Structure of purine nucleoside phosphorylase (DeoD) from Bacillus anthracis

Protein structures from the causative agent of anthrax (Bacillus anthracis) are being determined as part of a structural genomics programme. Amongst initial candidates for crystallographic analysis are enzymes involved in nucleotide biosynthesis, since these are recognized as potential targets in antibacterial therapy. Purine nucleoside phosphorylase is a key enzyme in the purine-salvage pathway. The crystal structure of purine nucleoside phosphorylase (DeoD) from B. anthracis has been solved by molecular replacement at 2.24 Å resolution and refined to an R factor of 18.4%. This is the first report of a DeoD structure from a Gram-positive bacterium

Evidence of traffic-related pollutant control in soil-based Sustainable Urban Drainage Systems (SUDS)

SUDS are being increasingly employed to control highway runoff and have the potential to protect groundwater and surface water quality by minimising the risks of both point and diffuse sources of pollution. While these systems are effective at retaining polluted solids by filtration and sedimentation processes, less is known of the detail of pollutant behaviour within SUDS structures. This paper reports on investigations carried out as part of a co-ordinated programme of controlled studies and field measurements at soft-engineered SUDS undertaken in the UK, observing the accumulation and behaviour of traffic-related heavy metals, oil and PAHs. The field data presented were collected from two extended detention basins serving the M74 motorway in the south-west of Scotland. Additional data were supplied from an experimental lysimeter soil core leaching study. Results show that basin design influences pollutant accumulation and behaviour in the basins. Management and/or control strategies are discussed for reducing the impact of traffic-related pollutants on the aqueous environment

Medium-term performance and maintenance of SUDS:a case-study of Hopwood Park Motorway Service Area, UK

One of the main barriers to implementing SUDS is concern about performance and maintenance costs since there are few well-documented case-studies. This paper summarizes studies conducted between 2000 and 2008 of the performance and maintenance of four SUDS management trains constructed in 1999 at the Hopwood Park Motorway Service Area, central England. Assessments were made of the wildlife value and sedimentation in the SUDS ponds, the hydraulic performance of the coach park management train, water quality in all management trains, and soil/sediment composition in the grass filter strip, interceptor and ponds. Maintenance procedures and costs were also reviewed. Results demonstrate the benefits of a management train approach over individual SUDS units for flow attenuation, water treatment, spillage containment and maintenance. Peak flows, pond sediment depth and contaminant concentrations in sediment and water decreased through the coach park management train. Of the 2007 annual landscape budget of £15,000 for the whole site, the maintenance costs for SUDS only accounted for £2,500 compared to £4,000 for conventional drainage structures. Furthermore, since sediment has been attenuated in the management trains, the cost of sediment removal after the recommended period of three years was only £554 and, if the design is not compromised, less frequent removal will be required in future

The structure of Rph, an exoribonuclease from Bacillus anthracis, at 1.7 angstrom resolution

Maturation of tRNA precursors into functional tRNA molecules requires trimming of the primary transcript at both the 5' and 3' ends. Cleavage of nucleotides from the 3' stem of tRNA precursors, releasing nucleotide diphosphates, is accomplished in Bacillus by a phosphate-dependent exoribonuclease, Rph. The crystal structure of this enzyme from B. anthracis has been solved by molecular replacement to a resolution of 1.7 angstrom and refined to an R factor of 19.3%. There is one molecule in the asymmetric unit; the crystal packing reveals the assembly of the protein into a hexamer arranged as a trimer of dimers. The structure shows two sulfate ions bound in the active-site pocket, probably mimicking the phosphate substrate and the phosphate of the 3'-terminal nucleotide of the tRNA precursor. Three other bound sulfate ions point to likely RNA-binding sites

Role of the α-Amino Groups of the α and β Chains of Human Hemoglobin in Oxygen-linked Binding of Carbon Dioxide

