Post-combustion CO 2 capture and air separation are integral parts of the energy industry, although the available technologies remain inefficient, resulting in costly energy penalties. Here we report azo-bridged, nitrogen-rich, aromatic, water stable, nanoporous covalent organic polymers, which can be synthesized by catalyst-free direct coupling of aromatic nitro and amine moieties under basic conditions. Unlike other porous materials, azo-covalent organic polymers exhibit an unprecedented increase in CO 2 /N 2 selectivity with increasing temperature, reaching the highest value (288 at 323 K) reported to date. Here we observe that azo groups reject N 2 , thus making the framework N 2 -phobic. Monte Carlo simulations suggest that the origin of the N 2 phobicity of the azo-group is the entropic loss of N 2 gas molecules upon binding, although the adsorption is enthalpically favourable. Any gas separations that require the efficient exclusion of N 2 gas would do well to employ azo units in the sorbent chemistry.

PEPC [PEP (phosphoenolpyruvate) carboxylase] is a tightly controlled enzyme located at the core of plant C-metabolism that catalyses the irreversible β-carboxylation of PEP to form oxaloacetate and Pi. The critical role of PEPC in assimilating atmospheric CO(2) during C(4) and Crassulacean acid metabolism photosynthesis has been studied extensively. PEPC also fulfils a broad spectrum of non-photosynthetic functions, particularly the anaplerotic replenishment of tricarboxylic acid cycle intermediates consumed during biosynthesis and nitrogen assimilation. An impressive array of strategies has evolved to co-ordinate in vivo PEPC activity with cellular demands for C(4)-C(6) carboxylic acids. To achieve its diverse roles and complex regulation, PEPC belongs to a small multigene family encoding several closely related PTPCs (plant-type PEPCs), along with a distantly related BTPC (bacterial-type PEPC). PTPC genes encode ~110-kDa polypeptides containing conserved serine-phosphorylation and lysine-mono-ubiquitination sites, and typically exist as homotetrameric Class-1 PEPCs. In contrast, BTPC genes encode larger ~117-kDa polypeptides owing to a unique intrinsically disordered domain that mediates BTPC's tight interaction with co-expressed PTPC subunits. This association results in the formation of unusual ~900-kDa Class-2 PEPC hetero-octameric complexes that are desensitized to allosteric effectors. BTPC is a catalytic and regulatory subunit of Class-2 PEPC that is subject to multi-site regulatory phosphorylation in vivo. The interaction between divergent PEPC polypeptides within Class-2 PEPCs adds another layer of complexity to the evolution, physiological functions and metabolic control of this essential CO(2)-fixing plant enzyme. The present review summarizes exciting developments concerning the functions, post-translational controls and subcellular location of plant PTPC and BTPC isoenzymes.

Efficient CO 2 scrubbing without a significant energy penalty remains an outstanding challenge for the fossil fuel-burning industry where aqueous amine solutions are still widely used. Porous materials have long been evaluated for next generation CO 2 adsorbents. Porous polymers, robust and inexpensive, show promise as feasible materials for the capture of CO 2 from warm exhaust fumes. We report the syntheses of porous covalent organic polymers (COPs) with CO 2 adsorption capacities of up to 5616 mg g À1 (measured at high pressures, i.e. 200 bar) and industrially relevant temperatures (as warm as 65 C). COPs are stable in boiling water for at least one week and near infinite CO 2 /H 2 selectivity is observed.

Induction of intracellular and secreted acid phosphatases (APases) is a widespread response of orthophosphate (Pi)-starved (2Pi) plants. APases catalyze Pi hydrolysis from a broad range of phosphomonoesters at an acidic pH. The largest class of nonspecific plant APases is comprised of the purple APases (PAPs). Although the biochemical properties, subcellular location, and expression of several plant PAPs have been described, their physiological functions have not been fully resolved. Recent biochemical studies indicated that AtPAP26, one of 29 PAPs encoded by the Arabidopsis (Arabidopsis thaliana) genome, is the predominant intracellular APase, as well as a major secreted APase isozyme up-regulated by 2Pi Arabidopsis. An atpap26 T-DNA insertion mutant lacking AtPAP26 transcripts and 55-kD immunoreactive AtPAP26 polypeptides exhibited: (1) 9-and 5-fold lower shoot and root APase activity, respectively, which did not change in response to Pi starvation, (2) a 40% decrease in secreted APase activity during Pi deprivation, (3) 35% and 50% reductions in free and total Pi concentration, respectively, as well as 5-fold higher anthocyanin levels in shoots of soil-grown 2Pi plants, and (4) impaired shoot and root development when subjected to Pi deficiency. By contrast, no deleterious influence of AtPAP26 loss of function occurred under Pi-replete conditions, or during nitrogen or potassium-limited growth, or oxidative stress. Transient expression of AtPAP26-mCherry in Arabidopsis suspension cells verified that AtPAP26 is targeted to the cell vacuole. Our results confirm that AtPAP26 is a principal contributor to Pi stress-inducible APase activity, and that it plays an important role in the Pi metabolism of 2Pi Arabidopsis.Orthophosphate (Pi) is an essential plant macronutrient required for many pivotal metabolic processes such as photosynthesis and respiration. However, the massive use of Pi fertilizers in agriculture demonstrates how the free Pi level of many soils is suboptimal for plant growth. The world's reserves of rock phosphate, our major source of Pi fertilizers, are projected to be depleted by the end of this century (Vance et al., 2003). Furthermore, Pi runoff from fertilized fields into nearby surface waters results in environmentally destructive processes such as aquatic eutrophication and blooms of toxic cyanobacteria. Effective biotechnological strategies are needed to engineer Pi-efficient transgenic crops to ensure agricultural sustainability and a reduction in Pi fertilizer overuse. This necessitates a detailed understanding of Pi-starvation-inducible (PSI) gene expression and the complex morphological, physiological, and biochemical adaptations of Pi-deficient (2Pi) plants.A well-documented component of the plant Pi stress response is the up-regulation of intracellular and secreted acid phosphatases (APases; E.C. 3.1.3.2) that catalyze the hydrolysis of Pi from various phosphate monoesters and anhydrides in the acidic pH range (Tran et al., 2010a). APase induction by 2Pi plants has been correlated wit...