Sublimation 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 2026-08-01. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
Quality control for freeze-dried forms includes visual inspection, water content measurement, and reconstitution time. A satisfactory cake is typically uniform, porous, and intact, although minor shrinkage or cracking may be acceptable if specifications allow. Karl Fischer titration, thermal gravimetric analysis, and near-infrared spectroscopy are used to measure water content. Reconstitution is assessed by adding a specified diluent and recording the time and ease of dissolution. Microbiological and particulate tests are added when the product is sterile or intended for injection.
| 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. |
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.
After primary drying, secondary drying removes water that remains bound to the material. This stage raises the shelf temperature while maintaining low pressure, which encourages desorption of unfrozen water. Residual moisture can be reduced to a low percentage, improving stability for many products. The process parameters, including freezing rate, shelf temperature, and chamber pressure, influence the final pore structure and reconstitution behavior. Control of these variables helps prevent collapse or meltback during drying.
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.
Residual moisture is a key quality attribute for lyophilized products. Water that remains after secondary drying can affect chemical stability, cake structure, and shelf life. Karl Fischer titration is a common method for measuring water content in the dried solid. The target range varies by product, but many biologics are dried to between 0.5% and 3% water by weight. Acceptable limits are set during development and confirmed by stability studies.
Stability studies examine how temperature, humidity, and time influence a lyophilized product. Accelerated conditions provide early information about degradation pathways, while long-term studies support shelf-life claims. The glass transition temperature of the dried formulation can indicate its physical stability, and storage above this temperature may increase molecular mobility and lead to collapse or aggregation. Container closure integrity also matters because moisture or oxygen ingress can degrade the product, so vial stoppers and seals are part of the quality system.
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.
== Reception == Cold War 2 has grossed US$115 million worldwide. In Hong Kong, the film has grossed a total of HK$66,244,171, breaking the record as the highest-grossing domestic film in Hong Kong, and was also the third highest-grossing film of 2016 in the territory.
== Structure == Cholecystokinin is a member of the gastrin/cholecystokinin family of peptide hormones and is very similar in structure to gastrin, another gastrointestinal hormone. CCK and gastrin share the same five C-terminal amino acids. CCK is composed of varying numbers of amino acids depending on post-translational modification of the 150-amino acid precursor, preprocholecystokinin. Thus, the CCK peptide hormone exists in several forms, each identified by the number of amino acids it contains, e.g., CCK-58, CCK-33, CCK-22 and CCK-8. CCK58 assumes a helix-turn-helix configuration. Biological activity resides in the C-terminus of the peptide. Most CCK peptides have a sulfate group attached to a tyrosine located seven residues from the C-terminus (see tyrosine sulfation). This modification is crucial for the ability of CCK to activate the cholecystokinin A receptor. Nonsulfated CCK peptides also occur, which consequently cannot activate the CCK-A receptor, but their biological role remains unclear.
=== Advocacy groups === Even the Score, a coalition of women's groups brought together by a Sprout consultant, actively campaigned for the approval of flibanserin. The campaign emphasized that several approved treatments for male sexual dysfunction exist, while no such treatment for women was available. The group successfully obtained letters of support from the President of the National Organization for Women, the editor of the Journal of Sexual Medicine, and several members of Congress. Other organizations supporting the approval of flibanserin included the National Council of Women's Organizations, the Black Women's Health Imperative, the Association of Reproductive Health Professionals, National Consumers League, and the American Sexual Health Association. The approval was opposed by the National Women's Health Network, the National Center for Health Research and Our Bodies Ourselves. A representative of PharmedOut said "To approve this drug will set the worst kind of precedent—that companies that spend enough money can force the FDA to approve useless or dangerous drugs." An editorial in JAMA noted that, "Although flibanserin is not the first product to be supported by a consumer advocacy group in turn supported by pharmaceutical manufacturers, claims of gender bias regarding the FDA's regulation have been particularly noteworthy, as have the extent of advocacy efforts ranging from social media campaigns to letters from members of Congress".
