• Bulletin of the Korean Chemical Society
• /
• 제31권10호
• /
• pp.2877-2883
• /
• 2010

The folding kinetics of $WT^*$ ubiquitin variant with valine to alanine mutation at sequence position 26 (HubWA) was studied by stopped-flow fluorescence spectroscopy. While unfolding kinetics showed a single exponential phase, refolding reaction showed three exponential phases. The semi-logarithmic plot of urea concentration vs. rate constant for the first phase showed v-shape pattern while the second phase showed v-shape with roll-over effect at low urea concentration. The rate constant and the amplitude of the third phase were constant throughout the urea concentrations, suggesting that this phase represents parallel process due to the configurational isomerization. Interestingly, the first and second phases appeared to be coupled since the amplitude of the second phase increased at the expense of the amplitude of the first phase in increasing urea concentrations. This observation together with the roll-over effect in the second folding phase indicates the presence of intermediate state during the folding reaction of HubWA. Quantitative analysis of Hub-WA folding kinetics indicated that this intermediate state is on the folding pathway. Folding kinetics measurement of a mutant HubWA with hydrophobic core residue mutation, Val to Ala at residue position 17, suggested that the intermediate state has significant amount of native interactions, supporting the interpretation that the intermediate is on the folding pathway. It is considered that HubWA is a useful model protein to study the contribution of residues to protein folding process using folding kinetics measurements in conjunction with protein engineering.

• Carbon letters
• /
• 제4권1호
• /
• pp.31-35
• /
• 2003

The specific adsorption behaviors of activated carbons (ACs) treated with 30 wt% $H_3PO_4$ or NaOH were investigated in the removals of NO or $NH_3$. The acid and base values were determined by Boehm's titration method. And, the surface properties of ACs were studied by FT-IR and XPS analyses. Also, $N_2/77K$ adsorption isotherm characteristics, including the specific surface area and micropore volume were studied by BET and t-plot methods, respectively. From the adsorption tests of NO and $NH_3$, it was revealed in the case of acidic treatment on ACs that the $NH_3$ removal was more effective due to the increase of acidic functional groups in carbon surfaces. Also, the NO removal was increased, in the case of basic treatment, due to the improvement of basic functional groups, in spite of significant decreases of BET's specific surface area and total pore volume. It was found that the adsorption capacity of ACs was not only determined by the textural characteristics but also correlated with the surface functional groups in the acid-base intermolecular interactions.

• 한국자기공명학회논문지
• /
• 제19권1호
• /
• pp.1-10
• /
• 2015

Refinements with atomistic molecular dynamics (MD) simulation have contributed to improving the qualities of NMR structures. In most cases, the calculations with atomistic MD simulation for NMR structures employ generalized-Born implicit solvent model (GBIS) to take into accounts solvation effects. Developments in algorithms and computational capacities have ameliorated GBIS to approximate solvation effects that explicit solvents bring about. However, the quantitative comparison of NMR structures in the latest GBIS and explicit solvents is lacking. In this study, we report the direct comparison of NMR structures that atomistic MD simulation coupled with GBIS and water molecules refined. Two model proteins, GB1 and ubiquitin, were recalculated with experimental distance and torsion angle restraints, under a series of simulated annealing time steps. Whereas the root mean square deviations of the resulting structures were apparently similar, AMBER energies, the most favored regions in Ramachandran plot, and MolProbity clash scores witnessed that GBIS-refined structures had the better geometries. The outperformance by GBIS was distinct in the structure calculations with sparse experimental restraints. We show that the superiority stemmed, at least in parts, from the inclusion of all the pairs of non-bonded interactions. The shorter computational times with GBIS than those for explicit solvents makes GBIS a powerful method for improving structural qualities particularly under the conditions that experimental restraints are insufficient. We also propose a method to separate the native-like folds from non-violating diverged structures.

• 비파괴검사학회지
• /
• 제34권6호
• /
• pp.419-427
• /
• 2014

Nonlinear features of ultrasonic waves are more sensitive to the presence of a fatigue crack than their linear counterparts are. For this reason, the use of nonlinear ultrasonic techniques to detect a fatigue crack at its early stage has been widely investigated. Of the different proposed techniques, laser nonlinear wave modulation spectroscopy (LNWMS) is unique because a pulse laser is used to exert a single broadband input and a noncontact measurement can be performed. Broadband excitation causes a nonlinear source to exhibit modulation at multiple spectral peaks owing to interactions among various input frequency components. A feature called maximum sideband peak count difference (MSPCD), which is extracted from the spectral plot, measures the degree of crack-induced material nonlinearity. First, the ratios of spectral peaks whose amplitudes are above a moving threshold to the total number of peaks are computed for spectral signals obtained from the pristine and the current state of a target structure. Then, the difference of these ratios are computed as a function of the moving threshold. Finally, the MSPCD is defined as the maximum difference between these ratios. The basic premise is that the MSPCD will increase as the nonlinearity of the material increases. This technique has been used successfully for localizing fatigue cracks in metallic plates.

