This is a working overview of sublimation, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-04-25 and is reviewed periodically as new material appears.
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.
Lyophilization is a drying process in which a solvent, usually water, is removed from a frozen material by sublimation under reduced pressure. The material is first solidified, then placed under vacuum so that ice transitions directly to vapor without a bulk liquid phase. This approach suits heat-sensitive substances that would degrade during conventional evaporation. Primary drying removes unbound ice, while secondary drying reduces water that remains adsorbed to the solid matrix. The result is a porous, lightweight solid 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.
| Property | Value | Notes |
|---|---|---|
| Physical state | Solid, porous cake or powder | Depends on formulation and container |
| Typical storage temperature | 2–25 °C, protected from moisture | Some materials require colder conditions |
| Solubility class | Usually readily soluble after reconstitution | Not an intrinsic chemical property |
| Common analytical method | Karl Fischer titration | Used for residual moisture |
| Common synonyms | Freeze-drying; lyophilisation | Lyophilisation is a spelling variant |
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.
Lyophilization is a dehydration technique in which a product is frozen and the solvent is removed under reduced pressure. The low pressure allows ice to sublimate directly into vapor without passing through a bulk liquid phase. This differs from conventional drying, where heat drives evaporation and can damage heat-sensitive structures. The process is used for biological materials, pharmaceutical formulations, and some foods. Its main advantage is preservation of porous structure and rapid reconstitution.
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.
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.
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.
=== Dependence and withdrawal === Tolerance to phenibut easily develops with repeated use, leading to dependence. Withdrawal symptoms may occur upon discontinuation, and, in recreational users taking high doses, have been reported to include severe rebound anxiety, insomnia, aggression, irritability, agitation, visual and auditory hallucinations, seizures and acute psychosis. Baclofen has successfully been used for treatment of phenibut dependence.
The MMRV vaccine is a combination vaccine against measles, mumps, rubella (German measles), and varicella (chickenpox). It contains the combined measles vaccine, mumps vaccine, rubella vaccine, and varicella vaccine into a single injection. The MMRV vaccine has similar immunogenicity and overall safety profiles to the MMR vaccine administered with or without the varicella vaccine. The MMRV vaccine is typically given to children between one and two years of age. Several companies supply MMRV vaccines. Proquad is marketed by Merck and was approved in 2005, for use in the United States for children aged twelve months of age through twelve years of age. Stand-alone virus measles, mumps, rubella, and varicella vaccines had been previously licensed in 1963, 1967, 1969, and 1995, respectively. An MMRV vaccine called Priorix Tetra by GlaxoSmithKline is available in some of the member states of the European Union.
==== Behavior ==== Like in humans, serotonin is involved in regulating behavior in most other vertebrates. This includes not only response and social behaviors, but also influencing mood. Defects in serotonin pathways can lead to intense variations in mood, as well as symptoms of mood disorders, which can be present in more than just humans.
== References == Mesa MG, Duarte HÁ, Carretero JH, López MM, Vilas MM (May 2011). "De Marco Formula effectiveness as an adjunctive therapy to prevent infected ischemic diabetic foot amputation and reduce plasma fibrinogen". J Tissue Viability. 20 (2): 67–72. doi:10.1016/j.jtv.2010.12.003. PMID 21211975. Alvarez Duarte H, Fors López MM, Carretero JH, Vilas MM, García Mesa M (August 2010). "Tolerability and safety of conventional therapy combination with DeMarco formula for infected ischemic diabetic foot". J Tissue Viability. 19 (3): 116–22. doi:10.1016/j.jtv.2010.03.002. PMID 20570516. Mahia Vilas M, Hernández Carretero J, García Mesa M, Álvarez Duarte H, Valdés Pérez C, De Marco LG. (2010) "Microalbuminuria and immune system in patients with infected ischemic diabetic foot treated with De Marco Formula." Span. J. Surg. Res, Vol. XIII, Num. 1, (12–16), Año 2010. Miriam Mahía Vilas; Héctor T. Álvarez Duarte; José G. Hernández Carretero; Milagros García Mesa; María Eugenia Triana Mantilla; Alicia Rodríguez Pérez. "Utilidad de la fórmula De Marco en pacientes diabéticos con complicaciones vasculares y su acción inmunomoduladora sobre la función de los linfocitos T. (Usefulness of De Marco formula in diabetic patients suffering vascular complications and its immunomodulating action on the T lymphocyte function.)" [1] Revista Cubana de Angiología y Cirugía Vascular. 2008; 9(1) Duarte HA, Fernández Montequín JI, Fors López MM, Carretero JH, Vilas MM, Mesa MG. Duarte HA, Fernández Montequín JI, Fors López MM, Carretero JH, Vilas MM, Mesa MG (2009).
