If you have been reading about reversed-phase HPLC 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.
Last reviewed on 2026-02-27. Where a claim depends on a specific study, the study is described rather than over-claimed.
Once dissolved, the peptide is considerably less stable than the solid. Aqueous solutions are usually prepared at neutral to slightly acidic pH, filtered, and divided into single-use aliquots before freezing. Repeated freeze-thaw cycles are a common cause of avoidable loss and are best prevented by never refreezing a thawed aliquot. Adsorption to plastic and glass surfaces can lower the measured concentration of dilute solutions, particularly below roughly 0.1 mg/mL. Buffer choice, salt content, and container material all influence how much peptide remains detectable after storage.
Identity and purity are established with standard peptide methods. Reversed-phase HPLC with ultraviolet detection near 214 nm resolves the parent peak from deletion and truncation byproducts, and reports typically quote a main-peak percentage. Mass spectrometry by electrospray or MALDI-TOF confirms the expected molecular mass, while amino acid analysis or peptide mapping can verify composition when the sequence itself is in question. A certificate of analysis that pairs a chromatogram with a mass spectrum is more informative than a purity figure alone. Counter-ion content and residual solvents are separate specifications and are frequently omitted.
Semax is normally supplied as a lyophilized powder, and that form is the most stable. Suppliers commonly recommend storage at -20 °C in a desiccated container protected from light, with short-term handling at room temperature limited to weighing and transfer. Powder that has absorbed moisture degrades faster, so vials should be warmed to ambient temperature before opening to prevent condensation on the contents. Hygroscopic behavior is typical of short hydrophilic peptides, and humidity control matters more than temperature alone for long-term retention.
Solid material is normally kept at minus 20 degrees Celsius in a sealed, desiccated container. Reconstituted solutions are less stable and are usually divided into single-use aliquots before freezing. Repeated freeze-thaw cycles are avoided because they promote aggregation and loss of activity. Light exposure is minimized by using amber glassware or foil wrapping. Published stability data for this peptide are sparse, so recommended storage conditions rest mainly on general practice for short synthetic peptides rather than on dedicated study.
Identity and purity are commonly assessed by reversed-phase high-performance liquid chromatography, with ultraviolet detection near 214 nanometers for the peptide backbone. Mass spectrometry, either electrospray or matrix-assisted laser desorption, confirms molecular mass and detects truncation or modification products. Amino acid analysis can verify composition. Because the sequence contains no strongly absorbing aromatic residue apart from phenylalanine, detection wavelengths are chosen carefully. Purity values above 95 percent are typical for research-grade material.
| Property | Value | Notes |
|---|---|---|
| Solid storage temperature | -20 °C or below | Desiccated and protected from light |
| Solution storage temperature | -80 °C as single-use aliquots | Avoid repeated freeze-thaw cycles |
| Purity assessment method | RP-HPLC, around 214 nm | Reported as main-peak area percent |
| Identity confirmation method | ESI-MS or MALDI-TOF | Measured mass compared with calculated mass |
| Common synonyms | ACTH(4-10) analog; Met-Glu-His-Phe-Pro-Gly-Pro | Also written as Semaxum in some sources |
稳定性主要由水解与氧化两条路径支配。肽键在中性或弱酸性条件下相对稳定，遇到强碱或长时间高温则明显断裂；甲硫氨酸侧链容易被氧化成亚砜，使主峰前移并拉低实际含量。金属离子、光照和反复冻融会进一步促进降解或聚集。冻干粉在低温避光条件下可存放较长时间，配制后的水溶液通常需要冷藏并尽快用完。
纯度评估以反相高效液相色谱为主，通过主峰面积百分比给出粗略结果，再配合电喷雾质谱核对分子量。氨基酸分析可验证组成比例，手性色谱或毛细管电泳用于检查残基构型。常见杂质包括缺失序列的短肽、氧化产物与二聚体。由于多数市售品不附带完整检验报告，独立第三方检测常被用来核实标称值。
从分子层面看，Semax 是线性七肽，没有二硫键、糖基或脂链修饰，N 端为游离氨基，C 端为游离羧基。分子含组氨酸与谷氨酸侧链，因此在水和甲醇等极性溶剂中溶解良好，在非极性溶剂中溶解有限。计算分子量约为 814 Da，与其质子化离子的质荷比吻合，可用于质谱确认。
== Texture and taste == Over 33,000 species of fish and many more marine invertebrate species have been identified. Bromophenols, which are produced by marine algae, give marine animals an odor and taste that is absent from freshwater fish and invertebrates. Also, a chemical substance called dimethylsulfoniopropionate (DMSP) that is found in red and green algae is transferred into animals in the marine food chain. When broken down, dimethyl sulfide (DMS) is produced, and is often released during food preparation when fresh fish and shellfish are heated. In small quantities it creates a specific smell one associates with the ocean, but in larger quantities gives the impression of rotten seaweed and old fish. Another molecule known as TMAO occurs in fishes and gives them a distinct smell. It also exists in freshwater species, but becomes more numerous in the cells of an animal the deeper it lives, so fish from the deeper parts of the ocean have a stronger taste than species that live in shallow water. Eggs from seaweed contain sex pheromones called dictyopterenes, which are meant to attract the sperm. These pheromones are also found in edible seaweeds, which contributes to their aroma.
