Journal articles

A direct immunosensor has been developed using an acoustic wave device as a transducer. The device is based on an acoustic waveguide geometry that supports a Love wave. The biorecognition surface, formed on a gold layer, consisted of a biotinylated supported lipid layer which specifically bound streptavidin and, subsequently, biotinylated goat IgG. The modified surface was used as a model immunosensor and successfully detected rabbit anti-goat IgG in the concentration range 3 x 10(-8) - 10(-6) M.

The structural gene for heroin esterase was cloned from Rhodococcus sp. strain H1 and expressed in Escherichia coli BL21(DE3). The purified enzyme was found to be a tetramer with an M(r) of 137,000 and an apparent K(m) of 0.88 mM for 6-acetylmorphine. The G-x-S-x-G motif was observed in the deduced amino acid sequence, suggesting that the enzyme is a serin esterase.

We have used random chemical mutagenesis and a simple genetic screen to generate and isolate a thermostable mutant of luciferase from the North American firefly (Photinus pyralis). A single G-to-A transition mutation, resulting in the substitution of a glutamate for a lysine residue at position 354 in the protein sequence, was shown to be responsible for this enhanced thermostability. Replacement of Glu-354 with all possible amino acid residues was achieved using directed mutagenesis, and produced mutant enzymes with a range of thermostabilities.

Several key developments have occurred recently in the application of scanning probe microscopy to biology. These include the use of 'tapping-mode' atomic force microscopy both for the high-resolution imaging of biomolecules in liquids and for monitoring in situ biocatalysis, the use of atomic force microscopy as a force transducer to measure individual biological interactions, and the development of hybrid techniques such as scanning tunnelling microscopy coupled to confocal scanning laser microscopy.

Immunosensors are important analytical tools for monitoring antibody-antigen reactions in real time. Recent developments in immunosensors have produced systems that allow rapid and continuous analysis of the binding event without the requirement for added reagents or separation/washing steps. As a result, great interest has focused on commercializing immunosensors for applications in areas such as clinical, environmental and food analysis.

Illicit heroin is trafficked as a solid particulate drug, while heroin abuse is monitored by testing urine samples for its principal metabolites, morphine and morphine-3-glucuronide. Two novel bacterial enzymes were used in the development of a linked-enzyme assay for heroin and its metabolites: heroin esterase, which converts heroin to morphine, and morphine dehydrogenase, which oxidizes morphine to morphinone with the concomitant reduction of NADP+.

A convenient and efficient method for the site-specific incorporation of foreign cysteine residues at the C-termini of immunoglobulin G (IgG) using carboxypeptidase-Y-catalyzed transpeptidation is explored as a means of ensuring oriented immobilization of IgG on gold. A scanning tunnelling microscopic study of the immobilization of the modified IgG molecules on gold surfaces is reported.