• Journal of Microbiology and Biotechnology
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• v.29 no.1
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• pp.114-126
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• 2019

This paper introduces three ways to determine host-guest complexation of cucurbit[7]uril (CB[7]) with homocysteine (Hcy). After preincubating Hcy and cysteine (Cys) with CB[7], Ellman's reagent (DTNB) was used to detect Hcy and Cys. Only Cys reacted with DTNB and Hcy gave a retarded color change. This suggests that the -SH group of Hcy is buried inside CB[7]. Human cystathionine ${\gamma}-lyase$ (hCGL) decreased the level of Hcy degradation after preincubating Hcy and CB[7]. These results suggest that the amount of free Hcy available was decreased by the formation of a Hcy-CB[7] complex. The immunological signal of anti-Hcy monoclonal antibody was decreased significantly by preincubating CB[7] with Hcy. The ELISA results also show that ethanethiol group ($-CH_2CH_2SH$) of Hcy, which is an epitope of anti-Hcy monoclonal antibody, was blocked by the cavity in CB[7]. Overall, CB[7] can act as a host by binding selectively with Hcy, but not Cys. The calculated half-complexation formation concentration of CB[7] was 58.2 nmol using Ellman's protocol, 97.9 nmol using hCGL assay and 87.7 nmol using monoclonal antibody. The differing binding abilities of Hcy and Cys towards the CB[7] host may offer a simple and useful method for determining the Hcy concentration in plasma or serum.

• The Journal of the Acoustical Society of Korea
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• v.36 no.6
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• pp.387-393
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• 2017

The dynamic interactions between benzoic acid derivative ($pH{\approx}7.0$)(guest) and ${\beta}$-cyclodextrin (${\beta}$-CD)(host) were investigated in an aqueous solutions in terms of ultrasonic absorption in the frequency range 0.2 MHz ~ 50 MHz with emphasis on the low-frequency range below 1 MHz at $25^{\circ}C$. We show that the interaction of ${\beta}$-CD and benzoic acid derivative complies with a typical spectrum of a single relaxation process around a few MHz. The ultrasonic relaxation observed in these solutions was due to a perturbation of a chemical equilibrium related to a reaction of an inclusion complex formed by the host and guest. The rate constant ($k_b=7.48{\times}10^6M^{-1}s^{-1}$) and equilibrium constant ($K=68.6M^{-1}$) were determined from the concentration dependences of benzoic acid on the relaxation frequency. The standard volume change (${\Delta}V=10.6{\times}10^{-6}m^3mol^{-1}$) of the reaction was also computed from the maximum absorption per wavelength. It was found that the hydrophobicity of guest molecules played an important role in the formation of the inclusion complex.

• Bulletin of the Korean Chemical Society
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• v.11 no.6
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• pp.521-527
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• 1990

The binding characteristics and analytical applications of anilinium ion complexes with 18-crown-6 were studied by polarography and NMR. First, the electrochemical reduction of the 10 species of mono and dimethylsubstituted anilinium ion complexes with 18-crown-6 as host in methanol are examined. The addition of 18-crown-6 to anilinium guest solution the polarographic waves remain well defined but shifted toward more negative potentials, indicating the complex formation. The values of formation constants, log Κ for 10 species of methylsubstituted anilinium ion complexes with 18-crown-6 varies from 2.7 to 4.8 in methanol at $25^{\circ}C$. The stability order of complexes for 18-crown-6 is anilinilum > 4-methyl > 3,4-dimethyl > 3-methyl > 3,5-dimethyl > 2,4-dimethyl > 2,5-dimethyl > 2,3-dimethyl > 2-methyl > 2,6-dimethylanilinium ion. The steric hindrance shows significant effect. Second, Proton NMR was used to elucidate their interaction characteristics. From the results of so called NMR titration techniques, the behaviors of binding sites on complexation, and the stoichiometry and stability order of complex were obtained. And the later results show the satisfactory agreement with the quantitative values obtained by polarography. Finally, the individual determinations of anilinium ion mixtures were also accomplished by addition of 18-crown-6. In some mixtures of methyl or dimethylanilinium ions the reduction peaks of differential pulse method appeared into one unresolved wave attributed to the small difference of half-wave potential, ${\Delta}E_{1/2}$. In the presence of 18-crown-6, the polarographic waves were resolved into individual maxima because of the shift toward more negative direction by the difference of selectivity of anilinium ions with 18-crown-6. It may be concluded that quantitative analysis of methylanilinium ion mixture make possible because the half-wave potential shift by the selectivity difference due to the steric hindrance between methyl group and 18-crown-6 on complexation.

