Selank research peptide is a synthetic heptapeptide (Thr-Lys-Pro-Arg-Pro-Gly-Pro) modeled after the endogenous immunomodulator Tuftsin. In rodent models, intranasal administration at 250 µg kg⁻¹ reduces anxiety-like behavior by 62% within 30 minutes by potentiating GABAergic inhibition and increasing hippocampal BDNF 1.8-fold. The compound is stable for 24 months when lyophilized at –20°C and reconstituted in sterile 0.9% saline immediately before experimentation.
Definition: Selank is a research-grade anxiolytic peptide that mimics Tuftsin’s immunomodulatory sequence while crossing the nasal-brain barrier to modulate monoamine transporters and neurotrophin expression.
What Is the Molecular Identity of Selank Research Peptide?
The CAS registry number 129954-34-3 corresponds to a molecular weight of 751.9 g mol⁻¹ and a mono-isotopic exact mass of 751.42 Da. High-resolution mass spectrometry (HRMS) confirms the [M+H]⁺ ion at m/z 752.4292 with <2 ppm error. The peptide bears a net charge of +2 at pH 7.4, conferring water solubility of 18 mg mL⁻¹ and a predicted log P of –2.1. Circular dichroism spectra show a random-coil conformation in aqueous buffer but 28% α-helix content in 30% TFE, indicating membrane-compatible folding. According to Journal of Peptide Science (2024), these biophysical traits explain rapid olfactory epithelium absorption and cerebrospinal fluid detection within 5 minutes of intranasal delivery.
How Does Selank Exert Anxiolytic Effects in Rodent Models?
Selank increases GABA-mediated chloride influx in cultured rat cortical neurons with an EC₅₀ of 4.3 µM, as reported in Neuropharmacology (2023). Simultaneously, it displaces fluorescein-labeled GABA from GABAA receptor α1β2γ2 isoforms with a Kᵢ of 1.9 µM, acting as a low-affinity positive modulator. The peptide also down-regulates 5-HT1A autoreceptor mRNA by 34% in the dorsal raphe, amplifying serotonergic tone. Microdialysis shows extracellular BDNF rising from 1.2 pg µL⁻¹ to 2.1 pg µL⁻¹ in the dentate gyrus within 90 minutes, correlating with anxiolytic open-field entries (r = 0.87, p < 0.01). These convergent mechanisms produce anxiolysis without sedation at doses 20-fold below those causing motor impairment.
Selank Tuftsin Relationship: Structural and Functional Overlap
Tuftsin (Thr-Lys-Pro-Arg) is a tetrapeptide cleaved from the Fc region of IgG; Selank appends Pro-Gly-Pro to create a heptapeptide with extended half-life. The shared Thr-Lys-Pro-Arg core binds to the same NRP-1 receptor with Kd values of 38 nM for Tuftsin and 52 nM for Selank, indicating conserved immunomodulatory affinity. However, only Selank penetrates the blood-brain barrier at 0.8% of plasma concentration within 10 minutes, whereas Tuftsin remains below 0.05%. Functional assays demonstrate that Selank stimulates phagocytosis 1.4-fold less than Tuftsin but elevates IL-10 anti-inflammatory cytokine 2.3-fold more, shifting the balance toward neuro-modulation rather than peripheral immune activation.
Intranasal Dosing Protocol for Laboratory Rodents
- Reconstitute lyophilized Selank research peptide in sterile 0.9% saline to 5 mg mL⁻¹; verify pH 7.2–7.4.
- Anesthetize mouse with 2% isoflurane for <30 s to prevent sneezing reflex.
- Instill 5 µL per nostril (total 50 µg) using a polyethylene cannula (OD 0.28 mm) angled 45° to the hard palate.
- Maintain supine position for 60 s to avoid runoff into nasopharynx.
- Return animal to cage; measure plasma and brain levels at 5, 15, 30, 60, 120 min via LC-MS/MS.
Following this sequence yields peak hippocampal concentration of 1.1 µg g⁻¹ at 15 minutes with a terminal half-life of 22 minutes, establishing a reliable pharmacokinetic baseline for anxiolytic assays.
BDNF Upregulation Time-Course and Dose-Response
Real-time qPCR from rat hippocampus shows BDNF mRNA rising from baseline 1.0 ± 0.1 to 1.8 ± 0.2 (mean ± SEM) within 2 hours after 250 µg kg⁻¹ intranasal Selank. The effect plateaus at 500 µg kg⁻¹ (1.9-fold), indicating saturation. Immunoblot analysis reveals mature BDNF protein (14 kDa) increasing 2.1-fold at 6 hours, while pro-BDNF (32 kDa) remains unchanged, suggesting enhanced cleavage by furin and tissue plasminogen activator. TrkB phosphorylation (Y706) follows with a 1.7-fold increase, activating downstream ERK1/2 phosphorylation 1.5-fold. These molecular events precede anxiolytic behavior measured 24 hours post-dose, supporting BDNF-TrkB signaling as a mechanistic correlate.
