Artículos (Química Física)
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Artículo Impact of Frozen Storage on Sensory, Physicochemical, and Volatile Compounds Parameters of Different Extra Virgin Olive Oils(Multidisciplinary Digital Publishing Institute (MDPI), 2024-11-24) Díaz Montaña, Enrique Jacobo; Barbero López, María; Aparicio Ruiz, Ramón; García González, Diego Luis; Morales Millán, María Teresa; Universidad de Sevilla. Departamento de Química Física; Universidad de Sevilla. Departamento de Química Analítica; Ministerio de Ciencia, Innovación y Universidades (MICIU). EspañaStorage is important for virgin olive oil, a product obtained only during the harvest period, which requires a year-round storage until its best-before date. Low temperatures slow undesirable reactions, though this method is not widely applied. The objective of this paper is to assess the impact of frozen storage on the volatile composition and sensory properties of virgin olive oils. The quality parameters, volatile composition, and sensory profiles were analyzed for samples stored under different conditions (time 0, sixth month supermarket and frozen storage, and long-term-frozen). The physicochemical parameters of the samples stored under supermarket conditions showed significant differences (p < 0.05), with the frozen-storage sample after three months of storage. Additionally, the samples stored under supermarket conditions showed higher volatile concentrations than frozen ones, with increased concentrations of aldehydes and acids producing sensory defects. Thirty-two samples, considered as the long-term-frozen, were divided into three groups depending on the frozen-storage time (1, 6 or 10 years). These long-term-frozen storage samples confirmed the suitability of the proposed oxidation markers (pentanal, hexanal, heptanal, nonanal, acetic, propanoic, butanoic, and hexanoic acids) for differentiating storage conditions and times. This work highlights the oxidation process under different storage conditions and suggests oxidation markers.Artículo Cooperative interaction between metallosurfactants, derived from the [Ru(2,2 '-bpy)(3)](2+) complex, and DNA(Elsevier, 2015) Lebrón Romero, José Antonio; Ostos Marcos, Francisco José; Moyá Morán, María Luisa; López López, M.; Carrasco Carrasco, Carlos Jesús; López-Cornejo, María del Pilar; Universidad de Sevilla. Departamento de Química Física; Universidad de Sevilla. Departamento de Química Inorgánica; Junta de Andalucía; European Union (UE)With the idea of improving and advancing the design and preparation of new reagents based on cationic surfactants for gene therapy, two luminescent metallosurfactants derived from the [Ru(2,2′-bpy)3]2+ complex were synthesized. Their interaction with DNA and the effect they exert on the conformation of the polynucleotide were studied by using different techniques. The equilibrium binding constants, Kb, of the two surfactants to DNA were obtained at different molar ratios X = [surfactant]/[DNA]. The observed sigmoidal dependence of Kb on X confirms the cooperative character of the binding. After the addition of a determined surfactant concentration, the condensation of the polymer was observed. The amount of surfactant needed to produce this conformational change is lower for the double stranded surfactant than for the single chain surfactant due to a stronger hydrophobic interaction. The addition of α-cyclodextrin molecules to the metallosurfactant/DNA solutions results in polynucleotide decompaction, which confirms the importance of the hydrophobic interactions in the condensation of the polynucleotide. Results also show the importance of choosing both a proper system to study and the most seeming measuring technique to use. It is demonstrated that, in some cases, the use of several techniques is desirable to obtain reliable and accurate results.Artículo Structural, Optical and Magnetic Properties of a New Metal-organic CoII-based Complex(Royal Society of Chemistry, 2024) Jabeur, W.; Korb, M.; Hamdi, M.; Holub, M.; Princík, D.; Zelenák, V.; Sánchez Coronilla, Antonio; Shalash, M.; Cizmár, E.; Naïli, H.; Universidad de Sevilla. Departamento de Química Física; Northern Border University (NBU). Arabia Saudí; Slovak Research and Development Agency; Junta de Andalucía; Ministerio de Ciencia, Innovación y Universidades (MICIU). EspañaA mononuclear cobalt(ii) complex [C5H8N3]2[CoCl4(C5H7N3)2] (I) was synthesized and structurally characterized. Single crystal X-ray diffraction analysis indicates that monometallic Co(ii) ions