• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1108-1114
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• 2013

Photochemical reactions of fluoro- vs. nonfluoro-substituted polymethylenoxy chain linked phthalimide were carried out to explore how electronegative fluorine atoms inside the donor chain influence photocyclization reaction efficiencies and to briefly determine the alkali metal binding properties of the photoproducts. The results of this study show that the fluorine-substituted donor chain linked phthalimide undergoes inefficient photocyclization via single electron transfer (SET)-induced excited state pathways to generate 14-membered cyclic amidol compared to nonfluoro-analog due to low electron donor ability of the terminal oxygen donor site. These results show that photoinduced intramolecular SET processes arising from ${\alpha}$-silyl ether electron donors to phthalimides are largely dependent on the kinds of substituents inside donor chain. Finally, a preliminary study with the cyclic amidols generated in this effort showed that they have weak alkali metal cation binding properties regardless of absence/presence of fluoro-substituents.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.375.1-375.1
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• 2016

Polymerase chain reaction (PCR) has revolutionized genetics and become one of the most popular techniques in modern biological and medical sciences. It can be used not only as an in vitro DNA amplification method but also used in many bioassay applications. The PCR can be used to exponentially produce a large number of DNA copies from a small quantity of DNA molecules in a few hours. However, as unwanted DNA fragments are also often manufactured, the amplification efficiency of PCR is decreased. To overcome this limitation, several nanomaterials have been employed to increase the specificity of the PCR reaction. Recently, graphene has attracted a great interest for its excellent electron transfer, thermal and biocompatibility. Especially, gold nanoparticle-coated graphene oxide (GO/AuNPs) led to enhance electron and thermal transfer rate and low-charge transfer resistance. Therefore, we report the development of a demonstration for the PCR efficiency using a large-scale production of the GO and combination of gold nanoparticles. Because a thermal conductivity is an important factor for improving the PCR efficiency in different DNA polymerases and different size samples. When PCR use GO/AuNPs, the result of transmission electron microscopy and real-time quantitative PCR (qPCR) showed an enhanced PCR efficiency. We have demonstrated that GO/AuNPs would be simply outperformed for enhancing the specificity and efficiency of DNA amplification procedure.

• Bulletin of the Korean Chemical Society
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• v.9 no.4
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• pp.248-251
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• 1988

Mechanism of electrochemical polymerization of pyrrole (Py) on a Pt electrode in acidic aqueous solutions was studied by means of potentiostatic measurements, cyclic voltammetry and chronopotentiometry. Pyrrole molecule appeared to be initially oxidized via two-electron transfer step to produce oxidized pyrrole ion ($Py^+$), which was coupled with a non-oxidized pyrrole to yield a dimerized species, Py-Py. The Py-Py thus formed was further oxidized again via two-electron transfer step, which was followed by coupling with non-oxidized monomer and by concomitant expulsion of a $H^+$. Then the latter chain extension process was repeated. The chain extension and polypyrrole oxidation reactions occurred competitively.

• Macromolecular Research
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• v.17 no.4
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• pp.240-244
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• 2009

High molecular weight(MW), 3-arm star poly(methyl methacrylate)(PMMA) with a narrow MW distribution($M_n$=570,000 g/mol, PDI=1.36) was successfully synthesized by activators regenerated by electron transfer(ARGET) atom transfer radical polymerization(ATRP). The polymerization was carried out with a trifunctional initiator/$CuBr_2$/N,N,N',N",N"-pentamethyldiethy lenetriamine(PMDETA) initiator/catalyst system in the presence of a tin(II) 2-ethylhexanoate [$Sn(EH)_2$] reducing agent at $90^{\circ}C$. The concentration of the copper catalyst was as low as 30 ppm, and a high initiation efficiency of the initiating sites was obtained. The chain-end functionality of the high MW, 3-arm star PMMA was confirmed by a chain extension experiment with styrene via ARGET ATRP, using the same catalyst system.

• Journal of Photoscience
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• v.8 no.3_4
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• pp.99-104
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• 2001

Studies have been conducted to explore single electron transfer (SET) promoted photocyclization reactions of ($\omega$-phthalimidoalkylthio)acetic acids (alkyl=ethyl, n-propyl, n-butyl, n -hexyl and n-nonyl). Photocyclizations occur in methanol in modest yields to produce cyclized products in which phthalimide carbonyl carbon is bonded to the carbon of side chain in place of the carboxylic group. The initially formed cyclized products undergo efficient water eliminations to produce enthiol ethers in secondary ground state reactions.

