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Almandoz M.C.,National University of San Luis | Sancho M.I.,National University of San Luis | Duchowicz P.R.,Institute Investigaciones Fisicoquimicas Teoricas y Aplicadas INIFTA | Blanco S.E.,National University of San Luis
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2014

The solvatochromic behavior of trimethoprim (TMP) was analyzed using UV-Vis spectroscopy and DFT methods in neat and binary aqueous solvent mixtures. The effects of solvent dipolarity/polarizability and solvent-solute hydrogen bonding interactions on the absorption maxima were evaluated by means of the linear solvation energy relationship concept of Kamlet and Taft. This analysis indicated that both interactions play an important role in the position of the absorption maxima in neat solvents. The simulated absorption spectra of TMP and TMP:(solvent)n complexes in ACN and H2O using TD-DFT methods were in agreement with the experimental ones. Binary aqueous mixtures containing as co-solvents DMSO, ACN and EtOH were studied. Preferential solvation was detected as a nonideal behavior of the wavenumber curve respective to the analytical mole fraction of co-solvent in all binary systems. TMP molecules were preferentially solvated by the organic solvent over the whole composition range. Index of preferential solvation, as well as the influence of solvent parameters were calculated as a function of solvent composition. © 2014 Elsevier B.V. All rights reserved.

Munoz A.,University of La Laguna | Salvarezza R.C.,Institute Investigaciones Fisicoquimicas Teoricas y Aplicadas INIFTA
Langmuir | Year: 2010

A comparative study on the thermodynamic stability of the lying down (LD) and standing up (SU) phases of α,ω- butanedithiol (BDT) on unreconstructed (U) and on reconstructed (R) Au(111) surfaces is presented. The R surface is made of dithiol-Au adatom units. Density functional calculations (DFT) allow the estimation of the adsorption energy of the LD and SU BDT phases on both substrates. Surface free energies based on the DFT calculations show the coverage of the clean Au(111) surface by the LD phase, and the LD to SU phase transition as the chemical potential of the BDT molecule is increased. The LD and SU phases are more stable on R than on U substrates, suggesting that the Au(111) surface should reconstruct upon BDT adsorption. The stability analysis is extended to longer α,ω-dithiols. Results reveal that the LD to SU phase transition is favored as the hydrocarbon chain length of the dithiol molecule is increased. Changes in the hydrogen pressure affect the formation of the LD phase, while they have only minor effects on the LD to SU phase transitions. Our calculations explain the influence of the number of carbon atoms in the hydrocarbon chains, hydrogen pressure and dithiol pressure (or concentration) on dithiol adsorption, and phase transitions. This information is relevant to control the coverage, reactivity, and surface chemistry of the α,ω-dithiol self-assembled monolayers on Au surfaces. © 2010 American Chemical Society.

Comelli N.C.,National University of Catamarca | Duchowicz P.R.,Institute Investigaciones Fisicoquimicas Teoricas y Aplicadas INIFTA | Castro E.A.,Institute Investigaciones Fisicoquimicas Teoricas y Aplicadas INIFTA
European Journal of Pharmaceutical Sciences | Year: 2014

The inhibitory activity of 103 thiophene and 33 imidazopyridine derivatives against Polo-Like Kinase 1 (PLK1) expressed as pIC50 (-log IC 50) was predicted by QSAR modeling. Multivariate linear regression (MLR) was employed to model the relationship between 0D and 3D molecular descriptors and biological activities of molecules using the replacement method (MR) as variable selection tool. The 136 compounds were separated into several training and test sets. Two splitting approaches, distribution of biological data and structural diversity, and the statistical experimental design procedure D-optimal distance were applied to the dataset. The significance of the training set models was confirmed by statistically higher values of the internal leave one out cross-validated coefficient of determination (Q2) and external predictive coefficient of determination for the test set (Rtest2). The model developed from a training set, obtained with the D-optimal distance protocol and using 3D descriptor space along with activity values, separated chemical features that allowed to distinguish high and low pIC50 values reasonably well. Then, we verified that such model was sufficient to reliably and accurately predict the activity of external diverse structures. The model robustness was properly characterized by means of standard procedures and their applicability domain (AD) was analyzed by leverage method. © 2014 Elsevier B.V. All rights reserved.

