A practical reference on freeze-thaw: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-08-01. 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.
SR9009 is a synthetic small molecule studied as an agonist of the nuclear receptors REV-ERBα and REV-ERBβ. These receptors help regulate circadian rhythms, lipid metabolism, and inflammatory gene expression. In cell and animal experiments, SR9009 alters transcription of clock-controlled genes and metabolic pathways. The compound is not a hormone and does not resemble classical steroid structures. Its activity depends on binding to the ligand-binding domain of REV-ERB, where it can modify corepressor recruitment.
Research interest in SR9009 grew from studies of circadian biology and metabolic disease. Preclinical reports describe effects on exercise capacity, muscle metabolism, and blood lipid levels in rodents, but these findings come from controlled laboratory settings. The compound has low oral bioavailability in animals, which limits systemic exposure after swallowing. Investigators often use injected routes in experiments to achieve measurable plasma concentrations. Human clinical data are sparse, no approved therapeutic product exists, and whether animal effects translate to humans remains an open question.
Regulatory and sporting contexts treat SR9009 as a prohibited substance in many elite competitions. Its presence on banned lists reflects concerns about performance enhancement and unknown long-term safety. Analytical chemists have developed methods to detect the parent compound and its metabolites in urine and blood. Literature discussions distinguish between in vitro potency, animal pharmacology, and anecdotal human reports. The latter are difficult to verify because products sold online may lack purity or contain different compounds.
| 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 |
SR9009 is a synthetic small molecule developed as a REV-ERB agonist. It binds to REV-ERBα and REV-ERBβ, nuclear receptors that help regulate circadian rhythms and metabolic gene expression. In cell and animal studies, the compound alters lipid and glucose handling and influences skeletal muscle oxidative capacity. Its exact effects in humans remain largely uncharacterized because controlled clinical trials have not been reported. The molecule is frequently described in preclinical literature as a metabolic modulator.
Research interest in SR9009 grew from studies showing improved running endurance in mice after short treatment periods. Those experiments linked the compound to increased mitochondrial content and fatty acid oxidation in muscle, but the findings come from animal models and specific dosing schedules. Independent replication has been limited, and the pathways connecting REV-ERB activation to exercise performance are still being mapped. Whether similar responses occur in humans is an open question.
SR9009 is often grouped with compounds studied for circadian and metabolic regulation rather than with classical anabolic steroids. Its interactions with nuclear receptors differ from those of androgen receptor ligands, and its proposed mechanisms involve transcriptional control rather than direct hormone signaling. Some sources classify it as a metabolic modulator because of observed effects on energy utilization. The distinction matters for regulation and for interpreting research results across different compound classes.
SR9009 is generally described as poorly soluble in water and more soluble in organic solvents such as dimethyl sulfoxide and ethanol. Stock solutions are commonly prepared in an organic solvent before dilution into an aqueous buffer or vehicle. Precipitation can occur if the organic fraction is reduced too quickly or if the final concentration exceeds the compound's solubility limit. Sonication or gentle warming may aid dissolution in some protocols, but excessive heat can promote degradation. Container material and pH can also influence observed solubility.
For long-term storage, SR9009 is typically kept as a solid at low temperature, protected from moisture and light. Desiccated conditions limit hydrolysis, while opaque containers reduce photochemical breakdown. Solutions are less stable than solids and are often stored frozen in aliquots to avoid repeated freeze-thaw cycles. Stability data are not standardized across all suppliers, so users should rely on certificate-of-analysis information when available. Degradation may appear as color change, precipitate, or decreased chromatographic purity.
== Mass spectrometry techniques == Fragmentation can occur in the ion source (in-source fragmentation) where it has been used with electron ionization to help identify molecules and, recently (2020), with electrospray ionization it has been shown to provide the same benefit in facilitating molecular identification. Prior to these experiments, electrospray ionization in-source fragmentation was generally considered an undesired effect however, electrospray ionization using Enhanced In-Source Fragmentation/Annotation (EISA) has been shown to promote in-source fragmentation that creates fragment ions that are consistent with tandem mass spectrometers. Tandem mass spectrometry-generated fragmentation is typically made in the collision zone (post-source fragmentation) of a tandem mass spectrometer. EISA and collision-induced dissociation (CID) among other physical events that impact ions are a part of gas-phase ion chemistry.
== Research and contributions == Sheiner's research focused on developing mathematical models and data analysis techniques to quantitatively characterize the impact of drug therapy from observational data, gathered either during drug development trials or during routine patient care. The practical objective motivating his research was more efficient and informative clinical trials as well as the ability to optimize dosage recommendations for individual patients. His work has influenced clinical pharmacology as a scientific discipline as well as the pharmaceutical industry and drug regulation more broadly. Sheiner's models have been implemented via software such as NONMEM, co-developed with Barr Rosenberg. Among his many notable papers are "Modelling of individual pharmacokinetics for computer-aided drug dosage" in 1972, "Understanding the dose-effect relationship: clinical application of pharmacokinetic-pharmacodynamic models" co-written with Nick Holford in 1981, and "Learning versus confirming in clinical drug development" in 1997.
