A molecular dynamics study of the influence of chain branching on the properties of polymer systems

Die vorliegende Arbeit besch��ftigt sich mit dem Einflu�� von Kettenverzweigungen unterschiedlicher Topologien auf die statischen Eigenschaften von Polymeren. Diese Untersuchungen werden mit Hilfe von Monte-Carlo- und Molekular-Dynamik-Simulationen durchgef��hrt.Zun��chst werden einige theoretische Konzepte und Modelle eingef��hrt, welche die Beschreibung von Polymerketten auf mesoskopischen L��ngenskalen gestatten. Es werden wichtige Bestimmungsgr����en eingef��hrt und erl��utert, welche zur quantitativen Charakterisierung von Verzweigungsstrukturen bei Polymeren geeignet sind. Es wird ebenso auf die verwendeten Optimierungstechniken eingegangen, die bei der Implementierung des Computerprogrammes Verwendung fanden. Untersucht werden neben linearen Polymerketten unterschiedliche Topolgien -Sternpolymere mit variabler Armzahl, ��bergang von Sternpolymeren zu linearen Polymeren, Ketten mit variabler Zahl von Seitenketten, regul��re Dendrimere und hyperverzweigte Strukturen - in Abh��ngigkeit von der L��sungsmittelqualit��t. Es wird zun��chst eine gr��ndliche Analyse des verwendeten Simulationsmodells an sehr langen linearen Einzelketten vorgenommen. Die Skalierungseigenschaften der linearen Ketten werden untersucht in dem gesamten L��sungsmittelbereich vom guten L��sungsmittel bis hin zu weitgehend kollabierten Ketten im schlechten L��sungsmittel. Ein wichtiges Ergebnis dieser Arbeit ist die Best��tigung der Korrekturen zum Skalenverhalten des hydrodynamischen Radius Rh. Dieses Ergebnis war m��glich aufgrund der gro��en gew��hlten Kettenl��ngen und der hohen Qualit��t der erhaltenen Daten in dieser Arbeit, insbesondere bei den linearen ketten, und es steht im Widerspruch zu vielen bisherigen Simulations-Studien und experimentellen Arbeiten. Diese Korrekturen zum Skalenverhalten wurden nicht nur f��r die linearen Ketten, sondern auch f��r Sternpolymere mit unterchiedlicher Armzahl gezeigt. F��r lineare Ketten wird der Einflu�� von Polydispersit��t untersucht.Es wird gezeigt, da�� eine eindeutige Abbildung von L��ngenskalen zwischen Simulationsmodell und Experiment nicht m��glich ist, da die zu diesem Zweck verwendete dimensionslose Gr����e eine zu schwache Abh��ngigkeit von der Polymerisation der Ketten besitzt. Ein Vergleich von Simulationsdaten mit industriellem Low-Density-Poly��thylen(LDPE) zeigt, da�� LDPE in Form von stark verzweigten Ketten vorliegt.F��r regul��re Dendrimere konnte ein hochgradiges Zur��ckfalten der Arme in die innere Kernregion nachgewiesen werden.

Polymer-liquid crystal interface: a molecular dynamics study

Liquid crystals (LCs) are an interesting class of soft condensed matter systems characterized by an unusual combination of fluidity and long-range order, mainly known for their applications in displays (LCDs). However, the interest in LC continues to grow pushed by their application in new technologies in medicine, optical imaging, micro and nano technologies etc. In LCDs uniaxial alignment of LCs is mainly achieved by a rubbing process. During this treatment, the surfaces of polymer coated display substrates are rubbed in one direction by a rotating cylinder covered with a rubbing cloth. Basically, LC alignment involves two possible aligning directions: uniaxial planar (homogeneous) and vertical (homeotropic) to the display substrate. An interesting unresolved question concerning LCs regards the origin of their alignment on rubbed surfaces, and in particular on the polymeric ones used in the display industry. Most studies have shown that LCs on the surface of the rubbed polymer film layer are lying parallel to the rubbing direction. In these systems, micrometric grooves are generated on the film surface along the rubbing direction and also the polymer chains are stretched in this direction. Both the parallel aligned microgrooves and the polymer chains at the film surface may play a role in the LC alignment and it is not easy to quantify the effect of each contribution. The work described in this thesis is an attempt to find new microscopic evidences on the origin of LC alignment on polymeric surfaces through molecular dynamics (MD) simulations, which allow the investigation of the phenomenon with atomic detail. The importance of the arrangement of the polymeric chains in LCs alignment was studied by performing MD simulations of a thin film of a typical nematic LC, 4-cyano-4���-pentylbiphenyl (5CB), in contact with two different polymers: poly(methyl methacrylate)(PMMA) and polystyrene (PS). At least four factors are believed to influence the LC alignment: 1. the interactions of LCs with the backbone vinyl chains; 2. the interactions of LCs with the oriented side groups; 3. the anisotropic interactions of LCs with nanometric grooves; 4. the presence of static surface charges. Here we exclude the effect of microgrooves and of static surface charges from our virtual experiment, by using flat and neutral polymer surfaces, with the aim of isolating the chemical driving factors influencing the alignment of LC phases on polymeric surfaces.

