Charge-State Ion Separation for Reduced Peak Overlap in Top-Down MS
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Solution Overview
Problem
In top-down mass spectrometry protein analysis, extensive overlap of mass or mass-to-charge peaks hinders sequence coverage of large proteins, as even high-resolution mass spectrometers fail to deconvolve these overlaps, and existing methods using multiple TDC detectors are inefficient and require additional processing.
Innovation Solution
A system and method utilizing a single electron multiplier ADC detector to separate ions into multiple mass spectra based on charge state by detecting ion pulses, calculating peaks, and storing them in different data sets corresponding to predetermined intensity ranges, ensuring accurate peak positioning and reducing overlap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple TDC detectors are used to separate ions by charge state, then peak overlap is reduced, but device complexity and processing requirements increase
Solution Approach 1:
The patent combines multiple detector functions into a single TDC detector by using multiple CFD devices with different discriminator levels. This single detector system processes all ions simultaneously, eliminating the need for multiple separate TDC detectors while maintaining the ability to separate ions by charge state through digital subtraction of spectra obtained at different CFD levels.
Solution Approach 2:
The single TDC detector is made multi-functional by configuring it with multiple CFD devices operating at different discriminator levels. This allows one detector to perform the work of multiple detectors by capturing ion signals at different intensity thresholds and processing them through digital subtraction to isolate specific charge states.
2Measurement precision
If higher mass resolution is used to reduce peak overlap, then measurement precision improves, but productivity and analysis time decrease
Solution Approach 1:
Instead of changing the mass spectrometer's resolution parameter, the patent changes the detection parameter by using multiple CFD discriminator levels. This allows charge state separation through digital processing of data collected at a single resolution setting, maintaining analysis speed while improving peak separation through computational methods rather than instrumental resolution increases.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively separates ions by charge state, reducing peak overlap and maintaining accurate peak positions, thereby improving sequence coverage in top-down protein analysis.
Implementation Method 1
In conventional electron multiplier detectors, the number of primary electrons generated depends on the charge state of the incident ions (highly charged ions generate more primary electrons, hence a more intense electron signal)
Data Source
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AI summary
Intensity measurements made by electron multiplier and image-charge detectors are proportional to charge state. These intensities are used to separate detected ions into different data sets and create mass spectra from the different data sets. Ion measurements are separated by charge state using (i) a single electron multiplier detector, (ii) a single image-charge detector, or (iii) multiple electron multiplier ADC detectors. Using (i), the intensity of a peak calculated from each measured pulse is compared to predetermined intensity ranges and each peak is stored in a corresponding data set. Using (ii), each measured transient time-domain signal is converted to frequency-domain peaks, the intensity of each frequency-domain peak is compared to predetermined intensity ranges, and each peak is stored in a corresponding data set. Using (iii), each detector is adapted to measure a predetermined intensity range and store calculated peaks from the measured pulses in corresponding data sets.