If you have been reading about reversed-phase HPLC and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2026-07-16. Numbers and descriptions here follow the published literature rather than marketing material.
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.
The molecule is a synthetic 39-amino-acid peptide whose backbone derives from the sequence of human glucose-dependent insulinotropic polypeptide, with several substitutions that raise metabolic stability and shift receptor preference. A C20 fatty diacid is attached through a short linker to a lysine side chain, a modification that increases binding to serum albumin. The reported monoisotopic mass is approximately 4813 Da. Near neutral pH the peptide carries a net negative charge, and the lipid tail makes the molecule markedly more hydrophobic than the unmodified parent sequence.
Dual agonism at the GIP and GLP-1 receptors underlies the observed pharmacology. Activation of GLP-1 receptors raises glucose-dependent insulin release, lowers glucagon secretion, slows gastric emptying and reduces appetite. GIP receptor activation contributes additional effects on adipose tissue and on energy balance, and the combined action on appetite appears larger than either pathway alone in animal models. Signalling bias and the relative contribution of each receptor arm to weight-related effects remain areas of active investigation.
| Property | Value | Notes |
|---|---|---|
| Appearance | white to off-white powder | Lyophilised solid form |
| Solubility | pH dependent; low near pI | Minimum close to pH 5.4 |
| Storage temperature | -20 C solid; 2-8 C solution | Protect from light |
| Isoelectric point | approx. pH 5.4 | Controls solubility minimum |
| Common analytical method | RP-HPLC with mass detection | Purity and identity checks |
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。
Tirzepatide 是一种由 39 个氨基酸组成的合成肽，分子结构上以 GIP 序列为骨架并引入脂肪酸侧链修饰，使其能够同时与葡萄糖依赖性促胰岛素多肽（GIP）受体和胰高血糖素样肽-1（GLP-1）受体结合。这种双重激动特性使它在同类肽类药物中区别于选择性 GLP-1 受体激动剂。该分子最早由一家制药公司在 2010 年代报道，随后进入糖尿病与体重管理领域的临床研究。
在生理层面，GIP 与 GLP-1 均为肠道内分泌细胞分泌的肠促胰素，进食后参与胰岛素分泌调节与胃排空抑制。Tirzepatide 通过同时激活这两条信号通路，使胰岛素分泌的葡萄糖依赖性增强，并延缓冲胃排空、降低食欲信号。与单一 GLP-1 激动相比，双靶点作用在血糖控制和体重变化上的效应幅度更大，但具体贡献比例仍在研究之中。
Analytical characterization of tirzepatide typically employs reversed-phase high-performance liquid chromatography (RP-HPLC) for purity assessment and peptide mapping. Mass spectrometry, often coupled with electrospray ionization, confirms molecular weight and sequence integrity. Amino acid analysis and capillary electrophoresis may also be used to detect impurities or degradation products. These methods are essential for batch release and stability studies.
Storage recommendations for tirzepatide generally specify refrigeration at 2–8 °C to maintain stability. The peptide should be protected from light and kept in its original packaging to prevent aggregation or adsorption. Freezing is not recommended because freeze-thaw cycles can cause aggregation or precipitation. Once dispensed, storage conditions and in-use periods follow product-specific labeling, which may allow room temperature storage for a limited time.
Degradation pathways for tirzepatide include deamidation, oxidation, and aggregation, which are common for therapeutic peptides. These processes can be monitored by size-exclusion chromatography (SEC) for aggregates and ion-exchange chromatography for charge variants. Forced degradation studies under acidic, basic, oxidative, and thermal stress help identify potential impurities. The exact stability profile depends on formulation, concentration, and container-closure system.
Peptide-based pharmaceutical products such as tirzepatide require controlled temperature management to preserve structural integrity. Manufacturer labeling generally specifies refrigeration at 2 to 8 degrees Celsius before first use, with protection from light and freezing. Exposure to repeated temperature cycling can promote aggregation or deamidation, which alters the analytical profile even when the visible solution appears unchanged. Once a product is in use, the permitted storage window and temperature range are defined by the specific labeled presentation rather than by general peptide rules.
