen bond is an incipient ionic bond. Exploration of the potential energy surface confirmed the identified minimum and provided support for vibrationally induced intramolecular proton transfer within the complex. The T-shaped geometry that possesses C(2v) symmetry presents a saddle point on the top of the barrier to the in-plane bending of the hydrogen above and below the axis that connects centers of masses of the monomers. The height of this barrier is 7.257 Kcal/mol, which is higher in energy than the hydrogen bending frequency by 909.2 cm(-1). The calculated harmonic oscillator vibrational frequencies showed that the H-F stretch vibrational transition in the complex is redshifted by 2564 cm(-1) and gained significant intensity (by at least a factor of 30) with respect to the transition in the HF monomer. These results make the O(2)(-)-HF complex an excellent prototype for infrared spectroscopic investigations on open-shell complexes with vibrationally induced proton transfer. PMID:23298038

Fawzy, Wafaa M; Elsayed, Mahmoud; Zhang, Yuchen

2013-01-01

259

Correlated ab initio investigations on the intermolecular and intramolecular potential energy surfaces in the ground electronic state of the O2(-)(X2?g)-HF(X1?+) complex.  

UK PubMed Central (United Kingdom)

This work reports the first highly correlated ab initio study of the intermolecular and intramolecular potential energy surfaces in the ground electronic state of the O(2)(-)(X(2)?(g))-HF(X(1)?(+)) complex. Accurate electronic structure calculations were performed using the coupled cluster method including single and double excitations with addition of the perturbative triples correction [CCSD(T)] with the Dunning's correlation consistent basis sets aug-cc-pVnZ, n = 2-5. Also, the explicitly correlated CCSD(T)-F12a level of theory was employed with the AVnZ basis as well as the Peterson and co-workers VnZ-F12 basis sets with n = 2 and 3. Results of all levels of calculations predicted two equivalent minimum energy structures of planar geometry and C(s) symmetry along the A" surface of the complex, whereas the A' surface is repulsive. Values of the geometrical parameters and the counterpoise corrected dissociation energies (Cp-D(e)) that were calculated using the CCSD(T)-F12a/VnZ-F12 level of theory are in excellent agreement with those obtained from the CCSD(T)/aug-cc-pV5Z calculations. The minimum energy structure is characterized by a very short hydrogen bond of length of 1.328 Å, with elongation of the HF bond distance in the complex by 0.133 Å, and D(e) value of 32.313 Kcal/mol. Mulliken atomic charges showed that 65% of the negative charge is localized on the hydrogen bonded end of the superoxide radical and the HF unit becomes considerably polarized in the complex. These results suggest that the hydrogen bond is an incipient ionic bond. Exploration of the potential energy surface confirmed the identified minimum and provided support for vibrationally induced intramolecular proton transfer within the complex. The T-shaped geometry that possesses C(2v) symmetry presents a saddle point on the top of the barrier to the in-plane bending of the hydrogen above and below the axis that connects centers of masses of the monomers. The height of this barrier is 7.257 Kcal/mol, which is higher in energy than the hydrogen bending frequency by 909.2 cm(-1). The calculated harmonic oscillator vibrational frequencies showed that the H-F stretch vibrational transition in the complex is redshifted by 2564 cm(-1) and gained significant intensity (by at least a factor of 30) with respect to the transition in the HF monomer. These results make the O(2)(-)-HF complex an excellent prototype for infrared spectroscopic investigations on open-shell complexes with vibrationally induced proton transfer.

Fawzy WM; Elsayed M; Zhang Y

2013-01-01

260

Spectroscopic studies on the intermolecular charge transfer interaction of Fe(II)- and Fe(III)-phthalocyanines with 2,3,5,6-tetrachloro-1,4-benzoquinone and its application in colorimetric sensing of amino acids and amines.  

Science.gov (United States)

The interactions of Fe(II)Pc and Fe(III)Pc with ?-acceptor 2,3,5,6-tetrachloro-1,4-benzoquinone (p-chloranil, p-CHL) have been investigated spectroscopically (UV/vis and FT-IR) and spectrofluorimetrically at three different temperatures. The stoichiometry of the complexes was found to be 1:1. The results of electronic spectral studies indicated that the formation constant for Fe(II)Pc-p-CHL system is found to be higher than that for Fe(III)Pc-p-CHL system. This observation is well supported by the results of fluorescence quenching studies and the association constants calculated for Fe(II)Pc-p-CHL system is 4.2 × 10(3) mol L(-1) and that for Fe(III)Pc-p-CHL system is 2.2 × 10(3) mol L(-1). The data are discussed in terms of physico-chemical parameters viz. molar extinction coefficient, oscillator strength, dipole moment, ionization potential, dissociation energy and thermodynamic parameters. The results indicated that the formation of ?-? CT complex is spontaneous and endothermic. Preliminary studies indicated that the CT complex can effectively be used as a colorimetric agent for sensing amino acids and amines. PMID:22074888

Balraj, Chellamuthu; Elango, Kuppanagounder P

2011-10-04

 
 
 
 
261

New models for intermolecular repulsion and their application to Van Der Waals complexes and crystals of organic molecules  

International Nuclear Information System (INIS)

Model intermolecular potentials are required for simulations of molecules in the gas, liquid, or solid phase. The widely used isotropic atom-atom model potentials are empirically fitted and based on the assumptions of transferability, combining rules and that atoms in molecules are spherical. This thesis develops a non-empirical method of modelling repulsion by applying the overlap model, which we show as a general non-empirical method of deriving repulsion potentials for a specific molecule. In this thesis, the repulsion parameters for an exponential atom-atom model potential are obtained from the ab initio charge density of a small organic molecule by making the assumption that the repulsion is proportional to the overlap of a pair of molecules. The proportionality constant is fixed by a limited number of intermolecular perturbation theory (IMPT) calculations. To complete the model potential, the electrostatic interaction is represented by a distributed multipole analysis, and the Slater-Kirkwood formula is used for the dispersion. These non-empirical potentials can reproduce experimental crystal structure when applied to crystal structure prediction of an oxyboryl derivative. A detailed study on further improving the overlap model was carried out for phenol-water, by including other minor intermolecular contributions of charge-transfer and penetration. High quality ab initio calculations on the complex were performed for use in comparison. To compare with experimental data, diffusion Monte Carlo simulations were performed with the potential, so that the effects of anharmonic zero-point motion on structure and energy of the system are included. When the system is too large for an IMPT calculation, the proportionality constant can be determined empirically by fitting the cell volume as shown in our study of crystal structures of chlorothalonil. This is used with an anisotropic repulsion model that has been derived for Cl and N atoms in chlorothalonil. This model potential reproduces the crystal structure well, and is used to predict other polymorphs by a search for minima in the lattice energy. (author)

2001-01-01

262

Intermolecular electron transfer promoted by directional donor-acceptor attractions in self-assembled diketopyrrolopyrrole-thiophene films.  

UK PubMed Central (United Kingdom)

The photophysics of a symmetric triad consisting of two bithiophene (BT) units covalently linked to a central diketopyrrolopyrrole unit (DPP) has been investigated both in dichloromethane and in the thin film. The DPP-BT film exhibits a red-shifted low-energy absorption band compared to its solution, which is indicative of efficient ?-? interactions in the solid-state phase. The steady-state and time-resolved fluorescence results revealed that the photoluminescence was subjected to severe emission quenching when DPP-BT changes from its solution phase to its film form. Further femtosecond transient absorption studies clarified that rapid intermolecular electron transfer accounts for the considerable fluorescence quenching event. The structural characterization of DPP-BT nanobelts, based on GIXRD and SAED patterns, suggested that the composite may be self-assembled into a slipped face-to-face configuration in the film, providing compact interlayer D-A interactions. As a result, intermolecular electron transfer is promoted by the favorable donor-acceptor attractions between the adjacent molecules. Moreover, this packing configuration provides a moderate channel for charge transportation. The hole mobility, which was measured based on a single-belt field-effect transistor, was found to be around 0.07 cm(2) V(-1) s(-1). Our observation reveals the role of spatial orientation in photophysical processes and the consequential semiconductor performance, providing guidance for the development and self-assembly of new opto-electronic molecules.

Liu H; Jia H; Wang L; Wu Y; Zhan C; Fu H; Yao J

2012-11-01

263

Intermolecular electron transfer promoted by directional donor-acceptor attractions in self-assembled diketopyrrolopyrrole-thiophene films.  

Science.gov (United States)

The photophysics of a symmetric triad consisting of two bithiophene (BT) units covalently linked to a central diketopyrrolopyrrole unit (DPP) has been investigated both in dichloromethane and in the thin film. The DPP-BT film exhibits a red-shifted low-energy absorption band compared to its solution, which is indicative of efficient ?-? interactions in the solid-state phase. The steady-state and time-resolved fluorescence results revealed that the photoluminescence was subjected to severe emission quenching when DPP-BT changes from its solution phase to its film form. Further femtosecond transient absorption studies clarified that rapid intermolecular electron transfer accounts for the considerable fluorescence quenching event. The structural characterization of DPP-BT nanobelts, based on GIXRD and SAED patterns, suggested that the composite may be self-assembled into a slipped face-to-face configuration in the film, providing compact interlayer D-A interactions. As a result, intermolecular electron transfer is promoted by the favorable donor-acceptor attractions between the adjacent molecules. Moreover, this packing configuration provides a moderate channel for charge transportation. The hole mobility, which was measured based on a single-belt field-effect transistor, was found to be around 0.07 cm(2) V(-1) s(-1). Our observation reveals the role of spatial orientation in photophysical processes and the consequential semiconductor performance, providing guidance for the development and self-assembly of new opto-electronic molecules. PMID:22951990

Liu, Huiying; Jia, Hui; Wang, Lanfen; Wu, Yishi; Zhan, Chuanlang; Fu, Hongbing; Yao, Jiannian

2012-11-01

264

Selective Intermolecular Amination of C?H Bonds at Tertiary Carbon Centers.  

UK PubMed Central (United Kingdom)

C-H insertion: A method for intermolecular amination of tertiary C?H bonds is described that uses limiting amounts of substrate and a convenient phenol-derived nitrogen source. Structure-selectivity and mechanistic studies suggest that steric interaction between the substrate and active oxidant is the principal determinant of product selectivity.

Roizen JL; Zalatan DN; Du Bois J

2013-09-01

265

Intra- and intermolecular forces dependent main chain conformations of esters of ?,?-dehydroamino acids  

Science.gov (United States)

Crystalline state conformations of (Z)-?Abu and ?Val esters are reported for the first time.Differences in conformations of the ?Xaa esters and amides were found and explained.An influence of the ?Xaa side chain on conformation adopted was determined.An interplay of the intra- and intermolecular interactions on conformations is discussed.

Siod?ak, Dawid; Bujak, Maciej; Sta?, Monika

2013-09-01

266

An in vitro network of intermolecular interactions between viral RNA segments of an avian H5N2 influenza A virus: comparison with a human H3N2 virus.  

UK PubMed Central (United Kingdom)

The genome of influenza A viruses (IAV) is split into eight viral RNAs (vRNAs) that are encapsidated as viral ribonucleoproteins. The existence of a segment-specific packaging mechanism is well established, but the molecular basis of this mechanism remains to be deciphered. Selective packaging could be mediated by direct interaction between the vRNA packaging regions, but such interactions have never been demonstrated in virions. Recently, we showed that the eight vRNAs of a human H3N2 IAV form a single interaction network in vitro that involves regions of the vRNAs known to contain packaging signals in the case of H1N1 IAV strains. Here, we show that the eight vRNAs of an avian H5N2 IAV also form a single network of interactions in vitro, but, interestingly, the interactions and the regions of the vRNAs they involve differ from those described for the human H3N2 virus. We identified the vRNA sequences involved in five of these interactions at the nucleotide level, and in two cases, we validated the existence of the interaction using compensatory mutations in the interacting sequences. Electron tomography also revealed significant differences in the interactions taking place between viral ribonucleoproteins in H5N2 and H3N2 virions, despite their canonical '7 + 1' arrangement.

Gavazzi C; Isel C; Fournier E; Moules V; Cavalier A; Thomas D; Lina B; Marquet R

2013-01-01

267

[High-energy electron-positron interactions  

International Nuclear Information System (INIS)

The purpose of the research was the study of electron-positron interactions at high energies using the Time Projection Chamber (TPC) at the Positron Electron Project (PEP) at SLAC. The TPC detector had an initial data gathering from 1982 until 1986 and accumulated a data sample with an integrated luminosity of -150 pb-1 at an electron-positron energy of 29 GeV. The data runs in the 1988--1990 time period (yielding ? pb-1) were abbreviated, due to the need of the laboratory to give highest priority to the new Stanford Linear Collider (SLC). The TPC collaboration decided in 1991 to discontinue data taking, but has continued the collaboration for the purpose of completing the analysis of the data. When UMass joined the SLD project, it was being designed as a new state-of-the-art detector for studying electron-positron interactions at energies in the vicinity of 91 GeV, the Z0 mass. The detector was completed and installed at the interaction point of the SLC in 1991, at which time an initial, ''engineering run'' allowed the debugging of detector components and provided a data sample of ?1,000 events with hadronic Z0 decays. In 1992 the SLC provided beams of polarized electrons and the SLD collected a data sample in excess of 11,000 hadronic Z0 events produced by polarized electrons, allowing unique measurements of some of the parameters of the standard model. This project is continuing to take data in 1993 with increased polarization and higher luminosity. This report reviews the research work performed under the contract, and survey's the physics results

1993-01-01

268

Investigate the interaction between dark matter and dark energy  

CERN Document Server

In this paper we investigate the interaction between dark matter and dark energy by considering two different interacting scenarios, i.e. the cases of constant interaction function and variable interaction function. By fitting the current observational data to constrain the interacting models, it is found that the interacting strength is non-vanishing, but weak for the case of constant interaction function, and the interaction is not obvious for the case of variable interaction function. In addition, for seeing the influence from interaction we also investigate the evolutions of interaction function, effective state parameter for dark energy and energy density of dark matter. At last some geometrical quantities in the interacting scenarios are discussed.

Lu, Jianbo; Jin, Yongyi; Wang, Yan

2012-01-01

269

Six-dimensional vibrational analysis of coupled intermolecular vibrations in a binary cluster  

International Nuclear Information System (INIS)

We report on full- (six-) dimensional calculations of the intermolecular vibrations of a binary aromatic-solvent cluster. An exact Hamiltonian for this kind of interaction is modified in a general manner in order to perform calculations of molecules without symmetry. The binary cluster phenol(H2O)1 is used as a test case since its intermolecular vibrations are anharmonic and highly coupled. The formulation of the Schroedinger equation leads to a complex-valued eigenvalue problem with a dimension larger than two million, which is solved by filter diagonalization to obtain both eigenvalues and eigenvectors. With the knowledge of the eigenvectors, an interpretation of all eigenvalues is possible by a characterization with pseudoquantum numbers that are related to the widely used nomenclature of intermolecular normal motions in aromatic(solvent) clusters.

2004-07-15

270

ENERGY DERIVATIVES FOR CONFIGURATION INTERACTION WAVEFUNCTIONS  

Energy Technology Data Exchange (ETDEWEB)

Equations providing the first and second derivatives of a configuration interaction (CI) energy with respect to an external parameter are provided. We assume no restriction on the form of the CI expansion built from molecular orbitals obtained in a multiconfiguration Hartree-Fock (MCHF) calculation. Also the coupled perturbed multi-configuration Hartree-Fock formalism is presented for a general MCHF wavefunction and provides the first order and second order changes of the molecular orbital expansion coefficients with respect to an external parameter.

Dupuis, M.

1980-09-01

271

Correlations in high-energy interactions  

International Nuclear Information System (INIS)

The short-range correlations in rapidity whose existence has been firmly established in high-energy interactions are used to explain chaotic multiplicity behavior in proton-nucleon collisions at 800 GeV. In order to determine the values of higher-order moments from the second-order moment, we have used the pure birth approximation which is in agreement with the ''linked pair'' approximation of Carruthers. The calculated values of the normalized factorial moments for a given bin size show a good agreement with our data.

1994-01-01

272

Correlations in high-energy interactions  

Science.gov (United States)

The short-range correlations in rapidity whose existence has been firmly established in high-energy interactions are used to explain chaotic multiplicity behavior in proton-nucleon collisions at 800 GeV. In order to determine the values of higher-order moments from the second-order moment, we have used the pure birth approximation which is in agreement with the ``linked pair'' approximation of Carruthers. The calculated values of the normalized factorial moments for a given bin size show a good agreement with our data.

Parashar, Neeti; Bhasin, V. S.; Panchapakesan, N.; Shivpuri, R. K.; Soni, S. K.

