This is a working overview of pentapeptide, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-06-03 and is reviewed periodically as new material appears.
杂质谱一般包含缺失序列片段、差向异构体、氧化产物以及残留溶剂或反离子，其中组氨酸与芳香残基的氧化常被重点关注。反相色谱中这类杂质往往紧邻主峰洗脱，因此方法需要足够的分离度并经过系统适用性验证。纯度百分比的解读依赖于检测波长与梯度条件，不同实验室公布的数字不宜直接横向比较。参考标准品有助于跨批次对照，但其自身赋值同样需要可追溯来源。
冻干状态下的肽通常比溶液状态更稳定，常规做法是维持 -20 °C 或更低温度、保持干燥并避开强光。复溶后的降解主要来自水解、氧化与脱酰胺，速率受 pH、缓冲液种类、离子强度与温度共同影响，碱性条件一般会加快这些反应。反复冻融会造成聚集与容器吸附损失，分装保存能降低该风险。容器材质与金属离子也可能参与氧化过程，需与操作条件一并考虑。
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.
| Property | Value | Notes |
|---|---|---|
| 纯度检测 | RP-HPLC，214 nm | 乙腈/水梯度，含 0.1% 三氟乙酸 |
| 身份确认 | ESI-MS 或 LC-MS/MS | 比对实测与理论分子量 |
| 冻干粉储存 | -20 °C，干燥避光 | 分装可减少开盖次数 |
| 复溶液储存 | 2-8 °C，短期使用 | 避免反复冻融与长时间室温放置 |
| 主要降解途径 | 水解、氧化、脱酰胺 | 碱性 pH 与强光会加快反应 |
Ipamorelin is a synthetic pentapeptide that belongs to the growth hormone secretagogue class. It acts as an agonist at the ghrelin receptor, also called the growth hormone secretagogue receptor type 1a. The compound was designed in the 1990s during a search for agents that release growth hormone with fewer off-target hormonal effects than earlier secretagogues. It appears in the research literature under several sequence-based names. Material supplied for laboratory work is normally a lyophilized solid, and it is not marketed as an approved therapeutic in major jurisdictions.
The molecule contains five residues, including alpha-aminoisobutyric acid, D-2-naphthylalanine, and D-phenylalanine, and it ends in a lysine amide. Non-natural and D-configured residues make the chain less susceptible to common peptidases, which helps explain its resistance to rapid breakdown. Its molecular formula is C38H49N9O5, corresponding to a free-base mass near 711.9 daltons. The C-terminal amide removes a negative charge and is a recurring feature in receptor-active peptides of this family. These structural choices are usually discussed as the basis for its selectivity profile.
At the molecular level, ipamorelin acts as an agonist at the growth hormone secretagogue receptor, also called the ghrelin receptor or GHS-R1a. Binding to this receptor on pituitary somatotroph cells triggers a signaling cascade that leads to growth hormone release. The effect is mediated through phospholipase C and calcium mobilization rather than through the cyclic AMP pathway used by growth hormone releasing hormone. The two pathways are complementary, and combined stimulation produces a larger response than either alone.
Compared with other secretagogues such as GHRP-2, GHRP-6, and hexarelin, ipamorelin is described as more selective. Published animal work reports little or no increase in adrenocorticotropic hormone, cortisol, or prolactin at doses that release growth hormone. This selectivity is the property most often cited in the research literature. Whether the same profile holds across species and dosing schedules remains an open question, since human data are limited and come largely from small studies.
Ipamorelin is a synthetic pentapeptide that belongs to the growth hormone secretagogue family. Its sequence is Aib-His-D-2-Nal-D-Phe-Lys-NH2, and its molecular mass is approximately 711.9 daltons. The compound was described in the late 1990s by researchers seeking molecules that release growth hormone with fewer side effects than earlier secretagogues. It is a laboratory and research compound, not an approved medicine in most jurisdictions.
In September 2015, the FDA issued a warning related to canagliflozin (Invokana) and canagliflozin/metformin (Invokamet) due to decreased bone mineral density and therefore increased risk of bone fractures. Using gliflozins in combination therapy with metformin can lower the risk of hypoglycemia compared to other type 2 diabetes treatments such as sulfonylureas and insulin. Increased risk of lower limb amputation is associated with canagliflozin, but further data is needed to confirm this risk associated with different gliflozins. A European Medicines Agency review concluded that there is a potential increased risk of lower limb amputation (mostly affecting the toes) in people taking canagliflozin, dapagliflozin and empagliflozin. In August 2018, the FDA issued a warning of an increased risk of Fournier gangrene in patients using SGLT2 inhibitors. The absolute risk is considered very low. In the FDA Adverse Event Reporting System an increase was reported in events of acute kidney injury associated with SGLT2 inhibitors, though data from clinical trials actually showed a reduction in such events with SGLT-2 treatment.
