• Bulletin of the Korean Chemical Society
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• 제30권9호
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• pp.2051-2056
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• 2009

The rate constants of alkaline fading of malachite green ($MG^+$) was measured in the presence of nonionic (TX-100), cationic (DTAB) and anionic (SDS) surfactants. This reaction was studied under pseudo-first-order conditions at 283∼303 K. The rate of fading reaction showed noticeable dependence on the electrical charge of the used surfactants. It was observed that the reaction rate constants were increased in the presence of TX-100 and DTAB and decreased in the presence of SDS. According to Hughs-Ingold rules for nucleophilic substitution reactions, the electric charge of MG/surfactant compound along with decrease in dielectric constant of $MG^+$ micro-environment in this compound varies the rate of fading reaction. Binding constants of surfactant molecules to $MG^+$ were calculated using cooperativity, pseudo-phase ion exchange and classical models and the related thermodynamic parameters were obtained by classical model. The results show that the binding of $MG^+$ to TX-100 is exothermic and binding of $MG^+$ to DTAB and SDS in some concentration ranges of the used surfactants is endothermic and in the other ones is exothermic.

• Journal of Microbiology and Biotechnology
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• 제22권8호
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• pp.1118-1126
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• 2012

Four putative GH12 genes were found in the Fusarium graminearum genome. The corresponding proteins were expressed in Escherichia coli, purified, and evaluated. FGSG_05851 and FGSG_11037 displayed high activities towards xyloglucan ($V_{max}$ of 4 and $11{\mu}mol/min$, respectively), whereas FGSG_07892 and FGSG_16349 were much less active with this substrate (0.081 and $0.004{\mu}mol/min$, respectively). However, all four of these enzymes had a similar binding affinity for xyloglucan. Xyloglucan was the substrate preferred by FGSG_05851, in contrast to the three other enzymes, which preferred ${\beta}$-glucan or lichenan. Therefore, FGSG_05851 is a xyloglucan-specific glucanase (E.C. 3.2.1.151) rather than an endoglucanase (E.C. 3.2.1.4) with broad substrate specificity. FGSG_11037 displayed a peculiar behavior in that the xyloglucan binding was highly cooperative, with a Hill coefficient of 2.5. Finally, FGSG_05851 essentially degraded xyloglucan into hepta-, octa-, and nonasaccharides, whereas the three other enzymes yielded hepta- and octa-saccharides as well as larger molecules.

• BMB Reports
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• 제29권1호
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• pp.1-10
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• 1996

The binding interaction of ethidium to a series of synthetic deoxyoligonucleotides containing a B-Z junction between left-handed Z-DNA and right-handed B-DNA, was studied. The series of deoxyoligonucleotides was designed so as to vary a dinucleotide step immediately adjacent to a B-Z junction region. Ethidium binds to the right-handed DNA forms and hybrid B-Z forms which contain a B-Z junction, in a highly cooperative manner. In a series of deoxyoligonucleotides, the binding affinity of ethidium with DNA forms which were initially hybrid B-Z forms shows over an order of magnitude higher than that with any other DNA forms, which were entirely in B-form DNA The cooperativity of binding isotherms were described by an allosteric binding model and by a neighbor exclusion model. The binding data were statistically compared for two models. The conformation of allosterically converted DNA forms under binding with ethidium is found to be different from that of the initial B-form DNA as examined by CD spectra. The ratio of the binding constant was interestingly correlated to the free energy of base unstacking and the conformational conversion of the dinucleotide. The more the base stacking of the dinucleotide is unstable, or the harder the conversion of B to A conformation, the higher the ratio of the binding constant of ethidium with the allosterically converted DNA forms and with the initial B-Z hybrid forms. DNA sequence around a B-Z junction region affects the binding affinity of ethidium. The results in this study demonstrate that ethidium could preferentially interact with unusual DNA structures.

• Macromolecular Research
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• 제14권4호
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• pp.416-423
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• 2006

The dynamic mechanical thermal properties of poly(hexamethylene terephthalate) (PHT), poly(1,4-cyclohexylenedimethylene terephthalate) (PCT) and their P(HT-co-CT) random copolymers in the amorphous state were examined as a function of temperature and frequency. All the samples exhibited two main relaxation processes in the plot of tan ${\delta}$ versus temperature: the primary ${\alpha}$-relaxation associated with the glass transition and the secondary ${\beta}$-relaxation attributed to the local segmental motions of mostly cyclohexylene rings for PCT and to cooperative motions of methylene, carboxyl, and phenylene groups for PHT. Both ${\alpha}$- and ${\beta}$-relaxation temperatures increased with increasing CT content. The activation energy of the ${\alpha}$-relaxation increased with increasing CT content, whereas that of the ${\beta}$-relaxation decreased. The sub-glassy secondary ${\beta}$-relaxation processes of PCT and PHT were investigated in terms of the cooperativity of main-chain segmental motions.

