Synthesis and properties of polyethersulphone–polydimethyisiloxane block copolymers

High molecular weight alternating block copolymers of polyethesulphone (PES) and polydimethylsiloxane (PDMS) were prepared by the condensation of dimethylamino-terminated PDMS oligomers and hydroxy-terminated PES oligomers in 1,2-dichlorobenzene. Microphase separation of the block copolymers at exceptionally short block lengths was observed by differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The Si? O? C intersegment linkage in these materials appeared to display poor hydrolytic stability which is contrary to results obtained for other block copolymers.     

Electrochemical Detection of TNT at Cobalt Phthalocyanine Mediated Screen‐Printed Electrodes and Application to Detection of Airborne Vapours

We describe the use of cobalt phthalocyanine as a mediator to improve the sensitivity for the electrochemical detection of TNT. Commercial screen‐printed electrodes containing cobalt phthalocyanine were employed for determination of TNT. Improved sensitivities compared to screen‐printed carbon electrodes without phthalocyanine were observed, current response for cyclic voltammetric measurements at modified electrodes being at least double that of unmodified electrodes. A synergistic effect between oxygen and TNT reduction was also observed. Correlation between TNT concentrations and sensor output was observed between 0–200 µM TNT. Initial proof‐of‐concept experiments combining electrochemical determinations, with the use of an air‐sampling cyclone, are also reported.     

A new application of scanning electrochemical microscopy for the label-free interrogation of antibody-antigen interactions

Within this work we present a ‘proof of principle’ study for the use of scanning electrochemical microscopy (SECM) to detect and image biomolecular interactions in a label-free assay as a potential alternative to current fluorescence techniques. Screen-printed carbon electrodes were used as the substrate for the deposition of a dotted array, where the dots consist of biotinylated polyethyleneimine. These were then further derivatised, first with neutravidin and then with a biotinylated antibody to the protein neuron specific enolase (NSE). SECM using a ferrocene carboxylic acid mediator showed clear differences between the array and the surrounding unmodified carbon. Imaging of the arrays before and following exposure to various concentrations of the antigen showed clear evidence for specific binding of the NSE antigen to the antibody derivatised dots. Non-specific binding was quantified. Control experiments with other proteins showed only non-specific binding across the whole of the substrate, thereby confirming that specific binding does occur between the antibody and antigen at the surface of the dots. Binding of the antigen was accompanied by a measured increase in current response, which may be explained in terms of protein electrostatic interaction and hydrophobic interactions to the mediator, thereby increasing the localised mediator flux. A calibration curve was obtained between 500 fg mL⁻¹ to 200 pg mL⁻¹ NSE which demonstrated a logarithmic relationship between the current change upon binding and antigen concentration without the need for any labelling of the substrate.     

A weight-function approach for determining watershed initial conditions for combustion waves

In many generic combustion models, one finds that a combustionwave will develop with a specific wave speed. However, thereare possible initial temperature profiles which do not evolveinto such waves, but rather die out to the ambient temperature.There can exist, in some models, a clear distinction betweenthose initial conditions that do evolve into combustion wavesand those that do not; this is sometimes referred to as thewatershed initial condition. When fuel consumption is consideredto be negligible, analytical methods can be used to obtain theexact watershed. In this paper, we consider the problem of determiningpseudo-watersheds and ascertaining the relationship betweenthese pseudo-watersheds and the exact watersheds. In the processa novel weight-function approach for infinite spatial domainsis developed.     

A new application of scanning electrochemical microscopy for the label-free interrogation of antibody–antigen interactions: Part 2

Within this paper we describe the use of scanning electrochemical microscopy (SECM) to fabricate a dotted array of biotinylated polyethyleneimine which was then used to immobilise first neutravidin and then a biotinylated antibody towards a relevant antigen of interest (PSA, NTx, ciprofloxacin). These antigens were selected both for their clinical relevance but also since they display a broad range of molecular weights, to determine whether the size of the antigen used effects the sensitivity of this approach. The SECM was then used to image the binding of both complementary and non-complementary antigens in a label-free assay. Imaging of the arrays before and following exposure to various concentrations of antigen in buffer showed clear evidence for specific binding of the complementary antigens to the antibody functionalised dots. Non-specific binding was also quantified by control experiments with other antigens. This demonstrated non-specific binding across the whole of the substrate, thereby confirming that specific binding does occur between the antibody and antigen of interest at the surface of the dots. The binding of ciprofloxacin was investigated both in simple buffer solution and in a more complex media, bovine milk.     

