A practical reference on Oxidation: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-03-27 and is reviewed periodically as new material appears.
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.
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.
| 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. |
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.
Light, oxygen, and pH influence peptide integrity through specific side-chain reactions. Methionine and cysteine residues are susceptible to oxidation, and tryptophan can degrade under strong light. Inert gas overlays and amber glass or opaque containers reduce these risks. pH affects charge, solubility, and the rate of deamidation or aggregation; a value that minimizes one pathway may increase another. The optimal pH and buffer for a given peptide are often determined experimentally, and open questions remain about predicting stability from sequence alone.
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.
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.
The only drug currently approved for stroke treatment is tPA, which can cause dangerous brain bleeding. In 2005, Griffin et al proposed using Activated Protein C in conjunction with tPA to protect the brain from tPA’s harmful side-effects. APC activates protease-activated receptor 1 (PAR-1), which plays a role in the interaction of coagulation and inflammation. The 3K3A-APC was designed to have more activity at protease-activated receptor 1 (PAR-1) and less anticoagulative effect than activated protein C. The phase 2 trial, RHAPSODY, was performed in the lab of Berislav Zlokovic, the scientific founder of ZZ Biotech, to determine safety and tolerability of the drug. A phase 3 $30 million trial, RHAPSODY-2, was planned to determine safety and efficacy for treatment of ischemic stroke. However, on November 16, 2023, the National Institutes of Health (NIH) paused the start of the human trial of 3K3A-APC after an investigation by Science Magazine.
ASBMB Award for Exemplary Contributions to Education ASBMB Leadership Awards ASBMB–Merck Award ASBMB Young Investigator Award Avanti Award in Lipids Bert and Natalie Vallee Award in Biomedical Science DeLano Award for Computational Biosciences Earl and Thressa Stadtman Distinguished Scientist Award Earl and Thressa Stadtman Young Scholar Award Herbert Tabor Research Award Mildred Cohn Award in Biological Chemistry - The Mildred Cohn Award in Biological Chemistry was established in 2013 to honor the scientific achievements of Mildred Cohn. Cohn was the first female president of the society, in 1978. The award of $5,000 is presented annually to a scientist who has made substantial advances in understanding biological chemistry using innovative physical approaches. The recipient is expected to deliver the Mildred Cohn Award lecture at the annual meeting. Ruth Kirschstein Diversity in Science Award The Alice and C. C. Wang Award in Molecular Parasitology Walter A. Shaw Young Investigator Award in Lipid Research William C. Rose Award
Binding curves describe the binding behavior of ligand to a protein. Curves can be characterized by their shape, sigmoidal or hyperbolic, which reflect whether or not the protein exhibits cooperative or noncooperative binding behavior respectively. Typically, the x-axis describes the concentration of ligand and the y-axis describes the fractional saturation of ligands bound to all available binding sites. The Michaelis Menten equation is usually used when determining the shape of the curve. The Michaelis Menten equation is derived based on steady-state conditions and accounts for the enzyme reactions taking place in a solution. However, when the reaction takes place while the enzyme is bound to a substrate, the kinetics play out differently. Modeling with binding curves are useful when evaluating the binding affinities of oxygen to hemoglobin and myoglobin in the blood. Hemoglobin, which has four heme groups, exhibits cooperative binding. This means that the binding of oxygen to a heme group on hemoglobin induces a favorable conformation change that allows for increased binding favorability of oxygen for the next heme groups. In these circumstances, the binding curve of hemoglobin will be sigmoidal due to its increased binding favorability for oxygen. Since myoglobin has only one heme group, it exhibits noncooperative binding which is hyperbolic on a binding curve.
S-adenosyl-L-methionine = 1-aminocyclopropane-1-carboxylate + S-methyl-5′-thioadenosine Like other PLP dependent enzymes, it catalyzes the reaction through a quinonoid zwitterion intermediate and uses cofactor pyridoxal phosphate (PLP, the active form of vitamin B6) for stabilization. This enzyme belongs to the family of lyases, specifically carbon-sulfur lyases. The systematic name of this enzyme class is S-adenosyl-L-methionine S-methyl-5′-thioadenosine-lyase (1-aminocyclopropane-1-carboxylate-forming). Other names in common use include 1-aminocyclopropanecarboxylate synthase, 1-aminocyclopropane-1-carboxylic acid synthase, 1-aminocyclopropane-1-carboxylate synthetase, aminocyclopropanecarboxylic acid synthase, aminocyclopropanecarboxylate synthase, ACC synthase, and S-adenosyl-L-methionine methylthioadenosine-lyase. This enzyme participates in propanoate metabolism. It employs one cofactor, pyridoxal phosphate.
