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최혜영 ( Choe Hye Yeong ),김태형 ( Kim Tae Hyeong ),손소희 ( Son So Hui ),공병기 ( Gong Byeong Gi ),최창용 ( Choe Chang Yong ),김동곤 ( Kim Dong Gon ),장미경 ( Jang Mi Gyeong ),노홍균 ( No Hong Gyun ),나재운 ( Na Jae Un ) 한국키틴키토산학회 2004 한국키틴키토산학회지 Vol.9 No.1
α-, β- and γ-chitin were isolated from crab shell, squid pen, beetles cuticles by acid, alkali treatment and α-, β- and γ-chitosan were prepared from α-, β- and γ-chitin. Chemical compositions of raw materials and elemental of chitin and chitosan were analyzed. A weight-average molecular weight and degree of deacetylation (DDA) were determines by viscometry and Kina titration. Its structural characterization was analyzed by FT-IR spectrophotometer and solid state CP/MAS C NMR spectrophotometer. A molecular weight of α-, β- and γ-chitin were determined by viscometer resulting in 701. 612, and 524, kDa, respectively. A molecular weight of α-, β- and γ-chitosan were calculated with 603., 607 and 329 kDa, respectively. The DDA of α-, β- and γ-chitin were 21.8%, 32.3% and 44.7%, respectively. The DDA of α-, β- and γ-chitosan were 97.1%, 99.2% and 96.6%, respectively. At the FT-IR spectra of chitin, α-, β- chitin. And at the FT_IR sectra of chitosan, absorption band of amide I and amide H decreased because of the deacetylation of chitin, where as the absorption band of amine group was newly formed. From solid state CP/MAS C NMR spectra of chitin, two signals appeared at around 73 and 75 ppm assigned to C3 and C5 carbon atoms in α-chitin are sharply resolved, the signals of C3 and C5 in β-chitin shows singlet at around 74 ppm. In case of γ-chitin, two signals show at around 73 and 75 ppm assigned to C3 and C5 carbon atoms. From solid stat CP/MAS C NMR spectra of chitosan, the carbon of the C1-C6 positions were cleared identified and peaks of CH_3 and C=0 decreased significantly because of the deacetylation
Interpretation of Carboxymethylation in Cellulose Pretreatment by 1H-NMR Spectroscopy
Woo-Young Song,Audrey Zahra,Soo-Jeong Shin,Rahmini 한국펄프·종이공학회 2024 펄프.종이기술 Vol.56 No.1
Carboxymethylation reaction in cellulose was investigated with sodium hydroxide concentration, monochloroacetic acid concentration, temperature, and reaction time as main variables. The degree of carboxymethylation in cellulose was analyzed by phenolphthalein titration, IR spectroscopy, and 1H-NMR spectroscopy methods. The NMR spectroscopic method showed more accurate DS (degree of substitution) values than other IR spectroscopy or titration methods. IR method had the advantage of quick measurement but was difficult in baseline correction. The titration method needed longer data acquisition time and higher deviation to less accuracy. Carboxymethylation in cellulose was run in SN2 reaction by sodium hydroxide and monochloroacetic acid concentration with main variables. Substitution position was analyzed by 1H-NMR spectroscopic with acid hydrolysates of carboxymethylated cellulose. Carboxymethylation in lower reaction temperatures led to more C6-hydorxyl substitution reactions in cellulose, but the C6- and C2-hydroxyl group position competed with increasing reaction temperature.
Protein-ligand interaction investigated by HSQC titration study
이준화 한국자기공명학회 2018 Journal of the Korean Magnetic Resonance Society Vol.22 No.4
Chemical shift perturbation (CSP) is a simple NMR technique for studying binding of a protein to various ligands. CSP is the only technique that can directly provide both a value for the dissociation constant and a binding site from the same set of measurements. To accurately analyze the CSP data, the exact binding mode such as multiple binding, should be carefully considered. In this review, we analyzed systematically the CSP data with multiple modes. This analysis might provide insight into the mechanism on how proteins selectively recognize their target ligands to achieve the biological function.
Protein-ligand interaction investigated by HSQC titration study
Lee, Joon-Hwa Korean Magnetic Resonance Society 2018 Journal of the Korean Magnetic Resonance Society Vol.22 No.4
Chemical shift perturbation (CSP) is a simple NMR technique for studying binding of a protein to various ligands. CSP is the only technique that can directly provide both a value for the dissociation constant and a binding site from the same set of measurements. To accurately analyze the CSP data, the exact binding mode such as multiple binding, should be carefully considered. In this review, we analyzed systematically the CSP data with multiple modes. This analysis might provide insight into the mechanism on how proteins selectively recognize their target ligands to achieve the biological function.
Pressure titration of the monomeric variant of transthyretin
김보경,김진해 한국자기공명학회 2023 Journal of the Korean Magnetic Resonance Society Vol.27 No.1
Transthyretin (TTR) is an indispensable transporter protein of thyroxine and a retinol molecule in humans. TTR has a stable homo-tetrameric structure in its native state, while upon dissociation into monomers, it becomes aggregation-prone and can form an amyloid fibril. Although the amyloidogenic propensity of TTR has been known and investigated since the late 1990s, the structural information regarding TTR’s amyloidogenic species is still elusive. Here, we employed high-pressure nuclear magnetic resonance (HP-NMR) approaches on the monomeric variant of TTR (TTR[F87M/L110M]; M-TTR) and observed that it experiences a two-step transition in response to the pressurized condition. Our study demonstrated that M-TTR in an ambient condition has heterogeneous structural features, which is likely related to the amyloidogenic propensity of TTR.
