Everything below concerns Collapse temperature. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-07-19. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Common name | Freeze-drying | Lyophilization is the technical synonym. |
| Typical chamber pressure | 0.01–0.1 mbar | Below the triple point of water. |
| Primary drying temperature | −40 to −10 °C | Depends on formulation and equipment. |
| Residual moisture | 1–5% | Target for many pharmaceutical products. |
| Typical equipment | Vacuum freeze-dryer | Includes drying chamber and condenser. |
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.
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.
D-amino acid oxidase activator (DAOA, also known as G72) is a protein enriched in various parts of brain, spinal cord, and testis. DAOA is thought to interact with D-amino acid oxidase, a peroxisomal enzyme, and its gene was associated with schizophrenia in a number of studies. In separate studies it has been shown to confer susceptibility to bipolar disorder. Therefore, it has been important in researching whether the Kraepelinian dichotomy is genuine. The gene itself was discovered during an investigation of chromosomal 13q22-q34 region, which was previously linked to schizophrenia. G72 is transcribed into several proteins due to alternative splicing; the longest protein is called LG72 and consists of 153 amino acids. Although the protein was initially found to interact with DAO in yeast 2-hybrid experiment, one recent in vivo experiment showed LG72 presence only in mitochondria and failed to confirm the interaction.
The rate of climb is good and the high speed in level flight is exceptionally good at all altitudes, from sea level to 40,000 feet. The airplane is very maneuverable with good controllability at indicated speeds up to 400 MPH [sic]. The stability about all axes is good and the rate of roll is excellent; however, the radius of turn is fairly large for a fighter. The cockpit layout is excellent, but visibility is poor on the ground and only fair in level flight. Kurt Bühligen, the third-highest scoring German fighter pilot of World War II's Western Front (with 112 confirmed victories, three against Mustangs), later stated:
==== MeSH D12.125.154 – amino acids, neutral ==== MeSH D12.125.154.049 – asparagine MeSH D12.125.154.299 – cysteine MeSH D12.125.154.424 – glutamine MeSH D12.125.154.549 – methionine MeSH D12.125.154.800 – serine MeSH D12.125.154.900 – threonine
Sources: en.wikipedia.org
Actinium (89Ac) has no stable isotopes and no characteristic terrestrial isotopic composition, thus a standard atomic weight cannot be given. There are 34 known isotopes, from 203Ac to 236Ac, and 9 isomers. Three isotopes are found in nature, 225Ac, 227Ac and 228Ac, as intermediate decay products of, respectively, 237Np, 235U, and 232Th. 228Ac and 225Ac are extremely rare, so almost all natural actinium is 227Ac. The most stable isotopes are 227Ac with a half-life of 21.772 years, 225Ac with a half-life of 9.919 days, and 226Ac with a half-life of 29.37 hours. All other isotopes have half-lives under seven hours, and most under a minute. The shortest-lived known isotope is 217Ac with a half-life of 69 ns. Purified 227Ac comes into equilibrium with its decay products (mainly 227Th and 223Ra) after 185 days.
=== Interaction with nucleic acids === One of the important properties of lactoferrin is its ability to bind with nucleic acids. The fraction of protein extracted from milk, contains 3.3% RNA, but, the protein preferably binds to double-stranded DNA rather than single-stranded DNA. The ability of lactoferrin to bind DNA is used for its isolation and purification using affinity chromatography with columns containing immobilized DNA-containing sorbents, such as agarose with the immobilized single-stranded DNA.
=== PMB === PMB (Probability Matrix from Blocks) of 2004 uses the additivity of evolutionary distances to improve on BLOSUM's analysis of the BLOCKS database. The up-to-date 2001 version of BLOCKS was used to generate a new set of BLOSUM matrices. The "observed substitution frequencies" found in these BLOSUM matrices are used to estimate actual substitution frequencies (with higher evolutionary distance, i.e. lower r, some later replacement can mask earlier replacements). PMB thus defines a true evolutionary model like PAM and JTT do. It is not a symmetric matrix.
Sources: en.wikipedia.org
Conventional drying uses heat to evaporate water from a material, while lyophilization freezes the material and removes water by sublimation under vacuum. This avoids the liquid phase and reduces thermal damage to sensitive substances. The result is a porous cake that reconstitutes quickly.
A vacuum lowers the pressure below the triple point of water, allowing ice to sublimate directly into vapor without melting. It also removes water vapor from the product chamber and speeds up the drying process. Without vacuum, the ice would melt rather than sublimate.
Not all substances are suitable for lyophilization. Materials must form a stable frozen matrix and tolerate freezing and low pressure. Some small molecules, oils, or volatile compounds may not form a proper cake or may be lost during processing.
Lyophilization relies on sublimation, so water moves from solid ice to vapor without becoming liquid. The material is frozen, pressure is reduced, and controlled heat is supplied. Vapor is captured on a cold condenser, leaving a dry porous solid.