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.
Last reviewed on 2026-01-05. Where a claim depends on a specific study, the study is described rather than over-claimed.
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 is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen so that water becomes ice; then the surrounding pressure is lowered below the vapor pressure of ice. Heat is applied gently so ice changes directly to vapor without passing through a bulk liquid phase. The vapor is collected on a cold condenser, leaving a dry porous matrix. This process differs from simple evaporation because the material remains frozen during the main drying stage.
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.
The physics of lyophilization depends on phase boundaries and heat and mass transfer. During primary drying, heat supplied to the product must equal the latent heat of sublimation, while water vapor moves through the drying cake to the condenser. If shelf temperature or pressure is set too high, the ice front can exceed the collapse temperature, causing meltback or pore collapse. If conditions are too cold, drying slows and costs rise. Formulation excipients, vial geometry, and freezing rate alter these limits.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Freeze-drying, lyophilisation | Lyophilisation is the British spelling; the process is not simple evaporation. |
| Primary drying pressure | 0.05–0.3 mbar | Pressure must remain below the vapor pressure of ice at the product temperature. |
| Sublimation temperature | Below 0 °C | Ice changes directly to vapor while the product remains frozen. |
| Typical shelf temperature | −40 to −10 °C | Exact setting depends on formulation critical temperature and equipment. |
| Cycle duration | 12–72 hours | Time varies with fill volume, formulation, and dryer performance. |
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.
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.
A formulation often contains excipients that protect the active ingredient during freezing and drying. Bulking agents provide structure, while lyoprotectants stabilize sensitive molecules. The freezing step can produce ice crystals whose size and distribution affect the drying rate, and cycle design includes freezing, annealing, and drying phases. If the product temperature rises above a critical value, the cake may collapse or lose its porous structure. Successful lyophilization therefore depends on the interaction between formulation, equipment, and cycle design.
Lyophilization is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen to convert liquid water into ice. Next, the pressure is reduced below the triple point of water so that ice changes directly into vapor without passing through a liquid phase. This step is called primary drying. The result is a porous solid or cake that retains the original shape of the frozen solution.
==== Post-Apollo NASA: Shifting goals and budget cuts ==== NASA had ambitious follow-on human spaceflight plans as it reached its lunar goal but soon discovered it had expended most of its political capital to do so. A victim of its own success, Apollo had achieved its first landing goal with enough spacecraft and Saturn V launchers left for a total of ten lunar landings through Apollo 20, conducting extended-duration missions and transporting the landing crews in Lunar Roving Vehicles on the last five. NASA also planned an Apollo Applications Program (AAP) to develop a longer-duration Earth orbital workshop (later named Skylab) from a spent S-IVB upper stage, to be constructed in orbit using several launches of the smaller Saturn IB launch vehicle. In February 1969, President Richard M. Nixon convened a "space task group" to set recommendations for the future US civilian space program, headed by his vice president, Spiro T. Agnew. Agnew was an enthusiastic proponent of NASA's follow-up plans for permanent space stations in Earth and lunar orbit, perhaps a base on the lunar surface, and the first human flight to Mars as early as 1986 or as late as 2000. These would be serviced by an infrastructure of a reusable Space Transportation System, including an Earth-to-orbit Space Shuttle. Nixon had a 'better sense' of the declining political support in Congress for new Apollo-style programs, which had disappeared with the achievement of the landing, and he intended to pursue détente with the USSR and China, which he hoped might ease Cold War tensions.
Most Pakistanis, according to a Pew Research Center (PEW) poll, favour Sharia law as the official law, and 94 percent of them identify more with religion than nationality compared to Muslims in other nations.
=== Allied with Venezuela === The Washington Post wrote in October that Maduro had written to Russia's Vladimir Putin, asking for help with "defensive radars, military aircraft repairs and potentially missiles", and that Maduro had contacted "China and Iran, soliciting military assistance and equipment to strengthen the country's defenses". According to The Wall Street Journal, China and Russia are "Maduro's two most powerful allies" and they have "previously provided military equipment, maintenance and training, say analysts, along with economic assistance", but along with Maduro's other traditional allies of Cuba and Iran, they are unlikely to lend significant support help beyond words of support.
