• Applied Chemistry for Engineering
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• v.24 no.5
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• pp.443-455
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• 2013

Electrochemical studies on charge transfer reactions across the interface between two immiscible electrolyte solutions (ITIES) have greatly attracted researcher's attentions due to their wide applicability in research fields such as ion sensing and biosensing, modeling of biomembranes, pharmacokinetics, phase-transfer catalysis, fuel generation and solar energy conversion. In particular, there have been extensive efforts made on developing sensing platforms for ionic species and biomolecules via gelifying one of the liquid phases to improve mechanical stability in addition to creating microscale interfaces to reduce ohmic loss. In this review, we will mainly discuss on the basic principles, applications and future aspects of various sensing platforms utilizing ion transfer reactions across the ITIES. The ITIES is classified into four types : (i) a conventional liquid/liquid interface, (ii) a micropipette supported liquid/liquid interface, (iii) a single microhole or an array of microholes supported liquid/ liquid interface on a thin polymer film, and (iv) a microhole array liquid/liquid interface on a silicon membrane. Research efforts on developing ion selective sensors for water pollutants as well as biomolecule sensors will be highlighted based on the use of direct and assisted ion transfer reactions across these different ITIES configurations.

• Analytical Science and Technology
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• v.17 no.3
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• pp.251-262
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• 2004

It is for the purpose of investigating the tritium distribution in the leachates, the raw and treated leachates and the condensates of the methane gas, which have occurred from domestic solid waste landfills. Also it aims to measure the tritium distribution level on the colloid size of the leachates, the raw and treated leachates. It was found that the major inorganic contaminants of the leachates were Na, K, Ca, Mg, $NH{_4}^+$-N and $Cl^-$. The mean tritium level of the raw leachates of the investigated 13 landfill sites for 6 months was 17 ~ 1196 TU. It corresponded to a several scores or hundreds of magnitude higher value than that of the normal environmental sample level except for two landfill sites. Also such a high concentration of the tritium was found in the treated leachates and methane gas condensates as well. Nevertheless it is important to emphasize that the tritium level which was found in this research is about 100 times lower than the tritium limit for the drinking water quality. And most of the tritium existed in the dissolved colloid of the leachate of which the colloid size is below $0.45{\mu}m$. Also, according to the tritium analysis results of the leachates after filtration with $0.45{\mu}m$ membrane filter for some landfills, it is likely that some tritium of the leachate would be distributed in a colloid size over $0.45{\mu}m$. In general the relationship between the tritium and other contaminants in the raw leachate was low, but it was relatively high between the tritium and TOC. However, the tritium content in the leachate had no meaningful relationship with the scale, hydrological characteristics and age of the landfill.

• Applied Biological Chemistry
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• v.42 no.1
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• pp.49-57
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• 1999

Enzymatic hydrolysis with tuna pyloric caeca crude enzyme(TPCCE) was performed to recover a protein hydrolysate from hoki frame, fish processing by-product. Optimum hydrolytic conditions were pH 10.0, temperature $50^{\circ}C$, and incubation time 12 hrs, and then the degree of hydrolysis was about 60%. The yield of the hydrolysate from hoki frame by enzymatic hydrolysis was approximately 77% on a dry weight basis. The prepared protein hydrolysates were also fractionated through a series of 30, 10, 5 and 1 kDa molecular weight cut-off (MWCO) membranes in order to investigate the effect of their functionalities according to the difference of their molecular size. As the result of studying functionalities of the hydrolysates, 1 K hydrolysate showed the highest solubility over all pHs, and 30 and 10 K hydrolysate showed more excellent emulsifying property and whippability than the other hydrolysates.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.1
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• pp.47-53
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• 2011

$SF_6$ (Sulfur hexafluoride) possesses high GWP (Global Warming Potential) as sepcified by the IPCC (Intergonvernmental Panel of Climate Change). Recently, the recovery-separtion of $SF_6$ research area, including permeation properties studies using various membrane's materials and the practical operation of recovery-separtion using membrane of waste $SF_6$ gas is in the initial state. The separation efficiency of a single $SF_6$ and waste $SF_6$ mixture was evaluated using a PSF (polysulfone), PC (tetra-bromo polycarbonate) and PI (polyimide) hollow fiber membranes. According to the results of single gases permeation properties, PI membrane has the highest permselectivity of $N_2$ gas in $N_2/SF_6$ gas. Under the condition of P=0.5 MPa, the highest concentration of recovered $SF_6$ is 95.6 vol % in the separation experiment of $SF_6/N_2$ mixture gas by PC membrane. Under the operation pressure of P=0.3 MPa at a fixed retentate flow rate fixed of 150 cc/min, the maximum recovery efficiency of $SF_6$ is up to 97.8% by PSF membrane. From the results above, it is thought that the separation and recovery technique of $SF_6$ gas using membrane will be used as the representative eco-technology in the $SF_6$ gas treatment in the future.

