Helena M. Petrilli

Ab-initio calculations of the formation energies of BCC-based superlattices in the FeAl system

Abstract First-principles calculations of the total energies of A2 iron and aluminum, B2 (FeAl), B32 (FeAl) and D0 3 (Fe 3 Al and FeAl 3 ) compounds were performed in the frame of density functional theory (DFT) using the Full Potential - Linear Augmented Plane Wave method (FP-LAPW). These results have been used to obtain formation energies of the respective ground states. The calculated formation energies of the D0 3 (Fe 3 Al) and B2 (FeAl) compounds show excellent agreement with available calorimetric data on standard enthalpies of formation of FeAl alloys up to 50 at.% aluminum. As the FeAl system has a controversial magnetic behavior when described by ab-initio methods in the DFT, this agreement is remarkable.

Hyperfine interactions in silicon quantum dots

We present an all-electron calculation of the hyperfine parameters for conduction electrons in Si, showing that: (i) all parameters scale linearly with the spin density at a

Mefenamic Acid Anti-Inflammatory Drug: Probing Its Polymorphs by Vibrational (IR and Raman) and Solid-State NMR Spectroscopies

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Oxindole-Schiff base copper(II) complexes interactions with human serum albumin: Spectroscopic, oxidative damage, and computational studies

Si site; (ii) the isotropic term is over 30 times larger than the anisotropic part; (iii) conduction electron charge density at a Si nucleus is consistent with experimental estimates; (iv) Overhauser fields in natural Si quantum dots (QDs) are two orders of magnitude smaller than in GaAs QDs. This reinforces the outstanding performance of Si in keeping spin coherence and opens access to reliable quantitative information aiming at spintronic applications.

Delivery system for mefenamic acid based on the nanocarrier layered double hydroxide: Physicochemical characterization and evaluation of anti-inflammatory and antinociceptive potential.

This work deals with the spectroscopic (supported by quantum chemistry calculations), structural, and morphological characterization of mefenamic acid (2-[(2,3-(dimethylphenyl)amino] benzoic acid) polymorphs, known as forms I and II. Polymorph I was obtained by recrystallization in ethanol, while form II was reached by heating form I up to 175 °C, to promote the solid phase transition. Experimental and theoretical vibrational band assignments were performed considering the presence of centrosymmetric dimers. Besides band shifts in the 3345-3310 cm(-1) range, important vibrational modes to distinguish the polymorphs are related to out-of-phase and in-phase N-H bending at 1582 (Raman)/1577 (IR) cm(-1) and 1575 (Raman)/1568 (IR) cm(-1) for forms I and II, respectively. In IR spectra, bands assigned to N-H bending out of plane are observed at 626 and 575 cm(-1) for polymorphs I and II, respectively. Solid-state (13)C NMR spectra pointed out distinct chemical shifts for the dimethylphenyl group: 135.8 to 127.6 ppm (carbon bonded to N) and 139.4 to 143.3 ppm (carbon bonded to methyl group) for forms I and II, respectively.

Layered double hydroxide and sulindac coiled and scrolled nanoassemblies for storage and drug release

CD and EPR were used to characterize interactions of oxindole-Schiff base copper(II) complexes with human serum albumin (HSA). These imine ligands form very stable complexes with copper, and can efficiently compete for this metal ion towards the specific N-terminal binding site of the protein, consisting of the amino acid sequence Asp-Ala-His. Relative stability constants for the corresponding complexes were estimated from CD data, using the protein as competitive ligand, with values of log K(CuL) in the range 15.7-18.1, very close to that of [Cu(HSA)] itself, with log K(CuHSA) 16.2. Some of the complexes are also able to interfere in the alpha-helix structure of the protein, while others seem not to affect it. EPR spectra corroborate those results, indicating at least two different metal species in solution, depending on the imine ligand. Oxidative damage to the protein after incubation with these copper(II) complexes, particularly in the presence of hydrogen peroxide, was monitored by carbonyl groups formation, and was observed to be more severe when conformational features of the protein were modified. Complementary EPR spin-trapping data indicated significant formation of hydroxyl and carbon centered radicals, consistent with an oxidative mechanism. Theoretical calculations at density functional theory (DFT) level were employed to evaluate Cu(II)-L binding energies, L-->Cu(II) donation, and Cu(II)-->L back-donation, by considering the Schiff bases and the N-terminal site of HSA as ligands. These results complement previous studies on cytotoxicity, nuclease and pro-apoptotic properties of this kind of copper(II) complexes, providing additional information about their possibilities of transport and disposition in blood plasma.

Industrial Scale Isolation, Structural and Spectroscopic Characterization of Epiisopiloturine from Pilocarpus microphyllus Stapf Leaves: A Promising Alkaloid against Schistosomiasis.

