• The Journal of Natural Sciences
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• v.8 no.2
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• pp.35-41
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• 1996

To find the substrate interacting site of the MCAT1, charged amino acid residues in the transmembrane domain were changed to opposite charged amino acids and studied the arginine uptake, gp70 binding, efflux and protein expression using the Xenopus oocyte expression method. Among the five mutants of MCAT1, the D403K showed the most interesting characteristics, which had normal gp70 binding but low arginine uptake function, that means the normal expression on the membrane but decreased transport function. All mutants except K211E showed decreased arginine efflux, and kinetic study showed decreased Vmax. Together, Clu(403) residue of MCAT1 may show the possible substrate interacting site in the transmembrane domain of MCAT1.

• Journal of Acupuncture Research
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• v.18 no.2
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• pp.111-122
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• 2001

Objectives ; This study was undertaken to determine if Salviae Radix herb-acupuncture (SRA) exerts protective effect against alterations in membrane transport function in rabbits with mercury chloride (Hg)-induced acute renal failure. Methods and Results ; The administration of Hg at a subcutaneous single dose of 10mg/kg caused a reduction in GFR to 9.4% of the basal value and an increase in fractional Na+ excretion to 10-fold, indicating generation of acute renal failure. When animals were acupunctured with $0.5m{\ell}$ of SRA extract (0.1%) in both sides of Shinsu(BL23) for 7 days prod to Hg administration, such changes were significantly attenuated. The fractional excretion of glucose and phosphate was increased to approximately 132-fold and 7-fold, respectively, in rabbits treated with Hg alone, but the fractional excretion of glucose was increased to 26-fold and that of phosphate was not different from the basal value in SRA-pretreated rabbits. Uptakes of glucose and phosphate in purified isolated brush-border membrane and $Na^+-K^+$-ATPase activity in microsomal fraction were inhibited in rabbits treated with Hg alone, suggesting that impairment in proximal reabsorption of glucose and phosphate is resulted from a direct damage of membrane transport carriers and disruption of the normal $Na^+$ gradient. Conclusions ; Such changes were prevented by SRA. Uptakes of organic ions, PAH and TEA, in renal cortical slices were inhibited by the administration of Hg, which was prevented by SRA. Pretreatment of an antioxidant DPPD attenuated the increase in the fractional excretion of glucose and phosphate induced by the administration of Hg.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.626-631
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• 2021

One of the nonlinear electrokinetic phenomena around ion exchange membrane is electroconvective instability which can be found in various electrokinetic applications such as electrodialysis, electrochemical battery, microfluidic analysis platform, etc. Such instability acts as a positive transport mechanism for the electrodialysis via amplifying mass transport rate. On the other hands, in the electrochemical battery and the microfluidic applications, the instability provokes unwanted mass transport. In this research, to control the electroconvective instability, the onset of the instability was analyzed as a function of confinement effect as well as applied voltage. As a result, we figured out that the dynamic behavior of electroconvective instability transited as a sequence of stable regime - static regime - chaotic regime depending on the applied voltage and confinement effect. Furthermore, stability curves about the dynamic transition were numerically determined as well. Conclusively, the confinement effect on electroconvective instability can be applied for effective means to control the electrokinetic chaos.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3377-3382
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• 2007

In proton exchange membrane fuel cell, the heat is generated at the catalyst layer as result of exothermic electrochemical reaction. This heat increases temperature of gas diffusion layer and membrane whose conductivity is very sensitive to humidity, function of temperature. So it is very important to analysis heat transfer through fuel cell to maintain temperature at specified range. In this paper numerical simulation was done including reversible, irreversible, ionic resistance, water formation loss to source term of energy equation. Results show that irreversible and water formation loss contributes mainly to energy source term and as current density increases, all of energy source terms become increased and Nusselt number is increased as results of more heat generation. Particularly irreversible loss is found to be predominant among the all energy source and water formation at cathode channel influences the temperature distribution of fuel cell greatly.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.373-373
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• 2009