Sources: en.wikipedia.org
===== MeSH D08.811.682.047 – alcohol oxidoreductases ===== MeSH D08.811.682.047.050 – acetoin dehydrogenase MeSH D08.811.682.047.070 – alcohol dehydrogenase MeSH D08.811.682.047.150 – carbohydrate dehydrogenases MeSH D08.811.682.047.150.225 – fructuronate reductase MeSH D08.811.682.047.150.250 – galactose dehydrogenases MeSH D08.811.682.047.150.270 – glucose dehydrogenases MeSH D08.811.682.047.150.270.500 – glucose 1-dehydrogenase MeSH D08.811.682.047.150.300 – glucosephosphate dehydrogenase MeSH D08.811.682.047.150.600 – phosphogluconate dehydrogenase MeSH D08.811.682.047.150.650 – phosphoglycerate dehydrogenase MeSH D08.811.682.047.150.700 – sugar alcohol dehydrogenases MeSH D08.811.682.047.150.700.075 – aldehyde reductase MeSH D08.811.682.047.150.700.237 – d-xylulose reductase MeSH D08.811.682.047.150.700.400 – glycerolphosphate dehydrogenase MeSH D08.811.682.047.150.700.400.500 – glycerol-3-phosphate dehydrogenase (nad+) MeSH D08.811.682.047.150.700.437 – l-gulonolactone oxidase MeSH D08.811.682.047.150.700.475 – l-iditol 2-dehydrogenase MeSH D08.811.682.047.150.700.649 – mannitol dehydrogenase MeSH D08.811.682.047.150.900 – uridine diphosphate glucose dehydrogenase MeSH D08.811.682.047.180 – choline dehydrogenase MeSH D08.811.682.047.210 – galactose oxidase MeSH D08.811.682.047.239 – glucose oxidase MeSH D08.811.682.047.370 – homoserine dehydrogenase MeSH D08.811.682.047.370.060 – aspartokinase homoserine dehydrogenase MeSH D08.811.682.047.385 – 3-hydroxyacyl coa dehydrogenases MeSH D08.811.682.047.385.415 – hydroxymethylglutaryl coa reductases MeSH D08.811.682.047.385.415.250 – hydroxymethylglutaryl-coa reductases, nad-dependent MeSH D08.811.682.047.385.415.750 – hydroxymethylglutaryl-coa-reductases, nadp-dependent MeSH D08.811.682.047.393 – hydroxybutyrate dehydrogenase MeSH D08.811.682.047.428 – Hydroxyprostaglandin dehydrogenase MeSH D08.811.682.047.432 – hydroxypyruvate reductase MeSH D08.811.682.047.436 – hydroxysteroid dehydrogenases MeSH D08.811.682.047.436.174 – 11-beta-hydroxysteroid dehydrogenases MeSH D08.811.682.047.436.174.300 – 11-beta-hydroxysteroid dehydrogenase type 1 MeSH D08.811.682.047.436.174.600 – 11-beta-hydroxysteroid dehydrogenase type 2 MeSH D08.811.682.047.436.350 – 3-hydroxysteroid dehydrogenases MeSH D08.811.682.047.436.350.100 – 3alpha-hydroxysteroid dehydrogenase (B-specific) MeSH D08.811.682.047.436.350.150 – cholesterol oxidase MeSH D08.811.682.047.436.350.700 – progesterone reductase MeSH D08.811.682.047.436.375 – 17-hydroxysteroid dehydrogenases MeSH D08.811.682.047.436.375.280 – estradiol dehydrogenases MeSH D08.811.682.047.436.400 – 20-hydroxysteroid dehydrogenases MeSH D08.811.682.047.436.400.074 – 20alpha-hydroxysteroid dehydrogenase MeSH D08.811.682.047.436.400.150 – cortisone reductase MeSH D08.811.682.047.485 – imp dehydrogenase MeSH D08.811.682.047.497 – isocitrate dehydrogenase MeSH D08.811.682.047.500 – 3-isopropylmalate dehydrogenase MeSH D08.811.682.047.524 – ketol-acid reductoisomerase MeSH D08.811.682.047.551 – lactate dehydrogenases MeSH D08.811.682.047.551.249 – epsilon-crystallins MeSH D08.811.682.047.551.400 – l-lactate dehydrogenase MeSH D08.811.682.047.551.500 – l-lactate dehydrogenase (cytochrome) MeSH D08.811.682.047.605 – malate dehydrogenase MeSH D08.811.682.047.748 – malate dehydrogenase (nadp+) MeSH D08.811.682.047.892 – xanthine dehydrogenase MeSH D08.811.682.047.928 – xanthine oxidase
The Regional Centre for Biotechnology (RCB) is an autonomous institution of education, training and research established under the auspices of United Nations Educational, Scientific and Cultural Organization (UNESCO) and Department of Biotechnology (DBT, India). The Parliament has passed the Regional Centre for Biotechnology Bill, 2016 to provide statutory status to the existing institution. Dr. Arvind Sahu is the executive director of RCB.
