A practical reference on Reference standard: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-06-07 and is reviewed periodically as new material appears.
Both receptors are class B G protein-coupled receptors that signal largely through Gs-mediated cyclic AMP production. Activation within pancreatic islets increases glucose-dependent insulin secretion and suppresses glucagon release when glucose is elevated. Outside the pancreas, signaling in the central nervous system and gut appears to influence appetite and gastric emptying. The relative contribution of each receptor to observed clinical effects remains under investigation, and the two pathways are not simply additive in practice.
Reported outcomes in large trials include dose-dependent weight reduction and improvements in glycemic markers over periods ranging from several months to more than a year. Whether the compound alters long-term cardiovascular or renal outcomes is being examined in dedicated outcome studies, so those questions remain open. Labeling describes gastrointestinal effects such as nausea and diarrhea, which tend to appear during dose escalation. Discontinuation rates and the durability of effects after treatment stops vary across study populations and are still debated.
Tirzepatide is a synthetic peptide developed as a dual agonist at the glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 receptors. Its structure is built on a GIP-derived backbone with non-natural amino acid substitutions and a fatty diacid side chain that promotes albumin binding and slows clearance. That modification supports once-weekly subcutaneous dosing. Registrational trial programs reported reductions in body weight and glycated hemoglobin alongside the drug's glycemic effects.
Tirzepatide is a synthetic peptide built from thirty-nine amino acids. Its sequence is derived from native glucose-dependent insulinotropic polypeptide, or GIP, with several non-natural residues and a fatty diacid side chain attached through a linker. The molecule behaves as a dual agonist at two incretin receptors, GIP and GLP-1, instead of targeting a single receptor. This dual engagement separates it from earlier single-receptor incretin compounds and underpins most of its reported pharmacological activity.
At the receptor level, the compound binds both GIP and GLP-1 receptors and triggers downstream signalling that raises cyclic AMP in target cells. GLP-1 receptor activation is associated with glucose-dependent insulin release, slower gastric emptying, and reduced appetite signalling. GIP receptor activation contributes effects that are less completely characterised, and how much each receptor adds to the overall clinical response is still an open question. The two pathways appear to interact in a complementary rather than a purely additive way.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic 39-residue peptide | GIP-derived backbone with non-natural residues |
| Molar mass | Approximately 4.8 kDa | Peptide chain plus linker and lipid modifications |
| Appearance | White to off-white powder | Typical of lyophilized research material |
| Solubility | Soluble in water and aqueous buffer | Practically insoluble in nonpolar solvents |
| Storage temperature | Typically −20 °C for dry powder | Solutions usually held at 2–8 °C short term |
脂肪酸侧链的存在使该肽与血浆白蛋白结合能力增强，从而延长循环半衰期，支持每周一次给药的用药间隔。白蛋白结合同时改变组织分布特征，减慢肾脏清除速度。该设计思路在多种长效肽类药物中被反复采用，属于既定的药代动力学策略。
该化合物的名称与结构由国际非专利名称体系统一维持，不同文献中出现的同义写法主要在拼写顺序或盐形式描述上不同。研究者通常通过受体结合实验、细胞内环磷酸腺苷积累测定以及动物模型来确认其双激动活性。相当一部分分子层面的细节——例如两条受体通路之间的信号交叉作用——尚处于开放问题状态。
当前公开资料把 tirzepatide 归为肠促胰素类受体双重激动剂。它并非激素天然变体，而是经过序列改造的工程化肽。其分子量、等电点与疏水性等基础参数已在药典和化学数据库中收录，可作为分析检测和质量研究的参照。
Development of tirzepatide took place under a research program that sought to test whether simultaneous engagement of two incretin receptors would produce greater metabolic effects than single-receptor agonism. Clinical trials were organized into the SURPASS series for type 2 diabetes and the SURMOUNT series for obesity and weight management. Regulatory clearance for type 2 diabetes came in 2022 in the United States, followed by approval for chronic weight management in 2023. The trial programs reported reductions in glycated hemoglobin and body weight relative to comparators, though long-term cardiovascular and durability data continue to accumulate.
The peptide backbone contains 39 amino acids and includes alpha-aminoisobutyric acid residues, which are not among the standard proteinogenic set. A C20 fatty diacid moiety is attached through a linker, allowing the compound to bind serum albumin and extend its circulation time. This albumin binding is the main reason the molecule supports once-weekly administration rather than more frequent dosing. The measured molecular mass is approximately 4,813 daltons, placing it firmly in the peptide rather than small-molecule class.
