SRM Assay for Src Protein Quantitation in FFPE Tissue
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Solution Overview
Problem
Existing methods for mass spectrometric analysis of the Src protein in formalin-fixed tissue samples are hindered by the instability and difficulty in detecting specific peptides, making it challenging to obtain reliable and accurate quantitative data for cancer diagnosis and treatment strategies.
Innovation Solution
Identification and use of optimized peptides derived from the Src protein, which are stable and effectively ionizable, allowing for precise Selected Reaction Monitoring (SRM) assays in complex protein lysates, including those from formalin-fixed tissues, using techniques like tandem mass spectrometry and triple quadrupole mass spectrometry for relative and absolute quantitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional mass spectrometric methods are used to analyze Src protein in formalin-fixed tissue samples, then the analysis can be performed with standard protocols, but the peptide detection is unreliable and quantitative data is inaccurate due to peptide instability and ionization difficulties
Solution Approach 1:
The patent applies parameter changes by modifying the peptide selection criteria to identify peptides with optimal mass-to-charge ratios and ionization efficiency. The method selects specific peptides from the Src protein that exhibit stable ionization characteristics in formalin-fixed tissue, changing the parameters of peptide selection (mass, charge state, ionization efficiency) to resolve the contradiction between measurement precision and detection reliability.
Solution Approach 2:
The patent uses synthetic peptide standards that replicate the exact sequence and post-translational modifications of endogenous Src peptides. These synthetic copies serve as internal standards for quantitative measurement, enabling accurate and reliable detection by providing a stable reference that mimics the behavior of native peptides under the same ionization and detection conditions.
2Adaptability or versatility
If standard peptide sequences are used for mass spectrometry analysis, then the assay can be applied broadly, but the peptides are unstable and difficult to detect in formalin-fixed tissue samples
Solution Approach 1:
The patent applies local quality by selecting specific regions (local sequences) within the Src protein that generate peptides with enhanced stability and detectability. Rather than using uniform peptide selection across the entire protein, the method identifies particular local segments that resist degradation in formalin-fixed tissues and ionize efficiently, thus maintaining assay versatility while improving peptide stability.
3Loss of information
If comprehensive protein analysis is performed on complex protein lysates, then complete protein profiling is achieved, but the detection of specific Src peptides is obscured by background interference
Solution Approach 1:
The patent extracts specific Src-derived peptides from the complex protein lysate background by using targeted selected reaction monitoring (SRM) mass spectrometry. The method isolates and monitors specific precursor ions corresponding to Src peptides and their fragment ions, effectively extracting the signal of interest from the complex background of other proteins and peptides in the lysate, thereby preventing information loss while simplifying detection.
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
Enables accurate and precise measurement of Src protein levels in cancer tissues, facilitating cancer diagnosis and personalized treatment strategies by providing reliable quantitative data on peptide expression and modification levels.
Implementation Method 1
mass spectrometry-based Selected Reaction Monitoring (SRM) assay
Implementation Method 2
techniques like tandem mass spectrometry and triple quadrupole mass spectrometry
Implementation Method 3
which are stable and effectively ionizable
Data Source
AI summary
Objective quantitation of the c-Src protein directly in cancer patient tissue can aid in determining die aggressiveness of an individual patient's tumor as well as help make more informed decisions about choice of therapy. However, fee c-Src protein is currently analyzed directly in formalin fixed patient tissue only by immunohistoehemistry methodology which is at best subjectively semi-quantitative. This invention describes an objective quantitative assay for the c-Sre protein using mass spectrometry as the analytical methodology, Specific peptides, experimentally discovered characteristics about the peptides, and experimentally established assay conditions based on those peptide characteristics are provided for use in a mass speetronieiry-based Selected Reaction Monitoring (SRM) assay in order to measure relative- or absolute quantitative levels of c-Src directly in a protein preparation obtained from a formalin fixed cancer patient tissue sample.