For label-free and real-time affinity measurements, Creative Biolabs provides advanced Surface Plasmon Resonance (SPR) and Bio-Layer Interferometry (BLI) services based on Biacore, ProteOn and Octet systems. Our strong expertise and extensive experience can provide high-quality services of affinity and kinetics measurement for small molecules (molecular weight lower than 1000 D), which can satisfy your different demands.
High-throughput small molecules screening has been proved to be important in clinical development (such as diagnostics and therapeutics). The main challenge of small molecules screening is the low response level due to their small molecular sizes, which needs solvents to maintain the analyte solubility, and the rapid interactions between small molecules and candidates. To solve the low response level problem, sensor surface is prepared with high levels of ligand (usually 8,000 to 10,000 Response Units for an average-sized protein). For small molecules screening, samples are normally prepared with a fixed concentration in the same buffer because usually there is no opportunity to optimize buffer conditions or concentration.The main experimental conditions for small molecules affinity measurement and screening include:
There are two paths to evaluate the small molecules affinity: First, the binding responses are compared for analyte molecular weight, and a cut-off level is set. The cut-off can be determined by comparison with the response obtained from known non-binders (negative controls) or set to some level chosen in relation to the distribution of response values. Second, kinetic properties are compared to plot the association rate constant (Ka) against the dissociation rate constant (Kd) on logarithmic axis. Diagonal lines in this plot represent constant affinity, so the compounds that underlying on the same diagonal but separated from each other have the same affinity but different kinetics.
Figure 1. The affinity analysis is represented by diagonal lines. Compounds on the same diagonal have the same affinity but differ in kinetics. (Biacore Assay Handbook)Our custom affinity measurement services for small molecules can achieve: