glass transition raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-02-13. Anything still debated is marked as such rather than presented as settled.
Quality assessment of a lyophilized product includes cake appearance, residual moisture, reconstitution time, and container closure integrity. A uniform, porous cake suggests that freezing and drying stayed within the formulation's design space. Cracks, shrinkage, meltback, or a glassy film can indicate thermal abuse or a formulation problem. Analysts also test for subvisible particles and sterility when the product requires those specifications. Visual inspection alone cannot confirm biological activity or chemical stability, so it is combined with analytical methods.
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.
Quality control also examines cake structure, color, and reconstitution behavior. A collapsed or shrunken cake can indicate a thermal excursion during drying. Analytical methods such as X-ray diffraction, differential scanning calorimetry, and near-infrared spectroscopy can detect crystallinity or moisture distribution. Regulatory expectations focus on validated assays and lot-to-lot consistency. Questions remain about how well accelerated stability tests predict long-term behavior for every formulation. Visual inspection remains common but is subjective without trained reviewers and reference images.
After lyophilization, a product's quality depends on residual moisture, cake appearance, and reconstitution time. Residual moisture is often measured by Karl Fischer titration or thermogravimetric analysis. A low moisture content can slow chemical degradation, but overly dry cakes may be brittle or slow to dissolve. Stability studies track these attributes over months under defined temperature and humidity conditions. Batch records link these measurements to specific process runs and help identify trends before a product fails specification.
Storage conditions for dried products usually aim to exclude moisture and oxygen. Vials are sealed under vacuum or with an inert gas, and stoppers must maintain a barrier during transport. Temperature recommendations vary; some materials remain stable at room temperature, while others need refrigeration or frozen storage. Humidity control is critical because dried cakes can absorb water rapidly once a container is opened. Desiccant packs and moisture-barrier bags add further protection during shipping.
| Property | Value | Notes |
|---|---|---|
| Cake appearance | Uniform porous plug | Cracks, shrinkage, or meltback suggest process deviation. |
| Reconstitution time | 10 seconds to 5 minutes | Depends on cake structure, diluent, and agitation. |
| Typical storage humidity | Below 60% relative humidity | Lower humidity limits moisture uptake by hygroscopic cakes. |
| Container closure | Glass vial, elastomer stopper, crimp seal | Seal integrity limits moisture and oxygen ingress. |
| Common moisture test | Karl Fischer titration | Measures residual water content in the dried solid. |
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.
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.
Reconstitution involves adding a suitable diluent, often sterile water or a buffer, to the dried cake. Gentle swirling or inversion helps dissolve the material without creating excessive foam. The time required for complete dissolution can range from seconds to several minutes and depends on the cake structure and the diluent. Improper reconstitution, such as vigorous shaking or using the wrong diluent, can cause protein aggregation or loss of activity. After reconstitution, the product may have a limited shelf life and should be used according to its labeling.
Lyophilized products are typically hygroscopic and require protection from moisture during storage. Manufacturers seal them in glass vials, often under vacuum or an inert gas such as nitrogen. The container closure system, including the stopper and crimp seal, must prevent water vapor ingress. Storage temperature varies from controlled room temperature to refrigerated or frozen conditions, depending on the formulation. Humidity-controlled environments are essential because even brief exposure to ambient air can degrade the product.
Stability of a lyophilized product depends on its glass transition temperature, the temperature at which the amorphous cake transitions from a glassy to a rubbery state. Storage below this temperature minimizes molecular mobility and slows chemical degradation. If the storage temperature exceeds the glass transition temperature, the cake may collapse, shrink, or become sticky. Accelerated stability studies at elevated temperatures and humidity help predict shelf life, but they do not always reflect real-time behavior. Residual moisture content also plays a critical role in long-term stability.
