The short version of selectivity fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-06-05. Anything still debated is marked as such rather than presented as settled.
Ipamorelin 是一种合成五肽，序列为 Aib-His-D-2-Nal-D-Phe-Lys-NH2，分子式 C38H49N9O5，游离碱分子量约 711.85 g/mol。它属于生长激素促分泌素（GHS）家族，作用靶点是胃饥饿素受体 GHS-R1a。该化合物由诺和诺德的研究团队在二十世纪九十年代末报道，设计目标是提高对生长激素释放的选择性。C 端酰胺化与 N 端 Aib 残基是两个用于抵抗肽酶降解的结构特征。
在 GHS 家族中，早期肽类如 GHRP-6 与 GHRP-2 会同时促进生长激素、皮质醇与催乳素的释放，并明显增加食欲。Ipamorelin 在动物与早期人体研究中表现出对生长激素释放的相对选择性，对上述其他激素的影响较小。这种差异通常归因于受体结合模式与下游信号偏向的不同，而完整的分子解释仍有待补充。需要区分的是，选择性是研究观察中的相对程度，并非绝对界限。
从用途定位看，ipamorelin 目前主要以研究用肽的身份被讨论，未见主要药品监管机构将其批准为治疗药物。市售材料通常标注仅供研究使用，不得用于人体或诊断程序。文献中它常与生长激素促分泌素、GHS-R1a 激动剂、胃饥饿素拟似物等表述并列出现。既有研究的样本量普遍偏小，因此对其效应强度与一致性的描述应保持谨慎。
The compound was developed at Novo Nordisk during the 1990s as part of a programme seeking secretagogues with improved selectivity. It was described in the peer-reviewed literature in 1998 alongside related pentapeptides from the same series. Investigators advanced it because it raised growth hormone output in animal models while leaving other pituitary hormones comparatively unaffected. The development code NNC 26-0161 appears in earlier reports, and ipamorelin later became the common designation in published work.
Selectivity is the property most often attached to this peptide. Published animal and early human studies record increases in growth hormone release after administration, with adrenocorticotropic hormone and cortisol responses remaining small by comparison. Effects on appetite-related pathways also appear weaker than those reported for several earlier secretagogues. Reviews that compare members of the growth hormone secretagogue family cite these findings frequently, though the receptor-level explanation for the selectivity continues to be debated rather than settled.
Ipamorelin is a synthetic pentapeptide classified as a growth hormone secretagogue. Its sequence, Aib-His-D-2-Nal-D-Phe-Lys-NH2, combines three non-proteinogenic residues with a C-terminal amide. The N-terminal aminoisobutyric acid unit and the two aromatic D-amino acids distinguish it from peptides assembled only from standard L-amino acids. Its formula is C38H49N9O5, corresponding to an average mass near 711.9 Da. At neutral pH the molecule carries a net positive charge, a property that shapes its behaviour in chromatographic and electrophoretic systems.
| Property | Value | Notes |
|---|---|---|
| 分子式 | C38H49N9O5 | 五肽，C 端酰胺化 |
| 分子量 | 约 711.85 g/mol | 游离碱形式 |
| 外观 | 白色至类白色冻干粉 | 研究用材料的常见形态 |
| 溶解性 | 溶于水及 DMSO 等极性溶剂 | 建议现配现用 |
| 储存温度 | -20 °C 或更低 | 干燥、避光、限制冻融次数 |
Structural features distinguish the molecule from earlier secretagogues. An alpha-aminoisobutyric acid residue near the N-terminus and a D-naphthylalanine substitution increase receptor affinity, while C-terminal amidation improves resistance to exopeptidases. These modifications are associated with reduced stimulation of appetite and of the hypothalamic-pituitary-adrenal axis compared with hexarelin or growth hormone releasing peptide-6. Whether the same profile applies at every dose level studied is a matter of ongoing investigation rather than settled consensus.
Ipamorelin is a synthetic pentapeptide that acts as an agonist at the ghrelin receptor, also called the growth hormone secretagogue receptor type 1a. Its sequence incorporates non-natural residues, which slows enzymatic breakdown relative to short native peptides. In laboratory and early clinical work the compound is described as a selective growth hormone secretagogue because it raises growth hormone with comparatively little effect on other pituitary outputs. The degree to which that selectivity holds across species and dosing regimens remains an open question in the published literature.