Identity and purity assessment of tirzepatide relies primarily on reversed-phase high-performance liquid chromatography coupled with ultraviolet detection. Mass spectrometry, often in electrospray ionization mode, confirms the molecular mass and detects sequence-related impurities. Peptide mapping after enzymatic digestion provides residue-level confirmation of the backbone. Each method addresses a different question: chromatography for purity and related substances, mass measurement for identity, and mapping for sequence fidelity. No single technique covers all three.
Research and analytical settings increasingly require documentation of peptide origin and chain of custody. Certificate of analysis documents typically report purity by chromatographic area, mass confirmation, appearance, and residual solvent or counterion content. Independent verification by an accredited laboratory is common when a material will be used in a regulated study. Open questions remain about how well compendial methods transfer between laboratories, and about which impurity thresholds are meaningful for materials not intended for clinical use.
=== Evidence === At trial, the prosecution presented evidence from parents, clinicians and expert witnesses. The mother of Baby E testified that she had heard her son cry and found blood around his mouth while Letby was present; Letby attributed the blood to a nasogastric tube. Baby E died later that day. Letby subsequently sent a sympathy card to the family, photographs of which were later found on her phone. The court also heard that she had been advised more than once not to enter a room where bereaved parents were grieving. Prosecutors cited text messages sent by Letby to colleagues, which they said showed inappropriate interest in clinical events. Messages included offers to take additional intensive‑care shifts shortly after deaths or collapses, expressions of frustration when not allocated to intensive‑care rooms, and comments about fate following a series of deaths. The court also heard that Letby had searched for the families of several infants on Facebook, sometimes on anniversaries or significant dates. She told the jury this reflected general curiosity and frequent phone use. Consultants testified that they believed suspicious incidents began after Letby qualified to work in intensive care in 2015 and that the pattern of collapses shifted after she was moved from night to day shifts in 2016. One consultant said he had found Letby standing over a deteriorating infant in February 2016 and believed she had not intervened promptly; the infant survived.
== Stakeholders == Since BDNF is associated with neurodegenerative and psychiatric disorders, multiple groups are affected by its measurement and clinical interpretation. Lower BDNF levels have been found to signify Alzheimer's disease and major depressive disorders. As a result, patients with neurological or mood disorders may be affected by how BDNF is diagnosed, treated, monitored, or rehabilitated. Clinicians, such as neurologists and psychiatrists, have expressed interest in BDNF being a potential biomarker for tracking disease progression and therapeutic response. However, current standard measurement techniques rely mainly on serum or plasma sampling using enzyme-linked immunosorbent assays, commonly known as ELISA. This requires laboratory infrastructure and invasive blood collection, making it a restrictive monitoring process for patients. Due to this, researchers and diagnostic developers have explored alternative detection strategies, including non-invasive sampling methods and biosensor-based platforms. The ultimate goal of these is to improve accessibility and enable longitudinal monitoring of BDNF levels. Broader implementation of reliable BDNF measurement may influence clinical decision-making and public health approaches to neurodegenerative and psychiatric conditions.
