peptide stability raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-01-12. Anything still debated is marked as such rather than presented as settled.
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.
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.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography, with mass spectrometry used to confirm molecular mass and sequence information. Amino acid analysis and peptide mapping may supplement these methods. Certified reference standards are scarce, and many commercial lots are sold as research chemicals without a pharmacopoeial monograph. Regulatory treatment differs by country: Selank is a registered prescription medicine in Russia, while in the European Union and the United States it is not an approved drug and may fall under research-chemical or unapproved-product frameworks.
Selank is a hydrophilic peptide and dissolves readily in water and in aqueous buffers. The lyophilised powder is typically a white to off-white solid. Because short peptides are prone to hydrolysis and oxidation, handling benefits from limiting exposure to heat, moisture and strong light. Working solutions are commonly prepared in sterile water or saline, and repeated freeze-thaw cycles are avoided to reduce aggregation and loss of activity. These practices reflect general laboratory convention rather than published stability specifications.
Dry powder is normally held at -20 degrees Celsius or lower, in a sealed container with desiccant and protection from light. Reconstituted solutions are usually kept at 2 to 8 degrees Celsius for short periods and frozen for longer ones. Proline residues at several positions are generally associated with some resistance to peptidase attack, but chemical stability still declines at neutral to alkaline pH and at elevated temperature. Exact shelf-life figures are product-specific and are not standardised across suppliers.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Tuftsin analogue |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form: TKPRPGP |
| Molecular formula | C33H57N11O9 | Calculated for the free peptide |
| Molecular weight | About 751.9 g/mol | Derived from the sequence |
| Appearance | White to off-white powder | Typical lyophilised form |
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.
Handling follows standard practice for research peptides. Material is weighed in a low-humidity environment because the powder absorbs atmospheric moisture. Purity is reported as the percentage area of the main peak in a chromatogram, with specifications commonly set at 95 percent or higher; values below that threshold indicate the presence of truncated or modified species. Residual trifluoroacetate from purification is often present and may affect mass balance. Certificates of analysis should state the analytical method, the column and gradient used, and the lot-specific retention time so that results can be compared across suppliers.
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.
Published clinical evidence is limited. Most controlled trials were conducted in Russia, enrolled modest numbers of participants, and appeared in Russian-language journals, which restricts independent verification. Reported outcomes include lower anxiety scores, improved attention and memory measures, and changes in fatigue ratings. Reviews written in English note methodological limitations such as small samples and inconsistent endpoints. Whether the compound produces clinically meaningful benefit relative to established anxiolytics is therefore an open question rather than an established finding.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences as a structural analogue of tuftsin, a naturally occurring tetrapeptide fragment of the immunoglobulin heavy chain. The added Pro-Gly-Pro tail was intended to slow enzymatic degradation and extend biological activity. In Russia it is registered as an anxiolytic nasal preparation, while regulators elsewhere have not approved it for clinical use.
==== Decomposition of mass ==== In order to quickly generate a manageable number of molecular formula candidates, the monoisotopic mass is decomposed into all possible molecular formulas that would lead to this mass. There are two definitions of the monoisotopic mass: (1) the sum of the masses of the most abundant naturally occurring stable isotope of each atom (i.e. the highest peak of the isotope pattern) (2) the sum of the masses of the lightest naturally occurring stable isotope of each atom (i.e. the peak of the isotope pattern with the lowest mass). For small molecules, the lightest peak is also mostly the highest peak of the isotope pattern. However, in the computational context of SIRIUS, the second definition is used. Decomposing the monoisotopic mass into all possible molecular formulas requires a mass interval taking into account the measurement inaccuracy of the instrument. This real-valued decomposition is transformed into a problem instance with integer masses by using a blowup factor. The resulting problem is known as Change-making problem which is well-studied and can be solved in runtime linear in the size of the output.
=== Use and abuse === Flupentixol/melitracen is the single most popular antidepressant in China, according to 2013–2018 prescription data. It is generally not prescribed by psychiatrists, but by clinicians working in other areas, mainly gastroenterologists, cardiologists, endocrinologists, neurologists, even general physicians and surgeons. Only when a patient encounters a side effect on this drug are they referred to a psychiatrist. DXY.cn notes a significant lack of evidence-based guidance on using and discontinuing this medication despite its widespread use in China. Adverse effects from longer-term use and withdrawal symptoms have been reported. Self-medication with this drug used to be common in India; it still is in China, where pharmacies exercise little care to ensure the existence of a prescription. It is also easily obtained in Lebanon without a prescription. In a study of Lebanese emergency department patients who take flupentixol/melitracen, 36% (45 out of 125) were diagnosed as having a substance use disorder for this medication under the DSM-V criteria. Among Jordanian pharmacists, 70.6% were willing to dispense the medication in situations including malpractice.
=== January === 1 January Helen Hogan, educator (Hillmorton High School, WEA), editor of poetry anthologies, and Māori studies scholar (born 1923). Lyn Fleming, Police senior sergeant and first policewoman in New Zealand to be killed in the line of duty (born 1963). 2 January – Lex Clark, Olympic rower (1964) (born 1943). 3 January Kate Coolahan, commercial artist, fashion illustrator, printmaker, and design educator (Wellington Polytechnic) (born 1929). Dame Tariana Turia, politician, Labour list MP (1996–2002), MP for Te Tai Hauāuru (2002–2014), co-leader of the Māori Party (2004–2014), Minister for the Community and Voluntary Sector (2003–2004, 2008–2011), Minister for Disability Issues (2009–2014), Minister for Whānau Ora (2010–2014) (born 1944). 5 January Philippa Blair, artist (born 1945). Lou Robinson, structural engineer and heritage advocate (born 1943). 7 January – Arthur Pomeroy, classical scholar (Victoria University of Wellington), chess player and administrator (born 1953). 18 January – Russell Marshall, politician and diplomat, MP for Wanganui (1972–1990), Minister of Education (1984–1987), Minister of Foreign Affairs (1987–1990), chancellor of Victoria University of Wellington (2000–2002), High Commissioner to the United Kingdom (2002–2005) (born 1936). 19 January – David Johnston, disaster researcher (Massey University) (born 1966). 20 January – Richard Hipa, Niuean public servant and politician, Secretary of Government (2008–2017), Member of the Niue Assembly (2020–2023) (born 1957). 21 January Diana Beaglehole, historian (born 1938).
