Reduction of iron by decarboxylation in the formation of magnetite nanoparticles.

The process of formation of magnetite nanoparticles has been investigated by liquid chromatography and mass spectroscopy in the liquid phase decomposition of either Fe(III) acetylacetonate with decanoic acid or Fe(III) decanoate. In both cases, the dissociation into radicals of the iron carboxylate bonds provides the reduction of the Fe(III) cations and the oxygen atoms required for the formation of the mixed-valence inverse spinel magnetite structure. A reaction mechanism is proposed.

Stable radical cores: a key for bipolar charge transport in glass forming carbazole and indole derivatives.

Stable radical adducts of the TTM series bearing carbazolyl or indolyl fragments show bipolar transport properties with mobility values among the highest detected in glassy small molecules. Bipolarity is attributed to the radical character, while the heterocyclic ring confers the adducts the glassy morphological states and the non-dispersive regimes for charge transport.

Differential behavior of amino-imino constitutional isomers in nonlinear optical processes.

A detailed study of the "blocked" amino-imino tautomers derived from N-acridine-substituted 2-aminobenzothiazole--and their effect on the nonlinear optical response--is presented. The synthesis, characterization, and nonlinear optical properties of these frozen tautomers, namely, N-methyl-N-(2-nitroacridin-6-yl)-2-aminobenzothia-zole and 3-methyl-N-(7-nitroacridin-3-yl)-2-iminobenzothiazole, are reported. A theoretical model based on valence-bond theory is also proposed and used to analyze the effects of the nuclear configuration corresponding to each frozen tautomer structure.

Multiple interactions in the self-association of porphyrin discotic mesogens.

The conformational preferences and the self-associational behaviors of two hemin-derived porphyrin compounds, a tetramethyl ester and a liquid crystalline tetrakis(3,5-didodecyloxyphenyl)ester, have been studied by UV/vis and (1)H NMR spectroscopy in solution. Results indicate that the 3,5-didodecyloxyphenyl units play an important role in both the conformational and the self-associational behaviors of the mesomorphic tetraester. In the monomeric, nonassociated species, the two propionic 3,5-didodecyloxyphenyl esters establish mutual CH/pi interactions that restrict the fluctuative behavior of the chains.

Taking advantage of the radical character of tris(2,4,6-trichlorophenyl)methyl to synthesize new paramagnetic glassy molecular materials.

This paper describes the synthesis of the novel bis[4-(N-carbazolyl)-2,6-dichlorophenyl](2,4,6-trichlorophenyl)methyl radical (2*) and tris[4-(N-carbazolyl)-2,6-dichlorophenyl]methyl radical (3*). A Friedel-Crafts reaction on [4-(N-carbazolyl)-2,6-dichlorophenyl)bis(2,4,6-trichlorophenyl]methyl radical (1*), 2*, and 3* leads to the introduction of acyl chains in the 3- and 6-positions of the carbazolyl moiety without impairment of the radical character of the molecule to give radicals 5*, 6*, and 7*. All of these novel radical adducts are thermally stable, 5* and 6* being amorphous solids by differential scanning calorimetry.

Perturbation of the dimer interface of triosephosphate isomerase and its effect on Trypanosoma cruzi.

Background: Chagas disease affects around 18 million people in the American continent. Unfortunately, there is no satisfactory treatment for the disease. The drugs currently used are not specific and exert serious toxic effects.

Red organic light-emitting radical adducts of carbazole and tris(2,4,6-trichlorotriphenyl)methyl radical that exhibit high thermal stability and electrochemical amphotericity.

Synthesis and characterization of new carbazolyl derivatives with a pendant stable radical of the TTM (tris-2,4,6-trichlorophenylmethyl radical) series are reported. The EPR spectra, electrochemical properties, absorption spectra, and luminescent properties of these radical adducts have been studied. All of them show electrochemical amphotericity being reduced and oxidized to their corresponding stable charged species.

Visible second-harmonic light generated from a self-organized centrosymmetric lattice of nanospheres.

We designed and fabricated a centrosymmetric material where one may be able to consider an efficient quadratic nonlinear interaction. We followed a solid phase-supported organic synthesis methodology to covalently bind a large number of highly nonlinear molecules to the surface of polystyrene nanospheres. Such chemically modified optically nonlinear latex spheres, when suspended in water, are seen to perfectly self-organize into a centrosymmetric lattice.

