1H NMR Measurements of the Phase Transition of (NH₄)₃H(SO₄)₂ Single Crystals

S. H. Choi,Moohee Lee,Ae Ran Lim,K. S. Han,S. K. Kwon,S. K. Nam 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.2

$^1$H nuclear magnetic resonance (NMR) experiments have been performed in the temperature range of 30 -- 300 K at 7 T to investigate the phase-dependent nature of the dynamic network of hydrogen bonds in a ((NH₄)₃H(SO₄)₂ single crystal. The crystal has six phases, which are ferroelectric, antiferroelectric, incommensurate, antiferroelectric, ferroelastic, and superionic with the respective transition temperatures of 63, 133, 139, 256 and 413 K. The spin-lattice relaxation time, T₁, of ¹H NMR is similar for the ammonium protons and the hydrogen-bond protons over the entire range of experimental temperatures. The T₁, of ¹H NMR gradually decreases down to 120 K and starts to steeply increase below 100 K. Then, the T₁ shows an abrupt decrease below 68 K with a sharp minimum at 63 K, where the ferroelectric transition occurs. The ¹H NMR spectrum shifts to the high-frequency side at temperatures below 63 K due to the ferroelectric phase transition. This behavior of the T₁ and the spectrum confirms a dramatic change in the dynamics of hydrogen bonds associated with the ferroelectric phase transition at 63 K. $^1$H nuclear magnetic resonance (NMR) experiments have been performed in the temperature range of 30 -- 300 K at 7 T to investigate the phase-dependent nature of the dynamic network of hydrogen bonds in a ((NH₄)₃H(SO₄)₂ single crystal. The crystal has six phases, which are ferroelectric, antiferroelectric, incommensurate, antiferroelectric, ferroelastic, and superionic with the respective transition temperatures of 63, 133, 139, 256 and 413 K. The spin-lattice relaxation time, T₁, of ¹H NMR is similar for the ammonium protons and the hydrogen-bond protons over the entire range of experimental temperatures. The T₁, of ¹H NMR gradually decreases down to 120 K and starts to steeply increase below 100 K. Then, the T₁ shows an abrupt decrease below 68 K with a sharp minimum at 63 K, where the ferroelectric transition occurs. The ¹H NMR spectrum shifts to the high-frequency side at temperatures below 63 K due to the ferroelectric phase transition. This behavior of the T₁ and the spectrum confirms a dramatic change in the dynamics of hydrogen bonds associated with the ferroelectric phase transition at 63 K.

Geochemical modeling of CO₂-water-rock interactions for two different hydrochemical types of CO₂-rich springs in Kangwon District, Korea

Choi, B.Y.,Yun, S.T.,Kim, K.H.,Choi, H.S.,Chae, G.T.,Lee, P.K. Elsevier 2014 Journal of geochemical exploration Vol.144 No.1

