反相色谱 raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2025-10-01. Anything still debated is marked as such rather than presented as settled.
常规纯度与身份确认依赖反相高效液相色谱，并辅以质谱测定分子量。氨基酸组成分析可用于验证序列构成，肽图分析则能进一步定位修饰或降解产物。杂质谱通常关注缺失序列肽、截短片段和氧化产物。不同方法的检出限并不相同，因此各实验室报告的纯度数值不宜直接横向比较。
多数实验室与市售的 Semax 以冻干粉形式提供。冻干粉通常建议保存在 -20 °C 或更低温度下，同时避免光照与反复升温。短期运输有时采用冷藏条件，但长期保存仍以冷冻为主。分包操作应尽量减少开盖次数，以降低吸湿和微生物污染的风险。开封后若未一次用完，建议在干燥环境中密封并尽快放回低温储存。
溶液状态的稳定性明显低于冻干粉。肽类在水溶液中可能经历水解、氧化与聚集，其中甲硫氨酸和天冬酰胺等残基常是敏感位点。Semax 含有甲硫氨酸，因此氧化风险相对突出。工作液一般主张现配现用，或冷藏并在数日内用尽。缓冲液种类、pH 和离子强度都会影响降解速率，而关于最佳条件的公开数据并不统一。
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.
Solid semax is typically supplied as a lyophilised powder that is hygroscopic and sensitive to moisture, light, and repeated temperature cycling. Long-term storage of the dry peptide is generally recommended at approximately -20 degrees Celsius, while shorter working periods may use refrigeration at 2 to 8 degrees Celsius. Vials should remain tightly closed and desiccated when brought to room temperature, because condensation can damage the material before it is weighed. Dividing a batch into aliquots is preferable to thawing one container repeatedly.
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.
| Property | Value | Notes |
|---|---|---|
| 外观 | 白色至类白色粉末 | 常见于冻干制剂 |
| 溶解度 | 易溶于水 | 在极性溶剂中一般也可溶 |
| 建议储存温度 | -20 °C | 冻干粉，避光密封 |
| 常见分析手段 | 反相高效液相色谱 | 常与质谱联用 |
| 主要降解路径 | 水解与氧化 | 溶液状态更显著 |
Semax binds to melanocortin receptors and is thought to influence neuronal survival and plasticity rather than to act through the adrenal axis. Laboratory work has shown increased expression of brain-derived neurotrophic factor and nerve growth factor in treated tissue. Changes in c-Fos, a marker of neuronal activation, have also been reported. Because the peptide is rapidly degraded by peptidases, its effects are generally attributed to downstream signaling cascades rather than to sustained receptor occupancy.
Published studies are dominated by animal models of stroke, ischemia, and cognitive impairment, with a smaller number of human trials conducted in Russia. Many of the human reports are small, single-center, and published in Russian-language journals, which limits independent scrutiny. Outcome measures vary between studies and often rely on clinician-rated scales rather than objective biomarkers. Systematic reviews have noted the methodological weaknesses and called for larger, preregistered trials before firm conclusions can be drawn.
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。
=== Nominal mass === The nominal mass for an element is the mass number of its most abundant naturally occurring stable isotope, and for an ion or molecule, the nominal mass is the sum of the nominal masses of the constituent atoms. Isotope abundances are tabulated by IUPAC: for example carbon has two stable isotopes 12C at 98.9% natural abundance and 13C at 1.1% natural abundance, thus the nominal mass of carbon is 12. The nominal mass is not always the lowest mass number, for example iron has isotopes 54Fe, 56Fe, 57Fe, and 58Fe with abundances 6%, 92%, 2%, and 0.3%, respectively, and a nominal mass of 56 Da. For a molecule, the nominal mass is obtained by summing the nominal masses of the constituent elements, for example water has two hydrogen atoms with nominal mass 1 Da and one oxygen atom with nominal mass 16 Da, therefore the nominal mass of H2O is 18 Da. In mass spectrometry, the difference between the nominal mass and the monoisotopic mass is the mass defect (see § mass defect. This differs from the definition of mass defect used in physics which is the difference between the mass of a composite particle and the sum of the masses of its constituent parts.