PURPOSE The anionic form of the drug mefenamic acid intercalated into the nanocarrier layered double hydroxide (LDH-Mef) was evaluated by anti-inflammatory and antinociceptive assays. METHODS The LDH-Mef material was characterized by a set of physicochemical techniques, which was supported by Density Functional Theory calculations. The pharmacological effects of LDH-Mef (40 wt% of drug) were evaluated by hemolytic, anti-inflammatory activity and antinociceptive assays. RESULTS In vivo assays were conducted for the first time in order to assess the LDH-Mef potential. The hemolytic effects decreased for the intercalated Mef as demonstrated by the higher tolerated hemolytic concentration (1.83 mM) compared to mefenamic acid (MefH), 0.48 mM. Pretreatment of animals with MefH or LDH-Mef reduced carrageenan-, dextran sulfate- and PGE2-induced paw edema. MefH or LDH-Mef also decrease total leucocytes and neutrophil counts of the peritoneal cavity after inflammation induction with carrageenan. In the nociception model, oral pretreatment with LDH-Mef reduced mechanical hypernociception carrageenan-induced after 3-4h and also the number of writhings induced by acetic acid. CONCLUSIONS This work shows the increase of the anti-inflammatory and antinociceptive potential of the drug confined into the LDH, as well as, its hemolytic effect.

Electric field gradients at Ta in Zr and Hf inter-metallic compounds

Sulindac, a non-steroidal anti-inflammatory of the indene acetic acid class, was immobilized inside layered double hydroxide Mg2Al and Zn2Al (LDH) nanovessels through a one pot reaction. LDH–drug materials were characterized by chemical elemental analysis, X-ray diffraction (XRD) (one dimensional electron distribution along the c-stacking axis, pair distribution function analysis), scanning and transmission electron microscopies, mass coupled thermal analyses, vibrational infrared and Raman spectroscopies, and solid state 13C NMR. Density Functional Theory (DFT) calculations were performed for sulindac (protonated and deprotonated forms) with the aim to assign the LDH–drug spectroscopic results. All converge towards a spatial organization of interleaved sulindac molecules close to that reported for the pristine polymorph II crystal structure. Of relevance for human treatment because of its biocompatibility and non-immunogenic effect, in vitro sulindac release experiments were performed in a phosphate buffer mimicking biological fluids and release profiles were refined using kinetic models.

Interactions of di-imine copper(II) complexes with albumin: competitive equilibria, promoted oxidative damage and DFT studies

This paper presents an industrial scale process for extraction, purification, and isolation of epiisopiloturine (EPI) (2(3H)-Furanone,dihydro-3-(hydroxyphenylmethyl)-4-[(1-methyl-1H-imidazol-4-yl)methyl]-, [3S-[3a(R*),4b]]), which is an alkaloid from jaborandi leaves (Pilocarpus microphyllus Stapf). Additionally for the first time a set of structural and spectroscopic techniques were used to characterize this alkaloid. EPI has shown schistomicidal activity against adults and young forms, as well as the reduction of the egg laying adult worms and low toxicity to mammalian cells (in vitro). At first, the extraction of EPI was done with toluene and methylene chloride to obtain a solution that was alkalinized with ammonium carbonate. The remaining solution was treated in sequence by acidification, filtration and alkalinization. These industrial procedures are necessary in order to remove impurities and subsequent application of the high performance liquid chromatography (HPLC). The HPLC was employed also to remove other alkaloids, to obtain EPI purity higher than 98%. The viability of the method was confirmed through HPLC and electrospray mass spectrometry, that yielded a pseudo molecular ion of m/z equal to 287.1 Da. EPI structure was characterized by single crystal X-ray diffraction (XRD), 1H and 13C nuclear magnetic resonance (NMR) in deuterated methanol/chloroform solution, vibrational spectroscopy and mass coupled thermal analyses. EPI molecule presents a parallel alignment of the benzene and the methyl imidazol ring separated by an interplanar spacing of 3.758 Å indicating a π-π bond interaction. The imidazole alkaloid melts at 225°C and decomposes above 230°C under air. EPI structure was used in theoretical Density Functional Theory calculations, considering the single crystal XRD data in order to simulate the NMR, infrared and Raman spectra of the molecule, and performs the signals attribution.

Application of standard DFT theory for nonbonded interactions in soft matter: Prototype study of poly‐para‐phenylene

Abstract Here we calculate the electric field gradient (EFG) at the nucleus of the substitutional Ta impurity site in Zr 2 T and Hf 2 T (T=Cu, Ag, Au, and Pd) C11 b inter-metallic compounds. We use the ab initio FP-LAPW method as embodied in the Wien97 code in a super-cell approach and include lattice relaxations around the impurity. Our results are compared with EFG values inferred from measurements of the quadrupole coupling constants at the 111 Ta probe in these compounds performed with the time differential perturbed angular correlation (TDPAC) technique. We also performed EFG calculations for the pure inter-metallic compounds. Through the comparison of theoretical and experimental EFGs in these cases, we elucidate the role played by the Ta probe in the TDPAC measurements of Hf and Zr compounds. Our results show that, although the EFGs at the Hf site are very similar to the EFGs at the Ta impurity, there is no direct correlation between the Zr and Ta EFGs.