The short version of oxidation fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-01-17. Anything still debated is marked as such rather than presented as settled.
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.
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.
Lyophilization removes water under vacuum from a frozen solution, leaving a porous cake or powder. Formulation excipients such as sugars or polyols can stabilize structure during freezing and drying and can raise the glass transition temperature. Residual moisture in the final product remains a critical variable because even small amounts can support hydrolysis over time. Storage recommendations often specify desiccation, darkness, and low temperature, though exact conditions depend on the peptide and its intended use. Stability studies measure changes under defined conditions rather than predicting absolute shelf life.
Peptides are short chains of amino acids linked by amide bonds. Their stability depends on sequence, length, and the chemical environment. Common degradation routes include hydrolysis of the peptide backbone, oxidation of methionine or cysteine residues, deamidation of asparagine or glutamine, and aggregation through hydrophobic or electrostatic interactions. These processes can alter mass, charge, or biological activity, so storage conditions aim to slow them. The relative importance of each route varies widely among peptides.
Water is a central factor in peptide degradation because it enables hydrolysis and mobilizes reactive species. Lyophilized or dry powders typically remain stable for longer than solutions when kept cool and dry. Oxygen can drive oxidation, particularly for sulfur-containing residues, while light can catalyze side-chain damage. Buffer choice and pH influence charge state and can accelerate or slow deamidation and aggregation. Freeze-thaw cycles may concentrate solutes or promote ice-induced aggregation, so minimizing such cycles is a common handling goal.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilized solid; may appear fluffy or crystalline |
| Solubility class | Water-soluble or sparingly soluble | Depends on sequence and counter-ion content |
| Typical storage temperature | -20 °C or lower for solids | Refrigeration may suffice for short-term use |
| Common analytical method | Reverse-phase HPLC | Purity and degradation products are often assessed by UV detection |
| Primary stability risks | Moisture, oxygen, light, heat | Aggregation and hydrolysis can also occur in solution |
Aseptic technique reduces microbial and particulate contamination when a peptide solution will be used in cell culture or other sensitive applications. Work in a clean area, use sterile containers and filtered tips, and avoid touching vial interiors. Preparing aliquots immediately after dissolution limits repeated temperature cycling, which is a common cause of aggregation and activity loss. Low-binding plastic tubes are preferred for peptides that adsorb to surfaces, especially hydrophobic or positively charged sequences. Labels should record identity, solvent, concentration, and preparation date so that later use can be traced.
Shipping and short-term transfer require attention to temperature control and physical stability. Frozen solutions are commonly sent on dry ice, while lyophilized powders may travel with gel packs or insulated packaging. Thawing should be done slowly on ice or in a refrigerator, not by vigorous heating, and the solution should be mixed gently before use. Temperature loggers can document excursions during transit, but their presence does not prove that a peptide remained stable. Analytical checks such as chromatography or mass spectrometry can verify identity and purity after storage or shipping.
Reconstitution begins with selecting a solvent that dissolves the peptide without causing degradation. Water or aqueous buffer is suitable for many hydrophilic sequences, while hydrophobic peptides may require a small amount of organic solvent such as acetonitrile or dimethyl sulfoxide before dilution. The solvent is added to the vial rather than the powder being scraped out, and the mixture is swirled or inverted gently to avoid foaming. Complete dissolution should be confirmed visually, and insoluble material may indicate aggregation or impurities. Because solvent tolerance varies, published solubility information or a small test dissolution can guide handling.
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.
Peptides are short chains of amino acids whose physical and chemical stability depends on sequence, length, and conformation. The amide backbone can hydrolyze under acidic or basic conditions, while side chains such as methionine, cysteine, and tryptophan are prone to oxidation. Aggregation may occur when hydrophobic regions associate, especially near surfaces or at high concentration. Because these pathways differ among peptides, no single storage condition applies to all sequences. Stability studies therefore examine each peptide under defined temperature, pH, and humidity ranges.