• Analytical Science and Technology
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• v.27 no.1
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• pp.34-40
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• 2014

SPLITT fractionation (SF) allows continuous (and thus a preparative scale) separation of micronsized particles into two size fractions ('fraction-a' and 'fraction-b'). SF is usually carried out in a thin rectangular channel with two inlets and two outlets, which is equipped with flow stream splitters at the inlet and the outlet of the channel, respectively. A new large scale splitter-less gravitational SF (GSF) system had been assembled, which was designed to eliminate the flow stream splitters and thus is operated by the full feed depletion (FFD) mode (FFD-GSF). In the FFD mode, there is only one inlet through which the sample is fed. There is no carrier liquid fed into the channel, and thus prevents the sample dilution. The effects of the sample-feeding flow rate, the channel thickness on the fractionation efficiency (FE, number % of particles that have the size predicted by theory) of FFD-GSF was investigated using industrial polyurethane (PU) latex beads. The carrier liquid was water containing 0.1% FL-70 (particle dispersing agent) and 0.02% sodium azide (used as bactericide). The sample loading rate was varied from about 4 to 7 L/hr with the sample concentration fixed at 0.01%. The GSF channel thickness was varied from 900 to $1300{\mu}m$. Particles exiting the GSF channel were collected and monitored by optical microscopy (OM). Sample recovery was monitored by collecting the fractionated particles on a $0.45{\mu}m$ membrane filter. It was found that FE of fraction-a was increased as the channel thickness increases, and FE of fraction-b was increased as the flow rate was increased. In all cases, the sample recovery has higher than 95%. It seems the new splitter-less FFD GSF system could become a useful tool for large scale separations of various types of micron-sized particles.

• Applied Biological Chemistry
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• v.41 no.2
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• pp.130-136
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• 1998

Microsomes of tomato roots were prepared and the activities of microsomal ATPases were measured in order to understand the molecular mechanisms of various ion transports. The activities of plasma membrane $H^+-ATPase$ and vacuolar $H^+-ATPase$ were evaluated to ${\sim}30%$ and ${\sim}38%$ of total microsomal ATPase activity by using their specific inhibitor, vanadate and nitrate $(NO^-_3)$, respectively. The inhibitory effects of vanadate and $NO^-_3$ were additive and the simultaneous additions of these two inhibitors decreased the total activity up to $50{\sim}70%$. The microsomal ATPase activity was regulated key pH and the maximal activity was obtained at pH 7.4. The activity of microsomal ATPase was increased by $K^+$ up to ${\sim}30%$ at the concentration of $K^+$ above 10 mM. However, the $K^+-induced$ increase in the activity was completely inhibited by the simultaneous addition of $Na^+$. To identify the ATPase activity regulated by $K^+$, the effects of specific inhibitors were measured. Vanadate and $NO^-_3$ inhibited total ATPase activity by 27% and 32% in the absence, of $K^+$ and by 27% and 40% in the presence of 120 mM $K^+$, respectively. These results suggest that $K^+$ increases the activity of $NO^-_3-sensitive$ vacuolar $H^+-ATPase$ but not that of vanadate-sensitive plasma membrane $H^+-ATPase$ since vanadate has no effect on $K^+-induced$ increase in ATPase activity. The microsomal ATPase activity was also decreased by increasing $Ca^{2+}$ concentration. Interestingly, $NO^-_3$ blocked the $Ca^{2+}-induced$ inhibition of microsomal ATPase activity; however, vanadate had no effect. These results imply that vacuolar $H^+-ATPase$ is activated by $K^+$ and inhibited by $Ca^{2+}$.

• Applied Chemistry for Engineering
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• v.33 no.2
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• pp.173-178
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• 2022

A lateral flow immunoassay (LFIA) method using carbon nanodot@silica as a signaling material was developed for analyzing the concentration of retinol-binding protein 4 (RBP4), one of the lung cancer biomarkers. Instead of antibodies mainly used as bioreceptors in nitrocellulose membranes in LFIA for protein detection, aptamers that are more economical, easy to store for a long time, and have strong affinities toward specific target proteins were used. A 5' terminal of biotin-modified aptamer specific to RBP4 was first reacted with neutravidin followed by spraying the mixture on the membrane in order to immobilize the aptamer in a porous membrane by the strong binding affinity between biotin and neutravidin. Carbon nanodot@silica nanoparticles with blue fluorescent signal covalently conjugated to the RBP4 antibody, and RBP4 were injected in a lateral flow manner on to the surface bound aptamer to form a sandwich complex. Surfactant concentrations, ionic strength, and additional blocking reagents were added to the running buffer solution to optimize the fluorescent signal off from the sandwich complex which was correlated to the concentration of RBP4. A 10 mM Tris (pH 7.4) running buffer containing 150 mM NaCl and 0.05% Tween-20 with 0.6 M ethanolamine as a blocking agent showed the optimum assay condition for carbon nanodot@silica-based LFIA. The results indicate that an aptamer, more economical and easier to store for a long time can be used as an alternative immobilizing probe for antibody in a LFIA device which can be used as a point-of-care diagnosis kit for lung cancer diseases.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.3
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• pp.194-201
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• 2009

