Electricity-powered artificial root nodule.

Root nodules are agricultural-important symbiotic plant-microbe composites in which microorganisms receive energy from plants and reduce dinitrogen (N2) into fertilizers. Mimicking root nodules using artificial devices can enable renewable energy-driven fertilizer production. This task is challenging due to the necessity of a microscopic dioxygen (O2) concentration gradient, which reconciles anaerobic N2 fixation with O2-rich atmosphere. Here we report our designed electricity-powered biological|inorganic hybrid system that possesses the function of root nodules. We construct silicon-based microwire array electrodes and replicate the O2 gradient of root nodules in the array. The wire array compatibly accommodates N2-fixing symbiotic bacteria, which receive energy and reducing equivalents from inorganic catalysts on microwires, and fix N2 in the air into biomass and free ammonia. A N2 reduction rate up to 6.5 mg N2 per gram dry biomass per hour is observed in the device, about two orders of magnitude higher than the natural counterparts

THE EFFECTS OF RARE EARTHS ON ACTIVITY AND SURFACE PROPERTIES OF Ru/γ-AL2O3 CATALYST FOR WATER GAS SHIFT REACTION

A series of Ru-RE/γ-AL2O3 (RE = Ce, Pr, La, Sm, Tb or Gd) and Ru/γ-AL2O3 catalysts were prepared by impregnation method. The influence of rare earths on the catalytic performance of Ru/γ-AL2O3 catalyst for the water gas shift reaction was studied. The catalysts were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption (TPD), and CO chemisorption. The results show that the addition of rare earths increases the catalytic activity of Ru based catalyst. Among these cerium is the most remarkably. The addition of cerium increases the active surface area, improves the dispersion of ruthenium, and weakens the interaction between ruthenium and the support. Cerium also affects the adsorption and reduction properties of Ru/γ-AL2O3 catalyst. KEY WORDS: Rare earths, Ruthenium-based catalyst, Water gas shift reaction Bull. Chem. Soc. Ethiop. 2007, 21(3), 389-395

Calcium -dependent protein kinases are myristoylated and associated with different membranes in Arabidopsis thaliana

In plants, calcium-dependent protein kinases (CDPKs) are the predominant calcium-stimulated kinases and are known to be involved in many cellular processes. CDPK enzymatic activity previously has been detected in many locations in plant cells, including the membrane fraction. However, little is known about the subcellular locations of individual CDPKs or the mechanisms involved in targeting them to those locations. Arabidopsis contains 34 genes that are predicted to encode CDPKs and 28 of the predicted CDPK proteins have potential myristoylation motifs at their amino termini. Myristate is a 14-carbon saturated fatty acid that is attached co-translationally to the amino-terminal glycine of a nascent protein. Myristoylation can facilitate membrane binding and/or protein-protein interactions. In these studies, Arabidopsis CDPK isoforms AtCPK1, AtCPK2, AtCPK5 and AtCPK6 have been investigated and the subcellular membrane location of each isoform, as well as the role that myristoylation plays in membrane association, have been addressed. An in vitro coupled transcription/translation system was used to demonstrate that AtCPK1, AtCPK2, AtCPK5 and AtCPK6 can be myristoylated and a mutation of the myristoylation site from glycine to alanine (G2A) in AtCPK2 and AtCPK5 prevented myristoylation in vitro. Subcellular localization studies were conducted using both aqueous two-phase partitioning and sucrose density gradient fractionation of plant microsomes. AtCPK1 and AtCPK2 are associated with the endoplasmic reticulum and AtCPK5 and AtCPK6 are associated with the plasma membrane. Disruption of the myristoylation site (G2A mutation) decreased CDPK membrane binding. Using a translational fusion with the beta-glucuronidase (GUS) reporter gene, I have demonstrated that the amino terminal region of AtCPK2 and AtCPK5 contains sufficient information for correct membrane localization. My results indicate that myristoylation is important in membrane association of CDPKs, that different CDPK isoforms are targeted to different subcellular membrane locations and that the amino terminal region of CDPKs contains specific subcellular targeting information