== Chemical structure == Dinosterol is a C30 sterol characterized by four fused rings (three six-membered and one five-membered), seven methyl groups, an olefin in its side-chain, and a secondary alcohol. The double bond in the side chain is located at the 22 position, and dinosterol's methyl groups are at the 20, 23, 24 and 25 positions of the side chain. The structure of dinosterol is established as 4α,23,24-trimethyl-5α-cholest-22-en-3β-ol. Dinosterol contains an unusual pattern of side-chain alkylation with methyl groups at C-23 and C-24. This substitution motif was thought to be unique to dinoflagellate sterols, until Volkman et al. (1993) found a diatom belonging to the genus Navicula, which contains several 4-methyl sterols including dinosterol.
Sources: en.wikipedia.org
In 1972, eight remarkably preserved mummies were discovered at an abandoned Inuit settlement called Qilakitsoq, in Greenland. The "Greenland Mummies" consisted of a six-month-old baby, a four-year-old boy, and six women of various ages, who died around 500 years ago. Their bodies were naturally mummified by the sub-zero temperatures and dry winds in the cave in which they were found.
== Pathophysiology == The cause of the disease is the lack of a fully functional insulin receptor, which has a profound effect during fetal development and thereafter. In one case, it was found (by culturing pancreatic cells) that the receptor produced by the mutant allele is only about 15% as effective as the normal receptor. The beta cells in the pancreas, which make and store insulin and release it on an as-needed basis, are often found to be very large or numerous. The role of insulin in the body is to facilitate the entrance of glucose into the cell. Once insulin binds to the insulin receptors on the cell surface, the insulin receptors will send a signal that will ultimately bring the glucose transporter protein GLUT4 to attach to the cell membrane. Additionally, once insulin is bound to the insulin receptors, it will also initiate several signaling cascades that will promote cell growth and differentiation, protein synthesis, glucose synthesis, and the inhibition of gluconeogenesis through several metabolic pathways. A malfunctioning insulin receptor would thus not be able to properly initiate the signaling cascades for the aforementioned cellular processes. Many of the problems associated with Donohue syndrome may be due to the insulin receptor binding the insulin-like growth factor, regulating the growth of the embryo, in addition to its well-known role in the regulation of blood sugar.
Copper is an essential trace element that is vital to the health of all living things (plants, animals and microorganisms). In humans, copper is essential to the proper functioning of organs and metabolic processes. Also, in humans, copper helps maintain the nervous system, immune system, brain development, and activates genes, as well as assisting in the production of connective tissues, blood vessels, and energy. The human body has complex homeostatic mechanisms that regulate a constant supply of available copper, while eliminating excess copper, if needed to assure homeostasis. However, like all essential elements and nutrients, too much or too little nutritional ingestion of copper can result in a corresponding condition of copper excess or deficiency in the body, each of which has its own unique set of adverse health effects. Daily dietary standards for copper have been set by various health agencies around the world. Standards adopted by some nations recommend different copper intake levels for adults, pregnant women, infants, and children, corresponding to the varying need for copper during different stages of life. Organ meats, shellfish, nuts, seeds, chocolate, potatoes, and mushrooms are sources of dietary copper. Copper is commonly available in dietary supplements and is included in multivitamin products.
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.
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.