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High-resolution (600 MHz) 1H and 13C chemical shift and 2D HETCOR NMR spectra of [60]PCBM were recorded. Resonances from every carbon atom of the ester, phenyl and cyclo-fullerenyl groups, were fully accounted. Assignments of the fullerene cyclopropa-ring, and all phenyl and ester carbons to their respective resonances were based on a HETCOR 2D NMR spectrum. Remaining fullerene assignments were made to a high level of confidence with the aid of an ωB97X hybrid HF/DFT simulation of the 13C NMR spectrum employing a triple zeta Dunning-type basis set. The best result was obtained with the range-separation parameter ω set effectively to zero. This indicates that the fraction of HF in the HF/DFT hybrid at very short range is the dominant factor in achieving good NMR results, that ωB97X with its 15.77% HF fraction at rij = 0 seems very well suited, and that allowing the HF fraction to increase with range is not particularly beneficial. The resulting spectrum had a remarkable qualitative agreement with experiment with a very low mean absolute error for fullerene carbons of 0.09 ppm, which was considerably lower than the 0.28 ppm of the more commonly used B3LYP/6-31G(d,p) method.

We discuss how the use of the conventional Lorentz–Bertholet mixing rules for the Lennard–Jones potentials for water and methane in simulations of their mixture in the methane hydrate clathrates un...

The many-body polarization energy is the major source of non-additivity in strongly polar systems such as water. This non-additivity is often considerable and must be included, if only in an average manner, to correctly describe the physical properties of the system. Models for the polarization energy are usually parameterized using experimental data, or theoretical estimates of the many-body effects. Here we show how many-body polarization models can be developed for water complexes using data for the monomer and dimer only using ideas recently developed in the field of intermolecular perturbation theory and state-of-the-art approaches for calculating distributed molecular properties based on the iterated stockholder atoms (ISA) algorithm. We show how these models can be calculated, and validate their accuracy in describing the many-body non-additive energies of a range of water clusters. We further investigate their sensitivity to the details of the polarization damping models used. We show how our very best polarization models yield many-body energies that agree with those computed with coupled-cluster methods, but at a fraction of the computational cost., Comment: 21 pages, 19 figures, SI

We report a study of the absorption of CO2 into a number of zinc imidazolate framework structures, and subsequent desorption, using the molecular dynamics simulation method with force fields partly developed by ourselves. The simulations primarily give results concerning the mechanism of CO2 absorption under conditions likely to be found in industrial waste gas streams. In particular we compare the rate of uptake of CO2 for different ZIFs. We also show that it is possible to observe desorption by reduced pressure and high temperature. These characteristics confirm that ZIFs might be suitable for CO2 absorption within an industrial capture and sequestration process.

Photochemical reactions are essential to a large number of important industrial and biological processes. A method for monitoring photochemical reaction kinetics and the dynamics of molecular excitations with spatial resolution within the active molecule would allow a rigorous exploration of the pathway and mechanism of photophysical and photochemical processes. Here we demonstrate that laser-excited muon pump-probe spin spectroscopy (photo-μSR) can temporally and spatially map these processes with a spatial resolution at the single-carbon level in a molecule with a pentacene backbone. The observed time-dependent light-induced changes of an avoided level crossing resonance demonstrate that the photochemical reactivity of a specific carbon atom is modified as a result of the presence of the excited state wavefunction. This demonstrates the sensitivity and potential of this technique in probing molecular excitations and photochemistry.

We report the results of a series of molecular dynamics simulations on a number of zinc zeolitic imidazolate framework (ZIF) structures together with some lattice dynamics calculations on ZIF-4, providing information about the flexibilities of these structures. The simulations have used a force field we developed based on ab initio calculations of clusters of ligands and metal cations. We have shown that there are instabilities of the structures of some ZIF structures at low temperatures and high pressures. A rigidity analysis based on the Rigid Unit Mode model shows considerable degree of network flexibility, including a significant elastic flexibility.

In the effective fragment potential (EFP) method the Coulomb potential is represented using a set of multipole moments generated by the distributed multipole analysis (DMA) method. Misquitta, Stone, and Fazeli recently developed a basis space-iterated stockholder atom (BS-ISA) method to generate multipole moments. This study assesses the accuracy of the EFP interaction energies using sets of multipole moments generated from the BS-ISA method, and from several versions of the DMA method (such as analytic and numeric grid-based), with varying basis sets. Both methods lead to reasonable results, although using certain implementations of the DMA method can result in large errors. With respect to the CCSD(T)/CBS interaction energies, the mean unsigned error (MUE) of the EFP method for the S22 data set using BS-ISA-generated multipole moments and DMA-generated multipole moments (using a small basis set and the analytic DMA procedure) is 0.78 and 0.72 kcal/mol, respectively. The MUE accuracy is on the same order as MP2 and SCS-MP2. The MUEs are lower than in a previous study benchmarking the EFP method without the EFP charge transfer term, demonstrating that the charge transfer term increases the accuracy of the EFP method. Regardless of the multipole moment method used, it is likely that much of the error is due to an insufficient short-range electrostatic term (i.e., charge penetration term), as shown by comparisons with symmetry-adapted perturbation theory.

