• Korean Journal of Materials Research
• /
• v.26 no.12
• /
• pp.751-756
• /
• 2016

Graphite was diffusion-bonded by hot-pressing to W-25Re alloy using a Ti interlayer. For the joining, a uniaxial pressure of 25 MPa was applied at $1600^{\circ}C$ for 2 hrs in an argon atmosphere with a heating rate of $10^{\circ}C\;min^{-1}$. The interfacial microstructure and elemental distribution of the W-25Re/Ti/Graphite joints were analyzed by scanning electron microscopy (SEM). Hot-pressed joints appeared to form a stable interlayer without any micro-cracking, pores, or defects. To investigate the high-temperature stability of the W-25Re/Ti/Graphite joint, an oxy-acetylene torch test was conducted for 30 seconds with oxygen and acetylene at a 1.3:1 ratio. Cross-sectional analysis of the joint was performed to compare the thickness of the oxide layer and its chemical composition. The thickness of W-25Re changed from 250 to $20{\mu}m$. In the elemental analysis, a high fraction of rhenium was detected at the surface oxidation layer of W-25Re, while the W-25Re matrix was found to maintain the initial weight ratio. Tungsten was first reacted with oxygen at a torch temperature over $2500^{\circ}C$ to form a tungsten oxide layer on the surface of W-25Re. Then, the remaining rhenium was subsequently reacted with oxygen to form rhenium oxide. The interfacial microstructure of the Ti-containing interlayer was stable after the torch test at a temperature over $2500^{\circ}C$.

• Korean Journal of Food Science and Technology
• /
• v.30 no.2
• /
• pp.407-412
• /
• 1998

The proteins extracted from beef, pork and chicken meats were irradiated with up to 100 kGy at room temperature. The extracted proteins were evaluated on their in vitro digestibility by incubating successively with pepsin and pancreatin conjugate. Amino acid compositions and SDS-PAGE pattern were also analyzedin for these proteins. Gamma irradiation within the applied dose range (up to 100 kGy) produced negligible in in vitro digestibility and amino acid composition. Analysis of gamma-irradiated proteins by SDS-PAGE revealed radiolysis of ovalbumin to proteins or peptides with lower molecular weight. On the other hand, the proteins directly extracted from irradiated meats containing moisture were also evaluated for their in vitro digestibility, amino acid compositions and SDS-PAGE pattern. However, the results obtained from this experiment were similar to those of irradiated proteins after extraction from the meats.

• Proceedings of the Korean Society of Applied Pharmacology
• /
• 1997.04a
• /
• pp.86-86
• /
• 1997

Human annexin I is a member of annexin family of calcium dependent phospholipid binding proteins, which have been implicated in various physiological roles including phospholipase A$_2$ (PLA$_2$) inhibition, membrane fusion and calcium channel activity. In this work, the structure of N-terminally truncated human annexin I (Δ-annexin I) and its interactions with Ca$\^$2+/, ATP and cAMP were studied at atomic level by using $^1$H, $\^$15/N, $\^$l3/C NMR (nuclear magnetic resonance) spectroscopy. The effect of Ca$\^$2+/ binding on the structure of Δ-annexin I was investigated, and compared with that of Mg$\^$2+/ binding. The addition of Ca$\^$2+/ to Δ-annexin I caused some changes in the high field and low field regions of $^1$H NMR spectra. Whereas, upon addition of Mg$\^$2+/ to Δ-annexin I, almost no change could be observed. Also we found that the binding ratio of ATP to Δ-annexin I is 1. Because Δ-annexin I is a large protein with 35 kDa molecular weight, site-specific (carbonyl-$\^$l3/C, amide-$\^$15/N) labeling technique was used to determine the interaction sites of Δ-annexin I with Ca$\^$2+/ and ATP. Assignments of all the histidinyl carbonyl carbon resonances have been completed by using Δ-annexin I along with its specific 1,2-subdomain. The carbonyl carbon resonances originating from His52 and His246 of Δ-annexin I were significantly affected by Ca$\^$2+/ binding, and some Tyr and Phe resonances were also affected. The carbonyl carbon resonances originating from His52 is significantly affected by ATP binding, therefore His52 seems to be involved in the ATP binding site of Δ-annexin I.

