• Bulletin of the Korean Chemical Society
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• 제26권1호
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• pp.32-33
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• 2005

• Bulletin of the Korean Chemical Society
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• 제10권4호
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• pp.377-381
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• 1989

The spectroscopic properties of $FO^+$ and FO were investigated by ab initio calculation. Several different levels of theory, $MP3/6-31G^*,\;MP4/6-311G^*\;and\;CISD/6-31G^*$, were tried and compared with experimental results of FO. In the overall performance the CISD showed the best agreement. Based on these results the spectroscopic constants of $FO^+$ are predicted.

• Bulletin of the Korean Chemical Society
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• 제14권4호
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• pp.476-480
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• 1993

The ab initio calculations were performed on ClO and $ClO^+$ using the configuration interaction and M${\phi}$ller-Plesset methods of several different levels of approximation. Three different basis sets, 66 contracted Gaussian-type orbitals,6-31$G^*$ and 6-311$G^*$, were employed in this calculation. The results of calculation were compared with the experimental values of ClO. The values from the calculation with 66cGTO basis set gave excellent agreement with the experimental values. The spectroscopic constants of $ClO^+$ were also predicted.

• 한국생물정보학회:학술대회논문집
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• 한국생물정보시스템생물학회 2000년도 International Symposium on Bioinformatics
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• pp.32-34
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• 2000

Computational chemistry is a discipline using computational methods for the calculation of molecular structure, properties, and reaction or for the simulation of molecular behavior. Relating and turning the complexity of data from genomics, high-throughput screening, combinatorial chemical synthesis, gene-expression investigations, pharmacogenomics, and proteomics into useful information and knowledge is the primary goal of bioinformatics. In particular, the structure-based molecular design is one of essential fields in bioinformatics and it can be called as structural bioinformatics. Therefore, the conformational analysis for proteins and peptides using the techniques of computational chemistry is expected to play a role in structural bioinformatics. There are two major computational methods for conformational analysis of proteins and peptides; one is the molecular orbital (MO) method and the other is the force field (or empirical potential function) method. The MO method can be classified into ab initio and semiempirical methods, which have been applied to relatively small and large molecules, respectively. However, the improvement in computer hardwares and softwares enables us to use the ab initio MO method for relatively larger biomolecules with up to v100 atoms or ∼800 basis functions. In order to show how computational chemistry can be used in structural bioinformatics, 1 will present on (1) cis-trans isomerization of proline dipeptide and its derivatives, (2) positional preference of proline in ${\alpha}$-helices, and (3) conformations and activities of Arg-Gly-Asp-containing tetrapeptides.

• Bulletin of the Korean Chemical Society
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• 제25권12호
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• pp.1855-1858
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• 2004

Molecular geometries for the cationic and neutral species of OXO (X=Cl, Br, and I) are optimized using the Hartree-Fock (HF) theory, the second order Moller-Plesset perturbation theory (MP2), the density functional theory with the B3LYP hybrid functional (B3LYP), and the coupled cluster theory using single and double excitation with a perturbational treatment of triplet excitation (CCSD[T]) methods, with two basis sets of triple zeta plus polarization quality. The single point calculations for these species are performed at the CCSD(T,Full) level. The harmonic vibrational frequencies for these species are calculated at the HF, MP2, B3LYP and CCSD(T) levels. The adiabatic ionization potential for OIO is calculated to be 936.7 kJ/mol at the CCSD(T,Full) level and the correct value is estimated to be around 945.4 kJ/mol.

• Bulletin of the Korean Chemical Society
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• 제24권4호
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• pp.494-498
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• 2003

The transition from aromatics to heteroaromatics is very attractive since it provides an extremely large structural variety, the chemical functionality as well as the possibilities for electronic tuning of the fullerene properties. A synthesis of heterofullerenes in macroscopic quantities is unknown however the spectrometric detection of $C_{59}B$ has been reported. The electronic structures of $C_{(60-2x)}(BN)_x$ systems, isoelectronic with $C_{60}$ have been explored by Extended Hukel, AM1 and ab initio methods. The polyhedral assembly energy are 7.7 kcal greater than $C_{60}$ when one B-N unit is substituted with C-C unit. The assembly energies are getting bigger if more B-N unit is introduced. We focus on HOMO-LUMO energy gap and the stability effects in $C_{(60-2x)}(BN)_x$ with different compositions of $(BN)_x$ moiety. The bonding properties of the substituent atoms were investigated in detail.

• 대한화학회지
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• 제27권6호
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• pp.399-404
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• 1983

아미드와 아미드-용매계의 C=O stretching band에 해당하는 Raman 스펙트럼으로 부터 카르보닐기와 질소에 치환된 알킬기가 수소결합에 미치는 영향을 조사하였다. Formamide 계에서는 상호작용의 세기가 아미드-아미드>아미드-물>아미드-알코올 순으로 감소했으며, acetamide와 propionamide 계에서는 아미드-물>아미드-아미드>아미드-알코올 순으로 감소하였다. 카르보닐기에 알킬기가 치환되면 카르보닐기의 proton acceptor의 세기가 증가되며, 질소에 알킬기가 치환되면 proton donorcity가 감소함을 보이는데 이는 이론적인 계산 결과와도 일치한다.

• 대한화학회지
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• 제54권3호
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• pp.275-282
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• 2010

분자 내 수소결합 가능성을 가지고 있는 2-fluorocyclopropanemethanol과 2-chlorocyclopropanemethanol에 대하여 MP2/6-311++G(d,p) 방법과 B3LYP/6-311++G(d,p) 방법으로 최적화 계산을 수행하였다. 두 분자 모두 가장 안정한 conformer에서 O-H의 수소가 F나 Cl을 향하고 있어 수소결합 가능성을 보이기는 하나 $H{\cdots}F$, $H{\cdots}Cl$ 거리가 van der Waals radii보다 커서 강한 수소결합이라 보기 힘들고 두 번째 안정한 conformer의 경우가 가까운 $H{\cdots}F$, $H{\cdots}Cl$ 거리를 보이며 더 강한 수소결합 가능성을 보였다. 그러나 에너지가 5 ~ 7 kJ 더 높게 나타났다. Methanol group과 F나 Cl이 서로 반대 방향을 향할 때 일반적으로 안정하나 앞의 가장 안정한 conformer보다는 에너지가 높다.