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Molecular dynamics study of admixture influence on structural properties and stability of fatty acid Langmuir monolayers
Kubániová, Denisa ; Roeselová, Martina (advisor) ; Barvík, Ivan (referee)
Using the classical molecular dynamics simulations, the interfacial partitioning of selected aromatic species, namely benzoic acid and neutral and zwitterionic form of L-phenylalanine, was studied in the three slab systems: a) aqueous organics solution, b) palmitic acid monolayer in tilted condensed phase at aqueous organics solution and c) palmitic acid monolayer in tilted condensed - 2D gas phase coexistence at aqueous organics solution. The surface activity and the tendency to aggregate in particular at the air- aqueous and palmitic acid-aqueous interface was confirmed for all of the investigated aromatic species. The results of the simulation performed for the system of palmitic acid monolayer at benzoic acid solution were compared with the literature results of a similar simulation that employed a different parametrization. The comparison showed that the behaviour of the aromatic species at the fatty acid monolayer-aqueous interface strongly depends on the force field. The structural properties of the palmitic acid Langmuir monolayers were evaluated by means of the chain tilt angle and the headgroup region dihedral angle distributions analysis depending on the surface film density and the adsorbed aromatic species. The simulations mimicking the isothermal compression of the mixed monolayer in the...
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Molecular dynamics study of admixture influence on structural properties and stability of fatty acid Langmuir monolayers
Kubániová, Denisa ; Roeselová, Martina (advisor)
Using the classical molecular dynamics simulations, the interfacial partitioning of selected aromatic species, namely benzoic acid and neutral and zwitterionic form of L-phenylalanine, was studied in the three slab systems: a) aqueous organics solution, b) palmitic acid monolayer in tilted condensed phase at aqueous organics solution and c) palmitic acid monolayer in tilted condensed - 2D gas phase coexistence at aqueous organics solution. The surface activity and the tendency to aggregate in particular at the air- aqueous and palmitic acid-aqueous interface was confirmed for all of the investigated aromatic species. The results of the simulation performed for the system of palmitic acid monolayer at benzoic acid solution were compared with the literature results of a similar simulation that employed a different parametrization. The comparison showed that the behaviour of the aromatic species at the fatty acid monolayer-aqueous interface strongly depends on the force field. The structural properties of the palmitic acid Langmuir monolayers were evaluated by means of the chain tilt angle and the headgroup region dihedral angle distributions analysis depending on the surface film density and the adsorbed aromatic species. The simulations mimicking the isothermal compression of the mixed monolayer in the...
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Molecular dynamics study of admixture influence on structural properties and stability of fatty acid Langmuir monolayers
Kubániová, Denisa ; Roeselová, Martina (advisor)
Using the classical molecular dynamics simulations, the interfacial partitioning of selected aromatic species, namely benzoic acid and neutral and zwitterionic form of L-phenylalanine, was studied in the three slab systems: a) aqueous organics solution, b) palmitic acid monolayer in tilted condensed phase at aqueous organics solution and c) palmitic acid monolayer in tilted condensed - 2D gas phase coexistence at aqueous organics solution. The surface activity and the tendency to aggregate in particular at the air- aqueous and palmitic acid-aqueous interface was confirmed for all of the investigated aromatic species. The results of the simulation performed for the system of palmitic acid monolayer at benzoic acid solution were compared with the literature results of a similar simulation that employed a different parametrization. The comparison showed that the behaviour of the aromatic species at the fatty acid monolayer-aqueous interface strongly depends on the force field. The structural properties of the palmitic acid Langmuir monolayers were evaluated by means of the chain tilt angle and the headgroup region dihedral angle distributions analysis depending on the surface film density and the adsorbed aromatic species. The simulations mimicking the isothermal compression of the mixed monolayer in the...
