This is a working overview of lyophilization, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-10-03. 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.
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.
| 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 |
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.
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.
Reported pharmacological effects center on reduced anxiety-like behavior in animal models and on measures of memory and learning. Proposed contributing mechanisms include modulation of GABAergic signaling, shifts in monoamine turnover, and changes in the activity of enzymes that degrade neuropeptides. Effects on the expression of genes linked to neuroplasticity have also been described. No single molecular target is widely accepted, and whether the behavioral findings arise from one pathway or several remains an open question.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed as a stabilized analogue of tuftsin, a naturally occurring tetrapeptide fragment derived from the immunoglobulin heavy chain. The additional Pro-Gly-Pro segment at the carboxyl terminus is intended to slow enzymatic cleavage. The compound is usually described in the literature as a synthetic peptide with anxiolytic and cognitive-related activity, a label that reflects a research context rather than an approved therapeutic category.
Most published work on selank originates from a small number of research groups in the Russian Federation. A large share of that record appears in Russian-language journals, which limits access for readers who rely on English-indexed databases. Independent replication by laboratories outside the original research network is sparse in publicly available sources. This concentration of origin and language is a frequently noted feature when the compound is summarized in broader reviews of synthetic peptides.
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.
Regulatory treatment varies by jurisdiction. In Russia the compound is a registered prescription product, while in the European Union and the United States it is generally handled as a research chemical without a marketing authorization. Suppliers therefore operate outside pharmaceutical oversight, and buyers rely on supplier documentation for purity and identity claims. Chain of custody and third-party testing are the main verification tools. Analysts note that the absence of a pharmacopoeial monograph for research-grade material limits standardization across vendors.
Purity assessment relies mainly on reverse-phase high-performance liquid chromatography with ultraviolet detection. Because the peptide lacks a strong chromophore, detection often uses backbone absorbance near 214 nm. Identity is confirmed by mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, comparing the measured mass against the expected value. Amino acid analysis can verify composition after acid hydrolysis. Diastereomer content and residual counterions are reported less often, although both can influence biological assays.
It is common in particle physics to use eV/c2 as a unit of mass. Here, eV (electronvolt) is a unit of energy (the kinetic energy of an electron accelerated over one volt, 1.6×10−19 J), and c is the speed of light in vacuum. Energy and mass are related through E = mc2. This definition is useful for a linear particle accelerator when accelerating electrons.
As a salt, its dominant use is as an emulsifier for the emulsion polymerization of fluoropolymers such as PTFE, polyvinylidene fluoride, and fluoroelastomers. For this use, 3M subsidiary Dyneon has a replacement emulsifer despite DuPont stating PFOA is an "essential processing aid". In the past PFOA was used in the production of Gore-Tex as it is PTFE-based. In PTFE processing, PFOA is in aqueous solution and forms micelles that contain tetrafluoroethylene and the growing polymer. PFOA can be used to stabilize fluoropolymer and fluoroelastomer suspensions before further industrial processing and in ion-pair reversed-phase liquid chromatography it can act as an extraction agent. PFOA also finds uses in electronic products and as an industrial fluorosurfactant. In a 2009 EPA study of 116 products, purchased between March 2007 and May 2008 and found to contain at least 0.01% fluorine by weight, the concentrations of PFOA were determined. Concentrations shown below range from not detected, or ND, (with the detection limit in parentheses) to 6750 with concentrations in nanograms of PFOA per gram of sample (parts per billion) unless stated otherwise.
==== Surgery ==== Tranexamic acid is sometimes used in orthopedic surgery to reduce blood loss, to the extent of reducing or altogether abolishing the need for perioperative blood transfusion. It is of proven value in clearing the field of surgery and reducing blood loss when given before or after surgery. Drain and number of transfusions are reduced. In surgical corrections of craniosynostosis in children it reduces the need for blood transfusions. In spinal surgery (e.g., scoliosis), correction with posterior spinal fusion using instrumentation, to prevent excessive blood loss. In cardiac surgery, both with and without cardiopulmonary bypass (e.g., coronary artery bypass surgery), it is used to prevent excessive blood loss.
