A Study on Urban Water Reuse Management Modeling

Water reuse is being recognized as a sustainable urban water management strategy and is becoming increasingly attractive in urban water resources management. This paper focuses on urban water reuse planning and management in the context of sustainable development, and introduces a state of the art urban water reuse management model which utilizes a network flow optimization model and various stochastic programming methods. The objective of the model is to minimize the overall cost of the system subject to technological, societal and environmental constraints, therefore the optimum allocation of urban water resources can be obtained. Uncertainty issues associated with water demand and treatment quality are modeled by introducing stochastic programming methods, namely, twostage stochastic recourse programming and chance-constraint programming. An application is presented in order to demonstrate the modeling process and to analyze the impact of uncertainties. This research is important in aiding the achievement in sustainable urban water resource management practices

Electric-field-induced melting of the randomly pinned charge-ordered states of rare-earth manganates and associated effects

Films of charge-ordered Nd0.5Ca0.5MnO3, Gd0.5Ca0.5MnO3, Y0.5Ca0.5MnO3, and Nd0.5Sr0.5MnO3 show insulator-metal transitions on the passage of small electrical currents. That such an electric-field-induced transition occurs even in Y0.5Ca0.5MnO3 where the charge-ordered state is not affected by magnetic fields is noteworthy. The transition is attributed to the depinning of the randomly pinned charge solid. These materials also exhibit an interesting memory effect probably due to the randomness of the strength as well as the position of the pinning centers

E2 ubiquitin-conjugating enzymes, UBE2D1 and UBE2D2, regulate VEGFR2 dynamics and endothelial function

Vascular endothelial growth factor receptor 2 (VEGFR2) regulates endothelial function and angiogenesis. VEGFR2 undergoes ubiquitination which programs this receptor for trafficking and proteolysis but the ubiquitin-modifying enzymes involved are ill-defined. Herein, we used a reverse genetics screen of the human E2 family of ubiquitin-conjugating enzymes to identify gene products which regulate VEGFR2 ubiquitination and proteolysis. We find that depletion of either UBE2D1 or UBE2D2 in endothelial cells cause a rise in steady-state VEGFR2 levels. This rise in plasma membrane VEGFR2 levels impact on VEGF-A-stimulated signalling, with increased activation of canonical MAPK, phospholipase C1, and Akt pathways. Analysis of biosynthetic VEGFR2 is consistent with a role for UBE2D enzymes in influencing plasma membrane VEGFR2 levels. Cell surface biotinylation and recycling studies show an increase in VEGFR2 recycling to the plasma membrane upon reduction in UBE2D levels. Depletion of either UBE2D1 or UBE2D2 stimulates endothelial tubulogenesis which is consistent with increased VEGFR2 plasma membrane levels promoting the cellular response to exogenous VEGF-A. Our studies identify a key role for UBE2D1 and UBE2D2 in regulating VEGFR2 function in angiogenesis

The E2 ubiquitin-conjugating enzymes UBE2D1 and UBE2D2 regulate VEGFR2 dynamics and endothelial function

Vascular endothelial growth factor receptor 2 (VEGFR2, encoded by KDR) regulates endothelial function and angiogenesis. VEGFR2 undergoes ubiquitination that programs this receptor for trafficking and proteolysis, but the ubiquitin-modifying enzymes involved are ill-defined. Herein, we used a reverse genetics screen for the human E2 family of ubiquitin-conjugating enzymes to identify gene products that regulate VEGFR2 ubiquitination and proteolysis. We found that depletion of either UBE2D1 or UBE2D2 in endothelial cells caused a rise in steady-state VEGFR2 levels. This rise in plasma membrane VEGFR2 levels impacted on VEGF-A-stimulated signalling, with increased activation of canonical MAPK, phospholipase Cγ1 and Akt pathways. Analysis of biosynthetic VEGFR2 is consistent with a role for UBE2D enzymes in influencing plasma membrane VEGFR2 levels. Cell-surface-specific biotinylation and recycling studies showed an increase in VEGFR2 recycling to the plasma membrane upon reduction in UBE2D levels. Depletion of either UBE2D1 or UBE2D2 stimulated endothelial tubulogenesis, which is consistent with increased VEGFR2 plasma membrane levels promoting the cellular response to exogenous VEGF-A. Our studies identify a key role for UBE2D1 and UBE2D2 in regulating VEGFR2 function in angiogenesis

Quantifying the phosphorylation timescales of receptor–ligand complexes: a Markovian matrix-analytic approach

