Crystal Structure of H227A Mutant of Arginine Kinase in Daphnia magna Suggests the Importance of Its Stability

Arginine kinase (AK) plays a crucial role in the survival of Daphnia magna, a water flea and a common planktonic invertebrate sensitive to water pollution, owing to the production of bioenergy. AK from D. magna (DmAK) has four highly conserved histidine residues, namely, H90, H227, H284, and H315 in the amino acid sequence. In contrast to DmAK WT (wild type), the enzyme activity of the H227A mutant decreases by 18%. To identify the structure-function relationship of this H227A mutant enzyme, the crystal 3D X-ray structure has been determined and an unfolding assay using anilino-1-naphthalenesulfonic acid (ANS) fluorescence has been undertaken. The results revealed that when compared to the DmAK WT, the hydrogen bonding between H227 and A135 was broken in the H227A crystal structure. This suggests that H227 residue, closed to the arginine binding site, plays an important role in maintaining the structural stability and maximizing the enzyme activity through hydrogen bonding with the backbone oxygen of A135.     

Degradable alkoxide-crosslinked hydrogels

Degradable acrylate hydrogels have been synthesized by using hydrolytically unstable crosslinkers which break down with prolonged exposure to water. Chelated zirconium alkoxide compounds were used to crosslink poly(N-isopropylacrylamide) gels which degraded within days to weeks as the crosslinkers hydrolyze. Several types of crosslinkers were synthesized by varying the zirconium alkoxide and the number of crosslinking vinyl groups attached to the alkoxide cluster. UV spectroscopy and rheological measurements were used to follow the degradation of these gels. © 1996 John Wiley & Sons, Inc.     

Scribing and cutting a blue LED wafer using a Q-switched. Nd:YAG laser

Chemical doping of single-wall carbon nanohorns (SWNHs) with K and Br was examined by vapor-phase reaction and studied by Raman scattering. Electro-chemical Li-ion doping using an electrolyte of LiAsF₆ in a mixture (1:1 by volume) of ethylene carbonate and diethyl carbonate was also carried out. All these experiments indicate that an anomalously small charge transfer occurs in saturation-doped SWNHs using these reagents, in sharp contrast to the behavior observed for single-wall carbon nanotube bundles and graphite. This rather remarkable result is not understood at present. Received: 13 July 2000 / Accepted: 14 July 2000 / Published online: 5 October 2000     

Synthesis and characterization of new soluble cardo polyamide‐imides containing cyclododecyl groups

A new cardo diimide‐dicarboxylic acid, 1,1‐bis[4‐(4‐trimellitimidophenoxy)phenyl]cyclododecane (BTPCD), containing a pendant cyclododecyl group was synthesized by the condensation reaction of 1,1‐bis[4‐(4‐aminophenoxy)phenyl]cyclododecane with trimellitic anhydride in glacial acetic acid. A series of new cardo polyamide‐imides were prepared by the direct polycondensation of BTPCD and various aromatic diamines in N‐methyl‐2‐pyrrolidinone (NMP) with triphenyl phosphite and pyridine as condensing agents. The polymers were produced in high yields and with moderate‐to‐high inherent viscosities of 0.72–1.02 dL g⁻¹. The number‐average and weight‐average molecular weights of the polymers ranged from 21,000 to 49,000 and 58,000 to 92,000, respectively. All the polymers exhibited excellent solubility and could be readily dissolved in various solvents such as NMP, N,N‐dimethylacetamide, N,N‐dimethylformamide, dimethyl sulfoxide, pyridine, cyclohexanone, and tetrahydrofuran. These polyamide‐imides had glass‐transition temperatures between 241 and 262 °C and 10% weight‐loss temperatures ranging from 469 to 511 °C in nitrogen. The polymer films had a tensile strength range of 79–108 MPa, an elongation at break range of 7–14%, and a tensile modulus range of 2.0–2.4 GPa. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2787–2793, 2000     

