This is a working overview of freeze-thaw cycle, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-05-10. Anything still debated is marked as such rather than presented as settled.
Analytical identification and purity assessment often use high-performance liquid chromatography with ultraviolet detection or mass spectrometry. Liquid chromatography–tandem mass spectrometry is used to detect and quantify SR9009 in biological matrices, including urine and blood, for anti-doping or pharmacokinetic studies. Nuclear magnetic resonance spectroscopy can confirm molecular structure. Stability depends on form and storage: the solid is generally more stable than solutions, and repeated freeze–thaw cycles may degrade samples. Purity is typically reported as a percentage from a certificate of analysis.
Regulatory treatment of SR9009 varies by country and context. It is not approved as a therapeutic drug by agencies such as the United States Food and Drug Administration or the European Medicines Agency. Sports authorities list it as a prohibited substance; the World Anti-Doping Agency classifies it among hormone and metabolic modulators. Legal status for personal possession or sale differs across jurisdictions, and some countries may restrict it under analog or research chemical laws. Buyers who seek verified material often rely on independent laboratory testing because online product labels may not match contents.
Detection of SR9009 in biological samples usually relies on liquid chromatography coupled to tandem mass spectrometry. This approach separates the compound from matrix components and identifies it by mass transitions. Because SR9009 can undergo metabolism, laboratories often look for both parent drug and specific metabolites. Sample preparation may involve protein precipitation or solid-phase extraction. Method validation examines sensitivity, carryover, and interference from related substances, and reference standards are required for accurate calibration.
Storage recommendations for SR9009 reference material typically specify a freezer at -20 °C or lower, with protection from moisture and light. Repeated freeze-thaw cycles can degrade small molecules and introduce variability. Stock solutions in dimethyl sulfoxide are often aliquoted to avoid repeated handling. Stability studies may examine degradation under heat, humidity, and light exposure. The compound's thiophene and nitro groups can participate in reactions that alter analytical signals over time, so such changes affect quantitative results.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Common supplier description |
| Solubility | Soluble in DMSO and ethanol | Low solubility in water |
| Typical storage | −20 °C, desiccated, dark | For research samples |
| Analytical method | LC-MS/MS | Used for detection and quantification |
| Regulatory status | Prohibited in sport | WADA metabolic modulator class |
Mechanistically, SR9009 binds the ligand-binding domain of REV-ERBα/β and enhances recruitment of corepressor complexes. This represses target genes rather than activating them. Because REV-ERB proteins normally compete with ROR proteins at shared response elements, the net effect depends on tissue and timing. Researchers use SR9009 to probe how nuclear receptor signaling links the clock to metabolism, inflammation, and muscle biology. Findings are largely preclinical, and the precise contribution of each receptor subtype remains under study.
SR9009 is frequently discussed in fitness and research-chemical contexts, yet it has no approved medical indication. Regulatory agencies have not authorized it for human use, and it is not a standard prescription drug. Some sports organizations list it as a prohibited substance because of its potential performance-enhancing properties. Published human data are sparse, so claims about its effects in people often rely on animal models or anecdotal reports. Quality and identity of online materials can vary widely.
SR9009 is a synthetic small molecule studied as a REV-ERB agonist. REV-ERBα and REV-ERBβ are nuclear receptors that help regulate circadian rhythms and metabolic gene expression. The compound was identified in academic screening efforts to find synthetic ligands for these receptors. In cell and animal studies, SR9009 alters transcription of genes involved in lipid and glucose metabolism, and it can shift circadian behavior. It is not an approved therapeutic agent.
1 May A preprint indicates Omicron subvariants BA.4 and BA.5 can cause a large share of reinfections, beyond the increase of reinfections caused by the Omicron lineage, even for people who were infected by Omicron BA.1 due to increases in immune evasion, especially for the unvaccinated. On 18 May, a study shows that immunity from an Omicron infection for unvaccinated and previously uninfected is weak "against non-Omicron variants". A preprint suggests that SARS-CoV-2 antibodies in or transmitted through the air are an unrecognized mechanism by which, transferred, passive immune protection occurs. However, if not sustained, protection from passive herd immunity is thought to wane over the course of weeks to months. 4 May NASA reports the sonification (converting astronomical data associated with pressure waves into sound) of the black hole at the center of the Perseus galaxy cluster. A single master gene that programs ear hair cells into either outer or inner ones is discovered, overcoming a major hurdle that had prevented the development of these cells to reverse hearing loss. A study complements life-cycle assessment studies, showing substantial deforestation reduction (56%) and climate change mitigation if only 20% of per-capita beef was replaced by microbial protein by 2050. A study suggests, using an epidemiological model, that by reducing the transferred viral load, face masks against COVID19 may be beneficial for variolation whereby "smaller infectious doses tend to yield milder infections, yet ultimately induce similar levels of immunity".
