A practical reference on 非天然氨基酸: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
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。
Reversed-phase high-performance liquid chromatography is the standard tool for assessing purity. Detection near 214 nanometers captures the peptide backbone, and the resulting chromatogram shows the main peak alongside related impurities. Electrospray ionization mass spectrometry confirms molecular mass and supports sequence verification. Common degradation products include oxidized residues, deamidated forms, and truncated fragments, each appearing as a distinct peak or shoulder in the trace.
Quality claims for research peptides vary widely across suppliers. A certificate of analysis should list purity by chromatography, the mass found by spectrometry, and the analytical conditions used. Independent testing at a third-party laboratory is a common way to check identity and purity, because documents alone cannot confirm what is inside a vial. Purity figures describe the proportion of the target peptide among detected species, and they say nothing about biological activity or sterility.
Lyophilized ipamorelin powder is the form usually supplied for laboratory work. Kept dry, protected from light, and held at minus 20 degrees Celsius or below, it remains stable for extended periods, often measured in years. Once dissolved, the peptide degrades faster through hydrolysis, oxidation, and deamidation, so solutions are typically refrigerated and used within weeks. Repeated freeze-thaw cycles and exposure to alkaline conditions accelerate loss of the parent compound.
| 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 |
Ipamorelin is a synthetic pentapeptide that belongs to the growth hormone secretagogue class of compounds. Researchers at a pharmaceutical company first described it in the 1990s while screening small peptides for growth hormone releasing activity. Its chain contains five amino acid residues, two of which are non-natural building blocks, including 2-aminoisobutyric acid and a naphthylalanine derivative. The molecule was designed to act at the ghrelin receptor while avoiding several effects observed with earlier secretagogues.
At the cellular level, ipamorelin binds the growth hormone secretagogue receptor, also called the ghrelin receptor. Activation of this receptor on pituitary somatotroph cells triggers a signaling cascade that leads to release of growth hormone into circulation. Because release follows a pulsatile pattern, studies often report peak concentration and total area under the curve rather than a single time point. Selectivity for this receptor is the property most frequently discussed in comparative work.
Compared with older secretagogues such as hexarelin or GHRP-6, ipamorelin shows weaker stimulation of cortisol, prolactin, and appetite in the animal models used for early characterization. Whether that selectivity is preserved across longer human exposures remains an open question, because published clinical data are limited in size and duration. Reported effects on food intake are generally described as modest. The compound is therefore treated in the literature as a relatively selective research tool rather than a fully characterized therapeutic agent.
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.
Lyophilized ipamorelin is generally held at minus twenty degrees Celsius or colder, protected from light and moisture. In solution the peptide is less stable, and degradation proceeds through hydrolysis of the amide backbone, oxidation of the histidine residue, and aggregation. Repeated freeze-thaw cycles accelerate these processes, so dividing material into single-use aliquots before freezing is common practice in research settings. Buffered formulations near neutral pH tend to show the slowest degradation, while strongly acidic or basic conditions raise hydrolysis rates. Stability data specific to ipamorelin are sparse, and much guidance is extrapolated from other short peptides.
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.
C-reactive protein (CRP), a marker of systemic inflammation, is also increased in obstructive sleep apnea (OSA). CRP and interleukin-6 (IL-6) levels were significantly higher in patients with OSA compared to obese control subjects. Patients with OSA have higher plasma CRP concentrations that increased corresponding to the severity of their apnea-hypopnea index score. Treatment of OSA with CPAP (continuous positive airway pressure) significantly alleviated the effect of OSA on CRP and IL-6 levels.
From the 17th century, and before modern developments in organic chemistry nomenclature, acetone was given many different names. They included "spirit of Saturn", which was given when it was thought to be a compound of lead and, later, "pyro-acetic spirit" and "pyro-acetic ester". Prior to the name "acetone" being coined by French chemists, it was named "mesit" (from the Greek μεσίτης, meaning mediator) by Carl Reichenbach, who also said that methyl alcohol consisted of mesit and ethyl alcohol. Names derived from mesit include mesitylene and mesityl oxide which were first synthesised from acetone. In 1839, the name "acetone" began to be used, because it was obtained from acetic acid. Unlike many compounds with the acet- prefix which have a 2-carbon chain, acetone has a 3-carbon chain. That has caused confusion because there can not be a ketone with 2 carbons. The prefix refers to acetone's relation to vinegar (acetum in Latin, also the source of the words "acid" and "acetic"), rather than its chemical structure.
With ring-opening polymerization, automated synthesis has been used for rapid screening and optimization, including with catalyst + initiator systems and their polymerization conditions. For example, Hoogenboom et al. determined the optimal temperature for the polymerization of 2-ethyl-2-oxazoline in dimethylacetamide (DMAc), allowing for individual heating of the parallel reactors, which shortened the time needed for preparation and analysis. To aid with the catalyst research for polyolefins, Symyx Technologies Inc. used automated synthesis to create a library of palladium and nickel catalysts, which were screened for ethylene polymerization. This process found that the largest polyethylene polymers were created by the complexes with the highest steric hindrance for the ortho-positions of the aryl rings, while electronic factors did not influence yield or molecular weight. In addition, Tuchbreiter and Mülhaupt used automated synthesis to demonstrate the improvements of minireactors for the polymerization of olefins, with quality improving as compared to utilizing simple arrays.
