The short version of RP-HPLC fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-04-20. Anything still debated is marked as such rather than presented as settled.
Published research has focused mainly on neurological and cognitive endpoints in animal models, with proposed mechanisms involving brain-derived neurotrophic factor and related signalling pathways. A substantial share of the human data originates from a limited number of research groups, and independent replication in other countries remains sparse. Regulatory status reflects that distribution: the peptide is registered as a medicine in Russia and appears in some neighbouring markets, while elsewhere it is handled as a research chemical without approved therapeutic labelling. Questions about dose-response relationships, long-term effects, and comparability across studies are still open.
Lyophilised powder is normally kept at -20 °C in a desiccated container, with some suppliers recommending -80 °C for long-term archival storage. Repeated freeze-thaw cycles are the most common cause of avoidable loss, so aliquoting before freezing reduces variability between working sessions. Dissolved peptide is far less stable than the dry solid and is usually prepared fresh or held briefly at 4 °C. Aqueous solutions support both hydrolysis of the backbone and oxidation of the N-terminal methionine, and these two routes dominate degradation under ordinary laboratory conditions.
Identity and purity are confirmed with reversed-phase high-performance liquid chromatography, typically monitored at 214 nanometres where the peptide bond absorbs. Mass spectrometry, either electrospray or MALDI-TOF, verifies molecular mass against the theoretical value and detects truncation or adduct formation. Amino acid analysis and peptide mapping provide additional confirmation when required. The most frequently reported impurities are deletion sequences from incomplete coupling, methionine sulfoxide from oxidation, and dimeric species formed through non-covalent aggregation. Impurity profiles depend strongly on the synthesis and purification route chosen by the producer.
Clinical reports describe use in ischaemic stroke, transient ischaemic attack, optic nerve conditions, and cognitive complaints, but most of these studies are small and were conducted in a single region. Systematic reviews have generally described the evidence base as limited in size and variable in methodological quality. Randomised controlled data suitable for international regulatory assessment are scarce. As a result, major treatment guidelines outside Russia do not include the peptide, and interest in it remains largely research-driven rather than routine clinical.
Semax is a synthetic heptapeptide with the sequence Met-Glu-His-Phe-Pro-Gly-Pro. It is described in the literature as an analogue of the ACTH(4–10) fragment, a short N-terminal portion of adrenocorticotropic hormone that retains some neurotropic activity without the full hormonal effects of the parent peptide. The molecule carries a methionine residue at the N-terminus and two proline residues near the C-terminus, features that shape both its interactions with receptor systems and its chemical stability. The free peptide corresponds to the formula C37H51N9O10S and a molecular mass near 813.9 Da.
| Property | Value | Notes |
|---|---|---|
| Purity assay | RP-HPLC, UV 214 nm | Typical research grade 95 percent or higher |
| Mass confirmation | ESI-MS or MALDI-TOF | Compared with theoretical value |
| Main degradation route | Methionine oxidation | Sulfoxide formation in solution |
| Powder storage | -20 °C, desiccated | Amber vial, minimal headspace |
| Working solution | Sterile water or saline | Prepare fresh; avoid repeated thawing |
Dissolution is normally performed in water, phosphate-buffered saline, or normal saline, since the peptide is freely soluble in aqueous media and is rarely handled with strong organic solvents. Solution pH should be kept near neutral, because extreme acidity or alkalinity accelerates backbone hydrolysis and encourages oxidation of the methionine side chain. Once dissolved, the material is less stable than the dry powder and is commonly divided into single-use portions and frozen. Buffers containing primary amines, such as Tris, are often avoided because of possible side reactions.
Purity assessment relies mainly on reversed-phase high-performance liquid chromatography, which separates the target heptapeptide from truncated sequences, deletion analogues, and oxidised forms. Mass spectrometry, usually coupled to liquid chromatography, confirms identity through the expected molecular ion and reveals modifications such as methionine sulfoxide formation. Amino acid analysis can verify composition, and tandem mass spectrometry supports sequence confirmation. Ultraviolet detection near 254 to 280 nanometres is convenient because the phenylalanine and histidine residues absorb in that region. Nuclear magnetic resonance is rarely used for routine release testing.
