Tuftsin analog raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2025-08-11. Anything still debated is marked as such rather than presented as settled.
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.
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.
| 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 |
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.
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.
== Diagnosis == The clinical definition of ordinary smallpox is an illness with acute onset of fever followed by a rash characterized by firm, deep-seated vesicles or pustules in the same stage of development without other apparent cause. Before the availability of laboratory testing, doctors could diagnose smallpox by touch alone, due to the distinctively hard pustules. Microscopically, poxviruses produce characteristic cytoplasmic inclusion bodies, the most important of which are known as Guarnieri bodies, and are the sites of viral replication. Guarnieri bodies are readily identified in skin biopsies stained with hematoxylin and eosin, and appear as pink blobs. They are found in virtually all poxvirus infections but the absence of Guarnieri bodies could not be used to rule out smallpox. The diagnosis of an orthopoxvirus infection can also be made rapidly by electron microscopic examination of pustular fluid or scabs. All orthopoxviruses exhibit identical brick-shaped virions by electron microscopy. Definitive laboratory identification of variola virus involved growing the virus on chorioallantoic membrane (part of a chicken embryo) and examining the resulting pock lesions under defined temperature conditions. Strains were characterized by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis. Serologic tests and enzyme linked immunosorbent assays (ELISA), which measured variola virus-specific immunoglobulin and antigen were also developed to assist in the diagnosis of infection.
It has the potential of enhancing protein tyrosine phosphorylation, which takes place during capacitation, and its effects are inhibited in the presence of lidocaine and tetrodotoxin. Veratridine has not been reported to have any effect on the acrosome reaction on its own, but it is able to block the progesterone-induced acrosome reaction. Moreover, veratridine has the effect of turning the membrane potential to a more positive one and also modifies the effect of progesterone on [Ca2+]i and sperm membrane potential. The activation of Nav1.8 is a key point in Veratradine's mechanism of action and, consequently, this sodium ion channel coordinates the effects of this compound. Veratradine also activates additional NaV channels. These facts contribute to support the importance of these Veratradine-sensitive proteins in the regulation of mature sperm function, such as human sperm fertility acquisition regulating motility, capacitation and the progesterone-induced acrosome reaction. Veratridine has been synthetically modified to introduce a photoswitchable azobenzene group (azoveratridine) that allows controlling the NaV potentiating activity with light in neurons and cardiac cells. Using this method, further late-stage modifications are possible, including the introduction of fluorescent and radioactive tags.
==== Clinical progestogenic potency and effects ==== Because of studies that used IA, it was incorrectly believed for many years that oral progesterone could easily achieve luteal phase levels of progesterone or beyond and could produce considerable progestogenic effects. In actuality, the very low levels of progesterone with oral administration, as measured by reliable methods like LC–MS, appear to be insufficient for robust progestogenic effects. This is evidenced by the fact that, in contrast to almost all progestins, an increased risk of endometrial cancer has been observed when oral progesterone is combined with an estrogen in menopausal hormone therapy. This finding suggests that typical clinical doses of oral progesterone may be insufficient for full endometrial protection. However, in spite of the very low levels of progesterone achieved, typical clinical doses of oral progesterone are effective in preventing estrogen-induced endometrial hyperplasia. On the other hand, oral progesterone fails to produce full endometrial secretory transformation, and is considered to be inappropriate for use in assisted reproduction, whereas vaginal and intramuscular progesterone are effective. Even 600 mg/day oral progesterone, which is a very high dosage, fails to produce full luteal-phase endometrial changes, although doses of 300 to 600 mg/day oral progesterone have reportedly been used for luteal support in assisted reproduction. Research on whether oral non-micronized progesterone has a thermogenic effect has shown conflicting findings in different studies.
Sources: en.wikipedia.org
Some of the multiple activities of thymosin β4 unrelated to actin may be mediated by a tetrapeptide enzymically cleaved from its N-terminus, N-acetyl-ser-asp-lys-pro, brand names Seraspenide or Goralatide, best known as an inhibitor of the proliferation of haematopoietic (blood-cell precursor) stem cells of bone marrow.
== Santos syndrome == Santos syndrome is characterized by short stature, fibular agenesis or hypoplasia, clubfeet with oligodactyly, acromial dimples, limited forearm/hand range of motion, and severe nail hypoplasia or anonychia. It is caused by a homozygous mutation in the WNT7A gene, leading to a phenotype similar to Fuhrmann syndrome but with preaxial polydactyly and less severe limb defects. The inheritance pattern is autosomal dominant with incomplete penetrance. This mutation has a recent origin (73 years) and is located inside a Native-american homozygous haplotype. It was discovered by Silvana Santos, a Brazilian researcher who won the 100 Woman BBC prize in 2024.
=== Video games === In April 2026, Austin was revealed to be added to Fortnite. He is the sixth WWE outfit added to the game following -- John Cena, Becky Lynch, Bianca Belair, Cody Rhodes and The Undertaker. Dwayne Johnson appears in the game but not as himself or The Rock but in an acting role using his likeness for the character The Foundation.
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.
Identity is confirmed by matching the retention time in reversed-phase chromatography against a reference standard and by measuring the molecular mass with mass spectrometry. Tandem mass spectrometry or amino acid analysis can verify the sequence of the seven residues. Because the peptide contains no aromatic amino acids, detection at 280 nm is not useful.