Mesoscopic Architectures Made of Electrically Charged Binary Colloidal Nanosheets in Aqueous System

Inorganic layered materials can be converted to colloidal liquid crystals through exfoliation into inorganic nanosheets, and binary nanosheet colloids exhibit rich phase behavior characterized by multiphase coexistence. In particular, niobate–clay binary nanosheet colloids are characterized by phase separation at a mesoscopic (∼several tens of micrometers) scale whereas they are apparently homogeneous at a macroscopic scale. Although the mesoscopic structure of the niobate–clay binary colloid is advantageous to realize unusual photochemical functions, the structure itself has not been clearly demonstrated in real space. The present study investigated the structure of niobate–clay binary nanosheet colloids in detail. Four clay nanosheets (hectorite, saponite, fluorohectorite, and tetrasilisic mica) with different lateral sizes were compared. Small-angle X-ray scattering (SAXS) indicated lamellar ordering of niobate nanosheets in the binary colloid. The basal spacing of the lamellar phase was reduced by increasing the concentration of clay nanosheets, indicating the compression of the liquid crystalline niobate phase by the isotropic clay phase. Scattering and fluorescence microscope observations using confocal laser scanning microscopy (CLSM) demonstrated the phase separation of niobate and clay nanosheets in real space. Niobate nanosheets assembled into domains of several tens of micrometers whereas clay nanosheets were located in voids between the niobate domains. The results clearly confirmed the spatial separation of two nanosheets and the phase separation at a mesoscopic scale. Distribution of clay nanosheets is dependent on the employed clay nanosheets; the nanosheets with large lateral length are more localized or assembled. This is in harmony with larger basal spacings of niobate lamellar phase for large clay particles. Although three-dimensional compression of the niobate phase by the coexisting clay phase was observed at low clay concentrations, the basal spacing of niobate phase was almost constant irrespective of niobate concentrations at high clay concentrations, which was ascribed to competition of compression by clay phase and restoring of the niobate phase

Synaptic activity prompts γ-secretase–mediated cleavage of EphA4 and dendritic spine formation

Alzheimer's disease is an age-dependent neurodegenerative disorder that is characterized by a progressive decline in cognitive function. γ-secretase dysfunction is evident in many cases of early onset familial Alzheimer's disease. However, the mechanism by which γ-secretase dysfunction results in memory loss and neurodegeneration is not fully understood. Here, we demonstrate that γ-secretase is localized at synapses and regulates spine formation. We identify EphA4, one of the Ephrin receptor family members, as a substrate of γ-secretase, and find that EphA4 processing is enhanced by synaptic activity. Moreover, overexpression of EphA4 intracellular domain increases the number of dendritic spines by activating the Rac signaling pathway. These findings reveal a function for EphA4-mediated intracellular signaling in the morphogenesis of dendritic spines and suggest that the processing of EphA4 by γ-secretase affects the pathogenesis of Alzheimer's disease

Induction of endosomal/lysosomal pathways in differentiating osteoblasts as revealed by combined proteomic and transcriptomic analyses

AbstractWe have analyzed proteome changes associated with bone-forming osteoblast differentiation by quantitative differential proteomic and transcriptomic analyses using in vitro differentiation model. Sixty nine proteins were found up-regulated (>2-fold) and 18 were down-regulated (<0.5-fold) at protein level. The mRNA levels of these proteins were then analyzed by quantitative real-time PCR combined with clustering analysis. The most prominent cluster with increased protein and mRNA levels contains endosomal and lysosomal proteins, demonstrating the drastic induction of degradative endosomal/lysosomal pathways in osteoblasts. Osteoblasts, therefore, are involved not only in the synthesis but also in the turnover of the extracellular matrix proteins such as collagens

Mesoscopic architectures made of electrically charged binary colloidal nanosheets in aqueous system

Inorganic layered materials can be converted to colloidal liquid crystals through exfoliation into inorganic nanosheets, and binary nanosheet colloids exhibit rich phase behavior characterized by multiphase coexistence. In particular, niobate-clay binary nanosheet colloids are characterized by phase separation at a mesoscopic (∼several tens of micrometers) scale whereas they are apparently homogeneous at a macroscopic scale. Although the mesoscopic structure of the niobate-clay binary colloid is advantageous to realize unusual photochemical functions, the structure itself has not been clearly demonstrated in real space. The present study investigated the structure of niobate-clay binary nanosheet colloids in detail. Four clay nanosheets (hectorite, saponite, fluorohectorite, and tetrasilisic mica) with different lateral sizes were compared. Small-angle X-ray scattering (SAXS) indicated lamellar ordering of niobate nanosheets in the binary colloid. The basal spacing of the lamellar phase was reduced by increasing the concentration of clay nanosheets, indicating the compression of the liquid crystalline niobate phase by the isotropic clay phase. Scattering and fluorescence microscope observations using confocal laser scanning microscopy (CLSM) demonstrated the phase separation of niobate and clay nanosheets in real space. Niobate nanosheets assembled into domains of several tens of micrometers whereas clay nanosheets were located in voids between the niobate domains. The results clearly confirmed the spatial separation of two nanosheets and the phase separation at a mesoscopic scale. Distribution of clay nanosheets is dependent on the employed clay nanosheets; the nanosheets with large lateral length are more localized or assembled. This is in harmony with larger basal spacings of niobate lamellar phase for large clay particles. Although three-dimensional compression of the niobate phase by the coexisting clay phase was observed at low clay concentrations, the basal spacing of niobate phase was almost constant irrespective of niobate concentrations at high clay concentrations, which was ascribed to competition of compression by clay phase and restoring of the niobate phase

Comparative analysis of DNA aberrated by irradiation using PCR and simulation methods

International symposium on innovative technology for radiation risk study 200