Which of the following methods first ionizes a protein before separation and detection?
Which of the following methods first ionizes a protein before separation and detection?
Select an option to attempt
Correct Answer: Option C
Explanation
Mass spectrometry (MS) is the only method listed that requires IONISATION of the analyte before analysis. In protein MS: Electrospray Ionisation (ESI) — spray of protein solution through high-voltage needle creates multiply-charged ions () at atmospheric pressure, ideal for coupling with LC (LC-MS/MS). Matrix-Assisted Laser Desorption/Ionisation (MALDI) — protein co-crystallised with UV-absorbing matrix, laser pulse causes desorption and ionisation. Ions are then separated by mass-to-charge ratio () in the analyser (TOF, quadrupole, Orbitrap). NMR — exploits nuclear spin in magnetic fields (no ionisation). Reverse phase HPLC — separation by hydrophobicity (no ionisation). Fluorescence spectroscopy — excites fluorophores with light (no ionisation).