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- 저자 : 함시현 (검색결과 6 건)
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Theoretical Study on the Conformations of Homooxacalix[4]arenes
함시현 대한화학회 2004 Bulletin of the Korean Chemical Society Vol.25 No.12
The conformational preference of tetrahomodioxacalix[4]arenes with three different para substituents on the phenolic ring has been investigated by using ab initio molecular orbital theory (RHF/6-31G*) and density functional theory (B3LYP/6-31G*). The stability order is predicted to be cone > C-1,2-alternate > partial cone > 1,3-alternate > COC-1,2-alternate. The distorted cone conformation is found to be most stable in a gas phase and the calculated results are in agreement with the reported 1H NMR and X-ray experimental observations. The substitution of methylene with dimethyleneoxa bridges increases the size of the annulus of the molecule, its conformational mobility, and the number of hydrogen bonding patterns. The thermodynamic stability and the conformational characteristics of tetrahomodioxacalix[4]arenes are discussed in regards of the number of phenolic hydrogen bonding patterns and the polarity of a molecule. The substituent effects on the para position of the phenolic ring are also introduced.
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A New Computational Method for Protein?Ligand Binding Thermodynamics
정성호,함시현 대한화학회 2019 Bulletin of the Korean Chemical Society Vol.40 No.2
We develop a new computational method for protein?ligand binding thermodynamics that combines alchemical transformations and the liquid theory. This method requires only the solute configurations during alchemical transformations, and solvent effects are incorporated through the solvation free energy. It is demonstrated that the new method yields the relative binding free energy that agrees well with the one from the conventional explicit solvent-free energy simulations. The development reported here opens up new possibilities for faster binding free energy computations and easier access to the enthalpy and entropy components.
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Hyunjung Park,Jooyeon Hong,함시현,Raju Nandhakumar,김관묵 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.2
Novel binol aldehydes derivatized at 2' hydroxy position with both uryl and acetamide groups (2), and diuryl groups (3) have been synthesized. Both were designed for streospecific binding and chirality conversion of general dipeptides with support of multiple hydrogen bonding donor sites in the receptors. The receptors, 2 and 3, converted the chirality of N-terminal amino acids of peptides such as Ala-Gly, Met-Gly, Leu-Gly and His-Gly with stereoselectivity on D-form over L-form. The stereoselectivity ratios were in the range of 5-11, somewhat higher than those of the binol receptor with mono uryl group (1). The DFT calculation at the B3LYP/6-31G*//MPWB1K/6-31G* level revealed that 3-D-Ala-Gly was 2.2 kcal/mol more stable than 3-L-Ala-Gly. The considerable steric hindrance between the methyl group of the alanine and the imine CH moiety of the receptor seems to be the main contributing factor for the thermodynamic preference.
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Computational Study on the Conformational Characteristics of Calix[4]pyrrole Derivatives
Jooyeon Hong,Minkyung Son,함시현 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.2
The comparative study of three calix[4]heterocycles (calix[4]pyrrole, calix[4]furan, and calix[4]thiophene) has been theoretically performed by using high-level density functional theory (DFT) at the MPWB1K/6-311G**//B3LYP/6- 311G** level. The effect of different hetero-atoms (nitrogen, oxygen, and sulfur) placed in the heterocycles on the conformational flexibility, thermodynamic stability order, cavity sizes, charge distributions, and binding propensities are examined. The thermodynamic stability differences between the conformers are found to be much greater in calix[4]pyrrole compared to those in calix[4]furan and calix[4]thiophene. Relatively larger NH group and higher dipole of a pyrrole ring in calix[4]pyrrole contribute to the higher energy barrier for the conformational conversions and relatively rigid potential energy surface compared to the case of calix[4]furan and calix[4]thiophene. The computational results herein provide theoretical understanding of the conformational flexibility and the thermodynamic nature which can be applied to understand the complexation behavior of the three calix[4]heterocycles.
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Jooyeon Hong,이제욱,함시현 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.2
The structural and energetic preferences of thiacalix[4]biscrown-5 with and without alkali metal ions (Na+, K+, Rb+and Cs+) have been theoretically investigated for the first time using molecular dynamic (MD) simulations and density functional theory (MPWB1K/6-31G(d)//B3LYP/6-31G(d)) methods. The formation of the metal ion complex by the host is mainly driven by the electrostatic attraction between crown-5 oxygens and a cation together with the minor contribution of the cation-π interaction between two facing phenyl rings around the cation. The computed binding energies and the atomic charge distribution analysis for the metal binding complexes indicate the selectivity toward a potassium ion. The theoretical results herein explain the experimentally observed extractability order by this host towards various alkali metal ions. The physical nature and the driving forces for cation recognition by this host are discussed in detail.
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유정아,이은영,박지윤,이승택,함시현,조경현 한국분자세포생물학회 2015 Molecules and cells Vol.38 No.6
Apolipoprotein A-I and A-IV are protein constituents of high-density lipoproteins although their functional difference in lipoprotein metabolism is still unclear. To compare anti-atherogenic properties between apoA-I and apoA-4, we characterized both proteins in lipid-free and lipidbound state. In lipid-free state, apoA4 showed two distinct bands, around 78 and 67 Å on native gel electrophoresis, while apoA-I showed scattered band pattern less than 71 Å. In reconstituted HDL (rHDL) state, apoA-4 showed three major bands around 101 Å and 113 Å, while apoA-I-rHDL showed almost single band around 98 Å size. Lipid-free apoA-I showed 2.9-fold higher phospholipid binding ability than apoA-4. In lipid-free state, BS3-crosslinking revealed that apoA-4 showed less multimerization tendency upto dimer, while apoA-I showed pentamerization. In rHDL state (95:1), apoA-4 was existed as dimer as like as apoA-I. With higher phospholipid content (255:1), five apoA-I and three apoA-4 were required to the bigger rHDL formation. Regardless of particle size, apoA-I-rHDL showed superior LCAT activation ability than apoA-4-rHDL. Uptake of acetylated LDL was inhibited by apoA-I in both lipid-free and lipidbound state, while apoA-4 inhibited it only lipid-free state. ApoA-4 showed less anti-atherogenic activity with more sensitivity to glycation. In conclusion, apoA-4 showed inferior physiological functions in lipid-bound state, compared with those of apoA-I, to induce more pro-atherosclerotic properties.
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