Temperature is a primary variable because most degradation reactions slow as thermal energy decreases. Lyophilized powders are commonly held at -20 °C for routine work and at -80 °C for longer archival periods, though exact recommendations depend on the peptide. Solutions are less stable than dry powders in many cases, and repeated freeze-thaw cycles can promote aggregation or precipitation. Inert atmospheres, such as argon or nitrogen, can limit oxidation for oxygen-sensitive sequences. Desiccants reduce water activity, which lowers hydrolysis rates during storage.
Light exposure can damage aromatic residues and certain labels, so amber vials or opaque containers are often used. pH control matters in solution, as extreme acidity or alkalinity accelerates backbone cleavage; buffers may also introduce ions that affect solubility. Microbial growth is a concern for aqueous preparations that lack preservatives, though many research peptides are handled in sterile or low-bioburden conditions. Container materials can adsorb peptides, particularly hydrophobic or positively charged sequences, reducing recovery. These factors interact, meaning storage decisions balance chemical stability, physical state, and intended use.
Van Zeggeren, F.; Storey, S. H. (1970). The Computation of Chemical Equilibria. Cambridge University Press. Mainly concerned with gas-phase equilibria. Leggett, D. J., ed. (1985). Computational Methods for the Determination of Formation Constants. Plenum Press. Martell, A. E.; Motekaitis, R. J. (1992). The Determination and Use of Stability Constants. Wiley-VCH.
In situ is a Latin phrase meaning 'in the place' or 'on site', derived from in ('in') and situ (ablative of situs, lit. 'place'). The term refers to studying or working with something in its natural or original location rather than moving it elsewhere. This approach preserves environmental factors and relationships that might be lost when materials or specimens are relocated to controlled settings. In comparison, ex situ ('out of the place') methods involve removing materials or specimens for study, preservation, or modification under controlled conditions, often at the expense of their original context. The earliest recorded use of in situ in English dates back to the mid-17th century. Its use in scientific literature expanded from the late 19th century onward, beginning in medicine and engineering, and later spreading to a wide range of disciplines. The natural sciences typically use in situ methods to study phenomena in their original context. In geology, field studies of soil composition and rock formations may provide direct insights into Earth's processes. Biologists observe organisms in their natural habitats to understand behaviors and ecological interactions that cannot be reproduced in a laboratory. In chemistry and experimental physics, in situ techniques make it possible to watch substances and reactions as they occur, capturing transient phenomena in real time. The scope of in situ methods extends into applied sciences and the humanities. In aerospace engineering, in situ inspections and monitoring systems evaluate performance without interrupting operations.
Biko's given name "Bantu" means "people" in IsiXhosa; Biko interpreted this in terms of the saying "Umntu ngumntu ngabantu" ("a person is a person by means of other people"). As a child he was nicknamed "Goofy" and "Xwaku-Xwaku", the latter a reference to his unkempt appearance. He was raised in his family's Anglican Christian faith. In 1950, when Biko was four, his father fell ill, was hospitalised in St. Matthew's Hospital, Keiskammahoek, and died, making the family dependent on his mother's income. Biko spent two years at St. Andrews Primary School and four at Charles Morgan Higher Primary School, both in Ginsberg. Regarded as a particularly intelligent pupil, he was allowed to skip a year. In 1963 he transferred to the Forbes Grant Secondary School in the township. Biko excelled at maths and English and topped the class in his exams. In 1964 the Ginsberg community offered him a bursary to join his brother Khaya as a student at Lovedale, a prestigious boarding school in Alice, Eastern Cape. Within three months of Steve's arrival, Khaya was accused of having connections to Poqo, the armed wing of the Pan Africanist Congress (PAC), an African nationalist group which the government had banned. Both Khaya and Steve were arrested and interrogated by the police; the former was convicted, then acquitted on appeal. No clear evidence of Steve's connection to Poqo was presented, but he was expelled from Lovedale. Commenting later on this situation, he stated: "I began to develop an attitude which was much more directed at authority than at anything else.
