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 2025-12-23. Numbers and descriptions here follow the published literature rather than marketing material.
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.
A typical cycle begins with freezing, sometimes including an annealing step to control ice crystal size. Freezing conditions influence the pore network that later allows vapor escape. During primary drying, shelf temperature and chamber pressure are set so heat enters the product while its temperature stays below the collapse or eutectic point. Secondary drying then raises the shelf temperature to desorb bound water and lower residual moisture. Cycle design depends on formulation, fill volume, container type, and equipment capability.
The physics of lyophilization couples heat transfer, mass transfer, and phase behavior. Sublimation requires a vapor pressure difference between the ice front and the chamber, and the dried layer adds resistance to vapor flow. Amorphous formulations are characterized by a glass transition temperature of the maximally freeze-concentrated solute, often denoted Tg'. Crystalline bulking agents can provide structure, while amorphous excipients stabilize labile components. Open questions remain about spatial heterogeneity, edge effects, and how laboratory cycles scale to production.
| Property | Value | Notes |
|---|---|---|
| Common synonym | Freeze-drying | Same dehydration operation |
| Typical vacuum | 10-100 Pa | Pressure during primary drying |
| Primary drying temperature | -40 to -10 °C | Below collapse temperature for many formulations |
| Cycle duration | 12-72 hours | Varies with load, container, and formulation |
| Key phase change | Sublimation | Solid ice to water vapor |
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.
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.
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.
Formulation composition influences whether freeze-drying produces an intact cake or a collapsed mass. Excipients such as sugars and polymers can raise the collapse temperature and provide bulk during drying. The critical temperature for primary drying is often the collapse temperature or the glass transition temperature of the maximally concentrated phase. If the product temperature exceeds this threshold, the frozen matrix may soften and lose structure. Established practice therefore links shelf temperature and chamber pressure to the formulation's thermal properties.
The physics of freeze-drying couples heat transfer, mass transfer, and phase change. Heat supplied through the shelf must reach the sublimation front without melting the ice or degrading the product. Water vapor then travels through the already dried layer and leaves the chamber, where low pressure and cold traps keep it from returning. The dried layer acts as a resistance to vapor flow, so drying rate changes as the front recedes. Open questions remain about how pore structure and formulation heterogeneity affect drying uniformity at larger scales.
Lyophilization removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts liquid water into ice and concentrates dissolved solids. Primary drying then lowers chamber pressure so ice changes directly into vapor without passing through a liquid phase. Secondary drying raises the shelf temperature to remove bound water that remains after ice sublimation. The result is a dry, porous structure that can be reconstituted later.
==== Reactions of lysines ==== The nucleophilic lysine residue is commonly targeted site in protein bioconjugation, typically through amine-reactive N-hydroxysuccinimidyl (NHS) esters. To obtain optimal number of deprotonated lysine residues, the pH of the aqueous solution must be below the pKa of the lysine ammonium group, which is around 10.5, so the typical pH of the reaction is about 8 and 9. The common reagent for the coupling reaction is NHS-ester (shown in the first reaction below in Figure 1), which reacts with nucleophilic lysine through a lysine acylation mechanism. Other similar reagents are isocyanates and isothiocyanates that undergo a similar mechanism (shown in the second and third reactions in Figure 1 below). Benzoyl fluorides (shown in the last reaction below in Figure 1), which allows for lysine modification of proteins under mild conditions (low temperature, physiological pH), were recently proposed as an alternative to classically used lysine specific reagents.
In the field of pharmacokinetics, the area under the curve (AUC) is the definite integral of the concentration of a drug in blood plasma as a function of time (this can be done using liquid chromatography–mass spectrometry). In practice, the drug concentration is measured at certain discrete points in time and the trapezoidal rule is used to estimate AUC. In pharmacology, the area under the plot of plasma concentration of a drug versus time after dosage (called "area under the curve" or AUC) gives insight into the extent of exposure to a drug and its clearance rate from the body.
