A practical reference on mass spectrometry: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-04-02. Anything still debated is marked as such rather than presented as settled.
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。
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。
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.
Quality documentation for research-grade peptide usually includes a certificate of analysis stating purity, identity, and residual counterion content. Batch-to-batch variation in purity and salt form is a recognized issue, and comparisons across suppliers require attention to the exact counterion, for example acetate versus trifluoroacetate. Sequence verification by tandem mass spectrometry provides stronger evidence than a single mass measurement. For any study reporting biological results, the analytical method and the measured purity should be stated explicitly. Independent verification of supplier claims is considered good practice.
| Property | Value | Notes |
|---|---|---|
| 分子式 | C37H51N9O10S | 游离碱形式 |
| 等电点 | 约 6.5 | 估算值，随缓冲体系变化 |
| 主要降解途径 | 水解与氧化 | 侧链氧化最为常见 |
| 溶液储存 | 2 至 8 摄氏度避光 | 避免反复冻融 |
| 常规分析手段 | 反相色谱与质谱联用 | 氨基酸分析辅助核对 |
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.
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.
In the process of treating epilepsy, Wilder Penfield produced maps of the location of various functions (motor, sensory, memory, vision) in the brain. He summarized his findings in a 1950 book called The Cerebral Cortex of Man. Wilder Penfield and his co-investigators Edwin Boldrey and Theodore Rasmussen are considered to be the originators of the cortical homunculus. The understanding of neurons and of nervous system function became increasingly precise and molecular during the 20th century. For example, in 1952, Alan Lloyd Hodgkin and Andrew Huxley presented a mathematical model for the transmission of electrical signals in neurons of the giant axon of a squid, which they called "action potentials", and how they are initiated and propagated, known as the Hodgkin–Huxley model. In 1961–1962, Richard FitzHugh and J. Nagumo simplified Hodgkin–Huxley, in what is called the FitzHugh–Nagumo model. In 1962, Bernard Katz modeled neurotransmission across the space between neurons known as synapses. Beginning in 1966, Eric Kandel and collaborators examined biochemical changes in neurons associated with learning and memory storage in Aplysia. In 1981 Catherine Morris and Harold Lecar combined these models in the Morris–Lecar model. Such increasingly quantitative work gave rise to numerous biological neuron models and models of neural computation. As a result of the increasing interest about the nervous system, several prominent neuroscience organizations have been formed to provide a forum to all neuroscientists during the 20th century.
== Nuclear processes == A nuclide is considered to "exist" if it has a half-life greater than 2 ×10−14s. This is an arbitrary boundary; shorter half-lives are considered resonances, such as a system undergoing a nuclear reaction. This time scale is characteristic of the strong interaction which creates the nuclear force. Only nuclides are considered to decay and produce radioactivity. Nuclides can be stable or unstable. Unstable nuclides decay, possibly in several steps, until they become stable. There are 251 known stable nuclides. The number of unstable nuclides discovered has grown, with about 3000 known in 2006. The most common and consequently historically the most important forms of natural radioactive decay involve the emission of alpha-particles, beta-particles, and gamma rays. Each of these correspond to a fundamental interaction predominantly responsible for the radioactivity:
When binding to the signaling molecule, the receptor protein changes in some way and starts the process of transduction, which can occur in a single step or as a series of changes in a sequence of different molecules (called a signal transduction pathway). The molecules that compose these pathways are known as relay molecules. The multistep process of the transduction stage is often composed of the activation of proteins by addition or removal of phosphate groups or even the release of other small molecules or ions that can act as messengers. The amplification of a signal is one of the benefits to this multiple step sequence. Other benefits include more opportunities for regulation than simpler systems do and the fine-tuning of the response, in both unicellular and multicellular organisms. In some cases, receptor activation caused by ligand binding to a receptor is directly coupled to the cell's response to the ligand. For example, the neurotransmitter GABA can activate a cell surface receptor that is part of an ion channel. GABA binding to a GABAA receptor on a neuron opens a chloride-selective ion channel that is part of the receptor. GABAA receptor activation allows negatively charged chloride ions to move into the neuron, which inhibits the ability of the neuron to produce action potentials. However, for many cell surface receptors, ligand-receptor interactions are not directly linked to the cell's response.
=== Politics === Though considered a political backwater of the federation for much of the 50s and 60s, the 70s saw the ascension of a strong Bosnian political elite. While working within the communist system, politicians such as Džemal Bijedić, Branko Mikulić and Hamdija Pozderac reinforced and protected the sovereignty of Bosnia and Herzegovina. Their efforts proved key during the turbulent period following Tito's death in 1980, and are today considered some of the early steps towards Bosnian independence. However, the republic hardly escaped the increasingly nationalistic climate of the time unscathed. Following the death of Tito in 1980, rising nationalist ideas primarily noted in Serbian academia, pressured Bosnia to deal with allegations of rising nationalism in their own society. One of the most controversial events that were taken by a Bosnian political leadership was a so-called Sarajevo process in 1983 where, under significant pressure from Serbia's political leadership, Bosnian political elite used their influence to secure convictions for several Bosniak nationalists as a type of a political sacrifice to gain political points in the fight against Serbian nationalists. The Sarajevo process centered on convicting Alija Izetbegović for writing "The Islamic Declaration", a literary work which was in the Yugoslav communist regime considered a radical approach towards socialist ideals of former Yugoslavia that were based on suppression of nationalism and any violation of that doctrine was punishable by law.
