Selank — analytical characterisation
Chromatographic conditions, identity, related substances, presentation, reconstitution and in-use stability.
§6Analytical characterisation
§6.1Chromatographic conditions
- Column
- C18 with aqueous-compatible phase; a very polar, doubly basic heptapeptide
- Mobile phase and gradient
- A: 0.1 % trifluoroacetic acid in water; B: acetonitrile. Gradient 2–25 % B over 20 min
- Detection
- UV 214 nm only — no aromatic residue at all, so 280 nm purity claims for Selank are erroneous
- Retention
- Very early; retention is poor and void-region coelution is a real risk
§6.2Identity by mass spectrometry
[M+H]⁺ at m/z 752.4; [M+2H]²⁺ at m/z 376.7.[3]
§6.3Related substances and degradation
Table 7. Related substances recorded for Selank, with the process or storage route that generates each and its analytical signature.
| Related substance | Origin | Analytical signature |
|---|---|---|
| Diketopiperazine at Pro-Gly-Pro or Lys-Pro | Cyclisation | −18 Da; three prolines make this sequence particularly prone |
| Des-Thr1 | Incomplete coupling | −101 Da |
| Arginine-related side products | Guanidine chemistry during synthesis | Variable; arginine incorporation is among the more troublesome couplings |
| Sequence-scrambled variants | Coupling errors | Isobaric; require a resolving method |
| Counter-ion | Purification | Lys2, Arg4 and the N-terminus are basic; counter-ion content on a 752 Da peptide with three basic sites can exceed 20 % by mass |
Degradation routes
- Diketopiperazine formation
- Peptide-bond hydrolysis
- No oxidation-sensitive residues, so the compound is oxidatively robust
§7Presentation, reconstitution and storage
§7.1Presentation and reconstitution
- Presentation
- Intranasal solution (approved Russian presentation); lyophilised powder in research supply
- Reconstitution
- A 30 mg vial with 3.0 mL gives 10 mg/mL; 300 µg is 0.03 mL, that is 3 units — again below reliable measurement on a U-100 syringe.
- Storage, lyophilised
- −20 °C, desiccated
- Storage, reconstituted
- 2–8 °C
- In-use period
- No supported claim
Selank and Semax are frequently supplied and discussed together. Analytically they differ in one respect that matters: Semax has an oxidation-labile N-terminal methionine and Selank has none, so their storage requirements are not interchangeable.
§7.2In-use stability
Applicable standards: CEI-MS-01 · CEI-MS-02 · CEI-MS-03 · CEI-MS-04 · CEI-MS-05 · CEI-MS-06. The full series is at methodological standards.
Working calculators: reconstitution and insulin-unit conversion · purity against peptide content · certificate minimum-data checker.
References cited on this page
References are numbered in order of first citation in this document. Each superscript in the text links to its entry below.
- United States Pharmacopeial Convention. General Chapter ⟨1225⟩ Validation of Compendial Procedures. United States Pharmacopeia — National Formulary (USP–NF) 2024;USP 2024 Issue 1. identifier not held by the Institute
- International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use. ICH Q2(R2) Validation of Analytical Procedures. ICH Harmonised Guideline 2023;Step 4 version, 1 November 2023. identifier not held by the Institute
- International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use. ICH Q6B Specifications: Test Procedures and Acceptance Criteria for Biotechnological/Biological Products. ICH Harmonised Tripartite Guideline 1999;Step 4 version. identifier not held by the Institute
- International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use. ICH Q1A(R2) Stability Testing of New Drug Substances and Products. ICH Harmonised Tripartite Guideline 2003;Step 4 version. identifier not held by the Institute
- Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharmaceutical Research 2010;27(4):544–575. doi:10.1007/s11095-009-0045-6 · PMID 20143256
Identifiers are reproduced only where the Institute holds them. Where a digital object identifier or PubMed identifier is not shown, the Institute has recorded the journal and year and has not constructed an identifier.