• Bulletin of the Korean Chemical Society
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• v.33 no.1
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• pp.100-104
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• 2012

Thrombin is a serine protease that catalyzes the conversion of soluble fibrinogen to insoluble fibrin, and thus induces physiological and pathological blood coagulation. Therefore, it is important to detect thrombin in blood serum for purposes of diagnosis. To achieve this goal, it has been suggested that a 15-mer aptamer strongly binds with thrombin to form a G-quartet structure of the aptamer. Generally, 5'-end thiol-functionalized aptamer has been used as an anti-thrombin binder. Herein, we evaluate the possibility of utilizing a 3'-SH aptasensor for thrombin detection using SPR spectroscopy, and compare the enhancement of the electrochemical signal of the thrombin-aptamer bound on a porous gold substrate. Although the two aptamers have similar configurations, in SPR analysis, the 3'-SH aptamer was a effective aptasensor as well as 5'-SH aptamer. Results from electrochemical analysis showed that the porous gold substrate acted as a good substrate for an aptasensor and demonstrated 5-fold enhancement of current change, as compared to gold thin film.

• Bulletin of the Korean Chemical Society
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• v.33 no.1
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• pp.171-176
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• 2012

A novel chemiluminescence (CL) system was established for the determination of cytosine arabinoside (Ara-C) in pharmaceutical preparations. It was showed that a clear CL signal was observed when Eosin Y mixed with Fenton reagent. The CL intensity was decreased significantly when Ara-C was added to the reaction system and partially scavenged the hydroxyl radicals in the solution. The extent of decrease in the CL intensity had a good stoichiometrical relationship with the Ara-C concentration. Based on this, we developed a new method for the determination of Ara-C using a flow injection analysis (FIA) technique with CL detection. Under the optimal conditions, the linear range of Ara-C concentration was $6.0{\times}10^{-9}\sim1.0{\times}10^{-7}mol/L$ (R = 0.9982) with a detection limit of $7.6{\times}10^{-10}mol/L$ (S/N=3), the RSD was 5.6% for $6.0{\times}10^{-8}mol/L$ Ara-C (n = 11). The method was successfully applied to the determination of Ara-C in injection samples. The possible chemiluminescence reaction mechanism was discussed.

• Bulletin of the Korean Chemical Society
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• v.24 no.8
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• pp.1119-1125
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• 2003

Coherent multidimensional vibrational spectroscopy is a new technique for establishing correlations between features in vibrational spectra that are caused by intra- and intermolecular interactions. These interactions cause cross-peaks between vibrational transitions that reflect the coupling. In this paper, we use Doubly Vibrationally Enhanced Infrared Spectroscopy (DOVE-IR) and DOVE-Raman processes to obtain coherent two dimensional vibrational spectra. The spectra are fitted to obtain the dephasing rates and third order susceptibilities $(χ^{(3)})$ for the nonlinear processes. We show that the DOVE $χ^{(3)}$ values are directly related to the molar absorptivities and Raman $χ^{(3)}$. We then use these relationships to obtain estimates for the $χ^{(3)}$ of the stimulated photon echo and $χ^{(5)}$ of the six wave mixing spectroscopies, respectively. We also predict the ratio of the cascaded four wave mixing signal to the six wave mixing signal.

• Bulletin of the Korean Chemical Society
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• v.34 no.3
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• pp.793-800
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• 2013

A few years ago, the plasmon-induced electronic coupling (PIEC) model was proposed in the literature to explain small changes in the surface-enhanced Raman scattering (SERS) in nanogap systems. If this model is correct, it will be very helpful in both basic and application fields. In light of this, we carefully reexamined its appropriateness. Poly(4-vinylpyridine) (P4VP) used in the earlier work was, however, never a proper layer, since most adsorbates not only adsorbed onto Ag nanoparticles sitting on P4VP but also penetrated into the P4VP layer deposited initially onto a flat Ag substrate, ultimately ending up in the SERS hot sites. Using 1,4-phenylenediisocyanide and 4-nitrophenol as the affixing layer and the foreign adsorbate, respectively, we could clearly reveal that the PIEC model is not suited for explaining the Raman signal in a nanogap system. Most of the Raman signal must have arisen from molecules situated at the gap center.

• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3357-3361
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• 2013

Alumina microfibers with porous structures were prepared through hydrothermal reaction, and then used to modify the surface of carbon paste electrode (CPE). After modification with alumina microfibers, the electrochemical activity of CPE was found to be greatly improved. On the surface of alumina microfibers-modified CPE, the oxidation peak current of salvianolic acid B, a main bioactive compound in Danshen with anti-oxidative and anti-inflammatory effects, was remarkably increased compared with that on the bare CPE surface. The influences of pH value, amount of alumina microfibers and accumulation time were studied. Based on the strong signal amplification effects of alumina microfibers, a novel electrochemical method was developed for the detection of salvianolic acid B. The linear range was from 5 ${\mu}gL^{-1}$ to 0.3 mg $L^{-1}$, and the detection limit was 2 ${\mu}gL^{-1}$ (2.78 nM) after 1-min accumulation. The new method was successfully used to detect salvianolic acid B in ShuangDan oral liquid samples, and the recovery was over the range from 97.4% to 102.9%.

