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Calculate mass changes for common post-translational and synthetic modifications applied to a peptide. Enter a sequence or molecular weight, then select modifications to apply.
Common peptide presets
Enter a peptide sequence or molecular weight to see results
Educational purposes only
This calculator uses average amino acid residue weights and standard modification mass shifts. Actual masses may vary due to site-specific chemistry, incomplete modifications, or instrument calibration. PEG masses are nominal averages. Isotope labeling assumes uniform labeling of all atoms. Always verify with experimental mass spectrometry data.