External quality assessment in microbiology: comparison of results from Belgian and Canadian laboratories with regard to their ability to identify <Emphasis Type="Italic">Streptococcus pyogenes</Emphasis>

Clinical Microbiology Proficiency Testing (CMPT; Canada) and the Institute of Public Health (IPH; Belgium) set up a joint external quality assessment (EQA) project in which they sent identical simulated clinical samples to their respective participants. Samples were sent out as throat swabs containing Streptococcus pyogenes (as pathogen) and viridans streptococci (as commensal). Results from identification by the Belgian laboratories were excellent: 99.5% detected the group A streptococci. About 10% of the Canadian laboratories reported the absence of reportable β-haemolytic streptococci, although for most of them the issue was one of non-examination of small or pin-point streptococci. Overall, Canadian and Belgian laboratories performed well in this EQA; the joint project clearly showed that although many similarities exist, there are differences between laboratories in treating EQA samples and reporting results.     

Naturally occurring esterification reactions with bryostatin

Bryostatin structures share a commonality of a central bryophan ring, but each differs due to two groups (R(1) and R(2)) that are attached to the bryophan ring via ester bonds. This research examines the impact that conditions such as UV light, acidic and basic conditions can have on the bryostatin structure in the presence of octanoic acid and water. Mass spectrometry (MS) measurements suggest that bryostatin can easily rearrange into various structures under natural conditions by reacting with carboxylates that are ubiquitous in nature. A second set of measurements suggest bryostatin can be hydrolyzed by water, a reaction that has significant implications in both medicinal applications and extraction procedures.     

Cu(II) coordination chemistry of patellamide derivatives: possible biological functions of cyclic pseudopeptides

Two synthetic derivatives of the naturally occurring cyclic pseudooctapeptides patellamide A-F and ascidiacyclamide, that is, H(4)pat(2), H(4)pat(3), as well as their Cu(II) complexes are described. These cyclic peptide derivatives differ from the naturally occurring macrocycles by the variation of the incorporated heterocyclic donor groups and the configuration of the amino acids connecting the heterocycles. The exchange of the oxazoline and thiazole groups by dimethylimidazoles or methyloxazoles leads to more rigid macrocycles, and the changes in the configuration of the side chains leads to significant differences in the folding of the cyclic peptides. These variations allow a detailed study of the various possible structural changes on the chemistry of the Cu(II) complexes formed. The coordination of Cu(II) with these macrocyclic species was monitored by high-resolution electrospray mass spectrometry (ESI-MS), spectrophotometric (UV/Vis) and circular dichroic (CD) titrations, and electron paramagnetic resonance (EPR) spectroscopy. Density functional theory (DFT) calculations and molecular mechanics (MM) simulations have been used to model the structures of the Cu(II) complexes and provide a detailed understanding of their geometric preferences and conformational flexibility. This is related to the Cu(II) coordination chemistry and the reactivity of the dinuclear Cu(II) complexes towards CO(2) fixation. The variation observed between the natural and various synthetic peptide systems enables conclusions about structure-reactivity correlations, and our results also provide information on why nature might have chosen oxazolines and thiazoles as incorporated heterocycles.     

Modified normal-phase ion-pair chromatographic methods for the facile separation and purification of imidazolium-based ionic compounds

Imidazolium- and oligo(imidazolium)-based ionic organic compounds are important in the design of room-temperature ionic liquid materials; however, the chromatographic analysis and separation of such compounds are often difficult. A convenient and inexpensive method for effective thin-layer chromatography (TLC) analysis and column chromatography separation of imidazolium-based ionic compounds is presented. Normal-phase ion-pair TLC is used to effectively analyze homologous mixtures of these ionic compounds. Subsequent separation of the mixtures is performed using ion-pair flash chromatography on normal-phase silica gel, yielding high levels of recovery. This method also results in a complete exchange of the counter anion on the imidazolium compounds to the anion of the ion-pair reagent.     

Shallow water equations for power law and Bingham fluids

In this note,we provide a consistant thin layer theory for power law and Bingham incompressible fluids flowing down an inclined plane under the effect of gravity.The derivation of such equations is based on formal asymptotic expansions of solutions of Cauchy momentum equations in the shallow water scaling and in the neighbourhood of steady solutions so that we can close the average equations on the fluid height h and the total discharge rate q.