Sources: en.wikipedia.org
In line with these studies, Adorno produced an analysis of the Californian radio preacher Martin Luther Thomas. Fascist propaganda of this sort, Adorno wrote, "simply takes people for what they are: genuine children of today's standardized mass culture who have been robbed to a great extent of their autonomy and spontaneity." Adorno wrote that fascist propaganda encourages identification with an authoritarian personality characterized by traits such as obedience and extreme aggression.The result of these labors, the 1950 study The Authoritarian Personality, was pioneering in its combination of quantitative and qualitative methods of collecting and evaluating data as well as its development of the F-scale personality test. After the USA entered the war in 1941, the situation of the émigrés, now classed "enemy aliens", became increasingly restricted. Forbidden from leaving their homes between 8pm and 6am and from going more than five miles from their houses, émigrés like Adorno, who was not naturalized until November 1943, were severely restricted in their movements. In addition to the aphorisms that conclude Dialectic of Enlightenment, Adorno put together a collection of aphorisms in honor of Horkheimer's 50th birthday that was later published as Minima Moralia: Reflections from Damaged Life. These fragmentary writings, inspired by a renewed reading of Nietzsche, treated issues like emigration, totalitarianism, and individuality, as well as everyday matters such as giving presents, dwelling, and the impossibility of love.
The network concept was made up of acu-tracts, such as a line down the arms, where it said acupoints were located. Some of the sites acupuncturists use needles at today still have the same names as those given to them by the Yellow Emperor's Classic. Numerous additional documents were published over the centuries introducing new acupoints. By the 4th century AD, most of the acupuncture sites in use today had been named and identified.
The mevalonate pathway, also known as the isoprenoid pathway or HMG-CoA reductase pathway, is an essential metabolic pathway present in eukaryotes, archaea, and some bacteria. The pathway produces two five-carbon building blocks called isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP), which are used to make isoprenoids, a diverse class of over 30,000 biomolecules such as cholesterol, vitamin K, coenzyme Q10, and all steroid hormones. The mevalonate pathway begins with acetyl-CoA and ends with the production of IPP and DMAPP. It is best known as the target of statins, a class of cholesterol lowering drugs. Statins inhibit HMG-CoA reductase within the mevalonate pathway.
Sources: en.wikipedia.org
=== Historiography === Gordon, LaTisha. "‘The decline of liberalism was inevitable in twentieth-century Britain.’How far do you agree with this statement?." Sussex Undergraduate Politics Journal: 65-71. online simplified survey. Häusermann, Silja, Georg Picot, and Dominik Geering. "Review article: Rethinking party politics and the welfare state–recent advances in the literature". British Journal of Political Science 43#1 (2013): 221–240.online. St. John, Ian. The Historiography of Gladstone and Disraeli (Anthem Press, 2016) 402 pp. excerpt. Thompson, J. A. "The Historians and the Decline of the Liberal Party." Albion 22#1, (1990), pp. 65–83, online.
dopaquinone + cysteine → 5-S-cysteinyldopa → benzothiazine intermediate → pheomelanin dopaquinone + cysteine → 2-S-cysteinyldopa → benzothiazine intermediate → pheomelanin Also, dopaquinone can be converted to leucodopachrome and follow two more pathways to the eumelanins
Due to ZAPU's close relationship with the Soviet Union, ZANU found itself ostracised by the Soviet bloc but soon found a new ally in the People's Republic of China. Its political ideology was somewhat more influenced by the principles of Maoism than ZAPU, and a sympathetic Chinese government soon agreed to furnish weapons and training for ZANU's own war effort. After UDI, ZANU formed its own military wing, the Zimbabwe African National Liberation Army (ZANLA). While ZANLA and ZIPRA both planned for an armed struggle against the Rhodesian government, their respective leadership disagreed on the means of conducting the insurgency. ZIPRA favoured Soviet thinking, placing an emphasis on acquiring sophisticated weaponry in the hopes of winning a conventional battle like the Viet Minh at Dien Bien Phu. ZANLA placed greater emphasis on the politicisation of the local populace in the areas it operated, and favoured a more irregular style of warfare.
Sources: en.wikipedia.org
电喷雾或基质辅助激光解吸电离质谱是常用手段，测得的质子化离子质荷比可换算为分子量。结果与理论值落在合理误差内，才支持结构一致的判断。
甲硫氨酸侧链含硫醚，在氧气、光照或金属离子存在时容易被氧化。氧化产物极性略增，常在色谱图上表现为主峰之前的肩峰或前伸峰。
通常建议冷藏避光，并在较短时间内使用。不存在适用于所有配方的统一期限，具体取决于浓度、缓冲体系与容器材质。
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.