Vi capsular polysaccharide vaccine (ViCPS) against typhoid caused by the Typhi serotype of Salmonella enterica. Instead of being a protein, the Vi antigen is a bacterial capsule polysacchide, made up of a long sugar chain linked to a lipid. Capsular vaccines like ViCPS tend to be weak at eliciting immune responses in children. Making a conjugate vaccine by linking the polysacchide with a toxoid increases the efficacy.
== Technology development == The roots of liquid chromatography extend back over a century ago to 1900, when Russian botanist Mikhail Tsvet began experimenting with plant pigments in chlorophyll. He noted that, when a solvent was applied, distinct bands appeared that migrated at different rates along a stationary phase. For this new observation, he coined the term “chromatography,” a colored picture. His first lecture on the subject was presented in 1903, but his most important contribution occurred three years later, in 1906, when the paper “Adsorption analysis and chromatographic method. Applications on the chemistry of chlorophyll,” was published. Rivalry with a colleague who readily and vocally denounced his work meant that chromatographic analysis was shelved for almost 25 years. The great irony of the matter is that it was his rival's students who later took up the chromatography banner in their work with carotins. Greatly unchanged from Tswett's time until the 1940s, normal phase chromatography was performed by passing a gravity-fed solvent through small glass tubes packed with pellicular adsorbent beads. It was in the 1940s, however, that there was a great revolution in gas chromatography (GC). Although GC was a wonderful technique for analyzing inorganic compounds, less than 20% of organic molecules are able to be separated using this technique. It was Richard Synge, who in 1952 won the Nobel Prize in Chemistry for his work with partition chromatography, who applied the theoretical knowledge gained from his work in GC to LC.
Sources: en.wikipedia.org
Narrated by Martin Jarvis 7 August Turbo: Qualifying Boost, Paul Ray and electronic engineer Steve Taylor, who designed the engine management unit, at Cosworth; each year in Formula 1, the permitted fuel was reduced - for 1986, it was 195 litres; the EEC-IV electronic fuel injection system, an EPROM design; the Lola THL2 is tested at Boreham Circuit in Essex on 21 February 1986, with Patrick Tambay; Geoff Goddard, of Cosworth, who designed the overall engine; automotive engineer Neil Oatley; aerodynamicist Ross Brawn at Cranfield Institute of Technology; 4 March 1986 at Donington Park in Leicestershire; the Haas Lola team, and Cosworth development engineer Martin Walters; the Lotus 98T, of Team Lotus, with its Renault engine; the wastegate of a turbocharger compressor; the 1986 San Marino Grand Prix in northern Italy on 27 April 1986; the Chernobyl disaster had taken place the day before; Paul Ray notices that the exhaust has cracked near the turbocharger; Narrated by Martin Jarvis, produced by Patrick Uden, made by Uden Associates 14 August Prisoner of Consciousness, Sir Jonathan Miller looked at his research into human memory, and 48-year-old BBC musician Clive Wearing, who could not remember more than 10 seconds; Miller had made The Body in Question for the BBC in 1978, with much of the future Equinox team. Directed by John Dollar, produced by Patrick Uden, and made by Uden Associates 21 August A Short History of the Future: The City.
== Structure and function == The formyl peptide receptor (FPR) belongs to the class of receptors possessing seven hydrophobic transmembrane domains. The conformation of the FPR is stabilized by several interactions. These include potential salt bridge formation between Arg84-Arg205, Lys85-Arg205, and Lys85-Asp284 which help determine the three-dimensional structure of transmembrane domains, as well as positively charged residues (Arg, Lys) which interact with negatively charged phosphates. Furthermore, residue Arg163 may interact with the ligand binding pocket of the second extracellular loop of the FPR. With respect to binding of the formyl Met-Leu-Phe peptide, there are additional potential interactions which include hydrogen bonding interactions between Arg84 and Lys85 of the first extracellular loop and the N-formyl group of the ligand as well as the peptide backbone of formyl Met-Leu-Phe which can form similar interactions. The formyl-Met moiety of the ligand was shown to form disulfide bridges with Cys residues, and an interaction with Arg163 was also demonstrated. (It is important to mention that some interaction which stabilize the conformation of the receptor may also influence ligand-binding.) Some oligopeptides were also described as characteristic constituents linked to Asn-s of the extracellular N terminal part and to the ligand binding pocket of the second extracellular loop. These components can also determine or make more specific the ligand-receptor interaction.