The sixth blind test of organic crystal structure prediction (CSP) methods has been held, with five target systems: a small nearly rigid molecule, a polymorphic former drug candidate, a chloride salt hydrate, a co-crystal and a bulky flexible molecule. This blind test has seen substantial growth in the number of participants, with the broad range of prediction methods giving a unique insight into the state of the art in the field. Significant progress has been seen in treating flexible molecules, usage of hierarchical approaches to ranking structures, the application of density-functional approximations, and the establishment of new workflows and `best practices´ for performing CSP calculations. All of the targets, apart from a single potentially disordered Z?? = 2 polymorph of the drug candidate, were predicted by at least one submission. Despite many remaining challenges, it is clear that CSP methods are becoming more applicable to a wider range of real systems, including salts, hydrates and larger flexible molecules. The results also highlight the potential for CSP calculations to complement and augment experimental studies of organic solid forms. Fil: Reilly, Anthony M.. Cambridge Crystallographic Data Centre; Fil: Cooper, Richard I.. Chemistry Research Laboratory; Fil: Adjiman, Claire S.. Imperial College London; Reino Unido Fil: Bhattacharya, Saswata. Fritz Haber Institute Of The Max Planck Society; Fil: Boese, A. Daniel. Karl-franzens-universitat Graz; Austria Fil: Brandenburg, Jan Gerit. Colegio Universitario de Londres; Reino Unido. Universitat Bonn; Alemania Fil: Bygrave, Peter J.. University of Southampton; Reino Unido Fil: Bylsma, Rita. Radboud Universiteit Nijmegen; Países Bajos Fil: Campbell, Josh E.. University of Southampton; Reino Unido Fil: Car, Roberto. University of Princeton; Estados Unidos Fil: Case, David H.. University of Southampton; Reino Unido Fil: Chadha, Renu. University Institute Of Pharmaceutical Sciences India; India Fil: Cole, Jason C.. Cambridge Crystallographic Data Centre; Fil: Cosburn, Katherine. University of Tulane; Estados Unidos. University of Toronto; Canadá Fil: Cuppen, Herma M.. Radboud Universiteit Nijmegen; Países Bajos Fil: Curtis, Farren. University of Tulane; Estados Unidos. University of Carnegie Mellon; Estados Unidos Fil: Day, Graeme M.. University of Southampton; Reino Unido Fil: DiStasio, Robert A.. University of Princeton; Estados Unidos. Cornell University; Estados Unidos Fil: Dzyabchenko, Alexander. Karpov Institute Of Physical Chemistry; Fil: Van Eijck, Bouke P.. University of Utrecht; Países Bajos. Utrecht University; Países Bajos Fil: Elking, Dennis M.. Openeye Scientific Software, Inc; Fil: Van Den Ende, Joost A.. Radboud Universiteit Nijmegen; Países Bajos Fil: Facelli, Julio C.. University of Utah; Estados Unidos Fil: Ferraro, Marta B.. Universidad de Buenos Aires; Argentina Fil: Fusti-Molnar, Laszlo. Openeye Scientific Software, Inc; Fil: Gatsiou, Christina-Anna. Imperial College London; Reino Unido Fil: Gee, Thomas S.. University of Southampton; Reino Unido Fil: De Gelder, René. Radboud Universiteit Nijmegen; Países Bajos Fil: Ghiringhelli, Luca M.. Fritz Haber Institute Of The Max Planck Society; Fil: Goto, Hitoshi. Toyohashi University Of Technology; Fil: Grimme, Stefan. Universitat Bonn; Alemania Fil: Guo, Rui. Colegio Universitario de Londres; Reino Unido Fil: Hofmann, Detlef W. M.. Flexcryst; . Polaris; Fil: Hoja, Johannes. Fritz Haber Institute Of The Max Planck Society; Fil: Hylton, Rebecca K.. Colegio Universitario de Londres; Reino Unido Fil: Iuzzolino, Luca. Colegio Universitario de Londres; Reino Unido Fil: Jankiewicz, Wojciech. University Of Silesia In Katowice; Fil: De Jong, Daniël T.. Radboud Universiteit Nijmegen; Países Bajos Fil: Kendrick, John. University Of Bradford; Fil: De Klerk, Niek J. J.. Radboud Universiteit Nijmegen; Países Bajos Fil: Ko, Hsin-Yu. University of Princeton; Estados Unidos Fil: Kuleshova, Liudmila N.. Flexcryst; Fil: Li, Xiayue. University of Tulane; Estados Unidos. Argonne National Laboratory; Estados Unidos Fil: Lohani, Sanjaya. University of Tulane; Estados Unidos Fil: Leusen, Frank J. J.. University Of Bradford; Fil: Lund, Albert M.. University of Utah; Estados Unidos. Openeye Scientific Software, Inc; Fil: Lv, Jian. Jilin University; China Fil: Ma, Yanming. Jilin University; China Fil: Marom, Noa. University of Carnegie Mellon; Estados Unidos. University of Tulane; Estados Unidos Fil: Masunov, Artëm E.. University Of Central Florida; . National Research Nuclear University Mephi; Fil: McCabe, Patrick. Cambridge Crystallographic Data Centre; Fil: McMahon, David P.. University of Southampton; Reino Unido Fil: Meekes, Hugo. Radboud Universiteit Nijmegen; Países Bajos Fil: Metz, Michael P.. University Of Delaware; Fil: Misquitta, Alston J.. Queen Mary, University Of London; Fil: Mohamed, Sharmarke. Khalifa University Of Science And Technology; Fil: Monserrat, Bartomeu. Rutgers, The State University Of New Jersey; . University of Cambridge; Estados Unidos Fil: Needs, Richard J.. University of Cambridge; Estados Unidos Fil: Neumann, Marcus A.. No especifica; Fil: Nyman, Jonas. University of Southampton; Reino Unido Fil: Obata, Shigeaki. Toyohashi University Of Technology; Fil: Oberhofer, Harald. Universitat Technical Zu Munich; Alemania Fil: Oganov, Artem R.. Northwestern Polytechnical University; China. Skolkovo Institute Of Science And Technology; . Moscow Institute Of Physics And Technology; . Stony Brook University; Fil: Orendt, Anita M.. University of Utah; Estados Unidos Fil: Pagola, Gabriel Ignacio. Universidad de Buenos Aires; Argentina Fil: Pantelides, Constantinos C.. Imperial College London; Reino Unido Fil: Pickard, Chris J.. University of Cambridge; Estados Unidos. Colegio Universitario de Londres; Reino Unido Fil: Podeszwa, Rafal. University Of Silesia In Katowice; Fil: Price, Louise S.. Colegio Universitario de Londres; Reino Unido Fil: Price, Sarah L.. Colegio Universitario de Londres; Reino Unido Fil: Pulido, Angeles. University of Southampton; Reino Unido Fil: Read, Murray G.. Cambridge Crystallographic Data Centre; Fil: Reuter, Karsten. Universitat Technical Zu Munich; Alemania Fil: Schneider, Elia. University of New York; Estados Unidos Fil: Schober, Christoph. Universitat Technical Zu Munich; Alemania Fil: Shields, Gregory P.. Cambridge Crystallographic Data Centre; Fil: Singh, Pawanpreet. University Institute Of Pharmaceutical Sciences India; India Fil: Sugden, Isaac J.. Imperial College London; Reino Unido Fil: Szalewicz, Krzysztof. University Of Delaware; Fil: Taylor, Christopher R.. University of Southampton; Reino Unido Fil: Tkatchenko, Alexandre. University Of Luxembourg; . Fritz Haber Institute Of The Max Planck Society; Fil: Tuckerman, Mark E.. University of New York; Estados Unidos. New York University Shanghai; China. Courant Institute Of Mathematical Sciences; Fil: Vacarro, Francesca. University of Tulane; Estados Unidos. Loyola University New Orleans; Fil: Vasileiadis, Manolis. Imperial College London; Reino Unido Fil: Vazquez-Mayagoitia, Alvaro. Argonne National Laboratory; Estados Unidos Fil: Vogt, Leslie. University of New York; Estados Unidos Fil: Wang, Yanchao. Jilin University; China Fil: Watson, Rona E.. Colegio Universitario de Londres; Reino Unido Fil: De Wijs, Gilles A.. Radboud Universiteit Nijmegen; Países Bajos Fil: Yang, Jack. University of Southampton; Reino Unido Fil: Zhu, Qiang. Stony Brook University; Fil: Groom, Colin R.. Cambridge Crystallographic Data Centre