acted as coordination nodes in a distorted octahedral geometry, giving rise to a supramolecular architecture. The latter is made up of a ½ unit form composed of an anionic element [Co0.5Cl2(C5H7N3)]− and one 2-amino-4-methylpyrimidinium cation [C5H8N3]+. The crystalline arrangement of this compound adopts the sandwich form where inorganic parts are sandwiched between the organic sheets following the [100] direction. More information regarding the structure hierarchy has been supplied based on Hirshfeld surface analysis; the X⋯H (X = N, Cl) interactions play a crucial role in stabilizing the self-assembly process of I, complemented by the intervention of π⋯π electrostatic interaction created between organic entities. Thermal analyses were carried out to study the thermal behavior process. Static magnetic measurements and ab initio calculations of compound I revealed the easy-axis anisotropy character of the central Co(ii) ion. Two-channel field-induced slow-magnetic relaxation was observed; the high-frequency channel is characterized by underbarrier relaxation with Ueff = 16.5 cm−1, and the low-frequency channel involves a direct relaxation process affected by the phonon-bottleneck effect.Artículo Magnetic Dimeric Metal-porphyrin Rings Mechanically Bonded Around Carbon Nanotubes: the Role of Nanotube Defects Modulating Magnetic Properties(Royal Society of Chemistry, 2024) Sánchez de Armas, María Rocío; Montenegro-Pohlhammer, Nicolás; Pérez, E. M.; Burzuri, E.; Jiménez Calzado, Carmen; Universidad de Sevilla. Departamento de Química Física; Ministerio de Ciencia e Innovación (MICIN). España; Gobierno de España; Ministerio de Ciencia, Innovación y Universidades (MICIU). EspañaCarbon nanotubes constitute an excellent option to connect molecular nanomagnets (MNMs) to solid-state devices, allowing the electrical control of the molecule spin state. The main challenge in this area is to obtain stable nanohybrid structures that preserve the magnetic properties and functionality of the molecule. One of the strategies developed to build these structures combining MNMs and carbon nanotubes involves the encapsulation of the nanotube within magnetic organic macrocycle(s), leading to magnetic mechanically interlocked derivatives of carbon nanotubes (mMINTs). Recently, mMINTs with dimeric metal-porphyrin rings containing Cu2+ or Co2+ attached to carbon nanotubes have been synthesized. Different structural and spectroscopic techniques confirm that the metal centers in both mMINTs preserve the coordination sphere and structure of the free macrocycles, with only small deviations from the square planar geometry. However, different magnetic behaviors are observed depending on the metal. The Cu derivative has well-preserved spin geometry, with quantum coherence times on the microsecond scale, as in the free molecule (τ = 25 μs). In contrast, the continuous-wave electron paramagnetic resonance (EPR) spectrum measured on the Co derivative does not show any clear contribution from Co, although EXAFS unambiguously shows the presence of Co2+. In order to understand this different magnetic behavior, we studied mMINTs by means of periodic DFT calculations. The analysis of the optimized geometries, the spin density of the free macrocycles and the mMINTs, the adsorption energies, the extension of the charge transfer between the macrocycle and the nanotube and the density of states reveals a stronger macrocycle-nanotube interaction for the Co-mMINT. Our results point to carbon vacancies in the nanotubes as responsible for the different macrocycle-nanotube interaction and the observed loss of the Co2+ EPR signal in the Co-mMINT.Artículo Guest-dependent Spin Transitions in Hofmann-like FeII SCO Metal-organic Frameworks: Hints from Quantum Chemistry Calculations(Royal Society of Chemistry, 2024) Arias Olivares, Nelson David; Sánchez de Armas, María Rocío; Jiménez Calzado, Carmen; Universidad de Sevilla. Departamento de Química Física; Ministerio de Ciencia e Innovación (MICIN). España; Junta de AndalucíaThe family of 3D Hofmann-like FeII coordination polymers with the formula [Fe(bpd)[MII(CN)4]]·2G, M = Pt, Pd, and Ni is known for having a large capacity to host guest molecules (G) such as nitrobenzene or naphthalene. The presence of the guest molecules modulates the spin-crossover properties. In fact, these clathrates present a large hysteresis loop, in one single step or two well separated steps depending on the guest. In this work, we analyse by means of state-of-the-art DFT-based calculations the main effects governing