Cell-Free Synthesis of Selenoproteins in High Yield and Purity for Selective Protein Tagging

The selenol group of selenocysteine is much more nucleophilic than the thiol group of cysteine. Selenocysteine residues in proteins thus offer reactive points for rapid post-translational modification. Herein, we show that selenoproteins can be expressed in high yield and purity by cell-free protein synthesis by global substitution of cysteine by selenocysteine. Complete alkylation of solvent-exposed selenocysteine residues was achieved in 10 minutes with 4-chloromethylene dipicolinic acid (4Cl-MDPA) under conditions that left cysteine residues unchanged even after overnight incubation. Gd^III−Gd^III distances measured by double electron–electron resonance (DEER) experiments of maltose binding protein (MBP) containing two selenocysteine residues tagged with 4Cl-MDPA-Gd^III were indistinguishable from Gd^III−Gd^III distances measured of MBP containing cysteine reacted with 4Br-MDPA tags.     

Quasi-solid-state dye-sensitized solar cells utilizing TiO2/graphite composite counter electrode and TiO2/N719 sensitizer photoelectrode for low-cost power generation

Journal of Materials Science: Materials in Electronics - Dye-sensitized solar cells (DSCs) have evolved through the highest devotion of the research community as a low-cost alternative for...     

Efficiency enhancement by mixed cation effect in dye-sensitized solar cells with a PVdF based gel polymer electrolyte

This paper reports the effect of using a mixed iodide salt system with two dissimilar cations to enhance the efficiency of dye-sensitized solar cells made with polyvinylidenefluoride (PVdF) based gel electrolyte. Instead of a single iodide salt, a mixture of potassium iodide (KI) with a small K⁺ cation and tetrapropylammonium iodide (Pr₄NI) with a bulky Pr₄N⁺ cation were used to provide the required iodide ion conductivity. Solar cells of configuration FTO/TiO₂/Dye/electrolyte/Pt/FTO were fabricated using a mesoporous TiO₂ electrode sensitized with a Ruthenium dye (N719). With identical electrolyte compositions, the cells with KI and Pr₄NI alone gave efficiencies of 2.37% and 2.90% respectively. The cell with the mixed iodide system, KI:Pr₄NI = 16.6:83.4 (% weight ratio), however, showed an enhanced efficiency of 3.92% with a short circuit current density of 9.16 mA cm⁻², open circuit voltage of 674.4 mV and a fill factor of 63.4%.     

Infrared radiation active,novel nanocomposite photocatalyst for water splitting

In this report, we investigated an infrared photon active catalytic system for the conversion of solar energy into chemical energy in which we introduced an effective “Dark Photocatalyst” for photolysis of water. The Ag₂O/TiO₂ composite catalyst containing 28% of silver and 72% of titanium was synthesised by a simple chemical deposition method. The catalyst was found to be active in the infrared region of the solar spectrum or in the dark and hydrogen production was demonstrated for the first using low-energy 800–1200 nm IR radiation. Sub-band gap phonon assisted multi-photon excitation is proposed for the observed infrared photocatalytic activity of Ag₂O/TiO₂ composite.     

Policy conflict analysis for diffserv quality of service management

Policy-based management provides the ability to (re-)configure differentiated services networks so that desired Quality of Service (QoS) goals are achieved. This requires implementing network provisioning decisions, performing admission control, and adapting bandwidth allocation to emerging traffic demands. A policy-based approach facilitates flexibility and adaptability as policies can be dynamically changed without modifying the underlying implementation. However, inconsistencies may arise in the policy specification. In this paper we provide a comprehensive set of QoS policies for managing Differentiated Services (DiffServ) networks, and classify the possible conflicts that can arise between them. We demonstrate the use of Event Calculus and formal reasoning for the analysis of both static and dynamic conflicts in a semi-automated fashion. In addition, we present a conflict analysis tool that provides network administrators with a user-friendly environment for determining and resolving potential inconsistencies. The tool has been extensively tested with large numbers of policies over a range of conflict types.     

