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...

The high frequency reciprocating rig (HFRR) is typically used to determine the lubricity of diesel fuels and has been accepted as the universal test apparatus in most countries of the world. A study was undertaken to analyse results obtained with the HFRR instrument by identifying crucial factors contributing to friction and wear mechanisms during a lubricity test under given conditions that may lead to a better understanding of test results obtained. The transient temperature distribution on a semiinfinite disk due to a circular continuous oscillatory heat source was also modelled. The model was used to calculate the contact temperature of a contact similar to what can be expected in the HFRR apparatus. For lubricated tests a mixture of n-hexadecane (cetane) as base fluid and palmitic acid as lubricity additive was used. Experimental results, including results obtained by running unlubricated (dry) tests and results obtained from literature were all considered to formulate the hypothesis that a fully functional additive film will not survive the full duration of the lubricity test, which is 75 minutes (ISO 12156-1, 2003). Friction values obtained in the experiments conducted were much higher than what is expected for boundary films formed by long chain carboxylic acids. Comparable friction values were obtained in the first few seconds of the tests, but the friction values increased indicating the destruction of the boundary film. Metal oxide lubrication dominates for the remainder of the test. Information of the exact mechanism prevailing in the crucial first few seconds of the test should be obtained by increasing the data acquisition rate of the apparatus. It is believed that junction growth through adhesion is the dominant factor in the initial stages of the test. GCxGC/TOF-MS showed the formation of hexane and heptane, which is a strong indication of the catalytic decomposition of the C16-hydrocarbons in the sample. / Dissertation (MEng)--University of Pretoria, 2010. / Chemical Engineering / unrestricted

Palmitic acid (PA), a type of saturated fatty acids, induces cardiovascular diseases by causing cardiomyocyte apoptosis with unclear mechanisms. Akt participates in PA-induced cardiomyocyte apoptosis. GSK-3β is a substrate of Akt, we investigated its role in PA-induced apoptosis. We reveal that PA inhibits GSK-3β phosphorylation accompanied by inactivation of Akt in H9c2 cardiomyocytes. We also reveal that inhibition the activity of GSK-3β by its inhibitor LiCl or knockdown by siRNA significantly attenuates PA-induced cardiomyocyte apoptosis, this suggesting that GSK-3β plays a pro-apoptotic role. To detect its downstream factors, we analyzed the roles of JNK, p38 MAPK and β-arrestin 2 (β-Arr2). Here, we report that GSK-3β regulate PA-induced cardiomyocyte apoptosis by affecting the distribution of β-Arr2. PA diminishes the protein level of β-Arr2 and changes its distribution from nucleus to cytoplasm. Either inhibition of β-Arr2 by its siRNA or overexpression of its protein level by transfection of β-Arr2 full-length plasmid promotes PA-induced cardiomyocyte apoptosis, which remind us to focus on the changes of its location. β-Arr2 siRNA decreased the background level of β-Arr2 in nucleus in normal H9c2 cells. Overexpression of β-Arr2 increased cytoplasm level of β-Arr2 as PA did. While LiCl, the inhibitor of GSK-3β decreased PA-induced apoptosis, accompany with increased nucleus level of β-Arr2. Then we concluded that GSK-3β is closely associated with cardiomyocyte apoptosis induced by PA, it performs its pro-apoptotic function by affecting the location of β-Arr2. LiCl inhibits PA-induced cardiomyocyte apoptosis, which might provide novel therapeutic for cardiovascular diseases induced by metabolic syndrome.

O fluido multifásico complexo (suco de açaí) tem uma forte interação com membranas poliméricas ou cerâmicas de microfiltração e a formação de incrustação depende da composição e das condições de dinâmica de fluidos. Neste estudo experimental foi investigada a influência dos dois principais ácidos graxos presentes no açaí, ácido oleico e ácido palmítico, em misturas com água e no processo de microfiltração tangencial com membranas cerâmicas de alumina com um tamanho de poro nominal de 0,2 \'mü\'m. Mediu-se o fluxo de permeado em função do tempo, nas pressões transmembranas de 300 kPa, 400 kPa e 500 kPa. Para o fluxo da corrente de alimentação foram encontrados valores de Reynolds numa faixa de 9500 a 31000. Cada amostra de misturas de água/ácido oleico, água/ácido palmítico e água/ácidos oleico e palmítico, foi estudada em três séries de ensaios realizados durante 180 minutos e 72 minutos para a mistura água/ácido palmítico, a temperatura em 25 ºC. Analisou-se as incrustações resultantes e as fortes interações fluido/membrana utilizando o modelo de resistência em série e imagens tomadas por microscopia eletrônica de varredura (MEV). Os melhores resultados de permeado encontrados para a mistura de água/ácido oleico foram para Re = 33000, no entanto, resultados satisfatórios foram encontrados para Re = 20000. Agora para a água/ácido palmítico foram encontrados para Re = 20000. Os melhores resultados de permeado para a mistura água/ácidos oleico e palmítico foram para Re = 31000. De acordo com os resultados das resistências, a mistura água/ácido causa um bloqueio dos poros da membrana, resultando em uma maior diminuição do fluxo transmembrana. A limpeza foi eficiente para reduzir a resistência associada com a polarização. / The complex fluid multiphase (açaí juice) has a strong interaction with polymeric or ceramic membranes for microfiltration fouling and its formation depends on the fluid composition and fluid dynamics conditions. In this experimental study was investigated the influence of two major fatty acids present in açaí, oleic acid and palmitic acid in mixtures with water and in the process of crossflow microfiltration with ceramic membranes. In the separation process is used alumina ceramic membrane with a nominal pore size of 0.2 micrometers. The permeate flux was measured in function of time using the 300 kPa, 400 kPa and 500 kPa for the transmembrane pressure. The flow of feed stream and its respective value of Reynolds were in range of: 8900-3300. For each sample of mixtures oleic acid/water and palmitic acid/water and palmitic acid, oleic acid/ water, three series of experiments were conducted for 180 minutes and 72 minutes for mixture palmitic acid/water at temperature in 25 Celcius. For analyze of fouling resulting from strong interactions fluid/membrane was used the model of resistance in series and images taken via scanning electron microscopy (SEM). The best results for mixing oleic acid/water were to Re = 33000, however, satisfactory results were found for Re = 20000. Now for the palmitic acid/water were found to Re = 20000. For mixture palmitic acid, oleic acid/ water were found to Re = 31000. According to the results of the resistances, the mixture oleic acid/water cause a blockage of the pores of the membrane resulting in a greater decrease of the transmembrane flow. The cleaning is efficient for reducing the resistance associated with the polarization.

Espécies reativas de oxigênio e nitrogênio controlam várias funções celulares, no entanto, quantidades excessivas destas espécies causam disfunções. Com o envelhecimento, há aumento da produção destas espécies, e de citocinas, que também exercem efeitos deletérios na musculatura esquelética, e da concentração plasmática de ácidos graxos. Contudo, a possível rassociação entre o aumento da produção de espécies reativas e de citocinas pelo músculo esquelético e da concentração plasmática de ácidos graxos não foi ainda investigada. O presente estudo teve como objetivo avaliar a modulação da produção muscular de espécies reativas de oxigênio e nitrogênio e de citocinas pelo ácido palmítico e pela eletroestimulação moderada. O ácido palmítico aumentou a produção de superóxido (via mitocôndria e NADPH oxidase), óxido nítrico (via iNOS) e citocinas (IL-6 e CINC-2), além de ativar o NF-kB. A eletroestimulação aumentou a produção de superóxido (via mitocôndria e sistema xantina-xantina oxidase), óxido nítrico (via iNOS) e ativou o NF-kB. Não foi observado aumento de citocinas no protocolo de eletroestimulação. O ácido palmítico, portanto, controla a produção de espécies reativas e citocinas pelo músculo. A eletroestimulação, também aumenta a produção destas espécies. Assim, o estresse oxidativo muscular é controlado pela atividade contrátil e as concentrações de ácidos graxos plasmáticos. / Reactive oxygen and nitrogen species play a key role in several cell functions, however, high concentrations of these species cause cell dysfunction. High production of reactive species, and cytokines, which also induce skeletal muscle injury, and an increase of plasma concentration of fatty acids are observed in aging. However, an association between the augment in the production of reactive species and cytokines by skeletal muscle and of plasma fatty acid concentrations was not investigated yet. The aim of the present study was to evaluate the modulation of production of reactive oxygen and nitrogen species and of cytokines by palmitic acid and electrical stimulation muscle contraction. Palmitic acid increased the production of superoxide (through mitochondria and NADPH oxidase), nitric oxide (by iNOS), and citokynes (IL-6 and CINC-2), and induced NF-kB activation. The electrical stimulation-muscle contraction increased the production of superoxide (through mitochondria and xanthine-xanthine oxidase system), nitric oxide (by iNOS), and induced NF-kB activation. There was no change in the production of cytokines in the electrical stimulation protocol. In conclusion, palmitic acid raised the production of reactive oxygen and nitrogen species and cytokines by skeletal muscle. Electrical stimulation-muscle contraction also increased the production of these reactive species. Therefore, muscle oxidative stress is controlled by the muscle contractile activity and plasma fatty acid levels.

