Novel metallamacrocyclic gold(I) thiolate cluster complex: structure and luminescence of [Au9(mu-dppm)4(mu-p-tc)6](PF6)3

The structure of a novel metallamacrocyclic phosphine gold(I) thiolate cluster, [Au9(mu-dppm)4(mu-p-tc)6](PF6)3, where dppm = bis(diphenylphosphine)methane and p-tc = p-thiocresolate, is reported and shows AuAu attractions of approximately 3.0 A and gold(I) atoms linked to thiolate and phosphine ligands in distorted trigonal and nearly linear geometries.     

Effects of HeNe laser irradiation on experimental paracoccidioidomycotic lesions

Paracoccidioidomycosis (PCM) is the most prevalent human mycosis in Latin America. The infection is thought to take place firstly in the lungs and then may disseminate to other organs and tissues. Treatment by currently available antifungals is lengthy, the drugs may have undesirable side effects, and some are costly. Occasional resistant strains of Paracoccidioides brasiliensis, the causative agent of PCM, have been reported. So, the search for more efficient treatments or adjuvant therapies has to be continued. In this work, we evaluated the effects of HeNe laser irradiation on cutaneous inflammatory lesions caused by the inoculation of 5 x 10(6)/0.1ml yeasts cells into the back footpad of Balb/c mice. HeNe irradiation (lambda=632.8nm, 3mW, incident energy of 3J/cm(2)) was applied at days 7, 8 and 9 post-infection and histological and immunohistochemical analysis were done. Unirradiated animals were used as controls. The results showed that laser-treated mice presented reduction of footpad edema, faster cutaneous wound healing, confluent granuloma, diffuse- and more loosely distributed immunolabeling for TNF-alpha, enhanced labeling of IFN-gamma and any P. brasiliensis form detected, whereas multiple viable fungi were seen in diffuse widespread granulomas obtained from non-treated mice foot-pad. Fungi that were harvested from laser-treated animals presented no capability of growth in vitro as compared to those obtained from non-treated mice. We conclude that HeNe laser irradiation was able to inhibit the progress of inflammatory local reaction produced by P. brasiliensis infection and influence local cytokines production. We suggest that this treatment modality can be a useful coadjuvant tool to be combined with antifungal agents in the treatment of PCM ulcerations. The mechanisms involved in laser therapy of PCM lesions need further investigation.     

Simultaneous determination of glutathione and cysteine concentrations and 2H enrichments in microvolumes of neonatal blood using gas chromatography–mass spectrometry

A method is described whereby the concentrations and ²H isotope enrichment of glutathione (GSH) and cysteine can be simultaneously determined in a single gas chromatography–mass spectrometry run following derivatization as their N,S-ethoxycarbonyl methyl esters. Improvements of the derivatization protocol and the use of a short gas chromatography column combined with single-ion monitoring allow for rapid quantification of these parameters with acceptable precision and reproducibility (coefficient of variation less than 5%). The method makes possible their quantitative measurement in very small volumes (50 μL) of human umbilical cord blood, and is thus suitable for determining the cysteine and GSH concentrations and ²H isotope enrichments in blood samples from neonates or in other conditions in which sample size is restricted. It is shown that the fractional synthesis rate of human umbilical erythrocyte lysates in vitro is several-fold greater than that measured in vivo.     

Formation of a cationic gold(I) complex and disulfide by oxidation of the antiarthritic gold drug auranofin

The mechanism of action of auranofin, an antiarthritic gold(I) drug, is unknown, but several studies suggest that oxidation may be important for its biochemical effect. Bulk electrolysis studies on auranofin [(Et(3)P)Au(TATG); TATG = 2,3,4,6-tetraacetyl-1-thio-d-glucopyranosato] at +1.2 and +1.6 V versus Ag/AgCl in 0.1 M Bu(4)NBF(4)/CH(2)Cl(2) results in n values of 0.5 and >2 electrons, respectively. Oxidation of auranofin with the mild oxidant, Cp(2)Fe(+), results in formation of disulfide and a digold(I) cation with a bridging thiolate ligand, [(Et(3)PAu)(2)(mu-TATG)](+) (1). The X-ray structure of the PMe(3) analogue, [(Me(3)PAu)(2)(mu-TATG)](NO(3)) (2), is reported. Compound 2 forms a tetranuclear cluster containing an almost perfect square of four gold atoms with Au.Au distances averaging 3.14 A. The complex crystallizes in the tetragonal space group P4(2)2(1)2 with cell constants a = 26.1758(6) A, b = 26.1758(6) A, c = 9.7781(3) A, alpha = beta = gamma = 90 degrees, V = 6699.7(3) A(3), Z = 4, R1 = 0.0644, and wR2 = 0.1152. A mechanism for oxidation of auranofin and possible biological implications are discussed.     

Influence of viral infection on essential oil composition of Ocimum basilicum (Lamiaceae)

Ocimum basilicum L., popularly known as sweet basil, is a Lamiaceae species whose essential oil is mainly composed of monoterpenes, sesquiterpenes and phenylpropanoids. The contents of these compounds can be affected by abiotic and biotic factors such as infections caused by viruses. The main goal of this research was an investigation of the effects of viral infection on the essential oil profile of common basil. Seeds of O. basilicum L. cv. Genovese were sowed and kept in a greenhouse. Plants presenting two pairs of leaves above the cotyledons were inoculated with an unidentified virus isolated from a field plant showing chlorotic yellow spots and foliar deformation. Essential oils of healthy and infected plants were extracted by hydrodistillation and analyzed by GCMS. Changes in essential oil composition due to viral infection were observed. Methyleugenol and p-cresol,2,6-di-tert-butyl were the main constituents. However, methyleugenol contents were significantly decreased in infected plants.     

