scholarly journals Polarizable charge equilibration model for predicting accurate electrostatic interactions in molecules and solids

2017 ◽  
Vol 146 (12) ◽  
pp. 124117 ◽  
Author(s):  
Saber Naserifar ◽  
Daniel J. Brooks ◽  
William A. Goddard ◽  
Vaclav Cvicek
Keyword(s):  
Electrostatic Interactions ◽  
Charge Equilibration ◽  
Equilibration Model

scholarly journals Polarizable Charge Equilibration Model for Transition-Metal Elements

2018 ◽  
Vol 122 (48) ◽  
pp. 9350-9358 ◽  
Author(s):  
Soonho Kwon ◽  
Saber Naserifar ◽  
Hyuck Mo Lee ◽  
William A. Goddard
Keyword(s):  
Transition Metal ◽  
Metal Elements ◽  
Charge Equilibration ◽  
Equilibration Model ◽  
Transition Metal Elements

Template mediated crystal engineering

1994 ◽  
Vol 52 ◽  
pp. 480-481
Author(s):  
Brigid R. Heywood ◽  
S. Champ
Keyword(s):  
Crystal Engineering ◽  
Electrostatic Interactions ◽  
Alkyl Chain ◽  
Crystallographic Axis ◽  
Two Dimensional ◽  
Engineering Process ◽  
Solution Interface ◽  
Extensive Program ◽  
Geometric Homology ◽  
Long Alkyl Chain

Recent work on the crystallisation of inorganic crystals under compressed monomolecular surfactant films has shown that two dimensional templates can be used to promote the oriented nucleation of solids. When a suitable long alkyl chain surfactant is cast on the crystallisation media a monodispersied population of crystals forms exclusively at the monolayer/solution interface. Each crystal is aligned with a specific crystallographic axis perpendicular to the plane of the monolayer suggesting that nucleation is facilitated by recognition events between the nascent inorganic solid and the organic template.For example, monolayers of the long alkyl chain surfactant, stearic acid will promote the oriented nucleation of the calcium carbonate polymorph, calcite, on the (100) face, whereas compressed monolayers of n-eicosyl sulphate will induce calcite nucleation on the (001) face, (Figure 1 & 2). An extensive program of research has confirmed the general principle that molecular recognition events at the interface (including electrostatic interactions, geometric homology, stereochemical complementarity) can be used to promote the crystal engineering process.

Characteristics of the Interaction between Thrombin Exosite1 and the Sequence 269-297 of Platelet Glycoprotein Ibα

1998 ◽  
Vol 80 (08) ◽  
pp. 310-315 ◽  
Author(s):  
Marie-Christine Bouton ◽  
Christophe Thurieau ◽  
Marie-Claude Guillin ◽  
Martine Jandrot-Perrus
Keyword(s):  
Platelet Activation ◽  
Electrostatic Interactions ◽  
Platelet Glycoprotein ◽  
Thrombin Receptor ◽  
Central Position ◽  
Amidolytic Activity ◽  
N Terminus ◽  
Hydrolysis Of ◽  
Chemical Cross Linking ◽  
Positively Charged

SummaryThe interaction between GPIb and thrombin promotes platelet activation elicited via the hydrolysis of the thrombin receptor and involves structures located on the segment 238-290 within the N-terminal domain of GPIbα and the positively charged exosite 1 on thrombin. We have investigated the ability of peptides derived from the 269-287 sequence of GPIbα to interact with thrombin. Three peptides were synthesized, including Ibα 269-287 and two scrambled peptides R1 and R2 which are comparable to Ibα 269-287 with regards to their content and distribution of anionic residues. However, R2 differs from both Ibα 269-287 and R1 by the shifting of one proline from a central position to the N-terminus. By chemical cross-linking, we observed the formation of a complex between 125I-Ibα 269-287 and α-thrombin that was inhibited by hirudin, the C-terminal peptide of hirudin, sodium pyrophosphate but not by heparin. The complex did not form when γ-thrombin was substituted for α-thrombin. Ibα 269-287 produced only slight changes in thrombin amidolytic activity and inhibited thrombin binding to fibrin. R1 and R2 also formed complexes with α-thrombin, modified slightly its catalytic activity and inhibited its binding to fibrin. Peptides Ibα 269-287 and R1 inhibited platelet aggregation and secretion induced by low thrombin concentrations whereas R2 was without effect. Our results indicate that Ibα 269-287 interacts with thrombin exosite 1 via mainly electrostatic interactions, which explains why the scrambled peptides also interact with exosite 1. Nevertheless, the lack of effect of R2 on thrombin-induced platelet activation suggests that proline 280 is important for thrombin interaction with GPIb.

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.

Solubilization of Itraconazole by Surfactants and Phospholipid-Surfactant Mixtures: Interplay of Amphiphile Structure, pH and Electrostatic Interactions

2020 ◽  
Author(s):  
Zahari Vinarov ◽  
Gabriela Gancheva ◽  
Nikola Burdzhiev ◽  
Slavka S. Tcholakova
Keyword(s):  
Nmr Spectroscopy ◽  
Electrostatic Interactions ◽  
Triazole Ring ◽  
Water Soluble ◽  
Single Chain ◽  
Surfactant Mixtures ◽  
Solubilization Capacity ◽  
Water Soluble Drugs ◽  
Hydrophobic Chain ◽  
Brick Dust

Although surfactants are frequently used in enabling formulations of poorly water-soluble drugs, the link between their structure and drug solubilization capacity is still unclear. We studied the solubilization of the “brick-dust” molecule itraconazole by 16 surfactants and 3 phospholipid:surfactant mixtures. NMR spectroscopy was used to study in more details the drug-surfactant interactions. Very high solubility of itraconazole (up to 3.6 g/L) was measured in anionic surfactant micelles at pH = 3, due to electrostatic attraction between the oppositely charged (at this pH) drug and surfactant molecules. <sup>1</sup>H NMR spectroscopy showed that itraconazole is ionized at two sites (2+ charge) at these conditions: in the phenoxy-linked piperazine nitrogen and in the dioxolane-linked triazole ring. The increase of amphiphile hydrophobic chain length had a markedly different effect, depending on the amphiphile type: the solubilization capacity of single-chain surfactants increased, whereas a decrease was observed for double-chained surfactants (phosphatidylglycerols). The excellent correlation between the chain melting temperatures of phosphatidylglycerols and itraconazole solubilization illustrated the importance of hydrophobic chain mobility. This study provides rules for selection of itraconazole solubilizers among classical single-chain surfactants and phospholipids. The basic physics underpinning the described effects suggests that these rules should be transferrable to other “brick-dust” molecules.

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