Common degradation pathways include oxidation of the methionine side chain, hydrolysis of the peptide backbone, and aggregation under unfavourable pH or concentration. Stability studies typically monitor the main peak by chromatography and report total related substances as a percentage. Because no official monograph exists, acceptance criteria vary between laboratories, and reported purity values are not directly comparable across suppliers. Analysts therefore document the method, column, and detection wavelength alongside each result, and open questions remain about how much biological activity the oxidised forms retain.
Regulatory status varies sharply by country. Semax is registered for medical use in Russia, where it appears in formularies as a nasal solution, and it also holds registration in a small number of neighbouring states. It has no approval from the United States Food and Drug Administration or the European Medicines Agency, and it is not a scheduled controlled substance in most jurisdictions. Elsewhere it circulates mainly as laboratory material, so purity documentation comes from suppliers rather than from a national pharmacopoeia.
Semax is a synthetic peptide created in the Soviet Union during the early 1980s by researchers working in Moscow. It was built from the short adrenocorticotropic hormone fragment known as ACTH(4-10), and the chain was then extended with three additional amino acids. The resulting molecule was named semax and entered clinical use in Russia in 1994. It is generally described as a nootropic and neuroprotective agent rather than as a hormone analogue.
The parent fragment ACTH(4-10) carries the sequence Met-Glu-His-Phe-Arg-Trp-Gly. Semax replaces the arginine and tryptophan positions with a proline-glycine-proline tail, giving Met-Glu-His-Phe-Pro-Gly-Pro. That change removes residues associated with adrenal stimulation, so the peptide does not drive cortisol release the way full ACTH does. This distinction shapes how the compound is grouped in the literature, where it sits with neuropeptides and peptide neuromodulators rather than with corticosteroids.
Risk of developing CJD increases with age. CJD incidence was 3.5 cases per million among those over 50 years of age between 1979 and 2017. Approximately 85% of CJD cases are sporadic, and 10–15% of CJD cases are due to inherited mutations of the prion protein gene. CJD deaths and age-adjusted death rate in the United States indicate an increasing trend in the number of deaths between 1979 and 2017. Although not fully understood, additional information suggests that CJD rates in nonwhite groups are lower than in whites. While the mean onset is approximately 67 years of age, cases of sCJD have been reported as young as 17 years and over 80 years of age. Mental capabilities rapidly deteriorate and the average amount of time from onset of symptoms to death is 7 to 9 months. According to a 2020 systematic review on the international epidemiology of CJD:
=== Pharmacodynamics === Methocinnamox is an opioid receptor antagonist, it works at the μ-opioid receptor. By acting as an antagonist, it binds to the receptor but does not activate it, thus blocking the action of agonists such as heroin and fentanyl. It is a pseudo-irreversible non-competitive antagonist of the μ-opioid receptor and a competitive antagonist of the κ- and δ-opioid receptors. Methocinnamox has affinity values for the opioid receptors of 0.6 nM for the μ-opioid receptor, 2.2 nM for the δ-opioid receptor, and 4.9 nM for the κ-opioid receptor. Hence, it has about 3.7-fold preferential affinity for the μ-opioid receptor over the δ-opioid receptor and about 8.2-fold higher affinity for the μ-opioid receptor over the κ-opioid receptor. The antagonism of the μ-opioid receptor by methocinnamox is not irreversible as the drug does not form a covalent bond with the receptor. This is in contrast to prototypical μ-opioid receptor alkylating agents like β-funaltrexamine and β-chlornaltrexamine. However, in spite of its lack of covalent binding to the μ-opioid receptor, methocinnamox appears to not dissociate from the μ-opioid receptor or dissociates from it extremely slowly. Hence, methocinnamox has been described as a pseudo-irreversible antagonist of the μ-opioid receptor or as a "functionally irreversible" antagonist. The mechanism underlying the pseudo-irreversible antagonism of methocinnamox hasn't been fully elucidated.