=== Discontinued === Acolbifene/prasterone (dehydroepiandrosterone/acolbifene; DHEA/acolbifene; prasterone/acolbifene; Femivia) – combination of acolbifene (selective estrogen receptor modulator (SERM)) and prasterone (dehydroepiandrosterone; DHEA) (androgen, other actions) – decreased libido [68] Alprostadil SEPA (prostaglandin E1 SEPA; alprostadil/soft enhancement of percutaneous absorption; Topiglan) – prostaglandin E1 (PGE1) agonist – erectile dysfunction [69] Alprostadil/lidocaine (NM02216; NM100061) – combination of alprostadil (prostaglandin E1 (PGE1) agonist) and lidocaine (sodium channel blocker, local anesthetic) – premature ejaculation [70] Amesergide (LY-237733; LY237733; LY-237,733) – serotonin 5-HT2A, 5-HT2B, and 5-HT2C receptor antagonist, other actions – erectile dysfunction, premature ejaculation [71] Apomorphine inhalation (VR-004; VR-040; VR-400) – non-selective dopamine receptor agonist, other actions – erectile dysfunction, female sexual dysfunction [72] Apomorphine intranasal – non-selective dopamine receptor agonist, other actions – erectile dysfunction [73] Avanafil (Razatus; Spedra; Stendra; TA-1790; Zepeed) – phosphodiesterase PDE5 inhibitor – female sexual dysfunction, premature ejaculation [74] BAY-604552 (BAY98-7081; sGC activator) – guanylate cyclase stimulant – erectile dysfunction [75] Bremelanotide (Rekynda; Vyleesi; PT-141) – melanocortin MC4 receptor agonist – erectile dysfunction [76] CP-866087 (CP-866,087) – μ-opioid receptor antagonist – female sexual dysfunction [77] DA-8031 (DA8031) – selective serotonin reuptake inhibitor (SSRI) – premature ejaculation [78] Dapoxetine (IMD dapoxetine; YHD-1044) – selective serotonin reuptake inhibitor (SSRI) – premature ejaculation [79] Delequamine (RS-15385; RS-15385197) – α2-adrenergic receptor antagonist – erectile dysfunction [80] Estradiol/testosterone transdermal (testosterone/estradiol transdermal) – combination of estradiol (estrogen) and testosterone (androgen) – female sexual dysfunction [81] GM-1485 (GPI-1485; NIL-A) – immunophilin modulator – erectile dysfunction [82] Heparin/lidocaine/sodium bicarbonate (alkalised lidocaine and heparin formulation; Hep-Lido-A compounded formulation; U-101; URG-101) – combination of heparin (Factor Xa inhibitor, thrombin inhibitor), lidocaine (sodium channel blocker, local anesthetic), and sodium bicarbonate (absorption enhancer) – dyspareunia [83] hMaxi-K gene therapy (pVAX/hSlo; URO-902) – gene transference – erectile dysfunction [84] INO-1001 (INO1001; Pardex) – poly(ADP-ribose) polymerase inhibitor – erectile dysfunction [85] LGD-2941 (LGD2941; LGD122941; LGD-122941) – selective androgen receptor modulator (SARM) – female sexual dysfunction, male sexual dysfunction [86] Melanotan II (MT-II; PT-14) – melanocortin receptor agonist – erectile dysfunction, male sexual dysfunction [87] Milnacipran (Dalcipran; F-2207; Impulsor; Ixel; Joncia; Midacipran; Midalcipran; Savella; TN-912; Toledomin) – serotonin–norepinephrine reuptake inhibitor (SNRI) – vulvodynia [88] Nitroglycerin topical (Anogesic; Cellegesic; Rectiv; Rectogesic) – nitric oxide donor – dyspareunia, vulvodynia [89] NMI-870 – α2-adrenergic receptor antagonist, nitric oxide donor – erectile dysfunction, female sexual dysfunction [90] Oxytocin (oxytocin gel; oxytocin topical; Vagitocin) – oxytocin receptor agonist – atrophic vaginitis [91] Pagoclone (IP-456; Panex; RP-62955) – GABAA receptor positive allosteric modulator and nonbenzodiazepine/cyclopyrrolone – premature ejaculation [92] PF-446687 (PF-00446687; PF-446,687) – melanocortin MC4 receptor agonist – sexual function disorders [93] PF-592379 (PF-000592379; PF-592,379) – dopamine D3 receptor agonist – erectile dysfunction [94] Research programme: therapeutics - Re-Pharm (RP-0217; RP0217) – protein phosphatase 2A (PP2A) inhibitor – sexual function disorders [95] [96] RO-0282425 (RO0282425) – melanocortin MC4 receptor agonist – erectile dysfunction [97] RTN-001 (KD-027; SLX-2101; SLx-2101) – phosphodiesterase PDE5 inhibitor – erectile dysfunction [98] SAR-407899 (SAR407899; SAR407899A) – Rho-associated kinase inhibitor – erectile dysfunction [99] Sertraline (Aremis; Besitran; CP-51974; CP-51974-01; Gladem; J Zoloft; Lustral; Serad; Serlain; Tatig; Zoloft) – selective serotonin reuptake inhibitor (SSRI) – premature ejaculation [100] Sildenafil (Revatio; Revatio IV; UK-92480; Viagra) – phosphodiesterase PDE5 inhibitor – female sexual dysfunction [101] Tadalafil (Adcirca; Cialis; GF-196960; IC-351; LY-450190; Zalutia) – phosphodiesterase PDE5 inhibitor – female sexual