This is a working overview of freeze–thaw cycle, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-03-02 and is reviewed periodically as new material appears.
化学修饰延长了分子在体内的停留时间，使较低频次的给药安排成为可能。脂肪酸侧链通过与白蛋白结合延缓清除，非天然氨基酸则降低酶解速率。这些修饰同时改变分子的溶解性与稳定性，需要在制剂设计和储存条件中一并考虑。修饰引入的免疫原性风险也属于开发过程中需要评估的项目。
该化合物处于临床试验阶段，尚未在多数地区取得上市许可。公开信息主要来自企业公告、学术会议摘要与试验注册平台记录，完整数据仍在逐步披露。关于长期疗效与安全性的判断，需要等待规模更大、随访更久的研究结果，目前不宜对最终结论作出预判。
retatrutide 是一种人工合成的多肽，设计目标是同时作用于 GIP、GLP-1 与胰高血糖素三种受体。这种三重激动设计试图把多条代谢通路的调节整合进单一分子，而不是只依赖一种肠促胰素受体。分子骨架以天然肽序列为基础，经过非天然氨基酸替换和脂肪酸侧链修饰，以获得更长的作用时间。该方向属于多受体激动剂研究的一部分，与双重激动剂的工作并行推进。
Development has progressed through early- and mid-stage human studies in adults with obesity and with type 2 diabetes. Published phase 2 data reported reductions in body weight and improvements in glycemic markers over the treatment period. No regulatory agency has approved the compound for any indication, and it remains available only within controlled research settings. Whether benefits observed in trials translate into durable outcomes after treatment stops is not yet established.
Retatrutide is an investigational synthetic peptide that acts as an agonist at three distinct G protein-coupled receptors. It combines activity at the glucagon-like peptide-1 receptor, the glucose-dependent insulinotropic polypeptide receptor, and the glucagon receptor within a single molecule. This multi-receptor profile distinguishes it from earlier incretin-based compounds that engage one or two of these pathways. Researchers designed the molecule to test whether simultaneous activation produces greater metabolic effects than single or dual agonism alone.
| Property | Value | Notes |
|---|---|---|
| 分子类别 | 合成多肽 | 含非天然氨基酸与脂肪酸侧链 |
| 分子量 | 约 4.7 kDa | 多肽量级，精确值随计法而异 |
| 外观 | 白色至类白色冻干粉 | 常见冻干形态，供复溶使用 |
| 溶解性 | 易溶于水 | 复溶后为澄清至微乳光液体 |
| 常见同义词 | LY3437943 | 开发阶段使用的代号 |
Identity and purity are established with reversed-phase high-performance liquid chromatography and mass spectrometry. Chromatographic profiles reveal related impurities, truncated sequences, and oxidation products, while mass measurement confirms the expected molecular mass. Purity values for research material are typically reported as a percentage by peak area. Reference standards help calibrate retention behavior across instruments. Independent laboratories emphasize method suitability because results depend heavily on column chemistry, gradient, and detection wavelength. Batch-to-batch comparison relies on the same validated method.
Investigational peptide material is commonly distributed as a lyophilized powder in sealed vials. The solid form appears as a white to off-white cake or powder and is hygroscopic once opened. Peptides of this size are sensitive to moisture, repeated freeze-thaw cycles, and prolonged exposure to ambient light. Handling practices therefore emphasize desiccation, minimal vial opening, and cold storage. Working aliquots are often prepared to avoid repeatedly warming the bulk container.
Solid peptide is generally held as a lyophilised powder at low temperature to slow degradation, with desiccant to limit moisture uptake. Reconstituted solutions are less stable and are usually kept refrigerated and protected from light for short periods. Repeated freeze-thaw cycles are avoided because they encourage aggregation. Laboratory handling includes work in a fume hood or laminar flow cabinet to limit inhalation and contamination. Weighing and transfer steps are performed with antistatic tools to reduce static-driven loss of fine powder.