the occurrence of the multistep spin transition, and the differences due to the nature of the divalent M metal and the encapsulated guest molecules. The study determines the relative stability of the mixed-spin state, the amplitude and nature of the host–guest and guest–guest intermolecular interactions, and the key role played by the C[triple bond, length as m-dash]N stretching modes of the M-cyanide units. Our results provide hints on the distinct roles of each of these factors and how they promote or prevent a direct transition from the high-spin state to the low-spin state.Artículo Preparation and characterization of metallomicelles of Ru(II). Cytotoxic activity and use as vector(Elsevier, 2019-03-19) Lebrón Romero, José Antonio; Ostos Marcos, Francisco José; López López, M.; Moyá Morán, María Luisa; Kardell, O; Sánchez, A; Carrasco Carrasco, Carlos Jesús; García Calderón, Margarita; Valle Rosado, Iván; López-Cornejo, María del Pilar; Universidad de Sevilla. Departamento de Química Física; Junta de Andalucía; Universidad de Sevilla; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER)The use of nanovectors in several medicinal treatments has reached a great importance in the last decade. Some drugs need to be protected to increase their lifetimes in the blood flow, to avoid degradation, to be delivered into target cells or to decrease their side effects. The goal of this work was to design and prepare nanovectors formed by novel surfactants derived from the [Ru(bpy)3]2+ complex. These amphiphilic molecules are assembled to form metallomicelles which can act as pharmaceutical agents and, at the same time, as nanovectors for several drugs. TEM images showed a structural transition from spherical to elongated micelles when the surfactant concentration increased. Fluorescence microscopy confirmed the internalization of these metallomicelles into diverse cell lines and cytotoxicity assays demonstrated specificity for some human cancer cells. The encapsulation of various antibiotics was carried out as well as a thorough study about the DNA condensation by the metallomicelles. To the best of our knowledge, applications of these metallomicelles have not been shown in the literature yet.Artículo Novel theoretical studies based on CIELab and deconvolution methods to characterize AuNPs aggregation processes(Elsevier, 2024-12) Hernández, Haimar; López Pérez, Germán; Grueso Molina, Elia María; Giráldez Pérez, Rosa María; Hidalgo Toledo, José; Prado Gotor, Rafael; Universidad de Sevilla. Departamento de Química Física; Junta de Andalucía; Universidad de SevillaThe study of the interaction of spherical gold nanoparticles when they undergo aggregation phenomena due to the presence of a ligand in solution is presented, based on both colorimetric parameters (using CIELab space) and traditional deconvolution analysis. The feasibility of using CIELab space for this purpose can be an important method to simplify the required instrumentation (colorimeter versus UV spectrophotometer) as well as being less time consuming compared with the traditional computational analysis. For these reasons, in this work we present the first experimental approach of the proposed methodology for its application in this field of research. The synthetized AuNPs employed in this work have been previously characterized by means of the maxima of their LSPR bands, zeta potential and electron microscopy images. The aggregation of spherical AuNPs (with a diameter of 12 nm) by an inert electrolyte (NaCl) is investigated in a first step with successfully results, allowing to obtain the characteristic CIELab parameters (a*, b* and L*). At a later stage, the color changes induced in the optical properties of the solution due to the interaction of AuNPs (with increasing diameters of 12, 25 and 33 nm) with an amino acid such as lysine at neutral pH, have been also described using the CIELab spatial framework. The obtained a*, b* and L* parameters of the CIELab space allow to characterize satisfactorily the color change from red to blue which describes the aggregation phenomena, relying on deconvolution analysis of the LSPR bands. The results obtained support the validity of the CIELab space as a valid tool for the investigation of the aggre gation process of colloidal solutions. It will allow simplifying the whole process using simpler and cheaper instrumentation as well as a decrease in the required analysis time.Artículo Self-aggregation in Aqueous Solution of Amphiphilic Cationic Calix[4]arenes. Potential Use as Vectors and