Tatsuya Oshima

Degradation of methyl orange using short-wavelength UV irradiation with oxygen microbubbles

A novel wastewater treatment technique using 8 W low-pressure mercury lamps in the presence of uniform-sized microbubbles (diameter = 5.79 microm) was investigated for the decomposition of methyl orange as a model compound in aqueous solution. Photodegradation experiments were conducted with a BLB black light blue lamp (365 nm), a UV-C germicidal lamp (254 nm) and an ozone lamp (185 nm+254 nm) both with and without oxygen microbubbles. The results show that the oxygen microbubbles accelerated the decolorization rate of methyl orange under 185+254 nm irradiation. In contrast, the microbubbles under 365 and 254 nm irradiation were unaffected on the decolorization of methyl orange. It was found that the pseudo-zero order decolorization reaction constant in microbubble system is 2.1 times higher than that in conventional large bubble system. Total organic carbon (TOC) reduction rate of methyl orange was greatly enhanced by oxygen microbubble under 185+254 nm irradiation, however, TOC reduction rate by nitrogen microbubble was much slower than that with 185+254 nm irradiation only. Possible reaction mechanisms for the decolorization and mineralization of methyl orange both with oxygen and nitrogen mirobubbles were proposed in this study.

Extraction and separation of a lysine-rich protein by formation of supramolecule between crown ether and protein in aqueous two-phase system.

The macrocyclic calixarenes and crown ethers have recently been found to form hydrophobic complexes with the cationic protein cytochrome c (Cyt-c), by recognizing lysine residues on the protein surface. In the present study, it was found that the distribution of cytochrome c in Li(2)SO(4)/PEG aqueous two-phase system (ATPS) can be controlled by complexation with the crown ether dicyclohexano-18-crown-6 (DCH18C6). The protein was quantitatively extracted into the PEG-rich phase in the presence of DCH18C6 and perchlorate ion. Of various crown ethers and their analogues that were investigated, only DCH18C6 was able to extract cytochrome c into the PEG-rich phase. Extraction of cytochrome c in the ATPS using DCH18C6 is complete within 5 min. Cytochrome c complexed with DCH18C6 in the PEG-rich phase was quantitatively recovered into a salt-rich phase using K(2)SO(4) by ion exchange of potassium ion and cationic protein in the cationic protein complex with DCH18C6. Selective extraction of cationic proteins was demonstrated in the ATPS. Under optimum conditions, the lysine-rich protein cytochrome c was selectively extracted over other cationic proteins using DCH18C6.

Cellulose aerogel regenerated from ionic liquid solution for immobilized metal affinity adsorption.

Surface morphology of cellulosic adsorbents is expected to influence the adsorption behavior of biomacromolecules. In the present study, cellulose aerogel regenerated from ionic liquid solution was prepared for use as a polymer support for protein adsorption. Iminodiacetic acid groups were introduced to the aerogel for immobilized metal affinity adsorption of proteins. A Cu(II)-immobilized iminodiacetic acid cellulose aerogel (Cu(II)-IDA-CA), which has a large specific surface area, showed a higher adsorption capacity than Cu(II)-immobilized iminodiacetic acid bacterial cellulose (Cu(II)-IDA-BC) and Cu(II)-immobilized iminodiacetic acid plant cellulose (Cu(II)-IDA-PC). In contrast, the Cu(II)-immobilized cellulosic adsorbents showed similar adsorption capacities for smaller amino acid and peptides. The results show that cellulose aerogels are useful as polymer supports with high protein adsorption capacities.

Selective extraction and transport of copper(II) with new alkylated pyridinecarboxylic acid derivatives.

