Molecules Of Different Polarity Research Articles

An Insight into the Molecular Electronic Structure of Graphene Oxides and Their Interactions with Molecules of Different Polarities Using Quantum Chemical and COSMO-RS Calculations.

A systematic theoretical study on the molecular electronic structure of graphene and its oxides, including their interactions with molecular species of different polarity, was carried out. The influence of the O/C atomic ratio in the graphene oxides was also evaluated. Quantum chemical and COSMO-based statistical-thermodynamic calculations were performed. Geometry optimizations demonstrated that graphene sheets are structurally distorted by oxygen substitution, although they show high resistance to deformation. Furthermore, under axial O-C bonding, proton-donor and proton-acceptor centers are created on the graphene oxide surface, which could acquire an amphoteric character. In low-oxidized graphene oxides, H-bonding centers coexist with neutral highly polarizable π electron clouds. Deep graphene oxidation is also related to the formation of a quasi-two-dimensional H-bond network. These two phenomena are responsible for the exceptional adsorption and catalytic properties and the potential proton conductivity of graphene oxides. The current calculations demonstrated that the interactions of polar molecular species with deep-oxidized graphene derivatives are thermodynamically favorable, but not with low-oxidized ones. The capacity of the quantum chemical and COSMO-RS calculations to model all these issues opens the possibility of selecting or designing graphene-based materials with optimized properties for specific applications. Also, they are valuable in selecting/designing solvents with good exfoliant properties with respect to certain graphene derivatives.

Exploring the Properties of Unilamellar Vesicle Bilayers Formed by Ionic Liquid Surfactants for Future Applications in Nanomedicine.

Two ionic liquids (ILs) with amphiphilic properties composed of 1-butyl-3-methylimidazolium dioctylsulfosuccinate (bmim-AOT) and 1-hexyl-3-methylimidazolium dioctylsulfosuccinate (hmim-AOT) form unilamellar vesicles spontaneously simply by dissolving the IL-like surfactant in water. These novel vesicles were characterized using two different and highly sensitive fluorescent probes: 6-propionyl-2-(dimethylaminonaphthalene) (PRODAN) and trans-4-[4-(dimethylamino)-styryl]-1-methylpyridinium iodide (HC). These fluorescent probes provide information about the physicochemical properties of the bilayer, such as micropolarity, microviscosity, and electron-donor capacity. In addition, the biocompatibility of these vesicles with the blood medium was evaluated, and their toxicity was determined using Dictyostelium discoideum amoebas. First, using PRODAN and HC, it was found that the bilayer composition and the chemical structure of the ions at the interface produced differences between both amphiphiles, making the vesicles different. Thus, the bilayer of hmim-AOT vesicles is less polar, more rigid, and has a lower electron-donor capacity than those made by bmim-AOT. Finally, the results obtained from the hemolysis studies and the growth behavior of unicellular amoebas, particularly utilizing the D. discoideum assay, showed that both vesicular systems do not produce toxic effects up to a concentration of 0.02 mg/mL. This elegant assay, devoid of animal usage, highlights the potential of these newly organized systems for the delivery of drugs and bioactive molecules of different polarities.

Effects of surfactant on the molecules of different polarity of solubilization: Based on the study of micellar microscopic morphology mechanism

