Aliquoting 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 2025-07-28. Where a claim depends on a specific study, the study is described rather than over-claimed.
Handling begins before a peptide arrives at the bench. Containers should be inspected for cracks, loose caps, or visible moisture, and labels should record identity, lot, and receipt date. Lyophilized material is often allowed to equilibrate to room temperature before opening to prevent condensation on the powder. Gloves and a clean workspace reduce contamination and static-related loss. Once opened, the vial may be purged with inert gas and resealed if the peptide is sensitive to oxygen or humidity. These steps are procedural safeguards rather than guarantees of stability.
Reconstitution introduces new risks because the peptide contacts solvent, air, and container surfaces. The chosen solvent should match the peptide's solubility profile, and buffer salts, pH, and ionic strength can affect dissolution and subsequent stability. Gentle mixing is preferred over vigorous vortexing, which can create interfaces and shear. If the solution is not clear, the cause may be incomplete dissolution, aggregation, or insoluble counter-ions rather than a simple concentration problem. Filtration is sometimes used, but filters can adsorb peptides and alter measured concentration.
Cold-chain practice relies on documented temperature ranges, calibrated monitoring, and minimized excursions. Shipments may use insulated boxes, phase-change materials, or dry ice, with data loggers to record conditions. Upon receipt, the recipient should verify the logger trace and place items into long-term storage promptly. Repeated warming and cooling during transfers can be more harmful than a single controlled excursion. For solutions, dividing material into single-use aliquots reduces the number of thawing and refreezing events and limits repeated opening of the same container.
Peptides are short chains of amino acids linked by amide bonds, and their storage stability depends on sequence, length, and three-dimensional structure. Chemical degradation can occur through hydrolysis, oxidation, deamidation, and aggregation, while physical changes such as precipitation or surface adsorption reduce recovery. Storage conditions are chosen to slow these processes without altering the peptide itself. Because peptides vary widely, no single condition suits every sequence, so laboratories often establish stability empirically for each batch.
Temperature is a primary factor because most degradation reactions proceed more slowly at lower temperatures. Lyophilized peptides are commonly held at -20 °C or below, although some sequences remain stable at 2–8 °C for limited periods. Moisture uptake during handling can accelerate hydrolysis, so sealed containers and desiccants are used. Solutions are generally less stable than powders and may require freezing at -80 °C or refrigeration, depending on the peptide. Repeated freeze-thaw cycles can promote aggregation even when the storage temperature is otherwise suitable.
| Property | Value | Notes |
|---|---|---|
| Container material | Glass or polypropylene | Low-binding options reduce peptide adsorption |
| Typical shipping condition | Dry ice or gel packs | Choice depends on required temperature range |
| Light protection | Amber vial or foil wrap | Reduces photodegradation of sensitive residues |
| Reconstitution solvent | Water, buffer, or organic co-solvent | Depends on peptide solubility and assay requirements |
| Temperature monitoring | Data logger or indicator | Documents excursions during transport and storage |
Reconstitution is a critical handling step. The appropriate solvent—often sterile water, phosphate-buffered saline, or a water-acetonitrile mixture—is chosen based on peptide solubility. Adding solvent gently down the vial wall and swirling, rather than vortexing, reduces foaming and shear stress. The resulting solution should be clear; visible particles indicate incomplete dissolution or contamination. Concentration is recorded accurately because it affects subsequent use. If the peptide is not fully soluble, a small amount of organic solvent or a different buffer may be required, but this changes the final composition.
After reconstitution, solutions are divided into single-use aliquots and stored at -80°C. Labels include peptide name, concentration, buffer composition, date, and lot number. Freeze-thaw cycles are minimized by thawing only the needed aliquot on ice or at room temperature. Some peptides benefit from the addition of a carrier protein, such as bovine serum albumin, or a cryoprotectant like glycerol to reduce adsorption to plastic. Glass vials with low-binding surfaces are preferred for dilute solutions. Shipping of frozen aliquots uses dry ice and insulated containers to maintain the cold chain.
