Surface Plasmon Resonance

Surface Plasmon Resonance (SPR) is the gold standard for interaction analysis. The method allows to monitor molecular binding at a chip surface in the low pg range in real-time by measuring refractive index changes, without the need of a (fluorescence) label. One interaction partner, the probe, is immobilised in a flow cell of the chip, a dilution series of the analyte is injected in a concentration range between 1/10 to 10x KD. The measured sensorgrams, consisting of an injection and a dissociation phase, are evaluated by global fitting (using all curves) that reveal the association and dissociation rate constant (ka, kd), and the equilibrium dissociation constant, KD (1/KA, affinity). SPR allows to study all kind of molecular interactions of immobilised probes including proteins and protein complexes, peptides, DNA, carbohydrates, lipopolysaccharides, and other classes of compounds, with matching binding partners.

Sensorgram of hybridization of a dye labeled 7 nt oligonucleotide to a 24 nt oligonucleotide immobilised on the chip surface. Kinetic constants (ka, kd, KD) can be obtained by a global fit of data (A), or plotting the equilibrium intensities (plateau values) (B). Measurements were conducted to investigate the effect of a dye label on hybridisation.
For details see Sobek et al. Molecules 2020, 25(22), 5369

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