Navegando por Palavras-chave "Biomembrane"
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- ItemSomente MetadadadosComparative study of liponucleosides in Langmuir monolayers as cell membrane models(Elsevier B.V., 2011-01-01) Montanha, E. A.; Caseli, L. [UNIFESP]; Kaczmarek, O.; Liebscher, J.; Huster, D.; Oliveira, O. N.; Universidade Federal de São Paulo (UNIFESP); Universidade de São Paulo (USP); Humboldt Univ; Univ LeipzigLiponucleosides may assist the anchoring of nucleic acid nitrogen bases into biological membranes for tailored nanobiotechnological applications. To this end precise knowledge about the biophysical and chemical details at the membrane surface is required. in this paper, we used Langmuir monolayers as simplified cell membrane models and studied the insertion of five lipidated nucleosides. These molecules varied in the type of the covalently attached lipid group, the nucleobase, and the number of hydrophobic moieties attached to the nucleoside. All five lipidated nucleosides were found to be surface-active and capable of forming stable monolayers. They could also be incorporated into dipalmitoylphosphatidylcholine (DPPC) monolayers, four of which induced expansion in the surface pressure isotherm and a decrease in the surface compression modulus of DPPC. in contrast, one nucleoside possessing three alkyl chain modifications formed very condensed monolayers and induced film condensation and an increase in the compression modulus for the DPPC monolayer, thus reflecting the importance of the ability of the nucleoside molecules to be arranged in a closely packed manner. the implications of these results lie on the possibility of tuning nucleic acid pairing by modifying structural characteristics of the liponucleosides. (C) 2010 Elsevier B.V. All rights reserved.
- ItemSomente MetadadadosDispersion of chitosan in liquid crystalline lamellar phase: Production of biofriendly hydrogel of nano cubic topology(Elsevier Sci Ltd, 2017) Mathews, Patrick D.; Mertins, Omar [UNIFESP]Bicontinuous cubic phases were produced with introduction of chitosan in phospholipid/water hydro gel, providing composites of defined molecular organization. The ratio of lipid/water was constant and swelling of lipids bilayer is delimited by incorporation of polymer molecules into the structure. By means of synchrotron small angle X-ray scattering we identified topologies of coexisting cubic phases. The expected liquid crystalline L-alpha, lamellar phase was suppressed by 0.2 wt% chitosan leading to formation of diamond Pn3m and gyroid la3d cubic topology, with close lattice distances. An increment to 0.4 wt% chitosan caused large increase in Pn3m lattice distance. However a higher 0.6 wt% evolved this phase to a newly acquired primitive Im3m topology. The structuring process of the three-dimensional complex network is principally governed by demands of chitosan physical requirements over lipids bilayers interfacial curvature. The composite hydrogel of specific topologies presents reduced time release of gallic acid and may find application as new material for time-sustained delivery of bioactive compounds. (C) 2016 Elsevier Ltd. All rights reserved.
- ItemSomente MetadadadosEstudos sobre a interação entre o receptor HER2 e trastuzumabe em filmes de Langmuir e filmes de Langmuir-Blodgett(Universidade Federal de São Paulo, 2016-08-25) Sakai, Andrei [UNIFESP]; Caseli, Luciano [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)The present work aimed to characterize the interactions between the HER2 receptor and trastuzumab (Tmab) using Langmuir and Langmuir-Blodgett films as biomembrane models. The comprehension of individual interactions of Tmab with membrane biomolecules was enabled by a bottom-up methodology based on the comparison between films produced from cellular extracts (parental and tumorigenic lines) and films produced from synthetic lipids. Firstly, the cell lines were tested regarding the overexpression of HER2 on the cell surface, and then considering the viability, proliferation, apoptotic behavior when treated with Tmab. Subsequently, the formation of stable membranes containing phospholipids and proteins produced from cell extracts on the air-water interface was proved by tensiometry, surface potential, vibrational spectroscopy (PM-IRRAS), Brewster Angle Microscopy (BAM) and Atomic Force Microscopy (AFM); by which aggregates and domains were observed. Different lipid compositions of the cellular models were detected by Thin Layer Chromatography (HPTLC), and they are likely to modulate the specific and dissimilar interactions of Tmab with each cell line, serving as reference for lipid-based membranes production. Tmab induced formation of phases and domains on the cell-based membranes, affecting directly its fluidity. Moreover, Tmab presented more noteworthy interaction with DPPE films, inducing a membrane expansion in a higher extent. In general, the results indicate that Tmab not only interacts with the HER2 receptor, but it also affects the fluidity of the structural and molecular architecture of the phospholipidic membrane, which may be related to molecular mechanism of its pharmacological action.
- ItemSomente MetadadadosInteração de violaceína com modelos de membranas(Universidade Federal de São Paulo, 2017-03-28) Souza, Karine Damaceno de [UNIFESP]; Caseli, Luciano [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Violacein is a violet pigment produced by the gram-negative bacterium Chromobacterium violaceum, which exhibits a multiplicity of biological effects, from which we can highlight bactericidal, antitumoral, antihagasic, antileishmanial and antiviral actions. However, its efficacy is still not fully proven, and the mechanisms of action and interaction of the drug with cells and biomembranes at the molecular level are not yet fully understood. In this work, Langmuir lipid films were used as cell membrane models to study at a molecular level the interactions and effects caused by violacein. First, it was observed that violacein, which is poorly soluble in water, presents superficial activity induced by the presence of a monomolecular lipid film, demonstrating that the drug has a favorable interaction with membrane models. The lipids used were dipalmitoyl phosphatidylcholine (DPPC), dipalmitoyl phosphatidylserine (DPPS), and cholesterol, which were dissolved in chloroform and dispersed at the air-water interface. For mixed drug-lipid monolayers, violacein was incorporated into the lipid monolayers by inserting aliquots of the compound after lipid scattering. The adsorption of the drug was evaluated by measurements of surface pressure, infrared reflection-absorption spectroscopy with polarization modulation (PM-IRRAS) and Brewster angle microscopy (BAM). The monolayers were then compressed to obtain surface-area pressure isotherms. After adsorbing to the monolayers, violacein expands them by shifting the surface-area pressure-isotherms of the lipids to higher molecular areas. The films of DPPC and violacein reached pressure values around 50mN/m and mean molecular area of 70 to 55 Å2/mol. DPPS and violacein films reached a pressure of around 55 mN/m and a mean molecular area around 55 to 60 Å2/mol. Cholesterol films reached pressure values around 50mN/m and a molecular area of 45 Å2/mol. These isotherms suggest that violacein is incorporated into the DPPC, DPPS and cholesterol monolayers between the lipid chains. PM-IRRAS spectra show that the bands attributed to vibrational transitions of chemical groups present in the lipids are altered in terms of position and relative intensity, demonstrating the violacein-lipid affinity. Images obtained by BAM showed alteration in the interfacial morphology of the lipid films after incorporation of the drug. In general, the action of violacein on monolayers is governed primarily by non-electrostatic intermolecular interactions. Violacein was added inside unilamellar vesicles (LUVs), showing that it can not easily break the lipid bilayer by moving into the extra aqueous medium.