• Journal of the Korean Magnetic Resonance Society
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• v.5 no.2
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• pp.66-72
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• 2001

The noise suppression of time domain NMR data by discrete wavelet transform with high order Daubechies wavelet coefficients exhibits severe peak distortion and incomplete noise suppression near real signal. However, the fact that even a shift averaged Harr wavelet transform with a set of Daubechies wavelet coefficients (1/2, -l/2) can be used as a new and excellent tool to distinguish real peaks from the noise contaminated NMR signal is introduced. New algorithms of shift averaged Harr wavelet were developed and quantitatively evaluated in terms of threshold and signal to noise ratio (SNR).

• Journal of the Korean Magnetic Resonance Society
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• v.4 no.2
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• pp.116-124
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• 2000

Singular value decomposition (SVD) has been used during past few decades in the advanced NMR data processing and in many applicable areas. A new modified SVD, piecewise polynomial truncated SVD (PPTSVD) was developed far the large solvent peak suppression and noise elimination in U signal processing. PPTSVD consists of two algorithms of truncated SVD (TSVD) and L$_1$ problems. In TSVD, some unwanted large solvent peaks and noises are suppressed with a certain son threshold value while signal and noise in raw data are resolved and eliminated out in L$_1$ problem routine. The advantage of the current PPTSVD method compared to many SVD methods is to give the better S/N ratio in spectrum, and less time consuming job that can be applicable to multidimensional NMR data processing.

• Journal of Integrative Natural Science
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• v.6 no.2
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• pp.65-70
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• 2013

1,1-Bis(n-butyl)-2,3,4,5-tetraphenyl-1-silacyclopentadiene (3) and 1,1-bis(t-butyl)-2,3,4,5-tetraphenyl-1-silacyclopentadiene (4) are synthesized from the reaction of the versatile silole dianion (2) with n-butyl bromide and t-butyl bromide. Reduction of (3) and (4) with an excess of lithium to give 1,1-bis(n-butyl)-2,5-dilithio-2,3,4,5-tetraphenyl-1-silacyclopenta-3-enide (6) and 1,1-bis(t-butyl)-2,5-dilithio-2,3,4,5-tetraphenyl-1-silacyclopenta-3-enide (7). $^{13}C$-NMR study of two 2,5-carbodianions (6 and 7) shows tert-carbanion at 73.18 and 78.12 ppm respectively. Two bulky tert-butyl groups in (7) increase the inversion barrier at the tert-carbanion, line broadenings of tert-butyl groups in $^1H$ and $^{13}C$-NMR spectrum are observed.

• Proceedings of the KOSOMBE Conference
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• v.1993 no.11
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• pp.63-66
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• 1993

Localized NMR spectra were obtained from phantom by OSIRIS technique. The selected volume, which can be controlled by frequency and its bandwidth, was 0.125cc out of 25cc and free of contamination from outer volume. With this technique NMR spectrum of a living tissue can be obtained without biopsy. i.e. in vivo state in which the metabolism of tissue may be quite different from in in vitro state. It is expected of this technique to be useful in the study of metabolism of living tissue as well as in diagnosis of deseases.

• Bulletin of the Korean Chemical Society
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• v.20 no.10
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• pp.1149-1152
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• 1999

1H NMR spectrum of a DMF-d7 solution containing 4-aminopyrimidine and [SiW11CoIIO39]6- (SiW11Co) shows separate peaks from two linkage isomers, a and b, in which N(1) and N(3) of the pyrimidine ring are coordinated to SiW11Co, respectively. The signal from the amine group in the isomer a exhibits temperature dependence that is characteristic of a two-site exchange problem. Rates of internal rotation of the amine group were determined by simulating the NMR spectra at 5-35℃. The amine group of free 4-aminopyrimidine also shows temperature-dependent spectra at lower temperatures; rates of internal rotation at (-25)-25℃ were determined. The internal rotation of the amine group in the complex is much slower than that for free 4-aminopyrimidine, indicating that π-character of the C-N bond increases on coordination to SiW11Co. The amine group in the isomer b does not show such behavior. It is probable that hydrogen bonding between N-H and a bridging oxygen atom of SiW11Co prevents it from rotating at low temperatures.

• Analytical Science and Technology
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• v.7 no.2
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• pp.213-224
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• 1994