Espécies reativas de oxigênio e nitrogênio controlam várias funções celulares, no entanto, quantidades excessivas destas espécies causam disfunções. Com o envelhecimento, há aumento da produção destas espécies, e de citocinas, que também exercem efeitos deletérios na musculatura esquelética, e da concentração plasmática de ácidos graxos. Contudo, a possível rassociação entre o aumento da produção de espécies reativas e de citocinas pelo músculo esquelético e da concentração plasmática de ácidos graxos não foi ainda investigada. O presente estudo teve como objetivo avaliar a modulação da produção muscular de espécies reativas de oxigênio e nitrogênio e de citocinas pelo ácido palmítico e pela eletroestimulação moderada. O ácido palmítico aumentou a produção de superóxido (via mitocôndria e NADPH oxidase), óxido nítrico (via iNOS) e citocinas (IL-6 e CINC-2), além de ativar o NF-kB. A eletroestimulação aumentou a produção de superóxido (via mitocôndria e sistema xantina-xantina oxidase), óxido nítrico (via iNOS) e ativou o NF-kB. Não foi observado aumento de citocinas no protocolo de eletroestimulação. O ácido palmítico, portanto, controla a produção de espécies reativas e citocinas pelo músculo. A eletroestimulação, também aumenta a produção destas espécies. Assim, o estresse oxidativo muscular é controlado pela atividade contrátil e as concentrações de ácidos graxos plasmáticos. / Reactive oxygen and nitrogen species play a key role in several cell functions, however, high concentrations of these species cause cell dysfunction. High production of reactive species, and cytokines, which also induce skeletal muscle injury, and an increase of plasma concentration of fatty acids are observed in aging. However, an association between the augment in the production of reactive species and cytokines by skeletal muscle and of plasma fatty acid concentrations was not investigated yet. The aim of the present study was to evaluate the modulation of production of reactive oxygen and nitrogen species and of cytokines by palmitic acid and electrical stimulation muscle contraction. Palmitic acid increased the production of superoxide (through mitochondria and NADPH oxidase), nitric oxide (by iNOS), and citokynes (IL-6 and CINC-2), and induced NF-kB activation. The electrical stimulation-muscle contraction increased the production of superoxide (through mitochondria and xanthine-xanthine oxidase system), nitric oxide (by iNOS), and induced NF-kB activation. There was no change in the production of cytokines in the electrical stimulation protocol. In conclusion, palmitic acid raised the production of reactive oxygen and nitrogen species and cytokines by skeletal muscle. Electrical stimulation-muscle contraction also increased the production of these reactive species. Therefore, muscle oxidative stress is controlled by the muscle contractile activity and plasma fatty acid levels.