Short-range repulsion within intermolecular force fields is conventionally described by either Lennard-Jones (A/r(12)) or Born-Mayer (A exp(-Br)) forms. Despite their widespread use, these simple functional forms are often unable to describe the interaction energy accurately over a broad range of intermolecular distances, thus creating challenges in the development of ab initio force fields and potentially leading to decreased accuracy and transferability. Herein, we derive a novel short-range functional form based on a simple Slater-like model of overlapping atomic densities and an iterated stockholder atom (ISA) partitioning of the molecular electron density. We demonstrate that this Slater-ISA methodology yields a more accurate, transferable, and robust description of the short-range interactions at minimal additional computational cost compared to standard Lennard-Jones or Born-Mayer approaches. Finally, we show how this methodology can be adapted to yield the standard Born-Mayer functional form while still retaining many of the advantages of the Slater-ISA approach.

This work builds on our recently published anisotropic potential for polycyclic aromatic hydrocarbons (PAH) [T.S. Totton, A.J. Misquitta, M. Kraft, J. Chem. Theory Comput. 6 (2010) 683] by developing a new transferable electrostatic model for PAH molecules. Using this model, the atomic charge parameters used in the PAH anisotropic potential may be rapidly calculated from a set of predefined parameters rather than from molecule-specific ab initio calculations. The importance of the out-of-the-plane quadrupolar moments is highlighted and they are used as the basis for an accurate and transferable electrostatic model for PAHs. This model exhibits an r.m.s. deviation of 1.7 kJ mol - 1 - an order of magnitude less than previous models.

The results of the fifth blind test of crystal structure prediction, which show important success with more challenging large and flexible molecules, are presented and discussed., Following on from the success of the previous crystal structure prediction blind tests (CSP1999, CSP2001, CSP2004 and CSP2007), a fifth such collaborative project (CSP2010) was organized at the Cambridge Crystallographic Data Centre. A range of methodologies was used by the participating groups in order to evaluate the ability of the current computational methods to predict the crystal structures of the six organic molecules chosen as targets for this blind test. The first four targets, two rigid molecules, one semi-flexible molecule and a 1:1 salt, matched the criteria for the targets from CSP2007, while the last two targets belonged to two new challenging categories – a larger, much more flexible molecule and a hydrate with more than one polymorph. Each group submitted three predictions for each target it attempted. There was at least one successful prediction for each target, and two groups were able to successfully predict the structure of the large flexible molecule as their first place submission. The results show that while not as many groups successfully predicted the structures of the three smallest molecules as in CSP2007, there is now evidence that methodologies such as dispersion-corrected density functional theory (DFT-D) are able to reliably do so. The results also highlight the many challenges posed by more complex systems and show that there are still issues to be overcome.

In this paper we present studies of clusters assembled from polycyclic aromatic hydrocarbon (PAH) molecules similar in size to small soot particles. The clusters studied were comprised of coronene (C 24 H 12 ) or pyrene (C 16 H 10 ) molecules and represent the types of soot precursor molecule typically found in flame environments. A stochastic ‘basin-hopping’ global optimisation scheme was used to locate low-lying local minima on the potential energy surface of the molecular clusters. TEM-style projections of the resulting geometries show similarities with those observed experimentally in TEM images of soot particles. The mass densities of these clusters have also been calculated and are lower than bulk values of the pure crystalline PAH structures. They are also significantly lower than the standard value of 1.8 g/cm 3 used in our soot models. Consequently we have varied the mass density between 1.0 g/cm 3 and 1.8 g/cm 3 to examine the effects of varying soot density on our soot model and observed how the shape of the particle size distribution changes. Based on similarities between nascent soot particles and PAH clusters a more accurate soot density is likely to be significantly lower than 1.8 g/cm 3 . As such, for modelling purposes, we recommend that the density of nascent soot should be taken to be the value obtained for our coronene cluster of 1.12 g/cm 3 .

In Symmetry-Adapted Perturbation Theory the charge-transfer energy is normally absorbed into the induction energy, but it can be treated separately. There are two contributions: the long-range or polarization term, which ignores effects due to exchange of electrons between the interacting molecules, and an exchange term. The sum of the two is much smaller than the polarization term, by up to an order of magnitude. The net contribution to hydrogen bond energies is a few kJ mol −1 at equilibrium, and is approximately proportional to the exchange-repulsion energy at other geometries and no more than 10% of it in magnitude.

Accurate atom–atom dispersion coefficients are needed if we are to be able to successfully model the intermolecular interactions between organic molecules. To go beyond the usual C 6 description we have to resort to accurate ab initio methods, and we use the Williams–Stone–Misquitta methodology to obtain anisotropic distributed dispersion coefficients to C 12 on each atomic site. Comparisons with SAPT(DFT) energies show that the resulting descriptions are very accurate, even for molecular contacts, where the asymptotic series is thought to be invalid. The complexity of our most accurate models limits their applicability, so we explore simplifications that are more suitable for use in calculations of the condensed phase, in particular, we describe a means of calculating optimized isotropic C 6 models that can be readily used in conventional programs.

We have constructed an intermolecular potential for the 1,3-dibromo-2-chloro-5-fluorobenzene molecule from first principles using SAPT(DFT) interaction energy calculations and the Williams–Stone–Misquitta method for obtaining molecular properties in distributed form. This molecule was included in the fourth Blind Test of crystal structure prediction organised by the Cambridge Crystallographic Data Centre. Using our potential, we have predicted the crystal structure of C 6 Br 2 ClFH 2 and found the lowest energy solution to be in excellent agreement with the experimentally observed crystal when it was subsequently revealed.