• Bulletin of the Korean Chemical Society
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• v.26 no.1
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• pp.19-31
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• 2005

During the last decade, the exploration of nanoscale device and circuitry based on molecules has gained increasing interest. In parallel with this, considerable effort is being devoted to the development of molecular photonic/electronic materials based on various porphyrin arrays. This involves light as an input/output signal and excitation energy migration as a mechanism for signal transmission. Absorption of a photon at the light collector end of the porphyrin array yields the excited state, which migrates among the intervening pigments until reaching the emitter, whereupon another photon is emitted. As a consequence, it is relevant to understand the excitation energy transfer (EET) processes occurring in various forms of porphyrin arrays for the applications as artificial light harvesting arrays and molecular photonic/electronic wires. Since the excitonic (dipole) and electronic (conjugation) couplings between the adjacent porphyrin moieties in porphyrin arrays govern the EET processes, we have characterized the EET rates of various forms of multiporphyrin arrays (linear, cyclic, and box) based on various time-resolved spectroscopic measurements. We believe that our observations provide a platform for further development of molecular photonic/electronic materials based on porphyrin arrays.

• Journal of the Korean Chemical Society
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• v.14 no.4
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• pp.341-345
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• 1970

An improved derivative thermometric titration apparatus designed around operational amplifiers is described which is capable of monitoring the small temperature change and of computing the derivatives for accentuation of the titration end point that is difficult to locate by extrapolation methods. The instrument is constructed of four commercial operational amplifiers. A use of dummy cell provides the subtraction means for compensation of the initial temperature and random temperature fluctuations with a resultant gain in signal-to-noise ratio. The successive differentiation action of the computer has been nearly "perfect," so that the two breaks (blank or starting and end point of the titration curve can be located with the precision of 0.2% by observing two peak points on the second derivative curve. Arrangements useful in obtaining such a good derivative response that is exactly proportional to the input signal are discussed. Plots of the enthalphogram and its derivatives are presented, with the results of several titrations used to evaluate the performance of the apparatus.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1534-1535
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• 2007

This paper describes a novel microfluidic device with a microfabricated electrospray source for a sheathless electrospray ionization interface to a mass spectrometer. This electrospray ionization-mass spectrometry (ESI-MS) device consists of a triangular-shaped metal emitter, allowing the generation of an efficient electrospray for peptide detection, and microfluidic channels monolithically in a glass microchip. The performance of the proposed interface was evaluated by opimizing its experimental condition and spraying standard peptides. The spraying has high signal strength and stability, with a relative standard deviation of 2.9% and singly-charged and doubly-charged peaks of the peptides were successfully detected. The metal emitter source showed a good performance to be comparable to commercially available emitters in signal strength and stability.

• Journal of Microbiology and Biotechnology
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• v.9 no.5
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• pp.576-581
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• 1999

Effects of signal sequences, protein sizes and dissolved oxygen on the secretion of human lysozyme from a recombinant yeast were experimentally characterized. The systems consisted of Saccharomyces cerevisiae host SEY2102 that was transformed with two different plasmids. These plasmids were identical with an exception to the plasmid pMC614, which contained the native yeast MFα1 sequence and the plasmid pMC632 with the non-native rat α-amylase signal sequence. The expression of human lysozyme was controlled by the ADHI promoter. The native yeast MFαl signal sequence was more efficient than the non-native rat α-amylase signal sequence in directing the secretion of human lysozyme. Lysozyme secreted with the α-amylase signal was retained inside the cells and released to the medium very slowly, thereby causing a lower cell growth rate and a decreased product secretion rate. Lysozyme was secreted more efficiently than invertase, which is an order of magnitude bigger in molecular size compared to lysozyme, which was under the direction of the MFαl signal sequence, suggesting that protein sizes may affect the secretion efficiency. When expressed in anaerobic conditions in the medium where the ADHI promoter was derepressed, the amount of lysozyme secreted was about twice higher than that of the aerobic culture. However, the secretion rates were identical. This result showed that the dissolved oxygen level may affect the efficiency of protein secretion only, and not the secretion rate of the product protein.

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1295-1300
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• 2010

The $CO_2-CH_4$ reaction catalyzed by Ni/silicon wafers was kinetically studied by using a photoacoustic technique. The catalytic reaction was performed at various partial pressures of $CO_2$ and $CH_4$ (50 Torr total pressure of $CO_2/CH_4/N_2$) in the temperature range of 500 - $650^{\circ}C$ in a static reactor system. The photoacoustic signal that varied with the $CO_2$ concentration during the catalytic reaction was recorded as a function of time. Under the reaction conditions, the $CO_2$ photoacoustic measurements showed the as-prepared Ni thin film sample to be inactive for the reaction, while the $CO_2/CH_4$ reactions carried out in the presence of the sample pre-treated in $H_2$ at $600^{\circ}C$ were associated with significant time-dependent changes in the $CO_2$ photoacoustic signal. The rate of $CO_2$ disappearance was measured from the $CO_2$ photoacoustic signal data in the early reaction period of 50 - 150 sec to obtain precise kinetic data. The apparent activation energy for $CO_2$ consumption was determined to be 6.9 kcal/mol from the $CO_2$ disappearance rates. The partial reaction orders, determined from the $CO_2$ disappearance rates measured at various $PCO{_2}'S$ and $PCH{_4}'S$ at $600^{\circ}C$, were determined to be 0.33 for $CH_4$ and 0.63 for $CO_2$, respectively. Kinetic data obtained in these measurements were compared with previous works and were discussed to construct a catalytic reaction mechanism for the $CO_2-CH_4$ reaction over Ni/silicon wafer at low pressures.