• Bulletin of the Korean Chemical Society
• /
• 제28권5호
• /
• pp.730-736
• /
• 2007

The interaction of a polyoxometal (POM), K6SiW11Co(H2O)O39.10H2O (K6) as a Keggin, with human serum albumin (HSA) was studied by different methods and techniques. Binding studies show two sets of binding sites for interaction of POM to HSA. Binding analysis and isothermal calorimetery revealed that, the first set of binding site has lower number of bound ligand per mole of protein (ν), lower Hill constant (n), higher binding constant (K), more negative entropy (ΔS) and more electrostatic interaction in comparison to the second set of binding site. In addition, differential scanning calorimetery (DSC) and spectrophotometery data showed that, there are two energetic domains. The first domain is less stable (lower Tm and Cp) which corresponds to the tail segment of HSA and another with more stability is related to the head segment of HSA. Polyoxometal also decreases the stability of protein as Tm, secondary and tertiary structure as well as quenching of the fluorescence decrease. On other hand, perturbations in tertiary structure are more than secondary structure.

• 한국연소학회:학술대회논문집
• /
• 한국연소학회 2007년도 제34회 KOSCO SYMPOSIUM 논문집
• /
• pp.191-196
• /
• 2007

The enhancement of flame stability in coflow jets has been investigated experimentally by observing the liftoff behaviors of nonpremixed propane and methane flames in the electric fields. The liftoff or blowoff velocities has been measured in terms of the applied AC voltages and frequency. The experimental results showed that the liftoff velocity could be extended significantly just by applying the high voltage to the central fuel nozzle both for propane and methane. As increasing the applied voltage, the liftoff velocity increases almost linearly with the applied voltage and have its maximum value at certain applied voltage. After that, the liftoff velocity showed decrease with the applied voltage. Through the experimental observation, we found that the liftoff velocity could be correlated well with the applied voltage and frequency in the linearly increasing regime. And after having maximum in the liftoff velocity, it was observed that the liftoff velocity decreases with the applied voltage irrespective of AC frequencies. To visualize the change of flame structure with electric fields, planar laser induced fluorescence technique was adopted, and the enhancement of flame stability has been explained based on the flame structural change in electric fields.

• Bulletin of the Korean Chemical Society
• /
• 제34권6호
• /
• pp.1637-1642
• /
• 2013

We carried out the melt copolymerization reactions of 1,2-bis(diethylamino)tetramethyldisilane with several aryldiols such as, 4,4'-biphenol, 4,4'-isopropylidenediphenol, 9H-fluoren-9,9-dimethanol, and 4,4'-(9-fluorenylidene) bis(2-phenoxyethanol) to afford poly[oxy(arylene)oxy(tetramethyldisilylene)]s containing fluorescent aromatic chromophore groups in the polymer main chain: poly[oxy(4,4'-biphenylene)oxy(tetramethyldisilylene)], poly[oxy{(4,4'-isopropylidene) diphenylene}oxy(tetramethyldisilylene)], poly[oxy(9H-fluorene-9,9-dimethylene) oxy(tetramethyldisilylene)], and poly[oxy{4,4'-(9-fluorenylidene)bis(2-phenoxyethylene)}oxy(tetramethyldisilnylene)]. These prepared materials are soluble in common organic solvents such as $CHCl_3$ and THF. The obtained polymers were characterized by several spectroscopic methods such as $^1H$, $^{13}C$, and $^{29}Si$ NMR. Further, FTIR spectra of all the polymers exhibited characteristic Si-O stretching frequencies at 1014-1087 $cm^{-1}$. These polymeric materials in THF showed strong maximum absorption peaks at 268-281 nm, strong maximum excitation peaks at 263-291 nm, and strong maximum fluorescence emission bands at 314-362 nm due to the presence of tetramethyldisilylene and several arylene chromophores in the polymer main chain. TGA thermograms indicated that most of the polymers were stable up to $200^{\circ}C$ with a weight loss of 3-16% in nitrogen.

