If you have been reading about freeze-thaw cycle and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2026-01-28. Numbers and descriptions here follow the published literature rather than marketing material.
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.
Reported activity for Selank centers on anxiolytic and nootropic effects. Russian clinical reports describe use in anxiety and in cognitive or attention-related complaints. Most of this evidence comes from studies conducted by the same research groups that developed the peptide. Independent replication in other countries remains limited, and no major Western regulatory agency has approved the compound for any indication. The gap between local reports and external verification is a recurring point in discussions of the peptide.
Tuftsin, the parent structure, is a naturally occurring immunomodulatory tetrapeptide released from the Fc region of immunoglobulin G by spleen enzymes. Selank extends this four-residue sequence with three additional amino acids. The stated rationale is that the added tail slows enzymatic breakdown and may influence receptor interactions. How the full heptapeptide behaves at the molecular level is not firmly established, and proposed mechanisms often involve indirect modulation of neurotransmitter or immune signaling rather than a single defined target.
Selank is a synthetic heptapeptide developed in Russia. Its sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, a seven-residue chain built around the natural tetrapeptide tuftsin. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences first described the compound in the mid-1990s. The design combined the tuftsin core with an added Pro-Gly-Pro tail, a modification intended to extend the molecule's stability in biological fluids. Published work on the peptide has appeared mainly in Russian-language journals.
| Property | Value | Notes |
|---|---|---|
| Solubility | Freely soluble in water | Also in aqueous buffers |
| Typical purity (HPLC) | 95 percent or higher | Lot-dependent |
| Dry powder storage | Minus 20 degrees Celsius | Sealed, dry, protected from light |
| Solution storage | 2 to 8 degrees Celsius | Short-term use |
| Identity confirmation | Mass spectrometry | ESI or MALDI-TOF |
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.
Outside its country of origin the compound is generally handled as a research chemical rather than an approved medicine. No regulatory approval from the United States Food and Drug Administration or the European Medicines Agency has been granted for human use. Identity and purity are normally checked by reverse-phase high-performance liquid chromatography, with mass spectrometry used to confirm the molecular mass. Lyophilised material is stored cold and desiccated, and repeated freeze-thaw cycles are avoided.
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.
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.
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.
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.
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.
=== Tau in Frontotemporal Lobar Degeneration (FTLD) === The tau protein is one of the most common aggregated proteins in frontotemporal lobar degeneration (FTLD), the pathology underlying FTD disorders, the other being TDP-43. While protein aggregation underlies FTLD tauopathies, the specific tau isoforms present and the morphology of the aggregates vary across subtypes. FTLD tauopathies are predominantly associated with the 3R and 4R tau isoforms. The “Pick bodies” characteristic of the FTLD tauopathy known as “Pick’s disease” is associated with 3R tau. Progressive supranuclear palsy (PSP) and corticobasal syndrome/degeneration (CBS/CBD), meanwhile, are associated with the 4R isoform. There is evidence that a ratio of 3R and 4R tau is essential for preventing neurodegeneration, and that alterations in this ratio are believed to drive FTLD and related disorders without requiring co-occurrence with other pathologies. FTD-tau appears to be sporadic in the majority of people diagnosed, but researchers do not yet fully understand the pathological mechanisms. Inherited pathogenic variants in the MAPT gene, however, are responsible for a fraction of people diagnosed with FTD-tau. Within and between families, FTD due to MAPT presents with significant heterogeneity in the symptoms that may be present, underscoring the possibility for genetic modifiers and environmental factors to influence clinical presentation. Intronic variants in MAPT, and most variants in exon 10, affect the 3R/4R tau ratio, contributing significantly to the development of FTLD pathology.
His group then went on to apply the same technique to assess rates of gluconeogenesis in patients with poorly controlled T2D and demonstrated that virtually all of their increased glucose production can be attributed to increased rates of gluconeogenesis and that metformin lowers hepatic glucose production in these individuals by decreasing the rate of hepatic gluconeogenesis. He also demonstrated that metformin suppresses hepatic gluconeogenesis by inhibiting Complex IV and altering the cytosolic redox state. His lab developed the Positional Isotopomer NMR Tracer Analysis (PINTA) method to measure hepatic mitochondrial fluxes. With this, they showed mechanisms by which caloric restriction reverses diabetes, how leptin maintains gluconeogenesis during fasting, how the glucose-alanine cycle regulates hepatic fat oxidation, and how glucagon stimulates gluconeogenesis via the IP3R1 receptor and CaMKII. His research has also explored how adiponectin, leptin, and fibroblast growth factors (FGF-1, FGF-19, and FGF-21) regulate hepatic glucose metabolism. Contrary to the prevailing view that insulin acutely suppresses hepatic gluconeogenesis through FoxO1-mediated transcriptional repression, Shulman's team showed that suppression occurs mainly through inhibition of white adipocyte lipolysis, reducing glycerol and fatty acid flux to the liver. This leads to decreased acetyl-CoA activation of pyruvate carboxylase and lower glycerol-derived glucose production.
