Biotinylated steroid derivatives as ligands for biospecific interaction analysis with monoclonal antibodies using immunosensor devices.

Systematic ligand-binding studies of the biospecific interaction between steroids and antisteroid antibodies can be performed in real time using biosensor techniques. In this study, quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) biosensor systems were applied. Different biotinylated testosterone (T) and 17beta-estradiol (E2) derivatives were preincubated with streptavidin and immobilized on the sensor surfaces.

Multicentre evaluation of an enzyme-immunoassay for cortisol determination.

The present paper describes a multicentre evaluation of a one step enzyme-immunoassay for the determination of cortisol in serum or plasma. Data from the investigation were analysed in terms of imprecision, detection limit, and correlation with other test methods. Within-run and between-run imprecisions (coefficient of variation) of Enzymun-Test Cortisol were less than 8% and 12%, respectively.

Does dimeric melittin occur in aqueous solutions?

Melittin, a peptide from bee venom, is known to undergo a monomer / tetramer conversion in aqueous solutions. We have studied the possible participation of dimers in the association equilibrium of melittin by sedimentation equilibrium experiments in the analytical ultracentrifuge and subsequent mathematical analysis of the concentration distributions obtained. It was found that the dimeric state is not significantly populated, the contribution of dimer to the total peptide weight probably being below 0.

The nature of the stable noncovalent dimers of band 3 protein from erythrocyte membranes in solutions of Triton X-100.

Stable noncovalent dimers of band 3 protein from human erythrocyte membranes, in which state the protein is thought to exist after solubilization by the nonionic detergent Triton X-100, do not occur when purified batches of the detergent are used. Instead, the protein is in a monomer/dimer/tetramer association equilibrium. The stable dimers do appear, however, when the detergent has been 'aged'.

The state of association of band 3 protein of the human erythrocyte membrane in solutions of nonionic detergents.

Band 3 protein, the anion transport protein of the human erythrocyte membrane, was solubilized and purified in aqueous solutions of two nonionic detergents: Ammonyx-LO (dimethyl laurylamine oxide) and C12E9 (nonaethylene glycol lauryl ether). The state of association of the purified protein was studied by analytical ultracentrifugation. Band 3 protein solubilized and studied in solutions of Ammonyx-LO was found to be in a monomer/dimer/tetramer association equilibrium.