1994-09-01

273

Correlations in high-energy interactions  

Energy Technology Data Exchange (ETDEWEB)

The short-range correlations in rapidity whose existence has been firmly established in high-energy interactions are used to explain chaotic multiplicity behavior in proton-nucleon collisions at 800 GeV. In order to determine the values of higher-order moments from the second-order moment, we have used the pure birth approximation which is in agreement with the linked pair'' approximation of Carruthers. The calculated values of the normalized factorial moments for a given bin size show a good agreement with our data.

Parashar, N.; Bhasin, V.S.; Panchapakesan, N.; Shivpuri, R.K. (Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India)); Soni, S.K. (Department of Physics, S.G.T.B. Khalsa College, University of Delhi, Delhi 110007 (India))

1994-09-01

274

Hydrogen-antihydrogen interactions at low energies  

International Nuclear Information System (INIS)

The main cause of loss of trapped AH is due to collisions with H2 and He. As a first step towards treating these reactions we are studying the interaction of AH with H. We have carried out variational calculations to determine an upper bound to the smallest internuclear distance at which the light particles are still bound to the nuclei. We are currently in the process of taking into account the motion of the nuclei. This will enable us to calculate cross-sections for low energy H-AH scattering.

1999-01-01

275

Hydrogen-antihydrogen interactions at low energies  

Energy Technology Data Exchange (ETDEWEB)

The main cause of loss of trapped AH is due to collisions with H{sub 2} and He. As a first step towards treating these reactions we are studying the interaction of AH with H. We have carried out variational calculations to determine an upper bound to the smallest internuclear distance at which the light particles are still bound to the nuclei. We are currently in the process of taking into account the motion of the nuclei. This will enable us to calculate cross-sections for low energy H-AH scattering.

Armour, E.A.G.; Carr, J.M.; Zeman, V. [University of Nottingham, School of Mathematical Sciences (United Kingdom)

1999-06-15

276

Interaction between Dark Energy and Dark Matter Crosses Non-interacting Line  

CERN Multimedia

It is found by Cai and Su that the interaction between dark energy and cold dark matter is likely to cross the non-interacting line. Motivated by this, we suggest a form of interaction between dark energy and dark matter, which changes from negative to positive as our universe changing from deceleration to acceleration. It is found that the interaction is favored by the second law of thermodynamics. Furthermore, we apple the interaction to the interacting holographic dark energy model. We find that the interacting model works well.

Sun, Cheng-Yi

2012-01-01

277

Evaluation of intermolecular forces in a circulating system.  

Science.gov (United States)

Intercellular interactions, which are mediated by a variety of complex intercellular molecules through the processes of formation and dissociation of molecular bonds, play a critical role in regulating cellular functions in biological systems. Various approaches are applied to evaluate intercellular or molecular bonding forces. To quantify the intermolecular interaction forces, flow chamber has become a meaningful technique as it can ultimately mimic the cellular microenvironment in vivo under physiological flow conditions. Hydrodynamic forces are usually used to predict the intercellular forces down to the single molecular level. However, results show that only using hydrodynamic force will overestimate up to 30% of the receptor-ligand strength when the non-specific forces such as Derjaguin-Landau-Verway-Overbeek (DLVO) forces become un-neglected. Due to the nature of high ion concentration in the physiological condition, electrostatic force is largely screened which will cause DLVO force unbalanced. In this study, we propose to take account of the DLVO force, including van der Waals (VDW) force and electrostatic force, to predict the intermolecular forces of a cell doublet and cell-substrate model in a circulating system. Results also show that the DLVO force has a nonlinear effect as the cell-cell or cell-substrate distance changes. In addition, we used the framework of high accuracy hydrodynamic theories proved in colloidal systems. It is concluded that DLVO force could not be ignored in quantitative studies of molecular interaction forces in circulating system. More accurate prediction of intercellular forces needs to take account of both hydrodynamic force and DLVO force. PMID:21843592

Guo, Qiuquan; Liu, Mei; Yang, Jun

2011-08-05

278

Evaluation of intermolecular forces in a circulating system.  

UK PubMed Central (United Kingdom)

Intercellular interactions, which are mediated by a variety of complex intercellular molecules through the processes of formation and dissociation of molecular bonds, play a critical role in regulating cellular functions in biological systems. Various approaches are applied to evaluate intercellular or molecular bonding forces. To quantify the intermolecular interaction forces, flow chamber has become a meaningful technique as it can ultimately mimic the cellular microenvironment in vivo under physiological flow conditions. Hydrodynamic forces are usually used to predict the intercellular forces down to the single molecular level. However, results show that only using hydrodynamic force will overestimate up to 30% of the receptor-ligand strength when the non-specific forces such as Derjaguin-Landau-Verway-Overbeek (DLVO) forces become un-neglected. Due to the nature of high ion concentration in the physiological condition, electrostatic force is largely screened which will cause DLVO force unbalanced. In this study, we propose to take account of the DLVO force, including van der Waals (VDW) force and electrostatic force, to predict the intermolecular forces of a cell doublet and cell-substrate model in a circulating system. Results also show that the DLVO force has a nonlinear effect as the cell-cell or cell-substrate distance changes. In addition, we used the framework of high accuracy hydrodynamic theories proved in colloidal systems. It is concluded that DLVO force could not be ignored in quantitative studies of molecular interaction forces in circulating system. More accurate prediction of intercellular forces needs to take account of both hydrodynamic force and DLVO force.

Guo Q; Liu M; Yang J

2011-11-01

279

Calculation of the absolute thermodynamic properties of association of host-guest systems from the intermolecular potential of mean force.  

UK PubMed Central (United Kingdom)

The authors report calculations of the intermolecular potential of mean force (PMF) in the case of the host-guest interaction. The host-guest system is defined by a water soluble calixarene and a cation. With an organic cation such as the tetramethylammonium cation, the calixarene forms an insertion complex, whereas with the Lanthane cation, the supramolecular assembly is an outer-sphere complex. The authors apply a modified free energy perturbation method and the force constraint technique to establish the PMF profiles as a function of the separation distance between the host and guest. They use the PMF profile for the calculation of the absolute thermodynamic properties of association that they compare to the experimental values previously determined. They finish by giving some structural features of the insertion and outer-sphere complexes at the Gibbs free energy minimum.

Ghoufi A; Malfreyt P

2006-12-01

280

A simple and reliable approach to docking protein-protein complexes from very sparse NOE-derived intermolecular distance restraints  

International Nuclear Information System (INIS)

[en] A simple and reliable approach for docking protein-protein complexes from very sparse NOE-derived intermolecular distance restraints (as few as three from a single point) in combination with a novel representation for an attractive potential between mapped interaction surfaces is described. Unambiguous assignments of very sparse intermolecular NOEs are obtained using a reverse labeling strategy in which one the components is fully deuterated with the exception of selective protonation of the ?-methyl groups of isoleucine, while the other component is uniformly 13C-labeled. This labeling strategy can be readily extended to selective protonation of Ala, Leu, Val or Met. The attractive potential is described by a 'reduced' radius of gyration potential applied specifically to a subset of interfacial residues (those with an accessible surface area ? 50% in the free proteins) that have been delineated by chemical shift perturbation. Docking is achieved by rigid body minimization on the basis of a target function comprising the sparse NOE distance restraints, a van der Waals repulsion potential and the 'reduced' radius of gyration potential. The method is demonstrated for two protein-protein complexes (EIN-HPr and IIAGlc-HPr) from the bacterial phosphotransferase system. In both cases, starting from 100 different random orientations of the X-ray structures of the free proteins, 100% convergence is achieved to a single cluster (with near identical atomic positions) with an overall backbone accuracy of ?2 A. The approach described is not limited to NMR, since interfaces can also be mapped by alanine scanning mutagenesis, and sparse intermolecular distance restraints can be derived from double cycle mutagenesis, cross-linking combined with mass spectrometry, or fluorescence energy transfer

2006-01-01

 
 
 
 
281

A new intermolecular mechanism to selectively drive photoinduced damages  

CERN Multimedia

Low-energy electrons (LEEs) are known to be effective in causing strand breaks in DNA. Recent experiments show that an important direct source of LEEs is the intermolecular Coulombic decay (ICD) process. Here we propose a new cascade mechanism initiated by core excitation and terminated by ICD and demonstrate its properties. Explicit calculations show that the energies of the emitted ICD-electrons can be controlled by selecting the initial atomic excitation. The properties of the cascade may have interesting applications in the fields of electron spectroscopy and radiation damage. Initiating such a cascade by resonant X-ray absorption from a high-Z element embedded in a cancerous cell nucleus, ICD will deliver genotoxic particles \\textit{locally} at the absorption site, increasing in that way the controllability of the induced damage.

Gokhberg, Kirill; Kuleff, Alexander I; Cederbaum, Lorenz S

2013-01-01

282

Coupled effects of substrate adhesion and intermolecular forces on polymer thin film glass-transition behavior.  

UK PubMed Central (United Kingdom)

Intermolecular noncovalent forces between polymer chains influence the mobility and glass-transition temperature (Tg), where weaker interchain interactions, all else being the same, typically results in lower bulk polymer Tg. Using molecular dynamics simulations, here we show that this relation can become invalid for supported ultrathin films when the substrate-polymer interaction is extremely strong and the polymer-polymer interactions are much weaker. This contrasting trend is found to be due to a more pronounced substrate-induced appreciation of the film Tg for polymers with weaker intermolecular interactions and low bulk Tg. We show that optimizing this coupling between substrate adhesion and bulk Tg maximizes thin film Tg, paving the way for tuning film properties through interface nanoengineering.

Xia W; Keten S

2013-10-01

283

Probing intermolecular couplings in liquid water with two-dimensional infrared photon echo spectroscopy.  

Science.gov (United States)

Two-dimensional infrared photon echo and pump probe studies of the OH stretch vibration provide a sensitive probe of the correlations and couplings in the hydrogen bond network of liquid water. The nonlinear response is simulated using numerical integration of the Schrodinger equation with a Hamiltonian constructed to explicitly treat intermolecular coupling and nonadiabatic effects in the highly disordered singly and doubly excited vibrational exciton manifolds. The simulated two-dimensional spectra are in close agreement with our recent experimental results. The high sensitivity of the OH stretch vibration to the bath dynamics is found to arise from intramolecular mixing between states in the two-dimensional anharmonic OH stretch potential. Surprisingly small intermolecular couplings reproduce the experimentally observed intermolecular energy transfer times. PMID:18500848

Paarmann, A; Hayashi, T; Mukamel, S; Miller, R J D

2008-05-21

284

Low-energy electron interactions with biomolecules  

Science.gov (United States)

Low-energy electron interactions with biomolecules have been the focus of sustained attention over the past decade. The demonstration by Sanche and coworkers that even subexcitation and subionization electrons can induce strand breaks in DNA opened a new frontier in understanding radiation damage to living systems. Many studies of DNA subunits and their analogues, both experimental and theoretical, have elucidated likely mechanisms by which slow electrons attach to and disrupt DNA, although the full picture is far from clear and some elements of it remain controversial. Increasing attention is also being given to low-energy electron collisions with amino acids in order to explore possible mechanisms of electron-mediated radiation damage to proteins. In a completely different context, electron-biomolecule collisions are fundamental to spark ignition and cumbustion of biofuels such as methanol and ethanol. Not to be overlooked, either, is the simplest but most ubiquitous biomolecule of all, water, whose low-energy electron cross sections remain surprisingly ill-characterized. This talk will survery recent ab initio computational studies using the Schwinger multichannel method of DNA- and protein-related molecules, alcohols, and water. Much of the work to be presented was carried out in collaboration with experimentalists who undertook complementary measurements, allowing for useful comparisons to be made. Although the primary focus will be on electronically elastic collisions relevant to dissociative attachment and electron transport, electron-impact excitation cross sections for water will be presented and discussed.

Winstead, Carl

2012-06-01

285

Allowance for intermolecular forces of attraction in the derivation of kinetic equations  

International Nuclear Information System (INIS)

This paper proposes a method for solving the Bogolyubov hierarchy for dense gases with real interaction potentials. The idea of the method is to decouple each equation of the hierarchy with respect to scales that characterize the strength of the intermolecular repulsion and attraction. Kinetic equations for moderately dense and dense gases are derived and some model equations of the kinetic theory of dense gases with real interaction potentials are constructed

1986-01-01

286

Allowance for intermolecular forces of attraction in the derivation of kinetic equations  

Energy Technology Data Exchange (ETDEWEB)

This paper proposes a method for solving the Bogolyubov hierarchy for dense gases with real interaction potentials. The idea of the method is to decouple each equation of the hierarchy with respect to scales that characterize the strength of the intermolecular repulsion and attraction. Kinetic equations for moderately dense and dense gases are derived and some model equations of the kinetic theory of dense gases with real interaction potentials are constructed.

Rudyak, V.Y.; Yanenko, N.N.

1986-02-01

287

Long-range intermolecular dispersion forces and circular dichroism spectra from first-principles calculations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This work presents first-principles calculations of long-range intermolecular dispersion energies between two atoms or molecules and of electronic circular dichroism spectra of chiral molecules. The former is expressed in terms of the C6 dipole-dipole dispersion coefficients ??, and the latter is gi...

Jiemchooroj, Auayporn

288

First-principles calculations of long-range intermolecular dispersion forces  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This work presents first-principles calculations of long-range intermolecular dispersion energies between two atoms or molecules as expressed in terms of the C6 dipole-dipole dispersion coefficients. In a series of publications, it has been shown by us that the complex linear polarization propagator...

Jiemchooroj, Auayporn

289

High energy photon-neutrino interactions  

Energy Technology Data Exchange (ETDEWEB)

A general decomposition of the amplitudes for the 2 {r_arrow} 2 processes {gamma}{nu} {r_arrow} {gamma}{nu} and {gamma}{gamma} {r_arrow} {nu}{bar {nu}} is obtained using gauge invariance and Bose symmetry. The restrictions implied by this decomposition are investigated for the reaction {gamma}{gamma} {r_arrow} {nu}{bar {nu}} by computing the one-loop helicity amplitudes in the standard model. In the center of mass, where {radical}s = 2{omega}, the cross section grows roughly as {omega}{sup 6} up to the threshold for W-boson production, {radical}s = 2m{sub W}. Astrophysical implications of very high energy photon-neutrino interactions are discussed.

Abbasabadi, A. [Ferris State Univ., Big Rapids, MI (United States); Devoto, A. [Univ. di Cagliari (France). Dipt. di Fisica]|[I.N.F.N., Cagliari (France). Sezione di Cagliari; Dicus, D.A. [Univ. of Texas, Austin, TX (United States); Repko, W.W. [Michigan State Univ., East Lansing, MI (United States). Dept. of Physics and Astronomy

1998-07-14

290

Effect of intermolecular hydrogen bonding on the micro-mechanical properties of high performance organic fibers  

Science.gov (United States)

Since their introduction in the early 1970s, high performance organic fibers have gained an increasingly significant role in a wide range of weight-sensitive applications. However, the use of organic fibers in structural applications has been restricted by their performance under compression. Organic fibers have a fibrillar structure in which the lack of strong lateral support between fibrils results in failure at low compressive loads. Despite the relevance of lateral interactions on organic fiber mechanical properties, there is not a reliable method to measure and quantify the effect of hydrogen bonding on fiber compressive properties. The mechanisms by which intermolecular hydrogen bonding affects fiber compressive properties have been elucidated by analyzing the state of hydrogen bonding in M5, a poly-pyridobisimidazole experimental fiber developed by Akzo Nobel. An experimental methodology based on FTIR microspectroscopy has been developed in order to detect and quantify the state of hydrogen bonding in M5 fibers with varying degrees of heat treatment. The methodology has shown that in the as-spun material, 72% of the N-H vibration groups are hydrogen-bonded to water, while in the fully heat-treated fiber more than 90% of the N-H vibration groups develop intermolecular hydrogen bonds. Saturation of previously annealed M5 fiber has been shown to result in a reduction of the measured degree of intermolecular hydrogen bonding from 93 to 64%, providing the first direct evidence of partial reversibility of hydrogen bonding in high performance organic fibers. The compressive properties of five high performance organic fibers with varying degrees of lateral molecular interactions have been analyzed. A novel micro-mechanical technique applies an axial compressive load on a segment of free fiber in order to quantify the axial compressive modulus of single filaments. The resulting ratios of axial compressive to tensile modulus show values ranging between 0.3--1.0, depending on the type and degree of intermolecular interactions present in the fiber. The assumption of equal tensile and compressive modulus necessary to determine single fiber axial compressive strength from the elastica loop test has been relaxed by deriving a compressive strength equation based on the analysis of the flexural response of a fiber with different modulus in tension and compression. Using the FTIR methodology to quantify the degree of intermolecular hydrogen bonding in M5 fiber as a function of annealing conditions, and the micro-mechanical techniques suitable for the evaluation of the effect of intermolecular interactions on fiber compressive properties, a direct relationship between the degree of intermolecular hydrogen bonding in the fiber and the measured compressive strength values is established.

