Utilizing uncertainty factors in minimal risk levels derivation

While both 31P and 113Cd are present at locations of interest in many different macromolecular systems, heteronuclear-detected relaxation measurements on these nuclei have been restrained by limitations in either resolution or signal-to-noise ratio. We have developed heteroTOCSY-based methods to overcome both of these problems. Two-dimensional versions of these experiments were utilized to measure 31P T1 and T2 values in DNA oligonucleotides; the additional resolution offered by a second dimension allowed determination of these values for most of the 31P resonances in a DNA dodecamer. The results from the experiments indicated that there was little significant variation in T1 values for the different phosphates in the DNA dodecamer; however, the T2 values showed a clear pattern, with lower values in the interior of the sequence than at the ends of the helix. Furthermore, a significant correlation between 31P chemical shifts and T2 values was observed. One-dimensional, frequency-selective versions of these experiments were also developed for use on systems containing a smaller number of heteronuclear spins. These methods were applied to investigate the heteronuclear relaxation properties of 113Cd in 113Cd2LAC9(61), a Cys6Zn2 DNA-binding domain. Data from the experiments confirm biochemical evidence that more significant differences occur in the metal-protein interactions between the two metal-binding sites than has been previously identified for proteins containing this motif.     

Intracellular location of inapparently infecting Chlamydia in synovial tissue from patients with Reiter's syndrome

Culture of Chlamydia trachomatis from synovial tissues/fluids from Reiter's syndrome (RS) patients frequently yields negative results. However, we have identified chlamydial RNA at that site in such patients, suggesting that viable organisms may be present. Here we define the cellular location of chlamydia within the synovium via in situ hybridization. Using a chlamydial ribosomal RNA-directed probe, we show that synovial tissue from culture-negative RS patients gives strong hybridization which is often localized to a subsynovial cell layer, rather than to the synovial lining; in some cases, hybridizing cells are dispersed through the synovium. All hybridization signal is located within host cells, indicating that infectious extracellular elementary bodies are rare or absent. These data confirm the extensive intracellular presence of inapparent chlamydia in the synovia of RS patients and provide some insight into the usual culture negativity of synovial tissues for the organism.     

Insight into the Mechanism of Phenylacetate Decarboxylase (PhdB), a Toluene-Producing Glycyl Radical Enzyme

We recently reported the discovery of phenylacetate decarboxylase (PhdB), representing one of only ten glycyl-radical-enzyme reaction types known, and a promising biotechnological tool for first-time biochemical synthesis of toluene from renewable resources. Here, we used experimental and computational data to evaluate the plausibility of three candidate PhdB mechanisms, involving either attack at the phenylacetate methylene carbon or carboxyl group [via H-atom abstraction from COOH or single-electron oxidation of COO⁻ (Kolbe-type decarboxylation)]. In vitro experimental data included assays with F-labeled phenylacetate, kinetic studies, and tests with site-directed PhdB mutants; computational data involved estimation of reaction energetics using density functional theory (DFT). The DFT results indicated that all three mechanisms are thermodynamically challenging (beyond the range of many known enzymes in terms of endergonicity or activation energy barrier), reflecting the formidable demands on PhdB for catalysis of this reaction. Evidence that PhdB was able to bind α,α-difluorophenylacetate but was unable to catalyze its decarboxylation supported the enzyme's abstraction of a methylene H atom. Diminished activity of H327A and Y691F mutants was consistent with proposed proton donor roles for His327 and Tyr691. Collectively, these and other data most strongly support PhdB attack at the methylene carbon.     

Towards a Practical and Efficient Copper-Catalyzed Trifluoromethylation of Aryl Halides

The first copper-catalyzed trifluoromethylation of aryl halides was developed that utilizes inexpensive trifluoroacetates. Providing low concentrations of the most economically attractive and atom-efficient trifluoromethylation reagent this new protocol is advantageous compared to known procedures both economically and ecologically.     

