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Lee, M.,Park, Y.,Lee, H. North Holland ; Elsevier Science Ltd 2013 Chemical physics letters Vol.567 No.-
The adsorption selectivities between dithiothreitol (DTT) and 1,4-butanedithiol 2,3-diamino (BDD) were revealed through density functional theory (DFT) calculations. DFT calculations predict that DTT does not stably adsorb onto the Ge(100) surface because both hydroxyl and thiol group in DTT serve as similar nucleophilic groups, therefore they are not selective. However, BDD is predicted to adsorb stably onto the Ge(100) surface because the amine and thiol groups in BDD operate relatively different nucleophilic group, and it is selective. The adsorption energies of BDD onto the Ge(100) surface suggested that an S-H dissociated N2-H dissociation bonded structure is the most stable structure.
Lee, M.,Yoon, J.,Song, H.,Lee, B.,Lam, D.T.,Yoon, J.,Baek, K.,Clevers, H.,Jeong, Y. Academic Press 2017 Developmental biology Vol.424 No.1
<P>The thalamus acts as a central integrator for processing and relaying sensory and motor information to and from the cerebral cortex, and the habenula plays pivotal roles in emotive decision making by modulating dopaminergic and serotonergic circuits. These neural compartments are derived from a common developmental progenitor domain, called prosomere 2, in the caudal forebrain. Thalamic and habenular neurons exhibit distinct molecular profile, neurochemical identity, and axonal circuitry. However, the mechanisms of how their progenitors in prosomere 2 give rise to these two populations of neurons and contribute to the forebrain circuitry remains unclear. In this study, we discovered a previously unrecognized role for Tcf7l2, a transcription factor known as the canonical Wnt nuclear effector and diabetes risk-conferring gene, in establishing neuronal identity and circuits of the caudal forebrain. Using genetic and chemical axon tracers, we showed that efferent axons of the thalamus, known as the thalamocortical axons (TCAs), failed to elongate normally and strayed from their normal course to inappropriate locations in the absence of Tcf7l2. Further experiments with thalamic explants revealed that the pathfinding defects of Tcf7l2-deficient TCAs were associated at least in part with downregulation of guidance receptors Robol and Robo2 expression. Moreover, the fasciculus retroflexus, the main habenular output tract, was missing in embryos lacking Tcf7l2. These axonal defects may result from dysregulation of Nrp2 guidance receptor. Strikingly, loss of Tcf7l2 caused a post-mitotic identity switch between thalamic and habenular neurons. Despite normal acquisition of progenitor identity in prosomere 2, Tcf7l2-deficient thalamic neurons adopted a molecular profile of a neighboring forebrain derivative, the habenula. Conversely, habenular neurons failed to maintain their normal post-mitotic neuronal identity and acquired a subset of thalamic neuronal features in the absence of Tcf7l2. Our findings suggest a unique role for Tcf7l2 in generating distinct neuronal phenotypes from homogeneous progenitor population, and provide a better understanding of the mechanism underlying neuronal specification, differentiation, and connectivity of the developing caudal forebrain.</P>
FUNCTIONAL PROPERTIES CHANGE OF PIGSKIN COLLAGEN BY CHEMICAL MODIFICATION
Lee, M.,Kwon, S.H. Asian Australasian Association of Animal Productio 1991 Animal Bioscience Vol.4 No.4
The relationship between the possible structural change due to chemical modifications and functionality changes was studied in pigskin collagen. Amino groups in collagen were modified by succinylation and reductive alkylation. Carboxyl groups were modified using carbodiimide. Thermal denaturation temperature of collagen increased remarkably by carboxyl groups modification whereas decreased by succinylation and reductive alkylation. Emulsifying capacity was improved by reductive alkylation and carboxyl groups modification while emulsion stability was improved by succinylation. Chemical modifications increased solubility whereas decreased the foaming capacity of collagen. Viscosity of collagen at various pH varied with methods of modification.
DEVELOPMENT OF A NEW MISFIRE DETECTION SYSTEM USING NEURAL NETWORK
Lee, M.,Yoon, M.,SunWoo, M.,Park, S.,Lee, K. The Korean Society of Automotive Engineers 2006 International journal of automotive technology Vol.7 No.5
The detection of engine misfire events is one of major concerns in engine control due to its negative effect on air pollution and engine performance. In this paper, a misfire detection system based on crankshaft angular speed fluctuation is developed. Synthetic variable method is adopted for the preprocessing of crankshaft angular speed. This method successfully estimates the work output of each cylinder by finding the effect of combustion energy on the crankshaft rotational speed or acceleration after virtually removing the effect of the internal inertia forces from the measured crankshaft speed signals. The detection system is developed using neural network with the revised synthetic angular acceleration as input which is derived from the preprocessing. Mathematical simulation is carried out for developing and verifying the misfire detection system. Finally, the reliability of the developed system is validated through an experiment.
