• 한국자기공명학회논문지
• /
• 제8권1호
• /
• pp.55-61
• /
• 2004

Biosupramolecular systems such as biological membranes usually fluid under physiological conditions$^1$. Therefore, solid-state NMR has been used to investigate biosupramolecular systems. But solid-state NMR spectra contain a large number of overlapping resonances and are rather difficult to analyze. These problem has to be overcome by selective isotope labeling. We constructed a deuterium NMR probe for AM400 NMR spectrometer, which is mainly used for liquid samples. To overcome the fluidity problem, a saddle type coil was designed. The efficiency was systematically investigated for two kinds of coil geometry, solenoid and saddle types. Our results suggest that solenoids are superior to saddle type coils in the sensitivity. However, the letter fits better to fluid samples such as biosupramolecular systems.

• Bulletin of the Korean Chemical Society
• /
• 제11권5호
• /
• pp.435-438
• /
• 1990

Primary and secondary ${\alpha}$-deuterium kinetic isotope effects are determined with deuterated aniline nucleophiles in the nucleophilic substitution reactions of benzyl benzenesulfonates and 1-phenylethyl benzenesulfonates in acetonitrile at 30.0^{\circ}C. The $k_H/k_D$ values support our previous conclusions regarding the transition state structures proposed for the two reactions based on the cross-interaction constants ${\rho}_{ij}$; the former is a typical $S_N2$ reaction whereas in the latter the four-center transition state may be involved.

• Bulletin of the Korean Chemical Society
• /
• 제19권12호
• /
• pp.1334-1336
• /
• 1998

Kinetic studies are carried out on the reactions of 2-chloro-2-propen-1-yl arenesulfonates with anilines and N,N-dimethylanilines in acetonitrilile at 45.0 ℃. The 2-chloro substituent is found to deactive the allyl moiety with considerable decrease in the rates. The sign and magnitude of the cross-interaction constant (ρxz 0.3) and the inverse secondary kinetic isotope effect (kH/kD 0.92) support an SN2 mechanism with a relatively tight transition state. The possibility of an SN2' mechanism can be safely precluded based on the ρxz values observed.

• 자원환경지질
• /
• 제46권2호
• /
• pp.153-163
• /
• 2013

옥천 금-은광상은 시대미상의 변성퇴적암류내에 발달된 NE 또는 NW 계열의 열극대를 충진한 2개조의 석영맥으로 구성된 열수맥상광상이다. 본 광상의 석영맥은 주로 괴상으로 산출되며 일부 각력상 및 정동구조가 관찰되고 연장성은 최소 50 m, 맥폭은 0.1에서 0.3 m 정도이다. 이들 석영맥에서 산출되는 광물은 황철석, 석영, 견운모, 녹니석 및 점토광물로 구성된 열수변질광물과 황철석, 자류철석, 유비철석, 섬아연석, 황동석 및 방연석으로 구성된 황화광물이 관찰된다. 유체포유물 자료에 의하면, 광화시기 광석광물의 침전과 관련된 균일화온도와 염농도는 각각 $184{\sim}362^{\circ}C$, 0.0~6.6 wt.% NaCl 로서 광화유체가 천수의 혼입에 의한 냉각과 희석작용이 있었음을 지시한다. 황(${\delta}^{34}S$: 0.4~8.4‰)의 기원은 주로 화성기원과 일부 모암내의 황에서 유래된 것으로 해석된다. 산소(${\delta}^{18}O$: 4.9~12.1‰)와 수소(${\delta}D$: -92~74‰) 동위원소값의 자료로 볼 때, 이 광상의 광화유체는 마그마 기원 또는 천수 기원의 유체로 생각되며 광화작용이 진행됨에 따라 기원이 다른 천수의 혼입이 작용한 것으로 해석할 수 있다.