Determining the macro-solubilization capacities and micro-mechanism of surfactant micelles with low concentration is significant for the optimization of the medium of displacement and the further enhanced oil recovery. In this study, the solubilization capacities and interaction of polar anisole, nonpolar white oil and kerosene (polar and nonpolar) in SDBS and industrial betaine were compared from microscopic to macroscopic point of view with cryogenic transmission electron microscopy, dynamic light scattering and UV–Vis's spectroscopy. The study finds that the solubilization capacities were positively correlated with the concentration of micelles and the polar of molecules. Considering the importance of morphology of micelles to the solubilization capacities, and the morphology of micelles gradually changed from spherical to vesicle with increasing concentration. And the size of micelles was determined, and size were roughly in common with the concentration below 1 wt% or else the size of betaine was bigger than that of SDBS, which indicated that betaine might be larger and more likely to form vesicles than SDBS at the same concentration. Moreover, anisole is localized in the surface of micelles and size of solubilizing anisole was the biggest, which indicates the solubilization maxima was positively correlated with the volume of swelling micelle. These results imply that the concentration, morphology and solubilization location of micelles appear to important factors affecting the solubilization performance of surfactant. • Solubilization of micelles: The solubilization capacity of betaine and SDBS is positively correlated with concentration of surfactance and that of SDBS was greatly higher than betaine at same concentration no matter what additions solubilized. • Morphology of micelles: Morphology of micelles gradually changed from spherical to vesicle with increasing concentration. • Size of micelles: The type of particle diameters indicates slightly that the ability of morphological transformation for SDBS is better than betaine solution with medium concentration. For high concentration of micelles, the conclusion is the opposite. • Solubilization site: The polar composition of anisole mainly solubilized in the surface of micelles and the nonpolar of white oil solubilized in the core.

Methodological Considerations for Lipid and Polar Component Analyses in Human Skin Stratum Corneum.

Collection of skin very top layer, called stratum corneum, by tape stripping and the analysis of stratum corneum components by mass spectrometry provides multiple advantages for clinical studies that aim to understand the origins of allergic skin diseases and food allergy. However, such a methodology has multiple challenges on the way of complex stratum corneum analysis when molecules of different polarity are needed to be analyzed from minimal amount of skin tape strips. This review provides an overview of current knowledge about lipid and polar molecules in the skin, discusses challenging aspects of sample processing when dealing with skin tape strips, and provides some guidance towards approaches that generate complex, quantitative, normalized to total sample protein data that fit best the purpose of analysis of stratum corneum components for the purpose of clinical trials.

Solubility and Aggregation of Selected Proteins Interpreted on the Basis of Hydrophobicity Distribution.

Protein solubility is based on the compatibility of the specific protein surface with the polar aquatic environment. The exposure of polar residues to the protein surface promotes the protein’s solubility in the polar environment. The aquatic environment also influences the folding process by favoring the centralization of hydrophobic residues with the simultaneous exposure to polar residues. The degree of compatibility of the residue distribution, with the model of the concentration of hydrophobic residues in the center of the molecule, with the simultaneous exposure of polar residues is determined by the sequence of amino acids in the chain. The fuzzy oil drop model enables the quantification of the degree of compatibility of the hydrophobicity distribution observed in the protein to a form fully consistent with the Gaussian 3D function, which expresses an idealized distribution that meets the preferences of the polar water environment. The varied degrees of compatibility of the distribution observed with the idealized one allow the prediction of preferences to interactions with molecules of different polarity, including water molecules in particular. This paper analyzes a set of proteins with different levels of hydrophobicity distribution in the context of the solubility of a given protein and the possibility of complex formation.

Molecular Basis for the Morphological Transitions of Surfactant Wormlike Micelles Triggered by Encapsulated Nonpolar Molecules.

Surfactant wormlike micelles are prone to experience morphological changes, including the transition to spherical micelles, upon the addition of nonpolar additives. These morphological transitions have profound implications in diverse technological areas, such as the oil and personal-care industries. In this work, additive-induced morphological transitions in wormlike micelles were studied using a molecular theory that predicts the equilibrium morphology and internal molecular organization of the micelles as a function of their composition and the molecular properties of their components. The model successfully captures the transition from wormlike to spherical micelles upon the addition of a nonpolar molecule. Moreover, the predicted effects of the concentration, molecular structure, and degree of hydrophobicity of the nonpolar additive on the wormlike-to-sphere transition are shown to be in good agreement with experimental trends in the literature. The theory predicts that the location of the additive in the micelle (core or hydrophobic-hydrophilic interface) depends on the additive hydrophobicity and content, and the morphology of the micelles. Based on the results of our model, simple molecular mechanisms were proposed to explain the morphological transitions of wormlike micelles upon the addition of nonpolar molecules of different polarities.