• Journal of the Korean Magnetic Resonance Society
• /
• v.2 no.2
• /
• pp.141-151
• /
• 1998

Human annexin I is a member of annexin family of calcium dependent phospholipid binding proteins, which have been implicated in various physiological roles including phospholipase A2(PLA2) inhibition, membrane fusion and calcium channel activity. In this work, the structure of N-terminally truncated human annexin I ({{{{ DELTA }}-annexin I) and its interactions with Ca2+, ATP and cAMP were studied at atomic level by using nuclear magnetic resonance (NMR) spectroscopy. The effect of Ca2+ binding on the structure of {{{{ DELTA }}-annexin I was investigated. The addition of Ca2+ to {{{{ DELTA }}-annexin I caused some changes in 13C NMR spectra. Carbonyl carbon resonances of some histidines were significantly broadened by Ca2+ binding. However, in the case of methionine, phenylalanine, and tyrosin, small changes could be observed. We found that ATP and cAMP bind {{{{ DELTA }}-annexin I, and the binding ratio of ATP to {{{{ DELTA }}-annexin I is 1. These results are well consistent with the report that cAMP and ATP interact with annexin I, and affect the calcium channels formed by annexin I. Because {{{{ DELTA }}-annexin I is a large protein with 35 kDa molecular weight, site-specific (carbonyl-13C) labeling technique was used to study the interaction sites of {{{{ DELTA }}-annexin I with Ca2+. NMR study was focused on the carbonyl carbon resonances of tyrosine, phenylalanine, methionine and histidine residues of {{{{ DELTA }}-annexin I because the number of these amino acids is small in the amino acid sequence of {{{{ DELTA }}-annexin I.

• Macromolecular Research
• /
• v.13 no.2
• /
• pp.135-140
• /
• 2005

Poly(vinyl alcohol) (PVA) membranes crosslinked with poly(acrylic acid-co-maleic acid) (PAM) were prepared to investigate the effect of aging on their morphology by swelling them for up to 7 days. PAM was used both as a crosslinking agent and as a donor of the hydrophilic-COOH group. A $30 wt\%$ weight loss of the dry membrane was observed in the swelling test after 6 days. The surface of the membrane was dramatically changed after the swelling test. The surface roughness of the PVA/PAM membrane was increased, as determined by atomic force microscopy (AFM). The swelling loosened the polymer structure, due to the release of the unreacted polymer and the decomposition of the ester bond, thereby resulting in an increase in the free volume capable of containing water molecules. The water molecules present in the form of free water were determined by differential scanning calorimetry (DSC). The fraction of free water increased with increasing swelling time. The swelling of the membrane may provide space for the transport of protons and increase the mobility of the protonic charge carriers. The proton conductivity of the membranes measured at T= 30 and $50^{\circ}C$ was in the range of $10^{-3} to 10^{-2} S/cm$, and slightly increased with increasing swelling time and temperature.

• Polymer(Korea)
• /
• v.37 no.3
• /
• pp.332-341
• /
• 2013

H-shaped amphiphilic pentablock copolymers $(PSt)_2-b-PCL-b-PEO-b-PCL-b-(PSt)_2$ was synthesized via chemoenzymatic method by combining enzyme-catalyzed ring-opening polymerization (eROP) of ${\varepsilon}$-caprolactone (${\varepsilon}$-CL) and atom transfer radical polymerization (ATRP) of styrene. By this process, we obtained copolymers with controlled molecular weight and low polydispersity. The structure and composition of the obtained copolymers were characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC) and infrared spectroscopy analysis (IR). The crystallization behavior of the copolymers was analyzed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The crystallization behavior of the H-shaped block copolymers demonstrated a PCL dominate crystallization. The self-assembly behavior of the copolymers was investigated in aqueous media. The hydrodynamic diameters of the copolymer micelles in aqueous solution were measured by dynamic light scattering (DLS). The morphology of the copolymer micelles was observed by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The hydrodynamic diameters of spherical micelles declined gradually with the increase of the hydrophobic chain lengths of the copolymers. The critical micelle concentration (CMC) values were determined from fluorescence emission, and it was found that the CMCs decreased with an increase of PSt hydrophobic block lengths.

• Journal of Nutrition and Health
• /
• v.30 no.4
• /
• pp.406-414
• /
• 1997

It has been known that dietary phytate decreases the absorption of body zinc pool which is composed of the dietary and endogenous zinc in the body. The purpose of this study was to examine the effect of phytate on the absorption of total bodyzinc in Zn-depleted rats. Rats were Zn-depleted with either low(0.8%) or high(1.6%) Ca diet containing sodium phytate for 4 weeks. After zinc depletion, rats were assigned into phytate or non-phytate dietary groups within each low-or high-Ca dietary group. ant feces were collected for 2 weeks of the initial collection and 1 week after dietary crossover, during which the phytate and the non-phytate diet was switched over within the same Ca group. The content of Zn and Ca measured by atomic absorption spectrophotometer and phytate content was analyzed. food intake was higher in the high Ca group than in the low Ca group(p <0.0001), and was also higher in the non-phytate group than in the phytate group(p <0.0001). Food intake and phytate level affected body weight gain in rats(p <0.0001). Zinc excretion in the total feces was higher in the phytate group than in the non-phytate group at both low and high Ca level(p <0.0001), except during the crossover collection period in high Ca group. Calcium, however, didn't show any synergistic effect on phytate effect(p <0.05). This study showed that phytate decreased the absorption of total body zinc at both low and high Ca levels in Zn-depleted rats. A large portion of total body zinc originated from the endogenous zinc pool in these rats. The results of the present study showed the same effect of phytate on the endogenous zinc in Zn-depleted rats as in a previous study, confirming that phytate adversely affects zinc bioavailability, especially under marginal and poor zinc nutrition.

