Personal dosimetry of exposure to mobile telephone base stations? An epidemiologic feasibility study comparing the Maschek dosimeter prototype and the Antennessa DSP‐090 system

The aim of our study was to test the feasibility and reliability of personal dosimetry. Twenty-four hour exposure assessment was carried out in 42 children, 57 adolescents, and 64 adults using the Maschek dosimeter prototype. Self-reported exposure to mobile phone frequencies were compared with the dosimetry results. In addition, dosimetry readings of the Maschek device and those of the Antennessa DSP-090 were compared in 40 subjects. Self-reported exposures were not associated with dosimetry readings. The measurement results of the two dosimeters were in moderate agreement (r(Spearman) = 0.35; P = .03). Personal dosimetry for exposure to mobile phone base station might be feasible in epidemiologic studies. However, the consistency seems to be moderate.     

New mono and dinuclear arene ruthenium chloro complexes containing ester substituents

The dinuclear arene ruthenium complexes [RuCl₂{C₆H₅(CH₂)₃OCO-p-C₆H₄-OC₈H₁₇}]₂ (1) and [RuCl₂{p-C₆H₄(CH₂COOCH₂CH₃)₂}]₂ (2) have been obtained by dehydrogenation of the corresponding cyclohexadiene derivative with ruthenium chloride hydrate. The single-crystal X-ray structure analysis of 2 shows the arene ligands to be involved in slipped-parallel π-π stacking interactions with neighbouring molecules, thus forming infinite chains along the b-axis. The dinuclear complexes 1 and 2 react with two equivalents of triphenylphosphine (PPh₃) to give in excellent yield the corresponding mononuclear phosphine complexes [RuCl₂{C₆H₅(CH₂)₃OCO-p-C₆H₄-OC₈H₁₇}(PPh₃)] (3) and [RuCl₂{p-C₆H₄(CH₂COOCH₂CH₃)₂}(PPh₃)] (4), respectively. The single-crystal X-ray structure analysis of 4 reveals the formation of a dimer through two C-H?Cl interactions in the solid state.     

Structure and reaction geometry of geranylgeranyl diphosphate synthase from Sinapis alba

The crystal structure of the geranylgeranyl diphosphate synthase from Sinapis alba (mustard) has been solved in two crystal forms at 1.8 and 2.0 A resolutions. In one of these forms, the dimeric enzyme binds one molecule of the final product geranylgeranyl diphosphate in one subunit. The chainfold of the enzyme corresponds to that of other members of the farnesyl diphosphate synthase family. Whereas the binding modes of the two substrates dimethylallyl diphosphate and isopentenyl diphosphate at the allyl and isopentenyl sites, respectively, have been established with other members of the family, the complex structure presented reveals for the first time the binding mode of a reaction product at the isopentenyl site. The binding geometry of substrates and product in conjunction with the protein environment and the established chemistry of the reaction provide a clear picture of the reaction steps and atom displacements. Moreover, a comparison with a ligated homologous structure outlined an appreciable induced fit: helix alpha8 and its environment undergo a large conformational change when either the substrate dimethylallyl diphosphate or an analogue is bound to the allyl site; only a minor conformational change occurs when the other substrate isopentenyl diphosphate or the product is bound to the isopentenyl site.     

Ceramic methyltrioxorhenium

The metal oxide polymeric methyltrioxorhenium [(CH₃)_xReO₃]_∞ is a unique representative of a layered inherent-conducting organometallic polymer which adopts the structural motifs of classical perovskites in two dimensions (2D) in form of methyl-deficient, corner-sharing ReO₅(CH₃) octahedra. In order to improve the characteristics of polymeric methyltrioxorhenium with respect to its physical properties and potential usage as an inherent-conducting polymer we tried to optimise the synthetic routes of polymeric modifications of 1 to obtain a sintered ceramic material, denoted as ceramic MTO. Ceramic MTO formed in a solvent-free synthesis via auto-polymerisation and subsequent sintering processing displays clearly different mechanical and physical properties from polymeric MTO synthesised in aqueous solution. Ceramic MTO is shown to display activated ReC and ReO bonds relative to MTO. These electronic and structural characteristics of ceramic MTO are also reflected by a different chemical reactivity compared with its monomeric parent compound. First examples of the unprecedented reactivity of ceramic MTO in the field of amine oxidations are shown - results which warrant further exploitation.     

