• Preventive Nutrition and Food Science
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• v.3 no.2
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• pp.143-151
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• 1998

Protein -surfactant interactions have been investigate by measuring ζ-potential of $\beta$-lactoglobulin-coated emulsion droplets and $\beta$-lactoglobulin in solution in the rpesenceof surfactant, with particular emphasis on the effect of protein heat treatment(7$0^{\circ}C$, 30min). When ionic surfactant (SDS or DATEM) is added to the protein solution, the ζ-potential of the mixture is found to increase with increasing surfactant concentration, indicating surfactant binding to the protein molecules. For heat-denatured protein,it has been observed that the ζ-potential tends to be lower than that of the native protein. The effect of surfactant on emulsions is rather complicated .With SDS, small amounts of surfactant addition induce a sharp increase in zeta potential arising from the specific interaction of surfactant with protein. With further surfacant addition, there is a gradual reductio in the ζ-potential, presumably caused by the displacement of adsorped protein (and protein-surfactant complex) from the emulsion droplet surfac by the excess of SDS molecules. At even higher surfactant concentrations, the measured zeta potential appears to increase slightly, possibly due to the formation of a surfactant measured zeta potential appears to increase slightly, possibly due to the formation of surfactant micellar structure at the oil droplet surface. This behaviour contrastswith the results of the corresponding systems containing the anionic emulsifier DATEM, in which the ζ-potential of the system is found to increase continuously with R, particularly at very low surfactant concentration. Overall, such behaviour is consisten with a combination of complexation and competitive displacement between surfactant and protein occurring at the oil-water interface. In addition, it has also been found that above the CMC, there is a time-dependent increase in the negative ζ-potential of emulsion droplets in solutions of SDS, possibly due to the solublization of oil droplets into surfactant micelles in the aqueous bulk phase.

• Bulletin of the Korean Chemical Society
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• v.21 no.9
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• pp.867-874
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• 2000

Two new azobenzene crown ether calix[4]arenes, 10 and 11, were synthesized by two pathways. In the first pathway,two ethoxy nitrobenzene groups were attached to t-butylcalix[4]arenes in a 1,3 position. Subsequent reduction ofthe nitrobenzene group s by metallic zinc in an alkaline solution afforded 10 and 11 in8% and 12%,respectively. In the second pathway,an azobenzene containing two glycolic units was prepared prior connect-ing to t-butylcalix[4]arenes. The yields from the second approach (5%, 8% for 10 and 11, respectively) were lower than those from the former approach. Single crystals of 10 suitable for X-ray crystallography was ob-tained by recrystallization in methanol.Both the X-ray structure and the 1H-NMR spectrum of 10 indicated that the stereoisomer of the azobenzene moiety was trans and the calixarene platform was in cone conformation. 1H NMR spectroscopy suggested that 10 underwent an observable cis-trans isomerization in CDCl3 under room light and upon UV irradiation with cis:trans ratios of 33:67 and 36:64,respectively. Compound 6 which was the precursor of 11showed fluxional behavior and was found to have mixed conformations ofcone and partial cone with a ratio of 47:53 at -30 $^{\circ}C.$ 1H NMR spectrum of 11 suggested that 11 was initially isolated as cis azobenzene with calix[4]arene in cone conformation and underwent conformational interconversion through calix[4]arene annulas in a similar fashion to 6 upon exposing to light. The complexation studies of 10 with picrate salts of Na+ and K+ using 1H NMR spectroscopysuggested that Na+ preferred to bind the cis form of 10 while K+ preferred to bind the trans form. The stereoisomer of the azobenzene unit in 11 changed partially from cis to trans upon complexing with K+.

• Bulletin of the Korean Chemical Society
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• v.19 no.9
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• pp.897-906
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• 1998

