Membrane binding assay

Enzyme Immunosensors. Enzyme immunosensors are enzyme immunoassays coupled with electrochemical sensors. These sensors (qv) require multiple steps for analyte determination, and either sandwich assays or competitive binding assays maybe used. Both of these assays use antibodies for the analyte of interest attached to a membrane on the surface of an electrochemical sensor. In the sandwich assay type, the membrane-bound antibody binds the sample antigen, which in turn binds another antibody that is enzyme-labeled. This immunosensor is then placed in a solution containing the substrate for the labeling enzyme and the rate of product formation is measured electrochemically. The rate of the reaction is proportional to the amount of bound enzyme and thus to the amount of the analyte antigen. The sandwich assay can be used only with antigens capable of binding two different antibodies simultaneously (53). 

Salminen, O., Whiteaker, P., Grady, S.R., Collins, A.C., McIntosh, J.M., Marks, M.J. The subunit composition and pharmacology of alpha-Conotoxin Mil-binding nicotinic acetylcholine receptors studied by a novel membrane-binding assay. Neuropharmacology. 48 696, 2005. 

Though there are hardly any restrictions to choosing a target, pharmacological receptors are investigated most frequently. The nature of the receptor, v hether it is membrane-bound or soluble, determines which separation technique is used to terminate the binding assay. For the former, filtration or centrifugation are favored as separation steps, while for the latter suitable methods are gel filtration, equilibrium dialysis, precipitation or adsorption of the nonbound marker by charcoal [23, 24]. 

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