Leal Ayala, Angel Andres

291

Intermolecular iodine-iodine interactions in bis(pyridine-3-carboxylato)[tetrakis(4-iodophenyl)porphyrinato]tin(IV) and bis(pyrimidine-5-carboxylato)[tetrakis(4-iodophenyl)porphyrinato]tin(IV).  

UK PubMed Central (United Kingdom)

Crystals of bis(pyridine-3-carboxylato)[tetrakis(4-iodophenyl)porphyrinato]tin(IV) dimethylformamide sesquisolvate, [Sn(C44H24I4N4)(C6H4NO2)2]·1.5C3H7NO, (I), and bis(pyrimidine-5-carboxylato)[tetrakis(4-iodophenyl)porphyrinato]tin(IV) dimethylformamide sesquisolvate, [Sn(C44H24I4N4)(C5H3N2O2)2]·1.5C3H7NO, (II), exhibit interporphyrin iodine-iodine halogen bonds, which direct the supramolecular assembly of the porphyrin entities into halogen-bonded layers. Each molecule interacts with its four nearest neighbours within the layer via eight I...I interactions at approximately 3.8 and 4.0?Å. The two structures are isomorphous and isometric, with the metalloporphyrin complexes located on centres of crystallographic inversion.

Titi HM; Patra R; Goldberg I

2013-09-01

292

Intermolecular iodine-iodine interactions in bis(pyridine-3-carboxylato)[tetrakis(4-iodophenyl)porphyrinato]tin(IV) and bis(pyrimidine-5-carboxylato)[tetrakis(4-iodophenyl)porphyrinato]tin(IV).  

Science.gov (United States)

Crystals of bis(pyridine-3-carboxylato)[tetrakis(4-iodophenyl)porphyrinato]tin(IV) dimethylformamide sesquisolvate, [Sn(C44H24I4N4)(C6H4NO2)2]·1.5C3H7NO, (I), and bis(pyrimidine-5-carboxylato)[tetrakis(4-iodophenyl)porphyrinato]tin(IV) dimethylformamide sesquisolvate, [Sn(C44H24I4N4)(C5H3N2O2)2]·1.5C3H7NO, (II), exhibit interporphyrin iodine-iodine halogen bonds, which direct the supramolecular assembly of the porphyrin entities into halogen-bonded layers. Each molecule interacts with its four nearest neighbours within the layer via eight I...I interactions at approximately 3.8 and 4.0?Å. The two structures are isomorphous and isometric, with the metalloporphyrin complexes located on centres of crystallographic inversion. PMID:24005511

Titi, Hatem M; Patra, Ranjan; Goldberg, Israel

2013-08-03

293

Intermolecular potential for methane in zeolite A and Y: adsorption isotherm and related properties  

Energy Technology Data Exchange (ETDEWEB)

Based on energies derived from ab initio calculations on methane in zeolite A and Y a more accurate intermolecular potential is proposed for hydrocarbon-zeolite interaction. We then employ the proposed potential POTJI (consisting of sets ABCHA and ABCHY) as well as another potential (termed KDMG) based on the work of Kiselev and Du and Murad and Gubbins in grand canonical Monte Carlo simulations to obtain adsorption isotherms and molecular dynamics simulations to obtain self-diffusion coefficients. For methane in zeolite A we show that the derived potential predicts accurately adsorption isotherm, heats of sorption and diffusion coefficients. For methane in zeolite Y a somewhat less accurate reproduction of adsorption isotherm is obtained. In general, these potentials predict values that are closer to experimentally obtained values than existing potential. Radial distribution function is more structured than for existing KDMG potential. Translational diffusion coefficients are generally lower than KDMG potential while the rotational diffusion coefficients are actually higher than seen for KDMG potential. Further, it is seen that the set of potential parameters derived for zeolites A and Y are similar suggesting that it might be possible to derive one unified set of parameters that would perform reasonably across a large set of zeolite structures. Similar transferability of potentials across the range of hydrocarbons may also be possible. Finally, these results suggest that it may be possible to derive accurate classical potentials for interaction between organic and inorganic systems based on ab initio calculations. (authors)

Ghorai, Kr.; Yashonath, S. [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore (India); Sluiter, M.; Kawazoe, Y. [Tohoku Univ., Institute of Material Research, Sendai (Japan)

2006-07-01

294

Long-range interaction of small soot particles. [Brief summary  

Energy Technology Data Exchange (ETDEWEB)

The origins of van der Waals or intermolecular forces between condensed media are discussed. Methods for the calculation of energies and collision rate enhancements are reviewed briefly. It is pointed out that the subject of long-range interactions of small soot particles is in its beginning stage.

Marlow, W.H.

1982-01-01

295

The Growth of Structure in Interacting Dark Energy Models  

CERN Document Server

If dark energy interacts with dark matter, there is a change in the background evolution of the universe, since the dark matter density no longer evolves as a^{-3}. In addition, the non-gravitational interaction affects the growth of structure. In principle, these changes allow us to detect and constrain an interaction in the dark sector. Here we investigate the growth factor and the weak lensing signal for a class of interacting dark energy models. In these models, the interaction is determined by a linear combination of the dark sector densities, with constant energy transfer rates. Assuming a normalization to today's values of dark matter density and overdensity, the signal of the interaction is an enhancement (suppression) of both the growth factor and the lensing power, when the energy transfer in the background is from dark matter to dark energy (dark energy to dark matter).

Caldera-Cabral, Gabriela; Schaefer, Bjoern Malte

2009-01-01

296

IMPROPER HYDROGEN BONDS - A THEORETICAL STUDY ABOUT THE MOLECULAR STRUCTURE OF INTERMOLECULAR SYSTEMS FORMED BY H3C-H+?...X AND H3C+?...H-Y WITH X = CL- OR F- AND Y = CL OR F  

Directory of Open Access Journals (Sweden)

Full Text Available In this work is presented a theoretical study of the molecular properties of the H3C-H...X and H3C+?...H-Y intermolecular systems with X = CL- or F- and Y = Cl or F. In the H3C-H...X complex, it is formed a traditional hydrogen bond between the CL- or F- anions and the hydrogen atom of the methyl. About the H3C+?...H-Y complex, it was observed an improper hydrogen bond because the carbon atom of the methyl cation function as a proton acceptor. In this insight, the capacity of methane to interact with halogen anions (CL- or F-) and molecular acids (HCl or HF) was examined at the B3LYP/6-311++G(3df,3dp) level of calculation. Moreover, the interaction strengths of the H3C-H...X and H3C+?...H-Y complexes was evaluated by computing their intermolecular distances and binding energies. Finally, QTAIM calculations also were executed with the purpose to examine the intermolecular interactions through the quantification of their electronic densities (p) as well as by the interpretation of the Laplacian operators ().

B.G OLIVEIRA

2009-01-01

297

Theoretical study of intermolecular energy transfer involving electronically excited molecules: He(/sup 1/S) + H/sub 2/(B /sup 1/. sigma. /sub u//sup +/). [Solution for coupled channel equations  

Energy Technology Data Exchange (ETDEWEB)

To further understanding of gas phase collision dynamics involving electronically-excited molecules, a fully quantum mechanical study of He + H/sub 2/(B /sup 1/..sigma../sub u//sup +/) was undertaken. Iterative natural orbital configuration interaction (CI) calculations were performed to obtain the interaction potential between He and H/sub 2/(B /sup 1/..sigma../sub u//sup +/). The potential energy surface (PES) is highly anisotropic and has a van der Waals well of about 0.03 eV for C/sub 2v/ approach. Avoided PES crossings occur with He + H/sub 2/(E,F /sup 1/..sigma../sub g//sup +/) and with He + H/sub 2/(X /sup 1/..sigma../sub g//sup +/) and cause a local maximum and a deep minimum in the He + H/sub 2/(B /sup 1/..sigma../sub u//sup +/) PES, respectively. The crossing with He + H/sub 2/(X /sup 1/..sigma../sub g//sup +/) provides a mechanism for fluorescence quenching. The computed CI energies were combined with previous multi-reference double excitation CI calculations and fit with analytic functions for convenience in scattering calculations. Accurate dipole polarizabilities and quadrupole moment of H/sub 2/(B /sup 1/..sigma../sub u//sup +/) were computed for use in the multipole expansion, which is the analytic form of the long-range PES. 129 refs., 28 figs., 35 tabs.

Grimes, R.M.

1986-11-01

298

A reliable semi-empirical approach for evaluating the isotropic intermolecular forces between closed shell systems  

International Nuclear Information System (INIS)

A relatively simple tractable scheme for the evaluation of the isotropic intermolecular potential between two closed-shell systems, which contains one adjustable parameter, is proposed and tested using He-He, Ne-Ne, Ar-Ar, Kr-Kr, and H2-H2 interactions as models. The approach is based on expressing the potential as a sum of exchange (Esub(x)) and coulomb (Esub(c)) contributions. A semi-empirical approximation, which is a simple function of the first order coulomb energy (Esub(c)sup((1))), is used to represent Esub(x). The representation for Esub(c) is based on Esub(c)sup((1)) and a suitably universally damped asymptotic expansion of the second-order coulomb energy through O(R-10). The adjustable parameter formally occurs in the representation for Esub(x) and influences the balance between Esub(x) and Esub(c) in the representation of the potential. The results obtained for the model systems are in excellent agreement with reliable literature potentials, many of which contain several adjustable parameters, and suggest that the scheme proposed here is capable of yielding reliable potentials for 0.3 approximately

1979-01-01

299

An empirical multi-parameter anisotropic intermolecular potential, collision-induced absorption and predicted collision-induced light scattering spectra for CF4-He  

International Nuclear Information System (INIS)

Graphical abstract: The calculated thermophysical and transport properties using an anisotropic intermolecular potential of CF4-He have been presented. With this potential, the collision induced absorption and scattering spectra have been calculated. Highlights: ? We have determined an approximate anisotropic intermolecular potential for CF4-He. ? The thermophysical and transport properties are calculated for this system. ? We have adopted a model for the induced dipole moment ?(r) with adjustable parameters. ? The lineshapes of absorption using these models of potential and moment are calculated. ? With a suitable model of the induced anisotropy, the lineshape of scattering is computed. - Abstract: An approximate anisotropic intermolecular potential for the interaction of CF4 with He is developed by simultaneously fitting the Exponential Morse-Morse-Morse-Spline-van der Waals (EM3SV) potential form to high energy beam results, interaction pressure virial coefficients, diffusion coefficients, mixture viscosity and thermal conductivity. The collision-induced absorption spectrum of this system at 213 K has been calculated using the empirical models of the induced dipole moment and the interaction potential. Theoretical zeroth, first and second moments of this spectrum using various models for the induced dipole moment and interatomic potential are compared to the experimental values. Also, with this potential and with a suitable model for the anisotropy, the lineshape calculations have been used to predict a reasonable experimental spectrum of the induced light scattering. The results show that these models of the potential, the induced dipole moment and the induced anisotropy are the most accurate models reported to date for this mixture.

1221-01-00

300

An Intermolecular Vibration Model for Lattice Ice  

Directory of Open Access Journals (Sweden)

Full Text Available Lattice ice with tetrahedral arrangement is studied using a modified Einstein’s model that incorporates the hindered translational and rotational vibration bands into a harmonic oscillation system. The fundamental frequencies for hindered translational and rotational vibrations are assigned based on the intermolecular vibration bands as well as thermodynamic properties from existing experimental data. Analytical forms for thermodynamic properties are available for the modified model, with three hindered translational bands at (65, 229, 229) cm-1 and three effective hindered rotational bands at 560 cm-1. The derived results are good for temperatures higher than 30 K. To improve the model below 30 K, Lorentzian broadening correction is added. This simple model helps unveil the physical picture of ice lattice vibration behavior.

Kuo-Ting Wang; Quinn M. Brewster

2010-01-01

 
 
 
 
301

An Intermolecular Vibration Model for Lattice Ice  

Directory of Open Access Journals (Sweden)

Full Text Available Lattice ice with tetrahedral arrangement is studied using a modified Einstein’s model that incorporates the hinderedtranslational and rotational vibration bands into a harmonic oscillation system. The fundamental frequencies forhindered translational and rotational vibrations are assigned based on the intermolecular vibration bands as well asthermodynamic properties from existing experimental data. Analytical forms for thermodynamic properties areavailable for the modified model, with three hindered translational bands at (65, 229, 229) cm-1 and three effectivehindered rotational bands at 560 cm-1. The derived results are good for temperatures higher than 30 K. To improvethe model below 30 K, Lorentzian broadening correction is added. This simple model helps unveil the physicalpicture of ice lattice vibration behavior.

Kuo-Ting Wang; M. Quinn Brewster

2010-01-01

302

Virtual photon interactions in high energy QCD  

Energy Technology Data Exchange (ETDEWEB)

We study the interactions of virtual photons in the high energy limit of quantum chromodynamics (QCD). The subject is discussed in terms of two closely linked applications: the calculation of the total cross section for {gamma}{sup *}{gamma}{sup *}-scattering and the description of DIS in the colour dipole model. We calculate virtual corrections in {alpha}{sub s} to the process {gamma}{sup *} q {yields} (qq)q and the tree level process {gamma}{sup *} q {yields} (qqg)q in the high energy limit. From this calculation we obtain one-loop corrections to the effective {gamma}{sup *}-reggeon-qq-vertex in the helicity basis of the virtual photon and the qq-pair. The loop integrals for the virtual corrections have been performed and expressed in dimensional regularization in terms of logarithms and dilogarithms. We have convoluted the virtual one-loop matrix elements with tree level matrix elements and expressed the integrals over the phase space of the qq-pair explicitly in terms of a set of standard integrals. The real corrections have been calculated and, in case of the longitudinal polarization, expressed in factorized form. From these calculations, the impact factor of virtual photons will be determined, allowing for a first prediction of the total cross section for {gamma}{sup *}{gamma}{sup *}-scattering in the next-to-leading-log s approximation. The calculations in this thesis extend the photon wave function picture in the colour dipole model to next-to-leading order. For this purpose, the real corrections with a qqg final state are analyzed in transverse configuration space and interpreted as a first higher Fock component of the photon wave function. In addition, the matrix elements that have been calculated in this thesis are needed for the calculation of jet cross sections. (orig.)

Gieseke, S.

2001-07-01

303

Energy Conscious Interactive Communication for Sensor Networks  

CERN Document Server

In this work, we are concerned with maximizing the lifetime of a cluster of sensors engaged in single-hop communication with a base-station. In a data-gathering network, the spatio-temporal correlation in sensor data induces data-redundancy. Also, the interaction between two communicating parties is well-known to reduce the communication complexity. This paper proposes a formalism that exploits these two opportunities to reduce the number of bits transmitted by a sensor node in a cluster, hence enhancing its lifetime. We argue that our approach has several inherent advantages in scenarios where the sensor nodes are acutely energy and computing-power constrained, but the base-station is not so. This provides us an opportunity to develop communication protocols, where most of the computing and communication is done by the base-station. The proposed framework casts the sensor nodes and base-station communication problem as the problem of multiple informants with correlated information communicating with a recipi...

Agnihotri, Samar

2007-01-01

304

Interaction of hypertritons with nuclei at high energies  

Energy Technology Data Exchange (ETDEWEB)

Calculations of the integral cross sections of the Coulomb and diffraction interactions of hypertritons are performed. The possibilities to determine the hypertriton binding energy with a higher precision, to refine information on the {Lambda}d interaction and other details of the hypertriton structure and interaction by means of the suggested measurements are also shown. (orig.). 17 refs.

Evlanov, M.V.; Sokolov, A.M.; Tartakovsky, V.K. [Institute for Nucl. Res., Kiev (Ukraine); Khorozov, S.A.; Lukstins, J. [Joint Institute for Nuclear Research, Dubna, Moscow Region, 141980 (Russian Federation)

1998-03-30

305

Dark Mass Creation During EWPT Via Dark Energy Interaction  

CERN Multimedia

We add Dark Matter Dark Energy terms with a quintessence field interacting with a Dark Matter field to a MSSM EW Lagrangian previously used to calculate the magnetic field created during the EWPT. From the expectation value of the quintessence field we estimate the Dark Matter mass for parameters used in previous work on Dark Matter-Dark Energy interactions.

Kisslinger, Leonard S

2013-01-01

306

Very High Energy Cosmic Rays and Their Interactions  

CERN Multimedia

The investigation of high energy cosmic rays and their interactions is a very active field of research. This article summarizes the progress made during the last years as reflected by the contributions to the XIII International Symposium on Very High Energy Cosmic Ray Interactions held in Pylos, Greece.

