Aqua cadmium cyanide coordination polymer with nitronyl nitroxide radical

A new three-dimensional diamagnetic metal nitronyl nitroxide radical coordination polymer with an aqua cadmium cyanide framework Cd(NIT4py)(H₂O)Cd(CN)₄·H₂O 1, was synthesized. X-ray crystallography reveals that the structure consists of 3D aqua cadmium cyanide built up by octahedral Cd^II coordinating to NIT4py and tetrahedral Cd^II (CN)₄ units. Magnetic measurements show that the χ_mT values are nearly constant at higher temperature. The lower χ_mT values at lower temperature are related to intermolecular antiferromagnetic interactions of the radicals, which arise due to the hydrogen bonded network (T_N = 21 K).     

Rebirth of a dead Belousov-Zhabotinsky oscillator

Long time behaviors of the Belousov-Zhabotinsky (BZ) reaction are experimentally analyzed in a closed reactor. The amplitude of the oscillation is suddenly damped after about 10 h. After about 5-20 h, the dead oscillator is suddenly restored with nearly the same amplitude as before it stopped its oscillation for certain values of the concentrations of sodium bromate and malonic acid (MA). With the other domains of the concentrations, the oscillator simply damps and never restores its oscillation. The phase diagram of the different types of damping behaviors as a function of the concentrations is obtained.     

π Back-bonding of iron(II) complexes supported by tris(pyrid-2-ylmethyl)amine and its nitro-substituted derivatives

The electronic and geometric structures of a series of iron(II) complexes supported by tetradentate tris(pyrid-2-ylmethyl)amine-type ligands with different numbers of 4-nitropyridine groups, [(PyCH(2))(3-n)(4-NO(2)PyCH(2))(n)N] (n = 0-3), were examined by X-ray absorption fine-structure and variable-temperature (1)H NMR spectroscopies and theoretical calculations to reveal how the low-spin state is stabilized through π back-bonding interactions between iron(II) and 4-nitropyridine donor group(s).     

Design of main-chain polymers of chiral imidazolidinone for asymmetric organocatalysis application

Main-chain polymers of chiral imidazolidinone were successfully synthesized by reaction of chiral imidazolidinone dimers with disulfonic acid. Chiral imidazolidinones were incorporated into the main-chain of the polymer by ionic bonding. These polymers could be used as polymeric chiral organocatalysts for asymmetric Diels-Alder reactions.     

Structural basis for oxygen sensing and signal transduction of the heme-based sensor protein Aer2 from Pseudomonas aeruginosa

The crystal structure of a truncated Aer2, a signal transducer protein from Pseudomonas aeruginosa, consisting of the heme-containing PAS and di-HAMP domains revealed that a distal tryptophan residue (Trp283) plays an important role in stabilizing the heme-bound O(2) and intra-molecular signal transduction upon O(2) binding.     

Detection of cellular damage by hydrogen peroxide using SV40-T2 cells on shear horizontal surface acoustic wave (SH-SAW) sensor

The rat lung epithelial cell line SV40-T2 was used to develop a cellular biosensing system to assay for environmental toxicants. The novel approach on which this system is based involves direct attachment of cultured rat or human cells onto a cell-adhesive matrix on the device through which shear horizontal surface acoustic waves (SH-SAW) are transmitted using 50 MHz SAW resonator. This novel design enables sensitive monitoring of changes of the electrophysical characteristics of cells, such as their conductivity and relative permittivity. A time-dependent change of phase of SAW and change of insertion loss (change of amplitude) were observed when the cells were treated with 0.5 or 1.0 mM H₂O₂. The change of insertion loss was biphasic, with an early phase (1–3 h) and a late phase (3–6 h). The late phase coincided with the destruction of cell–cell tight junctions detected by measurement of the transepithelial electrical resistance and paracellular permeability; in contrast, the early phase coincided with the destruction of intracellular actin filaments by H₂O₂. The early-phase effect of H₂O₂ on phase shift may be attributable to the change of intracellular permittivity by a change of cellular polarity. Immunofluorescence microscopy showed the disappearance of zonula occludens protein 1 from the region of cell–cell contact. These results suggest the correlation between the change of insertion loss as an SAW parameter and the destruction of tight junctions of the cells on the SH-SAW device in the late phase.     

Effects of GaAs and Ga2O3 on magnetometric behavior of iron oxide particles in rabbit lungs

Intratracheal instillation of a GaAs suspension has been histopathologically shown to induce a diffuse pulmonary response. In the present study, magnetometry was used to evaluate the effects of intratracheally instilled GaAs and Ga₂O₃ on the behavior of externally magnetized iron oxide (Fe₃O₄) particles instilled in rabbit lung. Magnetometric evaluation of the effects of GaAs in rabbits dosed with 30 mg or 300 mg per animal showed a significantly decreased relaxation of iron oxide particles at 1, 3, 7, 14, 21 and 28 days following instillation compared with the controls. On the other hand, in the rabbits exposed to Ga₂O₃, significantly reduced decay constants were observed only on the first and third days following instillation. Relaxation indicates a rapid decrease of remanent magnetic field following magnetization of the lungs due to random rotation of phagocytosed iron oxide particles in macrophages. Clearance of the iron oxide particles was measured by serial determinations of the remanent magnetic field at the end of magnetization estimated from relaxation curves. Clearance was significantly impaired at 14, 21 and 28 days after instillation in rabbits exposed to both doses of GaAs. Slightly delayed clearance was also observed in rabbits exposed to Ga₂O₃. Histological examination of lungs instilled with GaAs indicated active phagocytosis of GaAs and iron oxide particles by pulmonary macrophages, as well as pneumonocytes hyperplasia with marked thickening of the alveolar walls. Minimal histological changes with retention of iron oxide particles were found in the lungs exposed to Ga₂O₃.