Interactions between proteins and their complementary biomolecules (whether they are other proteins, antibodies, metabolites or drug molecules) are characterized by rates of association (Ka) and dissociation (Kd) referred to as on- and off-rates, respectively.
The ratio of the off-rate over the on-rate yields what is called the equilibrium dissociation constant (KD) which provides a useful measure for which to compare the strengths of any given interactions. The lower the KD the stronger the interaction and vice versa.
For example, during the COVID-19 pandemic a highly contagious variant of the SARS-CoV-2 virus called Alpha emerged in the UK and spread more rapidly than its parent wild-type Wuhan strain. Researchers have found that Alpha variant spread more rapidly likely because it obtained in its Spike receptor binding domain (RBD) a single mutation which drastically lowered the KD of its binding to the human cell receptor ACE2, increasing binding strength between the viral RBD and the ACE2 proteins by 10-fold (See  ,).
Surface plasmon resonance (SPR) is a technique that can directly measure the on- and off-rates for the interactions between proteins and their targets and has been a gold-standard technique applied to study and characterize biochemical interactions for over 30 years.
Traditionally, SPR studies in both academia and biopharma have been limited to interrogating only a handful of proteins of interest that require expression and purification, followed by on-instrument immobilization onto sensors which increases assay times and reduces protein quality. INanoBio’s SPOC technology removes these barriers to discovery by providing a scalable solution to high-throughput kinetic analysis of hundreds of proteins at once. Within a few minutes users can install SPOC biosensors and screen for interaction kinetics to hundreds and later thousands of proteins of interest with the possibility to regenerate the sensor surface for repeated screening and analysis