• Macromolecular Research
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• v.15 no.3
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• pp.234-237
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• 2007

3,4-Bis-(3,4-dicarboxyphenylcarboxyethoxy)-4'-nitrostilbene dianhydride was prepared and reacted with 4,4'-(hexafluoroisopropylidene)dianiline to yield a novel Y-type polyimide containing the 3,4-dioxynitrostilbenyl group as an NLO-chromophore, which constituted part of the polymer backbone. The resulting polyimide was soluble in polar solvents such as acetone and N,N-dimethylformamide. The polymer exhibited good thermal stability up to $370^{\circ}C$ in the thermogravimetric analysis. The glass-transition temperature ($T_g$) obtained from the differential scanning calorimetry thermogram was near to $153^{\circ}C$. The second harmonic generation (SHG) coefficient ($d_{33}$) of the poled polymer film at the fundamental wavelength of $1064\;cm^{-1}$ was around $2.15\;{\times}\;10^{-8}\;esu$ (9.01 pm/V). The dipole alignment exhibited exceptionally high thermal stability even at a temperature $30^{\circ}C$ above the $T_g$, and there was no SHG decay below $180^{\circ}C$ because of the partial main chain character of the polymer structure.

• Analytical Science and Technology
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• v.19 no.3
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• pp.189-193
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• 2006

Chromatographic separation of glycerol monostearate, glycerol distearate and glycerol tristearate (GMS, GDS, and GTS) has been performed by normal phase HPLC method utilizing a Zorbax silica ($250{\times}4.6mm$, $5{\mu}m$) column and hexane-hexane, IPA and ethyl acetate mixtures as the eluent within 20 min. The observed reproducibility was less than 5% RSD, Suggesting that ELSD was an effective tool for detection of the glycerol stearates of low volatility without chromophore. The detection limits were in the concentration range of 0.3~2 mg/L, and the calibration curves (the log-log plots) were linear in the range of 4~1000 mg/L (with the slopes of 1.06~1.32). The application of the analytical procedure without pretreatment demonstrated that the proposed chromatographic method would be practical for a routine analysis of commercial products.

• Journal of Photoscience
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• v.9 no.2
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• pp.122-125
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• 2002

Coherent oscillations in is fluorescence dynamics of W.-t. PYP and its site-directed mutants have been observed. Two oscillatory modes coupled with the ultrafast fluorescence due to the twisting of the excited chromophore were identified, a high ftequency mode (∼135 cm$\^$-1/) with ∼550 is damping time and a low frequency overdamped mode (-45 cm$\^$-1/) with ∼250 is damping time, respectively. Both modes disappear in the fluorescence dynamics of denatured PYP emphasizing the important role of the protein nanospace as the environment for photoreaction. The qualitative picture of fluorescence dynamics in site-directed mutants was rather similar to that in W.-t. PYP, i.e., similar oscillatory modes (∼130-140 cm$\^$-1/ and ∼40-70 cm$\^$-1/) have been observed. This indicates that the vibrational modes and electron-vibration couplings do not change dramatically due to the mutation though the damping time of low frequency mode a little decreases as the protein nanospace structure becomes looser and more disordered by mutation. On the other hand, in the case of some PYP analogues, the qualitative picture of fluorescence dynamics changes, showing the familiar picture of solvation effect whereas the oscillations are almost damped. Comparative analyses of these observations are presented.

• Journal of Photoscience
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• v.9 no.2
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• pp.5-8
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• 2002

Photoperiodism is an important adaptive phenomenon in various physiological parameters including reproduction to cope with seasonal changes. Involvement of extraretinal photoreceptors in the photoperiodism in non-mammalian vertebrates has been well established. In addition, circadian clock system is known to be involved in the photoperiodic time measurement. The pathway consists of light-input system, time measurement system (circadian clock), gonadotropin releasing hormone (GnRH) production in the hypothalamus, luteinizing hormone (LH) and follicle stimulating hormone (FSH) production in the pituitary, and final gonadal development. Recently, several laboratories reported photopigments newly cloned in the pineal, eyes and deep brain in addition to already known visual pigments in the retina. These are pinopsin, parapinopsin, VA-opsin, melanopsin, etc. All these photopigments belong to the opsin family having retinal as the chromophore. However, the function of these photopigments remains unknown. I reviewed the studies on the location of the photopigments by immunocytochemistry. I also discussed the results on the action spectra for induction of gonadal development in relation with the location of the photoreceptors. Various physiologically active substances distribute in the vertebrate brain. Such substances are GnRH, GnIH, neuropeptide Y, vasoactive intestinal peptide, c-Fos, galanin, neurosteroids, etc. I summarized the immunhistochemical studies on the distribution and the photoperiodic changes of these substances and discussed the route from the deep brain photoreceptor to GnRH cells.

