secondary drying 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.
Last reviewed on 2026-08-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Process name | Lyophilization or freeze-drying | Both terms appear in technical standards and literature. |
| Phase transition | Sublimation | Solid ice becomes vapor without a liquid step. |
| Typical chamber pressure | 0.05-0.5 mbar | Range depends on product temperature and equipment. |
| Typical product temperature | -40 °C to -10 °C | Measured during primary drying; formulation sets limits. |
| Water content after drying | 0.5-3% w/w | Target varies by material and stability needs. |
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.
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.
After primary drying, secondary drying removes water that remains bound to the material. This stage raises the shelf temperature while maintaining low pressure, which encourages desorption of unfrozen water. Residual moisture can be reduced to a low percentage, improving stability for many products. The process parameters, including freezing rate, shelf temperature, and chamber pressure, influence the final pore structure and reconstitution behavior. Control of these variables helps prevent collapse or meltback during drying.
A formulation often contains excipients that protect the active ingredient during freezing and drying. Bulking agents provide structure, while lyoprotectants stabilize sensitive molecules. The freezing step can produce ice crystals whose size and distribution affect the drying rate, and cycle design includes freezing, annealing, and drying phases. If the product temperature rises above a critical value, the cake may collapse or lose its porous structure. Successful lyophilization therefore depends on the interaction between formulation, equipment, and cycle design.
Lyophilization is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen to convert liquid water into ice. Next, the pressure is reduced below the triple point of water so that ice changes directly into vapor without passing through a liquid phase. This step is called primary drying. The result is a porous solid or cake that retains the original shape of the frozen solution.
Lyophilized products are typically stored as sealed solids in vials or syringes. Moisture ingress is a major concern because many dried cakes are hygroscopic and can lose stability when exposed to humid air. Storage temperature depends on the formulation; some products are kept refrigerated, while others are stable at room temperature. Container closure integrity and headspace moisture are often monitored. Light protection may also be required for some photosensitive materials.
Quality control for lyophilized materials includes visual inspection, residual moisture measurement, and reconstitution testing. Cake appearance can reveal process problems such as collapse, shrinkage, or meltback, although appearance alone does not prove potency. Residual moisture is commonly measured by Karl Fischer titration or by loss on drying. Reconstitution time is checked because a slow or incomplete dissolve can indicate a change in pore structure. Stability studies track these attributes over time under defined temperature and humidity conditions.
Analytical methods for lyophilized solids must account for the low moisture content and the fragile cake. Karl Fischer titration is widely used for water content, while near-infrared spectroscopy can measure moisture non-destructively in sealed containers. X-ray diffraction and modulated differential scanning calorimetry help identify crystalline or amorphous phases. Residual solvent analysis may be needed if organic solvents were used during formulation. The combination of these methods supports batch release and long-term stability assessment.
== Research == In 2020, Diabetes Severity Score (DISSCO) was developed which is a tool that could be better than HbA1c identify if a person's condition is declining. It uses a computer algorithm to analyze data from anonymized electronic patient records and produces a score based on 34 indicators.
=== Neuroprotection and DNA repair === Estrogen regulated DNA repair mechanisms in the brain have neuroprotective effects. Estrogen regulates the transcription of DNA base excision repair genes as well as the translocation of the base excision repair enzymes between different subcellular compartments. Estrogen provides neuroprotection by modulating the endocannabinoid system activity, primarily through the regulation of fatty acid amide hydrolase (FAAH) enzyme expression and the endocannabinoid receptor Cβ1 levels. The protective effects appears to work through a fine-tuning mechanism where by estrogen both suppresses excessive endocannabinoid signaling at the Cβ1receptor (which can be neurotoxic under stress) while simultaneously maintaining physiological endocannabinoid tine needed for normal neural function.
