Large-Scale Conformational Transitions and Dimerization Are Encoded in the Amino-Acid Sequences of Hsp70 Chaperones

Hsp70s are a class of ubiquitous and highly conserved molecular chaperones playing a central role in the regulation of proteostasis in the cell. Hsp70s assist a myriad of cellular processes by binding unfolded or misfolded substrates during a complex biochemical cycle involving large-scale structural rearrangements. Here we show that an analysis of coevolution at the residue level fully captures the characteristic large-scale conformational transitions of this protein family, and predicts an evolutionary conserved–and thus functional–homo-dimeric arrangement. Furthermore, we highlight that the features encoding the Hsp70 dimer are more conserved in bacterial than in eukaryotic sequences, suggesting that the known Hsp70/Hsp110 hetero-dimer is a eukaryotic specialization built on a pre-existing template.     

Apical membrane potentials and intracellular potassium and sodium activities in the gallbladder of the freshwater turtle Mauremys caspica

Open-tip and liquid ion-exchanger microelectrodes were used to measure transapical membrane potential (Va), fractional voltage ratio (fa) and intracellular sodium and potassium activities (aiNa, aiK) in Mauremys caspica gallbladder under open circuit conditions. The average values (+/- SEM) for Va and fa were -32 +/- 3 and 0.20 +/- 0.03 mV respectively. aiNa and aiK were, respectively, 17 +/- 4 and 82 +/- 7 mM. These results suggest that the mechanisms of Na+ and K+ transport in this tissue are essentially similar to those observed in leaky epithelia in general.     

Gregariousness affects performance and defensive reactions in swallowtail caterpillars

1. Group living in caterpillars may enhance individual performance due to sharing of costs associated with individual tasks when dealing with biotic or abiotic ecological factors. 2. In the gregarious caterpillar Battus polydamas archidamas (Papilionidae) egg clusters and caterpillar groups vary in size. We hypothesized that individual survival would be higher in larger groups and that group living would enhance individual performance: shorter development time and/or reduced frequency of (presumably costly) defensive reactions in larvae and larger adult size. We also tested whether the group size conferring the highest survival to laboratory-reared caterpillars matched the most frequent egg clutch size in the field. 3. We collected egg clutches in the field and reared caterpillars in groups of 1, 6, 10, and 14 individuals. We quantified larval survival and stage duration as well as adult mass under laboratory conditions, excluding natural enemies. We also recorded the frequency of larval defensive reactions (thrashing and osmeterium display) against a tactile stimulus of first-instar larvae. 4. Group living enhanced caterpillar survival, particularly during the first instars, when caterpillars are 100% gregarious. Groups of intermediate size reduced larval development time but group living did not affect adult mass. Individual caterpillars in groups showed defensive reactions less frequently than solitary individuals, revealing a cost-saving feature of gregariousness for this swallowtail species. The most frequent clutch size in the field (9–10 eggs) did not match the larval group with highest survival (14 individuals), but did match the group with shortest development time.     

Relationship between Riparian Vegetation and Stream Benthic Communities at Three Spatial Scales

We examined the influence of riparian vegetation on macroinvertebrate community structure in streams of the Upper Thames River watershed in southwestern Ontario. Thirty-three μ-basins (129–1458 ha) were used to identify land cover variables that influenced stream macroinvertebrates. Micro-basins represented the entire drainage area of study streams and were similar in stream order (first, second) and land cover (agricultural or forest; no urban). We described the structure and composition of riparian vegetation and benthic macroinvertebrate communities at the outflow reach. The nature of the land cover was quantified for the stream network buffer (30 m) and the whole μ-basin. The objective of this study was to measure the magnitude and nature of the relationship between the riparian vegetation and benthic macroinvertebrate community at the outflow reach, stream network buffer, and whole μ-basin scales. Taxon richness (including total number of Ephemeroptera, Plecoptera, and Trichoptera taxa) and Simpson’s diversity of the macroinvertebrate community all increased with increased tree cover in the riparian zone at the outflow reach scale. Simpson’s equitability was lower with greater agricultural land cover in the stream network buffer. No relationship between the macroinvertebrate community and land cover was found at the whole μ-basin scale. Analysis of the influence of land cover on stream communities within a spatial hierarchy is important for understanding the interactions of stream ecosystems with their adjacent landscapes.     

Imidazolium-Catalyzed Synthesis of an Imidazolium Catalyst

Origins of Life and Evolution of Biospheres - The chemistry of imidazolium-catalyzed imidazolium synthesis was studied as part of an effort to develop a plausible prebiotic synthesis of a small...