Publications

Abstract The most important limitation of antifungal QSAR models is that they predict the biological activity of drugs against only one fungal species. This is determined due the fact that most of the up-to-date reported molecular descriptors encode only information about the molecular structure. Consequently, predicting the probability with which a drug is active against different fungal species with a single unifying model is a goal of major importance. Herein, we use the Markov Chain theory to calculate new multi-target spectral moments to fit a QSAR model that predicts the antifungal activity of more than 280 drugs against 90 fungi species. Linear discriminant analysis (LDA) was used to classify drugs into two classes as active or non-active against the different tested fungal species whose data we processed. The model correctly classifies 12434 out of 12566 non-active compounds (98.95%) and 421 out of 468 active compounds (89.96%). Overall training predictability was 98.63%. Validation of the model was carried out by means of external predicting series, the model classifying, thus, 6216 out of 6277 non-active compounds and 215 out of 239 active compounds. Overall training predictability was 98.7%. The present is the first attempt to calculate, within a unifying framework, the probabilities of antifungal action of drugs against many different species based on spectral moment's analysis.

Abstract A set of four N-thenoylthiocarbamic-O-n-alkylesters, where alkylester = propylester, butylester, pentylester and hexylester were structurally characterized in solid state by single crystal X-ray diffractometry. The supramolecular structure for each compound is stabilised by N-H center dot center dot center dot O hydrogen bonds. For each compound gaseous phase ab initio geometry optimizations for several conformations were performed at the B3LYP/6-311++G(d,p) level of theory in order to evaluate and compare the calculated geometry with the experimental molecular crystal geometry as well as to evaluate the energetic difference between several alkyl conformations. The compounds were further analysed by FTIR spectroscopy and the experimental FTIR spectra were compared with the calculated ones at B3LYP/6-311++G(d,p) level of theory. The structural results for the set were further used in the interpretation of the odd and even effect found previously in their thermophysical properties.

Abstract The antiviral QSAR models have an important limitation today. They predict the biological activity of drugs against only one viral species. This is determined by the fact that most of the current reported molecular descriptors encode only information about the molecular Structure. As a result, predicting the probability with which a drug is active against different viral species with a single unifying model is a goal of major importance. In this work, we use Markov Chain theory to calculate new multi-target spectral moments to fit a QSAR model for drugs active against 40 viral species. The model is based on 500 drugs (including active and non-active compounds) tested as antiviral agents in the recent literature; not all drugs were predicted against all viruses, but only those with experimental values. The database also contains 207 well-known compounds (not as recent as the previous ones) reported in the Merck Index with other activities that do not include antiviral action against any virus species. We used Linear Discriminant Analysis (LDA) to classify all these drugs into two classes as active or non-active against the different viral species tested, whose data we processed. The model correctly classifies 5129 out of 5594 non-active compounds (91.69%) and 412 out of 422 active compounds (97.63%). Overall training predictability was 92.34%. The validation of the model was carried out by means of external predicting series, the model classifying, thus, 2568 out of 2779 non-active compounds and 224 out of 229 active compounds. Overall training predictability was 92.82%. The present work reports the first attempts to calculate within a unified framework the probabilities of antiviral drugs against different virus species based on a spectral moment analysis.

Abstract The formation and microstructure of a novel microemulsion based on a salt-free catanionic surfactant have been examined by considering the hexadecyltrimethylammonium octylsulfonate (TASo)-decane-D(2)O system and using small-angle neutron scattering and self-diffusion NMR. With focus on the emulsification failure boundary, o/w discrete droplets have been observed and characterized for all of the studied microemulsion range. The evaluation of the experimental data was facilitated by using structure factors of a model system composed of charged particles interacting with a screened Coulomb potential. Furthermore, a more simplified model involving a charge regulation mechanism has been employed. Both approaches support the view that the droplets are mainly spherical, fairly monodisperse, and charged. The net charge of the surfactant film is a consequence of the partial dissociation of the short-chain counterpart, owing to its higher solubility. We have further quantified how the droplet charge varies with volume fraction and, from that dependence, explained the unusual phase behavior of the TASo-water system, a seldom found coexistence of two lamellar liquid-crystalline phases in a binary system. This coexistence is quantitatively modeled in terms of a fine balance between the attractive and repulsive colloidal forces acting within the system.

Abstract The standard (p(o) = 0.1 MPa) molar enthalpies of formation of 2,4,6-trichloronitrobenzene, 2,3,5,6-tetrachloronitrobenzene, and pentachloronitrobenzene, in the crystalline state, at T = 298.15 K, were derived from the standard massic energies of combustion, in oxygen, at T = 298.15 K, measured by rotating-bomb combustion calorimetry. The standard molar enthalpies of sublimation, at T = 298.15 K, of 2,4,6-trichloronitrobenzene and pentachloronitrobenzene, were determined from the dependence with the temperature of the vapour pressures, measured by the Knudsen mass-loss effusion method, whereas for 2,3,5,6-tetrachloronitrobenzene, the Calvet drop microcalori metric technique was used. [GRAPHICS] The experimental values are also compared with estimates based on G3(MP2)//B3LYP computations, which have also been extended to all the isomers of the trichloro- and tetrachloronitrobenzene that were not studied experimentally.

