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• A saturated matrix solution is prepared in ACN-H20 or MeOH-H2O
• A droplet (0.5 uL) is deposited on the MALDI target
• The same volume of analyte solution is deposited onto the either dried or wet matrix drop
• Molar ratios of matrix:analyte are usually > 1000.
• The sample is allowed to dry and is ready for MALDI-TOF analysis
Detection of hemoglobin mutant (beta79D-E) by MALDI-MS
normal
Hb Miyazonomutation
Y. Wada, J. Chromatrogr. B 781, 2002, 291.
MALDI-MS can analyze mixtures of smaller molecules,
e.g. standard peptides. (M+H)+ ions are observed.
Bradykinin
Angiotensin II
Substance P
Angiotensin I
Bombesin
ACTH 1-17
ACTH 18-39
Exact mass: 952.5098
High resolution (10000)
Monoisotopic peak
C = 12.000
H = 1.007825
N = 14.003074
O = 15.9949146
S = 31.972071
Advantages:
More tolerant to impurities than electrospray
Allows solid samples to be stored and reprocessed
Direct mass measurement (single charging) due to TOF analyzer
Good for non volatile, thermolabile and high MW compounds
Mixture analysis possible
Disadvantages:
Dry plate does not allow interfacing with liquid flow technique
Very high vacuum required (10-7 torr)
Quantitation difficult due to surface roughness
Very little fragmentation