freeze-drying raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-06-29 and is reviewed periodically as new material appears.
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.
Misconceptions about lyophilization include the idea that dried products are indefinitely stable or that vacuum sealing eliminates all degradation. Chemical reactions can continue in the solid state, and some proteins lose activity even at low moisture. Another misconception is that any freeze-dryer cycle can be scaled by time alone; heat and mass transfer differ with equipment and load. Open questions remain about predicting long-term stability from short accelerated studies, particularly for amorphous formulations. Real-time stability data remain the standard for shelf-life assignment.
After lyophilization, the dried product is often sealed under vacuum or an inert gas to limit moisture and oxygen exposure. Vials, stoppers, and seals must maintain their barrier throughout shelf life. Storage temperature depends on product sensitivity: some cakes tolerate controlled room temperature, while labile biologics require refrigeration. Humidity is a critical variable because dried cakes are hygroscopic and can absorb water when exposed to air. Handling procedures therefore limit open-vial time and use desiccated environments for sampling.
Quality control for lyophilized materials examines appearance, reconstitution time, residual moisture, and mechanical integrity. An acceptable cake is usually uniform and porous, though appearance alone does not prove stability. Karl Fischer titration is a common method for water content, while differential scanning calorimetry can reveal glass transition events. Stability studies track potency, aggregation, and moisture over time under defined temperature and humidity conditions. Specifications are product-specific and may include sterility and endotoxin tests for sterile preparations.
| 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. |
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.
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.
Stability programs monitor lyophilized products under defined temperature and humidity conditions over time. Real-time studies at recommended storage conditions are the reference, while accelerated studies provide early signals of degradation pathways. Because a dry cake can still undergo oxidation, hydrolysis, or aggregation, stability depends on residual moisture, excipients, and container headspace. Open questions include how best to predict long-term stability from short accelerated runs and how vial-to-vial variability affects shelf life. Current guidance treats these predictions as product-specific rather than universally generalizable.
Freeze-dried materials are hygroscopic to varying degrees and can take up moisture after drying. Storage therefore often uses sealed glass vials, rubber stoppers, and crimp seals to limit contact with ambient humidity. A desiccant may be included for moisture-sensitive products, although it is not universal. Controlled room temperature is sufficient for many lyophilizates, while others require refrigeration or freezing. Moisture ingress remains a primary cause of cake collapse, chemical degradation, and loss of reconstitution performance.
The physics of lyophilization depends on phase boundaries and heat and mass transfer. During primary drying, heat supplied to the product must equal the latent heat of sublimation, while water vapor moves through the drying cake to the condenser. If shelf temperature or pressure is set too high, the ice front can exceed the collapse temperature, causing meltback or pore collapse. If conditions are too cold, drying slows and costs rise. Formulation excipients, vial geometry, and freezing rate alter these limits.
Equipment for lyophilization includes a vacuum chamber, temperature-controlled shelves, a condenser, and a vacuum pump. A refrigeration system cools the shelves and condenser below the product's freezing point. Process monitoring often uses Pirani and capacitance manometers, thermocouples, and resistance sensors. Cycle development balances product quality with time and energy use. Some products are annealed during freezing to improve crystallization of bulking agents. Open questions remain about scaling cycles between laboratory, pilot, and production freeze-dryers.
edulis in Sweden after 1818, and is honoured in the local vernacular name Karljohanssvamp, as well as the Danish name Karl Johan svamp. The monarch cultivated the fungus about his residence, Rosersberg Palace.
== External links == Quantum Dots: Technical Status and Market Prospects Quantum dots that produce white light could be the light bulb's successor Single quantum dots optical properties Quantum dot on arxiv.org Quantum Dots Research and Technical Data Simulation and interactive visualization of Quantum Dots wave function
Photoactivated peptides are modified natural or synthetic peptides whose functions can be activated or controlled using light. These peptides incorporate light-sensitive elements that allow for precise regulation their biological activity in both space and time. The activation can be either irreversible, as in the case of caged peptides with photocleavable protecting groups, or reversible, utilizing molecular photoswitches like azobenzenes or diarylethenes, and diarylethenes By incorporating these light-responsive components into the peptide structure, peptide properties, functions, and biological activities can be manipulated with high precision. This approach enables targeted activation of peptides in specific areas, making photoactivated peptides valuable tools for applications in cancer therapy, drug delivery, and probing molecular interactions in living cells and in organisms.