• Bulletin of the Korean Chemical Society
• /
• 제32권4호
• /
• pp.1303-1309
• /
• 2011

Melt copolymerization reactions of bis(diethylamino)tetramethyldisiloxane with several aryldiols were carried out to afford poly(carbotetramethyldisiloxane)s containing fluorescent aromatic chromophore groups in the polymer main chain: poly{oxy(4,4'-biphenylene)oxytetramethyldisiloxane}, poly{oxy(1,4-phenylene)oxytetramethyldisiloxane}, poly[oxy{(4,4'-isopropylidene)diphenylene}oxytetramethyldisiloxane], poly[oxy{(4,4'-hexafluoroisopropylidene)diphenylene}oxytetramethyldisiloxane], poly{oxy(2,6-naphthalene)oxytetramethyldisiloxane}, poly[oxy{4,4'-(9-fluorenylidene)diphenylene}oxytetramethyldisiloxane], poly{oxy(fluorene-9,9-dimethylene)oxytetramethyldisiloxane}, and poly[oxy{4,4'-(9-fluorenylidene)bis(2-phenoxyethylene)}oxytetramethyldisiloxane]. These materials are soluble in common organic solvents such as $CHCl_3$ and THF. The FTIR spectra of all the polymers exhibit the characteristic Si-O-C stretching frequencies at 1021-1082 $cm^{-1}$. In the THF solution, the polymeric materials show strong maximum absorption peaks at 215-311 nm, with strong maximum excitation peaks at 250-310 nm, and strong maximum fluorescence emission bands at 310-360 nm. TGA thermograms indicate that most of the polymers are stable up to $200^{\circ}C$ with a weight loss of less than 10% in nitrogen.

• Bulletin of the Korean Chemical Society
• /
• 제28권7호
• /
• pp.1175-1182
• /
• 2007

A series of new organic semiconductors hexyl end-capped thiophene-anthracene oligomers containing the anthracene moiety in the center of the oligomers are synthesized. The target oligomers have been obtained by Stille coupling reactions as key step reactions. The synthesized thiophene-anthracene oligomers were characterized by 1H-NMR, 13C-NMR and high-resolution mass spectroscopy, respectively. All of the oligomers are soluble in chlorinated solvents. Their optical, thermal and electrochemical properties were measured. The hexyl end-capped oligomers and their unsubstituted oligomers exhibit the same absorption behavior in dilute toluene solution. Hexyl end-capped bis-terthienylanthracene oligomer is observed to show liquid crystalline mesophase at 166 oC in heating process. The thermal analyses as well as the electrochemical measurement data indicate that the designed materials show better thermal and oxidation stability than the corresponding oligothiophenes without anthracene core. Fluorescence lifetimes and fluorescence quantum yields of the thiophene-anthracene oligomers are measured to be 10-14 ps and 3.4-9.9 × 10?3 which are much shorter and lower than those of oligothiophenes respectively.

• Bulletin of the Korean Chemical Society
• /
• 제33권6호
• /
• pp.2031-2036
• /
• 2012

Melt copolymerization reactions of several bis(diethylamino)silane derivatives, bis(diethylamino)methylphenylsilane, bis(diethylamino)methyloctylsilane, 1,2-bis(diethylamino)tetramethyldisilane, and 1,3-bis(diethylamino) tetramethyldisiloxane, with 2,7-dihydroxyfluoren-9-one were carried out to yield poly[oxy(2,7-fluoren- 9-onenylene)oxy(diorganosilylene)]s bearing the fluoren-9-one fluorescent aromatic group in the polymer main chain: poly[oxy(2,7-fluoren-9-onenylene)oxy(methylphenylsilylene)], poly[oxy(2,7-fluoren-9-onenylene) oxy(methyloctylsilylene)], poly[oxy(2,7-fluoren-9-onenylene)oxy(tetramethyldisilylene)], and poly[oxy- (2,7-fluoren-9-onenylene)oxy(tetramethyldisiloxanylene)]. These polymeric materials are soluble in common organic solvents such as $CHCl_3$ and THF. FTIR spectra of all the materials reveal characteristic Si-O-C stretching frequencies at 1012-1018 $cm^{-1}$. In the THF solution, the prepared materials show strong maximum absorption peaks at 258-270 nm, strong maximum excitation peaks at 260-280 nm, and strong maximum fluorescence emission bands at 310-420 nm. TGA thermograms suggest that most of the polymers are essentially stable to $200^{\circ}C$ without any weight loss and up to $300^{\circ}C$ with only a weight loss of less than 5% in nitrogen.

