freeze-thaw raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
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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.
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.
The compound has a calculated molecular weight near 751.9 daltons and carries a net positive charge at physiological pH because of its arginine residue. It dissolves freely in water and in common aqueous buffers, and typically appears as a white or off-white lyophilized powder. The amide backbone makes the molecule susceptible to peptidases, which limits oral use and favors intranasal or parenteral routes. Nomenclature in the literature varies: the substance is also described by the sequence abbreviation TP-7 and by a Russian trade designation.
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.
| 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 |
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.
Lyophilized selank is normally supplied as a dry powder and is considered stable for extended periods when kept cold and dry. Moisture uptake is the main practical threat, because absorbed water promotes both hydrolysis and aggregation in the solid state. Vials are usually warmed to room temperature before opening so that condensation does not form on the powder. Supplier documentation commonly specifies -20 °C for routine storage, with -80 °C used for material intended to be archived for years.
Enzymatic stability motivates the extra three residues at the carboxyl end. Native tuftsin is cleaved quickly by circulating aminopeptidases and carboxypeptidases, which limits its duration of action and its usefulness as a tool compound. Extending the chain with proline-rich segments is a common design tactic because proline constrains the backbone and slows proteolysis. The same Pro-Gly-Pro motif appears in other Russian-developed peptides of the era. Whether the full seven-residue chain is required for activity, or whether it acts mainly as a prodrug releasing tuftsin, remains unresolved.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. Its four N-terminal residues reproduce tuftsin, a tetrapeptide fragment of the immunoglobulin heavy chain, while the C-terminal Pro-Gly-Pro extension is a synthetic addition. The peptide has a molecular mass near 752 daltons and carries a net positive charge at physiological pH because of the arginine and lysine side chains. Published indexes list it under the name Selank and the sequence abbreviation TKPRPGP. Solid-phase peptide synthesis is the standard production route for research quantities.
Quantification in biological matrices relies on liquid chromatography coupled to tandem mass spectrometry with stable-isotope internal standards. Low plasma concentrations and adsorption to container surfaces both complicate measurement. Solid-phase extraction is often needed to reduce matrix interference before injection. Reported limits of quantification differ widely between laboratories, which makes direct comparison of pharmacokinetic results difficult and limits meta-analysis.
Peptide bonds are vulnerable to protease attack, and Selank is no exception. Measured half-life in serum is short, on the order of minutes in several reports, which explains why intranasal administration is the common route described in the literature. Absorption across the nasal mucosa partially bypasses first-pass hepatic metabolism. Quantitative data on human bioavailability remain limited and are difficult to compare across studies.
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.
Published work on this peptide almost always uses intranasal delivery, with drops or a spray applied to the nasal mucosa. Some animal experiments have used subcutaneous or intraperitoneal injection, and a smaller number have compared routes directly. Oral administration is not a focus of the literature, because short peptides of this size are broken down by digestive enzymes and cross intestinal barriers poorly. How much of an intranasal dose reaches the bloodstream intact in humans remains an open question.
Animal studies have examined behaviour in tests of anxiety, memory retention and stress response, and several report changes in neurotrophic or neurotransmitter-related markers. The human evidence base is much smaller, consisting mainly of short trials conducted in Russia with limited reporting in English-language journals. Sample sizes are modest and outcome measures vary between studies, so the findings are best described as preliminary. Independent replication under modern trial standards has not been widely reported.
==== During transplantation ==== While during infection T cell exhaustion can develop following persistent antigen exposure after graft transplant similar situation arises with alloantigen presence. It was shown that T cell response diminishes over time after kidney transplant. These data suggest T cell exhaustion plays an important role in tolerance of a graft mainly by depletion of alloreactive CD8 T cells. Several studies showed positive effect of chronic infection on graft acceptance and its long-term survival mediated partly by T cell exhaustion. It was also shown that recipient T cell exhaustion provides sufficient conditions for NK cell transfer. While there are data showing that induction of T cell exhaustion can be beneficial for transplantation it also carries disadvantages among which can be counted increased number of infections and the risk of tumor development.
== Efforts against proliferation == Antiproliferation or anti-proliferation: inhibiting cell multiplication; also efforts to slow, stop, or prevent the spread of weapons (nuclear, chemical, biological weapons, missiles) and technology, small arms, illicit drugs Counterproliferation or counter-proliferation: efforts to slow, stop, or prevent the spread of weapons (nuclear, chemical, biological weapons, missiles) and technology, small arms, illicit drugs
Austin further cemented his heel turn the following Thursday on SmackDown!, when, during an interview with Jim Ross about his actions at WrestleMania, he thought Ross was denouncing their friendship and then assaulted Ross. Austin and Triple H became a team known as The Two-Man Power Trip. Austin altered his character considerably over the next few months by becoming a whiny, temperamental prima donna who complained incessantly when he felt he was not getting respect. He also developed a strange infatuation with McMahon, going to great lengths to impress him, even going so far as to hug him and bring him presents. Austin and Triple H ran roughshod over all their opponents, until coming up against The Undertaker and Kane. After defeating them for the WWF Tag Team Championship at Backlash on April 29, they held the tag team titles, the WWF Championship (Austin) and the Intercontinental Championship (Triple H) all at once. On the May 21 episode of Raw is War, Austin and Triple H defended the WWF Tag Team Championship against Chris Benoit and Chris Jericho; during the match, Triple H legitimately tore his quadriceps, and the team lost the match and the tag team championship. Austin officially broke up The Power Trip on that week's SmackDown!, criticizing Triple H for his injury and for hitting him with the sledgehammer. He continued to align himself with McMahon and began feuding with Jericho and Benoit by himself, leading to a triple-threat match at King of the Ring on June 24; despite interference from the debuting Booker T, Austin retained the championship.