Two kinds of N-(6-alkylamido)-2-pyridine carboxylic acid with a pyridine moiety and a carboxylic acid as chelating ligands were newly synthesized for the selective extraction and the transport of copper(II) from aqueous solution. Liquid-liquid extraction was carried out to examine the extraction ability of extractants with metal ions. The selectivity for the metal ions with N-6-(2-ethylhexylamido)-2-pyridine carboxylic acid (EHPA) was in the following order: Cu(II)>>Zn(II) approximately Pb(II) approximately Ni(II) approximately Co(II)>Cd(II)>Mn(II). All metals tested in this study were selectively extracted at a lower pH by 2-3 units compared with commercial available alkyl carboxylic acids such as naphthenic acid and Versatic 10. The extraction equilibria of copper(II) were measured by a batchwise method at 303K with EHPA and N-6-(t-dodecylamido)-2-pyridinecarboxylic acid (t-DAPA). Copper(II) was extracted as a 1:2 complex according to the following reaction: Cu(2+)+2(HR )(2)=CuR(2)2HR +2H(+). The extraction equilibrium constant, K(ex) was evaluated and the values were found to be 1.13 and 0.31 for EHPA and t-DAPA, respectively. It was demonstrated that t-DAPA was very stable to be incorporated into a polymer inclusion membrane (PIM) consisting of cellulose triacetate (CTA) as a base polymer and 2-nitrophenyl octylether (NPOE) as a plasticizer. This novel PIM containing t-DAPA as a carrier exhibited an excellent copper(II) transport characteristic and a high selectivity for copper(II) over cadmium(II) from aqueous solution.

Enhanced water dispersibility of coenzyme Q10 by complexation with albumin hydrolysate.

The biologically important coenzyme Q10 (CoQ10) is widely used as a drug for chronic heart failure, as a nutritional supplement, and in cosmetics. However, the oral bioavailability of CoQ10 is poor due to its extremely low solubility in aqueous media. In this study, complexation of CoQ10 with albumin hydrolysate as a peptide mixture (Pep) was shown to enhance the water dispersibility of CoQ10. An aqueous solution of Pep and an acetone solution of CoQ10 were mixed and lyophilized to obtain a white-yellow powder containing peptides and CoQ10 complex (Q10-Pep). The water dispersibility of Q10-Pep was much higher than that of CoQ10 alone and increased with the quantity of Pep. The particle size of Q10-Pep in aqueous media was 170-280 nm, suggesting that Q10-Pep was present as a hydrocolloidal material. Characterization of Q10-Pep using differential scanning calorimetry showed that CoQ10 was incorporated in the hydrocolloid in an amorphous state.

Enhancement of water solubility of indomethacin by complexation with protein hydrolysate

Complex formation between indomethacin (Indo) and casein hydrolysate was developed as a novel technique for enhancing the water solubility of Indo. The complex (Indo-Pep) was prepared by mixing an ethanol solution of Indo and an aqueous solution of peptide mixture, followed by lyophilization. The water solubility of Indo-Pep under weakly acidic and neutral conditions is much higher than that of Indo alone. The water solubility of Indo increased with increasing quantity of peptide. Characterization of Indo-Pep using scanning electron microscopy, differential scanning calorimetry, and X-ray diffraction showed that Indo was incorporated in Indo-Pep in an amorphous state. The fluorescence quenching of Indo-Pep also suggested complexation between Indo and the peptides. An aqueous solution of Indo-Pep was fractioned by centrifugation followed by filtration using membrane filters and ultrafilters. Analysis of the fractions by dynamic light scattering and ultraviolet-visible spectroscopy showed that Indo-Pep consisted of small particles and was not a hydrocolloidal material.