We compare two methods for estimating the induction energy in organic molecular crystals by approximating the charge density polarization in the crystalline state. The first is a distributed atomic polarizability model combined with distributed multipole moments, derived from ab initio monomer properties. The second uses an ab initio calculation of the molecular charge density in a point-charge field. Various parameters of the models, such as the rank of polarizability model, effect of self-consistent iterations, and damping, are investigated. The methods are applied to a range of observed and predicted crystal structures of three particularly challenging molecules, namely oxalyl dihydrazide, 3-azabicyclo[3,3,1]nonane-2,4-dione, and carbamazepine, as well as demonstrating the importance of induction in the naphthalene crystal. The two models agree well considering the different approximations made, and it is shown that the induction energy can be an important discriminator in the relative lattice energies of structures with substantially different hydrogen-bonding motifs.

Recent developments in ab initio intermolecular perturbation theory, using density functional theory, have made it possible to calculate intermolecular interactions between organic molecules of 30 or more atoms routinely and accurately. Related methods can provide accurate distributed properties of such molecules (multipoles and polarizabilities). These developments open up new possibilities for accurate ab initio atom–atom potentials, at a time when applications have raised new challenges, in that aspects of the interaction energy that were once ignored must now be accounted for. This review seeks to show how modern ab initio methods in intermolecular perturbation theory, and new methods for distributing molecular response properties, can be used to develop a new generation of atom–atom potentials.

In part 1 of this two-part investigation we set out the theoretical basis for constructing accurate models of the induction energy of clusters of moderately sized organic molecules. In this paper we use these techniques to develop a variety of accurate distributed polarizability models for a set of representative molecules that include formamide, N-methyl propanamide, benzene, and 3-azabicyclo[3.3.1]nonane-2,4-dione. We have also explored damping, penetration, and basis set effects. In particular, we have provided a way to treat the damping of the induction expansion. Different approximations to the induction energy are evaluated against accurate SAPT(DFT) energies, and we demonstrate the accuracy of our induction models on the formamide−water dimer.

The induction energy often plays a very important role in determining the structure and properties of clusters of organic molecules, but only in recent years has an effort been made to include this energy in such calculations, notably in the field of organic crystal structure prediction. In this paper and the following one in this issue we provide ab initio methods suitable for the accurate inclusion of the induction energy for molecules containing as many as 30 atoms or so. These techniques are based on Symmetry-Adapted Perturbation Theory using Density Functional Theory [SAPT(DFT)] and use distributed polarizabilities computed using the recently developed density-fitting algorithm with constrained refinement. With this approach we are able to obtain induction models of varying complexity and study the effects of overlap and related numerical issues. Basis set effects on the exact and asymptotic induction energies are investigated, and the roles of higher-order induction energies and many-body effects are explored.

Standard empirical atom-atom potentials are shown to be unable to describe the binding of polycyclic aromatic hydrocarbon (PAH) molecules in the variety of configurations seen in clusters. The main reason for this inadequacy is the lack of anisotropy in these potentials. We have constructed an anisotropic atom-atom intermolecular potential for the benzene molecule from first principles using a symmetry-adapted perturbation theory based on density functional theory (SAPT(DFT)), interaction energy calculations and the Williams-Stone-Misquitta method for obtaining molecular properties in distributed form. Using this potential as a starting point, we have constructed a transferable anisotropic potential to model intermolecular interactions between PAHs. This new potential has been shown to accurately model interaction energies for a variety of dimer configurations for four different PAH molecules, including certain configurations which are poorly modeled with current isotropic potentials. It is intended that this potential will form the basis for further work on the aggregation of PAHs.

Symmetry-adapted perturbation theory based on Kohn–Sham determinants, SAPT(KS), was shown before to perform poorly for the electrostatic energy which is potentially exact in this approach. We demonstrate that some deficiencies of SAPT(KS) result from wrong asymptotics of exchange-correlation potentials. On applying an asymptotic correction, we were not only able to recover the electrostatics, but also the first-order exchange and second-order induction and exchange-induction energies fairly accurate. Dispersion is still reproduced poorly but can be computed reasonably accurately from the damped asymptotic expansion.

First-principles-based, linearly scaling algorithm has been developed for calculations of dispersion energies from frequency-dependent density susceptibility (FDDS) functions with account of charge-overlap effects. The transition densities in FDDSs are fitted by a set of auxiliary atom-centered functions. The terms in the dispersion energy expression involving products of such functions are computed using either the unexpanded (exact) formula or from inexpensive asymptotic expansions, depending on the location of these functions relative to the dimer configuration. This approach leads to significant savings of computational resources. In particular, for a dimer consisting of two elongated monomers with 81 atoms each in a head-to-head configuration, the most favorable case for our algorithm, a 43-fold speedup has been achieved while the approximate dispersion energy differs by less than 1% from that computed using the standard unexpanded approach. In contrast, the dispersion energy computed from the distributed asymptotic expansion differs by dozens of percent in the van der Waals minimum region. A further increase of the size of each monomer would result in only small increased costs since all the additional terms would be computed from the asymptotic expansion.

