Peptide reference · Synthetic heptapeptide (tuftsin analog)
Selank COA check: molecular weight, formula and what to look for
Use these reference values to check the identity result on a Selank Certificate of Analysis. The theoretical average molecular weight of Selank is 751.87 Da and the monoisotopic mass is 751.434 Da.
Check a Selank COA nowSelank reference data
| Name | Selank |
|---|---|
| Also known as | TP-7 |
| Type | Synthetic heptapeptide (tuftsin analog) |
| Molecular formula | C33H57N11O9 |
| Average molecular weight | 751.87 g/mol (Da) |
| Monoisotopic mass | 751.4341 Da |
| Residues | 7 |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro |
| Reference source | PubChem CID 11765600 (formula and mass cross-checked) |
Expected mass spectrometry ions
A Selank COA may list one of these m/z values instead of the neutral mass. That is still consistent with Selank. How charge states work.
| Ion | m/z (monoisotopic) | m/z (average) |
|---|---|---|
| [M+H]+ | 752.44 | 752.88 |
| [M+2H]2+ | 376.72 | 376.94 |
| [M+3H]3+ | 251.49 | 251.63 |
What else can show up on a Selank COA
Masses calculated from Selank's formula and sequence for the adducts, degradation products and synthesis impurities a lab report can show. A match tells you what the extra peak probably is.
| Signal | Value | What it means |
|---|---|---|
| Na adduct, deconvoluted (M + 21.98) | 773.42 Da | Sodium adduct: an MS artifact, not a separate impurity. The [M+Na]+ ion itself is at M + 22.99 |
| K adduct, deconvoluted (M + 37.96) | 789.39 Da | Potassium adduct: an MS artifact. The [M+K]+ ion itself is at M + 38.96 |
| TFA adduct (M + 113.99) | 865.43 Da | Trifluoroacetic acid from purification seen as an adduct; residual TFA salt is real vial content |
Deletion sequences (5): one residue missing
| Signal | Value | What it means |
|---|---|---|
| des-Thr (M − 101.05) | 650.39 Da | Deletion sequence missing one Thr |
| des-Lys (M − 128.09) | 623.34 Da | Deletion sequence missing one Lys |
| des-Pro (M − 97.05) | 654.38 Da | Deletion sequence missing one Pro |
| des-Arg (M − 156.10) | 595.33 Da | Deletion sequence missing one Arg |
| des-Gly (M − 57.02) | 694.41 Da | Deletion sequence missing one Gly |
Adduct rows are deconvoluted masses (the shift seen against [M+H]+); the singly charged [M+Na]+ ion itself sits at M + 22.99. Deletion masses alone can't say which copy of a repeated residue is missing.
Short peptides like Selank (7 residues) are easy to make cleanly, so 98% HPLC purity should be the floor, not the goal. The full checklist is in how to read a peptide COA.
Selank-specific things to watch
Selank is a linear seven-residue peptide built from the tuftsin sequence (TKPR) plus a PGP tail. Reference mass is about 751.9 Da.
With two basic residues (Lys, Arg), Selank ionizes readily in positive mode: look for [M+H]⁺ near 752.4 m/z and [M+2H]²⁺ near 376.7 m/z.
Its sibling product N-Acetyl Selank is 42 Da heavier (acetyl group). If your result is about 42 Da high, check whether you were sold the acetylated version.
Selank has no methionine, tryptophan, cysteine, asparagine or aspartic acid, so oxidation, deamidation and aspartimide aren't expected. An unexplained +16 or -18 Da peak on a Selank COA is a reason to ask questions, not a normal impurity.
A missing proline gives about 654.4 Da; the deletion table on this page lists the rest. Selank is often sold as a nasal-spray solution, so check whether the COA tested the solution you'll receive or the powder before it was dissolved.
Compounds with similar mass
If a COA's mass is off, compare it with these neighbors. A match to one of them can point to a mislabeled product.
- Ipamorelin: 711.85 Da (-40.02 Da)
- Semax: 813.92 Da (+62.05 Da)
- GHRP-2: 817.97 Da (+66.10 Da)
Sources
- PubChem CID 11765600: Selank formula and reference mass.
- CIAAW: Standard atomic weights: Used to calculate average molecular weights.
- NIST CODATA: proton mass: Used to convert m/z charge states to neutral mass.
- PeptideCOACheck methodology: How the checker's thresholds work.
Last updated . Written and maintained under our editorial policy. Found an error? See corrections.
Frequently asked questions
What mass should N-Acetyl Selank show?
About 793.9 Da average, 42 Da above plain Selank (751.9 Da).
Does Selank oxidize?
It has no methionine, tryptophan or cysteine, so oxidation isn't a normal degradation route. A +16 Da peak deserves a question.
What does 376.7 m/z mean on a Selank COA?
The [M+2H]2+ ion. Selank's lysine and arginine make it ionize readily in positive mode.
For laboratory research use only. This page describes analytical chemistry data. It is not medical advice and makes no claim about effects in humans or animals.