Oxytocin Molecular Weight, Sequence & CAS Reference
This analytical reference sheet provides essential molecular specifications, chemical structure details, and sequence parameters for oxytocin. Designed for laboratory investigators, it details formula weights, salt forms, counterion adjustments, and primary sequence data required for precise in vitro and preclinical experimentation.
Quick answer
This analytical reference sheet provides essential molecular specifications, chemical structure details, and sequence parameters for oxytocin. Designed for laboratory investigators, it details formula weights, salt forms, counterion adjustments, and primary sequence data required for precise in vitro and preclinical experimentation.
Key takeaways
- [Oxytocin](/research-peptides/oxytocin) is a classic nonapeptide neurohormone widely studied in biochemical, neurological, and physiological research models.
- The primary sequence of [oxytocin](/research-peptides/oxytocin) consists of nine amino acid residues arranged with an intramolecular disulfide bridge.
- Synthesized peptides are isolated following cleavage and purification via reverse-phase high-performance liquid chromatography (RP-HPLC).
- [Oxytocin](/research-peptides/oxytocin) shares structural homology with other neurohypophysial peptides, forming part of a well-studied class of evolutionary conserved signaling molecules.
Chemical Identity and Primary Molecular Specifications
Oxytocin is a classic nonapeptide neurohormone widely studied in biochemical, neurological, and physiological research models. Characterized by a conserved cyclic structure, this research compound is utilized in laboratory settings to analyze receptor binding kinetics, signal transduction pathways, and cellular response mechanisms. When planning quantitative assays, laboratory researchers require exact physical parameters to calculate precise molar concentrations and working dilutions.
The canonical chemical formula for free-base oxytocin is C43H66N12O12S2, yielding a calculated monoisotopic mass of 1006.44 Da and a standard average molecular weight of approximately 1007.19 g/mol. Assigned the Chemical Abstracts Service reference standard CAS 50-56-6, oxytocin is synthesized via solid-phase peptide synthesis (SPPS) for controlled lab applications. Researchers examining our catalog of high-purity research peptides can reference these baseline values when preparing research-grade oxytocin 10mg vials for experimental protocols.
Amino Acid Sequence and Structural Topography
The primary sequence of oxytocin consists of nine amino acid residues arranged with an intramolecular disulfide bridge. In standard single-letter amino acid code, the sequence is represented as CYIQNCPLG-NH2. Represented in three-letter notation, the sequence is H-Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly-NH2, featuring a C-terminal amidation that is critical for receptor selectivity and metabolic stability during in vitro testing.
Structurally, an intramolecular disulfide bond connects the cysteine residue at position 1 to the cysteine residue at position 6. This covalent linkage forms a 20-membered cyclic hexapeptide ring structure (Cys1-Tyr2-Ile3-Gln4-Asn5-Cys6), from which a tripeptide carboxyl-terminal tail (Pro7-Leu8-Gly9-NH2) extends. This rigid cyclic backbone is a key determinant for target binding in cell-based assays. Researchers can explore additional structural studies and sequence datasets within the PX1 research library.
Salt Forms, Counterion Impact, and Net Peptide Content
Synthesized peptides are isolated following cleavage and purification via reverse-phase high-performance liquid chromatography (RP-HPLC). During this process, trifluoroacetic acid (TFA) or acetic acid is routinely used as a mobile phase modifier. Consequently, research-grade oxytocin is supplied as a lyophilized salt, typically as an acetate salt or trifluoroacetate (TFA) salt form. Understanding the specific counterion present is vital for calculating exact net peptide content.
Gross lyophilized powder weight includes the active peptide molecule, bound counterions (such as TFA- or CH3COO-), and residual atmospheric moisture. Net peptide content usually ranges between 75% and 85% of total powder mass. For example, a 10 mg vial of lyophilized powder with an 80% net peptide content contains 8.0 mg of actual oxytocin peptide. To ensure accurate molar calculations in laboratory assays, investigators must inspect the lot-specific Certificate of Analysis (COA) to verify net peptide purity and counterion percentage prior to reconstitution.
Comparative Structure: Oxytocin, Vasopressin, and Carbetocin
Oxytocin shares structural homology with other neurohypophysial peptides, forming part of a well-studied class of evolutionary conserved signaling molecules. Small alterations in amino acid sequence yield substantial shifts in receptor selectivity, biological activity, and physical properties across different preclinical models.
Comparing these compounds highlights the structural determinants of receptor affinity. Oxytocin differs from arginine vasopressin at positions 3 and 8; oxytocin features isoleucine and leucine at these positions, whereas arginine vasopressin contains phenylalanine and arginine, drastically shifting its affinity toward vasopressin V1a and V2 receptors. Furthermore, synthetic analogs such as carbetocin incorporate a modified N-terminal group and a thioether bridge in place of the native disulfide bond, conferring enhanced enzymatic stability in preclinical research. Evaluating these structural variants assists researchers in selecting the appropriate molecule for specific receptor-binding assays.
