Surface Infrared Spectroscopic Study on Label-Free Detection of Antigen-Antibody Interactions: Discrimination between Specific and Nonspecific Signals using Protein Secondary Structure Analysis

Abstract

This paper reviews our recent approaches for a label-free detection of protein-protein interactions which can perform simultaneous protein conformational analysis by using infrared absorption spectroscopy in the multiple internal reflection geometry (MIR-IRAS). Using this method, the target protein was detected in aqueous solution phase based on the peak height of the protein amide I and amide II bands, while discrimination of specific and nonspecific signals is made based on the secondary structure of the target protein. An antigen-antibody interaction on semiconductor surfaces was investigated as a model system, since it is well-known that antibodies largely consist of β-sheet structures. The features of our approach using MIR-IRAS combined with protein secondary structure analysis were discussed in terms of sensitivity, capability of quantitative analysis, and specific/nonspecific discrimination.