• Bulletin of the Korean Chemical Society
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• v.17 no.2
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• pp.201-205
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• 1996

The crystal and molecular structure of thiourea dioxide, (NH2)2CSO2, was determined by x-ray single crystal diffraction techniques. Lattice constants are a=10.669(2), b=10.119(2), and c=3.9151(5) Å with the space group Pnma and Z=4. The thiourea portion of the molecule has a planar conformation. When the two oxygen atoms are included, the sulfur atom is at the apex of a trigonal pyramid formed with the two oxygen atoms and the carbon atom as the base. The crystal structure is stabilized by strong intermolecular hydrogen bonds. Ab initio calculations were performed to investigate the bonding features and reactivity of thiourea dioxide. The calculated bond order of S-C is only 0.481. The hydrogen bond energy was computed to be 22.3 kcal/mol for dimer. MEP analysis reveals that the sites on nucleophilic reactions are S and C atoms.

• Bulletin of the Korean Chemical Society
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• v.5 no.4
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• pp.158-162
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• 1984

The crystal structure of chloramphenicol base, $C_9H_{l2}N_2O_4$, the deacylated base of antibiotic chloramphenicol, has been determined by X-ray diffraction techniques using diffractometer data obtained by the ${\omega}-2{\theta}$ scan technique with CuK${\alpha}$ radiation from a crystal with space group symmetry $P2_12_12_1$ and unit cell parameters a = 22.322(6), b = 7.535(6), c = 5.781(5) ${\AA}$. The structure was solved by direct methods and refined by full-matrix least-squares to a final R = 0.051 for the 573 observed reflections. The overall conformation of the base is quite different from those of the chloramphenicol congeners which are similar despite the presence of many rotatable single bonds. The propane chain in the base is bent with respect to the phenyl ring, while it is extended in the chloramphenicol congeners. There is no intramolecular hydrogen bond between the hydroxyl groups of the propanediol moiety. All of the molecules in the crystal lattice are connected by a three-dimensional hydrogen bonding network.

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.408.1-408.1
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• 2002

A interpolymer complexes composed of poly(acrylic acid)(PAA) and po!y(vinyl alcohol)(PVA) were prepared by template polymerization of acrylic acid in the presence of PVA for mucoadhesive drug delivery. FT -IR results showed that the PAA/PVA interpolymer complex was formed by hydrogen bonding between the carboxyl groups of PAA and the hydroxyl group of PVA. The dissolution rate or the swelling ratio of the PAA/PVA interpolymer complexes was dependent on the pH and molecular weight of PVA that was used as a template. (omitted)

• Applied Chemistry for Engineering
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• v.33 no.4
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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.

• Advances in nano research
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• v.15 no.1
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• pp.49-57
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• 2023

As composite materials are used in many applications, the modern world looks forward to significant progress. An overview of the application of composite fiber materials in sports equipment is provided in this article, focusing primarily on the advantages of these materials when applied to sports equipment, as well as an Analysis of the influence of sports equipment of fiber-reinforced composite material on social sports development. The present study investigated surface morphology and physical and mechanical properties of S-glass fiber epoxy composites containing Al₂O₃ nanofillers (for example, 1 wt%, 2 wt%, 3 wt%, 4 wt%). A mechanical stirrer and ultrasonication combined the Al₂O₃ nanofiller with the matrix in varying amounts. A compression molding method was used to produce sheet composites. A first physical observation is well done, which confirms that nanoparticles are deposited on the fiber, and adhesive bonds are formed. Al₂O₃ nanofiller crystalline structure was investigated by X-ray diffraction, and its surface morphology was examined by scanning electron microscope (SEM). In the experimental test, nanofiller content was added at a rate of 1, 2, and 3% by weight, which caused a gradual decrease in void fraction by 2.851, 2.533, and 1.724%, respectively, an increase from 2.7%. The atomic bonding mechanism shows molecular bonding between nanoparticles and fibers. At temperatures between 60 ℃ and 380 ℃, Thermogravimetric Analysis (TGA) analysis shows that NPs deposition improves the thermal properties of the fibers and causes negligible weight reduction (percentage). Thermal stability of the composites was therefore presented up to 380 ℃. The Fourier Transform Infrared Spectrometer (FTIR) spectrum confirms that nanoparticles have been deposited successfully on the fiber.

• Journal of Applied Biological Chemistry
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• v.54 no.1
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• pp.56-62
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• 2011

Molecular docking of polyhydroxy substituted flavone analogues (1-25) as substrate molecules to the active site of tyrosinase (PDB ID: Deoxy-form (2ZMX) & Oxy-form (1WX2)) and Free-Wilson analysis were studied to understand the roles of hydroxyl substituents ($R_1-R_9$) in substrate molecules for the tyrosinase inhibitory activation. It is founded from Free-Wilson analysis that the $R_1$=hydroxyl among $R_1-R_9$ substituents had the strongest influence on the tyrosinase inhibitory activity. H-bonds between the hydroxyl substituents of substrate molecules and amino acid residues in the active site of tyrosinase were contributed to make a stable substrate-receptor complex compound. Particularly, it is proposed from the findings that the noncompetitive inhibitory activation would take place via H-bonding between peroxide oxygen (Per404) atom in the active site of tyrosinase and the hydroxyl substituents in substrate molecule.

