A highly regioselective bisselenation of allenes with diphenyl diselenide catalyzed by tetrakis(triphenylphosphine)palladium(0)

Tetrakis(triphenylphosphine)palladium(0) acts as an effective catalyst for highly regioselective bisselenation of allenes with diphenyl diselenide.     

Dynamic character of human growth hormone and its receptor: normal mode analysis

Human growth hormone (hGH) induces dimerization of its binding protein (hGHbp). hGH binds to the first hGHbp (bp1) on site 1, and then the hGH-bp1 heterodimer complex binds to the second hGHbp (bp2) on site 2. Although the interactions of hGH and hGHbps have been studied from different viewpoints, few studies from a dynamic viewpoint have been reported. Especially, since in the SCOP domain database hGHbp is classified as two clear immunoglobulin-like domains, it is of interest to understand how hGH interacts with the hGHbp domains. Therefore, we carried out normal mode analysis (NMA) of free hGH, free bp1, free bp2, and the hGH-bp1 heterodimer complex, as well as the hGH-bp1-bp2 ternary complex to investigate how the dynamics of the proteins change before and after forming the complexes. NMA showed that the domain motion between the N-terminal and the C-terminal domains of free bp1 markedly decreased after binding to hGH, and that the domain motion of bp2 decreased similarly after binding to the hGH-bp1 heterodimer complex. The present study demonstrates that hGH regulates the inter-domain motions of both hGHbps.     

A supported liquid membrane encapsulating a surfactant-lipase complex for the selective separation of organic acids

We have developed a novel, lipase-facilitated, supported liquid membrane (SLM) for the selective separation of organic acids by encapsulating a surfactant-lipase complex in the liquid membrane phase. This system exhibited a high transport efficiency for 3-phenoxypropionic acid and enabled the selective separation of organic acids due to the different solubilities of the acids in the organic phase and the variable substrate specificity of the surfactant-lipase complex in the liquid membrane phase. We found that various parameters, such as the amount of surfactant-lipase complex in the SLM, the lipase concentration in the receiving phase, and the ethanol concentration in the feed phase, affected the transport behavior of organic acids. The optimum conditions were 5 g L(-1) of the surfactant-CRL complex in the SLM (CRL=lipase from Candida rugosa), 8 g L(-1) of PPL in the receiving phase (PPL=lipase from porcine pancreas), and an ethanol concentration of 50 vol %. Furthermore, we achieved high enantioselective transport of (S)-ibuprofen attributable to the enantioselectivity of the surfactant-CRL complex.     

Highly enantioselective separation using a supported liquid membrane encapsulating surfactant-enzyme complex

We developed a highly enantioselective separation system for the optically active compounds, (S)-ibuprofen and l-phenylalanine, from their racemic mixtures by employing a supported liquid membrane (SLM) encapsulating a surfactant-lipase complex (or a surfactant-alpha-chymotrypsin complex). In the present system, enzymes encapsulated in the liquid-membrane phase effectively drove the enantioselective transport of optically active compounds through the SLM. This novel SLM allowed high enantioselectivity (ee over 91%) in the optical resolution of racemic ibuprofen and phenylalanine.     

Volatility of tellurium and various fission products in heated nitric acid solutions

The volatility of tellurium and some other fission products was radiochemically studied in heated nitric acid solutions. As tracers ¹²¹Te produced by bremsstrahlung of an electron LINAC and other fission products produced by neutron irradiation were used. The distribution rate of radionuclides between the mother solution and the condensate, was considered as volatility, and was determined. The volatility of tellurium was found to be small and close to that of cesium. Volatilization tests were also performed in the presence of large amounts of solutes.The authors wish to thank Mr. Roy Jacobus for his help in preparing this paper.     

Polystyrenes with structurally different oligosiloxanes as p-substituents for oxygen permeable membrane materials

Polystyrenes with structurally different oligosiloxanes as p-substituents were synthesized and the selective oxygen permeation through the polymer film was studied. It was found that the structure of the p-oligosiloxane substituents had great effects not only on the glass transition temperature of the polymer but also on the oxygen permeation behavior through the polymer film. Trimethylsiloxyl groups, especially, were shown to play an essential role in enhancing the permeability.     

Total synthesis of monocyclic β-lactam antibiotics,nocardicin A and D

The total synthesis of monocyclic β-lactam antibiotics, nocardicins A (1a) and D (1d), is described. 3-Aminonocardicinic acid (3-ANA, 2) was synthesized from p-hydroxyphenylglycine via an acid chloride-imine cyloaddition reaction. The side chain amino acid 13 was prepared via a key step of condensation of p-hydroxyacetophenone and α-phthalimidobutyrolactone. Acylation of 3-ANA with 13 gave nocardicin D, from which nocardicin A was obtained by oximation.     

