Mass Spectrometry Protein Quantification Using Product Ion Intensities
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Solution Overview
Problem
Conventional LC/MS systems face challenges in accurately quantifying proteins due to saturation limits and dynamic range issues, leading to underestimation of protein abundance at high concentrations and unreliable precursor ion intensity measurements.
Innovation Solution
The method involves determining the intensity sum of precursor and product ions using a calibration standard, adjusting for fragmentation efficiency, and employing product ion intensities when precursor ion intensities exceed saturation limits to extend the dynamic range and ensure accurate protein quantification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If precursor ion intensities are used for quantification, then quantification is simple and direct, but measurement accuracy deteriorates when precursor ion intensities exceed saturation limits
Solution Approach 1:
The patent changes the measurement parameter from precursor ion intensity to product ion intensity when precursor ions exceed saturation limits. This allows the system to adapt to different concentration ranges by selecting appropriate measurement parameters, thereby maintaining accuracy across a broader dynamic range.
Solution Approach 2:
The patent introduces product ions as an intermediary measurement target. Instead of directly measuring saturated precursor ions, the system measures product ions generated from precursor ions, which serve as a reliable proxy for quantification when direct precursor measurement fails.
2Productivity
If only precursor ion intensities are measured, then the analysis process is simple and fast, but the dynamic range for accurate quantification is limited
Solution Approach 1:
The patent implements a dynamic measurement strategy where the system automatically selects between measuring precursor ions and product ions based on the concentration range. This dynamic adaptation allows the system to maintain high productivity for low-concentration samples while extending the dynamic range for high-concentration samples.
Solution Approach 2:
The patent makes the mass spectrometry system multi-functional by enabling it to perform both precursor ion measurement and product ion measurement. This universality allows a single system to handle a broader range of sample concentrations without requiring separate measurement modes or instruments.
3Adaptability or versatility
If product ion intensities are used instead of precursor ion intensities, then the dynamic range is extended, but the measurement process becomes more complex
Solution Approach 1:
The patent segments the quantification process into two distinct measurement modes: precursor ion measurement for low-concentration samples and product ion measurement for high-concentration samples. This segmentation allows each mode to be optimized independently, managing complexity by dividing the overall process into manageable segments based on concentration ranges.
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 precise and reliable quantification of proteins across a broader concentration range by utilizing both precursor and product ion intensities, correcting for saturation effects and improving the accuracy of protein abundance estimation.
Implementation Method 1
molecules from the sample are ionized to form ions
Implementation Method 2
Chromatography is a technique for separating compounds, such as those held in solution, where the compounds will exhibit different affinity for a separation medium in contact with the solution
Data Source
AI summary
Techniques are described for quantification of molecules in a sample. Mass spectrometry is performed to obtain ionization intensities for precursor and product ions originating from a particular molecule. A first stet of precursor ions having the highest ionization intensities and originating from the particular molecule is determined. For each of the one or precursors in the first set, determined is a second set of one or more product ions that are fragments associated with said each precursor and have the highest ionization in intensities of product ions associated with said each precursor. An intensity sum is calculated for the particular molecule by adding ionization intensities of product ions included in the second sets for the one or more precursors in the first set. The intensity sum is compared to information included in a calibration standard. A quantity of the particular molecule in the sample is determined based on said comparing.