Spectroscopic properties from hybrid QM, MM molecular dynamics simulation

The central aim of this thesis work is the application and further development of a hybrid quantum mechanical/molecular mechanics (QM/MM) based approach to compute spectroscopic properties of molecules in complex chemical environments from electronic structure theory. In the framework of this thesis, an existing density functional theory implementation of the QM/MM approach is first used to calculate the nuclear magnetic resonance (NMR) solvent shifts of an adenine molecule in aqueous solution. The findings show that the aqueous solvation with its strongly fluctuating hydrogen bond network leads to specific changes in the NMR resonance lines. Besides the absolute values, also the ordering of the NMR lines changes under the influence of the solvating water molecules. Without the QM/MM scheme, a quantum chemical calculation could have led to an incorrect assignment of these lines. The second part of this thesis describes a methodological improvement of the QM/MM method that is designed for cases in which a covalent chemical bond crosses the QM/MM boundary. The development consists in an automatized protocol to optimize a so-called capping potential that saturates the electronic subsystem in the QM region. The optimization scheme is capable of tuning the parameters in such a way that the deviations of the electronic orbitals between the regular and the truncated (and "capped") molecule are minimized. This in turn results in a considerable improvement of the structural and spectroscopic parameters when computed with the new optimized capping potential within the QM/MM technique. This optimization scheme is applied and benchmarked on the example of truncated carbon-carbon bonds in a set of small test molecules. It turns out that the optimized capping potentials yield an excellent agreement of NMR chemical shifts and protonation energies with respect to the corresponding full molecules. These results are very promising, so that the application to larger biological complexes will significantly improve the reliability of the prediction of the related spectroscopic properties.