• 영미문화
• /
• 제18권3호
• /
• pp.93-113
• /
• 2018

This paper examines C. S. Lewis's view of myth and religion in the mid-twentieth century England. Lewis provided his social and cultural criticisms for materialistic contemporary culture and a decline in religiosity in Till We Have Faces (1956). Under the agitated influence of the time period and social movements in which he had lived, Lewis's writing uncovers dynamic interactions with the traumatized world aroused by two World Wars and the apocalyptic aura of an upcoming new world. The narrative of Lewis's novel Till We Have Faces, in a larger perspective, presents the mixtures of mythic motifs and nostalgia. On the plot basis, the novel depicts contemporary spiritual blindness and national dissociations. Many criticisms of Lewis have not been exploring the author's keen knowledge of the modern society because of his conspicuous depictions of evil and grace involving religious and medievalist views. Nonetheless, the paper explores how Lewis's apocalyptical views, related to turmoil and nostalgia, uncover complexities of his religious dilemmas between restoring the deteriorated status of the privileged. Ultimately, it analyzes Lewis's consciousness of the social changes related to the larger, more often than not psychological, context of redefining the national empire.

• 한국작물학회지
• /
• 제8권1호
• /
• pp.1-4
• /
• 1970

단백자원으로서 가장 중요한 작물인 대두의 자실수량, 단백 및 유분수량이 품종별로 파종기 및 석회시용량의 차이에 따라서 어떻게 영양을 받는가를 구명하기 위하여 우리나라 중부지방의 주요대두품종 충북백, 육우 003 및 장단백목을 공시하여 파종기를 5월 22일(대두단작재배) 및 6월 11일(맥후작재배) 및 7월 1일 (만파재배)로 달리하고 석회시용량을 10a당, 0.5kg, 100kg으로 다르게 처리하여 본 시험을 1969년 서울대학교 농과대학 부속농장에서 실시하였다. 본 시험성적에서 나타난 대두의 수량형질, 단백 및 유분수량에 대한 결과를 요약하면 다음과 같다. 1. 공시된 품종중 육우003의 자실수량이 가장높았다는데 이는 육우003에 주당협수가 다른 품종보다 현저히 많다는 데에서 기인되었다. 단백함량은 충북백>육우003>장단백목의 순위였고 지유함량은 장단백목>충북백>육우003의 순위였으나 단위면적당 단백수량 및 지유수량은 자실수량이 많았던 륙우003가 가장 많았다. 그러나 이와같은 품종간 수량차이는 파종기에 따라서 각각 다르게 나타나고 있으므로 설계재배에 있어서는 품종과 파종기간의 관계를 크게 고려하여야 할 것이다. 2. 제1파종기와 제2파종기간에 자실수량차이는 없었으며 만파재배인 제3파종기에서는 자실수량이 현저히 감소되었다. 이와같은 현상은 제3파종기에서 1주당협수의 감소가 현저했기 때문으로 고찰된다. 단백질함량과 지유함량은 파종기에 따라 별로 변화하지는 않았으나 단백수량 및 지유수량은 제3파종기에서 자실수량의 감소와 함께 현저히 감소하였다. 3. 석회시용량의 증가에 따라서 분지수 협수가 증가하였으며 자실수량도 증가하였다. 본 시험에서는 자실수량이 석회 100kg/10a 시요구에서 가장 높았다. 단백함량도 석회시용량을 증가함에 따라 증가하였으나 지유함량은 석회무시용구가 가장 높았다. 단백수량은 석회시용량의 증가에 따라 자실수량 및 단백함량이 같이 증가되었기 때문에 현저히 증수되었으며 지유함량은 자실수량의 증가에 의해서만 증수되었다. 4. 수량형질간의 상관관계를 보면 경장과 주당경중, 100립중 및 자실수량간에 주당경중과 주당맥수 및 자실수량간에, 주당분지수와 100립중간에, 주당협수와 자실수량간에, 100립중과 단백함량간에는 고도의 정(+)의 상관관계를 인정할수 있었으며, 주당협수와 100립중간에는 부(-)의 상관관계가 있었다.

