Everything below concerns secondary drying. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-03-15. Numbers and descriptions here follow the published literature rather than marketing material.
The process generally proceeds in three stages: freezing, primary drying, and secondary drying. During freezing, controlled cooling converts water into ice and may also crystallize or vitrify solutes. In primary drying, the pressure is lowered below the triple point, and heat is supplied so ice sublimes directly to vapor. Secondary drying removes water that remains bound to the solid matrix, yielding a low final water content. Product temperature must stay below the collapse or glass transition temperature to maintain structure. Cycle design therefore balances shelf temperature, chamber pressure, and time.
Freeze-drying is used for materials whose activity or structure depends on low temperature and low water content. Examples include certain biologics, diagnostic reagents, starter cultures, coffee, and porous inorganic precursors. The dried product forms a cake whose porosity aids rapid wetting and dissolution. Main drawbacks are high energy use, long cycle times, and sensitivity to formulation and equipment variation. Questions remain about how freezing rates and ice morphology affect batch uniformity, especially when moving from laboratory to production scale.
Lyophilization, also called freeze-drying, is a dehydration process in which a solvent, usually water, is frozen and then removed by sublimation under reduced pressure. The method preserves heat-sensitive materials that would degrade in conventional drying. Large-scale use grew during the mid-twentieth century for blood plasma and antibiotics, and it later expanded to vaccines, enzymes, foods, and advanced materials. The process produces a dry, porous solid that usually reconstitutes rapidly. It is distinct from simple evaporation because the solvent bypasses the liquid phase during primary removal.
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.
| Property | Value | Notes |
|---|---|---|
| Common names | Lyophilization; freeze-drying | Terms used interchangeably. |
| Phase change | Sublimation | Ice converts directly to vapor under vacuum. |
| Typical chamber pressure | 0.01–1 mbar | Below the triple point of water. |
| Primary drying product temperature | −40 to −10 °C | Kept below collapse or glass transition temperature. |
| Water content after drying | 0.5–3% w/w | Varies with formulation and cycle. |
The process usually has three stages: freezing, primary drying, and secondary drying. Freezing sets the ice crystal structure and can determine pore size in the final cake. Primary drying removes free ice by sublimation at low pressure and low shelf temperature. Secondary drying removes bound water by raising the shelf temperature, although some water may remain as part of the solid. Cycle parameters depend on formulation, fill volume, vial type, and equipment performance.
The physical chemistry of freezing influences whether a formulation forms an amorphous glass or a crystalline solid. Amorphous systems can collapse if product temperature rises above the glass transition temperature of the freeze concentrate. Crystalline systems may show eutectic melting, where ice and solute melt together at a fixed temperature. Formulators add bulking agents, lyoprotectants, and buffers to preserve structure and biological activity. The optimum cycle keeps product temperature below critical thresholds during primary drying while allowing efficient sublimation.
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.
Freezing is the first stage and sets the ice structure that later becomes the pore network. The formulation is cooled below its freezing point, often with a controlled ramp, and solutes concentrate as ice forms. Primary drying then lowers chamber pressure and supplies heat to sublime the ice. The product temperature must stay below its collapse or eutectic temperature to prevent structural loss. Secondary drying raises the temperature modestly to remove bound water and achieve a low residual moisture.
A freeze-dryer consists of a vacuum chamber, temperature-controlled shelves, a condenser, and a vacuum pump. Vials, ampoules, or bulk trays hold the product during the cycle. The condenser traps water vapor as ice at a temperature lower than the product. Cycle development balances shelf temperature, chamber pressure, and time. Scale-up can be difficult because heat and mass transfer change with equipment size, so process analytical tools and conservative validation are often used.
Lyophilization is a dehydration technique in which a product is frozen and the solvent is removed under reduced pressure. The low pressure allows ice to sublimate directly into vapor without passing through a bulk liquid phase. This differs from conventional drying, where heat drives evaporation and can damage heat-sensitive structures. The process is used for biological materials, pharmaceutical formulations, and some foods. Its main advantage is preservation of porous structure and rapid reconstitution.
Lyophilization removes water by freezing a material and then lowering pressure so ice changes directly to vapor. The process relies on sublimation, the phase transition from solid to gas without an intermediate liquid state. Because the material remains frozen during primary drying, the structure often stays porous. This porous matrix can rehydrate quickly when water is added back. The low pressure also allows vapor to leave the solid matrix without boiling.
A typical cycle begins with freezing, which fixes the material into a solid and determines ice crystal size. Primary drying then raises heat under vacuum so ice sublimes, often near or below the collapse temperature of the formulation. Secondary drying removes bound water that remains after ice is gone, usually by gently warming the product. Each stage balances heat input against pressure to avoid melting or structural damage. Temperature probes and pressure sensors guide the transition between stages.
In practice, lyophilization is slower and more energy intensive than simple drying. Cycle times can range from hours to several days depending on load, container, and formulation. Amorphous materials may require excipients that help preserve structure during freezing and drying. The method is widely used for biological materials, pharmaceuticals, and foods where heat drying would cause unacceptable change. Open questions remain about scaling cycles between laboratory and production equipment, and this gap affects technology transfer.