O fluido multifásico complexo (suco de açaí) tem uma forte interação com membranas poliméricas ou cerâmicas de microfiltração e a formação de incrustação depende da composição e das condições de dinâmica de fluidos. Neste estudo experimental foi investigada a influência dos dois principais ácidos graxos presentes no açaí, ácido oleico e ácido palmítico, em misturas com água e no processo de microfiltração tangencial com membranas cerâmicas de alumina com um tamanho de poro nominal de 0,2 \'mü\'m. Mediu-se o fluxo de permeado em função do tempo, nas pressões transmembranas de 300 kPa, 400 kPa e 500 kPa. Para o fluxo da corrente de alimentação foram encontrados valores de Reynolds numa faixa de 9500 a 31000. Cada amostra de misturas de água/ácido oleico, água/ácido palmítico e água/ácidos oleico e palmítico, foi estudada em três séries de ensaios realizados durante 180 minutos e 72 minutos para a mistura água/ácido palmítico, a temperatura em 25 ºC. Analisou-se as incrustações resultantes e as fortes interações fluido/membrana utilizando o modelo de resistência em série e imagens tomadas por microscopia eletrônica de varredura (MEV). Os melhores resultados de permeado encontrados para a mistura de água/ácido oleico foram para Re = 33000, no entanto, resultados satisfatórios foram encontrados para Re = 20000. Agora para a água/ácido palmítico foram encontrados para Re = 20000. Os melhores resultados de permeado para a mistura água/ácidos oleico e palmítico foram para Re = 31000. De acordo com os resultados das resistências, a mistura água/ácido causa um bloqueio dos poros da membrana, resultando em uma maior diminuição do fluxo transmembrana. A limpeza foi eficiente para reduzir a resistência associada com a polarização. / The complex fluid multiphase (açaí juice) has a strong interaction with polymeric or ceramic membranes for microfiltration fouling and its formation depends on the fluid composition and fluid dynamics conditions. In this experimental study was investigated the influence of two major fatty acids present in açaí, oleic acid and palmitic acid in mixtures with water and in the process of crossflow microfiltration with ceramic membranes. In the separation process is used alumina ceramic membrane with a nominal pore size of 0.2 micrometers. The permeate flux was measured in function of time using the 300 kPa, 400 kPa and 500 kPa for the transmembrane pressure. The flow of feed stream and its respective value of Reynolds were in range of: 8900-3300. For each sample of mixtures oleic acid/water and palmitic acid/water and palmitic acid, oleic acid/ water, three series of experiments were conducted for 180 minutes and 72 minutes for mixture palmitic acid/water at temperature in 25 Celcius. For analyze of fouling resulting from strong interactions fluid/membrane was used the model of resistance in series and images taken via scanning electron microscopy (SEM). The best results for mixing oleic acid/water were to Re = 33000, however, satisfactory results were found for Re = 20000. Now for the palmitic acid/water were found to Re = 20000. For mixture palmitic acid, oleic acid/ water were found to Re = 31000. According to the results of the resistances, the mixture oleic acid/water cause a blockage of the pores of the membrane resulting in a greater decrease of the transmembrane flow. The cleaning is efficient for reducing the resistance associated with the polarization.

L’acide gras synthase, codé par le gène FASN, est une protéine multi-enzyme homodimérique responsable de la lipogenèse de novo à partir de l’acétyl-CoA et du malonyl- CoA. La finalité de cette lipogenèse est la production de l’acide palmitique, un acide gras simple, précurseur des acides gras à très longues chaînes. L’acide palmitique est impliqué dans plusieurs processus biologiques, dont la palmitoylation qui permet d’ancrer diverses protéines à la membrane cellulaire sous-tendant, entre autres, la transmission synaptique. Le rôle de l’acide gras synthase dans le développement embryonnaire est bien établi. En effet, il est exprimé de manière ubiquitaire dans l’embryon, principalement dans les tissus en pleine croissance et soumis à un remodelage, participant ainsi activement au développement cérébral. Par conséquent, des mutations du gène FASN ont été associées à plusieurs maladies, incluant divers types de cancers, les maladies cardiovasculaires, mais également, plus récemment, à certaines maladies du neurodéveloppement, incluant les troubles du spectre de l’autisme. Des données récentes des laboratoires Rossignol et Campeau, au CHU Ste-Justine, suggèrent un lien entre des mutations récessives ou de novo du gène FASN et des formes précoces d’épilepsie avec atteinte cognitive (encéphalopathies épileptogènes). Nous postulons que les mutations du gène FASN modifient la synthèse de l’acide palmitique et perturbent le développement des réseaux neuronaux, en altérant la migration, le développement morphologique, l’excitabilité et/ou la fonction synaptique