Release of aquatic carbon from two peatland catchments in E. Finland during the spring snowmelt period

Spring snowmelt in the arctic and boreal regions represents the most significant event in the hydrological year. We measured concentrations and fluxes of different carbon species in 2 small contrasting (control v drained) forested peatland catchments in E. Finland between April and June 2008 and compared these to long-term annual fluxes. Measurements were made using a combination of continuous sensors (CO₂, temperature, pH, discharge) and routine spot sampling (DOC, POC, DIC, CO₂, CH₄, N₂O). The highest concentrations of CO₂ and CH₄ in streamwater were observed under low flow conditions before the spring flood event, reflecting accumulation and downstream release of gaseous C at the end of the winter period. Over the length of the study mean CH₄ concentrations were 10× higher in the drained site. The snowmelt event was associated with a dilution of DOC and CO₂, with the drained catchment showing a much flashier hydrological response compared to the control site, and post-event, a slower recovery in DOC and CO₂ concentrations. Fluxes of all carbon species during the snowmelt event were significant and represented 37?C45% of the annual flux. This highlights the challenge of quantifying aquatic C fluxes in areas with large temporal variability and suggests that inability to ??capture?? the spring snowmelt event may lead to under-estimation of C fluxes in northern regions.     

Automated approach for the evaluation of glutathione-S-transferase P1-1 inhibition by organometallic anticancer compounds

A novel automated method based on sequential injection analysis (SIA), a non-segmented flow injection technique, was developed to evaluate glutathione S-transferase P1-1 (GST P1-1) activity in the presence of organometallic complexes with putative anticancer activity. The assay is based on the reaction of L-glutathione (GSH) and 1-chloro-2,4-dinitrobenzene (CDNB) in the presence of GST P1-1 to afford the GS-DNB conjugate and the reaction may be monitored by an increase in absorbance at 340 nm. A series of ruthenium, iron, osmium and iridium complexes were evaluated as GST P1-1 inhibitors by evaluating their half-maximal inhibitory concentration (IC₅₀). An iridium compound displays the lowest IC₅₀ value of 6.7 ± 0.7 µM and an iron compound displays the highest IC₅₀ value of 275 ± 9 µM. The SIA method is simple to use, robust, reliable, and efficient and uses fewer reagents than batch methods and each analysis takes only 5 minutes.     

The kinetic and equilibrium molten globule intermediates of apoleghemoglobin differ in structure

An important question in protein folding is whether molten globule states formed under equilibrium conditions are good structural models for kinetic folding intermediates. The structures of the kinetic and equilibrium intermediates in the folding of the plant globin apoleghemoglobin have been compared at high resolution by quench-flow pH-pulse labeling and interrupted hydrogen/deuterium exchange analyzed in dimethyl sulfoxide. Unlike its well studied homolog apomyoglobin, where the equilibrium and kinetic intermediates are quite similar, there are striking structural differences between the intermediates formed by apoleghemoglobin. In the kinetic intermediate, formed during the burst phase of the quench-flow experiment, protected amides and helical structure are found mainly in the regions corresponding to the G and H helices of the folded protein, and in parts of the E helix and CE loop regions, whereas in the equilibrium intermediate, amide protection and helical structure are seen in parts of the A and B helix regions, as well as in the G and H regions, and the E helix remains largely unfolded. These results suggest that the structure of the molten globule intermediate of apoleghemoglobin is more plastic than that of apomyoglobin, so that it is readily transformed depending on the solution conditions, particularly pH. Thus, in the case of apoleghemoglobin at least, the equilibrium molten globule formed under destabilizing conditions at acid pH is not a good model for the compact intermediate formed during kinetic refolding experiments. Our high-precision kinetic analysis also reveals an additional slow phase during the folding of apoleghemoglobin, which is not observed for apomyoglobin. Hydrogen exchange pulse-labeling experiments show that the slow-folding phase is associated with residues in the CE loop, which probably forms non-native structure in the intermediate that must be resolved before folding can proceed to completion.     

Solution structure of the N-terminal zinc fingers of the Xenopus laevis double-stranded RNA-binding protein ZFa

Several zinc finger proteins have been discovered recently that bind specifically to double-stranded RNA. These include the mammalian JAZ and wig proteins, and the seven-zinc finger protein ZFa from Xenopus laevis. We have determined the solution structure of a 127 residue fragment of ZFa, which consists of two zinc finger domains connected by a linker that remains unstructured in the free protein in solution. The first zinc finger consists of a three-stranded beta-sheet and three helices, while the second finger contains only a two-stranded sheet and two helices. The common structures of the core regions of the two fingers are superimposable. Each finger has a highly electropositive surface that maps to a helix-kink-helix motif. There is no evidence for interactions between the two fingers, consistent with the length (24 residues) and unstructured nature of the intervening linker. Comparison with a number of other proteins shows similarities in the topology and arrangement of secondary structure elements with canonical DNA-binding zinc fingers, with protein interaction motifs such as FOG zinc fingers, and with other DNA-binding and RNA-binding proteins that do not contain zinc. However, in none of these cases does the alignment of these structures with the ZFa zinc fingers produce a consistent picture of a plausible RNA-binding interface. We conclude that the ZFa zinc fingers represent a new motif for the binding of double-stranded RNA.     

Death and blindness due to overdose of quinine.

During 1953-83 there were 48 admissions to the regional poisoning treatment centre, Edinburgh, for overdose of quinine including 19 since 1978. Six patients were blind and one had ventricular tachycardia. Stellate ganglion block was performed without benefit in seven patients. No patient died, but three deaths from cardiotoxicity occurred in a further 71 patients reported to the Scottish Poisons Information Bureau. Plasma quinine concentration related to time from ingestion was found to be a useful predictor of visual toxicity.