Several isotopomers of cyclooctanone were prepared by selective deuterium substitution. Intrinsic isotope effects on $^{13}C$ NMR chemical shifts of these isotopomers were investigated systematically at low temperature. These istope effects were discussed in relation to the preferred boat-chair conformation of cyclooctanone. Deuterium isotope effects on NMR chemical shifts have been known for a long time. Especially in a conformationally mobile molecule, isotope perturbation could affect NMR signals through a combination of isotope effects on equilibria and intrinsic effects. The distinction between intrinsic and nonintrinsic effects is quite difficult at ambient temperature due to involvement of both equilibrium and intrinsic isotope effects. However if equilibria between possible conformers of cyclooctanone are slowed down enough on the NMR time scale by lowering temperature, it should be possible to measure intrinsic isotope shifts from the separated signals at low temperature. $^{13}C$ NMR has been successfully utilized in the study on molecular conformation in solution when one deals with stable conformers or molecules were rapid interconversion occurs at ambient temperature. The study of dynamic processes in general requires analysis of spectra at several temperature. Anet et al. did $^1H$ NMR study of cyclooctanone at low temperature to freeze out a stable conformation, but were not able initially to deduce which conformation was stable because of the complexity of alkyl region in the $^1H$ NMR spectrum. They also reported the $^1H$ and $^{13}C$ NMR spectra of the $C_9-C_{16}$ cycloalkanones with changing temperature from $-80^{\circ}C$ to $-170^{\circ}C$, but they did not report a variable temperature $^{13}C$ NMR study of cyclooctanone. For the analysis of the intrinsic isotope effect with relation to cylooctanone conformation, $^{13}C$ NMR spectra are obtained in the present work at low temperatures (up to $-150^{\circ}C$) in order to find the chemical shifts at the temperature at which the dynamic process can be "frozen-out" on the NMR time scale and cyclooctanone can be observed as a stable conformation. Both the ring inversion and pseudorotational processes must be "frozen-out" in order to see separate resonances for all eight carbons in cyclooctanone. In contrast to $^1H$ spectra, slowing down just the ring inversion process has no apparent effects on the $^{13}C$ spectra because exchange of environments within the pairs of methylene carbons can still occur by the pseudorotational process. Several isotopomers of cyclooctanone were prepared by selective deuterium substitution (fig. 1) : complete deuterium labeling at C-2 and C-8 positions gave cyclooctanone-2, 2, 8, $8-D_4$ : complete labeling at C-2 and C-7 positions afforded the 2, 2, 7, $7-D_4$ isotopomer : di-deuteration at C-3 gave the 3, $3-D_2$ isotopomer : mono-deuteration provided cyclooctanone-2-D, 4-D and 5-D isotopomers : and partial deuteration on the C-2 and C-8 position, with a chiral and difunctional case catalyst, gave the trans-2, $8-D_2$ isotopomer. These isotopomer were investigated systematically in relation with cyclooctanone conformation and intrinsic isotope effects on $^{13}C$ NMR chemical shifts at low temperature. The determination of the intrinsic effects could help in the analysis of the more complex effects at higher temperature. For quantitative analysis of intrinsic isotope effects, the $^{13}C$ NMR spectrum has been obtained for a mixture of the labeled and unlabeled compounds because the signal separations are very small.

• YAKHAK HOEJI
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• v.18 no.2
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• pp.161-164
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• 1974

m-Hydroxyaniline was reported to be converted to m-methoxyaniline with dimethylsulfate. However, while repeating the experiment with the same reaction condition, it was learned that the reaction product was not m-methoxyaniline but m-methoxy dimethylaniline. It was confirmed with nmr and ir spectrum and the comparison of bp and mp of the derivatives. Elemental analyses of the derivatives were also consistant with the fact N-dimethylation along with O-methylation occurred.

• Progress in Medical Physics
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• v.12 no.1
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• pp.31-39
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• 2001

NMR spectroscopy enables us to measure the molar concentration of the metabolites in the organisms, and this technique is the only method to measure the concentration non-invasively. The proton NMR spectroscopy has been used to study the biochemical changes in human as well as in animal brain. MRI uses the proton densities and its relaxation times for reconstructing images, but MRS gives the biochemical changes inside the body. NMR spectroscopy could provide the information which MRI and CT could not, and this makes NMR spectroscopy more useful in diagnosing diseases. This study was tried to develop the quantitation of the molar concentration of the metabolites in the brain using the proton MR spectroscopy. The spectra of each metabolites was obtained, and the proton MR spectra was obtained from the insula gray matter areas of the 16 volunteers. And this spectra was analyzed to estimated the molar concentrations of the metabolites in the region. The results showed the very similar to those of the others.

• Journal of the Korean Wood Science and Technology
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• v.37 no.1
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• pp.114-120
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• 2009

The bark of Populus alba ${\times}$ glandulosa was collected, air-dried and extracted with 70% aqueous acetone. Then it was successively partitioned with n-hexane, $CH_2Cl_2$, EtOAc and $H_2O$. Repeated Sephadex LH-20 column chromatography and preparative TLC on the EtOAc soluble fraction gave a grandidentatin isomer. The structure was elucidated as grandidentatin A (cis-2-hydroxycyclohexyl 6-O-p-coumaroyl-${\beta}$-D-glucopyranoside) on the basis of spectroscopic evidences such as $^1H$-NMR, $^{13}C$-NMR, 2D-NMR and MALDI TOF-MS spectrum followed by acid hydrolysis. Grandidentatin A was identified here for the first time in Populus alba ${\times}$ glandulosa bark, and to the bset of our knowledge it has not been reported in any other literature.

• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.69-69
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• 2003

Human CD99 is a ubiquitous 32-kDa transmembrane protein encoded by the mic2 gene. The major cellular functions of CD99 protein are related to homotypic cell adhension, apoptosis, vesicular protein transport, and differentiation of thymocytes or T cells. Recently it has been reported that expression of a splice variant of CD99 transmembrane protein (Type I and Type II) increases invasive ability of human breast cancer cells. To understand structural basis for cellular functions of CD99 (Type I), we have initiated studies on hCD99$^{TMcytoI}$ and hCD99$^{cytoI}$ using circular dichroism (CD) and multi-dimensional NMR spectroscopy. CD spectrum of hCD99$^{TMcytoI}$ in the presence of 200mM DPC and CHAPS displayed an existence $\alpha$-helical conformation. The solution structure of hCD99$^{cytoI}$ determined by NMR is composed of one N-terminal $\alpha$-helix, $\alpha$A, two C-terminal short $\alpha$-helix segments, $\alpha$B and $\alpha$C. While $\alpha$A and $\alpha$B are connected by the long flexible loop, $\alpha$B and $\alpha$C connected by type III$\beta$-turn. Although it has been rarely figured out the correlation between structure and functional mechanism of hCD99$^{TMcytoI}$ and hCD99$^{cytoI}$, there is possibility of dimerization or oligomerization. In addition, the feasible mechanism of hCD99$^{cytoI}$ is that it could have intramolecular interaction between the N- and C- terminal domain through large flexible AB loop.