Everything below concerns Secondary drying. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-09-25. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Handling practices aim to prevent moisture ingress and mechanical damage. Vials should remain stoppered and crimped until use, and reconstitution should follow the labeled diluent and volume. Shipping may involve temperature-controlled containers and desiccants, but direct contact between desiccant and product is avoided. Regulatory guidance expects documented storage conditions, excursion assessments, and stability commitments. Open questions remain about how best to predict long-term stability from short accelerated studies for every formulation class.
Lyophilization, or freeze-drying, removes water from a material by freezing it and then lowering pressure so ice changes directly to vapor. The process relies on sublimation, the phase transition from solid to gas without an intervening liquid state. It is used for heat-sensitive materials that would degrade in conventional drying. The three stages are freezing, primary drying, and secondary drying, each with distinct temperature and pressure requirements. In practice, cycle design balances these variables.
Freezing determines ice crystal structure and pore size, which affect drying speed and product uniformity. Rapid freezing creates small crystals, while slow freezing creates larger crystals and often faster sublimation. During primary drying, chamber pressure is held below the vapor pressure of ice, and shelf temperature supplies heat for sublimation. The ice front recedes, leaving a porous matrix. Thermal limits such as collapse and eutectic temperatures set safe boundaries for formulation. These limits vary with solute composition and concentration.
Secondary drying removes bound water that remains after ice sublimation. Shelf temperature is raised gradually while pressure remains low, reducing water content to a target range. Over-drying can cause brittleness or electrostatic issues, while under-drying affects stability. The endpoint is often judged by pressure rise tests, temperature measurements, or water content analysis. Scale-up depends on matching heat and mass transfer across equipment sizes. Small changes in shelf temperature or pressure can alter cycle length substantially.
| Property | Value | Notes |
|---|---|---|
| Typical appearance | White to off-white porous cake or powder | Color and structure vary with formulation. |
| Typical reconstitution time | Seconds to several minutes | Diluent, agitation, and temperature affect rate. |
| Typical storage temperature | 2–8 °C, 15–25 °C, or ≤−20 °C | Product-specific; protect from moisture and light. |
| Typical container closure | Glass vial with rubber stopper and crimp seal | Closure must limit moisture ingress. |
| Typical stability indicator | Residual moisture, potency, and reconstitution time | Monitored throughout shelf life. |
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.
Handling and storage practices aim to keep the cake intact and dry. Vials are typically stored upright at controlled temperatures, often between 2 °C and 8 °C or at -20 °C for longer-term use. Reconstitution involves adding a suitable diluent and gently mixing until the solid dissolves. Shaking or rapid injection of diluent can create foam or damage sensitive molecules. Once reconstituted, the product may require refrigeration and use within a defined period.
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.
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.
== Causes == Researchers have mapped Urbach–Wiethe disease to chromosome 1 at 1q21 and specifically identified the extracellular matrix protein 1 (ECM1) gene as the gene containing mutations that can lead to the development of the condition. At this point, 41 different mutations within ECM1 have been reported to lead to Urbach–Wiethe disease. These were all homozygous loss-of-function mutations (i.e. nonsense, frameshift or internal deletions). It is an autosomal recessive condition, requiring two mutated copies of the ECM1 gene to cause the disease. ECM1 codes for a glycoprotein of previously unknown origin. The discovery that the loss of ECM1 expression leads to the symptoms associated with Urbach–Wiethe disease suggests that ECM1 may contribute to skin adhesion, epidermal differentiation, and wound healing and scarring. It is also thought to play a role in endochondral bone formation, tumor biology, endothelial cell proliferation and blood vessel formation. The dermatological symptoms are caused by a buildup of a hyaline material in the dermis and the thickening of the basement membranes in the skin. The nature of this material is unknown, but researchers have suggested that it may be a glycoprotein, a glycolipid, an acid mucopolysaccharide, altered collagen or elastic tissue.
