# TR&D 2 Metabolic Labels for Ultraplexed Protein Quantification p. 453

> **NIH NIH P41** · UNIVERSITY OF WISCONSIN-MADISON · 2020 · $217,722

## Abstract

Project Summary 
Proteome quantification has become an increasingly essential component of modern biology and translational 
medicine. Whether targeted or global, stable isotope incorporation with mass spectrometry (MS) analysis is a 
core technique for protein abundance measurement. There are numerous approaches to introduce stable 
isotopes into peptides, the most frequently used being stable isotope labeling with amino acids in cell culture 
(SILAC) and isobaric tagging (e.g., tandem mass tags, TMT, or iTRAQ). These methods incorporate heavy 
isotopes to increase mass by at least 1 Da. SILAC, the quantification gold standard, for example, typically utilizes 
a 4 Da spacing to limit the isotopic cluster overlap of the heavy and light peptides. This requirement limits the 
quantitative capacity of SILAC to triplex. The reason for this is twofold: (1) the mass of the amino acids can only 
be elevated to ~ +12 Da; and (2) mass spectral complexity is increased as multiple isotopic clusters are 
introduced. Isobaric tagging eliminates the latter problem by concealing the quantitative information in the MS1 
scan, thereby permitting a much higher level of multiplexing. That said, isobaric tagging, being a chemical tag, 
is not amenable to in vivo labeling. Further, quantitative data can only be obtained for peptides that are selected 
for MS2.

## Key facts

- **NIH application ID:** 9988438
- **Project number:** 5P41GM108538-05
- **Recipient organization:** UNIVERSITY OF WISCONSIN-MADISON
- **Principal Investigator:** Joshua J Coon
- **Activity code:** P41 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $217,722
- **Award type:** 5
- **Project period:** — → —

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9988438

## Citation

> US National Institutes of Health, RePORTER application 9988438, TR&D 2 Metabolic Labels for Ultraplexed Protein Quantification p. 453 (5P41GM108538-05). Retrieved via AI Analytics 2026-06-15 from https://api.ai-analytics.org/grant/nih/9988438. Licensed CC0.

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