Structural differences in triosephosphate isomerase from different species and discovery of a multitrypanosomatid inhibitor.

We examined the interfaces of homodimeric triosephosphate isomerase (TIM) from eight different species. The crystal structures of the enzymes showed that a portion of the interface is markedly similar in TIMs from Trypanosoma cruzi (TcTIM), Trypanosoma brucei, and Leishmania mexicana and significantly different from that of TIMs from human, yeast, chicken, Plasmodium falciparum, and Entamoeba histolytica. Since this interfacial region is central in the stability of TcTIM, we hypothesized that it would be possible to find agents that selectively affect the stability of TIMs from the three trypanosomatids.

Inactivation of triosephosphate isomerase from Trypanosoma cruzi by an agent that perturbs its dimer interface.

We characterized by crystallographic, calorimetric and biochemical methods the action of a low molecular weight compound, 3-(2-benzothiazolylthio)-1-propanesulfonic acid (compound 8) that binds to the dimer interface of triosephosphate isomerase from Trypanosoma cruzi (TcTIM) and thereby abolishes its function with a high level of selectivity. The kinetics of TcTIM inactivation by the agent and isothermal titration calorimetry experiments showed that the binding of two molecules of the compound per enzyme is needed for inactivation. The binding of the first molecule is endothermic, and that of the second exothermic.

The first asymmetrically beta-polysubstituted porphyrin-based hexagonal columnar liquid crystal.

The preparation of a new beta-tetrasubstituted porphyrin through a short synthesis with liquid crystalline properties in a wide range of temperatures including room temperature is described.

Highly specific inactivation of triosephosphate isomerase from Trypanosoma cruzi.

We searched for molecules that selectively inactivate homodimeric triosephosphate isomerase from Trypanosoma cruzi (TcTIM), the parasite that causes Chagas' disease. We found that some benzothiazoles inactivate the enzyme. The most potent were 3-(2-benzothiazolylthio)-propanesulfonic acid, 2-(p-aminophenyl)-6-methylbenzothiazole-7-sulfonic acid, and 2-(2-4(4-aminophenyl)benzothiazole-6-methylbenzothiazole-7-sulfonic acid.

Synthesis and pharmacological evaluation of new 4-2-(7-heterocyclemethoxynaftalen-2-ylmethoxy)ethylbenzoic acids as LTD(4)-antagonists.

A group of new 4-[2-(7-heterocyclemethoxynaftalen-2-ylmethoxy)ethyl]benzoic acids have been synthesized and pharmacologically evaluated as LTD(4)-antagonists. Thiazole derivatives, especially 4-[2-[7-(4-cyclobutylthiazole-2-ylmethoxyl)naphthalen- 2-ylmetho-xy]et hyl]benzoic acid, present considerable activity and improved pharmacokinetic profiles in comparison with our quinoline containing lead molecule confirming the interest of our compounds as potentially oral antiasthmatics and that the 4-alkylthiazole system can be considered as bioisosteric of the quinoline ring at least in our series of compounds.

Evaluation of practical chromatographic procedures for identification of clinical isolates of mycobacteria.

After experimental conditions were established, 366 strains of mycobacteria belonging to 23 different species were studied for fatty acids, secondary alcohols, and mycolic acid cleavage products by capillary gas-liquid chromatography. Additionally, the mycolic acid pattern was studied by thin-layer chromatography. Capillary gas-liquid chromatography allowed direct identification of the following Mycobacterium spp.

A novel mycolic acid in a Mycobacterium sp. from the environment.

A fast-growing, non-photochromogenic mycobacterium isolated from the environment exhibited, on thin-layer chromatograms, a characteristic pattern of mycolates composed of unsaturated mycolates and also an unknown more polar component. Spectroscopic analysis and chemical degradation showed that this latter component was a novel mycolic acid containing a methoxy group at the omega-1 position (instead of omega-17 and omega-18 in known methoxymycolates), and two double bonds in the long mero aldehyde chain (instead of one as in known mycolates with additional oxygenated groups).

Structure of (-)-1-phenylethylammonium hydrogen (+)-tartrate.

C8H12N+.C4H5O6-, Mr = 271.27, monoclinic, P21, a = 6.