Slow-Equilibration Approximation in Kinetic Size Exclusion Chromatography

Area of Science:

• Biochemistry
• Analytical Chemistry
• Chemical Kinetics

Background:

• Kinetic size exclusion chromatography with mass spectrometry detection (KSEC-MS) is a label-free method for studying reversible protein-small molecule binding kinetics.
• Current data extraction from KSEC-MS chromatograms is complex due to limited separation of protein and complex, necessitating time-consuming numerical methods.

Purpose of the Study:

• To introduce the first non-numerical (analytical) approach for determining rate constants in protein-small molecule interactions using KSEC-MS data.
• To provide a simpler and faster tool for analytical scientists to process KSEC-MS data.

Main Methods:

• Development of an analytical method based on the slow-equilibration approximation.
• Application to KSEC-MS chromatograms exhibiting two distinct peaks.
• Error analysis to validate the approximation's accuracy.

Main Results:

• The proposed analytical approach offers a significant improvement over existing numerical methods for KSEC-MS data analysis.
• The slow-equilibration approximation ensures rate constant errors below 20% under typical conditions for specific interactions (e.g., receptor-ligand, protein-drug).
• The method is applicable when the ratio of characteristic separation to equilibration times is less than 0.1.

Conclusions:

• The developed analytical solution provides a rapid and straightforward tool for processing KSEC-MS data, facilitating the study of protein-small molecule binding kinetics.
• This analytical approach has the potential for adaptation to other kinetic-separation techniques, such as nonequilibrium capillary electrophoresis of equilibrium mixtures (NECEEM).