The short version of reversed-phase HPLC fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-05-13 and is reviewed periodically as new material appears.
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.
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.
Lyophilised material kept dry at minus 20 degrees Celsius or colder is the most stable form, and suppliers commonly state a shelf life of two years or more under those conditions. Once dissolved, degradation accelerates through hydrolysis and deamidation, particularly at alkaline pH or elevated temperature. Working solutions are usually divided into single-use aliquots to avoid repeated freeze-thaw cycles. The choice of reconstitution solvent affects both stability and the ionic strength of the final preparation.
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.
| Property | Value | Notes |
|---|---|---|
| Identity confirmation | Reversed-phase HPLC retention time versus reference standard | Retention depends on column, gradient, and ion-pairing agent |
| Mass confirmation | Electrospray or MALDI mass spectrometry | Doubly protonated ion near m/z 377 is consistent with about 752 Da |
| Typical purity specification | 95 percent or higher by chromatographic peak area | Lower values suggest truncated or modified peptide species |
| Storage of lyophilized powder | -20 °C, desiccated, protected from light | Powder tolerates long storage better than solution |
| Storage of solution | 2-8 °C for short periods | Freeze-thaw cycling promotes aggregation and surface adsorption |
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.
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.
Measuring peptide exposure inside the brain is technically difficult. Selank is degraded rapidly in plasma, and assays must separate intact peptide from fragments, which favors targeted mass spectrometry over immunoassays alone. Reported half-lives are short, on the order of minutes, so effects observed hours later are attributed to downstream signaling rather than to the parent compound. Blood-brain barrier permeability is debated and rarely quantified directly. Gaps include absent dose-response characterization, inconsistent reporting of purity, and almost no pharmacokinetic data from human participants.
Selank is studied chiefly as an animal-model anxiolytic with proposed secondary effects on memory and immune signaling. Reported mechanisms include modulation of the GABA-A receptor complex, inhibition of enkephalin-degrading enzymes, and shifts in monoamine turnover within limbic structures. Some experiments describe increased expression of brain-derived neurotrophic factor in the hippocampus after repeated dosing. No single molecular target has been confirmed, and the peptide does not bind any receptor with the selectivity typical of a conventional small-molecule drug. Mechanism therefore remains a set of hypotheses rather than an established pathway.
Laboratory work relies on standard behavioral paradigms. Rodents are tested in the elevated plus maze, open field, and passive avoidance tasks, with outcomes compared against diazepam or vehicle controls. Intranasal dosing is used most often because it bypasses first-pass metabolism, though intraperitoneal and intravenous routes also appear in published protocols. Biochemical endpoints include tissue BDNF concentrations, cytokine levels, and monoamine metabolites. Human data are limited to small Russian trials reporting reduced anxiety scores; most were not prospectively registered, and few employed independent outcome assessment.
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.
Proposed mechanisms centre on modulation of the GABAergic system, with reports of altered expression of genes related to GABA-A receptor subunits and changed monoamine turnover. Some studies describe inhibition of enkephalinase, the enzyme that degrades endogenous enkephalins, which may prolong opioid peptide signalling. Effects on brain-derived neurotrophic factor and on cytokine expression have also been reported. These findings come largely from animal models and small human studies, and the precise primary target remains unresolved.
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.
Restrictive Type: In the most recent months leading up to the evaluation, the patient has not engaged in binging and purging via laxative or diuretic abuse, enemas, or self-induced vomiting. The weight loss accomplished in this patient is mainly through the use of one or more of the following methods: fasting, dieting, and excessive exercise. Binge-eating / Purging Type: In the last few months, the patient has recurrently engaged in binge-purge cycles.
=== Grasslands === It was reported that approximately 34 percent (33.85 million mu; 22,600 km2) of the region's total surface consisted of grassland. This figure is down from approximately 40 percent in the 1990s. The grasslands are spread over the dry desert-steppe area in the northeast (which forms a part of the Inner Mongolian steppe region), and the hilly pastures located on the semi-arid Loess Plateau in the south. It is ascertained that the grasslands of Ningxia have been degraded to various degrees. Scientists debate the extent to which this degradation occurs over space and time. Historical research has also found limited evidence of expanding grassland degradation and desertification in Ningxia. A major component of land management in Ningxia is a ban on open grazing, which has been in place since 2003. The ecological and socio-economic effects of this Grazing Ban in relation to the grasslands and pastoralists' livelihood are contested. The ban stipulates that animal husbandry be limited to enclosed pens and no open grazing be permitted in certain time periods set by the Autonomous Region's People's Government.
== Health effects == There is inconclusive clinical data whether specific vitamin K2 supplementation confers any beneficial effects compared to vitamin K1 which is the most common form in supplements. In vitro studies show certain cellular effects of vitamin K2 in bone which are not observed with the K1 variant (including bone marrow stem cell (BMSC) proliferation, and stimulation of osteoblast differentiation). The effects of vitamin K2 appear to be accentuated when combined with vitamin D and in the setting of osteoporosis.