• 유변학
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• 제9권4호
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• pp.163-173
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• 1997

Polystyrene/polycarbonate 조성이 약 50/50인 3종류의 Poly(carbonate-g-styrene) 공중합체의 동적 탄성율, E*($\omega$)와 동적 스트레인-광학계수 O*($\omega$)을 유리전이 영역부근의 여러온도에서 동시에 측정하여 연구하였다. 두 개의 공중합체는 각각의 스티렌 그라프트쇄 에 5, 10 wt%의 MAH를 함유하고 있다. 이들 공중합체의 E*($\omega$)와 O*($\omega$)완화거동과 그라 프트 공중합체의 상용성과 연관하여 비교 고찰하였다. 공중합체들의 E*($\omega$)는 전형적인 무 정형 고분자의 유리전이 완하거동을 보였으며 정성적인 차이를 발견할수 없었다. 그러나 고 강도의 단일 tan$\delta$분산의 저주파수 영역에 미세분산을 나타내, 공중합체는 2상으로 분리되 어 있음이 추정되엇다. 폴리스티렌 그라프트체에 무수 말레인산 함유량이 증가함에 따라, 저 주파수 영역의 미세피크가 $\alpha$주분산에 병합되어 성분 고분자간의 상호 형동성이 증가함을 알수 있었다. 3공중합체의 유사한 기계적 특성과는 달리, 광학적 완화 스펙트럼 O*($\omega$)는 정 성적으로 명확한 차이를 보여 공중합체들의 광학완화 거동이 명확히 다름을 나타냈다. 기계 적 특성보다는 광학적 특성이 공중합체내의 성분 고분자의 미세한 완하 거동에 훨씬 민감한 응답을나타냈다. 이러한 특성적인 공중합체의 O*($\omega$)차이를 공중합체의 조성단일 고분자 PS, PC의 O*($\omega$)의 가성성을 가정하여 모사하였다 모사에서 구한 광학적 부분 기여 파라메 터를 사용하여 공중합체의 상용성을 고찰하였다.

• Molecules and Cells
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• 제38권1호
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• pp.33-39
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• 2015

The correction of disease-causing mutations by single-strand oligonucleotide-templated DNA repair (ssOR) is an attractive approach to gene therapy, but major improvements in ssOR efficiency and consistency are needed. The mechanism of ssOR is poorly understood but may involve annealing of oligonucleotides to transiently exposed single-stranded regions in the target duplex. In bacteria and yeast it has been shown that ssOR is promoted by expression of $Red{\beta}$, a single-strand DNA annealing protein from bacteriophage lambda. Here we show that $Red{\beta}$ expression is well tolerated in a human cell line where it consistently promotes ssOR. By use of short interfering RNA, we also show that ssOR is stimulated by the transient depletion of the endogenous DNA mismatch repair protein MSH2. Furthermore, we find that the effects of $Red{\beta}$ expression and MSH2 depletion on ssOR can be combined with a degree of cooperativity. These results suggest that oligonucleotide annealing and mismatch recognition are distinct but interdependent events in ssOR that can be usefully modulated in gene correction strategies.

• Bulletin of the Korean Chemical Society
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• 제21권12호
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• pp.1217-1221
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• 2000

L-alanine dehydrogenase from Bacillus subtilis exhibits allosteric kinetic properties in the presence of $ZN^{2+}$. $ZN^{2+}$ induces the binding of substrate (L-alanine) to be cooperative at pH 8.0. The effect of pH variation between pH 7.0 and pH 10.0 on the inhibition by $ZN^{2+}$ correlates with the pH effect on the $K_m$ values for L-alanine within these pH range indicating that $ZN^{2+}$ and substrate compete for the same site. No such cooperativity is induced by $ZN^{2+}$ when the reaction is carried out at pH 10. At this higher pH, $ZN^{2+}$ binds with the enzyme with lower affinity and noncompetitive with respect to L-alanine. Inhibition of L-alanine dehydrogenase by $ZN^{2+}$ depends on the ionic strength. Increase in KCI concentration reduced the inhibition, but allosteric property in $ZN^{2+}$ binding is conserved. A model for the regulatory mechanism of L-alanine dehydrogenase as a noncooperative substrate-cooperative cofactor allosteric enzyme, which is compatible in both concerted and the sequential allosteric mechanism, is proposed.

