Interactions between polycyclic aromatic hydrocarbons (PAHs) and phospholipids cause PAH migration into wet gums during the oil degumming process.

The refining process can reduce PAH contamination levels in vegetable oils, but the safety of byproducts requires further attention. We hypothesize that interactions between PAHs and phospholipids could contribute to PAH migration into the wet gums and subsequently evaluated the distribution of PAHs during different degumming processes. Enzymatic degumming achieved over 99.90 % removal of phospholipids from soybean oil and sunflower seed oil and minimized the toxic equivalency quotient of PAHs in wet gums (approximately 0.05 µg/kg). Notably, greater PAH reduction was correlated with greater phospholipid removal in degummed soybean oil. Quantum chemical calculations indicated that van der Waals forces between PAHs and phospholipids could cause PAH migration, with higher phospholipid contents and PAH contamination in soybean oil providing more favourable conditions than in sunflower seed oil. This study will help to improve the quality of edible oils and provide information on the mechanisms underlying PAH migration.

A Terrylene Bisimide based Universal Host for Aromatic Guests to Derive Contact Surface-Dependent Dispersion Energies.

π-π interactions are among the most important intermolecular interactions in supramolecular systems. Here we determine experimentally a universal parameter for their strength that is simply based on the size of the interacting contact surfaces. Toward this goal we designed a new cyclophane based on terrylene bisimide (TBI) π-walls connected by para-xylylene spacer units. With its extended π-surface this cyclophane proved to be an excellent and universal host for the complexation of π-conjugated guests, including small and large polycyclic aromatic hydrocarbons (PAHs) as well as dye molecules. The observed binding constants range up to 108 M-1 and show a linear dependence on the 2D area size of the guest molecules. This correlation can be used for the prediction of binding constants and for the design of new host-guest systems based on the herewith derived universal Gibbs interaction energy parameter of 0.31 kJ/molÅ2 in chloroform.

Understanding the Nature and Strength of Noncovalent Face-to-Face Arene-Fullerene Interactions.

Face-to-face noncovalent arene-fullerene interactions are important in several research fields such as synthetic chemistry, materials chemistry, and medicinal chemistry; however, their nature and strength are still poorly understood. In this study, we prepare a fullerene-based torsion balance containing thioanisole, phenol, naphthalene, azulene, and pyrene moieties as a unimolecular model system. Moreover, we compare the folding free energies between the folded and the unfolded conformers of a series of the molecular torsion balances to quantify noncovalent interactions between arenes and the fullerene surface. This work demonstrates that the contributions of polarizabilities, anionic charges, electronic dipole moments, and the number of arene rings to the interactions can be experimentally measured by analyzing the folding equilibrium of the molecular torsion balances.

ERα-agonist and ERß-antagonist bifunctional next-generation bisphenols with no halogens: BPAP, BPB, and BPZ.

As demonstrated for bisphenol AF (BPAF), the electrostatic halogen bond based on the London dispersion force of halogen atoms was found to be a major driving force of their bifunctional ERα-agonist and ERß-antagonist activities. Because similar electronic effects are anticipated for hydrocarbon groups (alkyl or aryl groups), we hypothesized that bisphenol compounds consisting of such groups also work bifunctionally. In the present study, we examined bisphenol AP (BPAP), B (BPB), and Z (BPZ). After recognizing their considerably strong receptor binding affinities, we evaluated the abilities of BPAP, BPB, and BPZ to activate ERα and ERß in a luciferase reporter gene assay. These bisphenols were fully active for ERα but completely inactive for ERß. When we examined their inhibitory activities for 17ß-estradiol in ERß by two different qualitative and quantitative analytical methods, we found that those bisphenols worked as definite antagonists. Consequently, they were established as bifunctional ERα-agonists and ERß-antagonists. The present structure-activity analyses revealed that the dispersion force works not only on the halogens but also on the hydrocarbon groups, and that it is a major driving force of bifunctional ERα-agonist and ERß-antagonist activities.

A Fullerene-Based Molecular Torsion Balance for Investigating Noncovalent Interactions at the C60 Surface.

To investigate the nature and strength of noncovalent interactions at the fullerene surface, molecular torsion balances consisting of C60 and organic moieties connected through a biphenyl linkage were synthesized. NMR and computational studies show that the unimolecular system remains in equilibrium between well-defined folded and unfolded conformers owing to restricted rotation around the biphenyl C-C bond. The energy differences between the two conformers depend on the substituents and is ascribed to differences in the intramolecular noncovalent interactions between the organic moieties and the fullerene surface. Fullerenes favor interacting with the π-faces of benzenes bearing electron-donating substituents. The correlation between the folding free energies and corresponding Hammett constants of the substituents in the arene-containing torsion balances reflects the contributions of the electrostatic interactions and dispersion force to face-to-face arene-fullerene interactions.

