title: Real-time, label-free detection of biomolecular interactions in sandwich assays by the oblique-incidence reflectivity difference technique.
abstract: One of the most important goals in proteomics is to detect the real-time kinetics of diverse biomolecular interactions. Fluorescence, which requires extrinsic tags, is a commonly and widely used method because of its high convenience and sensitivity. However, in order to maintain the conformational and functional integrality of biomolecules, label-free detection methods are highly under demand. We have developed the oblique-incidence reflectivity difference (OI-RD) technique for label-free, kinetic measurements of protein-biomolecule interactions. Incorporating the total internal refection geometry into the OI-RD technique, we are able to detect as low as 0.1% of a protein monolayer, and this sensitivity is comparable with other label-free techniques such as surface plasmon resonance (SPR). The unique advantage of OI-RD over SPR is no need for dielectric layers. Moreover, using a photodiode array as the detector enables multi-channel detection and also eliminates the over-time signal drift. In this paper, we demonstrate the applicability and feasibility of the OI-RD technique by measuring the kinetics of protein-protein and protein-small molecule interactions in sandwich assays.
authors.affiliation: Department of Physics, Fu-Jen Catholic University, New Taipei City 24205, Taiwan. 089957@mail.fju.edu.tw.
authors.forename: Yung-Shin
authors.initials: YS
authors.lastname: Sun
authors.affiliation: Department of Physics, University of California at Davis, Davis, CA 95616, USA. xdzhu@physics.ucdavis.edu.
authors.forename: Xiangdong
authors.initials: X
authors.lastname: Zhu
mesh_terms: D003199:Computer Systems; D004867:Equipment Design; D019544:Equipment Failure Analysis; D055096:Optical Devices; D010783:Photometry / Q000295:instrumentation*; D040081:Protein Array Analysis / Q000295:instrumentation*; D025941:Protein Interaction Mapping / Q000295:instrumentation*; D012031:Refractometry / Q000295:instrumentation*; D013194:Staining and Labeling