=== Magazine === OECD Observer, an award-winning magazine, was launched in 1962. The magazine appeared six times a year until 2010, and became quarterly in 2011 with the introduction of the OECD Yearbook, launched for the 50th anniversary of the organisation. The online and mobile editions contained news, analysis, reviews, commentaries and data on global economic, social and environmental challenges and listings of the latest OECD books. An OECD Observer Crossword was introduced in Q2 2013. The OECD Observer was last issued in the fourth quarter of 2019, with a double edition looking ahead at artificial intelligence, and a cover leading on why statistical offices should hire a comedian. The OECD Observer website closed in the first quarter of 2021; the archive can be consulted at www.oecd.org.
A 2013 review found the data too weak to support use of Chinese herbal medicine (CHM) for benign prostatic hyperplasia. A 2013 review found the research on the benefit and safety of CHM for idiopathic sudden sensorineural hearing loss is of poor quality and cannot be relied upon to support their use. A 2013 Cochrane review found inconclusive evidence that CHM reduces the severity of eczema. The traditional medicine ginger, which has shown anti-inflammatory properties in laboratory experiments, has been used to treat rheumatism, headache and digestive and respiratory issues, though there is no firm evidence supporting these uses. A 2012 Cochrane review found no difference in mortality rate among 640 SARS patients when Chinese herbs were used alongside Western medicine versus Western medicine exclusively, although they concluded some herbs may have improved symptoms and decreased corticosteroid doses. A 2012 Cochrane review found insufficient evidence to support the use of TCM for people with adhesive small bowel obstruction. A 2011 review found low quality evidence that suggests CHM improves the symptoms of Sjögren's syndrome. A 2011 Cochrane review found inconclusive evidence to support the use of TCM herbal medicines for treatment of hypercholesterolemia. A 2011 Cochrane review did not find improvement in fasting C-peptide when compared to insulin treatment for latent autoimmune diabetes in adults after 3 months. It is important to highlight that the studies available to be included in this review presented considerable flaws in quality and design.
Sources: en.wikipedia.org
== Glycosylation == Thy-1 is one of the most heavily glycosylated membrane proteins with a carbohydrate content up to 30% of its molecular mass. Thy-1 in most species has 3 N-glycosylation sites (Asn 23, 74 and 98) but no O-glycosylation. The composition of Thy-1 carbohydrate moieties varies considerably between different tissues or even among cells of the same lineage at different stages of differentiation: e.g., galactosamine only in brain Thy-1, sialic acid in thymic Thy-1 in far excess than brain Thy-1, that too increasing in parallel with T cell maturation. In this regard it has yet another historic association: Thy-1 happens to be the first glycoprotein in which cell type specificity of variant glycosylation on an invariant protein was demonstrated. Analysis of Differencial glycosylation of Thy-1 from brain and thymus showed that all the complex N-linked structures differed between the two forms, superimposed upon a site specific common core. In case of Thy-1 this core pattern was constituted by Asn23 carrying mostly oligomannose structures, Asn74 carrying the most extended complex structures, and Asn98 carrying smaller complex structure. The structure of the sugar residues in the GPI anchor and their associated esterified structures (e.g. additional fatty acids and alcohols) also can be cell type and species specific.
The 5-HT2C receptors are G protein–coupled receptors that are coupled to phospholipase C (PLC) via Gαq, phospholipase A2 (PLA2), and possibly Gα13. PLC metabolizes phosphatidylinositol 4,5-bisphosphate into inositol 1,4,5-triphosphate (IP3). IP3 regulates cellular Ca2+ flux by binding to IP3 receptors, inducing Ca2+ release. In addition, the activation of PLA2 also results in recruitment of a RhoA/PLD pathway through RhoA, an enzyme that regulates a wide spectrum of cellular functions through PLD (phospholipase D) target protein. The 5-HT2C receptors can also stimulate the extracellular signal-regulated kinase (ERK) pathway which is activated by neurotrophins and other neuroactive chemicals. Production of these chemicals effects neuronal differentiation, survival, regeneration, and structural and functional plasticity. Early studies of the ERK pathway showed that mood stabilizers for the treatment of manic-depressive illness stimulated the pathway. This led to the understanding that stimulation of the 5-HT2C receptors could regulate manic-depressive conditions in a manner similar to mood stabilizers. 5-HT2C receptors are located only within the CNS, where they can be found in several locations. The highest density of receptor expression is within the choroid plexus. Other brain locations include the nucleus of the solitary tract, dorsomedial hypothalamus, paraventricular hypothalamic nucleus and the amygdala, all of which are associated with regulation of food intake.
