This is a working overview of Heptapeptide, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-06-30. Anything still debated is marked as such rather than presented as settled.
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.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter notation. Its structure consists of the immunomodulatory tetrapeptide tuftsin, Thr-Lys-Pro-Arg, extended at the carboxyl terminus by a Pro-Gly-Pro segment. The molecular formula is commonly given as C33H57N11O9, corresponding to a monoisotopic mass near 751.4 Da and an average molecular mass near 751.9 Da. All seven residues are proteinogenic amino acids, and the molecule carries no modified side chains or non-natural linkages.
Quality assessment of Selank samples typically combines purity determination with identity confirmation and counter-ion analysis. Purity is usually reported as a percentage by chromatographic area, with values above 95 percent often quoted for research-grade material. Water content and residual solvents are checked in lyophilized batches because they affect both stability and accurate mass determination. A reported purity figure does not by itself establish that a sample is the intended sequence, so orthogonal methods are needed to rule out sequence isomers or truncation products.
Characterization of Selank in laboratory settings relies on standard peptide analytical techniques. Reverse-phase high-performance liquid chromatography separates the peptide from related impurities and degradation products, while mass spectrometry confirms molecular identity through accurate mass measurement. Amino acid analysis and peptide sequencing verify the primary structure when reference material is unavailable. Because Selank is a short chain, fragmentation-based analysis produces a diagnostic ion pattern that supports confident identification.
Peptide stability depends strongly on temperature, moisture, and pH. Lyophilized Selank is generally most stable when stored cold and dry, with freezer temperatures commonly used for long-term storage. In solution, the compound is susceptible to hydrolysis and to microbial growth if it is not handled aseptically. The C-terminal proline-rich extension appears to slow enzymatic cleavage relative to tuftsin, though quantitative degradation rates vary with the matrix and the conditions tested. Published stability data specific to Selank remain sparse.
| Property | Value | Notes |
|---|---|---|
| Peptide sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Seven residues; tuftsin plus a Pro-Gly-Pro tail |
| Molecular formula | C33H57N11O9 | Commonly reported value for the free peptide |
| Monoisotopic mass | Roughly 751.4 Da | Average molecular mass near 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as a lyophilized solid |
| Solubility class | Freely soluble in water | Also dissolves in saline and other polar solvents |
Pharmacokinetic data are sparse and largely derived from animal work. After intranasal administration the peptide appears in plasma within minutes, and reported half-lives are short, on the order of minutes to tens of minutes. Degradation proceeds through ordinary proteolytic cleavage into constituent amino acids and smaller fragments. Direct evidence that intact Selank reaches brain tissue in meaningful amounts is limited, and the extent of blood-brain barrier penetration is debated. Some authors argue that fragments, not the parent peptide, carry much of the observed activity.
Published clinical work is concentrated in Russian-language journals and generally involves small samples without independent replication. Systematic reviews in English note the shortage of randomised, placebo-controlled trials and the difficulty of verifying methods from translated reports. Outcome measures vary between studies, which complicates pooling of results. Interest in the compound as a cognitive or anxiolytic agent therefore rests on a thinner evidence base than the volume of citations suggests. Replication in well-powered trials with preregistered endpoints would be needed before firm conclusions about efficacy can be drawn.
Proposed mechanisms centre on the GABAergic system. Animal and tissue studies report changes in GABA-A receptor expression and reduced activity of GABA transaminase, the enzyme that degrades GABA. Effects on monoamine turnover, including serotonin and dopamine pathways, are also described, and a separate line of work links the peptide to increased expression of brain-derived neurotrophic factor in hippocampal tissue. Most of these findings come from rodent models and cell preparations. How the individual observations combine into a single coherent mode of action is not settled.
Lyophilised material kept dry at minus 20 degrees Celsius or colder is the most stable form, and suppliers commonly state a shelf life of two years or more under those conditions. Once dissolved, degradation accelerates through hydrolysis and deamidation, particularly at alkaline pH or elevated temperature. Working solutions are usually divided into single-use aliquots to avoid repeated freeze-thaw cycles. The choice of reconstitution solvent affects both stability and the ionic strength of the final preparation.
Reverse-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres is the standard purity method. Mass spectrometry, typically electrospray ionisation, confirms identity through the expected mass-to-charge pattern. Amino acid analysis can verify composition independently. Chiral purity requires separate techniques such as derivatisation followed by chromatographic separation, and such data are rarely reported for research-grade material.
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.
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.
