Binding Affinity

Understanding binding affinity is key to the appreciation of the intermolecular interactions driving biological processes, structural biology, and structure-function relationships. It is also measured as part of the drug discovery process to help design drugs that bind their targets selectively and specifically.

What is Binding Affinity?

Binding affinity is the strength of the binding interaction between a single biomolecule (e.g. protein or DNA) to its ligand/binding partner (e.g. drug or inhibitor). Binding affinity is typically measured and reported by the equilibrium dissociation constant (KD), which is used to evaluate and rank order strengths of bimolecular interactions. The smaller the KD value, the greater the binding affinity of the ligand for its target. The larger the KD value, the more weakly the target molecule and ligand are attracted to and bind to one another.

Binding affinity is influenced by non-covalent intermolecular interactions such as hydrogen bonding, electrostatic interactions, hydrophobic and Van der Waals forces between the two molecules. In addition, the binding affinity between a ligand and its target molecule may be affected by the presence of other molecules.

Why should I measure binding affinity for my application?

Whenever you are characterizing proteins, nucleic acids, and any biomolecule, understanding the binding affinity to substrates, inhibitors, and cofactors is key to the appreciation of the intermolecular interactions driving biological processes, structural biology, and structure-function relationships.

For drug discovery, binding affinity is also measured as to rank order hits binding to the target and help design drugs that bind their targets selectively and specifically.

There are many ways to measure binding affinity and dissociation constants, such as ELISAs, gel-shift assays, pull-down assays, equilibrium dialysis, analytical ultracentrifugation, surface plasmon resonance, and spectroscopic assays.

What binding affinity solutions does Malvern Panalytical offer?

Malvern Panalytical offers Isothermal Titration Calorimetry (ITC), which is a direct, label-free analytical technique that measures the binding affinity between any two molecules that interact with each other, such as a protein and a ligand. ITC measures the heat change associated with the binding event and is considered the “Gold Standard” of interaction analysis as it enables the study of a broad range of interactions and delivers highly quantitative KD values.

ITC measures KD values in the millimolar to the nanomolar range and determines the binding stoichiometry and binding thermodynamics of the interaction, which are also important in the characterization of intermolecular interactions.

The advantages of using ITC, compared to other binding assays, are:

· All binding interactions have an enthalpy change – heat is either released or absorbed

· ITC can be used to characterize simple 1:1 binding, and complex multiple binding events.

· Versatility – ITC can be performed with any samples, in most buffers between pH2-12

· Non-optical and non-spectroscopic

· No labeling – can use native molecules

· In solution – no immobilization needed

· Non-destructive – can recover sample after the binding experiment

· Minimal assay development

Why should I choose a Malvern Panalytical ITC product?

The MicroCal PEAQ-ITC is the latest isothermal titration calorimeter from Malvern Panalytical and is designed for performance and quality, with guided workflows, experimental design software, and a fully integrated wash module for consistently high-quality data. The MicroCal PEAQ-ITC has a 200 µL cell volume for minimal consumption of precious samples. The reaction cell is made with Hastelloy, which is non-reactive and easy to clean. The heat detection is sensitive for expert measurement of nanomolar KD values. The PEAQ-ITC comes with robust, rapid, and non-subjective data analysis software and can be automated for increased productivity.