Biological effects on serpentinite weathering

Serpentinites, perhaps more than any other rock type, control the composition and evolution of the development of the surrounding ecosystems. The bulk chemistry of serpentinite rocks, high in Mg and trace elements, and low in nutrients such as Ca, K, P, and N, causes an extreme and stressful environment for ecosystems. However, the role that those serpentine ecosystems play in development of serpentine soils has not been examined. Due to the unusual chemistry of serpentine soils, serpentine ecosystems have deeper and better-developed root systems than other ecosystems. The rhizosphere of serpentine systems, documented to produce abundant organic acids and siderophores, is also likely to impact serpentine soils. In order to test the effects of biological impacts on serpentine soil formation, soil pore waters were analyzed for organic acids. Furthermore, Fe-oxidizing bacteria have been detected using Biological Activity Reaction Tests (BARTs) and such bacteria were investigated by enrichment cultures. In addition to directly measuring the biological factors including organic acids, siderophores, and Fe-oxidizing bacteria, the impact of such weathering on soils and rock was examined using XRF, XRD, and SEM

Low self-control promotes the willingness to sacrifice in close relationships

Although previous theories and research have suggested that human behavior is automatically driven by selfish impulses (e.g., vengeance rather than forgiveness), the present research tested the hypothesis that in close relationships, people's impulsive inclination is to be prosocial and to sacrifice for their partner-to pursue the interests of the partner or of the relationship at some costs for the self. Results from four studies demonstrated that people with low self-control, relative to those with high self-control, reported greater willingness to sacrifice for their close others. Furthermore, Study 4 demonstrated that communal orientation was more strongly associated with sacrifice among participants with low self-control than participants with high self-control. This moderational pattern supports the hypothesis that communal orientation functions as a default approach to sacrifice in the context of close relationships. Taken together, these findings suggest that under certain crucial conditions in close relationships, gut-level impulses are more likely than deliberative considerations to promote prorelationship behavior. © The Author(s) 2013

Assembly, trafficking and function of gamma-secretase

gamma-Secretase catalyzes the final cleavage of the beta-amyloid precursor protein to generate amyloid-beta peptide, the principal component of amyloid plaques in the brains of patients suffering from Alzheimer's disease. Here, we review the identification of gamma-secretase as a protease complex and its assembly and trafficking to its site(s) of cellular function. In reconstitution experiments, gamma-secretase was found to be composed of four integral membrane proteins, presenilin (PS), nicastrin (NCT), PEN-2 and APH-1 that are essential and sufficient for gamma-secretase activity. PS, which serves as a catalytic subunit of gamma-secretase, was identified as a prototypic member of novel aspartyl proteases of the GxGD type. In human cells, gamma-secretase could be further defined as a heterogeneous activity consisting of distinct complexes that are composed of PS1 or PS2 and APH-1a or APH-1b homologues together with NCT and PEN-2. Using green fluorescent protein as a reporter we localized PS and gamma-secretase activity at the plasma membrane and endosomes. Investigation of gamma-secretase complex assembly in knockdown and knockout cells of the individual subunits allowed us to develop a model of complex assembly in which NCT and APH-1 first stabilize PS before PEN-2 assembles as the last component. Furthermore, we could map domains in PS and PEN-2 that govern assembly and trafficking of the complex. Finally, Rer1 was identified as a PEN-2-binding protein that serves a role as an auxiliary factor for gamma-secretase complex assembly. Copyright (c) 2006 S. Karger AG, Basel