Encontrados 18 documentos, a visualizar página 1 de 2
Aggregation and gelation in hydroxypropylmethyl cellulose aqueous solutions
Silva, Sérgio M. C.; Pinto, Fátima V.; Antunes, Filipe E.; Miguel, Maria G.; Sousa, João J. S.; Pais, Alberto A. C. C.http://www.sciencedirect.com/science/article/B6WHR-4TC923M-1/2/012a59092ead1ce270813efcf98c1fb2
Effect of the Head-Group Geometry of Amino Acid-Based Cationic Surfactants on I...
Jadhav, Vaibhav; Maiti, Souvik; Dasgupta, Antara; Das, Prasanta Kumar; Dias, Rita S.; Miguel, Maria G.; Lindman, BjörnThe interaction between DNA and different types of amino acid-based cationic surfactants was investigated. Particular attention was directed to determine the extent of influence of surfactant head-group geometry toward tuning the interaction behavior of these surfactants with DNA. An overview is obtained by gel retardation assay, isothermal titration calorimetry, fluorescence spectroscopy, and circular dichrois...
Interaction between DNA and Cationic Surfactants: Effect of DNA Conformation an...
Dias, Rita S.; Magno, Luís M.; Valente, Artur J. M.; Das, Dibyendu; Das, Prasanta K.; Maiti, Souvik; Miguel, Maria G.; Lindman, BjörnThe interactions between DNA and a number of different cationic surfactants, differing in headgroup polarity, were investigated by electric conductivity measurements and fluorescence microscopy. It was observed that, the critical association concentration (cac), characterizing the onset of surfactant binding to DNA, does not vary significantly with the architecture of the headgroup. However, comparing with the ...
PVA−DNA Cryogel Membranes: Characterization, Swelling, and Transport Studies
Papancea, Adina; Valente, Artur J. M.; Patachia, Silvia; Miguel, Maria G.; Lindman, BjörnDouble-stranded (ds) DNA from salmon testes has been incorporated into PVA hydrogels obtained by a technique of repeated freezing and thawing. The cryogels obtained are free of potential toxic species like chemical cross-linkers, and consequently, they can be used in pharmaceutical or medical applications. These cryogels show a good mechanical resistance and a white and opaque appearance caused by a heterogeneo...
Polymer-vesicle association
Antunes, Filipe E.; Marques, Eduardo F.; Miguel, Maria G.; Lindman, BjörnMixed polymer-surfactant systems have been intensively investigated in the last two decades, with the main focus on surfactant micelles as the surfactant aggregate in interaction. The main types of phase behavior, driving forces and structural/rheological effects at stake are now fairly well understood. Polymer-vesicle systems, on the other hand, have received comparatively less attention from a physico-chemica...
Effect of Headgroup on DNA−Cationic Surfactant Interactions
Dasgupta, Antara; Das, Prasanta Kumar; Dias, Rita S.; Miguel, Maria G.; Lindman, Björn; Jadhav, Vaibhav M.; Gnanamani, Muthaiah; Maiti, SouvikThe interaction behavior of DNA with different types of hydroxylated cationic surfactants has been studied. Attention was directed to how the introduction of hydroxyl substituents at the headgroup of the cationic surfactants affects the compaction of DNA. The DNA−cationic surfactant interaction was investigated at different charge ratios by several methods like UV melting, ethidium bromide exclusion, and gel el...
Viscoelasticity of a Nonionic Lamellar Phase
Medronho, B.; Miguel, Maria G.; Olsson, U.The linear viscoelastic properties of a nonionic lamellar phase in C-orientation were studied as a function of temperature by small-amplitude oscillatory measurements in the frequency range 0.5−5 Hz. An almost solidlike elastic response was observed at all studied temperatures, from 42 to 20 °C. In this range, the elastic modulus was found to increase strongly with decreasing temperature. The elasticity is attr...
Coil−Globule Transition of DNA Molecules Induced by Cationic Surfactants: A Dy...
Dias, Rita S.; Innerlohinger, Josef; Glatter, Otto; Miguel, Maria G.; Lindman, BjörnThe compaction and aggregation of DNA induced by cationic surfactants was studied by dynamic light scattering (DLS). Furthermore, the effect on surfactant-compacted DNA of the addition of nonionic amphiphiles and salt was studied. When using sufficiently low amounts of DNA and cetyltrimethylammonium bromide (CTAB), compacted DNA molecules could be monitored by the appearance of a band characterized by lower hyd...
Electrophoretic properties of complexes between DNA and the cationic surfactant...
Dias, Rita S.; Svingen, Roine; Gustavsson, Bodil; Lindman, Björn; Miguel, Maria G.; Åkerman, BjörnWe use agarose gel electrophoresis to characterize how the monovalent catioinic surfactant cetyltrimethylammonium bromide (CTAB) compacts double-stranded DNA, which is detected as a reduction in electrophoretic DNA velocity. The velocity reaches a plateau at a ratio R = 1.8 of CTAB to DNA-phosphate charges, i.e., above the neutralization point, and the complexes retain a net negative charge at least up to R = 2...
Mixed Systems of Hydrophobically Modified Polyelectrolytes: Controlling Rheolo...
Antunes, Filipe E.; Lindman, Björn; Miguel, Maria G.Rheology and phase separation were investigated for aqueous mixtures of two oppositely charged hydrophobically modified polyelectrolytes. The typical phase separation, normally seen for oppositely charged polymer mixtures, is dramatically reduced by the presence of hydrophobic modification, and phase separation is only detected close to the point of charge neutralization. While the two polyelectrolytes separate...
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