=== Atmospheric pressure === Atmospheric pressure (AP) matrix-assisted laser desorption/ionization (MALDI) is an ionization technique (ion source) that in contrast to vacuum MALDI operates at normal atmospheric environment. The main difference between vacuum MALDI and AP-MALDI is the pressure in which the ions are created. In vacuum MALDI, ions are typically produced at 10 mTorr or less while in AP-MALDI ions are formed in atmospheric pressure. In the past, the main disadvantage of the AP-MALDI technique compared to the conventional vacuum MALDI has been its limited sensitivity; however, ions can be transferred into the mass spectrometer with high efficiency and attomole detection limits have been reported. AP-MALDI is used in mass spectrometry (MS) in a variety of applications ranging from proteomics to drug discovery. Popular topics that are addressed by AP-MALDI mass spectrometry include: proteomics; mass analysis of DNA, RNA, PNA, lipids, oligosaccharides, phosphopeptides, bacteria, small molecules and synthetic polymers, similar applications as available also for vacuum MALDI instruments. The AP-MALDI ion source is easily coupled to an ion trap mass spectrometer or any other MS system equipped with electrospray ionization (ESI) or nanoESI source. MALDI with ionization at reduced pressure is known to produce mainly singly-charged ions (see "Ionization mechanism" below). In contrast, ionization at atmospheric pressure can generate highly-charged analytes as was first shown for infrared and later also for nitrogen lasers.
Transaminases or aminotransferases are enzymes that catalyze a transamination reaction between an amino acid and an α-keto acid. They are important in the synthesis of amino acids, which form proteins. Two important transaminase enzymes, aspartate transaminase (AST), and alanine transaminase (ALT), are commonly used as indicators of liver and cardiac health.
=== Iraqi === A United Nations report in March 1991 described the effect on Iraq of the US-led bombing campaign as "near apocalyptic", bringing back Iraq to the "pre-industrial age". The exact number of Iraqi combat casualties is unknown, but is believed to have been heavy. Some estimate that Iraq sustained between 20,000 and 35,000 fatalities. A report commissioned by the US Air Force estimated 10,000–12,000 Iraqi combat deaths in the air campaign, and as many as 10,000 casualties in the ground war. According to the Project on Defense Alternatives study, between 20,000 and 26,000 Iraqi military personnel were killed in the conflict, while 75,000 others were wounded. According to Kanan Makiya, "For the Iraqi people, the cost of enforcing the will of the United Nations has been grotesque." General Schwarzkopf talked about "a very, very large number of dead in these units, a very, very large number indeed." The chairman of the House Armed Services Committee, Les Aspin, estimated that "at least 65,000 Iraqi soldiers were killed". A figure was supported by Israeli sources who speak of "one to two hundred thousand Iraqi casualties." Most of the killing "took place during the ground war. Fleeing soldiers were bombed with a device known as a 'fuel-air explosive.'"
== Host plants == The cabbage looper is a generalist insect that can reside and feed on over 160 host plants. The looper's variety of hosts is partially due to the ability of its salivary glands to differentially express based on the host. For example, cabbage and tomato plants use defensive strategies involving different compounds, and the cabbage looper can combat either by upregulating the appropriate genes. The gland's high responsiveness to the diet allows for considerable flexibility in host plants. The cabbage looper's preferred hosts are crucifers such as cabbage and broccoli, because it grows faster on these plants, possibly due to nutritional or chemical differences. Tobacco can also be a host for the cabbage looper. However, it is not preferred because gummosis, a gummy substance produced by some plants, and trichomes, hair-like appendages, harm early larvae survival. Older larvae are more resistant to these defenses. The number of caterpillars on a plant can depend on a plant's maturity. Cabbages that mature early are less attractive, whereas cabbages just beginning to head are the most attractive. Among crucifers, there generally seems to be no preference for one specific type of crucifer, like kale over cabbage or broccoli over brussels sprouts. The only apparent preference is for red cabbage – nearby double the number of caterpillars were present on the red cabbage compared to the green. This suggests that the number of caterpillars on a host plant has less to do with the species of host than with the host's height and foliage.
According to disinformation experts and intelligence agencies, Russia spread disinformation ahead of the 2024 election to damage Biden and Democrats, boost candidates supporting isolationism, and undercut support for Ukraine aid and NATO. On September 4, 2024, the United States publicly accused Russia of interfering in the 2024 election and announced several steps to combat Russian influence including sanctions, indictments, and seizing of web domains used to spread propaganda and disinformation. U.S. intelligence agencies assessed that Russia preferred Trump to win the election, viewing him as more critical of American support for Ukraine.
