Tau PTM Quantification via Stable Isotope Mass Spectrometry
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for diagnosing and treating tauopathies, such as Alzheimer's disease, are limited by the inability to accurately quantify post-translational modifications (PTMs) of tau proteins, which are crucial for understanding disease progression and developing effective treatments.
Innovation Solution
A method involving the use of stable isotope-labeled tau proteins and mass spectrometry-based assays, like FLEXiTau, to quantify PTMs in tau peptides, allowing for the identification of specific modifications associated with different tauopathies through targeted selected reaction monitoring (SRM) and data-independent acquisition (DIA) techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mass spectrometry-based assays with stable isotope-labeled tau proteins are used, then measurement precision of tau PTMs is improved, but device complexity increases
Solution Approach 1:
Stable isotope-labeled tau proteins serve as internal standards (intermediaries) to mediate the quantification of endogenous tau PTMs. These labeled standards are mixed with patient samples at known ratios before proteolytic digestion, allowing precise measurement of PTM levels by comparing the abundance ratios of labeled to unlabeled tau peptides in mass spectrometry analysis
Solution Approach 2:
The method changes the physical-chemical parameters of tau proteins by introducing stable isotope labels (e.g., 13C, 15N) that alter the mass-to-charge ratio detectable by mass spectrometry. This parameter change enables differentiation between labeled and unlabeled tau peptides, facilitating accurate quantification of PTMs through mass spectral analysis
2Measurement precision
If targeted SRM and DIA techniques are employed, then measurement precision of specific tau PTMs is improved, but difficulty of detecting and measuring increases
Solution Approach 1:
The tau protein is segmented into specific peptide fragments through controlled proteolytic digestion using enzymes like trypsin. This segmentation allows mass spectrometry to detect and quantify specific PTMs at defined peptide sequences, improving measurement precision by focusing on discrete, identifiable targets rather than analyzing the entire protein
Solution Approach 2:
Proteolytic digestion is performed as a preliminary action before mass spectrometry analysis to convert intact tau proteins into smaller, more detectable peptides. This pre-processing step simplifies subsequent detection by generating peptides with known sequences and masses that can be targeted by SRM or DIA techniques
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 comprehensive analysis of tau PTMs, providing a molecular signature for diagnosing tauopathies and potentially leading to targeted therapies by distinguishing between various tauopathies based on unique PTM patterns.
Implementation Method 1
providing a second sample comprising a labeled tau protein; mixing the first sample and the second sample at an initial mixing ratio of tau protein to labeled tau protein
Implementation Method 2
subjecting the mixture to proteolytic digestion, generating tau peptide fragments and labeled tau peptide fragments
Implementation Method 3
quantifying the abundance of the tau peptide fragments and the labeled tau peptide fragments; measuring the ratio of the abundance
Data Source
AI summary
This disclosure relates to methods of determining the amount of post translational modification (PTM) associated with one or more tau peptide fragments of a tau protein in a sample, and methods of evaluating a subject for having a tauopathy, the methods comprising, in part, determining the amount of post translational modification (PTM) associated with one or more tau peptide fragments of a tau protein in a sample, and comparing the amount of the tau PTMs associated with one or more tau peptide fragments with one or more reference levels for the tau peptide fragments, thereby determining whether a subject has a tauopathy.