Examinando por Autor "Melguizo, Manuel"
Mostrando 1 - 8 de 8
- Resultados por página
- Opciones de ordenación
Ítem Anion-π and lone pair-π interactions with s-tetrazine-based ligands(Elsevier, 2019-07-05) Savastano, Matteo; García-Gallarín, Celeste; López-de-la-Torre, María Dolores; Bazzicalupi, Carla; Bianchi, Antonio; Melguizo, ManuelMost of traditional and contemporary interest in s-tetrazine derivatives focuses onto their redox properties, reactivity and energy density. In recent times, however, an increasing number of reports highlighted the possible usefulness of the s-tetrazine moiety as a binding site for anionic and electron rich species, according to the high and positive quadrupolar moment of this heterocycle and the consequent strength of anion-π and lone pair-π interactions. Herein, after giving a quick perspective on s-tetrazine properties and on how they foster these types of π interactions, we present statistical and critical examination of the available structural data, doing justice to the debated topic of the existence and directionality of anion- and lone pair-π interactions. Finally, available literature material concerning the usage of s-tetrazine as supramolecular binding site in solution, i.e. paving the way to applications such as molecular recognition and sensing, is presented and discussed.Ítem Crystal engineering of high explosives through lone pair-p interactions: Insights for improving thermal safety(Elsevier, 2023-09-15) Savastano, Matteo; López-de-la-Torre, María Dolores; Pagliai, Marco; Bazzicalupi, Carla; Melguizo, Manuel; Bianchi, Antonio; Poggi, Giovanna; Ridi, FrancescaIn this high-risk/high-reward study, we prepared complexes of a high explosive anion (picrate) with potentially explosive s-tetrazine-based ligands with the sole purpose of advancing the understanding of one of the weakest supramolecular forces: the lone pair-p interaction. This is a proof-of-concept study showing how lone pair-p contacts can be effectively used in crystal engineering, even of high explosives, and how the supramolecular architecture of the resulting crystalline phases influences their experimental thermokinetic properties. Herein we present XRD structures of 4 novel detonating compounds, all showcasing lone pair-p interactions, their thermal characterization (DSC, TGA), including the correlation of experimental thermokinetic parameters with crystal packing, and in silico explosion properties. This last aspect is relevant for improving the safety of high-energy materials.Ítem Expanding graphene properties by a simple S-doping methodology based on cold CS2 plasma(Elsevier, 2019-12-14) Abdelkader-Fernández, Victor Karim; Domingo-García, María; López Garzón, Francisco Javier; Fernandes, Diana M.; Freire, Cristina; López de la Torre, Maria Dolores; Melguizo, Manuel; Godino-Salido, Maria Luz; Pérez-Mendoza, ManuelFor the first time, graphene has been successfully doped with sulfur via short exposition to CS2 microwave cold plasmas, avoiding high-temperature and time/chemicals-consuming treatments. Different S-doped samples were obtained by varying the duration of plasma treatments, reaching a remarkable 2.3 at % of S content after only 5 min of exposition. The S-doped graphenes present several sulfur containing moieties, among which thioether groups resulted to be predominant. These moieties are covalently bond to graphene layers and exhibit good thermal and water stability. In addition, unlike others more conventional methods, S-doping via CS2 plasmas do not damage the structural order of graphene. The influence of sulfur doping on the graphene properties has been assessed through two different tests: on one side, the capture of Pd2+ ions in aqueous solution, and on the other, the electrocatalytic activity towards the production of oxygen from water (OER process). In both cases, the performance of the pristine graphene was significantly enhanced with S-doping. In addition, the capture of Pd2+ allows the formation of sulfur-Pd nanoclusters supported on the graphene surface, which are very useful in electrochemical devices.