In addition, endogenous progesterone levels naturally increase to extremely high concentrations during pregnancy, yet genital defects do not occur. In accordance, while total concentrations of progesterone in pregnant women at term are around 150 ng/mL (~500 nM), free or unbound and hence bioactive concentrations of progesterone are only about 3 ng/mL (~10 nM) due to the high plasma protein binding of progesterone, and these concentrations are still well below the aforementioned IC50 values for inhibition of 5α-reductase types 1 and 2. As with endogenous progesterone during pregnancy, exogenous supplemental progesterone during pregnancy has been found not to increase the risk of hypospadias in male infants. Although systemic progesterone does not appear to be an effective 5α-reductase inhibitor, topical progesterone may produce potent inhibition of 5α-reductase in the skin due to the very high local concentrations that occur. A study found that topical progesterone applied to the pubic area in men inhibited 5α-reductase in the skin in this region by 75%. In addition to inhibition of 5α-reductase, progesterone is metabolized by 5α-reductase into 5α-dihydroprogesterone (5α-DHP), a compound reported to have some antagonistic activity at the AR. However, this compound appears to have no systemic antiandrogenic activity. In spite of its apparent 5α-reductase inhibition, the effectiveness of topical progesterone in the treatment of pattern hair loss has been poor.
=== June === June 1 A firefighter is killed and another injured in a shooting at a Los Angeles County Fire Department station in Santa Clarita. A special election is held in New Mexico to fill a vacancy in its 1st congressional district left by Deb Haaland when she resigned to become President Biden's Secretary of the Interior. Democrat Melanie Stansbury wins with 79,837 of the 132,262 votes cast (60.36%). COVID-19 pandemic SARS-CoV-2 Delta variant becomes the dominant strain of COVID-19 in the United States. COVID-19 vaccines – Moderna seeks full approval from the FDA for the Moderna COVID-19 vaccine. Michigan lifts several face mask requirements at outdoor gatherings and loosens them at indoor gatherings and businesses. Fully vaccinated people are allowed to not wear masks in public, but unvaccinated and partially vaccinated people are still required to do so. June 2 – Paul Allard Hodgkins, a Tampa man who was seen in the U.S. Senate chamber during the January 6 riot at the United States Capitol, pleads guilty, making him the second suspect to do so after Jon Schaffer. June 3 – The FBI announces that it has opened an investigation into Postmaster General Louis DeJoy over campaign fundraising. June 4 Facebook's Oversight Board announces its ban on former President Donald Trump's personal account will last until January 2023. Trump was originally banned for posting a message supporting the January 6 insurrectionists.
Reversed-phase HPLC (RP-HPLC) is the most widespread mode of chromatography. It has a non-polar stationary phase and an aqueous, moderately polar mobile phase. RP-HPLC is so commonly used among the biologists and life science users, that it is often referred to as simply "HPLC". The pharmaceutical industry also regularly employs RP-HPLC to qualify drugs before their release. In the reversed phase methods, the substances are retained in the system the more hydrophobic they are. For the retention of organic materials, the stationary phases, are consisted mainly of porous granules of silica gel packed in the column. In shape, they are usually spheres of varying diameters (sub-2, 3, 5, 7, 10 μm), varying pore diameters (60, 100, 150, 300 Å). On their surface are chemically bonded straight chain alkyl ligands, such as C3, C4, C8, C18. The number counts the carbon atoms in a ligand. For example, a C3 ligand is a propyl. The longer the hydrocarbon ligand on the stationary phase, the longer the sample components can be retained. Most of the current methods of separation of biomedical materials use C18 stationary phase, sometimes called by a trade names such as ODS (octadecylsilane) or RP-18 (Reversed Phase 18). To make such stationary phases, one treat the surface of silica gel particles with RMe2SiCl, where R is a straight chain alkyl group such as C18H37 or C8H17. To separate aromatic compounds, or in general compounds with many pi bonds, the stationary phase can have phenyl surface ligands. At pH < 2, the bond between the ligand and the silica gel may dissolve.
Sources: en.wikipedia.org
== Recognition == In August 2024, Dei BioPharma was awarded "Best Pharma Company" at the African Excellence Awards hosted by MEA Markets in London. Members of the Ugandan Parliament commended the company for pioneering drug development in underrepresented areas such as oncology and vaccine production.
