Collapse temperature is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2026-01-29. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
Lyophilized solids are often hygroscopic, so handling occurs in controlled low-humidity areas or glove boxes when the material is exposed. Vials remain sealed with elastomeric stoppers and aluminum crimps until use, because airborne moisture can raise residual water and shorten shelf life. The porous cake is fragile and may crack, shrink, or powder during transport. Personnel typically avoid repeated warming and cooling of sealed units, which can draw moisture through closures. These practices aim to preserve the low water content achieved during drying.
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.
| 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. |
Lyophilization removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts liquid water into ice and fixes the structure of the sample. After freezing, primary drying lowers pressure so ice changes directly to vapor without passing through a liquid phase. Secondary drying then removes bound water that remains after ice sublimation. The result is a dry, porous solid that often retains its original shape.
The low pressure used during drying allows water vapor to move from the ice surface to a cold condenser. Energy supplied as heat drives sublimation but must stay below the collapse temperature of the frozen matrix. If the product becomes too warm, the frozen structure may soften or melt, reducing pore formation and slowing drying. Formulations often include bulking agents, stabilizers, or buffers to support a rigid cake. The final moisture content depends on formulation, freezing rate, and the length of secondary drying.
After drying, a lyophilized product is usually sealed under vacuum or an inert gas to limit moisture uptake. Residual water content is measured because small changes can alter chemical stability and cake appearance. Storage temperature depends on the material; many biological products are kept at 2–8 °C, while some require −20 °C or colder. Exposure to ambient humidity during handling can cause the porous solid to absorb water and collapse. Container closures and stoppers are therefore selected for low moisture transmission and compatibility.
Quality control for lyophilized materials includes visual inspection of the cake, measurement of residual moisture, and tests for reconstitution time. An acceptable cake is typically uniform and may be slightly porous; shrinkage, meltback, or cracks can indicate process deviations. Analytical methods such as Karl Fischer titration, thermogravimetric analysis, and near-infrared spectroscopy quantify water content. Reconstitution time is recorded because a very slow or incomplete dissolution can signal collapse or aggregation. Stability studies compare samples stored under defined temperature and humidity conditions over months or years.
University of Toronto Libraries Collection: Discovery and Early Development of Insulin, 1920–1925 CBC Digital Archives – Banting, Best, Macleod, Collip: Chasing a Cure for Diabetes Animations of insulin's action in the body at AboutKidsHealth.ca (archived 9 March 2011) Overview of all the structural information available in the PDB for UniProt: P01308 (Insulin) at the PDBe-KB.
Also, this tail movement can increase the number interactions between the histone tail and the DNA, increasing likelihood of nucleosome formation and potentially leading to the creation of higher-order chromatin structure. In trans, P38 leads to the opposite effects: allowing for Set2 to methylate K36. Set2 is only affected by isomerization of P38 when creating a trimethylated K36 (commonly written as K36me3), however, and not K36me2. Fpr4 also binds to P32 in H4, though its effects are minimal. In mammalian cells, the isomerization of H3P30 interacts with the phosphorylation of H3S28 (serine in the 28 position of histone H3) and the methylation of H3K27. hFKBP25 is a PPIase that is a homolog for Fpr4 in mammalian cells and is found to commonly be associated with the presence of HDACs. Cyp33 is a cyclophilin that has the ability to isomerize H3 proline residues at P16 and P30 positions. Histones H2A and H2B also have multiple proline residues near amino acids that when modified affect the activity surrounding the histone.
