Simon Weidmann1 and Renato Zenobi1
- Department of Chemistry and Applied Biosciences, ETH Zürich, CH-8093, Zürich, Switzerland
With the development of special ion conversion dynode (ICD) detectors for high-mass matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), the mass-to-charge ratio is no longer a limiting factor. Although these detectors have been successfully used in the past, there is lack of understanding of the basic processes in the detector. We present a systematic study to investigate the performance of such an ICD detector and separate the contributions of the MALDI process from the ones of the ion-to-secondary ion and the secondary ion-to-electron conversions. The performance was evaluated as a function of the voltages applied to the conversion dynodes and the sample amount utilized, and we found that the detector reflects the MALDI process correctly: limitations such as sensitivity or deviations from the expected signal intensity ratios originate from the MALDI process itself and not from the detector.
CovalX Technology Used (Click each option to learn more)
Protein concentrations were determined by UV/Vis absorption and then diluted to the desired concentration using PBS buffer (20 mM PBS, 100 mM NaCl).MBP and MBP3 were mixed in equimolar ratio in order to determine the relative response factor (Rrel). Protein solutions were then mixed with the matrix (sinapic acid (10 mg/mL in water: ACN:TFA (49.95:49.95:0.1; v/v/v)) and 0.5 μL of the final mixture was spotted onto a stainless steel MALDI plate before crystallization in ambient temperatures. The crystallized samples were placed in a MALDI mass spectrometer that had been modified with the CovalX HM2 detection system for analysis. Through this analysis, it was determined that ICD detectors are correct in their reflection of ion intensity generated because it matched that of the MALDI analysis.