de populations neuronales spécifiques, résultant en une hyperexcitabilité neuronale et à l’épilepsie. Pour explorer cette hypothèse, nous avons recueilli les informations cliniques de dix patients porteurs de mutations du gène FASN dans le cadre d’études génomiques en cours au CHU Ste- Justine et à travers le monde. Nous avons également généré un nouveau modèle murin de la maladie, exprimant une mutation retrouvée chez un membre de notre cohorte clinique, que nous avons caractérisé sur les plans histochimique et électrophysiologique. Nos données suggèrent que les mutations du gène FASN induisent chez l’humain un phénotype clinique de retard global du développement évoluant vers une déficience intellectuelle, s’accompagnant d’un éventail de signes neurologiques (déficit moteur, spasticité, réflexes ostéotendineux vifs, hypotonie et ataxie) et d’un risque accru d’épilepsie. De plus, notre modèle de souris knock-in Fasn.S154N révèle la fonction critique de ce gène dans le développement embryonnaire puisqu’une mutation homozygote entraîne une mortalité in utero. Par ailleurs, les souris porteuses de mutations hétérozygotes survivent et présentent un phénotype clinique rappelant celui observé chez les patients, incluant un comportement anxieux, une activité épileptique interictale à l’électroencéphalogramme ainsi qu’un abaissement du seuil convulsif lors d’une exposition au pentylenetetrazole (PTZ). Nous discutons certains mécanismes sous-jacents contribuant potentiellement au développement de l’épilepsie dans cette maladie, incluant une altération de l’activité de l’acide gras synthase au niveau du cortex préfrontal et de l’amygdale, une palmitoylation aberrante des protéines synaptiques, une plus grande vulnérabilité des cellules granulaires du gyrus denté, un dysfonctionnement des cellules souches neurales, une neurogénèse insuffisante, ainsi qu’une altération de la myélinisation et de la croissance axonale impactant la migration des interneurones. Ces mécanismes sont prédits pour altérer l’excitabilité neuronale et la transmission synaptique, perturbant la fonction des circuits. Des études subséquentes permettront d’élucider lesquels de ces divers mécanismes contribuent au phénotype clinique dans notre nouveau modèle murin de la maladie. / Fatty Acid Synthase is a large protein complex encoded by the FASN gene, which is responsible for de novo lipogenesis from acetyl-CoA and malonyl-CoA in the presence of NADPH. The endpoint of this process is the production of palmitic acid. The roles of fatty acid synthase in embryonic development are well established: it is ubiquitously expressed in early embryos, particularly in tissues undergoing active proliferation, outgrowth, and remodelling, and it is thus essential for normal brain development and neuronal function. Consequently, FASN gene mutations have been associated with several neurodevelopmental conditions, including autism spectrum disorders (ASD). Recently, the laboratories of Drs. E. Rossignol and P. Campeau at the CHU Ste-Justine (Université de Montréal), with their international collaborators, have identified 10 patients with neurodevelopmental disorders (i.e., developmental delay, intellectual disability and/or epilepsy) carrying recessive or de novo mutations in the FASN gene, supporting a critical role of FASN in regulating neuronal circuit development and function. However, the mechanisms by which mutations in the FASN gene result in epilepsy are unknown. We postulate that FASN mutations alter palmitic acid synthesis and disrupt neuronal network development, resulting in network hyperexcitability and epilepsy. In this study, we expand the phenotypic description of patients carrying FASN mutations, while generating a novel mouse model carrying a patient-derived FASN mutation to explore the underlying cellular and network mechanisms. Our data reveal that FASN mutations, in humans, generate neurodevelopmental disorders characterized by epilepsy, global developmental delay (GDD), intellectual disability (ID), and a broad range of neurological signs (motor deficit, spasticity, hyperreflexia, hypotony, and ataxia). In our knock-in FasnS154N mouse model, homozygous mutations resulted in prenatal lethality. In contrast, heterozygous mutations caused a clinical phenotype reminiscent of the patient phenotype, with anxiety-like behaviors, spontaneous interictal spikes on electroencephalograms (EEG), and a tendency to a reduced PTZ-induced seizure threshold. We discuss the potential underlying mechanisms, including an altered FAS activity within the prefrontal cortex and the amygdala, aberrant palmitoylation of postsynaptic density proteins, the vulnerability of dentate gyrus granules cell, altered neural stem cells activity and neurogenesis, improper axonal growth and myelination, resulting in altered neuronal excitability and synaptic function, aberrant network activities and epilepsy. These mechanisms will be explored in subsequent studies using our novel animal model.