Solubilization, Reconstitution, and Laboratory Handling
Lyophilized oxytocin presents as a white to off-white cake or powder. For optimal stability and recovery, reconstitution should be performed using sterile laboratory solvents such as bacteriostatic water, sterile water for injection, or phosphate-buffered saline (PBS, pH 7.4). Avoid high-shear agitation or vigorous vortexing, which can induce physical aggregation or rupture delicate secondary structures; gentle inversion or swirling is recommended.
To establish precise working concentrations for microplate or cell culture experiments, researchers should use the PX1 reconstitution calculator. Stock solutions should be aliquoted into single-use polypropylene tubes and stored at -20°C or -80°C to minimize freeze-thaw degradation. Lyophilized vials should be maintained at -20°C in a desiccated environment until solubilization.
Quality Verification: Analytical Mass Spectrometry and HPLC Protocols
Assessing the purity and molecular weight of synthetic oxytocin requires rigorous analytical instrumentation. High-Performance Liquid Chromatography (HPLC) is employed to determine chromatographic purity, ensuring the compound exceeds standard laboratory thresholds (typically ≥98% purity). Chromatograms confirm the absence of major truncation sequence impurities or improperly folded disulfide isomers.
Electrospray Ionization Mass Spectrometry (ESI-MS) or MALDI-TOF is simultaneously performed to verify the precise molecular mass. The observed mass peak must correspond to the calculated theoretical value of 1007.19 g/mol (or 1006.44 Da monoisotopic mass). PX1 Research ensures every lot undergoes independent third-party verification in ISO 17025 accredited facilities, confirming identity, purity, and low endotoxin thresholds (<0.01 EU/µg) suitable for rigorous in vitro research.
In Vitro Receptor Binding and Mechanism Targets
In preclinical laboratory settings, oxytocin is primarily utilized to investigate interactions with the G-protein coupled oxytocin receptor (OXTR). Receptor activation initiates a downstream intracellular cascade via the Gq/11 pathway, stimulating phospholipase C (PLC) activity, generating inositol trisphosphate (IP3) and diacylglycerol (DAG), and driving intracellular calcium mobilization.
Preclinical in vitro assays utilize oxytocin to characterize binding kinetics, receptor dimerization, and beta-arrestin recruitment patterns. In addition, animal models examine how oxytocin signaling modulates central neurotransmitter pathways, inflammatory pathways, and vascular tone. These studies are designed exclusively to further biochemical understanding in controlled experimental environments.
Sourcing Laboratory-Grade Oxytocin from PX1 Research
For dependable experimental outcomes, research institutions require reagents with verified consistency, high chemical purity, and complete lot traceability. PX1 Research synthesizes compounds in state-of-the-art, GMP-compliant USA facilities, adhering to stringent quality control criteria at every stage of production.
Every batch of oxytocin is backed by comprehensive analytical reporting, transparent counterion data, and rapid domestic distribution. Academic institutions, biotechnology firms, and institutional laboratories looking to secure bulk quantities or establish standing supply agreements can register for wholesale lab accounts to access direct supply pipelines and dedicated institutional support.
Frequently Asked Questions
What is the exact molecular weight and CAS number of oxytocin?
Oxytocin has an average molecular weight of approximately 1007.19 g/mol and a monoisotopic mass of 1006.44 Da. Its assigned Chemical Abstracts Service CAS number is 50-56-6.
What is the primary amino acid sequence of oxytocin?
The primary sequence of oxytocin is Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly-NH2 (CYIQNCPLG-NH2), featuring an intramolecular disulfide bridge between Cys1 and Cys6 and a C-terminal amide.
How does counterion content affect net peptide weight?
Lyophilized peptide salts contain counterions (such as TFA or acetate) and residual moisture. Net peptide content typically ranges between 75% and 85%. Researchers must adjust concentration calculations using the net peptide purity provided on the COA.
How should research-grade oxytocin be stored after reconstitution?
Reconstituted oxytocin solutions should be divided into single-use aliquots and stored at -20°C or -80°C to prevent freeze-thaw degradation. Lyophilized powder should be kept at -20°C away from moisture.
What analytical tests are used to verify oxytocin quality?
Purity is measured using Reverse-Phase High-Performance Liquid Chromatography (RP-HPLC), mass identity is verified via Electrospray Ionization Mass Spectrometry (ESI-MS), and safety for cell models is confirmed through endotoxin testing.
What is the difference between oxytocin and vasopressin?
Oxytocin and arginine vasopressin are homologous nonapeptides but differ at positions 3 and 8 (Ile3/Leu8 in oxytocin vs. Phe3/Arg8 in vasopressin), which drastically alters their receptor affinity profiles.
Is oxytocin supplied by PX1 Research suitable for human use?
No. All compounds supplied by PX1 Research are strictly intended for laboratory research use only in vitro or in preclinical animal models. They are not for human or veterinary administration.
What endotoxin limits apply to PX1 Research oxytocin?
PX1 Research oxytocin lots undergo testing to ensure endotoxin levels remain below strictly monitored research thresholds (typically <0.01 EU/µg), preventing endotoxin-induced interference in cell culture experiments.
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