Molecular dynamics simulations of sheared brush-like systems

Mit Hilfe von Molekulardynamik-Simulationen untersuchen wir b��rstenartige Systeme unter guten L��sungsmittelbedingungen. Diese Systeme sind, dank ihren vielf��ltigen Beschaffenheiten, die von Molekularparametern und ��u��eren Bedingungen abh��ngig sind, wichtig f��r viele industrielle Anwendungen. Man vermutet, dass die Polymerb��rsten eine entscheidende Rolle in der Natur wegen ihrer einzigartigen Gleiteigenschaften spielen. Ein vergr��bertes Modell wird verwendet, um die strukturellen und dynamischen Eigenschaften zweier hochkomprimierter Polymerb��rsten, die eine niedrige Reibung aufweisen, zu untersuchen. Allerdings sind die Lubrikationseigenschaften dieser Systeme, die in vielen biologischen Systemen vorhanden sind, beeinflu��t. Wir untersuchen so-genannte "weiche Kolloide", die zwischen den beiden Polymerb��rsten eingebettet sind, und wie diese Makroobjekte auf die Polymerb��rsten wirken.rnrnNicht-Gleichgewichts-Molekulardynamik-Simulationen werden durchgef��hrt, in denen die hydrodynamischen Wechselwirkungen durch die Anwendung des DPD-Thermostaten mit expliziten L��sungsmittelmolek��len ber��cksichtigt werden. Wir zeigen, dass die Kenntnis der Gleichgewichtseigenschaften des Systems erlaubt, dynamische Nichtgleichgewichtsigenschaften der Doppelschicht vorherzusagen.rnrnWir untersuchen, wie die effektive Wechselwirkung zwischen kolloidalen Einschl����en durch die Anwesenheit der B��rsten (in Abh��ngigkeit der Weichheit der Kolloide und der Pfropfdichte der B��rsten) beeinflu��t wird. Als n��chsten Schritt untersuchen wir die rheologische Antwort von solchen komplexen Doppelschichten auf Scherung. Wir entwickeln eine Skalen-Theorie, die die Abh��ngigkeit der makroskopischen Transporteigenschaften und der lateralen Ausdehnung der verankerten Ketten von der Weissenberg Zahl oberhalb des Bereichs, in dem die lineare Antwort-Theorie gilt, voraussagt. Die Vorhersagen der Theorie stimmen gut mit unseren und fr��heren numerischen Ergebnissen und neuen Experimenten ��berein. Unsere Theorie bietet die M��glichkeit, die Relaxationszeit der Doppelschicht zu berechnen. Wenn diese Zeit mit einer charakteristischen L��ngenskala kombiniert wird, kann auch das ''transiente'' (nicht-station��re) Verhalten beschrieben werden.rnrnrnWir untersuchen die Antwort des Drucktensors und die Deformation der B��rsten w��hrend der Scherinvertierung f��r grosse Weissenberg Zahlen. Wir entwickeln eine Vorhersage f��r die charakteristische Zeit, nach der das System wieder den station��ren Zustand erreicht.rnrnrnElektrostatik spielt eine bedeutende Rolle in vielen biologischen Prozessen. Die Lubrikationseigenschaften der Polymerb��rsten werden durch die Anwesenheit langreichweitiger Wechselwirkungen stark beeinflusst. F��r unterschiedliche St��rken der elektrostatischen Wechselwirkungen untersuchen wir rheologische Eigenschaften der Doppelschicht und vergleichen mit neutralen Systemen. Wir studieren den kontinuierlichen ��bergang der Systemeigenschaften von neutralen zu stark geladenen B��rsten durch Variation der Bjerruml��nge und der Ladungsdichte.

Novel algorithms for electronic structure based molecular dynamics with linear system-size scaling

Die vorliegende Arbeit behandelt die Entwicklung und Verbesserung von linear skalierenden Algorithmen f��r Elektronenstruktur basierte Molekulardynamik. Molekulardynamik ist eine Methode zur Computersimulation des komplexen Zusammenspiels zwischen Atomen und Molek��len bei endlicher Temperatur. Ein entscheidender Vorteil dieser Methode ist ihre hohe Genauigkeit und Vorhersagekraft. Allerdings verhindert der Rechenaufwand, welcher grunds��tzlich kubisch mit der Anzahl der Atome skaliert, die Anwendung auf gro��e Systeme und lange Zeitskalen. Ausgehend von einem neuen Formalismus, basierend auf dem gro��kanonischen Potential und einer Faktorisierung der Dichtematrix, wird die Diagonalisierung der entsprechenden Hamiltonmatrix vermieden. Dieser nutzt aus, dass die Hamilton- und die Dichtematrix aufgrund von Lokalisierung d��nn besetzt sind. Das reduziert den Rechenaufwand so, dass er linear mit der Systemgr����e skaliert. Um seine Effizienz zu demonstrieren, wird der daraus entstehende Algorithmus auf ein System mit fl��ssigem Methan angewandt, das extremem Druck (etwa 100 GPa) und extremer Temperatur (2000 - 8000 K) ausgesetzt ist. In der Simulation dissoziiert Methan bei Temperaturen oberhalb von 4000 K. Die Bildung von sp��-gebundenem polymerischen Kohlenstoff wird beobachtet. Die Simulationen liefern keinen Hinweis auf die Entstehung von Diamant und wirken sich daher auf die bisherigen Planetenmodelle von Neptun und Uranus aus. Da das Umgehen der Diagonalisierung der Hamiltonmatrix die Inversion von Matrizen mit sich bringt, wird zus��tzlich das Problem behandelt, eine (inverse) p-te Wurzel einer gegebenen Matrix zu berechnen. Dies resultiert in einer neuen Formel f��r symmetrisch positiv definite Matrizen. Sie verallgemeinert die Newton-Schulz Iteration, Altmans Formel f��r beschr��nkte und nicht singul��re Operatoren und Newtons Methode zur Berechnung von Nullstellen von Funktionen. Der Nachweis wird erbracht, dass die Konvergenzordnung immer mindestens quadratisch ist und adaptives Anpassen eines Parameters q in allen F��llen zu besseren Ergebnissen f��hrt.