As a practical matter, when platinum group metals are purified through dissolution in aqua regia, gold (commonly associated with PGMs) is precipitated by treatment with iron(II) chloride. Platinum in the filtrate, as hexachloroplatinate(IV), is converted to ammonium hexachloroplatinate by the addition of ammonium chloride. This ammonium salt is extremely insoluble, and it can be filtered off. Ignition (strong heating) converts it to platinum metal: 3 [NH4]2[PtCl6] → 3 Pt + 2 N2 + 2 [NH4]Cl + 16 HCl Unprecipitated hexachloroplatinate(IV) is reduced with elemental zinc, and a similar method is suitable for small scale recovery of platinum from laboratory residues. Aqua regia reacts with tin to form tin(IV) chloride, containing tin in its highest oxidation state: 4 HCl + 2 HNO3 + Sn → SnCl4 + NO2 + NO + 3 H2O Aqua regia can react with iron pyrite to form iron(III) chloride: FeS2 + 5 HNO3 + 3 HCl → FeCl3 + 2 H2SO4 + 5 NO + 2 H2O
Sources: en.wikipedia.org
PABA and its salts are used in nutritional epidemiological studies to assess the completeness of 24-hour urine collection for the determination of urinary sodium, potassium, or nitrogen levels. The potassium salt (potassium paraaminobenzoate, "aminobenzoate potassium") is used as a drug against fibrotic skin disorders, such as Peyronie's disease, under the brand name Potaba. There is a lack of strong evidence. It is believed to work by inhibiting fibroblast glycosaminoglycan secretion and stabilizing monoamine oxidase A activity. PABA is also occasionally used in pill form by sufferers of irritable bowel syndrome to treat its associated gastrointestinal symptoms. PABA derivatives have also been proposed to function as acetylcholinesterase inhibitors in diseases that cause deficient cholinergic systems, such as Alzheimer's disease.
Membrane blebbing: The cell membrane shows irregular buds known as blebs. Initially these are smaller surface blebs. Later these can grow into larger so-called dynamic membrane blebs. An important regulator of apoptotic cell membrane blebbing is ROCK1 (rho associated coiled-coil-containing protein kinase 1). Formation of membrane protrusions: Some cell types, under specific conditions, may develop different types of long, thin extensions of the cell membrane called membrane protrusions. Three types have been described: microtubule spikes, apoptopodia (feet of death), and beaded apoptopodia (the latter having a beads-on-a-string appearance). Pannexin 1 is an important component of membrane channels involved in the formation of apoptopodia and beaded apoptopodia. Fragmentation: The cell breaks apart into multiple vesicles called apoptotic bodies, which undergo phagocytosis. The plasma membrane protrusions may help bring apoptotic bodies closer to phagocytes.
The mechanism of transport for importers supports the alternating-access model. The resting state of importers is inward-facing, where the nucleotide binding domain (NBD) dimer interface is held open by the TMDs and facing outward but occluded from the cytoplasm. Upon docking of the closed, substrate-loaded binding protein towards the periplasmic side of the transmembrane domains, ATP binds and the NBD dimer closes. This switches the resting state of transporter into an outward-facing conformation, in which the TMDs have reoriented to receive substrate from the binding protein. After hydrolysis of ATP, the NBD dimer opens and substrate is released into the cytoplasm. Release of ADP and Pi reverts the transporter into its resting state. The only inconsistency of this mechanism to the ATP-switch model is that the conformation in its resting, nucleotide-free state is different from the expected outward-facing conformation. Although that is the case, the key point is that the NBD does not dimerize unless ATP and binding protein is bound to the transporter.
