• Title/Summary/Keyword: dimers

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Solubilization of Pyrimethamine, Antibacterial Drug, by Low-Molecular-Weight Succinoglycan Dimers Isolated from Shinorhizobium meliloti

  • Kim, Hwan-Hee;Kim, Kyoung-Tea;Choi, Jae-Min;Tahir, Muhammad Nazir;Cho, Eun-Ae;Choi, Young-Jin;Lee, Im-Soon;Jung, Seun-Ho
    • Bulletin of the Korean Chemical Society
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    • v.33 no.8
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    • pp.2731-2736
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    • 2012
  • The use of pyrimethamine as antibacterial drug is limited by the poor solubility. To enhance its solubility, we prepared complexes of pyrimethamine with low-molecular-weight succinoglycan isolated from Sinorhizobium meliloti. Low-molecular-weight succinoglycans are monomers, dimers, and trimers of the succinoglycan repeating unit. The monomers and dimers were separated into their three species (M1, M2, and M3) and four fractions (D1 to D4) using chromatographic techniques, which were shown to be nontoxic. The solubility of pyrimethamine was markedly increased up to 42 fold by succinoglycan D3, where the level of its solubility enhancement was even 8-20 fold higher comparing with cyclodextrin or its derivatives. The complex formation of succinoglycan D3 with pyrimethamine was confirmed by $^1H$ nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy, and molecular modeling studies. Herein, we suggest that the low-molecular-weight succinoglycans may be utilized as highly effective solubilizers of pyrimethamine for pharmaceutical purposes.

Theoretical Studies of Hydrogen Bond Interactions in 4-Substituted Benzoic Acids Dimers (4-치환된 벤조산 2합체에서의 수소 결합 상호작용에 대한 이론적 연구)

  • Beni, Alireza Salimi;Chermahini, Alireza Najafi;Sharghi, Hashem
    • Journal of the Korean Chemical Society
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    • v.55 no.3
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    • pp.392-399
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    • 2011
  • Two conformations of benzoic acid derivatives ($NH_2$, OH, H, F, Cl, CN, NO, $NO_2$) have been investigated at MP2, DFT and HF level using the 6-311++G(d,p) basis set. It was found that the cis isomers are more stable. Hydrogen bonding formation of benzoic acids has been estimated from stabilization energies. The calculated hydrogen-bonding energies of dimers showed a cooperative interaction in the cyclic ones. It was found that an electron-releasing group (ERG) into the phenyl rings resulted in the formation of more stable hydrogen bonding. Red shift of O-H bond was found from -565.3 to -589.3 for dimers. The natural bond orbital (NBO) analysis was applied to characterize nature of the interaction.

Synthesis of New Spiro[benzo[c]fluorene-7,9'-fluorene] Dimers and Their Optical Properties

  • Seo, Jeong-A;Lee, Chil-Won;Gong, Myoung-Seon
    • Bulletin of the Korean Chemical Society
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    • v.34 no.5
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    • pp.1414-1420
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    • 2013
  • Five novel spiro[benzo[c]fluorene-7,9'-fluorene] based dyes, including 5-[spiro[benzo[c]fluorene-7,9'-fluoren]-5-yl] spiro[benzo[c]fluorene-7,9'-fluorene] (7), 5-[spiro[benzo[c]fluorene-7,9'-fluoren]-9-yl] spiro[benzo[c]fluorene-7,9'-fluorene] (8), 5-[spiro[benzo[c]fluorene-7,9'-fluoren]-2'-yl] spiro[benzo[c]fluorene-7,9'-fluorene] (9), 9-[spiro[benzo[c]fluorene-7,9'-fluoren]-9-yl] spiro[benzo[c]fluorene-7,9'-fluorene] (10), and 2'-[spiro[benzo[c]-fluorene-7,9'-fluoren]-2'-yl] spiro[benzo[c]fluorene-7,9'-fluorene] (11) were successfully prepared from the corresponding halogen and boronic acid derivatives through the Suzuki coupling reaction, respectively. Chemical structures were confirmed by $^1H$ nuclear magnetic resonance (NMR), $^{13}C$ NMR, Fourier transforminfrared spectrscopy, mass spectroscopy, and elemental analysis. The thermal properties were determined by differential scanning calorimetry and thermal gravimetric analysis. The relationships between the optical and electrochemical properties and the combined positions between these dimers were systematically investigated using UV-vis, photoluminescence (PL), and photoelectron spectroscopy. These five dimers exhibited high fluorescent quantum yields and good morphological stability with high glass transition states > $174^{\circ}C$. Dimer 7 showed a UV absorbance peak at 353 nm, emission PL peak at 424 nm, and quantum efficiency of 0.62 in a cyclohexane solution.

