• BMB Reports
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• v.39 no.5
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• pp.530-536
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• 2006

Thermal conformational changes of human serum albumin (HSA) in phosphate buffer, 10 mM at pH = 7 are investigated using differential scanning calorimetric (DSC), circular dichroism (CD) and UV spectroscopic methods. The results indicate that temperature increment from $25^{\circ}C$ to $55^{\circ}C$ induces reversible conformational changes in the structure of HSA. Conformational change of HSA are shown to be a three-step process. Interestingly, melting temperature of the last domain is equal to the maximum value of fever in pathological conditions, i.e. $42^{\circ}C$. These conformational alterations are accompanied by a mild alteration of secondary structures. Study of HSA-SDS (sodium dodecyl sulphate) interaction at $45^{\circ}C$ and $35^{\circ}C$ reveals that SDS affects the HSA structure at least in three steps: the first two steps result in more stabilization and compactness of HSA structure, while the last one induces the unfolding of HSA. Since HSA has a more affinity for SDS at $45^{\circ}C$ compared to $35^{\circ}C$, It is suggested that the net negative charge of HSA is decreased in fever, which results in the decrease of HSA-associated cations and plasma osmolarity, and consequently, heat removal via the increase in urine volume.

• Molecules and Cells
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• v.25 no.2
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• pp.253-257
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• 2008

Acrolein is a highly electrophilic ${\alpha},{\beta}$-unsaturated aldehyde present in a number of environmental sources, especially cigarette smoke. It reacts strongly with the thiol groups of cysteine residues by Michael addition and has been reported to inhibit nuclear $factor-{\kappa}B$ ($NF-{\kappa}B$) activation by lipopolysaccharide (LPS). The mechanism by which it inhibits $NF-{\kappa}B$ is not clear. Toll-like receptors (TLRs) play a key role in sensing microbial components and inducing innate immune responses, and LPS-induced dimerization of TLR4 is required for activation of downstream signaling pathways. Thus, dimerization of TLR4 may be one of the first events involved in activating TLR4-mediated signaling pathways. Stimulation of TLR4 by LPS activates both myeloid differential factor 88 (MyD88)- and TIR domain-containing adapter inducing $IFN{\beta}$ (TRIF)-dependent signaling pathways leading to activation of $NF-{\kappa}B$ and IFN-regulatory factor 3 (IRF3). Acrolein inhibited $NF-{\kappa}B$ and IRF3 activation by LPS, but it did not inhibit $NF-{\kappa}B$ or IRF3 activation by MyD88, inhibitor ${\kappa}B$ kinase $(IKK){\beta}$, TRIF, or TNF-receptor-associated factor family member-associated $NF-{\kappa}B$ activator (TANK)-binding kinase 1 (TBK1). Acrolein inhibited LPS-induced dimerization of TLR4, which resulted in the down-regulation of $NF-{\kappa}B$ and IRF3 activation. These results suggest that activation of TLRs and subsequent immune/inflammatory responses induced by endogenous molecules or chronic infection can be modulated by certain chemicals with a structural motif that enables Michael addition.

• Journal of Power System Engineering
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• v.15 no.2
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• pp.13-18
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• 2011

This thesis is about the result of conducting a specific experiment for the development of noncontact vibration displacement sensor for measuring the spindle vibration that is used for conditional monitoring of machinery. One should be careful when using the eddy current type displacement sensor because the sensitivity of it is different according to the quality of the material. While the probe used for nondestructive inspection adopts the effect of transmitting the material by using the high frequency domain, the eddy current type displacement sensor uses the lower frequency of around 1MHz. Also, while the nondestructive probe uses the method of enhancing output by using the resonance zone, the vibration displacement sensor utilizes the stable zone by avoiding the resonance zone. Since the oscillator of the converter uses the "L" element as Probe, its characteristic changes with the variation of a relevant impedance. In other words, if the length of Probe's Cable gets extended (Impedance increase), the sensitivity declines accordingly. The effect of surrounding temperature was small, but the influence of the quality of Sensor Coil used was high. Moreover, following an experimental demonstration of the phenomenon where the sensitivity decreases as the frequency of the tested material increases from a frequency response test, the maximum frequency that could be measured was approximately 1KHz. It was noted that the degree of precision could be maintained by using the gap of the probe in the linear zone at the installation site.

