Publications

Abstract The aqueous self-assembly of a novel lysine-derived surfactant with a gemini-like architecture, designated here as 12-Lys-12, has been experimentally investigated for the amphiphile alone in water and in a mixture with dodecyltrimethylammonium bromide (DTAB). The neat surfactant forms interesting micrometer-sized rigid tubules in the dilute region, resulting in very viscous solutions. For the catanionic mixture with DTAB, various single and multiphase regions were identified (up to a total surfactant concentration of 1.5 wt %) by means of combined polarizing light microscopy, cryo-TEM, and NMR. In the DTAB-rich side, for a mixing molar ratio in the range 2 < DTAB/12-Lys-12 < 4, a region of stable, unilamellar vesicles can be found. Furthermore, it was found that upon addition of 12-Lys-12 to pure DTAB solutions, the mixed micelles grow and beyond a given mixing ratio, vesicles assemble and coexist with small micelles. The transition is not continuous, since there is a narrow mixing range where phase separation occurs. Self-diffusion measurements and cryo-TEM imaging show that the average vesicle radius is on the order of 30-40 nm.

Abstract The standard ( p(0)= 0.1 MPa) molar enthalpies of formation, Delta H-f(m)0, for crystalline phthalimides: phthalimide, N-ethylphthalimide and N-propylphthalimide were derived from the standard molar enthalpies of combustion, in oxygen, at the temperature 298.15 K, measured by static bomb-combustion calorimetry, as, respectively, - ( 318.0 +/- 1.7), - (350.1 +/- 2.7) and - ( 377.3 +/- 2.2) kJ mol(-1). The standard molar enthalpies of sublimation, Delta H-8(cr)m(0), at T=298.15 K were derived by the Clausius-Clapeyron equation, from the temperature dependence of the vapour pressures for phthalimide, as (106.9 +/- 1.2) kJ mol(-1) and from high temperature Calvet microcalorimetry for phthalimide, N-ethylphthalimide and N-propylphthalimide as, respectively, (106.3 +/- 1.3), (91.0 +/- 1.2) and (98.2 +/- 1.4) kJ mol(-1). The derived standard molar enthalpies of formation, in the gaseous state, are analysed in terms of enthalpic increments and interpreted in terms of molecular structure.

Abstract Eight structurally similar dihydroxy and trihydroxyphenolic acids (protocatechuic acid, 3,4-dihydroxyphenylacetic acid, hydrocaffeic acid, caffeic acid, gallic acid, 3,4,5-trihydroxyphenylacetic acid, 3-(3,4,5-trihydroxyphenyl) propanoic acid and 3-(3,4,5-trihydroxyphenyl)propenoic acid) were examined for their total antioxidant capacity (TAC). Furthermore, their ability to scavenge peroxyl radicals, generated by AAPH in liposomes, was determined. The antioxidant/pro-oxidant activity of the compounds was screened using the 2'-deoxyguanosine assay. All compounds behave as radical scavengers, with 3,4,5-trihydroxyphenylacetic acid being the most potent. Nevertheless, in the lipid peroxidation assay an inverse ranking order was observed, 3,4-dihydroxyphenylacetic acid being the most effective compound. All the dihydroxylated compounds showed a pro-oxidant behaviour leading to an increase of 50% in 8-OH-dG induction. From the structure-antioxidant activity relationship studies performed it may be concluded that the number of phenolic groups and the type of the alkyl spacer between the carboxylic acid and the aromatic ring strongly influence the antioxidant activity.

Abstract The molecule of the title compound, C(23)H(40)O(4)Si(2), features an approximate non-crystallographic C(2) symmetry axis. The aldehyde group is disordered over two positions with similar occupancies. The geometry of the isolated molecule was studied by ab initio quantum mechanical calculations employing a molecular orbital Hartree - Fock method. The calculations reproduce well the equilibrium geometry but slightly overestimate the value of the Si - O bond lengths of the trioxadisilepine ring.

Abstract The anticancer (cytotoxicity against human mammary gland adenocarcinoma cells) and anti-inflammatory properties (COX-2 inhibition) of the hydroxycinnamic derivatives trans-3-(3,4,5-trihydroxyphenyl)-2-propenoic acid, trans-ethyl(3,4,5-trihydroxyphenyl)-2-propenoate and diethyl 2-(3,4,5-trihydroxy-phenylmethylene)malonate were screened. Data point out a putative correlation between anti-inflammatory and anticancer properties and suggest hydroxycinnamic derivatives as promising lead compounds for the development of anti-inflammatory/chemopreventive agents.