Sources: en.wikipedia.org
=== Emotional changes === A 2017 population-based, matched-cohort study of 93,197 men aged 66 years and older with BPH found that finasteride and dutasteride were associated with a significantly increased risk of depression (HRTooltip Hazard ratio, 1.94; 95% CITooltip Confidence interval, 1.73–2.16) and self-harm (HR, 1.88; 95% CI, 1.34–2.64) during the first 18 months of treatment, but were not associated with an increased risk of suicide (HR, 0.88; 95% CI, 0.53–1.45). After the initial 18 months of therapy, the risk of self-harm was no longer heightened, whereas the elevation in risk of depression lessened but remained marginally increased (HR, 1.22; 95% CI, 1.08–1.37). The absolute increase in the rate of depression was 247 per 100,000 patient-years and of self-harm was 17 per 100,000 patient-years. As such, on the basis of these findings, it has been stated that cases of depression in patients that are attributable to 5-ARIs will be encountered on occasion, while cases of self-harm attributable to 5-ARIs will be encountered very rarely. There were no differences in the rates of depression, self-harm, and suicide between finasteride and dutasteride, suggesting that the specific 5-ARI used does not influence the risks. The absolute risks of self-harm and depression with 5-ARIs remain low (0.14% and 2.0%, respectively).
Compared to the standard suicide-rate for women of the general populace, the suicide-rate for women with augmented breasts remained constant until 10-years post-implantation, yet, it increased to 4.5 times greater at the 11-year mark, and so remained until the 19-year mark, when it increased to 6 times greater at 20-years post-implantation. Moreover, additional to the suicide-risk, women with breast implants also faced a trebled death-risk from alcoholism and the abuse of prescription and recreational drugs. Although seven studies have statistically connected a woman's breast augmentation to a greater suicide-rate, the research indicates that breast augmentation surgery does not increase the death rate; and that, in the first instance, it is the psychopathologically-inclined woman who is more likely to undergo a breast augmentation procedure. The study Effect of Breast Augmentation Mammoplasty on Self-Esteem and Sexuality: A Quantitative Analysis (2007), reported that the women attributed their improved self image, self-esteem, and increased, satisfactory sexual functioning to having undergone breast augmentation; the cohort, aged 21–57 years, averaged post-operative self-esteem increases that ranged from 20.7 to 24.9 points on the 30-point Rosenberg self-esteem scale, which data supported the 78.6 per cent increase in the woman's libido, relative to her pre-operative level of libido.
, to determine various relationships between transmittance and concentration, and absorbance and concentration. Because a spectrophotometer measures the wavelength of a compound through its color, a dye-binding substance can be added so that it can undergo a color change and be measured. It is possible to know the concentrations of a two-component mixture using the absorption spectra of the standard solutions of each component. To do this, it is necessary to know the extinction coefficient of this mixture at two wavelengths and the extinction coefficients of solutions that contain the known weights of the two components. In addition to the traditional Beer-Lamberts law model, cuvette based label free spectroscopy can be used, which add an optical filter in the pathways of the light, enabling the spectrophotometer to quantify concentration, size and refractive index of samples following the hands law. Spectrophotometers have been developed and improved over decades and have been widely used among chemists. Additionally, spectrophotometers are specialized to measure either UV or Visible light wavelength absorbance values. It is considered to be a highly accurate instrument that is also very sensitive and therefore extremely precise, especially in determining color change. This method is also convenient for use in laboratory experiments because it is an inexpensive and relatively simple process.
=== Electric energy === Auditory brainstem implant Cranial electrotherapy stimulation Deep brain stimulation Electrical brain stimulation Electroanalgesia Electroconvulsive therapy (ECT) Functional electrical stimulation (FES) Hypoglossal nerve stimulation Neurofeedback Microcurrent electrical neuromuscular stimulator Occipital nerve stimulation (ONS) Percutaneous tibial nerve stimulation (PTNS) Peripheral nerve stimulation Sacral nerve stimulation (SNS) / sacral neuromodulation (SNM) Transcranial direct current stimulation (tDCS) Transcranial alternating current stimulation (tACS) Transcranial pulsed current stimulation (tPCS) Transcranial random noise stimulation (tRNS) Transcutaneous electrical nerve stimulation (TENS) Vagus nerve stimulation
Sources: en.wikipedia.org
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.
Lyophilized powder is normally stored desiccated at -20 °C, protected from light and moisture. Powder kept under these conditions is generally stable for long periods. Solutions are less stable and are usually prepared immediately before use.
A purity value from one chromatographic method does not capture every possible impurity. Related peptides with similar retention behavior, counterions, and residual solvents may not appear in the same analysis. Independent testing with an orthogonal method provides stronger assurance of identity and content.
Dry powder is best kept sealed, protected from light, and held at minus 20 degrees Celsius or below. Desiccant packaging helps limit moisture uptake because the material is hygroscopic. A sealed vial should be allowed to equilibrate to room temperature before opening to reduce condensation.