Sources: en.wikipedia.org
Depressants are psychoactive drugs that temporarily diminish the function or activity of a specific part of the body or mind. Colloquially, depressants are known as "downers", and users generally take them to feel more relaxed and less tense. Examples of these kinds of effects may include anxiolysis, sedation, and hypotension. Depressants are widely used throughout the world as prescription medicines and as illicit substances. When these are used, effects may include anxiolysis (reduction of anxiety), analgesia (pain relief), sedation, somnolence, cognitive/memory impairment, dissociation, muscle relaxation, lowered blood pressure/heart rate, respiratory depression, anesthesia, and anticonvulsant effects. Depressants exert their effects through a number of different pharmacological mechanisms, the most prominent of which include potentiation of GABA or opioid activity, and inhibition of adrenergic, histamine or acetylcholine activity. Some are also capable of inducing feelings of euphoria. The most widely used depressant by far is alcohol (i.e. ethanol). Stimulants or "uppers", such as amphetamines or cocaine, which increase mental or physical function, have an opposite effect to depressants. Depressants, in particular alcohol, can precipitate psychosis. A 2019 systematic review and meta-analysis by Murrie et al. found that the rate of transition from opioid, alcohol and sedative induced psychosis to schizophrenia was 12%, 10% and 9% respectively.
=== Styrene-butane co-polymers === Styrene-butane co-polymers can be produced with a low butene content. Styrene-butane co-polymers include PS-I and SBC (see below), both co-polymers are impact resistant. PS-I is prepared by graft co-polymerization, SBC by anionic block co-polymerization, which makes it transparent in case of appropriate block size. If styrene-butane co-polymer has a high butylene content, styrene-butadiene rubber (SBR) is formed. The impact strength of styrene-butadiene co-polymers is based on phase separation, polystyrene and poly-butane are not soluble in each other (see Flory–Huggins solution theory). Co-polymerization creates a boundary layer without complete mixing. The butadiene fractions (the "rubber phase") assemble to form particles embedded in a polystyrene matrix. A decisive factor for the improved impact strength of styrene-butadiene copolymers is their higher absorption capacity for deformation work. Without applied force, the rubber phase initially behaves like a filler. Under tensile stress, crazes (microcracks) are formed, which spread to the rubber particles. The energy of the propagating crack is then transferred to the rubber particles along its path. A large number of cracks give the originally rigid material a laminated structure. The formation of each lamella contributes to the consumption of energy and thus to an increase in elongation at break. Polystyrene homo-polymers deform when a force is applied until they break.
These effects were not noted in its medicinal use in the 1950s and 1960s, and reports of physical violence on PCP have often been shown to be unfounded. Recreational doses of the drug also occasionally appear to induce a psychotic state, with emotional and cognitive impairment that resembles a schizophrenic episode. Users generally report feeling detached from reality. Symptoms are summarized by the mnemonic device RED DANES: rage, erythema (redness of skin), dilated pupils, delusions, amnesia, nystagmus (oscillation of the eyeball when moving laterally), excitation, and skin dryness.