Signal transduction begins when the peptide binds GHSR-1a on pituitary somatotrophs. The receptor couples to Gq/11 proteins, activating phospholipase C, which cleaves phosphatidylinositol bisphosphate into inositol trisphosphate and diacylglycerol. Inositol trisphosphate releases calcium from intracellular stores, and the resulting rise in cytosolic calcium drives growth hormone vesicle fusion. Concurrent Gs coupling and cyclic AMP elevation have also been reported, and the relative contribution of each arm to the overall secretory response is not fully settled.
Quality control for research-grade ipamorelin is not governed by a single harmonized pharmacopeial monograph, so certificates of analysis vary between suppliers. Common tests include appearance, solubility, water content, peptide content by quantitative amino acid analysis, and residual counterion measurement. Independent verification by an outside laboratory is often used to confirm identity and purity claims. Salt form, counterion content, and residual solvent levels are frequently unspecified, which complicates direct comparison between lots and leaves reproducibility partly unresolved.
Identity and purity assessment of ipamorelin relies mainly on reversed-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometers, a wavelength where the peptide backbone absorbs. Mass confirmation is typically obtained by electrospray ionization mass spectrometry or by liquid chromatography coupled to mass spectrometry, comparing the observed mass with the calculated value. Amino acid analysis and peptide mapping after enzymatic digestion can confirm the sequence. Impurity profiles include deletion peptides, truncated fragments, and oxidation products, reported as relative area percentages.
Prior to the 2018 reforms, the People's Armed Police Gold Corps (Chinese: 武警黄金部队) was a branch of the PAP whose role switched multiple times in history, however it was mostly dedicated to finding gold deposits, mining gold and providing law enforcement at gold mines.
The Joint Committee for Traceability in Laboratory Medicine or JCTLM is collaboration between the International Bureau of Weights and Measures (BIPM), the International Federation for Clinical Chemistry and Laboratory Medicine (IFCC), and the International Laboratory Accreditation Cooperation (ILAC). The goal of the JCTLM is to provide a worldwide platform to promote and give guidance on internationally recognized and accepted equivalence of measurements in laboratory medicine and traceability to appropriate measurement standards.
Polycyclic aromatic hydrocarbons (PAH) are the most common and abundant polyatomic molecules in the observable universe, and are a major store of carbon. They seem to have formed shortly after the Big Bang, and are associated with new stars and exoplanets. They are a likely constituent of Earth's primordial sea. PAHs have been detected in nebulae, and in the interstellar medium, in comets, and in meteorites. A star, HH 46-IR, resembling the sun early in its life, is surrounded by a disk of material which contains molecules including cyanide compounds, hydrocarbons, and carbon monoxide. PAHs in the interstellar medium can be transformed through hydrogenation, oxygenation, and hydroxylation to more complex organic compounds used in living cells.
==== Elimination ==== The clearance of oxycodone is 0.8 L/min. Oxycodone and its metabolites are mainly excreted in urine. Therefore, oxycodone accumulates in patients with kidney impairment. Oxycodone is eliminated in the urine 10% as unchanged oxycodone, 45% ± 21% as N-demethylated metabolites (noroxycodone, noroxymorphone, noroxycodols), 11 ± 6% as O-demethylated metabolites (oxymorphone, oxymorphols), and 8% ± 6% as 6-keto-reduced metabolites (oxycodols).
Sources: en.wikipedia.org
Most substances relevant to biology are chiral, such as carbohydrates (sugars, starch, and cellulose), all but one of the amino acids that are the building blocks of proteins, and the nucleic acids. Naturally occurring triglycerides are often chiral, but not always. In living organisms, one typically finds only one of the two enantiomers of a chiral compound. For that reason, organisms that consume a chiral compound usually can metabolize only one of its enantiomers. For the same reason, the potencies or effects of enantiomers of a pharmaceutical can differ sharply.
