• The Korean Journal of Physiology and Pharmacology
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• v.2 no.1
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• pp.21-30
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• 1998

The effects of GABA and glutamate on the horizontal cells were explored by an intracellular recording method to discern the mechanisms of receptive field formation by chemical coupling in the catfish outer retina. The results suggest that the horizontal cells of the catfish retina might use GABA as their transmitters and that the GABAergic system contributes to the formation of receptive fields of the horizontal cells. GABAC receptors may be involved in a chemical coupling between horizontal cells and concerned with the depolarizing actions by GABA on horizontal cells in the catfish retina. Since the chloride equilibrium potential is more positive than the dark membrane potential in horizontal cells, GABA released from a horizontal cell may depolarize the neighboring horizontal cells. Thus a chemical coupling between horizontal cells may be formed. $GABA_A$ receptors also may be involved in the negative feedback mechanism between photoreceptor and horizontal cell. And glutamate may be involved in connecting positive and negative feedback systems since it potentiated the GABA's actions. Therefore, it is presumed that large receptive fields in the catfish retina are formed not only by electrical coupling but also by chemical coupling between horizontal cells. And information travels laterally by pathways involving both electrical coupling composed of gap junctions and chemical coupling in the retinal network.

• Bulletin of the Korean Chemical Society
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• v.24 no.11
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• pp.1632-1636
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• 2003

Palladium-catalyzed cross-coupling reactions of neopentyloxysulfonylphenyl bromides with arylboronic acids provided a variety of neopentyl biphenylsulfonates in good yields. 2-Bromo- and 4-bromobenzenesulfonates underwent the coupling reaction more rapidly than 3-bromobenzenesulfonate, while chlorobenzenesulfonate did not produce the coupling product under the standard reaction conditions.

• Elastomers and Composites
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• v.49 no.3
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• pp.239-244
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• 2014

Reaction between silica and silane coupling agent without solvent was investigated using transmission mode Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Bis[3-(triethoxysilylpropyl) tetrasulfide] (TESPT) was used as a silane coupling agent. After removing the unreacted TESPT, formation of chemical bonds was analyzed using FTIR and content of reacted TESPT was determined using TGA. Content of the coupling agent bonded to silica increased with increase in the coupling agent content, but the oligomers were formed by condensation reaction between coupling agents when the coupling agent was used to excess. In order to identify bonds formed among silica, coupling agent, and rubber, a silica-coupling agent-BR model composite was prepared by reaction of the modified silica with liquid BR of low molecular weight and chemical bond formation of silica-coupling agent-BR was investigated. Unreacted rubber was removed with solvent and analysis was performed using FTIR and TGA. BR was reacted with the coupling agent of the modified silica to form chemical bonds. Polarity of silica surface was strikingly reduced and particle size of silica was increased by chemical bond formation of silica-coupling agent-BR.

• Journal of the Korean Chemical Society
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• v.57 no.3
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• pp.361-364
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• 2013

A modified synthetic approach to the synthesis of heterocyclic food mutagens, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PHIP) and 2-amino-1,6-dimethylimidazo[4,5-b]pyridine (DMIP) is reported. This route highlights an optimized palladium catalysed Buchwald cross-coupling of 2-halo-1-methyl-imidazo[4,5-b]pyridine with benzophenoneimine followed by acidic hydrolysis to yield compound 7. Using finely tailored conditions, Suzuki cross-coupling reactions with highly efficient catalytic systems were performed as the final step on 8 to introduce the aryl group and methyl group on the heterocyclic core.

• Bulletin of the Korean Chemical Society
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• v.34 no.5
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• pp.1477-1480
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• 2013

The Suzuki cross-coupling reactions proceeded in excellent yields when it was catalyzed by magnetically recyclable nanocatalyst. This nanocatalyst provided very high catalytic activity with low loading level (1 mol %), because the palladium nanoparticles were so small in size (~2 nm) and located on the surface of the nanocomposite. It was also easily recovered from the reaction mixture using a magnet and reused for six consecutive cycles.

• Bulletin of the Korean Chemical Society
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• v.22 no.10
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• pp.1145-1148
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• 2001

• Journal of the Korean Chemical Society
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• v.16 no.3
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• pp.166-177
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• 1972

This paper reports the reaction of monoiodoperfluorocycloakense with alkyl lithium and activated copper repectively resulting in various coupling products. Of particular interests are compounds of the following composition. The physical properties of the various compounds are given along with a discussion relating to the mechanistic pathways involved in the coupling reactions.

• Journal of the Korean Chemical Society
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• v.21 no.3
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• pp.180-186
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• 1977

The preparation of 1-chloro-2-iodoperfluorocycloalkenes was achieved with a short reaction time and a high yield when the starting compound was iodinated via the metalation process using an alkyllithium reagent. Especially, the high yield of 1-chloro-2-iodo-perfluorocyclohexene was obtained when 1,2-dichloroperfluorocyclohexene was iodinated via the same reaction conditions. The coupling reaction of 1,2-dihaloperfluorocycloalkenes was also achieved with a lower reaction temperature and a shorter reaction time when the equal slurry mixture of fluorocycloolefines and DMF was reacted at a high pressure in a sublimer. The yield of the coupling product was greatly improved by this process. For a typical example, the coupling reaction of the 1-chloro-2-iodotetrafluorocyclobutene was proceeded with a higher yield of the product than that of the reported reaction, when the present method was adopted. A plausible reaction mechanism of the present coupling reactiont was proposed and the physical characteristics of the coupling product were confirmed.

• Bulletin of the Korean Chemical Society
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• v.20 no.10
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• pp.1205-1208
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• 1999

27Al NMR chemical shielding, quadrupolar coupling, and dipolar coupling interactions for corundum (α-Al2O3) are determined from the single-crystal 27 Al NMR spectra according to the rotation about three orthogonal axis. 27 Al NMR parameters obtained in this work with high accuracy are as follows: δiso = 7.4(4) ppm, QCC = 2.30(4) MHz, h = 0.08(3), and R = 2.0(3) kHz. This work appears to be the first NMR measurement of an aluminum-aluminum dipolar coupling interaction in α-Al2O3 crystals.

• Elastomers and Composites
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• v.25 no.2
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• pp.112-116
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• 1990

In this study, as one way of developing the new cross-linking method that is curable in water, kinetic analysis of solution reaction between CR and silane coupling agents was attemped. First, CR was reacted with silane coupling agents in solution state. According to the time, reaction quantity was pursued by gas chromatography. Also, reaction rate coefficient and activation energy were calculated from the reaction quantity. Silane coupling agents which were used in this study were MPS, CPS and VES.