• Polymer(Korea)
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• v.33 no.6
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• pp.615-619
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• 2009

Pd-POSS nanoparticles were produced from the reaction of palladium (II) acetate and octa(3-aminopropyl)octasilsesquioxane octahydrochloride (POSS-${NH_3}^+$) in methanol at room temperature. Pd-POSS nanoparticles with a mean diameter of 60-80 nm were the highly ordered spherical aggregates. In contrast, Pd nanoparticles with a size of 4.0 nm were obtained when POSS-${NH_3}^+$ was not introduced. Pd-POSS/PAA nanocomposites of Pd-POSS nanoparticles and poly(acrylic acid) (PAA) were fabricated by utilizing ionic interactions between positively charged Pd-POSS nanoparticles and negatively charged carboxylate groups of PAA. PAA was used as a cross-linker for the preparation of hybrid nanocomposites with the controlled organized structures of Pd-POSS nanoparticles. That is, the self-organization of Pd-POSS nanoparticles was formed into the shape of continuous lines by using PAA as a cross-linker. The composition, structure, surface morphology, and thermal stability of the Pd-POSS/PAA nanocomposites were studied by FE-SEM, AFM, TEM, FT-IR, and TGA.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.729-732
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• 2012

Herein we report the in-situ synthesis and direct decoration of chalcogenide naoparticles (NPs) onto multiwalled carbon nanotubes (MWCNTs) through an ionic liquid-assisted sonochemical method (ILASM). The as-obtained MWCNT/$BMimBF_4$/CdTe, MWCNT/$BMimBF_4$/ZnTe and MWCNT/$BMimBF_4$/ZnSe nanocomposites were characterized by TEM images and EDS spectra. In particular, the morphologies of nanocomposites such as bump-like, rough, and smooth core-shell structures were strongly influenced by the type of precursors and the interactions with MWCNT. This synthetic strategy opens a new way to directly synthesize and deposit semiconducting NPs (s-NPs) onto CNTs, which consist of binary components obtained from two precursors with different reaction rates.

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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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.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.24-27
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• 2009

Solid-state dye-sensitized solar cells (DSSCs) have been constructed employing supramolecular electrolytes with multiple hydrogen bonding. A supramolecule was facilely synthesized by one-pot reaction between the amines of methyl isocytosine (MIC) and the epoxy groups of poly(ethylene glycol diglycidyl ether) (PEGDGE) to produce quadruple hydrogen bonding units. Hydrogen bonding interactions and dissolution behavior of salt in supramolecular electrolytes are investigated. The ionic conductivity of the supramolecular electrolytes with ionic liquid, i.e. 1-methyl-3-propylimidazolium iodide (MPII) reaches $8.5{\times}10^{-5}$ S/cm at room temperature, which is higher than that with metal salt (KI). A worm-like morphology is observed in the FE-SEM micrographs of $TiO_2$ nanoporous layer, due to the connection of $TiO_2$ nanoparticles resulting from adequate coating by electrolytes. DSSCs employing the supramolecular electrolytes with MPII and KI exhibit an energy conversion efficiency of 2.5 % and 0.5 %, respectively, at 100 $mW/cm^2$, indicating the importance of the cation of salt. Solar cell performances were further improved up to 3.7 % upon introduction of poly(ethylene glycol dimethyl ether) (PEGDME) with 500 g/mol.

• Journal of Pharmaceutical Investigation
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• v.18 no.3
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• pp.113-123
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• 1988

A series of water-soluble polyparacyclophanes bearing two diphenylmethane or two diphenyl ether skeletons were investigated to develop useful host compounds by using 1-anilinonaphthalene-6-sulfonate (ANS) and 2-p-toluidinylnaphthalene-6-sulfonate (TNS) as fluorescent hydrophobic substrates in aqueous solution. It was noteworthy that remarkable fluorescent enhancements and blue shifts of ANS and TNS were observed only in the presence of 1,6,20,25-tetraaza[6.1.6.1] paracyclophane (CPM 44) and 1,6,21,27-tetraaza [7.1.7.1] paracyclophane (CPM 55) for diphenylmethane skeleton, and 1,7,21,27-tetraaza-14,34-dioxa [7.1.7.1] paracyclophane (CPE 55) and 1,8,22,29-tetraaza-15,36-dioxa [8.1.8.1] paracyclophane (CPE 66) for diphenyl ether skeleton, comparing with ${\alpha}-\;and\;{\beta}-cyclodextrins$. However, their acyclic analogues such as 4,4'-dimethylaminodiphenylmethane and 4,4'-dimethylaminodiphenyl ether, and paracyclophanes whose cavities were smaller showed only small effects under the same conditions. These facts suggested that hosts and substrates were in an intimate contact which would not occur without larger structures, and thus that guest molecules were strongly incorporated in the hydrophobic cavities of these larger paracyclophanes. The effects of pH on the fluorescent intensity of ANS-CPM 44, ANS-CPM 55, ANS-CPE 55, ANS-CPE 66, TNS-CPM 44, TNS-CPM 55, TNS-CPE 55 and TNS-CPE 66 systems were not significant below pH 2.0, but their fluorescent intensities were markedly reduced with increasing ionic strength.