Bacteria can also use a NADP-dependent glyceraldehyde 3-phosphate dehydrogenase for the same purpose. Like the pentose phosphate pathway, these pathways are related to parts of glycolysis. Another carbon metabolism-related pathway involved in the generation of NADPH is the mitochondrial folate cycle, which uses principally serine as a source of one-carbon units to sustain nucleotide synthesis and redox homeostasis in mitochondria. Mitochondrial folate cycle has been recently suggested as the principal contributor to NADPH generation in mitochondria of cancer cells. NADPH can also be generated through pathways unrelated to carbon metabolism. The ferredoxin reductase is such an example. Nicotinamide nucleotide transhydrogenase transfers the hydrogen between NAD(P)H and NAD(P)+, and is found in eukaryotic mitochondria and many bacteria. There are versions that depend on a proton gradient to work and ones that do not. Some anaerobic organisms use NADP+-linked hydrogenase, ripping a hydride from hydrogen gas to produce a proton and NADPH. Like NADH, NADPH is fluorescent. NADPH in aqueous solution excited at the nicotinamide absorbance of ~335 nm (near UV) has a fluorescence emission which peaks at 445-460 nm (violet to blue). NADP+ has no appreciable fluorescence.
Sattvic diet (also known as yogic diet), a plant-based diet which may also include dairy and honey, but excludes eggs, red lentils, durian, mushrooms, alliums, blue cheeses, fermented foods or sauces, and alcoholic drinks. Coffee, black or green tea, chocolate, nutmeg, and any other type of stimulant (including excessively pungent spices) are sometimes excluded, as well. Jain vegetarianism is a strict form of lacto-vegetarianism. It excludes meat, eggs, and honey, but it also excludes root vegetables and bulbs, such as potatoes, onions, and garlic. This is because ancient Jain botanical classifications identified these underground plant parts as hosts for dense colonies of microscopic life forms, known as nigoda. Because of this, the Jain diet is one of the earliest recorded food systems designed around microbiological conservation, extending the rule of nonviolence to micro-ecosystems. Beyond the exclusion of root vegetables, the Jain diet further restricts several specific plant categories based on early biological conservation principles:
Sources: en.wikipedia.org
Nucleonica nuclear science portal Nucleonica's Decay Engine for professional online decay calculations EPA – Radioactive Decay Government website listing isotopes and decay energies National Nuclear Data Center – freely available databases that can be used to check or construct decay chains IAEA – Live Chart of Nuclides (with decay chains) Decay Chain Finder
: examples include water in a lake with the inlet and outlet on opposite sides and radioactive material introduced high in the stratosphere by a nuclear bomb test and filtering down to the troposphere.
Jack Straw (born 3 August 1946), Christian, of Eastern European Jewish ancestry; served in Cabinet under Labour governments of Tony Blair and Gordon Brown as Home Secretary and Foreign Secretary; has written for The Guardian, Daily Mail, El País, The Independent, The Mirror UK, The Sun, The Telegraph, Financial Times, The Times, POLITICO, LSE Connect, Prospect Magazine, The New European and is author or co-author of the following books; The English Job: Understanding Iran and Why It Distrusts Britain (2019) ISBN 978-1785903991; Implementation of the Human Rights Act 1998: Minutes of Evidence, Wednesday 14 March 2001 (2001) ISBN 0-10-442701-9; Making Prisons Work: Prison Reform Trust Annual Lecture (1998) ISBN 0-946209-44-8; Future of Policing and Criminal Justice (Institute of Police & Criminological Studies Occasional Paper S.) 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Point-of-care ultrasound (POCUS) may be useful in the diagnosis of NF when MRI and CT are unavailable. It can also help rule out diagnoses that mimic earlier stages of NF, including deep vein thrombosis (DVT), superficial abscesses, and venous stasis. Linear probes are generally preferred for the assessment, especially in the extremities. Findings characteristic of NF include abnormal thickening, air, or fluid in the subcutaneous tissue. This can be summarized as the mnemonic "STAFF" (Subcutaneous irregularity or Thickening, Air, and Fascial Fluid). The official diagnosis of NF using ultrasound requires "the presence of BOTH diffuse subcutaneous thickening AND fascial fluid more than 2 mm." Gas in the subcutaneous tissue may show "dirty acoustic shadowing." However, similar to other imaging modalities, the absence of subcutaneous free air does not definitively rule out a diagnosis of NF, because this is a finding that often emerges later in the disease process. Of note, the quality and accuracy of POCUS are highly user-dependent. It may also be difficult to visualize NF over larger areas, or if there are many intervening layers of fat or muscle. It is still unclear whether POCUS improves the speed of diagnosis of NF or if it reduces the time to surgical intervention as a whole.