In preparation for the 1998 finals series, and despite losing six of their last eight to the Roos, legendary Essendon coach Kevin Sheedy publicly labelled North executives Greg Miller and Mark Dawson soft in response to comments from commentators that his Essendon team was soft. The Kangaroos beat Essendon in the much-hyped encounter that followed (a Qualifying Final), and North fans pelted Sheedy with marshmallows as he left the ground, although Sheedy was seemingly unfazed by the incident, encouraging a "Marshmallow Game" the next year and relishing in the fact that Sheedy's ulterior motive was to build up the game and draw a large crowd, which proved to be correct, drawing in 71,154 people to attend the game. In 2000, the Bombers thrashed North by 125 points in the 1st Qualifying Final. The biggest VFL/AFL comeback of all time occurred between the two teams when Essendon managed to come back from a 69-point deficit to win by 12 points in 2001. A meeting of the two rivals at the MCG in the 2014 AFL finals series in the 2nd Elimination Final resulted in North winning by 12 points. West Coast – A three-decade rivalry between the Essendon Bombers and the West Coast Eagles kicked off when Essendon coach Kevin Sheedy tied the windsock down on the School End outer terrace so the opposition would not know which way the wind was blowing. Sheedy later said of the incident three decades later, in jest, that it was because the brand sponsor had neglected to pay their account. When West Coast won the toss and kicked against the breeze, it looked as if Sheedy's plan had worked.
the patient possesses an area of exposed bone in the jaw persisting for more than 8 weeks, the patient must present with no history of radiation therapy to the head and neck the patient must be taking or have taken bisphosphonate medication. According to the updated 2009 BRONJ Position Paper published by the American Association of Oral and Maxillofacial Surgeons, both the potency of and the length of exposure to bisphosphonates are linked to the risk of developing bisphosphonate-associated osteonecrosis of the jaw. In the 2014 AAOMS update on MRONJ, a staging and treatment strategies table was created:
Sources: en.wikipedia.org
, where N is the Landau level and the double valley and double spin degeneracies give the factor of 4. These anomalies are present not only at extremely low temperatures but also at room temperature, i.e. at roughly 20 °C (293 K).
James Lamar Wittliff (born June 15, 1938) also known as Jim Wittliff, is an American Biochemist and Professor Emeritus of Biochemistry & Molecular Genetics at the University of Louisville. He was Chairman of the Department of Biochemistry at the University of Louisville School of Medicine and Dentistry from 1976-1983. Wittliff's laboratory was designated the National Reference Facility by the National Cancer Institute for performing quality assurance surveys of receptor biomarker testing in breast cancers for cooperative clinical trial groups in the United States and Canada. He is the co-developer with NEN/DuPont of the 1st FDA approved tests for quantifying levels of estrogen and progestin receptor proteins.
== Biological functions == Like most siderophores, pyoverdine is synthesized and secreted into the environment when the microorganism that produces it detects that intracellular iron concentrations have fallen below a preset threshold. Although iron is the fourth-most abundant element in the Earth's crust, solubility of biologically relevant iron compounds is exceedingly low, and is generally insufficient for the needs of most (but not all) microorganisms. Siderophores, which are typically quite soluble and have exceptionally high avidity for iron (III) (the avidity of some siderophores for iron exceeds 1040 M-1 and many of the strongest avidities ever observed in nature are exhibited by siderophores for iron), help increase bioavailability of iron by pulling it into aqueous solution. In addition to this role, pyoverdine has a number of other functions, including regulating virulence, limiting the growth of other bacterial species (and serving as a sort of antimicrobial) by limiting iron availability, and sequestering other metals and preventing their toxicity.
== Use in organic synthesis == Without the propionyl group on the oxygen, the non-esterified alcohol precursor of propoxyphene (both enantiomers, known as darvon alcohol and novrad alcohol) have been employed as stoichiometric chiral reagents for asymmetric carbonyl reduction reactions involving aluminium hydride reagents.
=== Comparison to other agents === Compared with azathioprine it has higher incidence of diarrhea, and no difference in risk of any of the other side effects in transplant patients. Mycophenolic acid is 15 times more expensive than azathioprine.