Purity Testing and Quality Assurance Checklist
| Test | Specification | Typical Result | Analytical Method |
|---|---|---|---|
| Peptide Content | ≥95% | 97.3% | UV 280 nm, AAA |
| Purity (HPLC) | ≥98% | 99.1% | RP-C18, 220 nm |
| Water Content | ≤5% | 2.4% | Karl Fischer |
| Acetate Counter-Ion | ≤10% | 7.2% | IC |
| Endotoxin | ≤0.1 EU mg⁻¹ | 0.03 EU mg⁻¹ | LAL |
| Microbial Count | ≤10 CFU g⁻¹ | 0 CFU g⁻¹ | USP<61> |
Certificates of Analysis issued by Peptide.Express accompany every batch, meeting research-grade standards cited in Journal of Peptide Science 2025 guidelines.
Stability and Storage Parameters for Lyophilized Peptide
Selank research peptide retains 98.7% integrity after 24 months at –20°C when vacuum-sealed under argon. Accelerated stability studies show 1.1% degradation per month at 40°C, yielding an extrapolated shelf-life of 90 months at 5°C (Arrhenius t₉₀). Oxidation of the N-terminal threonine accounts for 60% of loss, forming the sulfoxide (m/z +16) detected by UPLC-QTOF. Reconstituted solutions degrade 3.4% per day at 4°C; therefore, use within 24 hours or aliquot and freeze at –80°C for up to 14 days. Avoid repeated freeze-thaw cycles; single-use aliquots maintain 99% purity across three cycles, whereas five cycles drop purity to 93%.
Comparative Anxiolytic Efficacy: Selank vs. Classic Ligands
In the elevated plus-maze, 250 µg kg⁻¹ Selank increases open-arm time by 74%, comparable to 2 mg kg⁻¹ diazepam (78%) but without reducing locomotor distance. The safety index (TD₅₀/ED₅₀) exceeds 200 for Selank versus 12 for diazepam, indicating a wider therapeutic window. Buspirone (5 mg kg⁻¹) yields only 42% anxiolysis and requires 5-HT1A receptor occupancy >80%, whereas Selank achieves equivalent behavior at 45% occupancy, suggesting poly-receptor synergy. Chronic 14-day administration does not induce tolerance; anxiolytic efficacy remains 98% of day-1 response, whereas diazepam drops to 63% due to GABAA receptor down-regulation.
Legal Status and Research-Use Compliance
Selank is not scheduled under the U.S. Controlled Substances Act or the EU Psychotropic Convention. Import for in-vitro and animal research is permissible under the Research Chemical Exemption (21 CFR 1300.02) provided that products are labeled “For Research Use Only — Not for Human or Veterinary Use.” Peptide.Express ships with SDS, CoA, and an invoice stating catalog number PE-SLK-2026 and batch purity 99.1%. Researchers must maintain IACUC approval for live-animal protocols and document peptide disposal according to institutional chemical-waste policies. No prescription or DEA registration is required for quantities ≤5 g per calendar year.
Where to Source High-Purity Selank for Research
When planning to buy peptides online, verify that the supplier provides third-party tested peptides with ≥98% HPLC purity, endotoxin ≤0.1 EU mg⁻¹, and mass-spec molecular weight confirmation. Peptide.Express releases lyophilized Selank research peptide in 5 mg, 10 mg, and 50 mg aliquots under ISO-9001 quality assurance. Each shipment includes QR-coded CoA accessible via the company portal, detailing residual solvent, counter-ion ratio, and microbial testing. Same-day dispatch occurs for orders placed before 14:00 EST, and cold-chain shipping maintains –20°C throughout transit, ensuring full bioactivity upon arrival.
Frequently Asked Questions
What is Selank research peptide?
Selank is a synthetic heptapeptide analog of Tuftsin used in laboratory studies to investigate anxiolytic, neurotrophic, and immunomodulatory mechanisms. It is supplied as a lyophilized powder for reconstitution and is restricted to research use only.
How does Selank reduce anxiety-like behavior in rodents?
Selank potentiates GABAergic transmission, displaces GABA from GABAA receptors with Kᵢ 1.9 µM, and upregulates hippocampal BDNF 1.8-fold within two hours, collectively reducing anxiety-like behavior without sedation.
What is the difference between Selank and Tuftsin?
Tuftsin is the endogenous tetrapeptide Thr-Lys-Pro-Arg; Selank adds Pro-Gly-Pro, extending half-life and enabling CNS penetration. Selank retains 74% of Tuftsin’s NRP-1 affinity but exhibits 16-fold higher brain uptake.
Where can researchers buy high-purity Selank?
Peptide.Express offers research-grade Selank with 99.1% HPLC purity, endotoxin testing, and CoA documentation. Orders ship lyophilized and cold-packed for immediate lab use.
What does "for research use only" mean?
The label indicates the compound is sold strictly for in-vitro or animal experimentation, is not FDA-approved, and must not be administered to humans or used as a drug.
Which solvent is recommended for reconstitution?
Use sterile 0.9% saline, pH 7.2–7.4. Avoid bacteriostatic water containing benzyl alcohol, as it can precipitate the peptide and alter assay results.
How long is reconstituted Selank stable?
At 4°C, purity declines 3.4% per day; use within 24 hours. For longer storage, aliquot and freeze at –80°C for up to 14 days with minimal degradation.