Ítem Halide and hydroxide anion binding in water(Royal Society of Chemistry, 2018-01-24) Savastano, Matteo; Bazzicalupi, Carla; García-Gallarín, Celeste; Giorgi, Claudia; López-de-la-Torre, María Dolores; Pichierri, Fabio; Bianchi, Antonio; Melguizo, ManuelThe formation of halide and hydroxide anion complexes with two ligands L1 (3,6 bis(morpholin-4-ylmethyl)-1,2,4,5-tetrazine) and L2 (3,6-bis(morpholin-4-ylethyl)-1,2,4,5-tetrazine) was studied in aqueous solution, by means of potentiometric and ITC procedures. In the solid state, HF2−, Cl− and Br− complexes of H2L22+ were analysed by single crystal XRD measurements. Further information on the latter was obtained with the use of density functional theory (DFT) calculations in combination with the polarizable continuum model (PCM). The presence of two halide or bifluoride HF2− (F–H–F−) anions forming anion–π interactions, respectively above and below the ligand tetrazine ring, is the leitmotiv of the [(H2L2)X2] (X = HF2, Cl, Br, I) complexes in the solid state, while hydrogen bonding between the anions and protonated morpholine ligand groups contributes to strengthen the anion–ligand interaction, in particular in the case of Cl− and Br−. In contrast to the solid state, only the anion : ligand complexes of 1 : 1 stoichiometry were found in solution. The stability of these complexes displays the peculiar trend I− > F− > Br− > Cl− which was rationalized in terms of electrostatic, hydrogen bond, anion–π interactions and solvent effects. DFT calculations performed on [(H2L2)X]+ (X = F, Cl, Br, I) in PCM water suggested that the ligand assumes a U-shaped conformation to form one anion–π and two salt bridge interactions with the included anions and furnished structural information to interpret the solvation effects affecting complex formation. The formation of hydroxide anion complexes with neutral (not protonated) L1 and L2 molecules represents an unprecedented case in water. The stability of the [L(OH)]− (L = L1, L2) complexes is comparable to or higher than the stability of halide complexes with protonated ligand molecules, their formation being promoted by largely favourable enthalpic contributions that prevail over unfavourable entropic changes.Ítem HBPEI-grafted carbon nanotubes for the effective retention of Pd2+ and Pt2+ through complexation(Royal Society of Chemistry, 2018-06-21) Abdelkader-Fernández, Victor Karim; Morales-Lara, Francisco; López de la Torre, Maria Dolores; Melguizo, Manuel; López Garzón, Francisco Javier; Domingo-García, María; Pérez-Mendoza, ManuelHyperbranched poly(ethyleneimine) (HBPEI) molecules in solution present high capacity to form stable complexes with transition metal ions due to the large number of amino groups ready to form chelates. We grafted HBPEI molecules to a multi-walled carbon nanotube (MWCNT) surface through covalent bonding, preparing solid hybrids which retain the chemical properties of the free poly-alkylamine molecules. In this way, we are able to transfer the complexation capacity of such molecules to a solid material adequate to act as a high-capacity sorbent for metal transition ions. We tested the HBPEI/MWCNT hybrids for the retention of Pd2+ and Pt2+ and the retention values obtained are much larger than those previously reported with fast retention kinetics. The kinetics and the XPS analysis of the metal ion/HBPEI/MWCNT ensemble indicate that the retention takes place through the formation of chelates with two or three nitrogen atoms and with Cl− anions as co-ligands. Moreover, the results allow us to tune the metal loading on the hybrids by controlling the solution conditions. This is important because the XPS valence band analysis demonstrates that metal complexation directly modifies the electronic behaviour of the carbon nanotubes, which supports the stable covalent bond between HBPEI molecules and MWCNT and opens the possibility for tuning the electronic properties of the tubes.Ítem Nitrated Fatty-Acids Distribution in Storage Biomolecules during Arabidopsis thaliana Development(MDPI, 2022-09) Valderrama, Raquel; Chaki, Mounira; Begara-Morales, Juan Carlos; Melguizo, Manuel; Barroso-Albarracín, Juan Bautista; Aranda-Caño, LorenaThe non-enzymatic interaction of polyunsaturated fatty acids with nitric oxide (NO) and de rived species results in the formation of nitrated fatty acids (NO2-FAs). These signaling molecules can release NO, reversibly esterify with complex lipids, and modulate protein function through the post translational modification called nitroalkylation. To date, NO2-FAs act as signaling molecules during plant development in plant systems and are involved in defense responses against abiotic stress conditions. In this work, the previously unknown storage biomolecules of NO2-FAs in Arabidopsis thaliana were identified. In addition, the distribution of NO2-FAs in storage biomolecules during