Kinetic determinations of molecular interactions using Biacore--minimum data requirements for efficient experimental design

Reliable kinetic estimates can be obtained from significantly less data than is commonly used today, particularly in the characterization of 1:1 interactions involving low molecular weight compounds and proteins. We have designed a rational and cost-effective strategy to determine kinetic constants using Biacore's surface plasmon resonance-based biosensors and show that the number of measurements necessary for accurate kinetic determinations can be greatly reduced, increasing sample throughput and saving sample material. Simulated and measured data for a range of possible 1:1 interactants were studied to find the minimum requirements of a data set for kinetic analysis. The results showed that kinetic constants in the region 10(4) < k(a) < 10(7) M(-1) s(-1) (association) and 10(-4) < k(d) < 10(-1) s(-1) (dissociation) could easily be determined in a 1:1 interaction model. Owing to the information-dense nature of Biacore data, only two sample concentrations were necessary to reliably determine the kinetics. A standard sample concentration series consisting of 10-fold dilutions between approximately 10 microM and approximately 1 nM consistently provided at least two concentrations with sufficient information about the interaction in this region. Determinations of the constants became increasingly unreliable outside this region. If the rate constants prove to be outside the specified region or the data fits poorly to the 1:1-MTL model, more experiments are required. General recommendations for the design of a cost-effective assay to deliver reliable kinetic measurements are provided.