• Journal of the Korea Concrete Institute
• /
• v.17 no.5 s.89
• /
• pp.821-828
• /
• 2005

To investigate the role of RH and temperature on the transport of chloride in the concrete, two groups of specimens were configured. For both groups, mix design was based on w/c=0.45, $400kg/m^3$ cement, $794kg/m^3$ fine aggregate and $858kg/m^3$ coarse aggregate. After specimen fabrication these were exposed to four different RH (35, 55, 75 and $95\%$ RH) and temperature (0, 20, 30 and $40^{\circ}C$) conditions. After 3 and 6 months $15\%$ NaCl exposure 5mm cores were taken. These cores were sliced and individual cores were ground to powder. In addition, to evaluate the effect of temperature on the chloride binding some powder samples were leached in the each of four temperature chambers. Chloride titration fur these was performed using FDOT acid titration method. Based upon the resultant data conclusions were reached regarding that 1) effective diffusion coefficient, $D_e$, increased with increasing exposure RH, suggesting that the size and number of water paths increased with elevated moisture content in the specimens, 2) $D_e$ increased with increasing temperature in the range of 0 to $40^{\circ}C$ possibly by elevated thermal activation of chloride ions and reduced chloride binding at higher temperature, 3) water soluble chloride concentration, $[Cl^-]_s$, increased with increasing temperature, and 4) chloride concentration profile for initially dry concrete specimens was higher than for the initially wet ones indicating pronounced capillary suction (sorption) occurred for the dry concrete specimens.

• Journal of the Korean Magnetic Resonance Society
• /
• v.6 no.1
• /
• pp.54-68
• /
• 2002

PEBP2/CBF (Polyomavirus Enhancer-core Binding Protein 2/Core Binding Factor), represents a new family of heterodimeric transcription factor. Those members play important roles in hematopoiesis and osteogenesis in mouse and human. PEBP2/CBF is a sequence-specific DNA binding protein. Each member of the PEBP2/CBF family of transcription factors is composed of two subunits, ${\alpha}$ and ${\beta}$. The evolutionarily conserved 128 amino acid region in ${\alpha}$ subunit has been called the Runt domain, which harbors two different activities, the ability to bind DNA and interact with the ${\beta}$ subunit. Recently, cDNA clones encoding the C. elegans Runt domain were isolated by screening a cDNA library. This gene was referred to run (Runt homologous gene). In this study, the basic experiments for the structural characterization of RUN protein were performed using spectroscopic methods. We have identified the structural properties of RUN using bioinformatics, CD and NMR. The limit temperature of the structural stability was up to 60$^{\circ}C$ with irreversible thermal process, and the structure of RUN seems to adopt ${\alpha}$ helices and one or more ${\beta}$ sheet or turn. The degree of NMR peak dispersion and intensity was increased by addition of glycine. Therefore, glycine could be used to alleviate the aggregation property of RUN in NMR experiment.

• KSBB Journal
• /
• v.29 no.4
• /
• pp.303-306
• /
• 2014

Antifreeze proteins (AFP) inhibit ice growth to permit the survival of polar organisms in the cold environments. The recombinant AFP from an Antarctic bacterium, Flavobacterium frigoris PS1, FfIBP (Flavobacterium frigoris ice-binding protein), was produced using Pichia pastoris expression system. The optimum fermentation temperature ($30^{\circ}C$) and pH (5) for FfIBP production were determined using a fed-batch culture system. The maximal cell density and purified FfIBP were 112 g/L and 70 mg/L, respectively. The thermal hysteresis (TH) activity (0.85) of FfIBP obtained using a glycerol-methanol fed-batch culture system was 2-fold higher than that of the LeIBP (Leucosporidium ice-binding protein). This work allows for large-scale production of FfIBP, which could be extended to further application studies using recombinant AFPs.

• Journal of Life Science
• /
• v.14 no.2
• /
• pp.309-314
• /
• 2004

Cyclic AMP receptor protein (CRP) is involved in the transcriptional regulation of more than 100 genes in E. coli. CRP dimer is converted into active form via the sequential conformation change of cAMP binding pocket, hinge region and HTH DNA binding motif by binding of cAMP. The temperature gradient gel electrophoresis (TGGE) was applied to CRP protein to know whether it was an efficient technique to study the conformational transitions and the thermal stability. TGGE showed the unfolding process of wild-type and S83G CRP proteins with the temperature gradient set from 29 to 71$^{\circ}C$ on nondenaturing polyacrylamide gel. Melting temperature (Tm) was 57$\pm$1 and 55$\pm$1$^{\circ}C$ for wild-type and S83G CRP, respectively in acidic buffer[89.8 mM Glycine and 24 mM Boric acid (pH 5.8)].

