• Bulletin of the Korean Chemical Society
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• v.29 no.2
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• pp.299-300
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• 2008

• International Journal of Oral Biology
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• v.38 no.4
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• pp.169-173
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• 2013

HyPer is the genetically encoded biosensor of intracellular hydrogen peroxide ($H_2O_2$), the most stable of the reactive oxygen species (ROS) generated by living cells. HyPer has a high sensitivity and specificity for detecting intracellular $H_2O_2$ by confocal laser microscopy. However, it was not known whether high speed ratiometric imaging of $H_2O_2$ by HyPer is possible. We thus investigated the sensitivity of HyPer in detecting changes to the intracellular $H_2O_2$ levels in HEK293 and PC12 cells using a microfluorometer imaging system. Increase in the HyPer ratio were clearly evident on stimulations of more than $100{\mu}M$ $H_2O_2$ and fast changes in the HyPer ratio were observed on ratiometric fluorescent images after $H_2O_2$ treatment. These results suggest that HyPer is a potent biosensor of the fast temporal production of intracellular $H_2O_2$.

• Journal of the Korean Society of Visualization
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• v.3 no.1
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• pp.3-19
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• 2005

Novel optical techniques are presented for three-dimensional tracking of nanoparticles; Optical Serial Sectioning Microscopy (OSSM) and Ratiometric Total Internal Reflection Fluorescent Microscopy (R-TIRFM). OSSM measures optically diffracted particle images, the so-called Point Spread Function (PSF), and dotermines the defocusing or line-of-sight location of the imaged particle measured from the focal plane. The line-of-sight Brownian motion detection using the OSSM technique is proposed in lieu of the more cumbersome two-dimensional Brownian motion tracking on the imaging plane as a potentially more effective tool to nonintrusively map the temperature fields for nanoparticle suspension fluids. On the other hand, R-TIRFM is presented to experimentally examine the classic theory on the near-wall hindered Brownian diffusive motion. An evanescent wave field from the total internal reflection of a 488-nm bandwidth of an argon-ion laser is used to provide a thin illumination field of an order of a few hundred nanometers from the wall. The experimental results show good agreement with the lateral hindrance theory, but show discrepancies from the normal hindrance theory. It is conjectured that the discrepancies can be attributed to the additional hindering effects, including electrostatic and electro-osmotic interactions between the negatively charged tracer particles and the glass surface.

• Bulletin of the Korean Chemical Society
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• v.28 no.10
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• pp.1818-1820
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• 2007

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2995-2998
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• 2010

• Journal of Microbiology and Biotechnology
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• v.26 no.3
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• pp.530-539
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• 2016

Bacterial light-oxygen-voltage-sensing photoreceptor-derived flavin mononucleotide (FMN)-based fluorescent proteins act as a promising distinct class of fluorescent proteins utilized for various biomedical and biotechnological applications. The key property of its independency towards oxygen for its chromophore maturation has greatly helped this protein to outperform the other fluorescent proteins such as GFP and DsRed for anaerobic applications. Here, we describe the feasibility of FMN-containing fluorescent protein FbFP as a metal-sensing probe by measuring the fluorescence emission changes of a protein with respect to the concentration of metal ions. In the present study, we demonstrated the mercury-sensing ability of FbFP protein and the possible amino acids responsible for metal binding. A ratiometric approach was employed here in order to exploit the fluorescence changes observed at two different emission maxima with respect to Hg²⁺ at micromolar concentration. The engineered variant FbFP_C56I showed high sensitivity towards Hg²⁺ and followed a good linear relationship from 0.1 to 3 μM of Hg²⁺. Thus, further engineering with a rational approach would enable the FbFP to be developed as a novel and highly selective and sensitive biosensor for other toxic heavy metal ions as well.

• The Korean Journal of Physiology and Pharmacology
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• v.19 no.4
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• pp.373-382
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• 2015

Fura-2 analogs are ratiometric fluoroprobes that are widely used for the quantitative measurement of [$Ca^{2+}$]. However, the dye usage is intrinsically limited, as the dyes require ultraviolet (UV) excitation, which can also generate great interference, mainly from nicotinamide adenine dinucleotide (NADH) autofluorescence. Specifically, this limitation causes serious problems for the quantitative measurement of mitochondrial [$Ca^{2+}$], as no available ratiometric dyes are excited in the visible range. Thus, NADH interference cannot be avoided during quantitative measurement of [$Ca^{2+}$] because the majority of NADH is located in the mitochondria. The emission intensity ratio of two different excitation wavelengths must be constant when the fluorescent dye concentration is the same. In accordance with this principle, we developed a novel online method that corrected NADH and Fura-2-FF interference. We simultaneously measured multiple parameters, including NADH, [$Ca^{2+}$], and pH/mitochondrial membrane potential; Fura-2-FF for mitochondrial [$Ca^{2+}$] and TMRE for ${\Psi}_m$ or carboxy-SNARF-1 for pH were used. With this novel method, we found that the resting mitochondrial [$Ca^{2+}$] concentration was $1.03{\mu}M$. This $1{\mu}M$ cytosolic $Ca^{2+}$ could theoretically increase to more than 100 mM in mitochondria. However, the mitochondrial [$Ca^{2+}$] increase was limited to ${\sim}30{\mu}M$ in the presence of $1{\mu}M$ cytosolic $Ca^{2+}$. Our method solved the problem of NADH signal contamination during the use of Fura-2 analogs, and therefore the method may be useful when NADH interference is expected.

• Journal of Electrical Engineering and Technology
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• v.1 no.3
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• pp.387-395
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• 2006

A review on advanced flow visualization techniques is presented particularly for applications to micro scale heat and mass transport measurements. Challenges, development and applications of micro scale visualization techniques are discussed for the study of heating/evaporating thin films, a heated micro channel, and a thermopneumatic micro pump. The developed methods are (1) Molecular Tagging Fluorescence Velocimetry (MTFV) using 10-nm caged seeding molecules (2) Micro Particle Velocimetry (MPIV) and (3) Ratiometric Laser Induced Fluorescence (LIF) for micro-resolution thermometry. These three methods are totally non-intrusive techniques and would be useful to investigate the temperature and flow characteristics in MEMS. Each of these techniques is discussed in three-fold: (1) its operating principle and operation, (2) its application and measurement results, and (3) its future challenges.

• Bulletin of the Korean Chemical Society
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• v.31 no.3
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• pp.624-629
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• 2010

The synthesis and evaluation of a novel calix[4]arene-based fluorescent chemosensor 1 for the detection of I. is described. The fluorescent changes observed upon addition of various anions show that 1 is selective for I. over other anions. Addition of I. results in ratiometric measurements with 1 : 1 complex ratio.

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1309-1313
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• 2010

The effects of boronic acid on the fluoride-selective chemosignaling behavior of a merocyanine dye were investigated. In the presence of phenylboronic acid (PBA), N-methylquinolinium-based merocyanine dye displayed fluoride-selective chromogenic signaling behavior over other commonly coexisting anions in the micromolar concentration range. Signaling is produced by a fluoride-induced displacement of the dye from its complex with PBA, resulting in a significant chromogenic signal for the fluoride ion. This signaling was successfully analyzed using a ratiometric analysis of the UV-vis absorption in response to changes in fluoride ion concentration. A PBA substituted with an electron withdrawing group was found to exhibit a more pronounced signal. Polymer-bound PBA also exhibited useful fluoride-selective signaling behavior.