[en] The 26S proteasome is responsible for degradation of abnormal intracellular proteins, including oxidatively damaged proteins and may play a role as a component of a cellular antioxidative system. However, little is known about regulation of proteasome expression. In the present study, regulation of proteasome expression by the bifunctional enzyme inducer and a specific signaling pathway for this regulation were investigated in murine neuroblastoma cells. Expression of catalytic core subunits including PSMB5 and peptidase activities of the proteasome were elevated following incubation with 3-methylcholanthrene (3-MC). Studies using reporter genes containing the murine Psmb5 promoter showed that transcriptional activity of this gene was enhanced by 3-MC. Overexpression of AhR/Arnt did not affect activation of the Pmsb5 promoter by 3-MC and deletion of the xenobiotic response elements (XREs) from this promoter exerted modest effects on inducibility in response to 3-MC. However, mutation of the proximal AREs of the Psmb5 promoter largely abrogated its inducibility by 3-MC. In addition, this promoter showed a blunted response toward 3-MC in the absence of nrf2; 3-MC incubation increased nuclear levels of Nrf2 only in wild-type cells. Collectively, these results indicate that expression of proteasome subunit PSMB5 is modulated by bifunctional enzyme inducers in a manner independent of the AhR/Arnt-XRE pathway but dependent upon the Nrf2-ARE pathway

[en] The characteristic of different types of isomeric forms of molecular exciplexes is presented on the base of semiempirical calculations of potential energy surfaces for molecular complexes, formed between anthracene (AN) and N,N-diethylaniline (DEA), naphthalene (NA) and triethylamine (TEA) and tetracyanobenzene (TCNB) and mesitylene (MS)

[en] The present study contributed towards establishing the status of a tropical and a moderate latitude marine ecosystem in terms of the concentration of anthropogenic, lipid associated, cyclic, halogenated hydrocarbons in surface sediments and benthic macroinvertebrates. Samples were obtained from the coastal region and the continental slope of Kenya (Indian Ocean), the Dutch coastal region and the continental shelf of the North Sea, and a bay area of Curacao (Netherlands Antilles, Caribbean). In surface sediments (Kenya), congeners CB28, CB52, CB101, CB118, CB153, CB138 and CB180, and the pesticides alpha-HCH and gamma-HCH, dieldrin, endrin and members of the DDT family were not identified, except in the estuarine zone of the Sabaki River. In North Sea surface sediment, the characteristics PCB pattern was always determined, and concentrations were particularly enhanced in sediment from the river mouths. Also, alpha-HCH, p,p'-DDD and p,p'-DDE were quantified in most samples. Regarding benthic invertebrates, CBs and p,p'-DDE were quantified. Some samples showed particularly enhanced levels in bivalve molluscs and certain penaeid prawns the Kenyan coastal region. The high levels present in the digestive (pyloric caeca) and reproductive (gonad) organs of seastar from the North Sea confirmed distinct concentration gradients. Sponges and tunicates from the bay area of Curacao accumulated CBs and p,p'-DDE, but not at very high concentrations. (author). 23 refs, 2 figs, 7 tabs

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[en] Using functionalized tips, the atomic resolution of a single organic molecule can be achieved by noncontact atomic force microscopy (nc-AFM) operating in the regime of short-ranged repulsive Pauli forces. To theoretically describe the atomic contrast in such AFM images, we propose a simple model in which the Pauli repulsion is assumed to follow a power law as a function of the probed charge density. As the exponent in this power law is found to be largely independent of the sample molecule, our model provides a general method for simulating atomically resolved AFM images of organic molecules. For a single perylene-tetracarboxylic-dianhydride (PTCDA) molecule imaged with a CO-terminated tip, we find excellent agreement with the experimental data. Our model eliminates the need to take into account the full tip and sample system and therefore reduces computational cost by three orders of magnitude. (paper)

[en] Energy flow and C-H_methyl and C-H_ring bond dissociations in vibrationally excited toluene in the collision with N₂ and O₂ have been studied by use of classical trajectory procedures. The energy lost by the vibrationally excited toluene upon collision is not large and it increases slowly with increasing total vibrational energy content between 5,000 and 45,000 cm^-1. Intermolecular energy transfer occurs via both of V-T and V-V transfers. Both of V-T and V-V transfers increase as the total vibrational energy of toluene increases. When the total energy content E_T of toluene is sufficiently high, either C-H bond can dissociate. The C-H_methyl dissociation probability is higher than the C-H_ring dissociation probability, and that in the collision with N₂ is larger than with O₂

[en] Data on methods for the preparation of naphthaldehydes, their physicochemical properties, structural characteristics and reactivities are generalised. Particular attention is given to procedures for formylation of naphthalenes and peri-interactions involving the aldehyde group in the α-position.

[en] This paper reports that world styrene demand, paced by a near doubling of combined requirements in East Asia and Oceania, could reach 19.3 million metric tons by 2000, an average growth rate of 3.7%/year. So concludes Chem Systems Inc., Tarrytown, N.Y., in a study of world styrene markets through the end of the century. Pacific Rim styrene production and consumption throughout the 1990s are predicted to make up increasingly larger shares of world markets, while demand and production lag in the U.S. and western Europe. Demand and capacity in other parts of the world will grow in real terms, increasing combined market shares only slightly. Most of the increase will be driven by demand in East Asia and Oceania, where consumption by century's end is expected to increase 4.48 million metric tons from 2.25 million tons in 1991. Meantime, Japan's styrene demand in 2000 is projected at 2.64 million tons, a 500,000 ton increase from 1991 demand but a net market loss of 1.9%

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No abstract available