The short version of size-exclusion chromatography fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-06-29 and is reviewed periodically as new material appears.
Long-term storage of the solid generally relies on temperatures at or below minus twenty degrees Celsius, while short-term working stocks may be held refrigerated. Light exposure is limited because photodegradation can alter side chains over extended periods. Solutions prepared for analysis are less stable than the dry powder and are typically used within the same working day. Buffer choice matters, since some aqueous conditions favor deamidation or oxidation at specific residues. Stability data are usually generated under defined accelerated conditions and then extrapolated with stated assumptions.
Identity and purity are established with reversed-phase high-performance liquid chromatography, often paired with mass spectrometry for confirmation of the expected mass. Peptide mapping after enzymatic digestion verifies the primary sequence and detects substitutions. Size-exclusion chromatography quantifies aggregates and fragments, which are the impurities most often tracked for peptides of this size. Residual solvents, counterions, and water content fall under separate tests described in pharmacopeial chapters. Circular dichroism or nuclear magnetic resonance may be used in research settings to probe secondary structure, though such methods are less common in routine release testing.
纯度评估通常综合反相色谱、体积排阻色谱与质谱三方面信息：前者反映疏水性杂质，后者反映聚集体，质谱则确认分子量与主要降解产物。有关降解途径的完整图谱——例如脱酰胺、氧化与水解各占多大比例——在不同储存条件下仍有差异，属于需要逐案验证的问题。
质量控制环节关注外观、含量、纯度、有关物质、水分与微生物限度等项目。检测结果需要有对照品和系统适用性数据支持，单次测定不足以判定批次的稳定性。实验室之间方法转移时，色谱柱品牌与梯度差异常导致保留时间漂移，因此方法验证十分必要。
固体状态的 tirzepatide 通常以冻干粉形式保存，推荐在低温、避光、干燥条件下存放，常见区间为 2 至 8 摄氏度，长期保存可考虑更低温度并避免反复冻融。冻融循环会导致肽链聚集或析出，从而影响后续定量结果。容器密封性与湿度控制同样是稳定性研究中反复强调的因素。
| Property | Value | Notes |
|---|---|---|
| Typical supplied form | Lyophilized powder | Hygroscopic, seal promptly after opening |
| Long-term storage temperature | At or below minus 20 C | Protect from repeated freeze-thaw |
| Working solution stability | Hours when refrigerated | Use within the same working day |
| Primary purity method | Reversed-phase HPLC | Often paired with mass spectrometry |
| Aggregate measurement | Size-exclusion chromatography | Reports high-molecular-weight species |
Stability depends strongly on physical form. The dry powder is generally regarded as stable for extended periods when held at or below minus twenty degrees Celsius in a sealed, desiccated container. In solution, degradation pathways include deamidation of asparagine and glutamine residues, oxidation of methionine, and aggregation. Reaction rates for these pathways rise with temperature. Repeated freezing and thawing of solutions promotes aggregation, and light exposure can accelerate some oxidative changes. Buffer composition and pH influence which pathway dominates at a given temperature.
Regulatory and quality discussions place the peptide within established guidance for synthetic peptides and biologics. Forced degradation studies, in which samples are exposed to heat, acid, base, peroxide, and light, identify likely degradation products and validate the selectivity of analytical methods. Reference standards allow comparison across laboratories and production batches. Purity specifications reported in the literature usually combine chromatographic purity with mass confirmation. Which impurity thresholds are meaningful for long-term behavior is still debated, and no single universal specification has been adopted across all jurisdictions.
Routine characterization relies on reversed-phase high-performance liquid chromatography, often coupled to mass spectrometry, to confirm identity and estimate purity. Peptide mapping after enzymatic digestion verifies the amino acid sequence and locates appended groups such as the fatty acid chain. Size-exclusion chromatography detects aggregates and fragments, while ion-exchange chromatography resolves charge variants. Circular dichroism and nuclear magnetic resonance supply secondary and higher-order structural information in research settings. No single technique covers every attribute, so laboratories combine orthogonal methods and compare outcomes against a reference standard where one exists.
Purified material is typically handled as a lyophilized powder kept at or below minus twenty degrees Celsius, shielded from light and moisture. In that state the solid remains stable for extended periods, although repeated freeze-thaw cycling can encourage aggregation. Once dissolved, aqueous solutions are less durable and are generally held cold and used within a brief window. Buffer composition, pH and ionic strength all influence degradation rates, and mildly acidic to neutral conditions are commonly examined. Actual shelf life depends on formulation, concentration and container, so stability limits are established experimentally rather than assumed.
