Four-Electron Reduction of Dioxygen on a Metal Surface: Models of Dissociative and Associative Mechanisms in a Homogeneous System.

Two different four-electron reductions of dioxygen (O2) on a metal surface are reproduced in homogeneous systems. The reaction of the highly unsaturated (56-electron) tetraruthenium tetrahydride complex 1 with O2 readily afforded the bis(µ3-oxo) complex 3 via a dissociative mechanism that includes large electronic and geometric changes, i.e., a four-electron oxidation of the metal centers and an increase of 8 in the number of valence electrons. In contrast, the tetraruthenium hexahydride complex 2 induces a smooth H-atom transfer to the incorporated O2 species, and the O-OH bond is cleaved to afford the mono(µ3-oxo) complex 4 via an associative mechanism. Density functional theory calculations suggest that the higher degree of unsaturation in the tetrahydride system induces a significant interaction between the tetraruthenium core and the O2 moiety, enabling the large changes required for the dissociative mechanism.

Cytokine biomarker candidates in breast milk associated with the development of atopic dermatitis in 6-month-old infants.

BACKGROUND: A few studies have reported that the quantity of selected cytokines/chemokines in breast milk might be associated with atopic dermatitis (AD). Using the multiplex cytokine assay system, we examined cytokines/chemokines in human milk in order to identify new biomarkers related to AD. METHODS: We recruited 49 infants with or without AD who participated in a birth cohort and measured the concentrations of cytokines/chemokines in the colostrum (collected within 4-5 days after birth) and mature milk (collected at 1 month postpartum) received by the infants. RESULTS: There were significant differences in the concentrations of interleukin (IL)-1ß and IL-12p40 in the colostrum, and in those of IL-4, eotaxin, granulocyte colony-stimulating factor (G-CSF), granulocyte macrophage colony-stimulating factor (GM-CSF), interferon (IFN)-α2 and MIP-1α in the mature milk between the milk received by infants who developed AD at the age of 6 months and that received by the control infants. There was weak to moderate correlation between those 6 cytokines/chemokines in mature milk. Atopic history and IgE levels of mothers were not related to cytokine/chemokine concentrations in breast milk. Logistic regression analyses showed that high levels of eotaxin in the mature milk were a risk for the development of AD at 6 months of age. CONCLUSION: These results suggest that several cytokines/chemokines, especially eotaxin, are potential biomarkers for development of AD in early infancy.

Ferrielectric smectic C phases stabilized using a chiral liquid crystal oligomer.

A chiral liquid crystal oligomer, (R)-1-methylheptyl 4'-{8-[4-(5-octylpyrimidin-2-yl)phenyloxy]octanoyloxy}biphenyl-4-carboxylate, was prepared. Its physical properties were investigated using optical microscopy, differential scanning calorimetry, and X-ray diffraction. The oligomer was found to exhibit two ferrielectric smectic C phases with a wide temperature range between ferroelectric and antiferroelectric smectic C phases. Furthermore, ferrielectric-like ordering was observed in a racemic mixture of the enantiomers. The oligomeric effect can produce highly chirality-dependent ordering in the racemic system.