Solid tirzepatide is handled as a lyophilised, hygroscopic peptide powder that should be kept desiccated, protected from light, and stored frozen, typically at or below minus twenty degrees Celsius for long-term retention. Material left at ambient temperature for extended periods can take up moisture, which promotes aggregation and deamidation. Commercial liquid presentations are kept refrigerated between two and eight degrees Celsius and are not frozen. Reconstituted laboratory solutions are generally held cold and used within a short window because hydrolysis and oxidation continue slowly in solution.
Identity and purity are usually established with reversed-phase high-performance liquid chromatography for the main peak and with mass spectrometry for the observed molecular mass. Peptide mapping after enzymatic digestion confirms the primary sequence, while amino acid analysis provides a quantitative composition check. Size-exclusion chromatography and ion-exchange chromatography are used to look for aggregates and charge variants. Water content, residual solvents, and counter-ion content are measured separately, since a lyophilised powder is often reported on an as-is basis unless a correction is applied.
Research-grade material circulates through suppliers that differ widely in documentation and testing practice, so a certificate of analysis is a starting point rather than proof of quality. Independent verification typically repeats chromatographic purity and mass confirmation on the received lot, and compares results against a retained reference standard. Regulatory status varies by jurisdiction, and a substance cleared as a medicine is not interchangeable with a research chemical of the same name. Open questions include how closely non-pharmaceutical lots match approved material in impurity profile and in aggregate content.
As a peptide, tirzepatide is handled as a lyophilised solid in research settings and as a preserved solution in finished products. Aqueous solubility is pH dependent and reaches a minimum near the isoelectric point, which lies close to pH 5.4. Stock solutions are typically prepared in neutral or slightly basic buffer to limit precipitation. The solid is hygroscopic and should be equilibrated to room temperature before opening so that condensation does not form on the powder surface.
Recommended storage for reference material is a freezer at approximately -20 degrees Celsius, protected from light and moisture. Commercial injectable presentations are stored refrigerated between 2 and 8 degrees Celsius and must not be frozen. Product labelling generally permits a limited period at controlled room temperature once dispensed, with the exact window depending on the presentation. Repeated temperature cycling is avoided because it can promote aggregation or deamidation of the peptide chain.
Identity and purity are assessed by reversed-phase high-performance liquid chromatography, with mass confirmation by electrospray ionisation mass spectrometry. Peptide mapping after enzymatic digestion verifies the primary sequence. Size-exclusion chromatography quantifies aggregates, while circular dichroism provides a secondary-structure fingerprint. Bioanalytical quantification in plasma uses immunoassay or LC-MS/MS. Reported purity for research-grade lots is commonly 95 percent or higher, and residual water content is checked by Karl Fischer titration.
As of 2024, it is unclear whether (S)-tetrahydropapaverine derives from (S)-reticuline or (S)-coclaurine: the difference is whether the piperidine nitrogen atom is methylated at any point during the biosynthetic sequence.
=== 1950 === January 5: The UK recognizes the People's Republic of China. The Republic of China severs diplomatic relations with the United Kingdom. January 13: Because of the failure to replace Taiwan with the People's Republic of China in the United Nations Security Council the Soviet Union boycotts the United Nations by having their diplomat Yakov Malik not attend any United Nations Security Council meetings. January 18: China officially recognizes the Democratic Republic of Vietnam. January 21: The last Kuomintang soldiers surrender on continental China. January 31: President Truman announces the beginning of the development of a hydrogen bomb. February 3: Soviet Union establishes diplomatic relations with Indonesia through an exchange of telegrams between Indonesian Vice-president, Mohammad Hatta and Soviet Foreign Minister Andrey Vyshinsky. February 7: The UK and the US recognize the State of Vietnam. February 9: Senator Joseph McCarthy first claims without evidence that Communists have infiltrated the U.S. State Department, leading to a controversial series of anti-Communist investigations in the United States. February 12: The Soviet Union and the People's Republic of China sign a pact of mutual defense. March 11: Kuomintang leader Chiang Kai-shek moves his capital to Taipei, Taiwan, establishing a stand-off with the People's Republic of China. April 7: United States State Department Director of Policy Planning Paul Nitze issues NSC 68, a classified report, arguing for the adoption of containment as the cornerstone of United States foreign policy.
