Matrix-Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF) mass spectrometry is a powerful and widely used technique for rapid peptide analysis. Its simplicity, speed, and tolerance for sample impurities make it an invaluable tool in peptide research.
How MALDI-TOF Works
Sample Preparation
- The peptide sample is mixed with a UV-absorbing matrix compound (e.g., α-CHCA, DHB, or sinapinic acid)
- The mixture is applied to a metal target plate and allowed to crystallize
- Matrix crystals incorporate the peptide molecules
Ionization
- A pulsed UV laser strikes the matrix crystals
- The matrix absorbs the laser energy and rapidly heats
- Both matrix and peptide molecules are desorbed into the gas phase
- Proton transfer from the matrix ionizes the peptide molecules
Mass Analysis
- Ionized peptides are accelerated by an electric field
- They travel through a field-free flight tube
- Lighter ions arrive at the detector before heavier ones
- Time-of-flight is converted to mass-to-charge ratio
Advantages for Peptide Analysis
- Speed — analysis takes seconds per sample
- Simplicity — minimal sample preparation
- Salt tolerance — works with moderate salt concentrations
- Soft ionization — predominantly produces singly charged molecular ions
- Wide mass range — effectively covers 500 to >100,000 Da
Applications
Molecular Weight Confirmation
The primary use in peptide quality control — verifying that the synthesized peptide has the expected molecular weight.
Peptide Mapping
After enzymatic digestion, MALDI-TOF identifies the resulting peptide fragments, confirming protein/peptide identity.
Synthesis Monitoring
Checking intermediate products during solid-phase peptide synthesis to ensure coupling efficiency.
Purity Assessment
Detecting impurities such as deletion sequences, truncated products, or chemical modifications.
Limitations
- Limited quantitative capability compared to ESI-MS
- Matrix-related interference in the low mass range (<700 Da)
- Less suitable for LC coupling than ESI
The Evolve Aminos Approach
MALDI-TOF is integral to our quality control workflow. Every peptide batch undergoes MALDI-TOF analysis for molecular weight verification, providing rapid confirmation that the product matches its expected identity.