=== Food fraud === In the United States, from 2008 to 2012, some people reported a bitter metallic taste ("pine mouth") that sometimes lasted for weeks after they ate pine nuts. After an international investigation, the FDA found that some manufacturers substituted a non-food species of pine nuts in place of more expensive edible pine nut species as a form of food fraud.
=== Molecular mechanism === At the molecular level, a cell senses insulin through insulin receptors, with the signal propagating through the insulin signal transduction pathway. Recent studies suggested that the pathway may operate as a bistable switch under physiologic conditions for certain types of cells, and insulin response may well be a threshold phenomenon. The pathway's sensitivity to insulin may be blunted by many factors such as lipolysis of free fatty acids, causing insulin resistance. From a broader perspective, however, sensitivity tuning (including sensitivity reduction) is a common practice for an organism to adapt to the changing environment or metabolic conditions. Pregnancy, for example, entails significant metabolic changes, during which the mother must decrease the insulin sensitivity of her muscles to conserve more glucose for both the maternal and fetal brains. This adaptation can occur by elevating the response threshold, thereby delaying the onset of sensitivity. This is achieved through the secretion of placental growth factor, which interferes with the interaction between insulin receptor substrate (IRS) and PI3K. This concept forms the basis of the adjustable threshold hypothesis of insulin resistance. Insulin resistance has been proposed to be a reaction to excess nutrition by superoxide dismutase in cell mitochondria that acts as an antioxidant defense mechanism. This link seems to exist under diverse causes of insulin resistance.
Sources: en.wikipedia.org
Langlykke who visited the Argentine lab once a year. In 1960, he offered Ondetti a job to work in the New Jersey laboratory. Within two days, Ondetti decided to take the job in New Jersey for $7800 a year.
It can be used as a catalyst for sodium production for the amateur chemist via the alcohol catalysed magnesium reduction process. Menthol is potentially ergogenic (performance enhancing) for athletic performance in hot environments
=== Silica aerogel === Silica aerogels are the most common type of aerogel, and the primary type in use or study. It is silica-based and can be derived from silica gel or by a modified Stöber process. Nicknames include frozen smoke, solid smoke, solid air, solid cloud, and blue smoke, owing to its translucent nature and the way light scatters in the material. The lowest-density silica nanofoam weighs 1,000 g/m3, which is the evacuated version of the record-aerogel of 1,900 g/m3. The density of air is 1,200 g/m3 (at 20 °C and 1 atm). The silica solidifies into three-dimensional, intertwined clusters that make up only 3% of the volume. Conduction through the solid is therefore very low. The remaining 97% of the volume is composed of air in extremely small nanopores. The air has little room to move, inhibiting both convection and gas-phase conduction. Silica aerogel also has a high optical transmission of ~99% and a low refractive index of ~1.05. It is very robust with respect to high power input beam in continuous wave regime and does not show any boiling or melting phenomena. This property permits to study high intensity nonlinear waves in the presence of disorder in regimes typically unaccessible by liquid materials, making it promising material for nonlinear optics. This aerogel has remarkable thermal insulative properties, although its thermal conductivity depends on formulation, density, pressure and measurement method.