Sources: en.wikipedia.org
=== EC 1.1.4 With a disulfide as acceptor === EC 1.1.4.1: Now EC 1.17.4.4, vitamin-K-epoxide reductase (warfarin-sensitive) EC 1.1.4.2: Now EC 1.17.4.5, vitamin-K-epoxide reductase (warfarin-insensitive)
It is on the World Health Organization's List of Essential Medicines. The World Health Organization classifies colistin as critically important for human medicine. It is available as a generic medication. It is derived from bacteria of the genus Paenibacillus.
Lee, Nick; Bessho, Yoshitaka; Wei, Kenneth; Szostak, Jack W.; Suga, Hiroaki (2000). "Ribozyme-catalyzed tRNA aminoacylation". Nature Structural Biology. 7 (1): 28–33. doi:10.1038/71225. PMID 10625423. S2CID 1831912. Ramaswamy, Krishna; Saito, Hirohide; Murakami, Hiroshi; Shiba, Kiyotaka; Suga, Hiroaki (2004). "Designer Ribozymes: Programming the tRNA Specificity into Flexizyme". Journal of the American Chemical Society. 126 (37): 11454–11455. Bibcode:2004JAChS.12611454R. doi:10.1021/ja046843y. PMID 15366888. Passioura, Toby; Suga, Hiroaki (2017). "A RaPID way to discover nonstandard macrocyclic peptide modulators of drug targets". Chemical Communications. 53 (12): 1931–1940. doi:10.1039/C6CC06951G. PMID 28091672.
inverted repeat A nucleotide sequence followed downstream on the same strand by its own reverse complement. The initial sequence and the reverse complement may be separated by any number of nucleotides, or may be immediately adjacent to each other; in the latter case, the composite sequence is also called a palindromic sequence. Inverted repeats are self-complementary by definition, a property which involves them in many biological functions and dysfunctions. Contrast direct repeat.
Sources: en.wikipedia.org
Red and white blood cells and platelets can be counted using a hemocytometer, a microscope slide containing a chamber that holds a specified volume of diluted blood. The hemocytometer's chamber is etched with a calibrated grid to aid in cell counting. The cells seen in the grid are counted and divided by the volume of blood examined, which is determined from the number of squares counted on the grid, to obtain the concentration of cells in the sample. Manual cell counts are labour-intensive and inaccurate compared to automated methods, so they are rarely used except in laboratories that do not have access to automated analyzers. To count white blood cells, the sample is diluted using a fluid containing a compound that lyses red blood cells, such as ammonium oxalate, acetic acid, or hydrochloric acid. Sometimes a stain is added to the diluent that highlights the nuclei of white blood cells, making them easier to identify. Manual platelet counts are performed in a similar manner, although some methods leave the red blood cells intact. Using a phase-contrast microscope, rather than a light microscope, can make platelets easier to identify. The manual red blood cell count is rarely performed, as it is inaccurate and other methods such as hemoglobinometry and the manual hematocrit are available for assessing red blood cells; but if it is necessary to do so, red blood cells can be counted in blood that has been diluted with saline. Hemoglobin can be measured manually using a spectrophotometer or colorimeter.
=== μ-opioid receptors === In clinical trials, the MOR is the main target of opioid ligand binding. While binding of the opioid to the MOR typically causes analgesia, there can be instances where hyperalgesia occurs. It has been speculated that the opposite analgesic and hyperanalgesic effects are due to different isoforms of the receptor. The MOR is a G protein-coupled receptor with seven transmembrane domains. Variants of the receptor have been discovered and are due to alternative splicing mechanisms. A particular receptor variant, 6TM MOR, has been heavily studied because of its role in nociception. The 6TM MOR is missing residues in the N-terminal region which has implications for the extracellular tail and first transmembrane domain. This causes an excitatory effect compared to the inhibition in the normal seven transmembrane domain receptor because of differences in G-protein activation. Studies on mice have shown silencing of the 6TM MOR variant decreased morphine-induced hyperalgesia which suggested G-protein coupling in the 6TM isoform could be a factor in the development of OIH.
As such, PBPK modeling can be used, inter alia, to evaluate the involvement of carrier-mediated transport, clearance saturation, enterohepatic recirculation of the parent compound, extra-hepatic/extra-gut elimination; higher in vivo solubility than predicted in vitro; drug-induced gastric emptying delays; gut loss and regional variation in gut absorption.
Sources: en.wikipedia.org
Yes. Lyophilization and freeze-drying are synonyms for the same vacuum-assisted sublimation process. The term lyophilization is more common in pharmaceutical and laboratory settings, while freeze-drying is widely used in food and general contexts.
Reduced pressure lowers the boiling point of water and allows ice to sublime below its triple point. Without sufficient vacuum, melting or boiling may occur instead of sublimation, which can damage the product structure.
Heat and mass transfer limit drying once the ice front recedes. The dried layer insulates the frozen core and resists vapor flow, so increasing shelf temperature too quickly can cause collapse or meltback.
Simple drying usually removes water by evaporation from a liquid or solid, often with heat. Lyophilization first freezes the material and then removes ice by sublimation under vacuum. This avoids prolonged exposure to liquid water and high temperatures.