• Smart Structures and Systems
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• v.10 no.3
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• pp.253-269
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• 2012

A split spectrum processing (SSP) method is proposed to accurately determine the time-of-flight (ToF) of damage-scattered waves by comparing the instantaneous amplitude variation degree (IAVD) of a wave signal captured from a damage case with that from the benchmark. The fundamental symmetrical ($S_0$) mode in aluminum plates without and with a notch is assessed. The efficiency of the proposed SSP method and Hilbert transform in determining the ToF of damage-scattered $S_0$ mode is evaluated for damage identification when the wave signals are severely contaminated by noise. Broadband noise can overwhelm damage-scattered wave signals in the time domain, and the Hilbert transform is only competent for determining the ToF of damage-scattered $S_0$ mode in a noise-free condition. However, the calibrated IAVD of the captured wave signal is minimally affected by noise, and the proposed SSP method is capable of determining the ToF of damage-scattered $S_0$ mode accurately even though the captured wave signal is severely contaminated by broadband noise, leading to the successful identification of damage (within an error on the order of the damage size) using a triangulation algorithm.

• The Journal of the Acoustical Society of Korea
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• v.15 no.5
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• pp.82-89
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• 1996

Application fields of ultrasonic transducers can be divided into two categories, a high ultrasonic resolution required field and a high ultrasonic power required field. This paper is aimed to determine the optimal properties of the matching layers of the transducer for each of the applications. Further, it is aimed to optimize the properties of the matching layers that show satisfactory performances for both of the application fields. Through the direct time domain analysis of the transmission and reflection behavior of the ultrasonic wave, apart from the conventional equivalent circuit analysis, and Fourier transformation of its results, we found the optimum acoustic impedances of the matching layers. The newly determined layers provide much better transducer performance-57% at most-than those obtained with conventional design methods. Based on the results, we also found the optimal acoustic impedances of the layers good for both of the application fields. For te optimization, we developed a new transducer performance evaluation parameter that can be applied to any type of ultrasonic transducers.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.5
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• pp.251-258
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• 2002

In this paper, the dipole-fed planar array antenna applied Yagi-Uda antenna away theory to microstrip antenna is designed and fabricated at X-band. The design procedure of the dipole-fed planar array antenna with the wide bandwidth is presented to be easily practiced to a wireless communication system. The radiation pattern, return loss and bandwidth of the antenna are improved by the finite differential time domain(FDTD) numerical method. The propriety of analysis of planar dipole antenna is proved from the measured data. From the measured results, the antenna maximum gain is 4.9dBi at center frequency of 10GHz and frequency bandwidth is about 40%. Front-to-back ratio is 16dB, and half-power beam-width of E-plane and H-plane are 117$^{\circ}$and 156$^{\circ}$, respectively. When VSWR of antenna is less than 2, the measured results are agreed well with the theoretical values in the frequency range from 7.4GHz to 11.88GHz.

• Toxicological Research
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• v.24 no.2
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• pp.101-107
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• 2008

Studies on hypoxia-signaling pathways have revealed novel Fe(II) and $\alpha$-ketoglutarate-dependent dioxygenases that hydroxylate prolyl or asparaginyl residues of a transactivator, Hypoxia-Inducible $Factor-\alpha(HIF-\alpha)$ protein. The recognition of these unprecedented dioxygenases has led to open a new paradigm that the hydroxylation mediates an instant post-translational modification of a protein in response to the changes in cellular concentrations of oxygen, reducing agents, or $\alpha$-ketoglutarate. Activity of $HIF-\alpha$ is repressed by two hydroxylases. One is $HIF-\alpha$ specific prolyl-hydroxylases, referred as prolyl-hydroxylase domain(PHD). The other is $HIF-\alpha$ specific asparaginyl-hydroxylase, referred as factor-inhibiting HIF-1(FIH-1). The facts (i) that many dioxygenases commonly use molecular oxygen and reducing agents during detoxification of xenobiotics, (ii) that detoxification reaction produces radicals and reactive oxygen species, and (iii) that activities of both PHD and FIH-1 are regulated by the changes in the balance between oxygen species and reducing agents, imply the possibility that the activity of $HIF-\alpha$ can be increased during detoxification process. The importance of $HIF-\alpha$ in cancer and ischemic diseases has been emphasized since its target genes mediate various hypoxic responses including angiogenesis, erythropoiesis, glycolysis, pH balance, metastasis, invasion and cell survival. Therefore, activators of PHDs and FIH-1 can be potential anticancer drugs which could reduce the activity of HIF, whereas inhibitors, for preventing ischemic diseases. This review highlights these novel dioxygenases, PHDs and FIH-1 as specific target against not only cancers but also ischemic diseases.

