A pendant proton shuttle on [Fe4N(CO)12]- alters product selectivity in formate vs. H2 production via the hydride [H-Fe4N(CO)12].

Proton relays are known to increase reaction rates for H2 evolution and lower overpotentials in electrocatalytic reactions. In this report we describe two electrocatalysts, [Fe4N(CO)11(PPh3)]- (1-) which has no proton relay, and hydroxyl-containing [Fe4N(CO)11(Ph2P(CH2)2OH)]- (2-). Solid state structures indicate that these phosphine-substituted clusters are direct analogs of [Fe4N(CO)12]- where one CO ligand has been replaced by a phosphine. We show that the proton relay changes the selectivity of reactions: CO2 is reduced selectively to formate by 1- in the absence of a relay, and protons are reduced to H2 under a CO2 atmosphere by 2-. These results implicate a hydride intermediate in the mechanism of the reactions and demonstrate the importance of controlling proton delivery to control product selectivity. Thermochemical measurements performed using infrared spectroelectrochemistry provided pKa and hydricity values for [HFe4N(CO)11(PPh3)]-, which are 23.7, and 45.5 kcal mol-1, respectively. The pKa of the hydroxyl group in 2- was determined to fall between 29 and 41, and this suggests that the proximity of the proton relay to the active catalytic site plays a significant role in the product selectivity observed, since the acidity alone does not account for the observed results. More generally, this work emphasizes the importance of substrate delivery kinetics in determining the selectivity of CO2 reduction reactions that proceed through metal-hydride intermediates

Transcriptomic and Exometabolomic Profiling Reveals Antagonistic and Defensive Modes of Clonostachys rosea Action Against Fusarium graminearum

The mycoparasite Clonostachys rosea ACM941 is under development as a biocontrol organism against Fusarium graminearum, the causative agent of Fusarium head blight in cereals. To identify molecular factors associated with this interaction, the transcriptomic and exometabolomic profiles of C. rosea and F. graminearum GZ3639 were compared during coculture. Prior to physical contact, the antagonistic activity of C. rosea correlated with a response heavily dominated by upregulation of polyketide synthase gene clusters, consistent with the detected accumulation of corresponding secondary metabolite products. Similarly, prior to contact, trichothecene gene clusters were upregulated in F. graminearum, while those responsible for fusarielin and fusarin biosynthesis were downregulated, correlating with an accumulation of trichothecene products in the interaction zone over time. A concomitant increase in 15-acetyl deoxynivalenol-3-glucoside in the interaction zone was also detected, with C. rosea established as the source of this detoxified mycotoxin. After hyphal contact, C. rosea was found to predominantly transcribe genes encoding cell wall–degradation enzymes, major facilitator superfamily sugar transporters, anion:cation symporters, as well as alternative carbon source utilization pathways, together indicative of a transition to necrotropism at this stage. F. graminearum notably activated the transcription of phosphate starvation pathway signature genes at this time. Overall, a number of signature molecular mechanisms likely contributing to antagonistic activity by C. rosea against F. graminearum, as well as its mycotoxin tolerance, are identified in this report, yielding several new testable hypotheses toward understanding the basis of C. rosea as a biocontrol agent for continued agronomic development and application

Overwintering Locations, Migrations, and Fidelity of Radio-Tagged Dolly Varden in the Hulahula River, Arctic National Wildlife Refuge, 2007–09

Essential overwintering habitats for anadromous Dolly Varden Salvelinus malma on Alaska’s North Slope appear to be limited to a small number of perennial springs, primarily in eastern Brooks Range drainages. Because future petrochemical development in the region continues to be a possibility, and development would require large quantities of freshwater, we sought to identify and document the overwintering areas used by Dolly Varden in the Hulahula River, eastern Brooks Range. In August 2007, we implanted 52 Dolly Varden with multi-year radio transmitters at a known overwintering area in the lower Hulahula River. Other wintering areas were located during 11 aerial surveys conducted over the next 2.5 years. A stationary receiver located in the lower Hulahula River provided migration timing information. Radio-tagged Dolly Varden used four discrete areas with perennial springs for overwintering in the Hulahula River drainage. The springs, totaling approximately 12 km in stream length, were located between river km 40 and 105. Radio-tagged Dolly Varden migrated downstream on their way to the Beaufort Sea in early June. Most tagged fish known to have survived the summer at sea returned to the Hulahula River during late July and August, but seven fish overwintered in other North Slope drainages. Within the Hulahula River drainage, 15 fish overwintered in more than one area during the three winters of the project, but only the four identified perennial spring areas were used. These data clearly indicate that the perennial springs in the Hulahula River are essential overwintering habitats for Dolly Varden.Les aires de concentration hivernales essentielles du Dolly Varden Salvelinus malma anadrome sur la North Slope de l’Alaska semblent limitées à un petit nombre de sources pérennes, principalement dans les bassins hydrographiques de l’est de la chaîne de Brooks. Puisqu’il est toujours possible qu’il y ait des aménagements pétrochimiques dans la région et que ceux-ci demanderaient de grandes quantités d’eau douce, nous avons tâché de déterminer les aires de concentration hivernales du Dolly Varden dans la rivière Hulahula faisant partie de l’est de la chaîne de Brooks, et nous les avons répertoriées. En août 2007, nous avons installé des émetteurs radio pluriannuels sur 52 poissons Dolly Varden dans une aire de concentration hivernale connue faisant partie de la rivière Hulahula inférieure. D’autres aires de concentration hivernales ont été repérées grâce à 11 levés aériens effectués au cours des 2,5 années qui ont suivi. Un récepteur fixe situé dans la rivière Hulahula inférieure nous a permis de relever des données sur le moment de la migration. Les Dolly Varden dotés d’émetteurs radio ont utilisé quatre sources discrètes où se trouvent des sources pérennes pour passer l’hiver, dans le bassin versant de la rivière Hulahula. Les sources, qui s’étendent sur une douzaine de kilomètres de longueur, étaient situées entre les kilomètres 40 et 105 de la rivière. Les Dolly Varden munis d’émetteurs radio ont migré en aval, en route vers la mer de Beaufort au début juin. La plupart des poissons avec émetteur ont survécu l’été à la mer et ont regagné la rivière Hulahula vers la fin de juillet et en août, mais sept poissons ont passé l’hiver dans d’autres bassins versants de la North Slope. Dans le bassin versant de la rivière Hulahula, 15 poissons ont passé l’hiver dans plus d’une aire au cours des trois hivers visés par le projet, mais seules les quatre sources pérennes déterminées ont été utilisées. Ces données indiquent clairement que les sources pérennes de la rivière Hulahula sont des aires de concentration hivernales essentielles pour le Dolly Varden