== Science and technology == Rational polynomial coefficient Reactive Plastic Curtain, a carbon-dioxide-absorbing device used in some rebreather breathing sets Regional Playback Control, a regional lockout technology for DVDs Remote procedure call, an inter-process communication technique in networked computing Open Network Computing Remote Procedure Call, IETF RPC, a.k.a. "Sun RPC" DCE/RPC, for Distributed Computing Environment by Open Software Foundation JSON-RPC, a "JSON encoded" variant XML-RPC, an "XML encoded" variant Resistive plate chamber, a simple type of particle detector used in experimental particle physics Reversed-phase chromatography, a chemistry technique Acorn Risc PC Rocket Pod Container, the interchangeable containers used to transport and launch missiles for use with the M270 Multiple Launch Rocket System Rotary phase converter, an electrical machine that converts power from one polyphase system (including frequency) to another, converting through rotary motion.
== Evolution == It is believed that components of the citric acid cycle were derived from anaerobic bacteria, and that the TCA cycle itself may have evolved more than once. It may even predate biosis: the substrates appear to undergo most of the reactions spontaneously in the presence of persulfate radicals. Alternatively, prebiotic synthesis of the citric acid cycle could have beginnings in the interstellar medium. Theoretically, several alternatives to the TCA cycle exist; however, the TCA cycle appears to be the most efficient. If several TCA alternatives had evolved independently, they all appear to have converged to the TCA cycle.
Sources: en.wikipedia.org
=== For La Niña === 2000 Mozambique flood 2010 Pakistan floods 2010–2011 Queensland floods 2010–2012 La Niña event 2010–2011 Southern Africa floods 2010–2013 Southern United States and Mexico drought 2011 East Africa drought 2020 Atlantic hurricane season 2021 eastern Australia floods 2022 Suriname floods 2023 Auckland Anniversary Weekend floods 2020–2023 La Niña event
=== Eye irritation === Freshly cut onions can produce a stinging sensation in the eyes of people nearby and often uncontrollable tears. This is caused by the release of a volatile liquid, syn-propanethial-S-oxide and its aerosol, which stimulates nerves in the eye. This gas is produced by a chain of reactions which serve as a defence mechanism: chopping an onion causes damage to cells which releases enzymes called alliinases. These break down amino acid sulfoxides and generate sulfenic acids. A specific sulfenic acid, 1-propenesulfenic acid, is rapidly acted on by a second enzyme, the lacrimatory factor synthase (LFS), producing the syn-propanethial-S-oxide. This gas diffuses through the air and soon reaches the eyes, where it activates sensory neurons. Lacrimal glands produce tears to dilute and flush out the irritant. Eye irritation can be minimised by cutting onions under running water or submerged in a basin of water. Leaving the root end intact also reduces irritation as the onion base has a higher concentration of sulphur compounds than the rest of the bulb.
=== Physical properties === A promethium atom has 61 electrons, arranged in the configuration [Xe] 4f5 6s2. The seven 4f and 6s electrons are valence electrons. In forming compounds, the atom loses its two outermost electrons and one 4f-electron, which belongs to an open subshell. The element's atomic radius is the second largest among all the lanthanides but is only slightly greater than those of the neighboring elements. It is the most notable exception to the general trend of the contraction of lanthanide atoms with the increase of their atomic numbers (lanthanide contraction). Many properties of promethium rely on its position among lanthanides and are intermediate between those of neodymium and samarium. For example, the melting point, the first three ionization energies, and the hydration energy are greater than those of neodymium and lower than those of samarium; similarly, the estimate for the boiling point, ionic (Pm3+) radius, and standard heat of formation of monatomic gas are greater than those of samarium and less than those of neodymium. Promethium has a double hexagonal close packed (dhcp) structure and a hardness of 63 kg/mm2. This low-temperature alpha form converts into a beta, body-centered cubic (bcc) phase upon heating to 890 °C.
== Comparisons with other drugs for type 2 diabetes == A study funded by Novo Nordisk, the U.S. distributor for Repaglinide, compared their product with Nateglinide in "A randomized, parallel-group, open-label, multicenter 16-week clinical trial". They concluded that the two were similar, but "repaglinide monotherapy was significantly more effective than nateglinide monotherapy in reducing HbA1c and FPG values after 16 weeks of therapy."
Sources: en.wikipedia.org
Vanillin is most prominent as the principal flavor and aroma compound in vanilla. Cured vanilla pods contain about 2% by dry weight vanillin. Relatively pure vanillin may be visible as a white dust or "frost" on the exteriors of cured pods of high quality. It is also found in Leptotes bicolor, a species of orchid native to Paraguay and southern Brazil, and the Southern Chinese red pine. At lower concentrations, vanillin contributes to the flavor and aroma profiles of foodstuffs as diverse as olive oil, butter, raspberry, and lychee fruits. Aging in oak barrels imparts vanillin to some wines, vinegar, and spirits. In other foods, heat treatment generates vanillin from other compounds. In this way, vanillin contributes to the flavor and aroma of coffee, maple syrup, and whole-grain products, including corn tortillas and oatmeal.
