Economic evaluation of water supply systems operated with solar-driven electro-chlorination in rural regions in Nepal, Egypt and Tanzania

Reliable data on the economic feasibility of small-scale rural water supply systems are insufficient, which hampers the allocation of funds to construct them, even as the need for their construction increases. To address this gap, three newly constructed water supply systems with water points in Nepal, Egypt, and Tanzania were accompanied by the authors throughout the planning and implementation phases and up to several years of operation. This study presents an analysis of their economic feasibility and suggests important factors for successful water supply system implementation at other rural locations. The initial investment for construction of the new water supply systems ranged from 23,600 € to 44,000 €, and operation and maintenance costs ranged from 547 € to 1921 € per year. The water price and actual multi-year average quantity of tapped water at each site were 7.7 €/m³ & 0.67 m³/d in Nepal, 0.7 €/m³ & 0.88 m³/d in Egypt and 0.9 €/m³ & 8.65 m³/d in Tanzania. Although the new water supply systems enjoyed acceptance among the consumers, the actual average water quantity tapped ranged from just 17 to 30 % of the demand for which the new supply systems were designed. While two of three sites successfully yielded a cash surplus through the sale of water, sufficient for operation, maintenance and basic repairs, no site showed a realistic chance of recovering the initial investment (reaching the break-even point) within the projected lifetime of the technical infrastructure. Reaching the break-even point within 5 years, which would be necessary to attract private investors, would require an unrealistic increase of the water price or the water consumption by factors ranging from 5.2 to 9.0. The economic viability of such systems therefore depends strongly on the quantity of water consumed and the water price, as well as the availability of funding from governments, NGOs or other sponsors not primarily interested in a financial return on their investment.

In Pursuit of Sustainability? Challenges for Deliberative Democracy in a Tasmanian Local Government

Sustainability may be viewed as a principled form of conduct. Among its effects is a growing emphasis on civil society and local governance through which the members of communities are encouraged to rethink democratic ideas and practices, and reconfigure how to live. Although normative, sustainability cannot properly be conceived as prescriptive; such a characteristic would undermine central elements of it, such as participation and equity. In this sense, requiring both mechanisms for community participation in decisionmaking and planning, and an ethic of engagement based on trust, reciprocity, and an acceptance of the rights of noncitizens and nonhuman nature, sustainability might also be construed as a deliberative form of democratic governance. Perhaps problematically, in the last decade this governmental aspect of sustainability has come to be associated with the procedures of communicative rationality. Supported by research conducted over three years in a local government in Tasmania, Australia, we argue that a deliberative and democratic praxis of sustainability may be effective only if and when underpinned by substantive changes to the exercise of power and leadership, and to the ways in which deliberative decisionmaking and planning are pursued. Communicative rationality alone is unlikely to achieve these ends.

The landscape of cytokinin binding by a plant nodulin

Nodulation is an extraordinary symbiotic interaction between leguminous plants and nitrogen-fixing bacteria (rhizobia) that assimilate atmospheric nitrogen (in root nodules) and convert it into compounds suitable for the plant host. A class of plant hormones called cytokinins are involved in the nodulation process. In the model legume Medicago truncatula, nodulin 13 (MtN13), which belongs to the pathogenesis-related proteins of class 10 (PR-10), is expressed in the outer cortex of the nodules. In general, PR-10 proteins are small and monomeric and have a characteristic fold with an internal hydrophobic cavity formed between a seven-stranded antiparallel β-sheet and a C-terminal α-helix. Previously, some PR-10 proteins not related to nodulation were found to bind cytokinins such as trans-zeatin. Here, four crystal structures of the MtN13 protein are reported in complexes with several cytokinins, namely trans-zeatin, N6-isopentenyladenine, kinetin and N6-benzyladenine. All four phytohormones are bound in the hydrophobic cavity in the same manner and have excellent definition in the electron-density maps. The binding of the cytokinins appears to be strong and specific and is reinforced by several hydrogen bonds. Although the binding stoichiometry is 1:1, the complex is actually dimeric, with a cytokinin molecule bound in each subunit. The ligand-binding site in each cavity is formed with the participation of a loop element from the other subunit, which plugs the only entrance to the cavity. Interestingly, a homodimer of MtN13 is also formed in solution, as confirmed by small-angle X-ray scattering (SAXS).

