freeze-thaw raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2025-09-06 and is reviewed periodically as new material appears.
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。
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.
Semax is supplied as a lyophilized powder that appears white to off-white. It dissolves readily in water, phosphate-buffered saline, and other aqueous media, which simplifies preparation of working solutions for laboratory use. The nasal products registered in Russia are dilute aqueous solutions, typically around 0.1 percent peptide by weight. Organic solvents are rarely necessary and can complicate handling. Because the peptide is hygroscopic, weighing should be performed quickly and with minimal exposure to ambient humidity.
| 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 |
The mechanisms attributed to semax are inferred from animal and cell studies rather than traced to one confirmed target. The most frequently cited pathway involves increased expression of brain-derived neurotrophic factor and nerve growth factor in hippocampal and cortical tissue. Some work points to engagement of melanocortin receptors, particularly MC4, which the parent ACTH fragment can activate. Effects on dopaminergic and serotonergic signalling have also been reported. No single account explains all observed results, and the relative weight of each pathway remains unsettled.
Published studies examine a fairly narrow set of endpoints. Rodent experiments commonly measure maze learning, infarct volume after induced ischemia, and tissue levels of neurotrophic factors. Clinical reports from Russian centres describe attention, memory and recovery scores in patients after stroke or transient ischemic attack. Most of those human studies are small and few have been repeated by independent groups. Outcome measures differ between studies, which limits direct comparison.
Circulation time for the peptide is short because peptidases cleave it readily. The Pro-Gly-Pro tail is thought to slow breakdown compared with the bare ACTH fragment, but the gain appears modest. Absorption after intranasal dosing is limited, and only a fraction of a dose is expected to reach the central nervous system. Laboratory concentrations therefore sit well above levels achieved systemically, a gap that complicates translation from bench findings to clinical claims.
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.
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.
== Methods of studying proteins == In proteomics, there are multiple methods to study proteins. Generally, proteins may be detected by using either antibodies (immunoassays), electrophoretic separation or mass spectrometry. If a complex biological sample is analyzed, either a very specific antibody needs to be used in quantitative dot blot analysis (QDB), or biochemical separation then needs to be used before the detection step, as there are too many analytes in the sample to perform accurate detection and quantification.
== Function == SENP1 catalyzes maturation of SUMO protein (small ubiquitin-related modifier). SENP1 causes hydrolysis of a peptide bond of SUMO in the conserved sequence Gly-Gly-|-Ala-Thr-Tyr at the C-terminus, which can then be conjugated to other proteins (sumoylation). In vertebrates there are three members of the family of SUMO: SUMO-1, -2 and -3. SENP1 can catalyze the maturation of any of these three. This conjugation of SUMO toward other proteins is similar to ubiquitination, however these modifications can lead to different outcomes depending on the type of protein being modified.
as it was in the general continuum equations and in the incompressible flow section. The compressible momentum Navier–Stokes equation results from the following assumptions on the Cauchy stress tensor:
== Optical properties == PS demonstrates optical properties based on porosity and complex refractive indices of Si and the medium inside the pores. Effective refractive index of PS can be modelled by means of effective medium approximations (EMA). Usually generalised Bruggeman model is used. If the refractive index of the medium inside pores is high, the effective refractive index of PS will be high as well. This phenomenon causes the spectrum to shift towards longer wavelength.