• Molecules and Cells
• /
• v.27 no.2
• /
• pp.149-157
• /
• 2009

In both gram-positive and several gram-negative bacteria, the transcription of dnaK and groE operons is negatively regulated by HrcA; however, the mechanism modulating HrcA protein activity upon thermal stress remains elusive. Here, we demonstrate that HrcA is modulated via reduction and oligomerization in vitro. Native-PAGE analysis was used to reveal the oligomeric structure of HrcA. The oligomeric HrcA structure became monomeric following treatment with the reducing agent dithothreitol, and this process was reversed by treatment with hydrogen peroxide. Moreover, the mutant HrcA C118S exhibited reduced binding to CIRCE elements and became less oligomerized, suggesting that cysteine residue 118 is important for CIRCE element binding as well as oligomerization. Conversely, HrcA mutant C280S exhibited increased oligomerization. An HrcA double mutant (C118S, C280S) was monomeric and exhibited a level of oligomerization and CIRCE binding similar to wild type HrcA, suggesting that cysteine residues 118 and 280 may function as checks to one another during oligomer formation. Biochemical fractionation of E. coli cells overexpressing HrcA revealed the presence of HrcA in the membrane fraction. Together, these results suggest that the two HrcA cysteine residues at positions 118 and 280 function as reduction sensors in the membrane and mediate oligomerization upon stress.

• BMB Reports
• /
• v.40 no.3
• /
• pp.315-324
• /
• 2007

The novel $\alpha$-amylase purified from locally isolated strain, Bacillus sp. KR-8104, (KRA) (Enzyme Microb Technol; 2005; 36: 666-671) is active in a wide range of pH. The enzyme maximum activity is at pH 4.0 and it retains 90% of activity at pH 3.5. The irreversible thermoinactivation patterns of KRA and the enzyme activity are not changed in the presence and absence of $Ca^{2+}$ and EDTA. Therefore, KRA acts as a $Ca^{2+}$-independent enzyme. Based on circular dichroism (CD) data from thermal unfolding of the enzyme recorded at 222 nm, addition of $Ca^{2+}$ and EDTA similar to its irreversible thermoinactivation, does not influence the thermal denaturation of the enzyme and its Tm. The amino acid sequence of KRA was obtained from the nucleotide sequencing of PCR products of encoding gene. The deduced amino acid sequence of the enzyme revealed a very high sequence homology to Bacillus amyloliquefaciens (BAA) (85% identity, 90% similarity) and Bacillus licheniformis $\alpha$-amylases (BLA) (81% identity, 88% similarity). To elucidate and understand these characteristics of the $\alpha$-amylase, a model of 3D structure of KRA was constructed using the crystal structure of the mutant of BLA as the platform and refined with a molecular dynamics (MD) simulation program. Interestingly enough, there is only one amino acid substitution for KRA in comparison with BLA and BAA in the region involved in the calcium-binding sites. On the other hand, there are many amino acid differences between BLA and KRA at the interface of A and B domains and around the metal triad and active site area. These alterations could have a role in stabilizing the native structure of the loop in the active site cleft and maintenance and stabilization of the putative metal triad-binding site. The amino acid differences at the active site cleft and around the catalytic residues might affect their pKa values and consequently shift its pH profile. In addition, the intrinsic fluorescence intensity of the enzyme at 350 nm does not show considerable change at pH 3.5-7.0.

