MALDI-TOF Mass Spectrometry
Matrix-assisted laser desorption/ionisation time-of-flight — a mass spectrometry technique particularly suited to peptide and protein analysis. MALDI-TOF provides rapid, accurate molecular weight determination and is widely used for quality control identity testing of synthetic peptides.
Technical Context
MALDI process: peptide sample mixed with UV-absorbing matrix (alpha-cyano-4-hydroxycinnamic acid — CHCA — is standard for peptides) → co-crystallised on a metal target plate → pulsed UV laser (337nm nitrogen laser or 355nm Nd:YAG) → matrix absorbs energy and vaporises, carrying analyte into gas phase as singly charged ions → ions accelerated through electric field → flight time through field-free drift tube is proportional to √(m/z) → detector measures arrival time. Advantages: rapid analysis (<1 minute per sample), tolerant of salts and buffers, produces primarily singly charged ions (simplifying spectra), and suitable for high-throughput screening. For peptide QC: measured mass is compared to theoretical mass calculated from the sequence. Mass accuracy of ±0.1 Da is typical for modern MALDI-TOF instruments. MALDI imaging MS can map peptide distribution in tissue sections — an emerging research tool.