• Journal of Korean Dental Science
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• 제11권1호
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• pp.5-13
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• 2018

Purpose: Surface treatment with pH buffering agent has been developed to achieve higher and faster osseointegration. The aim of this study was to evaluate its influence by measuring removal torque and analyzing histological characteristics. Materials and Methods: Titanium implants with following surfaces were used in this study: sand-blasted acid-etched (SA) surface (SA group as control I group), SA surface in calcium chloride aqueous solution (CA group as control II group) and SA surface coated with pH buffering agent (pH group as test group). Removal torque test after 2 weeks and bone-to-implant contact and bone area analyses at 2 and 4 weeks were performed. Result: The rotational torque values at 2 weeks were significantly higher in pH group ($107.5{\pm}6.2Ncm$, P<0.05). The mean values of bone-to-implant contact at 2 and 4 weeks were both higher in pH group ($93.0%{\pm}6.4%$ at 2 weeks, $88.6%{\pm}5.5%$ at 4 weeks) than in SA group ($49.7%{\pm}9.7%$ at 2 weeks, $47.3%{\pm}20.1%$ at 4 weeks) and CA group ($73.7%{\pm}12.4%$ at 2 weeks, $72.5%{\pm}10.9%$ at 4 weeks) with significances (P<0.05). The means of bone area showed significantly higher numbers in pH group ($39.5%{\pm}11.3%$ at 2 weeks, $71.9%{\pm}10.9%$ at 4 weeks, P<0.05). Conclusion: Our findings demonstrated that surface modification with pH buffering agent improved early osseointegration with superior biomechanical property.

• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2508-2512
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• 2012

Cold shock proteins (CSPs) are a family of proteins induced at low temperatures. CSPs bind to single-stranded nucleic acids through the ribonucleoprotein 1 and 2 (RNP 1 and 2) binding motifs. CSPs play an essential role in cold adaptation by regulating transcription and translation via molecular chaperones. The solution nuclear magnetic resonance (NMR) or X-ray crystal structures of several CSPs from various microorganisms have been determined, but structural characteristics of psychrophilic CSPs have not been studied. Therefore, we optimized the purification process to obtain highly pure Lm-Csp and determined the three-dimensional structure model of Lm-Csp by comparative homology modeling using MODELLER on the basis of the solution NMR structure of Bs-CspB. Lm-Csp consists of a ${\beta}$-barrel structure, which includes antiparallel ${\beta}$ strands (G4-N10, F15-I18, V26-H29, A46-D50, and P58-Q64). The template protein, Bs-CspB, shares a similar ${\beta}$ sheet structure and an identical chain fold to Lm-Csp. However, the sheets in Lm-Csp were much shorter than those of Bs-CspB. The Lm-Csp side chains, E2 and R20 form a salt bridge, thus, stabilizing the Lm-Csp structure. To evaluate the contribution of this ionic interaction as well as that of the hydrophobic patch on protein stability, we investigated the secondary structures of wild type and mutant protein (W8, F15, and R20) of Lm-Csp using circular dichroism (CD) spectroscopy. The results showed that solvent-exposed aromatic side chains as well as residues participating in ionic interactions are very important for structural stability. Further studies on the three-dimensional structure and dynamics of Lm-Csp using NMR spectroscopy are required.

• Bulletin of the Korean Chemical Society
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• 제30권9호
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• pp.2083-2086
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• 2009

Human vascular endothelial growth factor receptor 2 (hVEGFR2) is an important signaling protein involved in angiogenesis and attractive drug target in cancer therapy. It has been reported that flavonols, a class of flavonoids, have anti-angiogenic activity in various cancer cell lines. We performed receptor-oriented pharmacophore based in silico screening for identification of hVEGFR2 inhibitors from flavonol database. By comparing with three X-ray complex structures of hVEGFR2 and its inhibitors, we evaluated the specific interactions between inhibitors and receptors and determined a single pharmacophore map. This map consisted of four features, a hydrogen bonding acceptor (HBA) on Cys917, two hydrogen bonding donors on Glu917 (HBD1) and Glu883 (HBD2), and one hydrophobic interaction (Lipo) with Val846, Ala864, Val897, Val914 and Phe1045 of hVEGFR2. Using this map, we searched a flavonol database including 9 typical flavonols and proposed that five flavonols, kaempferol, quercetin, fisetin, morin, and rhamnetin can be potent inhibitors of hVEGFR2. 3-OH of C-ring and 4’-OH of B-ring of flavonols are the essential features for hVEGFR2 inhibition. This study will be helpful for understanding the mechanism of inhibition of hVEGFR2 by natural products.