Sources: en.wikipedia.org
Thomas Cashman, 34, is convicted of shooting dead nine-year-old Olivia Pratt-Korbel in her Liverpool home in August 2022. The Parliamentary Standards Committee recommends that former Scottish National Party MP Margaret Ferrier be suspended from the House of Commons for 30 days for breaching COVID-19 regulations in September 2020 when she took a train home from London following a positive COVID test. 31 March Figures released by the Office for National Statistics show an 0.1% growth in the UK economy for the final three months of 2022, revising previous figures that had suggested no growth over that period. COVID-19 in the UK: The UK Health Security Agency confirms the NHS COVID-19 contact tracing app will close on 27 April following a decline in its use.
The Fo transmembrane domain is involved in the movement of ions across the membrane. The bacterial FoF1-ATPase consists of the soluble F1 domain and the transmembrane Fo domain, which is composed of several subunits with varying stoichiometry. There are two subunits, γ, and ε, that form the central stalk and they are linked to Fo. Fo contains a c-subunit oligomer in the shape of a ring (c-ring). The α subunit is close to the subunit b2 and makes up the stalk that connects the transmembrane subunits to the α3β3 and δ subunits. F-ATP synthases are identical in appearance and function except for the mitochondrial FoF1-ATP synthase, which contains 7-9 additional subunits. The electrochemical potential is what causes the c-ring to rotate in a clockwise direction for ATP synthesis. This causes the central stalk and the catalytic domain to change shape. Rotating the c-ring causes three ATP molecules to be made, which then causes H+ to move from the P-side (positive-side) of the membrane to the N-side (negative-side) of the membrane. The counterclockwise rotation of the c-ring is driven by ATP hydrolysis and ions move from the N-side to the P-side, which helps to build up electrochemical potential.
=== Cancer === Preliminary studies suggest that FFAR2 may be involved in some types of cancer. 1) One study found that FFAR2 levels were elevated in human stomach and colorectal cancers although another study reported that FFAR2 levels were markedly deceased in human colorectal cancer. These results suggest that FFAR2 may promote the development and/or progression of human stomach cancer but its impact on human colorectal cancer requires further study. 2) In a dextran sulfate sodium-induced model of inflammation-associated colon cancer, FFAR2 knockdown mice developed larger and more tumors than control mice. This study suggests that FFAR2 inhibits the development and/or progression of inflammation-associated colon carcinoma in mice; its role in human inflammation-associated colorectal cancer (e.g., colorectal cancer developing in ulcerative colitis) has not been clarified. 3) Compared to their normal lung tissues, the lung cancer tissues of 42 patients had lower levels of FFAR2 but not FFAR1, FFAR3, or FFAR4. 4) Butyric acid inhibited the proliferation of and triggered apoptosis in cultured human A549 lung cancer cells; further studies in A549 as well as H1299 human lung cancer cells found that propionic acid inhibited their stimulated migration, invasiveness, and colony growth in cell culture assays but did not do so in FFAR2 gene knockout A549 or H1299 cells. These results suggest that FFAR2 may inhibit the development and/or progression of human lung cancer.
Sources: en.wikipedia.org
Collapse occurs when the product temperature rises above its collapse or eutectic temperature during drying. The frozen matrix loses structure, producing a shrunken or melted appearance. This can slow reconstitution and may affect stability.
Karl Fischer titration is a common method, along with loss on drying and thermogravimetric analysis. Each method has different sensitivity and sample requirements. Results should be interpreted with the product's formulation and container in mind.
No. Lyophilization removes water but is not a sterilization step. Sterile products are typically filtered and filled aseptically before freezing, and container closure integrity is maintained afterward.
Conventional drying uses heat to evaporate liquid water, often at temperatures that can degrade sensitive materials. Lyophilization freezes the material first and then removes water by sublimation under vacuum. This avoids prolonged exposure to liquid water and high heat.