A new synthesis has been developed for 1-thia-4,7-diazacyclononane and the complexation behavior of a particular derivative has been explored. The pentadentate ligand 4,7-bis(2-pyridylmethyl)-l-thia-4,7-diazacyclononane ([9]$N_2SPY_2$) and its iron(Ⅱ) and manganese(Ⅱ) complexes were prepared and characterized. Magnetic moments of 5.17 and 5.90 μB respectively, indicate that the iron(Ⅱ) and manganese(Ⅱ) complexes are high spin. Charge transfer transitions (d-π*) occur for [Fe(Ⅱ)([9]$N_2SPY_2)(X)]^{n+}$at 27027, 25000, and 24390 cm-1 for X=$H_2O$, Cl-, and OH-, respectively. In acetonitrile solution, the cyclic voltammogram of the manganese(Ⅱ) complex exhibits a redox couple at 0.92 V vs. NHE while the redox potentials for [Fe(Il)([9]$N_2SPY_2)(X)]^{n+}$ are 0.70, 0.66, and 0.37 V vs. NHE for X=$H_2O$, Cl-, and OH-, respectively. The d-π* charge transfer energy and Fe(Ⅱ)/Fe(Ⅲ) redox potential for [Fe(Ⅱ)([9]$N_2SPY_2)(X)]^{n+}$ increase in the same order: $H_2O>Cl^- >OH^-$. The crystal structures of the iron(Ⅱ) and manganese(Ⅱ) complexes reveal that the metal ions are sixcoordinate, binding to four nitrogen atoms and a sulfur atom from the pentadentate ligand, as well as a chloride anion, with the chloride and sulfur atoms in cis positions. The two metals have similar coordination geometries, which are closer to trigonal prismatic than octahedral. In both iron and manganese complexes, the M-N($sp_3$) trans to Cl- is 0.07 Å longer than the one cis to Cl- , and M-N($sp^2$) trans to S is 0.05 longer than the one cis to S atom.

• Bulletin of the Korean Chemical Society
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• v.19 no.6
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• pp.671-676
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• 1998

The formation and dissociation rates of $Ce^{3+}$ Complexes of the 1,4,7,10-tetraaza-13,16-dioxacyclooctadecane-NN', N",N"'-tetraacetic acid (1), 1,4,7,10-tetraaza-13,16-dioxacyclooctadecane-N,N',N",N"'-tetramethylacetic acid (2), and 1,4,7,10-tetraaza-13,16-dioxacyclooctadecane-N,N',N",N"'-tetrapropionic acid (3) have been measured by the use of stopped-flow spectrophotometry. Observations were made at 25.0±0.1 ℃ and at an ionic strength of 0.10 M $NaClO_4$. The complexation of $Ce^{3+}$ ion with 1 and 2 proceeds through the formation of an intermediate complex $(CeH_3L^{2+})^*$ in which the $Ce^{3+}$ ion is incompletely coordinated. This may then lead to be a final product in the rate-determining step. Between pH 4.76 and 5.76, the diprotonated $(H_2L^{2-})$ from is revealed to be a kinetically active species despite of its low concentration. The stability constants $(logK(CeH_3L^{2+}))$ and specific water-assisted rate constants $(k_{OH})$ of intermediate complexes have been determined from the kinetic data. The dissociation reactions of $Ce^{3+}$ complexes of 1, 2, and 3 were investigated with $Cu^{2+}$, ions as a scavenger in acetate buffer. All complexes exhibit acid-independent and acid-catalyzed contributions. The effect of buffer and $Cu^{2+}$ concentration on the dissociation rate has also been investigated. The ligand effect on the dissociation rate of $Ce^{3+}$ complexes is discussed in terms of the side-pendant arms and the chelate ring sizes of the ligands.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.6
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• pp.634-640
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• 2015

Chelating agents have been proposed to improve the efficiency of phytoextraction of heavy metal hyperaccumulator. However, little studies to elucidate mechanism of chelating agents to increase cadmium (Cd) extractability have been conducted. The objectives of this study were to evaluate effect of different chelating agents on Cd extractability and to determine mechanism of Cd mobilization affected by these agents. An arable soil was spiked with inorganic Cd ($CdCl_2$) to give a total Cd concentration of $20mgCdkg^{-1}$. Ethylenediaminetetraacetic acid (EDTA) and citric acid (CA) were selected and mixed with the arable soil at the rates of 0 and $5mmolkg^{-1}$. The mixture soils were incubated at $25^{\circ}C$ for 4 weeks in dark condition. Concentration of F1 Cd fractions (water soluble) significantly increased with addition of EDTA but did not changed with addition of CA. Especially; concentration of F5 Cd fractions (residual) significantly increased with addition of CA. Increase in water soluble with EDTA might be attributed to complexation of Cd and EDTA. Dissolved organic carbon concentration significantly increased with EDTA addition, but did not with CA implying that considerable amount of CA was decomposed to inorganic carbon by microorganism. Log activity of carbonate ($CO_3{^{2-}}$) which might be generated from CA increased with addition of CA. Increase in residual Cd fraction might be due to precipitation of Cd as $CdCO_3$. As a result, EDTA was effective in increasing Cd extractability, by contrast CA had significant effect in reducing Cd extractability.