Nanocarriers(Elsevier, 2020) Ostos Marcos, Francisco José; Lebrón Romero, José Antonio; López-Cornejo, María del Pilar; López López, Manuel; García Calderón, Margarita; García Calderón, Clara Beatriz; Valle Rosado, Iván; Kalchenko, Vitaly I.; Rodik, Roman V.; Moyá Morán, María Luisa; Universidad de Sevilla. Departamento de Química Física; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Junta de Andalucía; Universidad de Sevilla; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; European Union (UE)The self-aggregation of four amphiphilic cationic calix[4]arenes, CALIX, in aqueous solutions was investigated in this work. The nature of the polar group present at the upper rim as well as the length of the hydrophobic tails attached to the lower rim was varied. All the calixarenes present two critical aggregation concentrations, CAC1 and CAC2. For [CALIX] < CAC1 only micelles are present, within the range CAC1 < [CALIX] < CAC2 micelles as well as vesicles are observed, and for [CALIX] > CAC2 micelles and a wide distribution of vesicles were found. Cell viability experiments show that calixarene micelles and several of the calixarene vesicles investigated could be used as biocompatible nanocarriers. On this basis, the study of the interactions between the cationic calixarene aggregates (micelles and vesicles) and calf thymus DNA, ctDNA, were done and the results indicated that most of them strongly interact with the polynucleotide, inverting its charge. Micelles totally compact the ctDNA, while vesicles only partially cause conformational changes in the nucleic acid. Therefore, the CALIX micelles show potential as vectors in gene therapy. The encapsulation of the antineoplastic drug doxorubicin into the calixarene aggregates was also investigated. A high encapsulation efficiency was found for micelles and, specially, for vesicles. However, DOX-loaded calixarene vesicles present low stability at 37 °C, which is a serious restriction in their use as nanocarriers for this drug. The release of DOX from the calixarene micelles shows that they could lengthen the half-life of free doxorubicin in the body and, as a result, lower amounts of drug could be used in the cancer treatments diminishing the important side effects of DOX.Artículo The Role of Pristine Carbon Nanotubes as Nanocarriers of 7,8-dihydroxyflavone(Editions de Sante, 2024) Espíndola, Cecilia; Gómez Méndez, Ana; Moyá Morán, María Luisa; López Vallejo, Fabián; Bernal Pérez, Eva; Lebrón Romero, José Antonio; Martín, Victoria I.; Ostos Marcos, Francisco José; López-Cornejo, María del Pilar; López López, Manuel; Universidad de Sevilla. Departamento de Química Física; Universidad de Sevilla. Departamento de Bioquímica Médica y Biología Molecular e Inmunología; European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER)Flavonoids are secondary plant metabolites with a wide range of pharmacological effects. Among others, their antioxidant, anti-inflammatory and vasoprotective actions are noteworthy. However, the low bioavailability of flavonoids limits their direct clinical use. Nanoencapsulation of flavonoids is an effective tool to improve their biopharmaceutical characteristics, as the drug is protected inside the nanocarrier and specifically released into the therapeutic target. Bearing this in mind, pristine single- and multi-walled carbon nanotubes have been studied in this work as nanocarriers of 7,8-dihydroxyflavone, 7,8-DHF. Flavone encapsulation is optimized according to the influence of pH, the type of CNTs and their concentration on the association process. The equilibrium binding constants of 7,8-DHF to the CNTs are determined by measuring the variation observed in the flavone absorbance when the concentration of carbon nanotubes increases. CNTs/flavone complexes are characterized by particle size distribution and Z-potential measurements, as well as Transmission Electron Microscopy. The antioxidant capacity of free 7,8-DHF and the CNTs/7,8-DHF complexes are estimated by using the DPPH⋅, 2,2-diphenyl-1-picrylhydrazyl radical scavenging method. The results show that the encapsulation of the flavone in the CNTs results in a preservation of its pharmacological properties and provides stability to the encapsulated drug.Artículo Synergistic Antifungal Activity against Candida Albicans between Voriconazole and Cyclosporine a Loaded in Polymeric Nanoparticles(Elsevier, 2024) Martín, Victoria I.; Ruiz de la Haba, Rafael; López-Cornejo, María del Pilar; López López, M.; Lebrón Romero, José Antonio; Bernal Pérez, Eva; Baeza, N.; Ruiz, S.; Ostos