• Bulletin of the Korean Chemical Society
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• 제3권2호
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• pp.60-66
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• 1982

In relation to denaturation of proteins, thermally induced conformational change of poly(D-glutamic acid) was studied in the presence of poly(vinyl alcohol) at low pH, where poly(D-glutamic acid) undergoes a helix-to-${\beta}$ transition without any other polymer. In a dilute solution, poly(vinyl alcohol) enhanced the ${\alpah}-to-{\beta}_1$ transition of poly(D-glutamic acid) due to intermolecular interaction between the two polymers. On the other hand, this conformational change was interrupted to a large extent in a concentrated solution, due to the interpenetration of poly(vinyl alcohol) chain into poly(D-glutamic acid) chain which prevented the intramolecular association of poly(D-glutamic acid) chain. A conformational change from ${\beta}_1\;to\;{\beta}_2$ of poly(D-glutamic acid) was observed for the films obtained by casting during annealing the mixture solutions. The ${\beta}_2$ content in the cast film increased with increasing poly(vinyl alcohol) content in the mixture.

• Bulletin of the Korean Chemical Society
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• 제19권4호
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• pp.444-449
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• 1998

The kinetics of the formation of triplex $poly(dA){\cdot}[poly(dT)]_2$ from poly(dA)·poly(dT) and poly(dT) is examined by various optical spectroscopic methods, including absorption, circular and linear dichroism (LD) spectroscopy. In the pseudo first order condition, where the poly(dT) concentration is kept lower than that of duplex, the association of the poly(dT) is enhanced by the presence of ethidium; the rate constant is proportional to the amount of ethidium in the mixture. When the concentration of the duplex and the single strand is the same, a spectral change is explained by double exponential curves, indicating that at least two steps are involved, the fast association and slow rearrangement steps. In contrast to the pseudo first order kinetics, the association step in an equimolar condition is not affected by the presence of ethidium. In the rearrangement step, the magnitude of LD decreases with an increase in ethidium concentration, suggesting that the bending of polynucleotide around the intercalation site occurs in the rearrangement step.

• Bulletin of the Korean Chemical Society
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• 제21권10호
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• pp.1052-1054
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• 2000

Binding geometries of $[Ru(II)(110-phenanthroline)_2L]^2+$, complexes (where L = dipyrido [3,2-a:2',3'-c]phena-zine (DPPZ) or benzodipyrido[3,2-a:2',3'-c] phenazine (BDPPZ)) to poly(dG)${\cdot}$poly(dC)${\cdot}$poly(dC) + triplex DNA (CGC + triplex) has been investigated by linear dichroism and normal absorption spectroscopy. Analysis of the linear dichroism for the CGC+ triplex and $[Ru(II)(phen)_2BDPPZ]^2+$ complex indicates that the extended ligand of the metal complex lie perpendicular to the polynucleotide helix axis. Together with strong hypochromism and red shift in the interligand absorption region, we concluded that the extended BDPPZ or DPPZ ligand in-tercalated between the bases of polynucleotide. The spectral properties of the metal complexes bound to CGC+ triplex are similar to those bound to $poly(dA)[poly(dT)]^2$ triplex (Choi et al., Biochemistry 1997, 36, 214), sug-gesting that the metal complex is located in the minor groove of the CGC+ triplex.

• Bulletin of the Korean Chemical Society
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• 제18권5호
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• pp.510-514
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• 1997

We studied the interaction of 4',6-diamidino-2-phenylindole (DAPI) with single stranded poly(dA) using optical spectroscopic methods, including absorption, circular dichroism (CD), and fluorescence spectroscopy. The temperature-dependent conformation of poly(dA) was also investigated. The conformation of poly(dA) varied with temperature, which is explained by the stacking-destacking process of the adenine bases, resulting from the sugar conformation. The hypochromicity and red-shift in the absorption spectroscopy, the lack of CD change in the drag absorption region, and the fluorescence behavior, especially a great accessibility of the I2 quencher to the poly(dA)-bound DAPI, suggest that DAPI binds to the outside of poly(dA). The Job plot for the DAPI-poly(dA) mixture demonstrated that a stoichiometry of one DAPI molecule binds to the one phosphate of poly(dA).