plant development was determined, with phytosterol esters (SE) and TAGs being reservoir biomolecules in seeds, which were replaced by phospholipids and proteins in the vegetative, generative, and senescence stages. The detected esterified NO2-FAs were nitro-linolenic acid (NO2-Ln), nitro-oleic acid (NO2-OA), and nitro-linoleic acid (NO2-LA). The last two were detected for the first time in Arabidopsis. The levels of the three NO2-FAs that were esterified in both lipid and protein storage biomolecules showed a decreasing pattern throughout Arabidopsis development. Esterification of NO2-FAs in phospholipids and proteins highlights their involvement in both biomembrane dynamics and signaling processes, respectively, during Arabidopsis plant development.Ítem Nitro-Oleic Acid-Mediated Nitroalkylation Modulates the Antioxidant Function of Cytosolic Peroxiredoxin Tsa1 during Heat Stress in Saccharomyces cerevisiae(MDPI, 2022-05-14) Aranda-Caño, Lorena; Valderrama, Raquel; Pedrajas, José Rafael; Begara-Morales, Juan Carlos; Chaki, Mounira; Padilla-Serrano, María Nieves; Melguizo, Manuel; López-Jaramillo, Francisco Javier; Barroso-Albarracín, Juan BautistaHeat stress is one of the abiotic stresses that leads to oxidative stress. To protect themselves, yeast cells activate the antioxidant response, in which cytosolic peroxiredoxin Tsa1 plays an important role in hydrogen peroxide removal. Concomitantly, the activation of the heat shock response (HSR) is also triggered. Nitro-fatty acids are signaling molecules generated by the interaction of reactive nitrogen species with unsaturated fatty acids. These molecules have been detected in animals and plants. They exert their signaling function mainly through a post-translational modification called nitroalkylation. In addition, these molecules are closely related to the induction of the HSR. In this work, the endogenous presence of nitro-oleic acid (NO2-OA) in Saccharomyces cerevisiae is identified for the first time by LC-MS/MS. Both hydrogen peroxide levels and Tsa1 activity increased after heat stress with no change in protein content. The nitroalkylation of recombinant Tsa1 with NO2-OA was also observed. It is important to point out that cysteine 47 (peroxidatic) and cysteine 171 (resolving) are the main residues responsible for protein activity. Moreover, the in vivo nitroalkylation of Tsa1 peroxidatic cysteine disappeared during heat stress as the hydrogen peroxide generated in this situation caused the rupture of the NO2-OA binding to the protein and, thus, restored Tsa1 activity. Finally, the amino acid targets susceptible to nitroalkylation and the modulatory effect of this PTM on the enzymatic activity of Tsa1 are also shown in vitro and in vivo. This mechanism of response was faster than that involving the induction of genes and the synthesis of new proteins and could be considered as a key element in the fine-tuning regulation of defence mechanisms against oxidative stress in yeast.Ítem Supramolecular forces and their interplay in stabilizing complexes of organic anions: tuning binding selectivity in water(Royal Society of Chemistry, 2019-11-20) Savastano, Matteo; Bazzicalupi, Carla; García-Gallarín, Celeste; López-de-la-Torre, María Dolores; Bianchi, Antonio; Melguizo, ManuelHow do different supramolecular forces contribute to the stabilization of complexes of organic anions in water? Oftentimes, when debating such a theme, we refer to broad concepts like positive or negative cooperative effects; the focus of the present work is rather on their interplay, i.e. on the way different kinds of stabilizing interactions (salt bridges, H-bonds, anion–π interactions, π–π stacking, solvent effects, etc.) dialogue among themselves. What happens if we tune the strengths of salt bridges by altering the basicity of the anion? What if we change the geometry of the charged group? How does shifting towards more hydrophilic or hydrophobic anions impact the stability of complexes in water? What happens in the solid state? Will aromatic anions go for a π–π stacking or an anion–π interaction mode and do they all behave in the same manner? Does the host/guest size make any difference? What if we play with regiochemistry: will one of the isomers be selectively recognized? Here we present a case study featuring the tetrazine-based ligands L1 and L2 and a series of selected organic anions; potentiometric, NMR, and XRD data and in silico simulations are employed to render such a complex picture.