Climate variability and change are drivers of salmonellosis in Australia: 1991 to 2019.

Salmonellosis is a climate-sensitive gastroenteritis with over 92 million cases and over 50,000 deaths a year globally. Australia has high rates of salmonellosis compared with other industrialised nations. This study used a negative binomial time-series regression model to investigate the association between Australian salmonellosis notifications and monthly climate variables including El Niño Southern Oscillation (ENSO) and mean temperature anomaly from 1991 to 2019. Between 1991 and 2019 in Australia there were 275,753 salmonellosis notifications and the median annual rate for salmonellosis was 40.1 per 100,000 population. Salmonellosis notifications exhibited strong seasonality, reaching a peak in summer and a minimum in winter. There was an estimated increase of 3.4 % in salmonellosis cases nationally per 1 °C increase in monthly mean temperature anomaly (incidence rate ratio [IRR] of 1.034, 95 % confidence interval [CI]: 1.009, 1.059). Similar associations between salmonellosis and mean temperature anomaly were found for some states. Mean temperature anomaly exhibited an upward trend of 0.9 °C over the period 1991 to 2019. Additionally, a positive association was found between salmonellosis in Australia and ENSO whereby El Niño periods were associated with 7.9 % more salmonellosis cases compared to neutral periods (IRR 1.079, 95 % CI: 1.019, 1.143). A similar ENSO association was detected in the two eastern states of New South Wales and Queensland. This study suggests public health preventative measures to reduce salmonellosis could be enhanced in some regions during El Niño as well as during times of increased temperatures.

Structure and dynamics of conjugated polymers in liquid crystalline solvents.

A combination of single-molecule spectroscopy and analysis with simulations is used to provide detailed information about the structural and dynamic properties of a fluorescent polymer MEH-PPV (poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene]) immersed in a nematic and smectic solvent. In nematic solvents, single-polymer molecules are oriented strongly along the solvent director, much more so than the solvent molecules, confirming Onsager's old prediction. The diffusion anisotropy parallel and perpendicular to the solvent director, however, is less than two, which is similar to that of a spherical colloid in a nematic solvent. In smectic solvents, there is a second orientation of the dissolved polymer perpendicular to the solvent director, which we hypothesize is caused by the polymer occupying the interlayer volume. The research discussed here emphasizes the importance of organization in complex fluids and suggests that the interplay of order on different length scales could be exploited to fabricate novel nanostructured materials.

Nematic solvation of segmented polymer chains.

We examine the effect of polymer chain segmentation on the recently discovered ability of nematic solvents to elongate and align polymer chain solutes. Coordinated single molecule spectroscopy and beads-on-a-chain simulations are used to study the orientational and conformational order of a series of segmented conjugated polymers, dissolved in the nematic liquid crystal 5CB. The order parameters for alignment and elongation are both observed to decrease with increasing segmentation, reflecting an interplay among conformational entropy, solvation anisotropy, and bending energy of the chain.

Selection of peptides with semiconductor binding specificity for directed nanocrystal assembly.

In biological systems, organic molecules exert a remarkable level of control over the nucleation and mineral phase of inorganic materials such as calcium carbonate and silica, and over the assembly of crystallites and other nanoscale building blocks into complex structures required for biological function. This ability to direct the assembly of nanoscale components into controlled and sophisticated structures has motivated intense efforts to develop assembly methods that mimic or exploit the recognition capabilities and interactions found in biological systems. Of particular value would be methods that could be applied to materials with interesting electronic or optical properties, but natural evolution has not selected for interactions between biomolecules and such materials. However, peptides with limited selectivity for binding to metal surfaces and metal oxide surfaces have been successfully selected. Here we extend this approach and show that combinatorial phage-display libraries can be used to evolve peptides that bind to a range of semiconductor surfaces with high specificity, depending on the crystallographic orientation and composition of the structurally similar materials we have used. As electronic devices contain structurally related materials in close proximity, such peptides may find use for the controlled placement and assembly of a variety of practically important materials, thus broadening the scope for 'bottom-up' fabrication approaches.

Intra-tRNA distance measurements for nucleocapsid proteindependent tRNA unwinding during priming of HIV reverse transcription.

We report here the direct measurement of intra-tRNA distances during annealing of the tRNA primer to the HIV RNA genome. This key step in the initiation of retroviral reverse transcription involves hybridization of one strand of the acceptor arm of a specific lysine tRNA to the primer binding site on the RNA genome. Although the mechanism of tRNA unwinding and annealing is not known, previous studies have shown that HIV nucleocapsid protein (NC) greatly accelerates primer/template binary complex formation in vitro. An open question is whether NC alone unwinds the primer or whether unwinding by NC requires the RNA genome. We monitored the annealing process in solution by using fluorescence resonance energy transfer (FRET). Distance measurements demonstrate unequivocally that the tRNA acceptor stem is not substantially unwound by NC in the absence of the RNA genome, that is, unwinding is not separable from hybridization. Moreover, FRET measurements show that both heat- and NC-mediated annealing result in an approximately 40-A increase in the separation of the two ends of the tRNA acceptor arm on binding to the template. This large increase in separation of the two ends suggests a complete displacement of the nonhybridized strand of the acceptor stem in the initiation complex.

Rates of DNA-mediated electron transfer between metallointercalators.

Ultrafast emission and absorption spectroscopies were used to measure the kinetics of DNA-mediated electron transfer reactions between metal complexes intercalated into DNA. In the presence of rhodium(III) acceptor, a substantial fraction of photoexcited donor exhibits fast oxidative quenching (>3 x 10(10) per second). Transient-absorption experiments indicate that, for a series of donors, the majority of back electron transfer is also very fast (approximately 10(10) per second). This rate is independent of the loading of acceptors on the helix, but is sensitive to sequence and pi stacking. The cooperative binding of donor and acceptor is considered unlikely on the basis of structural models and DNA photocleavage studies of binding. These data show that the DNA double helix differs significantly from proteins as a bridge for electron transfer.

Vibrational modes and the dynamic solvent effect in electron and proton transfer.

This article primarily reviews recent work on ultrafast experiments on excited state intramolecular electron and proton transfer, with an emphasis on experiments on chemical systems that have been analyzed theoretically. In particular, those systems that have been quantitatively characterized by static spectroscopy, which provides detailed information about the reaction potential energy surface and about other parameters that are necessary to make a direct comparison to theoretical predictions, are described.