Sources: en.wikipedia.org
(p) .signature (UNIX shell/Internet standard file name) (a/i) Special Interest Group (a/i) Strasbourg Illkirch-Graffenstaden Basket (French basketball club) SIGCAT – (a) Special Interest Group for CD-ROM Applications and Technology SIGINT – (p) Signals Intelligence SIGMET – (p) Significant Meteorological Information SIIT (i) Saskatchewan Indian Institute of Technologies (Canadian university) Sirindhorn International Institute of Technology (Thai university) Stateless IP/ICMP Translation algorithm SIMAC – (a) Semantic Interaction with Music Audio Contents SIMLAS – (p) Soldier Integrated Multipurpose Laser System SIMM – (a) Single In-line Memory Module SIMNET – (p) SIMulator NETwork, later SIMulation NETwork SIMNET-D - (p) SIMNET-Developmental SIMP – (a) Strongly Interacting Massive Particle SIMPLE (a) Satellite Interactive Multimedia Platform for Low-cost Earth stations (p) Savings Incentive Match Plan for Employees (as used in SIMPLE IRA) (a) Standard Interface for Multiple Platform Link Evaluation (NATO STANAG 5602) sin – (s) Sinhala language (ISO 639-2 code) SIN – (a) Social insurance number (Canada) SINCGARS – (p) SINgle Channel Ground and Airborne Radio System SIP (i) Session Initiation Protocol State Implementation Plan System Improvement Program Systematic investment plan SIPP – (a) Self-Invested Personal Pension Siri – (a) Speech Interpretation and Recognition Interface (Apple iOS software) SIRI – (a) Service Interface for Real Time Information SIRS — (a) Systemic inflammatory response syndrome SiS – (i) Silicon Integrated Systems SIS – (i) UK Secret Intelligence Service (also known as MI6) SISO (a) Simulation Interoperability Standards Organization Society of Independent Show Organizers SIW – (i) Simulation Interoperability Workshop SIYSS – (i) Stockholm International Youth Science Seminar
== Etymology == The term forensic stems from the Latin word, forēnsis (3rd declension, adjective), meaning "of a forum, place of assembly". The history of the term originates in Roman times, where many judicial processes, such as trials and preliminary hearings, were held in the forum. This origin is the source of the two modern usages of the word forensic—as a form of legal evidence; and as a category of public presentation. In modern use, the term forensics is often used in place of "forensic science". The word "science", is derived from the Latin word for 'knowledge' and is today closely tied to the scientific method, a systematic way of acquiring knowledge. Taken together, forensic science means the use of scientific methods and processes for crime solving.
== Success of insulin == MacLeod was overseeing the work of Frederick Banting and Charles Best in their search for a treatment for diabetes which they had begun in May 1921. In December, when Banting and Best were having difficulties in refining the pancreatic extract, MacLeod freed Collip from his other research to enable him to join the research team. Collip's task was to prepare insulin in a more pure, usable form than Banting and Best had been able to achieve to date. In January 1922, after 14-year-old Leonard Thompson suffered a severe allergic reaction to an injection of insulin, Collip achieved the goal of preparing a pancreatic extract pure enough for Thompson to recover and to use in clinical trials. Despite Collip's breakthrough, Banting was furious as he saw that "Collip's discoveries were not a cause for celebration but a new threat". At some point between January 17 and 24, Collip and Banting reportedly had a physical altercation in the labs, supposedly when "Collip visited Banting and Best in their lab and told them that he wasn’t going to share the latest extract formulation (which may or may not have had Macleod's blessing) and that he was contemplating leaving the research team and patenting the process on his own". A colleague later lampooned this incident with a "cartoon showing Banting sitting on Collip and titled 'The Discovery of Insulin.'" Nonetheless, successful trials were soon completed and the future of insulin was assured.