=== Biosynthesis === Estradiol, like other steroid hormones, is derived from cholesterol. After side chain cleavage and using the Δ5 or the Δ4- pathway, androstenedione is the key intermediary. A portion of the androstenedione is converted to testosterone, which in turn undergoes conversion to estradiol by aromatase. In an alternative pathway, androstenedione is aromatized to estrone, which is subsequently converted to estradiol via 17β-hydroxysteroid dehydrogenase (17β-HSD). During the reproductive years, most estradiol in women is produced by the granulosa cells of the ovaries by the aromatization of androstenedione (produced in the theca folliculi cells) to estrone, followed by conversion of estrone to estradiol by 17β-HSD. Smaller amounts of estradiol are also produced by the adrenal cortex, and, in men, by the testes. Estradiol is not produced in the gonads only; in particular, fat cells produce active precursors to estradiol, and will continue to do so even after menopause. Estradiol is also produced in the brain and in arterial walls. In men, approximately 15 to 25% of circulating estradiol is produced in the testicles. The rest is synthesized via peripheral aromatization of testosterone into estradiol and of androstenedione into estrone (which is then transformed into estradiol via peripheral 17β-HSD). This peripheral aromatization occurs predominantly in adipose tissue, but also occurs in other tissues such as bone, liver, and the brain. Approximately 40 to 50 μg of estradiol is produced per day in men.
Aggregated proteins are associated with prion-related illnesses such as Creutzfeldt–Jakob disease, bovine spongiform encephalopathy (mad cow disease), amyloid-related illnesses such as Alzheimer's disease and familial amyloid cardiomyopathy or polyneuropathy, as well as intracellular aggregation diseases such as Huntington's and Parkinson's disease. These age onset degenerative diseases are associated with the aggregation of misfolded proteins into insoluble, extracellular aggregates and/or intracellular inclusions including cross-β amyloid fibrils. It is not completely clear whether the aggregates are the cause or merely a reflection of the loss of protein homeostasis, the balance between synthesis, folding, aggregation and protein turnover. Recently the European Medicines Agency approved the use of Tafamidis or Vyndaqel (a kinetic stabilizer of tetrameric transthyretin) for the treatment of transthyretin amyloid diseases. This suggests that the process of amyloid fibril formation (and not the fibrils themselves) causes the degeneration of post-mitotic tissue in human amyloid diseases. Misfolding and excessive degradation instead of folding and function leads to a number of proteinopathies, diseases such as antitrypsin-associated emphysema, cystic fibrosis and the lysosomal storage diseases, where loss of function is the origin of the disorder. While protein replacement therapy has historically been used to correct the latter disorders, an emerging approach is to use pharmaceutical chaperones to fold mutated proteins to render them functional.
Compounds eluting off the column are carried into a hydrogen fueled flame which excites specific elements in the molecules, and the excited elements (P,S, Halogens, Some Metals) emit light of specific characteristic wavelengths. The emitted light is filtered and detected by a photomultiplier tube. In particular, phosphorus emission is around 510–536 nm and sulfur emission is at 394 nm. With an atomic emission detector (AED), a sample eluting from a column enters a chamber which is energized by microwaves that induce a plasma. The plasma causes the analyte sample to decompose and certain elements generate an atomic emission spectra. The atomic emission spectra is diffracted by a diffraction grating and detected by a series of photomultiplier tubes or photo diodes. Electron capture detector (ECD) uses a radioactive beta particle (electron) source to measure the degree of electron capture. ECD are used for the detection of molecules containing electronegative / withdrawing elements and functional groups like halogens, carbonyl, nitriles, nitro groups, and organometalics. In this type of detector either nitrogen or 5% methane in argon is used as the mobile phase carrier gas. The carrier gas passes between two electrodes placed at the end of the column, and adjacent to the cathode (negative electrode) resides a radioactive foil such as 63Ni. The radioactive foil emits a beta particle (electron) which collides with and ionizes the carrier gas to generate more ions resulting in a current.
==== Prostate cancer ==== The Bombesin peptide has been shown to be overexpressed in BB2 receptors in prostate cancer. CB-TE2A a stable chelation system for 64Cu was incorporated with Bombesin analogs for in vitro and in vivo studies of prostate cancer. PET-CT imagining studies showed that it underwent uptake into prostate tumor xenografts selectively with decreased uptake into non target tissues. Other preclinical studies have shown that by targeting the gastrin-releasing peptide receptor pancreatic and breast cancer can also be detected.
Sources: en.wikipedia.org
Legality depends on the country and the intended use. In many places it is sold as a research chemical, but sports and medicine regulations restrict it.
Detection commonly uses liquid chromatography–tandem mass spectrometry. This method can identify the compound in urine or blood at low concentrations.
Typical guidance is −20 °C, dry, and protected from light. Solutions should be aliquoted and limited freeze–thaw cycles should be used.
Liquid chromatography-tandem mass spectrometry is a common approach. It can detect the parent compound and its metabolites in biological matrices.