Amphibians are a class of animals comprising frogs, salamanders and caecilians. They are tetrapods, but the caecilians and a few species of salamander have either no limbs or their limbs are much reduced in size. Their main bones are hollow and lightweight and are fully ossified and the vertebrae interlock with each other and have articular processes. Their ribs are usually short and may be fused to the vertebrae. Their skulls are mostly broad and short, and are often incompletely ossified. Their skin contains little keratin and lacks scales, but contains many mucous glands and in some species, poison glands. The hearts of amphibians have three chambers, two atria and one ventricle. They have a urinary bladder and nitrogenous waste products are excreted primarily as urea. Amphibians breathe by means of buccal pumping, a pump action in which air is first drawn into the buccopharyngeal region through the nostrils. These are then closed and the air is forced into the lungs by contraction of the throat. They supplement this with gas exchange through the skin which needs to be kept moist. In frogs the pelvic girdle is robust and the hind legs are much longer and stronger than the forelimbs. The feet have four or five digits and the toes are often webbed for swimming or have suction pads for climbing. Frogs have large eyes and no tail. Salamanders resemble lizards in appearance; their short legs project sideways, the belly is close to or in contact with the ground and they have a long tail. Caecilians superficially resemble earthworms and are limbless.
== History == In 1987, Dynacare Health Group acquired its first diagnostic laboratory—Quality Medical Laboratories and established Dynacare Laboratories. By 2015, Dynacare was part of the Central Medical Laboratories (CML), established in 1959 in Winnipeg, Manitoba. Dynacare was formed with the formation of an "operational partnership" in 1997 between Ontario's Bio-Science Laboratory and Gamma North Peel Partnership Inc. In 2002, Laboratory Corporation of America (LabCorp) acquired Dynacare Laboratories—one of the Dynacare partners—for US$480-million, while also assuming Dynacare debt worth $205-million. By 2002, Dynacare, just before LabCorp's takeover, had become the largest central clinical laboratory in western Canada, with a revenue in 2001 of $402.4-million and a profit of $11.7-million. By June 2020, DynaLIFE was operating 36 private laboratories in the Edmonton area and northern Alberta and had a contract with the Alberta government that is set to expire in 2022. In June 2020, Alberta Health Services, announced plans to outsource public community laboratory services to private companies. Gamma-Dynacare acquired LifeLabs Quebec. In 2013, DynaLIFE Medical Labs partnered with Dynacare, which operates laboratories in Alberta and across Canada. In 2015, Gamma-Dynacare Medical Laboratories rebranded itself back to Dynacare.
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By June 2009, Roche discontinued the Accutane brand amid falling market share and rising costs from personal injury lawsuits. However, Roche's overseas affiliates continue to sell isotretinoin as Roaccutane. In 2011, actor James Marshall sued Roche, alleging that Accutane had caused injuries requiring removal of his colon, but the jury denied his claim based on Marshall's pre-existing bowel disease.
== Malignant neoplasm of respiratory and intrathoracic organs (160–165) == 160 Malignant neoplasm of nasal cavities, middle ear, and accessory sinuses 161 Malignant neoplasm of larynx 162 Malignant neoplasm of trachea, bronchus, and lung 162.0 Trachea 162.2 Main bronchus 162.3 Upper lobe, bronchus or lung 162.4 Middle lobe, bronchus or lung 162.5 Lower lobe, bronchus or lung 162.8 Other parts of bronchus or lung 162.9 Bronchus and lung, unspecified 163 Malignant neoplasm of pleura 164 Malignant neoplasm of thymus, heart, and mediastinum 165 Malignant neoplasm of other and ill-defined sites within the respiratory system and intrathoracic organs
Substrate-level phosphorylation is a metabolic reaction that results in the production of ATP or GTP supported by the energy released from another high-energy bond that leads to phosphorylation of ADP or GDP to ATP or GTP (note that the reaction catalyzed by creatine kinase is not considered as "substrate-level phosphorylation"). This process uses some of the released chemical energy, namely the Gibbs free energy, to transfer a phosphoryl (PO3) group to ADP or GDP. Substrate-level phosphorylation occurs in glycolysis and in the citric acid cycle. Unlike oxidative phosphorylation, oxidation and phosphorylation are not coupled in the process of substrate-level phosphorylation, and reactive intermediates are most often gained in the course of oxidation processes in catabolism. Most ATP is generated by oxidative phosphorylation in aerobic or anaerobic respiration while substrate-level phosphorylation provides a quicker, less efficient source of ATP, independent of external electron acceptors. This is the case in human erythrocytes, which have no mitochondria, and in oxygen-depleted muscle. Substrate-level phosphorylation occurs in the cytoplasm of cells during glycolysis and in mitochondria during the Krebs cycle. In the pay-off phase of glycolysis, a net of 2 ATP are produced by substrate-level phosphorylation.
Chanterelle is the common name of several species of agaricomycetous fungi in the genera Cantharellus, Craterellus, Gomphus and Polyozellus. These fungi are orange, yellow or white, meaty and funnel-shaped. On the lower surface, most species have rounded, forked folds that run almost all the way down the stipe, which tapers down from the cap. Many species emit a fruity aroma and often have a mildly peppery taste. Chanterelles are found in Eurasia, North America and Africa, typically growing in forested areas. They initially gained popularity as an edible mushroom in the 18th century via their inclusion in French cuisine.