• Journal of the Korean Chemical Society
• /
• v.54 no.5
• /
• pp.573-578
• /
• 2010

In this study, iron(III)-2,4-dihydroxysalophen chloride (Fe(2,4-DHSalophen)Cl), has been synthesized by combination of 2,4-dihydroxysalophen (2,4-DHSalophen) with $FeCl_2$ in a solvent system. This complex combination was characterized using UV-vis and IR spectroscopies. Subsequently, the interaction between native calf thymus deoxyribonucleic acid (ct-DNA) and Fe(2,4-DHSalophen)Cl, was investigated in 10 mM Tris/HCl buffer solution, pH 7.2, using UV-visible absorption and fluorescence spectroscopies, thermal denaturation technique and viscosity measurements. From spectrophotometric titration experiments, the binding constant of Fe(2,4-DHSalophen)Cl with ct-DNA was found to be $(1.6{\pm}0.2){\times}10^3\;M^{-1}$. The fluorescence study represents the quenching effect of Fe(2,4-DHSalophen)Cl on bound ethidium bromide to DNA. The quenching process obeys linear Stern-Volmer equation in extended range of Fe(2,4-DHSalophen)Cl concentration. Thermal denaturation experiments represent the increasing melting temperature of DNA (about $4.3^{\circ}C$) due to binding of Fe(2,4-DHSalophen)Cl. These results are consistent with a binding mode dominated by interactions with the groove of ct-DNA.

• Food Science of Animal Resources
• /
• v.33 no.5
• /
• pp.664-671
• /
• 2013

The objective of this study was to investigate the effect of high pressure treatment and type of binding agents on the quality characteristics of restructured pork. For binding agents, 2% (w/w) isolated soy protein (SP), 0.5% (w/w) wheat flour (WF) and 0.5% (w/w) ${\kappa}$-carrageenan (KC) were incorporated into meat batter with or without 0.5% (w/w) glucono-${\delta}$-lactone (GdL). The restructured pork was pressurized at varying pressure levels (0.1-450 MPa) for 3 min under ambient temperature and thermal treated at $75^{\circ}C$ for 30 min. As quality parameters of restructured pork, pH, water binding properties, instrumental color and texture profile analysis were determined and compared with control (C, no binder). For type of binders, SP exhibited the best water binding properties, however, the impact on textural properties were lesser than KC and WF. The addition of GdL decreased the pH of restructured pork down to 0.4 unit, while high pressure processing prevented the moisture loss caused from pH decrease by GdL. In particular, meat restructuring efficiency of SP as a binder improved under the presence of GdL. Therefore, the present study demonstrated the potential advantages of low amount of GdL (0.5%, w/w) combined with protein based binder (SP) and high pressure processing in restructuring meat particles.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.33 no.5
• /
• pp.388-392
• /
• 2000

To improve functionality and characteristics of alginate from the sea tangle, Laminaria japonicus, partially depolymerized alginates (HAG-10, average molecular weight 10,000; HAG-50, average molecular weight 50,000; HAG-100, average molecular weight 100,000) were obtained with hydrolysis of alginate by heating at $12^{\circ}C$. Effects of the depolymerization on physicochemical properties were investigated in the antimutagenicity and binding capacity of cholesterol, glucose and cadmium. In the Ames mutagenicity test using Salmonella typhimurium TA 100, HAG-10, HAG-50, HAG-100 and intact alginate reduced effectively the mutagenicities induced by aflatoxin $B_1 (AFB_1)$ and N-methyl-N'-nitro-N-nitrosoguanidine(MNNG) and HAG-10 showed the strongest antimutagenicity among the tested samples. The binding capacity of cholesterol, glucose and cadmium at different pH in vitro depended highly on molecular weight of alginate, and the changes in binding capacity at different pH was not different.

• Korean Journal of Materials Research
• /
• v.26 no.6
• /
• pp.347-352
• /
• 2016

ZnO with wurtzite structure has a wide band gap of 3.37 eV. Because ZnO has a direct band gap and a large exciton binding energy, it has higher optical efficiency and thermal stability than the GaN material of blue light emitting devices. To fabricate ZnO devices with optical and thermal advantages, n-type and p-type doping are needed. Many research groups have devoted themselves to fabricating stable p-type ZnO. In this study, $As^+$ ion was implanted using an ion implanter to fabricate p-type ZnO. After the ion implant, rapid thermal annealing (RTA) was conducted to activate the arsenic dopants. First, the structural and optical properties of the ZnO thin films were investigated for as-grown, as-implanted, and annealed ZnO using FE-SEM, XRD, and PL, respectively. Then, the structural, optical, and electrical properties of the ZnO thin films, depending on the As ion dose variation and the RTA temperatures, were analyzed using the same methods. In our experiment, p-type ZnO thin films with a hole concentration of $1.263{\times}10^{18}cm^{-3}$ were obtained when the dose of $5{\times}10^{14}$ As $ions/cm^2$ was implanted and the RTA was conducted at $850^{\circ}C$ for 1 min.