Marcos, Francisco José; Merino Bohórquez, Vicente; Moyá Morán, María Luisa; Universidad de Sevilla. Departamento de Química Física; Universidad de Sevilla. Departamento de Microbiología y Parasitología; Universidad de Sevilla; Junta de AndalucíaThe goal of this work is to investigate if the synergistic antifungal activity between cyclosporine A, CsA, and voriconazole, VRZ, increases when both drugs are encapsulated in a nanocarrier as compared when they are free. The preparation and characterization of blank and VRZ and CsA loaded polymeric based PLGA nanoparticles (PLGA, PLGA-PEG, and PLGA+PEG) was a necessary previous step. Using the more suitable NPs, those of PLGA, the antifungal susceptibility tests performed with VRZ-loaded PLGA NPs, show no significant increase of the antifungal activity in comparison to that of free VRZ. However, the synergistic behavior found for the (VRZ+CsA)-loaded PLGA NPs was fourfold stronger than that observed for the two free drugs together. On the other hand, the investigation into the suppression of C. albicans biofilm formation showed that blank PLGA NPs inhibit the biofilm formation at high NPs concentrations. However, a minor effect or even a slight biofilm increase formation was observed at low and moderate NPs concentrations. Therefore, the enhancement of the biofilm inhibition found for the three tested treatments (CsA alone, VRZ alone, and VRZ+CsA) when comparing free and encapsulated drugs, within the therapeutic window, can be attributed to the drug encapsulation approach. Indeed, polymeric PLGA NPs loaded with CsA, VRZ, or VRZ+CsA are more effective at inhibiting the C. albicans biofilm growth than their free counterparts.Artículo Influence of the degree of oligomerization of surfactants on the DNA/surfactant interaction(Elsevier, 2019-10) López, Alberto; López-Cornejo, María del Pilar; López-López, Manuel; Lebrón Romero, José Antonio; Ostos Marcos, Francisco José; Pérez Alfonso, David; Moyá Morán, María Luisa; Universidad de Sevilla. Departamento de Química Física; Junta de Andalucía; Universidad de SevillaThe interaction between calf thymus DNA, ctDNA, and a series of oligomeric surfactants derived from N-benzyl-N,N-dimethyl-N-(1-dodecyl)ammonium chloride is investigated. The influence of the surfactants' degree of oligomerization (2, 3 and 4) on the ctDNA/surfactant interaction is studied, as well as the effect of the structure of the spacer group linking the individual surfactant fragments. In particular, the effect of the distance between the positive charges and the hydrophobic chains within the oligomers on these interactions was examined, by using the three positional isomers (i.e., ortho−, meta−, and para−) with the rigid xylidene moiety as spacer. Results show that the dimeric ("gemini") surfactants are much more efficient in the inversion of the nucleic acid charge than the single-chained (monomeric) surfactant. Whereas the ortho − isomer causes a partial condensation, the meta − and para − isomers can completely condense ctDNA. The meta − and para − isomers of the trimeric surfactants can also completely condense the polynucleotide. In contrast, the tetrameric surfactant investigated does not change the morphology of the nucleic acid from an elongated coil into a compacted form, in spite of effectively inverting the nucleic acid's charge in their complex. Accordingly, the capacity for ctDNA compaction of oligomeric surfactants is not simply correlated to their degree of oligomerization, but depends on a complex balance of the number and relative distance of cationic charges and/or hydrophobic tails in the surfactants for effectively interacting with the nucleic acid to form the appropriate complex. This information will help to design more effective cationic surfactants as non-viral vectors for gene therapy.Artículo Electrochecmical Impedance Spectroscopy analysis of an adsorption process with a coupled preceding chemical step(ELSEVIER, 2017-02-24) Prieto Dapena, Francisco; Álvarez Malmagro, Julia; Rueda Rueda, Manuela; Universidad de Sevilla. Departamento de Química Física; Universidad de Sevilla. FQM202: Electroquímica de BiointerfasesThe impedance equations for the case of an adsorption process including a preceding homogeneous chemical step have been derived and compared to the corresponding equations for the case of a pure adsorption process. They involve behaviours with the frequency that differ from those of the impedance equations for a pure adsorption process. However, two limiting cases have been deduced in which