• Journal of Plant Biotechnology
• /
• v.30 no.2
• /
• pp.201-206
• /
• 2003

Differential responses of red pepper plant and cultured cells to enhanced ${\gamma}$-ray($^{60}$ Co) and ultraviolet(UV) stress were investigated. In seed treatment, 1 Gy of ${\gamma}$-ray increased seedling dry weight up to 19.1%, but 50 Gy treatment markedly ingibited seed germination and subsequent growth of seedling. UV treatment to seed did not change the germination ability of seeds and the growth of seedlings regardless of duration of UV treatment until 24 hrs. In case of UV treatment to seedlings, plant injury was seriously progressed even after the seedlings were returned to no UV condition, and eventually all the leaves showed chlorosis by the stress. However, progress of plant injury by ${\gamma}$-ray stress slower than that caused by UV stress, and even at the high dose of ${\gamma}$-ray 50 Gy, did not caused the cholrosis of stressed plant leaf. Amount of electrolytes leakage from plant leaf by UV treatment for 24hrs was increased up to 28.8 folds in comparison with untreated control, whereas that of 50 Gy of ${\gamma}$-ray was increased only 1.2 folds. UV stress induced the production of capsidiol, antimicrobial phytoalexin, by activation of gene expression involved in capsidiol biosynthesis, such as sesquiterpene cyclase and cyclase and cytochrome P450 hydroxylase in the leaf and cultured cell, but ${\gamma}$-ray stress induced neither the production of capsidiol nor expression of the genes.

• Asian-Australasian Journal of Animal Sciences
• /
• v.19 no.7
• /
• pp.1033-1039
• /
• 2006

The metabolic response of Labeo rohita to thermal acclimation was assessed. Advanced fingerlings of L. rohita (average weight $31{\pm}1.4g$) were acclimated to 31, 33 and $36^{\circ}C$ compared with ambient temperatures ($26^{\circ}C$) for 30 days and different enzymes associated with stress response were estimated. Glycolytic enzyme-Lactate dehydrogenase, (LDH, E.C.1.1.1.27), TCA cycle enzyme-Malate dehydrogenase (MDH, E.C.1.1.1.37), Protein metabolizing enzymes-Aspartate amino transferase (AST, E.C.2.6.1.1) and Alanine amino transferase (ALT, E.C.2.6.1.2) of liver, gill and muscle, Gluconeogenic enzymes-Fructose 1,6 Bi phosphatase (FBPase, E.C. 3.1.3.11) and Glucose 6 phosphatase (G6Pase, E.C. 3.1.3.9) of liver and kidney were significantly (p<0.05) different with increasing acclimation temperatures. Heat Shock Protein-70 (HSP-70) was expressed in increasing intensity at 31, 33 and $36^{\circ}C$ but was not expressed at $26^{\circ}C$. Results suggest that higher acclimation temperatures enhance metabolism and L. rohita maintains homeostasis between $26-36^{\circ}C$ via an acclimation episode. Such adaptation appears to be facilitated by resorting to gluconeogenic and glycogenolytic pathways for energy mobilization and induction of HSPs.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.50 no.6
• /
• pp.675-683
• /
• 2017

Total mercury (T-Hg) and methyl mercury (MeHg) were determined in marine fisheries (41 species, n=87) commonly consumed in Korea, using a gold amalgamation method and gas chromatography-cold vapor atomic fluorescent spectroscopy, respectively. Concentrations of T-Hg and MeHg in all samples (31 fish, 4 crustaceans, 4 cephalopods, and 2 gastropod species) were in the range of 0.016-0.495 (mean, 0.093) mg/kg-wet and not detected-0.338 (mean, 0.067) mg/kg-wet, respectively. The concentrations of MeHg in marine fisheries were significantly correlated with T-Hg concentrations (P<0.001). The highest mean concentrations of T-Hg and MeHg were found in fish species, followed by crustaceans. The contribution of MeHg to T-Hg was in the range of 64-95% (mean, 83%) in cephalopods, 28-98% (mean, 69%) in fish, and 26-88% (mean, 57%) in crustaceans. The weekly intakes of T-Hg and MeHg by fisheries consumption for the Korean general population were estimated to be 0.463 and $0.338{\mu}g/kg$ body weight/week, respectively. The concentrations and intakes of T-Hg and MeHg were less than the allowable residue levels and in the range of 12 to 17% of the provisional tolerable weekly intake (PTWI) applied in Korea.