=== Region-specific versions === Valve deactivated accounts with CD keys that were purchased outside of the consumer's territory in order to maintain the integrity of region-specific licensing. This generated complaints from North American customers who had circumvented their Steam end-user license agreement by purchasing The Orange Box through cheaper, Asian retailers. Some customers who then purchased the game a second time from a local vendor experienced difficulty adding the new CD key to their accounts in order to activate their newly purchased games and also had trouble communicating with Steam's customer support team about this problem. Doug Lombardi of Valve stated, "Some of these users have subsequently purchased a legal copy after realizing the issue and were having difficulty removing the illegitimate keys from their Steam accounts. Anyone having this problem should contact Steam Support to have the Thai key removed from their Steam account." The German version of The Orange Box is set to a low violence mode in order to comply with German laws regulating the sale of violent video games. Blood effects are replaced by sparks and bullet wounds are replaced with dents as if the characters were metal robots. Additionally in Team Fortress 2, instead of body parts being scattered after a player's character is blown apart, various items such as hamburgers, coils, rubber ducks, and Chattery Teeth appear (known as "sillygibs" by the community). Characters from different classes leave different items and different ratios of these items when killed by explosives.
CLE peptides (CLAVATA3/Embryo Surrounding Region-Related) are a group of peptides found in plants that are involved with cell signaling. Production is controlled by the CLE genes. Upon binding to a CLE peptide receptor in another cell, a chain reaction of events occurs, which can lead to various physiological and developmental processes. This signaling pathway is conserved in diverse land plants.
An international organization, also known as an international institution or intergovernmental organization (IGO), is an association of states established by a treaty or other type of instrument governed by international law to pursue the common aim of its member states. An IGO possesses its own legal personality separate from its member states and can enter into legally binding agreements with other IGOs or with other states. The United Nations (UN), the Council of Europe, the African Union, the Organization of American States (OAS), the North Atlantic Treaty Organization (NATO), Mercosur, and BRICS are examples of IGOs. International organizations are composed of primarily member states, but may also include other entities, such as other international organizations, commercial firms, and nongovernmental organizations. Additionally, entities may hold observer status. Under international law, although treaties are typically between states, intergovernmental organizations also have the capacity to enter into treaties. The traditional view was that only states were subjects of international law, but with the founding of the United Nations, that view expanded to include intergovernmental organizations.
=== Preferred habitat === Bowfin prefer vegetated sloughs, lowland rivers and lakes, swamps, and backwater areas, and are occasionally found in brackish water. They are well camouflaged and difficult to spot in slow water with abundant vegetation. They often seek shelter under roots and submerged logs. Oxygen-poor environments can be tolerated because of their ability to breathe air.
Amyloids are formed of long unbranched fibers that are characterized by an extended β-sheet secondary structure in which individual β strands (β-strands) (coloured arrows in the adjacent figure) are arranged in an orientation perpendicular to the long axis of the fiber. Such a structure is known as cross-β structure. Each individual fiber may be 7–13 nanometres in width and a few micrometres in length. The main hallmarks recognised by different disciplines to classify protein aggregates as amyloid is the presence of a fibrillar morphology with the expected diameter, detected using transmission electron microscopy (TEM) or atomic force microscopy (AFM), the presence of a cross-β secondary structure, determined with circular dichroism, FTIR, solid-state nuclear magnetic resonance (ssNMR), X-ray crystallography, or X-ray fiber diffraction (often considered the "gold-standard" test to see whether a structure contains cross-β fibres), and an ability to stain with specific dyes, such as Congo red, thioflavin T or thioflavin S. The term "cross-β" was based on the observation of two sets of diffraction lines, one longitudinal and one transverse, that form a characteristic "cross" pattern. There are two characteristic scattering diffraction signals produced at 4.7 and 10 Å (0.47 nm and 1.0 nm), corresponding to the interstrand and stacking distances in β sheets. The "stacks" of β sheet are short and traverse the breadth of the amyloid fibril; the length of the amyloid fibril is built by aligned β-strands. The cross-β pattern is considered a diagnostic hallmark of amyloid structure.
Sources: en.wikipedia.org
A tendon is a tough, flexible band of fibrous connective tissue that connects muscles to bones. The extra-cellular connective tissue between muscle fibers binds to tendons at the distal and proximal ends, and the tendon binds to the periosteum of individual bones at the muscle's origin and insertion. As muscles contract, tendons transmit the forces to the relatively rigid bones, pulling on them and causing movement. Tendons can stretch substantially, allowing them to function as springs during movement. Cartilage is a resilient and smooth type of connective tissue that covers and protects the ends of long bones, and forms a structural component of many body parts including the rib cage, the neck and the bronchial tubes, and the intervertebral discs. It is classified into three types — elastic cartilage, hyaline cartilage, and fibrocartilage. Joints, also known as articulations, are structures that connect individual bones and may allow bones to move against each other to cause movement. Joints can be classified by structure and by function. Structurally, synovial joints are joints that are not directly joined, which are lubricated by a solution called synovial fluid; fibrous, bony, and cartilaginous joints are characterised by the presence of their respective connective tissues. There are three functional divisions of joints: Diarthroses, which allow extensive mobility between two or more articular heads. Amphiarthroses, which allow some movement. False joints or synarthroses, which allow little or no movement and are predominantly fibrous.
