Fungal pigments inhibit the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis of darkly pigmented fungi
Section snippets
Reagents
Acetonitrile (high-performance liquid chromatography [HPLC] grade), sodium citrate, and hydrochloric acid (6 N) were acquired from Fisher Scientific (Fairlawn, NJ, USA). Tricyclazole was acquired from Wako Pure Chemical Industries (Osaka, Japan). Malt extract agar (MEA) was acquired from Difco (Sparks, MD, USA). Deionized water (DDI) was produced with a Synthesis A-10 system (Millipore, Billerica, MA, USA). All other reagents were acquired from Sigma–Aldrich (St. Louis, MO, USA), and all
Results and discussion
Darkly pigmented fungi, such as A. niger, yield poor fingerprint mass spectra that contain only a few peaks of low relative abundance (Fig. 1). It is hypothesized that the presence of photo- and chemoprotective pigments, such as melanin, in the cell wall may suppress ionization and ultimately the MALDI-based detection of expressed proteins in the sample. To test this hypothesis, we examined the effect of spiking synthetic melanin into standard protein and peptide solutions. We observed
Conclusions
The presence of fungal melanin in MALDI sample deposits suppressed peptide and protein ion signals during the acquisition of MALDI–TOF mass spectra. Suppression of standard peptide and protein signals was observed on the addition of both commercially available synthetic melanin and melanins purified from A. niger to the MALDI sample. Suppression of peptide and protein [M+H]+ ion signals was observed at melanin concentrations greater than 1250 ng/spot, a concentration significantly less than the
Acknowledgments
The authors thank Diane Schwegler-Berry for help with the preparation and analysis with FESEM. The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health. This work was supported in part by an interagency agreement with the National Institute of Environmental Health Sciences (Y1-ES0001-06).
References (33)
- et al.
Matrix-assisted ultraviolet laser desorption of non-volatile compounds
Int. J. Mass Spectrom. Ion Processes
(1987) - et al.
Discrimination of Aspergillus isolates at the species and strain level by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry fingerprinting
Anal. Biochem.
(2008) The new time-of-flight mass spectrometry
Anal. Chem.
(1999)- et al.
Laser desorption ionization of proteins with molecular masses exceeding 10,000 Da
Anal. Chem.
(1988) - et al.
Characterization of microorganisms by MALDI mass spectrometry
Methods Mol. Biol.
(2009) - et al.
Rapid identification and typing of Listeria species by matrix-assisted laser desorption ionization–time of flight mass spectrometry
Appl. Environ. Microbiol.
(2008) - et al.
Identification and discrimination of Staphylococcus aureus strains using matrix-assisted laser desorption/ionization–time of flight mass spectrometry
Proteomics
(2002) - et al.
Highly efficient classification and identification of human pathogenic bacteria by MALDI–TOF MS
Mol. Cell. Proteomics
(2008) - et al.
The rapid identification of intact microorganisms using mass spectrometry
Nat. Biotechnol.
(1996) - et al.
Rapid discrimination between methicillin-sensitive and methicillin-resistant Staphylococcus aureus by intact cell mass spectrometry
J. Med. Microbiol.
(2000)
Microorganism identification by mass spectrometry and protein database searches
Anal. Chem.
Identification of Bacillus spores by matrix-assisted laser desorption ionization–mass spectrometry
Appl. Environ. Microbiol.
Discrimination of intact mycobacteria at the strain level: a combined MALDI–TOF MS and biostatistical analysis
Proteomics
Rapid identification of bacteria by direct matrix-assisted laser desorption/ionization mass spectrometric analysis of whole cells
Rapid Commun. Mass Spectrom.
Detection of pathogenic and non-pathogenic bacteria by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry
Rapid Commun. Mass Spectrom.
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