Germanium is a shiny grey-white solid. It has a density of 5.323 g/cm3 and is hard and brittle. It is mostly unreactive at room temperature but is slowly attacked by hot concentrated sulfuric or nitric acid. Germanium also reacts with molten caustic soda to yield sodium germanate Na2GeO3 and hydrogen gas. It melts at 938 °C. Germanium is a semiconductor with an electrical conductivity of around 2 × 10−2 S•cm−1 and a band gap of 0.67 eV. Liquid germanium is a metallic conductor, with an electrical conductivity similar to that of liquid mercury. Most of the chemistry of germanium is characteristic of a nonmetal. Whether or not germanium forms a cation is unclear, aside from the reported existence of the Ge2+ ion in a few esoteric compounds. It can form alloys with metals such as aluminium and gold. It shows fewer tendencies to anionic behaviour than ordinary nonmetals. Its solution chemistry is characterised by the formation of oxyanions. Germanium generally forms tetravalent (IV) compounds, and it can also form less stable divalent (II) compounds, in which it behaves more like a metal. Germanium analogues of all of the major types of silicates have been prepared. The metallic character of germanium is also suggested by the formation of various oxoacid salts. A phosphate [(HPO4)2Ge·H2O] and highly stable trifluoroacetate Ge(OCOCF3)4 have been described, as have Ge2(SO4)2, Ge(ClO4)4 and GeH2(C2O4)3. The oxide GeO2 is polymeric, amphoteric, and a glass former.
Heppell, along with 33 other Essendon players, whilst not returning a positive test 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 teammates 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 AFL season. In February 2017, Heppell was announced as Essendon's new captain, taking over from Brendon Goddard. In December 2019, he signed a two-year contract extension with Essendon, keeping him at the club until 2022. He re-signed for 2023 but stepped down as captain after six seasons in the role. On 13 August 2024, Heppell announced that he would retire at the conclusion of the 2024 AFL season. Heppell played a farewell game in the Bombers' final game of the season, against the Brisbane Lions at The Gabba.
==== Expiration date ==== The expiration date, required in several countries, specifies the date up to which the manufacturer guarantees the full potency and safety of a drug. In the United States, expiration dates are determined by regulations established by the FDA. The FDA advises consumers not to use products after their expiration dates. A study conducted by the U.S. Food and Drug Administration covered over 100 drugs, prescription and over-the-counter. The results showed that about 90% of them were safe and effective far past their original expiration date. At least one drug worked 15 years after its expiration date. Joel Davis, a former FDA expiration-date compliance chief, said that with a handful of exceptions—notably nitroglycerin, insulin, and some liquid antibiotics (outdated tetracyclines can cause Fanconi syndrome)—most expired drugs are probably effective. The American Medical Association issued a report and statement on Pharmaceutical Expiration Dates. The Harvard Medical School Family Health Guide notes that, with rare exceptions, "it's true the effectiveness of a drug may decrease over time, but much of the original potency still remains even a decade after the expiration date". The expiration date is the final day that the manufacturer guarantees the full potency and safety of a medication. Drug expiration dates exist on most medication labels, including prescription, over-the-counter and dietary supplements. U.S. pharmaceutical manufacturers are required by law to place expiration dates on prescription products prior to marketing.
=== Isotopic variation === The discovery of isotopes of oxygen in 1929 required a more precise definition of the unit. Two distinct definitions came into use. Chemists choose to define the AMU as 1/16 of the average mass of an oxygen atom as found in nature; that is, the average of the masses of the known isotopes, weighted by their natural abundance. Physicists, on the other hand, defined it as 1/16 of the mass of an atom of the isotope oxygen-16 (16O).
Sources: en.wikipedia.org
两者都是 GHS-R1a 激动剂，但 ipamorelin 在研究中显示出更高的生长激素释放选择性。早期资料显示它对皮质醇、催乳素与食欲的刺激弱于 GHRP-6。这些差异是相对程度，而非绝对区分。
公开资料中它主要以研究用肽的形式出现，未获主要监管机构批准用于治疗。可得材料通常标注仅供研究使用。任何临床用途的宣称都缺少监管依据。
序列中的 Aib 与 D-2-Nal 等非天然残基可提高对肽酶的抵抗能力，并影响受体结合的构象。这类修饰在合成肽设计中较为常见。它们也使常规氨基酸分析需要额外步骤才能确认序列。
Aib 即 α-氨基异丁酸，是一种非蛋白质源氨基酸，其侧链为两个甲基。它在肽链中倾向于诱导螺旋构象并限制骨架的柔性。这种刚性被认为有助于抵抗蛋白酶切割。