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Matrix‐assisted ionization mass spectrometry in targeted protein analysis – An initial evaluation
Author(s) -
Skjærvø Øystein,
Trimpin Sarah,
Halvorsen Trine Grønhaug
Publication year - 2021
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.8437
Subject(s) - chemistry , mass spectrometry , analyte , chromatography , electrospray ionization , matrix (chemical analysis) , analytical chemistry (journal) , selected reaction monitoring , triple quadrupole mass spectrometer , ionization , sample preparation , tandem mass spectrometry , ion , organic chemistry
Rationale Matrix‐assisted ionization (MAI) is a relatively new ionization technique for analysis by mass spectrometry (MS). The technique is simple and has been shown to be less influenced by matrix effects than e.g. electrospray ionization (ESI). These features are of interest in the targeted analysis of proteins from biological samples. Methods Targeted protein determination by MAI‐MS was evaluated using a triple quadrupole mass analyzer equipped with a stripped nanoESI source in selected reaction monitoring (SRM) mode. The proteins were analyzed using the bottom‐up approach with stable isotopic labeled peptides as internal standards (IS). The MAI matrix was 3‐nitrobenzonitrile dissolved in acetonitrile. Aqueous sample and matrix solution were mixed in a 1:3 volume ratio. One microlitre of the dried matrix/analyte sample was introduced into the inlet of the mass spectrometer where ionization commences. Results SRM settings established for ESI‐SRM‐MS of the peptides here investigated were applicable in MAI‐SRM‐MS for all evaluated peptides except one that is poorly soluble in water. Addition of IS provided efficient correction at most levels (relative standard deviation (RSD) ≤28% (except lowest digest level), r 2 ≥ 0.995). This was also true for the more complex biological matrices, diluted urine (1:1; RSD = 20% a synthetic peptide, NLLGLIEAK) and diluted digested serum (1:100; RSD = 7% digested cytochrome C). Biological matrix influenced the signal intensity unless sufficiently diluted. Conclusions The results demonstrate that MAI‐SRM‐MS has promising potential in targeted protein determination by the bottom‐up approach because of its simplicity, ease of use, and speed. However, more data is needed to confirm the results prior to application in a clinical setting.