==== Local government finance ==== In 1979 the Conservatives were strongly represented in local government, as a result of the unpopularity of the outgoing Labour government. Four of the five council associations were Conservative-controlled. Heseltine was able to persuade them to rein in their spending by 1% each year. Whereas previously overspending councils had received extra rate support grants from Whitehall, after six months Heseltine announced a list of fourteen overspending councils who were to have their grant cut, most of them inner London councils and only one of them, Hammersmith & Fulham, Conservative controlled. The move appeared blatantly political as many of the other 114 overspenders were Conservative councils. Council leaders who came to appeal to Heseltine were often humiliated by being interrogated about their budget, to demonstrate their lack of detailed knowledge, before the council treasurer was allowed to speak. From 1980 to 1981 relations with local government became increasingly confrontational, as Labour made large gains in local elections, with a new generation of council leaders such as Ken Livingstone in London and David Blunkett in Sheffield seeking to generate employment through their councils. Council spending now began to rise again, largely as a result of increases by the GLC, Merseyside and West Midlands councils; whereas Labour votes tended to be poorer and eligible for rate rebates, the burden of higher spending tended to fall on businesses and middle class homeowners.
Sources: en.wikipedia.org
Directed by Sheila Hayman, made by Uden Associates 8 November Rebuilding Berlin, how German telecommunication and electrical engineers found great difficulty in connecting the infrastructure and technology of East and West Berlin, which were largely totally incompatible, and why the two technological systems were so different; East and West Germany were founded in 1953; the trains in East (Deutsche Reichsbahn or DR) and West Germany ran on electric motors that worked in opposite ways; Erich Kratky of Berliner Verkehrsbetriebe (former West Berlin Public Transport) and how East Berlin drivers had 60% of those in West Berlin; Mahlow station, on the S2 line on the Berlin S-Bahn, was completely rebuilt in 1991, opening on 31 August 1992; before 1989, West Berlin could not connect to any neighbouring electrical power networks, so had to make all of its own power itself, by nine power stations; in 1992 West Berlin could not make enough electrical power;Jürgen Beyer of the East Berlin Electricity Board; in 1992 East and West Germany could not connect their electricity systems together; Klaus Krämer of the West Berlin Electricity Board, and how East German load frequency control (LFC) was not good enough for West Germany; East German power stations were polluting; Müggelsee in East Berlin; East Berlin had natural gas - from Russia - but West Berlin did not have natural gas, and had to produce its own gas from processing, and there were many more gas leaks in East Berlin, run by the Berlin Gas Board, and British Gas plc was installing most of the new plastic gas mains in East Berlin; one fifth of housing in East Berlin was uninhabitable, due to lack of renovation and unsafe electrical wiring; much housing in East Berlin did not have any bathrooms; the post system in East Berlin was three times slower than West Berlin, as it was all sorted by hand, and mail hand to be sent in standard envelopes only, in East Germany - the two post systems were incompatible, and East and West Germany had totally different postcode systems, although both had four digits, so a letter was put in front of each Deutsche Post postcode, to show if it was an East or West German postcode; in 1952, telephone connections between East and West Germany were stopped, but four lines were installed in 1972; the East German telephone exchanges were all mechanical, and could not transmit any digital communications; one in ten people in East Berlin had a phone - telecommunications in East Berlin were hopeless and expensive; in 1992 Deutsche Telekom connected East and West Berlin, and the price would be a local call, not the price of an international call, under the phrase Wir schaffen Verbingdungen; not only were East German telecommunications often impossible, but the Stasi secret police were listening in to most calls; Rudolf Reichel of the former East German Economic Institute; science research in East Germany had been greatly restricted; Volker Hassemer; East Germans viewed West Germans as selfish, and West Germans viewed East Germans as backward. Narrated by Su-Lin Looi, directed by Cosima Dannoritzer, produced by Karl Sabbagh, made by Skyscraper Productions 15 November 21st Century Jet, how the Boeing 777 moved from the drawing board to manufacture in 1992, with the innovative new method called CATIA; the Boeing 777 was the largest