The SBP-Tag will also bind to streptavidin or streptavidin reagents in solution. Applications of these engineered associations include the visualization of specific proteins within living cells, monitoring of the kinetics of the translation of individual proteins in an in vitro translation system, control of the integration of a multi-spanning membrane protein into the endoplasmic reticulum by fusing the SBP-Tag to the N-terminal translocation sequence and then halting integration with streptavidin and restarting integration with biotin. Fluorescent streptavidin reagents (e.g. streptavidin-HRP) can be used to visualize the SBP-tag by immunoblotting of SDS-PAGE. Additionally, antibodies to the SBP-tag are available commercially. The SBP-Tag has been used to reversibly immobilize recombinant proteins onto streptavidin-functionalized surfaces thereby permitting interaction assessment such as by surface plasmon resonance (SPR) techniques with re-use of the functionalized surface. SPR has also been used to compare the SBP-Tag with other streptavidin-binding peptides such as Strep-tag.
Sources: en.wikipedia.org
The C-terminal domain of ADP-ribose diphosphatase contains the Nudix sequence, a highly conserved amino acid sequence that is found in over 450 putative proteins in about 90 different species. A part of this sequence known as the Nudix fold is the catalytic part of the sequence. It is a structurally conserved loop-helix-loop motif that creates a scaffold for metal binding and pyrophosphatase chemistry in the enzyme. ADP-ribose hydrolases in general act as protective agents against excessive intracellular accumulation of ADP-ribose, as high intracellular levels of ADP-ribose can be damaging to the cell. ADP-ribose diphosphatase, in particular, hydrolyzes ADP-ribose into AMP and D-ribose 5-phosphate, both of which are intermediates of central metabolic pathways and therefore are easily reused. Other common names for ADP-ribose diphosphatase include ADP-ribose pyrophosphatase and ADPRase. ADP-ribose is commonly referred to as ADPR.
In response to a stimulus, GPCRs activate heterotrimeric G proteins. In order to turn off this response, or adapt to a persistent stimulus, active receptors need to be desensitized. The first step in desensitization is phosphorylation of the receptor by a class of serine/threonine kinases called G protein coupled receptor kinases (GRKs). GRK phosphorylation specifically prepares the activated receptor for arrestin binding. Arrestin binding to the receptor blocks further G protein-mediated signaling and targets receptors for internalization, and redirects signaling to alternative G protein-independent pathways, such as β-arrestin signaling. In addition to GPCRs, arrestins bind to other classes of cell surface receptors and a variety of other signaling proteins. Mammals express four arrestin subtypes and each arrestin subtype is known by multiple aliases. The systematic arrestin name (1–4) plus the most widely used aliases for each arrestin subtype are listed in bold below:
The presence of autoantibodies against citrullinated proteins in rheumatoid arthritis patients was first described in the mid-1970s when the biochemical basis of antibody reactivity against keratin and filaggrin was investigated. Subsequent studies demonstrated that autoantibodies from RA patients react with a series of different citrullinated antigens, including fibrinogen, deiminated Epstein–Barr virus nuclear antigen 1 and vimentin, which is a member of the intermediate filament family of proteins. Several assays for detecting ACPAs were developed in the following years, employing mutated citrullinated Vimentin (MCV-assay), filaggrin-derived peptides (CCP-assay) and viral citrullinated peptides (VCP-assay). A 2006 clinical study showed that anti viral citrullinated peptide (VCP) antibodies of the IgG and IgA isotypes represent a discriminating specific marker of rheumatoid arthritis from other chronic arthritides and disease controls, suggesting an independent production of each isotype. In 2010, ACPA testing has become substantial part of The 2010 ACR-EULAR classification criteria for rheumatoid arthritis.
Sources: en.wikipedia.org
An automated synthesis is very similar in procedure to performing a manual synthesis. The overseeing chemist decides on a target molecule then formulates the experimental plan, which is a sequential series of steps. Then, they collect the required equipment and execute the plan. The automated synthesis follows the same pathway, except that the computer devises and executes the experimental plan. However, human revision is usually still required to ensure the automated route is practical and there are no implicit steps or conditions missing from the proposed procedure. In organic synthesis, organic synthesis software is used to automate the process of identifying sequences of reactions or routes that can be used to synthesize organic compounds.
Human chorionic gonadotropin can be used as a tumor marker, as its β subunit is secreted by some cancers including seminoma, choriocarcinoma, teratoma with elements of choriocarcinoma, other germ cell tumors, hydatidiform mole, and islet cell tumor. For this reason, a positive result in males can be a test for testicular cancer. The normal range for men is between 0-5 mIU/mL. Combined with alpha-fetoprotein, β-HCG is an excellent tumor marker for the monitoring of germ cell tumors.
Erythromycin, Mitemcinal and related antibiotics act as non-peptide motilin agonists, and are sometimes used for their ability to stimulate gastrointestinal motility. In the case of erythromycin, it is its hemiketal intermediate, formed after an oral dose in the low-pH environment of the stomach lumen, which directly acts on the motilin receptor. Administration of a low dose of erythromycin will induce peristalsis, which provides additional support for the conclusion that motilin secretion triggers this pattern of gastrointestinal motility, rather than results from it. However, some of erythromycin's properties, including antibiotic activity, are not appropriate for a drug designed for chronic use over a patient's lifetime. New motilin agonists are erythromycin-based; however, it may be that this class of drugs becomes redundant. Growth hormone secretagogue receptors share 52% of their DNA with motilin receptors, and agonists of these receptors, termed ghrelins, can bring about similar effects to motilin agonists. Camicinal is a motilin agonist under development. Xylitol ingestion also increases motilin secretion, which may be related to xylitol's ability to cause diarrhea.
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。