Tetracyano-2,2-bipyridineiron(iii), an improved electron acceptor for the spectrophotometric assay of beta-oxidation and of succinate dehydrogenase in intact mitochondria.

A recently described direct reading assay for beta-oxidation and for succinate oxidation in intact mitochondria using [Fe(CN)6]3- as final electron acceptor [Osmundsen & Bremer (1977) Biochem. J. 164. 621--633] has been improved by using instead tetracyano-2,2-bipyridineiron(III) [Fe(CN)4(bpy)]-, which gives a 2.6 times greater absorbance change on reduction. Some physical and kinetic properties of [Fe(CN)4(bpy)]- are described. The use of exogenous cytochrome c(III) as electron acceptor was also tested; this gives the largest absorbance change, although the absolute rate of reaction is only approx. one-third of that using [Fe(CN)6]3- or [Fe(CN)4(bpy)]-.     

Multiple stressors on biotic interactions: how climate change and alien species interact to affect pollination

Global change may substantially affect biodiversity and ecosystem functioning but little is known about its effects on essential biotic interactions. Since different environmental drivers rarely act in isolation it is important to consider interactive effects. Here, we focus on how two key drivers of anthropogenic environmental change, climate change and the introduction of alien species, affect plant–pollinator interactions. Based on a literature survey we identify climatically sensitive aspects of species interactions, assess potential effects of climate change on these mechanisms, and derive hypotheses that may form the basis of future research. We find that both climate change and alien species will ultimately lead to the creation of novel communities. In these communities certain interactions may no longer occur while there will also be potential for the emergence of new relationships. Alien species can both partly compensate for the often negative effects of climate change but also amplify them in some cases. Since potential positive effects are often restricted to generalist interactions among species, climate change and alien species in combination can result in significant threats to more specialist interactions involving native species.     

Detection of a β-Lactamase Markedly Active Against Carbenicillin in a Strain of Pseudomonas aeruginosa

Examination of the substrate profile of a number of beta-lactamases synthesized by strains of Pseudomonas aeruginosa has shown the presence of at least two distinct types of enzyme, one of which is more active against carbenicillin than against benzyl penicillin.     

Millennial Climatic Fluctuations Are Key to the Structure of Last Glacial Ecosystems

Whereas fossil evidence indicates extensive treeless vegetation and diverse grazing megafauna in Europe and northern Asia during the last glacial, experiments combining vegetation models and climate models have to-date simulated widespread persistence of trees. Resolving this conflict is key to understanding both last glacial ecosystems and extinction of most of the mega-herbivores. Using a dynamic vegetation model (DVM) we explored the implications of the differing climatic conditions generated by a general circulation model (GCM) in “normal” and “hosing” experiments. Whilst the former approximate interstadial conditions, the latter, designed to mimic Heinrich Events, approximate stadial conditions. The “hosing” experiments gave simulated European vegetation much closer in composition to that inferred from fossil evidence than did the “normal” experiments. Given the short duration of interstadials, and the rate at which forest cover expanded during the late-glacial and early Holocene, our results demonstrate the importance of millennial variability in determining the character of last glacial ecosystems.     

VASP governs actin dynamics by modulating filament anchoring

Actin filament dynamics at the cell membrane are important for cell-matrix and cell-cell adhesions and the protrusion of the leading edge. Since actin filaments must be connected to the cell membrane to exert forces but must also detach from the membrane to allow it to move and evolve, the balance between actin filament tethering and detachment at adhesion sites and the leading edge is key for cell shape changes and motility. How this fine tuning is performed in cells remains an open question, but possible candidates are the Drosophila enabled/vasodilator-stimulated phosphoprotein (Ena/VASP) family of proteins, which localize to dynamic actin structures in the cell. Here we study VASP-mediated actin-related proteins 2/3 (Arp2/3) complex-dependent actin dynamics using a substrate that mimics the fluid properties of the cell membrane: an oil-water interface. We show evidence that polymerization activators undergo diffusion and convection on the fluid surface, due to continual attachment and detachment to the actin network. These dynamics are enhanced in the presence of VASP, and we observe cycles of catastrophic detachment of the actin network from the surface, resulting in stop-and-go motion. These results point to a role for VASP in the modulation of filament anchoring, with implications for actin dynamics at cell adhesions and at the leading edge of the cell.