Heptapeptide is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2025-09-25. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
Proposed mechanisms center on modulation of the GABA system, but no single molecular target has been confirmed. Rodent studies report changes in GABA-A receptor expression and in the turnover of serotonin, dopamine, and norepinephrine in several brain regions. Increases in brain-derived neurotrophic factor and its receptor have also been described after repeated administration. These findings come largely from animal models, and the degree to which they describe human neurochemistry remains an open question. The mechanism is best characterized as multi-system and not fully resolved.
Pharmacokinetic data are limited. Like most short peptides, Selank is vulnerable to plasma and tissue peptidases, and its measured half-life in circulation is short, on a minutes scale. The Pro-Gly-Pro tail slows this degradation but does not eliminate it. Intranasal administration is the route described in most reports, with absorption through the nasal mucosa and a hypothesized path into the central nervous system that avoids the blood-brain barrier. Direct measurements of human brain exposure are unavailable, so distribution claims rest on inference from animal work.
| 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 |
Identity and purity of selank are established with reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The peptide elutes from C18 columns with acetonitrile gradients in water containing trifluoroacetic acid or formic acid, and detection is usually performed by ultraviolet absorbance near 214 nm. Electrospray ionization in positive mode gives a doubly protonated ion near m/z 377, consistent with a mass of about 752 Da. Amino acid analysis or tandem mass spectrometry of fragment ions confirms the sequence. Because the molecule has no aromatic residues, it lacks a usable 280 nm chromophore, so low-wavelength detection or mass spectrometry is required.
Peptide bonds in selank are susceptible to hydrolysis under strongly acidic or basic conditions, and the terminal proline residues are vulnerable to exopeptidase activity in biological samples. Lyophilized powder stored dry at -20 °C typically remains stable for extended periods, whereas aqueous solutions degrade faster and may lose measurable purity within days to weeks depending on pH, temperature, and microbial load. Repeated freeze-thaw cycles promote aggregation and adsorption to container surfaces. For analytical work, solutions are usually prepared fresh, kept cold, and used within a single working day.
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.
This work stimulated research in the area, and two years later the first NLS was identified in SV40 Large T-antigen (or SV40, for short). However, a functional NLS could not be identified in another nuclear protein simply on the basis of similarity to the SV40 NLS. In fact, only a small percentage of cellular (non-viral) nuclear proteins contained a sequence similar to the SV40 NLS. A detailed examination of nucleoplasmin identified a sequence with two elements made up of basic amino acids separated by a spacer arm. One of these elements was similar to the SV40 NLS but was not able to direct a protein to the cell nucleus when attached to a non-nuclear reporter protein. Both elements are required. This kind of NLS has become known as a bipartite classical NLS. The bipartite NLS is now known to represent the major class of NLS found in cellular nuclear proteins and structural analysis has revealed how the signal is recognized by a receptor (importin α) protein (the structural basis of some monopartite NLSs is also known). Many of the molecular details of nuclear protein import are now known. This was made possible by the demonstration that nuclear protein import is a two-step process; the nuclear protein binds to the nuclear pore complex in a process that does not require energy. This is followed by an energy-dependent translocation of the nuclear protein through the channel of the pore complex.
Mass spectrometry is one of the key methods to study the proteome. Some important mass spectrometry methods include Orbitrap Mass Spectrometry, MALDI (Matrix Assisted Laser Desorption/Ionization), and ESI (Electrospray Ionization). Peptide mass fingerprinting identifies a protein by cleaving it into short peptides and then deduces the protein's identity by matching the observed peptide masses against a sequence database. Tandem mass spectrometry, on the other hand, can get sequence information from individual peptides by isolating them, colliding them with a non-reactive gas, and then cataloguing the fragment ions produced. In May 2014, a draft map of the human proteome was published in Nature. This map was generated using high-resolution Fourier-transform mass spectrometry. This study profiled 30 histologically normal human samples resulting in the identification of proteins coded by 17,294 genes. This accounts for around 84% of the total annotated protein-coding genes.
==== Diabetes ==== A meta-analysis reported that vitamin D supplementation significantly reduced the risk of type 2 diabetes for non-obese people with prediabetes. Another meta-analysis reported that vitamin D supplementation significantly improved glycemic control [homeostatic model assessment-insulin resistance (HOMA-IR)], hemoglobin A1C (HbA1C), and fasting blood glucose (FBG) in individuals with type 2 diabetes. In prospective studies, high versus low levels of vitamin D were respectively associated with a significant decrease in risk of type 2 diabetes, combined type 2 diabetes and prediabetes, and prediabetes. A systematic review included one clinical trial that showed vitamin D supplementation together with insulin maintained levels of fasting C-peptide after 12 months better than insulin alone.
Sources: en.wikipedia.org
In its wild-type form, the IDH1 enzyme is active in the cytoplasm and peroxisomes, where it catalyzes the conversion of isocitrate into α-ketoglutarate (α-KG) as part of the citric acid cycle. This process generates NADPH, a vital molecule that supports antioxidant defenses and biosynthetic processes. When mutated, IDH1 undergoes a neomorphic transformation, shifting its function. The altered enzyme converts α-KG into D-2-hydroxyglutarate (D-2HG), an oncometabolite. Elevated D-2HG levels disrupt normal cellular processes by inhibiting α-KG–dependent dioxygenases, leading to epigenetic changes, DNA hypermethylation, and impaired differentiation. Moreover, the mutation redirects NADPH consumption, increasing oxidative stress, which further drives tumor development. The accumulation of D-2HG and elevated oxidative stress play a critical role in reshaping the tumor microenvironment, positioning the R132H mutation as a prime target for IDH inhibitors. These therapies aim to restore regular metabolic functions and reduce tumor aggressiveness, offering a promising avenue for glioma treatment. In addition to being mutated in diffuse gliomas, IDH1 has also been shown to harbor mutations in human acute myeloid leukemia. The IDH1 mutation is considered a driver alteration and occurs early during tumorigenesis, in specific in glioma and glioblastoma multiforme, its possible use as a new tumour-specific antigen to induce antitumor immunity for the cancer treatment has recently been prompted.
=== Kevin Rawle === Kevin Rawle (Pip Torrens) is the brash, conniving editor-in-chief of The Patriot, a right-leaning tabloid owned by Lord Norton. Yasmin enlists Kevin to circulate a fictitious claim that the Labour government suppressed an internal memo voicing concerns about Tender's fraudulent practices, thereby pinning the company's failure on the government and protecting her from legal and reputational fallout. She, Kevin and Norton attempt to persuade Labour MP Jennifer Bevan to be their source, but she refuses on principle. Yasmin later has Harper pass on the claim to FinDigest editor Edward Burgess, who publishes it; The Patriot then amplifies the claim, leading to the resignation of business secretary Lisa Dearn and opening Tender to fraud investigations and a new audit.
== Taxonomy == The plant is part of the family Lamiaceae. A later described species, named S. sieboldii, in dedication to the German-Dutch botanist and japanologist Philipp Franz von Siebold, is considered to be a synonym.
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.
Reports describe effects on GABA-A receptor expression, monoamine turnover, and neurotrophic factor levels. These are proposed mechanisms drawn mainly from animal models. No single molecular target has been established.