High-Throughput Surface Plasmon Resonance (SPR)

SPR sensor chips typically consist of a thin metal film, commonly gold, deposited on a glass substrate. The metal film is coated with a thin layer of a biocompatible material, often a self-assembled monolayer, to which the biomolecules of interest can be immobilized.

The sensor surface is then exposed to a liquid sample containing the analytes or target molecules. The interaction between the immobilized ligands and the analytes leads to changes in the refractive index at the surface, which can be detected and analyzed in real time.

SPR-based biosensors rely on the detection of changes in the evanescent electromagnetic field that occurs at the metal-dielectric interface when the surface plasmons are excited.

The excitation of surface plasmons is achieved by coupling a beam of polarized light, to the metal film at a specific angle known as the resonance angle. This angle is determined by the refractive index of the sample medium and the properties of the metal film.

The resonance condition is highly sensitive to changes at the metal-dielectric interface, such as the binding of a biomolecule, making SPR a powerful tool for studying biomolecular interactions.

When the incident light beam hits the metal-dielectric interface at the resonance angle, it generates an evanescent wave that extends into the sample medium. This evanescent wave interacts with the analytes in the sample, leading to changes in the refractive index near the surface. These changes can be detected as alterations in the intensity or angle of the reflected light.

A detector measures these changes, and the resulting signal is processed to obtain information about the binding events occurring on the sensor surface. By monitoring the changes in the SPR signal over time, scientists can gain valuable insights into the kinetics and affinity of biomolecular interactions of the binding process.

The rate at which the signal changes provides information about the association and dissociation of the analytes with the immobilized ligands, allowing the calculation of kinetic parameters such as association rate constants (k_a or k_on) and dissociation rate constants (k_d or k_off). The equilibrium binding affinity (K_D) can also be calculated as the ratio of k_d and k_a or also be determined by analyzing the steady-state signal.

SPR-based biosensors enable the monitoring of dynamic processes and the analysis of fast-binding interactions. They are also highly sensitive, allowing the detection of small molecule analytes at low concentrations.

SPR technology has a wide range of applications, including drug discovery, antibody screening, protein-protein interactions, and nucleic acid interactions which provide valuable information about binding kinetics, analyte concentration, and the thermodynamics of these interactions in a label-free and real-time manner, making it an indispensable tool in many research and development settings.

Surface Plasmon Resonance is a cutting-edge technology that provides a powerful tool for studying and understanding molecular interactions. It's a key player in advancing our knowledge in biochemistry and related fields, contributing significantly to the development of new drugs and therapies.