김홍석,최흥진,남학현,김기수,차근식,Seon-Yun Bae,Jun-Hyeak Choi,심준호 대한화학회 2008 Bulletin of the Korean Chemical Society Vol.29 No.2
The efficient synthesis of four mesitylene-based receptors 1-4 and their potentiometric response characteristics to alkali metal, alkaline earth metal, and transition metal ions, under various pH conditions are outlined. Receptor 1-based electrode exhibited more sensitive response to Ag+ ion (49 mV/decade of range from 10-6 to 10-2 M) than the 2-based electrode (47 mV/decade of range from 3 ´ 10-5 to 10-2 M), while the 3- and 4-based ones revealed sub-Nernstian below 40 mV/pAg+. All electrodes showed substantial responses to Ag+ ion under acidic condition, but there was almost nil-response to other transition metal ions (Fe₂+, Co₂+, Zn₂+, Ni₂+, Pb₂+, Cd₂+, Cu₂+ and Hg₂+). The association constant of receptor 1 toward Ag+ ion, measured by 1H NMR titration, showed the largest value (200 M-1) among the tested receptors. The results were interpreted with semi empirically-modeled structures.
Kim, Hong-Seok,Bae, Seon-Yun,Kim, Ki-Soo,Choi, Jun-Hyeak,Choi, Heung-Jin,Shim, Jun-Ho,Cha, Geun-Sig,Nam, Hak-Hyun Korean Chemical Society 2008 Bulletin of the Korean Chemical Society Vol.29 No.2
The efficient synthesis of four mesitylene-based receptors 1-4 and their potentiometric response characteristics to alkali metal, alkaline earth metal, and transition metal ions, under various pH conditions are outlined. Receptor 1-based electrode exhibited more sensitive response to Ag+ ion (49 mV/decade of range from 10-6 to 10-2 M) than the 2-based electrode (47 mV/decade of range from 3 ´ 10-5 to 10-2 M), while the 3- and 4-based ones revealed sub-Nernstian below 40 mV/pAg+. All electrodes showed substantial responses to Ag+ ion under acidic condition, but there was almost nil-response to other transition metal ions (Fe2+, Co2+, Zn2+, Ni2+, Pb2+, Cd2+, Cu2+ and Hg2+). The association constant of receptor 1 toward Ag+ ion, measured by 1H NMR titration, showed the largest value (200 M-1) among the tested receptors. The results were interpreted with semi empirically-modeled structures.
Formation of a Unique 1:2 Calcium-Calixquinone Complex in Aqueous Media
Kang, Sun-Kil,Lee, One-Sun,Chang, Suk-Kyu,Chung, Doo-Soo,Kim, Ha-Suck,Chung, Taek-Dong Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.3
We report the complexation behavior of calix[4]arenemonoquinone-triacid (CTAQ), which is an electroactive and water-soluble receptor for calcium ion. UV-visible and NMR spectroscopic studies revealed that CTAQ in aqueous media forms 1:2 as well as 1:1 (metal ion:CTAQ) stoichiometric complexes with $Ca^{2+}$, $Sr^{2+}$, and $Ba^{2+}$ ions. The nonlinear fitting of titration curves based on UV-visible absorption spectra showed that the binding constants of CTAQ for $Ca^{2+}$ ion are 4 $({\pm}2){\times}10^6\;M^{-1}$ for 1:1 and 1.4 $({\pm}0.5){\times}10^{11}\;M^{-2}$ for 1:2 complex. NMR conformational studies and the titration curves corroborate that the $Ca^{2+}$:CTAQ complex in aqueous solution is not present in the form of merely 1:1 one, being consistent with UV-visible spectrophotometric results. The Monte Carlo simulation supports the presence of a stable conformer of 1:2 complexes in which a $Ca^{2+}$ ion is interposed between two CTAQs at the global minimum. This is the first model of 1:2 stoichiometric complex of calix[4]arene and alkaline earth ions in aqueous media.
Syed Mashhood Ali*,Mamoru Koketsu,Fahmeena Asmat 대한화학회 2006 Bulletin of the Korean Chemical Society Vol.27 No.9
A detailed spectroscopic study (1H NMR, COSY, ROESY) of complexation of venlafaxine hydrochloride (VEN) with b-cyclodextrin (b-CD) was carried out in solution. The stoichiometry of the complex was determined to be 1 : 1 and penetration of aromatic ring into b-Cyclodextrin cavity was confirmed from primary rim side, with the help of ROESY spectral data. The structure of the venlafaxine hydrochloride-b-CD complex has been proposed. The association constant was determined to be 234 M-1.
Formation of a Unique 1:2 Calcium-Calixquinone Complex in Aqueous Media
Sun Kil Kang,이원선,장석규,정두수,Hasuck Kim,정택동 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.3
We report the complexation behavior of calix[4]arenemonoquinone-triacid (CTAQ), which is an electroactive and water-soluble receptor for calcium ion. UV-visible and NMR spectroscopic studies revealed that CTAQ in aqueous media forms 1:2 as well as 1:1 (metal ion:CTAQ) stoichiometric complexes with Ca^(2+), Sr^(2+), and Ba^(2+)ions. The nonlinear fitting of titration curves based on UV-visible absorption spectra showed that the binding constants of CTAQ for Ca^(2+) ion are 4 (± 2) × 10^6 M^(–1) for 1:1 and 1.4 (± 0.5) × 10^11 M^(–2) for 1:2 complex. NMR conformational studies and the titration curves corroborate that the Ca^(2+):CTAQ complex in aqueous solution is not present in the form of merely 1:1 one, being consistent with UV-visible spectrophotometric results. The Monte Carlo simulation supports the presence of a stable conformer of 1:2 complexes in which a Ca^(2+) ion is interposed between two CTAQs at the global minimum. This is the first model of 1:2 stoichiometric complex of calix[4]arene and alkaline earth ions in aqueous media.