Characterising a peptide of this size relies on a combination of chromatographic and mass spectrometric techniques. Reversed-phase high-performance liquid chromatography separates the intact molecule from related impurities, while electrospray mass spectrometry confirms molecular mass and detects truncation or oxidation products. Peptide mapping after enzymatic digestion verifies the amino acid sequence and locates modified residues. Because the molecule carries a lipid chain, assays must also distinguish the correctly conjugated product from incompletely acylated species.
Peptides in this class degrade mainly through hydrolysis, oxidation, and aggregation. The lipid modification improves plasma residence time but can also promote self-association in aqueous solution at higher concentrations. Oxidation of methionine and deamidation of asparagine residues are common chemical liabilities that accumulate during storage. Stability studies therefore track purity loss, aggregate formation, and changes in receptor-binding potency over time under defined temperature and humidity conditions.
Stability depends strongly on physical state. Dry powder is comparatively robust when held at -20 °C or below, desiccated and shielded from light; under those conditions degradation is slow and measured over years. Once dissolved, the peptide becomes far more vulnerable: backbone hydrolysis, oxidation of susceptible residues and aggregation all proceed faster in solution, and the rates climb with temperature and with pH far from neutral. Refrigerated storage at 2–8 °C extends usable life for short periods, and repeated freeze–thaw cycles are best avoided.
Identity and purity are established by instrumental methods rather than by appearance. Reversed-phase high-performance liquid chromatography separates the peptide from related impurities and yields a purity value, usually expressed as the share of total peak area. Mass spectrometry checks that the observed mass agrees with the mass calculated from the published sequence, while peptide mapping or amino acid analysis adds structural evidence. Water content, counter-ion identity and residual solvents are sometimes reported as well. A certificate of analysis should name the method behind each figure, because results are method-dependent.
Laboratory handling follows the conventions used for other synthetic peptides. Lyophilized material is weighed and dissolved in an aqueous diluent, typically sterile water or bacteriostatic water, using gentle swirling rather than vigorous shaking, because foaming stresses the chain. Solutions are prepared under clean conditions and, where sterility matters, passed through a suitable filter. Working portions are kept small so that stock material is not repeatedly warmed and cooled, a practice that limits both aggregation and gradual loss of activity.
Retatrutide is an investigational synthetic peptide engineered to activate three distinct hormone receptors within a single molecule. It targets the glucose-dependent insulinotropic polypeptide receptor, the glucagon-like peptide-1 receptor, and the glucagon receptor simultaneously. This triagonist design distinguishes it from earlier incretin-based compounds that act on one or two of these pathways. Structural modifications relative to native gut hormones extend its residence time in circulation. The molecule remains under clinical evaluation and is not approved for any indication.
Receptor activation produces downstream effects that differ by tissue. GLP-1 receptor signaling influences appetite regulation and insulin secretion in a glucose-dependent manner. GIP receptor activity contributes to metabolic handling of nutrients and may modulate adipose tissue. Glucagon receptor engagement raises energy expenditure and promotes hepatic lipid turnover, though the balance among these actions in humans is still being characterized. Preclinical models showed reductions in body weight and improved glycemic markers.
Macrophages and inflammatory components (within 1–2 days) Epithelial-mesenchymal interaction: re-epithelialization (phenotype change within hours, migration begins on day 1 or 2) Fibroblasts and myofibroblasts: progressive alignment, collagen production, and matrix contraction (between day 4 and day 14) Endothelial cells and angiogenesis (begins on day 4) Dermal matrix: elements of fabrication (begins on day 4, lasting 2 weeks) and alteration/remodeling (begins after week 2, lasting weeks to months—depending on wound size).
== Properties == All elements with atomic number greater than 94 decay quickly enough into lighter elements such that any atoms of these that may have existed when the Earth formed (about 4.6 billion years ago) have long since decayed. Synthetic elements now present on Earth are the product of atomic bombs or experiments that involve nuclear reactors or particle accelerators, via nuclear fusion or neutron absorption. Atomic mass for natural elements is based on weighted average abundance of natural isotopes in Earth's crust and atmosphere. For synthetic elements, there is no "natural isotope abundance". Therefore, for synthetic elements the total nucleon count (protons plus neutrons) of the most stable isotope, i.e., the isotope with the longest half-life—is listed in brackets as the atomic mass.