== Transportation units == Prior to the 2018 reforms, the People's Armed Police Transportation Corps (Chinese: 武警交通部队) was its own independent corps under the dual command of the PAP and the Ministry of Transport. During the 2018 reforms, the Transportation Corps was reorganised into part of the 1st and 2nd mobile corps. The mission of Transport units of the People's Armed Police is to conduct disaster relief and emergency repair on highways, bridges, tunnels, seaports railways and airports, security to construction projects related to national security along with law enforcement duties on highways in border regions.
In the United Kingdom clinical pharmacists are given independent prescriptive authority. Basic components of clinical pharmacy practice include prescribing drugs, administering drugs, monitoring prescriptions, managing drug use, and counselling patients.
==== Peptides ==== Prebiotic peptide synthesis could have occurred by several routes. Some center on high temperature/concentration conditions in which condensation becomes energetically favorable, while others use plausible prebiotic condensing agents. Experimental evidence for the formation of peptides in uniquely concentrated environments is bolstered by work suggesting that wet-dry cycles and the presence of specific salts can greatly increase spontaneous condensation of glycine into poly-glycine chains. Other work suggests that while mineral surfaces, such as those of pyrite, calcite, and rutile catalyze peptide condensation, they also catalyze their hydrolysis. The authors suggest that additional chemical activation or coupling would be necessary to produce peptides at sufficient concentrations. Thus, mineral surface catalysis, while important, is not sufficient alone for peptide synthesis. Many prebiotically plausible condensing/activating agents have been identified, including the following: cyanamide, dicyanamide, dicyandiamide, diaminomaleonitrile, urea, trimetaphosphate, NaCl, CuCl2, (Ni,Fe)S, CO, carbonyl sulfide (COS), carbon disulfide (CS2), SO2, and diammonium phosphate (DAP). A 2024 experiment used a sapphire substrate with a web of thin cracks under a heat flow, mimicking deep-ocean vents, to concentrate prebiotically relevant building blocks from a dilute mixture by up to three orders of magnitude. This could help to create biopolymers such as peptides.
== Clinical research == The feasibility of using recombinant human tropoelastin to promote elastin-fibre production and improve skin flexibility in wounds and scars has been studied. Although new elastin fibres were observed following the administration of recombinant human tropoelastin into fresh wounds, the treatment did not result in significant improvements in scar appearance or flexibility. Another line of research has investigated stimulation of endogenous elastin production in the skin. In an in vitro study, an amino acid–copper mixture increased elastin- and type I collagen-related gene expression and protein production in cultured human dermal fibroblasts compared with copper or the amino acid mixture alone. A subsequent open-label, single-centre clinical study evaluated a skin-booster formulation containing amino acids, copper sulfate and non-cross-linked hyaluronic acid, marketed as Elastic Lab. Five participants received four facial treatments at one-week intervals, and the outcomes were assessed one week after the final treatment. Instrumentally measured skin elasticity increased by 23.4% from baseline, while skin thickness and density increased by 7.3% and 12.5%, respectively. Improvements in skin hydration and periocular wrinkle depth were also reported. The study did not directly measure newly synthesised or deposited elastin fibres.
Sources: en.wikipedia.org
Israelite presence in Canaan was also established before Joshua's conquests according to a few biblical traditions. The history of the Israelite people can be divided into these categories, according to the Hebrew Bible:
== Drug target and mechanism of action == Keratinocyte growth factor (KGF) resides in the family of fibroblast growth factor (FGF). The drug's target is the KGF receptor. Through the binding of this drug to the aforementioned receptor, Palifermin stimulates epithelial cell proliferation, differentiation, and upregulation of cytoprotective mechanisms to reduce the symptoms of oral mucositis.
During HLF, koji-infused soybeans are exposed to air so that hydrolytic enzymes of the mold can continuously break down macronutrients within the soybean. Ample water, usually about 2 to 2.5 times the weight of the feed, is required to support sufficient microbial growth. High salt concentration (17–20%) is required to selectively inhibit microbial activity. HLF is generally carried out at 15–30 °C (59–86 °F), and requires a long ageing period, usually from 90 to 180 days. In the aging period, constant stirring of moromi (a mash/mixture of wheat (optionally), salt, soy beans, water, and fermenting yeast) is required for distributing nutrients, as well as flavoring compounds evenly. In some cases, moromi is exposed to direct sunlight to facilitate the decomposition of macronutrients. Due to the high salinity of HLF moromi, only anaerobic halophiles can survive in the medium. Also, the 15–30 °C (59–86 °F) temperature range allows only the growth of mesophiles. Similar to the fermentation of pickles, the primary lactic acid fermentation of sugars by halophiles reduces the pH of moromi down to acidic range. Low pH further limits the growth of undesirable microbes, but favors the growth of fermentative yeast which contributes to secondary fermentation that generates various flavoring compounds and odorants.