=== Controversy === In 2015 the UK's House of Commons attempted to get a two to four week limit mandate for prescribing benzodiazepines to replace the two to four week benzodiazepine prescribing guidelines, which are merely recommended.
== Values for common substances == There are multiple techniques to determine the pKa of a chemical, leading to some discrepancies between different sources. Well measured values are typically within 0.1 units of each other. Data presented here were taken at 25 °C in water. More values can be found in the Thermodynamics section, above. A table of pKa of carbon acids, measured in DMSO, can be found on the page on carbanions.
== Signs and symptoms == Arthritis entails inflammation within the joint, and presents as swelling, pain, stiffness and restricted joint movement. Symptoms of JIA vary. This is because JIA has several subtypes, which differ according to the number of affected joints, severity of disease, age of onset, prognosis and presence or absence of inflammation in other parts of the body. The key clinical feature in JIA is persistent swelling of the affected joints. Any joint can be affected, but large joints such as the knee and ankle are most commonly involved. Involvement of small joints of the hands and feet is more likely when many joints are affected ('polyarthritis'). Swollen joints may also feel warmer to touch. Swelling may be difficult to detect clinically, especially for joints such as those of the spine, sacroiliac joints, shoulder, hip, and jaw. Joint pain is an important symptom, although some children experience minimal or no pain with their arthritis. In these children, the first sign of arthritis may be limping, especially in the morning. Swelling and pain usually result in limited movement of the affected joints, for example a knee held bent causing a limp, or being unable to make a full fist. Limited movement may reduce a child's ability to fully participate in activities and undertake usual tasks such as those used for self-care. In some JIA subtypes, more non-specific symptoms of being unwell may be present, such as lethargy, fatigue and poor appetite. Children with systemic JIA usually present with fever and a classic rash and may become quite ill.
Sources: en.wikipedia.org
=== Pit vipers === The Crotalinae, commonly known as pit vipers, crotaline snakes (named for the Ancient Greek: κρόταλον krotalon castanet/rattle of a rattlesnake's tail), or pit adders, are a subfamily of venomous vipers found in Eurasia and the Americas. They are distinguished by the presence of a heat-sensing pit organ located between the eye and the nostril on both sides of the head. Currently, 22 genera and 151 species are recognized: These are also the only viperids found in the Americas. The groups of snakes represented here include rattlesnakes, lanceheads, and Asian pit vipers. The type genus for this subfamily is Crotalus, of which the type species is the timber rattlesnake, C. horridus.
=== First descriptions === In 1797, John Rollo reported on the results of treating two diabetic Army officers with a low-carbohydrate diet and medications. A very low-carbohydrate diet was the standard treatment for diabetes throughout the nineteenth century. In 1825, Jean Brillat-Savarin promoted a low-carb diet in his book, The Physiology of Taste. In 1863, William Banting, a formerly obese English undertaker and coffin maker, published "Letter on Corpulence Addressed to the Public", in which he described a diet for weight control giving up bread, butter, milk, sugar, beer, and potatoes. His booklet was widely read, so much so that some people used the term "Banting" for the activity now called "dieting". Physicians who advocated a low-carbohydrate diet consisting of large amounts of animal fat and protein to treat diabetes in the late 1800s include James Lomax Bardsley, Apollinaire Bouchardat and Frederick William Pavy. Arnaldo Cantani isolated his diabetic patients in locked rooms and prescribed them an exclusive animal-based diet. In the early 1900s Frederick Madison Allen developed a highly restrictive short term regime which was described by Walter R. Steiner at the 1916 annual convention of the Connecticut State Medical Society as The Starvation Treatment of Diabetes Mellitus. This diet was often administered in a hospital in order to better ensure compliance and safety.