• Journal of the Korean Applied Science and Technology
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• v.35 no.4
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• pp.1031-1037
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• 2018

The formation of a complex between PVP or HPC and iodine was indicated by a red shift in the tri-iode band while PVA-iodine complex showed its characterized band around 500 nm in pure aqueous media. Addition of surfactant SDS resulted in a disapperance of the characteristic blue color of the PVA-iodine complex indicating that the complex is not formed in aqueous surfactant media. However in case of PVP or HPC, presence of the monomers of SDS favored the complex formation but in higher concentration, the micelles of SDS decreased the complex. Complexation was found to increase with increasing content of n-propanol in the system since n-propanol inhibits the formation of gels or microgels in the polymer solution. But in case of PVA-iodine complex, addition of n-propanol led to conversion of bigger polyiodides into smaller ones, which is indicative of increased intermolecular hydrogen bond interaction between propanol and PVA effecting a decrease in the PVA aggregate space.

• Journal of Microbiology and Biotechnology
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• v.28 no.12
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• pp.2106-2112
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• 2018

Concanavalin A (ConA) interacts with carbohydrates as a lectin, and recent reports proposed its application for detecting a diversity of viruses and pathogens. Structural studies have detailed the interaction between ConA and carbohydrates and the metal coordination environment with manganese and calcium ions (Mn-Ca-ConA). In this study, ConA was crystallized with a cadmium-containing precipitant, and the refined structure indicates that $Mn^{2+}$ was replaced by $Cd^{2+}$ (Cd-Ca-ConA). The structural comparison with ConA demonstrates that the metal-coordinated residues of Cd-Ca-ConA, that is Glu8, Asp10, Asn14, Asp19, and His24, do not have conformational shifts, but residues for sugar binding, including Arg228, Tyr100, and Leu99, reorient their side chains, slightly. Previous studies demonstrated that excess cadmium ions can coordinate with other residues, including Glu87 and Glu183, which were not coordinated with $Cd^{2+}$ in this study. The trimeric ConA in this study coordinated $Cd^{2+}$ with other residues, including Asp80 and Asp82, for complex generation. The monomer does not have specific interaction near interface regions with the other monomer, but secondary cadmium coordinated with two aspartates (Asp80 and Asp82) from monomer 1 and one aspartate (Asp16) from monomer 2. This study demonstrated that complex generation was induced via coordination with secondary $Cd^{2+}$ and showed the application potential regarding the design of complex formation for specific interactions with target saccharides.

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.164-171
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• 2021

The europium sorption on Tamusu clay was investigated by batch sorption experiments and spectroscopic study under the condition of strong ionic strength. The results demonstrated that europium sorption on Tamusu clay increased rapidly with pH value, but decreased with the ionic strength of solution increased. The europium sorption also increased in the presence of humic acid, especially at low pH value. The sorption could be fitted by Freundlich isotherm model and the europium sorption on clay was spontaneous and endothermic reaction. Besides, the result indicates that ion exchange was the main process at low pH value, while inner-sphere surface complexation dominated the sorption process at high pH value. The Backscatter electron scanning/Energy Dispersive Spectrometer(BSE/EDS) and the effect of Na for europium sorption results further suggested that europium sorption on Tamusu clay mainly competed with Na at low pH value. Overall, the results in this research were of significance to understand the sorption behavior of europium on the geological media under high ionic strength.

• The Journal of Sustainable Design and Educational Environment Research
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• v.19 no.4
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• pp.1-14
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• 2020

This study is to make suggestions on the type and operation of community life SOC projects suitable for the use of idle facilities in elementary and secondary schools. To this end, we analyzed the types and operation of desirable utilization facilities according to regional characteristics through the analysis of cases utilizing Japanese idle classrooms and closed schools. As a result of the study, in areas with excellent accessibility to residents such as old downtowns and towns, libraries, entrepreneurship counseling and exhibition spaces, and lifelong education centers were desirable as part of the residents' convenience facilities. It was found that the facilities that could be used with families, such as an experiential training center, were being utilized.

• Food Science and Industry
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• v.51 no.3
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• pp.245-258
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• 2018

Natural and synthetic antibacterial materials are used in foods to avoid bacterial contamination-induced food poison and deterioration. Due to the human and environmental safety, natural products including plant extracts have been extensively added into foods as antibacterial materials. Since some of core molecules comprised in those plant extracts are hardly dissolved in aqueous phases or food matrixes, nanotechnological approaches have been suggested to overcome such obstacles. Here we report domestic and international various types of plant- or non-plant-origin antibacterial materials that have been commercialized and used for the food industry. To improve solubility and stability of such antibacterial materials, nano-encapsulation or nano-complexation methods are also investigated focusing on the utilization of dextrins and proteins as coating materials.