Abstract Human hemoglobin has been reacted with potassium cyanate and purified to yield three species, α2cβ2c,α2cβ2, and α2β2c, where superscript c denotes specific reaction of cyanate with the α-amino group of the particular chain. The effect of carbon dioxide on the oxygen affinity of these species in the presence and in the absence of 2,3-diphosphoglycerate has been measured. Carbon dioxide has no effect on the oxygen affinity of α2cβ2c, confirming that the usual lowering of the oxygen affinity of carbon dioxide in normal hemoglobin is mediated by the α-amino groups of the α and β chains. The lowering of the oxygen affinity of α2β2c by carbon dioxide was not affected by the presence or absence of 2,3-diphosphoglycerate, showing that 2,3-diphosphoglycerate does not interfere with the oxygen-linked binding of carbon dioxide at the α chain α-amino group. In α2cβ2 there was a much larger effect of carbon dioxide on the oxygen affinity in the absence of 2,3-diphosphoglycerate than in α2β2c; however, on addition of 2,3-diphosphoglycerate the effect of carbon dioxide on the oxygen affinity of α2cβ2 was much smaller and similar to that occurring in α2β2c. This shows that there is a large difference in the carbon dioxide binding constants of the β chain α-amino group in the oxy and deoxy forms of human hemoglobin, and that 2,3-diphosphoglycerate suppresses this difference, probably by binding strongly to the β chain α-amino group of deoxyhemoglobin and displacing any bound carbon dioxide

Super-Earths: A New Class of Planetary Bodies

Super-Earths, a class of planetary bodies with masses ranging from a few Earth-masses to slightly smaller than Uranus, have recently found a special place in the exoplanetary science. Being slightly larger than a typical terrestrial planet, super-Earths may have physical and dynamical characteristics similar to those of Earth whereas unlike terrestrial planets, they are relatively easier to detect. Because of their sizes, super-Earths can maintain moderate atmospheres and possibly dynamic interiors with plate tectonics. They also seem to be more common around low-mass stars where the habitable zone is in closer distances. This article presents a review of the current state of research on super-Earths, and discusses the models of the formation, dynamical evolution, and possible habitability of these objects. Given the recent advances in detection techniques, the detectability of super-Earths is also discussed, and a review of the prospects of their detection in the habitable zones of low-mass stars is presented.Comment: A (non-technical) review of the literature on the current state ofresearch on super-Earths. The topics include observation, formation, dynamical evolution, habitability, composition, interior dynamics, magnetic field, atmosphere, and propsect of detection. The article has 44 pages, 27 figures, and 203 references. It has been accepted for publication in the journal Contemporary Physics (2011

Vibrational properties of hexagonal LiBC: Infrared and Raman spectroscopy

The paper presents infrared reflectivity and micro-Raman scattering spectra of LiBC powder pellets. The experiment allowed assignment of frequencies of all infrared and Raman active zone center modes. Results are compared with available ab-initio calculations; prediction of large Born effective charges on the nodes of B-C graphene sheets is confirmed.Comment: 4 pages, 5 figures (change: Fig 2 replaced

Mars climate engineering using orbiting solar reflectors

The manned mission is seen as a first step towards a Mars surface exploration base-station and, later, establishing permanent settlement. The location and use of Mars's natural resources is vital to enable cost-effective long-duration human exploration and exploitation missions as well as subsequent human colonization. Planet resources include various crust-lodged materials, a low-pressure natural atmosphere, assorted forms of utilizable energy, lower gravity than Earth's, and ground placement advantages relative to human operability and living standards. Power resources may include using solar and wind energy, importation of nuclear reactors and the harvesting of geothermal potential. In fact, a new branch of human civilization could be established permanently on Mars in the next century. But, meantime, an inventory and proper social assessment of Mars's prospective energy and material resources is required. This book investigates the possibilities and limitations of various systems supplying manned bases on Mars with energy and other vital resources. The book collects together recent proposals and innovative options and solutions. It is a useful source of condensed information for specialists involved in current and impending Mars-related activities and a good starting point for young researchers