Frequently, neighborhood associations relied on restrictive covenants to mandate legal barriers to black homeownership in middle-class neighborhoods to avoid the radical disinvestment that would stem from a racially integrated neighborhood. During the legality of restrictive covenants, these deed restrictions were explicitly racist and took the form of; "people of color can't purchase this home", or only for the "Caucasian race". By leveraging the legally discriminatory capacity of restrictive covenants, neighborhood associations prioritized the stability of homeownership through the preservation of neighborhood investment and relatively high single-family home values. The homogenization of the economic and social fabric of middle-class neighborhoods reflected the white-afflicted segregation of Black Detroiters that confined these residents to Detroit's oldest and worst housing stock. However, in the midst of a mid-twentieth century movement for civil rights reform, certain hallmark legal cases of discrimination in housing such as Shelley vs Kraemer deemed restrictive covenants unconstitutional. Upon this Supreme Court ruling, neighborhood associations were forced to change their restrictive zoning regulations as black Detroiters began moving out of the dilapidated Detroit ghetto and sought residency in middle-class neighborhoods. Therefore, the repealing of restrictive covenants resulted in neighborhood associations relying on extralegal subversions of restrictive covenants to alternatively stunt black residential integration.
Sources: en.wikipedia.org
Although the number of births to foreign-born Hispanic women fell from 58% in 2000 to 50% in 2018, the share of births due to U.S.-born Hispanic women increased from 20% in 2000 to 24% in 2018. The number of births to foreign-born Asian women rose from 19% in 2000 to 24% in 2018 while that due to U.S.-born Asian women went from 1% in 2000 to 2% in 2018. In all, between 2000 and 2017, more births were to foreign-born than U.S.-born women.Members of Generation Z are slightly less likely to be foreign-born than Millennials; the fact that more American Latinos are born in the U.S. rather than abroad plays a role in making the first wave of Generation Z appear better educated than their predecessors. However, researchers note that this trend could be altered by changing immigration patterns and the younger members of Generation Z choosing alternate educational paths. 29% of Generation Z are children of immigrants or immigrants themselves, compared to 23% of Millennials when they were at the same age. As of 2019, 13.7% of the U.S. population is foreign-born, compared to 9.7% in 1997, when the first members of Generation Z had their birth cries. For this cohort, the number of people born in the United States reached a peak of 4.3 million in 2007. Not only are Americans becoming more and more racially diverse, but racial minorities are also becoming more geographically dispersed than ever before, as new immigrants settle in places other than the large metropolitan areas historically populated by migrants, such as New York City, Los Angeles, and San Francisco.
== Veterinary use == Hydrocodone is predominantly used as an antitussive in dogs. Hydrocodone has low oral bioavailability and provide poor analgesia in cats and dogs. One study in dogs found hydrocodone to be less effective than firocoxib for dogs undergoing a tibial-plateau-levelling osteotomy.
If a designer is interested only in the best sequence, the protein design algorithm only requires the lowest-energy conformation of the lowest-energy sequence. In these cases, the amino acid identity of each rotamer can be ignored and all rotamers belonging to different amino acids can be treated the same. Let ri be a rotamer at residue position i in the protein chain, and E(ri) the potential energy between the internal atoms of the rotamer. Let E(ri, rj) be the potential energy between ri and rotamer rj at residue position j. Then, we define the optimization problem as one of finding the conformation of minimum energy (ET):
Sources: en.wikipedia.org
The effect of botulinum toxin type-A on reducing and eliminating forehead wrinkles was first described and published by Richard Clark, MD, a plastic surgeon from Sacramento, California. In 1987 Clark was challenged with eliminating the disfigurement caused by only the right side of the forehead muscles functioning after the left side of the forehead was paralyzed during a facelift procedure. This patient had desired to look better from her facelift, but was experiencing bizarre unilateral right forehead eyebrow elevation while the left eyebrow drooped, and she constantly demonstrated deep expressive right forehead wrinkles while the left side was perfectly smooth due to the paralysis. Clark was aware that botulinum toxin was safely being used to treat babies with strabismus and he requested and was granted FDA approval to experiment with botulinum toxin to paralyze the moving and wrinkling normal functioning right forehead muscles to make both sides of the forehead appear the same. This study and case report of the cosmetic use of botulinum toxin to treat a cosmetic complication of a cosmetic surgery was the first report on the specific treatment of wrinkles and was published in the journal Plastic and Reconstructive Surgery in 1989. Editors of the journal of the American Society of Plastic Surgeons have clearly stated "the first described use of the toxin in aesthetic circumstances was by Clark and Berris in 1989." J. D. and J. A.
