Selank is a short synthetic peptide that is structurally based on a natural immune peptide fragment. The strongly basic character of the sequence determines its behaviour in chromatography.
What is Selank?
Selank is a heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. The first four amino acids correspond to the tetrapeptide tuftsin, a fragment derived from immunoglobulin G. Appended is the C-terminal tripeptide Pro-Gly-Pro, which increases stability against peptidases. The molecular mass is approximately 752 Da.
With lysine and arginine the sequence contains two strongly basic residues as well as three proline residues. Commercial material is usually present as a lyophilised white powder in acetate or trifluoroacetate salt form. The salt form influences the weighed portion and the calculation of the peptide content and should therefore be documented.
Research context
Selank is described in the neuroscience research literature, predominantly in publications from the Russian-speaking world, and is frequently treated there together with Semax. In the European Union there is no marketing authorisation as a medicinal product. For laboratory contexts it is relevant that the available literature relates to different preparations and manufacturing routes; comparability between batches can only be established via documented analytical data, not via the substance designation.
Analytical identification
- RP-HPLC on C18 phases with a water/acetonitrile gradient. Selank is pronouncedly polar and basic and therefore elutes very early. Without a shallow rising starting gradient there is a risk that the substance appears close to the dead volume and is not cleanly separated from polar impurities. An ion-pairing reagent such as trifluoroacetic acid is practically a precondition for symmetrical peaks with basic peptides, since the protonated lysine and arginine residues otherwise interact with residual silanol groups and cause tailing.
- LC-MS confirms the molecular mass of around 752 Da. Basic peptides show good ionisation in positive electrospray; in addition to the singly charged ion the doubly charged ion also frequently occurs, since two basic side chains can be protonated.
Selank contains no aromatic amino acids. Detection at 254 or 280 nm is therefore unsuitable; recording takes place exclusively via the absorption of the peptide bond at 214 to 220 nm. A purity figure without the detection wavelength named cannot be assessed for this peptide.
Purity and analytical interpretation
With heptapeptides, deletion sequences are usually well separated chromatographically from the main peak. More relevant in practice with Selank is the question of whether the gradient separates at all in the early elution range, since polar by-products and residual salts also appear there. The three proline residues can also cause cis/trans isomerism and thereby peak broadening or double peaks, which must not be confused with an impurity. In every case an area-percent value describes only the proportion of the detected signal, not the peptide content of the sample.
Documentation and batch traceability
Analytical documentation is only meaningful with a batch reference, method description, gradient conditions, detection wavelength and the associated raw data. Without this information a document cannot be assigned to a specific sample. Notes on the structure and reading of such documents can be found in the linked resources.
Storage and Stability
Lyophilised peptides are considerably more stable in the dry, light-protected state than in solution. For laboratory stocks, storage at minus 20 degrees Celsius, protection from moisture and light as well as avoiding repeated freeze-thaw cycles are common practice. Strongly hygroscopic salt forms take up moisture at room temperature, which can falsify the weighed portion. These details concern exclusively the handling of laboratory substances.
Further research resources
- HPLC in peptide analysis
- LC-MS in peptide analysis
- Understanding peptide purity
- How to read a Certificate of Analysis (COA)
- Batch testing and traceability
- Analysis and certificates
Associated catalogue products
This page serves exclusively as scientific and analytical information. It contains no dosage, application or treatment instructions. Products are not intended for use in humans or animals.