Scanning SWATH Offset Windows for Higher Precursor m/z Resolution
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Solution Overview
Problem
The resolution of scanning SWATH tandem mass spectrometry measurements in the precursor ion m/z dimension is limited by the speed of the precursor ion mass filter, leading to reduced fidelity and definition of peak assignment, making it difficult to identify the precursor ions responsible for product ions.
Innovation Solution
The method involves offsetting multiple scanning SWATH scans during each time cycle and applying a linear reconstruction algorithm, such as the Drizzle algorithm, to enhance the resolution of product ion intensities as a function of precursor ion m/z, allowing for more accurate deconvolution of product ions and improved data quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the precursor ion mass filter speed is increased to improve productivity, then the resolution and definition of precursor ion m/z measurements deteriorate
Solution Approach 1:
The precursor ion mass range is divided into multiple overlapping windows that are scanned sequentially. Each window is processed separately and then combined through deconvolution algorithms, allowing the system to achieve high resolution measurements without requiring the entire mass range to be scanned at once at high speed.
Solution Approach 2:
The patent introduces a temporal dimension to the mass filtering process by performing multiple scans with different offset positions. Instead of relying solely on the speed of a single mass filter scan, the system uses multiple slower scans at different positions and combines them computationally, effectively trading scan speed for measurement precision through dimensional expansion.
2Measurement precision
If the number of data points across the precursor ion mass range is increased to improve measurement precision, then the time required for scanning increases
Solution Approach 1:
Multiple scans with different offset positions are performed in advance before the final data analysis. These preliminary scans capture data from different segments of the mass range, which are then combined through deconvolution to produce the high-resolution spectrum, avoiding the need for a single extremely long scan.
Solution Approach 2:
Data from multiple separate scans at different offset positions are merged and combined through deconvolution algorithms. This merging process reconstructs the complete high-resolution mass spectrum by integrating information from all the individual scans, achieving high data point density without proportionally increasing total scan time.
3Adaptability or versatility
If the precursor ion mass selection window is scanned across the mass range to improve adaptability, then the definition of precursor ion m/z responsible for product ions deteriorates
Solution Approach 1:
The mass range is segmented into multiple overlapping selection windows, each scanned separately with high precision. The segmentation allows each individual window to be measured with sufficient definition while collectively covering the entire mass range, resolving the conflict between broad coverage and precise definition.
Solution Approach 2:
Deconvolution algorithms serve as an intermediary process that takes the scanned data from multiple windows and reconstructs the precise precursor ion m/z assignments. This computational intermediary recovers the lost definition information by analyzing the product ion patterns across the different scanned windows.
Data Source
AI summary
During each time cycle, a precursor ion transmission window is stepped in k overlapping steps that are Δm m/z apart entirely across a mass range from a starting mlm/z. The window is stepped n−1 more times starting at n−1 different offsets from ml between ml and ml+Δm. A total of n scans of the mass range. A total of k×n product ion spectra are produced that are a function of precursor ion m/z for each time cycle. A product ion is selected from the spectra. For at least one time cycle, an intensity of the product ion as a function of precursor ion m/z is reconstructed with a resolving power greater than Δm by combining intensities of the product ion measured during each of the n scans using a linear reconstruction algorithm, such as Drizzle.