This is a working overview of reconstitution, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
After reconstitution, dividing the solution into single-use aliquots limits multiple warming and cooling events and reduces contamination risk. Low-binding polypropylene tubes are often preferred because peptides can adsorb to glass or untreated plastic surfaces. Filling headspace with nitrogen or argon can slow oxidation, and amber or foil-wrapped containers reduce photodegradation. Each aliquot should be labeled with peptide identity, concentration, date, and storage conditions. Frozen aliquots should be thawed quickly and kept on ice until use.
When a peptide arrives, the vial should be inspected for damage, and its label, lot number, and accompanying analytical data should be recorded. Cold vials should equilibrate to room temperature before opening to prevent condensation on the powder. Moisture uptake can reduce stability and complicate accurate weighing or reconstitution. Inventory systems that track date, quantity, and storage location help prevent unnecessary temperature cycling. Personnel should follow institutional or manufacturer instructions for any specific peptide.
Reconstitution is often performed with sterile water, buffer, or a water-miscible organic solvent, depending on solubility. The solvent should be added gently along the vial wall, and the solution mixed by gentle swirling rather than vigorous vortexing, which can cause foaming and surface denaturation. Some sequences require a small amount of base or acid to dissolve, followed by pH adjustment. Preparing a concentrated stock solution can simplify later dilution, but the stock itself may have limited stability. Records of solvent, concentration, and date support reproducibility.
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.
| Property | Value | Notes |
|---|---|---|
| Container material | Type I borosilicate glass or polypropylene | Low peptide adsorption; avoid untreated polystyrene for dilute solutions. |
| Headspace gas | Nitrogen or argon | Inert gas reduces oxidation for methionine- or cysteine-containing peptides. |
| Light exposure | Amber vial or foil wrap | Limits photodegradation of tryptophan, tyrosine, and phenylalanine residues. |
| Reconstitution solvent | Water, buffer, or water-miscible organic solvent | Choice depends on sequence charge and hydrophobicity; use highest available purity. |
| Aliquot size | Single-use portions | Minimizes warming and cooling cycles and cross-contamination between uses. |
Moisture, oxygen, and light also affect peptide integrity. Lyophilized powders absorb water from the air, which can enable hydrolysis and conformational changes. Oxygen promotes oxidation of sensitive residues, so storage under inert gas or in sealed vials is common. Light exposure can cause photodegradation, particularly for peptides containing aromatic amino acids. Buffer choice and pH influence charge state and solubility; extremes of pH accelerate deamidation and hydrolysis. Adding stabilizers such as sugars or polyols can protect the peptide during freezing and drying. Optimal conditions are determined empirically for each peptide.
Peptides are short chains of amino acids that can undergo both chemical and physical degradation. Chemical pathways include hydrolysis of peptide bonds, oxidation of methionine or cysteine residues, deamidation of asparagine or glutamine, and isomerization of aspartate. Physical instability leads to aggregation, precipitation, or adsorption to surfaces. The rate of these processes depends on the peptide sequence, the formulation, and the storage environment. Because each peptide has a unique composition, no single storage condition applies to all peptides. Stability studies are therefore conducted to define suitable conditions for each specific molecule.
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.
== Veterinary uses == Thiamazole is commonly used in cats to treat hyperthyroidism. Despite 20% of cats treated with thiamazole testing positive for antinuclear antibody lupus erythematosus and immune-mediated haemolytic anemia, neither condition is associated with thiamazole in cats. Hepatic toxicity also occurs in a small but notable amount of cats treated with thiamazole. In July 2024, the US Food and Drug Administration (FDA) approved Felanorm, the first generic methimazole oral solution for the treatment of hyperthyroidism in cats. Felanorm contains the same active ingredient (methimazole) as the approved brand name drug product, Felimazole Coated Tablets, which were first approved in May 2009. In addition, the FDA determined that Felanorm contains no inactive ingredients that may significantly affect the bioavailability of the active ingredient. Felanorm is sponsored by Norbrook Laboratories based in the United Kingdom.
The Rockefeller Foundation continued funding German eugenics research even after it was clear that it was being used to rationalize discrimination against Jewish people and other groups, after the Nuremberg laws in 1935. In 1936, Rockefeller fulfilled pledges of $655,000 to Kaiser Wilhelm Institute, even though several distinguished Jewish scientists had been dropped from the institute at the time. The Rockefeller Foundation did not alert the world about the racist implications of Nazi ideology, but furthered and funded eugenic research through the 1930s. Even into the 1950s, Rockefeller continued to provide some funding for research borne out of German eugenics. The foundation also funded the relocation of scholars threatened by the Nazis to America in the 1930s, known as the Refugee Scholar Program and the Emergency Committee in Aid of Displaced Foreign Scholars. Some of the notable figures relocated or saved, among a total of 303 scholars, were Thomas Mann, Claude Lévi-Strauss and Leó Szilárd. The foundation helped The New School provide a haven for scholars threatened by the Nazis.
===== Mechanism of a single selectin binding ===== A single PSGL-1 and selectin binding is similar to conventional protein binding when the force is kept constant, with a dissociation constant. As the force exerted starts to increase, the dissociation constant decreases, causing binding to become stronger. As the force reach a threshold level of 11 pN, the dissociation constant starts to increase again, weakening the bond, causing the bond to exhibit a slip bond property.