the frequency behaviour of the impedance cannot be distinguished from the case of an adsorption process without any chemical step: the high frequency and the low frequency limits that hold for low and high values of the rate constant of the chemical reaction, respectively. The analysis as a function of the frequency is discussed on the basis of the complex frequency-normalized admittance plots and also based on the frequency dependence of the real and imaginary frequency-normalized admittance components. The influence of the values of the equilibrium and the rate constants of the chemical step is discussed for different adsorption kinetic regimes. In this way the conditions for detecting the chemical step are delimited and suitable analysis are proposed to obtain the adsorption parameters and the characteristic constants of the chemical step. The analysis is applied as an example, to the impedance of adenine adsorption on Au(111) electrodes from acidic solutions at a representative electrode potential. It is proved that the low frequency limit applies and the equilibrium constant for the chemical step is obtained.Artículo Electrochecmical Impedance Spectroscopy Analysis of an Adsorption Process with a Coupled Preceding Chemical Step(Elsevier, 2017) Prieto Dapena, Francisco; Rueda Rueda, Manuela; Álvarez Malmagro, Julia; Universidad de Sevilla. Departamento de Química Física; Ministerio de Economía y Competitividad (MINECO). España; Junta de AndalucíaThe impedance equations for the case of an adsorption process including a preceding homogeneous chemical step have been derived and compared to the corresponding equations for the case of a pure adsorption process. They involve behaviours with the frequency that differ from those of the impedance equations for a pure adsorption process. However, two limiting cases have been deduced in which the frequency behaviour of the impedance cannot be distinguished from the case of an adsorption process without any chemical step: the high frequency and the low frequency limits that hold for low and high values of the rate constant of the chemical reaction, respectively. The analysis as a function of the frequency is discussed on the basis of the complex frequency-normalized admittance plots and also based on the frequency dependence of the real and imaginary frequency-normalized admittance components. The influence of the values of the equilibrium and the rate constants of the chemical step is discussed for different adsorption kinetic regimes. In this way the conditions for detecting the chemical step are delimited and suitable analysis are proposed to obtain the adsorption parameters and the characteristic constants of the chemical step. The analysis is applied as an example, to the impedance of adenine adsorption on Au(111) electrodes from acidic solutions at a representative electrode potential. It is proved that the low frequency limit applies and the equilibrium constant for the chemical step is obtained.Artículo Importance of hydrophobic interactions in the single-chained cationic surfactant-DNA complexation(Elsevier, 2018-07-01) López-López, Manuel; López-Cornejo, María del Pilar; Martín, Victoria I.; Ostos Marcos, Francisco José; Checa Rodríguez, Cintia; Prados Carvajal, Rosario; Lebrón Romero, José Antonio; Huertas Sánchez, Pablo; Moyá Morán, María Luisa; Universidad de Sevilla. Departamento de Química Física; Universidad de Sevilla. Departamento de Biología Celular; Universidad de Sevilla. Departamento de Genética; Junta de Andalucía; Universidad de Sevilla; Ministerio de Economía y Competitividad (MINECO). EspañaThe 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 efficiencyArtículo Mechanism of Dinitrogen Photoactivation by P2PPhFe Complexes: Thermodynamic and Kinetic Computational Studies(American Chemical Society, 2024-10-23) Prada, C.; Dzib, E.; Núñez-Zarur, F.; Salvador, P.; Merino, G.; Jiménez Calzado, Carmen; Zapata-Rivera, J.; Universidad de Sevilla. Departamento de Química Física; European Union; Ministerio de Ciencia, Innovación y Universidades (MICINN). EspañaThe P2PPhFe(N2)(H)2 catalyst showed a significant ammonia yield under light irradiation. However, under thermal conditions, the hydrogen evolution reaction (HER) is favored over the nitrogen reduction reaction (N2RR), making P2PPhFe(N2)(H)2 an ideal system for studying the competition between both reactions. In this study, we used a series of computational tools to elucidate the photochemical reaction mechanism for the N2RR and thermal pathways leading to the HER with