• Bulletin of the Korean Chemical Society
• /
• 제23권2호
• /
• pp.221-224
• /
• 2002

Nucleophilic addition reactions of benzylamines (BA; $XC_6H_4CH_2NH_2$) to ethyl-${\alpha}$-cyanocinnamates (ECC;$YC_6H_4CH$=C(CN)COOEt) have been investigated in acetonitrile at $30.0^{\circ}C$. The rate is first order with respect to BA and ECC. The rate is slower than that expected from the additive effect of ${\sigma}^-$ or $R^-$ for the activating groups (CN and COOEt). Natural. bond orbital ${\pi}^{\ast}_{c=c}$ calculations show that the contribution of COOEt group may not be fully effective despite the coplanar molecular structure. The selectivity parameters including the cross-interaction constant (${\rho}_{xy}$ = -0.22) indicate that the addition occurs in a single step. The kinetic isotope effects ($k_H/k_D$=2.5-2.8) involving deuterated BA ($XC_6H_4CH_2ND_2$) nucleophiles and activation parameters (${\Delta}H^{\neq}=4{\sim}6\;kcal\;mol^{-1};{\Delta}S^{\neq}=-45{\sim}-52\;e.u.$) suggest a cyclic transition state in which N-$C_{\alpha}$ and H-$C_{\beta}$ bonds are formed concurrently.

• 자원환경지질
• /
• 제32권3호
• /
• pp.237-245
• /
• 1999

The Mujeong au-Ag hydrothermal vein type deposits occur within the Teriary igneous rocks of the Janggi basin. Ore minerals consist of pyrite, pyrrhotite, sphalertite, chalcopyrite, galena, cosalite, lillianite, argentite and electrum, and associated with epidotization, sericitization and pyritization. Fluid inclusion studies reveal that ore fluids were low saline with a simple NaCl-$H_{2}O$ system. Fluid inclusion data indicate that homogenization temperatures and salinities of fluid are 150 to $340^{\circ}C$ and 1.0 to 6.5wt.% NaCl equivalent, respectively. Sulfur isotope compositions of sulfied minerals ( ${\delta}^{34}S$=6.2 to 9.6$\textperthousand$) indicate that the ${\delta}^{34}S_{H2S}$ value of ore fluids was about 10.4$\textperthousand$. This ${\delta}^{34}S_{H2S}$ value is likely consistent with and hydrothermal sulfur, whereas the fluids were highly influenced by mixing with meteoric water. Measured and calculated oxygen and hydrogen isotope values (${\delta}^{18}O_{H2O}$=-2.7 to 3.4 $\textperthousand$, ${\delta}D_{H2O}$ = -83.6 to -52.7 $\textperthousand$) of ore forming fluids suggest mixing with hydrothermal and meteoric water. Equilibrium thermodynamic interpretation by mineral assemblages and chemistry indicates that sulfur fugacities (-log $fs_2$) ore forming fluids range from 9.0 to 12.6 atm stage II.

• Bulletin of the Korean Chemical Society
• /
• 제25권4호
• /
• pp.557-559
• /
• 2004

The aminolyses of anilinothioethers $(C_6H_5N(CH_3)CH_2SC_6H_4Z)$ in acetonitrile with benzylamines $(XC_6H_4CH_2NH_2)$ have been investigated. The rates are much lower in acetonitrile than in methanol (with aniline). The Bronsted ${\beta}_X$ values are similar but ${\beta}_Z$ values are smaller compared to those for the reactions in MeOH with anilines. The large negative ${\rho}_{XZ}({\cong}-0.8$, after correction for fall-off) value is interpreted to indicate a frontside attack $S_N2$ mechanism, in which the two oppositely changed reaction centers in the TS, $-N^{{\delta}+}{\cdots}S^{{\delta}-}-$, are in close vicinity increasing the interaction between nucleophile and leaving group. The inverse secondary kinetic isotope effects ($k_H/k_D$ < 1.0) are observed with deuterated benzylamines $(XC_6H_4CH_2ND_2)$.

