Category: Compound Identity

How peptide disulfide bonds are formed, why bridges scramble, and why mass and HPLC alone cannot show which cysteines are paired with which.

Why BPC-157 shows a broad or shouldered HPLC peak: slow proline cis-trans isomerization, how to tell it from impurities, and what it means for purity.

How disulfide, lactam and head-to-tail cyclization change a peptide, and why a matching mass cannot confirm the intended ring on its own.

What a CAS Registry Number identifies for a peptide, why salts, amides and complexes get separate numbers, and how to check one for errors.

Ipamorelin contains three non-standard residues: Aib, D-2-Nal and D-Phe. What mass, composition and HPLC can and cannot confirm about each.

Thymosin beta-4 vs TB-500: why the 43-residue protein and the synthetic actin-binding fragment differ, and how identity is confirmed analytically.

When a synthetic peptide is the same molecule as its natural counterpart, and where modifications, impurities and stereochemistry make them differ.

How a peptide’s isoelectric point is set by its sequence and termini, why solubility is lowest near the pI, and where it matters in analysis.

Sermorelin, tesamorelin, CJC-1295, ipamorelin and hexarelin compared by sequence, length, modifications and mass, and how the two classes differ on HPLC.

Cartalax, Chonluten, Livagen, Pinealon, Cortagen, Cardiogen and Epithalon compared by sequence and mass, with HPLC behaviour and counter-ion notes.