NH Tautomerism of N-Confused Porphyrin: Solvent/Substituent Effects and Isomerization Mechanism.

The effects of substituents and solvents on the NH tautomerism of N-confused porphyrin () were investigated. The structures, electronic states, and aromaticity of NH tautomers ( and ) were studied by absorption and nuclear magnetic resonance (H, C, and N) spectroscopies, single-crystal X-ray diffraction analysis, and theoretical calculations. The relative stability of the tautomers is highly affected by solvents, with the -type tautomer being more stable in nonpolar solvents, while the -type tautomer being highly stabilized in polar solvents with high donor numbers such as ,-dimethylformamide (DMF), pyridine, and acetone.

Capping Structure of Ligand-Cysteine on CdSe Magic-Sized Clusters.

Ligand molecules capping on clusters largely affect the formation and stabilization mechanism and the property of clusters. In semiconductor CdSe clusters, cysteine is used as one of the ligands and allows the formation of ultrastable (CdSe) magic-sized clusters. Cysteine has sulfhydryl, amine, and carboxylate groups, all of which have coordination ability to the CdSe surface, and the bonding states of the three functional groups of ligand-cysteine on the CdSe core have not been determined.

Hydride in BaTiO2.5H0.5: A Labile Ligand in Solid State Chemistry.

In synthesizing mixed anion oxides, direct syntheses have often been employed, usually involving high temperature and occasionally high pressure. Compared with these methods, here we show how the use of a titanium perovskite oxyhydride (BaTiO2.5H0.

Site-specific inhibitory mechanism for amyloid β42 aggregation by catechol-type flavonoids targeting the Lys residues.

The aggregation of the 42-residue amyloid β-protein (Aβ42) is involved in the pathogenesis of Alzheimer disease (AD). Numerous flavonoids exhibit inhibitory activity against Aβ42 aggregation, but their mechanism remains unclear in the molecular level. Here we propose the site-specific inhibitory mechanism of (+)-taxifolin, a catechol-type flavonoid, whose 3',4'-dihydroxyl groups of the B-ring plays a critical role.

An oxyhydride of BaTiO3 exhibiting hydride exchange and electronic conductivity.

In oxides, the substitution of non-oxide anions (F(-),S(2-),N(3-) and so on) for oxide introduces many properties, but the least commonly encountered substitution is where the hydride anion (H(-)) replaces oxygen to form an oxyhydride. Only a handful of oxyhydrides have been reported, mainly with electropositive main group elements or as layered cobalt oxides with unusually low oxidation states. Here, we present an oxyhydride of the perhaps most well-known perovskite, BaTiO(3), as an O(2-)/H(-) solid solution with hydride concentrations up to 20% of the anion sites.

Verification of the intermolecular parallel beta-sheet in E22K-Abeta42 aggregates by solid-state NMR using rotational resonance: implications for the supramolecular arrangement of the toxic conformer of Abeta42.

Formation of the intermolecular beta-sheet is a key event in the aggregation of 42-residue amyloid-beta (Abeta42). We have recently identified a physiological and toxic conformer, the turn positions of which are slightly different from each other, in the aggregates of E22K-Abeta42 (one of the mutants related to cerebral amyloid angiopathy). However, it remains unclear whether the intermolecular beta-sheet in the E22K-Abeta42 aggregates is parallel or antiparallel.