Impact of liquid composition and asphaltene properties on asphaltene aggregation using interaction energies

2021 ◽  
Author(s):  
Mahshid Nategh ◽  
Hojjat Mahdiyar ◽  
M. Reza Malayeri ◽  
Simon Unz ◽  
Michael Beckmann
Keyword(s):  
Liquid Composition ◽  
Interaction Energies

Intrinsic Stacking Interactions of Natural and Artificial Nucleobases

2019 ◽  
Author(s):  
Drew P. Harding ◽  
Laura J. Kingsley ◽  
Glen Spraggon ◽  
Steven Wheeler
Keyword(s):  
Gas Phase ◽  
Electrostatic Interactions ◽  
Density Functional ◽  
Molecular Descriptors ◽  
Stacking Interactions ◽  
Interaction Energies ◽  
Functional Theory ◽  
Binding Partner ◽  
Heavy Atoms ◽  
Wide Range

The intrinsic (gas-phase) stacking energies of natural and artificial nucleobases were explored using density functional theory (DFT) and correlated ab initio methods. Ranking the stacking strength of natural nucleobase dimers revealed a preference in binding partner similar to that seen from experiments, namely G > C > A > T > U. Decomposition of these interaction energies using symmetry-adapted perturbation theory (SAPT) showed that these dispersion dominated interactions are modulated by electrostatics. Artificial nucleobases showed a similar stacking preference for natural nucleobases and were also modulated by electrostatic interactions. A robust predictive multivariate model was developed that quantitively predicts the maximum stacking interaction between natural and a wide range of artificial nucleobases using molecular descriptors based on computed electrostatic potentials (ESPs) and the number of heavy atoms. This model should find utility in designing artificial nucleobase analogs that exhibit stacking interactions comparable to those of natural nucleobases. Further analysis of the descriptors in this model unveil the origin of superior stacking abilities of certain nucleobases, including cytosine and guanine.

On the Nature of Halide-Water Interactions: Insights from Many-Body Representations and Density Functional Theory

2019 ◽  
Author(s):  
Brandon B. Bizzarro ◽  
Colin K. Egan ◽  
Francesco Paesani
Keyword(s):  
Density Functional Theory ◽  
Charge Transfer ◽  
Molecular Orbital ◽  
Density Functional ◽  
Decomposition Analysis ◽  
Orbital Energy ◽  
Energy Decomposition Analysis ◽  
Interaction Energies ◽  
Many Body ◽  
Functional Theory

<div> <div> <div> <p>Interaction energies of halide-water dimers, X<sup>-</sup>(H<sub>2</sub>O), and trimers, X<sup>-</sup>(H<sub>2</sub>O)<sub>2</sub>, with X = F, Cl, Br, and I, are investigated using various many-body models and exchange-correlation functionals selected across the hierarchy of density functional theory (DFT) approximations. Analysis of the results obtained with the many-body models demonstrates the need to capture important short-range interactions in the regime of large inter-molecular orbital overlap, such as charge transfer and charge penetration. Failure to reproduce these effects can lead to large deviations relative to reference data calculated at the coupled cluster level of theory. Decompositions of interaction energies carried out with the absolutely localized molecular orbital energy decomposition analysis (ALMO-EDA) method demonstrate that permanent and inductive electrostatic energies are accurately reproduced by all classes of XC functionals (from generalized gradient corrected (GGA) to hybrid and range-separated functionals), while significant variance is found for charge transfer energies predicted by different XC functionals. Since GGA and hybrid XC functionals predict the most and least attractive charge transfer energies, respectively, the large variance is likely due to the delocalization error. In this scenario, the hybrid XC functionals are then expected to provide the most accurate charge transfer energies. The sum of Pauli repulsion and dispersion energies are the most varied among the XC functionals, but it is found that a correspondence between the interaction energy and the ALMO EDA total frozen energy may be used to determine accurate estimates for these contributions. </p> </div> </div> </div>

Ion solvation by dipolar aprotic solvents. An ab initio study

1987 ◽  
Vol 52 (1) ◽  
pp. 6-13 ◽  
Author(s):  
Petr Kyselka ◽  
Zdeněk Havlas ◽  
Ivo Sláma
Keyword(s):  
Ab Initio ◽  
Geometry Optimization ◽  
Molecular Structures ◽  
Dimethyl Sulphoxide ◽  
Ion Solvation ◽  
Interaction Energies ◽  
Ab Initio Study ◽  
Solvation Energies ◽  
Dipolar Aprotic Solvents ◽  
Complete Geometry Optimization

The paper deals with the solvation of Li+, Be2+, Na+, Mg2+, and Al3+ ions in dimethyl sulphoxide, dimethylformamide, acetonitrile, and water. The ab initio quantum chemical method was used to calculate the solvation energies, molecular structures, and charge distributions for the complexes water···ion, acetonitrile···ion, dimethyl sulphoxide···ion, and dimethylformamide···ion. The interaction energies were corrected for the superposition error. Complete geometry optimization was performed for the complex water···ion. Some generalizations are made on the basis of the results obtained.