Engel, R

2005-01-01

307

Interaction between DBI-essence and other Dark Energies  

CERN Document Server

The present work considers interaction between DBI-essence and other candidates of dark energies like modified Chaplygin gas, hessence, tachyonic field, and new agegraphic dark energy. The potentials of the fields have been reconstructed under interaction and their evolutions have been viewed against cosmic time $t$ and scalar field $\\phi$. Equation of state parameters have also been obtained. The nature of potentials and the equation of state parameters of the dark energies have been found graphically in presence of interaction (both small and large interaction).

Chattopadhyay, Surajit

2010-01-01

308

Breaking parameter degeneracy in interacting dark energy models from observations  

CERN Document Server

We study the interacting dark energy model with time varying dark energy equation of state. We examine the stability in the perturbation formalism and the degeneracy among the coupling between dark sectors, the time-dependent dark energy equation of state and dark matter abundance in the cosmic microwave background radiation. Further we discuss the possible ways to break such degeneracy by doing global fitting using the latest observational data and we get a tight constraint on the interaction between dark sectors.

Xu, Xiao-Dong; Wang, Bin

2011-01-01

309

Gold(I)-catalyzed enantioselective intermolecular hydroarylation of allenes with indoles and reaction mechanism by density functional theory calculations.  

UK PubMed Central (United Kingdom)

Chiral binuclear gold(I) phosphine complexes catalyze enantioselective intermolecular hydroarylation of allenes with indoles in high product yields (up to 90%) and with moderate enantioselectivities (up to 63%?ee). Among the gold(I) complexes examined, better ee values were obtained with binuclear gold(I) complexes, which displayed intramolecular Au(I)-Au(I) interactions. The binuclear gold(I) complex 4c [(AuCl)(2)(L3)] with chiral biaryl phosphine ligand (S)-(-)-MeO-biphep (L3) is the most efficient catalyst and gives the best ee value of up to 63%. Substituents on the allene reactants have a slight effect on the enantioselectivity of the reaction. Electron-withdrawing groups on the indole substrates decrease the enantioselectivity of the reaction. The relative reaction rates of the hydroarylation of 4-X-substituted 1,3-diarylallenes with N-methylindole in the presence of catalyst 4c [(AuCl)(2)(L3)]/AgOTf [L3 = (S)-(-)-MeO-biphep], determined through competition experiments, correlate (r(2) = 0.996) with the substituent constants ?. The slope value is -2.30, revealing both the build-up of positive charge at the allene and electrophilic nature of the reactive Au(I) species. Two plausible reaction pathways were investigated by density functional theory calculations, one pathway involving intermolecular nucleophilic addition of free indole to aurated allene intermediate and another pathway involving intramolecular nucleophilic addition of aurated indole to allene via diaurated intermediate E2. Calculated results revealed that the reaction likely proceeds via the first pathway with a lower activation energy. The role of Au(I)-Au(I) interactions in affecting the enantioselectivity is discussed.

Wang MZ; Zhou CY; Guo Z; Wong EL; Wong MK; Che CM

2011-03-01

310

Gold(I)-Catalyzed Enantioselective Intermolecular Hydroarylation of Allenes with Indoles and Reaction Mechanism by Density Functional Theory Calculations.  

UK PubMed Central (United Kingdom)

Chiral binuclear gold(I) phosphine complexes catalyze enantioselective intermolecular hydroarylation of allenes with indoles in high product yields (up to 90?%) and with moderate enantioselectivities (up to 63?%?ee). Among the gold(I) complexes examined, better ee values were obtained with binuclear gold(I) complexes, which displayed intramolecular Au(I)--Au(I) interactions. The binuclear gold(I) complex 4?c [(AuCl)(2)(L3)] with chiral biaryl phosphine ligand (S)-(-)-MeO-biphep (L3) is the most efficient catalyst and gives the best ee value of up to 63?%. Substituents on the allene reactants have a slight effect on the enantioselectivity of the reaction. Electron-withdrawing groups on the indole substrates decrease the enantioselectivity of the reaction. The relative reaction rates of the hydroarylation of 4-X-substituted 1,3-diarylallenes with N-methylindole in the presence of catalyst 4?c [(AuCl)(2)(L3)]/AgOTf [L3=(S)-(-)-MeO-biphep], determined through competition experiments, correlate (r(2)=0.996) with the substituent constants ?. The slope value is -2.30, revealing both the build-up of positive charge at the allene and electrophilic nature of the reactive Au(I) species. Two plausible reaction pathways were investigated by density functional theory calculations, one pathway involving intermolecular nucleophilic addition of free indole to aurated allene intermediate and another pathway involving intramolecular nucleophilic addition of aurated indole to allene via diaurated intermediate E2. Calculated results revealed that the reaction likely proceeds via the first pathway with a lower activation energy. The role of Au(I)--Au(I) interactions in affecting the enantioselectivity is discussed.

Wang MZ; Zhou CY; Guo Z; Wong EL; Wong MK; Che CM

2010-12-01

311

Energies and physicochemical properties of cation-? interactions in biological structures.  

Science.gov (United States)

The cation-? interactions occur frequently within or between proteins due to six (Phe, Tyr, Trp, Arg, Lys, and His) of the twenty natural amino acids potentially interacting with metallic cations via these interactions. In this study, quantum chemical calculations and molecular orbital (MO) theory are used to study the energies and properties of cation-? interactions in biological structures. The cation-? interactions of H? and Li? are similar to hydrogen bonds and lithium bonds, respectively, in which the small, naked cations H? and Li? are buried deep within the ?-electron density of aromatic molecules, forming stable cation-? bonds that are much stronger than the cation-? interactions of other alkali metal cations. The cation-? interactions of metallic cations with atomic masses greater than that of Li? arise mainly from the coordinate bond comprising empty valence atomic orbitals (AOs) of metallic cations and ?-MOs of aromatic molecules, though electrostatic interactions may also contribute to the cation-? interaction. The binding strength of cation-? interactions is determined by the charge and types of AOs in the metallic cations. Cation-? interaction energies are distance- and orientation-dependent; energies decrease with the distance (r) and the orientation angle (?). In solution, the cation-? energies decrease with the increase of the dielectric constant (?) of the solvent; however, solvation has less influence on the H?-? and H?O?-? interactions than on interactions with other cations. The conclusions from this study provide useful theoretical insights into the nature of cation-? interactions and may contribute to the development of better force field parameters for describing the molecular dynamics of cation-? interactions within and between proteins. PMID:22306412

Du, Qi-Shi; Meng, Jian-Zong; Liao, Si-Ming; Huang, Ri-Bo

2011-12-29

312

Energies and physicochemical properties of cation-? interactions in biological structures.  

UK PubMed Central (United Kingdom)

The cation-? interactions occur frequently within or between proteins due to six (Phe, Tyr, Trp, Arg, Lys, and His) of the twenty natural amino acids potentially interacting with metallic cations via these interactions. In this study, quantum chemical calculations and molecular orbital (MO) theory are used to study the energies and properties of cation-? interactions in biological structures. The cation-? interactions of H? and Li? are similar to hydrogen bonds and lithium bonds, respectively, in which the small, naked cations H? and Li? are buried deep within the ?-electron density of aromatic molecules, forming stable cation-? bonds that are much stronger than the cation-? interactions of other alkali metal cations. The cation-? interactions of metallic cations with atomic masses greater than that of Li? arise mainly from the coordinate bond comprising empty valence atomic orbitals (AOs) of metallic cations and ?-MOs of aromatic molecules, though electrostatic interactions may also contribute to the cation-? interaction. The binding strength of cation-? interactions is determined by the charge and types of AOs in the metallic cations. Cation-? interaction energies are distance- and orientation-dependent; energies decrease with the distance (r) and the orientation angle (?). In solution, the cation-? energies decrease with the increase of the dielectric constant (?) of the solvent; however, solvation has less influence on the H?-? and H?O?-? interactions than on interactions with other cations. The conclusions from this study provide useful theoretical insights into the nature of cation-? interactions and may contribute to the development of better force field parameters for describing the molecular dynamics of cation-? interactions within and between proteins.

Du QS; Meng JZ; Liao SM; Huang RB

2012-04-01

313

Thermodynamics with Interacting Dark Energy in Magnetic Universe  

Science.gov (United States)

In this paper, we investigate the validity of generalized second law of thermodynamics for FRW universe in the framework of non-linear electrodynamics. We assume that the universe is composed of dark matter, magnetic field and some unknown dark energy component with two different interacting terms Q and \\tilde{Q}. It is found that the energy transfer from dark energy to magnetic field depends upon the sign of interacting terms. For Q\\tilde{Q}. In this scenario, we calculate energy densities of dark matter and other dark energy fluid. We check the validity of generalized second law of thermodynamics bounded by Hubble, apparent, particle and event horizons. It turns out that this law always holds on the Hubble and apparent horizons but fails on the particle and event horizons for both interacting and non-interacting cases.

Sharif, Muhammad; Saleem, Rabia

2013-06-01

314

Cosmological Evolution With Interaction Between Dark Energy And Dark Matter  

CERN Document Server

In this review we consider in detail different theoretical topics associated with interaction in the dark sector. We study linear and nonlinear interactions which depend on the dark matter and dark energy densities. We consider a number of different models (including the holographic dark energy and dark energy in a fractal universe) with interacting dark energy (DE) and dark matter (DM), have done a thorough analysis of these models. The main task of this review was not only to give an idea about the modern set of different models of dark energy, but to show how much can be diverse dynamics of the universe in these models. We find that the dynamics of a Universe that contains interaction in the dark sector can differ significantly from the Standard Cosmological Model (SCM).

Bolotin, Yu L; Lemets, O A; Yerokhin, D A

2013-01-01

315

Load Matching and Grid Interaction of Net Zero Energy Buildings  

DEFF Research Database (Denmark)

“Net Zero Energy Building” has become a prominent wording to describe the synergy of energy efficient building and renewable energy utilization to reach a balanced energy budget over a yearly cycle. Taking into account the energy exchange with a grid infrastructure overcomes the limitations of seasonal energy storage on-site. Even though the wording “Net Zero Energy Building” focuses on the annual energy balance, large differences may occur between solution sets in the amount of grid interaction needed to reach the goal. The paper reports on the analysis of example buildings concerning the load matching and grid interaction. Indices to describe both issues are proposed and foreseen as part of a harmonized definition framework. The work is part of subtask A of the IEA SHCP Task40/ECBCS Annex 52: “Towards Net Zero Energy Solar Buildings”.

Voss, Karsten; Sartori, Igor

2010-01-01

316

Low Energy Neutrino-Nucleus Interactions  

International Nuclear Information System (INIS)

As the precision of neutrino oscillation experiments increases, correctly modeling neutrino-nucleus interactions is becoming ever more important. Uncertainties in nuclear form factors and nuclear structure result in uncertainties in determining oscillation parameters.

2004-10-14

317

Proinsulin intermolecular interactions during secretory trafficking in pancreatic ? cells.  

UK PubMed Central (United Kingdom)

Classically, exit from the endoplasmic reticulum (ER) is rate-limiting for secretory protein trafficking because protein folding/assembly occurs there. In this study, we have exploited "hPro-CpepSfGFP," a human proinsulin bearing "superfolder" green fluorescent C-peptide expressed in pancreatic ? cells where it is processed to human insulin and CpepSfGFP. Remarkably, steady-state accumulation of hPro-CpepSfGFP and endogenous proinsulin is in the Golgi region, as if final stages of protein folding/assembly were occurring there. The Golgi regional distribution of proinsulin is dynamic, influenced by fasting/refeeding, and increased with ? cell zinc deficiency. However, coexpression of ER-entrapped mutant proinsulin-C(A7)Y shifts the steady-state distribution of wild-type proinsulin to the ER. Endogenous proinsulin coprecipitates with hPro-CpepSfGFP and even more so with hProC(A7)Y-CpepSfGFP. Using Cerulean and Venus-tagged proinsulins, we find that both WT-WT and WT-mutant proinsulin pairs exhibit FRET. The data demonstrate that wild-type proinsulin dimerizes within the ER but accumulates at a poorly recognized slow step within the Golgi region, reflecting either slow kinetics of proinsulin hexamerization, steps in formation of nascent secretory granules, or other unknown molecular events. However, in the presence of ongoing misfolding of a subpopulation of proinsulin in ? cells, the rate-limiting step in transport of the remaining proinsulin shifts to the ER.

Haataja L; Snapp E; Wright J; Liu M; Hardy AB; Wheeler MB; Markwardt ML; Rizzo M; Arvan P

2013-01-01

318

Tuning Aryl?CH···O Intermolecular Interactions on Pt(111)  

DEFF Research Database (Denmark)

Scanning tunneling microscopy (STM) data are reported for the room-temperature adsorption of 2,2,2-trifluoroacetophenone (TFAP), 2,2,2-trifluorovinylbenzene (TFVB), octafluoroacetophenone (OFAP), and methyl benzoate (MB) on Pt(111). The objective of the study is to establish the role of aryl?CH···O bonding in forming self-assembled low-nuclearity structures at room temperature and to compare aryl?CH···O bonding by ester and ketone carbonyl functions. The STM images clearly evidence the formation of homochiral dimers and trimers of TFAP, and density functional theory (DFT) calculations reveal aryl?CH···O bonding as the driving force for dimer formation. In contrast to TFAP, chemisorbed TFVB and OFAP do not form such self-assembled structures as they lack carbonyl and aryl?CH groups, respectively. The self-assembly of MB on Pt(111) differs from that of TFAP, in that it can form structures stabilized by one, as distinct from two, aryl?CH···O bonds. The results are discussed with respect to the enantioselective hydrogenation of ?-ketoesters on cinchona modified Pt catalysts.

Demers-Carpentier, Vincent; Laliberte, Marc-Andre?

2011-01-01

319

Pollution prevention and energy conservation: Understanding the interactions  

International Nuclear Information System (INIS)

[en] The traditional view holds that pollution prevention is good for energy conservation and vice versa. Analysis of pollution prevention and energy conservation activities indicates, however, that interactions and synergies between environmental and energy factors can mean that pollution prevention can be energy intensive and, conversely, that energy conservation can lead to increased pollution. Full cost accounting, taking into account all media, must be performed before precise pollution prevention-energy conservation interrelationships can be characterized and quantified. Use of a pollution prevention-energy conservation matrix can further this understanding

1992-01-01

320

Calculations of potential energy surfaces using Monte Carlo configuration interaction  

Science.gov (United States)

We apply the method of Monte Carlo configuration interaction (MCCI) to calculate ground-state potential energy curves for a range of small molecules and compare the results with full configuration interaction. We show that the MCCI potential energy curve can be calculated to relatively good accuracy, as quantified using the non-parallelity error, using only a very small fraction of the full configuration interaction space. In most cases the potential curve is of better accuracy than its constituent single-point energies. We finally test the MCCI program on systems with basis sets beyond full configuration interaction: a lattice of 50 hydrogen atoms and ethylene. The results for ethylene agree fairly well with other computational work while for the lattice of 50 hydrogens we find that the fraction of the full configuration interaction space we were able to consider appears to be too small as, although some qualitative features are reproduced, the potential curve is less accurate.

Coe, Jeremy P.; Taylor, Daniel J.; Paterson, Martin J.

2012-11-01

 
 
 
 
321

Calculations of potential energy surfaces using Monte Carlo configuration interaction.  

UK PubMed Central (United Kingdom)

We apply the method of Monte Carlo configuration interaction (MCCI) to calculate ground-state potential energy curves for a range of small molecules and compare the results with full configuration interaction. We show that the MCCI potential energy curve can be calculated to relatively good accuracy, as quantified using the non-parallelity error, using only a very small fraction of the full configuration interaction space. In most cases the potential curve is of better accuracy than its constituent single-point energies. We finally test the MCCI program on systems with basis sets beyond full configuration interaction: a lattice of 50 hydrogen atoms and ethylene. The results for ethylene agree fairly well with other computational work while for the lattice of 50 hydrogens we find that the fraction of the full configuration interaction space we were able to consider appears to be too small as, although some qualitative features are reproduced, the potential curve is less accurate.

Coe JP; Taylor DJ; Paterson MJ

2012-11-01

322

Energy-economy interactions: implications for public policy analysis  

Energy Technology Data Exchange (ETDEWEB)

The goal of the dissertation is to develop a set of analytical tools capable of evaluating the economic effects of policy initiatives designed to promote energy efficiency improvements. The proposed methods are designed to explore the interactions of energy and capital. The dissertation demonstrates that these interactions are important determinants in developing sound energy policy. Motivating research into energy-economy modeling are three controversial energy policy issues. These issues include: evaluating the economic impacts of energy tax policy, determining whether energy and capital resources are complements or substitutes, and gauging the effect of increased energy prices on capital turnover. In addition to the methodological contributions which are offered, the dissertation demonstrates that these issues are meaningfully connected.