Di Virgilio A.L.,Institute Investigaciones Fisicoquimicas Teoricas y Aplicadas INIFTA | Reigosa M.,Instituto Multidisciplinario Of Biologia Celular Imbice | Arnal P.M.,Institute Investigaciones Fisicoquimicas Teoricas y Aplicadas INIFTA | Fernandez Lorenzo de Mele M.,Institute Investigaciones Fisicoquimicas Teoricas y Aplicadas INIFTA
Journal of Hazardous Materials | Year: 2010

The aim of this study was to analyze the cytotoxicity and genotoxicity of titanium oxide (TiO2) and aluminium oxide (Al2O3) nanoparticles (NPs) on Chinese hamster ovary (CHO-K1) cells using neutral red (NR), mitochondrial activity (by MTT assay), sister chromatid exchange (SCE), micronucleus (MN) formation, and cell cycle kinetics techniques. Results showed a dose-related cytotoxic effect evidenced after 24h by changes in lysosomal and mitochondrial dehydrogenase activity. Interestingly, transmission electronic microscopy (TEM) showed the formation of perinuclear vesicles in CHO-K1 cells after treatment with both NPs during 24h but no NP was detected in the nuclei. Genotoxic effects were shown by MN frequencies which significantly increased at 0.5 and 1μg/mL TiO2 and 0.5-10μg/mL Al2O3. SCE frequencies were higher for cells treated with 1-5μg/mL TiO2. The absence of metaphases evidenced cytotoxicity for higher concentrations of TiO2. No SCE induction was achieved after treatment with 1-25μg/mL Al2O3. In conclusion, findings showed cytotoxic and genotoxic effects of TiO2 and Al2O3 NPs on CHO-K1 cells. Possible causes of controversial reports are discussed further on. © 2010 Elsevier B.V.

Thomas A.H.,Institute Investigaciones Fisicoquimicas Teoricas y Aplicadas INIFTA | Serrano M.P.,Institute Investigaciones Fisicoquimicas Teoricas y Aplicadas INIFTA | Rahal V.,CNRS Laboratory for Molecular and Photochemical Reactions | Vicendo P.,CNRS Laboratory for Molecular and Photochemical Reactions | And 3 more authors.
Free Radical Biology and Medicine | Year: 2013

Pterins are normal components of cells and they have been previously identified as good photosensi-tizers under UV-A irradiation, inducing DNA damage and oxidation of nucleotides. In this work, we have investigated the ability of pterin (Ptr), the parent compound of oxidized pterins, to photosensitize the oxidation of another class of biomolecules, amino acids, using tryptophan (Trp) as a model compound. Irradiation of Ptr in the UV-A spectral range (350 nm) in aerated aqueous solutions containing Trp led to the consumption of the latter, whereas the Ptr concentration remained unchanged. Concomitantly, hydrogen peroxide (H2O2) was produced. Although Ptr is a singlet oxygen (1O2) sensitizer, the degradation of Trp was inhibited in O2-saturated solutions, indicating that a 1O2-mediated process (type II oxidation) was not an important pathway leading to Trp oxidation. By combining different analytical techniques, we could establish that a type I photooxidation was the prevailing mechanism, initiated by an electron transfer from the Trp molecule to the Ptr triplet excited state, yielding the corresponding radical ions (Trpd+/Trp(-H)d and Ptrd-). The Trp reaction products that could be identified by UPLC-mass spectrometry are in agreement with this conclusion. © 2013 Elsevier Inc. All rights reserved.

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