== Biosynthesis == 2,5-DKPs are synthesized by a variety of organisms including humans. In general, they arise by the action of a tRNA-dependent cyclodipeptide synthases, a type of enzyme responsible for creating a cyclic amide linkage between two peptides. The enzymes cyclodipeptide oxidase and S-adenosyl-methionine-dependent O/N methyltransferases act in tandem to chemically modify cyclic dipeptides.
== Molecular properties and chemical space of peptides == The chemical space of peptides is defined as a multidimensional landscape shaped by molecular descriptors or fingerprints. Within these frameworks, the distance between specific molecules serves as a proxy for chemical or functional similarity. This space can be mapped using primary amino acid sequences, three-dimensional structural data, or a combination of both. Key molecular properties used for mapping include molecular weight, lipophilicity (logP and logD), topological polar surface area (TPSA), and hydrogen-bond dynamics. Dimensionality-reduction techniques—such as Principal Component Analysis (PCA), t-SNE, and UMAP—are frequently employed alongside clustering algorithms to visualize peptide libraries and identify clusters with related biological activities. Peptides are distinguished from traditional small molecules by their unique combination of residue sequence, amide backbone flexibility, and susceptibility to chemical modifications, all of which dictate bioavailability and membrane permeability. Computational analysis is supported by notation systems like FASTA, HELM, and BILN for encoding both canonical and modified sequences. Modifications such as cyclization or the integration of non-natural amino acids significantly shift a peptide's position within the chemical space, altering its stability and target affinity. Consequently, chemical-space analysis is a vital tool for virtual screening and the discovery of shared bioactivity regions across different peptide families.
Sources: en.wikipedia.org
=== Pharmacokinetics === Clonazepam is lipid-soluble, rapidly crosses the blood–brain barrier, and penetrates the placenta. It is extensively metabolised into pharmacologically inactive metabolites, with only 2% of the unchanged drug excreted in the urine. Clonazepam is metabolized extensively via nitroreduction by cytochrome P450 enzymes, including CYP3A4. Erythromycin, clarithromycin, ritonavir, itraconazole, ketoconazole, nefazodone, cimetidine, and grapefruit juice are inhibitors of CYP3A4 and can affect the metabolism of benzodiazepines. It has an elimination half-life of 19–60 hours. Peak blood concentrations of 6.5–13.5 ng/mL were usually reached within 1–2 hours following a single 2 mg oral dose of micronized clonazepam in healthy adults. In some individuals, however, peak blood concentrations were reached at 4–8 hours. Clonazepam passes rapidly into the central nervous system, with levels in the brain corresponding with levels of unbound clonazepam in the blood serum. Clonazepam plasma levels are very unreliable amongst patients. Plasma levels of clonazepam can vary as much as tenfold between different patients. Clonazepam has plasma protein binding of 85%. Clonazepam passes through the blood–brain barrier easily, with blood and brain levels corresponding equally with each other. The metabolites of clonazepam include 7-aminoclonazepam, 7-acetaminoclonazepam and 3-hydroxy clonazepam. These metabolites are excreted by the kidney. It is effective for 6–8 hours in children, and 8–12 hours in adults.
After the 1986 People Power Revolution that toppled the regime of President Ferdinand Marcos, Duterte was appointed officer-in-charge vice mayor of Davao City by President Corazon Aquino. In the 1988 local elections, he ran for mayor under Lakas ng Dabaw, a local political alliance, defeating former OIC Mayor Zafiro Respicio by a narrow margin of 6,000 votes. As mayor of Davao City, Duterte made efforts to unite the different tribes and political groups in the city. He set a precedent by designating deputy mayors to represent the administrative districts, as well as the Lumad and Moro peoples in the city government; this was later copied by other cities in other parts of the Philippines. In December 1990, Duterte joined the Nacionalista Party upon the persuasion of Senator Juan Ponce Enrile. In 1992, he successfully defended his seat from 1st district representative Prospero Nograles. In 1995, after Flor Contemplacion, a Filipina, was executed in Singapore after confessing to a double murder, Duterte allegedly burned a flag of Singapore (though this claim was later denied) and joined 1,000 employees of Davao City in protest. In 1998, because he was term-limited to run again for mayor, Duterte ran and won as congressman of the city's 1st district under Laban ng Makabayang Masang Pilipino. He was a member of five House committees, namely: National Defense, Public Order and Security, Health, Transportation and Communications, and Cooperative Development. He filed 64 measures, including 45 bills, with one enacted into law—Republic Act No.