Relative humidity, membrane conductivity and water activity are critical parameters of polymer electrolyte membrane fuel cells (PEMFC) for high performance and reliability. These parameters are closely related with temperature. Moreover, the ideal values of these parameters are not always identical along the channels. Therefore, the cooling channel design and its operating condition should be well optimized along the all location of the channels. In the present study, we have performed a numerical investigation on the effects of cooling channels on performance of a PEMFC. Three-dimensional Navier-Stokes equations are solved with the energy equation including heat generated by the electrochemical reactions in the fuel cell. The present numerical model includes the gas diffusion layers (GDL) and serpentine channels for both anode and cathode gas flows, as well as cooling channels. To accurately predict the water transport across the membrane, the distribution of water content in the membrane is calculated by solving a nonlinear differential equation with a nonlinear coefficient, i.e., the water diffusivity which is a function of water content as well as temperature. Main emphasis is placed on the heat transfer between the solid bipolar plate and coolant flow. The present results show that local current density is affected by cooling channels due to the change of the oxygen concentration and the membrane conductivity as well as the water content. It is also found that the relative humidity is influenced by the generated water and the gas temperature and thus it affects the distribution of fuel concentration and the conductivity of the membrane, ultimately fuel cell performance. Unit-cell experiments are also carried out to validate the numerical models. The performance curves between the models and experiments show reasonable results.

• Journal of the Korean Chemical Society
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• v.36 no.6
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• pp.914-918
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• 1992

The preferential transport phenomena of neutral cation-anion moieties in neutral macrocycle-facilitated emulsion liquid membrane were described in this study. Emulsion membrane systems consisting of (1) aqueous source phase containing 0.001M $M(NO_3)_2$ (M = $Mn^{2+}$, $Co^{2+}$, $Ni^{2+}$, $Cu^{2+}$, $Zn^{2+}$, $Sr^{2+}$, $Cd^{2+}$, $Pb^{2+}$) (2) a toluene membrane containing 0.02M ligand (DB$N_3O_2$, DB18C6) and the surfactant span 80 (sorbitan mono oleate) (3% v/v) and (3) aqueous receiving phase containing $Na_2S_2O_3$ or $NaNO_3$ were studied with respect to the disappearence of metal ions from the source phase as a function of time. Cation transport rates for various two component equimolar mixture of metal ions were determinded. $Cd^{2+}$ was transported higher rates than the other $M^{2+}$ in the mixture solution.

• Korean Journal of Food Science and Technology
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• v.45 no.2
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• pp.137-141
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• 2013

Flavonoids have various biological activities; however, their cellular uptake mechanism is beginning to be understood only recently. This review focuses on cellular flavonoids transport mechanisms in both plants and animals. In plants, flavonoids exist in various cellular compartments, providing a specialized transport system. Newly synthesized flavonoids can be transported from the endoplasmic reticulum to the vacuoles or extracellular space via cellular trafficking pathway. Among membrane transporters, ATP binding cassette, multidrug and toxic extrusion, bilitranslocase homologue transporters play roles in both the influx and efflux of cellular flavonoids across the cell membrane. In recent years, extensive researches have provided a better understanding on the cellular flavonoid transport in mammalian cells. Bilitranslocase transports flavonoids in various tissues, including the liver, intestine and kidneys. However, other transport mechanisms are largely unknown and thus, further investigation should provide detailed mechanisms, which can potentially lead to an improved bioavailability and cellular function of flavonoids in humans.