The e1ectrocatalytic properties of heteropolyacids(HPAs) entrapped in covalently cross-linked sulfonated polyetheretherketone(CL-SPEEK/HPA) membranes have been studied for water electrolysis. The HPAs, including tungstophosphoric acid(TPA), molybdophosphoric acid(MoPA), and tungstosilicic acid(TSiA) were used as additives in the composite membranes. The MEA was prepared by a non-equilibrium impregnation-reduction(I-R) method, using reducing agent, sodium borohydride(NaBH4) and tetraamineplatinum(II) chloride(pt(NH$_3$)$_4$Cl$_2$). The electrocatalytic properties of composite membranes such as the cell voltage were in the order of magnitude CL-SPEEKlMoPA40 (wt%) > /TPA30 > /TSiA40. In the optimum cell applications for water electrolysis, the cell voltage of PtlPEM/Pt-Ru MEA with CL-SPEEKlTPA30 membrane was 1.75 V at 80$^{\circ}$C and I A/cm$^2$ and this voltage carried lower than that of 1.81 V of Nafion 117. Consequently, in regards of electrochemical and mechanical characteristics and oxidation durability, the newly developed CL-SPEEKITPA30 composite membrane exhibited a better performance than the others, but CLSPEEKlMoPA40 showed the best electrocatalytic activity (1.71 Vat 80$^{\circ}$C and 1 A/cm$^2$) among the composite membranes.

• Analytical Science and Technology
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• v.24 no.6
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• pp.429-434
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• 2011

In this study, a wet-sampler was developed for collection in water and simultaneous fractionation of micron-sized particles (e.g., pigment, airborne, etc.). In this new device, three cylinders (partially filled with water) through which air was forced to pass for sample collection are connected in a series. Particles of different sizes are collected in different cylinders, allowing simultaneous fractionation. An uniqueness of this new device is that it does not use any membrane filter. Microparticles are collected directly in cylinders filled partially with water. Also the particles are simultaneously fractionated within this device while they are being collected. The new device was employed for collection of airborne particles. The collected airborne particles were fractionated by using sedimentation field-flow fractionation, SdFFF), and observed with an optical microscopy (OM) for size and shape analysis. Also AAS and ICP-AES were used for composition analysis of the airborne particles. It is expected that the new device is applicable to collection and analysis of size distribution of various types of microparticles.

• BMB Reports
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• v.28 no.3
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• pp.221-226
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• 1995

Dopamine mediates inhibitory responses in Helix aspersa neurons from the right parietal lobe ("F-lobe") of the circumoesophageal ganglia. The effects appeared as a dose-dependent hyperpolarization of the plasma membrane and a decrease in the occurrence of spontaneous action potentials. The average hyperpolarization with 5 ${\mu}m$ dopamine was -12 mV (${\pm}1.5$mV, S.D., n=12). Dopamine also modulated the currents 'responsible for shaping the action potentials in these neurons. When dopamine was added and action potentials were triggered by an injection of current, the initial depolarization was slowed, the amplitude and the duration of action potentials were decreased, and the after-hyperpolarization was more pronounced. The amplitude and the duration of action potential were reduced about 15 mV and about 13% by 5 ${\mu}m$ dopamine, respectively. The effects of dopamine on the resting membrane potentials and the action potentials of Helix neurons were dose-dependent in the concentration range 0.1 ${\mu}m$ to 50 ${\mu}m$. In order to show 1) that the effects of dopamine were mediated by dopamine receptors rather than by direct action on ionic channels and 2) which type of dopamine receptor might be responsible for the various effects, we assayed the ability of mammalian dopamine receptor antagonists, SCH-23390 (antagonist of D1 receptor) and spiperone (antagonist of D2 receptor), to block the dopamine-dependent changes. The D1 and D2 antagonists partially inhibited the dopamine-dependent hyperpolarization and the decrease in action potential amplitude. They both completely blocked the decrease in action potential duration and the increase in action potential after-hyperpolarization. The dopamine-induced slowdown of the depolarization in the initial phase of the action potentials was less effected by SCH-23390 and spiperone. From the results we suggest 1) that Helix F-lobe neurons may have a single type of dopamine receptor that binds both SCH-23390 and spiperone and 2) that the dopamine receptor of Helix F-lobe neurons may be homologous with and primitive to the family of mammalian dopamine receptors.