Navegando por Palavras-chave "Detergents"

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    Solubilização de membranas modelo de diferentes composições pelo detergente triton X-100
    (Universidade Federal de São Paulo (UNIFESP), 2017-03-29) Mattei, Bruno [UNIFESP]; Riske, Karin do Amaral [UNIFESP]; http://lattes.cnpq.br/9178927522709552; http://lattes.cnpq.br/4260343698344529; Universidade Federal de São Paulo (UNIFESP)
    Detergents are amphiphilic molecules widely used as solubilizing agents Biological membranes. However, biological membranes treated with detergents Ac-ese insoluble fragments rich in sphingolipids and cholesterol. Due to similarities of These features have been associated with lipid rafts and the liquid phase The. Here the study of the physical-chemical aspects that govern the process of UUilllCATiOn of membrane mimetic models: lipid vesicles of controlled composition Pure or mixtures, mainly POPC, SM and cholesterol). Many different Techniques were used to study the solubilization process of lipid vesicles by Detergent TX-100, one of the most used detergents in Biological membranes. The general phenomenon and the size of the structures formed during the Solubilization was obtained by turbidity, static and / or dynamic light scattering; The aspects Thermodynamic properties of the detergent-lipid interaction were investigated by titration calorimetry And the possible interference of the detergent in the phase transition of lipids was investigated Differential scanning calorimetry; The ability of detergents to permeabilize the The membrane was investigated by kinetics of leakage of a fluorescent probe and microscopy Confocal; The process of solubilization of giant vesicles was evaluated by optical microscopy of Phase contrast and fluorescence. In the work, different lipid compositions were investigated (Pure phospholipids, binary lipid mixtures and ternary lipid mixtures) in order to obtain Information on the factors that influence the obtaining of insoluble membrane fragments. Through the experiments it was possible to conclude that pure cell membranes (POPC and SM), reaching the liquid-disordered phase and gel are totally soluble to the action of Detergent, whereas the addition of cholesterol, inducing a higher degree of Lipids leads to conditions in which the membranes are partially or totally insoluble; The factor of Insolubility is conditioned to cholesterol concentration in vesicles with binary mixtures Of lipids, reaching total insolubility in situations in which the membrane tends or reaches the Liquid-ordered phase; This is also reflected in the detergent affinity constant for these Membranes. In addition, vesicles in the gel phase are solubilized with lower concentrations of TX-100 than vesicles in the liquid-disordered phase, possibly due to the lower Ability of the membrane to accommodate detergents; Added to this, the addition of detergent Also appears to induce a phase transition in vesicles in the gel phase and a coexistence of Fluid phases in POPC: cholesterol vesicles. In ternary lipid mixtures, the situations in Higher solubility resistance is observed in regions with Greater fraction of SM and cotesterol. Finally, the membranes become permeable in TX-100 / lipid molars lower than the solubilization process, showing that even before To reach the bi-co-existent phase of the membrane, the detergent already changes the membrane structure.