Molecular interactions in nanocellulose assembly.

The contribution of hydrogen bonds and the London dispersion force in the cohesion of cellulose is discussed in the light of the structure, spectroscopic data, empirical molecular-modelling parameters and thermodynamics data of analogue molecules. The hydrogen bond of cellulose is mainly electrostatic, and the stabilization energy in cellulose for each hydrogen bond is estimated to be between 17 and 30 kJ mol-1 On average, hydroxyl groups of cellulose form hydrogen bonds comparable to those of other simple alcohols. The London dispersion interaction may be estimated from empirical attraction terms in molecular modelling by simple integration over all components. Although this interaction extends to relatively large distances in colloidal systems, the short-range interaction is dominant for the cohesion of cellulose and is equivalent to a compression of 3 GPa. Trends of heat of vaporization of alkyl alcohols and alkanes suggests a stabilization by such hydroxyl group hydrogen bonding to be of the order of 24 kJ mol-1, whereas the London dispersion force contributes about 0.41 kJ mol-1 Da-1 The simple arithmetic sum of the energy is consistent with the experimental enthalpy of sublimation of small sugars, where the main part of the cohesive energy comes from hydrogen bonds. For cellulose, because of the reduced number of hydroxyl groups, the London dispersion force provides the main contribution to intermolecular cohesion.This article is part of a discussion meeting issue 'New horizons for cellulose nanotechnology'.

ß-Cristobalite (001) surface as 4-formaminoantipyrine adsorbent: First principle study of the effect on adsorption of surface modification.

Silica based materials find applications as excipients and particularly as drug delivery agents for pharmaceutical drugs. Their performance can be crucially affected by surface treatments, as it can modify the adsorption (and release) of these formulations. The role of surface modification on the features of 4-formaminoantipyrine (FAA) adsorbed on ß-cristobalite (001) surface is studied by means of simulations based on the Density Functional Theory (DFT). Starting from the results of FAA in interaction with a dehydroxylated surface; a fully hydroxylated surface and a functionalized surface with benzalkonium chloride (BC) surfactant have been added to study the configurational landscape. Calculations suggest that the trend for FAA preferential adsorption on silica surfaces is: dehydroxylated>hydroxylated>BC-functionalized. The potential for hydrogen bonding causes the main contribution to the bonding while dispersion forces present an additional contribution independently of whether the drug is hydrogen-bonded or BC-bonded to the surface. Adsorption takes mainly place through nitrogen atoms in the heterocyclic ring, the carbonyl and amine functional groups. Associated mode's shifts and concurrent changes in bond length are also observed showing accordance between electronic and geometrical structure results. BC surfactant reduces the number of formed H-bonds and lowers the attractive molecule-surface interaction being it useful to prevent particle agglomeration and could favor drug release in therapies that requires faster but controlled delivery.

Interfacial Charge Transfer in Dye-Sensitized Solar Cells Using SCN-Free Terpyridine-Coordinated Ru Complex Dye and Co Complex Redox Couples.

The efficiency of dye-sensitized solar cells (DSSCs) using Ru complex dyes and Co complex redox couples has been increased with a strategy to prevent charge recombination via the addition of bulky or lengthy peripheral units to the dyes. However, despite the efforts, most of the DSSCs are still suffering from nonunity quantum efficiency and fast recombination. We examine the effect of SCN ligand, which has been used for many Ru complex dyes and could attract positively charged Co complexes. We find that replacing the ligands with 2,6-bis(2'-(4'-trifluoromethyl)pyrazolyl)pyridine increases the quantum efficiency and electron lifetime. With the combination of the replacement of SCN ligands and the addition of bulky moiety, ∼80% external quantum efficiency is achieved. These suggest that not only the addition of a blocking effect but also the reduction of electrostatic and dispersion forces between dyes and Co complexes are essential to control the charge separation and recombination processes.

Local response dispersion method in periodic systems: Implementation and assessment.

We report the implementation of the local response dispersion (LRD) method in an electronic structure program package aimed at periodic systems and an assessment combined with the Perdew-Burke-Ernzerhof (PBE) functional and its revised version (revPBE). The real-space numerical integration was implemented and performed exploiting the electron distribution given by the plane-wave basis set. The dispersion-corrected density functionals revPBE+LRD was found to be suitable for reproducing energetics, structures, and electron distributions in simple substances, molecular crystals, and physical adsorptions.