dysfunction [102] Tadalafil sublingual (APC-8000) – phosphodiesterase PDE5 inhibitor – erectile dysfunction [103] Tadalafil/tamsulosin (CKD-397; tamsulosin/tadalafil) – combination of tadalafil (phosphodiesterase PDE5 inhibitor) and tamsulosin (α1-adrenergic receptor antagonist) – erectile dysfunction [104] Tadalafil/tamsulosin (YBH-1603) – phosphodiesterase PDE5 inhibitor – erectile dysfunction [105] Testosterone topical (ESP-210) – androgen (androgen receptor agonist) – female sexual dysfunction [106] Testosterone transdermal (FemTestosterone TDS) – androgen (androgen receptor agonist) – female sexual dysfunction [107] Testosterone transdermal (Luramist; testosterone MDTS; testosterone transdermal spray) – androgen (androgen receptor agonist) – female sexual dysfunction [108] TEMPE (Topical Eutectic Mixture for Premature Ejaculation) – undefined mechanism of action – premature ejaculation [109] UK-357903 (UK-357,903) – phosphodiesterase PDE5 inhibitor – erectile dysfunction [110] UK-390957 (UK-390,957) – serotonin reuptake inhibitor (SRI) – premature ejaculation [111] UK-447841 (UK-447,841) – neprilysin inhibitor – female sexual dysfunction [112] VML-670 (VML670; CEB-1555) – serotonin 5-HT1A receptor agonist – female sexual dysfunction, male sexual dysfunction [113]
Sources: en.wikipedia.org
=== Thyroglobulin antibodies === In the clinical laboratory, thyroglobulin testing can be complicated by the presence of anti-thyroglobulin antibodies (ATAs, alternatively referred to as TgAb). Anti-thyroglobulin antibodies are present in 1 in 10 normal individuals, and a greater percentage of patients with thyroid carcinoma. The presence of these antibodies can result in falsely low (or rarely falsely high) levels of reported thyroglobulin, a problem that can be somewhat circumvented by concomitant testing for the presence of ATAs. The ideal strategy for a clinician's interpretation and management of patient care in the event of confounding detection of ATAs is testing to follow serial quantitative measurements (rather than a single laboratory measurement). ATAs are often found in patients with Hashimoto's thyroiditis or Graves' disease. Their presence is of limited use in the diagnosis of these diseases, since they may also be present in healthy euthyroid individuals. ATAs are also found in patients with Hashimoto's encephalopathy, a neuroendocrine disorder related to—but not caused by—Hashimoto's thyroiditis.
=== Catherine E. Costello Award for Exemplary Achievements in Proteomics (the former Catherine E. Costello Lifetime Achievement in Proteomics Award) (since 2019) === 2026 Lingjun Li 2025 Ileana Cristea 2024 Jennifer Van Eyk 2022 Catherine C. Fenselau 2019 Catherine E. Costello
==== Publications ==== The IIR has over 200 publications available on refrigeration technologies and applications: reference documents, guides, technical books, conference and congress papers and proceedings, tables and diagrams comprising the thermophysical properties of refrigerants. Books in the refrigeration field published by other publishers are also available for purchase.
Grandidier, A. (1899). Guide de l'immigrant à Madagascar (in French). Paris: A Colin et cie. Kurlansky, Mark (1997). Cod: A Biography of the Fish That Changed the World. New York: Walker. ISBN 0-8027-1326-2.
Sources: en.wikipedia.org
Solid material is normally kept frozen at about -20 degrees Celsius, desiccated and protected from light. Solutions are held cold and used within a defined window because degradation products accumulate over time.
Mass spectrometry, usually electrospray ionisation coupled to liquid chromatography, gives an observed mass for comparison with the theoretical value. Peptide mapping after digestion provides complementary sequence-level confirmation.
Short exposure during weighing and handling is generally tolerated, but prolonged storage above refrigerated conditions raises the risk of deamidation, oxidation, and aggregation. The rate depends on pH, buffer composition, and concentration.
It is a synthetic peptide of 39 amino acids bearing a lipid side chain. Its size and architecture place it outside the small-molecule class, and laboratories generally handle it with the precautions used for biologic-like molecules.