Koved, M.D.

1986-01-01

323

A study of intermolecular bonding in antimony triiodide by using Moessbauer effect of 129I  

International Nuclear Information System (INIS)

The 129I Moessbauer effect for antimony triiodide has been investigated at 4.2, 77 and 1350K. The Moessbauer spectrum showed only one species of iodine atom in the range of 4.20K to 1350K. The Moessbauer parameters obtained were in good agreement with those of the iodine (B) species of antimony triiodide in previous work. Furthermore, the intermolecular interaction, which is suggested from the X-ray analysis of the crystal structure, is discussed by using the Moessbauer parameters according to the idea of the resonance switching bond of the p-orbitals. The fractional importance of the intermolecular bond is found to be 24 percents. That is, the main bond is weakened to 76 percents, which is compatible with the increase of the main bond distance in the solid state. (auth.)

1977-01-01

324

Impact parameters of inelastic hadron interaction at high energies  

International Nuclear Information System (INIS)

The expression for impact parameters of inelastic hadron-hadron interaction with the defined number of charged particles in the final state is obtained from the absorptive model. The model satisfy the unitary condition in the direct reaction channel. The impact parameters of the inelastic pp interaction at ISR energies are calculated. It is found that the impact parameters of multiple production processes decrease with multiplicity growth and at fixed multiplicity they increase with energy.

1978-01-01

325

Comparison of hadronic interaction models at Auger energies  

Energy Technology Data Exchange (ETDEWEB)

The three hadronic interaction models DPMJET 2.55, QGSJET 01, and SIBYLL 2.1, implemented in the air shower simulation program CORSIKA, are compared in the energy range of interest for the Pierre Auger experiment. The model dependence of relevant quantities in individual hadronic interactions and air showers is investigated.

Heck, D. E-mail: dieter. heck@ik.fzk.de; Risse, M.; Knapp, J

2003-07-01

326

Comparison of Hadronic Interaction Models at Auger Energies  

CERN Document Server

The three hadronic interaction models DPMJET 2.55, QGSJET 01, and SIBYLL 2.1, implemented in the air shower simulation program CORSIKA, are compared in the energy range of interest for the Pierre Auger experiment. The model dependence of relevant quantities in individual hadronic interactions and air showers is investigated.

Heck, D; Knapp, J

2002-01-01

327

Comparison of hadronic interaction models at Auger energies  

International Nuclear Information System (INIS)

The three hadronic interaction models DPMJET 2.55, QGSJET 01, and SIBYLL 2.1, implemented in the air shower simulation program CORSIKA, are compared in the energy range of interest for the Pierre Auger experiment. The model dependence of relevant quantities in individual hadronic interactions and air showers is investigated.

2003-01-01

328

Gravitational Effects of Weak Interactions at TeV Energies  

CERN Multimedia

Recently there has been a lot of interest in the search for extra dimensions. If gravity propagates in extra dimensions then gravity would become as strong as other interactions. This could also lead to the production of mini black holes. Here we have discussed how even without considering extra dimensions gravitational effects of weak interactions could show up at TeV energies.

Sivaram, C

2008-01-01

329

High energy e+e- interactions  

International Nuclear Information System (INIS)

A review is given about the experimental studies of e+e- interactions. After a description of the PETRA and PEP storage rings the structure of leptons and the weak neutral current contributions to lepton pair production are discussed. Then experiments for the search for new particles, the jet formation in e+e- annihilation, and the quark and gluon fragmentation are described. (HSI).

1981-01-01

330

Magnon energies and exchange interactions in terbium  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The magnon density of states, and hence the magnetic contribution to the specific heat, and also the exchange interaction between ions in the same sublattice have been calculated for Tb at 90°K, using experimental results obtained by inelastic neutron scattering.

Houmann, Jens Christian Gylden

331

Interatomic (Intermolecular) Decay Processes in Clusters: Current Status and Outlook  

International Nuclear Information System (INIS)

Since their theoretical prediction a decade ago, interatomic (intermolecular) Coulombic decay (ICD) and related processes have been in the focus of intensive theoretical and experimental research. The spectacular progress in this direction has been stimulated both by the fundamental importance of the new electronic decay phenomena and by the exciting possibility of their practical application, for example in spectroscopy. We review the current status of the research of interatomic (intermolecular) decay phenomena in clusters and discuss some perspectives of this new field.

2007-11-29

332

Interacting ghost dark energy in Brans-Dicke theory  

International Nuclear Information System (INIS)

We investigate the QCD ghost model of dark energy in the framework of Brans-Dicke cosmology. First, we study the non-interacting ghost dark energy in a flat Brans-Dicke theory. In this case we obtain the equation of state and the deceleration parameters and a differential equation governing the evolution of ghost energy density. Interestingly enough, we find that the equation of state parameter of the non-interacting ghost dark energy can cross the phantom line (wD=-1) provided the parameters of the model are chosen suitably. Then, we generalize the study to the interacting ghost dark energy in both flat and non-flat Brans-Dicke framework and find out that the transition of wD to phantom regime can be more easily achieved for than when resort to the Einstein field equations is made.

2011-11-30

333

INTERACTION ENERGIES IN NON WATSON-CRICK PAIRS: AN AB INITIO STUDY OF G·U AND U·U PAIRS  

Directory of Open Access Journals (Sweden)

Full Text Available Ab initio calculations at the MP2/6-31G** level have been carried out on the non-Watson-Crick nucleic acids pairs G·U and U·U to obtain the interaction energies and to see whether the derived values are comparable or not with the canonical G-C, A-T and A-U pairs. Optimized geometries of the pairs show that the structural parameters of the isolated bases differ very little on pairing. The guanine -NH2 group does not participate in the hydrogen bonding formation and possesses a pyramidal structure; its intrinsic nonplanarity plays an important role in the out-of-plane intermolecular interactions. Thus, the G·U pair projects three hydrogen bonding acceptor sites, namely, N7(G), O6(G) and O4(U) to the RNA major groove. The interaction energy (DHºint) calculated for the G·U pair (-13.6 kcal/mol) is comparable to that determined for A-T (-13.0 kcal/mol), but considerable smaller than the experimental value reported for G-C (-21.0 kcal/mol). The U·U pair follows the trend that pairing between pyrimidines bases should have lower interacting energies than purine-pyrimidine pairs

SANDRA T MADARIAGA; J.GUILLERMO CONTRERAS; C.GLORIA SEGUEL

2005-01-01

334

INTERACTION ENERGIES IN NON WATSON-CRICK PAIRS: AN AB INITIO STUDY OF G·U AND U·U PAIRS  

Scientific Electronic Library Online (English)

Full Text Available Abstract in english Ab initio calculations at the MP2/6-31G** level have been carried out on the non-Watson-Crick nucleic acids pairs G·U and U·U to obtain the interaction energies and to see whether the derived values are comparable or not with the canonical G-C, A-T and A-U pairs. Optimized geometries of the pairs show that the structural parameters of the isolated bases differ very little on pairing. The guanine -NH2 group do (more) es not participate in the hydrogen bonding formation and possesses a pyramidal structure; its intrinsic nonplanarity plays an important role in the out-of-plane intermolecular interactions. Thus, the G·U pair projects three hydrogen bonding acceptor sites, namely, N7(G), O6(G) and O4(U) to the RNA major groove. The interaction energy (DHºint) calculated for the G·U pair (-13.6 kcal/mol) is comparable to that determined for A-T (-13.0 kcal/mol), but considerable smaller than the experimental value reported for G-C (-21.0 kcal/mol). The U·U pair follows the trend that pairing between pyrimidines bases should have lower interacting energies than purine-pyrimidine pairs

MADARIAGA, SANDRA T; CONTRERAS, J.GUILLERMO; SEGUEL, C.GLORIA

2005-03-01

335

Experimentally based contact energies decode interactions responsible for protein-DNA affinity and the role of molecular waters at the binding interface.  

UK PubMed Central (United Kingdom)

A major obstacle towards understanding the molecular basis of transcriptional regulation is the lack of a recognition code for protein-DNA interactions. Using high-quality crystal structures and binding data on the promiscuous family of C(2)H(2) zinc fingers (ZF), we decode 10 fundamental specific interactions responsible for protein-DNA recognition. The interactions include five hydrogen bond types, three atomic desolvation penalties, a favorable non-polar energy, and a novel water accessibility factor. We apply this code to three large datasets containing a total of 89 C(2)H(2) transcription factor (TF) mutants on the three ZFs of EGR. Guided by molecular dynamics simulations of individual ZFs, we map the interactions into homology models that embody all feasible intra- and intermolecular bonds, selecting for each sequence the structure with the lowest free energy. These interactions reproduce the change in affinity of 35 mutants of finger I (R(2) = 0.998), 23 mutants of finger II (R(2) = 0.96) and 31 finger III human domains (R(2) = 0.94). Our findings reveal recognition rules that depend on DNA sequence/structure, molecular water at the interface and induced fit of the C(2)H(2) TFs. Collectively, our method provides the first robust framework to decode the molecular basis of TFs binding to DNA.

Temiz NA; Camacho CJ

2009-07-01

336

Energy losses in interacting fine-particle magnetic composites  

International Nuclear Information System (INIS)

[en] The coercivity and energy losses in superparamagnetic (SPM) magnetite and FePt nanoparticle composites subjected to an external, alternating magnetic field have been calculated as a function of the mean particle size and packing density. The effect of interactions has been investigated by fitting the Sharrock law to the coercivity results as a function of the field cycle frequency of the magnetic field. This fitting leads to effective parameters for the anisotropy field HKeff and ?eff = KV/kBT, which are themselves dependent on the interaction strength. The increase or decrease in the coercivity with interactions depends upon the relative change of HKeff and ?eff, thus demonstrating the complex effect that interactions have in these nanoparticle composites. The interparticle interactions have a non-trivial effect on the energy loss per cycle. The energy loss is reduced for systems with larger particles since the reduction in coercivity together with a corresponding reduction in the remanence dominates. For small particle sizes, the energy loss is increased. The primary mechanism here seems to be an enhancement of the energy barrier due to interactions, which changes the nature of the particles from SPM to being thermally stable.

2010-12-01

337

Calculations of Potential Energy Surfaces Using Monte Carlo Configuration Interaction  

CERN Document Server

We apply the method of Monte Carlo configuration interaction (MCCI) to calculate ground-state potential energy curves for a range of small molecules and compare the results with full configuration interaction. We show that the MCCI potential energy curve can be calculated to relatively good accuracy, as quantified using the non-parallelity error, using only a very small fraction of the FCI space. In most cases the potential curve is of better accuracy than its constituent single-point energies. We finally test the MCCI program on systems with basis sets beyond full configuration interaction: a lattice of fifty hydrogen atoms and ethylene. The results for ethylene agree fairly well with other computational work while for the lattice of fifty hydrogens we find that the fraction of the full configuration interaction space we were able to consider appears to be too small as, although some qualitative features are reproduced, the potential curve is less accurate.

Coe, J P; Paterson, M J; 10.1063/1.4767052

2012-01-01

338

Energy Centroids in the presence of random interactions  

CERN Document Server

In this paper we study energy centroids such as those with fixed spin and isospin, those with fixed irreducible representations for bosons, in the presence of random two-body and/or three-body interactions. Our results show that regularities of energy centroids of fixed spin states reported in earlier works are more robust than expected.

Zhao, Y M; Yoshida, N; Ogawa, K; Yoshinaga, N; Kota, V K B

2005-01-01

339

Constraints on the interacting holographic dark energy model  

Energy Technology Data Exchange (ETDEWEB)

We examined the interacting holographic dark energy model in a universe with spatial curvature. Using the near-flatness condition and requiring that the universe is experiencing an accelerated expansion, we have constrained the parameter space of the model and found that the model can accommodate a transition of the dark energy from {omega}{sub D}>-1 to {omega}{sub D}<-1.

Wang Bin [Department of Physics, Fudan University, 200433 Shanghai (China)]. E-mail: wangb@fudan.edu.cn; Lin, C.-Y. [Department of Physics, National Dong Hwa University, Shoufeng, 974 Hualien, Taiwan (China)]. E-mail: lcyong@mail.ndhu.edu.tw; Abdalla, Elcio [Instituto de Fisica, Universidade de Sao Paulo, C.P. 66.318, CEP 05315-970, Sao Paulo (Brazil)]. E-mail: eabdalla@fma.if.usp.br

2006-06-22

340

Constraints on the interacting holographic dark energy model  

International Nuclear Information System (INIS)

We examined the interacting holographic dark energy model in a universe with spatial curvature. Using the near-flatness condition and requiring that the universe is experiencing an accelerated expansion, we have constrained the parameter space of the model and found that the model can accommodate a transition of the dark energy from ?D>-1 to ?D

2006-06-22

 
 
 
 
341

Dynamics of interacting phantom and quintessence dark energies  

CERN Document Server

We present models, in which phantom energy interacts with two different types of dark energies including variable modified Chaplygin gas (VMCG) and new modified Chaplygin gas (NMCG). We then construct potentials for these cases. It has been shown that the potential of the phantom field decreases from a higher value with the evolution of the Universe.

Farooq, M Umar; Debnath, Ujjal

2011-01-01

342

High energy nuclear interactions and QCD an introduction  

CERN Multimedia

The goal of these lectures, oriented towards the students just entering the field, is to provide an elementary introduction to QCD and the physics of nuclear interactions at high energies. We first introduce the general structure of QCD and discuss its main properties. Then we proceed to Glauber multiple scattering theory which lays the foundation for the theoretical treatment of nuclear interactions at high energies. We introduce the concept of Gribov's inelastic shadowing, crucial for the understanding of quantum formation effects. We outline the problems facing Glauber approach at high energies, and discuss how asymptotic freedom of QCD helps to resolve them, introducing the concepts of parton saturation and color glass condensate.

Kharzeev, Dima E

2002-01-01

343

Intermediate-energy hadron interactions, II  

Energy Technology Data Exchange (ETDEWEB)

The topics to be covered are as follows. I'll begin with new developments in NN ..-->.. NN..pi.. reactions. This will provide a natural lead-in to the main topic of this talk, which is dibaryons. This will be followed by discussion of elastic proton-deuteron and inelastic proton-alpha scattering. Then there will be a brief mention of two technical developments. Finally, I'll close by giving short remarks about two peculiarities that were found by theorists looking at strong interaction amplitudes. 15 refs., 3 figs.

Silbar, R.R.

1988-01-01

344

Intermediate-energy hadron interactions, II  

International Nuclear Information System (INIS)

The topics to be covered are as follows. I'll begin with new developments in NN ? NN? reactions. This will provide a natural lead-in to the main topic of this talk, which is dibaryons. This will be followed by discussion of elastic proton-deuteron and inelastic proton-alpha scattering. Then there will be a brief mention of two technical developments. Finally, I'll close by giving short remarks about two peculiarities that were found by theorists looking at strong interaction amplitudes. 15 refs., 3 figs

1988-01-01

345

Nucleon-nucleon interaction at medium energies  

International Nuclear Information System (INIS)

A summary of the medium energy nucleon-nucleon elastic and inelastic scattering data is presented from an experimenter's viewpoint. Motivation for additional measurements is given. Experiments which rely on the unique capabilities of the Indiana Cooler are emphasized. 65 references

1984-01-01

346

Binding energies of ? ? hypernuclei and the ? ? interaction  

International Nuclear Information System (INIS)

The binding energies of the ? ? hypernuclei /sub ? ?/10Be and /sub ? ?/6He were calculated variationally with a 2? + 2? and with an ? + 2? model respectively. For /sub ? ?/?110Be the integrations were made with Monte Carlo techniques while for /sub ? ?/6He direct numerical methods were used. A wide range of phenomenological ? ? potentials based on meson-exchange models was considered.

1984-04-01

347

Coupled Effects of the Substrate Adhesion and Intermolecular Forces on Polymer Thin Film Glass-Transition Behavior.  

UK PubMed Central (United Kingdom)

Intermolecular noncovalent forces between polymer chains influence the mobility and glass-transition temperature (T_g), where weaker interchain interactions, all else being the same, typically lower bulk polymer T_g. Using molecular dynamics simulations, here we show that this relation becomes invalid for supported ultra-thin films when the substrate-polymer interaction is extremely strong and the polymer-polymer interactions are much weaker. This contrasting trend is found to be due to a more pronounced substrate-induced appreciation of film T_g for polymers with weaker intermolecular interactions and low bulk T_g. We show that optimizing this coupling between substrate adhesion and bulk T_g maximizes thin film T_g, paving the way for tuning film properties through interface nanoengineering.

