Heptapeptide comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2026-03-10. Numbers and descriptions here follow the published literature rather than marketing material.
Lyophilized Selank, the dry powder form, is generally stored frozen at minus 20 degrees Celsius or colder for long-term keeping. The solid is hygroscopic and should stay sealed, dry, and protected from light. Once dissolved, the peptide is less stable and is usually held refrigerated at 2 to 8 degrees Celsius for short periods. Repeated freezing and thawing is avoided because it can promote aggregation and loss of activity. Buffers and pH choice also affect how long a solution remains usable.
Solubility behavior is a practical concern for handling. Selank dissolves readily in water and in common aqueous buffers, which simplifies preparation of working solutions. The choice of solvent, ionic strength, and pH can influence aggregation over time, particularly at higher concentrations. Aqueous solutions are typically sterile-filtered before use. Because stability depends on several variables, storage and handling notes should be treated as general guidance rather than fixed rules, and specific values are best confirmed against a certificate of analysis for each batch.
Characterization of Selank in a laboratory setting relies on standard peptide methods. Reverse-phase high-performance liquid chromatography separates the target from related impurities and provides a purity figure, commonly reported as 95 percent or higher. Mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, confirms the molecular mass and helps detect truncation or modification. Amino acid analysis can verify composition when a sequence-level check is needed. These techniques together establish identity and purity for a given lot.
Naming for this compound is not fully standardised in English sources. The spelling Selanc appears in some transliterations, and catalogue entries may instead list the peptide sequence itself as the identifier. Reference material sometimes groups it with other short synthetic peptides studied for behavioural effects, which can create confusion when citations are compared. Distinguishing the exact sequence from related tuftsin analogues is therefore a practical first step when reviewing any dataset or specification sheet.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, frequently abbreviated as TKPRPGP. It was designed as a structural analogue of tuftsin, a naturally occurring tetrapeptide released by enzymatic cleavage of the immunoglobulin heavy chain. The two additional proline residues at the C-terminal end extend the parent chain and change how the molecule behaves in solution. The free peptide has a calculated molecular mass of approximately 751.9 g/mol and is generally supplied as a lyophilised white to off-white powder.
Development work on the compound began in the 1980s and 1990s at the Institute of Molecular Genetics in Moscow, within the same research programme that produced the peptide Semax. Early investigators sought a tuftsin derivative with improved resistance to enzymatic breakdown and with activity in the central nervous system after peripheral administration. Most of the primary literature from this period was published in Russian, a factor that still shapes how easily the findings can be checked by outside groups.
| Property | Value | Notes |
|---|---|---|
| Solubility | Freely soluble in water | Also in aqueous buffers |
| Typical purity (HPLC) | 95 percent or higher | Lot-dependent |
| Dry powder storage | Minus 20 degrees Celsius | Sealed, dry, protected from light |
| Solution storage | 2 to 8 degrees Celsius | Short-term use |
| Identity confirmation | Mass spectrometry | ESI or MALDI-TOF |
The compound was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences during the 1980s and 1990s. The stated design goal was to retain the immunomodulatory and central nervous system activity attributed to tuftsin while improving resistance to enzymatic breakdown. Adding a proline-rich tail to the short parent peptide was a deliberate strategy, because proline residues restrict the conformations available to many peptidases. The same laboratory produced Semax, an ACTH fragment analog, and both compounds were developed in parallel as short, enzymatically stabilized peptides intended for intranasal use.
Selank is not a naturally occurring peptide and has no known endogenous counterpart in human physiology. Russian-language sources frequently call it TP-7, while English-language sources use the name Selank almost exclusively. Database indexing is uneven, partly because early reports appeared in regional journals that are not widely cataloged. Some summaries describe the material as a tuftsin analog and others as a synthetic heptapeptide; the labels overlap rather than conflict. Citing the primary sequence resolves ambiguity more reliably than the research or trade name alone.
Regulatory status differs sharply by region. Selank holds a Russian marketing authorization, where it is supplied mainly as nasal drops, while authorities elsewhere have not approved it for medical use. Material sold internationally is therefore usually labeled as a research chemical rather than a medicine. Peer-reviewed publications come predominantly from Russian laboratories, and sample sizes are generally small. Whether the compound produces comparable effects under independent, well-controlled replication remains an open question that the broader literature has not settled.
Selank is a synthetic heptapeptide developed in Russia as a structural analogue of tuftsin, a naturally occurring immunomodulatory tetrapeptide. Its sequence, Thr-Lys-Pro-Arg-Pro-Gly-Pro, keeps the tuftsin core at the N-terminus and appends a Pro-Gly-Pro tail. Researchers at the Institute of Molecular Genetics in Moscow synthesized the compound during the 1990s while searching for peptides with combined anxiolytic and immunomodulatory activity. The added tail was intended to resist enzymatic cleavage and prolong the molecule's presence in circulation.