First systematic band-filling control in organic conductors

The systematic study of band-filling control for four kinds of organic conductors with various kinds of ground states has succeeded. (1) By partial substitution of (GaCl(4))(-) by (MCl(4))(2-) [M = Co, Zn] in the anion blocking layer of lambda-ET(2)(GaCl(4))(-) [ET = bis(ethylenedithio)tetrathiafulvalene], single crystals of lambda-ET(2)(GaCl(4))(-)(1-x)(MCl(4))(2-)(x) [x = 0.0, 0.05, 0.06] have been obtained. The resistivity at room temperature decreases from 3 Omega cm (x = 0.0) to 0.1 Omega cm (x = 0.06) by doping to the antiferromagnet with an effective half-filled band (x = 0.0). (2) Another 2:1 (donor/anion) salt, delta'-ET(2)(GaCl(4))(-), which is a spin gap material, has been doped as delta'-ET(2)(GaCl(4))(-)(1-x)(MCl(4))(2-)(x) [x = 0.05, 0.14]. The resistivity is lowered from 10 Omega cm (x = 0.0) to 0.3 Omega cm (x = 0.14). For both 2:1 salts, the semiconducting behaviors have transferred to relatively conductive semiconducting ones by doping. (3) As for alpha-type 3:1 salts, the parent material is in a charge-ordering state such as alpha-(ET(+)ET(+)ET(0))(CoCl(4))(2-)(TCE), where the charge-ordered donors are dispersed in the two-dimensional conducting layer. Although the calculation of alpha-ET(3)(CoCl(4))(2-)(TCE) shows a band-insulating nature, and the crystal structure analysis indicates that this material is in a charge-ordering state, the metallic behavior down to 165 K has been observed. With doping of (GaCl(4))(-) to the alpha-system, isostructural alpha-ET(3)(CoCl(4))(2-)(1-x)(GaCl(4))(-)(x)(TCE) [x = 0.54, 0.57, 0.62] have been afforded, where the pattern of the horizontal stripe-type charge ordering changes with an increase of x. (4) By doping (GaCl(4))(-) to the 3:2 gapless band insulator which is isostructural to beta'-ET(3)(MCl(4))(2)(2-) [M = Zn, Mn], the obtained beta'-ET(3)(CoCl(4))(2-)(2-x)(GaCl(4))(-)(x) [x = 0.66, 0.88] shows metallic behavior down to 100 and 140 K, respectively. They are the first metallic states in organic conductors by band-filling control of the gapless band insulator. These systematic studies of band-filling control suggest that the doping to the gapless band insulator with a pseudo-1/2-filled band is most effective.     

Immunoassay of serum alpha(1)-antitrypsin by affinity-probe capillary isoelectric focusing using a fluorescence-labeled recombinant antibody fragment

An immunoassay for human alpha(1)-antitrypsin based on affinity-probe capillary isoelectric focusing (AP-CIEF) is described. The method is based on the separation of free and bound labeled antibody fragments by CIEF with laser-induced fluorescence detection. A recombinant Fab' fragment of mouse immunoglobulin G1 (IgG1) against human alpha(1)-antitrypsin was labeled with tetramethylrhodamine on the single cysteine residue at the hinge region. A single pI isomer of the labeled Fab' was purified by IEF in a slab of agarose gel and was then used as the affinity probe for alpha(1)-antitrypsin. The use of recombinant Fab' considerably simplified the labeling process. Although there was some difficulty in the quantification of native alpha(1)-antitrypsin with the affinity probe, carbamylation of the antigen sample by heat treatment with urea made the complex peaks appear reproducibly and more distinct, thus facilitating the identification and quantification of the complex. The system provided an almost linear response to a pure sample of alpha(1)-antitrypsin over a concentration range of 5-1000 ng/mL and the detection limit extended down to around 2 ng/mL. Alpha(1)-antitrypsin in a serum sample was determined using this system to be 1.2 mg/mL which is comparable to the reported value for the protein.     

Autoxidation of polystyrene catalyzed by cobalt salt and sodium bromide in chlorobenzene–acetic acid

In the oxidation of atactic polystyrene initiated by azobisisobutyronitrile, the kinetic chain length was obtained as 1.5. In the presence of cobalt salt and bromide ion, the rate of oxidation is first order with respect to the concentration of polymer and second order with respect to the concentration of cobalt. In addition, this rate is dependent on the molar ratio of NaBr to cobalt, independent of the partial pressure of oxygen and the molecular weight of polystyrene. The overall energy of activation is 22.5 kcal/mole. The molecular weight decreased from 152000 to 10 800 under the present conditions of oxidation. Carbon monoxide and carbon dioxide are the only significant volatile products. The primary product of oxidation is hydroperoxide. Benzaldehyde, acetophenone, and phenol were found as final products. The acetophenone-type structure and methyl endgroups were observed. The formation of phenol presented a large selfinhibiting effect in the oxidation of polystyrene. The oxidation of isotactic polystyrene gave a maximum rate of oxidation twofold higher than that of atactic polystyrene and a value of 17.0 kcal/mole for the overall energy of activation.