=== Campaigns === On November 8, 1980, Sanders announced his candidacy for mayor. He formally announced his campaign on December 16 at a City Hall press conference. Sanders selected Linda Niedweske as his campaign manager. The Citizens Party attempted to nominate Greg Guma for mayor, but Guma declined, saying it would be "difficult to run against another progressive candidate". Sanders had been convinced to run for the mayoralty by his close friend Richard Sugarman, an Orthodox Jewish professor of religious studies at the University of Vermont, who had shown him a ward-by-ward breakdown of the 1976 Vermont gubernatorial election, in which Sanders had run, that showed him receiving 12% of the vote in Burlington despite only getting 6% statewide. Sanders initially won the mayoral election by 22 votes against incumbent mayor Gordon Paquette, Richard Bove, and Joseph McGrath, but the margin was later reduced to 10 votes. Paquette did not contest the results of the recount. Paquette did not campaign or promote his candidacy since neither Sanders nor Bove was seen as a serious challenger. Sanders had not previously won an election. Paquette was also considered to have lost because he proposed an unpopular $0.65 per $100 raise in taxes that Sanders opposed. Sanders spent around $4,000 on his campaign. Sanders criticized the pro-development incumbent as an ally of prominent shopping center developer Antonio Pomerleau, while Paquette warned of ruin for Burlington if Sanders were elected.
Sources: en.wikipedia.org
Non-selective beta-blockers: propranolol, nadolol, timolol Beta-1-selective beta-blockers: atenolol, bisoprolol, metoprolol, esmolol Beta-blockers with vasodilating effect: labetalol, carvedilol, nebivolol Beta-blockers with intrinsic sympathomimetic activity: acebutolol, pindolol Some common side effects include increased airway resistance for non-selective beta-blockers, exacerbation of peripheral vascular diseases, and hypotension Beta-blockers are contraindicated in patients with second- or third-degree atrioventricular block. In particular, beta-blockers with intrinsic sympathomimetic activity are contraindicated in patients with myocardial infarction, heart failure or severe bradycardia. Beta-blockers should be used with caution in patients with asthma or chronic obstructive pulmonary disease (COPD) due to bronchoconstriction, and in patients with diabetes mellitus (DM) due to masking of hypoglycaemia.
== History == Established in 1984, the International Petroleum Investment Company (IPIC) was created to advance Abu Dhabi's natural petroleum wealth for the development of the emirate. Mubadala Development Company followed in 2002 to further diversify the economy. In June 2016, it was announced that Mubadala Development Company would merge with the International Petroleum Investment Company. In 2017, ownership of both MDC and IPIC was transferred to a newly created parent company, Mubadala Investment Company. The company is a wholly owned investment vehicle of the government of Abu Dhabi, and Sheikh Mansour bin Zayed Al Nahyan, vice-president and deputy prime minister of the United Arab Emirates, is chairman of the company.
=== Cancer cells === Cancer cells can manipulate cell signalling by producing excess levels of ROS, thereby constitutively activating pathways to promote their cellular growth and proliferation. Implicated pathways include NF-κB, PI3K, HIFs and MAPKs. In humans, mitochondrial ROS is required alongside those released in the oxidative burst for mitogenic pathway stimulation in oncogenic KRAS cells. However, in oncogenic Kras mice fibroblasts, NADPH oxidase inhibitors have been shown to be sufficient to block these growth factor pathways. Tumorigenic cells also simultaneously maintain high levels of antioxidants to protect against cancer cell death.
=== DuPont and the invention of nylon === Researchers at DuPont began developing cellulose-based fibers, culminating in the synthetic fiber rayon. DuPont's experience with rayon was an important precursor to its development and marketing of nylon. DuPont's invention of nylon spanned an eleven-year period, ranging from the initial research program in polymers in 1927 to its announcement in 1938, shortly before the opening of the 1939 New York World's Fair. The project grew from a new organizational structure at DuPont, suggested by Charles Stine in 1927, in which the chemical department would be composed of several small research teams that would focus on "pioneering research" in chemistry and would "lead to practical applications". Harvard instructor Wallace Hume Carothers was hired to direct the polymer research group. Initially he was allowed to focus on pure research, building on and testing the theories of German chemist Hermann Staudinger. He was very successful, as research he undertook greatly improved the knowledge of polymers and contributed to the science. Nylon was the first commercially successful synthetic thermoplastic polymer. DuPont began its research project in 1927. The first nylon, nylon 66, was synthesized on February 28, 1935, by Wallace Hume Carothers at DuPont's research facility at the DuPont Experimental Station. In response to Carothers' work, Paul Schlack at IG Farben developed nylon 6, a different molecule based on caprolactam, on January 29, 1938. In the spring of 1930, Carothers and his team had already synthesized two new polymers.
Sources: en.wikipedia.org
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.
Freeze-dried material is kept frozen, often at minus 20 degrees Celsius, and protected from light and moisture. Dissolved peptide is refrigerated for short-term use. Repeated freeze-thaw cycles are avoided.
A certificate of analysis typically lists purity by HPLC, the confirmed mass, appearance, and sometimes water or counter-ion content. It documents results for a specific batch. Details vary by supplier.
Selank is a synthetic peptide made of seven amino acids. It is modeled on tuftsin, a natural tetrapeptide, with an added three-residue tail. It is not a small-molecule drug.