Ipamorelin Molecular Weight, Sequence & CAS Reference

Chemical Identity & Physicochemical Overview

Ipamorelin (chemically identified as Aib-His-D-2Nal-D-Phe-Lys-NH2) is a synthetic pentapeptide derivative belonging to the growth hormone secretagogue (GHS) class. Originally developed to selectively target the growth hormone secretagogue receptor (GHS-R1a), this compound mimics the binding motif of endogenous ghrelin without engaging secondary neuroendocrine pathways. In laboratory environments, research-grade Ipamorelin is utilized to study receptor binding kinetics, signal transduction mechanisms, and somatotroph-specific cellular responses.

Establishing exact chemical parameters—such as absolute molecular weight, empirical formula, counterion presence, and sequence modifications—is essential for accurate molar preparation and analytical assay calibration. In contrast to unverified commercial samples, standardized reference materials must conform to strict physical metrics validated via nuclear magnetic resonance (NMR) spectroscopy, liquid chromatography-mass spectrometry (LC-MS), and high-performance liquid chromatography (HPLC).

Amino Acid Sequence & Structural Architecture

The primary structure of Ipamorelin consists of a modified pentapeptide sequence terminating with a C-terminal carboxamide modification. Its defined sequence is represented as follows:

Aib - L-His - D-2Nal - D-Phe - L-Lys - NH2

The presence of non-canonical and D-stereoisomeric amino acid residues provides significant structural stability against enzymatic cleavage by ubiquitous plasma endopeptidases. Specifically, the N-terminal alpha-aminoisobutyric acid (Aib) residue introduces steric hindrance around the N-terminus, while D-2-naphthylalanine (D-2Nal) and D-phenylalanine (D-Phe) enforce specific spatial conformations required for high-affinity GHS-R1a receptor engagement. The C-terminal lysine residue is modified via amidation (-NH2), neutralizing the terminal carboxylic acid charge to further enhance enzymatic resistance during long-duration in vitro stability trials across our broader catalog of research peptides.

Molecular Weight, Empirical Formula & Mass Spectrometry

The calculated monoisotopic and average molecular weights of Ipamorelin free base are derived from its elemental chemical composition:

Empirical Formula: C38H49N9O5 Monoisotopic Mass: 711.3857 Da Average Molecular Weight: 711.85 g/mol

When performing electrospray ionization mass spectrometry (ESI-MS) or matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF), researchers typically observe the protonated molecular ion peak [M+H]+ at m/z 712.39, along with doubly charged species [M+2H]2+ at m/z 356.70 depending on ionization energy and solvent matrix parameters. Accurate determination of these mass values is necessary for identifying degradation products, verifying sequence integrity, and confirming the absence of truncated peptide impurities following chemical synthesis.

CAS Registry Number & Chemical Identifiers

To ensure precise tracking across international chemical databases, regulatory literature, and material safety data sheets (MSDS), Ipamorelin is assigned distinct reference identifiers:

CAS Registry Number: 170851-70-4 IUPAC Chemical Name: (2S)-6-amino-2-[[(2R)-2-[[(2R)-2-[[(2S)-2-[[(2-amino-2-methylpropanoyl)amino]-3-(1H-imidazol-5-yl)propanoyl]amino]-3-naphthalen-2-ylpropanoyl]amino]-3-phenylpropanoyl]amino]hexanamide PubChem CID: 9831659 ChemSpider ID: 8007357

Referencing the verified CAS registry number ensures that laboratory procurement teams source authentic chemical entities, avoiding confusion with non-selective growth hormone secretagogues or improperly characterized structural analogs.

Salt Form Variations & Net Peptide Content Calculation

Lyophilized research peptides are rarely produced as 100% free bases. During the final purification step via preparative reverse-phase HPLC, mobile phase modifiers such as trifluoroacetic acid (TFA) or acetic acid are introduced, yielding the corresponding trifluoroacetate or acetate salt forms. Consequently, a portion of the total dry powder weight consists of counterions and bound residual moisture.

Net Peptide Content (NPC) represents the actual percentage of peptide mass relative to total dry powder weight (which includes salt counterions and residual water). For instance, a 5 mg vial of Ipamorelin acetate with an NPC of 80% contains 4.0 mg of pure peptide mass and 1.0 mg of counterion and moisture weight. When calculating molarity for precise cellular assays, researchers must account for the lot-specific NPC reported on the lot-specific Certificate of Analysis to maintain experimental reproducibility.

