• Bulletin of the Korean Chemical Society
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• 제14권2호
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• pp.262-265
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• 1993

Conformational free energy calculations using an empirical potential function and a hydration shell model (program CONBIO) were carried out on antifungal agent fluconazole in the unhydrated and hydrated states. The initial geometry of fluconazole was obtained from two minimized fragments of it using a molecular mechanics MMPMI and followed by minimizing with a semiempirical AM1 method. In both states, the feasible conformations were obtained from the calculations of conformational energy, conformational entropy, and hydration free energy by varying all the torsion angles of the molecule. The intramolecular hydrogen bonds of isopropyl hydroxyl hydrogen and triazole nitrogens and the structural flexibility are of significant importance in stabilizing the conformations of fluconazole in both states. Hydration is proved to be one of the essential factors in stabilizing the overall conformation in aqueous solution. Two F atoms of phenyl ring are not identified as an essential key in determining the stable conformations and may be responsible for the interaction with the receptor of fluconazole.

• Bulletin of the Korean Chemical Society
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• 제19권3호
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• pp.308-313
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• 1998

A thermally irreversible photochromic system, 2,3-bis(2,4,5-trimethyl-3-thienyl)maleic anhydride (MTMA), has been studied by semi-empirical molecular orbital methods. There are one pair of stable conformations for the closed-ring form and three pairs for the open-ring form, each pair consisting of two mirror-image conformations. Interconversion between the parallel and anti-parallel conformations of the open-ring form is restricted due to high energy barriers. Only the anti-parallel conformation appears to be responsible for photochromic cyclization. Thermostability of the compound is attributed to an avoided crossing at high energy in the ground states of the isomers, whereas the photoreactivity can be explained by the mutually connected excited singlet (S1) states of the isomers, forming a double well potential with a low energy barrier. The large solvent effects can be partly explained with the low dipole moment of the anti-parallel conformation of MTMA in the S1 state. The large variation of quantum efficiency suggests that excess vibronic energy can be utilized to provide the activation energy for the photochromic reaction.

• Bulletin of the Korean Chemical Society
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• 제10권4호
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• pp.352-356
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• 1989

The crystal structure of maltitol, 4-O-${\alpha}$ -D-glucopyranosyl-D-glucitol, has been determined by X-ray diffraction method. The crystal is orthorhombic with cell parameters of a = 8.170(1), b = 12.731(1), c = 13.679(3) ${\AA}$, space group $P2_12_12_1$ and z = 4. The structure was solved by direct methods and refined to R = 0.030 for 1181 observed reflections measured on a diffractometer. The ${\alpha}$-glucose ring has chair conformation. The carbon atom chain of the glucitol residue has the bent, ap, Psc, Psc conformation. The angle at the ring oxygen atom is $112.6^{\circ}$ and the one at the glucosidic oxygen is $117.1^{\circ}$. The molecules are linked by very complicated hydrogen bonds, and there is an intramolecular hydrogen bond between O(1') and O(2').

• BMB Reports
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• 제54권5호
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• pp.233-245
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• 2021

In eukaryotes, the genome is hierarchically packed inside the nucleus, which facilitates physical contact between cis-regulatory elements (CREs), such as enhancers and promoters. Accumulating evidence highlights the critical role of higher-order chromatin structure in precise regulation of spatiotemporal gene expression under diverse biological contexts including lineage commitment and cell activation by external stimulus. Genomics and imaging-based technologies, such as Hi-C and DNA fluorescence in situ hybridization (FISH), have revealed the key principles of genome folding, while newly developed tools focus on improvement in resolution, throughput and modality at single-cell and population levels, and challenge the knowledge obtained through conventional approaches. In this review, we discuss recent advances in our understanding of principles of higher-order chromosome conformation and technologies to investigate 4D chromatin interactions.

• 공업화학
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• 제33권4호
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• pp.425-430
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• 2022

L-alanine (LA, as an amino acid residue) pentamer model was used to investigate changes in the dihedral angle, intramolecular hydrogen bonding and formation energies during structural optimization. LA pentamers having four conformation types [𝛽: 𝜑/𝜓=t-/t+, 𝛼: 𝜑/𝜓=g-/g-, PP_II: 𝜑/𝜓=g-/t+ and P-like: 𝜑/𝜓= g-/g+] were carried out by quantum chemical calculations (QCC) [B3LYP/6-31G(d,p)]. In LA, 𝛽, 𝛼, and P-like types did not change by optimization, having an intra-molecular hydrogen bond: NH⋯OC (H-bond), and PP_II types in the absence of H-bond were transformed into P-like at the designated 𝜓 of 140°, and to 𝛽 at that of 160° or 175°. P-like and 𝛼 were about 0.5 kcal/mol/mu more stable than 𝛽. In order to understand the processes of the transformations, the changes of 𝜑/𝜓, distances of NH-OC (d_NH/CO) and formation energies (𝜟E, kcal/mol/mu) were examined.

• 국제학술발표논문집
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• The 1th International Conference on Construction Engineering and Project Management
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• pp.452-458
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• 2005

The Japanese construction industry has faced on lack of quality that is one of the strong confidence fields. It is said that the main reason of this trend is in the case of construction supervisor's defects. But real problems are both the degree of drawing's completion and design activities in construction phase by architect. The purpose of this paper examines that the role of construction supervisor in Japan is changing to the management field and construction conformation, based on the analysis of the WBS based on international comparison among Korea, China, the UK, the US, and Japan.

• International Journal of Advanced Culture Technology
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• 제11권2호
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• pp.323-329
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• 2023

In this study, Proline pentamer model was used to investigate change in the dihedral angle, intramolecular hydrogen bonding and formation energies during structural optimization. L-Proline (LP, as an imino acid residue) pentamers having four conformation types [β: φ/ψ=t−/t+, α: φ/ψ=g−/g−, PP_II: φ/ψ=g−/t+ and Plike: φ/ψ= g−/g+] were carried out by QCC [B3LYP/6-31G(d,p)]. The optimized structure and formation energy were examined for designated structure. In LP, P-like and PP_II types did not change by optimization, and β types were transformed into PP_II having no H-bond independently of the designated ψ values. PP_II was more stable than P-like by about 2.2 kcal/mol/mu. The hydrogen bond distances of d2(4-6) type H-bonds were 1.94 - 2.00Å. In order to understand the processes of the transformations, the changes of φ/ψ, distances of NH-OC (d_NH/CO) and formation energies (ΔE, kcal/mol/mu) were examined.

• 대한화학회지
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• 제39권2호
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• pp.132-135
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• 1995

• Bulletin of the Korean Chemical Society
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• 제24권2호
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• pp.151-152
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• 2003

• 한국동물학회:뉴스레터
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• 제12권2호
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• pp.6-7
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• 1995

No Abstract, See Full Text