1994: Ong Yeow Tian, a Singaporean hairstylist who was hanged on 25 November 1994 for murdering a police officer and shooting two other cops in 1989. 1995: Ng Theng Shuang, a Malaysian national, hanged on 14 July 1995 for discharging a firearm with intent to cause injury, after shooting 3 people during the attempted robbery of Tin Sing Goldsmiths in South Bridge Road in 1992. 1997: Lim Chwee Soon, hanged on 25 July 1997 for discharging a firearm seven times during the robbery of the Kee Hing Hung Rolex boutique at the People's Park Complex in 1995. 2001: Tay Chin Wah, a Singaporean taxi driver, was arrested for an unsolved 1995 case of shooting two men. He was sentenced to death on 21 February 2001, and hanged on 26 October 2001. 2006: Khor Kok Soon, one of Singapore's top ten fugitives, was charged in 2004 for firing a gun at 43-year-old police sergeant Lim Kiah Chin (who escaped unharmed) in 1984. He was sentenced to death in February 2005, and eventually hanged. Khor was also alleged to have killed 25-year-old truck driver Ong King Hock. 2006: Lim Thian Lai, a Singaporean gunman who was caught in 2004 for murdering an illegal moneylender Tan Tiong Huat back in 1997. Lim was found guilty of discharging a firearm and killing Tan by shooting, and sentenced to death in May 2005. He lost his appeal in September 2005 and had since been hanged. 2009: Tan Chor Jin, alias Tony Kia, nicknamed the "One-eyed Dragon" in Singapore media, was executed on 9 January 2009 for illegally discharging a firearm and killing 41-year-old nightclub owner Lim Hock Soon by shooting.
The consulting surgeon on the repeat surgery may not inform the first surgeon of the recurrence. The time it takes for a recurrent tumor to be visible to the patient might be 5 or more years. Quoted "cure" rates must be looked upon with the understanding that a 5-year cure rate might not necessarily be correct. As basal-cell carcinoma is a very slowly progressing tumor, a 5-year no recurrence rate might not be adequate. A longer follow-up might be needed to detect a slow-growing tumor left in the surgical scar. Poor training of the surgeon/pathologist/histotechnologist. While Mohs surgery is essentially a technical method of tissue handling and processing, the skill and training of the surgeon can greatly affect the outcome. Success requires a foundation of good tissue handling, good surgical skill, and hemostasis, based on the tissue processing and staining technique. A surgeon without a good histotechnologist does not have access to sufficiently high-quality information about the cancer, and a histotechnologist without a good surgeon can not produce quality slides. Originally, surgeons learned the procedure by spending a few hours to several months with Mohs or during their residencies. Today, many Mohs surgeons complete a fellowship after their dermatology residency, spending hundreds of hours observing and performing Mohs surgery under the careful supervision of highly experienced Mohs surgeons. This is the most comprehensive and thorough method of learning Mohs surgery. Others learn the technique in their dermatology residencies and through courses and preceptorships.
The business was founded by Tim Horton, who played in the National Hockey League from 1949 until his death in an auto crash in 1974. The first Tim Horton restaurant was in North Bay, Ontario, and sold hamburgers. The chain's first donut store opened on May 17, 1964, in Hamilton, Ontario, under the name Tim Horton Donuts. The name was later abbreviated to "Tim Horton's" and then changed to "Tim Hortons" without the possessive apostrophe. Soon after Horton opened the store, he met Ron Joyce, a former police constable in Hamilton. In 1965, Joyce took over the fledgling Tim Horton Donut Shop at 65 Ottawa Street North. By 1967, after opening two additional stores, the two became full partners. Upon Horton's death in 1974, Joyce bought out the Horton family's shares for $1 million and took over as sole owner of the existing chain of 40 stores, quickly and aggressively expanding the chain in both geography and product selection. The 500th store opened in 1991. Joyce's aggressive expansion of the business resulted in major changes to the Canadian coffee and donut restaurant market. Many independent donut shops and small chains were driven out of business, while Canada's per-capita ratio of donut shops surpassed that of all other countries. The Horton and Joyce partnership carried on, with the marriage of Joyce's son, Ron Joyce Jr., and Horton's eldest daughter, Jeri-Lynn Horton-Joyce, who were joint owners of Tim Hortons franchises in Cobourg, Ontario, until 2023 when the couple retired after 37 years.
Sources: en.wikipedia.org
It acts as an agonist at both the GIP and GLP-1 receptors, two related class B G protein-coupled receptors. This dual activity distinguishes it from single-receptor GLP-1 agonists. The clinical consequences of engaging both receptors are still being characterized.
It is given by subcutaneous injection, generally on a weekly schedule. Dosing usually begins low and increases in steps to limit gastrointestinal side effects. Formulated product is supplied as a ready-to-use pen or vial in most markets.
No. Receptor engagement is documented, but how central appetite circuits, gut signals, and insulinotropic effects combine is incompletely resolved. Investigators continue to separate GIP-driven from GLP-1-driven contributions in animal and human models.
It acts as a dual agonist at the GIP receptor and the GLP-1 receptor. This broader targeting profile distinguishes it from selective GLP-1 agonists, which engage only one receptor.