ABSTRACT
Experimental results from equimolar PEG and protein standards samples are presented from a MALDI-TOF mass spectrometer equipped with both ionizing detectors and the novel single molecule sensitive cryodetectors. The data are consistent with a model hypothesis suggesting that the observed decrease in signal strength in conventional ionizing detector MALDI-TOF mass spectrometers can be explained by the exponentially decreasing quantum efficiency of ionizing detectors. Cryodetectors, in contrast, have a mass independent detection efficiency of 100% on impact and provide additional information on the molecule state owing to the calorimetric nature of the detection mechanism.
Subject(s)
Proteome/isolation & purification , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/methods , Aluminum , Calorimetry , Polyethylene Glycols/chemistry , Polyethylene Glycols/isolation & purification , Polyethylene Glycols/standards , Proteome/chemistry , Proteome/standards , Reference Standards , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/instrumentationABSTRACT
Time-of-flight mass spectrometry-most notably matrix-assisted laser-desorption-ionization time-of-flight (MALDI-TOF) spectrometry-is an important class of techniques for the study of proteins and other biomolecules. Although these techniques provide excellent performance for masses up to about 20,000 daltons, there has been limited success in achieving good mass resolution at higher masses. This is because the sensitivity of the microchannel plate (MCP) detectors used in most systems decreases rapidly with increasing particle mass, limiting the utility of MCP detectors for very large masses. It has recently been proposed that cryogenic particle detectors may provide a solution to these difficulties. Cryogenic detectors measure the thermal energy deposited by the particle impact, and thus have a sensitivity that is largely independent of particle mass. Recent experiments have demonstrated the sensitivity of cryogenic particle detectors to single biomolecules, a quantum efficiency several orders of magnitude larger than the MCP detectors, and sensitivity to masses as large as 750,000 daltons. Here we present results demonstrating an order of magnitude better energy resolution than previous measurements, allowing direct determination of particle charge state during acceleration. Although application of these detectors to practical mass spectrometry will require further development of the detectors and cryogenics, these detectors can be used to elucidate the performance-limiting processes that occur in such systems.