Os ácidos graxos (AG) podem influenciar o processo secretório de insulina induzido pela glicose. Os AG ω3 interferem em diversos processos fisiológicos, sendo que nas ilhotas pancreáticas, os AG ω3 colaboram para a diminuição da lipotoxicidade induzida pelo ácido palmítico. Ao ácido palmítico são atribuídos efeitos deletérios em diversos tecidos, assim como nas células β, onde ele promove a alteração da composição dos fosfolípides de membrana, do potencial elétrico da mesma e consequentemente do processo de extrusão dos grânulos de insulina. A exposição crônica das células β ao excesso de ácido palmítico é tóxica, provocando diminuição da resposta secretória de insulina, redução da oxidação e captação de glicose e aumento de espécies reativas de oxigênio (EROs) que, em quantidades suprafisiológicas, irão contribuir para a falência e morte da célula β. As EROs podem ser de origem mitocondrial, através do metabolismo dos nutrientes ou ainda proveniente da ativação do complexo enzimático NADPH oxidase, o qual é modulado pela glicose e pelos AG, incluindo o ácido palmítico. Em contrapartida, os AG ω3 exercem efeitos anti-inflamatórios e antioxidantes em diversos sistemas, contribuindo para melhora de perfil lipídico e resistência periférica à insulina. O objetivo deste trabalho foi verificar o possível efeito protetor dos AG ω3 contra os efeitos deletérios do ácido palmítico em células β pancreáticas. Nas células β, a partir dos resultados obtidos, a presença de AG ω3 mostrou-se eficaz para prevenir o dano secretório e o aumento de EROs, além de contribuir para manutenção da viabilidade celular e da captação de glicose nas ilhotas tratadas com ácido palmítico, desempenhando um importante papel protetor na célula β. / Fatty acids (FA) may influence the process of glucose-induced insulin. The ω3 FA interferes in several physiological processes, and in the pancreatic islets collaborate to decrease the lipotoxicity induced by palmitic acid. Palmitic acid induces deleterious effects in several tissues, as well as in β cells, where it promotes the alteration of the membrane phospholipid composition, the plasma membrane electric potential, and consequently, the process of the insulin granules extrusion. Chronic exposure of β cells to high concentration of palmitic acid is toxic, leading to decreased insulin secretory response, reduced oxidation and uptake of glucose, and an increase in reactive oxygen species (ROS) which, in supraphysiological amounts, will contribute to β-cell failure and death. ROS may be of mitochondrial origin, through the metabolism of nutrients or even from the activation of the enzymatic complex NADPH oxidase, which is modulated by glucose and FA, including palmitic acid. In contrast, ω3 FA exerts anti-inflammatory and antioxidant effects in several systems, contributing to the improvement of lipid profile and peripheral resistance to insulin. The aim of this study was verify the protective possible effect of AG ω3 against the deleterious effects of palmitic acid on pancreatic β cells. Our results shown that the presence of ω3 FA was effective in preventing secretory damage and increase of EROs, also contributing to the maintenance of cell viability and glucose uptake in the islets treated with palmitic acid, playing an important β-cell protective role.

