MK-677 Molecular Weight, Sequence & CAS Reference

Chemical Identity and Structural Nomenclature

MK-677, commonly designated by its investigational code name Ibutamoren or Ibutamoren Mesylate, represents a potent, non-peptide growth hormone secretagogue (GHS). Unlike traditional peptide secretagogues comprising linear chains of amino acids, MK-677 belongs to the spiroindoline class of peptidomimetics. It was synthetically developed to mimic the natural somatotropic action of ghrelin, the endogenous ligand for the growth hormone secretagogue receptor 1a (GHS-R1a).

Because MK-677 is a small-molecule organic compound rather than a proteinaceous sequence, it lacks an amino acid sequence. Researchers evaluating MK-677 research material in laboratory assays should classify it as a synthetic spiroindoline derivative rather than a classical peptide chain. Its systematic IUPAC name is 2-amino-N-[(2R)-1-(1-methylsulfonylspiro[2H-indole-3,4'-piperidine]-1'-yl)-1-oxo-3-phenylpropan-2-yl]-2-methylpropanamide.

Molecular Formula, Weight, and CAS Registration

Precise mass spectrometry and elemental calculations establish the chemical baseline for MK-677 across analytical studies. In its free base form, the empirical molecular formula for MK-677 is C27H36N4O5S, corresponding to a monoisotopic molecular weight of 528.67 g/mol.

In laboratory research settings, MK-677 is most frequently supplied as a salt formulation to maximize solubility and benchtop stability, specifically as Ibutamoren Mesylate (methanesulfonate salt). The molecular formula for the mesylate salt complex is C27H36N4O5S · CH4O3S, yielding an aggregate molecular weight of 624.77 g/mol.

CAS registry assignments vary depending on the chemical state of the compound. The CAS Registry Number for MK-677 free base is 159752-10-0, whereas the CAS Registry Number for MK-677 methanesulfonate (mesylate) salt is 159634-47-6. Laboratory protocol documentation and material safety data sheets (MSDS) should reference CAS 159634-47-6 when utilizing salt-form reagents.

Sequence Analysis and Structural Distinctions

A common point of inquiry among biological researchers browsing the catalog of research peptides pertains to the primary amino acid sequence of MK-677. Strictly speaking, MK-677 does not possess a primary, secondary, or tertiary peptide sequence because it contains no peptide bonds (-CO-NH-) linking natural or unnatural L/D-amino acids.

Instead, the molecule was structurally engineered via rational drug design to reproduce the spatial conformation and pharmacophore features of ghrelin's active region. It features a central spiroindoline core, a sulfonamide moiety, and a modified d-phenylalanine derivative. This rigid, non-peptidic scaffold protects the compound from enzymatic cleavage by ubiquitous endopeptidases and dipeptidyl peptidases, providing high chemical stability in vitro compared to fragile linear peptides.

Salt Counterion Dynamics and Net Chemical Calculation

When performing quantitative assays or preparing working stock concentrations, researchers must account for the mass contribution of the counterion. In peptide chemistry, compounds are routinely prepared as trifluoroacetate (TFA) or acetate salts, which can account for 10% to 25% of the total measured dry weight.

For MK-677 mesylate, the methanesulfonate counterion (CH3SO3H, molecular weight ~96.10 g/mol) constitutes approximately 15.38% of the total molecular mass of the salt complex. Consequently, 100 mg of Ibutamoren Mesylate powder yields approximately 84.62 mg of net active MK-677 free base. Researchers calibrating biological assays or calculating concentration curves can utilize our laboratory reconstitution calculator to ensure precise molar calculations across diverse solvent formulations.

Preclinical Mechanism of Action and Receptor Interaction

MK-677 functions as an oral GH secretagogue studied for sustained growth-hormone and IGF-1 elevation through ghrelin-receptor activation. Preclinical binding studies demonstrate high-affinity binding to the GHS-R1a receptor located in the anterior pituitary and hypothalamic nuclei.

In vitro functional assays and animal models indicate that MK-677 binding activates the phospholipase C (PLC) signaling cascade, generating inositol trisphosphate (IP3) and diacylglycerol (DAG). This pathway triggers intracellular calcium mobilization and protein kinase C activation, leading to the pulsatile release of endogenous growth hormone (GH). Furthermore, preclinical models demonstrate that continuous exposure leads to secondary elevations in systemic insulin-like growth factor 1 (IGF-1) without disrupting normal feedback loops or depleting pituitary GH stores.

Comparative Analytical Profile: MK-677 vs. Peptide Secretagogues

In somatotropic research, scientists frequently contrast non-peptide peptidomimetics with traditional short-chain peptide secretagogues. Comparing structural, physical, and operational parameters helps researchers select the appropriate agonist for specific in vitro assays.

While MK-677 presents a non-peptidic spiroindoline architecture (MW 624.77 g/mol as mesylate), classical peptide secretagogues rely on specific amino acid sequences. For instance, ipamorelin is a pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2, MW 711.86 g/mol) that selectively targets GHS-R1a with minimal impact on cortisol or prolactin. Similarly, GHRP-6 is a hexapeptide (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2, MW 873.01 g/mol) that stimulates GH release but exhibits secondary binding effects. In contrast, growth hormone-releasing hormone (GHRH) analogs like CJC-1295 act via distinct GHRH receptors rather than GHS-R1a. Comparative data across these compounds are cataloged in the PX1 peptide research library.

Solubility, Stability, and Reconstitution Parameters

The mesylate salt form of MK-677 demonstrates favorable solubility profiles across standard laboratory solvents compared to its lipophilic free base counterpart. Standard solubility guidelines for in vitro formulation include:

• Dimethyl Sulfoxide (DMSO): Highly soluble (up to 50 mg/mL at room temperature), recommended for stock solution preparation. • Anhydrous Ethanol: Soluble (up to 25 mg/mL), suitable for organic assays. • Deionized Water / PBS (pH 7.2): Sparingly soluble in pure aqueous buffers; mild heating (37°C) or sonication may be required for concentrations exceeding 5 mg/mL.

Stock solutions prepared in DMSO should be aliquoted and stored at -80°C to prevent degradation over extended periods. Lyophilized powders remain stable at room temperature for short duration transport but should be stored at -20°C upon receipt.

Analytical Quality Verification: COA, HPLC, and Mass Spectrometry

To guarantee reproducible laboratory data, researchers must confirm chemical purity and identity prior to initiating experiments. Low-grade research chemicals often harbor residual synthesis solvents, unreacted intermediates, or incorrect salt ratios.

PX1 Research enforces strict analytical protocol validation. Every lot of MK-677 undergoes High-Performance Liquid Chromatography (HPLC) to confirm optical purity above 99% and Mass Spectrometry (MS) to verify the expected molecular mass peak at m/z 529.2 [M+H]+ for the free base core. Researchers can review lot-specific test parameters directly by inspecting our transparent Certificate of Analysis (COA) repository.

PX1 Research Supply Chain Standards for Laboratory Reagents

PX1 Research provides certified research compounds exclusively manufactured in USA-based, GMP-compliant facilities. Our ISO 17025 accredited partner laboratories perform comprehensive quality control testing, including bacterial endotoxin assays (LAL test) to ensure reagents meet rigorous standards for sensitive cellular models.

All laboratory orders ship directly from our state-of-the-art distribution centers in California and Arizona, with same-day fulfillment for orders placed Monday through Friday. Whether acquiring single vials for bench research or establishing institutional supply lines through bulk lab orders, PX1 Research delivers fully traceably characterized materials for preclinical experimentation.