Xia W; Keten S

2013-09-01

348

Self-energies and the interactions of particles with surfaces  

Energy Technology Data Exchange (ETDEWEB)

We have in this paper reviewed the method of treating many-body problems by means of an effective interaction self-energy. We have developed an alternatvie approach to the self-energy which is simpler and more straight-forward than standard methods, and we have illustrated its use with two examples of a charge interacting with a metal surface. In each case the self-energy produces the classical image potential together with corrections due to quantum mechanical effects. This method has also been successfully applied to the problem of an atom interacting with a surface. Corrections to the Van der Waals dispersion force are obtained, and via the non-conservative imaginary parts to /summation//sub i/(z) we discuss transition rates and energy exchange. 14 refs., 1 fig.

Manson, J.R.; Ritchie, R.H.; Echenique, P.M.; Gras-Marti, A.

1987-01-01

349

An analysis of two textbooks on the topic of intermolecular forces  

Directory of Open Access Journals (Sweden)

Full Text Available This paper describes the analysis of two commonly used high school (Grades 11 and 12) chemistry textbooks in Singapore to determine if the content presented in the topic of intermolecular forces is consistent with the concepts and propositional knowledge identified by the authors as essential for the learning and understanding of the topic according to the Singapore high school chemistry syllabus. The authors found that the two textbooks did not adequately discuss the electrostatic nature of intermolecular forces, and the factors influencing the polarity of bonds/molecules, hydrogen bonding and instantaneous dipole-induced dipole interactions. The insufficient coverage of the above areas may lead to students having alternative conceptions of intermolecular forces as they may have incomplete or little understanding of the concepts involved and relationships between these concepts. Thus, teachers need to analyse textbooks carefully before using the textbooks so that they can be more aware of the difficulties that students may face when reading the textbooks, and attend to these areas by careful elaboration and integration of concepts in their lessons.

Tan Kim Chwee, Daniel; Chan Kim Sen

2004-01-01

350

A simple model for low energy ion-solid interactions  

International Nuclear Information System (INIS)

A simple analytical model for ion-solid interactions, suitable for low energy beam depositions, is reported. An approximation for the nuclear stopping power is used to obtain the analytic solution for the deposited energy in the solid. The ratio of the deposited energy in the bulk to the energy deposited in the surface yields a ceiling for the beam energy above which more defects are generated in the bulk resulting in defective films. The numerical evaluations agree with the existing results in the literature. copyright 1997 American Institute of Physics

1997-01-01

351

A simple model for low energy ion-solid interactions  

Energy Technology Data Exchange (ETDEWEB)

A simple analytical model for ion-solid interactions, suitable for low energy beam depositions, is reported. An approximation for the nuclear stopping power is used to obtain the analytic solution for the deposited energy in the solid. The ratio of the deposited energy in the bulk to the energy deposited in the surface yields a ceiling for the beam energy above which more defects are generated in the bulk resulting in defective films. The numerical evaluations agree with the existing results in the literature. {copyright} {ital 1997 American Institute of Physics.}

Mohajerzadeh, S.; Selvakumar, C.R. [Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)

1997-04-01

352

Vibronic spectra of perylene bisimide oligomers: effects of intermolecular charge-transfer excitation and conformational flexibility.  

UK PubMed Central (United Kingdom)

We have recently presented a theoretical study on the temperature-dependent absorption and photoluminescence spectroscopy of rubrene multichromophores by combining the time-dependent long-range-corrected density functional theory with the Frenkel exciton model (Gao; et al. J. Phys. Chem. A2009, 113, 12847). The spectra of rubrene multichromophores up to heptamers have been calculated and the effects of exciton-phonon coupling and temperature on the photophysical properties of both H- and J-aggregated oligomers were addressed. However, in that work the contribution of intermolecular charge-transfer excitons (CTEs) to vibronic spectra was not addressed. Here we take into account the effect of CTEs for the absorption and emission spectra of the aggregated perylene bisimide (PBI) oligomers in order to have a quantitative explanation to the experimental absorption and emission spectra of the PBI dyes. The role of intermolecular CTEs is discussed for different intermolecular orientations and distances. The simulations demonstrate that the contribution of CTEs becomes significant when the intermolecular distance is less than 4.5 Å for the ?-? stacked PBI aggregates, and the mixed exciton model is prerequisite to explain the experimentally observed red-shift of the absorption spectra in this case. The large Stokes shift of the emission spectra can be reproduced by our model, and it is induced by the asymmetric nature of the lowest excitonic state of the H-aggregated oligomers. The experimentally observed broad emission bands come from two species with different conformations. As for J-aggregated PBI oligomers, the interactions of FEs induce the red-shift and the increase of the relative intensity of 0-0 peak of the absorption spectra with more aggregated units.

Gao F; Zhao Y; Liang W

2011-03-01

353

Vibronic spectra of perylene bisimide oligomers: effects of intermolecular charge-transfer excitation and conformational flexibility.  

Science.gov (United States)

We have recently presented a theoretical study on the temperature-dependent absorption and photoluminescence spectroscopy of rubrene multichromophores by combining the time-dependent long-range-corrected density functional theory with the Frenkel exciton model (Gao; et al. J. Phys. Chem. A2009, 113, 12847). The spectra of rubrene multichromophores up to heptamers have been calculated and the effects of exciton-phonon coupling and temperature on the photophysical properties of both H- and J-aggregated oligomers were addressed. However, in that work the contribution of intermolecular charge-transfer excitons (CTEs) to vibronic spectra was not addressed. Here we take into account the effect of CTEs for the absorption and emission spectra of the aggregated perylene bisimide (PBI) oligomers in order to have a quantitative explanation to the experimental absorption and emission spectra of the PBI dyes. The role of intermolecular CTEs is discussed for different intermolecular orientations and distances. The simulations demonstrate that the contribution of CTEs becomes significant when the intermolecular distance is less than 4.5 Å for the ?-? stacked PBI aggregates, and the mixed exciton model is prerequisite to explain the experimentally observed red-shift of the absorption spectra in this case. The large Stokes shift of the emission spectra can be reproduced by our model, and it is induced by the asymmetric nature of the lowest excitonic state of the H-aggregated oligomers. The experimentally observed broad emission bands come from two species with different conformations. As for J-aggregated PBI oligomers, the interactions of FEs induce the red-shift and the increase of the relative intensity of 0-0 peak of the absorption spectra with more aggregated units. PMID:21384839

Gao, Fang; Zhao, Yi; Liang, WanZhen

2011-03-08

354

Pion-nucleon interaction at low energy  

Energy Technology Data Exchange (ETDEWEB)

The ..pi../sup -/p ..-->.. ..gamma..n and ..pi../sup -/p ..-->.. ..pi../sup 0/n reactions were studied for laboratory pion kinetic energies of 50, 66, 80, 95, 110, and 125 MeV at 9 angles between 30/sup 0/ and 140/sup 0/, using a large NaI(T1) detector, TINA. The results are much more accurate than previous data. The radiative capture differential cross-sections are compared with previous data and with several calculations and will specify more precisely the isoscalar amplitudes in multipole analyses. They are consistent with earlier data and confirm the principle of detailed balance, but indicate that the theoretical calculations cannot reproduce the nucleon data adequately below resonance. The charge exchange differential cross-sections are obtained by unfolding the energy spectra of the ..pi../sup 0/ ..gamma..-ray decay, and agree with the Karlsruhe and VPI phase-shift analyses. Pion-nucleon phase-shifts and scattering lengths are calculated and the results are in good agreement with data from the elastic scattering channels and support isospin invariance in this energy region.

Bagheri, A.

1986-01-01

355

Low-energy antiproton-neon interaction  

International Nuclear Information System (INIS)

By means of a streamer chamber exposed to the LEAR antiproton beams, the total reaction cross sections, the charged-prong multiplicity distributions and lower limits for the production of negative pions and Ksub(s)0 in the anti p-Ne interaction were measured at 19.6, 48.7 and 179.6 MeV. Annihilation was found to be dominant over all other non-elastic anti p-Ne processes. An analysis of Ne and other nuclei data in the frame of the Glauber theory allowed us to determine the ratio between the anti p-n and the anti p-p cross sections. An analysis in the light of INC model predictions allowed us to show up events which can be interpreted as annihilations having occurred deeply inside the nuclei. (orig.)

1986-05-05

356

Model chemistry calculations of thiophene dimer interactions: origin of pi-stacking.  

UK PubMed Central (United Kingdom)

The intermolecular interaction energies of thiophene dimers have been calculated by using an aromatic intermolecular interaction (AIMI) model (a model chemistry for the evaluation of intermolecular interactions between aromatic molecules). The CCSD(T) interaction energy at the basis set limit has been estimated from the MP2 interaction energy near the basis set limit and the CCSD(T) correction term obtained by using a medium-size basis set. The calculated interaction energies of the parallel and perpendicular thiophene dimers are -1.71 and -3.12 kcal/mol, respectively. The substantial attractive interaction in the thiophene dimer, even where the molecules are well separated, shows that the major source of attraction is not short-range interactions such as charge transfer but rather long-range interactions such as electrostatic and dispersion. The inclusion of electron correlation increases the attraction significantly. The dispersion interaction is found to be the major source of attraction in the thiophene dimer. The calculated total interaction energy of the thiophene dimer is highly orientation dependent. Although electrostatic interaction is substantially weaker than dispersion interaction, it is highly orientation dependent, and therefore electrostatic interaction play an important role in the orientation dependence of the total interaction energy. The large attractive interaction in the perpendicular dimer is the cause of the preference for the herringbone structure in the crystals of nonsubstituted oligothiophenes (alpha-terthienyls), and the steric repulsion between the beta-substituents is the cause of the pi-stacked structure in the crystals of some beta-substituted oligothiophenes.

Tsuzuki S; Honda K; Azumi R

2002-10-01

357

Vibrational Spectra of ??-Type BEDT-TTF Salts: Relationship between Conducting Property, Time-Averaged Site Charge and Inter-Molecular Distance  

Directory of Open Access Journals (Sweden)

Full Text Available The relationship between the conducting behavior and the degree of charge fluctuation in the ??-type BEDT-TTF salts is reviewed from the standpoints of vibrational spectroscopy and crystal structure. A group of ??-type ET salts demonstrates the best model compounds for achieving the above relationship because the two-dimensional structure is simple and great diversity in conducting behavior is realized under ambient pressure. After describing the requirement for the model compound, the methodology for analyzing the results of the vibrational spectra is presented. Vibrational spectroscopy provides the time-averaged molecular charge, the charge distribution in the two-dimensional layer, and the inter-molecular interactions, etc. The experimental results applied to 2/3-filled and 3/4-filled ??-type ET salts are reported. These experimental results suggest that the conducting property, the difference in the time-averaged molecular charges between the ionic and neutral-like sites, the alternation in the inter-molecular distances and the energy levels in the charge distributions are relevant to one another. The difference in the time-averaged molecular charges, ??, is a useful criterion for indicating conducting behavior. All superconductors presented in this review are characterized as small but finite ??.

Takashi Yamamoto

2012-01-01

358

Structure and Intermolecular Vibrations of Perylene- trans-1,2-Dichloroethene, a Weak Charge-Transfer Complex.  

UK PubMed Central (United Kingdom)

The vibronic spectra of strong charge-transfer complexes are often congested or diffuse and therefore difficult to analyze. We present the spectra of the pi-stacked complex perylene-trans-1,2-dichloroethene, which is in the limit of weak charge transfer, the electronic excitation remaining largely confined to the perylene moiety. The complex is formed in a supersonic jet and its S_0 <-> S_1 spectra are investigated by two-color resonant two-photon ionization (2C-R2PI) and fluorescence spectroscopies. Under optimized conditions, vibrationally cold (T_{vib} ~ 9 K) and well resolved spectra are obtained. These are dominated by vibrational progressions in the "hindered-rotation" R_c intermolecular vibration with very low frequencies of 11 cm-1 (S_0) and 13 cm-1 (S_1). The intermolecular T_z stretch and the R_a and R_b bend vibrations are also observed. The normally symmetry-forbidden intramolecular 1a_u "twisting" vibration of perylene also appears, showing that the pi-stacking interaction deforms the perylene moiety, lowering its local symmetry from D_{2h} to D_2. We calculate the structure and vibrations of this complex using six different density functional theory (DFT) methods (CAM-B3LYP, BH\\&HLYP, B97-D3, omegaB97X-D, M06 and M06-2X) and compare the results to those calculated by correlated wave-function methods (SCS-MP2 and SCS-CC2). The structures and vibrational frequencies predicted with the CAM-B3LYP and BH\\&HLYP methods disagree with the other calculations and with experiment. The other four DFT and the ab initio methods all predict a pi-stacked "centered" structure with nearly co-planar perylene and dichloroethene moieties and intermolecular binding energies of D_e=-20.8 to -26.1 kcal/mol. The 0_0^0 band of the S_0\\rightarrow S_1 transition is red-shifted by delta nu= -301 cm-1 relative to that of perylene, implying that the D_e increases by 3.6 kJ/mol or ~15\\% upon electronic excitation. The intermolecular vibrational frequencies are assigned to the calculated R_c, T_z, R_a and R_b vibrations by comparing to the observed/calculated frequencies and S_0\\leftrightarrow S_1 Franck-Condon factors. Of the three DFT methods tested, the hybrid-meta-GGA functional M06-2X shows the best agreement with the experimental electronic transition energies, spectral shifts and vibronic spectra, closely followed by the omegaB97X-D functional, while the M06 functional gives inferior results.

Balmer FA; Ottiger P; Pfaffen C; Leutwyler S

2013-09-01

359

Meson-nuclear interactions at medium energies  

Energy Technology Data Exchange (ETDEWEB)

A brief review of selected directions in medium energy physics is given. Special attention is paid to the propagation of hadrons in the nuclear medium which results in a modification of the free properties of the probe hadron and the nucleus. Such modifications are germane to our understanding of both particles and nuclei. Examples are given involving pion and kaon scattering, absorption and production from nuclei. Some of what has been learned is summarized and some of the hopes for the future are outlined.

Eisenstein, R.A.

1981-01-01

360

Electron-gas plus damped-dispersion model for intermolecular forces: the rare-gas and H2-He, H2-Ne, and H2-Ar potentials  

International Nuclear Information System (INIS)

The modified Gordon-Kim (MGK) electron-gas model for the calculation of the short-range repulsive interactions between closed-shell atoms and molecules is used with a damped-dispersion term of a form suggested by Hepburn et al. to calculate the intermolecular potentials between the rare-gas atoms and H2-He, H2-Ne, and H2-Ar. The damping function for the dispersion energies is found by comparison with the experimental Ar-Ar potential and is then used without change for all other interactions. Except for interactions involving Ne atoms, the results for the atom-atom interactions are uniformly quite good, with an average deviation from experiment in the position of the minimum (neglecting those involving Ne atoms) of only 0.7%. Both the radical V0(r) and anisotropic V2(r) terms of the atom-molecule results are compared with experiment. The calculated V0(r) potentials for He-H2 and Ar-H2 show close agreement with experiment, though the V2 terms are less well determined. All interactions involving Ne atoms are too repulsive. The errors in the potentials involving Ne atoms are attributed to errors in the treatment of the exchange energy in the MGK model. 29 references, 11 figures, 5 tables

1984-09-13

 
 
 
 
361

Empirical proton-neutron interaction energies and nuclear structure  

International Nuclear Information System (INIS)

[en] Empirical proton-neutron (p-n) interaction energies are extracted for all even-even nuclei with well-known binding energies using a simple double difference equation. Three features are disclosed: a systematic decrease of p-n interaction strengths (excepting N=Z nuclei) with increasing A, large interaction strengths for N=Z nuclei, and microstructure in doubly magic and deformed regions. Shell model calculations are used to explain the behavior of N=Z and other nuclei in the sd shell. Arguments based on orbit occupancy are introduced to explain microstructure effects in heavier nuclei and are given quantitative support by simple microscopic Nilsson and Shell Model calculations. The analysis sheds light on the relative roles of monopole and quadrupole components of the p-n interaction in determining nuclear structure. 19 refs., 5 figs

1990-01-01

362

Alleviation of Cosmic Age Problem In Interacting Dark Energy Model  

CERN Multimedia

We investigate the cosmic age problem associated with the old high-$z$ quasar APM 08279 + 5255 and the oldest globular cluster M 107, both being difficult to accommodate in $\\Lambda$CDM model. By evaluating the age of the Universe in a model that has an extremely phantom like form of dark energy (DE), we show that simply introducing the dark energy alone does not remove the problem, and the interaction between dark matter (DM) and DE need to be taken into account. Next, as examples, we consider two interacting DE models. It is found that both these two interacting DE Models can predict a cosmic age much greater than that of $\\Lambda$CDM model at any redshift, and thus substantially alleviate the cosmic age problem. Therefore, the interaction between DM and DE is the crucial factor required to make the predicted cosmic ages consistent with observations.