Hydromorphone is available in parenteral, rectal, subcutaneous, and oral formulations, and also can be administered via epidural or intrathecal injection. Hydromorphone also has been administered via nebulization to treat shortness of breath, but it is not used as a route for pain control due to low bioavailability. Transdermal delivery systems are also under consideration to induce local skin analgesia. Concentrated aqueous solutions of hydromorphone hydrochloride have a visibly different refractive index from pure water, isotonic 9‰ (0·9 per cent) saline and the like, especially when stored in clear ampoules and phials may acquire a slight clear amber discolouration upon exposure to light; this reportedly has no effect on the potency of the solution, but 14-dihydromorphinones such as hydromorphone, oxymorphone, and relatives come with instructions to protect from light. Ampoules of solution which have developed a precipitate should be discarded. Battery-powered intrathecal drug delivery systems are implanted for chronic pain when other options are ruled out, such as surgery and traditional pharmacotherapy, provided that the patient is considered a suitable fit in terms of any contraindications, both physiological and psychological. An extended-release (once-daily) version of hydromorphone is available in the United States. Previously, an extended-release version of hydromorphone, Palladone, was available before being voluntarily withdrawn from the market after a July 2005 FDA advisory warned of a high overdose potential when taken with alcohol.
== History == Carfilzomib is derived from epoxomicin, a natural product that was shown by the laboratory of Craig Crews at Yale University to inhibit the proteasome. The Crews laboratory subsequently invented a more specific derivative of epoxomicin named YU101, which was licensed to Proteolix, Inc. Scientists at Proteolix invented a new, distinct compound that had potential use as a drug in humans, known as carfilzomib. Proteolix advanced carfilzomib to multiple phase I and II clinical trials, including a pivotal phase 2 clinical trial designed to seek accelerated approval. Clinical trials for carfilzomib continue under Onyx Pharmaceuticals, which acquired Proteolix in 2009. In January 2011, the FDA granted carfilzomib fast-track status, allowing Onyx to initiate a rolling submission of its new drug application for carfilzomib. In December 2011, the FDA granted Onyx standard review designation, for its new drug application submission based on the 003-A1 study, an open-label, single-arm phase IIb trial. The trial evaluated 266 heavily-pretreated patients with relapsed and refractory multiple myeloma who had received at least two prior therapies, including bortezomib and either thalidomide or lenalidomide. Initial approval was based on response rate. Data demonstrating an overall survival benefit was demonstrated in the ENDEAVOR trial and approved by the FDA.
Sources: en.wikipedia.org
Lyophilized peptides have low water activity, which slows hydrolysis and many oxidative pathways. Low temperatures further reduce residual chemical reactivity and microbial growth risk. The exact temperature depends on peptide stability data and expected storage duration.
Common pathways include hydrolysis, oxidation, deamidation, and aggregation. Their rates depend on pH, moisture, oxygen, trace metals, light, and temperature. Container surfaces and air-liquid interfaces can also promote loss or structural change.
No. Freezing can concentrate salts and buffer species, cause pH shifts, and damage peptides during ice crystal formation. Repeated freeze-thaw cycles are particularly disruptive. Refrigeration or single-use aliquots may be preferable for some solutions.
Peptide degradation can arise from hydrolysis, oxidation, deamidation, and aggregation. The dominant route depends on the peptide sequence and the storage environment. Temperature, moisture, oxygen, light, and pH all influence the rate.