P. aeruginosa SGNH hydrolase-like proteins AlgJ and AlgX have similar topology but separate and distinct roles in alginate acetylation.

The O-acetylation of polysaccharides is a common modification used by pathogenic organisms to protect against external forces. Pseudomonas aeruginosa secretes the anionic, O-acetylated exopolysaccharide alginate during chronic infection in the lungs of cystic fibrosis patients to form the major constituent of a protective biofilm matrix. Four proteins have been implicated in the O-acetylation of alginate, AlgIJF and AlgX. To probe the biological function of AlgJ, we determined its structure to 1.83 Å resolution. AlgJ is a SGNH hydrolase-like protein, which while structurally similar to the N-terminal domain of AlgX exhibits a distinctly different electrostatic surface potential. Consistent with other SGNH hydrolases, we identified a conserved catalytic triad composed of D190, H192 and S288 and demonstrated that AlgJ exhibits acetylesterase activity in vitro. Residues in the AlgJ signature motifs were found to form an extensive network of interactions that are critical for O-acetylation of alginate in vivo. Using two different electrospray ionization mass spectrometry (ESI-MS) assays we compared the abilities of AlgJ and AlgX to bind and acetylate alginate. Binding studies using defined length polymannuronic acid revealed that AlgJ exhibits either weak or no detectable polymer binding while AlgX binds polymannuronic acid specifically in a length-dependent manner. Additionally, AlgX was capable of utilizing the surrogate acetyl-donor 4-nitrophenyl acetate to catalyze the O-acetylation of polymannuronic acid. Our results, combined with previously published in vivo data, suggest that the annotated O-acetyltransferases AlgJ and AlgX have separate and distinct roles in O-acetylation. Our refined model for alginate acetylation places AlgX as the terminal acetlytransferase and provides a rationale for the variability in the number of proteins required for polysaccharide O-acetylation.

Electroanalysis at the nanoscale.

This article reviews the state of the art of silicon chip-based nanoelectrochemical devices for sensing applications. We first describe analyte mass transport to nanoscale electrodes and emphasize understanding the importance of mass transport for the design of nanoelectrode arrays. We then describe bottom-up and top-down approaches to nanoelectrode fabrication and integration at silicon substrates. Finally, we explore recent examples of on-chip nanoelectrodes employed as sensors and diagnostics, finishing with a brief look at future applications.

Aminoacyl-tRNA synthetases as drug targets in eukaryotic parasites.

Aminoacyl-tRNA synthetases are central enzymes in protein translation, providing the charged tRNAs needed for appropriate construction of peptide chains. These enzymes have long been pursued as drug targets in bacteria and fungi, but the past decade has seen considerable research on aminoacyl-tRNA synthetases in eukaryotic parasites. Existing inhibitors of bacterial tRNA synthetases have been adapted for parasite use, novel inhibitors have been developed against parasite enzymes, and tRNA synthetases have been identified as the targets for compounds in use or development as antiparasitic drugs. Crystal structures have now been solved for many parasite tRNA synthetases, and opportunities for selective inhibition are becoming apparent. For different biological reasons, tRNA synthetases appear to be promising drug targets against parasites as diverse as Plasmodium (causative agent of malaria), Brugia (causative agent of lymphatic filariasis), and Trypanosoma (causative agents of Chagas disease and human African trypanosomiasis). Here we review recent developments in drug discovery and target characterisation for parasite aminoacyl-tRNA synthetases.

Highly sensitive detection of nitroaromatic explosives at discrete nanowire arrays.

We show a photolithography technique that permits gold nanowire array electrodes to be routinely fabricated at reasonable cost. Nanowire electrode arrays offer the potential for enhancements in electroanalysis such as increased signal-to-noise ratio and increased sensitivity while also allowing quantitative detection at much lower concentrations. We explore application of nanowire array electrodes to the detection of different nitroaromatic species. Characteristic reduction peaks of nitro groups are not observed at nanowire array electrodes using sweep voltammetric methods. By contrast, clear and well-defined reduction peaks are resolved using potential step square wave voltammetry. A Principle Component Analysis technique is employed to discriminate between nitroaromatic species including structural isomers of DNT. The analysis indicates that all compounds are successfully discriminated by unsupervised cluster analysis. Finally, the magnitude of the reduction peak at -671 mV for different concentrations of TNT exhibited excellent linearity with increasing concentrations enabling sub-150 ng mL(-1) limits of detection.