Sources: en.wikipedia.org
== Description == The adult lesser mealworm beetle is roughly 6 mm long and widely oval in shape. It is shiny black or brown with reddish brown elytra, the color variable among individuals and changing with age. Much of the body surface is dotted with puncture-like impressions. The antennae are paler at the tips and are covered in tiny, yellowish hairs. The elytra have shallow longitudinal grooves. The eggs are narrow, whitish or tan, and about 1.5 mm long. The larvae somewhat resemble other mealworms, such as the common mealworm (Tenebrio molitor), but are smaller, measuring up to 11 mm long at the final subadult stage. They are tapering and segmented, with three pairs of legs toward the front end, and whitish when newly emerged from the egg and darken to a yellow-brown. They become pale when preparing to molt between instar stages six to 11 instars occur.
=== Drugs that induce a type 1 diabetes like syndrome === Some medicines can reduce insulin production or damage β cells, resulting in a disease that resembles type 1 diabetes. The antiviral drug didanosine triggers pancreas inflammation in 5 to 10% of those who take it, sometimes causing lasting β-cell damage. Similarly, up to 5% of those who take the anti-protozoal drug pentamidine experience β-cell destruction and diabetes. Several other drugs cause diabetes by reversibly reducing insulin secretion, namely statins (which may also damage β cells), the post-transplant immunosuppressants cyclosporin A and tacrolimus, the leukemia drug L-asparaginase, and the antibiotic gatifloxicin.
== Guest appearances == Several celebrities or future celebrities made uncredited appearances, either as part of the main storyline or in brief segments; among these were Richard Sanders who later gained fame playing Les Nessman on WKRP in Cincinnati. Ordinary citizens were interviewed by the kids in selected segments of some episodes in a "man on the street" format.
== Adverse effects == Dutasteride has overall been found to be well tolerated in studies of both men and women, producing minimal side effects. Adverse effects include headache and gastrointestinal discomfort. Isolated reports of menstrual changes, acne, and dizziness also exist. A small risk of sexual side effects has been documented in men taking the drug during the first few months of therapy. The FDA added a black-box warning to dutasteride in 2011 describing an increased risk of high-grade prostate cancer in those who take the drug. No direct mechanistic link between 5α-reductase inhibitors and prostate cancer has been established. This is not due to a direct link between dutasteride or other 5α-reductase inhibitors and cancer per se, but rather that those who take 5α-reductase inhibitors may have a decrease in prostate-specific antigen (PSA) levels, and therefore increases in PSA (which are an indicator of possible cancer) may be masked in those who take the drug. This is thought to delay cancer diagnosis so that patients taking 5α-reductase inhibitors present with a higher-grade tumor at the time of diagnosis. The American Urological Association advises that increased risk for patients taking these drugs leads to higher prostate cancer-specific and all-cause mortality. The AUA also advises that this effect can be alleviated with more frequent screening and lower PSA cutoffs for diagnostic biopsies in men taking dutasteride or other 5α-reductase inhibitors. Dutasteride is known to reduce the growth and prevalence of benign prostate tumors.
