Bremelanotide Specs: Sequence, MW & CAS
Part of the full Bremelanotide guide - a synthetic cyclic heptapeptide; alpha-melanocyte-stimulating hormone reference compound, identity-verified with a COA on every vial.
In brief
The molecular specification of PT-141 ties together a precise identity that researchers use to verify material and interpret its behavior. The entry records the name bremelanotide, a molecular formula of C50H68N14O10, an average molecular weight of 1025.2 g/mol (with a monoisotopic mass near 1024.5), and the free-base CAS Registry Number 189691-06-3, corroborated by a PubChem Compound ID of 9941379. Its full sequence is written as Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH, a cyclic heptapeptide whose backbone is closed by a lactam bridge between the Asp and Lys side chains. Each of these descriptors carries practical meaning: the formula and weight underpin the reconstitution math, the CAS and CID anchor material identity across databases, and the sequence notation encodes the exact structural devices that drive the pharmacology. The sections below unpack what these specification fields mean and how the sequence connects to function.
To the molecule
Molecular specifications
Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH (N-acetyl-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys], lactam-bridged between Asp and Lys side chains)The detail
A closer look
01
Identity descriptors: formula, weight, CAS and CID
The molecular formula C50H68N14O10 enumerates the exact atomic composition of one bremelanotide molecule, and it is recorded in PubChem under CID 9941379 and corroborated through ChemicalBook against CAS 189691-06-3. The average molecular weight of 1025.2 g/mol is the mass figure used in every concentration calculation, while the monoisotopic value of roughly 1024.5 is the mass that mass-spectrometry identity checks target. The CAS Registry Number 189691-06-3 designates the free base specifically, an important qualifier because salt forms would carry different numbers and masses. Together these identifiers let a laboratory cross-reference a received material against authoritative records, confirm it is the intended free-base compound rather than a salt or analog, and feed the correct molecular weight into stock-preparation arithmetic. They form the verifiable backbone of the spec card.
02
Sequence notation and structure-function meaning
The sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH is dense with functional information. Ac- marks the N-acetyl cap; Nle is norleucine, an unnatural residue substituting at the position; the cyclo[...] notation and the explicit Asp-Lys lactam bridge denote the side-chain-to-side-chain ring that cyclizes the heptapeptide; and D-Phe signals the inverted-stereochemistry phenylalanine. Read against the mechanism, every one of these elements is load-bearing. The acetyl cap and the lactam ring constrain the conformation and resist enzymatic cleavage; the ring pre-organizes the embedded His-D-Phe-Arg-Trp pharmacophore that engages the receptor orthosteric pocket; and the D-Phe both shapes the active geometry and adds degradation resistance. The sequence is therefore not just an identity string but a compact map of the structure-activity features that make this molecule a stable, MC4R-preferring melanocortin reference ligand.
The fine print: products are sold for laboratory research use only and are not for human or animal consumption. Bodily introduction into humans or animals is strictly prohibited by law. Bremelanotide is not a drug and is not intended to diagnose, treat, cure, or prevent any disease. These statements have not been evaluated by the FDA.