Victoria Isabel Martín
University of Seville
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Featured researches published by Victoria Isabel Martín.
Journal of Colloid and Interface Science | 2010
María del Mar Graciani; Amalia Rodríguez; Victoria Isabel Martín; María Luisa Moyá
Micellization and micellar growth of cationic dimeric surfactants of the alkanedyil-alpha,omega-bis(dimethyldodecylammonium) bromide type, 12-s-12,2Br(-) (s=3, 4, 6), in the presence of various amounts of 1-butanol, 1-pentanol, and 1-hexanol have been investigated. The influence of the nature and concentration of alcohol on the cmc, on the micellar ionization degree, on the average micellar aggregation number, and on the polarity of the micellar interfacial region was investigated by using conductivity and fluorescence measurements. Subsequently, effects of alcohol addition on the surfactant concentration range where sphere to rod transitions occur were examined and information about changes in the micropolarity and in the microviscosity accompanying the morphological transition was obtained. The experimental results were explained by considering the variations in the different contributions to the Gibbs energy of micellization caused by the presence of alcohols. The study of the reaction methyl naphthalene-2-sulfonate+Br(-) in some water-alcohol 12-6-12,2Br(-) micellar solutions provided information about the characteristics of the dimeric micelles as microreactors and show the complexity of the microheterogeneous systems studied.
Journal of Physical Chemistry B | 2010
Victoria Isabel Martín; Amalia Rodríguez; María del Mar Graciani; Inmaculada Robina; María Luisa Moyá
The micellization and micellar growth in pure aqueous alkanediyl-alpha-omega-bis(dodecyldimethylammonium) bromide, 12-s-12,2Br(-) (with s = 2,5,6,8,10,12), and N-decanoyl-N-methylglucamide MEGA10 solutions and their mixtures are investigated at 303 K. Application of different theoretical approaches to the binary mixtures shows a nonideal behavior. It also shows that the spacer length does not play an important role in the attractive interactions shown by the mixed systems. The sphere-to-rod morphological transition in the pure dimeric micellar solutions is studied at 303 K. From comparison of these results with those at 298 K the key role played by the spacer in the micellar growth is shown. The spacer length controls not only the surfactant concentration at which the morphological transition happens but also the sign of the enthalpy change accompanying the sphere-to-rod equilibrium. Spacers with an even number of methylenes show smaller C* values than those with an odd number of -CH(2)- units. An endothermic enthalpy change is found for even spacers whereas an exothermic enthalpy change is found for odd spacers. To the authors knowledge, this is the first time this experimental trend has been shown. Addition of MEGA10 diminishes the tendency of the aggregates to grow. An increment in the solution mole fraction of MEGA10 makes the formation of elongated micelles difficult. Microviscosity measurements provide additional information about the influence of the MEGA10 content on the sphere-to-rod transition.
Langmuir | 2010
María del Mar Graciani; Amalia Rodríguez; Victoria Isabel Martín; Gaspar Fernández; María Luisa Moyá
The reaction methyl naphthalene-2-sulfonate + Br(-) was investigated in several alkanediyl-α-ω-bis(dodecyldimethylammonium) bromide, 12-s-12,2Br(-) (with s = 2, 3, 4, 5, 6, 8, 10, 12), micellar solutions in the absence and in the presence of various additives. The additives were 1,2-propylene glycol, which remains in the bulk phase, N-decyl N-methylglucamide, MEGA10, which forms mixed micelles with the dimeric surfactants, and 1-butanol, which distributes between the aqueous and micellar phases. Information about the micellar reaction media was obtained by using conductivity and fluorescence measurements. In all cases, with the exception of water-1,2-prop 12-5-12,2Br(-) micellar solutions, with 30% weight percentage of the organic solvent, a sphere-to-rod transition takes place upon increasing surfactant concentration. In order to quantitatively explain the experimental data within the whole surfactant concentration range, a kinetic equation based on the pseudophase kinetic model was considered, together with the decrease in the micellar ionization degree accompanying micellar growth. However, theoretical predictions did not agree with the experimental kinetic data for surfactant concentrations above the morphological transition. An empirical kinetic equation was proposed in order to explain the data. It contains a parameter b which is assumed to account for the medium micellar kinetic effects caused by the morphological transition. The use of this empirical equation permits the quantitative rationalization of the kinetic micellar effects in the whole surfactant concentration range.