Sofer, G.; Hagel, L. (1997). Handbook of Process Chromatography: A guide to Optimization, Scale-up, and Validation. Academic Press, 158-161. ISBN 0-12-654266-X Tours, N. and Sandle, T. Comparison of dry-heat depyrogenation using three different types of Gram-negative bacterial endotoxin, European Journal of Parenteral and Pharmaceutical Sciences, Volume 13, No.1, 2008, pp. 17–20
All lepidosaurs and turtles have a three-chambered heart consisting of two atria, one variably partitioned ventricle, and two aortas that lead to the systemic circulation. The degree of mixing of oxygenated and deoxygenated blood in the three-chambered heart varies depending on the species and physiological state. Under different conditions, deoxygenated blood can be shunted back to the body or oxygenated blood can be shunted back to the lungs. This variation in blood flow has been hypothesized to allow more effective thermoregulation and longer diving times for aquatic species, but has not been shown to be a fitness advantage.
Sources: en.wikipedia.org
An article he read about the pancreas piqued Banting's interest in diabetes. Banting had to give a talk on the pancreas to one of his classes at the University of Western Ontario on November 1, 1920, and he was therefore reading reports that other scientists had written. Research by Naunyn, Minkowski, Opie, Sharpey-Schafer, and others suggested that diabetes resulted from a lack of a protein hormone secreted by the islets of Langerhans in the pancreas. Schafer had named this putative hormone "insulin". The hormone was thought to control the metabolism of sugar; its lack led to an increase of sugar in the blood which was then excreted in urine. Attempts to extract insulin from ground-up pancreas cells were unsuccessful, likely because of the destruction of the insulin by the proteolysis enzyme of the pancreas. The challenge was to find a way to extract insulin from the pancreas prior to its destruction. Moses Barron published an article in 1920 which described experimental closure of the pancreatic duct by ligature; this further influenced Banting's thinking. The procedure caused deterioration of the cells of the pancreas that secrete trypsin which breaks down insulin, but it left the islets of Langerhans intact. Banting realized that this procedure would destroy the trypsin-secreting cells but not the insulin. Once the trypsin-secreting cells had died, insulin could be extracted from the islets of Langerhans. Banting discussed this approach with John Macleod, professor of physiology at the University of Toronto.
Dehydroepiandrosterone (DHEA), also known as androstenolone, is an endogenous steroid hormone precursor. It is one of the most abundant circulating steroids in humans. DHEA is produced in the adrenal glands, the gonads, and the brain. It functions as a metabolic intermediate in the biosynthesis of the androgen and estrogen sex steroids both in the gonads and in various other tissues. However, DHEA also has a variety of potential biological effects in its own right, binding to an array of nuclear and cell surface receptors, and acting as a neurosteroid and modulator of neurotrophic factor receptors. In the United States, DHEA is sold as an over-the-counter supplement, and medication called prasterone.
is the mean square radius of branched and linear macromolecules with identical molar masses. By utilizing MALS in conjunction with a concentration detector as described above, one create a log-log plot of the root-mean-square radius vs molar mass. The slope of this plot yields the branching ratio, g. In addition to branching, the log-log plot of size vs. molar mass indicates the shape or conformation of a macromolecule. An increase in the slope of the plot indicates a variation in conformation of a polymer from spherical to random coil to linear. Combining the mean-square radius from MALS with the hydrodynamic radius
== History == During the mid 20th century, the question "can machines think?" became intriguing and popular among scientists, primarily to add humanistic characteristics to machine behavior. John McCarthy, who was one of the prime researchers of this field, termed this concept of machine intelligence as "artificial intelligence" (AI) during the Dartmouth summer in 1956. AI is usually defined as the capacity of a machine to perform operations that are analogous to human cognitive capabilities. Much research to create AI was done during the 20th century. Also around the mid 20th century, science, especially biology, faced a fast-increasing need to develop a "man-computer symbiosis", to aid scientists in solving problems. For example, the structural analysis of myoglobin, hemoglobin, and other proteins relentlessly needed instrumentation development due to its complexity. In the early 1960s, Joshua Lederberg started working with computers and quickly became tremendously interested in creating interactive computers to help him in his exobiology research. Specifically, he was interested in designing computing systems to help him study alien organic compounds. Lederberg had been heading a team designing instruments for the Mars Viking lander to search for precursor molecules of life in samples of the Mars surface, using a mass spectrometer coupled with a minicomputer.
Sources: en.wikipedia.org
肽键在 214 nm 附近有较强吸收，适合检测缺少芳香侧链的短肽。该波长的基线受流动相组成与梯度影响较大。因此流动相与梯度条件需要固定并完整记录。
仅凭保留时间不足以定性，通常需要质谱给出与理论值一致的分子量。进一步可用碎裂谱与参考谱比对。保留时间、分子量与碎裂谱三者吻合时，身份判断较为可靠。
这取决于缓冲液、pH、温度与微生物负荷，并不存在通用时限。常见做法是分装冷冻并尽量缩短室温放置时间。出现浑浊或沉淀时应弃用并重新配制。
碱性 pH、较高温度、强光照射与反复冻融都会加快水解、氧化或脱酰胺。溶液中的金属离子也可能催化氧化。控制这些变量比单纯降低浓度更有效。