jet aircraft to have been developed mostly by computer, with assembly beginning in January 1993; there were 10,000 people in the 777 programme, who met the managers in a weekly meeting; meeting the needs of Robert Crandall of American Airlines, and competition from the new Airbus A340; parts of the tail were built in Australia; the nose cone and flaps were made in Italy; the landing gear was made in Canada, the US, and France; parts of the wing ribs and passenger doors were made in Japan; the nose landing gear door was made in Belfast; some of the electronics was made in England; there were about 230 design teams, from different manufacturers; the CATIA system was a digital mockup; Thomas Gaffney, head of passenger doors; Henry Shomber, one of the chief engineers; John Roundhill, a chief project engineer; United Airlines placed the first order, which started the project; Al Tyler of Aerospace Technologies of Australia (ASTA), who made the 777 rudder - the company became Boeing Australia; John King, Baron King of Wartnaby of British Airways visits to look at legroom for the new 777. Narrated by Simon Prebble, directed by Karl Sabbagh, made by Skyscraper Productions 22 November The Puzzle of HIV, scientists after ten years did not understand how HIV worked; immunologists Anthony Fauci and Max Essex; Angus Dalgleish of St George's, University of London; virologist Stephen S. Morse, and the origination of viruses, and how most pandemics originated in China; Stella Knight of the MRC, and dendritic cells, researched by Brigid Balfour; French immunologist Jean-Claude Ameisen of the Pasteur Institute of Lille; virologist Jonas Salk; Claude Nicolau, and the CD4 glycoprotein. Narrated by Scottish actress Sandra Clark, directed by Nigel Maslin, produced by Chris Haws, made by InCA Productions 29 November The Alpha Link, much of medical understanding of radiation protection and health comes from what occurred in Japan in August 1945. Martin Gardner (1940–93), an epidemiologist, and Professor of Medical Statistics at the University of Southampton, thought that health was affected by working in a nuclear power station, which the British nuclear industry vehemently would not believe. Directed by Vivienne King, made by Box Productions 6 December Toying with the Future, about electronic children's toys, visiting Ocean Software in Manchester; Brian Sutton-Smith of the University of Pennsylvania, and how toys were small replicas of large world events; Eugene F. Provenzo of the University of Miami and how the culture of childhood began in the early 1700s, and how German Friedrich Fröbel developed educational toys in the early 1800s, but it often lacked fun; Meccano Ltd sets, developed by Frank Hornby, launching the international Meccano Guild network of children's mechanical clubs in 1919, publicised by the Meccano Magazine; Richard Gregory, neuropsychologist at the University of Bristol, and his Exploratory Hands-on Science Centre, which closed in 1999, replaced by We the Curious in 2000; toy designer Patrick Rylands; Gary Bracey of Ocean Software; Keith Tinman, computer game musician; Elizabeth Curran of GameTek; Ocean Software designers Ray Coffey, James Higgins and Dawn Drake. Directed by Christopher Rawlence, produced by Debra Hauer, made by Rawlence Hauer Productions 13 December The Elements, a repeat of the 20 October 1991 episode 20 December E.T. Please Phone Earth, about the SETI Institute, with Prof Philip Morrison, a professor of physics at MIT, who played a starring if not dangerous role in the Manhattan Project; Jill Tarter at the Hat Creek Radio Observatory in California; Dr John Billingham, a British medical doctor at the Ames Research Center in California; Prof Antony Hewish of the University of Cambridge, who discovered pulsars in 1967; Frank Drake, and his work at the National Radio Astronomy Observatory in Green Bank, West Virginia; Barney Oliver of SETI; David Blair of the University of Western Australia; Paul Horowitz of Harvard University; the Ohio State University Radio Observatory (known as Big Ear) and its 1977 Wow! signal; Jack Cohen; chemist Stanley Miller and his 1953 experiment; blind SETI investigator Kent Cullers; and biologist Jared Diamond from UCLA. Jointly made with ABC of Australia, narrated by Heather Couper, directed by Richard Smith, produced by Stuart Carter, made by Pioneer Productions
== Early life == Darshan Ranganathan was born as Darshan Markan on 4 June 1941 to Vidyavati Markan and Shanti Swarup in Delhi. She was educated in Delhi and received a Ph.D. in chemistry from Delhi University in 1967. First hired as a lecturer, she became head of the Chemistry Department at Miranda College, Delhi, and went on to receive an 1851 Research Fellowship from the Royal Commission for the Exhibition of 1851, to enable her to conduct postdoctoral work at Imperial College London with Professor D.H.R. Barton.