Real-time time-dependent density functional theory using density fitting and the continuous fast multipole method.

An implementation of real-time time-dependent density functional theory (RT-TDDFT) within the TURBOMOLE program package is reported using Gaussian-type orbitals as basis functions, second and fourth order Magnus propagator, and the self-consistent field as well as the predictor-corrector time integration schemes. The Coulomb contribution to the Kohn-Sham matrix is calculated combining density fitting approximation and the continuous fast multipole method. Performance of the implementation is benchmarked for molecular systems with different sizes and dimensionalities. For linear alkane chains, the wall time for density matrix time propagation step is comparable to the Kohn-Sham (KS) matrix construction. However, for larger two- and three-dimensional molecules, with up to about 5,000 basis functions, the computational effort of RT-TDDFT calculations is dominated by the KS matrix evaluation. In addition, the maximum time step is evaluated using a set of small molecules of different polarities. The photoabsorption spectra of several molecular systems calculated using RT-TDDFT are compared to those obtained using linear response time-dependent density functional theory and coupled cluster methods.

Comparative skin penetration profiles of formulations including ultradeformable liposomes as potential nanocosmeceutical carriers.

Ultradeformable liposomes are promising carriers for cosmeceutical actives as they can be loaded with molecules of different polarities, and they present unique penetration properties. While those features have already been tested, we wanted to know whether their special penetration properties could be maintained after incorporation in diverse cosmetic vehicles, including commercial products already in the market. Ultradeformable liposomes loaded with a lipophilic and a hydrophilic fluorescent probe were prepared by lipid film resuspension, followed by extrusion and incorporation to different vehicles and commercial products. Penetration was determined in human and pig skin by incubation, with the Saarbrücken penetration model, followed by the recovery of the probes or by fluorescence microscopy. The incorporation of ultradeformable liposomes to cosmetic vehicles did not alter their penetration in most of the cases for human skin explants. Pig skin penetration presented significant differences compared with human explants. Ultradeformable liposomes could be useful as versatile cosmeceutical carriers in final product formulations.

Depth-resolved impact of integration process on porosity and solvent diffusion in a SiOCH low-k material

The impact of plasma etching and chemical wet cleaning on solvent diffusion in porous network of a SiOCH low-k dielectric material is studied. Characterization of porosity and pore size distribution by means of ellipso-porosimetry and positron annihilation lifetime spectroscopy are presented. The results are compared with solvent diffusion kinetics, measured using probe molecules of different polarity, surface energies and molecular sizes. Infrared spectroscopy, Doppler broadening of annihilation radiation and time-of-flight secondary ion mass spectrometry measurements are also performed to investigate material modifications causing variations of diffusion kinetics.

Diffusion of polar and non-polar molecules in a polymer membrane

Diffusion of small molecules of different polarities in polymeric membranes is the most interesting in terms of studying thermodynamic and kinetic parameters of the separation process of liquid multicomponent organic mixtures. In the paper, the principle emphasis is made on diffusion mechanisms of polar and non–polar molecules in flexible, non–polar organic–silicon polymers. For estimating the diffusion rate and determining diffusion mechanisms, the experiments on adsorption and desorption of a number of samples at constant temperature and pressure have been conducted. Dynamics of the curves shows possible kinetic processes, occurring in polymer at its dissolution into non–polar solvents differing in a molecular size. The similar studies have been carried out using polar solvents with different dipole molecular moments. It has shown that the limited dissolution rate for polar solvents compared to non–polar ones is low. It has been found that the principal mechanism of diffusion in the polymer under its dissolving in polar solvents is the Fickian diffusion. Herewith, at the beginning of a sorption process the diffusion runs very fast, and then the process slows down significantly and a macromolecular matrix manages to complete relaxation, not allowing the solvent molecules to deform the lattice further. In the process of dissolving the polymer in solvents with non–polar molecules the main mechanism of diffusion is not the Fickian diffusion. Moreover, a more low–molecular solvent causes a high degree of swelling that is associated with a higher mobility of molecules and the possibility of their rapid penetration into the polymer depth at the beginning of dissolving. A long time “tail” while desorbing the polymer, dissolved in non–polar solvents shows that there is a second diffusion type. There are obvious micropores in the polymer, through which small non–polar molecules can be trapped and can form clusters with polymer alloys. When desorbing the temperature of carrying out the process is not sufficient for activating such centers.

