Navegando por Palavras-chave "PM-IRRAS"

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    Block copolymers of o-PPV organized at the molecular scale as Langmuir and Langmuir-Blodgett films
    (Elsevier B.V., 2014-08-01) Ferreira, Gabriel Cervoni [UNIFESP]; Caseli, Luciano [UNIFESP]; Peres, Laura Oliveira [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    The control over the molecular architecture of polymeric films can be useful to enhance the properties of polymeric devices. in this paper, poly(o-phenylene vinylene) was spread on the air-water interface in order to form stable Langmuir monolayers. These films were investigated with measurements of surface pressure, surface potential, and polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS). They were transferred from the air-water interface to solid supports through the Langmuir-Blodgett (LB) technique, and characterized with PM-IRRAS and atomic force microscopy, with the viability of the film as an optical device investigated with fluorescence spectroscopy. the immobilization of polymeric chains on solid supports as LB films may provide a high control of their molecular properties, which may enable such molecular architecture to be applied as an optoelectronic device. (C) 2014 Elsevier B.V. All rights reserved.
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    The interaction of mefloquine hydrochloride with cell membrane models at the air-water interface is modulated by the monolayer lipid composition
    (Elsevier B.V., 2014-10-01) Goto, Thiago Eichi [UNIFESP]; Caseli, Luciano [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    The antiparasitic properties of antiparasitic drugs are believed to be associated with their interactions with the protozoan membrane, encouraging research on the identification of membrane sites capable of drug binding. in this study, we investigated the interaction of mefloquine hydrochloride, known to be effective against malaria, with cell membrane models represented by Langmuir monolayers of selected lipids. It is shown that even small amounts of the drug affect the surface pressure-area isotherms as well as surface vibrational spectra of some lipid monolayers, which points to a significant interaction. the effects on the latter depend on the electrical charge of the monolayer-forming molecules, with the drug activity being particularly distinctive for negatively charged lipids. Therefore, the lipid composition of the monolayer modulates the interaction with the lipophilic drug, which may have important implications in understanding how the drug acts on specific sites of the protozoan membrane. (C) 2014 Elsevier Inc. All rights reserved.
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    Molecular-level interactions of an azopolymer and poly(dodecylmethacrylate) in mixed Langmuir and Langmuir-Blodgett films for optical storage
    (Elsevier B.V., 2010-06-01) Ceridorio, Lucineia F.; Balogh, Debora T.; Caseli, Luciano [UNIFESP]; Cardoso, Marcos R.; Viitala, Tapani; Mendonca, Cleber R.; Oliveira, Osvaldo N.; Universidade de São Paulo (USP); Universidade Federal de São Paulo (UNIFESP); KSV Instruments Ltda
    The applicability of azopolymers in optical storage can be extended through the use of nanostructured films produced with the Langmuir-Blodgett (LB) technique, but the film properties need to be optimized since these polymers generally do not form stable Langmuir films to be transferred onto solid substrates Here, photoinduced birefringence was investigated for mixed Langmuir-Blodgett films from the homopolymers 4-[N-ethyl-N-(2-methacryloxyethyl)1-4'-nitroazobenzene (HPDR1-MA) and poly(dodecylmethacrylate) (HPDod-MA) the interactions between these polymers were studied in Langmuir and LB films Surface pressure-area isotherms pointed to molecular-level interactions for proportions of 51 mf%, 41 mf% and 31 mf% of HPDR1-MA. Phase segregation was not apparent in the BAM images, in which the morphology of the blend film was clearly different from that of the Langmuir films of neat homopolymers Through PM-IRRAS, we noted that the interaction between the azopolymer and HPDod-MA affected the orientation of carbonyl groups Strong interactions for the mixture with 41 mf% of poly(dodecylmethacrylate) led to stable Langmuir films that were transferred onto solid supports as LB films the photoinduced birefringence of 101-layer mixed LB films show features that make these films useful for optical storage, with the advantage of short writing times in comparison to other azopolymer films (C) 2010 Elsevier Inc All rights reserved
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    Organization of polythiophenes at ultrathin films mixed with stearic acid investigated with polarization-modulation infrared reflection-absorption spectroscopy
    (Elsevier Science Bv, 2017) da Silva, Edilene Assuncao; Caseli, Luciano [UNIFESP]; Olivati, Clarissa de Almeida
    In this present work, the polymers poly(3-alkylthiophene)s, regioregular poly(3-butylthiophene), poly(3-hexylthiophene) and poly(3-octylthiophene) were spread at the air-water interface to form Langmuir monolayers. They formed stable films by mixing them with Stearic Acid (SA), as confirmed with surface pressure-area isotherms and polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS). The floating monolayers were transferred from the liquid interface to solid supports by using the Langmuir-Blodgett (LB) and Langmuir-Schaeffer (LS) techniques, and characterized with PM-IRRAS. Surface pressure-area isotherms showed that SA monolayers are expanded upon polymer incorporation altering the rheological properties of the monolayer since the monolayer became less elastic at higher pressures and presented first-order transitions at lower pressures. PM-IRRAS showed that the organization of the films is affected at the molecular level depending on the chemical structure of the polymer chosen. Among the polymers analysed, the poly(3-butylthiophene) shows a more irregular conformational behaviour depending on the amount of stearic acid. The conformation of the films when transferred to solid support changes and is dependent on the type of deposition (LB or LS). The importance of this paper relies on the fact that SA can be employed to help the formation of stable floating monolayers of these polythiophenes at the air-water interface, and the successful transfer to solid supports may provide nanostructured films with a high control of their molecular properties, which may enable a molecular architecture to be applied as electronic devices of interest.
