Everything below concerns freeze-thaw cycle. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-08-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilised solid form |
| Solubility class | Freely soluble in water | Hydrophilic heptapeptide |
| Dry storage temperature | -20 degrees Celsius or lower | Sealed, desiccated, protected from light |
| Solution storage | 2 to 8 degrees Celsius short term | Avoid repeated freeze-thaw cycles |
| Common identification method | Reversed-phase HPLC with mass spectrometry | Confirms purity and molecular mass |
Selank is a synthetic heptapeptide developed in Russia during the 1990s. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences designed it as a stabilized analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The compound has been studied primarily for its reported anxiolytic and nootropic effects. It remains largely unknown in Western pharmacology and is not approved as a medicine by major regulators such as the FDA or the EMA.
The primary structure of Selank is Thr-Lys-Pro-Arg-Pro-Gly-Pro, corresponding to the molecular formula C33H57N11O9 and a monoisotopic mass of roughly 751.9 daltons. The N-terminal threonine and the arginine residue in the fourth position are shared with tuftsin, which carries the sequence Thr-Lys-Pro-Arg. The three additional residues at the C-terminus, Pro-Gly-Pro, extend the chain and are associated with greater resistance to enzymatic degradation. This extension also separates Selank from the shorter parent peptide.
Reverse-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres is the standard purity method. Mass spectrometry, typically electrospray ionisation, confirms identity through the expected mass-to-charge pattern. Amino acid analysis can verify composition independently. Chiral purity requires separate techniques such as derivatisation followed by chromatographic separation, and such data are rarely reported for research-grade material.
Quantification in biological matrices relies on liquid chromatography coupled to tandem mass spectrometry with stable-isotope internal standards. Low plasma concentrations and adsorption to container surfaces both complicate measurement. Solid-phase extraction is often needed to reduce matrix interference before injection. Reported limits of quantification differ widely between laboratories, which makes direct comparison of pharmacokinetic results difficult and limits meta-analysis.
Peptide bonds are vulnerable to protease attack, and Selank is no exception. Measured half-life in serum is short, on the order of minutes in several reports, which explains why intranasal administration is the common route described in the literature. Absorption across the nasal mucosa partially bypasses first-pass hepatic metabolism. Quantitative data on human bioavailability remain limited and are difficult to compare across studies.
For example, capillary electrophoresis or liquid chromatography could be used if the analyte can be ionized and has a high vapor pressure, but it is also soluble in polar solvents. On the other hand, gas chromatography is the best way to test a substance that is stable at high temperatures but has a low vapor pressure. When compared to gas or liquid chromatography, supercritical fluid chromatography is a better way to measure chiral inversion because it uses mass spectrometers and a green method.
Allan L. Goldstein is emeritus professor in the Department of Biochemistry and Molecular Medicine at the George Washington University School of Medicine. He chaired the department from 1978 until March 2009 and was awarded emeritus status in 2013. He is an authority on the thymus gland and the workings of the immune system, and co-discoverer (with Abraham White) of the thymosins, a family of hormone-like peptides isolated from the thymus gland.
Jung decided that his near-psychotic experiences were of value and, in private, he induced hallucinations or, in his words, a process of "active imagination". He recorded everything he experienced in small journals, which Jung referred to in the singular as his Black Book, considering it a "single integral whole", even though some of these original journals have a brown cover. Jung described his 1912 book as "an attempt, only partially successful, to create a wider setting for medical psychology and to bring the whole of the psychic phenomena within its purview". The book was later revised and retitled Symbols of Transformation in 1952. The material Jung wrote was subjected to several edits, hand-written and typed, including another, "second layer" of text, his continual psychological interpretations during the process of editing. Around 1915, Jung commissioned a large red leather-bound book, and began to transcribe his notes and paint, working intermittently for sixteen years. Jung left no posthumous instructions about the final disposition of what he called the Liber Novus or Red Book. Sonu Shamdasani, a historian of psychology from London, tried for three years to persuade Jung's resistant heirs to have it published. Ulrich Hoerni, Jung's grandson who manages the Jung archives, decided to publish it when the necessary additional funds were raised through the Philemon Foundation. Up to September 2008, fewer than about two dozen people had ever seen it. In 2007, two technicians for DigitalFusion, working with New York City publishers W. W.
=== Eradication === In 2015, the caseload of the illness fell to zero in 16 countries that used MenAfriVac in mass vaccination campaigns. Ten other countries have not launched vaccination programs. Epidemics were expected to return in about 15 years unless MenAfriVac becomes a routine childhood vaccination as WHO recommended. The tetanus toxoid protein used in the vaccine increased the share of people with long-term tetanus immunity from 20% to 59%, although it is not strong enough to stand alone against tetanus. Neonatal tetanus kills nearly 50,000 newborns a year in sub-Saharan Africa. Rates of neonatal tetanus fell by 25% in countries following a MenAfriVac campaign.
Sources: en.wikipedia.org
=== Proton pumps === A proton pump is any process that creates a proton gradient across a membrane. Protons can be physically moved across a membrane, as seen in mitochondrial Complexes I and IV. The same effect can be produced by moving electrons in the opposite direction. The result is the disappearance of a proton from the cytoplasm and the appearance of a proton in the periplasm. Mitochondrial Complex III is this second type of proton pump, which is mediated by a quinone (the Q cycle). Some dehydrogenases are proton pumps, while others are not. Most oxidases and reductases are proton pumps, but some are not. Cytochrome bc1 is a proton pump found in many, but not all, bacteria (not in E. coli). As the name implies, bacterial bc1 is similar to mitochondrial bc1 (Complex III).
The Life Sciences Institute (LSI) is a collaborative, multidisciplinary research institution located on the campus of the University of Michigan in Ann Arbor. It encompasses 27 faculty-led teams from 13 schools and departments throughout U-M. Of the university's $823 million in research expenditures, more than half is allocated for research in the life sciences, and the LSI is a cornerstone of this effort.
Breakthrough T1D (formerly JDRF) is a type 1 diabetes (T1D) research and advocacy organization. Breakthrough T1D funds research for the development of new therapies and treatments for type 1 diabetes. The organization advocates for federal research funding toward new technologies and treatments and works with regulatory and policy officials to disburse funds. Breakthrough T1D also has partnerships with academia, industry, and clinicians to accelerate research into potential cures for T1D. The organization has been described as "the leading global organization funding T1D research".
Sources: en.wikipedia.org
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.
Reversed-phase HPLC establishes purity, while mass spectrometry confirms the expected molecular mass. Sequence confirmation may use tandem mass spectrometry or peptide mapping. A certificate of analysis typically reports these results alongside the analytical method applied.
In Russia it is a registered medicine available by prescription. In many other countries it is not approved for human use and is supplied only as a research chemical. Import and possession rules differ by jurisdiction, and buyers are responsible for checking local requirements.
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.