The surface reactivity of chalk (biogenic calcite) with hydrophilic and hydrophobic functional groups

The surface properties of calcium carbonate minerals play an important role in a number of industrial and biological processes. Properties such as wettability and adsorption control liquid–solid interface behaviour and thus have a strong influence on processes such as biomineralisation, remediation of aquifers and oil recovery. We investigated how two model molecules of different polarity, namely water and ethanol, interact with reservoir and outcrop chalk samples and we compared their behaviour with that of pure, inorganically precipitated calcite. Thermodynamic quantities, such as the work of wetting, surface energy and isosteric adsorption enthalpy, were determined from vapour adsorption isotherms. The chalks were studied fresh and after extraction of organic residues that were originally present in these samples. The work of wetting correlates with the amount of organic matter present in the chalk samples but we observed a fundamental difference between the adsorption properties of chalk and pure, inorganically precipitated calcite toward the less polar, ethanol molecule. Further analysis of the chemical composition of the organic matter extracted from the chalk samples was made by gas chromatography (GC–MS). Monitoring surface composition by X-ray photoelectron spectroscopy (XPS) before and after extraction of the organic material, and with atomic force microscopy (AFM), showed that nanometer sized clay crystals observed on the chalk particle surfaces could be an important part of the reason for the differences. Removal of the extractable portion of the hydrocarbons liberates adsorption sites that have different wetting properties than the rest of the chalk and these have an energy distribution that is similar to clays. Thus, the results exemplify the complexity of biogenic calcite adsorption behaviour and demonstrate that chalk wetting in drinking water aquifers as well as oil reservoirs is controlled partly by the nanoparticles of clay that have grown on the chalk surfaces and partly by adsorbed organic material.

Surface energy analysis (SEA) study of hyaluronan powders

Results of inverse gas chromatography adsorption/desorption experiments of selected probes on sodium hyaluronate powder material are presented. It was found that a dominating was a dispersive surface energy part thus indicating low polarity character of the studied HA powder. For 0% coverage 30mJ/m2 total surface energy was found. There was found a relatively high inhomogeneity of the surface structure of the studied polymer powder. A total surface energy distribution was ranging from 10 to 34mJ/m2 with maximum at 18.5mJ/m2. It was similarly as in the previous case of surface energy profile controlled by dispersive part. By measuring free energy profiles dependencies for selected probe molecules of different polarity there was found approximately seven-fold higher energy content (15kJ/mol) in comparison to dichloromethane (2kJ/mol). There were determined work of cohesion and work of adhesion (water) on HA surface.

Interaction of Retinoic Acid Radical Cation with Lysozyme and Antioxidants: Laser Flash Photolysis Study in Microemulsion

All-trans retinoic acid (ATRA) plays essential roles in the normal biological processes and the treatment of cancer and skin diseases. Considering its photosensitive property, many studies have been focused on the photochemistry of ATRA. In this study, we investigated the transient phenomena in the laser flash photolysis (LFP) of ATRA in microemulsion to further understand the photochemistry of ATRA. Results show that 355 nm LFP of ATRA in both acidic and alkaline conditions leads to the generation of retinoic acid cation radicals (ATRA(•+)) via biphotonic processes. The employment of microemulsion system allows us to investigate the reaction of hydrophobic ATRA(•+) with molecules of different polarity. Therefore, we studied the reaction activity of ATRA(•+) to many hydrophobic and hydrophilic molecules. Results show that ATRA(•+) can efficiently interact with lysozyme, tyrosine, tryptophan and many antioxidants, such as curcumin (Cur), vitamin C (VC) and gallic acid (GA). The apparent rate constants of these reactions were measured and compared. These findings suggest that ATRA(•+) is a reactive transient product which may pose damage to lysozyme, and antioxidants, such as Cur, VC and GA, may inactivate ATRA(•+) by efficient quenching reactions.