Peptides are short chains of amino acids whose physical and chemical stability depends on sequence, length, conformation, and the surrounding matrix. In the solid state, lyophilized powders are generally more stable than solutions because low water activity slows hydrolysis and oxidation. Residual moisture, oxygen, trace metals, and light can still promote degradation over time. Storage recommendations therefore balance temperature, humidity, and container integrity rather than relying on a single condition. The optimal condition for a given peptide is often determined empirically because no universal rule covers every sequence.
In aqueous solution, peptides are vulnerable to hydrolysis, oxidation, deamidation, and aggregation, with rates influenced by pH, temperature, buffer composition, and ionic strength. Acidic or neutral pH ranges often slow deamidation, while extreme pH can accelerate peptide bond cleavage. Dissolved oxygen and redox-active metal ions contribute to oxidation of methionine, cysteine, and tryptophan residues. Aggregation may be driven by hydrophobic interactions or by interfaces such as air-liquid and container surfaces. Because these pathways interact, solution storage usually requires tighter control than storage of dried material.
Temperature is the most common controlled variable, but its effect is not linear. Lower temperatures reduce most chemical reaction rates, yet freezing can concentrate solutes and create pH shifts in the remaining liquid phase. Repeated freeze-thaw cycles can denature or aggregate some peptides, especially those with hydrophobic segments. For lyophilized powders, desiccation and protection from moisture are often more important than deep freezing. For solutions, the choice between refrigeration and freezing depends on peptide concentration, buffer components, and the intended duration of storage.
Handling begins with receipt and inspection. Vials should be checked for damage, label integrity, and temperature history. Lyophilized peptides should be allowed to equilibrate to room temperature before opening to prevent condensation. Solutions should be prepared in a clean, calibrated environment using appropriate solvents. Personal protective equipment and containment reduce exposure and contamination. Documentation of lot number, date, and storage location supports traceability. The goal is to limit repeated temperature changes, moisture exposure, and microbial contamination.
Reconstitution solvent depends on peptide solubility and intended use; water, buffer, or small amounts of organic solvent may be needed. After dissolution, solutions are typically aliquoted into single-use portions to avoid repeated freeze-thaw cycles. Aliquots are stored at -20 °C or -80 °C, depending on stability. Labels include concentration, solvent, date, and operator. Sterile filtration may be used when microbial control is required, but filters can adsorb peptides. The optimal concentration and solvent are often determined empirically.
Cold-chain shipping uses insulated containers, phase-change packs, and temperature indicators. Dry ice maintains -70 °C or lower but requires venting to avoid pressure buildup. Gel packs provide 2-8 °C for shorter transit. Upon arrival, recipients should record temperature indicators and transfer vials promptly to storage. Deviations from specified conditions should be documented and may require analytical re-check. The effect of a brief temperature excursion is peptide-specific and not always predictable from general rules.
In column chromatography, the column contains a packed column of solid particles, finely ground powders, or gels. This is called the stationary phase or adsorbent. It is most often made of silica gel or alumina. Cellulose powder has often been used in the past. A wide range of stationary phases are available in order to different forms of column chromatographies: ion exchange chromatography, reversed-phase chromatography (RP), affinity chromatography or expanded bed adsorption (EBA). The solid phase may be microporous for an increased surface, though EBA uses a fluidized bed. In general, one should use much more stationary phase than the analyte mixture. For silica column chromatography in particular, for each gram of dry mass of the analyte mixture, there should be 20 to 100 grams of the stationary phase. Using more silica would increase the resolving power of the chromatography, but also make it slower.