Colloids and Surfaces B: Biointerfaces | 2014
J.P. García; E. Marrón; Victoria Isabel Martín; María Luisa Moyá; P. Lopez-Cornejo
A multifaceted study on the interaction of calf-thymus DNA with two different cationic gemini surfactants alkanediyl-α-ω-bis(dodecyldimethyl-amonium)bromide, 12-s-12,2Br(-) (with s=2, G2, and 10, G10) was carried out. The measurements were done at different molar ratios X=[surfactant]/[DNA]. Results show two different conformational changes in DNA: a first compaction of the polynucleotide corresponding to a partial conformational (not total) change of DNA from an extended coil state to a globular state that happens at the lower molar ratio X. A second change corresponds to a breaking of the partial condensation, that is, the transition from the compacted state to a new more extended conformation (for the higher X values) different to the initial extension. According to circular dichroism spectra and dynamic light scattering measurements, this new state of DNA seems to be similar to a ψ-phase. Measurements confirm that interactions involved in the compaction are different to those previously obtained for the analog surfactant CTAB. X values at which the conformational changes happen depend on the length of the spacer in the surfactant along with the charge of the polar heads.
Colloids and Surfaces B: Biointerfaces | 2016
Beatriz Sarrión; Eva Bernal; Victoria Isabel Martín; Manuel López-López; P. Lopez-Cornejo; Margarita García-Calderón; María Luisa Moyá
Several cationic dimeric surfactants have shown high affinity towards DNA. Bis-quaternary ammonium salts (m-s-m) have been the most common type of dimeric surfactants investigated and it is generally admitted that those that posses a short spacer (s≤3) show better efficiency to bind or compact DNA. However, experimental results in this work show that 12-s-12 surfactants with long spacers make the surfactant/ctDNA complexation more favorable than those with short spacers. A larger contribution of the hydrophobic interactions, which control the binding Gibbs energy, as well as a higher average charge of the surfactant molecules bound to the nucleic acid, which favors the electrostatic attractions, could explain the experimental observations. Dimeric surfactants with intermediate spacer length seem to be the less efficient for DNA binding.
Journal of Colloid and Interface Science | 2018
Manuel López-López; P. Lopez-Cornejo; Victoria Isabel Martín; Francisco José Ostos; Cintia Checa-Rodríguez; Rosario Prados-Carvajal; José Antonio Lebrón; Pablo Huertas; María Luisa Moyá
The goal of this work was to understand the key factors determining the DNA compacting capacity of single-chained cationic surfactants. Fluorescence, zeta potential, circular dichroism, gel electrophoresis and AFM measurements were carried out in order to study the condensation of the nucleic acid resulting from the formation of the surfactant-DNA complexes. The apparent equilibrium binding constant of the surfactants to the nucleic acid, Kapp, estimated from the experimental results obtained in the ethidium bromide competitive binding experiments, can be considered directly related to the ability of a given surfactant as a DNA compacting agent. The plot of ln(Kapp) vs. ln(cmc), cmc being the critical micelle concentration, for all the bromide and chloride surfactants studied, was found to be a reasonably good linear correlation. This result shows that hydrophobic interactions mainly control the surfactant DNA compaction efficiency.
