Charge-State Mass Spectra Separation for Peak Overlap Reduction
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Solution Overview
Problem
In top-down mass spectrometry protein analysis, the overlap of mass or mass-to-charge (m/z) peaks in a mass spectrum is significant, leading to loss of large product ions and limited sequence coverage, even with high-resolution mass spectrometers, due to the inability to effectively deconvolve heavily overlapped peaks.
Innovation Solution
The system and method involve using a single electron multiplier ADC detector, an image-charge detector, or multiple electron multiplier ADC detectors to separate ions into two or more mass spectra based on charge state by detecting pulses or transient time-domain signals, calculating peak intensities, and comparing them to predetermined ranges to create separate mass spectra, thereby reducing peak overlap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-resolution mass spectrometers (FT-ICR or orbitrap) are used, then mass resolution is improved, but peak overlap cannot be fully resolved due to extensive overlapping of product ion peaks with different charge states
Solution Approach 1:
The patent segments the single mass spectrum into multiple charge-state-specific mass spectra by detecting ion pulses with different intensities. Electron multiplier detectors measure ion pulse intensities that correlate with charge states, allowing separation of overlapping peaks from ions with different charge states into distinct spectra. This segmentation resolves the peak overlap problem that cannot be solved by resolution alone.
Solution Approach 2:
The patent changes the detection parameter from单一的m/z ratio to include ion pulse intensity as an additional dimension for separation. By utilizing the intensity information from electron multiplier detectors that correlates with ion charge state, the system creates multiple spectra differentiated by charge state, effectively resolving overlaps that persist even at high mass resolution.
2Loss of information
If a single electron multiplier ADC detector is used to separate ions by charge state based on pulse intensity, then peak overlap is reduced, but the system complexity increases compared to conventional single-spectrum acquisition
Solution Approach 1:
The patent introduces an intermediary processing step where the ADC detector converts analog ion pulse signals into digital data that can be sorted by intensity. This intermediary digital representation allows flexible post-acquisition separation of ions into charge-state-specific groups without requiring complex hardware modifications, resolving peak overlap through software-based classification of the digitalized signal intensities.
3Measurement precision
If multiple electron multiplier ADC detectors measuring different intensity ranges are used, then charge state separation is improved, but the device complexity and cost increase
Solution Approach 1:
The patent implements partial separation by using a single ADC detector to capture the full intensity range, then applying software-based thresholding to create multiple charge-state-specific spectra. This partial action approach achieves effective charge state separation without the excessive complexity of multiple physical detectors, as the single detector's full-range measurements can be computationally divided into separate charge state groups.
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 reduces peak overlap, allowing for better separation and analysis of ions with different charge states, improving sequence coverage and data accuracy in mass spectrometry, especially 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)
Implementation Method 2
a mass analyzer of a mass spectrometer is instructed to detect a pulse for each ion impacting an electron multiplier ADC detector from a plurality of ions that are transmitted to the mass analyzer by the mass spectrometer
Data Source
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.