Surface plasmon resonance
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Joined: Jun 2010
08-10-2010, 03:21 PM
Surface plasmon resonance
Surface plasmon resonance (SPR) is a phenomenon occurring at metal surfaces(typically gold and silver) when an incident light beam strikes the surface at a particular angle.Depending on the thickness of a molecular layer at the metal surface,the SPR phenomenon results in a graded reduction in intensity of the reflected light.Biomedical applications take advantage of the exquisite sensitivity of SPR to the refractive index of the medium next to the metal surface, which makes it possible to measure accurately the adsorption of molecules on the metal surface an their eventual interactions with specific ligands. The last ten years have seen a tremendous development of SPR use in biomedical applications.
The technique is applied not only to the measurement in real time of the kinetics of ligands receptor interactions and to the screening of lead compounds in the pharmaceutical industry, but also to the measurement DNA hybridization, enzyme- substrate interactions, in polyclonal antibody characterization, epitope mapping, protein conformation studies and label free immunoassays. Conventional SPR is applied in specialized biosensing instruments. These instruments use expensive sensor chips of limited reuse capacity and require complex chemistry for ligand or protein immobilization. Laboratory has successfully applied SPR with colloidal gold particles in buffered solutions. This application offers many advantages over conventional SPR. The support is cheap, easily synthesized, and can be coated with various proteins or protein ligand complexes by charge adsorption. With colloidal gold, the SPR phenomenon can be monitored in any UV spectrophotometer. For high throughput applications we have adapted the technology in an automated clinical chemistry analyzer. This simple technology finds application in label free quantitative immunoassay techniques for proteins and small analytes, in conformational studies with proteins as well as real time association dissociation measurements of receptor ligand interactions for high throughput screening and lead optimization.
During the last two decades we have witnessed remarkable research and development activity aimed at the realization of optical sensors for the measurement of chemical and biological quantities. First optical chemical sensors were based on the measurement of changes in absorption spectrum and were developed for the measurement of CO2 and O2 concentration. Since then a large variety of optical methods have been used in chemical sensors and biosensors including elipsometry, spectroscopy, interferometry spectroscopy of guided modes in optical wave guide structures and surface plasmon resonance .
The potential of surface plasmon resonance for characterization of thin films and monitoring process at metal interfaces was recognized in the late seventies. In 1982 the use of SPR for gas detection and biosensing was demonstrated by Nylander and lieberg . Since then SPR sensing has been receiving continuously growing attention from scientific community. Development of new SPR sensing configurations as well as applications of SPR sensing devices for the measurement of physical , chemical and biological quantities have been described . The SPR sensor technology has been commercialized by several companies and become a leading technology in the field of direct real time observation of the biomolecular interaction.
The phenomenon of anomalous diffraction on diffraction gratings due to the excitation of surface plasma waves was first described in the beginning of the twentieth century by Wood. In the late sixties, optical excitation of surface plasmons by the method of attenuated total reflection was demonstrated by Kretschmann and Otto .
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|Tagged Pages: plasmon, seminar on resonance physics, surface plasmon resonance, immobilization of enzymes,|
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