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Association of a Hydrophobically Modified Polyelectrolyte and a Block Copolymer...
Costa, Telma; Schillén, Karin; Miguel, Maria da G.; Lindman, Björn; Melo, J. Seixas deBy using absorption and fluorescence (steady-state and time-resolved) techniques, the interaction between a poly(acrylic acid) (PAA), randomly grafted with pyrene (Py) units (PAAMePy55), and a triblock copolymer of poly(ethylene oxide) and poly(propylene oxide) (EO20PO68EO20, P123) was investigated. From the fluorescence data, it is shown that upon addition of P123 a decrease of the (pyrene−pyrene, Py−Py) intra...
Complex Formation between a Fluorescently-Labeled Polyelectrolyte and a Tribloc...
Costa, Telma; Melo, J. Seixas de; Miguel, Maria da G.; Lindman, Björn; Schillén, KarinThe association between a randomly pyrene labeled PAA polymer (PAAMePy55) and a PEO−PPO−PEO triblock copolymer (P123) in aqueous solutions of different NaCl concentrations and pHs has been studied by means of dynamic light scattering (DLS) and steady-state fluorescence spectroscopy at 40 °C. At acidic pH values, in the low P123/PAAMePy55 molar ratio regime (i.e., at low P123 concentrations), the relaxation time...
Solubilization of Poly{1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)] fluore...
Burrows, Hugh D.; Tapia, María J.; Fonseca, Sofia M.; Pradhan, Swapna; Scherf, Ullrich; Silva, Cláudia L.; Pais, Alberto A. C. C.; Valente, Artur J. M.In the presence of the nonionic alkyloxyethylene surfactant n-dodecylpentaoxyethylene glycol ether (C12E5), the anionic conjugated polyelectrolyte (CPE) poly{1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl} (PBS-PFP) dissolves in water, leading to a blue shift in fluorescence and dramatic increases in fluorescence quantum yields above the surfactant critical micelle concentration (cmc). No si...
Cationic agents for DNA compaction
Gaweda, Sylwia; Morán, M. Carmen; Pais, Alberto A. C. C.; Dias, Rita S.; Schillén, Karin; Lindman, Björn; Miguel, M. GraçaFluorescence microscopy was used to investigate the conformational changes of individual T4 DNA molecules induced by different compacting agents, namely the cationic surfactants, cetyltrimethylammonium bromide (CTAB) and chloride (CTAC), iron(III), lysozyme, and protamine sulfate. A protocol for establishing size estimates is suggested to obtain reproducible results. Observations show that in the presence of ly...
Fluorescence studies on the interaction between pyrene-labelled poly(acrylic ac...
Melo, J. Sérgio Seixas de; Costa, Telma; Oliveira, Noémia; Schillén, KarinThe interactions, in aqueous media, between a pyrene-labelled polyelectrolyte poly(acrylic acid) (PAAMePy) with two different degrees of labelling and beta- and gamma-cyclodextrins (beta- and gamma-CD) were studied using absorption and fluorescence (steady-state and time-resolved) techniques. In addition to qualitative and quantitative parameters obtained from absorption and steady-state fluorescence spectra, t...
Self-Assembly of a Hydrophobically Modified Naphthalene-Labeled Poly(acrylic ac...
Costa, Telma; Miguel, M. G.; Lindman, Björn; Schillén, Karin; Lima, J. C.; Melo, J. Seixas deThe solution properties of two water-soluble polymers, poly(acrylic acid) (PAA), covalently labeled with the fluorescent hydrophobic dye naphthalene (Np), have been investigated in water:organic solvent mixtures. The naphthalene chromophores have been randomly attached, onto the polymer, with two different degrees of labeling. Fluorescence measurements (steady-state and time-resolved) have been used to follow t...