Molecular dynamics simulations of silicate and borate glasses and melts : structure, diffusion dynamics and vibrational properties

Molecular dynamics simulations of silicate and borate glasses and melts: Structure, diffusion dynamics and vibrational properties. In this work computer simulations of the model glass formers SiO2 and B2O3 are presented, using the techniques of classical molecular dynamics (MD) simulations and quantum mechanical calculations, based on density functional theory (DFT). The latter limits the system size to about 100���200 atoms. SiO2 and B2O3 are the two most important network formers for industrial applications of oxide glasses. Glass samples are generated by means of a quench from the melt with classical MD simulations and a subsequent structural relaxation with DFT forces. In addition, full ab initio quenches are carried out with a significantly faster cooling rate. In principle, the structural properties are in good agreement with experimental results from neutron and X-ray scattering, in all cases. A special focus is on the study of vibrational properties, as they give access to low-temperature thermodynamic properties. The vibrational spectra are calculated by the so-called ���frozen phonon��� method. In all cases, the DFT curves show an acceptable agreement with experimental results of inelastic neutron scattering. In case of the model glass former B2O3, a new classical interaction potential is parametrized, based on the liquid trajectory of an ab initio MD simulation at 2300 K. In this course, a structural fitting routine is used. The inclusion of 3-body angular interactions leads to a significantly improved agreement of the liquid properties of the classical MD and ab initio MD simulations. However, the generated glass structures, in all cases, show a significantly lower fraction of 3-membered planar boroxol rings as predicted by experimental results (f=60%-80%). The largest boroxol ring fraction of f=15��5% is observed in the full ab initio quenches from 2300 K. In case of SiO2, the glass structures after the quantum mechanical relaxation are the basis for calculations of the linear thermal expansion coefficient ��L(T), employing the quasi-harmonic approximation. The striking observation is a change change of sign of ��L(T) going along with a temperature range of negative ��L(T) at low temperatures, which is in good agreement with experimental results.

Quantum Mechanical Study of Sulfuric Acid Hydration: Atmospheric Implications

The role of the binary nucleation of sulfuric acid in aerosol formation and its implications for global warming is one of the fundamental unsettled questions in atmospheric chemistry. We have investigated the thermodynamics of sulfuric acid hydration using ab initio quantum mechanical methods. For H2SO4(H2O)n where n = 1���6, we used a scheme combining molecular dynamics configurational sampling with high-level ab initio calculations to locate the global and many low lying local minima for each cluster size. For each isomer, we extrapolated the M��ller���Plesset perturbation theory (MP2) energies to their complete basis set (CBS) limit and added finite temperature corrections within the rigid-rotor-harmonic-oscillator (RRHO) model using scaled harmonic vibrational frequencies. We found that ionic pair (HSO4�����H3O+)(H2O)n���1 clusters are competitive with the neutral (H2SO4)(H2O)n clusters for n ��� 3 and are more stable than neutral clusters for n ��� 4 depending on the temperature. The Boltzmann averaged Gibbs free energies for the formation of H2SO4(H2O)n clusters are favorable in colder regions of the troposphere (T = 216.65���273.15 K) for n = 1���6, but the formation of clusters with n ��� 5 is not favorable at higher (T > 273.15 K) temperatures. Our results suggest the critical cluster of a binary H2SO4���H2O system must contain more than one H2SO4 and are in concert with recent findings(1) that the role of binary nucleation is small at ambient conditions, but significant at colder regions of the troposphere. Overall, the results support the idea that binary nucleation of sulfuric acid and water cannot account for nucleation of sulfuric acid in the lower troposphere.

Hydration of the Bisulfate Ion: Atmospheric Implications

Using molecular dynamics configurational sampling combined with ab initio energy calculations, we determined the low energy isomers of the bisulfate hydrates. We calculated the CCSD(T) complete basis set (CBS) binding electronic and Gibbs free energies for 53 low energy isomers of HSO4���(H2O)n=1���6 and derived the thermodynamics of adding waters sequentially to the bisulfate ion and its hydrates. Comparing the HSO4���/H2O system to the neutral H2SO4/H2O cluster, water binds more strongly to the anion than it does to the neutral molecules. The difference in the binding thermodynamics of HSO4���/H2O and H2SO4/H2O systems decreases with increasing number of waters. The thermodynamics for the formation of HSO4���(H2O)n=1���5 is favorable at 298.15 K, and that of HSO4���(H2O)n=1���6 is favorable for T < 273.15 K. The HSO4��� ion is almost always hydrated at temperatures and relative humidity values encountered in the troposphere. Because the bisulfate ion binds more strongly to sulfuric acid than it does to water, it is expected to play a role in ion-induced nucleation by forming a strong complex with sulfuric acid and water, thus facilitating the formation of a critical nucleus.

