This is a working overview of Secondary drying, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-02-10 and is reviewed periodically as new material appears.
Industries use lyophilization for pharmaceuticals, biological products, and food preservation. In the pharmaceutical sector, it extends the shelf life of injectable drugs, vaccines, and proteins that are unstable in aqueous solution. Food manufacturers apply freeze-drying to coffee, fruits, and ready meals to retain flavor and texture. The process is energy-intensive and requires specialized equipment, which limits its use to high-value products. Ongoing research examines how formulation and process parameters affect the quality of the final dried product.
Lyophilization, also known as freeze-drying, is a process that removes water from a material by freezing it and then reducing pressure to allow ice to sublimate directly into vapor. The method begins with a freezing step that solidifies the water content. Next, primary drying lowers the pressure below the triple point of water, enabling sublimation without passing through a liquid phase. A final secondary drying step removes bound water through desorption. This sequence produces a dry, porous cake that can be reconstituted later.
The process relies on the phase diagram of water, where the triple point marks the conditions at which ice, liquid water, and vapor coexist. By maintaining pressure below this point, typically around 0.01 to 0.1 millibar, sublimation becomes the dominant mechanism. Formulations often include excipients such as sugars or polymers that act as lyoprotectants and bulking agents. These additives help preserve the structure of the active ingredient and prevent collapse during drying. The choice of excipient and freezing rate influences the final cake morphology and stability.
Quality control for lyophilized products includes appearance, cake structure, reconstitution time, pH, residual moisture, and potency. Residual moisture is a key attribute because excess water can reduce stability, while excessively low moisture may cause structural changes or aggregation in some systems. Stability studies compare real-time and accelerated conditions to estimate shelf life. Analytical methods must be validated for the specific matrix, container, and moisture range. Sterility and container integrity are also monitored for sterile products.
Handling practices aim to prevent moisture ingress and mechanical damage. Vials should remain stoppered and crimped until use, and reconstitution should follow the labeled diluent and volume. Shipping may involve temperature-controlled containers and desiccants, but direct contact between desiccant and product is avoided. Regulatory guidance expects documented storage conditions, excursion assessments, and stability commitments. Open questions remain about how best to predict long-term stability from short accelerated studies for every formulation class.
After lyophilization, the product is usually a porous cake or powder with a large internal surface area. This structure can absorb moisture quickly if exposed to humid air, so vials are sealed under vacuum or an inert gas. Moisture uptake may lower the glass transition temperature of the dried matrix and accelerate chemical or physical degradation. Storage conditions therefore depend on the formulation, container, and intended shelf life. Some products remain stable at room temperature, while others require refrigeration or freezing.
| Property | Value | Notes |
|---|---|---|
| Common name | Freeze-drying | Lyophilization is the technical synonym. |
| Typical chamber pressure | 0.01–0.1 mbar | Below the triple point of water. |
| Primary drying temperature | −40 to −10 °C | Depends on formulation and equipment. |
| Residual moisture | 1–5% | Target for many pharmaceutical products. |
| Typical equipment | Vacuum freeze-dryer | Includes drying chamber and condenser. |
Equipment for lyophilization includes a vacuum chamber, temperature-controlled shelves, a condenser, and a vacuum pump. A refrigeration system cools the shelves and condenser below the product's freezing point. Process monitoring often uses Pirani and capacitance manometers, thermocouples, and resistance sensors. Cycle development balances product quality with time and energy use. Some products are annealed during freezing to improve crystallization of bulking agents. Open questions remain about scaling cycles between laboratory, pilot, and production freeze-dryers.
Lyophilization, also called freeze-drying, removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts free water into ice and may also produce a glassy phase. Primary drying then lowers chamber pressure so ice sublimes directly to vapor without passing through a liquid stage. Secondary drying raises the temperature modestly to remove bound water. The result is a porous, dry solid that usually reconstitutes quickly. Each stage influences pore structure, residual moisture, and stability.
Quality control for freeze-dried forms includes visual inspection, water content measurement, and reconstitution time. A satisfactory cake is typically uniform, porous, and intact, although minor shrinkage or cracking may be acceptable if specifications allow. Karl Fischer titration, thermal gravimetric analysis, and near-infrared spectroscopy are used to measure water content. Reconstitution is assessed by adding a specified diluent and recording the time and ease of dissolution. Microbiological and particulate tests are added when the product is sterile or intended for injection.
Stability of a lyophilized solid depends on water content, temperature, and the physical state of the formulation. Amorphous products may slowly absorb moisture and drop below their glass transition temperature, causing collapse or crystallization. Some proteins and peptides can aggregate even in a dry state, especially when exposed to heat or moisture. Accelerated stability studies at elevated temperature and humidity help estimate shelf life, but real-time data remain the basis for expiration dating.