scholarly journals Interactions between large molecules pose a puzzle for reference quantum mechanical methods

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yasmine S. Al-Hamdani ◽  
Péter R. Nagy ◽  
Andrea Zen ◽  
Dennis Barton ◽  
Mihály Kállay ◽  
...  
Keyword(s):  
Experimental Information ◽  
Quantum Mechanical ◽  
Interaction Energies ◽  
Small Organic Molecules ◽  
Large Molecules ◽  
Reference Information ◽  
Mechanical Methods ◽  
Non Covalent Interactions ◽  
Semi Empirical ◽  
Covalent Interactions

AbstractQuantum-mechanical methods are used for understanding molecular interactions throughout the natural sciences. Quantum diffusion Monte Carlo (DMC) and coupled cluster with single, double, and perturbative triple excitations [CCSD(T)] are state-of-the-art trusted wavefunction methods that have been shown to yield accurate interaction energies for small organic molecules. These methods provide valuable reference information for widely-used semi-empirical and machine learning potentials, especially where experimental information is scarce. However, agreement for systems beyond small molecules is a crucial remaining milestone for cementing the benchmark accuracy of these methods. We show that CCSD(T) and DMC interaction energies are not consistent for a set of polarizable supramolecules. Whilst there is agreement for some of the complexes, in a few key systems disagreements of up to 8 kcal mol−1 remain. These findings thus indicate that more caution is required when aiming at reproducible non-covalent interactions between extended molecules.

scholarly journals Quantum chemical benchmark databases of gold-standard dimer interaction energies

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Alexander G. Donchev ◽  
Andrew G. Taube ◽  
Elizabeth Decolvenaere ◽  
Cory Hargus ◽  
Robert T. McGibbon ◽  
...  
Keyword(s):  
Machine Learning ◽  
Gold Standard ◽  
Training Data ◽  
Structure Theory ◽  
Cluster Method ◽  
Coupled Cluster ◽  
Interaction Energies ◽  
Gold Standard Method ◽  
Representative Subset ◽  
Semi Empirical

AbstractAdvances in computational chemistry create an ongoing need for larger and higher-quality datasets that characterize noncovalent molecular interactions. We present three benchmark collections of quantum mechanical data, covering approximately 3,700 distinct types of interacting molecule pairs. The first collection, which we refer to as DES370K, contains interaction energies for more than 370,000 dimer geometries. These were computed using the coupled-cluster method with single, double, and perturbative triple excitations [CCSD(T)], which is widely regarded as the gold-standard method in electronic structure theory. Our second benchmark collection, a core representative subset of DES370K called DES15K, is intended for more computationally demanding applications of the data. Finally, DES5M, our third collection, comprises interaction energies for nearly 5,000,000 dimer geometries; these were calculated using SNS-MP2, a machine learning approach that provides results with accuracy comparable to that of our coupled-cluster training data. These datasets may prove useful in the development of density functionals, empirically corrected wavefunction-based approaches, semi-empirical methods, force fields, and models trained using machine learning methods.

scholarly journals Specificity of the HIV-1 Protease on Substrates Representing the Cleavage Site in the Proximal Zinc-Finger of HIV-1 Nucleocapsid Protein

Viruses ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1092
Author(s):  
János András Mótyán ◽  
Márió Miczi ◽  
Stephen Oroszlan ◽  
József Tőzsér
Keyword(s):  
Amino Acid ◽  
Zinc Finger ◽  
Cleavage Site ◽  
Potential Role ◽  
Binding Mode ◽  
Interaction Energies ◽  
Vitro Assay ◽  
Hiv 1

To explore the sequence context-dependent nature of the human immunodeficiency virus type 1 (HIV-1) protease’s specificity and to provide a rationale for viral mutagenesis to study the potential role of the nucleocapsid (NC) processing in HIV-1 replication, synthetic oligopeptide substrates representing the wild-type and modified versions of the proximal cleavage site of HIV-1 NC were assayed as substrates of the HIV-1 protease (PR). The S1′ substrate binding site of HIV-1 PR was studied by an in vitro assay using KIVKCF↓NCGK decapeptides having amino acid substitutions of N17 residue of the cleavage site of the first zinc-finger domain, and in silico calculations were also performed to investigate amino acid preferences of S1′ site. Second site substitutions have also been designed to produce “revertant” substrates and convert a non-hydrolysable sequence (having glycine in place of N17) to a substrate. The specificity constants obtained for peptides containing non-charged P1′ substitutions correlated well with the residue volume, while the correlation with the calculated interaction energies showed the importance of hydrophobicity: interaction energies with polar residues were related to substantially lower specificity constants. Cleavable “revertants” showed one residue shift of cleavage position due to an alternative productive binding mode, and surprisingly, a double cleavage of a substrate was also observed. The results revealed the importance of alternative binding possibilities of substrates into the HIV-1 PR. The introduction of the “revertant” mutations into infectious virus clones may provide further insights into the potential role of NC processing in the early phase of the viral life-cycle.

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