Selank (Thr-Lys-Pro-Arg-Pro-Gly-Pro): preparation and storage
Intended for research use only. Not a medicinal product.
Contents (8 sections)
Identity and material form
Selank is the heptapeptide Thr-Lys-Pro-Arg-Pro-Gly-Pro, abbreviated TKPRPGP. It combines the tuftsin sequence TKPR with a C-terminal PGP extension. Tuftsin, Selank and Selank fragments are different reagents. N-acetyl-Selank and amidated Selank also require separate identification because terminal modifications change the molecule.
MedChemExpress lists 751.87 g/mol for the unmodified form. Lysine and arginine make counterion and pH documentation relevant; the name Selank does not establish the acetate or trifluoroacetate content of a particular lyophilisate. For quantitative work, keep salt-form and peptide-content records alongside HPLC results.
What the research context means
Kost and colleagues found that Selank and Semax inhibited enkephalin-degrading enzymes in human serum [1]. They also tested fragments and obtained different results according to length. This directly affects sample preparation: loss of intact heptapeptide and loss of the measured effect need not occur together.
Serum in this experiment is an active enzymatic matrix. Preservation in a clean solvent does not establish preservation after contact with serum. For reaction-rate measurements, addition time, incubation temperature and reaction stopping must be consistent across samples. Arbitrary addition of protease inhibitors can change the very activity being measured.
Solvent and final matrix
The public MedChemExpress catalogue describes dissolution of its Selank in DMSO. That demonstrates a solvent option for one material, rather than proving that another salt cannot form an aqueous solution. Do not infer solubility from sequence charge alone. The actual batch specification and a small-sample test determine the starting choice.
In an enzyme assay, DMSO, benzyl alcohol or a substantial pH change may affect the final signal. Test them in a Selank-free control. For highly dilute samples, compare quantitative recovery after contact with the selected tubes; this tests possible surface losses rather than assuming that a particular plastic necessarily binds Selank.
Laboratory calculation example
A hypothetical 1.00 mg/mL stock of pure unmodified Selank corresponds to 1.330 mmol/L at 751.87 g/mol. Obtaining 20.0 µmol/L in a final 1.00 mL requires 15.0 µL, rounded to practical transfer precision. If the stock is in DMSO, its final fraction is about 1.50% by volume. The assay must tolerate that fraction; this number is not a recommended exposure.
Simply adding more medium while retaining the same peptide amount lowers the DMSO fraction but also changes peptide concentration. A different validated stock concentration, another acceptable solvent or a different experimental design is needed.
Quality checks during handling
For a serum assay, separate two questions: preservation of Selank in stock and its behaviour after addition to serum. The first control compares stock against fresh material; the second needs time points in the working matrix. Freezing collected samples is not automatically a neutral way to stop a reaction. The stopping method must preserve the measured component without introducing preparation losses.
If enzyme inhibition changes while intact Selank concentration remains constant, check serum-batch enzyme activity and indicator-reaction conditions. If intact peptide declines, investigate fragment formation. Activity of pentapeptide fragments in the cited paper means that a preserved functional effect cannot establish chemical purity.
Do not transfer a tuftsin preparation protocol to Selank without checking it. The PGP extension changes sequence and molecule number at a given mass. Comparison requires separate quantity confirmation and matching final matrices. Define mixing and holding steps before the series begins.
Dry material and solution need separate conditions
For long-term storage of a dry synthetic peptide, use a freezer, commonly −20 °C or below, where the specification supports it. Allow the sealed vial to reach room temperature before opening so moisture does not condense on cold powder. A refrigerator at +2–8 °C can be a working option for dry material needed within a week or a month only when the supplier supports that interval. Planning to use a vial soon does not establish its shelf life.
A solution needs its own record: solvent, concentration, pH, preparation date, temperature and permitted holding time. Do not transfer the dry-material expiry to the solution. Where freezing is supported, prepare aliquots for individual experiments; thawing the remainder again needs separate validation. Bacteriostatic water contains a preservative that can change a cell-assay result and is not a default solvent for every peptide.
Practical questions
Can tuftsin replace Selank? No: the PGP extension is part of the reagent identity. Does “stable” relative to another peptide establish a one-month solution shelf life? No. Comparative enzymatic resistance and storage in a vial are different measurements.
Can residual Selank be assessed through serum enzyme activity alone? That is a functional endpoint that may also respond to fragments. Measuring intact Selank requires an analytical method that separates components.
Monograph · Product page · Certificates of analysis
General reagent preparation · Bacteriostatic water compatibility · Storage and expiry
Sources
- Kost N. V., Sokolov O. Yu., Gabaeva M. V., Grivennikov I. A.. Semax and Selank Inhibit the Enkephalin-Degrading Enzymes of Human Serum. 2001.
MedChemExpress: selank. Reference characteristics of that catalogue material; not a specification for a Longeva batch.
End of article
Selank
for laboratory research
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