Secondary drying removes bound water that remains after ice sublimation. Shelf temperature is raised gradually while pressure remains low, reducing water content to a target range. Over-drying can cause brittleness or electrostatic issues, while under-drying affects stability. The endpoint is often judged by pressure rise tests, temperature measurements, or water content analysis. Scale-up depends on matching heat and mass transfer across equipment sizes. Small changes in shelf temperature or pressure can alter cycle length substantially.
Lyophilization, or freeze-drying, removes water from a material by freezing it and then lowering pressure so ice changes directly to vapor. The process relies on sublimation, the phase transition from solid to gas without an intervening liquid state. It is used for heat-sensitive materials that would degrade in conventional drying. The three stages are freezing, primary drying, and secondary drying, each with distinct temperature and pressure requirements. In practice, cycle design balances these variables.
Storage conditions depend on the formulation and the intended shelf life. Many pharmaceutical and biological freeze-dried products are kept at 2–8 °C, while some stable foods and reagents tolerate room temperature. Others require −20 °C or colder to slow chemical degradation or aggregation. Protection from light and oxygen is common because oxidation can continue in the dry state. Stability studies usually monitor potency, appearance, moisture, and reconstitution time over months or years. Predictions from accelerated studies are useful but may not fully capture real-time changes.
Quality control for freeze-dried lots combines visual inspection with instrumental tests. Cake appearance, color, and shrinkage are recorded against a reference, while residual moisture is measured by Karl Fischer titration or loss on drying. Thermal analysis can reveal phase transitions and crystallization events, and X-ray diffraction distinguishes amorphous from crystalline solids. Microbiological tests and container closure integrity checks are also routine for sterile products. Analytical methods must be validated for the matrix, because excipients and low moisture can affect accuracy. Open questions include how best to predict long-term stability from short-term data.
In the 2024 presidential election, Americans aged 18 to 29 voted for Kamala Harris by a margin of only four points, according to exit polls conducted by the Associated Press. Donald Trump and his Republican Party made considerable gains among young voters, especially young men and European Americans. Among Gen-Z women, while those of ethnic-minority backgrounds overwhelmingly supported Harris, those of European ancestry were evenly split between Harris and Trump. This election has broken the historical trend of young people generally voting for Democrats. Generation Z has been shifting towards the right since 2020. Even so, polls conducted after that election showed that the majority of Generation Z disapproved of the performance of President Donald Trump because he had failed to address their concerns about the economy, especially inflation and the cost of living.
Angiogenesis is the physiological process through which new blood vessels form from pre-existing vessels, formed in the earlier stage of vasculogenesis. Angiogenesis continues the growth of the vasculature mainly by processes of sprouting and splitting, but processes such as coalescent angiogenesis, vessel elongation and vessel cooption also play a role. Vasculogenesis is the embryonic formation of endothelial cells from mesoderm cell precursors, and from neovascularization, although discussions are not always precise (especially in older texts). The first vessels in the developing embryo form through vasculogenesis, after which angiogenesis is responsible for most, if not all, blood vessel growth during development and in disease. Angiogenesis is a normal and vital process in growth and development, as well as in wound healing and in the formation of granulation tissue. However, it is also a fundamental step in the transition of tumors from a benign to malignant state, leading to the use of angiogenesis inhibitors in the treatment of cancer. The essential role of angiogenesis in tumor growth was first proposed in 1971 by Judah Folkman, who described tumors as "hot and bloody," illustrating that, at least for many tumor types, flush perfusion and even hyperemia are characteristic.
== History == The concept of fatty acid (acide gras) was introduced in 1813 by Michel Eugène Chevreul, though he initially used some variant terms: graisse acide and acide huileux ("acid fat" and "oily acid").
Since the 2000s, cursive writing has been de-emphasized in public education. As a result, Generation Z are less likely to read and write in cursive. Some states introduced legislation to teach it in their jurisdiction, partly because some 80% of historical records and documents of the United States was written by hand in cursive. The percentage of American fourth-graders proficient in reading declined during the late 2010s, according to the National Assessment of Educational Progress (NAEP). There have been numerous reports in the 2010s on how U.S. students were falling behind their international counterparts in the STEM subjects, especially those from (East) Asia. For example, American schoolchildren put up a mediocre performance on the Program for International Student Assessment (PISA), administered to fifteen-year-old students around the world on reading comprehension, mathematics, and science, falling in the middle of the pack in 2015. In fact, reading scores dropped for all ethnic groups except Asians in the late 2010s, according to the NAEP. Nevertheless, American students ranked above the OECD average in science and computer literacy, as of 2021. As of 2024, NAEP data showed that the reading and mathematical skills of American schoolchildren on average still had not recovered from the COVID-19 pandemic. Furthermore, while the strongest students had regained lost grounds, the weakest continued to fall behind. An emphasis on rote memorization and speed gives as many as one in three students age five and up mathematical anxiety.