==== Affinity selection ==== A generalized AS-MS workflow begins with the pre-incubation of purified protein solutions (i.e. target proteins) with chemical libraries in microplates. Assays can be designed to contain sufficiently high protein concentrations to prevent competition for binding sites between structural analogs, ensuring that hits across a range of affinities can be identified; inversely, assays can contain low protein concentrations to allow for distinction between high and low affinity analogs and to inform structure-activity relationships. The choice of a chemical library is less stringent than other high-throughput screening strategies owing to the lack of functional readouts, which would otherwise require deconvolution of the source compound that generates biological activity. Thus, the typical range for AS-MS is 400-3,000 compounds per pool. Other considerations for screening are more practical, such as a need to balance desired compound concentration, which is usually in the micromolar range, with the fact that compound stock solutions are typically stored as 10 millimolar solutions, effectively capping the number of compounds screened in the thousands. After appropriate test compounds and targets are selected and incubated, ligand-protein complexes can be separated by a variety of means.
Excretion: It is common for proteins and peptides to be excreted via the hepatic and renal pathways. In the liver, the amino acids present undergo transamination. This way the amino acids are converted into ammonia and keto acids. Lastly, these substances are excreted via the kidney. However, it is important to take into account that α-bungarotoxin binds irreversibly to the receptors, which would result in a very low metabolic and excretion rate, as most of the neurotoxin would be present at the receptor sites.
The main ingredients of the extracellular matrix are glycoproteins secreted by the cells. The most abundant glycoprotein in the ECM of most animal cells is collagen, which forms strong fibers outside the cells. In fact, collagen accounts for about 40% of the total protein in the human body. The collagen fibers are embedded in a network woven from proteoglycans. A proteoglycan molecule consists of a small core protein with many carbohydrate chains covalently attached, so that it may be up to 95% carbohydrate. Large proteoglycan complexes can form when hundreds of proteoglycans become noncovalently attached to a single long polysaccharide molecule. Some cells are attached to the ECM by still other ECM glycoproteins such as fibronectin. Fibronectin and other ECM proteins bind to cell surface receptor proteins called integrins that are built into the plasma membrane. Integrins span the membrane and bind on the cytoplasmic side to associated proteins attached to microfilaments of the cytoskeleton. The name integrin is based on the word integrate, integrins are in a position to transmit signals between the ECM and the cytoskeleton and thus to integrate changes occurring outside and inside the cell. Current research on fibronectin, other ECM molecules, and integrins is revealing the influential role of the ECM in the lives of cells. By communicating with a cell through integrins, the ECM can regulate a cell's behavior.
Sources: en.wikipedia.org
A 2012 review focused on antidepressants and sleep found that mirtazapine reduced the time it took to fall asleep and improved the quality of sleep in many people with sleep disorders caused by depression, but that it could also disturb sleep in many people, especially at higher doses, causing restless leg syndrome in 8 to 28% of people and in rare cases causes REM sleep behavior disorder. This seemingly paradoxical dose–response curve of mirtazapine with respect to somnolence is owed to the exceptionally high affinity of the drug for the histamine H1, 5-HT2A, and 5-HT2C receptors; exhibiting near exclusive occupation of these receptors at doses ≤15 mg. However, at higher doses, inverse agonism and constitutive activation of the α2A-, α2B-, and α2C-adrenergic receptors begins to offset activity at H1 receptors leading to decreased somnolence and even a subjective sensation of "activation" in treated patients. A 2018 analysis of 21 antidepressants found them to be fairly similar overall. It found tentative evidence for mirtazapine being in the more effective group and middle in tolerability. After one week of usage, mirtazapine was found to have an earlier onset of action compared to selective serotonin reuptake inhibitors.
The process of pasteurizing donkey milk deactivates bacterial and viral contaminants. Donkey milk contains immune-enhancing compounds (in particular lysozyme and lactoferrin) to help protect infants from disease. In addition, the flavour and appearance of donkey milk are attractive to children.
Anti-Peruvian (Spanish: Antiperuanismo), or Peruvophobia, refers to negative feelings, fear, hatred and discrimination toward and/or against Peruvians based on a combination of historical, cultural, and ethnic prejudices. It arose since the 19th century in some societies as a consequence of their territorial expansion. It germinated as a tendency in the nationalisms of neighboring countries, mainly Ecuador, Chile and to a lesser extent due to the disputed origin of different cultural manifestations, such as recipes and gastronomic preparations (such as pisco or picarones) or folkloric dances (such as the diablada or the morenada) whose origin is disputed or shared with Chile and Bolivia. In addition, due to different political and ideological differences with the Bolivarian leaders and their Chavista sympathizers in Venezuela. It can manifest itself in many ways, such as individual hatred or discrimination, tabloid media, attacks by groups organized for that purpose, even on social networks.
