Selected reaction monitoring

Selected Reaction Monitoring (SRM), also known as Multiple Reaction Monitoring (MRM) when multiple reactions are monitored, is a highly specific and sensitive mass spectrometry (MS) technique used for quantifying or identifying specific substances within a sample. This method is widely utilized in the fields of biochemistry, pharmacology, and molecular biology, particularly in the analysis of proteins, peptides, and small molecules.

Overview

SRM operates on triple quadrupole mass spectrometers. The technique involves the selection of a particular precursor ion (the ion of interest) in the first quadrupole, fragmentation of this ion in the second quadrupole (collision cell), and the detection of a specific fragment ion in the third quadrupole. This process allows for the precise quantification and identification of molecules in complex mixtures by monitoring the transition from a specific precursor ion to a specific fragment ion, known as a transition.

Applications

SRM is extensively used in various scientific and medical fields. In clinical research, it is employed for the quantification of drugs, metabolites, and biomarkers in biological fluids, which is crucial for pharmacokinetics, toxicology, and biomarker discovery. In proteomics, SRM is used to quantify proteins and peptides with high specificity and sensitivity, aiding in the understanding of cellular processes and disease mechanisms.

Advantages

The main advantages of SRM include its high specificity, sensitivity, and quantitative accuracy. These characteristics make it an invaluable tool for detecting and quantifying low-abundance compounds in complex biological matrices. Additionally, SRM can be highly multiplexed, allowing for the simultaneous monitoring of hundreds of transitions, which is beneficial for large-scale studies.

Challenges

Despite its advantages, SRM faces several challenges. The method requires extensive method development and validation for each target molecule, which can be time-consuming. Furthermore, the selection of appropriate precursor and fragment ions is critical for the success of the assay, necessitating a deep understanding of the molecular structure and fragmentation patterns of the analytes.

Future Directions

Advancements in mass spectrometry technology and bioinformatics are expanding the capabilities of SRM. Improvements in sensitivity, speed, and data analysis software are enabling more comprehensive and high-throughput analyses. The integration of SRM data with other omics data, such as genomics and metabolomics, is paving the way for a more holistic understanding of biological systems and disease.

See Also

• Mass spectrometry
• Proteomics
• Pharmacokinetics
• Biomarker discovery