Dynamic Precursor Isolation Windows for Mass Spectrometry Coverage
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Solution Overview
Problem
Current data-dependent acquisition methods in mass spectrometry are target-specific and limit MS/MS coverage, resulting in information gaps that hinder retrospective data mining and comprehensive protein profiling, particularly in translational/clinical research.
Innovation Solution
A method that varies precursor isolation windows based on MS1 precursor topology, allowing for dynamic selection of tandem mass spectral acquisition parameters to exhaustively sample the user-specified MS mass range, ensuring broader precursor m/z space coverage across chromatographic peaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If target-specific DDA methods are used with narrow isolation width, then MS/MS spectrum identification is improved, but MS/MS coverage and precursor mass range coverage are limited
Solution Approach 1:
The patent implements dynamic adjustment of isolation window width based on real-time precursor ion intensity. High-intensity precursors are isolated with narrow windows for high-quality spectra, while low-intensity precursors use wider windows to ensure sufficient ion transmission. This dynamic parameter adaptation resolves the contradiction between identification quality and coverage breadth.
Solution Approach 2:
The system changes the isolation window parameter dynamically during data-dependent acquisition based on precursor intensity thresholds. When precursor intensity exceeds a threshold, a narrow isolation window (e.g., 0.5 m/z) is applied for high-resolution identification; when below the threshold, a wider window (e.g., 2.0 m/z) is used to maintain adequate ion statistics, thereby achieving both precise identification and broad coverage.
2Ease of operation
If conventional DDA methods with static parameters are used, then automated real-time decisions are simplified, but information gaps remain that make retrospective data mining difficult
Solution Approach 1:
The patent applies partial DDA by selectively targeting only the most intense precursors in each cycle rather than attempting to analyze all detected ions. This partial action approach ensures high-quality spectra for key analytes while maintaining adequate sampling across the full mass range, reducing information gaps without overwhelming the system complexity.
Solution Approach 2:
The system performs multiple sequential DDA cycles across the chromatographic peak, continuously acquiring MS/MS spectra as precursors elute. This continuous sampling ensures that information is captured throughout the entire peak width, eliminating gaps that would occur with single-cycle approaches and enabling comprehensive retrospective analysis.
3Measurement precision
If narrow isolation width is used for targeted precursors, then identification quality is improved, but the number of precursors that can be analyzed per cycle is reduced
Solution Approach 1:
The patent applies different isolation window widths to different precursors based on their local characteristics (intensity). High-intensity precursors receive narrow isolation windows for high-quality identification, while lower-intensity precursors are analyzed with wider windows. This localized quality adjustment maintains identification quality for key analytes while increasing overall precursor throughput.
Data Source
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AI summary
A variable data dependent acquisition/dynamic exclusion (vDDA/DE) method selects target m/z range utilizing a MS1 precursor topography map over the most recently acquired MS spectrum to identify the precursor m/z values and MS/MS acquisition parameters to improve the selection of the next data-dependent MS/MS acquisition. The topography used to define the next set of DDA scan events is defined by previous tandem MS scan events defined by precursor quadrupole isolation windows as well as all detected compounds contained within the specific tandem MS events. At least some of the parameters used for MS/MS data acquisition are dynamic so as to exhaustively sample the user specified MS mass range with MS/MS information. These parameters include the quadrupole MS isolation width and symmetry around the targeted m/z value. Using this approach, a greater proportion of the precursor m/z space is effectively and efficiently sampled per chromatographic peak width.