Dong-A University

βPix is a guanine nucleotide exchange factor for the Rac1 and Cdc42 small GTPases, which play important roles in dendritic spine morphogenesis by modulating actin cytoskeleton organization. The formation and plasticity of the dendritic spines are essential for normal brain function. Among the alternatively spliced βPix isoforms, βPix-b and βPix-d are expressed specifically in neurons. Our previous studies using cultured hippocampal neurons identified the roles of βPix-b and βPix-d in spine formation and neurite development, respectively. Here, we analyzed the in vivo role of the neuronal βPix isoforms in brain development and function by using βPix neuronal isoform knockout (βPix-NIKO) mice, in which the expression of the βPix-b and βPix-d isoforms is blocked, while the expression of the ubiquitous βPix-a isoform is maintained. Loss of the neuronal βPix isoforms leads to reduced activity of Rac1 and Cdc42, decreased dendritic complexity and spine density, and increased GluN2B and Ca²⁺/calmodulin-dependent protein kinase IIα expression in the hippocampus. The defects in neurite development, dendritic spine maturation, and synaptic density in cultured βPix-NIKO hippocampal neurons were rescued by the expression of βPix-b or βPix-d. In behavioral studies, βPix-NIKO mice exhibited robust deficits in novel object recognition and decreased anxiety levels. Our findings suggest that neuronal morphogenetic signaling by the neuronal βPix isoforms contributes to normal behaviors.

Accurate evaluation and quantification of nanomaterials are crucial in hazard and risk assessment.In this study, we tested simplified proteinase K (PK)-mediated digestion methods via a UV-Vis spectrophotometer for sensitive and accurate quantification of carbon black (CB) on the lung burden.We evaluated enzyme activity and digestion efficiency under different buffer conditions for lung burden digestion, focusing on the effects of varying surfactant and calcium chloride concentrationsThe most effective conditions for PK characteristics with the model peptide substrate involved the use of Triton X-100, SDS, and CaCl₂.However, better results were observed for lung burden digestion when only SDS-containing media were used.Based on the influence of the interactions between lung burden tissue and PK, we improved the digestion efficiency and catalytic activity of PK.This led to 98 % recovery rates when 10 μg of PK was added to a buffer containing only the SDS surfactant within a 24-h reaction time.These results demonstrate that the reaction media significantly affects the enzymic reactions with different substrates.Proper conditions can be challenging to predict or engineer by solely studying the PK enzyme itself.Furthermore, this study provides potential fundamental features for future biomol. extraction designs and clearance kinetics, utilizing protein digestive enzymic strategies.

Small-pore zeolites are of technol. relevance to selectively adsorb CO₂ from fossil fuel flue gas, as well as from natural gas.Very recently, we have shown that CO₂ adsorption on the cesium-exchanged form of the channel-based small-pore zeolite phillipsite with a framework Si/Al ratio of 2.5 (Cs-PHI-2.5) operates by a new mechanism that includes Cs⁺ ion crowding and subsequent dispersal at a critical CO₂ pressure.Here we compare the CO₂ adsorption behavior at 25 - 45°C up to 1.0 bar of four Cs-PHI zeolites with different Si/Al ratios (2.1-3.6) and their dehydrated and CO₂-loaded structures to elucidate the effect of framework Al (or extra-framework Cs⁺ ion) content on this unprecedented adsorption mechanism.Structural anal. shows that when the number of Cs⁺ ions per PHI unit cell with 16 tetrahedral atoms lies between 4.9 (Si/Al = 2.1) and 4.5 (Si/Al = 2.5), the CO₂ adsorption properties of the resulting zeolites can be described by the cation crowding mechanism.However, when the number of Cs⁺ ions is 4.0 or smaller (Si/Al > 3.1), CO₂ adsorption is already dominated by the cooperative cation gating-framework breathing mechanism.We provide evidence for the existence of a threshold number of Cs+ ions per t-phi cage in Cs-PHI to manifest the cation crowding mechanism.