Cells interact with the extracellular environment by means of receptor molecules on their surface. Receptors can bind different ligands, leading to the formation of receptor–ligand complexes. For a subset of receptors, called receptor tyrosine kinases, binding to ligand enables sequential phosphorylation of intra-cellular residues, which initiates a signalling cascade that regulates cellular function and fate. Most mathematical modelling approaches employed to analyse receptor signalling are deterministic, especially when studying scenarios of high ligand concentration or large receptor numbers. There exist, however, biological scenarios where low copy numbers of ligands and/or receptors need to be considered, or where signalling by a few bound receptor–ligand complexes is enough to initiate a cellular response. Under these conditions stochastic approaches are appropriate, and in fact, different attempts have been made in the literature to measure the timescales of receptor signalling initiation in receptor–ligand systems. However, these approaches have made use of numerical simulations or approximations, such as moment-closure techniques. In this paper, we study, from an analytical perspective, the stochastic times to reach a given signalling threshold for two receptor–ligand models. We identify this time as an extinction time for a conveniently defined auxiliary absorbing continuous time Markov process, since receptor–ligand association/dissociation events can be analysed in terms of quasi-birth-and-death processes. We implement algorithmic techniques to compute the different order moments of this time, as well as the steady-state probability distribution of the system. A novel feature of the approach introduced here is that it allows one to quantify the role played by each kinetic rate in the timescales of signal initiation, and in the steady-state probability distribution of the system. Finally, we illustrate our approach by carrying out numerical studies for the vascular endothelial growth factor and one of its receptors, the vascular endothelial growth factor receptor of human endothelial cells

The secretion inhibitor Exo2 perturbs trafficking of Shiga toxin between endosomes and the trans-Golgi network

The small-molecule inhibitor Exo2 {4-hydroxy-3-methoxy-(5,6,7,8-tetrahydrol[1]benzothieno[2,3-d]pyrimidin-4-yl)hydraz-one benzaldehyde} has been reported to disrupt the Golgi apparatus completely and to stimulate Golgi–ER (endoplasmic reticulum) fusion in mammalian cells, akin to the well-characterized fungal toxin BFA (brefeldin A). It has also been reported that Exo2 does not affect the integrity of the TGN (trans-Golgi network), or the direct retrograde trafficking of the glycolipid-binding cholera toxin from the TGN to the ER lumen. We have examined the effects of BFA and Exo2, and found that both compounds are indistinguishable in their inhibition of anterograde transport and that both reagents significantly disrupt the morphology of the TGN in HeLa and in BS-C-1 cells. However, Exo2, unlike BFA, does not induce tubulation and merging of the TGN and endosomal compartments. Furthermore, and in contrast with its effects on cholera toxin, Exo2 significantly perturbs the delivery of Shiga toxin to the ER. Together, these results suggest that the likely target(s) of Exo2 operate at the level of the TGN, the Golgi and a subset of early endosomes, and thus Exo2 provides a more selective tool than BFA for examining membrane trafficking in mammalian cells

Endosome-to-plasma membrane recycling of VEGFR2 receptor tyrosine kinase regulates endothelial function and blood vessel formation.

Rab GTPases are implicated in endosome-to-plasma membrane recycling, but how such membrane traffic regulators control vascular endothelial growth factor receptor 2 (VEGFR2/KDR) dynamics and function are not well understood. Here, we evaluated two different recycling Rab GTPases, Rab4a and Rab11a, in regulating endothelial VEGFR2 trafficking and signalling with implications for endothelial cell migration, proliferation and angiogenesis. In primary endothelial cells, VEGFR2 displays co-localisation with Rab4a, but not Rab11a GTPase, on early endosomes. Expression of a guanosine diphosphate (GDP)-bound Rab4a S22N mutant caused increased VEGFR2 accumulation in endosomes. TfR and VEGFR2 exhibited differences in endosome-to-plasma membrane recycling in the presence of chloroquine. Depletion of Rab4a, but not Rab11a, levels stimulated VEGF-A-dependent intracellular signalling. However, depletion of either Rab4a or Rab11a levels inhibited VEGF-A-stimulated endothelial cell migration. Interestingly, depletion of Rab4a levels stimulated VEGF-A-regulated endothelial cell proliferation. Rab4a and Rab11a were also both required for endothelial tubulogenesis. Evaluation of a transgenic zebrafish model showed that both Rab4 and Rab11a are functionally required for blood vessel formation and animal viability. Rab-dependent endosome-to-plasma membrane recycling of VEGFR2 is important for intracellular signalling, cell migration and proliferation during angiogenesis