A novel approach for designing simple point charge models for liquid water with three interaction sites

A simultaneous improvement of the diffusion and dielectric properties of the simple point charge (SPC) model for liquid water appears to be very difficult with conventional reparametrization of the commonly used Lennard-Jones and Coulomb interaction functions and without including a self-energy correction in the effective pair-potential as is done in the SPC/E model. Here, a different approach to circumvent this problem is presented. A short-range interaction term, which corrects the oxygen-oxygen energy at small distances by small amounts of energy, was introduced in the nonbonded interaction function. This additional force-field term allows to derive new parameter sets for SPC-like water models that yield better agreement with experimental data on liquid water. Based on previous investigations of the force-field parameter dependence of the water properties of SPC-like models, the necessary parameter changes to obtain a lower diffusion coefficient and a larger dielectric permittivity were specified and accordingly six new models were developed. They all represent an improvement over SPC in terms of structural and diffusional properties, four of them show better dielectric properties also. One model, SPC/S, has been characterized in more detail, and represents most properties of liquid water better than SPC while avoiding the larger discrepancies with experimental values regarding density, thermal compressibility, energy, and free energy of the SPC/E model. We conclude that the use of a simple, short-ranged additional oxygen-oxygen interaction term makes a simultaneous improvement of the diffusion coefficient and the dielectric properties of water feasible.     

Efficient conversion of 6-cyanopurines into 6-alkoxyformimidoylpurines

An extremely simple method for the selective synthesis of 9-aryl and 9-alkyl 6-alkoxy or 6-alkoxyformimidoylpurines from the corresponding 6-cyanopurines is described. The reaction is carried out with methanol or ethanol in the presence of DBU. At room temperature, nucleophilic attack by the primary alcohol occurs selectively on the cyano carbon atom, leading to 6-alkoxyformimidoylpurines in good yields. Heating the reaction mixture at a temperature greater than or equal to 78 degrees C leads to nucleophilic substitution of the substituent in the 6-position by the alkoxy group, generating the corresponding 6-alkoxypurines, also in excellent yields. The 6-alkoxyformimidoylpurines were used as intermediates in the synthesis of 6-carboxamidinopurines by reaction with methylamine (for 9-methylpurine 5a) or methyl ammonium chloride (for 9-arylpurines and 5b and 5c).     

Cyclobutane ring opening of allene-enone photoadducts by mercury (II) perchlorate

Cyclobutane ring opening of some allene-enone photoadducts by Hg(ClO₄)₂ in acetone gave diketones which led, in some cases, to bicyclic ketols through intramolecular aldol condensation.     

Application of structural analogs of dimercaptosuccinic acid-functionalized silica nanoparticles (DMSA-[silica]) to adsorption of mercury, cadmium, and lead

In order to gain additional insight into mercury selectivity with nano-sized DMSA-[silica], we investigated a series of ligands related to DMSA, these are: monomercaptosuccinic acid; MMSA, 2-mercapto-4-methyl-5-thiazoleacetic acid; MCT, ortho-thiosalicylic acid; o-TSA and para-thiosalicylic acid; p-TSA. The MMSA chelate is structurally similar to DMSA except that it has only one thiol group. The chelates o-TSA and p-TSA each have one thiol and one carboxylic acid group. MCT includes neutral S and N atoms in close proximity to the thiolate binding site. MCT, o-TSA and p-TSA resemble each other in having equal numbers of carboxylic acid and thiol groups and formation of amide bonds with the linker on silica is expected to eliminate the carboxylate binding sites, making thiolates the only binding sites for Hg(II), Cd(II), and Pb(II) metals ions in the nano-sized; MMSA-[silica], MCT-[silica], o-TSA-[silica], and p-TSA-[silica]. Each of the nano-sized MMSA-[silica], MCT-[silica], o-TSA-[silica], and p-TSA-[silica], show a higher preference for Hg(II) over Cd(II) and Pb(II) compared to the same free chelates in solution, respectively. In addition, there are differences in the level of metal ion chelation for each functionalized silica nanoparticle. These differences in the degree of metal chelation for each functionalized silica nanoparticles surface are explained by the difference in thiolate/carboxylate ratio upon attachment to the surface and on steric reasons based on the orientation of the thiol groups on the surface. When attached via amide bond formation, the thiolate site in o-TSA-[silica] will face towards the silica surface, while for p-TSA-[silica], the thiolate site is expected to be pointed outwards and away from the silica surface. In comparing MMSA-[silica] to DMSA-[silica], the thiolate/carboxylate ratio decreases from 2/1 in DMSA-[silica] to 1/1 in MMSA-[silica] (assuming attachment via one amide bond in each case). This effect of increasing the ratio of thiolate to carboxylate upon attachment to the surface is believed to play a role in the selectivity enhancement towards Hg(II) over Cd(II) and Pb(II).