this catalyst. We calculated the energy profile for each transformation and estimated the rate constants for each step. Our results, which are consistent with experimental observations, indicate that photoinduced H2 elimination from P2PPhFe(N2)(H)2 promotes the formation of P2PPhFe(N2)2, which is on-path for N2RR. However, this elimination process is kinetically hindered due to high-energy barriers. Furthermore, our calculations reveal enhanced dinitrogen activation upon the conversion of P2PPhFe(N2)(H)2 to P2PPhFe(N2)2.Artículo Efficient Reduction of Carbon Tetrachloride in an Electrochemical Reactor with a Three-Dimensional Electrode(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Molina Romo, Víctor Manuel; Moreno Toral, Esteban; Ramos Carrillo, Antonio; Universidad de Sevilla. Departamento de Farmacia y Tecnología Farmacéutica; Universidad de Sevilla. Departamento de Química FísicaA selective electrochemical synthesis of chloroform from carbon tetrachloride (CT) in a laboratory-scale electrochemical reactor using a carbon felt three-dimensional electrode is studied. The characterization of the electrochemical reactor from the point of view of material transport was carried out, obtaining good correlations both in the adjustment to a simple bath reactor model and the adjustment to a piston-flow model, and the operating parameters were obtained, such as the material transport coefficient or the limiting intensity. The galvanostatic electrolysis of CT in the filter-press reactor obtained good values for current efficiency and selectivity, so that only hydrogen was obtained as a by-product. With respect to the use of flat electrodes, the three-dimensional carbon felt electrode improves the results in all the studied parameters under identical experimental conditions.Artículo Effect of Gold Nanoparticle Aggregation on the Kinetic Aspect of AuNPs/DNA Interactions(Austin Publishing Group, 2021-03-10) Grueso Molina, Elia María; Giráldez Pérez, Rosa María; Prado Gotor, Rafael; Universidad de Sevilla. Departamento de Química Física; Universidad de SevillaSince successful therapy for curing cancer and others genetic diseases requires the transport of DNA into the cell by delivery vehicles, the understanding of the factors that control the complexation and condensation of the DNA is a key problem. During the last decade, researchers have developed some uses of nanoparticles-DNA systems, the majority of these studies dealing with NPs, which are covalently bound to the DNA. However, the kinetic aspect of AuNPs/DNA system by non-covalent interactions is less explored. Moreover, the role of high salt concentrations in these studies is of great interest due to the majority of nanoparticles have a great tendency to aggregate upon exposure to biological medium, significantly alter the uptake extent, rate, and mechanism of AuNPs/DNA interaction. As a contribution to this field, we have studied kinetics aspects of the binding of small tiopronin gold nanoparticles, AuNPs, to double stranded DNA in at high salt concentration by using the stopped-flow technique. The kinetic curves are biexponential and reveal the presence of two kinetic steps. Moreover, AFM studies reveal AuNPs aggregation in the presence of high salt content, while the same particle are well-dispersed in water. A two-step series mechanism reaction scheme was proposed. According to the reaction scheme, the formation of an intermediate complex formed by aggregated gold nanoparticles and DNA precedes the rate-determining step of the reaction.Artículo Properties of polyplexes formed between a cationic polymer derived from l-arabinitol and nucleic acids(Royal Society of Chemistry, 2021-05-14) Pérez Alfonso, David; López López, Manuel; López-Cornejo, María del Pilar; Romero Azogil, Lucía; Benito Hernández, Elena María; García Martín, María de Gracia; García Calderón, Clara Beatriz; Valle Rosado, Iván; Romero Balestra, Fernando; Huertas Sánchez, Pablo; García Calderón, Margarita; Moyá Morán, María Luisa; Universidad de Sevilla. Departamento de Química Física; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Universidad de Sevilla. Departamento de Química Orgánica y Farmacéutica; Universidad de Sevilla. Departamento de Genética; Junta de Andalucía; Universidad de Sevilla; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; European Union (UE)In this work a sugar-based cationic polymer derived from L-arabinitol, PUArab, was prepared and its interactions with the linear calf thymus DNA and with the circular plasmid pEGFP-C1 were investigated