• Applied Chemistry for Engineering
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• v.28 no.4
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• pp.404-409
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• 2017

Natural polymer chitosan has been widely applied to medical fields due to its biochemical activities such as anticancer, antibacterial and lowering cholesterol in addition to biocompatibility and biodegradability. Currently, researches are being actively conducted to develop various drug-encapsulated chitosan nanoparticles for curing different diseases by applying chitosan to a drug delivery system. The free amine ($-NH_2$) group present in chitosan can bind to various hydrophobic groups by physical and chemical modification and the chitosan with hydrophobic groups can form shell-core nanoparticles by self-assembly when dispersed in water. In addition, an insoluble drug can increase the solubility against water when it was encapsulated in the core of chitosan nanoparticles. Also, the therapy effect can be maximized by minimizing side effects of drugs such as proteins, anticancer drugs and vaccines when they were encapsulated in the core of chitosan nanoparticles. Moreover, it is possible to control the particle size and release rate according to the hydrophobic group introduced to chitosan, so that it can be applied to a wide range of medical fields. The purpose of this review is to discuss the preparation and property of chitosan nanoparticles modified with various hydrophobic groups, and the application to drug delivery systems according to their property.

• Journal of the Korean institute of surface engineering
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• v.54 no.6
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• pp.357-364
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• 2021

In this study, DLC films deposited by PECVD were evaluated to the properties of super-hydrophobic by CF₄ treatment. The structure of DLC films were confirmed by Raman Spectra whether or not mixed sp³ (like diamond) peak and sp² (like graphite) peak. And the hydrogen contents in the DLC films (F-DLC) were measured by RBS analysis. In addition, DLC films were analyzed by scratch test for adhesion, nano-indentation for hardness and tribo-meter of Ball-on-disc type for friction coefficient. In the result of analysis, DLC films had traditional structure regardless of variation of hardness at constant conditions. Also adhesion of DLC film was increased as higher material hardness. Otherwise, friction coefficient was increased as lower material hardness. The DLC films were treated by CF₄ plasma treatment to enhance the properties of super-hydrophobic. And the DLC films were measured by ESEM(Enviromental Scanning Electron Microscope) for water condensation.

• Journal of the Korean Chemical Society
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• v.14 no.2
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• pp.161-168
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• 1970

In order to obtain the more effective evidence, supporting the hypothesis which have been previously described by former report that pepsin (EC 3.4. 4.1) forms a hydrophobic bond with the nonpolar side chain of its substrate, the inhibitory effect of carboxylic acids(from formic acid to iso-butyric acid) on the activity of pepsin to the synthetic dipeptide, N-Carbobenzoxy-L-glutamyl-L-tyrosine, was discussed. The kinetic study showed that the inhibition by carboxylic acids was competitive. The Kidecreased with increasing size of the inhibitor molecule. The $-{\Delta}F^{\circ}$increased linearly with increasing number of carbon atoms in the hydrocarbon chain of the inhibitor. It was confirmed that the hydrophobic bond between more than one side chain of amino acid residues(phenylalanine) in the binding region of the active center of pepsin and the side chain of amino acid residues in the substrate was formed as the first step of its enzymic mechanism. The inhibitory effect of carboxylic acids was due to the competition of the hydrocarbon group of the carboxylic acids with the side chain of the substrate for the hydrophobic binding site(the side chain of phenylalanine) of the pepsin.

• Journal of Photoscience
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• v.12 no.1
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• pp.25-32
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• 2005

Binding of N-Alkyl phenothiazines (NAP) to bovine serum albumin (BSA) was studied by spectroscopic methods.It was found that the phenothiazine ring common to all drugs makes major contribution to interaction. However, the nature of alkylamino group at position 10 influences the protein binding significantly. Stern-Volmer plots indicated the presence of static component in the quenching mechanism. The high magnitude of rate constant of quenching indicated that the process of energy transfer occurs by intermolecular interaction and thus the drug-binding site is in close proximity to tryptophan residues of BSA. Binding studies in presence of hydrophobic probe, 8-anilino-1-naphthalein-sulphonic acid showed that there is hydrophobic interaction between drug and the probe and they do not share common sites in BSA. Thermodynamic parameters obtained from data at different temperatures showed that the binding of NAP to BSA predominantly involve hydrophobic forces. The effects of some cations and anions common ions were investigated on NAP-BSA interactions. The CD spectrum of BSA in presence of drug showedthat binding of drug leads to change in the helicity of the protein.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.257-257
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• 2013