When fungal spores germinate, they initially form preliminary associations with common free-living algae in their vicinity. Additionally, the fungus can recruit compatible algal cells from neighboring lichen thalli—essentially extracting these partners—to help establish a complete symbiotic relationship. Native across Europe, parts of Asia, and coastal North Africa, X. parietina has a more limited and primarily coastal distribution in North America and Australia, where genetic evidence suggests human-mediated introduction. In recent decades, it has expanded inland in these regions, particularly in urban environments and areas affected by agricultural runoff, road salt application, and nitrogen deposition. The lichen grows slowly (averaging 2.6 mm (1⁄8 in) per year) but possesses considerable regenerative abilities, with fragments capable of developing into new thalli. It participates in a complex web of ecological interactions, hosting at least 41 species of lichen-dwelling fungi, while certain gastropods and microscopic rotifers contribute to its dispersal by consuming and excreting viable spores. The species has high diversity even within local populations, with distinct patterns linked to both geographic location and substrate type. This genetic variability, combined with the lichen's flexible associations with different photobiont strains, contributes to its ecological success. X. parietina serves as a bioindicator for monitoring air quality due to its capacity to accumulate environmental contaminants.
Pseudoephedrine, sold under the brand name Sudafed among others, is a sympathomimetic medication which is used as a nasal decongestant to treat nasal congestion. It also has many off-label uses, such as treatment of hypotension (low blood pressure). At higher doses, pseudoephedrine acts as a psychostimulant, appetite suppressant, and performance-enhancing drug; as a result, non-medicinal use of pseudoephedrine is common, and it is often considered an abused drug. The medication is administered orally. Side effects of pseudoephedrine include insomnia, elevated heart rate, increase in blood pressure, restlessness, dizziness, anxiety, and dry mouth. Rarely, pseudoephedrine has been associated with serious cardiovascular complications like heart attack and hemorrhagic stroke. Some people are more sensitive to its cardiovascular effects than others. Pseudoephedrine acts as a norepinephrine releasing agent, indirectly activating adrenergic receptors. As such, it is an indirectly acting sympathomimetic. Pseudoephedrine significantly crosses the blood-brain barrier, but has some peripheral selectivity due to its hydrophilicity. Chemically, pseudoephedrine is a substituted amphetamine and is closely related to ephedrine, phenylpropanolamine, and amphetamine. It is the (1S,2S)-enantiomer of β-hydroxy-N-methylamphetamine. Along with ephedrine, pseudoephedrine occurs naturally in ephedra, which has been used for thousands of years in traditional Chinese medicine. It was first isolated from ephedra in 1889.
The word "aptamer" is a neologism coined by Andrew D. Ellington and Jack Szostak in their first publication on the topic. They did not provide a precise definition, stating "We have termed these individual RNA sequences 'aptamers', from the Latin aptus, to fit." The word itself, however, derives from the Greek word ἅπτω, to connect or fit (as used by Homer (c. 8th century BC)) and μέρος, a component of something larger. A typical aptamer is a synthetically generated ligand exploiting the combinatorial diversity of DNA, RNA, XNA, or peptide to achieve strong, specific binding for a particular target molecule or family of target molecules. Aptamers are occasionally classified as "chemical antibodies" or "antibody mimics". However, most aptamers are small, with a molecular weight of 6-30 kDa, in contrast to the 150 kDa size of antibodies, and contain one binding site rather than the two matching antigen binding regions of a typical antibody.
Sources: en.wikipedia.org
Reversed-phase HPLC gives the main purity figure, most often with UV detection near 214 nanometres. Mass spectrometry then confirms the molecular mass. Together the two methods distinguish a correct sequence from a closely related impurity.
The main chemical risks are methionine oxidation and backbone hydrolysis in solution. Moisture and repeated temperature cycling accelerate both processes. Dry powder held cold and desiccated is considerably more stable than any reconstituted preparation.
It holds a medicine registration in Russia, where it has been used clinically for decades. In most other countries it is treated as a research chemical. That split explains the uneven distribution of clinical literature.
It is described as a synthetic analogue of the ACTH(4–10) fragment, a short segment of adrenocorticotropic hormone. Its sequence differs from that fragment and includes two proline residues, which influence stability and behaviour in solution.