This is because "anabolic" refers to muscle-building effects, while "androgenic" refers to induction and maintenance of male secondary sexual characteristics, but the latter in principle would include anabolic or muscle-building effects. Handelsman has argued that these terms should be discarded, and that instead, AAS should all simply be referred to as "androgens". Relatedly, Handelsman exclusively uses the term "androgen" to refer to these agents in his publications. Although the term "anabolic–androgenic steroid" is technically valid in describing two types of actions of these agents, Handelsman considers the term to be unnecessary and redundant. He likens it to hypothetical terms like "luteal–gestational progestins" or "mammary–uterine estrogens". Handelsman also notes that the term "anabolic steroid" is easily and unnecessarily confusable with corticosteroids. Besides AAS, Handelsman has criticized the term "selective androgen receptor modulator (SARM)" and claims about these agents as well.
== Early life and education == Robinson was born in Chicago. He received a BS in chemistry from the California Institute of Technology (Caltech) in 1963, and a PhD in biochemistry from the University of California, San Diego in 1968. His doctoral thesis was titled, Experiments on the synthesis and spectral characterization of cytochrome-related molecules.
Sources: en.wikipedia.org
Kidney involvement, in scleroderma, is considered a poor prognostic factor and frequently a cause of death. The most important clinical complication of scleroderma involving the kidney is scleroderma renal crisis (SRC), the symptoms of which are malignant hypertension (high blood pressure with evidence of acute organ damage), hyperreninemia (high renin levels), azotemia (kidney failure with accumulation of waste products in the blood), and microangiopathic hemolytic anemia (destruction of red blood cells). Apart from the high blood pressure, hematuria (blood in the urine) and proteinuria (protein loss in the urine) may be indicative of SRC. In the past, SRC was almost uniformly fatal. While outcomes have improved significantly with the use of ACE inhibitors, the prognosis is often guarded, as a significant number of patients are refractory to treatment and develop kidney failure. About 7–9% of all diffuse cutaneous scleroderma patients develop renal crisis at some point in the course of their disease. Patients who have rapid skin involvement have the highest risk of renal complications. It is most common in diffuse cutaneous scleroderma, and is often associated with antibodies against RNA polymerase (in 59% of cases). Many proceed to dialysis, although this can be stopped within three years in about a third of cases. Higher age and (paradoxically) a lower blood pressure at presentation make dialysis more likely to be needed. Treatments for SRC include ACE inhibitors.
== Usage == One mark of a good computer is the appearance of a piece of software specifically written for that machine that does something that, for a while at least, can only be done on that machine. The earliest recorded use of the term "killer app" in print is in the May 24, 1988 issue of PC Week: "Everybody has only one killer application. The secretary has a word processor. The manager has a spreadsheet." The definition of "killer app" came up during the deposition of Bill Gates in the United States v. Microsoft Corp. antitrust case. He had written an email in which he described Internet Explorer as a killer app. In the questioning, he said that the term meant "a popular application," and did not connote an application that would fuel sales of a larger product or one that would supplant its competition, as the Microsoft Computer Dictionary defined it. Introducing the iPhone in 2007, Steve Jobs said that "the killer app is making calls". Reviewing the iPhone's first decade, David Pierce for Wired wrote that although Jobs prioritized a good experience making calls in the phone's development, other features of the phone soon became more important, such as its data connectivity and the later ability to install third-party software. The World Wide Web (through the web browsers Mosaic and Netscape Navigator) is the killer app that popularized the Internet, as is the music sharing program Napster.
=== Primary drying === During the primary drying phase, the pressure is lowered (to the range of a few millibars), and enough heat is supplied to the material for the ice to sublimate. The amount of heat necessary can be calculated using the sublimating molecules' latent heat of sublimation. In this initial drying phase, about 95% of the water in the material is sublimated. This phase may be slow (can be several days in the industry), because, if too much heat is added, the material's structure could be altered. In this phase, pressure is controlled through the application of partial vacuum. The vacuum speeds up the sublimation, making it useful as a deliberate drying process. Furthermore, a cold condenser chamber and/or condenser plates provide a surface(s) for the water vapor to re-liquify and solidify on. In this range of pressure, the heat is brought mainly by conduction or radiation; the convection effect is negligible, due to the low air density.
