Source comparison
Understanding Peptide Content vs Net Weight
Peptide content is reported as a percentage of the net weight in the vial. A 5mg vial of MOTS-C with 78% peptide content contains 3.9mg of actual peptide and 1.1mg of counterions (typically acetate or trifluoroacetate from the purification process) plus residu
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- Peptide content is reported as a percentage of the net weight in the vial. A 5mg vial of MOTS-C with 78% peptide content contains 3.9mg of actual peptide and 1.1mg of counterions (typically acetate or trifluoroacetate from the purification process) plus residual moisture. This distinction affects reconstitution calculations. If you assume 5mg peptide and dissolve it in 5mL bacteriostatic water, your final concentration is 0.78mg/mL, not 1mg/mL.
- The counterion fraction is unavoidable. Peptides are purified through reversed-phase HPLC using acidic mobile phases, which leaves trifluoroacetic acid (TFA) or acetic acid bound to basic amino acid residues like arginine and lysine. During lyophilisation, these counterions remain associated with the peptide structure. Peptide content between 70–85% is normal and expected. Values below 70% suggest either excessive moisture absorption (storage failure) or incomplete lyophilisation (manufacturing defect).
- When calculating reconstitution volumes, always use the peptide content value from the COA, not the nominal fill weight on the vial label. If your experimental protocol requires 10mg MOTS-C total and the vial contains 78% peptide content, you need 12.8mg net weight to deliver 10mg active peptide. Ignoring this adjustment systematically underdoses every study by 22%. Enough to shift dose-response curves and compromise reproducibility.
- Without a COA tied to your specific vial's batch number, there's no way to verify what arrived. The label might say '10mg MOTS-C >98% purity'. But those numbers mean nothing without independent third-party analysis documented in a batch-specific report. At Real Peptides, every synthesis batch undergoes HPLC, mass spectrometry, and endotoxin testing before release, and the full analytical package is available with every order. That's not a differentiator. It's the baseline standard for research-grade material.
- If the batch numbers don't match, if the molecular weight is wrong, or if no chromatogram is attached. The peptide in your hand is not verified. Use it anyway and you're running experiments on an undefined compound. That's the reality most suppliers won't state plainly, because acknowledging it would require actually providing complete analytical documentation for every batch shipped.