Reconstitution Mathematics & Solution Handling for Assay Design

To achieve target concentrations for in vitro binding studies or cell culture applications, research personnel must reconstitute lyophilized peptide cakes using sterile laboratory solvents, such as Bacteriostatic Water (0.9% benzyl alcohol) or sterile deionized water.

Calculating final concentration requires adjusting for solvent volume and net peptide purity. For precise volumetric dilutions, researchers utilize an automated reconstitution calculator to convert total mass and net peptide content into accurate micromolar (µM) or millimolar (mM) stock solutions. Standard laboratory protocol recommends initial solubilization in a small volume of sterile aqueous buffer, avoiding vigorous mechanical agitation to prevent surface-induced aggregation or peptide shear stress.

Preclinical Mechanism of Action: Ghrelin Receptor Selectivity

Preclinical studies suggest that Ipamorelin functions as a highly selective agonist of the growth hormone secretagogue receptor (GHS-R1a). In vitro receptor binding assays demonstrate that Ipamorelin binds GHS-R1a with nanomolar affinity, triggering G-protein-coupled intracellular calcium mobilization and downstream somatotroph stimulation.

Unlike earlier generation secretagogues, animal studies indicate that Ipamorelin stimulates selective, pulsatile growth-hormone release without inducing significant elevations in secondary pituitary hormones such as cortisol, adrenocorticotropic hormone (ACTH), or prolactin. This high degree of receptor specificity makes Ipamorelin a valuable reference standard for evaluating downstream metabolic pathways and somatotropic axis signaling in cellular models without the confounding secondary endocrine activation seen in non-selective ligands.

Comparative Analysis: Ipamorelin vs. Related Secretagogues

Evaluating Ipamorelin alongside structurally and functionally related research compounds provides key insights into secretagogue selectivity and pharmacodynamics. The comparative table below highlights key parameters across related peptides studied within our peptide research hub:

Ipamorelin: Pentapeptide (Aib-His-D-2Nal-D-Phe-Lys-NH2) | MW: 711.85 g/mol | Selective GH secretagogue; no significant cortisol/prolactin elevation. GHRP-6: Hexapeptide (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2) | MW: 873.01 g/mol | Potent GH secretagogue; moderate elevation of ACTH, cortisol, and prolactin. Hexarelin: Hexapeptide (His-D-2-Me-Trp-Ala-Trp-D-Phe-Lys-NH2) | MW: 887.04 g/mol | High-affinity GHS-R agonist; demonstrates receptor desensitization upon prolonged exposure. CJC-1295 Without DAC: Tetradecapeptide derivative | MW: 3367.97 g/mol | GHRH receptor agonist; acts synergistically with GHS-R agonists in preclinical models.

Comparative in vitro assays indicate that while Hexarelin and GHRP-6 display high potency, Ipamorelin demonstrates superior target selectivity, avoiding non-target neuroendocrine receptor activation.

Analytical Purity & Quality Verification Standards

Maintaining rigorous quality control standards is critical for reliable preclinical research. Every synthesis lot of Ipamorelin supplied by PX1 Research undergoes stringent testing in independent ISO 17025 accredited laboratories located within the USA.

Purity is routinely verified via analytical HPLC, ensuring a minimum threshold of ≥99.0% purity. Chemical structure and molecular weight are confirmed using high-resolution electrospray ionization mass spectrometry (ESI-MS). Furthermore, routine kinetic chromogenic LAL assays are conducted to enforce strict endotoxin limits (<0.05 EU/mg), eliminating pyrogenic interference during cell culture experiments. Researchers purchasing for institutional facilities can also request volume quotes for bulk laboratory orders.

Laboratory Storage, Handling & Stability Protocols

Lyophilized Ipamorelin exhibits optimal stability when stored in desiccated environments at -20°C or -80°C, protected from direct light exposure. Under these conditions, the dry peptide retains structural integrity for up to 24 months from the date of synthesis.

Following reconstitution with sterile aqueous solvents, stock solutions should be aliquoted into single-use polypropylene microcentrifuge tubes to prevent repeated freeze-thaw cycles. Reconstituted aqueous solutions stored at 2°C to 8°C should be utilized within 30 days to mitigate hydrolysis of the C-terminal amide group or histidine oxidation. Experimental designs requiring extended storage of reconstituted materials should maintain temperatures at -80°C.