• Journal of Plant Biology
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• 제35권4호
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• pp.415-423
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• 1992

Chlamydomonas reinhardtii 21 gr(mt+) strain의 배우체로부터 두 종류의 DNA methylase를 부분 분리하여 몇가지 기질 DNA에 대한 효소 활성을 측정하였다. DNA methylase I과 II는 동일한 pH와 ionic strength에서 서로 상이한 물리적인 성질과 서로 다른 분자량을 가지며 DNA methylase I과 II는 모두가 DNA 염기 중 adenine보다는 cytosine에 methylation을 수행하는 것으로 생각된다. 합성 DNA를 사용한 실험에서 DNA methylase I과는 달리 DNA methylase II는 poly(dA-dC)·poly(dG-dT)에서 보다 poly(dG-dC)·poly(dG-dC)의 oligonucleotide에서 더 높은 효소활성을 나타내었다. Chlamydomonas reinhardtii에서 추출한 엽록체 DNA를 기질로 사용하였을 때 DNA methylase I과 II 모두가 배우체기 보다는 영양생장기의 엽록체 DNA에 더 높은 활성을 나타내었다.

• Bulletin of the Korean Chemical Society
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• 제30권11호
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• pp.2691-2696
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• 2009

Effects of representative group II and transition metal ions on the stability of the $poly(dA){\cdot}[poly(dT)]_2$ triplex were investigated by the van’t Hoff plot constructed from a thermal melting curve. The transition, $poly(dA){\cdot}[poly(dT)]_2\;{\rightarrow}\;poly(dA){\cdot}poly(dT)\;+\;poly(dT)$, was non-spontaneous with a positive Gibb’s free energy, endothermic (${\Delta}H^{\circ}$ > 0), and had a favorable entropy change (${\Delta}S^{\circ}$ > 0), as seen from the negative slope and positive y-intercept in the van’t Hoff plot. Therefore, the transition is driven by entropy change. The $Mg^{2+}$ ion was the most effective at stabilization of the triplex, with the effect decreasing in the order of $Mg^{2+}\;>\;Ca^{2+}\;>\;Sr^{2+}\;>\;Ba^{2+}$. A similar stabilization effect was found for the duplex to single strand transition: $poly(dA){\cdot}poly(dT)\;+\;poly(dT)\;→\;poly(dA)\;+\;2poly(dT)$, with a larger positive free energy. The transition metal ions, namely $Ni_{2+},\;Cu_{2+},\;and\;Zn_{2+}$, did not exhibit any effect on triplex stabilization, while showing little effect on duplex stabilization. The different effects on triplex stabilization between group II metal ions and the transition metal ions may be attributed to their difference in binding to DNA; transition metals are known to coordinate with DNA components, including phosphate groups, while group II metal ions conceivably bind DNA via electrostatic interactions. The $Cd_{2+}$ ion was an exception, effectively stabilizing the triplex and melting temperature of the third strand dissociation was higher than that observed in the presence of $Mg_{2+}$, even though it is in the same group with $Zn_{2+}$. The detailed behavior of the $Cd_{2+}$ ion is currently under investigation.

• 대한화학회지
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• 제44권1호
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• pp.45-51
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• 2000

안트라센 유도체-합성DNA의 결합형태를 여러 가지 분광학적인 방법들을 통해서 알아보았다. Methylamine과 methylethylenediamine, 즉, 길이가 다른 곁사슬을 가지는 안트라센 유도체들이 poly[d(A-T)2]와 $poly[d(G-C)_2]$의 이중나선에 결합했을 때의 분광학적인 특성은 흡광, 원편광스펙트럼에서 봉우리의 장파장으로 이동, 흡광도의 감소를 볼 수 있으며, 선편광스펙트럼에서는 DNA흡광 영역에서 강한 음의 봉우리가 나타나는 것으로 요약할 수 있다. 이러한 현상들은 안트라센·유도체들이 위의 두 가지 DNA의 염기쌍 사이에 삽입이 되어있다는 것을 증명한다. 곁사슬의 길이에 따른 분광학적인 특성에는 별 차이가 없는 것으로 보아 곁사슬의 길이는 결합형태에 영향을 미치지 앓는다는 것을 알 수 있다. 또한, 강한 에너지의 전달이 $pdy[d(A-T)_2]$와 $poly[d(I-C)_2]$에는 일어나지만 $poly[d(G-C)_2]$에는 일어나지 않는 것으로 보아 $poly[d(G-C)_2]$의 작은 흠쪽에 돌출해 있는 아민기가 DNA염기로부터의 에너지의 전달을 방해하고 있는 것으로 판단된다.

