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Title: Desorption electrospray ionization-mass spectrometry of proteins

Author
item SHIN, YONG-SEUNG - UNIVERSITY OF WYOMING
item Drolet, Barbara
item Mayer, Richard
item DOLENCE, KURT - UNIVERSITY OF WYOMING
item BASILE, FRANCO - UNIVERSITY OF WYOMING

Submitted to: Analytical Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2007
Publication Date: 5/1/2007
Citation: Shin, Y., Drolet, B.S., Mayer, R.T., Dolence, K., Basile, F. 2007. Desorption electrospray ionization-mass spectrometry of proteins. Analytical Chemistry. 79:3514-3518.

Interpretive Summary: There is a need to improve diagnostic/detection methods for microbes that might pose a threat to human, animal, and plant health. Early detection of pathogenic microorganisms by detecting their proteins can minimize the health hazards and spread of diseases. Desorption electrospray ionization-mass spectrometry (DESI-MS) was evaluated for the detection of proteins ranging in molecular mass from 12 to 66 kDa. Parameters were optimized for protein detection. Detection limits were obtained for all protein standards, and they were found to decrease with decreasing protein molecular mass. In this study, DESI-MS proved to be a rapid and robust method for accurate MW determination for proteins up to 17 kDa under ambient conditions. Finally, we demonstrated the DESI-MS detection of the bacteriophage MS2 capsid protein from crude samples with minimal sample preparation.

Technical Abstract: Desorption electrospray ionization-mass spectrometry (DESI-MS) was evaluated for the detection of proteins ranging in molecular mass from 12 to 66 kDa. Proteins were uniformly deposited on a solid surface without pretreatment and analyzed with a DESI source coupled to a quadrupole ion trap mass spectrometer. DESI-MS parameters optimized for protein detection included solvent flow rate, temperature of heated capillary tube, incident and reflection angle, sheath gas pressure, and ESI voltage. Detection limits were obtained for all protein standards, and they were found to decrease with decreasing protein molecular mass: for cytochrome c (12.3 kDa) and lysozyme (14.3 kDa) a detection limit of 4 ng/mm2 was obtained; for apomyoglobin (16.9 kDa) 20 ng/mm2; for â-lactoglobulin B (18.2 kDa) 50 ng/mm2; and for chymotrypsinogen A (25.6 kDa) 100 ng/mm2. The DESI-MS analysis of higher molecular mass proteins such as ovalbumin (44.4 kDa) and bovine serum albumin (66.4 kDa) yielded mass spectra of low signal-to-noise ratio, making their detection and molecular weight determination difficult. In this study, DESI-MS proved to be a rapid and robust method for accurate MW determination for proteins up to 17 kDa under ambient conditions. Finally, we demonstrated the DESI-MS detection of the bacteriophage MS2 capsid protein from crude samples with minimal sample preparation.