Naturally outflowing CO<SUB>2</SUB>-rich springs are a natural analogue of the seepage of sequestered CO<SUB>2</SUB> in geological storage sites. In Kangwon district of South Korea, two hydrochemically different types of CO<SUB>2</SUB>-rich springs (i.e., Ca-HCO<SUB>3</SUB>-type and Na-HCO<SUB>3</SUB>-type) occur together in a granitic terrain. Hydrochemical and water-isotope data (i.e., δ<SUP>18</SUP>O-δD and tritium) show that Na-HCO<SUB>3</SUB>-type springs have experienced significant silicate weathering processes over a long residence time at depths, while Ca-HCO<SUB>3</SUB>-type springs were formed by the mixing of Na-HCO<SUB>3</SUB>-type springs with shallow groundwater during ascent. In this study, diverse geochemical models including mixing, ion exchange and reaction path were investigated to verify the geochemical processes accounting for the occurrence of two contrasting types of CO<SUB>2</SUB>-rich springs. The mixing and ion exchange models reveal that Ca-HCO<SUB>3</SUB>-type springs are well explained by reverse cation exchange occurring during the mixing of Na-HCO<SUB>3</SUB>-type springs with shallow groundwater. The Na-HCO<SUB>3</SUB>-type springs are well explained by the reaction path modeling including the dissolution of silicate minerals (plagioclase, K-feldspar and biotite) and the precipitation of secondary minerals (calcite, kaolinite, muscovite and Mg-beidellite), implying that dissolved carbon is sequestered by calcite precipitation (i.e., mineral trapping). However, the concentrations of K in our modeling results are far below those of K observed in Na-HCO<SUB>3</SUB>-type springs, because of the precipitation of muscovite considered in the model, suggesting the partial disequilibrium state of the aquifer during the hydrolysis of K-feldspar under high P<SUB>CO'2</SUB> conditions. This result implies that to better predict long-term CO<SUB>2</SUB>-water-rock interactions in a geological storage site with abundant K-feldspar, the secondary K-bearing minerals should be carefully predicted, because a target aquifer can be far from chemical equilibrium during the storage period. This study shows that geochemical modeling can be effectively used to predict the hydrochemical changes of groundwater during long-term CO<SUB>2</SUB>-water-rock interactions and subsequent leakage toward surface in K-feldspar rich aquifer, although it should be included in a fully coupled computational approach between fluid flow, heat transfer and reactive mass transport processes in the future research.

[ $^1H$ ] Nuclear Magnetic Resonance Study of Ferroelectric $(NH_4)_3H(SO_4)_2$

Choi, S.H.,Han, K.S.,Kwon, S.K.,Nam, S.K.,Choi, H.H.,Lee, Moo-Hee,Lim, Ae-Ran Korean Magnetic Resonance Society 2007 Journal of the Korean Magnetic Resonance Society Vol.11 No.2

[ $^1H$ ] nuclear magnetic resonance (NMR) experiments have been performed at 30 - 300 K and 7 T to investigate dynamics of hydrogen bond network in the single crystal $(NH_4)_3H(SO_4)_2$. The two proton sites, ammonium proton and hydrogen-bond proton, are identified from the $^1H$ NMR MAS spectrum at 340 K. As temperature decreases, the $^1H$ NMR spectrum shifts to the higher frequency side with a larger linewidth. The spectrum at 65 K shows a distinctive change in line shape toward the ferroelectric transition at 63 K. The measured values of $T_1$ for ammonium and hydrogen-bond protons are similar in the whole range of temperature. $T_1$ of $^1H$ NMR shows a gradual decrease down to 120 K and starts to steeply increase below 100 K. Then $T_1$ shows abrupt decrease below 70 K with a sharp minimum at 63 K, where the ferroelectric transition occurs. This temperature dependence of spectrum and $T_1$ clearly prove that the large change in the dynamics of hydrogen bond network is associated with the ferroelectric phase transition at 63 K.

PCR - RFLP 기법을 이용해 젖소개량을 위한 유전적 표지로서 K- Casein 좌위의 유전자형 분석

정의룡(E . R . Chung),김우태(W . T . Kim),최석호(S . H . Choi),임태진(T . J . Rhim),한상기(S . K . Han) 한국축산학회 1995 한국축산학회지 Vol.37 No.1