• Applied Microscopy
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• v.48 no.4
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• pp.81-86
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• 2018

The respiratory chain complex forms a supercomplex (SC) in the inner mitochondrial membrane. This complex facilitates the process of electron transfer to produce the proton gradient used to synthesize ATP. Understanding the precise structure of the SC is considered an important challenge. However, it has not yet been reported. The development of a Cryo-electron microscopy (EM) technique provides an effective way to obtain high-resolution micrographs to determine the high-resolution three-dimensional structure of biomolecules. In this brief review, the currently reported Cryo-EM structures of the mammalian respirasome have been described in order to establish a direction for further research in the respiratory system.

• Bulletin of the Korean Chemical Society
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• v.27 no.3
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• pp.381-385
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• 2006

The temperature dependence on the electron transfer rate constant $(k_{app})$ for hydroquinone redox center in $H_2Q(CH_2)_n$SH-SAMs (n = 1, 4, 6, 8, 10, and 12) on gold electrode was investigated to obtain reorganization energy $(\lambda)$ using Laviron’s formalism and Arrhenius plot of ln $[k_{app}/T^{1/2}]$ vs. T^{-1} based on the Marcus densityof-states model. All the symmetry factors measured for the SAMs were relatively close to unity and rarely varied to temperature change as expected. The electron tunneling constant $(\beta)$ determined from the dependence of the $k_{app}$ on the distance between the redox center and the electrode surface gives almost the same $\beta$ values which are quite insensitive to temperature change. Good linear relationship of Arrhenius plot for all $H_2Q(CH_2)_n$SH-SAMs on gold electrode was obtained in the temperature range from 273 to 328 K. The slopes n Arrhenius plot deduced that $\lambda$ of hydroquinone moiety is ca. 1.3-1.4 eV irrespectively of alkyl chain length of the electroactive SAM.

• 한국생물공학회:학술대회논문집
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• 2005.04a
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• pp.18-18
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• 2005

Photoinduced electron transport process in nature such as photoelectric conversion and long-range electron transfer in photosynthetic organisms are known to occur not only very efficiently but also unidirectionally through the functional groups of biomolecules. The basic principles in the development of new functional devices can be inspired from the biological systems such as molecular recognition, electron transfer chain, or photosynthetic reaction center. By mimicking the organization of the biological system, molecular electronic devices can be realized $artificially^{1)}$. The nano-fabrication technology of biomolecules was applied to the development of nano-protein chip for simultaneously analyzing many kinds of proteins as a rapid tool for proteome research. The results showed that the self-assembled protein layer had an influence on the sensitivity of the fabricated bio-surface to the target molecules, which would give us a way to fabricate the nano-protein chip with high sensitivity. The results implicate that the biosurface fabrication using self-assembled protein molecules could be successfully applied to the construction of nanoscale bio-photodiode and nano-protein chip based on electrical detection.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.317-317
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• 2010

This paper reports syntheses of $TiO_2$ nanocubes and theirs application to DSSC. We synthesized $TiO_2$ nanocubes via solvothermal method using titanium isopropoxide (TTIP) and tetramethylammoiumhydroxide (TMAH). By adding longer alkyl chain ammonium hydroxide that slowed down the growth rate of the crystal, $TiO_2$ nanocubes were obtained with average particle size in the range of 40 nm to 70 nm. By TEM investigation, each particle was found to be single crystal of anatase having six-faces of (001) and {100} crystallographic planes truncated by {101} series of planes, which are clearly distinguishable from spherical nanoparticles. Among various application, utilizing nanocubes as photo-electrode in dye-sensitized solar cell, we investigated photo-electron conversion performances in comparison with spherical shaped $TiO_2$ nanoparticles by I-V characteristics and IPCE measurements, etc.. Photocurrent-transient analysis revealed that $TiO_2$ nanocubes have a higher transient electron transfer rate by more than 10 times compared with spherical particles of similar size. Fast electron transport along the cube edges having small curvature was suggested as a plausible origin of high diffusion coefficient of electron in nanocube $TiO_2$.

• Journal of Photoscience
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• v.7 no.4
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• pp.143-148
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• 2000

Studies have been conducted to explore single electron transfer(SET) promoted photocyclization of ($\omega$-phthalimidoalkoxy)acetic acids(alkoxy=ethoxy, n-propoxy and n-butyloxy). Photocyclizations occur in methanol or acetone in high yields to produce cyclized products in which phthalimide carbonyl carbon is bonded to the carbon of side chain in place of the carboxylic group. These photocyclizations are thought to proceed through pathways involving intramolecular SET from oxygen in the $\alpha$-carboxymethoxy groups to the singlet excited state phthalimide moieties followed by decarboxylation of the intermediate $\alpha$-carboxymethoxy cation fadicals and cyclizations by radical coupling. The photocyclizations occur ca. three times faster in both methanol or acetone with one equivalent of sodium hydroxide added to the reactions and occur slower in acetone than in methanol. The efficient and regiselective cyclization reactions observed for photolyses in methanol represent synthetically useful processes for construction of heterocyclic compounds.