NADH is rarely used for synthetic processes, the notable exception being gluconeogenesis. During fatty acid and cholesterol synthesis the reducing agent is NADPH. This difference exemplifies a general principle that NADPH is consumed during biosynthetic reactions, whereas NADH is generated in energy-yielding reactions. The source of the NADPH is two-fold. When malate is oxidatively decarboxylated by "NADP+-linked malic enzyme" pyruvate, CO2 and NADPH are formed. NADPH is also formed by the pentose phosphate pathway which converts glucose into ribose, which can be used in synthesis of nucleotides and nucleic acids, or it can be catabolized to pyruvate.
Sources: en.wikipedia.org
Hird's lawyer, Steven Amendola, asserted that the AFL withdrew all charges against Hird under the deeds of settlement that he and the club signed with the AFL. At the time of the media report, Hird was considering legal action against both the AFL and Demetriou. Essendon chairman Paul Little said that Hird would be wanted as the senior coach once his suspension was served and that he had been offered a two-year extension from 2015, which would have seen him coaching until the end of the 2016 season. However, Hird resigned after round 20 in August 2015, near the end of the season, with the team near the bottom of the ladder.
=== Research findings === 'The risk of MRONJ after dental extraction was significantly higher in patients treated with ARD (antiresorptive drugs) for oncological reasons (3.2%) than in those treated with ARD for OP (osteoporosis) (0.15%) (p < 0.0001). Dental extraction performed with adjusted extraction protocols decreased MRONJ development significantly. Potential risk indicators such as concomitant medications and pre-existing osteomyelitis were identified.'
=== Preservation === Examples of many styles of refrigerators and ice cars can be found at railroad museums around the world. The Western Pacific Railroad Museum at Portola, California features a very complete roster of 20th-century cars, including wood-bodied ice cars, steel-bodied ice cars, one of the earliest mechanical refrigerator cars, later mechanical refrigerator cars, and a cryogenic reefer, as well as several "insulated" boxcars also used for food transport.
=== Hydrothermal self-assembly === Graphene has been prepared by using a sugar like glucose, fructose, etc. This substrate-free "bottom-up" synthesis is safer, simpler and more environmentally friendly than exfoliation. The method can control the thickness, ranging from monolayer to multilayer, which is known as the "Tang-Lau Method".
=== Angiogenesis as a therapeutic target === Angiogenesis may be a target for combating diseases such as heart disease characterized by either poor vascularisation or abnormal vasculature. Application of specific compounds that may inhibit or induce the creation of new blood vessels in the body may help combat such diseases. The presence of blood vessels where there should be none may affect the mechanical properties of a tissue, increasing the likelihood of failure. The absence of blood vessels in a repairing or otherwise metabolically active tissue may inhibit repair or other essential functions. Several diseases, such as ischemic chronic wounds, are the result of failure or insufficient blood vessel formation and may be treated by a local expansion of blood vessels, thus bringing new nutrients to the site, facilitating repair. Other diseases, such as age-related macular degeneration, may be created by a local expansion of blood vessels, interfering with normal physiological processes. The modern clinical application of the principle of angiogenesis can be divided into two main areas: anti-angiogenic therapies, which angiogenic research began with, and pro-angiogenic therapies. Whereas anti-angiogenic therapies are being employed to fight cancer and malignancies, which require an abundance of oxygen and nutrients to proliferate, pro-angiogenic therapies are being explored as options to treat cardiovascular diseases, the number one cause of death in the Western world.
Sources: en.wikipedia.org
Each freeze-thaw cycle can degrade a fraction of the peptide and promote aggregation. Dividing a stock solution into single-use volumes removes repeated cycling as a variable. It also limits the time a thawed solution spends at room temperature.
A high main-peak percentage says little about identity, counter-ion content, or residual solvents. It also does not distinguish an isomer or a closely eluting analog. Mass confirmation and the accompanying documentation cover those gaps.
Salt form changes mass, solubility, and hygroscopicity, and acetate and trifluoroacetate salts behave differently in solution. Storage guidance still centers on -20 °C for powder and lower temperatures for solutions. The certificate should state which salt is present.
Solid peptide is best kept frozen at about minus 20 degrees Celsius in a sealed container with desiccant. It should be allowed to reach room temperature before opening to prevent condensation. Repeated warming and cooling of the same vial is discouraged.