Direct analysis of sedimentation equilibrium distributions reflecting complex formation between dissimilar reactants

Area of Science:

• Biochemistry
• Physical Chemistry
• Macromolecular Science

Background:

• Characterizing complex formation between dissimilar macromolecules is crucial for understanding biological processes.
• Thermodynamic nonideality can complicate the analysis of macromolecular interactions.
• Sedimentation equilibrium is a powerful technique for studying molecular interactions in solution.

Purpose of the Study:

• To develop and illustrate direct analytical procedures for characterizing thermodynamically ideal complex formation between dissimilar macromolecular reactants.
• To apply these methods to study the electrostatic interaction between ovalbumin and cytochrome c.
• To demonstrate the analysis of sedimentation equilibrium distributions under various experimental conditions.

Main Methods:

• Direct analysis of sedimentation equilibrium distributions.
• Application of analytical procedures for systems with separate, single-constituent, or composite distributions.
• Utilizing electrostatic interactions between ovalbumin and cytochrome c as a model system.

Main Results:

• An association constant of 63,000 (+/- 2000) M⁻¹ was obtained for the 1:1 interaction between ovalbumin and cytochrome c.
• The developed procedures were successfully applied to different scenarios of available experimental data.
• The simplicity of the direct analytical procedures was highlighted.

Conclusions:

• Direct analysis of sedimentation equilibrium distributions provides a robust method for characterizing complex formation between dissimilar macromolecules.
• These procedures are adaptable to various experimental data availability, including single or composite distributions.
• The developed methods offer potential for incorporating thermodynamic nonideality in future studies of macromolecular interactions.