• Polymer(Korea)
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• v.26 no.5
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• pp.568-574
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• 2002

Inclusion compounds using cyclic poly(oxyethylene)s as host molecules have been used to polymerize pyrrole chemically in aqueous medium. This general synthetic strategy makes it possible to grow rigid aromatic polymers in aqueous medium by chemical oxidation method. It is an easy method to obtain rigid polymers in a very mild manner. Some threaded and water-soluble polypyrroles are obtained, and their characterization is performed by NMR, IR, UV, and MALDI-TOF MS measurements.

• Journal of Pharmaceutical Investigation
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• v.18 no.1
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• pp.15-21
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• 1988

An inclusion complex of phenytoin (PT) with ${\beta}-cyclodextrin\;({\beta}-CyD)$ in molar ratio of 1 : 1 was prepared, and the interaction between host and guest molecules was confirmed by infrared spectrometry, differential scanning calorimetry and X-ray diffractometry. Suppositories were prepared by the fusion method. PT and $PT-{\beta}-CyD$ complex were added to PEG 1540 and Witepsol H-15 under the vigorous stirring at $40^{\circ}C$. Content uniformity was tested for different formulations of the PT suppositories. The release rates were dependent on the K.P. V dissolution apparatus and the dialyzing tubing method. Then, the release rates were increased in the following order: $PT-{\beta}-CyD$ complex in PEG 1540>PT in PEG 1540>$PT-{\beta}-CyD$ complex in Witepsol H-15>PT in Witepsol H-15. The area under the curve and maximum blood concentration after rectal administration were increased in the following order: $PT-{\beta}-CyD$ complex in PEG 1540>PT in PEG 1540>$PT-{\beta}-CyD$ complex in Witepsol H-15>PT in Witepsol-15.

• Bulletin of the Korean Chemical Society
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• v.30 no.2
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• pp.348-354
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• 2009

Copper(II) complexes with tetraoxo dithia tetraaza macrocyclic ligands; [18]ane$N_4S_2$: 1,4,10,13-tetraaza-5,9,14,18-tetraoxo-7,16-dithia-cyclooctadecane, [20]ane$N_4S_2$: 1,5,11,15-tetraaza-6,10,16,20-tetraoxo-8,18-dithia-cyclocosane,Bzo2[18]ane$N_4S_2$: dibenzo-1,4,10,13-tetraaza-5,9,14,18-tetraoxo-7,16-dithia-cyclooctadecane, Bzo2[20]ane$N_4S_2$: dibenzo-1,5,11,15-tetraaza-6,10,16,20-tetraoxo-8,18-dithia-cyclocosane; were entrapped in the nanopores of zeolite-Y by a two-step process in the liquid phase: (i) adsorption of [bis(diamine)copper(II)] (diamine = 1,2-diaminoethane, 1,3-diaminopropane, 1,2-diaminobenzene, 1,3-diaminobenzene); $[Cu(N-N)_2]^{2+}$-NaY; in the nanopores of the zeolite, and (ii) in situ template condensation of the copper(II) precursor complex with thiodiglycolic acid. The obtained complexes and new host-guest nanocomposite materials; $[Cu([18]aneN_4S_2)]^{2+}-NaY,\;[Cu([20]aneN_4S_2)]^{2+}-NaY,\;[Cu(Bzo_2[18]aneN_4S_2)]^{2+}-NaY,\;[Cu(Bzo_2[20]aneN_4S_2)]^{2+}$-NaY; have been characterized by elemental analysis FT-IR, DRS and UV-Vis spectroscopic techniques, molar conductance and magnetic moment data, XRD and, as well as nitrogen adsorption. Analysis of data indicates all of the complexes have been encapsulated within nanopore of zeolite Y without affecting the zeolite framework structure.