“Affimer” synthetic protein scaffolds block oxidized LDL binding to the LOX-1 scavenger receptor and inhibit ERK1/2 activation

In multicellular organisms, a variety of lipid-protein particles control the systemic flow of triacylglycerides, cholesterol and fatty acids between cells in different tissues. The chemical modification by oxidation of these particles can trigger pathological responses, mediated by a group of membrane proteins termed scavenger receptors. The lectin-like oxidised low-density lipoprotein (LOX-1) scavenger receptor binds to oxidized low density lipoprotein (oxLDL) and mediates both signaling and trafficking outcomes. Here, we identified 5 synthetic proteins termed Affimers from a phage display library, each capable of binding recombinant LOX-1 extracellular (oxLDL-binding) domain with high specificity. These Affimers, based on a phytocystatin scaffold with loop regions of variable sequence, were able to bind to the plasma membrane of HEK293T cells exclusively when human LOX-1 was expressed. Binding and uptake of fluorescently-labelled oxLDL by the LOX-1-expressing cell model was inhibited with sub-nanomolar potency by all 5 Affimers. ERK1/2 activation, stimulated by oxLDL binding to LOX-1, was also significantly inhibited (p<0.01) by pre-incubation with LOX-1-specific Affimers, but these Affimers had no direct agonistic effect. Molecular modeling indicated that the LOX-1-specific Affimers bound predominantly via their variable loop regions to the surface of the LOX-1 lectin-like domain that contains a distinctive arrangement of arginine residues previously implicated in oxLDL binding, involving interactions with both subunits of the native, stable scavenger receptor homodimer. These data provide a new class of synthetic tools to probe and potentially modulate the oxLDL/LOX-1 interaction that plays an important role in vascular disease

Use of abstraction and discharge data to improve the performance of a national‐scale hydrological model

Across the UK, water abstracted from ground, surface, and tidal stores is regulated through a system of licenses to protect both the sources and the environment. Similar permits are required for discharging wastewater to rivers or onto the ground. These abstractions and discharges can have a significant impact on UK Rivers, but measurements are not readily available, which discourages their use in hydrological models of river flows. However, these very unique data sets provide a means to improve the performance of spatially distributed hydrological models, particularly during periods when abstraction regulations change and at ungauged river locations. To demonstrate this, point source abstraction and discharge measurements across England have been transformed into 1 × 1 km resolution gridded data and used with an enhanced formulation of the Grid-to-Grid (G2G) hydrological model where these processes are mathematically represented. A comparison of G2G-simulated and gauged river flows for 605 catchments across England between 1999 and 2014 indicates that model simulation of river flows is generally improved at gauged locations downstream of abstraction/discharge sites. The main improvement is in the simulation of low flows, for which the median performance is improved by 10.7%, however, the impact on simulation of high river flows is more modest (1.5% improvement). These results demonstrate the potential gains available to the international hydrological and land-surface modeling community from using records of actual water use (where available) in models, in place of more widely used national statistics

Affinity purification of fibrinogen using an Affimer column

Background Fibrinogen is an abundant plasma protein with an essential role in blood coagulation and haemostasis thus receiving significant research interest. However, protein purification is time consuming and commercial preparations often have protein contaminants. The aim of this study was to develop a new method to purify high quality and functional fibrinogen. Methods Fibrinogen-specific Affimer protein, isolated using phage display systems, was immobilised to SulfoLink resin column and employed for fibrinogen purification from plasma samples. Fibrinogen was eluted using a high pH solution. Commercial human fibrinogen was also further purified using the Affimer column. Fibrinogen purity was determined by SDS-PAGE and mass spectrometry, while functionality was assessed using turbidimetric analysis. Results Affimer-purified fibrinogen from human plasma showed purity at least comparable to commercially available preparations and was able to form physiological fibrin networks. Further purification of commercially available fibrinogen using the Affimercolumn eliminated multiple contaminant proteins, a significant number of which are key elements of the coagulation cascade, including plasminogen and factor XIII. Conclusions The Affimercolumn represents a proof of concept novel, rapid method for isolating functional fibrinogen from plasma and for further purification of commercially available fibrinogen preparations. General significance Our methodology provides an efficient way of purifying functional fibrinogen with superior purity without the need of expensive pieces of equipment or the use of harsh conditions