Wang, Shuang

2008-01-01

363

Thermodynamics of dark energy interacting with dark matter and radiation  

International Nuclear Information System (INIS)

We investigate the validity of the generalized second law of thermodynamics, in the cosmological scenario where dark energy interacts with both dark matter and radiation. Calculating separately the entropy variation for each fluid component and for the apparent horizon itself, we show that the generalized second law is always and generally valid, independently of the specific interaction form, of the fluids equation-of-state parameters and of the background geometry.

2010-01-15

364

Neutral current neutrino-nucleus interactions at high energies  

CERN Multimedia

We present a QCD analysis of the neutral current neutrino-nucleus interaction at the small-x region using the color dipole formalism. This phenomenological approach is quite successful in describing experimental results in deep inelastic ep scattering and charged current neutrino-nucleus interactions at high energies. We present theoretical predictions for the relevant structure functions and the corresponding implications for the total NC neutrino cross section.

Ducati, M B Gay; Machado, M V T

2008-01-01

365

Stress and deformation in soft elastic bodies due to intermolecular forces  

Science.gov (United States)

Intermolecular interaction within one and between two incompressible, soft elastic bodies is studied at a continuous level. We show that the macroscopic effect of the interaction can be characterized by a deformation-dependent Maxwell stress. The divergence of the Maxwell stress gives the body force, while the inner product of it with the outward normal of a body generates the surface traction. Accordingly, we can replace the contribution of intermolecular forces to the deformation and stress in the body by that of either the body force or the surface traction. Both approaches are proved to be equivalent, in the sense that the resulting displacements are the same and the stresses are linked by an exact correspondence relation. If the deformation induced by the interaction is small, the equations are simplified up to the first order of the displacement gradient. Two examples are given as well to illustrate some features of local stress distribution in a body caused by self and other-body interactions.

He, L. H.

2013-06-01

366

Scaling attractors in interacting teleparallel dark energy  

CERN Document Server

It has been proposed recently the existence of a non-minimal coupling between a canonical scalar field (quintessence) and gravity in the framework of teleparallel gravity, motivated by similar constructions in the context of General Relativity. The dynamics of the model, known as teleparallel dark energy, has been further developed, but no scaling attractor has been found. Here we consider a model in which the non-minimal coupling is ruled by a dynamically changing $\\alpha\\equiv f_{,\\phi}/sqrt{f}$, with $f(\\phi)$ an arbitrary function of the scalar field $\\phi$. It is shown that in this case the existence of scaling attractors is possible, which means that the universe will eventually enter these scaling attractors, regardless of the initial conditions. As a consequence, the cosmological coincidence problem could be alleviated without fine-tunings.

Otalora, G

2013-01-01

367

Kaon nucleon interaction at intermediate energies  

International Nuclear Information System (INIS)

The kaon nucleon system in I = 0 and I = 1 states is studied in terms of a model lagrangian containing Yukawa terms and contact terms which represent effective short range forces in both isospin states. We compute all Feynman diagrams contributions up to the fourth order and use the Pade approximants method to construct S matrix elements satisfying unitarity. Using values already determined for the Yukawa coupling constants g sub(N?K) and g sub(N?K) and the well-known value for the scattering length in I = 1, it remains as the only free parameter in the model the strength of the contact term in I = 0. Results are discussed and compared with available experimental data at low and intermediate energies, for K0P ? K+n, K+p ? K+p and K+d ? K0pp processes. (Author).

1980-01-01

368

Density-functional based determination of intermolecular charge transfer properties for large-scale morphologies.  

UK PubMed Central (United Kingdom)

Theoretical studies of charge transport in organic conducting systems pose a unique challenge since they must describe both extremely short-ranged and fast processes (charge tunneling) and extremely long-ranged and slow ones (molecular ordering). The description of the mobility of electrons and holes in the hopping regime relies on the determination of intermolecular hopping rates in large-scale morphologies. Using Marcus theory these rates can be calculated from intermolecular transfer integrals and on-site energies. Here we present a detailed computational study on the accuracy and efficiency of density-functional theory based approaches to the determination of intermolecular transfer integrals. First, it is demonstrated how these can be obtained from quantum-chemistry calculations by forming the expectation value of a dimer Fock operator with frontier orbitals of two neighboring monomers based on a projective approach. We then consider the prototypical example of one pair out of a larger morphology of tris(8-hydroxyquinolinato)aluminium (Alq(3)) and study the influence of computational parameters, e.g. the choice of basis sets, exchange-correlation functional, and convergence criteria, on the calculated transfer integrals. The respective results are compared in order to derive an optimal strategy for future simulations based on the full morphology.

Baumeier B; Kirkpatrick J; Andrienko D

2010-09-01

369

Modeling the formaldehyde-graphene interaction using a formaldehyde-pyrene system.  

Science.gov (United States)

Study of the dynamics of H2CO confined within graphene sheets and sensing of H2CO by graphene require an analytic representation of the intermolecular potential between H2CO and graphene. To develop an intermolecular potential for H2CO interacting with graphene, ab initio calculations were performed at the MP2/MG3S, B97-D/MG3S and LPNO-CEPA/1/CBS levels of theory using H2CO-pyrene as a model. The intermolecular interactions were computed for three different orientations of formaldehyde approaching pyrene for a complete description of the interaction. The interaction energy obtained from the MP2, B97-D and LPNO-CEPA/1 methods were compared with the CCSD(T) method. The LPNO-CEPA/1/CBS method gives the best interaction energies compared to the CCSD(T)/CBS method. The LPNO-CEPA/1/CBS data obtained is fitted to an analytical potential energy function written as the sum of two-body interactions between the C atoms of pyrene and the C, H, O atoms of formaldehyde. The fitted potential energy function represents the ab initio data in excellent agreement for all the orientations considered. The analytical potential was also found to represent very well the interactions for two new orientations not considered in fitting, emphasizing the global nature of the analytic potential. The new potential is also compared with the van der Waals AMBER model. PMID:24026337

Dodda, Leela S; Lourderaj, Upakarasamy

2013-09-25

370

Modeling the formaldehyde-graphene interaction using a formaldehyde-pyrene system.  

UK PubMed Central (United Kingdom)

Study of the dynamics of H2CO confined within graphene sheets and sensing of H2CO by graphene require an analytic representation of the intermolecular potential between H2CO and graphene. To develop an intermolecular potential for H2CO interacting with graphene, ab initio calculations were performed at the MP2/MG3S, B97-D/MG3S and LPNO-CEPA/1/CBS levels of theory using H2CO-pyrene as a model. The intermolecular interactions were computed for three different orientations of formaldehyde approaching pyrene for a complete description of the interaction. The interaction energy obtained from the MP2, B97-D and LPNO-CEPA/1 methods were compared with the CCSD(T) method. The LPNO-CEPA/1/CBS method gives the best interaction energies compared to the CCSD(T)/CBS method. The LPNO-CEPA/1/CBS data obtained is fitted to an analytical potential energy function written as the sum of two-body interactions between the C atoms of pyrene and the C, H, O atoms of formaldehyde. The fitted potential energy function represents the ab initio data in excellent agreement for all the orientations considered. The analytical potential was also found to represent very well the interactions for two new orientations not considered in fitting, emphasizing the global nature of the analytic potential. The new potential is also compared with the van der Waals AMBER model.

Dodda LS; Lourderaj U

2013-09-01

371

Interactions of Policies for Renewable Energy and Climate  

Energy Technology Data Exchange (ETDEWEB)

This paper explores the relationships between climate policy and renewable energy policy instruments. It shows that, even where CO2 emissions are duly priced, specific incentives for supporting the early deployment of renewable energy technologies are justified by the steep learning curves of nascent technologies. This early investment reduces costs in the longer term and makes renewable energy affordable when it needs to be deployed on a very large scale to fully contribute to climate change mitigation and energy security. The paper also reveals other noteworthy interaction effects of climate policy and renewable policy instruments on the wholesale electricity prices in deregulated markets, which open new areas for future research.

NONE

2011-07-01

372

Interaction between Tachyon and Hessence (or Hantom) dark energies  

CERN Document Server

In this paper, we have considered that the universe is filled with tachyon, hessence (or hantom) dark energies. Subsequently we have investigated the interactions between tachyon and hessence (hantom) dark energies and calculated the potentials considering the power law form of the scale factor. It has been revealed that the tachyonic potential always decreases and hessence (or hantom) potential increases with corresponding fields. Furthermore, we have considered a correspondence between the hessence (or hantom) dark energy density and new variable modified Chaplygin gas energy density. From this, we have found the expressions of the arbitrary positive constants B0 and C of new variable modified Chaplygin gas.

Chattopadhyay, Surajit

2010-01-01

373

Flat Cosmology with Interacting Matter and Dark Energies  

CERN Document Server

Three models of a flat universe of interacting matter and dark energies with different low-redshift parameterizations of the dark energy equation of state are considered. The dark energy is assumed to vary with time like the trace of the energy-momentum tensor of cosmic matter. In the radiation-dominated era the models reduce to standard cosmology. In the matter-dominated era they are, for often quoted values of the cosmological parameters, consistent with data from supernovae Ia searches and with the data of Gurvits et al.(1999) for angular sizes of ultra compact radio sources.

Abdel-Rahman, A M M; Riad, Ihab F.

2005-01-01

374

Neutral current neutrino-nucleus interactions at high energies  

International Nuclear Information System (INIS)

We present a QCD analysis of the neutral current (NC) neutrino-nucleus interaction at the small-x region using the color dipole formalism. This phenomenological approach is quite successful in describing experimental results in deep inelastic ep scattering and charged current neutrino-nucleus interactions at high energies. We present theoretical predictions for the relevant structure functions and the corresponding implications for the total NC neutrino cross section. It is shown that at small x, the NC boson-nucleon cross section should exhibit the geometric scaling property that has important consequences for ultrahigh energy neutrino phenomenology.

2009-04-01

375

Transition of the dark energy equation of state in an interacting holographic dark energy model  

International Nuclear Information System (INIS)

A model of holographic dark energy with an interaction with matter fields has been investigated. Choosing the future event horizon as an IR cutoff, we have shown that the ratio of energy densities can vary with time. With the interaction between the two different constituents of the universe, we observed the evolution of the universe, from early deceleration to late time acceleration. In addition, we have found that such an interacting dark energy model can accommodate a transition of the dark energy from a normal state where wD>-1 to wD

2005-09-29

376

The interaction of He with vibrating HCN: Potential energy surface, bound states, and rotationally inelastic cross sections  

Science.gov (United States)

A four-dimensional potential energy surface representing the interaction between He and hydrogen cyanide (HCN) subjected to bending vibrational motion is presented. Ab initiocalculations were carried out at the coupled-cluster level with single and double excitations and a perturbative treatment of triple excitations, using a quadruple-zeta basis set and mid-bond functions. The global minimum is found in the linear He-HCN configuration with the H atom pointing towards helium at the intermolecular separation of 7.94 a0. The corresponding well depth is 30.35 cm-1. First, the quality of the new potential has been tested by performing two comparisons with previous theoretical and experimental works. (i) The rovibrational energy levels of the He-HCN complex for a rigid linear configuration of the HCN molecule have been calculated. The dissociation energy is 8.99 cm-1, which is slightly smaller than the semi-empirical value of 9.42 cm-1. The transitions frequencies are found to be in good agreement with the experimental data. (ii) We performed close coupling calculations of the rotational de-excitation of rigid linear HCN in collision with He and observed a close similarity with the theoretical data published in a recent study. Second, the effects of the vibrational bending of HCN have been investigated, both for the bound levels of the He-HCN system and for the rotationally inelastic cross sections. This was performed with an approximate method using the average of the interaction potential over the vibrational bending wavefunction. While this improves slightly the comparison of calculated transitions frequencies with experiment, the cross sections remain very close to those obtained with rigid linear HCN.

Denis-Alpizar, Otoniel; Stoecklin, Thierry; Halvick, Philippe; Dubernet, Marie-Lise

2013-07-01

377

The interaction of He with vibrating HCN: potential energy surface, bound states, and rotationally inelastic cross sections.  

UK PubMed Central (United Kingdom)

A four-dimensional potential energy surface representing the interaction between He and hydrogen cyanide (HCN) subjected to bending vibrational motion is presented. Ab initio calculations were carried out at the coupled-cluster level with single and double excitations and a perturbative treatment of triple excitations, using a quadruple-zeta basis set and mid-bond functions. The global minimum is found in the linear He-HCN configuration with the H atom pointing towards helium at the intermolecular separation of 7.94 a0. The corresponding well depth is 30.35 cm(-1). First, the quality of the new potential has been tested by performing two comparisons with previous theoretical and experimental works. (i) The rovibrational energy levels of the He-HCN complex for a rigid linear configuration of the HCN molecule have been calculated. The dissociation energy is 8.99 cm(-1), which is slightly smaller than the semi-empirical value of 9.42 cm(-1). The transitions frequencies are found to be in good agreement with the experimental data. (ii) We performed close coupling calculations of the rotational de-excitation of rigid linear HCN in collision with He and observed a close similarity with the theoretical data published in a recent study. Second, the effects of the vibrational bending of HCN have been investigated, both for the bound levels of the He-HCN system and for the rotationally inelastic cross sections. This was performed with an approximate method using the average of the interaction potential over the vibrational bending wavefunction. While this improves slightly the comparison of calculated transitions frequencies with experiment, the cross sections remain very close to those obtained with rigid linear HCN.

Denis-Alpizar O; Stoecklin T; Halvick P; Dubernet ML

2013-07-01

378

Photoinduced intra- and intermolecular electron transfer in solutions and in solid organized molecular assemblies.  

UK PubMed Central (United Kingdom)

The present paper highlights results of a systematic study of photoinduced electron transfer, where the fundamental aspects of the photochemistry occurring in solutions and in artificially or self-assembled molecular systems are combined and compared. In photochemical electron transfer (ET) reactions in solutions the electron donor, D, and acceptor, A, have to be or to diffuse to a short distance, which requires a high concentration of quencher molecules and/or long lifetimes of the excited donor or acceptor, which cannot always be arranged. The problem can partly be avoided by linking the donor and acceptor moieties covalently by a single bond, molecular chain or chains, or rigid bridge, forming D-A dyads. The covalent combination of porphyrin or phthalocyanine donors with an efficient electron acceptor, e.g. fullerene, has a two-fold effect on the electron transfer properties. Firstly, the electronic systems of the D-A pair result in a formation of an exciplex intermediate upon excitation both in solutions and in solid phases. The formation of the exciplex accelerates the ET rate, which was found to be as fast as >10(12) s(-1). Secondly, the total reorganization energy can be as small as 0.3 eV, even in polar solvents, which allows nanosecond lifetimes for the charge separated (CS) state. Molecular assemblies can form solid heterogeneous, but organized systems, e.g. molecular layers. This results in more complex charge separation and recombination dynamics. A distinct feature of the ET in organized assemblies is intermolecular interactions, which open a possibility for a charge migration both in the acceptor and in the donor layers, after the primary intramolecular exciplex formation and charge separation in the D-A dyad. The intramolecular ET is fast (35 ps) and efficient, but the formed interlayer CS states have lifetimes in microsecond or even second time domain. This is an important result considering possible applications.

Lemmetyinen H; Tkachenko NV; Efimov A; Niemi M

2011-01-01

379

Photoinduced intra- and intermolecular electron transfer in solutions and in solid organized molecular assemblies.  

Science.gov (United States)

The present paper highlights results of a systematic study of photoinduced electron transfer, where the fundamental aspects of the photochemistry occurring in solutions and in artificially or self-assembled molecular systems are combined and compared. In photochemical electron transfer (ET) reactions in solutions the electron donor, D, and acceptor, A, have to be or to diffuse to a short distance, which requires a high concentration of quencher molecules and/or long lifetimes of the excited donor or acceptor, which cannot always be arranged. The problem can partly be avoided by linking the donor and acceptor moieties covalently by a single bond, molecular chain or chains, or rigid bridge, forming D-A dyads. The covalent combination of porphyrin or phthalocyanine donors with an efficient electron acceptor, e.g. fullerene, has a two-fold effect on the electron transfer properties. Firstly, the electronic systems of the D-A pair result in a formation of an exciplex intermediate upon excitation both in solutions and in solid phases. The formation of the exciplex accelerates the ET rate, which was found to be as fast as >10(12) s(-1). Secondly, the total reorganization energy can be as small as 0.3 eV, even in polar solvents, which allows nanosecond lifetimes for the charge separated (CS) state. Molecular assemblies can form solid heterogeneous, but organized systems, e.g. molecular layers. This results in more complex charge separation and recombination dynamics. A distinct feature of the ET in organized assemblies is intermolecular interactions, which open a possibility for a charge migration both in the acceptor and in the donor layers, after the primary intramolecular exciplex formation and charge separation in the D-A dyad. The intramolecular ET is fast (35 ps) and efficient, but the formed interlayer CS states have lifetimes in microsecond or even second time domain. This is an important result considering possible applications. PMID:21031207

Lemmetyinen, Helge; Tkachenko, Nikolai V; Efimov, Alexander; Niemi, Marja

2010-10-29

380

Transition of the dark energy equation of state in an interacting holographic dark energy model  

Energy Technology Data Exchange (ETDEWEB)

A model of holographic dark energy with an interaction with matter fields has been investigated. Choosing the future event horizon as an IR cutoff, we have shown that the ratio of energy densities can vary with time. With the interaction between the two different constituents of the universe, we observed the evolution of the universe, from early deceleration to late time acceleration. In addition, we have found that such an interacting dark energy model can accommodate a transition of the dark energy from a normal state where w{sub D}>-1 to w{sub D}<-1 phantom regimes. Implications of interacting dark energy model for the observation of dark energy transition has been discussed.