Soliton Staircases and Standing Strain Waves in Confined Colloidal Crystals

We show by computer simulation of a two-dimensional crystal confined by corrugated walls that confinement can be used to impose a controllable mesoscopic superstructure of predominantly mechanical elastic character. Due to an interplay of the particle density of the system and the width D of the confining channel, "soliton staircases" can be created along both parallel confining boundaries, that give rise to standing strain waves in the entire crystal. The periodicity of these waves is of the same order as D. This mechanism should be useful for structure formation in the self-assembly of various nanoscopic materials.Comment: 22 pages, 5 figure

Identification of protein complexes with quantitative proteomics in S. cerevisiae

Lipids are the building blocks of cellular membranes that function as barriers and in compartmentalization of cellular processes, and recently, as important intracellular signalling molecules. However, unlike proteins, lipids are small hydrophobic molecules that traffic primarily by poorly described nonvesicular routes, which are hypothesized to occur at membrane contact sites (MCSs). MCSs are regions where the endoplasmic reticulum (ER) makes direct physical contact with a partnering organelle, e.g., plasma membrane (PM). The ER portion of ER-PM MCSs is enriched in lipid-synthesizing enzymes, suggesting that lipid synthesis is directed to these sites and implying that MCSs are important for lipid traffic. Yeast is an ideal model to study ER-PM MCSs because of their abundance, with over 1000 contacts per cell, and their conserved nature in all eukaryotes. Uncovering the proteins that constitute MCSs is critical to understanding how lipids traffic is accomplished in cells, and how they act as signaling molecules. We have found that an ER called Scs2p localize to ER-PM MCSs and is important for their formation. We are focused on uncovering the molecular partners of Scs2p. Identification of protein complexes traditionally relies on first resolving purified protein samples by gel electrophoresis, followed by in-gel digestion of protein bands and analysis of peptides by mass spectrometry. This often limits the study to a small subset of proteins. Also, protein complexes are exposed to denaturing or non-physiological conditions during the procedure. To circumvent these problems, we have implemented a large-scale quantitative proteomics technique to extract unbiased and quantified data. We use stable isotope labeling with amino acids in cell culture (SILAC) to incorporate staple isotope nuclei in proteins in an untagged control strain. Equal volumes of tagged culture and untagged, SILAC-labeled culture are mixed together and lysed by grinding in liquid nitrogen. We then carry out an affinity purification procedure to pull down protein complexes. Finally, we precipitate the protein sample, which is ready for analysis by high-performance liquid chromatography/ tandem mass spectrometry. Most importantly, proteins in the control strain are labeled by the heavy isotope and will produce a mass/ charge shift that can be quantified against the unlabeled proteins in the bait strain. Therefore, contaminants, or unspecific binding can be easily eliminated. By using this approach, we have identified several novel proteins that localize to ER-PM MCSs. Here we present a detailed description of our approach

"Getting Better All the Time?": Leadership Selection and the Manitoba NDP

In failing to achieve many of the benefits associated with delegate conventions, and realizing most of their shortcomings, the Manitoba New Democratic Party appears poised to adopt a new method of leadership selection. Based on the party’s base of support, history, and experiences during the most recent leadership race in 2009, the following analysis suggests NDP members may look most favourably upon a “hybrid” approach to selecting their next leader. This would allow the party to maintain many of the advantages of the convention model, while incorporating the strengths of a one-member, one-vote system