Sources: en.wikipedia.org
The four substrates of this enzyme are taxifolin, reduced nicotinamide adenine dinucleotide (NADH), oxygen, and a proton. Its products are dihydrogossypetin, oxidised NAD+, and water. Nicotinamide adenine dinucleotide phosphate can be used as an alternative cofactor. The enzyme is a flavin-containing monooxygenase that uses molecular oxygen as oxidant and incorporates one of its atoms into the starting material. The systematic name of this enzyme class is phenol,NADPH:oxygen oxidoreductase (2-hydroxylating). Other names in common use include phenol hydroxylase, and phenol o-hydroxylase. It uses flavin adenine dinucleotide as a second cofactor. The systematic name of this enzyme class is taxifolin,NAD(P)H:oxygen oxidoreductase (8-hydroxylating). This enzyme is also called taxifolin hydroxylase.
When gunfights finally erupted outside and around the television studio, they were almost always the result of miscommunication. One such example is when a group of Patriotic Guardsmen took up a defensive position in a building close to the television centre on the 23rd. It has not been established who took the first shots at around 17:00, but a gunfight soon ensued with those in the television station returning fire onto the position of the Patriotic guards, according to an aid worker who had set up a first aid station at the side of the television station, and who said that, afterwards, the group of Patriotic Guardsmen would later deny that they had fired first. This is only one of many examples of gunfights between pro-revolution forces after the flight of Ceaușescu on the 22nd. Scenes of major gunfights during this period include the television, radio and telephone buildings, as well as Casa Scânteii (the nation's print media center, which serves a similar role today under the name of the "House of the Free Press", Casa Presei Libere) and the post office in the district of Drumul Taberei; Palace Square (site of the Central Committee building, but also of the Central University Library, the national art museum in the former Royal Palace, and the Ateneul Român (Romanian Athenaeum), Bucharest's leading concert hall); the university and the adjoining University Square (one of the city's main intersections); Otopeni and Băneasa airports; hospitals; and the Ministry of Defence.
In fat cells, glucose is used to power reactions that synthesize some fat types and have other purposes. Glycogen is the body's "glucose energy storage" mechanism, because it is much more "space efficient" and less reactive than glucose itself. As a result of its importance in human health, glucose is an analyte in glucose tests that are common medical blood tests. Eating or fasting prior to taking a blood sample has an effect on analyses for glucose in the blood; a high fasting glucose blood sugar level may be a sign of prediabetes or diabetes mellitus. The glycemic index is an indicator of the speed of resorption and conversion to blood glucose levels from ingested carbohydrates, measured as the area under the curve of blood glucose levels after consumption in comparison to glucose (glucose is defined as 100). The clinical importance of the glycemic index is controversial, as foods with high fat contents slow the resorption of carbohydrates and lower the glycemic index, e.g. ice cream. An alternative indicator is the insulin index, measured as the impact of carbohydrate consumption on the blood insulin levels. The glycemic load is an indicator for the amount of glucose added to blood glucose levels after consumption, based on the glycemic index and the amount of consumed food.
== International and political work == In October 1945, Orr was elected Rector of the University of Glasgow after standing as an Independent Progressive candidate. He was elected as an independent Member of Parliament (MP) for the Combined Scottish Universities in a by-election in April 1945, and kept his seat at the general election shortly after. He resigned in 1946. After the Second World War, Boyd Orr resigned from the Rowett Institute, and took several posts, most notably as Director-General of the United Nations' new Food and Agriculture Organization (FAO). Although his tenure in this position was short (1945–1948), he worked not only to alleviate the immediate postwar food shortage through the International Emergency Food Committee (IEFC) but also to propose comprehensive plans for improving food production and its equitable distribution. His proposal to create a World Food Board to increase price stability by way of large scale commodity storage. Although the board failed to get the support of Britain and the US, Boyd Orr laid a firm foundation for the new UN-specialized agency. He then resigned from the FAO and became director of a number of companies and proved a canny investor in the stock market, making a considerable personal fortune. When he received the Nobel Peace Prize in 1949, he donated the entire financial award to organizations devoted to world peace and a united world government. He was elevated to the peerage in the 1949 New Year Honours as Baron Boyd-Orr, of Brechin Mearn in the County of Angus.