In zero field NMR all magnetic fields are shielded such that magnetic fields below 1 nT (nanotesla) are achieved and the nuclear precession frequencies of all nuclei are close to zero and indistinguishable. Under those circumstances the observed spectra are no-longer dictated by chemical shifts but primarily by J-coupling interactions which are independent of the external magnetic field. Since inductive detection schemes are not sensitive at very low frequencies, on the order of the J-couplings (typically between 0 and 1000 Hz), alternative detection schemes are used. Specifically, sensitive magnetometers turn out to be good detectors for zero field NMR. A zero magnetic field environment does not provide any polarization hence it is the combination of zero field NMR with hyperpolarization schemes that makes zero field NMR desirable.
Sources: en.wikipedia.org
Boletus edulis fruit bodies contain diverse phytochemicals, including 500 mg of ergosterol per 100 g of dried mushroom, and ergothioneine. The fruit bodies contain numerous polyphenols, especially a high content of rosmarinic acid, and organic acids (such as oxalic, citric, malic, succinic and fumaric acids), and alkaloids.
In addition to antioxidant actions, ascorbate anion, with its targeted accumulation in the brain and adrenal glands, also modulates the activity of dopamineergic, serotoninergic, GABA-ergic, glutamateergic neurotransmission and might be useful in the treatment of schizophrenia, major depressive disorder, bipolar disorder.
==== Dopamine ==== In certain brain regions, amphetamine increases the concentration of dopamine in the synaptic cleft by modulating DAT through several overlapping processes. Amphetamine can enter the presynaptic neuron either through DAT or, to a lesser extent, by diffusing across the neuronal membrane directly. As a consequence of DAT uptake, amphetamine produces competitive reuptake inhibition at the transporter. Upon entering the presynaptic neuron, amphetamine provokes the release of Ca2+ from endoplasmic reticulum stores, an effect that raises intracellular calcium to levels sufficient for downstream kinase-dependent signalling. In parallel, amphetamine also increases intracellular cAMPTooltip cyclic adenosine monophosphate, which activates protein kinase A (PKA) and protein kinase C (PKC), whilst elevated intracellular Ca2+ activates PKC alone. Phosphorylation of DAT by either kinase induces transporter internalization (non-competitive reuptake inhibition), but PKC-mediated phosphorylation alone induces the reversal of dopamine transport through DAT (i.e., dopamine efflux). TAAR1 has been identified as a biomolecular target of amphetamine that initiates some of amphetamine's kinase-dependent signaling cascades. When TAAR1 signals via Gs-coupled receptors, intracellular cAMP increases through adenylyl cyclase activation and activates PKA and PKC, in turn phosphorylating DAT.
Samples are dissolved or suspended in a "cocktail" containing a solvent (historically aromatic organics such as xylene or toluene, but more recently less hazardous solvents are used), typically some form of a surfactant, and "fluors" or scintillators which produce the light measured by the detector. Scintillators can be divided into primary and secondary phosphors, differing in their luminescence properties. Beta particles emitted from the isotopic sample transfer energy to the solvent molecules: the π cloud of the aromatic ring absorbs the energy of the emitted particle. The energized solvent molecules typically transfer the captured energy back and forth with other solvent molecules until the energy is finally transferred to a primary scintillator. The primary phosphor will emit photons following absorption of the transferred energy. Because that light emission may be at a wavelength that does not allow efficient detection, many cocktails contain secondary phosphors that absorb the fluorescence energy of the primary phosphor and re-emit at a longer wavelength. Two widely used primary and secondary fluors are 2,5-diphenyloxazole (PPO) with an emission maximum of 380 nm and 1,4-bis-2-(5-phenyloxazolyl)benzene (POPOP) with an emission maximum of 420 nm. The radioactive samples and cocktail are placed in small transparent or translucent (often glass or plastic) vials that are loaded into an instrument known as a liquid scintillation counter. Newer machines may use 96-well plates with individual filters in each well.
These are commonly used in shipping, because they sublime relatively slowly due to a low ratio of surface area to volume. Pellets are around 1 cm (0.4 in) in diameter and can be bagged easily. This form is suited to small scale use, for example at grocery stores and laboratories where it is stored in a thickly insulated chest. Density of pellets is 60–70% of the density of blocks. Dry ice is also produced as a byproduct of cryogenic air separation, an industry primarily concerned with manufacturing extremely cold liquids such as liquid nitrogen and liquid oxygen. In this process, carbon dioxide liquefies or freezes at a far higher temperature compared to that needed to liquefy nitrogen and oxygen. The carbon dioxide must be removed during the process to prevent dry ice from fouling the equipment, and once separated can be processed into commercial dry ice in a manner similar to that described above.
Sources: en.wikipedia.org
Dividing a stock into single-use portions usually reduces multiple thawing and refreezing events and lowers contamination risk. It also allows a needed amount to be removed without warming the entire supply.
Peptides can adsorb to some plastics and glass, especially at low concentrations, which reduces the measured amount in solution. Low-binding polypropylene tubes limit this loss and improve reproducibility.
Thawing on ice or in a cold water bath is generally preferred over rapid heating, which can accelerate degradation. Once thawed, the aliquot should be kept cold and used promptly rather than refrozen.
Multiple freezing and thawing events can cause aggregation, precipitation, or loss of soluble peptide. Dividing a solution into single-use aliquots before freezing reduces this risk. If multiple cycles are unavoidable, stability should be checked after thawing.