• Archives of Pharmacal Research
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• v.24 no.5
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• pp.455-465
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• 2001

The highly potent cytotoxic DNA-DNA cross-linker consists of two cyclopropa[c]pyrrolo[3,4-3]indol-4(5H)-ones insoles [(+)-CPI-I] joined by a bisamido pyrrole (abbreviated to "Pyrrole"). The Pyrrole is a synthetic analog of Bizelesin, which is currently in phase II clinical trials due to its excellent in vivo antitumor activity. The Pyrrole has 10 times more potent cytotoxicity than Bizelesin and mostly form DNA-DNA interstrand cross-links through the N3 of adenines spaced 7 bp apart. The Pyrrole requires a centrally positioned GC base pair for high cross-linking reactivity (i.e., $5^1$-T$AT_2$A*-$3^1$), while Bizelesin prefers purely AT-rich sequences (i.e., $5^1$-T$AT_4$A*-$3^1$, where /(equation omitted) represents the cross-strand adenine alkylation and A* represents an adenine alkylation) (Park et al., 1996). In this study, the high-field $^1$H-NMR and rMD studies are conducted on the 1 1-mer DNA duplex adduct of the Pyrrole where the 5′(equation omitted)TAGTTA*-3′sequence is cross-linked by the drug. A severe structural perturbation is observed in the intervening sequences of cross-linking site, while a normal B-DNA structure is maintained in the region next to the drug-modified adenines. Based upon these observations, we propose that the interplay between the bisamido pyrrole unit of the drug and central C/C base pair (hydrogen-bonding interactions) is involved in the process of cross-linking reaction, and sequence specificity is the outcome of those interactions. This study suggests a mechanism for the sequence specific cross-linking reaction of the Pyrrole, and provides a further insight to develop new DNA sequence selective and distortive cross-linking agents.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.45 no.4
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• pp.1-8
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• 2013

High loading of printing and writing grades with fillers has many advantageous aspects in papermaking because it allows decreasing fiber use and reducing manufacturing cost. High loading technology, however, has some disadvantageous aspects as well. It decreases physical properties of papers, especially strength properties. The problem associated with high loading can be reduced by applying surface sizing starch solution onto paper surface. It is important to control the penetration of the surface sizing starch solution into paper web to obtain the desired property improvement. In this study, the effect of the addition of two polymers into starch solution on paper properties has been examined. PVOH and polyDADMAC were used as polymeric additives for surface sizing with oxidized starch. Viscosity of starch solutions and surface roughness of dried starch films on glass slides showed that some interactions between polymeric additives and oxidized starch have been occurred and the most extensive interaction with starch solution was obtained with high molecular weight polyDADMAC. Low molecular weight PVOH was most effective in improving folding endurance and internal bond strength. On the other hand, polymer addition showed no effect on surface strength of paper. This indicates that not the level of starch holdout but the bonding strength of starch itself has predominant influence on surface strength of paper.

• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3429-3443
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• 2013

Chemokine receptor (CCR2) is a G protein-coupled receptor that contains seven transmembrane helices. Recent pharmaceutical research has focused on the antagonism of CCR2 and candidate drugs are currently undergoing clinical studies for the treatment of diseases like arthritis, multiple sclerosis, and type 2 diabetes. In this study, we analyzed the time dependent behavior of CCR2 docked with a potent 4-azetidinyl-1-aryl-cyclohexane (4AAC) derivative using molecular dynamics simulations (MDS) for 20 nanoseconds (ns). Homology modeling of CCR2 was performed and the 4AAC derivative was docked into this binding site. The docked model of selected conformations was then utilized to study the dynamic behavior of the 4AAC enzyme complexes inside lipid membrane. MDS of CCR2-16b of 4AAC complexes allowed us to refine the system since binding of an inhibitor to a receptor is a dynamic process and identify stable structures and better binding modes. Structure activity relationships (SAR) for 4AAC derivatives were investigated and reasons for the activities were determined. Probable binding pose for some CCR2 antagonists were determined from the perspectives of binding site. Initial modeling showed that Tyr49, Trp98, Ser101, Glu291, and additional residues are crucial for 4AAC binding, but MDS analysis showed that Ser101 may not be vital. 4AAC moved away from Ser101 and the hydrogen bonding between 4AAC and Ser101 vanished. The results of this study provide useful information regarding the structure-based drug design of CCR2 antagonists and additionally suggest key residues for further study by mutagenesis.

• Polymer(Korea)
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• v.26 no.6
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• pp.710-717
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• 2002

Molecularly imprinted polymers were prepared in particle forms by crosslinking methacrylic acid (MAA)) using all trans-retinoic acid as a template. The HPLC column packed with the prepared molecular imprinted polymers showed high capability in separation of retinoid derivatives. The column capacity factor and selectivity increased with increasing MAA to template ratio when the incorporated template amount was fixed, as it statistically generated more binding sites between host molecules and template. Molecularly imprinted polymer particles prepared via an emulsion polymerization method were round-shaped and their sizes were more uniformly distributed, but their separation capability was inferior to those obtained by solution polymerization method. It was presumably because the loss of interaction strength between MAA and the template due to hydrogen bonding either between MAA and water or between template and water during the synthesis of molecularly imprinted polymers.