Navegando por Palavras-chave "Monolayer"
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- ItemSomente MetadadadosInteração da enzima Beta-galactosidase em filmes lipídicos e poliméricos de Langmuir e Langmuir-Blodgett(Universidade Federal de São Paulo (UNIFESP), 2019-11-29) Araujo, Felipe Tejada [UNIFESP]; Caseli, Luciano [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)In this work we studied the interaction of β-galactosidase in Langmuir and Langmuir-Blodgett (LB) films of stearic acid (HSt) and poly (9,9-dioctylfluorene) -co-thiophene polymer (PDF-TF). The lipid was spread at the air-water interface forming Langmuir monolayers and the enzyme was inserted into the supporting aqueous phase of the lipid monolayer. The adsorption of the enzyme to the monolayer was studied by surface-area pressure isotherms, surface-area potential isotherms, Brewster angle microscopy and vibrational spectroscopy. The mixed monolayer (lipid / enzyme / polymer) was transferred to solid supports by the LB methodology and characterized by luminescence spectroscopy, vibrational spectroscopy, and atomic force microscopy, indicating the presence of the polymer and the enzyme. The enzymatic activity of immobilized lactase as LB film was evaluated against lactose hydrolysis was evaluated with UV-visible spectroscopy. In conclusion, the enzyme can be inserted into lipid films, partially maintaining its secondary structures and altering the morphology of LB films. Catalytic activity could be maintained at up to 60% of activity after one month after transfer to LB film, which makes the system viable for future applications in lactose biosensors.
- ItemAcesso aberto (Open Access)Interação da enzima lactase em filmes fosfolipídicos de Langmuir e Langmuir-Blodgett: possível aplicação para biossensores para lactose(Universidade Federal de São Paulo, 2017-10-06) Ayoub, Fabio de Paula [UNIFESP]; Caseli, Luciano [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)In this work the interaction of the enzyme lactase in Langmuir and Langmuir-Blodgett (LB) films of the phospholipid dimyristoylphosphatidic acid (DMPA) was studied. The phospholipid was spread at the air-water interface forming Langmuir monolayers, and the enzyme was inserted into the aqueous subphase that supported the lipid monolayer. The adsorption of the enzyme to the monolayer was studied by surface pressure-area isotherms, surface potential-area isotherms, Brewster angle microscopy, and by vibrational spectroscopy. The mixed monolayers phospholipid + enzyme was transferred to solid supports by the LB methodology and characterized by luminescence spectroscopy, vibrational spectroscopy, atomic force microscopy and nanogravimmetry by quartz crystal microbalance. The enzymatic activity of the lactase immobilized as LB film was evaluated and compared to the hydrolysis of lactose to glucose and galactose using UV-visible spectroscopy. As conclusion, the enzyme can be inserted into the lipid films, maintaining partially its secondary structures, and altering the morphology of the LB films. The catalytic activity could be maintained up to 84% of the activity in relation to the homogeneous medium, which makes the system feasible for future applications in lactose biosensors.
- 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.
- ItemSomente MetadadadosLangmuir and Langmuir-Blodgett films of Cl-PPV mixed with stearic acid: implication of the morphology on the surface and spectroscopy properties(Springer, 2015-03-01) Sakai, Andrei [UNIFESP]; Peres, Laura O. [UNIFESP]; Caseli, Luciano [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)The molecular architecture of polymeric films can be changed in order to obtain enhanced properties for the fabrication of optoelectronic devices. in this paper, poly(2-chloro-p-phenylenevinylene) was spread on the air-water interface and mixed with stearic acid in order to form stable Langmuir monolayers. These films were transferred from the air-water interface to solid supports as Langmuir-Blodgett (LB) films. the influence of Cl in the polymer chain was investigated with measurements of surface pressure, polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS), Brewster angle microscopy (BAM), atomic force microscopy (AFM), and fluorescence spectroscopy. the immobilization of this polymer on solid supports as LB films provided a high control of its morphological and luminescence properties, which may be useful tomanipulate structures at the molecular level to be applied as optoelectronic devices.