Under this theory, organized crime exists because legitimate markets leave many customers and potential customers unsatisfied. High demand for a particular good or service (e.g., drugs, prostitution, arms, slaves), low levels of risk detection and high profits lead to a conducive environment for entrepreneurial criminal groups to enter the market and profit by supplying those goods and services. For success, there must be:
Sources: en.wikipedia.org
The problem of optimizing ET (Equation (1)) can be easily formulated as an integer linear program (ILP). One of the most powerful formulations uses binary variables to represent the presence of a rotamer and edges in the final solution, and constraints the solution to have exactly one rotamer for each residue and one pairwise interaction for each pair of residues:
== Research == Baclofen is being studied for the treatment of alcoholism. Evidence as of 2019 is not conclusive enough to recommend its use for this purpose. In 2014, the French drug agency ANSM issued a three-year temporary recommendation allowing the use of baclofen in alcoholism. In 2018, baclofen received a Marketing Authorization for use in alcoholism treatment from the agency if all other treatments are not effective. It is being studied along with naltrexone and sorbitol for Charcot–Marie–Tooth disease (CMT), a hereditary disease that causes peripheral neuropathy. It is also being studied for cocaine addiction. Baclofen and other muscle relaxants are being studied for potential use for persistent hiccups. From 2014 to 2017, baclofen misuse, toxicity and use in suicide attempts among adults in the US increased. In his 2008 book, Le Dernier Verre (translated literally as The Last Glass or The End of My Addiction), French-American cardiologist Olivier Ameisen described how he treated his alcoholism with baclofen. Inspired by this book, an anonymous donor gave $750,000 to the University of Amsterdam in the Netherlands to initiate a clinical trial of high-dose baclofen, which Ameisen had called for since 2004. The researchers concluded, "In summary, the current study did not find evidence of a positive effect of either low or high doses of baclofen in AD patients. However, we cannot exclude the possibility that baclofen is an effective medication for the treatment of severe, heavy drinking AD patients not responding to or not accepting routine psychosocial interventions."
Flucytosine: The toxicity of flucytosine is increased and allows for a lower dose of amphotericin B. Amphotericin B may also facilitate entry of flucytosine into the fungal cell by interfering with the permeability of the fungal cell membrane. Diuretics or cisplatin: Increased renal toxicity and increased risk of hypokalemia Corticosteroids: Increased risk of hypokalemia Imidazole antifungals: Amphotericin B may antagonize the activity of ketoconazole and miconazole. The clinical significance of this interaction is unknown. Neuromuscular-blocking agents: Amphotericin B–induced hypokalemia may potentiate the effects of certain paralytic agents. Foscarnet, ganciclovir, tenofovir, adefovir: The risk of hematological and kidney side effects of amphotericin B is increased Zidovudine: Increased the risk of kidney and hematological toxicity. Other nephrotoxic drugs (such as aminoglycosides): Increased risk of serious renal damage Cytostatic drugs: Increased risk of kidney damage, low blood pressure, and airway spasms Transfusion of leukocytes: There is a risk that pulmonary (lung) damage may occur. Space the intervals between the application of amphotericin B and the transfusion, and monitor pulmonary function
4-Hydroxyphenylpyruvic acid (4-HPPA) is an intermediate in the metabolism of the amino acid phenylalanine. The aromatic side chain of phenylalanine is hydroxylated by the enzyme phenylalanine hydroxylase to form tyrosine. The conversion from tyrosine to 4-HPPA is in turn catalyzed by tyrosine aminotransferase. Additionally, 4-HPPA can be converted to homogentisic acid which is one of the precursors to ochronotic pigment. It is an intermediary compound in the biosynthesis of scytonemin.
=== Abundance === The table gives crustal abundances of the elements commonly to rarely recognised as metalloids. Some other elements are included for comparison: oxygen and xenon (the most and least abundant elements with stable isotopes); iron and the coinage metals copper, silver, and gold; and rhenium, the least abundant stable metal (aluminium is normally the most abundant metal). Various abundance estimates have been published; these often disagree to some extent.
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.
Selank is a synthetic seven-amino-acid peptide modeled on tuftsin, a fragment of the immunoglobulin G heavy chain. It was designed in Russia to combine anxiolytic and immunomodulatory properties in one molecule.