== Steered molecular dynamics (SMD) == Steered molecular dynamics (SMD) simulations, or force probe simulations, apply forces to a protein in order to manipulate its structure by pulling it along desired degrees of freedom. These experiments can be used to reveal structural changes in a protein at the atomic level. SMD is often used to simulate events such as mechanical unfolding or stretching. There are two typical protocols of SMD: one in which pulling velocity is held constant, and one in which applied force is constant. Typically, part of the studied system (e.g., an atom in a protein) is restrained by a harmonic potential. Forces are then applied to specific atoms at either a constant velocity or a constant force. Umbrella sampling is used to move the system along the desired reaction coordinate by varying, for example, the forces, distances, and angles manipulated in the simulation. Through umbrella sampling, all of the system's configurations—both high-energy and low-energy—are adequately sampled. Then, each configuration's change in free energy can be calculated as the potential of mean force. A popular method of computing PMF is through the weighted histogram analysis method (WHAM), which analyzes a series of umbrella sampling simulations. A lot of important applications of SMD are in the field of drug discovery and biomolecular sciences. For e.g.
==== Predation theory for multicellularity ==== This theory postulates that multicellularity arose as a means for prey to escape predation. Larger prey are less likely to be preyed upon, and larger predators are more likely to catch prey. Therefore it is likely that multicellularity arose when the first predators evolved. By assembling as a larger, multicelled organism, prey could escape the attempts of a predator. Therefore multicellularity was selectively favoured over unicellularity. This can be seen in a simple experiment conducted by Boraas et al. (1998). When a predatory protist, Ochromonas valencia, was introduced to a prey population of Chlorella vulgaris, it was seen that within less than 100 generations of the prey species a multicellular growth form of the alga became dominant. This is interesting because before the predator was introduced, the population of Chlorella vulgaris retained its unicellular growth form for thousands of generations. It is likely that it would have remained unicellular indefinitely if the selective pressure that was induced by the predators had not been introduced. After multiple generations with the predator, the algal species retained a growth form of 8-10 cells, which was large enough to avoid the predator, but small enough that each cell still had access to nutrients. This predator-prey relationship provides a likely reason for why it was beneficial for organisms to be multicellular.
Sources: en.wikipedia.org
== Neuroclasis classification == In 2025, Schroen et al. proposed a novel classification for nerve stretch injuries based on the distinct mechanical and structural failure pattern of stretch injuries compared to other injury mechanisms. Using a rat median nerve injury model, the authors found that peripheral nerves fail along an outside-in sequence of structural damage with two distinct degrees of in-continuity stretch injury. The first event of mechanical failure, called Epineuroclasis, causes disruption of the epineurium, exposing the overall intact endoneurial core. The second event of mechanical failure, Endoneuroclasis, is associated with severe endoneurial tube disorganization and vascular disruption despite macroscopic nerve continuity. Functional recovery is expected after Epineuroclasis, whereas Endoneuroclasis injury results in long-term dysfunction and formation of traumatic in-continuity neuromas.
Energy gels are edible carbohydrate gels that provide energy for exercise and promote recovery, commonly used in endurance events such as running, cycling, and triathlons. Energy gels are also referred to as endurance gels, sports gels, nutritional gels, and carbohydrate gels. Energy gels are packaged in small, single-serve plastic packets. Each packet has a strip with a small notch at the top that can be peeled off to reveal an opening through which the gel can be consumed. One-handed operation is often adopted by users to facilitate continuous exercise performance.
== Prognosis == Regardless of cause, UIP is relentlessly progressive, usually leading to respiratory failure and death without a lung transplant. Some patients do well for a prolonged period of time, but then deteriorate rapidly because of a superimposed acute illness (so-called "accelerated UIP"). The outlook for long-term survival is poor. In most studies, the median survival is 3 to 4 years. Patients with UIP in the setting of rheumatoid arthritis have a slightly better prognosis than UIP without a known cause (IPF).
== External links == "Anatomy photo:21:st-1500". SUNY Downstate Medical Center. Archived from the original on March 5, 2016. – "Mediastinum: Pericardium (pericardial sac)" thoraxlesson4 at The Anatomy Lesson by Wesley Norman (Georgetown University) (heartpericardium) Atlas image: ht_pericard2 at the University of Michigan Health System – "MRI of chest, lateral view"
Sources: en.wikipedia.org
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.
Selank is a synthetic analogue built on the tuftsin tetrapeptide Thr-Lys-Pro-Arg. Extra proline residues were added to the C-terminus during design work. That modification is intended to make the peptide less vulnerable to rapid enzymatic degradation.
Transliteration from Russian produces variant spellings such as Selanc. Many suppliers avoid the trade-style name entirely and list the peptide sequence. Comparing sequences rather than names is the reliable way to confirm two entries describe the same molecule.
Dry powder is normally held at -20 degrees Celsius or below in a sealed, light-protected container with desiccant. Brief room-temperature handling during weighing is generally tolerated. Storage instructions vary between suppliers, so the accompanying certificate of analysis should be followed.