If you have been reading about Collapse temperature and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2026-07-21. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
After drying, a lyophilized product is usually sealed under vacuum or an inert gas to limit moisture and oxygen exposure. The container closure system matters because stoppers and seals can allow moisture ingress over time. Storage conditions are selected from stability studies that track potency, cake appearance, and reconstitution behavior. Many freeze-dried materials are kept at controlled room temperature, while some require refrigeration or protection from light.
| 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 |
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.
Reconstitution involves adding a suitable diluent, often sterile water or a buffer, to the dried cake. Gentle swirling or inversion helps dissolve the material without creating excessive foam. The time required for complete dissolution can range from seconds to several minutes and depends on the cake structure and the diluent. Improper reconstitution, such as vigorous shaking or using the wrong diluent, can cause protein aggregation or loss of activity. After reconstitution, the product may have a limited shelf life and should be used according to its labeling.
Lyophilized products are typically hygroscopic and require protection from moisture during storage. Manufacturers seal them in glass vials, often under vacuum or an inert gas such as nitrogen. The container closure system, including the stopper and crimp seal, must prevent water vapor ingress. Storage temperature varies from controlled room temperature to refrigerated or frozen conditions, depending on the formulation. Humidity-controlled environments are essential because even brief exposure to ambient air can degrade the product.
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.
Freeze-drying is distinct from simple evaporation and from spray drying. Evaporation removes water at temperatures above freezing, while spray drying rapidly dries droplets in a heated gas stream. Lyophilization avoids high temperatures, which can be useful for heat-sensitive materials such as proteins, vaccines, and some foods. The porous cake produced by sublimation dissolves or rehydrates more quickly than a dense dried mass. Not all materials tolerate freezing or the pH shifts that can occur as solutes concentrate during ice formation.
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.
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.
Individuals with 3-M syndrome have severe prenatal growth retardation due to growth delays during fetal development resulting in a low birth weight. Growth delays continue after birth throughout childhood and adolescence, ultimately leading to a short stature. Growth delays and immature bone development (growth retardation and delayed bone maturation) typically continue after birth (postnatally), leading to short stature (dwarfism) with proportional development of the arms and legs (as opposed to short stature with abnormally small arms and legs). In most cases, infants with 3M syndrome are unusually small and have a low birth weight despite being carried to term.
Collisional excitation in mass spectrometry is the process where an ion collides with an atom or molecule and leads to an increase in the internal energy of the ion. Molecular ions are accelerated to high kinetic energy and then collide with neutral gas molecules (e.g. helium, nitrogen or argon). In the collision some of the kinetic energy is converted into internal energy which results in fragmentation in a process known as collision-induced dissociation. Collision-induced absorption and emission
Outer Membrane Vesicle (OMV) vaccines contain the outer membrane of a bacterium without any of its internal components or genetic material. Thus, ideally, they stimulate an immune response effective against the original bacteria without the risk of an infection. Genetic vaccines deliver nucleic acid that codes for an antigen into host cells, which then produce that antigen, stimulating an immune response. This category of vaccine includes DNA vaccines, RNA vaccines, and viral vector vaccines, which differ in the chemical form of nucleic acid and how it is delivered into host cells. A variety of vaccine types are under development; see Experimental Vaccine Types. Most vaccines are given by hypodermic or intramuscular injection as they are not absorbed reliably through the gut. Live attenuated polio and some typhoid and cholera vaccines are given orally in order to produce immunity based in the bowel.
RNA-dependent RNA polymerase (RdRp) or RNA replicase is an enzyme that catalyzes the replication of RNA from an RNA template. Specifically, it catalyzes synthesis of the RNA strand complementary to a given RNA template. This is in contrast to typical DNA-dependent RNA polymerases (DdRP), which all organisms use to catalyze the transcription of RNA from a DNA template. RdRp is an essential protein encoded in the genomes of most RNA-containing viruses that lack a DNA stage. Some eukaryotes also contain RdRps, which are involved in RNA interference and differ structurally from viral RdRps. Viral RdRps were discovered in the early 1960s from studies on Picornaviruses when it was observed that these viruses were not sensitive to actinomycin D, a drug that inhibits cellular DNA-directed RNA synthesis. This lack of sensitivity suggested the action of a virus-specific enzyme that could copy RNA from an RNA template.