Sources: en.wikipedia.org
=== Aerobic desaturation === Aerobic desaturation is the most widespread pathway for the synthesis of unsaturated fatty acids. It is utilized in all eukaryotes and some prokaryotes. This pathway utilizes desaturases to synthesize unsaturated fatty acids from full-length saturated fatty acid substrates. All desaturases require oxygen and ultimately consume NADH even though desaturation is an oxidative process. Desaturases are specific for the double bond they induce in the substrate. In Bacillus subtilis, the desaturase, Δ5-Des, is specific for inducing a cis-double bond at the Δ5 position. Saccharomyces cerevisiae contains one desaturase, Ole1p, which induces the cis-double bond at Δ9. In mammals the aerobic desaturation is catalyzed by a complex of three membrane-bound enzymes (NADH-cytochrome b5 reductase, cytochrome b5, and a desaturase). These enzymes allow molecular oxygen, O2, to interact with the saturated fatty acyl-CoA chain, forming a double bond and two molecules of water, H2O. Two electrons come from NADH + H+ and two from the single bond in the fatty acid chain. These mammalian enzymes are, however, incapable of introducing double bonds at carbon atoms beyond C-9 in the fatty acid chain..) Hence mammals cannot synthesize linoleate or linolenate (which have double bonds at the C-12 (= Δ12), or the C-12 and C-15 (= Δ12 and Δ15) positions, respectively, as well as at the Δ9 position), nor the polyunsaturated, 20-carbon arachidonic acid that is derived from linoleate.
Fructose: 38% Glucose: 31% Sucrose: 1% Water: 17% Other sugars: 9% (maltose, melezitose) Ash: 0.17% In this example the ash would include all the minerals in honey. Ashing is also performed prior to chemical analysis by inductively coupled plasma emission spectrometry.
=== Interpretation === The ability to quantitate the βhCG level is useful in monitoring germ cell and trophoblastic tumors, follow-up care after miscarriage, and diagnosis of and follow-up care after treatment of ectopic pregnancy. The lack of a visible fetus on vaginal ultrasound after βhCG levels reach 1500 mIU/mL is strongly indicative of an ectopic pregnancy. Still, even an hCG over 2000 IU/L does not necessarily exclude the presence of a viable intrauterine pregnancy in such cases. As pregnancy tests, quantitative blood tests and the most sensitive urine tests usually detect hCG between 6 and 12 days after ovulation. It must be taken into account, however, that total hCG levels may vary in a very wide range within the first 4 weeks of gestation, leading to false results during this period. A rise of 35% over 48 hours is proposed as the minimal rise consistent with a viable intrauterine pregnancy.
== Background == A QT interval is a value that is measured on an electrocardiogram. Measurements begin from the start of the Q wave to the end of the T wave. The value is an indication of the time it takes for a ventricle from the beginning of a contraction to the end of relaxation. The value for a normal QT interval is similar in males and females from birth up to adolescence. During infancy, a normal QTc is defined as 400±20 milliseconds. Before puberty, the 99th percentile of QTc values is 460 milliseconds. After puberty, this value increases to 470 milliseconds in males and 480 milliseconds in females. Torsades de pointes (TdP) is an arrhythmia. More specifically, it is one form of a polymorphic ventricular tachycardia that presents with a long QT interval. Diagnosis is made by electrocardiogram (EKG), which shows rapid irregular QRS complexes. The term "torsades de pointes" is translated from French as "twisting of the peaks" because the complexes appear to undulate, or twist around, the EKG baseline. TdP can be acquired by inheritance of a congenital long QT syndrome, or more commonly from the ingestion of a pharmacologic drug. During TdP episodes, patients have a heart rate of 200 to 250 beats/minute, which may present as palpitations or syncope. TdP often self-resolves, however, it may lead to ventricular fibrillation and cause sudden cardiac death.
By the end of the 1960s, peptides were phased out as drug candidates. Miguel Ondetti moved to the gastrointestinal hormone group in the mid 1960s. The first hormone to be studied by Ondetti's group was cholecystokinin, a digestion hormone. This product presented unique challenges because of the small amounts used in reactions. Unfortunately, bioassays were not quantitative enough to use for results and chemical reactions did not run well as such low amounts.
Sources: en.wikipedia.org
Primary drying removes ice by sublimation under vacuum. Secondary drying removes water that is bound to the material, often by warming the product after most ice has left. Both stages occur below temperatures that would cause unwanted melting.
Sublimation requires the solvent to remain solid so vapor leaves without passing through a liquid phase. If the product melts, the porous structure can collapse and drying becomes uneven. Maintaining frozen conditions preserves the intended physical form.
No, freeze-drying is a dehydration method, not a sterilization step. It can reduce water activity and limit microbial growth during storage, but it does not reliably kill microbes or remove endotoxins. Sterility must come from separate validated processes.
Freezing only converts liquid to solid. Lyophilization adds vacuum and controlled warming so frozen solvent sublimes, leaving a dry porous solid. The two steps are related but not interchangeable.