Analysis of Amyloid Beta 1-16 (Aβ16) Monomer and Dimer Using Electrospray Ionization Mass Spectrometry with Collision-Induced Dissociation

  • Kim, Kyoung Min;Kim, Ho-Tae
    • Mass Spectrometry Letters
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    • v.13 no.4
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    • pp.177-183
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    • 2022
  • The monomer and dimer structures of the amyloid fragment Aβ(1-16) sequence formed in H2O were investigated using electrospray ionization mass spectrometry (MS) and tandem MS (MS/MS). Aβ16 monomers and dimers were indicated by signals representing multiple proton adduct forms, [monomer+zH]n+ (=Mz+, z = charge state) and [dimer+zH]z+ (=Dz+), in the MS spectrum. Fragment ions of monomers and dimers were observed using collision-induced dissociation MS/MS. Peptide bond dissociation was mostly observed in the D1-D7 and V11-K16 regions of the MS/MS spectra for the monomer (or dimer), regardless of the monomer (or dimer) charge state. Both covalent and non-covalent bond dissociation processes were indicated by the MS/MS results for the dimers. During the non-covalent bond dissociation process, the D3+ dimer complex was separated into two components: the M1+ and M2+ subunits. During the covalent bond dissociation of the D3+ dimer complex, the b and y fragment ions attached to the monomer, (M+b10-15)z+ and (M+y9-15)z+, were thought to originate from the dissociation of the M2+ monomer component of the (M1++M2+) complex. Two different D3+ complex geometries exist; two distinguished interaction geometries resulting from interactions between the M1+ monomer and two different regions of M2+ (the N-terminus and C-terminus) are proposed. Intricate fragmentation patterns were observed in the MS/MS spectrum of the D5+ complex. The complicated nature of the MS/MS spectrum is attributable to the coexistence of two D5+ configurations, (M1++M4+) and (M2+M3+), in the Aβ16 solution.

Effect of Temperature on Formation of Polymer in Oxidation of Methyl Linoleate (Methyl Linoleate 산화중 중합체 형성에 미치는 온도의 영향)

  • Kim, In-Hwan;Kim, Chul-Jin;Kim, Dong-Hoon
    • Korean Journal of Food Science and Technology
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    • v.28 no.3
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    • pp.446-450
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    • 1996
  • To investigate the effect of heating conditions on the polymerization of methyl linoleate, the esters were heated at $60^{\circ}C,\;90^{\circ}C,\;120^{\circ}C$ and $150^{\circ}C$, respectively, with sparging oxygen for different periods of time. On the basis of the peroxide curve obtained at each of the four temperatures, four heating times were chosen for the analysis of the polymers and total oxidation products. Significant linear relationships were found between polymer contents and total oxidation product contents. The contents of polymers and their linkage types were analyzed by High Performance Size Exclusion Chromatography. The polymers formed at four temperatures were qualitatively identified as dimers. The dimers with peroxide linkages were detected from methyl linoleate oxidized at $60^{\circ}C\;and\;90^{\circ}C$ but they were not detected from methyl linoleate oxidized at $120^{\circ}C\;and\;150^{\circ}C$. Therefore, all dimers formed at $120^{\circ}C\;and\;150^{\circ}C$ seemed to be the ones with ether linkage or carbon to carbon linkage. The degradation rate of the dimers with peroxide linkages at $90^{\circ}C$ was faster than at $60^{\circ}C$.

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