In 1955, a USAF surgeon who advised the US Surgeon General wrote an article on how to make cars safer for those riding in it. Aside from the usual safety features, such as seat belts and padded dashboards, bumper shocks were introduced. In 1956, Ford tried unsuccessfully to interest Americans in purchasing safer cars with their Lifeguard safety package. (Its attempt nevertheless earns Ford Motor Trend's "Car of the Year" award for 1956.) In 1958, the United Nations established the World Forum for Harmonization of Vehicle Regulations, an international standards body advancing auto safety. Many of the most life saving safety innovations, like seat belts and roll cage construction were brought to market under its auspices. That same year, Volvo engineer Nils Bohlin invented and patented the three-point lap and shoulder seat belt, which became standard equipment on all Volvo cars in 1959. Over the next several decades, three-point safety belts were gradually mandated in all vehicles by regulators throughout the industrialised world. In 1959, American Motors Corporation offered the first optional head rests for the front seat. Also in 1959, the Cadillac Cyclone concept by Harley Earl had "a radar-based crash-avoidance system" located on the nose cones of the vehicle that would make audible and visual signals to the driver if there were obstacles in the vehicle's path.
Sources: en.wikipedia.org
3 cos Ω = 1 − 4 cos2 φ + ψ/2 The α-helix is tightly packed; there is almost no free space within the helix. The amino-acid side-chains are on the outside of the helix, and point roughly "downward" (i.e., toward the N-terminus), like the branches of an evergreen tree (Christmas tree effect). This directionality is sometimes used in preliminary, low-resolution electron-density maps to determine the direction of the protein backbone.
Agents that "bind" to the toxin can reduce free or active toxin present. It is possible for this binding to be nonspecific or specific. Activated charcoal is the non-specific binding agent most frequently utilised as it has strong adsorption capacity and could prevent the toxin's enterohepatic recirculation. Chelation agents, immunotherapy, and bioscavenger therapy are examples of specific binders. Urinary alkalization or hemadsorption may improve elimination in some circumstances.
ISCOM technology was invented in 1982 by Professor Bror Morein at the Swedish University of Agricultural Sciences in Uppsala. The key components of ISCOMs are the Quillaja saponins, which are derived from the bark of the Chilean soap-bark tree Quillaja saponaria Molina. Quillaja saponins are well known for their ability to activate the immune system. It is also known that saponins in general can have toxic side-effects, including the induction of haemolysis. However, when Quillaia saponins, cholesterol and phospholipids are mixed under the specific stoichiometry that forms ISCOMs, this haemolytic activity is practically eliminated, while the adjuvant activity is retained.
Microbial toxins are toxins produced by micro-organisms, including bacteria, fungi, protozoa, dinoflagellates, and viruses. Many microbial toxins promote infection and disease by directly damaging host tissues and by disabling the immune system. Endotoxins most commonly refer to the lipopolysaccharide (LPS) or lipooligosaccharide (LOS) that are in the outer plasma membrane of Gram-negative bacteria. The botulinum toxin, which is primarily produced by Clostridium botulinum and less frequently by other Clostridium species, is the most toxic substance known in the world. However, microbial toxins also have important uses in medical science and research. Currently, new methods of detecting bacterial toxins are being developed to better isolate and understand these toxins. Potential applications of toxin research include combating microbial virulence, the development of novel anticancer drugs and other medicines, and the use of toxins as tools in neurobiology and cellular biology.
