A second magnesium ion is critical for ATP binding in the kinase domain of the oncoprotein v-Fps

The activity of the kinase domain of the oncoprotein v-Fps was found to be sensitive to the concentration of magnesium ions. Plots of initial velocity versus free magnesium concentration are hyperbolic and do not extrapolate to the origin at stoichiometric ATP-Mg, indicating that there are two sites for metal chelation on the enzyme and the second is nonessential for catalysis. The second metal is strongly activating and increases the reaction rate constant almost 20-fold from 0.5 to 8.3 s-1 using 0.2 mM ATP-Mg and 1 mM peptide, EAEIYEAIE. This increase in rate is due to a large increase in the apparent affinity of ATP-Mg at high magnesium concentrations. At 0.5 and 10 mM free Mg2+, KATP-Mg is 3.6 and 0.22 mM, respectively. Extrapolation of the observed affinity of ATP-Mg to zero and infinite free metal indicates that KATP-Mg is greater than 8 mM in the absence of the second metal and 0.1 mM in the presence of the second metal, a minimum 80-fold enhancement. By comparison, free levels of the divalent ion do not influence maximum turnover (kcat) and have only a 2-fold effect on the Km for the peptide substrate between 0.5 and 20 mM free Mg2+. Viscosometric studies indicate that free Mg2+ does not influence the rates of phosphoryl transfer or net product release above 0.5 mM but does affect directly the dissociation constant for ATP-Mg. The Kd for ATP-Mg in the absence and presence of the second metal ion is >32 and 0.4 mM, respectively. At high magnesium concentrations, ATP-Mg and the peptide substrate bind independently, while at lower concentrations (0.5 mM), there is significant negative binding synergism suggesting that the second metal may help to reduce charge repulsion between ATP-Mg and the peptide. The data indicate that the first metal is sufficient for phosphoryl transfer. While the second metal could have some influence on phosphoryl transfer or product binding, it is a potent activator that functions minimally by controlling ATP-Mg binding.     

Quantitative methods for correlating dispersion and electrical conductivity in conductor–polymer nanostrand composites

The development of electrically conductive polymer composite systems continues to be an area of wide interest. In this work, a method is presented for quantifying the macro-scale dispersion characteristics of electrically conductive nickel nanostrands in polymer systems. A single polymer system is considered at multiple volume fractions of nanostrands, with variations in dispersion processing practices. Image analysis methods based on statistical homology parameters are developed to characterize samples of the dispersed nanostructure, including nearest neighbor distance, mean cluster size, area/perimeter ratios, and topological Betti number metrics. It is found that the Betti numbers are particularly well suited for monitoring nanostrands dispersed in polymer systems. Correlation of the dispersed structure to the electrical conductivity properties of the nanocomposite system is demonstrated. The method is well suited as a batch sampling technique for monitoring nanostructures during dispersion processes, and is also analogous for any dispersed system that involves highly structured materials.     

The Concept of Planned Development: A Presentation and Commentaries on the Contribution of Nathaniel Lichfield

This article and the commentaries which accompany it centres on a reflection by consultant-academic Nathaniel Lichfield on his work on planned development and the evaluation of the impacts of such development, over a career spanning the past 60 years. His work, in the UK and across the world, had a formative influence on generations of planners brought up on his texts. In this presentation, David Adams sets the context of his contribution. The heart of the article is a reflective synthesis by Lichfield on his own work from his first major contribution in 1956, to its evolution in the 1960s into the technique of the Planning Balance Sheet, and later, Community Impact Evaluation. His starting point is that there can be urban and regional planning which does not lead to physical development on the ground and there can be such development on the ground that has not been influenced by government led urban and regional planning. Neither of these is planned development. This takes place when the two are fused together in practice: the development and the government led planning. It is this simple concept, with particular emphasis on its economics, which was treated at length in the Economics of Planned Development (1956). In order to fully describe the concept, the book's contents are summarized in the first half of this article following an introduction of the background. Following the publication of the book, Lichfield's professional and academic work took him in many directions, much of which fell loosely under the ambit of the economics of planned development. His contributions were not written up as sequels to the book but rather in related books, papers and articles under an array of topics. He terms these 'the children of EPD'. They are described in the second half of the article, grouped in relation, as appropriate, to each of the main themes of the 1956 book and extensions of it. Lichfield's article is followed by three commentaries. The first, by Mike Teitz, positions his work and its later development in the changing context of the times. The second, by Barrie Needham, provides some critical thoughts on how well the concept of 'planned development' travels transnationally into different institutional contexts. The third, from consultant-planner Alan Wenban-Smith, himself working on policy evaluation in the UK, explores the practical and methodological robustness of Lichfield's concepts. Overall, the piece provides an input to reflections on the relation between state and market in the development process and on the evaluative stance the state should take to its interventions.     

Nitrogen gas supersaturation in the recent sediments of lake erie and two polluted harbors

Nitrogen gas distributions in sediment pore water were determined for cores collected in Lake Erie and two nearby harbors. Concentrations of N₂ gas ranged from 11.9 to 37.0 ml l⁻¹ and from 8.9 to 58.3 ml l⁻¹ for open lake and polluted harbor sediments, respectively. Maximum concentrations in the harbor sediments were as high as 3.5 times N₂ saturation calculated for the overlying water. Indirect diffusive flux estimates for nitrogen gas ranged from 20 to 32% of the particulate nitrogen sedimentation rate in Lake Erie. At one location, the amount of nitrogen gas lost by diffusion was calculated to be greater than the nitrogen deposited to the sediments. Nitrogen gas production and diffusive loss from surficial sediments probably represents a major pathway for nitrogen removal from Lake Erie.