<unk>  (ball-and-stick) bound to its carrier protein neurophysin (ribbons)<unk>  is a peptide of nine amino acids (a nonapeptide) in the sequence cysteine-tyrosine-isoleucine-glutamine-asparagine-cysteine-proline-leucine-glycine-amide (Cys – Tyr – Ile – Gln – Asn – Cys – Pro – Leu – Gly – NH2, or CYIQNCPLG-NH2); its C-terminus has been converted to a primary amide and a disulfide bridge joins the cysteine moieties.<unk>  has a molecular mass of 1007 Da, and one international unit (IU) of<unk>  is the equivalent of 1.68 μg of pure peptide. While the structure of<unk>  is highly conserved in placental mammals, a novel structure of<unk>  was reported in 2011 in marmosets, tamarins, and<unk> her new world primates. Genomic sequencing of the gene for<unk>  revealed a single in-frame mutation (thymine for cytosine) which results in a single amino acid substitution at the 8-position (proline for leucine). Since this original Lee et al. paper, two<unk> her laboratories have confirmed Pro8-OT and documented additional<unk>  structural variants in this primate taxon. Vargas-Pinilla et al. sequenced the coding regions of the<unk> T gene in<unk> her genera in new world primates and identified the following variants in addition to Leu8- and Pro8-OT: Ala8-OT, Thr8-OT, and Val3/Pro8-OT. Ren et al. identified a variant further, Phe2-OT in howler monkeys. The biologically active form of<unk> , commonly measured by RIA and/or HPLC techniques, is the<unk> idized octapeptide<unk>  disulfide, but<unk>  also exists as a reduced straight-chain (non-cyclic) dithiol nonapeptide called<unk> e. It has been theorized that<unk> e may act as a free radical scavenger, as donating an electron to a free radical allows<unk> e to be re-oxidized to<unk>  via the dehydroascorbate / ascorbate redox couple. Recent advances in analytical instrumental techniques highlighted the importance of liquid chromatography (LC) coupled with mass spectrometry (MS) for measuring<unk>  levels in various samples derived from biological sources. Most of these studies optimized the<unk>  quantification in electrospray ionization (ESI) positive mode, using M+H+ as the parent ion at mass-to-charge ratio (m/z) 1007.4 and the fragment ions as diagnostic peaks at m/z 991.0, m/z 723.2 and m/z 504.2. These important ion selections paved the way for the development of current methods of<unk>  quantification using MS instrumentation. The structure of<unk>  is very similar to that of vasopressin. Both are nonapeptides with a single disulfide bridge, differing only by two substitutions in the amino acid sequence (differences from<unk>  bolded for clarity): Cys – Tyr – Phe – Gln – Asn – Cys – Pro – Arg – Gly – NH2.<unk>  and vasopressin were isolated and their total synthesis reported in 1954, work for which Vincent du Vigneaud was awarded the 1955 Nobel Prize in Chemistry with the citation: "for his work on biochemically important sulphur compounds, especially for the first synthesis of a polypeptide hormone."<unk>  and vasopressin are the only known hormones released by the human posterior pituitary gland to act at a distance. However,<unk>  neurons make<unk> her peptides, including corticotropin-releasing hormone and dynorphin, for example, that act locally. The magnocellular neurosecretory cells that make<unk>  are adjacent to magnocellular neurosecretory cells that make vasopressin. These are large neuroendocrine neurons which are excitable and can generate action potentials.
Oxytocin
Prolene
Antigonadotropin
Progestogen
Progestogen 
Progonadotropin
Menotropin
Psilocin