Chonbuk National University

About: Chonbuk National University is a education organization based out in Jeonju, South Korea. It is known for research contribution in the topics: Apoptosis & Nanofiber. The organization has 14820 authors who have published 28884 publications receiving 554131 citations.

Facile Approach to Synthesize Au@ZnO Core-Shell Nanoparticles and Their Application for Highly Sensitive and Selective Gas Sensors.

Abstract: We successfully prepared Au@ZnO core-shell nanoparticles (CSNPs) by a facile low-temperature solution route and studied its gas-sensing properties. The obtained Au@ZnO CSNPs were carefully characterized by X-ray diffraction, transmission electron microscopy (TEM), high-resolution TEM, and UV-visible spectroscopy. Mostly spherical-shaped Au@ZnO CSNPs were formed by 10-15 nm Au NPs in the center and by 40-45 nm smooth ZnO shell outside. After the heat-treatment process at 500 °C, the crystallinity of ZnO shell was increased without any significant change in morphology of Au@ZnO CSNPs. The gas-sensing test of Au@ZnO CSNPs was examined at 300 °C for various gases including H2 and compared with pure ZnO NPs. The sensor Au@ZnO CSNPs showed the high sensitivity and selectivity to H2 at 300 °C. The response values of Au@ZnO CSNPs and pure ZnO NPs sensors to 100 ppm of H2 at 300 °C were 103.9 and 12.7, respectively. The improved response of Au@ZnO CSNPs was related to the electronic sensitization of Au NPs due to Schottky barrier formation. The high selectivity of Au@ZnO CSNPs sensor toward H2 gas might be due to the chemical as well as catalytic effect of Au NPs.

N-hexanoyl chitosan stabilized magnetic nanoparticles: Implication for cellular labeling and magnetic resonance imaging

Abstract: This project involved the synthesis of N-hexanoyl chitosan or simply modified chitosan (MC) stabilized iron oxide nanoparticles (MC-IOPs) and the biological evaluation of MC-IOPs. IOPs containing MC were prepared using conventional methods, and the extent of cell uptake was evaluated using mouse macrophages cell line (RAW cells). MC-IOPs were found to rapidly associate with the RAW cells, and saturation was typically reached within the 24 h of incubation at 37°C. Nearly 8.53 ± 0.31 pg iron/cell were bound or internalized at saturation. From these results, we conclude that MC-IOPs effectively deliver into RAW cells in vitro and we also hope MC-IOPs can be used for MRI enhancing agents in biomedical fields.

Crystal structure of pre-activated arrestin p44

Abstract: The crystal structure of arrestin-1 is reported, in which the activation step is mimicked by C-tail truncation; the structure of this pre-activated arrestin is markedly different from the basal state and gives an insight into the activation mechanism. Arrestin proteins are negative regulators of G-protein-coupled receptor (GPCR) function and also act as G-protein-independent signalling proteins. Before forming a high-affinity complex, arrestins must be activated, and two papers in this issue of Nature focus on the interaction between GCPRs and activated arrestin at the atomic scale. Yong Ju Kim et al. mimicked the initial activation step by truncating the carboxy terminus of arrestin to produce the naturally occurring splice variant called p44 and determined its crystal structure. This structure provides insight into the role of naturally occurring truncated arrestins in the visual system. Arun Shukla et al. present the structure of non-visual β-arrestin-1 in complex with an antibody fragment (Fab30) and a fully phosphorylated 29-amino-acid C-terminal peptide derived from a GPCR, the arginine vasopressin type 2 receptor. Taken together, these two studies reveal striking conformational changes associated with arrestin activation. Arrestins interact with G-protein-coupled receptors (GPCRs) to block interaction with G proteins1,2 and initiate G-protein-independent signalling3. Arrestins have a bi-lobed structure that is stabilized by a long carboxy-terminal tail (C-tail), and displacement of the C-tail by receptor-attached phosphates activates arrestins for binding active GPCRs4. Structures of the inactive state of arrestin are available5,6, but it is not known how C-tail displacement activates arrestin for receptor coupling. Here we present a 3.0 A crystal structure of the bovine arrestin-1 splice variant p44, in which the activation step is mimicked by C-tail truncation. The structure of this pre-activated arrestin is profoundly different from the basal state and gives insight into the activation mechanism. p44 displays breakage of the central polar core and other interlobe hydrogen-bond networks, leading to a ∼21° rotation of the two lobes as compared to basal arrestin-1. Rearrangements in key receptor-binding loops in the central crest region include the finger loop7,8,9, loop 139 (refs 8, 10, 11) and the sequence Asp 296–Asn 305 (or gate loop), here identified as controlling the polar core. We verified the role of these conformational alterations in arrestin activation and receptor binding by site-directed fluorescence spectroscopy. The data indicate a mechanism for arrestin activation in which C-tail displacement releases critical central-crest loops from restricted to extended receptor-interacting conformations. In parallel, increased flexibility between the two lobes facilitates a proper fitting of arrestin to the active receptor surface. Our results provide a snapshot of an arrestin ready to bind the active receptor, and give an insight into the role of naturally occurring truncated arrestins in the visual system.