• Bulletin of the Korean Chemical Society
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• 제28권5호
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• pp.725-729
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• 2007

We present calculations for the acetonitrile - water clusters to examine the nature of interactions in the mixed clusters. We calculate conformers of various composition, either of σ -type (-OH and -CN binding linearly) or π -type (-OH and -CN interacting perpendicularly) structures for the acetonitrile - water clusters. We predict that the IR frequency of the proton-accepting C≡N stretching mode red-shifts in the σ -type clusters and blueshifts in π -type conformers, whereas the proton-donating ?OH stretching frequency red-shifts in all cases. We find that this intriguing pattern also applies to the acetonitrile - water clusters of various molar ratio.

• 약학회지
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• 제41권6호
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• pp.765-772
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• 1997

Conformational analyses on thromboxane $A_2$ (Tx$A_2$) and thromboxane $A_2$ receptor antagonists (TxRA) were carried out by molecular mechanics method. Based on the assumption that active conformer is the nonintrahydrogen bonding and more stable former of Tx$A_2$ and TxRA, the molecular structural requirements for potent TxA2 receptor antagonists are like below: 1) The distance is 5.0-5.6${\AA}$ between C atom of carboxyl group and S atom of sulfonyl group or C atom which is bonded to hydroxyl group in the active conformers. 2) The putative active conformers of Tx$A_2$and TxRAs are hairpin-like forms.

• 생약학회지
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• 제9권1호
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• pp.1-9
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• 1978

The principle of Fourier Transform Nuclear Magnetic Resonance and its usefulness in the fields of pharmacy and biological sciences are described. 1. The $^1H\;and\;^{13}C$ NMR spectra of triostin A and its mixture with purine derivatives were taken. From the analysis of the spectra it has established that triostin A, which exists in two symmetric conformers in chloroform solution, forms complexes only with purine derivatives by the participation of one of the conformers. 2. Also, the $^{13}C$ NMR spectra of "intact" substances in the field of pharmacognosy were taken. From the spectra it was suggested that the method is very useful for natural product research in cooperation with the chemical method.

• Bulletin of the Korean Chemical Society
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• 제15권6호
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• pp.483-488
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• 1994

Tetra acyl esters of p-tert-butylcalix[4]arene and calix[4]arene, including acetyl, propionyl, butyryl and isobutyryl, are synthesized and their conformations are inferred from $^1H-NMR$ and $^{13}C-NMR$ spectra. The conformer distribution is affected by the presence of t-butyl group, whereas the acylation products of p-t-butylcalix[4]arene are the cone conformers, those of calix[4]arene are mostly partial cone and/or 1,3-alternate conformers. The conformational outcome is also affected by the method of preparation, the NaH-induced reaction is prefered to the acid-induced reaction for cone and partial cone. Interestingly, 1,2-alternate conformer was isolated in 14% yield from the butyrylation of calix[4]arene.

• 대한화학회지
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• 제55권3호
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• pp.405-411
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• 2011

Methyl hydro-peroxide의 methyl group과 O-H에 F를 치환 시킨 fluoromethyl fluoroperoxide($CH_nF_{3-n}OOF$)의 안정한 conformers와 isomers에 대하여 MP2/6-311G(d,p) 방법과 B3LYP/6-311++G(d,p) 방법으로 최적화 계산을 수행하였고 vibrational frequencies를 구하였다. $CH_3OOF$와 $CH_2FOOF$, $CHF_2OOF$, $CF_3OOF$ 분자 모두 가장 안정한 형태는 skew 구조로 나타났으며 $CH_3OOH$와 비교할 때 대단히 짧은 O-O 결합길이를 갖는다. Trans, cis conformers의 경우 skew 형태보다 8-12 kcal/mol 정도 높은 에너지를 갖으며 O-O 결합길이는 훨씬 길어진다. $CH_2FOOF$, $CHF_2OOF$, $CF_3OOF$ 분자들은 methyl group의 F에 의한 induction 효과로 짧은 C-O 결합길이를 갖고 O-F 결합길이는 길어지나 치환된 F 원자의 수에 따른 구조변화는 그리 크지 않다.

• 대한화학회지
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• 제49권1호
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• pp.7-15
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• 2005

• 한국광과학회:학술대회논문집
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• 한국광과학회 2006년도 정기총회 및 제13회 학술대회 논문 초록
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• pp.70-70
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• 2006

• 대한화학회지
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• 제23권5호
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• pp.271-276
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• 1979

EHT 및 CNDO/2 분자궤도법을 사용하여 각종 이노시톨의 형태의 안정성을 결정하였다. EHT 계산결과는 실험사실과 일치하며 산소원자간의 비결합 1,3-상호작용을 올바르게 나타내 주었다. 또 EHT 결과에 따르면 수산기의 수소와 인접 산소간의 퍼텐셜 에너지가 형태 결정의 주요 요소의 하나임을 알 수 있었다. CNDO/2 방법은 고립쌍-고립쌍간의 불안정 요인이 되는 상호작용을 올바르게 나타내주지 못했으며 이것은 1,3-상호작용이 있는 형태의 안정도를 과도하게 나타내었다. 이노시톨의 형태연구에는 CNDO/2 방법보다 EHT 방법이 우수하다.

• BMB Reports
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• 제40권2호
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• pp.205-211
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• 2007

The stability curve - a plot of the Gibbs free energy of unfolding versus temperature - is calculated for bovine erythrocyte carbonic anhydrase in 150 mM sodium phosphate (pH = 7.0) from a combination of reversible differential scanning calorimetry measurements and isothermal guanidine hydrochloride titrations. The enzyme possesses two stable folded conformers with the conformational transition occurring at ~30$^{\circ}C$. The methodology yields a stability curve for the complete unfolding of the enzyme below this temperature but only the partial unfolding, to the molten globule state, above it. The transition state thermodynamics for the low- to physiological-temperature conformational change are calculated from slow-scan-rate differential scanning calorimetry measurements where it is found that the free energy barrier for the conversion is 90 kJ/mole and the transition state possesses a substantial unfolding quality. The data therefore suggest that the x-ray structure may differ considerably from the physiological structure and that the two conformers are not readily interconverted.

• 약학회지
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• 제38권3호
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• pp.230-237
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• 1994

The structure-activity relationships of (E)-chalcone-4-carboxylic acids, flavone-4'-carboxylic acids, two types of aromatic amides, terephthalic monoanilides, and (arylcarboxamido)benzoic acids, which were made by Shudo group, are discussed by conformation analysis(AM1) of retinoic acid and those compounds. Conformer of each compound is superimposed on the conformationally restricted compound, 4-(6,7,8,9-tetrahydro-6,6,9,9-tetramethyl-4H-4-oxonaphto[ 2,3-b]pyran-2-yl) benzoic acid(Fv80), possessing the strongest differentiation-inducing activity on human promyelocytic leukemia cells HL-60. The results indicated that the lengths between the carboxylic carbon and the two 6, 9 carbons binding to dimethyl, 1.20 nm and 1.09 nm, as well as the planarity of molecule are very important factors for the activity, especially 1.20 nm. In the case of the recently synthesized azulenic retinoic acids by Sato, et al. in 1993, the distance probably is also important, resulted from superimposing them on a Ch55 conformer and Fv80. The distance 1.0 nm is also important in Ch55. Several conformers of all-trans retinoic acid (RA) are well superimposed on the almost non-flexible Fv80, RA, 9-cis RA, and, specifically s-10,12 cis RA. And a simple hexangular model of RA is suggested to draw RA conformers easily without computer drawing model or molecular model.