Using a genomics-based reverse pharmacological approach for screening orphan G-protein coupled receptors, we have identified and cloned a novel high-affinity histamine receptor. This receptor, termed AXOR35, is most closely related to the H3 histamine receptor, sharing 37% protein sequence identity. A multiple responsive element/cyclic AMP-responsive element-luciferase reporter assay was used to identify histamine as a ligand for AXOR35. When transfected into human embryonic kidney 293 cells, the AXOR35 receptor showed a strong, dose-dependent calcium mobilization response to histamine and H3 receptor agonists including imetit and immepip. Radioligand binding confirmed that the AXOR35 receptor was a high-affinity histamine receptor. The pharmacology of the AXOR35 receptor was found to closely resemble that of the H3 receptor; the major difference was that (R)-alpha-methylhistamine was a low potency agonist of the AXOR35 receptor. Thioperamide is an antagonist at AXOR 35. Expression of AXOR35 mRNA in human tissues is highest in peripheral blood mononuclear cells and in tissues likely to contain high concentrations of blood cells, such as bone marrow and lung. In situ hybridization analysis of a wide survey of mouse tissues showed that mouse AXOR35 mRNA is selectively expressed in hippocampus. The identification and localization of this new histamine receptor will expand our understanding of the physiological and pathological roles of histamine and may provide additional opportunities for pharmacological modification of these actions.

Potential energy surface for the interaction of Ar with CO2 has been calculated using different levels of symmetry-adapted perturbation theory (SAPT) and the supermolecular many-body perturbation theory (MBPT) and coupled-cluster methods. These potentials have been used to compute the rovibrational spectra of Ar–CO2 and the interaction virial coefficients. The best reproduction of experimental data was achieved by the SAPT potential at the level of theory similar to the second-order of MBPT. The accuracy of this potential is in fact very close to that of the recent semiempirical surface of Hutson et al. [J. Chem. Phys. 106, 9130 (1996)] which was fitted to this set of data. Somewhat surprisingly, the more advanced methods considered here performed not as well.

In this work we assess a recently published anisotropic potential for polycyclic aromatic hydrocarbon (PAH) molecules (J. Chem. Theory Comput. 2010, 6, 683-695). Comparison to recent high-level symmetry-adapted perturbation theory based on density functional theory (SAPT(DFT)) results for coronene (C(24)H(12)) demonstrate the transferability of the potential while highlighting some limitations with simple point charge descriptions of the electrostatic interaction. The potential is also shown to reproduce second virial coefficients of benzene (C(6)H(6)) with high accuracy, and this is enhanced by using a distributed multipole model for the electrostatic interaction. The graphene dimer interaction energy and the exfoliation energy of graphite have been estimated by extrapolation of PAH interaction energies. The contribution of nonlocal fluctuations in the π electron density in graphite have also been estimated which increases the exfoliation energy by 3.0 meV atom(-1) to 47.6 meV atom(-1), which compares well to recent theoretical and experimental results.

