Everything below concerns pharmacokinetics. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-04-23. Where a claim depends on a specific study, the study is described rather than over-claimed.
The primary structure of Selank is Thr-Lys-Pro-Arg-Pro-Gly-Pro, corresponding to the molecular formula C33H57N11O9 and a monoisotopic mass of roughly 751.9 daltons. The N-terminal threonine and the arginine residue in the fourth position are shared with tuftsin, which carries the sequence Thr-Lys-Pro-Arg. The three additional residues at the C-terminus, Pro-Gly-Pro, extend the chain and are associated with greater resistance to enzymatic degradation. This extension also separates Selank from the shorter parent peptide.
Naming conventions place Selank in the same research family as Semax, another Russian-developed peptide investigated for cognitive effects. The two compounds share a lineage but differ in sequence and in the biological systems proposed as their targets. Semax descends from ACTH fragments, whereas Selank descends from tuftsin. Publications sometimes identify Selank by its full peptide sequence or by laboratory codes rather than one uniform trade name. Because replication outside Russia is limited, reports on its properties are best read alongside the study design and the purity of the material tested.
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 |
|---|---|---|
| Molecular class | Synthetic heptapeptide | Stabilized analog of tuftsin |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form: TKPRPGP |
| Molecular formula | C33H57N11O9 | Monoisotopic mass about 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as lyophilized solid |
| Solubility | Freely soluble in water | Also soluble in common polar solvents |
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.
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.
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.
== Causes == Hypothyroidism is caused by inadequate function of the gland itself (primary hypothyroidism), inadequate stimulation by thyroid-stimulating hormone from the pituitary gland (secondary hypothyroidism), or inadequate release of thyrotropin-releasing hormone from the brain's hypothalamus (tertiary hypothyroidism). Secondary and tertiary hypothyroidism are called "central" hypothyroidism. Primary hypothyroidism is about a thousandfold more common than central hypothyroidism. Iodine deficiency is the most common cause of primary hypothyroidism and endemic goiter worldwide. In areas of the world with sufficient dietary iodine, the autoimmune disease Hashimoto's thyroiditis (chronic autoimmune thyroiditis) is the most common cause of primary hypothyroidism. Hashimoto's may be associated with a goiter. It is characterized by infiltration of the thyroid gland with T lymphocytes and autoantibodies against specific thyroid antigens such as thyroid peroxidase, thyroglobulin and the TSH receptor. Hashimoto's thyroiditis is associated with other immune-mediated diseases such as type 1 diabetes, pernicious anemia, myasthenia gravis, celiac disease, rheumatoid arthritis, and systemic lupus erythematosus. It may occur as part of autoimmune polyendocrine syndrome (type 1 and type 2). After women give birth, about 5% develop postpartum thyroiditis which can occur up to nine months afterwards. This is characterized by a short period of hyperthyroidism followed by a period of hypothyroidism; 20–40% remain permanently hypothyroid.
== Education and career == Hong grew up in China and completed her B.A. degree in chemistry from Mount Holyoke College (summa cum laude) in 1992 and a Ph.D. degree from the University of California, Berkeley in 1996. There she worked in the laboratory of Alexander Pines to investigate phospholipid structure and dynamics using variable-angle-spinning NMR. After a one-year postdoctoral stint in the laboratory of Robert G. Griffin at the Massachusetts Institute of Technology, she went to University of Massachusetts Amherst and developed biosynthetic isotopic labeling approaches to advance protein structure determination by ssNMR. She started an assistant professorship at Iowa State University in 1999, became an associate professor in 2002 and full professor in 2004, and held the first John D. Corbett Professorship from 2007 to 2010. In 2014, she returned to the Massachusetts Institute of Technology as a professor of chemistry.
In January 2013, the FDA reported shortages of some, but not all, forms of doxycycline "caused by increased demand and manufacturing issues". Companies involved included an unnamed major generics manufacturer that ceased production in February 2013, Teva (which ceased production in May 2013), Mylan, Actavis, and Hikma Pharmaceuticals. The shortage came at a particularly bad time, since there were also shortages of an alternative antibiotic, tetracycline, at the same time. The market price for doxycycline dramatically increased in the United States in 2013 and early 2014 (from $20 to over $1800 for a bottle of 500 tablets), before decreasing again.
=== Tests === Thyroid function tests include a battery of blood tests, including the measurement of the thyroid hormones, as well as the measurement of thyroid stimulating hormone (TSH). They may reveal hyperthyroidism (high T3 and T4), hypothyroidism (low T3, T4), or subclinical hyperthyroidism (normal T3 and T4 with a low TSH). TSH levels are considered the most sensitive marker of thyroid dysfunction. They are however not always accurate, particularly if the cause of hypothyroidism is thought to be related to insufficient thyrotropin releasing hormone (TRH) secretion, in which case it may be low or falsely normal. In such a case a TRH stimulation test, in which TRH is given and TSH levels are measured at 30 and 60-minutes after, may be conducted. T3 and T4 can be measured directly. However, as the two thyroid hormones travel bound to other molecules, and it is the "free" component that is biologically active, free T3 and free T4 levels can be measured. T3 is preferred, because in hypothyroidism T3 levels may be normal. The ratio of bound to unbound thyroid hormones is known as the thyroid hormone binding ratio (THBR). It is also possible to measure directly the main carriers of the thyroid hormones, thyroglobulin and throxine-binding globulin. Thyroglobulin will also be measurable in a healthy thyroid, and will increase with inflammation, and may also be used to measure the success of thyroid removal or ablation. If successful, thyroglobulin should be undetectable.