July 29 Trevor Milton, billionaire and founder of the Nikola electric truck startup, is indicted on three counts of fraud. Suni Lee wins a gold medal in the gymnastics all-around competition, making her the first Asian American to win a gold medal in gymnastics during the Olympics. COVID-19 vaccination: Vermont becomes the first U.S. state to vaccinate 70% of children aged 12 to 17 years old. July 30 The Senate votes 66–28 to allow debates to begin on the Infrastructure Investment and Jobs Act. Tax returns of Donald Trump: The Department of Justice rules that the U.S. Treasury must hand the tax returns of former President Donald Trump to Congress. Swimming at the 2020 Summer Olympics: Caeleb Dressel breaks a world record in the 100m butterfly during the Olympics, finishing in 49.45 seconds. July 31 Florida swimmer Bobby Finke wins a gold medal at the 1500 metre freestyle event at the Olympics, becoming the first American to do so since Mike O'Brien. COVID-19 pandemic: Florida reports 21,683 cases of COVID-19, a new single-day record.
Sources: en.wikipedia.org
The connective tissue of the lungs is made up of elastic and collagen fibres that are interspersed between the capillaries and the alveolar walls. Elastin is the key protein of the extracellular matrix and is the main component of the elastic fibres. Elastin gives the necessary elasticity and resilience required for the persistent stretching involved in breathing, known as lung compliance. It is also responsible for the elastic recoil needed. Elastin is more concentrated in areas of high stress such as the openings of the alveoli, and alveolar junctions. The connective tissue links all the alveoli to form the lung parenchyma which has a sponge-like appearance. The alveoli have interconnecting air passages in their walls known as the pores of Kohn.
In chemistry, matter is defined as anything that has rest mass and volume (it takes up space) and is made up of particles. The particles that make up matter have rest mass as well – not all particles have rest mass, such as the photon. Matter can be a pure chemical substance or a mixture of substances.
Furthermore, the optimisation of the conditions for the protease in temperature and pH allows for the completion of the digestion of a sample in 30 min. Surfactant (detergents) can aid in the solubilization and denaturing of proteins in the gel and thereby shorten digestion times and increase protein cleavage and the number and amount of extracted peptides, especially for lipophilic proteins such as membrane proteins. Cleavable detergents are detergents that are cleaved after digestion, often under acidic conditions. This makes the addition of detergents compatible with mass spectrometry.
Sources: en.wikipedia.org
=== Secreted extracellular condensates === Secreted thyroglobulin colloid and colloid nodules of the thyroid gland Secreted casein 'micelles' of the mammary gland Serum albumin and globulins Secreted lysozyme
=== 1991 === 11 August After Desert Storm, the technology deployed in the Gulf War, and whether any lessons were learned - featured Major General Sir Peter de la Billière, Commander of the British Forces in the Gulf; a 66-foot-long F117 at King Khalid Air Base at Khamis Mushait on 16 January 1991 - the aircraft had no radar, but had the radar signature of a small bird; F117 pilot Major Greg Feest; Air Vice-Marshal Bill Written, the air commander of British Forces Middle East from November 1990; Colonel John A.
== Uses == Proline and its derivatives are often used as asymmetric catalysts in proline organocatalysis reactions. The CBS reduction and proline catalysed aldol condensation are prominent examples. In brewing, proteins rich in proline combine with polyphenols to produce haze (turbidity). L-Proline is an osmoprotectant and therefore is used in many pharmaceutical and biotechnological applications. The growth medium used in plant tissue culture may be supplemented with proline. This can increase growth, perhaps because it helps the plant tolerate the stresses of tissue culture. For proline's role in the stress response of plants, see § Biological activity.
== Confounders and Diagnostic Limitations == Several Systemic and age-related factors can severely limit the accuracy of skin turgor as a standalone diagnostic tool. In patients with hypernatremic dehydration, where sodium levels in the blood are abnormally high, water is pulled from the cells into the extracellular spaces, which keeps the skin feeling doughy rather than producing traditional tenting. Conversely, senior citizens naturally experience a sharp decline in dermal collagen synthesis and elastic fibers as they age. This natural loss of skin elasticity causes healthy, well-hydrated older adults to demonstrate prolonged tenting that can mistakenly be read as dehydration.
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.
SR9009 is a synthetic small molecule studied as an agonist of the REV-ERB nuclear receptors. It is not an approved medicine, and its effects in humans are not well characterized.