Gold nanowire electrodes in array: simulation study and experiments.

Recent developments in nanofabrication have enabled fabrication of robust and reproducible nanoelectrodes with enhanced performance, when compared to microelectrodes. A hybrid electron beam/photolithography technique is shown that permits discrete gold nanowire electrode arrays to be routinely fabricated at reasonable cost. Fabricated devices include twelve gold nanowire working electrode arrays, an on-chip gold counter electrode and an on-chip platinum pseudo reference electrode. Using potential sweep techniques, when diffusionally independent, these nanowires exhibit measurable currents in the nanoAmpere regime and display steady-state voltammograms even at very high scan rates (5000 mV s(-1)) indicative of fast analyte mass transport to the electrode. Nanowire electrode arrays offer the potential for enhancements in electroanalysis including increased signal to noise ratio and increased sensitivity while also allowing quantitative detection at much lower concentrations. However, to achieve this goal a full understanding of the diffusion profiles existing at nanowire arrays is required. To this end, we simulate the effects of altering inter-electrode separations on analyte diffusion for a range of scan rates at nanowire electrode arrays, and perform the corresponding experiments. We show that arrays with diffusionally independent concentration profiles demonstrate superior electrochemical performance compared to arrays with overlapping diffusion profiles when employing sweep voltammetric techniques. By contrast, we show that arrays with diffusionally overlapping profiles exhibit enhanced performance when employing step voltammetric techniques.

Fatigue reporting among aircrew: incidence rate and primary causes.

INTRODUCTION: In this study we describe our experience of voluntary fatigue reporting among pilots and cabin crew. METHOD: This was a prospective study to determine the crude incidence rate and primary cause of fatigue report form submission among cabin crew and pilots within one airline. All crew duties had already undergone scrutiny at the 'roster build' stage to ensure compliance with fatigue control measures. Reports were investigated by the airline's medical officer to determine the primary cause of fatigue and then allocated to one of five categories. The frequency and proportion of reports within each category was determined. RESULTS: The crude incidence rate of fatigue report submission was 103 and 68 cases per 1000 persons per year for pilots and cabin crew, respectively. The primary cause for 27% of reports was attributed to the rostered duty pattern. Of the reports, 24% were primarily caused by roster disruption, 17% by problems with layover accommodation or transport, 23% by a domestic issue, and 9% had no obvious cause or were deemed invalid. A subanalysis of the 'domestic' category revealed that half had a primary cause attributable to commuting to or from the workplace. CONCLUSION: The number and trend of reports received per month can be used to detect otherwise unknown fatigue hazards and identify where improvements can be made. Fatigue reports allow individual crewmembers to give vital feedback on 'whole-of-life' fatigue risks, both inside and outside the workplace.

Single on-chip gold nanowires for electrochemical biosensing of glucose.

The development of glucose diagnostic devices with low detection limits is of key importance in diabetes-related research. New highly sensitive sensors are required for non-invasive detection of glucose in bodily fluids, other than blood, and an electrochemical sensor based on a single gold nanowire for rapid, reliable and quantitative detection of low glucose concentrations (10 µM-1 mM), is presented in this paper. Single gold nanowire devices are fabricated at silicon chip substrates using a hybrid electron beam-photolithography approach. Critical dimensions of the nanowires are characterised using a combination of scanning electron and atomic force microscopies. Fabricated nanowire devices are characterised by direct electrical probing and cyclic voltammetry to explore functionality. The voltammetric detection of glucose was performed using ferrocene monocarboxylic acid as an oxidising mediator in the presence of glucose oxidase. The biosensor can be applied to the quantification of glucose in the range of 10 µM-100 mM, with an extremely high sensitivity of 7.2 mA mM(-1) cm(-2) and a low detection limit of 3 µM (S/N = 3). The sensor demonstrated high selectivity towards glucose with negligible interference from other oxidizable species including uric acid, ascorbic acid, mannose, fructose, salicylic acid (Aspirin) and acetaminophen (Paracetamol).

Single nanoskived nanowires for electrochemical applications.