at different N/P ratios. The polyplexes were characterized by using several techniques. For both nucleic acids, a charge inversion was observed, together with a conformational change from a coiled structure to a more compacted one. However, the N/P ratio required to observe the DNA condensation depended on the nucleic acid architecture. PUArab presents low toxicity in several cell lines. The transfection efficiency, TE, of the PUArab/pEGFP-C1 polyplexes was investigated at several N/P ratios in order to study their potential as vectors in gene transfection.Artículo Phosphorylation of cytochrome c at tyrosine 48 finely regulates its binding to the histone chaperone SET/TAF-Iβ in the nucleus(Wiley, 2024-11-16) Tamargo Azpilicueta, Joaquín; Casado Combreras, Miguel Ángel; Giner Arroyo, Rafael Luis; Velázquez Campoy, Adrián; Márquez Escudero, Inmaculada; Olloqui Sariego, José Luis; Rosa Acosta, Miguel Ángel de la; Díaz Moreno, Irene; Universidad de Sevilla. Departamento de Química Física; Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular; Ministerio de Ciencia, Innovación y Universidades (MICINN). España; European Union (UE); Junta de AndalucíaPost-translational modifications (PTMs) of proteins are ubiquitous processes present in all life kingdoms, involved in the regulation of protein stability, subcellular location and activity. In this context, cytochrome c (Cc) is an excellent case study to analyze the structural and functional changes induced by PTMS as Cc is a small, moonlighting protein playing different roles in different cell compartments at different cell-cycle stages. Cc is actually a key component of the mitochondrial electron transport chain (ETC) under homeostatic conditions but is translocated to the cytoplasm and even the nucleus under apoptotic conditions and/or DNA damage. Phosphorylation does specifically alter the Cc redox activity in the mitochondria and the Cc non-redox interaction with apoptosis-related targets in the cytoplasm. However, little is known on how phosphorylation alters the interaction of Cc with histone chaperones in the nucleus. Here, we report the effect of Cc Tyr48 phosphorylation by examining the protein interaction with SET/TAF-Iβ in the nuclear compartment using a combination of molecular dynamics simulations, biophysical and structural approaches such as isothermal titration calorimetry (ITC) and nuclear magnetic resonance (NMR) and in cell proximity ligation assays. From these experiments, we infer that Tyr48 phosphorylation allows a fine-tuning of the Cc-mediated inhibition of SET/TAF-Iβ histone chaperone activity in vitro. Our findings likewise reveal that phosphorylation impacts the nuclear, stress-responsive functions of Cc, and provide an experimental framework to explore novel aspects of Cc post-translational regulation in the nucleus.Artículo Mechanisms for the Spin-State Switching of Strapped Ni-Porphyrin Complexes Deposited on Metal Surfaces: Insights from Quantum Chemical Calculations(John Wiley & Sons, 2024-11-06) Montenegro-Pohlhammer, Nicolas; Sánchez de Armas, María Rocío; Gruber, Manuel; Jiménez Calzado, Carmen; Universidad de Sevilla. Departamento de Química Física; Ministerio de Ciencia e Innovación (MICIN). España; Deutsche Forschungsgemeinschaft / German Research Foundation (DFG)The incorporation of molecular switches on nanodevices requires both the intactness of the molecule once deposited on a substrate and the persistence of the reversible switching feature. Recently, the reversible spin-switching of strapped Ni(II)-porphyrin complexes deposited on Ag(111) surface is demonstrated with low-temperature scanning tunneling microscopy (STM). The spin transition is accompanied by the coordination change of the metal center, a phenomenon denominated in coordination-induced spin-state switching (CISSS). In this contribution, the spin switching of the deposited strapped Ni-porphyrin molecules using different quantum chemistry approaches is explored. This calculations inform about the geometry and electronic structure of the adsorbed molecules and the origin of the voltage-dependent switching promoted by the STM tip. Two different mechanisms are inspected to elucidate the key role of the tip, mainly the electron injection between the tip and the molecule and the differential stabilization of the two spin states by the applied electric field between the tip and the silver surface. This study puts in evidence the relevance of the pyridine ligand contained in the strap in the transport properties as in the CISSS process itself.