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Updated: Aug 13, 2026

Quantification of Proteins Using Peptide Immunoaffinity Enrichment Coupled with Mass Spectrometry
Published on: July 31, 2011
Chimeric structural isomer fragments as cost-efficient internal standards for amino acid quantification by mass
Luis Alberto De León-Jiménez1, Robert Winkler1
1Advanced Genomics Unit, Cinvestav, Km. 9.6 Libramiento Norte Carr. Irapuato-León, 36824 Irapuato, Gto, Mexico. robert.winkler@cinvestav.mx.
None:
Amino acid (AA) profiles from body fluids such as blood and urine are clinical indicators for diagnosing metabolic and hepatic diseases. Current quantitative methods, such as liquid chromatography-mass spectrometry (LC-MS) with isotopically labelled internal standards (ISs), are costly and technically demanding. This study proposes a cost-efficient alternative using structural isomers as ISs in a direct liquid infusion (DLI) tandem mass spectrometry (MS/MS) approach. The method leverages chimeric spectra and fragment intensity ratios to quantify AAs, demonstrating high linearity and precision even with a 3D ion trap mass analyser. This approach offers a viable strategy for AA quantification in preventive medicine, particularly for screening metabolic diseases such as phenylketonuria, diabetes, and liver dysfunction.
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