In cosmetic applications, botulinum toxin is considered relatively safe and effective for reduction of facial wrinkles, especially in the uppermost third of the face. Commercial forms are marketed under the brand names Botox Cosmetic/Vistabel from Allergan, Dysport/Azzalure from Galderma and Ipsen, Xeomin/Bocouture from Merz, Jeuveau/Nuceiva from Evolus, manufactured by Daewoong in South Korea. The effects of botulinum toxin injections for glabellar lines ("11's lines" between the eyes) typically last two to four months and in some cases, product-dependent, with some patients experiencing a longer duration of effect of up to six months or longer. Injection of botulinum toxin into the muscles under facial wrinkles causes relaxation of those muscles, resulting in the smoothing of the overlying skin. Smoothing of wrinkles is usually visible three to five days after injection, with maximum effect typically a week following injection. Muscles can be treated repeatedly to maintain the smoothed appearance. DaxibotulinumtoxinA (Daxxify) was approved for medical use in the United States in September 2022. It is indicated for the temporary improvement in the appearance of moderate to severe glabellar lines. DaxibotulinumtoxinA is an acetylcholine release inhibitor and neuromuscular blocking agent. The FDA approved daxibotulinumtoxinA based on evidence from two clinical trials (Studies GL-1 and GL-2), of 609 adults with moderate to severe glabellar lines. The trials were conducted at 30 sites in the United States and Canada.
Traditional soy sauces are made by mixing soybeans and grain with mold cultures such as Aspergillus oryzae and other related microorganisms and yeasts (the resulting mixture is called Koji in Japan; the term koji is used both for the mixture of soybeans, wheat, and mold as well as for the mold itself). Historically, the mixture was fermented naturally in large urns and under the sun, which was believed to contribute extra flavors. Today, the mixture is placed in a temperature- and humidity-controlled incubation chamber. Traditional soy sauces take months to make:
==== Bands ==== Opus (Austrian band), an Austrian pop-rock group Opus (Yugoslav band), a Yugoslav progressive rock group Opus (Latvian band), Latvian music group Pur (band), a German pop group originally known as "Opus"
== Controversy == In 2024, an Oregon man and the ACLU of Oregon filed a lawsuit against Grifols for its alleged "forever ban" on accepting plasma from gay men. The ACLU of Oregon states this alleged ban is discriminatory and a violation of Oregon's public accommodations laws. The plaintiff sought nearly $1 million in damages. In 2025, the U.S. Equal Employment Opportunity Commission (EEOC) sued Grifols for failing to accommodate a job applicant's disability, a violation of the Americans with Disabilities Act. In 2025, a Manitoba man sued Grifols, claiming a machine malfunction during plasmapheresis caused him a serious kidney injury. After the deaths of two individuals who gave plasma at Grifols facilities in Winnipeg, the company halted plasma collection in Canada effective August 2026 but indicated it remains ready to resume.
In clinical trials, requirements that must be met for an individual to be included in a study. These requirements help make sure that patients in a trial are similar to each other in terms of specific factors such as age, general health, and previous treatment. When all participants meet the same eligibility criteria, it gives researchers greater confidence that results of the study are caused by the intervention being tested and not by other factors. (NCI) Summary criteria for participant selection; includes Inclusion and Exclusion criteria. (NLM) Empirical
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== Principle == In the case of M13 filamentous phage display, the DNA encoding the protein of interest is inserted into the gene encoding either the minor (pIII) or the major (pVIII) coat protein. The modified coat protein gene and the rest of the phage genome is then introduced into E. coli bacteria, which produce phage virions with the relevant protein fragment as part of their outer coat phage and the DNA encoding for these proteins packaged inside the phage. The phages can then be selected using e.g. DNA or protein molecules immobilized on the surface of a microplate. Specifically, phages that display proteins that binds to those targets will remain attached, while others will be removed by washing. Those that remain can be eluted and amplified by bacterial infection. The repeated cycling of selection, elution and amplification is sometimes referred to as 'panning', in reference to the enrichment of a sample of gold by removing undesirable materials. Phage eluted in the final step can be sequenced to identify the selected proteins. During amplification step, additional mutations may be introduced into the genes encoding the proteins of interest, enabling a directed evolution protocol. Elution can be done combining low-pH elution buffer with sonification, which, in addition to loosening the peptide-target interaction, also serves to detach the target molecule from the immobilization surface. This ultrasound-based method enables single-step selection of a high-affinity peptide.
This glossary of chemistry terms is a list of terms and definitions relevant to chemistry, including chemical laws, diagrams and formulae, laboratory tools, glassware, and equipment. Chemistry is a physical science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions; it features an extensive vocabulary and a significant amount of jargon. Note: All periodic table references refer to the IUPAC Style of the Periodic Table.
