Electron Capture Dissociation Apparatus with DC Decelerating Field
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Solution Overview
Problem
Current methods for electron capture dissociation (ECD) in ion traps without magnetic fields, such as Paul traps, face challenges in delivering high fluxes of low-energy electrons and maintaining electron beam focus due to strong electrical fields, leading to inefficient fragmentation of large molecules like proteins and peptides.
Innovation Solution
An ECD apparatus with a linear multipole ion guide and an electron control device that decelerates electron beams using a DC decelerating field, ensuring low-energy electrons reach the ion trapping region effectively, and an electron emitter with a composite structure to optimize electron flux and focus, allowing for efficient ECD and hot ECD operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a Paul trap without magnetic field is used for ion confinement, then the device complexity is reduced compared to Penning traps, but the ability to deliver and focus low-energy electrons is deteriorated due to strong electrical fields
Solution Approach 1:
The electron source is segmented into multiple electrodes (emitter electrode, lens electrodes, decelerating electrode) that can be independently controlled. This segmentation allows the electron beam to be generated, focused, and decelerated in separate stages, enabling precise control of electron energy and focus despite the strong RF fields in the Paul trap.
Solution Approach 2:
Lens electrodes and a decelerating electrode are introduced as intermediary components between the electron emitter and the ion trapping region. These intermediaries shape the electron beam, control its energy, and protect the low-energy electrons from the strong RF fields, enabling reliable electron capture dissociation in a magnetic-field-free environment.
2Productivity
If high flux of electrons is delivered to the ion trapping region, then the productivity of ECD process is improved, but the electron beam focus is lost due to space charge effects and RF field deflection
Solution Approach 1:
The electron beam is pre-focused and pre-accelerated by lens electrodes before entering the ion trapping region. This preliminary action ensures that the beam is tightly focused and has the appropriate energy profile before encountering the ions, maximizing the ECD process efficiency while maintaining beam focus despite high electron flux.
Solution Approach 2:
The system uses periodic RF fields to confine ions while delivering electron beams in controlled pulses or continuous mode with synchronized timing. This periodic action allows high electron flux to be delivered efficiently while the RF field cycles provide opportunities for electron beam injection and maintain ion confinement, balancing productivity with beam focus.
3Measurement precision
If low-energy electrons (less than 3 eV) are used for ECD, then the fragmentation specificity is improved, but the electron flux density is reduced making the process less efficient
Solution Approach 1:
The system dynamically adjusts electron energy parameters by controlling the potential difference between the emitter and decelerating electrodes. By precisely controlling this voltage parameter, low-energy electrons (less than 3 eV) are delivered to maintain fragmentation specificity, while the electrode geometry and positioning compensate for reduced flux density to maintain adequate electron supply for efficient ECD.
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 effective fragmentation of ions by ensuring low-energy electrons interact with target ions, enhancing the fragmentation pathways and providing complementary fragment ion information, suitable for a broad mass range of target ions.
Implementation Method 1
decelerating the electron beam in a DC decelerating field of adjustable voltage potential directed along the electron beam direction
Implementation Method 2
An electron emitter is disposed outside the ion guide interior space
Implementation Method 3
The electron control device is configured for focusing an electron beam from the electron emitter toward the central axis
Implementation Method 4
If their energy is low enough, the electrons can be captured by the positively charged sites on the ions. The energy released in the exoergic capture process is released as internal energy in the ion which can then cause bond cleavage and dissociation
Data Source
AI summary
An electron capture dissociation apparatus comprises ion guide electrodes, an electron emitter, and an electron control device. The ion guide electrodes are arranged along a central axis and spaced circumferentially to circumscribe an interior space extending along the central axis. The electron emitter is disposed outside the interior space. The electron control device is configured for focusing an electron beam from the electron emitter toward the central axis, along a radial electron beam direction between two of the ion guide electrodes, and for decelerating the electron beam in a DC decelerating field of adjustable voltage potential directed along the electron beam direction.