Question

There are two main methods to get proteins into a gas phase for mass spectroscopy: electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI). Place the appropriate description of each ionization method in the appropriate space.

- Can be used for proteins or peptides that have been treated with proteases like trypsin

- Ionization evaporates solvent, leaving peptide in gas phase to travel through the separating mass spectrometer.

- Uses mass-to-charge (m/z) ratio to determine molecular mass

- Degrades and charges the peptide with high voltage

- Proteins or peptides are mixed in a solid matrix rather than a solution.

- Is based on the mass and acceleration though a chamber ending in a detector

- Laser will be absorbed by the peptide containing material releasing the peptide into the gas phase.

- Sample becomes ionized due to high voltage.

- Peptides become fragmented and charged due to laser exposure.


Which are ESI, MALDI or BOTH?

Answer 1

ESI method-

-Ionization evaporates solvent, leaving peptide in gas phase to travel through the separating mass spectrometer.

- Degrades and charges the peptide with high voltage.

- Sample becomes ionized due to high voltage.

MALDI Method-

-Proteins or peptides are mixed in a solid matrix rather than a solution.

- Laser will be absorbed by the peptide containing material releasing the peptide into the gas phase.

- Peptide becomes fragmented and charged due to Laser exposure.

Both methods-

- Can be used for proteins or peptides that have been treated with proteases like trypsin.

- Uses mass to charge (m/z) ratio to determine molecular mass.

- Is based on the mass and acceleration through a chamber ending in a detector.