After World War I, the victors settled border changes. The Treaty of Saint-Germain of 1919 ruled according to the 1915 London Pact, that the southern part of the Austrian crown land of Tyrol had to be ceded to the Kingdom of Italy, including the territory of the former Trent bishopric, roughly corresponding to the modern-day Trentino, as well as the south of the medieval Tyrol county, the present-day province of South Tyrol. Italy thus took control of the strategically important Alpine water divide at the Brenner Pass and over the south of Tyrol proper with its large German-speaking majority. Since 1949 both parts form the autonomous Italian Trentino-Alto Adige/Südtirol region. The northern part of Tyrol retained by the First Austrian Republic today forms the Austrian State of Tyrol with its East Tyrol exclave. In 1945 following World War II, Austrian attempts and South Tyrolean petitions to reunite South Tyrol with Austria were unsuccessful; Italy retained control. From 1972 onwards, the Italian Republic has granted further autonomy to the Trentino-Alto Adige/Südtirol region.
Sources: en.wikipedia.org
retinal + NAD+ + H2O → retinoic acid + NADH + H+ Retinoic acid is actively transported into the cell nucleus by CRABp2 where it regulates thousands of genes by binding directly to gene targets via retinoic acid receptors. In addition to retinol, retinal and retinoic acid, there are plant-, fungi- or bacteria-sourced carotenoids which can be metabolized to retinol, and are thus vitamin A vitamers. There are also what are referred to as 2nd, 3rd and 4th generation retinoids which are not considered vitamin A vitamers because they cannot be converted to retinol, retinal or all-trans-retinoic acid. Some are prescription drugs, oral or topical, for various indications. Examples are etretinate, acitretin, adapalene, bexarotene, tazarotene and trifarotene.
In contrast, CD8 T cells (in general, killer T cells) are able to recognize MHC class I molecules through the α3 domain of MHC class I (it does not recognize β2 microglobulin). T cell receptors are, in general, highly specific to particular peptide-MHC complexes. Some peptide sequences can only be presented by a specific type of MHC protein because they require specific amino acid sequences within the binding groove to associate with them. These are known as MHC-restricted peptides. If an individual does not express the relevant MHC protein needed for a given MHC-restricted peptide, they will not be able to present that antigen to T cells. This can be an important consideration in the design of vaccines, as a robust immune response should be generated in every vaccinee, which will not be possible if it has too many MHC-restricted peptide sequences and the vaccinee does not express the correct MHC polymorphism for effective presentation to T cells. Because the T cell receptor cannot recognize anything not presented on an MHC, conventional (see next paragraph) T cells are not capable of responding to non-peptide antigens (lipids, carbohydrates, etc), except in the case of post-translational modifications to peptides that end up being presented.
== Etymology and terminology == The English word breast derives from the Old English word brēost 'breast, bosom' from Proto-Germanic *breustam 'breast', from the Proto-Indo-European base *bhreus– 'to swell, to sprout'. The breast spelling conforms to the Scottish and North English dialectal pronunciations. The Merriam-Webster Dictionary states that "Middle English brest, [comes] from Old English brēost; akin to Old High German brust..., Old Irish brú [belly], [and] Russian bryukho"; the first known usage of the term was before the 12th century. Breasts is often used to refer to female breasts in particular, though the stricter anatomical term refers to the same region on members of either sex. Male breasts are sometimes referred to in the singular to mean the collective upper chest area, whereas female breasts are referred to in the plural unless speaking of a specific left or right breast. A large number of colloquial terms for female breasts are used in English, ranging from fairly polite terms to vulgar or slang. Some vulgar slang expressions may be considered to be derogatory or sexist to women.
=== Insulin interactions === D-chiro-inositol is known to be an important secondary messenger in insulin signal transduction. It accelerates the dephosphorylation of glycogen synthase and pyruvate dehydrogenase, rate limiting enzymes of non-oxidative and oxidative glucose disposal. Exogenous DCI may act to bypass defective normal epimerization of myo-inositol to DCI associated with insulin resistance and at least partially restore insulin sensitivity and glucose disposal. In clinical practice, it improves insulin signaling, thus restoring physiological insulin levels in resistant subjects.
=== Mass spectral quality === A key feature of this interface is to produce top quality EI spectra from compounds dissolved in a liquid phase. In this case, quality is intended as a measure of the degree of success in a virtual comparison with thousands of spectra stored in the electronic libraries. Identification capability in real-world applications, when peaks are small and noise is high, can be greatly influenced by the quality of ionization. A NIST library version 2.0d was used for comparison. In this case, identification capability is not compromised by the presence of solvent vapor residues and matching quality tops that of a typical GC-MS system.
Sources: en.wikipedia.org
Selank is a synthetic heptapeptide designed as a stabilized analog of the natural tetrapeptide tuftsin. It has been investigated mainly for anxiolytic and cognitive effects. It is not an approved pharmaceutical in most countries.
It was developed in Russia, at the Institute of Molecular Genetics of the Russian Academy of Sciences, during the 1990s. Most published research originates from Russian institutions. Independent international replication remains limited.
Tuftsin is a natural tetrapeptide with the sequence Thr-Lys-Pro-Arg that participates in immune signaling. Selank extends that sequence with Pro-Gly-Pro at the C-terminus. The added residues are linked to greater resistance to enzymatic breakdown.
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.