Factor XIII, or fibrin stabilizing factor, is a plasma protein and zymogen. It is activated by thrombin to factor XIIIa which crosslinks fibrin in coagulation. Deficiency of XIII worsens clot stability and increases bleeding tendency. Human XIII is a heterotetramer. It consists of 2 enzymatic A peptides and 2 non-enzymatic B peptides. XIIIa is a dimer of activated A peptides.
BrO3− + 5 Br− + 6 H+ → 3 Br2 + 3 H2O There were many failed attempts to obtain perbromates and perbromic acid, leading to some rationalisations as to why they should not exist, until 1968 when the anion was first synthesised from the radioactive beta decay of unstable 83SeO42−. Today, perbromates are produced by the oxidation of alkaline bromate solutions by fluorine gas. Excess bromate and fluoride are precipitated as silver bromate and calcium fluoride, and the perbromic acid solution may be purified. The perbromate ion is fairly inert at room temperature but is thermodynamically extremely oxidising, with extremely strong oxidising agents needed to produce it, such as fluorine or xenon difluoride. The Br–O bond in BrO4− is fairly weak, which corresponds to the general reluctance of the 4p elements arsenic, selenium, and bromine to attain their group oxidation state, as they come after the scandide contraction characterised by the poor shielding afforded by the radial-nodeless 3d orbitals.
== Procedure == IEF involves adding an ampholyte solution into immobilized pH gradient (IPG) gels. IPGs are the acrylamide gel matrix co-polymerized with the pH gradient, which result in completely stable gradients except the most alkaline (>12) pH values. The immobilized pH gradient is obtained by the continuous change in the ratio of immobilines. An immobiline is a weak acid or base defined by its pK value. A protein that is in a pH region below its isoelectric point (pI) will be positively charged and so will migrate toward the cathode (negatively charged electrode). As it migrates through a gradient of increasing pH, however, the protein's overall charge will decrease until the protein reaches the pH region that corresponds to its pI. At this point it has no net charge and so migration ceases (as there is no electrical attraction toward either electrode). As a result, the proteins become focused into sharp stationary bands with each protein positioned at a point in the pH gradient corresponding to its pI. The technique is capable of extremely high resolution with proteins differing by a single charge being fractionated into separate bands. Molecules to be focused are distributed over a medium that has a pH gradient (usually created by aliphatic ampholytes). An electric current is passed through the medium, creating a "positive" anode and "negative" cathode end. Negatively charged molecules migrate through the pH gradient in the medium toward the "positive" end while positively charged molecules move toward the "negative" end.
=== Environmental science === The hydrophobicity of a compound can give scientists an indication of how easily a compound might be taken up in groundwater to pollute waterways, and its toxicity to animals and aquatic life. Partition coefficient can also be used to predict the mobility of radionuclides in groundwater. In the field of hydrogeology, the octanol–water partition coefficient Kow is used to predict and model the migration of dissolved hydrophobic organic compounds in soil and groundwater.
Bacterial vaginosis is a condition of the vaginal microbiota in which an excessive growth of Gardnerella vaginalis and other mostly anaerobic bacteria displace the beneficial Lactobacilli species that maintain healthy vaginal microbial populations. Bacterial meningitis is a bacterial inflammation of the meninges, which are the protective membranes covering the brain and spinal cord. Bacterial pneumonia is a bacterial infection of the lungs. Urinary tract infection is predominantly caused by bacteria. Symptoms include the strong and frequent sensation or urge to urinate, pain during urination, and urine that is cloudy. The most frequent cause is Escherichia coli. Urine is typically sterile but contains a variety of salts and waste products. Bacteria can ascend into the bladder or kidney and causing cystitis and nephritis. Bacterial gastroenteritis is caused by enteric, pathogenic bacteria. These pathogenic species are usually distinct from the usually harmless bacteria of the normal gut flora. But a different strain of the same species may be pathogenic. The distinction is sometimes difficult as in the case of Escherichia. Bacterial skin infections include: Impetigo is a highly contagious bacterial skin infection commonly seen in children. It is caused by Staphylococcus aureus, and Streptococcus pyogenes. Erysipelas is an acute streptococcus bacterial infection of the deeper skin layers that spreads via with lymphatic system. Cellulitis is a diffuse inflammation of connective tissue with severe inflammation of dermal and subcutaneous layers of the skin.
