Peptide Sequencing Data Analysis Using ETD Fragmentation Filtering
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Solution Overview
Problem
Current methods for peptide sequencing, particularly using non-ergodic techniques like ETD, face challenges in interpreting highly charged product ions from large peptides and proteins, leading to complex spectra and difficulties in determining charge states, which increases computational requirements and time for database searches.
Innovation Solution
The method involves identifying and disregarding less useful spectral data from ETD fragmentation, assigning candidate charges to useful data, and utilizing first and second-order ion products to reduce the comparison data subset, thereby improving peptide sequence database searching capabilities and reducing computational and storage demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If non-ergodic techniques like ETD are used for fragmentation, then sequence-specific fragment formation is improved, but spectral data complexity increases and charge state determination becomes more difficult
Solution Approach 1:
The patent segments the complex spectral data by identifying and separating first-order ion products from second-order ion products. This segmentation allows the system to focus analysis on the most informative fragment ions while filtering out complicating signals, thereby reducing spectral complexity while preserving sequence-specific information.
Solution Approach 2:
The patent applies preliminary charge state assignment to ion products before database searching. By determining candidate charge states in advance using the relationship between precursor and product ion charges, the system prepares simplified, pre-processed data that reduces complexity during subsequent analysis steps.
2Measurement precision
If charge state determination is performed for all product ions, then identification accuracy is improved, but computational time and resources increase
Solution Approach 1:
The patent extracts only the necessary information for charge state determination by focusing on the relationship between precursor ion charge and product ion charge. Instead of analyzing all spectral features, the system extracts the mass-to-charge ratios and applies charge state logic, significantly reducing computational requirements while maintaining identification accuracy.
Solution Approach 2:
The patent performs partial charge state determination by assigning candidate charge states to only those ion products that provide the most useful sequencing information. This partial action approach avoids the excessive computational burden of analyzing every possible ion while still achieving sufficient identification accuracy.
3Loss of information
If all spectral data from ETD is used for database searching, then completeness of analysis is improved, but storage requirements and processing time increase
Solution Approach 1:
The patent extracts and retains only first-order ion products and their corresponding candidate charge states for database searching, discarding second-order ion products and other less useful spectral data. This extraction process reduces data storage requirements while preserving the essential information needed for complete peptide identification.
Solution Approach 2:
The patent discards redundant and less useful spectral data (second-order ion products, ions with uncertain charge states) while recovering and prioritizing the most informative data (first-order ion products with assigned candidate charge states). This selective discarding and recovering reduces data volume while maintaining analytical completeness.
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 enables faster and more accurate peptide sequencing by reducing CPU time, storage needs, and improving confidence in precursor identification, while minimizing unnecessary searches and data processing.
Implementation Method 1
Electron Transfer Dissociation (ETD). ECD and ETD occur on a time scale that is short compared with the internal energy distribution that occurs in the CID process, and consequently, most sequence specific fragment forming bond dissociations are typically randomly along the peptide backbone
Data Source
AI summary
In one aspect of the present invention, the less “useful” spectral data is disregarded from the spectral data resulting from the fragmentation by ETD and candidate charge states for the “useful” data assigned. Knowledge of the first order ion product charge state reduces the subset of comparison data hence aiding in the eventual identification of the precursor ion, and thus aiding in peptide sequence database searching capabilities. Such capabilities include, but are not limited to, computational requirements for database search and data storage, CPU time, the volume taken up on the hard disk to store results, visualization and dissemination of data, and overall improvement in the confidence in the precursor identification. Thus determination of the peptide sequence can be resolved in less time, costing less money, and requiring less computer power.