Isoaspartate Mass Spectrometry Using PIMT Labeling
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Solution Overview
Problem
Conventional peptide mapping methods struggle to distinguish aspartate from isoaspartate using mass spectrometry due to their identical mass, necessitating lengthy liquid chromatography gradients, which increases time and cost, and often overlook critical modifications involving isoaspartate.
Innovation Solution
The use of protein L-isoaspartyl methyltransferase (PIMT) to selectively modify isoaspartate residues into O-methyl isoaspartate, allowing differentiation from aspartate and asparagine residues through mass spectrometry without liquid chromatography, facilitated by detecting mass changes and the conversion of S-adenosylmethionine to S-adenosyl-homocysteine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional peptide mapping uses liquid chromatography to separate aspartate from isoaspartate, then separation is achieved, but analysis time increases significantly
Solution Approach 1:
The patent replaces the mechanical liquid chromatography separation system with a mass spectrometry-based detection system that uses enzymatic labeling. PIMT enzyme specifically labels isoaspartate residues, and the labeled peptides are detected by MS based on their mass-to-charge ratio, eliminating the need for time-consuming chromatographic separation while maintaining the ability to distinguish between aspartate and isoaspartate forms.
Solution Approach 2:
The patent introduces PIMT enzyme as an intermediary that selectively modifies isoaspartate residues by adding a mass tag. This intermediary enables indirect detection of isoaspartate through mass spectrometry, allowing differentiation from aspartate without requiring direct physical separation by chromatography.
2Measurement precision
If conventional peptide mapping uses extended liquid chromatography gradients, then isoaspartate detection is possible, but cost increases
Solution Approach 1:
The patent substitutes expensive extended liquid chromatography gradients with a more cost-effective mass spectrometry approach using enzymatic labeling. The PIMT-based labeling method requires standard MS instrumentation and eliminates the need for extended chromatography runs, reducing operational costs while maintaining isoaspartate detection capability.
3Productivity
If conventional peptide mapping uses standard mass spectrometry, then mass analysis is performed, but aspartate and isoaspartate cannot be distinguished
Solution Approach 1:
The patent uses PIMT enzyme as an intermediary that selectively modifies isoaspartate residues with a mass tag, creating a detectable mass difference between labeled isoaspartate and unlabeled aspartate. This enables standard mass spectrometry to distinguish between the two isomers based on their different mass-to-charge ratios, maintaining high analysis speed while achieving precise differentiation.
Solution Approach 2:
The patent changes the mass parameter of isoaspartate residues by enzymatic labeling with PIMT. The addition of the mass tag creates a distinguishable mass shift that allows mass spectrometry to differentiate between aspartate and isoaspartate based on their different mass-to-charge ratios, enabling precise measurement without compromising analysis throughput.
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 rapid and cost-effective detection and characterization of isoaspartate residues in therapeutic proteins, reducing analysis time and improving the accuracy of peptide mapping by eliminating the need for lengthy chromatography steps.
Implementation Method 1
polypeptides containing one or more isoaspartate residues, or suspected of containing one or more isoaspartate residues, are treated with L-isoaspartyl methyltransferase (PIMT), which is able to selectively modify isoaspartate
Implementation Method 2
The polypeptide is then analyzed using MS, where a mass change caused by the PIMT reaction is detected and characterized
Data Source
AI summary
Methods and compositions for detecting isoaspartate residues in polypeptides using mass spectrometry, and for distinguishing isoaspartate residues from aspartate and/or asparagine residues in a polypeptide using MS analysis. Polypeptides containing one or more isoaspartate residues, or suspected of containing one or more isoaspartate residues, are treated with L-isoaspartyl methyltransferase (PIMT), which is able to selectively modify isoaspartate and impart a mass change to the amino acid residue. The polypeptide is then analysed using mass spectrometry, where a mass change caused by the PIMT reaction is detected and characterized. Preferably, these methods are able to be performed without the use of liquid chromatography or other similar separation techniques prior to mass spectrometry analysis.