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CheY is a response regulator protein involved in bacterial chemotaxis. Much is known about its active and inactive conformations, but little is known about the mechanisms underlying long-range interactions or correlated motions. To investigate these events, molecular dynamics simulations were performed on the unphosphorylated, inactive structure from Salmonella typhimurium and the CheY−BeF3− active mimic structure (with BeF3− removed) from Escherichia coli. Simulations utilized both sequences in each conformation to discriminate sequence- and structure-specific behavior. The previously identified conformational differences between the inactive and active conformations of the strand-4-helix-4 loop, which are present in these simulations, arise from the structural, and not the sequence, differences. The simulations identify previously unreported structure-specific flexibility features in this loop and sequence-specific flexibility features in other regions of the protein. Both structure- and sequence-specific long-range interactions are observed in the active and inactive ensembles. In the inactive ensemble, two distinct mechanisms based on Thr-87 or Ile-95 rotameric forms, are observed for the previously identified g+ and g− rotamer sampling by Tyr-106. These molecular dynamics simulations have thus identified both sequence- and structure-specific differences in flexibility, long-range interactions, and rotameric form of key residues. Potential biological consequences of differential flexibility and long-range correlated motion are discussed.

The methods used by laboratories participating in FAPAS® proficiency testing covering trace metals have been reviewed. Techniques that tend to give the highest percentage of satisfactory z-scores are identified. Comparisons are made of digestion and extraction techniques, use of atomic absorption spectrophotometry (AA: graphite furnace and flame) and inductively coupled plasma techniques (ICP-OES and ICP-MS). It does not follow that one technique is more accurate than the others, because some individual laboratories consistently achieve satisfactory results using any of the five main digestion techniques and any of the major detection techniques. The results do, however, give an indication of which techniques are easier to perform correctly and with a high standard of accuracy. There are also other factors that may influence results such as instrument set-up, background correction and data analysis.

A number of triphenylmethane derivatives have been screened against 6-phosphogluconate dehydrogenase from Trypanosoma bruceiand sheep liver. Some of these compounds show good inhibition of the enzymes and also selectivity towards the parasite enzyme. Modelling was undertaken to dock the compounds into the active sites of both enzymes. Using a combination of DOCK 3.5 and FLEXIDOCK a correlation was obtained between docking score and both activity for the enzymes and selectivity. Visualisation of the docked structures of the inhibitors in the active sites of the enzymes yielded a possible explanation of the selectivity for the parasite enzyme.

Performance by participants in a large proficiency test in the food analysis sector is quantified as a function of concentration of the analyte and compared with the performance criteria used by the scheme provider to define fitness for purpose. The performance was found to fall short of the specification by only a small amount, evenly over the whole concentration range.