== Functions == Many proteins catalyze a chemical reaction. Other proteins fulfill structural, transport, or signaling roles. Furthermore, numerous proteins have the ability to aggregate into supramolecular assemblies. For example, a ribosome is made up of 90 proteins and RNA. A number of the currently known moonlighting proteins are evolutionarily derived from highly conserved enzymes, also called ancient enzymes. These enzymes are frequently speculated to have evolved moonlighting functions. Since highly conserved proteins are present in many different organisms, this increases the chance that they would develop secondary moonlighting functions. A high fraction of enzymes involved in glycolysis, an ancient universal metabolic pathway, exhibit moonlighting behavior. Furthermore, it has been suggested that as many as 7 out of 10 proteins in glycolysis and 7 out of 8 enzymes of the tricarboxylic acid cycle exhibit moonlighting behavior. An example of a moonlighting enzyme is pyruvate carboxylase. This enzyme catalyzes the carboxylation of pyruvate into oxaloacetate, thereby replenishing the tricarboxylic acid cycle. Surprisingly, in yeast species such as H. polymorpha and P. pastoris, pyruvate carboxylase is also essential for the proper targeting and assembly of the peroxisomal protein alcohol oxidase (AO). AO, the first enzyme of methanol metabolism, is a homo-octameric flavoenzyme. In wild type cells, this enzyme is present as enzymatically active AO octamers in the peroxisomal matrix.
Sources: en.wikipedia.org
deuterium Also hydrogen-2 or heavy hydrogen, and symbolized 2H or D. One of two stable isotopes of a hydrogen atom, the nucleus of which contains one proton and one neutron. Deuterium is both heavier and much less abundant in nature than the other stable isotope, known as protium (1H).
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== Detection of citrullinated peptides and proteins == Citrullinated peptides and proteins can be detected using antibodies targeting the citrullinated residues, or detected using mass spectrometry-based proteomics technologies. Citrullination of arginine results in a monoisotopic mass increase of +0.984016 Da, which can be measured with mass spectrometry. The mass shift is close to the mass difference between the different peptide isotopes of +1.008665 which can be mistaken for a citrullinated peptide, especially on low-resolution instruments. However, this is less of an issue with modern high resolution/high accuracy mass spectrometers. Furthermore, the mass shift is identical to the mass shift caused by deamidation of the amino acid asparagine or glutamine side chain, which are common modifications. Citrulline residues can be chemically modified with butanedione or by biotinylation prior to analysis, leading to a different mass shift, and this strategy has successfully been used to facilitate identification by mass spectrometry. Another approach is to utilize the neutral loss of isocyanic acid (HNCO) from citrulline residues when submitted to low energy collision induced dissociation fragmentation in mass spectrometers. The loss causes a mass shift of −43.0058 Da, which can be utilized by mass spectrometers to predominantly select citrullinated peptides for fragmentation (sequencing). Finally, the loss of positive charge at physiological pH caused by citrullination can be utilized. Prior to bottom-up proteomics analysis, proteins are enzymatically cleaved into peptides.
=== Other compartmental models === There are many modifications of the SIR model, including those that include births and deaths, where upon recovery there is no immunity (SIS model), where immunity lasts only for a short period of time (SIRS), where there is a latent period of the disease where the person is not infectious (SEIS and SEIR), and where infants can be born with immunity (MSIR). Also, compartments for vaccination, detection, or infected vectors like fleas, ticks, or mosquitoes can be added. Compartmental models can also be used to model multiple risk groups, and even the interaction of multiple pathogens.
=== Antimicrobial property === The ability of L. plantarum to produce antimicrobial substances helps them survive in the gastrointestinal tract of humans. The antimicrobial substances produced have shown significant effect on Gram-positive and Gram-negative bacteria.
Sources: en.wikipedia.org
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.
Reduced pressure keeps the solvent below its triple point, allowing ice to become vapor without melting. Vacuum also helps remove water vapor from the product chamber. The exact pressure is chosen with the formulation and equipment.
Residual moisture is water that remains in the dried solid after secondary drying. It is often measured by Karl Fischer titration, near-infrared spectroscopy, or thermogravimetry. Acceptable levels depend on the material and its stability profile.
Primary drying removes ice by sublimation at low pressure and low shelf temperature. Secondary drying removes bound water by raising the shelf temperature, often under the same vacuum. The two stages differ in the water state being removed.