An efficient, amine-specific iTRAQ labeling method improves the peptide and protein identification rates

Area of Science:

• Proteomics
• Analytical Chemistry
• Biochemistry

Background:

• Isotope tags for relative and absolute quantification (iTRAQ) are widely used for proteomics quantification.
• Standard iTRAQ labeling can react with hydroxyl groups (serine, threonine, tyrosine), especially near histidine, causing biases and reducing identification rates.

Purpose of the Study:

• To develop a novel iTRAQ labeling method that overcomes detrimental overlabeling while maintaining high amine labeling efficiency.
• To optimize reaction conditions including temperature, concentration, time, buffer, and pH.

Main Methods:

• Investigated the impact of various reaction parameters on iTRAQ labeling performance.
• Compared the novel method against the standard iTRAQ manufacturer's method.

Main Results:

• The novel method reduced overlabeled peptides by 55-fold compared to the standard method.
• Achieved comparable amine labeling efficiency.
• Eliminated systematic bias against histidyl- and hydroxyl-containing peptides.
• Increased peptide identification by 23.9% and protein identification by 9.8%.

Conclusions:

• The developed iTRAQ labeling method significantly enhances proteome quantification accuracy and sensitivity.
• This method offers superior performance by mitigating overlabeling issues inherent in standard iTRAQ protocols.