The interconnected CaCO3 coated SnO2 nanocrystalline dye-sensitized solar cell with superior performance

Design, Development, fabrication and investigation of the I–V characteristics of the DSSC based on interconnected 15 nm SnO₂ nanoparticles covered with a nano-scale thin layer of CaCO₃ are described. The presence of CaCO₃ has been confirmed by its characteristic XRD pattern and EDX plots. The thickness of the protective layer can be conveniently controlled by the molar ratio of SnO₂:CaCO₃ used in the preparation of the thin film and the optimum conditions for best performance of the DSSC are presented together with possible explanations for the variations observed when the molar ratio is changed. An optimum light-to-electricity conversion efficiency of 5.4% in the presence of a layer of CaCO₃ has been obtained which is 3.2 times enhancement over the cell prepared without CaCO₃. The characterization of the surface using different techniques is explained.     

Molecular adsorption on V2O3(0001)/Au(111) surfaces

The adsorption of carbon monoxide (CO), propane (C₃H₈) and propene (C₃H₆) on V₂O₃(0001) films grown on Au(111) was studied by Temperature Programmed Desorption (TPD) and X-ray Photoelectron Spectroscopy (XPS). The “oxidized” surface (i.e., as prepared exhibiting V=O termination), the “reduced” surface (i.e., V=O groups being removed by electron irradiation), as well as the oxygen pre-covered reduced surface were investigated. Both TPD and XPS indicate that the oxidized surface has little affinity for CO adsorption, while the reduced surface readily binds CO (CO amount approx. 10 times higher). Accordingly, CO can be used to titrate the presence or absence of vanadyl oxygen (via adsorption on the vanadium atoms) but also of defects like surface oxygen vacancies. For propane and propene, desorption of the parent molecules was the major process, i.e., surface reactions were absent under the applied conditions. When oxygen was pre-adsorbed on the reduced surface, the adsorption properties resembled that of the oxidized surface, i.e., the vanadyl groups were (partially) re-established. TPD and XPS provide a handle to differentiate the binding sites on the V₂O₃ surface. Dedicated to Prof. Konrad Hayek.     

Electrically conducting polypyrrole-fuller's earth nanocomposites: Their preparation and characterisation

Cu(II)-exchanged fuller's earth was prepared by ion-exchanging Ca²⁺ ions which are present within the interlayer of fuller's earth with Cu(II)ions by the solution-phase ion-exchange process. Pyrrole was introduced into Cu(II)-exchanged fuller's earth to spontaneously polymerize to within the interlayer to result in a nanocomposite of Cu(I)-polypyrrole-fuller's earth where both Cu(I) and polypyrrole occupy within the interlayer spaces of fuller's earth. The nanomaterial [Cu(I)-PPY-FE] has been fully characterized with X-ray diffraction studies, FTIR spectroscopy, DC polarisation test with both blocking stainless steel and non-blocking copper electrodes. The material is found to be a mixed conductor whose ionic mobility is 1.5 times faster than electronic mobility. DC polarisation studies also clearly revealed that the mobile ionic species in this material to be cuprous ions. AC impedance studies have been carried out with blocking stainless steel electrodes at different applied potentials. The necessary theoretical background to explain AC impedance results is also provided and the results obtained agree very well with the corresponding data obtained by other mutually independent methods. The electronic conductivities are around 3.0 × 10⁻⁴ S cm⁻¹ and the ionic conductivities are around 9.0 × 10⁻³ S cm⁻¹. The material may find applications in semi-fuel cells such as air-metal batteries.     

Expression and stabilization of galactose oxidase in Escherichia coli by directed evolution

We have used directed evolution methods to express a fungalenzyme, galactose oxidase (GOase), in functional form in Escherichiacoli. The evolved enzymes retain the activity and substratespecificity of the native fungal oxidase, but are more thermostable,are expressed at a much higher level (up to 10.8 mg/l of purifiedGOase), and have reduced negative charge compared to wild type,all properties which are expected to facilitate applicationsand further evolution of the enzyme. Spectroscopic characterizationof the recombinant enzymes reveals a tyrosyl radical of comparablestability to the native GOase from Fusarium.