Solution additives that desalt protein ions in native mass spectrometry

Area of Science:

• Analytical Chemistry
• Biochemistry
• Mass Spectrometry

Background:

• Native electrospray ionization mass spectrometry (ESI-MS) is crucial for protein analysis.
• Salt presence, like sodium chloride, interferes with ESI-MS by reducing ion abundance and increasing adducts.
• This interference complicates the accurate analysis of proteins and protein complexes.

Purpose of the Study:

• To investigate methods for reducing sodium ion adduction in ESI-MS.
• To improve the performance of ESI-MS for analyzing proteins and protein complexes in the presence of salts.
• To present a simple, effective solution for enhancing protein signal in mass spectrometry.

Main Methods:

• Utilized solution additives such as ammonium bromide and ammonium iodide.
• Analyzed the effect of these additives on sodium ion adduction to proteins using ESI-MS.
• Quantified the increase in relative abundances of fully protonated molecular ions for ubiquitin.

Main Results:

• Ammonium bromide and ammonium iodide addition significantly reduced sodium ion adduction to proteins.
• For ubiquitin, a 72-fold and 56-fold increase in protonated molecular ions was observed with ammonium bromide and iodide, respectively.
• The effectiveness is linked to the low proton affinity (PA) of the additive anions.

Conclusions:

• Low proton affinity anions effectively reduce sodium ion adduction in ESI-MS.
• This method enhances protein and protein complex analysis without requiring experimental modifications.
• It offers a simple and attractive alternative to traditional desalting methods prior to mass spectrometry.