Matrix optimization for matrix-assisted laser desorption/ionization mass spectrometry of oligosaccharides from human milk.
Neutral and acidic oligosaccharides from human milk were analyzed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI/MS). These experiments require suitable matrices; their selection and particularly their preparation protocols must be optimized. Important criteria are sensitivity, reproducibility, tolerance against impurities and resolution over a wide mass range. For analytical investigations of these oligosaccharides, containing labile fucosylated and sialylated components, another property of a matrix becomes a significant factor, namely the influence on ion stability and the extent of (metastable) fragmentation. The experience gained with the MALDI/MS of neutral and acidic oligosaccharides is summarized taking into account different intentions of measurement and typical problems, such as impurities after enzymatic treatment. For a rapid screening of an oligosaccharide sample, superior results were obtained with a new preparation technique using 5-chloro-2-mercaptobenzothiazole (CMBT) as the first layer for 2,5-dihydroxybenzoic acid. For structural analysis by post-source decay, CMBT as the first layer for 3-aminoquinoline is a favoured preparation protocol, because extensive fragmentation is achieved. For acidic oligosaccharides, a special preparation protocol makes it possible to determine the number of sialic acids by inducing highly effective cationization. Matrix-assisted laser desorption/ionization mass spectrometry; matrices; oligosaccharides; post-source decay.
Pfenninger
A
A
Division of Instrumental Analytical Chemistry, Johann Wolfgang Goethe University, Frankfurt/Main, Germany.
Karas
M
M
Finke
B
B
Stahl
B
B
Sawatzki
G
G
D005841:Gentisates; D006801:Humans; D062385:Hydroxybenzoates / Q000378:metabolism; D008895:Milk, Human / Q000737:chemistry*; D009844:Oligosaccharides / Q000032:analysis*; D011804:Quinolines / Q000378:metabolism; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012794:Sialic Acids / Q000032:analysis; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013844:Thiazoles / Q000378:metabolism
D005841:Gentisates; D062385:Hydroxybenzoates; D009844:Oligosaccharides; D011804:Quinolines; D012794:Sialic Acids; D013844:Thiazoles; C010925:2,5-dihydroxybenzoic acid