Quantum Mechanical Study of Sulfuric Acid Hydration: Atmospheric Implications

The role of the binary nucleation of sulfuric acid in aerosol formation and its implications for global warming is one of the fundamental unsettled questions in atmospheric chemistry. We have investigated the thermodynamics of sulfuric acid hydration using ab initio quantum mechanical methods. For H2SO4(H2O)n where n = 1���6, we used a scheme combining molecular dynamics configurational sampling with high-level ab initio calculations to locate the global and many low lying local minima for each cluster size. For each isomer, we extrapolated the M��ller���Plesset perturbation theory (MP2) energies to their complete basis set (CBS) limit and added finite temperature corrections within the rigid-rotor-harmonic-oscillator (RRHO) model using scaled harmonic vibrational frequencies. We found that ionic pair (HSO4�����H3O+)(H2O)n���1clusters are competitive with the neutral (H2SO4)(H2O)n clusters for n ��� 3 and are more stable than neutral clusters for n ��� 4 depending on the temperature. The Boltzmann averaged Gibbs free energies for the formation of H2SO4(H2O)n clusters are favorable in colder regions of the troposphere (T = 216.65���273.15 K) for n = 1���6, but the formation of clusters with n ��� 5 is not favorable at higher (T > 273.15 K) temperatures. Our results suggest the critical cluster of a binary H2SO4���H2O system must contain more than one H2SO4 and are in concert with recent findings(1) that the role of binary nucleation is small at ambient conditions, but significant at colder regions of the troposphere. Overall, the results support the idea that binary nucleation of sulfuric acid and water cannot account for nucleation of sulfuric acid in the lower troposphere.

Hydration of the Sulfuric Acid���Methylamine Complex and Implications for Aerosol Formation

The binary H2SO4���H2O nucleation is one of the most important pathways by which aerosols form in the atmosphere, and the presence of ternary species like amines increases aerosol formation rates. In this study, we focus on the hydration of a ternary system of sulfuric acid (H2SO4), methylamine (NH2CH3), and up to six waters to evaluate its implications for aerosol formation. By combining molecular dynamics (MD) sampling with high-level ab initio calculations, we determine the thermodynamics of forming H2SO4(NH2CH3)(H2O)n, where n = 0���6. Because it is a strong acid���base system, H2SO4���NH2CH3 quickly forms a tightly bound HSO4������NH3CH3+ complex that condenses water more readily than H2SO4 alone. The electronic binding energy of H2SO4���NH2CH3 is ���21.8 kcal mol���1 compared with ���16.8 kcal mol���1 for H2SO4���NH3 and ���12.8 kcal mol���1 for H2SO4���H2O. Adding one to two water molecules to the H2SO4���NH2CH3 complex is more favorable than adding to H2SO4 alone, yet there is no systematic difference for n ��� 3. However, the average number of water molecules around H2SO4���NH2CH3 is consistently higher than that of H2SO4, and it is fairly independent of temperature and relative humidity.

Hydration of the Sulfuric Acid-Methylamine Complex and Implications for Aerosol Formation

The binary H2SO4-H2O nucleation is one of the most important pathways by which aerosols form in the atmosphere, and the presence of ternary species like amines increases aerosol formation rates. In this study, we focus on the hydration of a ternary system of sulfuric acid (H2SO4), methylamine (NH2CH3), and up to six waters to evaluate its implications for aerosol formation. By combining molecular dynamics (MD) sampling with high-level ab initio calculations, we determine the thermodynamics of forming H2SO4(NH2CH3)(H2O)n, where n = 0-6. Because it is a strong acid-base system, H2SO4-NH2CH3 quickly forms a tightly bound HSO4(-)-NH3CH3(+) complex that condenses water more readily than H2SO4 alone. The electronic binding energy of H2SO4-NH2CH3 is -21.8 kcal mol(-1) compared with -16.8 kcal mol(-1) for H2SO4-NH3 and -12.8 kcal mol(-1) for H2SO4-H2O. Adding one to two water molecules to the H2SO4-NH2CH3 complex is more favorable than adding to H2SO4 alone, yet there is no systematic difference for n ��� 3. However, the average number of water molecules around H2SO4-NH2CH3 is consistently higher than that of H2SO4, and it is fairly independent of temperature and relative humidity.

