Semax Molecular Weight, Sequence & CAS Reference

Chemical Identification & Core Molecular Parameters

Semax is a synthetic heptapeptide derived from a fragment of adrenocorticotropic hormone (ACTH), specifically the ACTH(4-10) domain, stabilized at the C-terminus by a Proline-Glycine-Proline tripeptide sequence. In formal chemical nomenclature, it is classified as Met-Glu-His-Phe-Pro-Gly-Pro. When ordering or evaluating this compound for analytical research, laboratories must verify its identity against official registry parameters to ensure experimental reproducibility.

The molecular formula of free-base Semax is C37H51N9O9S, corresponding to a nominal monoisotopic molecular weight of 813.35 Da and a standard average molecular weight of 813.92 g/mol. Assigning exact mass values is critical during high-performance liquid chromatography (HPLC) combined with mass spectrometry (MS) verification. Researchers analyzing Semax 30mg vials from PX1 Research should align their mass spectra against this baseline average mass to confirm peptide identity.

The Chemical Abstracts Service (CAS) has assigned the registry number 80714-61-7 to Semax (free peptide base). Chemical vendors and regulatory bodies catalog this number to differentiate the parent sequence from truncated fragments or modified analogs. Accurate CAS verification prevents analytical cross-contamination when cross-referencing published biochemical literature in our centralized research library.

Primary Amino Acid Sequence & Structural Architecture

The primary structure of Semax consists of seven L-amino acids linked via standard peptide bonds. The precise sequence from the N-terminus to the C-terminus is defined as follows:

N-Terminus — L-Methionyl — L-Glutamyl — L-Histidyl — L-Phenylalanyl — L-Prolyl — Glycyl — L-Proline — C-Terminus (Met-Glu-His-Phe-Pro-Gly-Pro / single-letter code: MEHFPGP).

The foundational sequence Met-Glu-His-Phe (ACTH 4-7) confers the primary core biological sequence motif studied in electrophysiological and cellular signaling assays, while the attached C-terminal Pro-Gly-Pro sequence offers structural resistance against enzymatic breakdown by systemic carboxypeptidases and endopeptidases in vitro. This unique structural architecture makes Semax an essential target for investigating peptide degradation pathways, receptor binding kinetics, and neurotrophic factor gene expression in cellular models.

Salt Counterion Dynamics: TFA vs. Acetate Forms

During solid-phase peptide synthesis (SPPS), peptides are cleaved from the resin matrix using trifluoroacetic acid (TFA). As a result, raw synthesized Semax initially exists as a TFA salt, where protonated basic residues (such as the imidazole nitrogen on Histidine and the N-terminal amine) form ionic pairs with trifluoroacetate anions (CF3COO-).

For standard biochemical assays, TFA can introduce confounding cellular toxicity or alter pH dynamics in sensitive cell culture media. Therefore, high-grade research peptides undergo preparative HPLC ion-exchange steps to convert the peptide into an acetate salt form (CH3COO-). While acetate counterions are generally preferred for in vitro tissue culture and enzymatic studies, both counterion forms alter the apparent mass of the bulk lyophilized powder.

Laboratory researchers should distinguish between total lyophilized mass and net peptide content. A 30 mg vial of lyophilized powder contains the target peptide alongside salt counterions and residual bound water (hydration weight). Depending on the lyophilization cycle and counterion exchange efficiency, net peptide content typically ranges between 80% and 90% of the total measured mass. PX1 Research details net peptide content explicitly on every lot-specific certificate of analysis to allow precise molar concentration calculations.

Calculating Net Peptide Content and Molar Concentrations

To achieve accurate scientific results in quantitative in vitro assays, researchers must adjust their reconstitution calculations based on the net peptide purity and peptide content rather than relying strictly on total dry weight.

Net peptide content (expressed as a percentage) is calculated using nitrogen analysis (e.g., Kjeldahl method or elemental analysis) alongside HPLC purity determination. The formula to determine the actual weight of pure Semax peptide in a lyophilized vial is:

Actual Peptide Mass (mg) = Total Dry Mass (mg) × (HPLC Purity / 100) × (Net Peptide Content / 100)

For instance, if a vial contains 30.0 mg of dry cake with 99.2% HPLC purity and an 85.0% net peptide content, the true mass of Semax in the vial is 30.0 × 0.992 × 0.850 = 25.29 mg. When preparing stock solutions for receptor-binding assays or cell culture treatments, molarity should be calculated using this corrected peptide mass divided by the molecular weight (813.92 g/mol). To simplify stock solution preparation, researchers can utilize our free online reconstitution calculator.