For services to the community in Riseley, Bedfordshire. Christine Mary Gendall. For services to the community in Penzance, Cornwall. Terence Brian Gerry. For services to the community in Plymouth, Devon. Beth Laura Gevell. Co-Founder and Director, Arts for Life Project (UK). For services to Young People and to Charity. Amanda Elizabeth Giddins. Chair, Giddo's Gift. For voluntary and charitable services to Young People with Cancer. Kenneth Matthew Gillespie. For services to Young People through Scouting. James Bruce Gillett. For services to the community in Charvil and Reading, Berkshire. Janet Elizabeth Gloin. Manager and Coach, Women's Football, Orpington Football Club. For services to Association Football and to the community in the London Borough of Bromley. Geoffery Frederick Bewick Goldsbrough. Founder, Perennials Charity Rugby Club. For services to Charity in Northern Ireland. Sarah Louise Goodall. Watch Manager, West Yorkshire Fire and Rescue Service. For services to Fire and Rescue. Susan Joy Graham. Chair, Age UK Milton Keynes. For services to Older People in Milton Keynes and Buckinghamshire. Marc Anthony Grayston. Chief Instructor, Maru Karate Kai. For services to Disadvantaged Young People and to the community in Basildon, Essex. Beverley Michelle Greenwood. For services to the community in Glenfield, Leicestershire during Covid-19. Rachael Greenwood. For services to the community in Bramdean and Hinton Ampner, Hampshire. Richard Gregory. For services to the community in Basildon, Essex. Harbaksh Singh Grewal. Vice Chair, UK Punjab Heritage Association.
== Operations == JEOL Ltd. has four business segments. Electron Optics manufactures scanning electron microscopes, transmission electron microscopes and scanning probe microscopes, along with related equipment. The Analytical Instruments section's products include mass spectrometers, nuclear magnetic resonance and electron spin resonance equipment. The Industrial Equipment segment covers a range of equipment particularly targeted at the semiconductor industry, such as electron beam sources, wafer process monitors, and plasma gun series. Finally, the Medical Equipment segment manufactures automatic analysis devices, clinical diagnostic systems and amino acid analyzers.
Each member of the population typically progresses from susceptible to infectious to recovered. This can be shown as a flow diagram in which the boxes represent the different compartments and the arrows the transition between compartments (see diagram).
Sources: en.wikipedia.org
11 January – A scrub fire breaks out in Kūaotunu in the Coromandel Peninsula, consuming 36 hectares (89 acres) by the following day. 12 January – Mayor of Hamilton Paula Southgate announces that she would not be running for a third term during the 2025 New Zealand local elections. 13 January: New Zealand and the United Arab Emirates sign a comprehensive economic partnership agreement, cutting tariffs on 98.5% of New Zealand exports to that country. 14 January – Deputy Police Commissioner Jevon McSkimming is suspended from duties due to a criminal investigation by the Independent Police Conduct Authority and the New Zealand Police. 16 January: Hundreds including Police Commissioner Richard Chambers attend the funeral of slain Nelson Police officer Senior Sergeant Lyn Fleming. Health New Zealand confirms a baby who died in November 2024 as the first death caused by whooping cough since a whooping cough epidemic was declared on 22 November 2024. 17 January – Minister of Māori Development Tama Potaka announces an overhaul of the Waitangi Tribunal's membership. 18 January: A pod of about 30 whales are stranded near Pākawau in Golden Bay / Mohua, prompting a response from local iwi, the Department of Conservation(DOC) and Project Jonah. A juvenile beaked whale is stranded and refloated at New Brighton, Christchurch. 19 January: Prime Minister Christopher Luxon implements a cabinet reshuffle, resulting in the replacement of Shane Reti as health minister by Simeon Brown, and the promotion of James Meager to the new position of Minister for the South Island.
