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Updated: May 26, 2026
A Mass Spectrometry-Based Proteomics Approach for Global and High-Confidence Protein R-Methylation Analysis
Published on: April 28, 2022
Measurement of methotrexate polyglutamates in human erythrocytes by ion-pair UPLC-MS/MS
Leon van Haandel1, Mara L Becker, T D Williams
1Division of Clinical Pharmacology & Medical Toxicology, Children's Mercy Hospitals & Clinics, 2401 Gillham Road, Kansas City, MO 64108, USA.
Background:
Low-dose methotrexate is used for the treatment of rheumatoid arthritis and juvenile idiopathic arthritis, but its effectiveness greatly varies between individuals. Therapeutic drug monitoring of intracellular methotrexate metabolites, the γ-polyglutamates (MTXGlu(n)), in human erythrocytes has shown promise in providing a basis for individualization of therapy.
Results:
This work presents expedient methodology for the analysis of MTXGlu(1-7) in human erythrocytes by ion-pair UPLC with detection by tandem MS (UPLC-ESI-MS/MS). The use of N,N-dimethylheptylamine as an ion-pair agent was found to be favorable over others. Thermal extraction of erythrocyte lysates provides a simple one-step extraction procedure. The entire chromatographic run time is 6 min and the assay was validated within the therapeutic range of these metabolites
Conclusion:
The developed sample preparation procedure in combination with ion-pair UPLC-ESI-MS/MS analysis allowed for expedient quantitation of MTXGlu(1-7) in human erythrocytes. The rapid analysis time would enable therapeutic drug monitoring of MTXGlu(1-7) in the clinic.