• Korea-Australia Rheology Journal
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• 제14권4호
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• pp.189-201
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• 2002

The interaction between hydrophobically modified hydroxyethyl cellulose (hmHEC), containing approximately 1 wt% side-alkyl chains of $C_{16}$, and an anionic sodium dodecyl sulphate (SDS) surfactant was investigated. For a semi-dilute solution of 0.5 wt% hmHEC, the previously observed behaviour of a maximum in solution viscosity at intermediate SDS concentrations, followed by a drop at higher SDS concentrations, until above the cmc of surfactant when the solution resembles that of the unsubstituted polymer, was confirmed. Additionally, a two-phase region containing a hydrogel phase and a water-like supernatant was found at low SDS concentrations up to 0.2 wt%, a concentration which is akin to the critical association concentration, cac, of SDS in the presence of hmHEC. Above this concentration, SDS molecules bind strongly to form mixed micellar aggregates with the polymer alkyl side-chains, thus strengthening the network junctions, resulting in the observed increase in viscosity and elastic modulus of the solution. The shear behaviour of this polymer-surfactant complex during steady and step stress experiments was examined In great detail. Between SDS concentrations of 0.2 and 0.25 wt%, the shear viscosity of the hmHEC-polymer complex network undergoes shear-induced thickening, followed by a two-stage shear-induced fracture or break-up of the network. The thickening is thought to be due to structural rearrangement, causing the network of flexible polymers to expand, enabling some polymer hydrophobic groups to be converted from intra- to inter-chain associations. At higher applied stress, a partial local break-up of the network occurs, while at even higher stress, above the critical or network yield stress, a complete fracture of the network into small microgel-like units, Is believed to occur. This second network rupture is progressive with time of shear and no steady state in viscosity was observed even after 300 s. The structure which was reformed after the cessation of shear is found to be significantly different from the original state.

• Asian Pacific Journal of Cancer Prevention
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• 제14권12호
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• pp.7095-7100
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• 2013

Histone deacetylase (HDAC) inhibitors of cyclic peptide have been proved to be the most complex but the most stable and relative efficient inhibitors because of their large cap region. In this paper, a series of studies were carried out to evaluate the efficacy of synthetic bicyclic tetrapeptide inhibitors 1-5 containing hydroxamic acid referring molecular docking, anti-proliferation, morphology and apoptosis. Docking analysis, together with enzyme inhibitory results, verified the selective capability of inhibitor 4 to HDAC4, which might closely related to haematological tumorigenesis, with Phe227, Asp115, Pro32, His198 and Ser114 participating into hydrophobic interactions and Van der Waals force which was familiar with former study. Moreover, inhibitor 4 inhibited K562 cell line at the $IC_{50}$ value of 1.22 ${\mu}M$ which was 51-67 times more efficient than that for U937 and HL60 cell lines. Inhibitor 4 exhibited the cell cycle-arrested capability to leukemia at S phase or G2/M phase as well as apoptosis-induced ability in different degrees. Finally, we considered that bicyclic tetrapeptide inhibitors were promising inhibitors used in cancer treatment and inhibitor 4 could prevent K562 cell line well from proliferation, arrest cell cycle and induce K562 towards apoptosis to achieve the goals of reversing cancer cells which could become a potential leukemia therapeutic agent in the future.

• Journal of Microbiology and Biotechnology
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• 제26권4호
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• pp.659-665
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• 2016

The oligosaccharides in human milk constitute a major innate immunological mechanism by which breastfed infants gain protection against infectious diarrhea. Clostridium difficile is the most important cause of nosocomial diarrhea, and the C-terminus of toxin A with its carbohydrate binding site, TcdA-f2, demonstrates specific abolishment of cytotoxicity and receptor binding activity upon diethylpyrocarbonate modification of the histidine residues in TcdA. TcdA-f2 was cloned and expressed in E. coli BL21 (DE3). A human milk oligosaccharide (HMO) mixture displayed binding with TcdA-f2 at 38.2 respond units (RU) at the concentration of 20 μg/ml, whereas the eight purified HMOs showed binding with the carbohydrate binding site of TcdA-f2 at 3.3 to 14 RU depending on their structures via a surface plasma resonance biosensor. Among them, Lacto-N-fucopentaose V (LNFPV) and Lacto-N-neohexaose (LNnH) demonstrated tight binding to TcdA-f2 with docking energy of −9.48 kcal/mol and −12.81 kcal/mol, respectively. It displayed numerous hydrogen bonding and hydrophobic interactions with amino acid residues of TcdA-f2.

• Bulletin of the Korean Chemical Society
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• 제35권8호
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• pp.2523-2528
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• 2014