• Geomechanics and Engineering
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• v.12 no.3
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• pp.523-539
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• 2017

Clay soils are typical for their swelling properties upon absorption of water during rains and development of cracks during summer time owing to the profile desorption of water through the inter-connected soil pores by water vapour diffusion leading to evaporation. This type of unstable soil phenomenon by and large poses a serious threat to the strength and stability of structures when rest on such type of soils. Even as lime and cement are extensively used for stabilization of clay soils it has become imperative to find relatively cheaper alternative materials to bring out the desired properties within the clay soil domain. In the present era of catastrophic environmental degradation as a side effect to modernized manufacturing processes, industrialization and urbanization the creative idea would be treating the waste products in a beneficial way for reuse and recycling. Bottom ash and ecosand are construed as a waste product from cement industry. An optimal combination of bottom ash-eco sand can be thought of as a viable alternative to stabilize the clay soils by means of an effective dispersion dynamics associated with the inter connected network of pore spaces. A CATIA model was created and imported to ANSYS Fluent to study the dispersion dynamics. Ion migration from the bottom ash-ecosand pile was facilitated through natural formation of cracks in clay soil subjected to atmospheric conditions. Treated samples collected at different curing days from inner and outer zones at different depths were tested for, plasticity index, Unconfined Compressive Strength (UCS), free swell index, water content, Cation Exchange Capacity (CEC), pH and ion concentration to show the effectiveness of the method in improving the clay soil.

• BMB Reports
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• v.34 no.4
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• pp.355-364
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• 2001

Major human Nucleoside diphosphate kinases (NDPKs) exist as hetero-oligomers, consisting of NDPK-A and NDPK-B, rather than homo-oligomer. To investigate their biological function depending on the oligomeric structure in vivo, we characterized the biochemical properties of cellular NDPK. Cellular NDPKs, which are made up of a unique combination of isoforms, were purified from human erythrocyte and placenta. We found that cellular NDPK and recombinant isoforms NDPKs have their own distinct biochemical properties in autophosphorylation, stability toward heat or urea, and DNA binding. Cellular NDPK was found to have unique characteristics rather than the expected additive properties of recombinant isoforms. The mutations in the dimeric interface of NDPK-B (R34G, N69H or K135L) caused defective DNA binding and simultaneously reduced the enzymatic stability These results suggest that the oligomeric interaction could play a major role in the stability of catalytic domain and might be related to the regulation of various cellular functions of NDPK.

• BMB Reports
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• v.34 no.5
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• pp.402-407
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• 2001

Based on the currently proposed toxicity model for the different Bacillus thuringiensis Cry $\delta$-endotoxins, their pore-forming activity involves the insertion of the ${\alpha}4-{\alpha}5$ helical hairpin into the membrane of the target midgut epithelial cell. In this study, a number of polar or charged residues in helix 4 within domain I of the 65-kDa dipteranactive Cry11A toxin, Lys-123, Tyr-125, Asn-128, Ser-130, Gln-135, Arg-136, Gln-139 and Glu-141, were initially substituted with alanine by using PCR-based directed mutagenesis. All mutant toxins were expressed as cytoplasmic inclusions in Escherichia coli upon induction with IPTG. Similar to the wild-type protoxin inclusion, the solubility of each mutant inclusion in the carbonate buffer, pH 9.0, was relatively low When E. coli cells, expressing each of the mutant proteins, were tested for toxicity against Aedes aegypti mosquito-larvae, toxicity was completely abolished for the alanine substitution of arginine at position 136. However, mutations at the other positions still retained a high level of larvicidal activity Interestingly, further analysis of this critical arginine residue by specific mutagenesis showed that conversions of arginine-136 to aspartate, glutamine, or even to the most conserved residue lysine, also abolished the wild-type activity The results of this study revealed an important determinant in toxin function for the positively charged side chain of arginine-136 in helix 4 of the Cry11A toxin.