• 한국응용과학기술학회지
• /
• 제18권2호
• /
• pp.118-126
• /
• 2001

Micelle formation and adsorption at the $Ti0_{2}$ interface of a series of polystyrene-polythylene oxide(PS-PEO) block copolymer in aqueous solution was studied using fluorescence probing and small-angle X-ray methods. Further, the stability of aqueous $Ti0_{2}$ dispersion in the presence of copolymer was investigated by microelectrophoresis, optical density and sedimentation measurements. The dissolution of pyrene as fluorescent probe in aqueous surfactant solution leads to a slow decrease of the $I_{1}/I_{3}$ ratio, as the copolymer concentration increase; $I_{1}$ and $I_{3}$ are respectively the intensities of the first and third vibrionic peaks in the pyrene fluorescence emission. The behaviour was due to the characteristics of the copolymers and/or to the copolymer association efficiency in water. Moreover, the adsorption at the plateau level increases with decreasing PEO until chain length. The zeta potential of $TiO_{2}$ particles decreases with increasing copolymer concentration and reaches a plateau value. Finally, stabilization using block copolymers was more effective with samples having higher weight fractions of PS block.

• 생명과학회지
• /
• 제12권4호
• /
• pp.464-468
• /
• 2002

대장균 트립토판 중합효소(tryptophan synthase) $\alpha$ 소단 위체의 96번, 139번 과 258번 자리를 돌연변이 시킨 이중 돌연변이체 P96L/F139W, P6L/F258W와 삼중 돌연변이체 P96L/F139W/F258W의 효소 활성도와 형광 분광계를 이용한 분광학적 성질을 조사하였다. 이중 돌연변이체의 효소 활성도는 야생형과 유사하나 삼중 돌연변이체는 40% 감소된 활성도를 가진다. P96L/F139W 와 P96L/F258W의 형광세기는 야생형에 비해 감소하였으나 P96L/F139W/F258W는 야생형에 비해 증가하였다. 효소 활성도와 형광 결과는 96번의 치환이 8번 알파구조와 4번 베타 구조와 4번 알파구조 사이의 loop의 안정성에 영향을 준 것을 나타낸다. 이 결과로부터 P96L/F139W/F258W는 야생형과 다른 3차 구조를 가지나 139번과 258면 주위는 더 조밀한 구조를 가지고 있다는 것을 보여준다.

• Plant Biotechnology Reports
• /
• 제5권2호
• /
• pp.169-175
• /
• 2011

In this study, the JIP test was exploited to assess drought-tolerance of transgenic rice overexpressing OsNAC10. Two types of promoters, RCc3 (root-specific) and GOS2 (constitutive), were used to drive the transcription factor OsNAC10, a gene involved in diverse functions including stress responses. Three-month-old plants were exposed to drought for 1 week and their fluorescence kinetics was evaluated. Our results showed that drought-treated non-transgenic plants (NT) have higher fluorescence intensity at the J phase (2 ms) compared to transgenic plants, indicating a decline in electron transport beyond the reduced plastoquinone ($Q_A^-$). As manifested by negative L bands, transgenic plants also showed higher energetic connectivity and stability over NT plants under drought conditions. Also, the pool size of the end electron acceptor at the photosystem I was reduced more in NT than in transgenic plants under drought conditions. Furthermore, the transgenic plants had higher $PI_{total}$, a combined parameter that reflects all the driving forces considered in JIP test, than NT plants under drought conditions. In particular, the $PI_{total}$ of the RCc3:OsNAC10 plants was higher than that of NT plants, which was in good agreement with their differences in grain yield. Thus, the JIP test proved to be practical for evaluating drought-tolerance of transgenic plants.

• BMB Reports
• /
• 제40권4호
• /
• pp.453-458
• /
• 2007

Bacterial luciferase is a heterodimeric enzyme, which catalyzes the light emission reaction, utilizing reduced FMN (FMNH2), a long chain aliphatic aldehyde and $O_2$, to produce green-blue light. This enzyme can be readily classed as slow or fast decay based on their rate of luminescence decay in a single turnover. Mutation of Glu175 in $\alpha$ subunit to Gly converted slow decay Xenorhabdus Luminescence luciferase to fast decay one. The following studies revealed that changing the luciferase flexibility and lake of Glu-flavin interactions are responsible for the unusual kinetic properties of mutant enzyme. Optical and thermodynamics studies have caused a decrease in free energy and anisotropy of mutant enzyme. Moreover, the role of Glu175 in transition state of folding pathway by use of stopped-flow fluorescence technique has been studied which suggesting that Glu175 is not involved in transition state of folding and appears as surface residue of the nucleus or as a member of one of a few alternative folding nuclei. These results suggest that mutation of Glu175 to Gly extended the structure of Xenorhabdus Luminescence luciferase, locally.