In the present study, at first, azo Schiff base ligand of (N,N'-bis(5-phenylazosalicylaldehyde)-ethylenediamine) ($H_2L$) has been synthesized by condensation reaction of 5-phenylazosalicylaldehyde and ethylenediamine in 2:1 molar ratio, respectively. Then, its cobalt complex (CoL) was synthesized by reaction of $Co(OAc)_2{\cdot}4H_2O$ with ligand ($H_2L$) in 1:1 molar ratio in ethanol solvent. This ligand and its cobalt complex containing azo functional groups were characterized using elemental analysis, $^1H$-NMR, UV-vis and IR spectroscopies. Subsequently, the interaction between native calf thymus deoxyribonucleic acid (ct-DNA) and CoL complex was investigated in 10 mM Tris/HCl buffer solution, pH = 7 using UV-vis absorption, thermal denaturation technique and viscosity measurements. From spectrophotometric titration experiments, the binding constant of CoL complex with ct-DNA was found to be $(2.4{\pm}0.2){\times}10^4M^{-1}$. The thermodynamic parameters were calculated by van't Hoff equation.The enthalpy and entropy changes were $5753.94{\pm}172.66kcal/mol$ and $43.93{\pm}1.18cal/mol{\cdot}K$ at $25^{\circ}C$, respectively. Thermal denaturation experiments represent the increasing of melting temperature of ct-DNA (about $0.93^{\circ}C$) due to binding of CoL complex. The results indicate that the process is entropy-driven and suggest that hydrophobic interactions are the main driving force for the complex formation.

• 대한화장품학회지
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• 제44권3호
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• pp.285-293
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• 2018

코아세르베이트의 구조는 모발의 오일 및 폴리머 같은 기능성 성분 흡착에 매우 큰 영향을 준다. 본 연구의 목적은 알킬 셀룰로오스와 구아검 간 복합 코아세르베이트의 혼합물에서 그 구조적인 결합의 특성을 밝히는데 있다. 모발에 흡착되면 모발에 뻣뻣함을 부여하는 구아검 컨디셔닝 폴리머가 오일과 함께 알킬 셀룰로오스와 혼합될 경우 동일 함량 및 알킬 셀룰로오스와의 비가 3 : 1일 경우에 모발을 매우 부드럽게 함을 발견하였다. 이는 글루코스링을 백본으로 하는 양이온 알킬기 셀룰로오스 폴리머와 구아검 폴리머를 혼합하여 오일을 결합시키면, 알킬 셀룰로오스의 친수성 부위와 음이온 계면활성제가 정전기적으로 결합하고, 알킬 셀룰로오스의 4급 알킬 암모늄기에 포함되는 알킬기가 계면활성제의 소수성 부위와 함께 결합함과 동시에, 구아검 코아세르베이트가 전체적으로 안정적인 구조를 이루게 하여 많은 양의 코아세르베이트를 생성하게 하는 것을 코아세르베이트 생성양 측정 및 모발 유연성 증대를 통해 확인하였다.

• Asian Pacific Journal of Cancer Prevention
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• 제17권1호
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• pp.51-55
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• 2016

Phytochemical investigation of Pistacia integerrima has highlighted isolation of two known compounds naringenin (1) and dihydrokaempferol (2). A crude extract and these isolated compounds were here evaluated for their effects on reversion of multidrug resistance (MDR) mediated by P-glycoprotein (P-gp). The multidrug resistance P-glycoprotein is a target for chemotherapeutic drugs from cancer cells. In the present study rhodamine-123 exclusion screening test on human mdr1 gene transfected mouse gene transfected L5178 and L5178Y mouse T-cell lymphoma cells showed excellent MDR reversing effects in a dose dependent manner. In-silico molecular docking investigations demonstrated a common binding site for Rhodamine123, and compounds naringenin and dihydrokaempferol. Our results showed that the relative docking energies estimated by docking softwares were in satisfactory correlation with the experimental activities. Preliminary interaction profile of P-gp docked complexes were also analysed in order to understand the nature of binding modes of these compounds. Our computational investigation suggested that the compounds interactions with the hydrophobic pocket of P-gp are mainly related to the inhibitory activity. Moreover this study s a platform for the discovery of novel natural compounds from herbal origin, as inhibitor molecules against the P-glycoprotein for the treatment of cancer.

• Bulletin of the Korean Chemical Society
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• 제29권5호
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• pp.921-927
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• 2008

Discovery of $\alpha$-glucosidase inhibitors has been actively pursued with the aim to develop therapeutics for the treatment of diabetes and the other carbohydrate mediated diseases. As a method for the discovery of new novel inhibitors of $\alpha$-glucosidase, we have addressed the performance of the computer-aided drug design protocol involving the homology modeling of $\alpha$-glucosidase and the structure-based virtual screening with the two docking tools: FlexX and the automated and improved AutoDock implementing the effects of ligand solvation in the scoring function. The homology modeling of $\alpha$-glucosidase from baker’s yeast provides a high-quality 3-D structure enabling the structure-based inhibitor design. Of the two docking programs under consideration, AutoDock is found to be more accurate than FlexX in terms of scoring putative ligands to the extent of 5-fold enhancement of hit rate in database screening when 1% of database coverage is used as a cutoff. A detailed binding mode analysis of the known inhibitors shows that they can be stabilized in the active site of $\alpha$- glucosidase through the simultaneous establishment of the multiple hydrogen bond and hydrophobic interactions. The present study demonstrates the usefulness of the automated AutoDock program with the improved scoring function as a docking tool for virtual screening of new $\alpha$-glucosidase inhibitors as well as for binding mode analysis to elucidate the activities of known inhibitors.