• Bulletin of the Korean Chemical Society
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• 제18권5호
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• pp.528-534
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• 1997

The conformation and stabilization effects of acridine derivatives 9-aminoacridine, an acridine with an aminoalkyl side chain, bis acridine (two acridines linked by an aminoalkyl side chain), and proflavin in the triplex helical poly(dA)·[poly(dT)]2 were investigated by optical spectroscopies. Based on the negative LD and weak positive CD in the acridine absorption wavelength region, we concluded that the acridine moiety of all derivatives are intercalated. We also examined the melting temperatures. Of all the compounds examined, the acridine with an amino alkyl side chain had the strongest effect on the stabilization of the third strand of a poly (dA)·[poly(dT)]2 triplex. The role of the side chain, based on this observation, is discussed.

• 폴리머
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• 제29권2호
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• pp.161-165
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• 2005

Octamethylcyclotetrasiloxane$(D_4)$과 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane$(D_3^{MePh})$을 1,1,3,3,-tetramethyl-1,3-divinylsiloxane(MVS)과 평형중합시켜 dimethylsiloxane과 methylphenylsiloxane block unit를 갖는 $\alpha,\omega-vinyl$ poly(dimethyl-methylphenyl)siloxane prepolymer(VPMPS)를 제조하였으며 또한 $D_4$와 1,3,5-trimethyl-1,3,5-trifluoropropylcyclotrisiloxane $(D_3^{M3,F3P})$을 1,1,3,3-tetramethyldisiloxane과 평형중합시켜 dimethylsiloxane과 methyltrifluoropropyl siloxane block unit를 갖는 $\alpha,\omega-hydrogen$ poly(dimethyl-methyltrifluoropropyl)siloxane prepolymer(HPDMFS)를 제조하였다. VPMPS, HPDMFS, 열전도 필터 및 촉매를 고속교반기에 가하고 $130^{\circ}C$에서 컴파운딩하여 저경도 poly(organosiloxane) rubber를 제조하였으며 이의 가교밀도는 $115^{\circ}C$에서 oscillation rheometer를 이용하여 측정하였다. 열전도성 충전제로 구상 알루미나를 Horsfield's packing model에 따라 평균입자경의 분포를 조절하여 제조한 composite TC-POXR-2의 열전도도가 1.13 W/mK, 그리고 TC-POXR-4가 1.19 W/mK였으며 이는 단일입자경을 갖는 충전제를 가하여 제조한 경우보다 높은 열전도성을 나타내었다.

• 폴리머
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• 제29권2호
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• pp.156-160
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• 2005

Octamethylcyclotetrasiloxane$(D_4)$과 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane$(D_3^{Me,Ph)$을 1,1,3,3-tetramethyl-1,3-divinyldisiloxane(MVS)과 평형중합시켜 실리콘의 Si원자에 dimethyl 및 methylphenyl기가 도입된 $\alpha,\omega-vinyl$ poly(dimethyl-methylphenyl) siloxane prepolymer(VPMPS)를 제조하였으며, 또한 $D_4$와 1,3,5-trimethylcyclotrisiloxane$(D_3^:Me,H})$을 1,1,3,3-tetramethyldisiloxane(MS)와 평형중합시켜 Si원자에 dimethyl 및 methylhydrogen기가 도입된 $\alpha,\omega-hydrogen$ poly (dimethyl-methyl) siloxane prepolymer(HPDMS)를 제조하였다. Poly(acrylic acid)(PAA)을 chelating agent로 하여 nickel(II) nitrate와 iron(III) nitrate를 솔-젤 방법으로 PAA 금속염을 제조하고 이틀을 소결시켜 nickel ferrite 나노 입자를 제조하였다. 제조한 nickel ferrite는 XRD 패턴으로 확인하고 입자의 크기를 TEM으로 측정하였다 1,3-Divinyltetramethyldisilazane(VMS)으로 표면처리한 나노 실리카, nickel ferrite, VPMPS, HPDMS 및 촉매를 고속 교반기에 가하고 $130^{\circ}C$에서 컴파운딩하여 poly(organosiloxane) rubber nanocomposites를 제조하였다. Nickel ferrite 함유한 nanocomposite, POX-30과 POX-50을 각각 제조하였으며 이들의 기계적 및 열전도 특성 그리고 체적 저항을 측정하였다.