Fe(PyTACN)‐Catalyzed cis‐Dihydroxylation of Olefins with Hydrogen Peroxide

A family of iron complexes with general formula [Fe(II)(^R,Y,XPyTACN)(CF₃SO₃)₂], where ^R,Y,XPyTACN=1‐[2′‐(4‐Y‐6‐X‐pyridyl)methyl]‐4,7‐dialkyl‐1,4,7‐triazacyclononane, X and Y refer to the groups at positions 4 and 6 of the pyridine, respectively, and R refers to the alkyl substitution at N‐4 and N‐7 of the triazacyclononane ring, are shown to be catalysts for efficient and selective alkene oxidation (epoxidation and cis‐dihydroxylation) employing hydrogen peroxide as oxidant. Complex [Fe(II)(^Me,Me,HPyTACN)(CF₃SO₃)₂] ( 7 ), was identified as the most efficient and selective cis‐dihydroxylation catalyst among the family. The high activity of 7 allows the oxidation of alkenes to proceed rapidly (30 min) at room temperature and under conditions where the olefin is not used in large amounts but instead is the limiting reagent. In the presence of 3 mol% of 7 , 2 equiv. of H₂O₂ as oxidant and 15 equiv. of water, in acetonitrile solution, alkenes are cis‐dihydroxylated reaching yields that might be interesting for synthetic purposes. Competition experiments show that 7 exhibits preferential selectivity towards the oxidation of cis olefins over the trans analogues, and also affords better yields and high [syn‐diol]/[epoxide] ratios when cis olefins are oxidized. For aliphatic substrates, reaction yields attained with the present system compare favourably with state of the art Fe‐catalyzed cis‐dihydroxylation systems, and it can be regarded as an attractive complement to the iron and manganese systems described recently and which show optimum activity against electron‐deficient and aromatic olefins.     

Gemeinsame österreichisch-ungarische Sedimentforschung im Rahmen des EFRE-Projektes SEDDON

The multiple uses of the Danube River for navigation, hydropower production and as a drinking water supply influence its ecological quality. Flow restrictions due to regulation as well as impacts on the sediment regime such as retention in the catchment area and interruption of the sediment continuum result in changes of the hydromorphological structures and can produce major problems in the context of sediment management. In light of these facts, cross-border investigations of sediment transport at the Danube River are called for. As there are no uniform research approaches shared by Austria and Hungary, the EU-funded project SEDDON (Sediment Research and Management at the Danube River) aims to compare different monitoring and modeling techniques used to determine sediment transport, and to develop mutual solutions. Further, the laboratory equipment currently used for hydraulic model experiments is evaluated and a research channel with a free flowing discharge of up to 10 m³/s without pumping will be constructed, allowing large-scale joint laboratory tests concerning sediment to be performed.     

Incidence of Tritrichomonas foetus in young replacement bulls following introduction into an infected herd

Three hundred 8-year-old Shorthorn and Santa Gertrudis bulls, with a 47% incidence of Tritrichomonas foetus infection in the 30 surveyed, were removed from a herd of approximately 6000 cows and replaced by 325 two-year-old Brahman bulls. A sample of 50 of the replacement bulls was examined at introduction and found to be uninfected. After 2 years, the incidence of infection in a sample of 80 of the replacement bulls was 4%. The results suggests that a major reduction in incidence of infection in extensively managed herds might be achieved by the exclusive use of young bulls for mating.     

The National Cancer Data Base report on the relationship of race and national origin to the histology of nasopharyngeal carcinoma

This study was undertaken to clarify several aspects of morphological and taxonomic characters of Physaloptera bispiculata Vaz and Pereira, 1935, a parasite of the water rat, Nectomys squamipes. The cephalic structures (including lips, papillae, teeth, amphids, and porous areas) and details of the posterior end of male and female adult worms were examined by scanning electron microscopy, leading to the addition of new taxonomic characters for this species. We consider P. bispiculata a valid species, based on a comparative analysis of the specific characters for P. bispiculata and P. getula Seurat, 1917, including the morphology and morphometry of body structures as well as number and disposition of caudal papillae of the males.     

Inappropriate use of daily mortality analyses to estimate longer-term mortality effects of air pollution

Identification of enterococci species by hybridization with recently designed species-specific and group-specific 23S rDNA-targeted oligonucleotide probes was superior to results obtained with a common biochemical test panel. Considering these findings, a molecular biological procedure for the detection of enterococci in water samples was developed. A short enrichment is followed by an amplification step and a hybridization reaction in microtiter plate format. The detection limit is about 1 CFU/ml, and results are available within 26 h.