Electroanalytical study on the interaction between proteins and their ligands

Some simple methods for an electrochemical binding assay for protein-ligand like avidin-biotin and lectin- sugar were developed. In a homogeneous binding assay based on the use of an electroactive label, following methods are proposed to obtain a sensitive electrochemical response. 1) In order to obtain an amplified electrode response without an enzyme label, an electron-transfer mediator was used as a label. 2) In order to use anodic stripping voltammetry for the sensitive detection of metal, a ligand labeled with a complex reagent was applied to the binding assay. 3) An accumulation of ligand to an ion exchange membrane electrode was investigated using a ligand labeled with a cationic electroactive molecule. 4) A highly sensitive detection of an electroactive labeled ligand was attempted by the potential regulating accumulation on a plain glassy carbon electrode. In a heterogeneous binding assay based on a technique without a label, some hydrophilic electroactive compounds were used as a redox marker to evaluate the protein-ligand interaction. A sensitive and selective binding assay could be achieved by monitoring the change in the electrode response of the redox marker. In addition, a development of screening method for endocrine disrupting chemicals using 17β-estradiol labeled with an electroactive compound was attempted. These electrochemical binding assays do not require a separation procedure prior to any measurements. Therefore, dynamic monitoring for the formation of the protein-ligand complex is possible.