== Science and technology == Caldwell 18 (NGC 185), a dwarf spheroidal galaxy of the Local Group in the constellation Cassiopeia Carbon-18 (C-18 or 18C), an isotope of carbon C18, the molecular formula of cyclo(18)carbon C18, an octadecyl-type hydrocarbon with 18 carbon atoms, such as Fatty acids such as Stearic acid, C18H36O2 Oleic acid C18H34O2 C18 bonded silica stationary phase column, a type of reversed-phase chromatography column IEC 60320 C18, a power connector Colorectal cancer (ICD-10 code) ISO/IEC 9899:2018 standard for the programming language C, informally named C18
Structural alignment attempts to establish homology between two or more polymer structures based on their shape and three-dimensional conformation. This process is usually applied to protein tertiary structures but can also be used for large RNA molecules. In contrast to simple structural superposition, where at least some equivalent residues of the two structures are known, structural alignment requires no a priori knowledge of equivalent positions. Structural alignment is a valuable tool for the comparison of proteins with low sequence similarity, where evolutionary relationships between proteins cannot be easily detected by standard sequence alignment techniques. Structural alignment can therefore be used to infer evolutionary relationships between proteins that share very little common sequence. Those relationships can then be characterized through structural phylogenetics. However, caution should be taken when interpreting any results as evidence for shared evolutionary ancestry due to the potential confounding effects of convergent evolution, by which unrelated or distantly-related amino acid sequences converge on a common tertiary structure. Structural alignments can compare two sequences or multiple sequences. Because these alignments rely on information about all the query sequences' three-dimensional conformations, the method can only be used on sequences where these structures are known. These are usually found by X-ray crystallography or NMR spectroscopy. It is possible to perform a structural alignment on structures produced by structure prediction methods.
Candesartan is administered clinically as the cyclohexyl 1-hydroxy ethyl carbonate ester, known as candesartan cilexetil. It is a cascading prodrug that is completely metabolised by esterases in the intestinal wall during absorption, releasing the active candesartan moiety. In the first step of the activation process, the carbonate group is hydrolyzed, releasing carbon dioxide. This reaction also produces cyclohexanol, a relatively non-toxic byproduct that contributes to the favorable safety profile of the prodrug. Another side product of the cascading mechanism is acetic acid, derived from the hydrolysis of the O-CH(CH3)- group; like cyclohexanol, it is also non-toxic and poses minimal risk during drug activation. The use of the prodrug form, candesartan cilexetil, enhances the bioavailability of candesartan. However, its absolute bioavailability remains relatively low, ranging from approximately 15% when administered as tablets to 40% as an oral solution. Candesartan has an IC50 of 15 μg/kg. The active form of candesartan is not used directly in clinical practice, as it would require higher dosing and is associated with a less favorable adverse event profile.
The expression host of choice for the expression of many proteins is Escherichia coli as the production of heterologous protein in E. coli is relatively simple and convenient, as well as being rapid and cheap. A large number of E. coli expression plasmids are also available for a wide variety of needs. Other bacteria used for protein production include Bacillus subtilis. Most heterologous proteins are expressed in the cytoplasm of E. coli. However, not all proteins formed may be soluble in the cytoplasm, and incorrectly folded proteins formed in cytoplasm can form insoluble aggregates called inclusion bodies. Such insoluble proteins will require refolding, which can be an involved process and may not necessarily produce high yield. Proteins which have disulphide bonds are often not able to fold correctly due to the reducing environment in the cytoplasm which prevents such bond formation, and a possible solution is to target the protein to the periplasmic space by the use of an N-terminal signal sequence. Another possibility is to manipulate the redox environment of the cytoplasm. Other more sophisticated systems are also being developed; such systems may allow for the expression of proteins previously thought impossible in E. coli, such as glycosylated proteins. The promoters used for these vector are usually based on the promoter of the lac operon or the T7 promoter, and they are normally regulated by the lac operator. These promoters may also be hybrids of different promoters, for example, the Tac-Promoter is a hybrid of trp and lac promoters.
Sources: en.wikipedia.org
Many dried cakes are hygroscopic and can adsorb water during storage or handling. Absorbed moisture may lower the glass transition temperature and promote chemical reactions. Sealed packaging and controlled humidity reduce this risk.
Cake collapse usually means the product became too warm during the drying cycle. The dried matrix loses porosity and may appear shrunken or glassy. Collapse can slow reconstitution and may signal altered stability, though not every collapsed cake fails specifications.
Karl Fischer titration is a common method for measuring residual water in lyophilized solids. Loss on drying and thermogravimetric analysis are also used in some settings. The chosen method should be validated for the specific formulation and moisture range.
Karl Fischer titration is a common reference method that quantifies water by a chemical reaction. Thermogravimetric analysis can also estimate moisture by weight loss on heating. Method choice depends on sample size and whether other volatile substances are present.