Submitted to: American Society for Mass Spectrometry
Publication Type: Abstract Only
Publication Acceptance Date: May 25, 2006
Publication Date: July 20, 2006
Citation: Shin, Y., Drolet, B.S., Mayer, R.T., Dolence, K., Basile, F. 2006. Detection of intact proteins with desi-ms: application to microorganism biomarker detection. American Society for Mass Spectrometry.
Interpretive Summary: Since the introduction of desorption electrospray ionization-mass spectrometry (DESI-MS), this technique has been applied to the analysis of explosives, pharmaceutical tablets, plant tissues, fruits, whole tissue1 and thin layer chromatography plates2. DESI-MS has shown high sensitivity, low detection limits and more importantly short analysis time as minimum to no sample preparation is required 3. Our laboratory is currently investigating the ability of DESI-MS for the detection of viral capsid proteins and other microbial biomarkers with minimal or no sample pre-processing steps. However, very limited attention has been placed on the detection of intact proteins. In this work, we conducted fundamental investigations of the various DESI-parameters with standard proteins prior to extending this work to the detection of microorganisms with DESI-MS.
DESI-MS was evaluated with proteins that range in molecular weight from 12 KDa to 66 KDa. Lyophilized protein samples were rehydrated with water, deposited on Plexiglas, and dried. In some experiments buckminsterfullerene (bucky ball, C60) was used as an additive to the nebulizing gas. Optimized conditions were 50% methanol-H2O with 0.1% acetic acidspray solvent, solvent flow 7 mL/min, sheath gas back pressure 250 psi, ESI voltage 6 kV, capillary tube temperature 325°C, incident angle 60°, and reflect angle of 10°. Detection limits of 2 ng/mm2 were obtained for cytochrome c (12.3 kDa) and lysozyme C (14.3 KDa). Detection limits for other proteins at these conditions were as follows: apomyoglobin (16.9 KDa) 10 ng/mm2 , B-lactoglubulin B (18.2 KDa) 50 10 ng/mm2, chymotrypsinogen A (25.6 KDa) 100 10 ng/mm2, chicken albumin (44.4 KDa) 2 mg/mm2, and bovine serum albumin (66.4 KDa) 2 mg/mm2. Use of C60 particles in the nebulizing gas increased signal intensity of DESI-MS by ca. 60% relative to the DESI-signal with no-C60 particles.