Once dissolved, the peptide is markedly less stable than the dry powder. Aqueous solutions are subject to backbone hydrolysis and to microbial growth when they are handled without sterile technique. Buffered solutions near neutral pH are common for short-term laboratory work, while acidic conditions are sometimes used to improve solubility. Analytical laboratories generally prepare working solutions fresh rather than storing them, and a residual water film left in a reopened vial can seed degradation even when the container appears dry.
Reversed-phase high-performance liquid chromatography is the standard technique for estimating peptide purity. The result is a peak-area percentage, which describes how much of the detected material elutes as the main peak in one run. Mass spectrometry confirms the molecular mass and can reveal truncated, adducted, or otherwise modified species. Amino acid analysis or tandem mass spectrometry can address sequence fidelity when identity is in doubt. None of these measurements, taken alone, establishes that a sample is fit for any specific purpose.
== Function == Protein kinase function has been evolutionarily conserved from Escherichia coli to Homo sapiens. Protein kinases play a role in a multitude of cellular processes, including division, proliferation, apoptosis, and differentiation. Phosphorylation usually results in a functional change of the target protein by changing structure, dynamics, enzyme activity, cellular location, or association with other proteins.
==== Units ==== Due to the variety of natural and synthetic compounds with vitamin E activity, there has historically been many different units that attempt to produce a measure of "vitamin E activity" using a weighted sum. The international unit measurement was used by the United States in 1968–2016. 1 IU is the biological equivalent of about 0.667 mg d (RRR)-alpha-tocopherol (2/3 mg exactly), or of 0.90 mg of dl-alpha-tocopherol (or of 1.0 mg of dl-alpha-tocopherol acetate), corresponding to the then-measured relative potency of stereoisomers. In May 2016, the measurements were revised, such that 1 mg "as alpha-tocopherol" of Vitamin E is 1 mg of d-alpha-tocopherol or 2 mg of dl-alpha-tocopherol. The change was originally started in 2000, when forms of vitamin E other than alpha-tocopherol were dropped from dietary calculations by the IOM. The UL amount disregards any conversion. The EFSA has never used an IU unit, and their measurement only considers RRR-alpha-tocopherol.
For services to the community in Martlesham, Suffolk. Brian Francis Bryceland, Senior Executive Officer, Department of Social Security. Cyril Percy Bunn. For services to Journalism in Cornwall. Christine Dorothe Burges. For services to Young People in Edenbndge, Kent. John Christopher Burne, Voluntary Observer, Meteorological Office, Kent. Patricia Rose Burnett. For services to Service Families in Hereford. Susan Marilyn Burns. For services to the Rela Goldhill Lodge, London and to Young Disabled People. Herbert Roy Butler. For services to the community in Frome, Somerset. William Anthony Butler. For political service. Maxwell Charles Cadmore. For services to Health Care in Swansea, South Wales. Walter Rounsfell Cairns, lately Literature Director, Scottish Arts Council. For services to Literature. William Martin Calderbank. For services to the Engineering Industry. Joseph Graham Campbell. For services to the community. Reginald John Cann, lately Maintenance Supervisor, Crown Estate Commissioners. Harold Canning, Chairman, Wolverhampton and Walsall Committee for the Employment of People with Disabilities. For services to the Employment of Disabled People. Pamela Kathleen Cannon, Revenue Typist, Board of Inland Revenue. Peter Andrew Carruthers. For services to Sport for People with Disabilities. Mary Shane Casement. For services to the Rehabilitation of Offenders. Allan Lewis Chambers. For services to Agriculture. Derek Chambers, Senior Investigation Officer, Her Majesty's Board of Customs and Excise.
If the concentration of ATP drops in alpha cells, this causes potassium ion channels in the plasma membrane to close. This causes depolarization across the membrane causing calcium ion channels to open, allowing calcium to flood into the cell. This increase in the cellular concentration of calcium causes secretory vesicles containing glucagon to fuse with the plasma membrane, thus causing the secretion of glucagon from the pancreas.
The reaction interconverts the nucleotide, guanosine monophosphate (GMP) and guanosine diphosphate (GDP) by transferring a phosphate group from the cofactor, adenosine triphosphate (ATP), which is converted to adenosine diphosphate (ADP). The enzyme has very widespread occurrence, for example in L cells, Escherichia coli, rat liver, and calf thymus. Guanylate kinase is essential for recycling GMP and indirectly, cGMP. In prokaryotes (such as Escherichia coli), lower eukaryotes (such as yeast) and in vertebrates, it is a highly conserved monomeric protein of about 200 amino acids which has been shown to be structurally similar to protein A57R (or SalG2R) from various strains of Vaccinia virus. Systems biology analyses carried out by the team of Andreas Dräger also identified a pivotal role of this enzyme in the replication of SARS-CoV-2 within the human airways.
