Publications by authors named "Alfonso Hernandez-Laguna"

Context: Lenalidomide (LEN) is used for the treatment of myeloma blood cancer disease. It has become one of the most efficient drugs to halt this disease. LEN is a low-soluble drug in aqueous media.

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  • - Peptides, particularly cysteine-asparagine-serine (CNS) and serine-asparagine (SN), are being researched for their potential as anti-inflammatory drugs, but their molecular interactions are not fully understood.
  • - The study utilized density functional theory (DFT) calculations to confirm the crystal structure of SN, which helped validate findings related to CNS and its spectroscopic properties.
  • - The research found that CNS can intercalate into montmorillonite (MNT), leading to significant changes in its conformation, which may enhance its stability and efficacy for therapeutic anti-inflammatory applications.
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Tetroxane derivatives are interesting drugs for antileishmaniasis and antimalaric treatments. The gas-phase thermal decomposition of 3,6,-dimethyl-1,2,4,5-tetroxane (DMT) and 3,3,6,6,-tetramethyl-1,2,4,5-tetroxane (acetone diperoxide (ACDP)) was studied at 493-543 K by direct gas chromatography by means of a flow reactor. The reaction is produced in the injector chamber at different temperatures.

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  • The use of antibiotics in agriculture has significantly increased, leading to rising levels of these substances in soil, particularly from intensive farming and human consumption.
  • This study examines how ciprofloxacin, an antibiotic, interacts with clay minerals in soils from Santa Rosa, Argentina, using both experimental methods and atomistic modeling.
  • Findings reveal two types of ciprofloxacin adsorption on clay minerals: a weakly bound form that gets released during desorption and a strongly bound form that persists in the soil.
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Layered double hydroxides (LDHs) are important components in terrestrial and extra-terrestrial environments. The presence of iron in these minerals provides them a wide potential application in environmental and materials sciences. In this work, the role of Fe in the crystallographic properties of LDHs M:M 2:1 with Mg:(Fe,Al), Mg:Fe, Zn:(Fe,Al), and Zn:Fe is investigated by means of quantum mechanical calculations based on the density functional theory (DFT).

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This work aimed at studying the potentiality of interactions between kaolinite surfaces and a protein-fragment (350-370 amino acid units) extracted from the glycoprotein E1 in the transmembrane domain (TMD) of hepatitis C virus capsid. A computational work was performed for locating the potential electrostatic interaction sites between kaolinite aluminol and siloxane surfaces and the residues of this protein-fragment ligand, monitoring the possible conformational changes. This hydrated neutralized kaolinite/protein-fragment system was simulated by means of molecular modeling based on atomistic force fields based on empirical interatomic potentials and molecular dynamic (MD) simulations.

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Muscovite (Ms) and phlogopite (Phl) belong to the 2:1 dioctahedral and trioctahedral layer silicates, respectively, and are the end members of Ms-Phl series minerals. This series was studied in the 2M polytype and modeled by the substitution of three Mg cations in the Phl octahedral sites by two Al and one vacancy, increasing the substitution up to reach the Ms. The series was computationally examined at DFT level as a function of pressure to 9 GPa.

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  • - Organic peroxides, like 3,6-dimethyl-1,2,4,5-tetroxane (DMT), have various properties including potential for antimicrobial use and explosive characteristics, which are explored through gas-phase thermolysis reaction mechanisms using DFT calculations.
  • - The research examines three reaction mechanisms (S-concerted, S-stepwise, and T-stepwise), finding that the S-stepwise mechanism is the most energetically favorable, producing acetaldehyde and oxygen with lower activation energies compared to the S-concerted mechanism.
  • - Notably, the study reveals that the transition from singlet to triplet state can occur at an intermediate stage, significantly impacting the reaction profile, with
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  • Clay minerals are important for various technological applications due to their versatility and ability to absorb and catalyze substances.
  • The study explores how glycine and its protonated form, glycinium, interact with montmorillonite clay, indicating that glycinium can replace potassium in the clay's layers and that this process is energetically favorable.
  • The results show that glycine is adsorbed in a zwitterionic state within the clay without water, with hydrogen bonds and electrostatic interactions playing a key role in this process, and the findings align with experimental data on intermolecular interactions.
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Anthelmintic praziquantel (PZQ) and its molecular and crystal lattice structures were studied by means of atomistic calculations based on empirical interatomic potentials and quantum mechanical methods (DFT). This chiral drug presents several crystal polymorphs due to the enantiomers (either R or S) or the racemic crystal, and different molecular conformations. The relative configurations of the carbonyl groups in PZQ define these conformations that produce different polymorphs.

