Mass Spectrometer Dynamic Exclusion for Peptide Analysis
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Solution Overview
Problem
Current mass spectrometry techniques face challenges in efficiently analyzing minute quantities of proteins and peptides, particularly when dealing with unknown impurity components, as they often prioritize high-intensity ions, leading to redundant measurements and difficulties in identifying low-intensity or pathologic proteins, and struggle to accurately select analysis targets based on mass number and valence rather than mass-to-charge ratio.
Innovation Solution
A system that determines whether each ion peak is an isotope peak in real-time, calculates the valence and mass number, and uses retention time to distinguish ion species, storing data on previously measured peptides in an internal database to avoid redundant measurements and select appropriate analysis targets, allowing for the analysis of minute sample amounts even with high impurity levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If data-dependent function selects parent ions in decreasing intensities for MS2 analysis, then high-intensity ions are prioritized for analysis, but redundant measurements of already-identified proteins occur and low-intensity pathologic proteins are missed
Solution Approach 1:
The system performs preliminary actions by storing mass spectral data and identification results in a database before subsequent measurements. The dynamic exclusion function uses this pre-stored information to automatically exclude already-identified ions from further MS2 analysis, preventing redundant measurements and enabling the system to focus on unidentified low-intensity ions.
Solution Approach 2:
The system implements feedback by continuously comparing newly detected ions against the database of previously identified ions. The dynamic exclusion function provides real-time feedback to the data-dependent acquisition system, adjusting ion selection based on identification history, thereby improving both efficiency and accuracy.
2Loss of time
If dynamic exclusion function excludes ions based on mass-to-charge ratio m/z, then redundant measurements are reduced, but ions with different mass numbers or valences having the same m/z cannot be distinguished
Solution Approach 1:
The system transitions from one-dimensional m/z-based exclusion to multi-dimensional ion characterization by calculating and using both mass number and valence information. This dimensional expansion allows the system to distinguish between ions with identical m/z but different mass numbers or valences, improving identification accuracy while maintaining time efficiency.
Solution Approach 2:
The system changes the parameters used for ion exclusion from solely m/z to a combination of mass number and valence. By calculating these additional parameters and using them in the exclusion logic, the system achieves more precise ion species identification without sacrificing measurement speed.
3Measurement precision
If multiple-stage dissociation is performed on all detected ions, then comprehensive analysis is achieved, but measurement time increases significantly and sample consumption increases
Solution Approach 1:
The system extracts and excludes ions that have already been identified from the pool of ions requiring MS2 analysis. By removing these already-analyzed ions from further dissociation steps, the system reduces unnecessary measurement time and sample consumption while maintaining comprehensive analysis of unidentified ions.
Solution Approach 2:
Instead of performing multiple-stage dissociation on all detected ions, the system applies partial action by selectively performing MS2 only on unidentified ions. This selective approach avoids excessive analysis of already-identified ions, optimizing the balance between analysis comprehensiveness and resource efficiency.
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 efficient and accurate selection of analysis targets, reducing redundant measurements and improving the analysis of low-intensity proteins by distinguishing ion species based on mass number and valence, thereby enhancing the identification of proteins and peptides, including those with chemical modifications.
Implementation Method 1
An RF voltage is applied to these electrodes such that a quadrupole electric field is formed at the center of these electrodes, thus enabling the trapping of gaseous ions three dimensionally
Implementation Method 2
a sample as the object of measurement is ionized, and a variety of resultant ions are delivered to a mass spectrometer for measuring the ion intensity for each mass-to-charge ratio
Implementation Method 3
the thus selected ion is dissociated and broken up by collision with gas molecules or the like
Data Source
AI summary
During the structural analysis of a protein or peptide by tandem mass spectroscopy, a peptide ion derived from a protein that has already been measured and that is expressed in great quantities is avoided as a tandem mass spectroscopy target. A peptide derived from a minute amount of protein, which has heretofore been difficult to analyze, can be automatically determined as a tandem mass spectroscopy target within the real time of measurement. Data concerning a protein that has already been measured and a peptide derived from the protein is automatically stored in an internal database. The stored data is collated with measured data with high accuracy to determine an isotope peak. In this way, the process of selecting a peptide peak that has not been measured as the target for the next tandem analysis can be performed within the real time of measurement and a redundant measurement of peptides derived from the same protein can be avoided. The information contained in the MSn spectrum is effectively utilized in each step of the MSn involving a multi-stage dissociation and mass spectroscopy (MSn), so that the flows for the determination of the next analysis content and the selection of the parent ion for the MSn+1 analysis, for example, can be optimized within the real time of measurement and with high efficiency and accuracy. Thus, a target of concern to the user can be subjected to tandem mass spectroscopy without wasteful measurement.