Encontrados 13 documentos, a visualizar página 1 de 2
Using Lanthanides as Probes for Polyelectrolyte-Metal Ion Interactions. Hydrati...
Costa, Diana; Ramos, M. Luísa; Burrows, Hugh D.; Tapia, M. José; Miguel, Maria da Graçahttp://www.sciencedirect.com/science/article/B6TFM-4SWFNW8-1/1/aadd2972e76576ca7bf5c347abd5a683
DNA encapsulation by biocompatible catanionic vesicles
Rosa, Mónica; Miguel, Maria da Graça; Lindman, BjörnThe encapsulation of DNA by catanionic vesicles has been investigated; the vesicles are composed of one cationic surfactant, in excess, and one anionic. Since cationic systems are often toxic, we introduced a novel divalent cationic amino-acid-based amphiphile, which may enhance transfection and appears to be nontoxic, in our catanionic vesicle mixtures. The cationic amphiphile is arginine-N-lauroyl amide dihyd...
The association of DNA and stable catanionic amino acid-based vesicles
Rosa, Mónica; Morán, María del Carmen; Miguel, Maria da Graça; Lindman, BjörnCationic surfactants associate strongly to DNA and compact but are often toxic. The interaction of some novel cationic amino acid-based surfactants, which may enhance transfection and appear to be nontoxic, is described. A cationic arginine-based surfactant, ALA, gives in combination with anionic surfactants spontaneously stable vesicles, and special attention is given to the association of these catanionic ves...
DNA−Cationic Surfactant Interactions Are Different for Double- and Single-Stran...
Rosa, Mónica; Dias, Rita; Miguel, Maria da Graça; Lindman, BjörnThe stability of DNA in solution and the phase behavior in mixtures with dodecyltrimethylammonium bromide (DTAB) were investigated. By means of circular dichroism, UV absorption, and differential scanning calorimetry, we found that for dilute solutions of DNA with no addition of salt the DNA molecules are in the single-stranded conformation, whereas the addition of a small amount of NaBr, 1 mM, is sufficient to...
Solution behaviour of lead(II) carboxylates in organic solvents
Burrows, Hugh D.; Miguel, Maria da Graça; Pereira, Rui P. C.; Proença, Nuno M. B.; Cardoso, Sónia M.C.; Geraldes, Carlos F. G. C.; Gil, M. HelenaThe solution behaviour has been studied of a series of even chain length lead(II) carboxylates (octanoate to octadecanoate) and the odd chain length lead(II) heptadecanoate in a variety of non-complexing organic solvents and in alcohols. In agreement with previous studies, solubility increases dramatically above a certain temperature, which depends on solute concentration, chain length and solvent. This solutio...
Deactivation processes of the lowest excited state of [UO2(H2O)5]2+ in aqueous ...
Formosinho, Sebastião J.; Burrows, Hugh D.; Miguel, Maria da Graça; Azenha, M. Emília D. G.; Saraiva, Isabel M.; Ribeiro, A. Catarina D. NA detailed analysis of the photophysical behaviour of uranyl ion in aqueous solutions at room temperature is given using literature data, together with results of new experimental and theoretical studies to see whether the decay mechanism of the lowest excited state involves physical deactivation by energy transfer or a chemical process through hydrogen atom abstraction. Comparison of the radiative lifetimes de...
The characterisation by luminescence spectroscopy of uranium(VI) incorporated i...
Azenha, M. E. D. G.; Miguel, Maria da Graça; Formosinho, S. J.; Burrows, H. D.Luminescence spectroscopy of solids at 77 K has been used to characterise the uranium(VI) species incorporated into [alpha]-alumina, [gamma]-alumina and zeolites Y and ZSM-20 by adsorption from solution and into ZSM-5 by chemical synthesis. With uranyl adsorbed from nitrate solutions onto [alpha]- and [gamma]-aluminas, the luminescence measurements show the dominant uranium species is schoepite, UO3·xH2O, in ag...
Association of surfactants and polymers studied by luminescence techniques
Miguel, Maria da GraçaLight emission spectroscopy has unique possibilities for the study of central issues of surfactants and associating polymers. With the help of luminescent probes, information may be obtained on matters such as molecular association, microstructure, and molecular dynamics; this constitutes an important contribution to the understanding and control of macroscopic properties, as well as biological function and tec...
Applications and limitations of uranyl ion as a photophysical probe
Burrows, Hugh D.; Miguel, Maria da GraçaUranyl ion has a long-lived luminescent excited state, which can be used as a probe for the aggregation behaviour in a variety of surfactant and polymeric systems. The general spectroscopy and photophysics of this species are discussed, and the applications to specific micellar, microemulsion, vesicular and liquid crystalline systems presented. It is shown that both dynamic and structural information can be obt...
Probing solute distribution and acid-base behaviour in water-in-oil microemulsi...
Miguel, Maria da Graça; Burrows, Hugh D.; Pereira, M. Alice Escaroupa; Varela, A. PaulaThe distribution and acid-base behaviour of the four solutes harmine, chromotropic acid (4,5-dihydroxynaphthalene-2,7-disulfonate, disodium salt), 2-naphthol and 5,10,15,20-tetrakis [4-trimethylammonium)phenyl]-21H,23H-porphine tetra-p-tosylate (TTMP) have been studied in water-in-oil (w/o) microemulsions using fluorescence and absorption spectroscopy. Carbon tetrachloride is a quencher of fluorescence of these...
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