• 생명과학회지
• /
• 제20권2호
• /
• pp.298-303
• /
• 2010

본 연구에서는 발아 후 2일된 옥수수 유식물의 뿌리 생장에 미치는 영향을 조사하였다. 5 mM에서 30 mM에 이르는 CsCl을 처리하였을 때 옥수수 뿌리와 자엽초 마디 위쪽 shoot의 생중량이 감소하였다. 뿌리의 길이 생장도 역시 동일한 농도 범위의 CsCl에 의하여 감소하였는데 CsCl을 처리할 때 60 mM의 KCl을 함께 처리하면 CsCl에 의하여 감소되었던 신장 생장이 일부 회복되었다. CsCl과 KCl의 관계를 Lineweaver-Burk plot으로 분석한 결과 10 mM - 30 mM CsCl은 KCl과 경쟁 관계에 있는 것으로 나타났지만 5 mM CsCl은 경쟁관계에서 벗어나는 것으로 나타나 주변의 CsCl 농도에 따라 KCl의 작용 모드가 다른 또 하나의 메커니즘이 존재하는 것으로 사료되었다. CsCl의 농도에 따라서 KCl과의 상호작용 모드가 달라지는 현상은 CsCl에 의하여 유도되는 옥수수뿌리 정단 하부의 횡축 팽창에서도 관찰되었다. 또한, CsCl은 10 mM 이상에서 농도 증가에 비례하여 $K^+$ transporter인 ZmKUP1의 발현을 유도하였지만 5 mM CsCl의 ZmKUP1 발현 효과는 뚜렷하게 관찰되지 않았다. 한편, CsCl 존재 하에서도 근단 분열 조직의 수축은 관찰되지 않았다. 종합하면, 외부에서 처리된 CsCl은 2일된 옥수수 유식물의 뿌리의 생중량과 신장을 감소시켰으며 정단 하부의 횡축 팽창을 유도하고 ZmKUP1의 발현을 촉진하였다. 그러나 근단 분열조직의 수축은 없었으므로 CsCl의 효과는 주로 세포 팽창과 관련되는 것으로 판단되며 $Cs^+$와 $K^+$의 경쟁 및 비경쟁적 상호작용을 모두 포함하는 복합적인 메커니즘이 존재하는 것으로 사료된다.

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

• Bulletin of the Korean Chemical Society
• /
• 제33권5호
• /
• pp.1551-1555
• /
• 2012

Second-order rate constants ($k_N$) have been measured spectrophotometrically for the reactions of benzyl 2-pyridyl carbonate $\mathbf{7}$ and $t$-butyl 2-pyridyl carbonate $\mathbf{8}$ with a series of alicyclic secondary amines in $H_2O$ at $25.0^{\circ}C$. Substrate $\mathbf{8}$ is less reactive than $\mathbf{7}$. Steric hindrance exerted by the bulky $t$-Bu group of $\mathbf{8}$ has been suggested to be responsible for the decreased reactivity. The Br${\o}$nsted-type plots for the reactions of $\mathbf{7}$ and $\mathbf{8}$ are linear with ${\beta}_{nuc}=0.49$ and 0.44, respectively, which is typical for reactions reported previously to proceed through a concerted mechanism. Aminolyses of $\mathbf{7}$ and $\mathbf{8}$ were expected to proceed through a zwitterionic tetrahedral intermediate $T^{\pm}$, which would be stabilized through an intramolecular H-bonding interaction. However, the kinetic results suggest that the reactions proceed through a concerted mechanism. The H-bonding interaction in $T^{\pm}$ has been suggested to accelerate the rate of leaving-group expulsion from $T^{\pm}$. Another factor that might accelerate expulsion of the leaving group is the "push" provided by the RO group in $T^{\pm}$ through resonance interactions. Thus, it has been concluded that the enhanced nucleofugality through the H-bonding interaction and the "push" provided by the RO group forces the reactions to proceed through a concerted mechanism.

• Bulletin of the Korean Chemical Society
• /
• 제32권4호
• /
• pp.1153-1157
• /
• 2011

A kinetic study is reported for aminolysis of S-4-nitrophenyl X-substituted thiobenzoates 3a-g in 80 mol % $H_2O$/20 mol % DMSO at $25.0{\pm}0.1^{\circ}C$. Thiol esters 3a-g are 7.8-47.6 fold more reactive than the corresponding oxygen esters (i.e., 4-nitrophenyl X-substituted benzoates 1a-g). Such reactivity order appears to be in accordance with the expectation that 4-nitrothiophenoxide in 3a-g is a better nucleofuge than 4-nitrophenoxide in 1a-g since the former is 2.64 pKa units less basic than the latter. Hammett plot for the reactions of 3a-g exhibit poor correlation coefficients ($R^2$ = 0.977-0.986) with negative deviation by substrates possessing an electrondonating group (EDG), while the Yukawa-Tsuno plots result in excellent linear correlation ($R^2$ = 0.995-0.997) with ${\rho}$ = 0.93-1.23 and r = 0.57-0.67, indicating that the negative deviation shown by substrates possessing an EDG is caused by ground-state stabilization through resonance interactions but not due to a change in ratedetermining step upon changing the nonleaving-group substituent X. The ${\rho}$ value increases as the incoming amine becomes more basic and more reactive, indicating that the RSP is not operative in the current reactions.