=== In apple === Present in the chloroplasts and mitochondria of all parts of an apple, PPO is the major enzyme responsible for enzymatic browning of apples. Due to an increase in consumer demand for pre-prepared fruits and vegetables, a solution for enzymatic browning has been a targeted area of research and new product development. As an example, pre-sliced apples are an appealing consumer product, but slicing apples induces PPO activity, leading to browning of the cut surfaces and lowering their esthetic quality. Browning also occurs in apple juices and purees when poorly handled or processed. Arctic apples, an example of genetically modified fruit engineered to reduce PPO activity, are a suite of trademarked apples that contain a non-browning trait derived by gene silencing to suppress the expression of PPO, thus inhibiting fruit browning.
=== Definition by Waterlow === In the 1970s, John Conrad Waterlow established a new classification system for malnutrition. Instead of using just weight for age measurements, Waterlow's system combines weight-for-height (indicating acute episodes of malnutrition) with height-for-age to show the stunting that results from chronic malnutrition. One advantage of the Waterlow classification is that weight for height can be calculated even if a child's age is unknown.
Sources: en.wikipedia.org
=== Among snakes === The question whether individual snakes are immune to their own venom has not yet been definitively settled, though an example is known of a cobra that self-envenomated, resulting in a large abscess requiring surgical intervention, but showing none of the other effects that would have proven rapidly lethal in prey species or humans. Furthermore, certain harmless species, such as the North American common kingsnake (Lampropeltis getula) and the Central and South American mussurana (Clelia spp.), are proof against the venom of the crotalines, which frequent the same districts, and which they are able to overpower and feed upon. The chicken snake (Spilotes pullatus) is the enemy of the fer-de-lance (Bothrops caribbaeus) in St. Lucia, and in their encounters, the chicken snake is invariably the victor. Repeated experiments have shown the European grass snake (Natrix natrix) not to be affected by the bite of the European adder (Vipera berus) and the European asp (Vipera aspis), this being due to the presence, in the blood of the harmless snake, of toxic principles secreted by the parotid and labial glands, and analogous to those of the venom of these vipers. Several North American species of rat snakes, as well as king snakes, have proven to be immune or highly resistant to the venom of rattlesnake species. The king cobra, which does prey on cobras, is said to be immune to their venom.
Dyson, along with 33 other Essendon players, was found guilty of using a banned performance-enhancing substance, thymosin beta-4, as part of Essendon's sports supplements program during the 2012 season. He and his team-mates were initially found not guilty in March 2015 by the AFL Anti-Doping Tribunal, but a guilty verdict was returned in January 2016 after an appeal by the World Anti-Doping Agency. He was suspended for two years which, with backdating, ended in November 2016; as a result, he served approximately fourteen months of his suspension and missed the entire 2016 suburban football season.
==== Australia ==== In Australia, LSD is classified as a Schedule 9 prohibited substance under the Poisons Standard (February 2017), indicating it may be abused or misused and its manufacture, possession, sale, or use should be prohibited except for approved research purposes. In Western Australia, the Misuse of Drugs Act 1981 provides guidelines for possession and trafficking of substances like LSD.
Small molecule inhibitors have been reported for both OGT and OGA that function in cells or in vivo. OGT inhibitors result in a global decrease of O-GlcNAc while OGA inhibitors result in a global increase of O-GlcNAc; these inhibitors are not able to modulate O-GlcNAc on specific proteins. Inhibition of the hexosamine biosynthetic pathway is also able to decrease O-GlcNAc levels. For instance, glutamine analogues azaserine and 6-diazo-5-oxo-L-norleucine (DON) can inhibit GFAT, though these molecules may also non-specifically affect other pathways.
Sources: en.wikipedia.org
一般不建议常温长期保存。多数说明指向 -20 °C 冷冻避光。常温运输通常被视为短期可接受，但会加快降解风险。
公开资料对此没有统一答案。普遍建议现配现用，或冷藏并在数日内用完。含甲硫氨酸的序列更易氧化，放置时间越长风险越高。
反相高效液相色谱是最常用的手段，配合质谱确认分子量。氨基酸组成分析和肽图分析可补充序列层面的验证。
Dry powder is usually kept at about -20 degrees Celsius for long-term storage and at 2 to 8 degrees Celsius for short working periods. Containers should stay sealed and protected from light and moisture to limit degradation.