In order to selectively remove oil and organic compound from water, silica nanoparticles with hydrophobic coating was used. Since silica nanoparticles are generally hydrophilic, removal efficiency of oil and organic compound, such as toluene, in water can be decreased due to competitive adsorption with water. In order to increase the removal efficiency of oil and toluene, hydrophobic polydimethylsiloxane (PDMS) was coated on silica nanoparticles in the form of thin film. Hydrophobic property of the PDMS-coated silica nanoparticles and hydrophilic silica nanoparticles were easily confirmed by putting it in the water, hydrophilic particle sinks but hydrophobic particle floats. PDMS coated silica nanoparticles were dispersed on a slide glass with epoxy glue on and the water contact angle on the surface was determined to be over $150^{\circ}$, which is called superhydrophobic. FT-IR spectroscopy was used to check the functional group on silica nanoparticle surface before and after PDMS coating. Then, PDMS coated silica nanoparticles were used to selectively remove oil and toluene from water, respectively. It was demonstrated that PDMS coated nanoaprticles selectively aggregates with oil and toluene in the water and floats in the form of gel and this gel remained floating over 7 days. Furthermore, column filled with hydrophobic PDMS coated silica nanoparticles and hydrophilic porous silica was prepared and tested for simultaneous removal of water-soluble and organic pollutant from water. PDMS coated silica nanoparticles have strong resistibility for water and has affinity for oil and organic compound removal. Therefore PDMS-coated silica nanoparticles can be applied in separating oil or organic solvents from water.

• Journal of the Korean Applied Science and Technology
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• v.27 no.4
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• pp.545-551
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• 2010

Hydrophobically monoendcapped poly(sodium acrylate)s formed hydrophobic microdomains in water. This was concluded on poly(sodium acrylate)s with a linear $C_{12}$-alkyl chain attached specifically at the end of the polymer. There was no well defined CMC (critical micelle concentration), but rather a gradual transition from a micelle free solution to a micelle solution. Steady state fluorescence spectroscopy indicates that the micro domains are rather hydrophobic. At pH 5 in the abscence of salt and at pH 9 in the prescence of 1 M sodium citrate the CAC (critical aggregation concentration) was in the range of 0.1 to 2.4 mM. However at pH 5 there was a linear increase in the transition concentration with a head-group size due to an increase in steric and electrostatic repulsions between polymer main chains. At pH 9 in the abscence of salt the transition concentration was in the range of 1 to 80 mM. For the larger polymers there was a effect which consisted of a concentration gradient of sodium counterion toward the hydrophobic domain. The effect was larger for the larger polymers because of the higher total sodium concentration and the less steep counterion concentration gradient.

• Journal of the Korean institute of surface engineering
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• v.54 no.5
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• pp.222-229
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• 2021

Icing causes various serious problems, where water vapor or water droplets adhere at cold conditions. Therefore, understanding of ice adhesion on solid surface and technology to reduce de-icing force are essential for surface finishing of metallic materials used in extreme environments and aircrafts. In this study, we controlled wettability of aluminum alloy using anodic oxidation, hydrophobic coating and lubricant-impregnation. In addition, surface porosity of anodized oxide layer was controlled to realize superhydrophilicity and superhydrophobicity. Then, de-icing force on these surfaces with a wide range of wettability and mobility of water was measured. The results show that the enhanced wettability of hydrophilic surface causes strong adhesion of ice. The hydrophobic coating on the nanoporous anodic oxide layer reduces the adhesion of ice, but the volume expansion of water during the freezing diminishes the effect. The lubricant-impregnated surface shows an extremely low adhesion of ice, since the lubricant inhibits the direct contact between ice and solid surface.

