glass transition comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2025-11-07. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | Porous, uniform cake or powder | Collapsed or shrunken cakes indicate process issues. |
| Reconstitution time | Seconds to several minutes | Depends on cake porosity, excipients, and diluent. |
| Residual moisture | 0.5-3% w/w | Product-specific; measured by Karl Fischer titration. |
| Typical storage temperature | 2-25 °C | Some biologics require 2-8 °C. |
| Container closure | Glass vial with elastomeric stopper | Sealed under vacuum or inert gas. |
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.
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.
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.
Quality control for freeze-dried lots combines visual inspection with instrumental tests. Cake appearance, color, and shrinkage are recorded against a reference, while residual moisture is measured by Karl Fischer titration or loss on drying. Thermal analysis can reveal phase transitions and crystallization events, and X-ray diffraction distinguishes amorphous from crystalline solids. Microbiological tests and container closure integrity checks are also routine for sterile products. Analytical methods must be validated for the matrix, because excipients and low moisture can affect accuracy. Open questions include how best to predict long-term stability from short-term data.
Lyophilized solids are often hygroscopic, so handling occurs in controlled low-humidity areas or glove boxes when the material is exposed. Vials remain sealed with elastomeric stoppers and aluminum crimps until use, because airborne moisture can raise residual water and shorten shelf life. The porous cake is fragile and may crack, shrink, or powder during transport. Personnel typically avoid repeated warming and cooling of sealed units, which can draw moisture through closures. These practices aim to preserve the low water content achieved during drying.
Storage conditions depend on the formulation and the intended shelf life. Many pharmaceutical and biological freeze-dried products are kept at 2–8 °C, while some stable foods and reagents tolerate room temperature. Others require −20 °C or colder to slow chemical degradation or aggregation. Protection from light and oxygen is common because oxidation can continue in the dry state. Stability studies usually monitor potency, appearance, moisture, and reconstitution time over months or years. Predictions from accelerated studies are useful but may not fully capture real-time changes.
==== Condensation polymerization ==== Condensation polymerization is an important class of step-growth polymerization, which is formed simply by the reaction of two monomers and results in the release of a water molecule. Since these polymers are typically made up of two or more monomers, the resulting end groups are from the monomer functionality. Examples of condensation polymers can be seen with polyamides, polyacetals and polyesters. An example of polyester is polyethylene terephthalate (PET), which is made from the monomers terephthalic acid and ethylene glycol. If one of the components in the polymerization is in excess, then that polymers functionality will be at the ends of the polymers (a carboxylic acid or alcohol group respectively).
This assumption arose from the dopamine hypothesis that maintains that both schizophrenia and bipolar disorder are a result of excessive dopamine activity. Furthermore, psychomotor stimulants like cocaine that increase dopamine levels can cause psychotic symptoms if taken in excess. Chlorpromazine and other typical antipsychotics are primarily blockers of D2 receptors. An almost perfect correlation exists between the therapeutic dose of a typical antipsychotic and the drug's affinity for the D2 receptor. Therefore, a larger dose is required if the drug's affinity for the D2 receptor is relatively weak. A correlation exists between average clinical potency and affinity of the antipsychotics for dopamine receptors. Chlorpromazine tends to have a greater effect at serotonin receptors than at D2 receptors, which is notably the opposite effect of the other typical antipsychotics. Therefore, chlorpromazine's effects on dopamine and serotonin receptors are more similar to the atypical antipsychotics than to the typical antipsychotics. Chlorpromazine and other antipsychotics with sedative properties such as promazine and thioridazine are among the most potent agents at α-adrenergic receptors. Furthermore, they are also among the most potent antipsychotics at histamine H1 receptors. This finding is in agreement with the pharmaceutical development of chlorpromazine and other antipsychotics as anti-histamine agents.
Epiboly is the stage of development for select organisms, such as the xenopus, sea urchin and zebrafish, when the cells of the embryo grow and migrate to the opposite end of the yolk sac to envelop it to continue developing.
Techniques such as the controlled encapsulation of individual gas bubbles to create hollow nanoparticles for synthesizing microbubbles with specific contents are vital for drug delivery systems. Both silica and titanium-based microparticles are used as durable shells after using gas to increase the flow velocity of the aqueous phase. A higher flow velocity allows greater control over the thickness of the aqueous shells. The emerging versatility of nanoparticles can be seen in the delivery of particle-loaded microdroplets being utilized in depot injections for drug delivery rather than the typical approach of injecting drugs intravenously. This is possible due to the low thickness of the shells which typically are in the range of 1 to 50 μm. More recent advancements in microfluidic particles allowed the synthesis of nanometer sized particles from biologically derived polymers. Using specific flow-focusing multiphase designs that control flow rate and temperature, the size of nanoparticle formation can be controlled along with the concentration and configuration of the droplets. Another technique for creating particle-loaded microdroplets is the use of lipid-hydrogel nanoparticles that can be manipulated into more narrowly shaped droplets, which is useful when soft or brittle materials must be used. These soft materials are especially important in the production of powders.
