Delayed Desorption Improves Protein Analysis by Desorption Electrospray Ionization Mass Spectrometry

Area of Science:

• Analytical Chemistry
• Biochemistry
• Mass Spectrometry

Background:

• Desorption electrospray ionization mass spectrometry (DESI-MS) faces sensitivity limitations with increasing protein molecular weight.
• Incomplete sample dissolution is a key factor hindering the detection of larger proteins in DESI-MS.

Purpose of the Study:

• To develop a novel two-step DESI-MS configuration to improve the analysis of larger proteins.
• To investigate the impact of increased dissolution time and multi-solvent application on protein detection sensitivity.

Main Methods:

• A unique two-step DESI-MS approach was developed, incorporating a prewetting solvent applied by a wetting quill proximal to the analysis.
• The system was optimized using a protein mixture (cytochrome c, myoglobin, chymotrypsinogen) and then applied to larger proteins like bovine serum albumin and goat serum.
• The effects of different solvent combinations, including acetonitrile with formic acid and ammonium bicarbonate, were evaluated.

Main Results:

• The two-step method significantly improved the detection of larger proteins, such as bovine serum albumin.
• Direct detection of albumin and other serum proteins from diluted goat serum was achieved.
• Specific solvent combinations enhanced the intensity of certain proteins (e.g., chymotrypsinogen) and facilitated adduct removal.

Conclusions:

• The developed two-step DESI-MS technique effectively increases dissolution times and enhances the detection of larger proteins.
• This method allows for the use of multiple solvents, offering synergistic effects and improved analytical outcomes.
• The findings present a promising advancement for sensitive protein analysis using DESI-MS, particularly for complex biological samples.