During his early years in the Senate, Biden focused on consumer protection and environmental issues and called for greater government accountability. In 1974, he described himself as liberal on civil rights and liberties, senior citizens' concerns, and healthcare, but conservative on other issues, including abortion and military conscription. Biden was the first U.S. senator to endorse Governor Jimmy Carter for president in the 1976 Democratic primary. Carter won the Democratic nomination and the 1976 election. Biden also worked on arms control. After Congress failed to ratify the SALT II Treaty signed in 1979 by Soviet general secretary Leonid Brezhnev and President Carter, Biden met with Soviet foreign minister Andrei Gromyko and secured changes that addressed the Senate Foreign Relations Committee's objections. He received considerable attention when he excoriated Secretary of State George Shultz at a Senate hearing for the Reagan administration's support of South Africa despite its policy of apartheid. In a congressional hearing in 1984, he objected to the Strategic Defense Initiative plan to construct autonomous systems of ICBM defense. Biden was an advocate for Delaware military installations, including Dover Air Force Base and New Castle Air National Guard Base. In the mid-1970s, Biden was one of the Senate's strongest opponents of race-integration busing. His Delaware constituents strongly opposed it, and such opposition nationwide later led his party to mostly abandon school integration policies.
Sources: en.wikipedia.org
=== Drugs === The anti-diabetic medication pioglitazone was shown in a mouse model of ALD to be effective at treating the metabolic effects of ALD, including metabolic failure and increased oxidative stress. Pioglitazone was also shown to prevent axonal degeneration and increase mitochondria levels, as well as stop the progression of locomotor decline in ALD model mice. Subsequently, the experimental drug leriglitazone has been developed as a more brain penetrant metabolite of pioglitazone. As of 2023, leriglitazone is in phase 2/3 clinical trials for adult and childhood cALD in the USA and the EU, and has completed a clinical trial for AMN.
A protein is considered to be misfolded if it cannot achieve its normal native state. This can be due to mutations in the amino acid sequence or to a disruption of the normal folding process by external factors. The misfolded protein typically contains beta sheets (β-sheets) that are organized in a supramolecular arrangement known as a cross-β structure. These β-sheet-rich assemblies are very stable, very insoluble, and generally resistant to proteolysis. The structural stability of these fibrillar assemblies is caused by extensive interactions between the protein monomers, formed by backbone hydrogen bonds between their β-strands. The misfolding of proteins can trigger the further misfolding and accumulation of other proteins into aggregates or oligomers. The increased levels of aggregated proteins in the cell leads to formation of amyloid-like structures which can cause neurodegenerative disorders and cell death. The amyloids are fibrillary structures that contain intermolecular hydrogen bonds which are highly insoluble and made from converted protein aggregates. Therefore, the proteasome pathway may not be efficient enough to degrade the misfolded proteins prior to aggregation. Misfolded proteins can interact with one another and form structured aggregates and gain toxicity through intermolecular interactions.
Some forms of MODY produce significant hyperglycemia and the typical signs and symptoms of diabetes: increased thirst and urination (polydipsia and polyuria). In contrast, many people with MODY have no signs or symptoms and are diagnosed either by accident, when a high glucose is discovered during testing for other reasons, or screening of relatives of a person discovered to have diabetes. Discovery of mild hyperglycemia during a routine glucose tolerance test for pregnancy is particularly characteristic. While the goals of diabetes management are the same no matter what type, there are two primary advantages of confirming a diagnosis of MODY.
== Living cells == According to some opinions, living eukaryotic cells perform isoelectric focusing of proteins in their interior to overcome a limitation of the rate of metabolic reaction by diffusion of enzymes and their reactants, and to regulate the rate of particular biochemical processes. By concentrating the enzymes of particular metabolic pathways into distinct and small regions of its interior, the cell can increase the rate of particular biochemical pathways by several orders of magnitude. By modification of the isoelectric point (pI) of molecules of an enzyme by, e.g., phosphorylation or dephosphorylation, the cell can transfer molecules of the enzyme between different parts of its interior, to switch on or switch off particular biochemical processes.
=== Gases === The solubility of gases in water is usually thought to decrease with temperature, but this only occurs to a certain temperature, before increasing again. For nitrogen, this minimum is 74 °C and for oxygen it is 94 °C Gases are soluble in superheated water at elevated pressures. Above the critical temperature, water is completely miscible with all gases. The increasing solubility of oxygen in particular allows superheated water to be used for wet oxidation processes.
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.
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.