We report on the organization and outcome of the fourth blind test of crystal structure prediction, an international collaborative project organized to evaluate the present state in computational methods of predicting the crystal structures of small organic molecules. There were 14 research groups which took part, using a variety of methods to generate and rank the most likely crystal structures for four target systems: three single-component crystal structures and a 1:1 cocrystal. Participants were challenged to predict the crystal structures of the four systems, given only their molecular diagrams, while the recently determined but as-yet unpublished crystal structures were withheld by an independent referee. Three predictions were allowed for each system. The results demonstrate a dramatic improvement in rates of success over previous blind tests; in total, there were 13 successful predictions and, for each of the four targets, at least two groups correctly predicted the observed crystal structure. The successes include one participating group who correctly predicted all four crystal structures as their first ranked choice, albeit at a considerable computational expense. The results reflect important improvements in modelling methods and suggest that, at least for the small and fairly rigid types of molecules included in this blind test, such calculations can be constructively applied to help understand crystallization and polymorphism of organic molecules. © 2009 International Union of Crystallography. Fil: Day, Graeme M.. University of Cambridge; Estados Unidos Fil: Cooper, Timothy G.. University of Cambridge; Estados Unidos Fil: Cruz-Cabeza, Aurora J.. University of Cambridge; Estados Unidos Fil: Hejczyk, Katarzyna E.. University of Cambridge; Estados Unidos Fil: Ammon, Herman L.. University of Maryland; Estados Unidos Fil: Boerrigter, Stephan X. M.. Purdue University; Estados Unidos Fil: Tan, Jeffrey S.. Purdue University; Estados Unidos Fil: Della Valle, Raffaele G.. Universidad de Bologna; Italia Fil: Venuti, Elisabetta. Universidad de Bologna; Italia Fil: Jose, Jovan. Savitribai Phule Pune University; India Fil: Gadre, Shridhar R.. Savitribai Phule Pune University; India Fil: Desiraju, Gautam R.. University Of Hyderabad; India Fil: Thakur, Tejender S.. University Of Hyderabad; India Fil: Van Eijck, Bouke P.. Utrecht University; Países Bajos. University of Utrecht; Países Bajos Fil: Facelli, Julio C.. University of Utah; Estados Unidos Fil: Bazterra, Victor E.. University of Utah; Estados Unidos Fil: Ferraro, Marta Beatriz. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina Fil: Neumann, Marcus A.. Avant-garde Materials Simulation; Fil: Leusen, Frank J. J.. University Of Bradford; Fil: Kendrick, John. University Of Bradford; Fil: Price, Sarah L.. Colegio Universitario de Londres; Reino Unido Fil: Misquitta, Alston J.. University of Cambridge; Estados Unidos. Colegio Universitario de Londres; Reino Unido Fil: Karamertzanis, Panagiotis G.. Colegio Universitario de Londres; Reino Unido Fil: Welch, Gareth W. A.. Colegio Universitario de Londres; Reino Unido Fil: Scheraga, Harold A.. Cornell University; Estados Unidos Fil: Arnautova, Yelena A.. Cornell University; Estados Unidos Fil: Schmidt, Martin U.. Goethe Universitat Frankfurt; Alemania Fil: Van De Streek, Jacco. Goethe Universitat Frankfurt; Alemania Fil: Wolf, Alexandra K.. Goethe Universitat Frankfurt; Alemania Fil: Schweizer, Bernd. Eth Zurich

A symmetry-adapted perturbation theory based on Kohn-Sham determinants [SAPT(KS)] and utilizing asymptotically corrected exchange-correlation potentials has been applied to the He2, Ne2, (H2O)2, and (CO2)2 dimers. It is shown that SAPT(KS) is able to recover the electrostatic, first-order exchange, second-order induction, and exchange-induction energies with an accuracy approaching and occasionally surpassing that of regular SAPT at the currently programmed theory level. The use of the asymptotic corrections is critical to achieve this accuracy. The SAPT(KS) results can be obtained at a small fraction of the time needed for regular SAPT calculations. The robustness of the SAPT(KS) method with respect to the basis set size is also demonstrated. A theoretical justification for high accuracy of SAPT(KS) predictions for the electrostatic, first-order exchange, and second-order induction energies has been provided.

A method is proposed for calculations of dispersion energy at finite intermonomer separations. It uses a generalized Casimir-Polder formula evaluated with dynamic density susceptibilities provided by time-dependent density-functional theory. The method recovers the dispersion energies of He, Ne, and H2O dimers to within 3% or better. Since the computational effort of the new algorithm scales approximately as the third power of system size, the method is much more efficient than standard wave-function methods capable of predicting the dispersion energy at a similarly high level of accuracy.

The clustering of polycyclic aromatic hydrocarbon (PAH) molecules is investigated in the context of soot particle inception and growth using an isotropic potential developed from the benchmark PAHAP potential. This potential is used to estimate equilibrium constants of dimerisation for five representative PAH molecules based on a statistical mechanics model. Molecular dynamics simulations are also performed to study the clustering of homomolecular systems at a range of temperatures. The results from both sets of calculations demonstrate that at flame temperatures pyrene (C(16)H(10)) dimerisation cannot be a key step in soot particle formation and that much larger molecules (e.g. circumcoronene, C(54)H(18)) are required to form small clusters at flame temperatures. The importance of using accurate descriptions of the intermolecular interactions is demonstrated by comparing results to those calculated with a popular literature potential with an order of magnitude variation in the level of clustering observed. By using an accurate intermolecular potential we are able to show that physical binding of PAH molecules based on van der Waals interactions alone can only be a viable soot inception mechanism if concentrations of large PAH molecules are significantly higher than currently thought.

A computationally efficient method for obtaining distributed polarizabilities of arbitrary rank using a constrained density-fitting algorithm is demonstrated on the hydrogen, carbon dioxide, formamide, and N-methylpropanamide molecules. A description of the molecular polarization in terms of local polarizabilities without charge-flow terms is obtained when the nonlocal components of the polarizability tensor are transformed away using the localization method of Le Sueur and Stone [Mol. Phys. 83, 293 (1994)]. The resulting local polarizabilities are shown to be stable with respect to basis set used, exhibiting none of the artifacts of earlier basis-space partitioning methods. We also investigate the transferability of the resulting local polarizability models.