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Molecular dynamics study of admixture influence on structural properties and stability of fatty acid Langmuir monolayers
Kubániová, Denisa ; Roeselová, Martina (advisor) ; Barvík, Ivan (referee)
Using the classical molecular dynamics simulations, the interfacial partitioning of selected aromatic species, namely benzoic acid and neutral and zwitterionic form of L-phenylalanine, was studied in the three slab systems: a) aqueous organics solution, b) palmitic acid monolayer in tilted condensed phase at aqueous organics solution and c) palmitic acid monolayer in tilted condensed - 2D gas phase coexistence at aqueous organics solution. The surface activity and the tendency to aggregate in particular at the air- aqueous and palmitic acid-aqueous interface was confirmed for all of the investigated aromatic species. The results of the simulation performed for the system of palmitic acid monolayer at benzoic acid solution were compared with the literature results of a similar simulation that employed a different parametrization. The comparison showed that the behaviour of the aromatic species at the fatty acid monolayer-aqueous interface strongly depends on the force field. The structural properties of the palmitic acid Langmuir monolayers were evaluated by means of the chain tilt angle and the headgroup region dihedral angle distributions analysis depending on the surface film density and the adsorbed aromatic species. The simulations mimicking the isothermal compression of the mixed monolayer in the...
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Interaction of aminoacids with phospholipid monolayers
Kukharchuk, Alexandra ; Roeselová, Martina (advisor) ; Pospíšil, Miroslav (referee)
The aim of the thesis is to get insight into the interactions between amino acids with a hydrophobic side- chain and a phospholipid monolayer on the water-air interface via molecular dynamics. There were three simulations performed: a) simulation of leucine in aqueous solution, b) simulation of leucine at the solution - air interface c) simulation of leucine solution with DPPC phospholipid monolayer at its surface. These simulations demonstrate that leucine shows surface activity and tendency to aggregate, particularly at the water surface. This tendency also remains in the presence of DPPC monolayer. In addition, intercalation of leucine between DPPC molecules was observed, leading to creation of small pores in the DPPC monolayer. The results of the simulation with leucine were compared with the results of a previously done analogous simulation with phenylalanine. The comparison showed that phenylalanine penetrates into the DPPC monolayer more than leucine, however the depth of penetration between DPPC molecules is almost the same for both amino acids. Powered by TCPDF (www.tcpdf.org)
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Does oxidation make the organic aerosol coatings more hydrophilic? Insight from molecular dynamics study of oxidized surfactant monolayers
Roeselová, Martina ; Khabiri, Morteza ; Cwiklik, Lukasz
Organic compounds are ubiquitous in atmospheric aerosols. The morphology and structure of the organic phase affect the optical properties of the aerosols, their heterogeneous reactivity as well as their ability to nucleate cloud droplets and ice particles. It is commonly assumed that atmospheric oxidative ageing of the organic material, leading to the formation of polar groups such as carbonyl (=O), hydroxyl (-OH) and carboxylic acid (-COOH), will render the aerosol particle surfaces increasingly more hydrophilic, hence, able to take up more water. Field measurements have shown that a large fraction of the organic material found in aerosols are surface active compounds, such as fatty acids and lipids(Tervahattu, 2002 and 2005). An inverted micelle structure, with an aqueous core surrounded by an organic surfactant layer, has thus been proposed for aqueous aerosols, both marine and continental (Donaldson, 2006). While recent experiments suggest the existence of more complex structures, such as organic inclusions and surfactant lenses (Dennis-Smither, 2012), a monolayer (ML) of surface active organics on an aqueous subphase (the so called Langmuir monolayers) represents the basic model system used in laboratory studies aimed at elucidating the effect of oxidative processes on structural properties of organic coatings on aerosol particles. In our previous work, we used molecular dynamics computer simulations to study the structure and stability of oxidized phospholipid MLs (Khabiri, 2012). In this contribution, we employed the molecular dynamics simulation technique to investigate – with atomistic resolution – structural changes occuring in a fatty acid ML upon moderate degree of oxidation.
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Molecular simulations unravel preference of haloalkanes for the air/water interface
Habartová, Alena ; Minofar, Babak ; Obisesan, A. ; Roeselová, Martina
Halogenated organics are emitted into the atmosphere from a variety of sources of both natural and anthropogenic origin (Finlayson-Pitts et al., 2000). Their uptake at the surface of aerosols can affect their reactivity, for example in processes which take part in ozone destruction due to production of reactive chlorine, bromine and iodine radicals. This study presents results of molecular dynamic (MD) simulations carried out to investigate the interaction of short-chain haloalkanes with aqueous surfaces. We report on a free energy minimum that the haloalkanes exhibit at the air/water interface.
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