Kynurenic acid (KYNA or KYN) is a product of the normal metabolism of amino acid L-tryptophan. It has been shown that kynurenic acid possesses neuroactive activity. It acts as an antiexcitotoxic and anticonvulsant, most likely through acting as an antagonist at excitatory amino acid receptors. Because of this activity, it may influence important neurophysiological and neuropathological processes. As a result, kynurenic acid has been considered for use in therapy in certain neurobiological disorders. Conversely, increased levels of kynurenic acid have also been linked to certain pathological conditions. Kynurenic acid was discovered in 1853 by the German chemist Justus von Liebig in dog urine, which it was apparently named after.
Sources: en.wikipedia.org
In 1883, the team played four matches in eight days in Adelaide: losing to Norwood (on 23 June) and defeating Port Adelaide (on 16 June), a combined South Australian team (on 18 June), and South Adelaide (on 20 June). The club played against the touring British footballers in 1888. In 1891, Essendon won their first VFA premiership, which they repeated in 1892, 1893 and 1894. One of the club's greatest players, Albert Thurgood, played for the club during this period, making his debut in 1892. Essendon (18 wins, 2 draws) was undefeated in the 1893 season.
Known in antiquity to such medical doctors as Hippocrates and Galen, noma was once reported around the world, including in Europe and the United States. The disease was well-known in the Netherlands in the 1500s and 1600s. The first clinical description of noma was in 1595 by a Dutch man, Carolus Battus. Dutch surgeon Cornelis van de Voorde first used the term "noma" to describe the disease in 1680. A European scientist, Gabriel Lund, attributed noma to poverty, cramped living conditions, and malnutrition in 1765. English medical doctor John Addington Symmonds linked the disease to previous infection with measles. The first surgical treatment for noma sequelae was performed in 1781. Surgical treatments for sequelae developed throughout the 1800s. In the late 1800s, scientists suspected that noma was caused by bacteria. With improvements in hygiene and nutrition, noma has disappeared from industrialized countries since the 20th century, except during World War II when it was endemic to the Auschwitz and Belsen concentration camps. The disease and treatments were studied by Berthold Epstein, a Czech medical doctor and forced-labor prisoner who had recommended the study under Josef Mengele's direction. Since 1970, there has been little research done on noma, with few exceptions. One such exception is Cyril Enwonwu, a Nigerian scientist focusing on noma.
In Vietnam, iced coffee (Vietnamese: cà phê đá, lit. 'iced coffee') is a traditional Vietnamese coffee recipe. It is created using coffee roasted between medium and dark. The drink is made by passing hot water through the grounds into a cup that already contains condensed milk. To serve the drink cold, ice is added to the cup. Variations involve additions of ice, sugar or condensed milk. A popular variation is cà phê sữa đá (or nâu đá in the North), which is iced coffee served with sweetened condensed milk. This is done by putting two to three teaspoons or more of condensed milk into the cup prior to the drip filter process.
Sources: en.wikipedia.org
Allow the sealed vial to reach room temperature before opening to reduce condensation. Use a suitable solvent and gentle mixing rather than vigorous agitation. Follow the supplier's solubility information when available.
Aliquots limit repeated thawing and refreezing and repeated vial opening, both of which can promote degradation. They also reduce the chance of contaminating an entire batch. Single-use portions should be labeled with identity, concentration, solvent, and date.
Inspect the package for damage and confirm that temperature indicators or data loggers stayed within the specified range. Check the vial condition and labeling before placing it into storage. Record any excursion or discrepancy for the supplier or quality system.
Removing water reduces hydrolytic and some oxidative degradation. Powder forms are generally more stable for long-term storage than solutions. Stability still depends on peptide sequence, residual moisture, and container conditions.