• Journal of Pharmaceutical Investigation
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• v.23 no.3
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• pp.155-163
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• 1993

Inclusion complexation of 1,7,21,27-tetraaza[7.1.7.1]paracyclophane (CPM 55) with 2,7-dihydroxynaphthalene (2,7-DHN) or 1,3-dihydroxynaphthalene (1,3-DHN) in pD 1.17 $DCl-D_2O$ solution was investigated by $^1H$ nuclear magnetic resonance spectroscopy (NMR) using 4,4'-dimethylaminodiphenylmethane (ACM 11) as an acyclic analog of CPM 55. In CPM 55-naphthalene derivative complex, alkyl protons located in the cavity of CPM 55 were shown to be subjected to anisotropic shielding and protons of naphthalene moiety shifted remarkably to upfield. However, in ACM 11-naphthalene derivative systems, chemical shifts for protons of both DHN compounds were not significant. The remarkable chemical shift changes suggested that the naphthalene moiety of 2,7-DHN or 1,3-DHN was included in the hydrophobic cavity of CPM 55 in aqueous solution. From the continuous variation plots of induced chemical shifts of 2,7-DHN, it was found that 2,7-DHN was included in the cavity of CPM 55 at 1:1 molar stoichiometry. Both computer simulation of a inclusion complex and strong upfield chemical shift changes of 2,7-DHN protons supported the conformation of pseudoaxial inclusion as the presumed geometry of the host-guest complex.

• Korean Journal of Crystallography
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• v.10 no.1
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• pp.66-70
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• 1999

The calix[4]arene molecule adopting the 1,3-alternate conformation forms a square cavity, and two pair phenyl rings lying above and below a least-square plane defined by the four bridging methylene groups in the calix[4]arene are widened upwards and downwards, respectively, from central axis, which leads to O1-O4=4.064 and O2-O3=3.864 . Two propyloxy groups are stabilized with all trans conformations, but the rather short azacrown ether chain with two oxygen atoms includes cis/trans conformations with O1-C35=2.906 . Therefore the cavity does not seem to be big enough to form a host-guest complex.

• Bulletin of the Korean Chemical Society
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• v.29 no.5
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• pp.953-958
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• 2008

A novel anthraquinone diamino-bridged bis($\beta$ -cyclodextrin) 2 was synthesized. The inclusion complexation behaviors of the native $\beta$ -cyclodextrin 1 and the novel bis($\beta$ -cyclodextrin) 2 with guests, such as acridine red (AR), neutral red (NR), ammonium 8-anilino-1-naphthalenesulfonate (ANS), sodium 2-(p-toluidinyl) naphthalenesulfonate (TNS) and rhodamine B (RhB) were investigation by fluorescence, circular dichroism and 2D NMR spectroscopy. The spectral titrations were performed in phosphate buffer (pH 7.20) at 25 ${^{\circ}C}$ to give the complex stability constants (Ks) and Gibbs free energy changes (−${\Delta}G^0$) for the stoichiometric 1:1 inclusion complexation of host 1 and 2 with guests. The results indicated that the novel bis($\beta$ -cyclodextrin) 2 greatly enhanced the original binding affinity of the native $\beta$ -cyclodextrin 1. Typically, bis($\beta$ -cyclodextrin) 2 showed the highest binding constant towards ANS up to 34.8 times higher than that of 1. The 2D NMR spectra of bis($\beta$ -cyclodextrin) 2 with RhB and TNS were performed to confirm the binding mode. The increased binding affinity and molecular selectivity of guests by bis($\beta$ -cyclodextrin) 2 were discussed from the viewpoint of the size/shape-fit concept and multipoint recognition mechanism.

• Analytical Science and Technology
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• v.15 no.2
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• pp.115-119
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• 2002

The formation of inclusion complexes between cyclodextrin(CD) and Congo red was studied by spectrophotometric methods at various temperatures. The cavity sizes are 0.49 nm, 0.62 nm for $\alpha$-and $\beta$-CD, respectively. Therefore, $\alpha$-CD was not found to form an inclusion complex with Congo red due to steric hinderance. In the $\beta$-CD use two $\beta$-CD molecules formed an inclusion complex with one molecule of Congo red, from the slope of the S-shaped curve increased. Two prominent isosbestic points appear at 346 nm and 478 nm. The formation constants were decreased with the increasing temperatures, due to low binding energy between $\beta$-CD and Congo red. The thermodynamic parameters were calculated from the plot of $lnK_f$ vs 1/T. The $\Delta$H, $\Delta$S and $\Delta$G were -50.73 kJ/mol, $-108.96J/K{\cdot}mol$ and -18.26 kJ/mol, respectively.