Genotypes of K-casein(K-CN) locus as a genetic marker linked to quantitative trait loci affecting traits of economic importance in dairy cattle were determined by PCR-RFLP method. Genomic DNA was prepared from blood of Holstein cows. The PCR was used to amplify an 874 by region between nucleotides 10592 and 11466 from exon IV to intron IV of the bovine K-CN gene using sense primer(5`-GTGCTGAGTAGGTATCCTAG-3`) and antisense primer(5`GTAGAGTGCAACAACACTGG-3`). After amplification, PCR products were digested with four restriction enzymes, Hind III, Rsa I, Taq I, and Pst I, and the fragments were separated by agarose gel electrophoresis for RFLP analysis of K-CN locus. In addition to screening for the known Hind III and Rsa I restriction site polymorphisms of K-CN locus, we have found additional RFLPs specific for the K-CN A and B alleles in Taca I and Pst I enzymes. The amplified DNA product digested with each restriction enzyme generated specific RFLP pattern that allowed precise identification of K-CN AA, BB or AB genotypes. The K-CN genotypes determined for cows by the PCR-RFLP method agreed completely with the phenotypes obtained from milk samples of the same individuals. Thus, PCR amplification and RFLP analysis was shown to be a rapid and sensitive method for the discrimination of K-CN genotypes directly at the DNA level in dairy cattle of any age or sex. Consequently, the PCR-RFLP method presented in this study can be used as a valuable tool for early selection of AI bulls and calves with desirable K-CN B gene or K-CN BB genotype affecting superior milk production traits for genetic improvement of Holstein dairy cattle.

1H Nuclear Magnetic Resonance study of Ferroelectric (NH4)3H(SO4)2

S. H. Choi,K. S. Han,S. K. Kwon,S. K. Nam,H. H. Choi,Moohee Lee,Ae Ran Lim 한국자기공명학회 2007 Journal of the Korean Magnetic Resonance Society Vol.11 No.2

1H nuclear magnetic resonance (NMR) experiments have been performed at 30 - 300 K and 7 T to investigate dynamics of hydrogen bond network in the single crystal (NH4)3H(SO4)2. The two proton sites, ammonium proton and hydrogen-bond proton, are identified from the 1H NMR MAS spectrum at 340 K. As temperature decreases, the 1H NMR spectrum shifts to the higher frequency side with a larger linewidth. The spectrum at 65 K shows a distinctive change in line shape toward the ferroelectric transition at 63 K. The measured values of T1 for ammonium and hydrogen-bond protons are similar in the whole range of temperature. T1 of 1H NMR shows a gradual decrease down to 120 K and starts to steeply increase below 100 K. Then T1 shows abrupt decrease below 70 K with a sharp minimum at 63 K, where the ferroelectric transition occurs. This temperature dependence of spectrum and T1 clearly prove that the large change in the dynamics of hydrogen bond network is associated with the ferroelectric phase transition at 63 K.

k-NN 분류를 이용한 유압유 미립자 검출 기반 연구

최병희(B. H. Choi),조예찬(Y. C. Jo),박정현(J. H. Park),최성운(S. W. Choi),조상훈(S. H. Cho),김바다(B. D. Kim),박기협(K. H. Park),김주호(J. H. Kim),이대엽(D. Lee) 유공압건설기계학회 2023 유공압건설기계학회 학술대회논문집 Vol.2023 No.5

In many equipment, including construction machinery that operates with hydraulic oil, it is very important to solve the problem of the generation of fine particles in the hydraulic circuit and the inability to use the equipment due to causes such as damage of parts and repair. In this study, as a base study to solve these problems, a study that can detect the color change of hydraulic oil due to particles mixed in hydraulic oil in real time using machine learning was conducted. Using the k-NN classification algorithm, the color change of hydraulic oil is classified into ten classes so that the color can be recognized in real time. It is planned to carry out the development of the sensor system in the following study.

高地馴化가 흰쥐의 運動能力에 미치는 影響

崔龍國,金炳吉,李鍾瓘,洪?基 大韓體育會 스포츠과학연구소 1966 스포츠科學硏究報告書 Vol.3 No.1

60th residues of ubiquitin and Nedd8 are located out of E2-binding surfaces, but are important for K48 ubiquitin-linkage

Choi, Y.S.,Jeon, Y.H.,Ryu, K.S.,Cheong, C. North-Holland Pub ; Elsevier Science Ltd 2009 FEBS letters Vol.583 No.20