• Journal of Photoscience
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• v.9 no.2
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• pp.41-43
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• 2002

In photoreceptor cells, light activates visual pigments consisting of a chromophore (retinal) and a protein moiety (opsin). Activated visual pigments trigger an enzymatic cascade, called phototransduction cascade, in which more than ten phototransduction proteins are participating. Two types of vertebrate photoreceptor cells, rods and cones, play roles in twilight and daylight vision, respectively. Cones are further classified into several subtypes based on their morphology and spectral sensitivity. Though the diversities of vertebrate photoreceptor cells are crucial for color discrimination and detection of light over a wider range of intensities, the molecular mechanism to characterize the photoreceptor types remains unclear. We investigated the amino acid sequences of about 50 vertebrate opsins, and found that these sequences can be classified into five fundamental subfamilies. Clear relationships were found between these subfamilies and their characteristic spectral sensitivities. In addition to opsins, we studied other phototransduction proteins. The amino acid sequences of phototransduction proteins can be classified into a few subfamilies. Even though their spectral sensitivity is considerably different, cones fundamentally share the phototransduction protein isoforms which are different from those found in rods. It is suggested that the difference in phototransduction proteins between rods and cones is responsible for their sensitivity to light. Isoforms and their selective expression may characterize individual photoreceptor cells, thus providing us with physiological functions such as color vision and daylight/twilight visions.

• Bulletin of the Korean Chemical Society
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• v.34 no.9
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• pp.2609-2615
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• 2013

A series of fluorene-carbazole copolymers containing the pendant phosphor chromophore $Ir(absn)_2(acac)$ (absn: 2-(1-naphthyl)benzothiazole; acac: acetylacetone) were designed and synthesized via Yamamoto coupling. In the film state, these copolymers exhibited absorption and emission peaks at approximately 389 and 426 nm, respectively, which originated from the fluorene backbone. However, in electroluminescent (EL) devices, a significantly red-shifted emission at approximately 611 nm was observed, which was attributed to the pendant iridium(III) complex. Using these copolymers as a single emission layer, polymer light-emitting devices with ITO/PEDOT:PSS/polymer:DNTPD/TmPyPb/LiF/Al configurations exhibited a saturated red emission at 611 nm. The attached iridium(III) complex had a significant effect on the EL performance. A maximum luminous efficiency of 0.85 cd/A, maximum external quantum efficiency of 0.77, maximum power efficiency of 0.48 lm/W, and maximum luminance of 883 $cd/m^2$ were achieved from a device fabricated with the copolymer containing the iridium(III) complex in a 2% molar ratio.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.1
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• pp.80-85
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• 2007

We report the electro-optical properties of the sensory rhodopsin II using a near-field scanning microwave microscope(NSMM). Rhodopsin was known as a photoreceptor pigment with a retinal as a chromophore via a protonated Schiff base and consists of seven ${\alpha}-helical$ transmembrane segments. The sensory rhodopsin II, expressing E. coli UT5600 with endogenous retinal biosynthesis system and purified with $Ni^{-2}-NTA$ affinity chromatography in the presence of 0.02 % DM (Dodecyl Maltoside) from Natronomonas pharaonis. We measured the absorption spectra and the transients difference of sensory rhodopsin II from Natronomonas pharaonis using a UV/VIS spectrophotometer with Nd-Yag Laser (532 nm). The absorption spectra of NpSR II showed a typical rhodopsin spectrum with a left shoulder region and the photointermediates spectra of NpSR II-ground state (${\lambda}max=498\;nm$), NpSR II-M state (${\lambda}max=390\;nm$), and NpSR II-O state (${\lambda}max=550\;nm$) during the photocycle. The observed photocycle reaction was confirmed by measuring the microwave reflection coefficient $S_{11}$ at an operating frequency of f=3.93-3.95 GHz and compared with the results of a photocycle of NpSR II.

