Optimizing separation conditions for proteins and peptides using imaged capillary isoelectric focusing

Area of Science:

• Biochemistry
• Analytical Chemistry
• Protein Science

Background:

• Automated imaged capillary isoelectric focusing (imaged cIEF) offers advanced protein analysis capabilities.
• Optimizing separation conditions is crucial for maximizing the potential of imaged cIEF.
• Reproducibility and stability of capillary coatings are key factors in reliable cIEF separations.

Purpose of the Study:

• To optimize separation conditions for antibodies, glycoproteins, and peptides using imaged cIEF.
• To evaluate the performance and longevity of different capillary coatings for cIEF.
• To establish methods for preventing protein precipitation and enhancing solubility during imaged cIEF analysis.

Main Methods:

• Optimization of buffer compositions and voltage gradients for imaged cIEF.
• Testing of polyacrylamide and fluorocarbon capillary coatings for reproducibility and durability (>100 runs).
• Addition of salts (up to 30 mM Na+), urea (up to 6 M), and glycerol (up to 20%) to improve protein solubility and prevent precipitation.

Main Results:

• Polyacrylamide and fluorocarbon coatings demonstrated reproducible and durable performance in cIEF.
• Addition of salts, urea, and glycerol effectively prevented protein precipitation and enhanced solubility.
• A voltage gradient successfully mitigated high current issues at the start of focusing for salt-containing samples.
• Imaged cIEF was successfully applied for the quantitation of monoclonal antibodies.

Conclusions:

• Optimized imaged cIEF conditions significantly enhance the analysis of antibodies, glycoproteins, and peptides.
• The chosen capillary coatings provide reliable and long-lasting performance for cIEF.
• Strategies for managing protein solubility and precipitation are effective, enabling accurate quantitation, particularly for monoclonal antibodies.