Measuring protein synthesis using metabolic ²H labeling, high-resolution mass spectrometry, and an algorithm

Area of Science:

• Biochemistry
• Analytical Chemistry
• Metabolomics

Background:

• Estimating protein dynamics in vivo is crucial for understanding physiological processes.
• Previous methods using heavy water ((2)H(2)O) and mass spectrometry required extensive sample purification and tissue-specific amino acid labeling.
• A simplified approach is needed to accurately quantify protein kinetics.

Purpose of the Study:

• To develop and validate a novel method for in vivo protein synthesis rate estimation.
• To simplify the measurement of deuterium incorporation into proteins using heavy water labeling.
• To demonstrate the utility of this method in a physiological context, such as nutritional status.

Main Methods:

• Utilized nanospray linear trap Fourier transform ion cyclotron resonance mass spectrometry (LTQ FT-ICR MS) for simultaneous isotopic enrichment measurement.
• Employed heavy water ((2)H(2)O) as a tracer for in vivo labeling.
• Developed a mathematical algorithm to process mass spectrometry data and calculate precursor/product labeling ratios.

Main Results:

• Successfully measured isotopic enrichment of peptides and protein-bound amino acids simultaneously.
• Established a method to obtain precursor/product labeling ratios by measuring water and protein/peptide labeling, minimizing amino acid analysis.
• Demonstrated the method's ability to detect changes in albumin synthesis in rats under different nutritional statuses.

Conclusions:

• The developed LTQ FT-ICR MS method offers a more streamlined approach for quantifying in vivo protein kinetics.
• This technique reduces the complexity of sample preparation and analysis compared to previous methods.
• The approach is sensitive enough to detect nutritional effects on protein synthesis, highlighting its potential for physiological research.