Sources: en.wikipedia.org
== See also == American Society of Anesthesiologists Anesthetic technician – Type of healthcare professional Nurse anesthetist – Advanced Practice Registered Nurse with expertise in anesthesia Local anesthetic – Medications to reversibly block pain Neuromuscular-blocking drug – Type of paralyzing anesthetic including lepto- and pachycurares
=== Nomenclature === The nomenclature of modified GFPs is often confusing due to overlapping mapping of several GFP versions onto a single name. For example, mGFP often refers to a GFP with an N-terminal palmitoylation that causes the GFP to bind to cell membranes. However, the same term is also used to refer to monomeric GFP, which is often achieved by the dimer interface breaking A206K mutation. Wild-type GFP has a weak dimerization tendency at concentrations above 5 mg/mL. mGFP also stands for "modified GFP", which has been optimized through amino acid exchange for stable expression in plant cells.
== Plasma proteins for clinical use == Many of the proteins in plasma have important therapeutic uses. Albumin is commonly used to replenish and maintain blood volume after traumatic injury, during surgery, and during plasma exchange. Since albumin is the most abundant protein in the plasma its use may be the most well known, but many other proteins, although present in low concentrations, can have important clinical uses. See table below.
=== 2018 American consulate bombing === On 2 December 2018, at approximately 7:30 CST, two grenades were thrown onto consular grounds in Guadalajara, with one of them exploding and causing a 16-inch (approximately 40 cm) hole in the wall of the building. At the time of the bombing, the consulate general office was closed and no injuries were sustained. It is unconfirmed if the attack was carried out by a cartel.
Sources: en.wikipedia.org
Clomipramine may interact with monoamine oxidase inhibitors (MAOIs) such as isocarboxazid, moclobemide, phenelzine, selegiline, and tranylcypromine. These combinations are generally avoided due to the severe risk of adverse reactions. The medication also interacts with antiarrhythmic agents because tricyclic antidepressants (TCAs) can significantly alter cardiac conduction. A specific pharmacokinetic interaction exists with quinidine; since clomipramine is metabolized by the enzyme CYP2D6 in vivo, quinidine can impede this process and raise drug levels. Similarly, diuretics pose a secondary risk; by potentially inducing hypokalaemia (low blood potassium), they increase the likelihood of QT interval prolongation and the life-threatening heart rhythm known as torsades de pointes. Furthermore, clomipramine reacts with selective serotonin reuptake inhibitors (SSRIs) through two distinct mechanisms. First, there is a risk of additive serotonergic effects that can lead to serotonin syndrome. Second, a pharmacokinetic interaction occurs with SSRIs that inhibit CYP2D6—specifically fluoxetine and paroxetine—which can lead to toxic levels of clomipramine in the bloodstream. This risk of serotonin toxicity or serotonin syndrome extends to other serotonergic agents, including triptans, other tricyclic antidepressants, and tramadol. Fluvoxamine increases the serotonergic effects of clomipramine and, likewise, clomipramine increases fluvoxamine levels.
==== European Union ==== Danish pharmaceutical company Lundbeck has licensed nalmefene from Biotie Therapies and performed clinical trials with nalmefene for treatment of alcohol dependence. In 2011, they submitted an application for their medication named Selincro to the European Medicines Agency. The medication was authorized for use in the EU in March 2013. and in October 2013, Scotland became the first country in the EU to prescribe the drug for alcohol dependence. England followed Scotland by offering the medication as a treatment for problem drinking in October 2014. In November 2014, nalmefene was approved as a possible treatment supplied by Britain's National Health Service (NHS) for reducing alcohol consumption in people with alcohol dependence.
=== Metabolomics === Borchers has also applied MRM-based mass spectrometry to targeted metabolomics. With Jun Han, he developed an LC–MS/MS method for profiling bile acids in human and mouse blood, combining the assay with a phospholipid-depletion solid-phase extraction step, which allowed a number of minor bile acids to be quantified in blood for the first time. The same collaboration produced a method for quantifying short-chain fatty acids in human feces, in which the acids are chemically derivatized with 3-nitrophenylhydrazine and measured against isotope-labelled internal standards.
Sources: en.wikipedia.org
Water promotes hydrolysis and deamidation, so removing it slows degradation during transport and storage. The dry solid is also less prone to microbial growth than a solution. Reconstitution is therefore performed close to the point of use.
Reversed-phase high-performance liquid chromatography is the standard method for purity and related substances. It separates the main peak from deletion sequences and oxidation products. Mass spectrometry is frequently used alongside it to confirm molecular identity.
Aggregates, truncated sequences, and oxidation products receive the most attention. Size-exclusion chromatography covers aggregates, while reversed-phase methods resolve many chemical variants. Limits are set according to the route of administration and the expected exposure.
建议在低温、避光、干燥环境中密封保存，常见条件为 2 至 8 摄氏度，长期存放可置于更低温度。应避免反复冻融，并尽量减少容器开启次数。