== Early life == Hari was born in Glasgow, Scotland, to a Scottish mother and Swiss father. His family relocated to London when he was an infant. His father was a bus driver and mother a nurse. Later, his mother worked in shelters for survivors of domestic violence. Hari said he was physically abused in his childhood by an unnamed adult while his father was away and his mother was ill. Hari attended the John Lyon School, an independent school affiliated with Harrow, and then Woodhouse College, a state sixth form in Finchley. He graduated from King's College, Cambridge, in 2001 with a double first in Social and Political Sciences.
=== Potential side effects === Tests in mice have indicated that BACE proteases, specifically BACE1, are necessary for the proper function of muscle spindles. These results raise the possibility that BACE inhibiting drugs currently being investigated for the treatment of Alzheimer's may have significant side effects related to impaired motor coordination, though BACE1 knockout mice are healthy.
Sources: en.wikipedia.org
== Clinical significance == Progression of epithelial cancer often relies on deep and regional lymph node invasion. The lamina propria, being one of the barriers to the submucosa, is an area where epithelial cancer invasion is of significance since lymphatic invasion is an independent predictor of lymph node metastasis, especially in gastric cancer. As soon as the tumors breach the basement membrane and reach the lamina propria, they are exposed to lymphatics which may increase the rate of metastasis and cancer progression. Deeper invasion into the submucosa will increase the exposure to lymphatics. Long-standing inflammation is a risk factor for the development of cancer. The lamina propria macrophages when under much stress release pro-inflammatory signals that may lead to increased probability of developing cancer. An example of this is the overactivation of the IL-6/STAT3 pathway, which has been linked to colitis-associated cancer.
; if it is equal to zero the chemical reaction is said to be at equilibrium. There exist only limited possible states of energy for electrons, atoms and molecules. These are determined by the rules of quantum mechanics, which require quantization of energy of a bound system. The atoms/molecules in a higher energy state are said to be excited. The molecules/atoms of substance in an excited energy state are often much more reactive; that is, more amenable to chemical reactions. The phase of a substance is invariably determined by its energy and the energy of its surroundings. When the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water (H2O); a liquid at room temperature because its molecules are bound by hydrogen bonds. Whereas hydrogen sulfide (H2S) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole–dipole interactions. The transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. However, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer.
=== eRF3 binding === The binding of eRF3 and GTP to eRF1 to form a complex is essential for termination of translation. The interaction between the C domains of both eRF1 and eRF3 is the major force holding the complex together. However, it was later discovered that the M domain also contributes to the stability of the complex. The positioning of eRF3 near the GGQ motif, which is in the C domain, allows greater catalytic effects of eRF1 hydrolyzing the peptidyl-tRNA.
Tertomotide (GV1001, EARPALLTSRLRFIPK) is a 16-amino acid peptide based on the 616‑626 position fragment of human telomerase reverse transcriptase protein (hTERT). It was originally developed as a possible subunit vaccine for various types of cancer, as it can trigger immune attack against cancer cells which overexpress telomerase, a common mutation found in malignant tumors. However, it does not block telomerase activity in healthy tissue and has been found to produce various useful activities in its own right including antiviral, antiinflammatory and antidepressant effects, and has been trialled for numerous other medical applications including Alzheimer's disease as well as its original role in the treatment of cancer.
== See also == 25-NB, BOx, HOT-x, scaline, 3C, DOx, 4C, Ψ-PEA, FLY, TWEETIO List of miscellaneous serotonin 5-HT2A receptor agonists The Shulgin Index Substituted amphetamines Substituted methoxyphenethylamine Substituted methylenedioxyphenethylamines Substituted phenethylamines Substituted tryptamines
Sources: en.wikipedia.org
The main change is sublimation, in which ice becomes water vapor without melting into liquid water. This occurs when the chamber pressure is held below the vapor pressure of ice while mild heat is supplied. The result is a dry, porous solid that retains much of its original shape.
Freezing determines ice crystal size, solute distribution, and the pore network left after drying. A slow or fast freezing rate can produce different cake structures and affect reconstitution. It also sets whether the formulation follows an amorphous or crystalline drying path.
It removes most free water during primary drying and part of the bound water during secondary drying. A small residual moisture content often remains and is specified for each product. Complete removal is generally neither practical nor desirable for stability.
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.