Encontrados 32 documentos, a visualizar página 1 de 4
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...
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...
Controlling the Morphology in DNA Condensation and Precipitation
Pinto, Maria F. V.; Morán, M. Carmen; Miguel, M. Graça; Lindman, Björn; Jurado, Amália S.; Pais, Alberto A. C. C.This work addresses the influence of solution inhomogeneity on conformation, aggregation, and coil/globule and bundle/single chain coexistence of T4 DNA molecules. The inhomogeneity is induced by mixing two solutions containing, respectively, protamine and DNA, with different relative concentrations, but aiming at producing the same final concentrations. The study was conducted by means of fluorescence microsco...
Mixed Protein Carriers for Modulating DNA Release
Morán, M. Carmen; Pais, Alberto A. C. C.; Ramalho, Amilcar; Miguel, M. Graça; Lindman, BjörnAqueous mixtures of oppositely charged polyelectrolytes undergo associative phase separation, resulting in coacervation, gelation, or precipitation. This phenomenon has been exploited in forming DNA gel particles by interfacial diffusion. We report here the formation of DNA gel particles by mixing solutions of double-stranded DNA with aqueous solutions containing two cationic proteins, lysozyme and protamine su...
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...
How does a non-ionic hydrophobically modified telechelic polymer interact with ...
Santos, Tiago dos; Medronho, Bruno; Antunes, Filipe E.; Lindman, Björn; Miguel, MariaThe association between hydrophobically modified polyethylene glycol, HM-PEG, and non-ionic vesicles of tetraethylene glycol monododecyl ether, C12E4, was investigated. HM-PEG is in a triblock form, with an alkyl chain attached to each hydrophilic polymer-end. Such polymer structure is denoted as telechelic. The vesicle average radius was measured by self-diffusion measurements. The system exhibits both a monop...
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...
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