Hybrid MS Acquisition Switching CID and ETD Modes
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Solution Overview
Problem
Current mass spectrometry methods face limitations in duty cycle efficiency and bias due to the isolation of precursor ions, and fragmentation techniques like Collision Induced Dissociation are limited in producing informative fragment ions for post-translationally modified peptides, especially when using Electron Transfer Dissociation over a wide mass-to-charge ratio range.
Innovation Solution
A method that dynamically switches between different fragmentation modes based on detected ions of interest, allowing for a full unbiased MS/MS data set over a wide mass-to-charge ratio range with high-duty cycle, by varying the mass-to-charge ratio or ion mobility of precursor ions and switching to a second fragmentation mode when specific ions are detected, such as Electron Transfer Dissociation when Collision Induced Dissociation is insufficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Collision Induced Dissociation is used to fragment parent ions over a wide mass-to-charge ratio range, then the duty cycle is improved and unbiased data acquisition is achieved, but the information content for post-translationally modified peptides is limited
Solution Approach 1:
The system dynamically switches between two fragmentation modes (CID and ETD) based on real-time detection of ions of interest. The mass spectrometer operates in a hybrid acquisition mode where the fragmentation technique is not fixed but adapts during the experiment, allowing optimal information extraction from different ion populations
Solution Approach 2:
The mass spectrometer is configured to perform multiple fragmentation functions using two different techniques (CID and ETD) within the same instrument. This multi-functionality allows the system to handle diverse analyte types and modification states, with each fragmentation mode contributing complementary information
2Loss of information
If Electron Transfer Dissociation is used to fragment parent ions, then informative fragment ions for post-translationally modified peptides are produced, but the method is limited when used over a wide mass-to-charge ratio range due to excessive charge flow
Solution Approach 1:
The system dynamically adjusts the fragmentation mode based on the current analytical needs and ion population characteristics. ETD is activated selectively when informative fragmentation is required, rather than being applied continuously, thus managing charge flow while maximizing information extraction
Solution Approach 2:
Different fragmentation qualities are applied to different ion populations. CID provides general fragmentation for most ions, while ETD provides specialized high-information fragmentation for specific ions of interest, particularly those with post-translational modifications
3Measurement precision
If parent or precursor ions are isolated by the mass filter sequentially, then specific ions can be fragmented, but other parent or precursor ions are discarded resulting in low duty cycle
Solution Approach 1:
The mass-to-charge ratio range is divided into multiple segments or windows that are scanned sequentially. Each window contains multiple parent ions that are transmitted simultaneously to the fragmentation cell, allowing parallel processing of multiple ion populations without requiring isolation of each individual ion
Solution Approach 2:
Multiple ion populations across different mass-to-charge ratios are merged into a single transmission stream to the fragmentation cell. The system combines the benefits of selective scanning with simultaneous transmission of multiple ion types, increasing overall throughput
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
Enables the acquisition of comprehensive and detailed fragment data with high-duty cycle and unbiased results in a single experimental run, overcoming the limitations of traditional methods by selectively applying more informative fragmentation techniques like Electron Transfer Dissociation when needed.
Implementation Method 1
mass filtering parent or precursor ions with a mass filter
Implementation Method 2
fragmenting or reacting the parent or precursor ions in the fragmentation or reaction device operating in the first fragmentation or reaction mode so as to produce first fragment or product ions
Implementation Method 3
The product or fragment ions are then mass analysed using a Time of Flight mass analyser
Implementation Method 4
Electron Transfer Dissociation ('ETD') is known to be particularly useful in the analysis of post translationally modified peptides
Data Source
AI summary
A method is disclosed wherein parent or precursor ions are fragmented or reacted according to a first fragmentation or reaction mode, and when an ion of interest is detected the method then temporarily switches to a second mode of fragmentation or reaction. This enables a full un-biased MS/MS data set to be provided over a wide mass to charge ratio range with high-duty cycle, together with complementary detailed fragment data of interest, in a single experimental run or acquisition.