Abstract The co-administration of methamphetamine (METH) and MOR (MOR)-like compounds is becoming increasingly popular among drug abusers. Recently, it was demonstrated that rats would self-inject METH-heroin combination and that this combination produced a greater rewarding effect than the identical doses of METH alone and it was further suggested that enhanced reward might underlie the popularity of this combination. However, there is null information on the effects of the MOR-METH combination on striatal dopaminergic transmission. In the present article, in vivo brain microdialysis was used to examine the effects of two METH doses (1 and 5 mg/kg, i.p.; [METH1: hyperlocomotion-inducing] and [METH5: stereotypy-inducing], respectively) and MOR (10 mg/kg, i.p. [MOR10]) either alone or in combination on dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) release in caudate putamen (CPu) in freely moving rats. METH1 evoked a transient threefold increase in DA overflow in only one-third of dosed rats. On the contrary, METH5 elicited a 11-fold increase in the extracellular DA levels 30 min after dosing and stayed significantly (P < 0.05) above control levels up to 1.5 h. On the other hand, MOR10 did not significantly change DA extracellular levels. MOR10-METH1 combination prolonged DA outflow for 1 h in all rats dosed without changing peak effect compared to METH1. On the other hand, MOR10-METH5 combination did not change the peak effect nor the DA outflow profile compared to METH5 alone. Consistently, there is a concentration-dependent decrease in DOPAC efflux evoked by METH: METH1 evoked a smaller decrease in DOPAC outflow showing a tendency for returning to basal values whereas METH5 kept DOPAC extracellular levels reduced throughout the experiment. Again, MOR10 did not significantly change DOPAC extracellular levels. MOR delayed the onset without changing METH effect on the DOPAC output. These findings provide suggestive evidence that MOR potentiated the increase in extracellular DA levels induced by a low dose of METH. Thus, this combination yields a profile of action that might underlie the reinforcing properties sought by drug addicts.

Abstract A new electrically calibrated calorimetric system to measure heat capacities of solids has been designed and tested by determining the heat capacity of sapphire and benzoic acid in the temperature range 298-393 K. Comparison of the obtained results with recommended adiabatic calorimetry data showed that the maximum and average absolute deviations were 3.3% and 1.6%, respectively. The technique provides a convenient alternative to routine heat capacity determinations by DSC, since the experiments are faster and, in general, the results have better accuracy. In addition, the sample cells can be kept under argon or nitrogen atmosphere thus enabling the study of air sensitive compounds.

Abstract The gas-phase standard molar enthalpies of formation of the three monoiodoanilines were derived from the enthalpies of combustion in the condensed phases. measured by rotating-bomb calorimetry and their enthalpies of sublimation/vaporization obtained by Calvet microcalorimetry at T = 298.15 K. The standard enthalpies of formation for these compounds and for the diiodoaniline isomers were determined by DFT calculations. The theoretical calculations were performed with the B3LYP/6-31G(d):SBKJ-VDZ and B3LYP/6-311G(2d, 2p):SBKJ-VDZ approaches. Estimated values are in excellent agreement with the reported experimental numbers derived in the present Letter.

Abstract The enthalpies of combustion, heat capacities, enthalpies of sublimation and enthalpies of formation of 2-tert-butylbenzimidazole (2tBuBIM) and 2-phenylimidazole (2PhIM) are reported and the results compared with those of benzene derivatives and a series of azoles (imidazoles, pyrazoles, benzimidazoles and indazoles). Theoretical estimates of the enthalpies of formation were obtained through the use of atom equivalent schemes. The necessary energies were obtained in single-point calculations at the B3LYP/6-311++G(d,p) on B3LYP/6-31G* optimized geometries. The comparison of experimental and calculated values of all studied compounds bearing H (unsubstituted), methyl (Me) ethyl (Et), propyl (Pr), isopropyl (iPr), tert-butyl (tBu), benzyl (Bn) and phenyl (Ph) groups show remarkable homogeneity. The remarkable consistency of both the calculated and experimental results allows us to predict with reasonable certainty the missing experimental values. The crystal and molecular structure of the 2-benzylbenzimidazole (2BnBIM) has been determined by X-ray analysis. The observed molecular conformation permits the crystal being built up through N-H...N hydrogen bonds and van der Waals contacts between the molecules. An attempt has been made to relate the crystal structure to the enthalpies of sublimation.