Biochips: an evolving clinical technology

The first biochips are already in use. They are computer-chip look-alikes intended to speedily, reliably, and inexpensively perform the sequential procedures that compose a medical test. Current applications lie chiefly in the analysis of genes. The devices may soon facilitate screening of potential drugs. Clinically, the immediate goal is to enable biochips to serve point-of-care diagnosis.

Isolation of human cardiac endothelin receptors by a peptide-receptor mobility shift assay

1. A peptide-protein mobility shift assay has been developed, using native polyacrylamide-gel electrophoresis, that enables the isolation of de-natured receptor proteins from small amounts of human cardiac tissue. 2. Radiolabelled endothelin-1 and related peptides were used to identify and isolate endothelin receptors from partially purified membrane extracts of human atrial tissue. 3. Binding analysis using radiolabelled endothelin-1 gave an equilibrium dissociation constant (Kd) of 2 nmol/l, similar to results from binding experiments conducted directly on tissue. 4. Peptide-receptor complexes were electroeluted from native gels and dissociated. Receptor material was characterized by dot-immunobinding analysis of eluates using an antibody raised against a predicted human endothelin receptor sequence.

Simultaneous electroelution of proteins from denaturing or native gels into a well matrix

An electroelution device that is based on a semidry blotter and that allows the simultaneous elution of proteins or other charged macromolecules from one-dimensional gels is described. It consists of a central plate that has a matrix of oblong wells arranged in eight columns of 32 wells each, such that when a gel is placed on the plate each lane of bands is underlaid by a column of wells. The plate is placed between the electrodes of a semidry blotter and the wells are sealed by a dialysis membrane resting on polyacrylamide gel block, prior to being filled with transfer buffer. Using radiolabeled molecular weight standards resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, elution is shown to require 30-60 min for 90% or better of proteins between 10 and 120 kDa to be removed from the gel. The recovery volume is 200 microliters per well and losses due to adsorption onto the dialysis membrane are minimal. beta-Galactosidase eluted from a nonreducing, nondenaturing gel was shown to be quantitatively active. The advantages of the device include its ease of assembly and operation, its speed, its reproducibility, and the fact that no gel slicing is required since all proteins are eluted simultaneously, allowing large-scale screening of multiple protein fractions.

Characterisation of potential adhesins of the bacterium Pasteuria penetrans, and of putative receptors on the cuticle of Meloidogyne incognita, a nematode host

Pasteuria penetrans spores were fragmented by glass bead vortexing, producing exosporial membranes and spore fragments, which consisted of fibre bundles. Both exosporia and spore fragments are capable of host-specific attachment to the cuticle of Meloidogyne incognita, a root-knot nematode host. Putative M. incognita receptors appear to be soluble in beta-mercaptoethanol (BME) but not SDS, and are also sensitive to tryptic digestion and deglycosylation by endoglycosidase F. Polyclonal antibodies against intact spores and spore fragments of antispore antibodies produced 100% inhibition. The antibodies, however, did not show preferential staining of particular spore structures in thin section immunolabelling studies. Exposure of Pasteuria penetrans spores to HCl or urea-SDS-dithiothreitol renders them incapable of attachment to their host juveniles and extensively disrupts fibres that surround the spore core. Protein extracts from spore fragments or from exosporial membranes are identical, and urea-BME extracts from either structure, but not SDS extracts, can inhibit the attachment of spores to juveniles by 60–80%. An inhibitory BME extract from spore fragments was analysed by anion-exchange chromatography and adsorption onto host cuticle followed by immunoblotting. It appeared to contain six potential spore adhesins of approximate Mr 24–29, 38–47, 59, 89, 126, and 190 (x10(3)). Lectin affinity blotting with wheat germ agglutinin and concanavalin A showed that all of these proteins bear terminal N-acetylglucosamine residues and the 38–47 kDa band also bears terminal Glc/Man residues.(ABSTRACT TRUNCATED AT 250 WORDS)