Ultrahigh-resolution structure of a BPTI mutant

The crystal structure of a mutant of bovine pancreatic trypsin inhibitor has been refined to 0.86 A resolution using low-temperature synchrotron data. The variant contains three mutations in the binding loop (Thr11Ala, Pro13Ala, Lys15Arg) and an unrelated Met52Leu substitution. Refinement with anisotropic displacement parameters and with removal of main-chain stereochemical restraints converged with R = 0.1035. The use of full-matrix refinement provided an estimate of the variances in the derived parameters. Some stereochemical parameters, such as the planarity of the peptide group and the value of the N-C(alpha)-C angle, show a wide spread, suggesting that the standard values used as restraints in protein structure refinements may not always be entirely appropriate. Comparison with the recently determined room-temperature structure of the same mutant at 1.42 A resolution confirms the previous observations and provides new details, such as a double conformation of the main chain at Leu29 and at Gly56-Gly57, a high proportion (over 20%) of residues in double conformations, correlation of disorder through lattice contacts and the positions of H atoms, including those in water molecules, and their involvement in C-H...O and N-H...pi hydrogen bonds.

Human cystatin C, an amyloidogenic protein, dimerizes through three-dimensional domain swapping

The crystal structure of human cystatin C, a protein with amyloidogenic properties and a potent inhibitor of cysteine proteases, reveals how the protein refolds to produce very tight two-fold symmetric dimers while retaining the secondary structure of the monomeric form. The dimerization occurs through three-dimensional domain swapping, a mechanism for forming oligomeric proteins. The reconstituted monomer-like domains are similar to chicken cystatin except for one inhibitory loop that unfolds to form the 'open interface' of the dimer. The structure explains the tendency of human cystatin C to dimerize and suggests a mechanism for its aggregation in the brain arteries of elderly people with amyloid angiopathy. A more severe 'conformational disease' is associated with the L68Q mutant of human cystatin C, which causes massive amyloidosis, cerebral hemorrhage and death in young adults. The structure of the three-dimensional domain-swapped dimers shows how the L68Q mutation destabilizes the monomers and makes the partially unfolded intermediate less unstable. Higher aggregates may arise through the three-dimensional domain-swapping mechanism occurring in an open-ended fashion in which partially unfolded molecules are linked into infinite chains.

Expression of a selenomethionyl derivative and preliminary crystallographic studies of human cystatin C

Human cystatin C, a protein with amyloidogenic properties and a potent inhibitor of papain-like mammalian proteases, has been produced in its full-length form by recombinant techniques and crystallized in two polymorphic forms: cubic and tetragonal. A selenomethionyl derivative of the protein, obtained by Escherichia coli expression and with complete Met-->Se-Met substitution confirmed by mass spectrometry, amino-acid analysis and X-ray absorption spectra, was crystallized in the cubic form. A truncated variant of the protein, lacking ten N-terminal residues, has also been crystallized. The crystals of this variant are tetragonal and, like the two polymorphs of the full-length protein, contain multiple copies of the molecule in the asymmetric unit, suggesting oligomerization of the protein.

Stabilizing bound O2 in myoglobin by valine68 (E11) to asparagine substitution

The isopropyl side chain of valine68 in myoglobin has been replaced by the acetamide side chain of asparagine in an attempt to engineer higher oxygen affinity. The asparagine replacement introduces a second hydrogen bond donor group into the distal heme pocket which could further stabilize bound oxygen. The Val68 to Asn substitution leads to approximately 3-fold increases in oxygen affinity and 4-6-fold decreases in CO affinity. As a result, the M-value (KCO/KO2) is lowered 15-20-fold to a value close to unity. An even larger enhancement of O2 affinity is seen when asparagine68 is inserted into H64L sperm whale myoglobin which lacks a distal histidine. The overall rate constants for oxygen and carbon monoxide binding to the single V68N myoglobin mutants are uniformly lower than those for the wild-type protein. In contrast, the overall rate constant for NO association is unchanged. Analyses of time courses monitoring the geminate recombination of ligands following nanosecond and picosecond flash photolysis of MbNO and MbO2 indicate that the barrier to ligand binding from within the heme pocket has been raised with little effect on the barrier to diffusion of the ligand into the pocket from the solvent. The crystal structures of the aquomet, deoxy, oxy, and carbon monoxy forms of the V68N mutant have been determined to resolutions ranging from 1.75 to 2.2 A at 150 K. The overall structures are very similar to those of the wild-type protein with the principal alterations taking place within and around the distal heme pocket. In all four structures the asparagine68 side chain lies almost parallel to the plane of the heme with its amide group directed toward the back of the distal heme pocket. The coordinated water molecule in the aquomet form and the bound oxygen in the oxy form can form hydrogen-bonding interactions with both the Asn68 amide group and the imidazole side chain of His64. Surprisingly, in the carbon monoxy form of the V68N mutant, the histidine64 side chain has swung completely out the distal pocket, its place being taken by two ordered water molecules. Overall, these functional and structural results show that the asparagine68 side chain (i) forms a strong hydrogen bond with bound oxygen through its -NH2 group but (ii) sterically hinders the approach of ligands to the iron from within the distal heme pocket.