In this work, we fabricate gold nanowires with well controlled critical dimensions using a recently demonstrated facile approach termed nanoskiving. Nanowires are fabricated with lengths of several hundreds of micrometers and are easily electrically contacted using overlay electrodes. Following fabrication, nanowire device performance is assessed using both electrical and electrochemical characterization techniques. We observe low electrical resistances with typical linear Ohmic responses from fully packaged nanowire devices. Steady-state cyclic voltammograms in ferrocenemonocarboxylic acid demonstrate scan rate independence up to 1000 mV s(-1). Electrochemical responses are excellently described by classical Butler-Volmer kinetics, displaying a fast, heterogeneous electron transfer kinetics, k(0) = 2.27 ± 0.02 cm s(-1), α = 0.4 ± 0.01. Direct reduction of hydrogen peroxide is observed at nanowires across the 110 pM to 1 mM concentration range, without the need for chemical modification, demonstrating the potential of these devices for electrochemical applications.

Phylogenetic structure and species boundaries in the mountain pitviper Ovophis monticola (Serpentes: Viperidae: Crotalinae) in Asia.

We investigated phylogenetic structure and morphological variation in Asian mountain pitvipers of the genus Ovophis (comprising 3-4 species some of which are considered polytypic) by sequencing four mitochondrial markers (cytochrome b, NADH dehydrogenase subunit 4, 12S and 16S rRNA) from 72 specimens, and analysed them in a Bayesian framework together with another 26 sequences from closely related genera. We reconstructed the region of origin and direction of dispersal of the major clades, and of Ovophis as a whole, using likelihood framework analysis. We also defined morphogroups from 280 specimens from across the range of Ovophis to allow the geographic extent of the major clades to be determined, as well as to allow inclusion of specimens lacking sequence data. Phylogenetic analyses confirmed the monophyly of Ovophis as currently defined, and revealed that it contains two major lineages, eastern (mainly Chinese) and western, with both occurring in southwestern China, central and northern Viet Nam. The most likely origin of the genus, and of individual lineages, coincides with the northeastern boundary of the Indomalayan hotspot. Major diversification in this species group likely corresponded to major climatic changes arising from the uplift of the Tibetan Plateau in the early to mid Miocene. With reference to the defined morphogroups, we suggest that at least five species are present and provide appropriate names. With a few exceptions, the newly defined species boundaries do not correspond to the existing taxonomy.

Estimating genetic variability in non-model taxa: a general procedure for discriminating sequence errors from actual variation.

Genetic variation is the driving force of evolution and as such is of central interest for biologists. However, inadequate discrimination of errors from true genetic variation could lead to incorrect estimates of gene copy number, population genetic parameters, phylogenetic relationships and the deposition of gene and protein sequences in databases that are not actually present in any organism. Misincorporation errors in multi-template PCR cloning methods, still commonly used for obtaining novel gene sequences in non-model species, are difficult to detect, as no previous information may be available about the number of expected copies of genes belonging to multi-gene families. However, studies employing these techniques rarely describe in any great detail how errors arising in the amplification process were detected and accounted for. Here, we estimated the rate of base misincorporation of a widely-used PCR-cloning method, using a single copy mitochondrial gene from a single individual to minimise variation in the template DNA, as 1.62×10(-3) errors per site, or 9.26×10(-5) per site per duplication. The distribution of errors among sequences closely matched that predicted by a binomial distribution function. The empirically estimated error rate was applied to data, obtained using the same methods, from the Phospholipase A(2) toxin family from the pitviper Ovophis monticola. The distribution of differences detected closely matched the expected distribution of errors and we conclude that, when undertaking gene discovery or assessment of genetic diversity using this error-prone method, it will be informative to empirically determine the rate of base misincorporation.

The early days of IVF outside the UK.