Sources: en.wikipedia.org
Abortive initiation is a normal process of transcription and occurs both in vitro and in vivo. After each nucleotide-addition step in initial transcription, RNA polymerase, stochastically, can proceed on the pathway toward promoter escape (productive initiation) or can release the RNA product and revert to the RNA polymerase-promoter open complex (abortive initiation). During this early stage of transcription, RNA polymerase enters a phase during which dissociation of the transcription complex energetically competes with the elongation process. Abortive cycling is not caused by strong binding between the initiation complex and the promoter.
The main method of treatment for potential death from signaling-related diseases involves either increasing or decreasing the susceptibility of apoptosis in diseased cells, depending on whether the disease is caused by either the inhibition of or excess apoptosis. For instance, treatments aim to restore apoptosis to treat diseases with deficient cell death and to increase the apoptotic threshold to treat diseases involved with excessive cell death. To stimulate apoptosis, one can increase the number of death receptor ligands (such as TNF or TRAIL), antagonize the anti-apoptotic Bcl-2 pathway, or introduce Smac mimetics to inhibit the inhibitor (IAPs). The addition of agents such as Herceptin, Iressa, or Gleevec works to stop cells from cycling and causes apoptosis activation by blocking growth and survival signaling further upstream. Finally, adding p53-MDM2 complexes displaces p53 and activates the p53 pathway, leading to cell cycle arrest and apoptosis. Many different methods can be used either to stimulate or to inhibit apoptosis in various places along the death signaling pathway. Apoptosis is a multi-step, multi-pathway cell-death programme that is inherent in every cell of the body. In cancer, the apoptosis cell-division ratio is altered. Cancer treatment by chemotherapy and irradiation kills target cells primarily by inducing apoptosis.
Negative mass selection, which is removal of plants/seeds with unwanted properties, can be done when preparing seed for planting, at field visits during the growing season and at harvest. Removing unhealthy/deceased plants from the field is a simple way to improve the population. Before planting it is normal procedure to clean the seed to remove seeds from weeds and this will also remove small seeds, introducing a weak selection towards bigger kernels. Seed can also be sorted according to color or protein content.
4-Aminosalicylic acid, also known as para-aminosalicylic acid (PAS) and sold under the brand name Paser among others, is an antibiotic primarily used to treat tuberculosis. Specifically it is used to treat active drug resistant tuberculosis together with other antituberculosis medications. It has also been used as a second line agent to sulfasalazine in people with inflammatory bowel disease such as ulcerative colitis and Crohn's disease. It is typically taken by mouth. Common side effects include nausea, abdominal pain, and diarrhea. Other side effects may include liver inflammation and allergic reactions. It is not recommended in people with end stage kidney disease. While there does not appear to be harm with use during pregnancy it has not been well studied in this population. 4-Aminosalicylic acid is believed to work by blocking the ability of bacteria to make folic acid. 4-Aminosalicylic acid was first made in 1902, and came into medical use in 1943. It is on the World Health Organization's List of Essential Medicines.
24. Adv Gerontol. 2008;21(1):68-73. [Biological activity of regulatory peptides in model experiments in vitro]. [Article in Russian] Kozina LS, Arutiunian AV, Stvolinskiĭ SL, Khavinson VKh. Biological effects of short regulatory peptides, pinealon, vesugen, vilon and epitalon were studied in model experiments in vitro. These peptides were found not to demonstrate direct antioxidant activity but be able to restrict lipid peroxidation of human lipoproteins by modification of their structure. The short peptides increase stability of red blood cell membranes toward osmotic hemolysis. They also elevate the stationary level of intracellular reactive oxygen species and at the same time decrease (all excepting epitalon) percent of dead cells in neuronal population. The suggestion was made that under in vivo conditions, short peptides may participate in apoptosis/necrosis regulation.
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.
Sealed vials or containers should be kept at the temperature specified by stability data, often controlled room temperature or 2–8 °C. Moisture and oxygen barriers are important because both can degrade sensitive materials. Opened containers may need immediate use or protection from ambient humidity.