Abstract Glutathione capped CdTe quantum dots (QD) were synthesised using a simple experimental procedure and two samples were subjected of study (QD(550) and QD(600)). The maximum of the excitation and emission spectra and the emission full width of half maximum of these two QD were: QD(550), 307, 550 and 37 nm; QD(600), 307, 600 and 39 nm. The steady state fluorescence properties of the two QD undergo variation when the pH of the aqueous solution is varied and are characterised by different apparent pKa: QD(550), 5.2 +/- 0.1; QD(600), 6.3 +/- 0.3. The fluorescence intensity of the QD(550) is markedly quenched by the presence of micromolar quantities of Pb(II) ion (Stern-Volmer constant of about 7 x 10(5) M(-1)). PARAFAC analysis of the excitation emission matrices (EEM) of QD(550) acquired as function of the Pb(II) ion showed that only one linearly independent component describes the quenching of the QD(550) by the Pb(II) ion allowing robust estimation of the excitation and emission spectra and of the quenching profiles.

Abstract The standard (p degrees = 0.1 MPa) molar enthalpies of formation of 2,4-, 2.5-,3,4- and 3,5-dichloronitrobenzene isomers, in the crystalline state, at T = 298.15 K, were derived from the standard (p degrees = 0.1 MPa) massic energies of combustion, in oxygen, at T = 298.15 K, measured by rotating bomb combustion calorimetry. The standard molar enthalpies of sublimation of the four isomers, at T = 298.15 K, were obtained by high-temperature Calvet microcalorimetry. [GRAPHICS] From the determined experimental results, the values of the gaseous standard (p degrees = 0.1 MPa) molar enthalpies of formation were derived. The gas-phase enthalpies of formation of all the six chloronitrobenzene isomers were also estimated by the Cox scheme and by computational thermochemistry methods and compared with the available experimental values.

Abstract The standard (p degrees = 0.1 MPa) molar enthalpies of formation in the liquid phase of three isomers of bromoanisole were derived from the standard molar energies of combustion, in oxygen, which yields CO(2)(g) and HBr center dot 600H(2)O(l), at T = 298.15 K, measured by rotating bomb combustion calorimetry. The determination of the standard molar enthalpies of vaporization of these compounds, at T = 298.15 K, was done by Calvet microcalorimetry using the high-temperature vacuum sublimation technique. Combining the former sets of experimental results, the standard molar enthalpies of formation, in the gas-phase, were derived. The gas-phase enthalpies of formation were also estimated by means of the empirical scheme developed by Cox and by density functional theory calculations performed at the B3LYP/6-31 +G(d) level of theory. [GRAPHICS]

Abstract The standard (p degrees = 0.1 MPa) molar enthalpies of formation in the liquid phase of three isomers Of fluoroanisole were derived from the standard molar energies of combustion, in oxygen, to yield CO(2)(g) and HF . 10H(2)O(I), at T = 298.15 K. measured by rotating bomb combustion calorimetry. The standard molar enthalpies of vaporization Of these Compounds, also at T = 298.15 K, were determined using Calvet microcalorimetry. [GRAPHICS] The standard molar enthalpies of formation in the gaseous phase, at T= 298.15 K, were derived from the former two experimental quantities. These values are also compared with estimates based on two different methodologies: one using the empirical scheme developed by Cox and the other one based on high-level density functional theory calculations using the B3LYP hybrid exchange-correlation energy functional at the 6-311++G(d,p) basis set. The computed values and the estimated values using the Cox method compare well with the experimental results obtained in this work.

Abstract The present work reports the values of the standard (p degrees = 0.1 MPa) molar enthalpies of formation in the condensed phase of the three isomers of monofluorophenol derived from the standard molar energies of combustion, in oxygen, to yield CO(2)(g) and HF center dot 10H(2)O(1), at T = 298.15 K, measured by rotating bomb combustion calorimetry, as well as the values of the standard molar enthalpies of sublimation or vaporization, at T = 298.15 K, determined using high temperature Calvet microcalorimetry. Combining the former two experimental quantities, the standard molar enthalpies of formation in the gaseous phase were derived, at T 298.15 K: Delta(f)H degrees(m)(2-fluorophenol, g) = -(294.5 +/- 1.6) kJ . mol(-1), Delta(f)H degrees(m)(3-fluorophenol, g) = -(292.8 +/- 1.7) kJ.mol(-1), and Delta(f)H degrees(m)(44-fluorophenol, g) = -(287.6 +/- 2.1) kJ.mol(-1). The experimental values of the gas-phase enthalpies of formation of each compound were compared with estimates using the empirical scheme developed by Cox and with the calculated values based on high-level density functional theory calculations using the B3LYP hybrid exchange-correlation energy functional at the 6-3 11 ++G(d,p) basis set.