What the molecule is
Selank is a synthetic heptapeptide with the sequence TKPRPGP and an average mass near 751.9 daltons, supplied as a lyophilised powder, acetate salt.
Its design starts from tuftsin, the tetrapeptide threonyl lysyl prolyl arginine, which was described by Victor Najjar and Kenji Nishioka in 1970 as a fragment released from the heavy chain of immunoglobulin G. Tuftsin was named after Tufts University, where the work was done, and it was characterised in the context of stimulating phagocytic cells.
Selank extends that tetrapeptide with a proline glycine proline tail at the carboxyl terminus. The purpose of that extension is chemical rather than biological in origin. Short peptides are cleared quickly by exopeptidases that trim residues from the chain ends, and proline resists cleavage by many of those enzymes because of the constrained ring in its side chain. The proline glycine proline motif therefore acts as a protective cap that extends the working lifetime of the parent tetrapeptide. The peptide was developed at the Institute of Molecular Genetics of the Russian Academy of Sciences.
Published research context
Published research on Selank comes predominantly from Russian institutions, and a substantial portion of the primary literature is published in Russian language journals. That is a practical point for anyone planning work in this area, because the accessible English language record is thinner than the total volume of published work would suggest.
Research areas in the published record include gene expression profiling in rodent brain tissue, studies of peptide stability and fragmentation in biological matrices, and behavioural studies in rodent models. The tuftsin parent has its own separate and older literature in immunology.
The proline glycine proline motif is itself of interest, because it appears in several peptides of this family and is sometimes studied as a fragment in its own right. Whether the extension is purely protective or contributes activity of its own has been raised in the literature, and it is a distinction worth holding in mind when comparing a capped analogue against its uncapped parent.
Findings in rodent and cell systems describe those systems. This material is supplied for laboratory research only.
How each lot is characterised
Seven residues is a short chain, and synthesis of such a peptide is generally clean, so a well made lot shows a sharp, well resolved main peak. Purity is measured by reversed phase high performance liquid chromatography at 214 nanometres.
One chromatographic feature is specific to proline rich sequences and worth anticipating. The peptide bond preceding a proline residue can adopt either a cis or a trans configuration, and interconversion between them is slow on the chromatographic timescale. A peptide with three prolines can therefore show peak broadening or, in some conditions, partially resolved shoulders that reflect conformers of the same molecule rather than genuine impurities. Running the column at elevated temperature speeds the interconversion and sharpens the peak.
Identity is confirmed by electrospray ionisation mass spectrometry against the theoretical mass. The certificate also records appearance, net peptide content, water content and counter ion.
Handling on the bench
Store the unopened vial at minus twenty degrees, dark and desiccated. Bring it to room temperature before opening so that condensation does not form on cold powder.
Reconstitute with bacteriostatic water added slowly down the vial wall and swirled gently to dissolve. Short hydrophilic peptides of this kind dissolve readily in aqueous buffer, and the arginine and lysine residues give the molecule a net positive charge at neutral pH, which aids solubility.
That same positive charge means the peptide will adsorb onto negatively charged surfaces, including ordinary glass and some plastics, which matters at low working concentrations. Low binding tubes are worth using. Refrigerate after reconstitution, aliquot for single use, and avoid repeated freeze and thaw cycles.
Specification
| Form | Lyophilised powder, acetate salt |
|---|---|
| Sequence | TKPRPGP |
| Residues | 7 |
| Average mass | 751.9 Da |
| Fill size | 10 mg |
| Storage | Minus 20 degrees, dark and desiccated |
References
- Najjar VA, Nishioka K (1970). Tuftsin: a natural phagocytosis stimulating peptide. Nature, volume 228.
For research use only
Products are supplied for laboratory research by qualified researchers and institutions. They are not for human or veterinary use, not for diagnostic or therapeutic use, and are not drugs, foods or cosmetics.