Electron ionization in LC-MS: recent developments and applications of the direct-EI LC-MS interface

The purpose of this article is to underline the possibility of efficiently using electron ionization (EI) in liquid chromatography (LC) and mass spectrometry (MS). From a historical perspective, EI accompanied the first attempts in LC-MS but, owing to several technical shortcomings, it was soon outshined by soft, atmospheric pressure ionization (API) techniques. Nowadays, two modern approaches, supersonic molecular beam LC-MS and direct-EI LC-MS, offer a valid alterative to API, and preserve the advantages of EI also in LC-MS applications. These advantages can be summarized in three crucial aspects: automated library identification; identification of unknown compounds, owing to EI extensive fragment information; inertness to coeluted matrix interferences owing to very unlikely ion-ion and ion-molecule interactions in the EI gas-phase environment. The direct-EI LC-MS interface is a simple and efficient solution able to produce high-quality, interpretable EI spectra from a wide range of low molecular weight molecules of different polarity. Because of the low operative flow rates, this interface relies on a nano-LC technology that helps in reducing the impact of the mobile phase on the gas-phase environment of EI. This review provides an extensive discussion on the role of EI in LC-MS interfacing, and presents in detail several performance aspects of the direct-EI LC-MS interface, especially in terms of response, mass-spectral quality, and matrix effects. In addition, several key applications are also reported.

Organochlorine Pesticides by LC−MS

Contamination of water resources by organochlorine pesticides (OCPs) continues to receive widespread attention because of the increasing concern regarding their high persistence and bioaccumulation. These organic pollutants are not amenable by liquid chromatography (LC) coupled to atmospheric pressure ionization-mass spectrometry, which represents the method of choice for the characterization of pesticide residues in water. Gas chromatography-mass spectrometry provides excellent response for OCPs, but it falls short when complex, multiresidue analyses are required. As recently demonstrated, an efficient EI-based LC-MS interface can generate very good spectra for an extremely wide range of small-medium molecular weight molecules of different polarity and can represent a valid tool in solving the analytical challenge of analyzing OCPs by LC-MS. Based on this assumption, we present a new approach for the determination of 12 OCPs in water samples. The method requires a solid-phase extraction preconcentration step followed by nanoscale liquid chromatography coupled to a direct-electron ionization direct interface (Direct-EI). Direct-EI is a miniaturized interface for efficiently coupling a liquid chromatograph with an EI mass spectrometer. The capability to acquire high-quality EI spectra in a wide range of concentrations, and to operate in selected ion monitoring mode during analyses, allowed a precise quantification of the OCPs. Without sample injection enrichment, limits of detection of the method span from 0.044 to 0.33 microg/L, corresponding to an instrumental detection limit of 120-850 pg. In addition, a careful evaluation of the matrix effect showed that the response of the Direct-EI interface was never affected by sample interferences. From our knowledge, the proposed method represents the first application of LC-MS in the analysis of organochlorine pesticides.

Electrostatic versus polarization effects in the adsorption of aromatic molecules of variedpolarity on an insulating hydrophobic surface

Ab initio calculations have been used to investigate the electronic and energeticbehaviour accompanying the adsorption of aromatic molecules of different polaritiesonto an insulating hydrophobic surface, as a convenient model for the study ofcharacteristic weak adsorption processes in biochemistry (ligand–receptor interactions)and geochemistry (aromatic pollutants on soil minerals). Four poly-chlorinateddibenzo-p-dioxin molecules of different polarities were chosen as adsorbates; the surface was the (001)surface of pyrophyllite, a chemically inert, weakly polar, covalently bonded surface. Thefairly weak interactions were observed to be dominated by local electrostatics rather thanglobal multipoles or hybridization. The polarization induced on the adsorbate has beenanalysed. A small transfer of electron density was also observed from the molecule to thesurface.