=== Approaches === Psychiatric illnesses can be conceptualised in several different ways. The biomedical approach examines signs and symptoms and compares them with diagnostic criteria. Mental illness can be assessed, conversely, through a narrative which tries to incorporate symptoms into a meaningful life history and to frame them as responses to external conditions. For example, the Power Threat Meaning Framework (PTMF) is a conceptual approach to understanding mental distress that serves as an alternative to traditional psychiatric diagnostic systems. Rather than viewing distress primarily as a symptom of an underlying mental disorder, the framework emphasizes the role of adversity, trauma, social inequalities, relationships, and cultural contexts in shaping people's experiences, and proposes that many forms of distress can be understood as meaningful responses to difficult circumstances. Both approaches are considered important in the field of psychiatry, but have not sufficiently reconciled to settle controversy over either the selection of a psychiatric paradigm or the specification of psychopathology. The biopsychosocial model is used to explain the multifactorial origins of clinical impairment, recognizing that biological, psychological, and social factors all play a role in health and disease. Once a medical professional diagnoses a patient there are numerous ways that they could choose to treat the patient. Often psychiatrists will develop a treatment strategy that incorporates different facets of different approaches into one.
== Epidemiology == Sack–Barabas syndrome is rare and has an estimated prevalence of 1 in 100,000 to 200,000. The initial clinical manifestation of vascular problems in patients with SBS is early, about 25% have their first symptoms at age 20 and more than 80% of patients have had at least one complication by the age of 40. The median survival for one study of SBS patients was only 48 years.
=== All-cause mortality === Two meta-analyses concluded that as a dietary supplement, vitamin E neither improved nor impaired all-cause mortality. A meta-analysis of long-term clinical trials reported a non-significant 2% increase in all-cause mortality when alpha-tocopherol was the only supplement used. The same journal article reported a statistically significant 3% increase for results when alpha-tocopherol was used in combination with other nutrients (vitamin A, vitamin C, beta-carotene, selenium).
Sources: en.wikipedia.org
== Adverse events == The safety of benzhydrocodone/APAP was evaluated in a total of 200 healthy adults in six phase 1 studies. The subjects received at least one oral dose of benzhydrocodone/APAP. The most common adverse events in these studies were nausea (21.5%), somnolence (18.5%), vomiting (13.0%), constipation (12.0%), pruritus (11.5%), dizziness (7.5%) and headache (6.0%). Benzhydrocodone/APAP use with serotonergic drugs can cause serotonin syndrome. Mixed agonist/antagonist and partial agonist opioids may reduce the analgesic effect of benzhydrocodone/APAP or cause withdrawal symptoms. MAOIs can increase the effects of benzhydrocodone/APAP.
According to the fluid mosaic model of S. J. Singer and G. L. Nicolson (1972), which replaced the earlier model of Davson and Danielli, biological membranes can be considered as a two-dimensional liquid in which lipid and protein molecules diffuse more or less easily. Although the lipid bilayers that form the basis of the membranes do indeed form two-dimensional liquids by themselves, the plasma membrane also contains a large quantity of proteins, which provide more structure. Examples of such structures are protein-protein complexes, pickets and fences formed by the actin-based cytoskeleton, and potentially lipid rafts.
Several case studies studying deletions in the 7p22.3 genomic region, where the SNX8 gene is located, found that it contributes to neurodevelopmental problems with considerable impairments in the motor, cognitive and socio-emotional areas, with malformations in the heart and craniofacial structures, with developmental, intellectual and language delay, with mild intellectual disability and with cognitive impairment associated with autism in some cases. This idea is supported by the fact that the overlapping deleted regions of the different patients of these studies contained SNX8, which suggests that it is one of the accountable genes.
