Journal articles

The sensitivity of surface plasmon resonance techniques to changes in local interfacial refractive index has been exploited to detect immuno-complex formation in two model biochemical systems. A gold-coated diffraction grating has been used to excite surface plasmons at the gold/solution interface to which either human immunoglobulin G or the immunoglobulin fraction of sheep antiserum to human serum albumin was physically adsorbed.

The fabrication and operation of a microelectronic conductimetric biosensor is described. The device monitors the change in solution conductance occasioned by the catalytic action of enzymes immobilised over a planar conductance cell comprising serpentined and interdigitated metal conductor tracks. The output of the instrument was linear over a 3 min period on addition of urea to a sample cell overlaid with immobilised urease. The responses to any given urea concentration were reproducible to within approximately +/- 1%. The device responds to urea present in serum samples.

Biosensors are analytical devices that respond selectively to analytes in an appropriate sample and convert their concentration into an electrical signal via a combination of a biological recognition system and an electrochemical, optical or other transducer. Such devices will find application in medicine, agriculture, environmental monitoring and the bioprocessing industries.

C.I. Reactive Blue 2 analogues were bonded onto an agarose support matrix by a novel method which entailed immobilisation by the anthraquinone ring 1-amino group as opposed to the usual triazine ring coupling methods. Dyes with spacer arms attached to the anthraquinone ring 1-amino group were synthesised by reacting methoxytriazine analogues of C.I. Reactive Blue 2 with chloroacetyl chloride and ethylenediamine. Unlike the blue parent dyes, all C.I. Reactive Blue 2 analogues with derivatised anthraquinone ring 1-amino groups were of a characteristic red colour.

The design, synthesis and chromatographic operation of a new range of stable and selective immobilized dye affinity adsorbents for potential application in the purification of pharmaceutical proteins is described. Computer aided molecular design has been exploited to design novel dye ligands which show a predictable selectivity for the target protein and which, when coupled to stable perfluoropolymer supports, yield high capacity, low leakage adsorbents for affinity chromatography.

This review introduces biosensors as analytical devices that respond selectively to analytes in appropriate samples and convert their concentrations into electrical signals via a combination of a biological recognition system and a suitable transducer. The last decade has seen dramatic advances in the design of sensor configurations, the marriage of biological systems with modern monolithic silicon and optical technologies, the development of effective electron-exchange systems and the introduction of direct immunosensors.

There is a need to develop sensors for real-time monitoring of volatile organic compounds (VOCs) and hydrocarbon gases in both external and indoor environments, since these compounds are of growing concern in human health and welfare. Current measurement technology for VOCs requires sophisticated equipment and lacks the prospect for rapid real-time monitoring. Holographic sensors can give a direct reading of the analyte concentration as a color change. We report a technique for recording holographic sensors by laser ablation of silver particles formed in situ by diffusion.

No one technique for multiplexing 100+ label-free measurements in a single well or flowcell has yet gained wide acceptance, probably because the added complexity introduced by the multiplexing element is seen to outweigh any possible cost advantage, or the multiplexing scheme itself is not flexible enough to accommodate the desired combinations of immobilization conditions and target/analyte molecules.

Affinity adsorbents comprising monodisperse spherical synthetic macroporous beads offer the prospect of high-capacity, high-resolution separation of proteins at low operating pressures. Purpose-designed biomimetic dyes were covalently attached to Dynospheres XP-3507 beads and exploited for the purification of calf intestine alkaline phosphatase and human urine urokinase from crude extracts.

The molecular basis for the recognition of glucose as a germinant molecule by spores of Bacillus megaterium QM B1551 has been examined. A chromosome-located locus (BMQ_1820, renamed gerWB) is shown to encode a receptor B-protein subunit that interacts with the GerUA and GerUC proteins to form a receptor that is cognate for both glucose and leucine. GerWB represents the third receptor B protein that binds to glucose in this strain.