• Korea-Australia Rheology Journal
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• v.19 no.2
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• pp.51-59
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• 2007

A polyelectrolyte chain confined in a slit nanochannel exhibits a structural transition from the one in free space. In this paper, the effect of the long-range electrostatic interactions between the xanthan polyelectrolyte and the slit wall on the confined xanthan conformation is investigated via the Brownian dynamics simulation. A neutral and two negatively charged surfaces of polydimethylsiloxane (PDMS) and glass are combined to make four kinds of slit channels with different charge characteristics: i) neutral-neutral, ii) glass-glass, iii) neutral-PDMS and iv) neutral-glass walls. Their walls are characterized by uniform surface charge densities determined from experimental data of zeta potential. Both the nonmonotonic chain size variation and the loss of long-range bond vector correlation, previously observed under confinement in the PDMS-PDMS slit, are also found in the neutral slit, demonstrating the nonelectrostatic origin of such crossover behaviors. As expected, the effect of wall charges is negligible at sufficiently high medium ionic strength of 100mM but it becomes significant in the opposite limit of 0.01mM. In the latter case, the high charge density of glass walls strengthens the effective confinement of a negatively charged polyelectrolyte and produces a xanthan structure comparable to that confined in a much narrower neutral slit. The obtained structural data suggest the possibility of controlling the structure of confined polyelectrolytes by the modification of surface charge characteristics of micro/nanofluidic devices in combination with the adjustment of the medium ionic strength.

• Journal of Environmental Science International
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• v.14 no.6
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• pp.525-532
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• 2005

Polyelectrolyte titration, which was called colloid titration is based on the stoichiometric reaction between oppositely charged polyelectrolytes, This can be used, for instance, to determine the charge density of a cationic polyelectrolyte, using an anionic polyelectrolyte of known charge density, such as potassium polyvinyl sulfate (PPVS). The technique requires a suitable method of end-point detection and there are several possibilities. In this work, two methods have been investigated: visual titrimetry based on the color change of a cationic dye (o-toluidine blue, o-Tb) and spectrophotometry based on the absorbance change corresponding to the color change of the same dye. These have been applied to several cationic polyelectrolytes with different charge density and molecular weight. In all cases, the cationic charge was due to quaternary nitrogen groups. In the case of cationic dye, it was shown that the sharpness depends on the charge density of cationic polyelectrolyte. With the polyelectrolytes of lower charge density, the binding to PPVS is weaker and binding of the dye to PPVS can occur before all of the polyelectrolyte charge has been neutralized. However, by carrying out titrations at several polyelectrolyte concentrations, good linear relationships were found, from which reliable charge density values could be derived. Effects of pH and ionic strength were also briefly investigated. For cationic polyelectrolytes (copolymers of acrylamide and dimethylaminoethy] acrylate), there was some loss of charge at higher pH values, probably as a result of hydrolysis. Increasing ionic strength causes a less distinct color change of o-Tb, as a result of weaker electrostatic interactions.

• Analytical Science and Technology
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• v.13 no.4
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• pp.433-439
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• 2000

Adsorption behaviors of Ni(II) ions were investigated using amorphous alumina as adsorbent. In the adsorption kinetic study, it was observed that Ni(II) ions were bound to the alumina surface in two adsorption stages, the rapid and slow adsorption stages. The rapid adsorption proceeded within 1 hr, thereafter the slow adsorption occurred. The results of adsorption isotherm experiments showed that the Ni(II) adsorption obeyed the Langmuir-Freundlich isotherm, and that the adsorption enhanced with increasing pH. The change in ionic strength did not exhibit a conspicuous trend in Ni(II) adsorption, thereby suggesting that the adsorption occurs through surface complexation rather than electrostatic interactions. The amounts of adsorption were measured with varying pH at three different Ni(II) concentrations under the condition of constant ionic strength, showing that with increasing Ni(II) concentration, the percentage of adsorption decreased and the adsorption edge was shifted to a higher pH value.

• Applied Chemistry for Engineering
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• v.32 no.4
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• pp.371-378
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• 2021

The formation of hydrophilic surface based on polymers has received great attention due to the anti-adhesion of bacteria on solid substrates. Anti-adhesion coatings are aimed at suppressing the initial step of biofilm formation via non-cytotoxic mechanisms, and surfaces applied hydrophilic or ionic polymers showed the anti-adhesion effect for bioentities, such as proteins and bacteria. This is attributed to the formation of surface barrier from hydration layers, repulsions and osmotic stresses from polymer brushes, and electrostatic interactions between ionic polymers and cell surfaces. The antifouling polymer coating is usually fabricated by the grafting method through the bonding with functional groups on surfaces and the deposition method utilizing biomimetic anchors. This mini-review is a summary of representative antifouling polymers, coating strategies, and antibacterial efficacy. Furthermore, we will discuss consideration on the large area surface coating for application to public facilities and industry.

• Molecules and Cells
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• v.42 no.6
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• pp.460-469
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• 2019

Bacterial ${\alpha}-type$ carbonic anhydrase (${\alpha}-CA$) is a zinc metalloenzyme that catalyzes the reversible and extremely rapid interconversion of carbon dioxide to bicarbonate. In this study, we report the first crystal structure of a hyperthermostable ${\alpha}-CA$ from Persephonella marina EX-H1 (pmCA) in the absence and presence of competitive inhibitor, acetazolamide. The structure reveals a compactly folded pmCA homodimer in which each monomer consists of a 10-stranded ${\beta}-sheet$ in the center. The catalytic zinc ion is coordinated by three highly conserved histidine residues with an exchangeable fourth ligand (a water molecule, a bicarbonate anion, or the sulfonamide group of acetazolamide). Together with an intramolecular disulfide bond, extensive interfacial networks of hydrogen bonds, ionic and hydrophobic interactions stabilize the dimeric structure and are likely responsible for the high thermal stability. We also identified novel binding sites for calcium ions at the crystallographic interface, which serve as molecular glue linking negatively charged and otherwise repulsive surfaces. Furthermore, this large negatively charged patch appears to further increase the thermostability at alkaline pH range via favorable charge-charge interactions between pmCA and solvent molecules. These findings may assist development of novel ${\alpha}-CAs$ with improved thermal and/or alkaline stability for applications such as $CO_2$ capture and sequestration.