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Changes in Hydration of Lanthanide Ions on Binding to DNA in Aqueous Solution
Costa, Diana; Burrows, Hugh D.; Miguel, M. da GraçaThe interaction of the trivalent lanthanides Ce(III), Eu(III), and Tb(III) with sodium deoxyribonucleic acid (DNA) in aqueous solution has been studied using their luminescence spectra and decays. Complexation with DNA is indicated by changes in luminescence intensity. In the system terbium(III)−DNA, changes in luminescence with pH are suggested to be due to the protonation of phosphate groups. The degree of hy...
Cation Association with Sodium Dodecyl Sulfate Micelles As Seen by Lanthanide L...
Tapia, María José; Burrows, Hugh D.; Azenha, M. Emília D. G.; Miguel, M. da Graça; Pais, A. A. C. C.; Sarraguça, J. M. G.The interaction of trivalent lanthanides with sodium dodecyl sulfate micelles (SDS) in aqueous solution has been studied by a variety of experimental techniques. Potentiometric measurements with a sodium selective electrode, steady-state fluorescence spectra of Ce(III), emission lifetime measurements of Ce(III), Tb(III), and Eu(III), and electronic paramagnetic resonance spectra (EPR) of Gd(III) all show that t...
Monitoring Ternary Systems of C12E5/Water/Tetradecane via the Fluorescence of S...
Hungerford, Graham; Castanheira, Elisabete M. S.; Oliveira, M. Elisabete C. D. Real; Miguel, M. da Graça; Burrows, Hugh D.In this work ternary systems of the nonionic surfactant C12E5 (C12H25(OCH2CH2)5OH), tetradecane, and water were probed by the use of steady state and time-resolved fluorescence. Microemulsions, which were rich in oil, rich in water, and also both continuous in oil and water, were monitored via the application of solvatochromic fluorescent probes. The hydrophobic laser dye Nile Red was used to report from the si...
Size of Sodium Dodecyl Sulfate Micelles in Aqueous Solutions as Studied by Posi...
Duplâtre, G.; Marques, M. F. Ferreira; Miguel, M. da GraçaThe micelles formed by sodium dodecyl sulfate (SDS) are studied in aqueous solutions at 294 K as a function of nominal SDS concentration (C) using positron lifetime spectroscopy. In a four-component analysis of the data, it appears that the lifetime (τ3) of the positronium triplet state (o-Ps) in the aqueous phase decreases significantly with increasing C. Preliminary results on sodium methanesulfonate solution...
Four-Component Analysis and Modeling of Positron Annihilation Lifetime Paramete...
Marques, M. F. Ferreira; Burrows, H. D.; Miguel, M. da Graça; Lima, A. P. de; Gil, C. Lopes; Duplâtre, G.Reverse micelles are studied in sodium AOT/water/isooctane mixtures as functions of AOT concentration (CAOT), water to AOT mole ratio (w0) and temperature (T), from 294 to 333 K, using positron annihilation lifetime spectroscopy (LS). By four-component analysis of the spectra, it is possible to extract the LS parameters (intensities, Ii, and lifetimes, τi) of the triplet positronium (o-Ps) present in the aqueou...
β-Carbolines. 2. Rate Constants of Proton Transfer from Multiexponential Decays...
Dias, A.; Varela, A. P.; Miguel, M. da Graça; Becker, R. S.; Burrows, H. D.; Maçanita, A. L.The β-carbolines present a complex problem involving multiple equilibria in the excited state in hydrogen-bonding solvents including water. Three excited state species exist: neutral, cation, and zwitterion. Here we examine the multiple equilibria and excited state kinetics of harmine, using time-resolved and steady state fluorescence techniques. From an analysis of the multiexponential decays, measured at the...
Comment on Excited-State Acid-Base Kinetics and Equilibria in Norharmane
Varela, A. P.; Dias, A.; Miguel, M. da Graça; Becker, Ralph S.; Maçanita, A. L.http://dx.doi.org/10.1021/j100007a065
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