ESR imaging investigations of two‐phase systems

The possibilities of electron spin resonance (ESR) and electron spin resonance imaging (ESRI) for investigating the properties of the spin probes TEMPO and TEMPOL in two-phase systems have been examined in the systems water/n-octanol, Miglyol/Miglyol, and Precirol/Miglyol. Phases and regions of the phase boundary could be mapped successfully by means of the isotropic hyperfine coupling constants, and, moreover, the quantification of rotational and lateral diffusion of the spin probes was possible. For the quantitative treatment of the micropolarity, a simplified empirical model was established on the basis of the Nernst distribution and the experimentally determined isotropic hyperfine coupling constants. The model does not only describe the summarized micropolarities of coexisting phases, but also the region of the phase boundary, where solvent molecules of different polarities and tendencies to form hydrogen bonds compete to interact with the NO group of the spin probe.

Prenematic Behavior of the Electric-Field-Induced Increment of the Basic Thermodynamic Quantities of Isotropic Mesogenic Liquids of Different Polarity

Temperature dependences of the static dielectric permittivity and its derivative, obtained for isotropic mesogenic liquids composed of the molecules of different polarity in relation to the basic thermodynamic quantities (internal energy, entropy, and Helmholtz free energy), are analyzed. A role of the molecular polarity in the dielectric behavior of the liquids in the vicinity of the isotropic to nematic phase transition is discussed.

Hosting Ability of Mesoporous Micelle-Templated Silicas toward Organic Molecules of Different Polarity

Spin probe water solutions were adsorbed onto differently treated micelle-templated silicas (MTS) of different pore sizes to analyze the hosting ability of the MTS surface toward different organic molecules. The MTS synthesis was performed at 388 K by self-assembly of inorganic silica and micelles of cetyltrimethylammonium bromide (CTAB) to which different amounts of 1,3,5 trimethylbenzene (TMB) were added at different TMB/CTAB ratios to modify the pore size: 40, 65, and 80 Å pore diameter were obtained for TMB/CTAB ratio = 0, 2.7, and 13, respectively. As-synthesized MTS, calcined MTS, and octyldimethyl(C8) grafted MTS were used. These MTS were characterized by means of nitrogen sorption isotherms and TEM as homoporous silica with regular and reproducible structure. Different spin probes (nitroxides) were taken as models for different types of organic molecules, namely, neutral and charged molecules and surfactants. The computer aided analysis of the electron paramagnetic resonance (EPR) spectra of these probes provided information on the hosting ability of the differently treated solid surface in respect of the different structure and hydrophilicity of the probes. The spectral analysis allowed the depiction of the probable distribution and location of the different probes at the differently treated silica surfaces. For the as-synthesized MTS, void space became available for the probe adsorption in vicinity of the surface when TMB was used in the synthesis and then evaporated. For the calcined MTSs, the hydrophobic sites at the solid surface, namely, siloxanes, increased by increasing the TMB content in the synthesis mixture. The binding of the EPR probe with the surface of these MTS is favored when both hydrophilic and hydrophobic interactions occur, as found with surfactant probes bearing both a hydrophilic and a hydrophobic moiety. For the C8-grafted MTSs, the results provided a proof of the quality of grafting: the surface is largely hydrophobic and favors self-aggregation of the surfactant probes, led by chain−chain interactions.

Effect of microporosity and oxygen surface groups of activated carbon in the adsorption of molecules of different polarity

This work describes the adsorption of molecules with different polarity (N{sub 2}SO{sub 2}H{sub 2}O, and CH{sub 3}OH) on microporous activated carbons with different amounts of oxygen surface groups. The results presented show that both the microporosity and the chemical nature of the carbon surface affect the adsorption process: for nonpolar molecules (i.e., N{sub 2}) the adsorption is mainly influenced by the porous structure, but the nature and amount of oxygen surface groups are extremely important in the adsorption of polar molecules, the more important the higher the polarity of the molecule. On the other hand, there is a noticeable change in the adsorption mechanism of polar molecules at low relative pressures, the change being more drastic for carbons with wide micropores and low content of oxygen surface groups. 20 refs., 9 figs., 4 tabs.