Lee, M.,Won, Y.,Shin, Y.,Kim, J.H.,Chun, J.S. Published for the Society by Baillère Tinda 2016 Osteoarthritis and Cartilage Vol.24 No.1
<P>Objective: Hypoxia-inducible factor (HIF)-2 alpha and the zinc-ZIP8-MTF1 axis in chondrocytes serve as catabolic regulators of osteoarthritic cartilage destruction by regulating the expression of catabolic factor genes. We explored possible crosstalk between these signaling pathways and its biological significance in osteoarthritis (OA). Methods: Microarray analysis, various mRNA and protein assays were conducted using primary cultured mouse articular chondrocytes and experimental OA cartilage to reveal molecular mechanisms underlying the crosstalk between HIF-2 alpha and the zinc-ZIP8-MTF1 axis. Experimental OA in mice was induced by intra-articular (IA) injection of adenovirus expressing HIF-2 alpha (Ad-Epas1), ZIP8 (Ad-Zip8), or MTF1 (Ad-Mtf1) in wild-type mice or mice with cartilage-specific conditional knockout of HIF-2 alpha (Epas1(fl/fl); Col2a1-Cre), ZIP8 (Zip8(fl/fl); Col2a1-Cre), or MTF1 (Mtf1(fl/fl); Col2a1-Cre). Results: HIF-2 alpha activated the zinc-ZIP8-MTF1 axis in chondrocytes by upregulating the Zn2+ transporter ZIP8, thereby increasing Zn2+ influx and activating the downstream transcription factor MTF1. The zinc-ZIP8-MTF1 axis, in turn, acted as a novel transcriptional regulator of HIF-2 alpha. HIF-2 alpha-induced activation of the zinc-ZIP8-MTF1 axis amplified HIF-2 alpha regulation of OA cartilage destruction by synergistically promoting expression of matrix-degrading enzymes. Thus, HIF-2 alpha-induced activation of the zinc-ZIP8-MTF1 axis, together with zinc-ZIP8-MTF1 regulation of HIF-2 alpha, acted collectively to synergistically promote expression of matrix-degrading enzymes and OA cartilage destruction. Conclusion: Our findings identify a reciprocal activation mechanism involving HIF-2 alpha and the zinc-ZIP8-MTF1 axis during OA pathogenesis that amplifies catabolic signaling and cartilage destruction. (C) 2015 The Authors. Published by Elsevier Ltd and Osteoarthritis Research Society International.</P>
Lee, M.,Oh, S.Y.,Pathak, T.S.,Paeng, I.R.,Cho, B.Y.,Paeng, K.J. Elsevier 2007 Journal of chromatography Vol.1160 No.1-2
A simple and selective one-step solid-phase extraction procedure using chemically modified polymer resin (Amberlite XAD-4) with crown ether was investigated for the measurement of urinary catecholamines. After loading the urine samples (adjusted to pH 4) on the synthesized adsorbent cartridge, the column was washed with methanol followed by water and then the adsorbed catecholamines were eluted by 1.0mL of 6.0M acetic acid. The effectiveness of sample clean-up method was demonstrated by reversed-phase ion-pair high-performance liquid chromatography with electrochemical detection. Under optimal condition, the recoveries of epinephrine, norepinephrine, and dopamine from spiked urine sample were >86% for all catecholamines. The detection limits (n=5) for epinephrine, norepinephrine, and dopamine were 37, 52, and 46nmol/L, respectively.
Lee, M.,Shin, S. J.,Oh, Y. T.,Jung, D. C.,Cho, N. H.,Choi, Y. D.,Park, S. Y. Springer Science + Business Media 2017 European radiology Vol.27 No.9
<P>aEuro cent As a non-contrast MRI technique, fusion MRI is useful for bladder cancer.</P>
Lee, M.,Lee, J.,Kang, C.,Kim, K.,Jang, H.,Kim, B.,Jang, G. Springer Science + Business Media 2016 Microsystem Technologies Vol.22 No.6
<P>We propose a method to predict the oil injection time of fluid dynamic bearings (FDBs) with a tied shaft by applying Kirchhoff's pressure law. Since the oil is injected by capillary phenomenon, the volume flow rate can be calculated by utilizing Kirchhoff's pressure law. Then, we calculated the oil injection time of the FDBs with a tied shaft by dividing the volume flow rate by the clearance volumes of the journal bearing, the thrust bearing, and the recirculation channel (RC), respectively. We generated simulation models of the FDBs used in a 2.5aEuro(3) HDD spindle motor with a tied shaft. The total oil injection times of the FDBs with and without a RC were 0.302 and 0.335 s, respectively. Also, we verified the proposed method by measuring the oil injection time of FDBs with a RC. We applied the proposed method to predict and improve the oil injection time of the FDBs with a tied shaft due to the variation of major parameters affecting the oil injection time.</P>