Flexible Ultrathin PolyDVB/EVB Composite Membranes for the Optimization of a Lactate Sensor

An ultrathin composite membrane has been developed as the outer covering barrier in a model amperometric lactate oxidase enzyme electrode. The membrane was formed by cathodic electropolymerization of divinylbenzene/ethylvinylbenzene at the surface of a gold coated polyester support membrane. Permeability coefficients were determined for O₂ and lactate across membranes with a range of polymer thicknesses. Anionic interferents (such as ascorbate) were screened from the working electrode by the composite membrane. The composite enzyme electrode showed an increased working concentration range and extended linearity of responses in comparison to an uncoated enzyme electrode.     

Construction and interrogation of enzyme microarrays using scanning electrochemical microscopy - optimisation of adsorption and determination of enzymatic activity

Scanning electrochemical microscopy (SECM) has been used to image and study the catalytic activity of horseradish peroxidase (HRP) immobilised in a patterned fashion onto glass slides. Microarrays of HRP islands could be deposited on amino-modified glass slides using glutaraldehyde crosslinking combined with the SECM being used as a micro-deposition device. The enzymatic activity of the immobilised enzyme on the surface was in the presence of its substrate observed to give rise to substantial positive feedback between the slide and the SECM microelectrode tip. Conversely when either blank slides - or slides coated with HRP which had been subsequently thermally denatured were utilised, these showed negative feedback effects. Various conditions such as enzyme concentration, incubation time and substrate concentration were systematically varied to optimise sensitivity. Regular arrays of HRP could be assembled and when imaged, displayed lower limits of detection of 1.2 × 10(-12) mol ml(-1) of benzoquinone.     

Synthesis of cytotoxic cyanobactin,Wewakazole B

We report herein the synthesis of cytotoxic cyanobactin, Wewakazole B through an efficient solution-phase approach. The key steps of the synthesis are the macrocyclic lactamization of linear dodecapeptide and construction of two hexapeptides with three different substituted oxazole rings.     

Evaluation of Poly(o‐phenylenediamine) Films for Application as Insulating Layers upon Carbon Substrates for Use within Sonochemically Fabricated Microelectrode Arrays

The formation of insulating layers of poly(o‐phenylenediamine) via electropolymerization was performed on single carbon screen‐printed electrodes. The effects of experimental parameters on the properties of the film were investigated, allowing for technique optimization. These conditions were then used to deposit films upon surfaces of 100 interconnected electrodes, with cyclic voltammetry used to study the electroactivity of the resulting electrodes. The insulating property of the film, for use in the formation of microelectrode array amperometric sensors, was evaluated. Finally, the insulated sensors were exposed to ultrasonic ablation to form microelectrode arrays, and these were subsequently assessed using optical and electrochemical techniques.     

Sound pressure level and spectral balance linearity and symmetry in the messa di voce of female classical singers

The messa di voce, in its pure form a crescendo and decrescendo on one note, has been revered for centuries in classical singing, but the pedagogical assumptions of linearity and symmetry have received little critical assessment, especially across a wide fundamental frequency (F0) range. Five trained female classical singers performed a total of 318 messe di voce across their musical F0 range to identify its acoustical characteristics and the influence of F0. Sound pressure level (SPL) range was generally greater during crescendo at higher F0's and during decrescendo at lower FO's. Change in SPL during the messa di voce was predominantly nonlinear, and the shape of the SPL traces differed greatly between crescendo and decrescendo. Nonlinearity in SPL change was not related to SPL range but did show a F0 influence in decrescendo. Change in spectral balance (0-2 vs. 2-4 kHz) with respect to SPL change showed markedly more symmetry than linearity, so that changes in the mode of phonation during the messa di voce were dependent upon SPL regardless of whether the singer was in crescendo or decrescendo. Perceptual and physiological implications are discussed.