In this article the history of IVF in geographical regions outside the UK are traced by pioneers of that time. Following the birth of Louise Brown in 1978, live births after IVF occurred in Australia in 1980, in the USA in 1981 and in Sweden and France in 1982. Following the first IVF birth in Australia, the Government of Victoria established a review of IVF research and practice which led to the proclamation of the Infertility (Medical Procedures) Act 1984, the first legislation to regulate IVF and its associated human embryo research. Despite such restriction, IVF doctors and scientists from Victoria, especially those under the leadership of Carl Wood, Alan Trounson and Ian Johnston continued to initiate new treatments for infertility and new methods for delivering this treatment. In the USA IVF research began on animals as early as the 1930s, when Pincus and Enzmann at Harvard were involved in attempts at IVF in the rabbit. In the 1940s, John Rock attempted human IVF with 138 human oocytes without success. In 1965, Bob Edwards was with Georgeanna and Howard Jones at Johns Hopkins where attempts were made to fertilize oocytes in vitro. Clinical IVF began in earnest in the USA in 1980 with the first birth in 1981 achieved by the use of HMG--a first successful use with IVF. In France, two groups Frydman and Testart (Clamart) and Cohen, Mandelbaum and Plachot (Sevres) focused their research in particular directions. In 1981, the Clamart group developed a plasma assay for the initial rise in LH. The Sevres group developed a transport technique. Plachot produced a long series of cytogenetic analyses of oocytes and human embryos. Mandelbaum described the microstructures of the human oocyte. The start of IVF in France benefited from the help of animal researchers from the Institut National de la Recherche Agronomique. The first babies were born in Clamart in February 1982 and in Sèvres in June 1982. Important contributions to the development of IVF from the Nordic countries include techniques for ovarian stimulation, sonographic techniques for monitoring and vaginal oocyte retrieval and also unique possibilities for monitoring IVF safety. These developments, in combination with relatively permissive laws for the practice of reproductive medicine and relatively generous reimbursement policies, as well as a general public confidence in IVF, have led to an exceptionally high availability of IVF, within international comparison.

Do aposematism and Batesian mimicry require bright colours? A test, using European viper markings.

Predator avoidance of noxious prey, aposematism and defensive mimicry are normally associated with bright, contrasting patterns and colours. However, noxious prey may be unable to evolve conspicuous coloration because of other selective constraints, such as the need to be inconspicuous to their own prey or to specialist predators. Many venomous snakes, particularly most vipers, display patterns that are apparently cryptic, but nevertheless highly characteristic, and appear to be mimicked by other, non-venomous snakes. However, predator avoidance of viper patterns has never been demonstrated experimentally. Here, the analysis of 813 avian attacks on 12,636 Plasticine snake models in the field shows that models bearing the characteristic zigzag band of the adder (Vipera berus) are attacked significantly less frequently than plain models. This suggests that predator avoidance of inconspicuously but characteristically patterned noxious prey is possible. Our findings emphasize the importance of mimicry in the ecological and morphological diversification of advanced snakes.

Distinguishing medical practice and research: the special case of IVF.

KIE: The debate over the acceptability of human embryo research takes place within the context of a broader regulatory framework for experimentation with human subjects. Using the Australian situation for illustration, Gaze and Dawson examine the concepts of therapeutic, nontherapeutic, and destructive experimentation in medical practice. They explore the problems of applying these concepts to human embryo research by asking whether the embryo or the woman undergoing in vitro fertilization (IVF) treatment is the experimental subject. They argue that when the embryo is treated as the sole subject, the woman is lost sight of, and that research that is therapeutic for the embryo may be nontherapeutic for her. Regulation of embryo research should take into account the relationship between research and the woman's treatment, the dependence of embryos upon women for gestation, and the empirical, uncertain nature of biomedical knowledge.^ieng

IVF technology and the argument from potential.

KIE: Singer and Dawson point out that two arguments against abortion, that the embryo is entitled to protection because from fertilization it is (1) a human being or (2) a potential human being, are also used by opponents of embryo experimentation. They focus on the second argument, evaluating the notion of potentiality as it applies to gametes, to the unimplanted embryo, to the implanted developing embryo, and to the embryo created by in vitro fertilization (IVF). They argue that there is a crucial distinction between natural reproduction, in which all that is needed for the embryo to have a prospect of reaching its potential is for those involved to refrain from stopping it, and IVF, in which the embryo cannot develop into a person without a deliberate human act. Reproductive techniques necessitate our rethinking of established views about potentiality, and how it should be applied to the embryo in a laboratory.^ieng

Segmentation and moral status in vivo and in vitro: a scientific perspective.

KIE: A basic consideration in research on human embryos is the controversy about when the embryo acquires moral status. The author refutes the contention that segmentation is the determinant of moral status. She notes that segmentation, as a stage in embryonic development, does not coincide with the development of "irreversible individuality" upon which the segmentation argument depends. Dawson also finds a lack of clarity in the meaning of "individuality." These problems, she maintains, prevent segmentation from being morally important and render the proposed 14-day limit on embryo research unnecessary. Dawson concludes that to introduce a time restriction on embryo research is premature because it is based on an inadequate philosophical argument.^ieng