Recently, three of us have proposed a method [Phys. Rev. Lett. 91, 33201 (2003)] for an accurate calculation of the dispersion energy utilizing frequency-dependent density susceptibilities of monomers obtained from time-dependent density-functional theory (DFT). In the present paper, we report numerical calculations for the helium, neon, water, and carbon dioxide dimers and show that for a wide range of intermonomer separations, including the van der Waals and short-range repulsion regions, the method provides dispersion energies with accuracies comparable to those that can be achieved using the current most sophisticated wave-function methods. If the dispersion energy is combined with (i) the electrostatic and first-order exchange interaction energies as defined in symmetry-adapted perturbation theory (SAPT) but computed using monomer Kohn-Sham (KS) determinants, and (ii) the induction energy computed using the coupled KS static response theory, (iii) the exchange-induction and exchange-dispersion energies computed using KS orbitals and orbital energies, the resulting method, denoted by SAPT(DFT), produces very accurate total interaction potentials. For the helium dimer, the only system with nearly exact benchmark values, SAPT(DFT) reproduces the interaction energy to within about 2% at the minimum and to a similar accuracy for all other distances ranging from the strongly repulsive to the asymptotic region. For the remaining systems investigated by us, the quality of the SAPT(DFT) interaction energies is so high that these energies may actually be more accurate than the best available results obtained with wave-function techniques. At the same time, SAPT(DFT) is much more computationally efficient than any method previously used for calculating the dispersion and other interaction energy components at this level of accuracy.

Ab initio calculations of five two-dimensional intermolecular potential energy surfaces of the Ne–HCN dimer have been performed using the symmetry-adapted perturbation theory and the supermolecular method at different levels of electron correlation. A basis set of spdf-symmetry orbitals (including midbond functions) was used. HCN was assumed linear with interatomic distances fixed at their vibrationally averaged 〈r−2〉−1/2 values. Fits to all calculated potential energy surfaces were obtained in the form of angular expansions incorporating the ab initio asymptotic coefficients. It has been found that high-order correlation effects are very important for Ne–HCN and contribute about 20% to the well depth. All of the five surfaces feature a global minimum at the linear Ne–HCN geometry and a narrow and relatively flat valley surrounding HCN. Rovibrational calculations on the surfaces yielded rotational spectra and a rotational constant whose relative differences from their experimental counterparts range from ...

Tris-disrupted and intact brush border membrane preparations from mucosa of hamster jejunum were capable of preferentially binding actively transported D-glucose in a similar manner. Density gradient centrifugation of the Tris-disrupted brush borders indicated that D-glucose was bound to a fraction containing the cores or inner material of the microvilli. The properties of this binding were examined with the Tris-disrupted brush border preparation. Actively transported sugars competitively inhibited preferential D-glucose binding, whereas no effect was observed with nonactively transported sugars. Neither actively nor nonactively transported amino acids affected D-glucose binding. D-Glucosamine, which is not actively transported, was inhibitory to preferential D-glucose binding as well as to the active transport of D-glucose by everted sacs of hamster jejunum. No inhibitory effect was observed with the same concentration of D-galactosamine. Preferential D-glucose binding was also inhibited by sulfhydryl-reacting compounds, Ca2+, and Li+ ions. On the other hand, Mg2+ was shown to be stimulatory and Na+, NH4+, and K+ had no effect on this phenomenon. The results of these experiments suggest that preferential D-glucose binding to brush borders is related to the initial step in active sugar transport by the small intestine.

1. 1. Everted sacs of rat jejunum, ileum, and colon were used to investigate the possibility of active F − transport. Fluoride was placed in equal concentration in both compartments at the initial levels of 0.083, 0.167, and 1.670 mM. A secretion of F − against its electrochemical gradient was observed across ileum at 0.167 mM F − and either 1.9 or 1.0 mM Ca 2+ , and across jejunum and ileum at 0.167 and 1.670 mM F − in the presence of 0.5 mM Ca 2+ . 2. 2. When 0.167 mM F − was placed initially on either the mucosal or the serosal| side, at 1.9 mM Ca 2+ , fluoride crossed each section of the intestine freely in both the absorptive and secretory directions. The translocation of F − , however, was greater in the direction of secretion with jejunal and ileal sacs. 3. 3. With equal initial concentration of F − in both compartments, alteration of| the exogenous Ca 2+ concentration and also the addition of 2,4-dinitrophenol affected only the net movement of F − in the mucosal compartment. Since the loss of F − from the serosal compartment was not influenced, it appeared that this effect was localized at the mucosal surface. 4. 4. The net movement of F − against its electrochemical gradient was inhibited| by the addition of 1 mM dinitrophenol at 0° confirming the existence of active F − transport in jejunum and ileum. A less active F − pump also appeared to exist in the colon.