== History == Reslizumab was initially developed by Chuan-Chu Chou at Schering-Plough and was previously known as SCH-55700. In 1993, Chou and his group at Schering-Plough were granted the patent for the design, cloning and expression of the reslizumab drug. Ception Therapeutics acquired the drug and continued its development under the name CTx55700. In 2010, Ception Therapeutics was acquired by Cephalon for $250 million and the drug continued under development under the codename CEP-38072. In 2011, Teva Pharmaceuticals acquired Cephalon for $6.8 billion and continued the development of reslizumab.
Sources: en.wikipedia.org
=== Agricultural === BASF supplies agricultural products and chemicals including fungicides, herbicides, insecticides and seed treatment products. The company also researches nutrigenomics. BASF opened a new crop protection technology center in Limburgerhof, Germany in 2016.
This has been proven in two cases in the United States in the 1980s where a couple of men's vasa deferentia were directly surgically attached to their efferent ducts and these men both subsequently impregnated their partners within the next couple of years. This has also been proven in a similar case in Western Europe in the early 1990s.
One DNA or RNA molecule differs from another primarily in the sequence of nucleotides. Nucleotide sequences are of great importance in biology since they carry the ultimate instructions that encode all biological molecules, molecular assemblies, subcellular and cellular structures, organs, and organisms, and directly enable cognition, memory, and behavior. Enormous efforts have gone into the development of experimental methods to determine the nucleotide sequence of biological DNA and RNA molecules, and today hundreds of millions of nucleotides are sequenced daily at genome centers and smaller laboratories worldwide. In addition to maintaining the GenBank nucleic acid sequence database, the National Center for Biotechnology Information (NCBI) provides analysis and retrieval resources for the data in GenBank and other biological data made available through the NCBI web site.
It's good to be with friends and family as we struggle to deal with this immense loss ... and try to celebrate this immense life. We are looking for all the usual things: comfort, purpose, answers, something to hold on to, a way to let him go in peace. Mostly, we are feeling heartbroken over the death of our beautiful friend. He was a sweet man with a keen sense of humor and a deep sense of humanity. He was an amazing musician, an inspiration, and a comfort to so many. He made great music and gifted it to the world. We are proud to have known him, to be his friend, and to create music with him. For the past decade, Layne struggled greatly—we can only hope that he has at last found some peace. We love you, Layne. Dearly. And we will miss you ... endlessly. In 2010, in an interview on VH1's Celebrity Rehab, former Alice in Chains bass player Mike Starr said that he was the last person to see Staley alive and had spent time with him the day before his death, April 4 (Starr's birthday). Starr claimed that Staley was very sick but would not call 9-1-1. They briefly argued, which ended with Starr storming out. Starr stated that Staley called after him as he left and said: "Not like this, don't leave like this." Starr expressed regret for not calling 9-1-1, and stated that Staley had threatened to sever their friendship if he did. Starr also regretted being high on benzodiazepines that night and having walked out of the door. Staley's mother was insistent that neither she nor anyone in her family blamed Starr for Staley's death, telling Starr: "Layne would forgive you.
At the top of the Communist Party was the Central Committee, elected at Party Congresses and Conferences. In turn, the Central Committee voted for a Politburo (called the Presidium between 1952 and 1966), Secretariat and the general secretary (First Secretary from 1953 to 1966), the de facto highest office in the Soviet Union. Depending on the degree of power consolidation, it was either the Politburo as a collective body or the General Secretary, who always was one of the Politburo members, that effectively led the party and the country (except for the period of the highly personalized authority of Stalin, exercised directly through his position in the Council of Ministers rather than the Politburo after 1941). They were not controlled by the general party membership, as the key principle of the party organization was democratic centralism, demanding strict subordination to higher bodies, and elections went uncontested, endorsing the candidates proposed from above. The Communist Party maintained its dominance over the state mainly through its control over the system of appointments. All senior government officials and most deputies of the Supreme Soviet were members of the CPSU. Of the party heads themselves, Stalin (1941–1953) and Khrushchev (1958–1964) were Premiers. Upon the forced retirement of Khrushchev, the party leader was prohibited from this kind of double membership, but the later General Secretaries for at least some part of their tenure occupied the mostly ceremonial position of Chairman of the Presidium of the Supreme Soviet, the nominal head of state.
Sources: en.wikipedia.org
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.
Storage temperature is set by the least stable component in the formulation. Proteins, vaccines, and some small molecules can degrade faster at higher temperatures. Refrigeration slows these changes but does not stop them completely.
Collapse occurs when the product exceeds its collapse or glass transition temperature during drying. The ice structure then loses support, and the cake may shrink, melt back, or become dense. Formulation and cycle adjustments are used to keep the product below that threshold.
Residual moisture can influence chemical degradation, cake collapse, and long-term stability. Low moisture levels usually improve stability, but each product has an optimal range.