BPC-157 vs BPC-157 Acetate: Salt Forms, Mass and Lab Reports

BPC-157 acetate is the same peptide as BPC-157, the 15-residue sequence GEPPPGKPADDAGLV, supplied as a salt with acetate counter-ions. The peptide itself is unchanged: formula C62H98N16O22, average mass about 1419.6 g/mol. What differs is what else is in the powder. Each acetate adds about 60 g/mol, so a fully formed di-acetate salt is about 1539.7 g/mol and about 92% peptide by mass. Synthetic peptides often leave purification as trifluoroacetate (TFA) salts instead, and “acetate” on a label usually means the TFA has been exchanged.

BPC-157 salt forms at a glance

Source: calculated from standard atomic masses (acetic acid 60.05 g/mol, trifluoroacetic acid 114.02 g/mol). Water, which every lyophilised solid also holds, is left out.

Research materials: Vortex supplies BPC-157 as a lyophilised research reagent: BPC-157 peptide 10mg. Lab reports: /coa/.

Why synthetic peptides are sold as salts

Most synthetic peptides are made by solid-phase synthesis. Cleavage from the resin and reversed-phase purification both use trifluoroacetic acid, so peptides with basic groups usually come out as trifluoroacetate salts [1]. The TFA ion is held tightly. Roux and colleagues compared three ways to exchange it on a model peptide: reversed-phase HPLC, ion-exchange resin, and deprotonating then reprotonating the amino groups. The first two exchanged TFA, partly to almost completely, for the counter-ion of a weaker acid such as acetic acid [1].

The counter-ion is not a detail. A review of peptide counter-ions notes that peptides commonly occur as salts with different counter-ions, and that the counter-ion affects structure and physicochemical properties [2]. Acetate and TFA salts of the same peptide are the same molecule in different solids. Our explainer on trifluoroacetic acid in peptides covers TFA in more depth.

How many counter-ions BPC-157 can carry

The number of counter-ions follows from the sequence. BPC-157 has two basic groups: the free N-terminal amine of glycine 1 and the side-chain amine of lysine 7. It has no arginine or histidine. It also has four acidic groups: glutamate 2, aspartates 10 and 11, and the free C-terminal acid. At neutral pH the peptide carries a net charge of about minus two.

Under the acidic conditions of purification, the two amines are protonated and the acidic groups are largely not ionised, so each amine can pair with one counter-ion. A fully formed salt therefore carries up to two acetate or TFA ions per molecule. Real lots can sit anywhere between, which is why counter-ion content is measured rather than assumed.

Some sellers also list a BPC-157 arginate. There the counter-ion is the amino acid L-arginine, paired with the peptide’s acidic groups rather than its amines. It is a third salt form with its own mass, and a label naming it is making a separate claim that needs its own counter-ion data.

What the salt form does to the numbers on a label

The salt form matters most for net content. If a “10 mg” label refers to the gross mass of powder, a di-acetate solid holds about 9.2 mg of peptide and a di-TFA solid about 8.6 mg, before residual water is counted. If the label refers to net peptide, the powder weighs more than 10 mg. A label alone does not say which.

Source: our arithmetic from the masses in the first table. Residual water lowers the peptide figure further.

How a lab report tells the forms apart

Identity by mass spectrometry: the same answer for every salt

In LC-MS, the counter-ion separates from the peptide, so every salt form gives the same peptide ions. Electrospray ionisation gives multiply charged ions for peptides and proteins [3]. For BPC-157 (monoisotopic mass 1418.70 Da), expect [M+H]⁺ at m/z 1419.71 and [M+2H]²⁺ at m/z 710.36. A correct identity result confirms the peptide. It does not say which salt the powder is.

Purity by HPLC: also blind to the salt

Reversed-phase separations of peptides are typically run at low pH, and selectivity depends on column and solvent [4]. Purity is reported as the peptide peak’s share of UV-detected peak area. Acetate and TFA do not appear as peptide peaks, so a 99% HPLC purity figure is the same for either salt. Our explainer on HPLC peptide purity covers what the figure measures.

Counter-ion and net content: the tests that differ

The salt form shows up in two measurements. A counter-ion assay, such as ion chromatography, measures acetate or TFA directly. Fluorine NMR or infrared spectroscopy can confirm whether TFA has been removed [1]. A net content assay measures how much peptide the vial holds, which reflects counter-ion and water together. A report that lists only HPLC purity and MS identity cannot confirm an “acetate” claim.

Source: references 1, 3 and 4. Our explainer on reading a peptide COA covers each field of a report.

Checking a lot of BPC-157

Vortex publishes lab reports at /coa/, summarised on the lab report data page. A report for the standalone BPC-157 10 mg product has not been published yet. The related BPC-157 + TB-500 10/10 mg product has a partner-facility report from ILS Laboratories (lot PS07-BCTB20) listing 99.94% HPLC purity and 21.12 mg combined net content. That net content figure is a measurement of peptide, so it already reflects whatever counter-ion and water the solid holds. For an identity-first overview of the peptide itself, see our BPC-157 overview.

Frequently asked questions

Is BPC-157 acetate the same peptide as BPC-157?

Yes. BPC-157 acetate is the same 15-residue peptide, GEPPPGKPADDAGLV, paired with acetate counter-ions. The salt form changes the mass of the solid, not the peptide.

What is the difference between BPC-157 acetate and BPC-157 TFA?

Only the counter-ion. Acetate adds about 60 g/mol per ion and trifluoroacetate about 114 g/mol, so a di-acetate solid is about 92% peptide by mass and a di-TFA solid about 86%. Peptides usually leave purification as TFA salts, and acetate forms are made by exchanging the TFA.

Does mass spectrometry show whether BPC-157 is the acetate?

No. In LC-MS the counter-ion separates from the peptide, so every salt form gives the same peptide ions, [M+H]+ at m/z 1419.71 and [M+2H]2+ at m/z 710.36. A counter-ion assay such as ion chromatography is needed to confirm acetate.

How much peptide is in 10 mg of BPC-157 acetate?

About 9.2 mg if the 10 mg is gross powder mass of a fully formed di-acetate, before residual water. If the label states net peptide, the vial holds 10 mg of peptide and weighs more. A net content result on the lab report settles which.

Research materials: BPC-157 peptide 10mg is supplied as a lyophilised research reagent. Published lab reports are at /coa/.

References

1. Roux S, Zékri E, Rousseau B, Paternostre M, Cintrat JC, Fay N. Elimination and exchange of trifluoroacetate counter-ion from cationic peptides: a critical evaluation of different approaches. J Pept Sci. 2008;14(3):354-359. PMID 18035848
2. Sikora K, Jaśkiewicz M, Neubauer D, Migoń D, Kamysz W. The role of counter-ions in peptides: an overview. Pharmaceuticals (Basel). 2020;13(12):442. PMID 33287352
3. Fenn JB, Mann M, Meng CK, Wong SF, Whitehouse CM. Electrospray ionization for mass spectrometry of large biomolecules. Science. 1989;246(4926):64-71. PMID 2675315
4. Mant CT, Cepeniene D, Hodges RS. Reversed-phase HPLC of peptides: assessing column and solvent selectivity on standard, polar-embedded and polar endcapped columns. J Sep Sci. 2010;33(19):3005-3021. PMID 21038458

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