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The FBI quickly identified the hijackers, including leader Atta, when his luggage was discovered at Boston's Logan Airport. Atta had been forced to check two of his three bags due to space limitations on the 19-seat commuter flight he took to Boston. Due to a new policy instituted to prevent flight delays, the luggage failed to make it aboard American Airlines Flight 11 as planned. The luggage contained the hijackers' names, assignments, and al-Qaeda connections. "It had all these Arab-language [sic] papers that amounted to the Rosetta stone of the investigation," said one FBI agent. Within hours of the attacks, the FBI released the names and in many cases the personal details of the suspected pilots and hijackers. Abu Jandal, who served as bin Laden's chief bodyguard for years, confirmed the identity of seven hijackers as al-Qaeda members during interrogations with the FBI on September 17. He had been jailed in a Yemeni prison since 2000. On September 27, photos of all 19 hijackers were released, along with information about possible nationalities and aliases. Fifteen of the men were from Saudi Arabia, two were from the United Arab Emirates, one was from Egypt, and one was from Lebanon.
mixture of 2 plasmids, one encoding the immunogen and the other encoding the cytokine single bi- or polycistronic vector, separated by spacer regions plasmid-encoded chimera, or fusion protein In general, co-administration of pro-inflammatory agents (such as various interleukins, tumor necrosis factor, and GM-CSF) plus TH2-inducing cytokines increase antibody responses, whereas pro-inflammatory agents and TH1-inducing cytokines decrease humoral responses and increase cytotoxic responses (more important in viral protection). Co-stimulatory molecules such as B7-1, B7-2 and CD40L are sometimes used. This concept was applied in topical administration of pDNA encoding IL-10. Plasmid encoding B7-1 (a ligand on APCs) successfully enhanced the immune response in tumour models. Mixing plasmids encoding GM-CSF and the circumsporozoite protein of P. yoelii (PyCSP) enhanced protection against subsequent challenge (whereas plasmid-encoded PyCSP alone did not). It was proposed that GM-CSF caused dendritic cells to present antigen more efficiently and enhance IL-2 production and TH cell activation, thus driving the increased immune response. This can be further enhanced by first priming with a pPyCSP and pGM-CSF mixture, followed by boosting with a recombinant poxvirus expressing PyCSP. However, co-injection of plasmids encoding GM-CSF (or IFN-γ, or IL-2) and a fusion protein of P. chabaudi merozoite surface protein 1 (C-terminus)-hepatitis B virus surface protein (PcMSP1-HBs) abolished protection against challenge, compared to protection acquired by delivery of pPcMSP1-HBs alone.
The AAA pathway involves the condensation of α-ketoglutarate and acetyl-CoA via the intermediate AAA for the synthesis of L-lysine. This pathway has been shown to be present in several yeast species, as well as protists and higher fungi. It has also been reported that an alternative variant of the AAA route has been found in Thermus thermophilus and Pyrococcus horikoshii, which could indicate that this pathway is more widely spread in prokaryotes than originally proposed. The first and rate-limiting step in the AAA pathway is the condensation reaction between acetyl-CoA and α‑ketoglutarate catalysed by homocitrate-synthase (HCS) (E.C 2.3.3.14) to give the intermediate homocitryl‑CoA, which is hydrolysed by the same enzyme to produce homocitrate. Homocitrate is enzymatically dehydrated by homoaconitase (HAc) (E.C 4.2.1.36) to yield cis-homoaconitate. HAc then catalyses a second reaction in which cis-homoaconitate undergoes rehydration to produce homoisocitrate. The resulting product undergoes an oxidative decarboxylation by homoisocitrate dehydrogenase (HIDH) (E.C 1.1.1.87) to yield α‑ketoadipate. AAA is then formed via a pyridoxal 5′-phosphate (PLP)-dependent aminotransferase (PLP-AT) (E.C 2.6.1.39), using glutamate as the amino donor. From this point on, the AAA pathway varies with [something is missing here ? -> at the very least, section header! ] on the kingdom.
Samoyeds' friendly and affable disposition makes them poor guard dogs; an aggressive Samoyed is rare. The breed is characterized by an alert and happy expression which has earned the nicknames "Sammie smile" and "smiley dog". With their tendency to bark, however, they can be diligent watch dogs, barking whenever something approaches their territory. Samoyeds are excellent companions, especially for small children or even other dogs, and they remain playful into old age. According to the Samoyed Club of America, when Samoyeds become bored, they may become destructive or start to dig.
=== Abnormal collagen === Abnormal collagen fibrils are often found in diabetes. Due to increased levels of lysyl oxidase, collagen increases cross-linking. This thickens the basement membrane, another hallmark of NL.
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.
No. Freeze-drying removes water but does not reliably kill microorganisms. Sterile lyophilized products are typically prepared aseptically before freezing or are sterilized by a validated method. Microbial control depends on the entire manufacturing process.