Sources: en.wikipedia.org
=== First World Cup appearance (1958–1962) === Colombia entered World Cup qualifying for the first time in 1961, meeting Peru over two legs under Argentine manager Pedernera, who had remained in the country after El Dorado as a coach. A 1–0 win in Bogotá on 30 April 1961 was followed by a 1–1 draw in Lima a week later, and Colombia advanced to the 1962 FIFA World Cup in Chile. Drawn in Group 1 with Uruguay, the Soviet Union and Yugoslavia, Colombia lost their opening match to Uruguay 2–1 on 30 May and were beaten 5–0 by Yugoslavia on 7 June, finishing bottom of the group with a single point from three games and five goals scored against eleven conceded. Their remaining fixture, however, produced one of the tournament's defining results. Facing the reigning European champions at the Estadio Carlos Dittborn in Arica on 3 June before a crowd of 8,040, with Brazilian referee João Filho officiating, Colombia trailed 3–0 inside eleven minutes to goals from Valentin Ivanov in the eighth and eleventh minutes either side of an Igor Chislenko strike in the tenth. Germán Aceros reduced the deficit in the 21st minute, but Viktor Ponedelnik restored a three-goal lead in the 56th. With twenty minutes remaining, Marcos Coll scored directly from a corner in the 68th minute, the ball creeping in at the near post past Lev Yashin — the only goal scored direct from a corner in World Cup history, and conceded by a goalkeeper then widely regarded as the world's finest. Antonio Rada struck in the 72nd minute and Marino Klinger completed the recovery late on to secure a 4–4 draw.
The antagonist has a peptide moiety. The nomenclature of the somatostatin receptor antagonists is also based on this order. The structure of somatostatin receptor antagonists are similar to that of the agonists. Some agonists were already approved by the FDA for clinical use, such as In-DTPA-octreotide and Ga-DOTATATE. Development started after the discovery of modifications that can be done to the octreotide group, a ssrt selective subtype agonist, to cause its agonistic effects to be lost and gain antagonistic effects. Different subtype receptor antagonists were later developed. Research has mostly been done on the sstr2 receptor antagonist, as the sstr2 receptor is expressed on most tumors. Somatostatin receptor antagonists are divided by generation based on the type of the subtype receptor antagonist. The first generation consists of sst2-ANT and BASS, which are sstr2 selective; and sst3-ODAN-8, which is selective for sstr3. After initial results of their increased sensitivity to neurocrine tumors appeared, ssrt2 selective antagonists that had even higher affinity were developed. These were LM3, JR10, and JR11, which make up the second generation. JR11 was shown to be the most effective among these 3 antagonists, and compounds that entered further clinical development to act as a PET imaging agent or therapeutic agent carried this subtype antagonist. The presence of a chelator coupled to the subtype antagonist was shown to have an effect on the biologic properties. Compounds were developed with 3 macrocyclic chelators: DOTA, NODAGA, and CB-TE2A.
Factors in this population may include inherited anatomical features, instability of ventilatory control, neuromuscular inefficiency of the dilator muscles of the upper airways, or a lower threshold for awakening in response to respiratory stimuli. Diagnosis of obstructive sleep apnea is significantly more common among people in relationships, who are alerted to their condition by being informed by their sleeping partner, since individuals with obstructive sleep apnea are often unaware of the condition. There is a stigma associated with loud snoring. It is not considered a feminine trait. Consequently, females are less likely to be told by their partners that they snore, or to admit it to themselves or doctors. Furthermore, CPAP (continuous positive airway pressure) machines are also perceived negatively by females. They are less likely to be utilized to their full extent in this group.
===== Macroscopic viscous flow ===== Macroscopic viscous flow fields can direct self-assembly of a random solution of particles into ordered crystals via the shear-assisted nucleation mechanism. However, the flow-induced self-assembly often occurs far from thermodynamic equilibrium and leads to amorphous aggregates of nanoparticles through a mechanism by which the shear flow field overcomes the repulsive energy barrier which stabilizes the nanoparticles against self-assembly in the absence of flow. The assembled particles aggregates tend to disassemble due to flow-induced breakup or when the flow is stopped or removed if the interparticle bonds are weak. Shear flows are also useful for jammed suspensions or random close packing. As these systems begin in nonequilibrium conditions, flow fields are useful in that they help the system relax towards a more ordered equilibrium. Flow fields are also useful when dealing with complex matrices that themselves exhibit rheological behavior. Flow can induce anisotropic viseoelastic stresses, which helps to overcome the matrix and cause self-assembly.
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。
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.