Everything below concerns freeze-thaw. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-08-18. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Characterization of Selank in a laboratory setting relies on standard peptide methods. Reverse-phase high-performance liquid chromatography separates the target from related impurities and provides a purity figure, commonly reported as 95 percent or higher. Mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, confirms the molecular mass and helps detect truncation or modification. Amino acid analysis can verify composition when a sequence-level check is needed. These techniques together establish identity and purity for a given lot.
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.
| Property | Value | Notes |
|---|---|---|
| Primary route studied | Intranasal | Also examined parenterally in animal work |
| Reported plasma half-life | Minutes to tens of minutes | Values vary widely between reports |
| Main model systems | Rodent behavioural and cell assays | Human trials are few and small |
| Principal proposed targets | GABA-A receptor, GABA transaminase | Monoamine and neurotrophic pathways also reported |
| Evidence grade | Preliminary | Limited independent replication |
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.
Clinical evidence comes mainly from small studies conducted in Russia, several of which were open-label or lacked robust blinding. Reported outcomes include lower anxiety scores, changes in attention measures, and effects on asthenic states following illness. Sample sizes are typically in the tens of participants, and independent replication outside the region is scarce. Reviews published in English generally note the limited methodological quality of the underlying trials. Whether the compound produces clinically meaningful effects under rigorous conditions remains unresolved.
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.
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.
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.
Development took place at the Institute of Molecular Genetics of the Russian Academy of Sciences, where a series of short peptides were designed in the 1980s and 1990s. Selank was selected from variants of tuftsin that showed resistance to plasma peptidases. Russian regulatory approval covers it as an anxiolytic agent given intranasally. Outside that market the compound is normally handled as a research chemical rather than a medicine, and no widely recognised international pharmacopoeial monograph exists. The name Selank is a coined trade designation rather than a systematic chemical name.
=== Light scattering === Light scattering has been used for the detection and classification of bacteria. Approaches include analysis of the angular dependence of scattering as well as spectroscopic methods. Spectroscopic implementations include elastic light scattering and light scattering spectroscopy. Light scattering spectroscopy can be combined with microscopic imaging or dual-angle configurations to enable calibration-independent measurements. Light scattering spectroscopy, along with related confocal light absorption and scattering spectroscopic microscopy, has also been applied to the rapid identification of bacteria directly from whole blood.
== 3D holograms == In 1976, he became the holography assistant for the American new media artist Al Razutis. In 1978 he received Canadian government funding to build his own holography studio and study holographic special effects. He exhibited the results of this work in Vancouver at the Helen Pitt Gallery in June 1978 and again in Victoria at the Open Space Gallery in June 1979.
Some ANAs appear in several types of disease, resulting in lower specificity of the test. For example, IgM-rheumatoid factor (IgM-RF) have been shown to cross-react with ANA giving falsely positive immunofluorescence. Positive ANA as well as anti-DNA antibodies have been reported in patients with autoimmune thyroid disease. ANA can have a positive test result in up to 45% of people with autoimmune thyroid conditions or rheumatoid arthritis and up to 15% of people with HIV or hepatitis C. As per Lupus Foundation of America, "about 5% of the general population will have a positive ANA. However, at least 95% of the people who have a positive ANA do not have lupus. A positive ANA test can sometimes run in families, even if family members have no evidence of lupus." On the other hand, they say, although 95% of the patients who actually have lupus test positive for ANA, "Only a small percentage have a negative ANA, and many of those have other antibodies (such as anti-phospholipid antibodies, anti-Ro, anti-SSA) or their ANA converted from positive to negative from steroids, cytotoxic medications, or uremia (kidney failure)."
Sources: en.wikipedia.org
== Activity == Given its half-life, the radioactive activity of a gram of 60Co is close to 42 TBq (1,100 Ci). The absorbed dose constant, used in calculations of gamma-ray exposure, is related to the decay energy and time. For 60Co it is equal to 0.35 mSv/(GBq h) at one meter from the source. This allows calculation of the equivalent dose, which depends on distance and activity - for example, 2.8 GBq or 60 μg of 60Co, generates a dose of 1 mSv at 1 meter away, within an hour. Test sources, such as those used for school experiments, have an activity of <100 kBq. Devices for nondestructive material testing use sources with activities of 1 TBq and more. The decay energy of cobalt-60 amounts to about 26 watts per gram, about 40 times larger (by mass) than that of e.g. 238Pu but still not very significant for practical sources.
Resilin is a disordered protein; however, its segments may take on secondary structures under different conditions. It is discovered that peptide sequence encoded by exon 1 exhibit an unstructured form and cannot be crystallized, which allows the peptide sequence segment to be very soft and highly flexible. Exon 3 encoded peptide takes on the unstructured form before loading, but transforms to an ordered beta-turn structure once stress is applied. Meanwhile, segment encoded by exon 2 serves as a chitin binding domain. It is proposed that as stress is applied, or there is energy input, exon 1 encoded peptide responds immediately due to its high flexibility. Once this occurs, the energy is passed onto exon 3 encoded peptide, which transforms from the unstructured form to beta-turn structure to store energy. Once the stress or energy is removed, exon 3 encoded segment reverses the structural transformation and outputs the energy to exon 1 encoded segment. Another secondary structure exon 1 and exon 3 corresponding peptides may take on is the polyproline helix (PPII), indicated by the high occurrence of proline and glycine in these 2 segments. The PPII structure widely exists in elastomeric proteins, such as abductin, elastin, and titin. It is believed to contribute in the self-assembling process and the elasticity of the protein. The elastic mechanism of resilin is proposed to be entropy-related. Under relaxed state, the peptide is folded, and possesses a large entropy, but once it is stretched out, the entropy decreases as the peptide unfold.
==== Mesocorticolimbic pathway ==== Understanding the pathways in which drugs act and how drugs can alter those pathways is key when examining the biological basis of drug addiction. The reward pathway, known as the mesolimbic pathway, or its extension, the mesocorticolimbic pathway, is characterized by the interaction of several areas of the brain. Dopaminergic neurons in the ventral tegmental area (VTA) fire in response to cues that predict a reward and project to the nucleus accumbens through the mesolimbic pathway; nearly all addictive drugs increase dopamine release along this pathway, although they act on it by different routes. The nucleus accumbens, made up largely of GABAergic medium spiny neurons, is a principal target of these projections and is involved in learning conditioned responses to drug-associated cues, and in the growing sensitivity to those cues as addiction progresses. A further target is the prefrontal cortex, including the anterior cingulate and orbitofrontal cortices, which weighs competing information in determining whether a behavior is carried out and forms the associations between drug reward and environmental cues that give those cues their power. These cues are strong mediators of drug-seeking behavior and can trigger relapse even after months or years of abstinence.
Sources: en.wikipedia.org
Reports describe modulation of GABA signalling, changes in monoamine turnover and effects on neurotrophic factor expression. These observations come mainly from animal and cell studies. A single unifying mechanism has not been demonstrated.
The peptide enters plasma rapidly and is broken down by ordinary proteases into amino acids and shorter fragments. Reported half-lives are short. Whether meaningful amounts of the intact molecule reach the brain is an open question.
Most clinical reports are small, published in Russian and not independently replicated. English-language reviews highlight the absence of large randomised trials. Conclusions about efficacy should be treated as provisional.
Reverse-phase HPLC is the usual method and gives a percentage purity value. Mass spectrometry then confirms the molecular mass. Together they provide a basic identity and purity profile for a lot.