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The absolute quantification strategy: a general procedure for the quantification of proteins and post-translational
Donald S Kirkpatrick1, Scott A Gerber, Steven P Gygi
1Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
Methods (San Diego, Calif.)
|February 22, 2005
Summary
The absolute quantification (AQUA) strategy uses stable isotope-labeled peptides for precise protein measurement. This method enables accurate quantification of protein expression and post-translational modifications in cell lysates.
Area of Science:
- Proteomics
- Biochemistry
- Mass Spectrometry
Background:
- Biological mass spectrometry enables large-scale protein quantification.
- Current methods primarily offer relative quantification.
- A need exists for precise absolute quantification of proteins and modifications.
Purpose of the Study:
- To introduce and validate the absolute quantification (AQUA) strategy.
- To enable precise determination of protein expression and post-translational modification levels.
- To demonstrate AQUA's utility with an example of polyubiquitin chain formation.
Main Methods:
- Developed the absolute quantification (AQUA) strategy.
- Utilized synthetic, stable isotope-enriched peptides as internal standards.
- Employed selected reaction monitoring (SRM) in tandem mass spectrometry for analysis.
Main Results:
- The AQUA method allows direct detection and quantification of native peptides alongside isotope-labeled internal standards.
- Demonstrated successful application in measuring polyubiquitin chain formation (K48-linked).
- Achieved high sensitivity and precision in protein quantification.
Conclusions:
- The AQUA strategy provides a robust method for absolute protein quantification.
- It is effective for measuring both protein levels and post-translational modifications.
- The method's simplicity and reliance on widely available technology make it broadly applicable.