• 대한장애인치과학회지
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• 제10권1호
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• pp.38-42
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• 2014

본 증례에서는 특별한 주의가 필요한 장애인을 위한 효율적이고 전문적인 의료 전달을 위해 여러 과와의 협의를 통한 진료가 필요함을 알리고 있다. 특히 기관절개관을 가진 환자의 마취관리와 치과치료를 시행함에 있어서 전신상태 및 기관절개관에 대한 이해와 주의가 필요하다. 1. 충치치료를 주소로 내원한 22세 남환에서 기관내삽관의 활용을 통해 전신마취 하에서 치과치료를 성공적으로 전달하였다. 2. 환자는 발작의 위험성을 가지고 있었으며, 안전한 치과치료를 위해 전신마취를 행동조절의 방법으로 선택하였다. 3. 기관내삽관에는 여러 종류가 있으며, 그 중 전신마취 하에 호흡보조를 할 수 있는 종류는 커프를 가진, 이중내강의 형태로 된 관이다. 따라서, 기관내삽관을 가진 환자에서 전신마취 하 치과치료를 진행하기 위해서는 기관내삽관의 형태에 대한 적절한 평가 및 처치가 선행되어야 한다.

• 과학교육연구지
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• 제35권2호
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• pp.119-126
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• 2011

이 연구의 목적은 고등학교 화학 I 교과에서 small-scale chemistry (SSC)를 활용한 실험수업이 고등학생들의 학업성취도와 과학적 태도 및 과학에 관련된 태도에 미치는 영향을 알아보는 것이다. 연구를 위하여 고등학교 2학년 2개 학급을 실험집단과 통제집단으로 나누어 실험집단에는 SSC를 활용한 실험수업을, 통제집단에는 교과서에 제시된 전통적인 실험수업을 실시하였다. 연구 결과, SSC를 활용한 실험수업은 전통적인 실험수업에 비해 학업성취도를 향상시키는 효과가 있었으며, 과학적 태도에서는 자진성과 끈기성 및 협동성을, 과학에 관련된 태도에서는 과학의 사회적 의미와 과학교과에 대한 태도 및 과학에 대한 태도를 향상시키는 효과가 있었다. 그러므로 교육 현장에서는 SSC를 활용한 실험수업을 고등학교 화학교과에 적극적으로 활용할 필요가 있다.

• 미생물학회지
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• 제31권2호
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• pp.148-156
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• 1993

Kinetic parameters of purine nucleoside phosphorylase (PNP) from Saccharomyces cerevisiae were measured. The Michaelis constants determined for substrates of the enzyme were $ 2.0 * 10^{-4}$ M for inosine, $2.0 *10^{-3}$ M for deoxyinosine, $ 2.0 * 10^{-5}$ M for guanosine and $2.0 10 ^{-5}$ M for deoxyguanosine. According to the ratio of relative $K_{cat}$Km, substrate specificity of each nucleoside was in the order of guanosine or deoxyguanosine, inosine and deoxyinosine. Cosubstrate, phosphate, revealed downward curvature in Lineweaver-Burk plot at high concentrations, indicating a negative cooperativity between subunits. The inhibition constants for purine analogs were measured to be $ 6 * 10^{-4}$ M for formycin B as the competitive inhibitor of inosine, $ 9 * 10^{-6}$ M for guanine as the competitive inhibitor of guanosine, $2 * 10^{-4}$ M for hypoxanthine as the non competitive inhibitor of guanosine and $4.5 * 10 ^{-4}$ M for 6-mercaptopurine as the non competitive inhibitor of guanosine. Alternative substrates, guanosine, deoxyguanosine and adenosine were found to act as competitive inhibitors with Ki values o $f^ 2.0 * 10 {-5}$ M, $2.6 * 10^{-5}$ M and $8.5 * 10 ^{-4}$ M, respectively, when inosine was the variable substrate. Guanosine and deoxyguanosine were also observed as competitive inhibitors with the Ki values of $1.8 * 10^{-5}$ M and $ 3.0 * 10^{-5}$ M, respectively, when deoxyinesine was the variable substrate. The results of alternative substrate sstudies suggested that a single enzyme acted on different nucleosides, inosine, deoxyinosine, adenosine, guanosine and deoxyguanosine.e.