Wang Bin [Department of Physics, Fudan University, Shanghai 200433 (China)]. E-mail: wangb@fudan.edu.cn; Gong Yungui [College of Electronic Engineering, Chongqing University of Posts and Telecommunications, Chongqing 400065 (China)]. E-mail: gongyg@cqupt.edu.cn; Abdalla, Elcio [Instituto de Fisica, Universidade de Sao Paulo, C.P.66.318, CEP 05315-970, Sao Paulo (Brazil)]. E-mail: eabdalla@fma.if.usp.br

2005-09-29

 
 
 
 
381

Interaction of hypertritons with nuclei at intermediate and high energies  

International Nuclear Information System (INIS)

The integrated cross sections for the diffractive interaction of incident hypertritons with absorbing target nuclei and the cross sections for the Coulomb dissociation of hypertritons in the field of these nuclei are calculated as functions of the projectile kinetic energy, the hypertriton binding energy with respect to breakup into a ? hyperon and a deuteron, and the mass and charge numbers of the target nucleus. A general analysis of the cross sections is performed, and asymptotic formulas are obtained for them explicitly.

1997-01-01

382

Effective dark energy equation of state in interacting dark energy models  

Energy Technology Data Exchange (ETDEWEB)

In models where dark matter and dark energy interact non-minimally, the total amount of matter in a fixed comoving volume may vary from the time of recombination to the present time due to energy transfer between the two components. This implies that, in interacting dark energy models, the fractional matter density estimated using the cosmic microwave background assuming no interaction between dark matter and dark energy will in general be shifted with respect to its true value. This may result in an incorrect determination of the equation of state of dark energy if the interaction between dark matter and dark energy is not properly accounted for, even if the evolution of the Hubble parameter as a function of redshift is known with arbitrary precision. In this Letter we find an exact expression, as well as a simple analytical approximation, for the evolution of the effective equation of state of dark energy, assuming that the energy transfer rate between dark matter and dark energy is described by a simple two-parameter model. We also provide analytical examples where non-phantom interacting dark energy models mimic the background evolution and primary cosmic microwave background anisotropies of phantom dark energy models.

Avelino, P.P., E-mail: ppavelin@fc.up.pt [Centro de Astrofisica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Departamento de Fisica e Astronomia da Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Silva, H.M.R. da, E-mail: hilberto.silva@gmail.com [Departamento de Fisica e Astronomia da Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal)

2012-07-24

383

Wormhole solutions supported by interacting dark matter and dark energy  

CERN Multimedia

We show that the presence of a nonminimal interaction between dark matter and dark energy may lead to a violation of the null energy condition and to the formation of a configuration with nontrivial topology (a wormhole). In this it is assumed that both dark matter and dark energy satisfy the null energy condition, a violation of which takes place only in the inner high-density regions of the configuration. This is achieved by assuming that, in a high-density environment, a nonminimal coupling function changes its sign in comparison with the case where dark matter and dark energy have relatively low densities which are typical for a cosmological background. For this case, we find regular static, spherically symmetric solutions describing wormholes supported by dark matter nonminimally coupled to dark energy in the form of a quintessence scalar field.

Folomeev, Vladimir

2013-01-01

384

Intermolecular proton transfer in anionic complexes of uracil with alcohols  

Energy Technology Data Exchange (ETDEWEB)

A series of eighteen alcohols (ROH) has been designed with an enthalpy of deprotonation (HDP) in a range of 13.8-16.3 eV. The effects of excess electron attachment to the binary alcohol-uracil (ROH…U) complexes have been studied at the density functional level with a B3LYP exchange-correlation functional and at the second order Møller-Plesset perturbation theory level. The photoelectron spectra of anionic complexes of uracil with three alcohols (ethanol, 2,2,3,3,3-pentafluoroethanol and 1,1,1,3,3,3-hexafluoro-2-propanol) have been measured with 2.54 eV photons. For ROHs with deprotonation enthalpies larger than 14.8 eV only the ROH...U- minimum exists on the potential energy surface of the anionic complex. For alcohols with deprotonation enthalpies in a range of 14.3-14.8 eV two minima might exist on the anionic potential energy surface, which correspond to the RO-…HU. and ROH...U- structures. For ROHs with deprotonation enthalpies smaller than 14.3 eV, the excess electron attachment to the ROH…U complex always induces a barrier-free proton transfer from the hydroxyl group of ROH to the O8 atom of U, with the product being RO-…HU.. A driving force for the intermolecular proton transfer is to stabilize the excess negative charge localized on a ?* orbital of uracil. Therefore, these complexes with proton transferred to the anionic uracil are characterized by larger values of electron vertical detachment energy (VDE). The values of VDE for anionic complexes span a range from 1.0 to 2.3 eV and roughly correlate with the acidity of alcohols. However, there is a gap of ~0.5 eV in the values of VDE, which separates the two families, ROH...U- and RO-…HU., of anionic complexes. The energy of stabilization for the anionic complexes spans a range from 0.6 to 1.7 eV and roughly correlates with the acidity of alcohols. The measured photoelectron spectra are in good agreement with the theoretical predictions.

Haranczyk, Maciej; Rak, Janusz; Gutowski, Maciej S.; Radisic, Dunja; Stokes, Sarah T.; Bowen, Kit H.

2005-07-14

385

Intermolecular proton transfer in anionic complexes of uracil with alcohols  

International Nuclear Information System (INIS)

A series of eighteen alcohols (ROH) has been designed with an enthalpy of deprotonation (HDP) in a range of 13.8-16.3 eV. The effects of excess electron attachment to the binary alcohol-uracil (ROH...U) complexes have been studied at the density functional level with a B3LYP exchange-correlation functional and at the second order Moeller-Plesset perturbation theory level. The photoelectron spectra of anionic complexes of uracil with three alcohols (ethanol, 2,2,3,3,3-pentafluoroethanol and 1,1,1,3,3,3-hexafluoro-2-propanol) have been measured with 2.54 eV photons. For ROHs with deprotonation enthalpies larger than 14.8 eV only the ROH...U- minimum exists on the potential energy surface of the anionic complex. For alcohols with deprotonation enthalpies in a range of 14.3-14.8 eV two minima might exist on the anionic potential energy surface, which correspond to the RO-...HU. and ROH...U- structures. For ROHs with deprotonation enthalpies smaller than 14.3 eV, the excess electron attachment to the ROH...U complex always induces a barrier-free proton transfer from the hydroxyl group of ROH to the O8 atom of U, with the product being RO-...HU.. A driving force for the intermolecular proton transfer is to stabilize the excess negative charge localized on a orbital of uracil. Therefore, these complexes with proton transferred to the anionic uracil are characterized by larger values of electron vertical detachment energy (VDE). The values of VDE for anionic complexes span a range from 1.0 to 2.3 eV and roughly correlate with the acidity of alcohols. However, there is a gap of ?0.5 eV in the values of VDE, which separates the two families, ROH...U- and RO-...HU., of anionic complexes. The energy of stabilization for the anionic complexes spans a range from 0.6 to 1.7 eV and roughly correlates with the acidity of alcohols. The measured photoelectron spectra are in good agreement with the theoretical predictions

2005-07-14

386

Integrated Sachs-Wolfe effect in interacting dark energy models  

International Nuclear Information System (INIS)

Models with dark energy decaying into dark matter have been proposed in cosmology to solve the coincidence problem. We study the effect of such coupling on the cosmic microwave background temperature anisotropies. The interaction changes the rate of evolution of the metric potentials and the growth rate of matter density perturbations and modifies the integrated Sachs-Wolfe component of cosmic microwave background temperature anisotropies, enhancing the effect. Cross correlation of galaxy catalogs with cosmic microwave background maps provides a model-independent test to constrain the interaction. We particularize our analysis for a specific interacting model and show that galaxy catalogs with median redshifts zm=0.1-0.9 can rule out models with an interaction parameter strength of c2?0.1 better than 99.95% confidence level. Values of c2?0.01 are compatible with the data and may account for the possible discrepancy between the fraction of dark energy derived from Wilkinson microwave anisotropy probe 3 yr data and the fraction obtained from the integrated Sachs-Wolfe effect. Measuring the fraction of dark energy by these two methods could provide evidence of an interaction

2008-05-15

387

Hadronic interactions for high energy cosmic ray air showers  

Energy Technology Data Exchange (ETDEWEB)

Understanding hadronic interactions at high energies represents a very important ingredient for modeling high energy cosmic ray air showers. In this paper, a new approach to simulate hadronic interactions is presented, including hadron-hadron, hadron-nucleus, and nucleus-nucleus scattering. Such collisions are very complex, being composed of many components, and therefore some strategy is needed to construct a reliable model. The central point of our approach is the hypothesis, that the behavior of high energy interactions is universal (universality hypothesis). A model for hadronic interactions is constructed in a modular fashion. The individual modules, based on the universality hypothesis, are identified as building blocks for more elementary interactions (like e{sup +}e{sup -}, lepton-proton), and can therefore be studied in a much simpler context. With these building blocks under control, a quite reliable model is proposed for nucleus-nucleus, hadron-nucleus and hadron-hadron scattering, providing in particular very useful tests for the complicated numerical procedures using Monte Carlo techniques. (K.A.) 5 refs.

Drescher, H.J.; Hladik, M.; Werner, K. [Centre National de la Recherche Scientifique, 44 - Nantes (France). Lab. de Physique Subatomique et des Technologies Associees; Ostapchenko, S. [Moscow State Univ. (Russian Federation). Inst. of Nuclear Physics]|[Centre National de la Recherche Scientifique, 44 - Nantes (France). Lab. de Physique Subatomique et des Technologies Associees

1998-12-31

388

Experimental studies of pion-nucleus interactions at intermediate energies  

International Nuclear Information System (INIS)

This report summarizes the work on experimental research in intermediate energy nuclear physics carried out at New Mexico State University in 1991 under a great from the US Department of Energy. Most of these studies have involved investigations of various pion-nucleus interactions. The work has been carried out both with the LAMPF accelerator at the Los Alamos National Laboratory and with the cyclotron at the Paul Scherrer Institute (PSI) near Zurich, Switzerland. Part of the experimental work involves measurements of new data on double-charge-exchange scattering, using facilities at LAMPF which we helped modify, and on pion absorption, using a new detector system at PSI that covers nearly the full solid-angle region which we helped construct. Other work involved preparation for future experiments using polarized nuclear targets and a new high-resolution spectrometer system for detecting ?0 mesons. We also presented several proposals for works to be done in future years, involving studies related to pi-mesonic atoms, fundamental pion-nucleon interactions, studies of the difference between charged and neutral pion interactions with the nucleon, studies of the isospin structure of pion-nucleus interactions, and pion scattering from polarized 3He targets. This work is aimed at improving our understanding of the pion-nucleon interaction, of the pion-nucleus interaction mechanism, and of nuclear structure

1991-01-01

389

Experimental studies of pion-nucleus interactions at intermediate energies  

Energy Technology Data Exchange (ETDEWEB)

This report summarizes the work on experimental research in intermediate energy nuclear physics carried out at New Mexico State University in 1991 under a great from the US Department of Energy. Most of these studies have involved investigations of various pion-nucleus interactions. The work has been carried out both with the LAMPF accelerator at the Los Alamos National Laboratory and with the cyclotron at the Paul Scherrer Institute (PSI) near Zurich, Switzerland. Part of the experimental work involves measurements of new data on double-charge-exchange scattering, using facilities at LAMPF which we helped modify, and on pion absorption, using a new detector system at PSI that covers nearly the full solid-angle region which we helped construct. Other work involved preparation for future experiments using polarized nuclear targets and a new high-resolution spectrometer system for detecting {pi}{sup 0} mesons. We also presented several proposals for works to be done in future years, involving studies related to pi-mesonic atoms, fundamental pion-nucleon interactions, studies of the difference between charged and neutral pion interactions with the nucleon, studies of the isospin structure of pion-nucleus interactions, and pion scattering from polarized {sup 3}He targets. This work is aimed at improving our understanding of the pion-nucleon interaction, of the pion-nucleus interaction mechanism, and of nuclear structure.

1991-12-31

390

Open beauty production in high energy. pi. /sup -/-tungsten interactions  

Energy Technology Data Exchange (ETDEWEB)

We present a study of Banti B meson pair production in ..pi../sup -/-tungsten interactions at 140, 194 and 286 GeV incident pion energy. At 286 GeV, where we have the best statistics, we find a model-dependent Banti B production cross-section sigma/sub B/anti B = 14(+17-6)nbnucleon. (orig.)

Bordalo, P.; Busson, P.; Kluberg, L.; Romana, A.; Salmeron, R.; Vallee, C.; Blaising, J.J.; Degre, A.; Juillot, P.; Morand, R.

1988-06-01

391

MINT - A Simple Model for Low Energy Hadronic Interactions  

CERN Multimedia

The bulk of inelastic hadronic interactions is characterized by longitudinal phase space and exponentially damped transverse momentum spectra. A simple model with only a single adjustable parameter is presented, making it a very convenient tool for systematic studies, which gives a surprisingly good description of pA-collisions at 920 GeV beam energy.

Schmelling, M

2005-01-01

392

A new interpretation of high energy proton-nucleus interactions  

International Nuclear Information System (INIS)

The correlation between the properties of the heavy prong and the shower particle distributions from high energy proton-nucleus interactions are considered in a phenomenological model in which the number of collisions between the impinging proton and the nucleons inside the nucleus is the major parameter. (Auth.)

1975-08-15

393

An analytical potential energy function to model protonated peptide soft-landing experiments. The CH3NH3+/CH4 interactions.  

UK PubMed Central (United Kingdom)

To model soft-landing of peptide ions on surfaces, it is important to have accurate intermolecular potentials between these ions and surfaces. As part of this goal, ab initio calculations at the MP2/aug-cc-pVTZ level of theory, with basis set superposition error (BSSE) corrections, were performed to determine both the long-range attractive and short-range repulsive potentials for CH(4) interacting with the -NH(3)(+) group of CH(3)NH(3)(+). Potential energy curves for four different orientations between CH(4) and CH(3)NH(3)(+) were determined from the calculations to obtain accurate descriptions of the interactions between the atoms of CH(4) and those of -NH(3)(+). A universal analytic function was not found that could accurately represent both the long-range and short-range potentials for collision energies as high as those obtained in surface-induced-dissociation (SID) experiments. Instead, long-range and short-range analytic potentials were developed separately, by simultaneously fitting the four ab initio potential energy curves with a sum of two-body interactions between the atoms of CH(4) and -NH(3)(+), and then connecting these long-range and short-range two-body potentials with switching functions. Following a previous work [J. Am. Chem. Soc., 2002, 124, 1524], these two-body potentials may be used to describe the interactions of the N and H atoms of the -NH(3)(+) group of a protonated peptide ion with the H and C atoms of alkane-type surfaces such as alkyl thiol self-assembled monolayers and H-terminated diamond. Accurate short-range and long-range potentials are imperative to model protonated peptide ion soft-landing experiments. The former controls the collision energy transfer, whereas the latter describes the binding of the ion to the surface. A comparison of the ab initio potential energy curves for CH(3)NH(3)(+)/CH(4) with those for NH(4)(+)/CH(4) shows that they give nearly identical two-body interactions between the atoms of -NH(3)(+) and those of CH(4), showing that the smaller NH(4)(+)/CH(4) system may be used to obtain the two-body potentials. A comparison of the four ab initio potential energy curves reported here for CH(3)NH(3)(+)/CH(4), with those given by the AMBER and CHARMM molecular mechanical potentials, show that these latter potentials "roughly" approximate the long-range attractions, but are grossly in error for the short-range repulsions. The work reported here illustrates that high-level ab initio calculations of intermolecular potentials between small model molecules may be used to develop accurate analytical intermolecular potentials between peptide ions and surfaces.

Deb B; Hu W; Song K; Hase WL

2008-08-01