From 1928 to 1932, Albert Szent-Györgyi and Joseph L. Svirbely's Hungarian team, and Charles Glen King's American team, identified the anti-scorbutic factor. Szent-Györgyi isolated hexuronic acid from animal adrenal glands, and suspected it to be the antiscorbutic factor. In late 1931, Szent-Györgyi gave Svirbely the last of his adrenal-derived hexuronic acid with the suggestion that it might be the anti-scorbutic factor. By the spring of 1932, King's laboratory had proven this, but published the result without giving Szent-Györgyi credit for it. This led to a bitter dispute over priority. In 1933, Walter Norman Haworth chemically identified the vitamin as l-hexuronic acid, proving this by synthesis in 1933. Haworth and Szent-Györgyi proposed that L-hexuronic acid be named a-scorbic acid, and chemically l-ascorbic acid, in honor of its activity against scurvy. The term's etymology is from Latin, "a-" meaning away, or off from, while -scorbic is from Medieval Latin scorbuticus (pertaining to scurvy), cognate with Old Norse skyrbjugr, French scorbut, Dutch scheurbuik and Low German scharbock. Partly for this discovery, Szent-Györgyi was awarded the 1937 Nobel Prize in Medicine, and Haworth shared that year's Nobel Prize in Chemistry. In 1957, J. J. Burns showed that some mammals are susceptible to scurvy as their liver does not produce the enzyme l-gulonolactone oxidase, the last of the chain of four enzymes that synthesize vitamin C. American biochemist Irwin Stone was the first to exploit vitamin C for its food preservative properties.
Sources: en.wikipedia.org
Disulfiram inhibits the enzyme acetaldehyde dehydrogenase, which in turn results in buildup of acetaldehyde, a toxic metabolite of ethanol with unpleasant effects. The medication or drug is commonly used to treat alcohol use disorder, and results in immediate hangover-like symptoms upon consumption of alcohol, this effect is widely known as disulfiram effect.
=== Lifetime cumulative dose === Bleomycin should not exceed a lifetime cumulative dose greater than 400 units. Pulmonary toxicities, most commonly presenting as pulmonary fibrosis, are associated with doses of bleomycin greater than 400 units.
==== Bone metabolism ==== In mice and humans, alterations in serotonin levels and signalling have been shown to regulate bone mass. Mice that lack brain serotonin have osteopenia, while mice that lack gut serotonin have high bone density. In humans, increased blood serotonin levels have been shown to be a significant negative predictor of low bone density. Serotonin can also be synthesized, albeit at very low levels, in the bone cells. It mediates its actions on bone cells using three different receptors. Through 5-HT1B receptors, it negatively regulates bone mass, while it does so positively through 5-HT2B receptors and 5-HT2C receptors. There is very delicate balance between physiological role of gut serotonin and its pathology. Increase in the extracellular content of serotonin results in a complex relay of signals in the osteoblasts culminating in FoxO1/ Creb and ATF4 dependent transcriptional events. Following the 2008 findings that gut serotonin regulates bone mass, the mechanistic investigations into what regulates serotonin synthesis from the gut in the regulation of bone mass have started. Piezo1 has been shown to sense RNA in the gut and relay this information through serotonin synthesis to the bone by acting as a sensor of single-stranded RNA (ssRNA) governing 5-HT production. Intestinal epithelium-specific deletion of mouse Piezo1 profoundly disturbed gut peristalsis, impeded experimental colitis, and suppressed serum 5-HT levels. Because of systemic 5-HT deficiency, conditional knockout of Piezo1 increased bone formation.
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.
Karl Fischer titration is widely used because it is specific for water and works at low levels. Loss on drying is simpler but less specific, since volatile solvents or decomposition products can also be lost.