== Awards and honours == The HGSA honours one eminent member annually by inviting them to present the HGSA Oration at the Annual Scientific Meeting. Additionally, one outstanding mid-career researcher is invited to deliver a presentation at the Annual Scientific Meeting to showcase their work in the Sutherland Lecture, named in honour of Prof Grant Sutherland. Each year, the membership is invited to nominate eminent retiring members to Emeritus Membership of the Society. Nominations are called for members who have contributed significantly to the running and welfare of the Society for a Service Award. HGSA Council scrutinizes and considers these nominations before awarding.
Sources: en.wikipedia.org
== Use and effects == The drug produces similar autonomic and psychoactive effects as LSD in humans, although its hallucinogenic effects are less pronounced. It has been found to possess about one-sixth to one-eighth (i.e., ~15% overall) of the potency of LSD in inducing mydriasis (pupil dilation) and psychedelic effects, respectively, in humans. More specifically, 2,3-dihydro-LSD is psychedelic at doses of 3.0 to 4.5 μg/kg (210–315 μg for a 70-kg person), while LSD is hallucinogenic at doses of 0.5 to 1.0 μg/kg (35–70 μg for a 70-kg person). In addition to its greatly reduced potency compared to LSD, 2,3-dihydro-LSD has a delayed onset and time to peak effects relative to LSD. The duration of 2,3-dihydro-LSD was roughly 8 to 12 hours and was longer than that of LSD (which had a duration of about 7 hours in the study) as well.
February 4 The United States House of Representatives votes 230–199 to remove Representative Marjorie Taylor Greene (R-GA) from her assignments on the Education and Labor and Budget committees and following controversial comments made about the mass shootings in Parkland and Sandy Hook, as well as calling for violence towards Democrats, and the support of numerous conspiracy theories such as QAnon. Smartmatic files a $2.7 billion defamation lawsuit against the Fox Corporation and its cable news hosts Lou Dobbs, Jeanine Pirro, and Maria Bartiromo as well as frequent guests and ex-President Donald Trump's former lawyers Rudy Giuliani and Sidney Powell, who spread false conspiracy theories about them after the 2020 United States presidential election. February 5 U.S. Reps Andrew Clyde (R-GA) and Louie Gohmert (R-TX) are fined $5,000 for refusing to go through the metal detectors outside the House chamber. The U.S. Food and Drug Administration approves Breyanzi to treat large B-cell lymphoma. February 7 The Tampa Bay Buccaneers win Super Bowl LV, defeating the Kansas City Chiefs 31–9, making them the first wildcard team to win the Super Bowl since the 2010 Green Bay Packers and the first to win it in their home stadium. U.S. Rep Ron Wright (R–TX) passes away at the age of 67 after contracting COVID-19, making him the first sitting member of Congress to die of the disease. February 8 – South Dakota Constitutional Amendment A, which would have legalized recreational cannabis in South Dakota on July 1, is struck down as unconstitutional by judge Christina Klinger.
By definition, these compounds occur in nature, but the subfield includes anthropogenic species, such as pollutants (e.g., methylmercury) and drugs (e.g., Cisplatin). The field, which incorporates many aspects of biochemistry, includes many kinds of compounds, e.g., the phosphates in DNA, and also metal complexes containing ligands that range from biological macromolecules, commonly peptides, to ill-defined species such as humic acid, and to water (e.g., coordinated to gadolinium complexes employed for MRI). Traditionally bioinorganic chemistry focuses on electron- and energy-transfer in proteins relevant to respiration. Medicinal inorganic chemistry includes the study of both non-essential and essential elements with applications to diagnosis and therapies.
Sources: en.wikipedia.org
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.
Lowering pressure reduces the boiling point of water and allows ice to sublimate at temperatures below freezing. Vacuum also limits convective heat transfer, so heat is usually supplied by shelves or radiation. The pressure must stay below the vapor pressure of ice at the product temperature.
The cycle typically includes freezing, primary drying, and secondary drying. Freezing solidifies water and sets the pore structure; primary drying removes bulk ice; secondary drying removes bound water. Some cycles add annealing or pre-freezing steps.
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.