• Bulletin of the Korean Chemical Society
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• v.19 no.5
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• pp.569-575
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• 1998

Investigation of the structure of the gangliosides has proven to be very important in the understanding of their biological roles. We have determined the tertiary structure of asialoganglioside GM1 $(GA_1)$ using NMR spectroscopy and distance geometry calculations. All of the structures are very similar except the glycosidic torsion angles in the ring IV and ring III linkages. There are two low-energy structures for GA1, G1 and G2. G1 differs from G2 only in the IV-III glycosidic linkages and the orientation of acetamido group in ring III. There is a stable intramolecular hydrogen bond between the third hydroxyl group in ring I and the ring oxygen atom in ring II. Also, there may be a weak hydrogen bond between the second hydroxyl group in ring IV and the acetamido group in ring III. Small coupling constants of $^3J_{IH3,IOH3}\; and\; ^3J_{IVH2,IVOH2}$ support this result. Overall structural features of $(GA_1)$ are very similar to those of $(GM_1)$. It implicates that specificities of the sugar moieties in GM1 are caused not by their tertiary foldings, but mainly by the electrostatic interactions between the polar sialic acid and its receptors. Since it is evident that $(GA_1)$ is more hydrophobic than $(GA_1)$, a receptor with a hydrophobic binding site can recognize the $(GA_1)$ better than $(GA_1)$. Studies on the conformational properties of $(GA_1)$ may lead to a better understanding of the molecular basis of its functions.

• BMB Reports
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• v.40 no.2
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• pp.232-238
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• 2007

The p13 gene is uniquely present in Group II nucleopolyhedroviruses (NPVs) and some granuloviruses, but not in Group I NPVs. p13 gene was first described by our laboratory in Leucania separatamultiple nuclear polyhedrosis virus (Ls-p13) in 1995. However, the functions of Ls-P13 and of its homologues are unknown. When Ls-p13 was inserted into Autographa californica nucleopolyhedrovirus, a Group I NPV, polyhedra yield was inhibited. However, this inhibition was prevented when the leucine zipper-like domain of Ls-p13 was mutated. To determine the cause of this marked difference between Ls-P13 and leucine zipper mutated Ls-P13 (Ls-P13mL), oligomerization and secondary structure analyses were performed. High performance liquid chromatography and yeast two-hybrid assays indicated that neither Ls-P13 nor Ls-P13mL could form oligomers. Informatics and circular dichroism spectropolarimetry results further indicated marked secondary structural differences between Ls-P13 and Ls-P13mL. The LZLD of Ls-P13 has two extended heptad repeat units which form a hydrophobic surface, but it is short of a third hydrophobic heptad repeat unit for oligomerization. However, the mutated LZLD of Ls-P13mL lacks the above hydrophobic surface, and its secondary structure is markedly different. This difference in its secondary structure may explain why Ls-P13mL is unable to inhibit polyhedra yield.

• Journal of Korea Soil Environment Society
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• v.4 no.3
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• pp.17-24
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• 1999

The effects of hydrophobic chain length and its structure of nonionic surfactants on surfactant adsorption and contaminated diesel removal were studied in kaolin soil. Hydrocarbon chain length and double bond in hydrophobic tail group of nonionic surfactants affected surfactant adsorption and diesel removal efficiency from kaolin soil. The degrees of surfactant adsorption and diesel removal were closely related each other. Among nonionic surfactants we studied, surfactants with shorter hydrophobic chain length and higher HLB value showed lower degree of adsorption and higher efficiency of diesel removal. The existence of unsaturated carbons in the structure of hydrophobic chain enhanced diesel removal by reducing surfactant adsorption to kaolin soil. The best diesel removal was obtained after adsorption saturation was reached. If surfactant concentration was higher than a critical value, diesel removal was reduced probably because of precipitation. liquid crystal formation, or coacervation of surfactants at high concentration.