Στην παρούσα διπλωματική εργασία παρουσιάζονται Ατομιστικά Μοντέλα Διακριτών και Ενοποιημένων Ατόμων, τα οποία μπορούν να αποτελέσουν το πρώτο σημαντικό βήμα για τη μελέτη της βιολογικής μεμβράνης ή και ακόμα τη μελέτη συστημάτων μεμβρανών με πρωτεΐνες, σάκχαρα κ.α. Τέτοιες προσομοιώσεις θα μας δώσουν στοιχεία για μακροσκοπικές ιδιότητες της μεμβράνης (π.χ. διαχυτότητα) παρουσία συγκεκριμένων άλλων μακρομορίων. Αρχικά μελετάται σε ατομιστικό επίπεδο, με τα μοντέλα Διακριτών και Ενοποιημένων Ατόμων, τήγμα παλμιτικού οξέος (383Κ). Η καταλληλόλητα του νέου μοντέλου που εισήχθη για την περίπτωση των Ενοποιημένων Ατόμων εξετάζεται με βάση τις ιδιότητες διαμόρφωσης (λ.χ. κατανομές γωνιών) που εξάγονται από το μοντέλο Διακριτών Ατόμων. Στο μοντέλο Διακριτών Ατόμων χρησιμοποιήθηκε το αναλυτικότερο δυνατό δυναμικό (COMPASS). Τα αποτελέσματα ήταν άκρως ικανοποιητικά. Έχοντας ένα αξιόπιστο μοντέλο Ενοποιημένων Ατόμων προχωρήσαμε στο επόμενο βήμα. Επόμενο βήμα ήταν η μελέτη συστήματος παλμιτικού οξέος ανάμεσα από στρώμα νερού. Σημαντικό μειονέκτημα του μοντέλου Διακριτών Ατόμων για ένα τόσο μεγάλο σύστημα αποτελεί η περιορισμένη χρονική κλίμακα. Φαινόμενα σχηματισμού διπλοστοιβάδας παλμιτικού οξέος παρουσία νερού, είναι πολύ δύσκολο να μελετηθούν με χρήση μοντέλου Διακριτών Ατόμων λόγω των πολύ μικρών χρόνων που καλύπτουν. Επομένως, κρίνεται αναγκαία η χρήση μοντέλου Ενοποιημένων Ατόμων για το σύστημα PLM – νερό. Χρησιμοποιήσαμε το μοντέλο Ενοποιημένων Ατόμων που οι ίδιοι αναπτύξαμε, όπως και για την περίπτωση του τήγματος, για την περιγραφή του παλμιτικού οξέος, και το μοντέλο SPCE για το νερό, το οποίο είναι ευρέως αποδεκτό από την επιστημονική κοινότητα. Πέραν της σύγκρισης των μοντέλων Ενοποιημένων και Διακριτών Ατόμων που έγινε για το τήγμα του παλμιτικού οξέος, πραγματοποιήθηκαν και διάφοροι υπολογισμοί που αφορούν τη σταθεροποίηση του συστήματος (Autocorrelation faction of end-to-end distance vector), δομικές ιδιότητες (Radial Distribution Function), ιδιότητες διαμόρφωσης (angle distribution, radius of gyration, end-to-end distance vector) και θερμοδυναμικές ιδιότητες (density). Υπολογίστηκαν επίσης ο συντελεστής αυτοδιάχυσης (self diffusion coefficient) καθώς και το πλήθος δεσμών υδρογόνου. / This diploma thesis presents Atomistic Models of Discrete and Integrated atoms, which can be an important first step to study the biological membrane or even studying membrane systems with proteins, sugars, etc. Such simulations will give us data on macroscopic membrane properties (eg diffusivity) in the presence of certain other macromolecules. Initially we study melt palmitic acid (383K)in atomistic level. The suitability of the new model, introduced for the case of the Consolidated Atoms is examined by checking the configuration properties (eg angles distributions) derived from the model of Discrete Atoms. In the model of discrete atoms the disaggregated possible dynamic (COMPASS)was used. The results were highly satisfactory. Having a reliable model for Unified atoms we move to the next step. Next step was to study the system of palmitic acid between waterbed. Major drawback of the model of Discrete atoms for such a large system is the limited time scale. Phenomena of bilayer formation of palmitic acid in the presence of water is very difficult to be studied using discrete atoms model because of very short times covered. Therefore, it is necessary to use a model of integrated atoms for the system PLM - water. We used the model of Unified atoms we ourselves have developed, as in the case of the melt, for the description of palmitic acid, and the SPCE model for water, which is widely accepted by the scientific community. Beyond the comparison of models of integrated and discrete atoms made for the melt of palmitic acid, various calculations for the stabilisation the system (Autocorrelation faction of end-to-end distance vector), structural properties (Radial Distribution Function), properties configuration (angle distribution, radius of gyration, end-to-end distance vector) and thermodynamic properties (density)were made. The self-diffusion coefficient (self diffusion coefficient) and the number of hydrogen bonds were also calculated.