Protein analysis using capillary electrophoresis coupled to mass spectrometry through vibrating sharp-edge spray...

Area of Science:

• Analytical Chemistry
• Biochemistry
• Separation Science

Background:

• Capillary electrophoresis (CE) coupled with mass spectrometry (MS) typically requires acidic additives or organic solvents for ionization.
• Vibrating sharp-edge spray ionization (VSSI) is a voltage-free alternative for CE-MS interfacing, eliminating the need for such additives.
• This makes VSSI particularly attractive for sensitive protein analyses.

Purpose of the Study:

• To evaluate the efficacy of CE-VSSI for protein separation and detection without traditional ionization additives.
• To explore strategies for overcoming non-specific protein adsorption in capillary electrophoresis.
• To demonstrate the sensitivity and applicability of CE-VSSI for analyzing diverse protein types.

Main Methods:

• Capillary electrophoresis interfaced with vibrating sharp-edge spray ionization (CE-VSSI) was employed.
• Nanoflow sheath separations utilized low ionic strength aqueous solutions with serine to minimize suppression and adduction.
• Modified and unmodified fused silica capillaries were used to assess protein adsorption effects.

Main Results:

• Proteins were detected in the 2.5-10 µM range (0.1-1.2 ng injected mass).
• Anionic proteins were resolved on an unmodified capillary, while cationic proteins required acidic electrolytes or specialized coatings (lipid, zwitterionic, cationic) for effective separation.
• Separations were achieved within 6-15 minutes using coated capillaries, and a protein dimer was observed at 19 ng by adjusting MS inlet temperature.

Conclusions:

• CE-VSSI provides a viable, additive-free method for CE-MS protein analysis.
• Surface modification of capillaries is crucial for overcoming adsorption issues with cationic proteins.
• The VSSI interface demonstrates high sensitivity and adaptability for complex protein mixture analysis.