• Biomolecules & Therapeutics
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• v.27 no.3
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• pp.290-301
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• 2019

Paeonol has neuroprotective function, which could be useful for improving central nervous system disorder. The purpose of this study was to characterize the functional mechanism involved in brain transport of paeonol through blood-brain barrier (BBB). Brain transport of paeonol was characterized by internal carotid artery perfusion (ICAP), carotid artery single injection technique (brain uptake index, BUI) and intravenous (IV) injection technique in vivo. The transport mechanism of paeonol was examined using conditionally immortalized rat brain capillary endothelial cell line (TR-BBB) as an in vitro model of BBB. Brain volume of distribution (VD) of [$^3H$]paeonol in rat brain was about 6-fold higher than that of [$^{14}C$]sucrose, the vascular space marker of BBB. The uptake of [$^3H$]paeonol was concentration-dependent. Brain volume of distribution of paeonol and BUI as in vivo and inhibition of analog as in vitro studies presented significant reduction effect in the presence of unlabeled lipophilic compounds such as paeonol, imperatorin, diphenhydramine, pyrilamine, tramadol and ALC during the uptake of [$^3H$]paeonol. In addition, the uptake significantly decreased and increased at the acidic and alkaline pH in both extracellular and intracellular study, respectively. In the presence of metabolic inhibitor, the uptake reduced significantly but not affected by sodium free or membrane potential disruption. Similarly, paeonol uptake was not affected on OCTN2 or rPMAT siRNA transfection BBB cells. Interestingly. Paeonol is actively transported from the blood to brain across the BBB by a carrier mediated transporter system.

• Reproductive and Developmental Biology
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• v.39 no.4
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• pp.97-104
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• 2015

Glucose is universal and essential fuel of energy metabolism and in the synthesis pathways of all mammalian cells. Glucose is the one of the major precursors of lactose synthesis using glycolysis result in producing milk fat and protein. During the milk fat synthesis, lipoprotein lipase (LPL) and CD36 are required for glucose uptake. Various morecules such as acyl-CoA synthetase 1 (ACSL1) activity of acetyl-CoA synthetase 2 (ACSS2), ACACA, FASN AGPAT6, GPAM, LPIN1 are closely related with milk fat synthesis. Additionally, glucose plays a major role for synthesizing lactose. Activations of lactose synthesize enzymes such as membranebound enzyme, beta-1,4-galactosyl transferase (B4GALT), glucose-6-phosphate dehydrogenase (G6PD) are changed by concentration of glucose in blood resulting change of amount of lactose production. Glucose transporters are a wide group of membrane proteins that facilitate the transport of glucose over a plasma membrane. There are 2 types of glucose transporters which consisted facilitative glucose transporters (GLUT); and sodium-dependent transport, mediated by the Na+/glucose cotransporters (SGLT). Among them, GLUT1, GLUT8, GLUT12, SGLT1, SGLT2 are main glucose transporters which involved in mammary gland development and milk synthesis. However, more studies are required for revealing clear mechanism and function of other unknown genes and transporters. Therefore, understanding of the mechanisms of glucose usage and its regulation in mammary gland is very essential for enhancing the glucose utilization in the mammary gland and improving dairy productivity and efficiency.

• Journal of Korean Dental Science
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• v.4 no.2
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• pp.73-78
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• 2011

Purpose: $HCO_3{^-}$ is the most important ion to buffer the acidity of saliva. The transport of $HCO_3{^-}$ is mediated by electrogenic $Na^+/HCO_3{^-}$ cotransporter 1 (NBCe1), which expressed in various tissues including salivary glands, kidney and pancreas, etc. This experiment was performed to investigate regulatory site of NBCe1involved in the pH regulation using various mutants of NBCe1. Materials and Methods: Human parotid gland NBCe1 (hpNBCe1) and mutants by deletion of 1~285 bp and 1~1,035 bp were prepared. After microinjection of each cRNA to oocytes of Xenopus laevis, they were incubated for 2~3 days. The function of each protein was tested by electrophysiological method. Results: When oocytes were exposed to the $HCO_3{^-}$ buffered solution, 1~285 bp deleted mutant hpNBCe1 evoked a marked hyperpolarization ranging from -90 mV to -160 mV (average: -134 mV; n=12) compared to the full length of hpNBCe1. Although 1~1,035 bp deleted mutant hpNBCe1 was also expressed in the plasma membrane, but it did not show any changes of membrane potentials. Conclusion: Our deletion mutant study demonstrated that 1~285 bp of the NBCe1 is the major domain to determine $HCO_3{^-}$ transport ratio.