Which NICS method is most consistent with ring current analysis? Assessment in simple monocycles.

The aromaticity of benzene, Al4 2- cluster, cyclopropane, borazine and planar cyclooctatetraene (COT) was analyzed according to different strategies based on nucleus-independent chemical shift (NICS) computations. The analysis of NICS-components evolution along the main molecular axis seems to be the most adequate and simplest strategy to predict the aromatic or antiaromatic character of the studied systems. Moreover, the analysis of the σ- and π-electron contributions to the out-of-plane component of NICS (NICS zz ) leads to the same qualitative and quantitative conclusions previously obtained by the analysis of the magnetically induced ring current densities.

[Metalloproteinase activity in arteries and veins. Regulation with doxycycline]. / Actividad de metaloproteinasas de arterias y venas y su regulación mediante doxiciclina.

BACKGROUND: Alterations in the synthesis and degradation of extracellular matrix occur during atherogenesis. Metalloproteinases, whose activity may be inhibited with doxycicline in other tissues, play an important role in this process. AIMS: 1. To characterize metalloproteinase activities in internal mammary artery and saphenous vein, and 2. To assess the effect of doxycicline in the activity of metalloproteinases of these vessels and of cultured smooth muscle cells. METHODS: Segments of internal mammary arteries and saphenous veins and cultured smooth muscle cells were incubated with and without doxycicline. Metalloproteinases activity was assessed by zymography and Western Blot. RESULTS: Activity of metalloproteinase-9 in saphenous veins was 217% less than in internal mammary arteries. In these vessels doxycicline decreased metalloproteinase-9 activity by 207% and metalloproteinase-2 by 290%. Western Blot analysis showed that docycicline also inhibited metalloproteinase-1 expression. In cultured smooth muscle cells, the median inhibitory concentration of doxycicline for metalloproteinase-2 was 138 microM (r2 = 0.82). CONCLUSIONS: Internal mammary arteries and saphenous veins have different metalloproteinase activities, that are inhibited by doxycicline.

Solubilization of iron-containing minerals by soil microorganisms.

Eighty-eight strains of microorganisms were isolated from soils collected in northern and southern Chile, and 10 fungi which showed the highest solubilizing action upon the iron in granodiorite were then selected. These fungi were incubated with the following iron-containing minerals: augite, hornblende, biotite, magnetite, hematite, and the igneous rock granodiorite. The solubility of iron in these minerals depended on their nature, crystalline structure, the concentration of metabolic products, or all three. Complex formation could be the mechanism involved, as a strong cation-exchange resin was not able to extract Fe from culture solutions. This conclusion is also confirmed by the R(F) values obtained by thin-layer chromatography of iron-containing culture solutions.