==== Music ==== MDMA and ecstasy have featured in a number of songs, including Miley Cyrus's "We Can't Stop", Jay-Z and Alicia Keys' "Empire State of Mind", Fujiya & Miyagi's "Seratonin Rushes", Soulwax's "E Talking", Nonpoint's "Double Stacked", Green Velvet's "La La Land", Primal Scream's "Don't Fight It, Feel It", The Streets' "Blinded by the Lights", The Shamen's "Ebeneezer Goode", Missy Elliott's "4 My People", Pulp's "Sorted for E's & Wizz" and Hot Chip's "Over and Over".
== Bonding == Some models of bonding for desmosines, created through the study of bovine ligament elastin, suggest a combination of desmosine and secondary cross-linking to bind together peptide chains. This model has desmosine bonding near an alanine on the peptide chain, then to 3 other amino acids on the 2 peptide chains, despite being able to bond to up to 4 chains. It has been suggested that the secondary cross-linking occurs with either desmosine or lysinonorleucine, which maintains an alpha helix conformation in alanine rich sections on peptides. Both isodesmosine and desmosine can have similar bonding sites in elastin, though it rarely shown this way in nature. They more often will appear in close proximity to each other on the peptide chain.
Mass spectrometry measures mass-to-charge ratio of molecules using electric and magnetic fields. There are several ionization methods: electron ionization, chemical ionization, electrospray, fast atom bombardment, matrix-assisted laser desorption/ionization, and others. Also, mass spectrometry is categorized by approaches of mass analyzers: magnetic-sector, quadrupole mass analyzer, quadrupole ion trap, time-of-flight, Fourier transform ion cyclotron resonance, and so on.
Sources: en.wikipedia.org
==== Generic drugs ==== Generic drugs are chemical and therapeutic equivalents of name-brand drugs, normally whose patents have expired. Approved generic drugs should have the same dosage, safety, effectiveness, strength, stability, and quality, as well as route of administration. In general, they are less expensive than their name brand counterparts, are manufactured and marketed by rival companies and, in the 1990s, accounted for about a third of all prescriptions written in the United States. For a pharmaceutical company to gain approval to produce a generic drug, the FDA requires scientific evidence that the generic drug is interchangeable with or therapeutically equivalent to the originally approved drug. This is called an Abbreviated New Drug Application (ANDA). 80% of prescription drugs sold in the United States are generic brands.
== I == ICAT – Isotope-coded affinity tag ICP – Inductively coupled plasma ICRMS – Ion cyclotron resonance mass spectrometer IDMS – Isotope dilution mass spectrometry IJMS – International Journal of Mass Spectrometry IRMPD – Infrared multiphoton dissociation IKES – Ion kinetic energy spectrometry IMS – Ion mobility spectrometry IMSC – International Mass Spectrometry Conference IMSF – International Mass Spectrometry Foundation IRMS – Isotope ratio mass spectrometry IT – Ion trap ITMS – Ion trap mass spectrometry ITMS – Ion trap mobility spectrometry iTRAQ – Isobaric tag for relative and absolute quantitation
K is the clearance [mL/min] CU is the urine concentration [mmol/L] (in the USA often [mg/mL]) Q is the urine flow (volume/time) [mL/min] (often [mL/24 h]) CB is the plasma concentration [mmol/L] (in the USA often [mg/mL]) When the substance "C" is creatinine, an endogenous chemical that is excreted only by filtration, the clearance is an approximation of the glomerular filtration rate. Inulin clearance is less commonly used to precisely determine glomerular filtration rate. Note - the above equation (11) is valid only for the steady-state condition. If the substance being cleared is not at a constant plasma concentration (i.e. not at steady-state) K must be obtained from the (full) solution of the differential equation (9).
Sources: en.wikipedia.org
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter code. It combines the tetrapeptide tuftsin with a carboxyl-terminal Pro-Gly-Pro extension. This full sequence identifies the molecule more precisely than the research name.
No peptide with this exact sequence has been identified as an endogenous substance. It is a laboratory-designed analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The Pro-Gly-Pro extension has no known natural source.
Proline introduces conformational constraints that make a peptide less accessible to common peptidases. This is a standard stabilization strategy in peptide design. The added residues also increase the distance between the active tuftsin portion and typical cleavage sites.
The most common approach combines reverse-phase liquid chromatography with mass spectrometry. Chromatography separates the components while mass spectrometry confirms the molecular mass. Peptide sequencing or tandem mass analysis can further verify the amino acid order.