The effect of phenoxy oxygen atoms on extremely high extraction ability and less separation efficiency of trivalent rare earth elements with tetraphosphonic acid derivative of calix[4]arene

A cone confomational p-t-octylcalix[4]arene with four methylenephosphonic acids at the lower rim as well as its monomeric analog have been synthesized as a new extraction reagent to investigate the extraction behavior of the nine trivalent rare earth elements: Y, La, Pr, Nd, Sm, Eu, Gd, Ho and Er. The new calix[4]arene exhibited significantly higher extraction capacity than not only the monomeric derivative and the commercial extraction reagent, 2-ethylhexyl hydrogen 2-ethylhexylphosphonate, but also the cone conformational calix[4]arene extractants employed in our previous work, composed of a tetrapropylenephosphonic acid with a longer spacer, a tetraphosphonic acid at the upper rim, and tetraacetic acid at the lower rim. A dependence on the pH was observed for the new extractant in the highly acidic region, and the extraction took place via a simple ion-exchange mechanism. Using slope analysis, the stoichiometries of tetrameric and monomeric extractants to rare earth metal ions were determined to be 2:1 and 3:1, respectively. Using the proposed extraction equations, extraction equilibrium constants and separation factors were estimated. The extremely high extraction ability and moderate separation efficiency were attributed to the chelating effect of the phosphonic acid and the phenoxy oxygen atom. The effect of the phenoxy oxygen atom on extraction ability and separation efficiency of calix[4]arene derivatives was found to be significant.

Adsorption of histidine-containing dipeptides on copper(II) immobilized chelating resin from saline solution.

Adsorption of histidine-containing dipeptides such as carnosine (Car) was investigated using copper(II) immobilized cation exchange resins. Adsorption of Car was enhanced using Cu(II) immobilized resins, on the basis of metal affinity interactions. In particular, iminodiacetic acid chelating resin with immobilized Cu(II) (Cu-IDA) can adsorb Car from saline water. Car was adsorbed on Cu-IDA even in the presence of 1000 mM of NaCl. Adsorption of various amino acids on Cu-IDA was compared under same conditions. Histidine and the histidine-containing dipeptides were selectively adsorbed on Cu-IDA over other amino acids, both in the absence and in the presence of NaCl. Therefore, immobilized metal affinity adsorption is an efficient method for recovering histidine-containing dipeptides from saline water.

Recognition of Lysine Residues on Protein Surfaces Using Calixarenes and its Application

A macrocyclic calix[6]arene carboxylic acid derivative is found to extract lysine-rich protein cytochrome c from aqueous media into organic media through the complexation between the calixarene molecules and lysine residues on the surface of the protein. This article summarizes both the mechanism of protein extraction by the calixarene as well as the potential applications of the extraction process. The extraction process can be used for the purification of proteins through selective extraction and back-extraction under optimized conditions. On the other hand, the extracted protein exhibits enzymatic activity in organic media. The formation of a supramolecular complex by recognizing the residues on a protein surface can be construed as a novel recognition and/or modification method for biomacromolecules.

Selective extraction of histidine derivatives by metal affinity with a copper(II)–chelating ligand complex in an aqueous two-phase system

Affinity extraction based on the interaction between a target molecule and a specific affinity ligand offers a novel separation system for biomolecules in an aqueous two-phase system, however, most of affinity ligands are expensive. In the present study, metal affinity extraction of histidine (His) derivatives using a complex between Cu(II) and a commercially available chelating ligand was studied in a poly(ethylene glycol) (PEG)/Li2SO4 ATPS. Alizarin complexone (3-[N,N-bis(carboxymethyl)amino methyl]-1,2-dihydroxy anthraquinone, AC) was selected as the chelating ligand because of the good extractability of Cu(II) into the upper PEG-rich phase. On the basis of coordinate bonding with Cu(II), the extraction of His in the presence of the Cu(II)-AC complex under neutral condition was 73%, which was much higher than that under Cu(II) free condition (13%). Among a series of divalent transition metal ions (Cu(II), Ni(II), Co(II), and Zn(II)), Cu(II) was the most effective for the extraction of His. Derivatives of His were selectively extracted in the presence of many other amino acids because of the specificity of the interaction between Cu(II) and imidazole group of His. Extracted His was quantitatively stripped from the Cu(II)-AC complex using competitive complexation with agents such as iminodiacetic acid and imidazole.