Charge detection mass spectrometry with resolved charge states

Area of Science:

• Analytical Chemistry
• Biophysical Chemistry
• Mass Spectrometry

Background:

• Charge detection mass spectrometry (CDMS) is crucial for analyzing large biomolecules.
• Improving signal-to-noise ratio (S/N) is key to enhancing CDMS sensitivity.
• Cryogenic cooling of JFETs can reduce thermal noise in sensitive electronic components.

Purpose of the Study:

• To enhance the sensitivity of CDMS using a cryogenically cooled JFET.
• To achieve a lower limit of charge detection for biomolecules.
• To accurately measure charge states of proteins like cytochrome c and alcohol dehydrogenase (ADH) monomer.

Main Methods:

• Utilized a modified cone trap with a cryogenically cooled JFET for CDMS.
• Performed measurements on cytochrome c and ADH monomer ions.
• Analyzed ion trapping stability and detection efficiency at various charge states.

Main Results:

• Achieved detection of single ions with as few as 9 elementary charges (e).
• Demonstrated high detection efficiency (approaching 95% for ions >13 e).
• Obtained a root mean square deviation of ~2.2 e for ADH monomer ions (32-43 charges).
• Successfully trapped ions for over 1500 cycles, limited by background gas collisions.

Conclusions:

• Cryogenic JFET cooling significantly improves CDMS S/N ratio and sensitivity.
• The enhanced CDMS system allows for accurate charge state determination of large proteins.
• This technique provides a foundation for more precise mass spectrometry analysis of biomolecular ions.