Catalogue / Oxytocin
Oxytocin
A nine residue cyclic nonapeptide closed by a single disulfide bridge between cysteine 1 and cysteine 6, C-terminally amidated.
| Molecular formula | C43H66N12O12S2 |
| Average mass | 1007.19 Da |
| Monoisotopic mass | 1006.4365 Da |
| Residues | 9 |
| Termini | C-terminal amide, 1 disulfide bridge |
| Class | Signalling and mitochondrial peptides |
| Determination | Peptide analysis, catalogue compound |
| Price | 341 USD |
Computed at build time from the composition shown on this page, not transcribed from a supplier datasheet.
Oxytocin has an average molecular weight of 1007.19 daltons and a monoisotopic mass of 1006.4365 daltons. Identity is confirmed by matching the measured deconvoluted mass to that figure, and purity is reported separately by reversed-phase chromatography at 214 nm. The two numbers answer different questions and neither substitutes for the other.
| One letter | CYIQNCPLG |
| Three letter | Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly |
| Modifications | C-terminal amide, 1 disulfide bridge |
The formula and both masses in the table above are derived from this sequence and these terminal modifications. A reader who believes a figure is wrong can check the composition rather than take the number on trust, which is the point of publishing it this way.
A sequence is not an identity result. It is the expected composition against which a measured mass is compared, and the comparison is what appears on the certificate.
| Charge | m/z |
|---|---|
| [M+1H]+ | 1007.444 |
| [M+2H]2+ | 504.226 |
These are the ions an electrospray source is expected to produce for a neutral mass of 1006.4365 daltons, computed from the monoisotopic mass and the proton mass. They are what a raw spectrum should show before deconvolution.
A report that gives only a deconvoluted mass without the charge states it was derived from cannot be checked. Deconvolution is a calculation, and a calculation whose inputs are not shown is an assertion.
| The disulfide bridge must be intact. A reduced sample is two daltons heavier and has lost the ring, and a reducing agent anywhere in the preparation will produce that result artefactually. |
| Intermolecular disulfide scrambling gives dimers and higher oligomers. Size exclusion detects them; a purity chromatogram at 214 nm may not resolve them from the parent. |
| The peptide degrades in solution above pH 7 and the compendial monograph is specific about storage. |
Every compound fails in its own way. A generic peptide method applied without regard to these specifics produces a number that looks like a result and is not one.
Endogenous peptides with defined sequences, mostly unmodified, where the analytical question is simply whether the delivered material is the stated sequence at the stated mass.
LC-MS identity with deconvolution and RP-HPLC purity at 214 nm.
Where the delivered milligram figure matters rather than the percentage, net peptide content by combustion analysis and water by Karl Fischer are added, and the certificate carries a closed mass balance instead of a single purity number.
| LC-MS identity | Measured mass |
| RP-HPLC purity | Area at 214 nm |
| Net peptide content | Milligrams |
| Water content | Karl Fischer |
| Counter-ion | Ion chromatography |
| Bacterial endotoxins | USP <85> |
What is the molecular weight of Oxytocin?
The average molecular weight is 1007.19 daltons and the monoisotopic mass is 1006.4365 daltons, computed from the sequence CYIQNCPLG shown on this page. Both figures are calculated rather than transcribed, so they can be checked against the stated composition.
How is Oxytocin tested for purity and identity?
LC-MS identity with deconvolution and RP-HPLC purity at 214 nm. Purity describes the chromatographable fraction only and is not the same quantity as the peptide mass delivered per vial.
What goes wrong when Oxytocin is analysed?
The disulfide bridge must be intact. A reduced sample is two daltons heavier and has lost the ring, and a reducing agent anywhere in the preparation will produce that result artefactually.
What does Oxytocin analysis cost at ANALYTON?
Peptide analysis, catalogue compound is priced at 341 US dollars, covering the determinations described on this page. Content, safety and elemental determinations are ordered alongside and are priced separately on the price list.
Other compounds in this class
Updated 2026-09-01. Masses computed at build, not transcribed.