Gas-Phase HDX Labeling in Traveling-Wave Ion Guides
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Solution Overview
Problem
Current methods for gas-phase hydrogen/deuterium exchange (HDX) labeling in mass spectrometry face challenges such as complex exchange kinetics, vibrational excitation, and dissociation due to continuous ion accumulation and high reagent gas pressures, which complicate the interpretation of HDX kinetics and limit the resolution of conformational detection in protein-ligand complexes and macromolecular assemblies.
Innovation Solution
A mass spectrometer adapted for gas-phase HDX labeling using a traveling-wave ion guide (TWIG) allows for controlled deuterium labeling at adjustable pressures and times, enabling high-resolution detection of gaseous conformations by infusing labeling gases like ND3 into the TWIG, thereby controlling ion reaction times and avoiding interference from ambient water vapor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous ion accumulation and high reagent gas pressures are used for gas-phase HDX labeling, then labeling efficiency is improved, but exchange kinetics become complex and vibrational excitation/dissociation occurs
Solution Approach 1:
The patent applies periodic action by using pulsed ion injection combined with continuous reagent gas flow in the traveling-wave ion guide. Ions are injected in discrete pulses rather than continuously accumulated, which maintains labeling efficiency while preventing the complex exchange kinetics and vibrational excitation that occur with continuous accumulation. The pulsed injection scheme allows each ion packet to be labeled under controlled, consistent conditions.
Solution Approach 2:
The patent changes the pressure parameter by operating at moderate reagent gas pressures rather than high pressures. This parameter change reduces vibrational excitation and dissociation while maintaining adequate labeling efficiency through the extended interaction time provided by the traveling-wave ion guide's continuous ion confinement and pulsed injection approach.
2Quantity of substance
If longer ion reaction times are used for HDX labeling, then deuterium incorporation is improved, but gas-phase conformer interconversion increases
Solution Approach 1:
The patent applies preliminary action by performing HDX labeling immediately after electrospray ionization while ions are still in a near-native conformational state. The traveling-wave ion guide enables rapid labeling by confining ions in a continuous wave pattern, allowing sufficient deuterium incorporation to occur before conformer interconversion can significantly alter the conformational distribution.
Solution Approach 2:
The patent implements the skipping principle by rapidly completing the HDX labeling process within the traveling-wave ion guide before conformer interconversion can occur. The continuous ion confinement and optimized reagent gas exposure enable sufficient labeling to be achieved in a time frame that 'skips' over the timescale of conformer interconversion, preserving the native conformational information.
3Productivity
If ambient water vapor is present during gas-phase HDX, then labeling can occur, but interference from water vapor exchange complicates the measurement
Solution Approach 1:
The patent applies the inert atmosphere principle by using deuterated ammonia (ND3) as the reagent gas in the traveling-wave ion guide. ND3 provides a controlled deuterium source that exchanges with protein protons without the complications of ambient water vapor. The traveling-wave ion guide's sealed environment with controlled gas flow creates an inert-like atmosphere that prevents unwanted exchange with ambient moisture while maintaining efficient deuterium labeling.
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 provides sensitive, high-resolution detection of protein conformations shortly after electrospray ionization, reflecting native states and allowing for the differentiation between folded and unfolded protein forms, while minimizing interconversion of gas-phase protein conformers.
Implementation Method 1
a traveling electric potential wave is used to confine gaseous protein ions in a reaction region of the TWIG
Implementation Method 2
gas-phase HDX labeling of ions with or without ion mobility separation... infusing labeling gases like ND3 into the TWIG
Data Source
AI summary
A mass spectrometer (MS) that is adapted to allow rapid gas-phase hydrogen/deuterium exchange (HDX) labeling of ions in one or more traveling wave ion guides (TWIGs) with or without ion mobility separation. The addition of isotopic labeling by gas-phase HDX offers a sensitive alternative dimension for conformational detection, which enables high resolution detection of gaseous conformations based on shape and surface reactivity. Gas-phase, isotopic HDX labeling or “curtain” labeling, can be performed by infusing a reactive, isotopic labeling gas, e.g., ND3, into one or more of the traveling-ion wave guides (TWIG) in the MS. Analyte ions retained in the potential wells of a traveling wave generated by one or more of the TWIGs can be isotopic labeled at adjustable gas pressures. Labeling times can also be controlled by adjusting the speed of the traveling wave and can be performed within milliseconds of ionizations, probing protein conformations present in solution.