• Journal of Food Hygiene and Safety
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• v.9 no.3
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• pp.123-131
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• 1994

An enzyme-linked immunosorbent assay(ELISA) was developed for the detection of residual gentamicin(GM) in edible animal products. The immunogen(GM-KLH conjugate) and coating antigen(GM-BSA conjugate) were prepared by coupling GM sulfate to keyhole limpet hemocyanin(KLH) and bovine serum albumin(BSA) in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, respectively. Polyclonal antibody to GM was produced in rabbits(New Zealand White, female) by using the immunogen and the antibody titer was measured by indirect ELISA. A competitive ELISA was developed using GM-bovine serum albumin conjugate as a coating antigen, GM(as standards or sample), polyclonal antibody to GM, secondary antibody conjugated with horseradish peroxidase as an enzyme, and H2O2 and o-phenylenediamine dihydrochloride as a substrate and a chromophore, respectively. The detection limit of GM was 10 ng/ml and the standard curve of GM(n=26) was linear up to 10 $\mu\textrm{g}$/ml in this competitive ELISA system. There were no cross-reactivities of the partially purified antibody between GM and the various antibiotice such as amikacin, benzyl-penicillin, chloramphenicol, erythromycin, furazlidone, kanamycin, neomycin, oleandomycin, streptomycin, sulfathiazole and thiamphenicol(CR50<0.05%)

• Macromolecular Research
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• v.11 no.6
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• pp.431-436
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• 2003

A new photoconducting polymer, diphenyl hydrazone-substituted polysiloxane, was successfully synthesized by the hydrosilylation method and characterized by FT-IR, $^1$H-NMR, and $^{29}$ Si-NMR spectroscopy. The glass transition temperature (T$_{g}$) of the polysiloxane having pendant diphenyl hydrazone was ca. 62 $^{\circ}C$, which enabled a component of a low-T$_{g}$ photorefractive material to be prepared without the addition of any plasticizers. This polysiloxane, with 1 wt% of $C_{60}$ dopant, showed a high photoconductivity (2.8 ${\times}$ 10$^{-12}$ S/cm at 70 V/${\mu}{\textrm}{m}$) at 633 nm, which is necessary for fast build-up of the space-charge field. A photorefractive composite was prepared by adding a nonlinear optical chromophore, 2-{3-[2-(dibutylamino)-1-ethenyl]-5,5-dimethyl-2-cyclohexenylidene} malononitrile, into the photoconducting polysiloxane together with $C_{60}$ . This composite shows a large orientation birefringence ($\Delta$n = 2.6 ${\times}$ 10$^{-3}$ at 50 V/${\mu}{\textrm}{m}$) and a high diffraction efficiency of 81 % at an electric field of 40 V /${\mu}{\textrm}{m}$.textrm}{m}$.EX>.

• Journal of Microbiology and Biotechnology
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• v.17 no.1
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• pp.138-145
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• 2007

Anabaena sensory rhodopsin is a seven transmembrane protein that uses all-trans/13-cis retinal as a chromophore. About 22 residues in the retinal-binding pocket of microbial rhodopsins are conserved and important to control the quality of absorbing light and the function of ion transport or sensory transduction. The absorption maximum is 550 nm in the presence of all-trans retinal at dark. Here, we mutated Pro206 to Glu or Asp, of which the residue is conserved as Asp among all other microbial rhodopsins, and the absorption maximum and pKa of the proton acceptor group were measured by absorption spectroscopy at various pHs. Anabaena rhodopsin was expressed best in Escherichia coli in the absence of extra leader sequence when exogenous all-trans retinal was added. The wild-type Anabaena rhodopsin showed small absorption maximum changes between pH4 and 11. In addition, Pro206Asp showed 46 nm blue-shift at pH7.0. Pro206Glu or Asp may change the contribution to the electron distribution of the retinal that is involved in the major role of color tuning for this pigment. The critical residue Ser86 (Asp 96 position in bacteriorhodopsin: proton donor) for the pumping activity was replaced with Asp, but it did not change the proton pumping activity of Anabaena rhodopsin.