Predicting the Mechanical Properties of Carbon-Based Materials Using Molecular Dynamics

The development of innovative carbon-based materials can be greatly facilitated by molecular modeling techniques. Although molecular modeling has been used extensively to predict elastic properties of materials, modeling of more complex phenomenon such as fracture has only recently been possible with the development of new force fields such as ReaxFF, which is used in this work. It is not fully understood what molecular modeling parameters such as thermostat type, thermostat coupling, time step, system size, and strain rate are required for accurate modeling of fracture. Selection of modeling parameters to model fracture can be difficult and non-intuitive compared to modeling elastic properties using traditional force fields, and the errors generated by incorrect parameters may be non-obvious. These molecular modeling parameters are systematically investigated and their effects on the fracture of well-known carbon materials are analyzed. It is determined that for coupling coefficients of 250 fs and greater do not result in substantial differences in the stress-strain response of the materials using any thermostat type. A time step of 0.5 fs of smaller is required for accurate results. Strain rates greater than 2.2 ns-1 are sufficient to obtain repeatable results with slower strain rates for the materials studied. The results of this study indicate that further refinement of the Chenoweth parameter set is required to accurately predict the mechanical response of carbon-based systems. The ReaxFF has been used extensively to model systems in which bond breaking and formation occur. In particular ReaxFF has been used to model reactions of small molecules. Some elastic and fracture properties have been successfully modeled using ReaxFF in materials such as silicon and some metals. However, it is not clear if current parameterizations for ReaxFF are able to accurately reproduce the elastic and fracture properties of carbon materials. The stress-strain response of a new ReaxFF parameterization is compared to the previous parameterization and density functional theory results for well-known carbon materials. The new ReaxFF parameterization makes xv substantial improvements to the predicted mechanical response of carbon materials, and is found to be suitable for modeling the mechanical response of carbon materials. Finally, a new material composed of carbon nanotubes within an amorphous carbon (AC) matrix is modeled using the ReaxFF. Various parameters that may be experimentally controlled are investigated such as nanotube bundling, comparing multi-walled nanotube with single-walled nanotubes, and degree of functionalization of the nanotubes. Elastic and fracture properties are investigated for the composite systems and compared to results of pure-nanotube and pure-AC models. It is found that the arrangement of the nanotubes and degree of crosslinking may substantially affect the properties of the systems, particularly in the transverse directions.

Mechanisms of recognition and binding of ��-TTP to the plasma membrane by multi-scale molecular dynamics simulations

We used multiple sets of simulations both at the atomistic and coarse-grained level of resolution to investigate interaction and binding of ��-tochoperol transfer protein (��-TTP) to phosphatidylinositol phosphate lipids (PIPs). Our calculations indicate that enrichment of membranes with such lipids facilitate membrane anchoring. Atomistic models suggest that PIP can be incorporated into the binding cavity of ��-TTP and therefore confirm that such protein can work as lipid exchanger between the endosome and the plasma membrane. Comparison of the atomistic models of the ��-TTP-PIPs complex with membrane-bound ��-TTP revealed different roles for the various basic residues composing the basic patch that is key for the protein/ligand interaction. Such residues are of critical importance as several point mutations at their position lead to severe forms of ataxia with vitamin E deficiency (AVED) phenotypes. Specifically, R221 is main residue responsible for the stabilization of the complex. R68 and R192 exchange strong interactions in the protein or in the membrane complex only, suggesting that the two residues alternate contact formation, thus facilitating lipid flipping from the membrane into the protein cavity during the lipid exchange process. Finally, R59 shows weaker interactions with PIPs anyway with a clear preference for specific phosphorylation positions, hinting a role in early membrane selectivity for the protein. Altogether, our simulations reveal significant aspects at the atomistic scale of interactions of ��-TTP with the plasma membrane and with PIP, providing clarifications on the mechanism of intracellular vitamin E trafficking and helping establishing the role of key residue for the functionality of ��-TTP.