Oxytocin 2mg

What Oxytocin is

Oxytocin is a nonapeptide with the sequence Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly-NH2 (CYIQNCPLG-NH2). The cysteines at positions 1 and 6 are joined by an intramolecular disulfide bond, which closes the first six residues into a ring and leaves Pro-Leu-Gly as a three-residue tail. That tail ends in a glycinamide, so the C-terminus is a primary amide rather than a free acid. In 1953 it became the first peptide hormone to be prepared by chemical synthesis, work that made it a reference point in the history of peptide chemistry.

Its closest structural neighbor is arginine vasopressin, which uses the same ring-and-tail architecture and the same disulfide but carries phenylalanine at position 3 and arginine at position 8 in place of isoleucine and leucine. Those two substitutions shift the mass by about 77 Da and change the charge, so the two peptides are straightforward to tell apart by mass and retention even though they are often discussed together.

Oxytocin 2mg specification

How Oxytocin is analyzed

The disulfide is the center of any oxytocin analysis. A reduced, open-chain form sits 2 Da above the cyclic peptide and elutes at a different position, while disulfide scrambling between molecules gives covalent dimers near twice the monomer mass, sometimes as separate parallel and antiparallel peaks. A trisulfide variant carrying an extra sulfur atom (+32 Da) is another recognized by-product. The sequence has three amide-related weak points: Gln4, Asn5 and the C-terminal glycinamide can each deamidate, adding roughly 1 Da and usually producing a nearby peak. With one tyrosine and no tryptophan, the 280 nm response is modest, so purity is read on the peptide bond near 214 nm.

Oxytocin’s reverse-phase HPLC purity is published here on its product page. No batch or lot code is printed on the vial; its crimp and cap color ties it to the published run.

Research contexts for Oxytocin

• Oxytocin receptor (OXTR) binding assays in membrane preparations from transfected cell lines
• In-vitro selectivity panels comparing OXTR with the vasopressin V1a, V1b and V2 receptor subtypes
• Disulfide stability, scrambling and dimer-formation studies in cyclic peptides
• Deamidation kinetics at Gln, Asn and C-terminal amide positions under controlled pH

This oxytocin is a chemical reference material for in-vitro and analytical laboratory work only, and it is not a pharmaceutical preparation.

Oxytocin questions

Why is the oxytocin ring six residues rather than nine?

Only the two cysteines at positions 1 and 6 form the disulfide, so the ring spans residues 1 to 6 and positions 7 to 9 hang outside it as the Pro-Leu-Gly-NH2 tail.

What does a peak about 2 Da heavier mean?

It is consistent with the reduced, linear peptide in which the disulfide has not formed or has been broken, leaving two free thiols.

How does oxytocin differ from vasopressin?

At two positions: Ile3 and Leu8 in oxytocin versus Phe3 and Arg8 in arginine vasopressin. The shared disulfide ring and amidated tail are otherwise the same.