Analytical Mass Spectrometry & Quality Control Verification

Verification of Semax structural integrity requires two primary analytical techniques: Reverse-Phase High-Performance Liquid Chromatography (RP-HPLC) and Electrospray Ionization Mass Spectrometry (ESI-MS) or Matrix-Assisted Laser Desorption/Ionization (MALDI-TOF).

RP-HPLC measures chemical purity by separating the primary sequence from synthesis impurities, such as deletion sequences (e.g., lacking a single Proline or Glycine residue) or oxidized variants (e.g., Methionine sulfoxide). A high-purity batch should demonstrate a single, sharp chromatogram peak representing >98% total peak area under ultraviolet detection (typically at 214 nm and 280 nm).

ESI-MS confirms the exact molecular weight. Under positive ionization mode, Semax (MW 813.92 Da) characteristically displays a primary protonated molecular ion peak [M+H]+ at m/z 814.9, along with a doubly charged ion [M+2H]2+ at m/z 408.0. PX1 Research subjects every batch manufactured in our USA GMP-compliant facilities to rigorous ISO 17025 accredited testing to confirm these exact spectral signatures before releasing product lots for distribution.

Comparative Analysis: Semax vs. Related Synthetic Peptides

In neurochemical and peptide stability research, Semax is often evaluated alongside other synthetic sequence analogs and neuroactive compounds to compare enzymatic degradation rates, receptor binding affinity, and gene expression pathways. Comparing structural specifications across similar peptides helps researchers select appropriate control candidates for comparative in vitro studies.

For example, Selank is a synthetic heptapeptide derived from the human immunomodulatory peptide Tuftsin, featuring the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro and a molecular weight of 751.90 g/mol. While both Semax and Selank share the stabilizing C-terminal Pro-Gly-Pro motif, their N-terminal sequences impart vastly different chemical properties, hydrophobicities, and ionic charges at physiological pH.

Similarly, researchers studying tissue remodeling and peptide signaling often compare ACTH fragments with small signal peptides like GHK-Cu (Gly-His-Lys copper complex, MW 404.93 g/mol). Understanding how variation in amino acid length, net charge, and heavy metal chelation influences peptide half-life in culture medium allows investigators to refine experimental parameters across our complete catalog of all peptides.

Solubility Profile and In Vitro Reconstitution Guidelines

Semax exhibits high solubility in aqueous buffers due to its hydrophilic residues (Glutamic acid, Histidine) and relatively short sequence length. It is readily soluble in sterile bacteriostatic water, phosphate-buffered saline (PBS, pH 7.4), and standard laboratory cell culture media.

When reconstituting lyophilized Semax for laboratory experimentation, follow strict aseptic technique within a certified laminar flow hood:

1. Allow the lyophilized vial to equilibrate to room temperature (20°C to 25°C) prior to reconstitution to minimize condensation inside the vial.

2. Clean the rubber stopper using 70% isopropyl alcohol wipe.

3. Gently inject the calculated volume of sterile diluent (such as sterile water for injection or PBS) along the inner glass wall of the vial.

4. Swirl the vial gently in a circular motion until the powder dissolves completely. Never vortex or aggressively shake peptide solutions, as high shear stress can induce peptide denaturation or aggregation.

For laboratories requiring larger volume contracts or custom purity specifications for broad screening programs, PX1 Research provides dedicated support through our bulk wholesale portal.

Storage Parameters and Stability Profile

Lyophilized Semax exhibits excellent thermal stability when stored under proper environmental conditions. In its dry powder state, the peptide should be kept sealed at -20°C for long-term storage (up to 24 months) or 2°C to 8°C for short-term storage (up to 90 days), protected from direct light exposure.

Once reconstituted into an aqueous solution, the peptide bond structure becomes susceptible to hydrolysis and Methionine residue oxidation. Aliquots of reconstituted Semax should be kept at 2°C to 8°C and utilized within 14 to 30 days. If reconstituted stock solutions must be stored for extended periods, freeze the aliquots at -80°C to prevent degradation; avoid repeated freeze-thaw cycles, as ice crystal formation can sever peptide backbones.

Every shipment from PX1 Research originates from our centralized CA and AZ facilities, packaged with thermal monitoring materials to preserve sequence stability throughout transit.