Ionizable Isotopic Labeling Reagents for Metabolite Quantification
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Solution Overview
Problem
Current isotopic labeling reagents for relative quantification of metabolites in metabolomics studies face challenges such as limited compatibility with multiple functional groups, chromatographic shifts, non-ionizable end-products, and difficulty in labeling carboxylic acids, leading to imprecise quantification and interference in mass spectrometry analysis.
Innovation Solution
Development of ionizable isotopic labeling reagents, including methylacetimidate and cholamine derivatives, that react with both amine and carboxylic acid groups, increasing charge state and hydrophobicity, and producing ionizable end-products, which enhance mass spectrometry analysis and chromatographic separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional isotopic labeling reagents are used, then quantification of metabolites can be performed, but the reagents produce non-ionizable end-products that reduce sensitivity in mass spectrometry analysis
Solution Approach 1:
The patent modifies the chemical structure of labeling reagents to incorporate ionizable functional groups (carboxylic acids, phenols, or enols) that can donate protons to analytes. This parameter change in the reagent's chemical properties enables the formation of ionizable derivatized products, directly addressing the sensitivity issue in mass spectrometry while maintaining quantification capabilities.
Solution Approach 2:
The labeling reagents are designed as composite structures combining isotopic labels with ionizable functional groups. This composite approach allows the reagent to simultaneously provide isotopic labeling for quantification and ionizable groups for enhanced mass spectrometry detection, resolving the contradiction between quantification precision and detection sensitivity.
2Reliability
If labeling reagents are used to enhance mass spectrometry detection, then sensitivity improves, but chromatographic shifts occur that interfere with accurate quantification
Solution Approach 1:
The patent introduces deuterium labels at specific localized positions (such as the alpha-position) on the labeling reagent structure. This localized isotopic labeling minimizes chromatographic shifts while maintaining the ionizable functional groups necessary for sensitivity enhancement, thereby resolving the contradiction between sensitivity improvement and quantification accuracy.
3Measurement precision
If isotopic labeling is performed to achieve relative quantification, then metabolite ratios can be determined, but the reagents fail to react with multiple functional groups including carboxylic acids
Solution Approach 1:
The labeling reagents are designed with multiple ionizable functional groups (carboxylic acids, phenols, or enols) that can participate in proton transfer reactions with various analyte functional groups including amines and carboxylic acids. This multi-functional design enables the reagents to react with diverse metabolite structures, achieving both relative quantification capability and broad functional group compatibility.
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
These reagents enable precise relative quantification of metabolites by improving sensitivity and chromatographic separation, allowing for accurate analysis of metabolite ratios and identification of functional groups, even in complex biological samples.
Implementation Method 1
labeling reagents that react with both amine and carboxylic acid groups, increasing charge state and hydrophobicity, and producing ionizable end-products
Implementation Method 2
labeling reagents that react with both amine and carboxylic acid groups, increasing charge state and hydrophobicity, and producing ionizable end-products, which enhance mass spectrometry analysis and chromatographic separation
Data Source
AI summary
Relative quantification of metabolites by Electrospray Ionization Mass Spectrometry (ESI-MS) requiring a mechanism for simultaneous analysis of multiple analytes in two or more samples. Labeling reagents that are reactive to particular compound classes and differ only in their isotopic kit facilitating relative quantification and providing tangible evidence for the existence of specific functional groups. Heavy and light isotopic forms of methylacetimidate were synthesized and used as labeling reagents for quantification of amine-containing molecules, such as biological samples. Heavy and light isotopic forms of formaldehyde and cholamine were also synthesized and used independently as labeling reagents for quantification of amine-containing and carboxylic acid-containing molecules, such as found in biological samples. Advantageously, the labeled end-products are positively charged under normal acidic conditions involving conventional Liquid Chromatography Mass Spectrometry (LC/MS) applications. Labeled primary and secondary amine and carboxylic acid end-products also generated higher signals concerning mass-spectra than pre-cursor molecules and improved sensitivity. Improved accuracy concerning relative quantification was achieved by mixing heavy and light labeled Arabidopsis extracts in different ratios. Labeling strategy was further employed to ascertain differences in the amounts of amine-containing metabolites for two strains of Arabidopsis seeds.