• Bulletin of the Korean Chemical Society
• /
• 제32권6호
• /
• pp.1939-1944
• /
• 2011

The nucleophilic substitution reactions of bis(Y-aryl) chlorophosphates (1) with substituted anilines and deuterated anilines are investigated kinetically in acetonitrile at 35.0 $^{\circ}C$. The kinetic results of 1 are compared with those of Y-aryl phenyl chlorophosphates (2). The substrate 1 has one more identical substituent Y compared to substrate 2. The cross-interaction between Y and Y, due to additional substituent Y, is significant enough to result in the change of the sign of cross-interaction constant (CIC) from negative ${\rho}_{XY}$ = -1.31 (2) to positive ${\rho}_{XY}$ = +1.91 (1), indicating the change of reaction mechanism from a concerted $S_N2$ (2) to a stepwise mechanism with a rate-limiting leaving group departure from the intermediate (1). The deuterium kinetic isotope effects (DKIEs) involving deuterated anilines ($XC_6H_4ND_2$) show secondary inverse, $k_H/k_D$ = 0.61-0.87. The DKIEs invariably increase as substituent X changes from electron-donating to electron-withdrawing, while invariably decrease as substituent Y changes from electron-donating to electron-withdrawing. A stepwise mechanism with a rate-limiting bond breaking involving a predominant backside attack is proposed on the basis of positive sign of ${\rho}_{XY}$ and secondary inverse DKIEs.

• 자원환경지질
• /
• 제46권6호
• /
• pp.495-508
• /
• 2013

물의 $^{18}O/^{16}O$와 $^2H/H$ 조성을 레이저를 이용하여 분석하는 기술은 기존의 IRMS를 이용한 분석방식에 비해 간편한 시료 전처리, 쉬운 장비 유지보수와 현장에서도 응용이 가능하다는 장점을 가지고 있다. 현재 사용되는 레이저 방식을 이용한 물의 안정동위원소 분석은 분석원리에 따라 OA-ICOS(Off-Axis Integrated Cavity Output Spectroscopy)를 이용한 방식과 WS-CRDS(Wavelength-Scanned Cavity Ring-Down Spectroscopy)를 이용한 방식으로 구분된다. WS-CRDS 방식은 기화된 물 시료를 질소 가스를 이용해 광학 공동(optical cavity)로 이동시킨 후 특정 파장에서의 동위원소체가 가지고 있는 흡수도와 레이저를 투과시켜 광학 공동을 투과하여 나오는 레이저 신호의 감쇠시간의 비측정을 통해 수 ppb에서 수십 ppt까지의 감도로 물의 안정동위원소 조성이 측정 가능하다. 이 연구에서는 WS-CRDS 방식의 분석원리와실제 물시료를 활용하여 기기의 안정성과 동위원소비 질량분석기(Isotope Ratio Mass Spectrometry; IRMS) 방법과의 교차분석을 포함한 기기 성능평가 결과를 소개하고 수리학 분야에서 다양한 주제에 대한 적용 가능성을 제시하였다.

• 한국자기공명학회논문지
• /
• 제14권2호
• /
• pp.117-126
• /
• 2010

Hsp33 is a molecular chaperone achieving a holdase activity upon response to a dual stress by heat and oxidation. Despite several crystal structures available, the activation process is not clearly understood, because the structure inactive Hsp33 as its reduced, zinc-bound, monomeric form has not been solved yet. Thus, we initiated structural investigation of the reduced Hsp33 monomer by NMR. In this study, to overcome the high molecular weight (33 kDa), the protein was triply isotope-[$^{13}C$, $^{15}N$, $^2H$]-labeled and its inactive, monomeric state was ensured. 2D-[$^1H$, $^{15}N$]-TROSY and a series of triple resonance spectra could be successfully obtained on a high-field (900 MHz) NMR machine with a cryoprobe. However, under all of the different conditions tested, the number of resonances observed was significantly less than that expected from the amino acid sequence. Thus, a possible contribution of dynamic conformational exchange leading to a line broadening is suggested that might be important for activation process of Hsp33.