Colloids and Surfaces B: Biointerfaces | 2015
Victoria Isabel Martín; Beatriz Sarrión; Manuel López-López; P. Lopez-Cornejo; Inmaculada Robina; María Luisa Moyá
In this work the novel cationic surfactant derived from lysine (S)-5-acetamido-6-(dodecylamino)-N,N,N-trimethyl-6-oxohexan-1-ammonium chloride, LYCl, was prepared and the physicochemical characterization of its aqueous solutions was carried out. The binding of LYCl to bovine serum albumin, BSA, and to double stranded calf thymus DNA, ctDNA, was investigated using several techniques. Results show that LYCl binding to BSA is followed by a decrease in the α-helix content caused by the unfolding of the protein. LYCl association to ctDNA mainly occurs through groove binding and electrostatic interactions. These interactions cause morphological changes in the polynucleotide from an elongated coil structure to a more compact globular structure, resulting in the compaction of ctDNA. Addition of β-cyclodextrin, β-CD, to the BSA-LYCl and ctDNA-LYCl complexes is followed by the refolding of BSA and the decompaction of ctDNA. This can be explained by the ability of β-CD to hinder BSA-LYCl and ctDNA-LYCl interactions due to the stronger and more specific β-CD-LYCl hydrophobic interactions. The stoichiometry of the β-CD:LYCl inclusion complex and its formation equilibrium constant were determined in this work. The reported procedure using β-CD is an efficient way to refold proteins and to decompact DNA, after the morphological changes caused in the biomolecules by their interaction with cationic surfactants.
Journal of Colloid and Interface Science | 2017
Victoria Isabel Martín; Manuel Angulo; P. Lopez-Cornejo; Manuel López-López; María José Marchena; María Luisa Moyá
The assembly of a surfactant-based rotaxane by adding the labile aquopentacyanoferrate(II) ion to the previously formed pseudorotaxane between the surfactant 11-(isonicotinoyloxy)-N,N,N-triethyl-1-undecanaminium bromide and β-cyclodextrin was investigated by 1H NMR and kinetic measurements. NMR spectroscopy has showed that the rotaxane can be formed through two different mechanisms. The rotaxane can be unstoppered by using the pyridine ligand substitution reaction by the high-field cyanide ligand. In this work a new method is developed for the preparation of several new surfactant-based rotaxanes by changing the hydrophilic and hydrophobic regions of the surfactants and the nature of the macrocycle.
Journal of Colloid and Interface Science | 2012
Victoria Isabel Martín; Amalia Rodríguez; María del Mar Graciani; María Luisa Moyá
The micellization and micellar growth in the mixtures of N,N-dimethyl, N-phenyl,N-dodecylammonium bromide, PH12, N,N-dimethyl,N-ciclohexylmethyl,N-dodecylammonium bromide, CH12, and their two dimeric counterparts m-dimethylphenyl-α-ω-bis(dodecyldimethylammonium) bromide, 12PH12, and m-dimethylciclohexyl-α-ω-bis(dodecyldimethylammonium) bromide, 12CH12, with dodecyltrimethylammoniumbromide, DTAB, and with N-decanoyl N-methylglucamide, MEGA10, were investigated at 303 K. Circular dichroism, CD, experiments showed the formation of mixed micelles. Two-dimensional, 2D, rotating frame nuclear Overhauser effect spectroscopy (ROESY) experiments indicated that the arrangement of the rings in the pure and mixed micelles is similar, with the rings bent into the micelle interior avoiding contact with water. Application of different theoretical approaches shows that PH12 and CH12 mixtures with DTAB and with MEGA10 behave almost ideally. The binary systems of 12PH12 and 12CH12 with DTAB and with MEGA10 show a non-ideal behavior. An increment in the solution mole fraction of MEGA10 and DTAB diminishes the tendency of the micellar aggregates to grow.
Molecules | 2011
María del Mar Graciani; Amalia Rodríguez; Victoria Isabel Martín; María Luisa Moyá
The dehydrobromination reaction 2-(p-nitrophenyl)ethyl bromide + OH−was investigated in several alkanediyl-α-ω-bis(dodecyldimethylammonium) bromide, 12-s-12,2Br− (with s = 2, 3, 4, 5, 6, 8, 10, 12) micellar solutions, in the presence of NaOH 5 × 10−3 M. The kinetic data were quantitatively rationalized within the whole surfactant concentration range by using an equation based on the pseudophase ion-exchange model and taking the variations in the micellar ionization degree caused by the morphological transitions into account. The agreement between the theoretical and the experimental data was good in all the dimeric micellar media studied, except for the 12-2-12,2Br− micellar solutions. In this case, the strong tendency to micellar growth shown by the 12-2-12,2Br− micelles could be responsible for the lack of accordance. Results showed that the dimeric micelles accelerate the reaction more than two orders of magnitude as compared to water.