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    The role of the C-terminal region of pulchellin A-chain in the interaction with membrane model systems
    (Elsevier B.V., 2012-01-01) Reyes, Luis Fernando; Nobre, Thatyane Morimoto; Pavinatto, Felippe José; Zaniquelli, Maria Elisabete Darbello; Caseli, Luciano [UNIFESP]; Oliveira, Osvaldo N.; Araujo, Ana Paula Ulian; Universidade de São Paulo (USP); Universidade Federal de São Paulo (UNIFESP)
    Pulchellin is a Ribosome Inactivating Protein containing an A-chain (PAC), whose toxic activity requires crossing the endoplasmic reticulum (ER) membrane. in this paper, we investigate the interaction between recombinant PAC (rPAC) and Langmuir monolayers of dipalmitoyl phosphatidyl glycerol (DPPG), which served as membrane model. Three catalytically active, truncated PACs with increasing deletion of the C-terminal region, possessing 244,239 and 236 residues (rPAC(244), rPAC(239) and rPAC(236)), were studied. rPAC had the strongest interaction with the DPPG monolayer, inducing a large expansion in its surface pressure-area isotherm. the affinity to DPPG decreased with increased deletion of the C-terminal region. When the C-terminal region was deleted completely (rPAC(236)), the interaction was recovered, probably because other hydrophobic regions were exposed to the membrane. Using Polarization Modulated-Infrared Reflection Absorption Spectroscopy (PM-IRRAS) we observed that at a bare air/water interface rPAC comprised mainly alpha-helix structures, the C-terminal region had unordered structures when interacting with DPPG. for rPAC(236) the alpha-helices were preserved even in the presence of DPPG. These results confirm the importance of the C-terminal region for PAC-ER membrane interaction. the partial unfolding only with preserved C-terminal appears a key step for the protein to reach the cytosol and develop its toxic activity. (C) 2011 Elsevier B.V. All rights reserved.
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    Surface chemistry and spectroscopy studies on 1,4-naphthoquinone in cell membrane models using Langmuir monolayers
    (Elsevier B.V., 2013-07-15) Hussein, Nadia [UNIFESP]; Lopes, Carla Cristina [UNIFESP]; Pernambuco Filho, Paulo Castanho de Almeida [UNIFESP]; Carneiro, Bruna R. [UNIFESP]; Caseli, Luciano [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    Investigating the role of drugs whose pharmaceutical activity is associated with cell membranes is fundamental to comprehending the biochemical processes that occur on membrane surfaces. in this work, we examined the action of 1,4-naphthoquinone in lipid Langmuir monolayers at the air-water interface, which served as a model for half of a membrane, and investigated the molecular interactions involved with tensiometry and vibrational spectroscopy. the surface pressure-area isotherms exhibited a noticeable shift to a lower area in relation to 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dihexadecanoyl-sn-glycero-3-phospho-L-serine (DPPS) lipid monolayers, which indicated a disruption of the monolayer structure and solubilisation of the lipids towards the aqueous subphase. To better correlate to the action of this drug in biological membrane events, cell cultures that represented tumorigenic and non-tumorigenic cells were spread onto the air-water interface, and 1,4-naphthoquinone was then incorporated. While only slight changes were observed in the non-tumorigenic cells upon drug incorporation, significant changes were observed in the tumorigenic cells, on which the organisation of the Langmuir monolayers was disrupted as evidenced by tensiometry and vibrational spectroscopy. This work then shows that this drug interacts preferentially for specific surfaces. in simplified models, it has a higher effect for the negative charged DPPS rather than the zwitterionic DPPC; and for complex cell cultures, 1,4-naphthoquinone presents a more significant effect for that representing tumorigenic cells. (c) 2013 Elsevier Inc. All rights reserved.