BPC-157 vs TB-500: sequence, mass and identity data compared

The two names travel together because they are frequently sold as single vials and as combined blends. Chemically they have nothing in common: different parent proteins, different lengths, no shared sequence. Any comparison that matters at the bench is a comparison of identity data, purity data and handling, which is what the table above covers.

BPC-157 is a free-acid pentadecapeptide with a proline-rich N-terminal half (three consecutive prolines at positions 3-5) and an acidic Asp-Asp pair at positions 10-11. TB-500 is a short, strongly basic heptapeptide with two adjacent lysines and an acetylated N-terminus. Those features drive how each behaves in reversed-phase HPLC and in electrospray ionization.

In positive-mode electrospray, BPC-157 is usually seen as its singly and doubly protonated ions (about m/z 1420 and 711). TB-500, at 889 Da, gives an [M+H]+ near m/z 889-890 and an [M+2H]2+ near m/z 445. A sodium adduct [M+Na]+ about 22 units above [M+H]+ is common for both and is not evidence of a different compound.

A certificate that labels a mass spectrum as BPC-157 but shows its main peaks near 445 and 889, or the reverse, describes the wrong material or a mislabeled sample. That check takes seconds and needs no instrument, only the expected values. The LC-MS m/z calculator on this site prints them for any charge state.

1. Match the observed m/z to the expected value for the stated charge state (within the lab's reported tolerance).
2. Check whether the lab reports average or monoisotopic values; the difference is about 0.5-1 unit at this size.
3. Adducts (+Na, +K) and in-source fragments are normal; an unexplained dominant peak is a question for the lab.

HPLC-UV purity is the area of the main peak as a percentage of all detected peak area at the stated wavelength. It does not identify the peak (that is the job of the mass spectrum), and it does not report net peptide content: counter-ions such as acetate or trifluoroacetate and residual water are invisible to it. A certificate should therefore report purity, identity and measured quantity as three separate results.

Because TB-500 is small and very polar, it elutes early on many C18 gradients. An early, sharp main peak is not by itself a warning sign; a missing chromatogram is.

Ask for a lot-specific certificate with the testing laboratory's name, the lot or batch number printed on the vial, the report date, an HPLC chromatogram with the purity figure, a mass spectrum with observed and expected values, and the measured quantity for the exact vial size. Published Vitality Chems lot reports for both compounds are listed on the testing page and can be looked up by lot number.

For TB-500 specifically, check which molecule the certificate's mass data support: the 889 Da fragment or the 4963 Da full-length thymosin beta-4. The companion guide explains why the two are confused and how to tell from a certificate.