Aerobic benzoyl-coenzyme A (CoA) catabolic pathway in Azoarcus evansii: conversion of ring cleavage product by 3,4-dehydroadipyl-CoA semialdehyde dehydrogenase

Benzoate, a strategic intermediate in aerobic aromatic metabolism, is metabolized in various bacteria via an unorthodox pathway. The intermediates of this pathway are coenzyme A (CoA) thioesters throughout, and ring cleavage is nonoxygenolytic. The fate of the ring cleavage product 3,4-dehydroadipyl-CoA semialdehyde was studied in the beta-proteobacterium Azoarcus evansii. Cell extracts contained a benzoate-induced, NADP(+)-specific aldehyde dehydrogenase, which oxidized this intermediate. A postulated putative long-chain aldehyde dehydrogenase gene, which might encode this new enzyme, is located on a cluster of genes encoding enzymes and a transport system required for aerobic benzoate oxidation. The gene was expressed in Escherichia coli, and the maltose-binding protein-tagged enzyme was purified and studied. It is a homodimer composed of 54 kDa (without tag) subunits and was confirmed to be the desired 3,4-dehydroadipyl-CoA semialdehyde dehydrogenase. The reaction product was identified by nuclear magnetic resonance spectroscopy as the corresponding acid 3,4-dehydroadipyl-CoA. Hence, the intermediates of aerobic benzoyl-CoA catabolic pathway recognized so far are benzoyl-CoA; 2,3-dihydro-2,3-dihydroxybenzoyl-CoA; 3,4-dehydroadipyl-CoA semialdehyde plus formate; and 3,4-dehydroadipyl-CoA. The further metabolism is thought to lead to 3-oxoadipyl-CoA, the intermediate at which the conventional and the unorthodox pathways merge.     

Saccharomyces cerevisiae strain expressing a plant fatty acid desaturase produces polyunsaturated fatty acids and is susceptible to oxidative stress induced by lipid peroxidation

Although oxygen is essential for aerobic organisms, it also forms potentially harmful reactive oxygen species. For its simplicity, easy manipulation, and cultivation conditions, yeast is used as an attractive model in oxidative stress research. However, lack of polyunsaturated fatty acids in yeast membranes makes yeast unsuitable for research in the field of lipid peroxidation. Therefore, we have constructed a yeast strain expressing a Delta12 desaturase gene from the tropical rubber tree, Hevea brasiliensis. This yeast strain expresses the heterologous desaturase in an active form and, consequently, produces Delta9/Delta12 polyunsaturated fatty acids under inducing conditions. The functional expression of the heterologous desaturase did not affect cellular morphology or growth, indicating no general adverse effect on cellular physiology. However, the presence of polyunsaturated fatty acids changed the yeast's sensitivity to oxidative stress induced by addition of paraquat, tert-butylhydroperoxide, and hydrogen peroxide. This difference in sensitivity to the latter was followed by the formation of 4-hydroxy-2-nonenal, one of the end products of linoleic fatty acid peroxidation, which is known to play a role in cell growth control and signaling. Here we show that this yeast strain conditionally expressing the Delta12 desaturase gene provides a novel and well-defined eukaryotic model in lipid peroxidation research. Its potential to investigate the molecular basis of responses to oxidative stress, in particular the involvement of reactive aldehydes derived from fatty acid peroxidation, especially 4-hydroxy-2-nonenal, will be addressed.