Nedd8, a ubiquitin-like modifier, is covalently attached to various proteins. Although Nedd8 has higher sequence identity (57%) with ubiquitin, its conserved K48 residue cannot form covalent linkage with ubiquitin. To decipher the reason why Nedd8 cannot be an effective ubiquitin-acceptor, we compared the non-covalent interaction between Nedd8 and ubiquitin for various E2s using cross-saturation NMR technique. However, both Nedd8 and ubiquitin displayed almost identical non-covalent E2-binding properties. The K60 of Nedd8 was not present at the E2-binding surface, but its mutation to Asn converted Nedd8 into a ubiquitin-acceptor. The N60 ubiquitin mutants also displayed a decreased ubiquitin-accepting activity. These results suggest the presence of an uncharacterized determinant for the K48 ubiquitin-linkage that is not related to non-covalent E2-bindings. Structured summary: MINT-7263328: NEDD8 (uniprotkb:Q15843) and Ubiquitin (uniprotkb:P62988) physically interact (MI:0914) by enzymatic studies (MI:0415)

Characterization of glycosyl hydrolase family 3 β-N-acetylglucosaminidases from Thermotoga maritima and Thermotoga neapolitana

Choi, K.H.,Seo, J.Y.,Park, K.M.,Park, C.S.,Cha, J. Society for Bioscience and Bioengineering, Japan ; 2009 Journal of bioscience and bioengineering Vol.108 No.6

The genes encoding β-N-acetylglucosaminidase (nagA and cbsA) from Thermotoga maritima and Thermotoga neapolitana were cloned and expressed in Escherichia coli in order to investigate whether Thermotoga sp. is capable of utilizing chitin as a carbon source. NagA and CbsA were purified to homogeneity by HiTrap Q HP and Sephacryl S-200 HR column chromatography. Both enzymes were homodimers containing a family 3 glycoside hydrolase (GH3) catalytic domain, with a monomer molecular mass of 54 kDa. The optimal temperatures and pHs for the activities of the β-N-acetylglucosaminidases were found to be 65-75 <SUP>o</SUP>C and 7.0-8.0, respectively. Both enzymes hydrolyzed chitooligomers such as di-N-acetylchitobiose and tri-N-acetylchitotriose, and synthetic substrates such as p-nitrophenyl-β-d-glucose (pNPGlc), p-nitrophenyl N-acetyl β-d-glucosamine (pNPGlcNAc), p-nitrophenyl di-N-acetyl β-d-chitobiose (pNPGlcNAc<SUB>2</SUB>) and p-nitrophenyl tri-N-acetyl β-d-chitotriose (pNPGlcNAc<SUB>3</SUB>). However, the enzymes had no activity against p-nitrophenyl-β-d-galactose (pNPGal) and p-nitrophenyl N-acetyl β-d-galactosamine (pNPGalNAc) or highly polymerized chitin. The k<SUB>cat</SUB> and K<SUB>m</SUB> values were determined for pNPGlcNAc, pNPGlcNAc<SUB>2</SUB> and pNPGlcNAc<SUB>3</SUB>. The k<SUB>cat</SUB>/K<SUB>m</SUB> value for pNPGlcNAc was the highest among three synthetic substrates. NagA and CbsA initially hydrolyzed p-nitrophenyl substrates to give GlcNAc, suggesting that the enzymes have exo-activity with chitin oligosaccharides from the non-reducing ends, like other β-N-acetylglucosaminidases. However, NagA and CbsA can be distinguished from other GH3-type β-N-acetylglucosaminidases in that they are highly active against di-N-acetylchitobiose. Thus, the present results suggest that the physiological role of both enzymes is to degrade the chitooligosaccharides transported through membrane following hydrolysis of chitin into β-N-acetylglucosamine to be further metabolized in Thermotoga sp.

K-LAN 각 PSDN 연결을 위한 gateway machine의 구현에 관한 연구

송병권(B.K.Song),변준범(J.B.Byun),이광휘(K.H.Lee),안순신(S.S.An),최성수(S.S.Choi),신영석(Y.S.Shin),정광수(K.S.Chung),최양희(Y.H.Choi) 대한전자공학회 1986 대한전자공학회 학술대회 Vol.1986 No.6