ProIAPP consists of 67 amino acids, which follow a 22 amino acid signal peptide which is rapidly cleaved after translation of the 89 amino acid coding sequence. The human sequence (from N-terminus to C-terminus) is: (MGILKLQVFLIVLSVALNHLKA) TPIESHQVEKR^ KCNTATCATQRLANFLVHSSNNFGAILSSTNVGSNTYG^ KR^ NAVEVLKREPLNYLPL. The signal peptide is removed during translation of the protein and transport into the endoplasmic reticulum. Once inside the endoplasmic reticulum, a disulfide bond is formed between cysteine residues numbers 2 and 7. Later in the secretory pathway, the precursor undergoes additional proteolysis and posttranslational modification (indicated by ^). 11 amino acids are removed from the N-terminus by the enzyme proprotein convertase 2 (PC2) while 16 are removed from the C-terminus of the proIAPP molecule by proprotein convertase 1/3 (PC1/3). At the C-terminus Carboxypeptidase E then removes the terminal lysine and arginine residues. The terminal glycine amino acid that results from this cleavage allows the enzyme peptidylglycine alpha-amidating monooxygenase (PAM) to convert the terminal glycine to an amine group (releasing glycolate). After this step, the transformation from the precursor protein proIAPP to the biologically active IAPP (amylin) is complete (IAPP sequence: KCNTATCATQRLANFLVHSSNNFGAILSSTNVGSNTY-NH2).
Sources: en.wikipedia.org
Peptide aptamers consist of one or more peptide loops of variable sequence displayed by a protein scaffold. Derivatives known as tadpoles, in which peptide aptamer "heads" are covalently linked to unique sequence double-stranded DNA "tails", allow quantification of scarce target molecules in mixtures by PCR (using, for example, the quantitative real-time polymerase chain reaction) of their DNA tails. The peptides that form the aptamer variable regions are synthesized as part of the same polypeptide chain as the scaffold and are constrained at their N and C termini by linkage to it. This double structural constraint decreases the diversity of the 3D structures that the variable regions can adopt, and this reduction in structural diversity lowers the entropic cost of molecular binding when interaction with the target causes the variable regions to adopt a uniform structure.
Vaginal gels are forms of medication that are water-based. They are applied using a plastic applicator to distribute the gel throughout the length of the vaginal canal. These gels tend to have release kinetics that are fast acting, which makes them useful for treatment of irritations. Antibiotics are often distributed in the form of a gel for treatment of common infections, including sexually transmitted infections (STIs). The gels also have the benefit of being lubricating, which grants additional relief to symptoms of dryness and itching that is common with vaginal infections. Gels that are in the form of liposomal structure have been shown to retain substances for extensive periods of time, making them useful for slow release of drugs administered through the cervical drug delivery route
The first β-sheet structure was proposed by William Astbury in the 1930s. He proposed the idea of hydrogen bonding between the peptide bonds of parallel or antiparallel extended β-strands. However, Astbury did not have the necessary data on the bond geometry of the amino acids in order to build accurate models, especially since he did not then know that the peptide bond was planar. A refined version was proposed by Linus Pauling and Robert Corey in 1951. Their model incorporated the planarity of the peptide bond which they previously explained as resulting from keto-enol tautomerization.
All the proteolytic activity of the asparagine peptide lyases is only self-cleavages, then no further peptidase activity occurs. The main residue of the active site is the asparagine and there are other residues involved in the catalytic mechanism, which are different between the different families of asparagine peptide lyases. The cleavage mechanism consists in the cyclization of the asparagine, assisted by other active site residues. In certain conditions, the asparagine cyclic structure nucleophilically attacks its C-terminal peptide bond to the main chain forming a new bond to create a stable succinimide, cleaving itself from the main chain and consequently releasing the two halves of the product. No inhibitors are known.
Two species of AAV were recognised by the International Committee on Taxonomy of Viruses in 2013: adeno-associated dependoparvovirus A (formerly AAV-1, −2, −3 and −4) and adeno-associated dependoparvovirus B (formerly AAV-5). Until the 1990s, virtually all AAV biology was studied using AAV serotype 2. However, AAV is highly prevalent in humans and other primates and several serotypes have been isolated from various tissue samples. Serotypes 2, 3, 5, and 6 were discovered in human cells, AAV serotypes 1, 4, and 7–11 in nonhuman primate samples. As of 2006 there have been 11 AAV serotypes described, the 11th in 2004. AAV capsid proteins contain 12 hypervariable surface regions, with most variability occurring in the threefold proximal peaks, but the parvovirus genome in general presents highly conserved replication and structural genes across serotypes. All of the known serotypes can infect cells from multiple diverse tissue types.
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.
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.