Leukotriene B4 receptor-2 contributes to KRAS-driven lung tumor formation by promoting interleukin-6-mediated inflammation

Although lung cancer is the leading cause of cancer-related deaths worldwide and KRAS is the most frequently mutated oncogene in lung cancer cases, the mechanism by which KRAS mutation drives lung cancer has not been fully elucidated. Here, we report that the expression levels of leukotriene B₄ receptor-2 (BLT2) and its ligand-producing enzymes (5-LOX, 12-LOX) were highly increased by mutant KRAS and that BLT2 or 5-/12-LOX blockade attenuated KRAS-driven lung cell proliferation and production of interleukin-6 (IL-6), a principal proinflammatory mediator of lung cancer development. Next, we explored the roles of BLT2 and 5-/12-LOX in transgenic mice with lung-specific expression of mutant KRAS (Kras^G12D) and observed that BLT2 or 5-/12-LOX inhibition decreased IL-6 production and tumor formation. To further determine whether BLT2 is involved in KRAS-driven lung tumor formation, we established a Kras^G12D/BLT2-KO double-mutant mouse model. In the double-mutant mice, we observed significantly suppressed IL-6 production and lung tumor formation. Additionally, we observed high BLT2 expression in tissue samples from patients with KrasG12D-expressing lung adenocarcinoma, supporting the contributory role of BLT2 in KRAS-driven human lung cancer. Collectively, our results suggest that BLT2 is a potential contributor to KRAS-driven lung cancer and identify an attractive therapeutic target for KRAS-driven lung cancer.Subject terms: Non-small-cell lung cancer, Lipid signalling     

Dynamic output-feedback control for singular Markovian jump systems with partly unknown transition rates

Nonlinear Dynamics - This paper considers the problem of dynamic output-feedback stabilization for singular Markovian jump systems with partly unknown transition rates. First of all, for the...     

Polyopes affinis Suppressed IFN-γ- and TNF-α-Induced Inflammation in Human Keratinocytes via Down-Regulation of the NF-κB and STAT1 Pathways

Polyopes affinis is a red algal species commonly found on the South coast and near Jeju Island, Korea. This study aimed to determine whether P. affinis extracts can inhibit the pathogenesis of T-helper-2 (Th2)-mediated inflammation in a human keratinocyte cell line of atopic dermatitis (AD). Cells were incubated with 10 ng/mL of interferon gamma (IFN-γ) and 10 ng/mL of tumor necrosis factor-alpha (TNF-α) at various concentrations of PAB (10, 30, and 60 µg/mL) and PAA (100, 500, and 1000 µg/mL) extracts. A gene-ontology (GO)-enrichment analysis revealed that PAB significantly enriched the genes associated with biological processes such as cell adhesion, immune response, inflammation, and chemokine-mediated pathways. PAB suppressed the expression of the secretory proteins and mRNAs that are associated with the thymus and the production of activation-regulated chemokines (TARC/CCL17) and macrophage-derived chemokines (MDC/CCL22). The effect of the extract on mitogen-activated protein kinases (MAPKs) was related to its inhibition of TARC/CCL17 and MDC/CCL22 production by blocking NF-κB and STAT1 activation. These results suggest that seaweed extract may improve AD by regulating pro-inflammatory chemokines. In conclusion, we first confirmed the existence of phloroglucinol, a polyphenol formed from a precursor called phlorotannin, which is present in PAB, and this result proved the possibility of PAB being used as a treatment for AD.     

Development of advanced radiation sources at KAERI

The KAERI Center for Quantum Beam-Based Radiation Research, was founded in 2011. The center pursues the development of advanced radiation sources and their applications in biology, material science, and nuclear physics. There are two main research topics in the development of advanced radiation sources: a system with high-power T-ray pump and an ultrashort X-ray probe system and a compact electron storage ring based on a laser-accelerated electron beam.