• Journal of Life Science
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• v.11 no.1
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• pp.43-47
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• 2001

A mutant tryptophan synthase $\alpha$-subunit, where Pro28 was replaced with Leu, tends to be expressed in recombinant E. coli. CD and fluorescence spectra of this protein indicate some changes in secondary and tertiary structure. Wild type protein was more or less affected by {TEX}$Ca^{2+}${/TEX} ion in regards of the fluorescent properties of its native, unfolded and intermediate forms, but the mutant protein was not at all. The dramatic structural changes may be related to the aggregation of this mutant protein.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2949-2954
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• 2010

Ionic liquid-functionalized ordered mesoporous silica SBA-15 modified carbon paste electrode (CISPE) was fabricated and its electrochemical performance was investigated by cyclic voltammetry, electrochemical impedance spectra. The electrochemical behavior of $Cd^{2+}$, $Pb^{2+}$, $Cu^{2+}$ and $Hg^{2+}$ at CISPE was studied by differential pulse anodic stripping voltammetry (DPASV). Compared with carbon paste electrode, the stripping peak currents had a significant increase at CISPE. Under the optimized conditions, the detection limits were $8.0{\times}10^{-8}\;M$ ($Cd^{2+}$), $4.0{\times}10^{-8}\;M$ ($Pb^{2+}$), $6.0{\times}10^{-8}\;M$ ($Cu^{2+}$), $1.0{\times}10^{-8}\;M$ ($Hg^{2+}$), respectively. Furthermore, the present method was applied to the determination of $Cd^{2+}$, $Pb^{2+}$, $Cu^{2+}$ and $Hg^{2+}$ in water samples and people hair sample.

• Bulletin of the Korean Chemical Society
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• v.21 no.11
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• pp.1119-1124
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• 2000

$\beta-Cyclodextrin$ derivatives connected with diaza-18-crown-6 through flexible bridges (R) at the secondary face 1a-c (1a: R = $-(CH_2)4-;$ 1b: R = $-CH_2CH_2OCH_2CH2-;$ 1c: R = $-(CH_2)8-)$ have been prepared. The associa tion constants of 1 with (2-naphthoxy)alkylammonium ions (2a: alkyl = butyl; 2b: alkyl = octyl) were determined by induced circular dichroism (ICD) spectroscopy and it was found that the derivatization of $\beta-CD$ with the diazacrown resulted in enhanced binding with 2, compared to the native $\beta-CD.$ ICD Characteristics of the host-guest complexes indicate that a part of the alkylammonium moiety of 2 is protruded from the secondary side of the $\beta-CD$ cavity, and the guest molecules 2a and 2b move to the secondary and primary side, respectively, to make the binding of the ammonium group with the diaza-18-crown-6 moiety more feasible. The energy accompanied by the relocation of the guest molecules inside $\beta-CD$ moiety is compensated by the interaction energy between the ammonium ion and diazacrown ether.

• Journal of the Korean Chemical Society
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• v.57 no.6
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• pp.712-720
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• 2013

Microwave assisted syntheses of Zn(II), Cd(II) and Hg(II) complexes with 3-aminopyridine (3AP) and nitrite ($NO_2{^-}$) ions have been reported. The metal complexes were characterized by elemental analyses, molar conductance, IR, Far-IR, electronic, NMR ($^1H$, $^{13}C$), thermal and electron impact mass spectral studies. The spectroscopic studies reveal the composition, the nature of nitrite ligand in the complexes, electronic transitions, chemical environments of C and H atoms thermal degradation of the complexes. On the basis of characterization data, distorted tetrahedral geometry is suggested for Zn(II), Cd(II) and Hg(II) complexes. The organic ligand (3AP) and their metal complexes were screened against gram negative pathogenic bacteria and fungi in vitro. The results are compared with our previous report J. Korean Chem. Soc. 2013, 57, 341 on 4-aminopyridine and nitrite ion complexes of the same metal ions.

• Journal of Applied Biological Chemistry
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• v.64 no.2
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• pp.159-164
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• 2021

Heavy metals exist in soils in various chemical forms including free metal ions and organo-metal complexes. The ratio of free metal ions has been known to be highly associated with the plant absorption of heavy metals. This study aims to understand the effect of free ions and organo-metal complexes on the absorption of lead (Pb) and cadmium (Cd) by plants. For this, lettuce grown in a hydroponic system for 28 days was consequently grown another 48 hours using Pb and Cd solutions. The ratios of free ion to organo-metal complexes in the solutions were adjusted at 100:0, 90:10, 70:30, 60:40 by four different organic acids (citric, oxalic, acetic, and humic acid). After that, the concentration of Pb and Cd in lettuce were analyzed. The Pb and Cd absorption by lettuce was more relied on the types of organic acids treated and the type of metals rather than the ratio of free metal ions. For example, citric acid increased the Pb absorption while it decreased the Cd absorption by lettuce. There was no significant relationship between free metal ion ratios and both Pb and Cd uptake by lettuce. It could be explained that citric acid, a relatively higher molecular weight organic acid, has higher ion binding capacity, so it forms organo-Pb complex easily due to the higher affinity of Pb on the binding site in comparison with Cd. Consequently, this complexation would assist Pb uptake by lettuce.

