Ion Mobility Mass Spectrometry for Cross-Linked Peptide Identification
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Solution Overview
Problem
Current methods for identifying protein-protein and protein-biomolecular interactions, such as chemical cross-linking and mass spectrometry, face challenges in detecting and sequencing cross-linked peptides due to their low stoichiometry and the requirement for large protein quantities, limiting the understanding of these interactions and their role in biological processes and diseases.
Innovation Solution
A method combining ion mobility separation with mass spectrometry to distinguish and identify cross-linked peptides by analyzing ion mobility and mass spectral data, using enzymatic digestion and chemical cross-linking to form cross-linked protein complexes, followed by ionization, separation, and mass analysis of peptide ions to determine their interaction partners and sites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If chemical cross-linking and mass spectrometry are used to identify protein interactions, then protein-protein interaction information can be obtained, but cross-linked peptides are difficult to detect due to their low stoichiometry
Solution Approach 1:
The patent segments the analysis process into two distinct phases: first analyzing intact cross-linked protein complexes to detect cross-links based on mass and mobility characteristics, then performing enzymatic digestion to generate cross-linked peptides for further analysis. This segmentation allows detection at the complex level where cross-links are more abundant before proceeding to peptide-level identification.
Solution Approach 2:
The patent introduces an intermediary step of analyzing intact cross-linked protein complexes as a mediator between cross-linking and peptide analysis. This intermediary phase allows enrichment and detection of cross-linked species before enzymatic digestion, serving as a bridge that overcomes the low stoichiometry problem at the peptide level.
2Measurement precision
If physical techniques such as X-ray crystallography and NMR spectroscopy are used to study protein interactions, then spatial and topological organization can be determined, but large quantities of purified protein are required
Solution Approach 1:
The patent uses chemical cross-linking to create covalent copies or snapshots of transient protein-protein interactions. Instead of requiring large amounts of purified protein for structural techniques, the cross-linking reagents capture interaction states in situ, creating stable covalent bonds that preserve spatial information without needing extensive protein purification or large quantities.
3Measurement precision
If cross-linked peptides are analyzed by mass spectrometry alone, then mass information can be obtained, but cross-linked peptides remain difficult to observe and recognise
Solution Approach 1:
The patent merges ion mobility separation with mass spectrometry analysis to create a hybrid analytical approach. By combining the separation power of ion mobility (which resolves ions based on their size and shape in the gas phase) with the mass analysis capability of MS, the system can distinguish cross-linked peptides from the background of non-cross-linked peptides more effectively than either technique alone.
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 a rapid and sensitive method for protein interaction profiling, allowing for the identification of cross-linked peptides and their sites of interaction, improving the understanding of biological processes and disease progression.
Implementation Method 1
separating at least some of the peptide ions according to their ion mobility or their rate of change of ion mobility with electric field strength
Implementation Method 2
mass analysing at least some of the peptide ions and obtaining mass spectral data
Implementation Method 3
formation of covalent bonds between two proteins using bifunctional reagents containing reactive end groups
Data Source
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AI summary
A method of mass spectrometry is disclosed wherein cross- linked proteins are digested to form a plurality of peptides. The peptides are ionised and subjected to ion mobility separation followed by mass analysis. Peptide ions having a higher ion mobility than other peptide ions having substantially the same mass to charge ratio are identified as candidate cross-linked peptides. The candidate cross-linked peptides are subjected to either tandem mass spectrometry or Shotgun fragmentation and the resulting fragment ions mass analysed. The mass analysis of the fragment ions may be used to confirm whether or not a candidate cross-linked peptide does in fact relate to a cross-linked peptide.