== Fission products decay and burnup == One of the common fission products is 135Te, which undergoes beta decay with half-life of 19 seconds to 135I. 135I itself is a weak neutron absorber. It builds up in the reactor at a rate proportional to the rate of fission, which is proportional to the reactor thermal power. 135I undergoes beta decay with half-life of 6.57 hours to 135Xe. The yield of 135Xe for uranium fission is 6.3%; about 95% of 135Xe originates from decay of 135I. 135Xe is the most powerful known neutron absorber, with a cross section for thermal neutrons of 2.6×106 barns, so it acts as a "poison" that can slow or stop the chain reaction after a period of operation. This was discovered in the earliest nuclear reactors built by the Manhattan Project for plutonium production. As a result, the designers made provisions in the design to increase the reactor's reactivity (the number of neutrons per fission that go on to fission other atoms of nuclear fuel). 135Xe reactor poisoning played a major role in the Chernobyl disaster. By neutron capture, 135Xe is transformed ("burned") to 136Xe, which is effectively stable and does not significantly absorb neutrons. The burn rate is proportional to the neutron flux, which is proportional to the reactor power; a reactor running at twice the power has twice the xenon burn rate. The production rate is also proportional to reactor power, but due to the half-life time of 135I, this rate depends on the average power over the past several hours.
== Cancer == Hsp70 is overexpressed in melanoma and underexpressed in renal cell cancer. In breast cancer cell line (MCF7) has been found that not only Hsp90 interacted with estrogen receptor alpha (ERα) but also Hsp70-1 and Hsc70 interacted with ERα too. Given the role of heat shock proteins as an ancient defense system for stabilizing cells and eliminating old and damaged cells, this system has been co-opted by cancer cells to promote their growth. Increased Hsp70 in particular has been shown to inhibit apoptosis of cancer cells, and increased Hsp70 has been shown to be associated with or directly induce endometrial, lung, colon, prostate, and breast cancer, as well as leukemia. Hsp70 in cancer cells may be responsible for tumorigenesis and tumor progression by providing resistance to chemotherapy. Inhibition of Hsp70 has been shown to reduce the size of tumors and can cause their complete regression. Hsp70/Hsp90 is a particularly attractive target for therapeutics, because it is regulated by the inhibition of its ATPase activity, while other HSPs are regulated by nucleotides. Several inhibitors have been designed for Hsp70 that are currently in clinical trials, though as of now HSP90 inhibitors have been more successful. In addition, Hsp70 has been shown to be a regulator of the immune system, activating the immune system as an antigen. Thus, tumor-derived Hsp70 has been suggested as a potential vaccine or avenue to target for immunotherapy.
Sources: en.wikipedia.org
Along with most of the Commonwealth and Allied nations, Southern Rhodesia sent a delegation of soldiers, airmen and seamen to London to take part in the grand Victory Parade of 8 June 1946. The colony's contingent, led by Colonel R E B Long, marched after South Africa and before Newfoundland. The Southern Rhodesian colour guard comprised a white officer and two black sergeants of the Rhodesian African Rifles. During the royal visit to Southern Rhodesia in April 1947, King George VI accorded the prefix "Royal" to the Rhodesia Regiment in recognition of its contributions to the two World Wars, and agreed to be its Colonel-in-Chief.
=== Nervous system === Chronic pain can be divided into three categories. Nociceptive pain is pain caused by inflammation or damage to tissues. Neuropathic pain is pain caused by nerve damage. Nociplastic pain (or central sensitization) is less understood and is the common explanation of the pain experienced in fibromyalgia. Because the three forms of pain can overlap, fibromyalgia patients may experience nociceptive (e.g., rheumatic illnesses) and neuropathic (e.g., small fiber peripheral neuropathy) pain in addition to nociplastic pain.