• Journal of Environmental Science International
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• v.10 no.2
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• pp.153-158
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• 2001

The biosorption abilities of different parts of waste brown seaweeds and their derivatives to remove heavy metals (Cd, Zn, Pb, Cu, Fe, Ni, Mn) from waste were evaluated. The two parts of waste brown seaweeds (Undaria pinnatifida) were stems and sporophyls, and the brown seaweed derivatives were alginic fibers, active carbon added alginate(AC-alginate) and dealginate. The abilities of the sporophyls to adsorb the heavy metal ions were higher than those of stems, and those of alginates were slightly higher than those of dealginate in single ion solution. With decreasing the size of biosorbents, the velocity and the amount of adsorption increased. The abilities of alginate to remove the heavy metal ions increased in multi-ion solutions by adding active carbon to alginate. The selectivity of these biosorbents(alginate, AC-alginate) to lead ion was highest and to manganese ion was lowest.

• Journal of the Korean Chemical Society
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• v.24 no.2
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• pp.129-138
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• 1980

The formation constants of the mixed-ligand complexes in the Cd(II), Cu(II) and Pb(II)-Trien-OH system were studied by polarograph. The formation constant $(log{\beta}_{ij})$ was determined at $25^{\circ}C$ in the ionic strength of 0.1. It was also confirmed that the mixed ligand complexes in this system were formed above pH 10.2, 10.5 and 9.0 for Cu(II), Cd(II) and Pb(II) by the calculation of the distribution for complexes at the various pH. Masking of Cd(II) by conversion to anionic EDTA-complexes has been used to separate Cu(II) from Cd(II) through passage of a combined Trien-EDTA solution on an cationic resin column. The optimal condition for the separation of Cu(II) from Cd(II) is confirmed at the pH range above 9.0, not only by considering the theoretical equation of the conditional-exchange-constant of metal on the cation exchange resin,but also by calculating the distribution of the mixed ligand complexes in the resin at the various pH with computer. By analyzing the synthetic sample of Cu(II) and Cd(II) with a EDTA masking at pH 9.5, it is found that the results of the experiment are satisfied with the theoretical value.

• Journal of the Korean Chemical Society
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• v.43 no.2
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• pp.167-171
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• 1999

An investigation of the interaction of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Pb(II) and Ag(I) with two N,N'-dibenzylated nitrogen-oxygen mixed donor macrocyclic ligands, has been carried out. Tle log K values for the respective complexes in 95% methanol have been determined potentiometrically. Both ligands have formed stable complex with only Cu(II) and Ag(I) ion. Transport measurements in a bulk liquid membrane system exhibited a very high selectivity of Ag(I) ion over the other metal ions used.

• Korean Journal of Crystallography
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• v.4 no.2
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• pp.54-62
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• 1993

The crystal shnture of dehydrated fully Cd2+-exchanged zeolite A evacuated at 2 × 10-6 Torr and 650℃ (a:12.189(2) A) and of its iodine sorption corrplex (a:12.168(2)A) have been netsmlmn by single uystal x-ray diffraction techliques in the cubic space group hkTn at 21(1)℃. The strutures were refined to final error indices, Ri:0.057 and R2 =0.063 with 186 reflections and Rl:0.082 and R2:0.085 with 181 reflections, respectively, for which 1>3σ(In both structure, six lie at two distinguished threefold axes of unit cell ten the crystal structure of an iodine sorption complex of Cd6-A four Cd2+ ions are recessed 0.69(1) A into the large cavity to complex each with from the (111) plane of 0(3), whereas two Cd2+ ions recessed 0.68(1) A into the sodalite unit Awximately 4.0 l3ions per nit cell are sorbed. Each bridge between a Cd2+ ion and 8-ring oxygens ((I-I-I)= 117(1) ˚ and 0(1)-I(1)-I(2)=172(1)). The near linear I-I-0 angle and its interatomic distance (I-0=3.57(3) A) are indicative of a weak charge transfer interacticn between the frarrework oxygen and iodine. The existence of In3 inside the large cavity indicates that the If ions and H ions may be produced by reaction of In vapor with water molecules which maybe associated with Cd2+ ions in partially dehydrated Cd6-A In3- ions may be produced by the combination of I- and I2.

• Journal of the Korean Chemical Society
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• v.40 no.1
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• pp.44-49
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• 1996

The cadmium(Ⅱ)-carboxylate complexes of monocarboxylates and poly(acrylic acid) (PAA) in an aqueous solution were investigated using 113Cd NMR spectroscopy. From these spectral data the chemical shifts of the monocarboxylate (e.g. acetate, benzoate and propanoate) complexes of Cd(Ⅱ) were evaluated (CdL+: -22 to -24 ppm range; CdL2: -39 to -40 ppm range; L: carboxylate). The chemical shift of cadmium(Ⅱ) bound on PAA changed in value from -36.6 to -38.2 ppm when the [PAA]/[Cd] ratios were varied from 12 to 118 eq/mol at a constant pH of 6. The 113Cd chemical shift was sensitive to the change in solution pH: the chemical shift changed from 1.6 to -37.6 ppm when the pH was rasied from 1 to 6 at a constant [PAA]/[Cd] ratio of 39 eq/mol. These results show that under these conditions, the dominant species formed in solution is 1 : 2 complex (CdL2), and 1 : 1 complex (CdL+) is only formed at low pH, when polyanion concentration is low.