Nixtamalization ( nish-tə-mə-lih-ZAY-shən) is a process for the preparation of maize (corn), or other grain, in which the grain is soaked and cooked in an alkaline solution, usually limewater (but sometimes aqueous alkali metal carbonates), washed, and then hulled. The term can also refer to the removal via an alkali process of the pericarp from other grains such as sorghum. Nixtamalized corn has several benefits over unprocessed grain: It is more easily ground, its nutritional value is increased, flavor and aroma are improved, and mycotoxins are reduced by up to 97–100% (for aflatoxins). Lime and ash are highly alkaline: the alkalinity helps the dissolution of hemicellulose, the major glue-like component of the maize cell walls, and loosens the hulls from the kernels and softens the maize. The tryptophan in corn proteins is made more available for human absorption, thus helping to prevent niacin deficiency (pellagra). Tryptophan is the metabolic precursor of endogenous niacin (Vitamin B3). Some of the corn oil is broken down into emulsifying agents (monoglycerides and diglycerides), while bonding of the maize proteins to each other is also facilitated. The divalent calcium in lime acts as a cross-linking agent for protein and polysaccharide acidic side chains. While cornmeal made from untreated ground maize is unable by itself to form a dough on addition of water, nixtamalized cornmeal will form a dough, called masa.
Sources: en.wikipedia.org
=== Imaging procedure === Since 68Ga is a positron emitter, 68Ga-Trivehexin is applicable for PET imaging. However, PET is rarely used as a standalone imaging technique these days. Most clinics use PET/CT or even PET/MRI systems that acquire morphological and functional images in a single workflow and thus, provide more detailed and useful medical information to the physician. For clinical PET/CT diagnostics, an activity in the range of 80–150 MBq 68Ga-Trivehexin is injected intravenously (i.v.). The tracer then distributes with the blood flow and moves into tissues by diffusion, where it specifically binds to its target αvβ6-integrin, while an excess is excreted via the kidneys and the urine. As a result, 68Ga-Trivehexin and, therefore, the positron-emitting radionuclide 68Ga, is preferably accumulated by αvβ6-integrin abundant tissues (for example, tumor tissue). Next, a PET/CT scanner is used to detect the gamma radiation which is generated by the annihilation of the positrons emitted by 68Ga (not the actual positrons, which do not leave the body but travel only a few millimetres through the tissue). The spatial distribution of the annihilation events is reconstructed from the raw detector data (referred to as listmode data), which eventually delivers a 3-dimensional data set of radioactivity distribution in the body. These data allow the visualization of αvβ6-integrin positive tissues as 2-dimensional tomographic images or 3-dimensional volume rendering. Typically, the PET/CT imaging is performed 45–60 minutes after the i.v. administration of 68Ga-Trivehexin.
== Receptor == URP is an agonist for the UII receptor which is a G protein-coupled receptor with the alpha subunit Gαq11. This activates PKC which then activates PLC which increases the intercellular calcium concentration. It is found in many peripheral tissues, blood vessels, and also the brainstem cholinergic neurons of the laterodorsal tegmental (LDT) and the pedunculopontine tegmental nuclei (PPT).
DAD discovered in Gram-negative E. coli B membrane can convert L-amino acids into D-amino acids as well. Additionally, D-amino acid dehydrogenase is used in dye-linked dehydrogenase (dye-DHs) which uses artificial dyes such as 2,6-dichloroindophenol (DCIP) as their electron acceptor rather than using their natural electron acceptors. This can accelerate the reaction between the enzyme and the substrate when the electrons are being transferred.
Cotadutide is an experimental drug for the treatment of type 2 diabetes mellitus. It lowers blood glucose levels by mimicking the human hormones glucagon-like peptide 1 and glucagon, which play a role in blood sugar regulation. The drug is a peptide that is injected under the skin. Cotadutide is in Phase II clinical trials as of February 2021. Cotadutide, a therapeutic agent, was undergoing Phase II clinical trials. This stage of trials typically involves evaluating the drug's effectiveness and further assessing its safety in a larger group of participants, compared to earlier phases.
Sources: en.wikipedia.org
Conventional drying uses heat to evaporate water from a material, while lyophilization freezes the material and removes water by sublimation under vacuum. This avoids the liquid phase and reduces thermal damage to sensitive substances. The result is a porous cake that reconstitutes quickly.
A vacuum lowers the pressure below the triple point of water, allowing ice to sublimate directly into vapor without melting. It also removes water vapor from the product chamber and speeds up the drying process. Without vacuum, the ice would melt rather than sublimate.
Not all substances are suitable for lyophilization. Materials must form a stable frozen matrix and tolerate freezing and low pressure. Some small molecules, oils, or volatile compounds may not form a proper cake or may be lost during processing.
Collapse occurs when the product temperature rises above its collapse or eutectic temperature during drying. The frozen matrix loses structure, producing a shrunken or melted appearance. This can slow reconstitution and may affect stability.