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The spatial geometry and local environment of hydroxyl groups of the cis-vacant (cv) crystal polymorph of dioctahedral 2:1 phyllosilicates are studied by computational methods, doing especial emphasis on the hydrogen bonds and electrostatic interactions of the hydroxyl groups with the neighbor atoms. Different types of phyllosilicates are explored: with only tetrahedral charge, with only octahedral charge, with simultaneous octahedral and tetrahedral substitution, and with different interlayer cation (IC). The effect of these interactions on the spectroscopic properties of these hydroxyl groups is also studied.

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  • - Cyclic organic peroxides, like cyclic diperoxides, are highly reactive and can be explosive due to the weakness of O-O bonds, with methylformaldehyde diperoxide (MFDP) being studied for its thermolysis reaction products, including acetaldehyde, formaldehyde, and oxygen.
  • - Using Density Functional Theory (DFT) calculations, researchers explored the potential energy surface (PES) of MFDP, finding that the reaction proceeded through a diradical intermediate leading to two possible pathways for product formation.
  • - Results indicated that the triplet state (T) reaction pathway was more exothermic than the singlet state (S), and spin-orbit coupling allowed for a crossing between
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  • * The reaction proceeds by forming a guanylhydrazone-acetylcarbinol adduct, followed by dehydration, ring closure to create a 1,2,4-triazine, and final dehydration yielding 5-methyl 3-amino-1,2,4-triazine, with the first dehydration step being the slowest part of the process.
  • * The findings support previous experimental data highlighting AG's effectiveness in interacting with d
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This work presents a Density Functional Theory (DFT) study on the charge transport related properties of two quinoidal diketopyrrolopyrrole (DPP) based systems. System A, recently synthesized, shows high efficiency as n-type organic semiconductor material while system B, not synthesized yet, has a linking benzothiadiazole (BT) unit between DPP moieties and would display an ambipolar character. The use of tuned, long-range corrected (LRC) functionals allows one to predict HOMO, LUMO, and charge transport properties for compound A in concordance with those experimentally observed.

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  • A quantum mechanical study was conducted to calculate the vibrational energy levels and frequencies of protons in lithium niobate (LiNbO3) single crystals, including cases of hydrogen contamination.
  • A supercell model, involving a single hydrogen ion (H+) and lithium vacancy (Li+), was developed to derive a simplified Hamiltonian operator describing the proton vibrations within the crystal structure.
  • The calculations led to approximations of the proton's vibrational modes, revealing strong anharmonic behavior, with the transition frequencies aligning closely (within 1%) to experimental data, allowing for more accurate identification of certain vibrational bands.
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Density Functional Theory has been used to study the structural, electronic and charge-transport properties of two regio-regular head-to-tail polythiophene derivatives, i.e. poly(3-hexyl-thiophene), P3HT, and poly(3-oxyhexyl-thiophene), P3OHT.

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We have investigated the process of rehydroxylation of pyrophyllite as a limiting factor to the dehydroxylation upon thermal treatment. Car-Parrinello molecular dynamics simulations based on density functional theory have been used along with the metadynamics algorithm. Two possible rehydroxylation mechanisms reaction have been characterized, related to two possible intermediate structures along the rehydroxylation paths, and both involve the interaction of the apical oxygen atoms.

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We delineate the dehydroxylation reaction of pyrophyllite in detail by localizing the complete reaction path on the free energy surface obtained previously by Car-Parrinello molecular dynamics and the implemented metadynamics algorithm ( Molina-Montes et al. J. Phys.

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  • The dehydroxylation of pyrophyllite involves reacting hydroxyl (OH) groups and releasing water through two main mechanisms, one involving octahedral Al (3+) pairs and the other across dioctahedral vacancies.
  • First-principles molecular dynamics simulations demonstrate that both mechanisms show similar activation energy at 0 K, but at high temperatures, one mechanism has a lower free energy, affecting the reaction pathway.
  • The study highlights various semidehydroxylated intermediates produced during dehydroxylation and proposes a new mechanism emphasized by structural apical oxygens at high temperatures, which offers insight into temperature's role in favoring specific reaction pathways
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