Sources: en.wikipedia.org
== In vivo vs In vitro == In vivo staining (also called vital staining or intravital staining) is the process of dyeing living tissues. By causing certain cells or structures to take on contrasting colours, their form (morphology) or position within a cell or tissue can be readily seen and studied. The usual purpose is to reveal cytological details that might otherwise not be apparent; however, staining can also reveal where certain chemicals or specific chemical reactions are taking place within cells or tissues. In vitro staining involves colouring cells or structures that have been removed from their biological context. Certain stains are often combined to reveal more details and features than a single stain alone. Combined with specific protocols for fixation and sample preparation, scientists and physicians can use these standard techniques as consistent, repeatable diagnostic tools. A counterstain is stain that makes cells or structures more visible, when not completely visible with the principal stain.
=== Genetics === Genetic diseases of thiamine transport are rare but serious. Thiamine responsive megaloblastic anemia syndrome (TRMA) with diabetes mellitus and sensorineural deafness is an autosomal recessive disorder caused by mutations in the gene SLC19A2, a high affinity thiamine transporter. TRMA patients do not show signs of systemic thiamine deficiency, suggesting redundancy in the thiamine transport system. This has led to the discovery of a second high-affinity thiamine transporter, SLC19A3. Leigh disease (subacute necrotising encephalomyelopathy) is an inherited disorder that affects mostly infants in the first years of life and is invariably fatal. Pathological similarities between Leigh disease and WE led to the hypothesis that the cause was a defect in thiamine metabolism. One of the most consistent findings has been an abnormality of the activation of the pyruvate dehydrogenase complex. Mutations in the SLC19A3 gene have been linked to biotin-thiamine responsive basal ganglia disease, which is treated with pharmacological doses of thiamine and biotin, another B vitamin. Other disorders in which a putative role for thiamine has been implicated include subacute necrotising encephalomyelopathy, opsoclonus myoclonus syndrome (a paraneoplastic syndrome), and Nigerian seasonal ataxia (or African seasonal ataxia). In addition, several inherited disorders of ThDP-dependent enzymes have been reported, which may respond to thiamine treatment.
=== Conversion to esters, amides, anhydrides === Widely practiced reactions convert carboxylic acids into esters, amides, carboxylate salts, acid chlorides, acid anhydrides, and alcohols. Their conversion to esters is widely used, e.g. in the production of polyesters. Likewise, carboxylic acids are converted into amides, but this conversion typically does not occur by direct reaction of the carboxylic acid and the amine. Instead esters are typical precursors to amides. The conversion of amino acids into peptides is a significant biochemical process that requires ATP. Converting a carboxylic acid to an amide is possible, but not straightforward. Instead of acting as a nucleophile, an amine will react as a base in the presence of a carboxylic acid to give the ammonium carboxylate salt. Heating the salt to above 100 °C will drive off water and lead to the formation of the amide. This method of synthesizing amides is industrially important, and has laboratory applications as well. In the presence of a strong acid catalyst, carboxylic acids can condense to form acid anhydrides. The condensation produces water, however, which can hydrolyze the anhydride back to the starting carboxylic acids. Thus, the formation of the anhydride via condensation is an equilibrium process. Under acid-catalyzed conditions, carboxylic acids will react with alcohols to form esters via the Fischer esterification reaction, which is also an equilibrium process. Alternatively, diazomethane can be used to convert an acid to an ester.
== Types of Ion Detectors == Flame ionization detector (FID) -- uses a flame to produce ions Electron capture detector (ECD) -- uses beta radiation Photo-ionization detector (PID) -- uses UV light to produce ions Helium ionization detector (HID) -- uses a radioactive source to produce helium ions, which in turn ionize the components Discharge ionization detector (DID) -- uses an electric spark source to produce helium ions, which in turn ionize the components Pulsed discharge ionization detector (PDD) -- similar to a Discharge ionization detector (DID), but uses a different sort of spark
Sources: en.wikipedia.org
Reverse-phase HPLC is the usual method and gives a percentage purity value. Mass spectrometry then confirms the molecular mass. Together they provide a basic identity and purity profile for a lot.
Freeze-dried material is kept frozen, often at minus 20 degrees Celsius, and protected from light and moisture. Dissolved peptide is refrigerated for short-term use. Repeated freeze-thaw cycles are avoided.
A certificate of analysis typically lists purity by HPLC, the confirmed mass, appearance, and sometimes water or counter-ion content. It documents results for a specific batch. Details vary by supplier.
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, commonly written as TKPRPGP. It shares the first four residues with tuftsin and carries three prolines in the chain. The proline-rich tail is the main structural feature that separates it from the parent tetrapeptide.