== Units == The SI unit of dynamic viscosity is the newton-second per metre squared (N·s/m2), also frequently expressed in the equivalent forms pascal-second (Pa·s), kilogram per meter per second (kg·m−1·s−1) and poiseuille (Pl). The CGS unit is the poise (P, or g·cm−1·s−1 = 0.1 Pa·s), named after Jean Léonard Marie Poiseuille. It is commonly expressed, particularly in ASTM standards, as centipoise (cP). The centipoise is convenient because the viscosity of water at 20 °C is about 1 cP, and one centipoise is equal to the SI millipascal second (mPa·s). The SI unit of kinematic viscosity is metre squared per second (m2/s), whereas the CGS unit for kinematic viscosity is the stokes (St, or cm2·s−1 = 0.0001 m2·s−1), named after Sir George Gabriel Stokes. In U.S. usage, stoke is sometimes used as the singular form. The submultiple centistokes (cSt) is often used instead, 1 cSt = 1 mm2·s−1 = 10−6 m2·s−1. 1 cSt is 1 cP divided by 1000 kg/m^3, close to the density of water. The kinematic viscosity of water at 20 °C is about 1 cSt. The most frequently used systems of US customary, or Imperial, units are the British Gravitational (BG) and English Engineering (EE). In the BG system, dynamic viscosity has units of pound-seconds per square foot (lb·s/ft2), and in the EE system it has units of pound-force-seconds per square foot (lbf·s/ft2). The pound and pound-force are equivalent; the two systems differ only in how force and mass are defined.
=== Lysine === Lysine is synthesized from aspartate via the diaminopimelate (DAP) pathway. The initial two stages of the DAP pathway are catalyzed by aspartokinase and aspartate semialdehyde dehydrogenase. These enzymes play a key role in the biosynthesis of lysine, threonine, and methionine. There are two bifunctional aspartokinase/homoserine dehydrogenases, ThrA and MetL, in addition to a monofunctional aspartokinase, LysC. Transcription of aspartokinase genes is regulated by concentrations of the subsequently produced amino acids, lysine, threonine, and methionine. The higher these amino acids concentrations, the less the gene is transcribed. ThrA and LysC are also feed-back inhibited by threonine and lysine. Finally, DAP decarboxylase LysA mediates the last step of the lysine synthesis and is common for all studied bacterial species. The formation of aspartate kinase (AK), which catalyzes the phosphorylation of aspartate and initiates its conversion into other amino acids, is also inhibited by both lysine and threonine, which prevents the formation of the amino acids derived from aspartate. Additionally, high lysine concentrations inhibit the activity of dihydrodipicolinate synthase (DHPS). So, in addition to inhibiting the first enzyme of the aspartate families biosynthetic pathway, lysine also inhibits the activity of the first enzyme after the branch point, i.e. the enzyme that is specific for lysine's own synthesis.
==== Tax expenditures ==== The term "tax expenditures" refers to income exclusions, deductions, preferential rates, and credits that reduce revenues for any given level of tax rates in the individual, payroll, and corporate income tax systems. Like conventional spending, they contribute to the federal budget deficit. They also influence choices about working, saving, and investing, and affect the distribution of income. The amount of reduced federal revenues are significant, estimated by CBO at nearly 8% GDP or about $1.5 trillion in 2017, for scale roughly half the revenue collected by the government and nearly three times as large as the budget deficit. Since eliminating a tax expenditure changes economic behavior, the amount of additional revenue that would be generated is somewhat less than the estimated size of the tax expenditure. CBO reported that the following were among the largest individual (non-corporate) tax expenditures in 2013:
Sources: en.wikipedia.org
指同一个分子能激活 GIP、GLP-1 和胰高血糖素三类受体。它与只激活一到两种受体的同类分子在设计思路上有所区别。这种设计的目的在于覆盖更多代谢调节通路。
天然肽类在体内容易被酶解并快速清除。脂肪酸侧链与非天然氨基酸可以延缓清除、降低酶解速率。修饰后的分子因此更适合较长间隔的给药安排。
公开资料主要来自临床阶段的报告与注册平台记录。这些材料提供的是阶段性信息，而非最终结论。完整的安全性与有效性数据仍在积累中。
Retatrutide is an investigational synthetic peptide that activates three metabolic receptors: GLP-1, GIP, and glucagon. It is being studied for obesity and type 2 diabetes. It has not been approved for clinical use.