A-CHCA

Fig. 10.14. MALDI spectra of protein extracts from Bacillus species (matrix a-CHCA). (a) B. anthracis (Sterne), (b) B. thuringiensis (4A1), (c) B. cereus (6E1), (d) B. sub-...

NC-C=CH-COOH a-Cyano- 4-hydroxy- cinnamic acid (a-CHCA) 337 nm 355 nm peptides, proteins, oligosaccharides... 

Traditional methods to generate peptide maps involve fractionation of complex mixtures of peptides in a protein digest either with one-dimensional SDS-PAGE or RP-HPLC [28,29]. The mass spectrometry peptide-mapping protocol, in principle, is similar to these techniques, but it provides an added dimension of structure-specific data (i.e., the molecular mass). MALDI-MS [30,31], ESl-MS [32], LC/ESI-MS [33], and CE/ESI-MS [34] have currently replaced the traditional biochemical approaches. MALDI allows the direct analysis of unfractionated protein digests. The commonly used matrices are sinapinic acid, a-cyano-4-hydroxy cinnamic acid (a-CHCA), and 2,5-dihydroxybenzoic acid (DHB). 

FIGURE 3.4 An example of the severe ion suppression effect on the tissue surface. A peptide solution (0.5 pL of 100 nM ACTH) was spotted on both ITO glass slide smface and brain-homogenate section. After the spraying of matrix solution (10 mg/mL a-cyano-4-hydroxycinnamic add [a-CHCA] 50% acetonitrile, 0.1% TFA), the spotted peptide was visuaUzed by IMS. 

The heterogeneous nature of the MALDl matrix as well as the imeven analyte distribution within it have been identified as one of the major somces of variance in signal strength between spots of a single MALDl sample preparation. The effect of this uneven distribution on the variance of MALDl mass spectral profiles of bacteria was quantified by using a spray-based method to homogeneously deposits, coli samples (suspended in a CHCA matrix solution) onto the MALDl plate (Fig. 2.6) (Toh-Boyo et al. 2012). 

Matrices sinapinic acid and a-cyano-4-hydroxycinnamic acid (a-CHCA). 

Ozo-isooapronsiuie-atbylester 3, 689. a-Chca.i8ocapron8 uEa-atbyle3tei 3, 600. MethylathylbreiutraubeiuaiiinAthyleater 3. 690. 

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