A practical reference on LC-MS/MS: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-04-28 and is reviewed periodically as new material appears.
GW501516 acts as a selective agonist at PPARδ, a nuclear receptor that regulates transcription of genes involved in lipid handling and energy metabolism. Activation of PPARδ in preclinical models increases fatty acid oxidation, mitochondrial biogenesis, and exercise endurance in rodents. These effects have made the compound a subject of metabolic research and also a target for sport anti-doping rules. In humans, however, controlled studies are limited, and whether similar endurance or metabolic changes occur at tolerated exposures remains an open question. The receptor’s broad tissue distribution also means downstream effects may vary by organ and condition.
Detection of GW501516 in biological samples generally relies on liquid chromatography coupled with tandem mass spectrometry. Urine is a common matrix in anti-doping analysis, while blood or plasma may be used in research settings. Sample preparation can involve enzymatic hydrolysis, protein precipitation, or solid-phase extraction before instrumental analysis. Because the compound undergoes metabolism, assays may target the parent molecule, one or more metabolites, or both. Detection windows are not fixed; they depend on factors such as dose, route, individual metabolism, and assay sensitivity. Reference standards are required for accurate identification and quantification.
Handling and quality assessment of cardarine reference material follow general laboratory practices for poorly characterized compounds. It typically appears as a white to off-white powder and is sparingly soluble in water but soluble in organic solvents such as dimethyl sulfoxide and ethanol. Storage recommendations usually specify a cool, dry, dark place, with long-term storage at low temperature and desiccation. Purity may be checked by high-performance liquid chromatography with ultraviolet detection, while identity is confirmed by mass spectrometry and nuclear magnetic resonance. No pharmacopeial monograph exists, so reported purity and stability depend on the supplier’s methods.
Cardarine has no approved therapeutic indication and is not marketed as a medicine. The World Anti-Doping Agency lists GW501516 as a prohibited substance at all times, covering both in-competition and out-of-competition periods. National laws vary: some countries treat it as an unapproved drug subject to import controls, while others have specific restrictions on sale for human consumption. It is often sold as a research chemical, a label that does not imply safety or legality. Enforcement actions have targeted online vendors and shipments.
Anti-doping laboratories identify GW501516 and related metabolites using liquid chromatography coupled with tandem mass spectrometry. Urine is the most common matrix, though blood and dried blood spots may also be analyzed. The method targets the parent compound and phase I and phase II metabolites, which extend the detection window. Because the substance is prohibited at all times, athletes can be tested outside competition. Detection limits and windows depend on the assay, sample type, and individual metabolism.
Cardarine is frequently described as a fat-burning or endurance-enhancing supplement, but these claims exceed the available evidence. The compound is not a hormone, steroid, or selective androgen receptor modulator. Research articles discuss it as a tool compound for studying PPARδ biology, while anti-doping literature focuses on its abuse and detection. Quality of unapproved products is uncertain, and independent analyses have found impurities or incorrect labeling. Open questions include whether human cancer risk resembles that seen in rodents and how often non-athletes use the substance.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Visual description for typical solid reference material. |
| Solubility | Poorly soluble in water; soluble in DMSO | Solubility depends on solvent, purity, and form. |
| Storage | Cool, dry, protected from light | Long-term storage often uses low temperature and desiccant. |
| Common analytical method | LC-MS/MS | Used for detection and quantification in biological matrices. |
| Common synonyms | GW-501516; GW501516; endurobol | Naming varies among literature, vendors, and databases. |
Cardarine is a common name for GW501516, a synthetic compound developed in the 1990s through research collaborations involving GlaxoSmithKline. It belongs to a class of molecules known as peroxisome proliferator-activated receptor delta agonists. Early studies explored its effects on lipid metabolism and energy expenditure in animal models. The compound was never approved as a human medicine, and clinical development was discontinued. In the years since, it has appeared in fitness and bodybuilding communities as a performance-enhancing substance. Regulatory agencies classify it as an unapproved drug.
PPARδ is a nuclear receptor that regulates gene expression related to fatty acid oxidation, glucose homeostasis, and mitochondrial function. GW501516 binds to this receptor with high affinity and activates downstream signaling in skeletal muscle and other tissues. Animal studies reported increased endurance and altered fuel preference, but human data remain limited and inconsistent. The precise relationship between receptor activation and observed physiological changes is still an area of active investigation. Researchers have also examined whether the compound affects inflammation or cell proliferation. No approved therapeutic indication exists for cardarine.
Cardarine is prohibited in competitive sport under the World Anti-Doping Agency code, where it is classified as a metabolic modulator. It is not approved as a prescription medicine in the United States, European Union, or other major markets. Regulatory action has focused on its presence in sports and in products marketed as research chemicals. Because it has no accepted medical indication, supply is often unregulated. This status creates legal and safety uncertainties for anyone who encounters the substance.
Anti-doping laboratories detect GW501516 and its metabolites using liquid chromatography-tandem mass spectrometry. Urine is the most common matrix, though blood and dried blood spots may also be used in some programs. Detection depends on factors such as dose, timing, metabolism, and the sensitivity of the assay. Published methods describe limits of detection in the low nanogram per milliliter range for related compounds. Exact detection windows are not fixed for all situations and remain an area of ongoing study.
== Analysis of structure == The internal structure of sea ice can be analyzed using scanning electron microscopy and water-soluble resin. Brine can be drained from the sea ice using centrifugation at sufficiently cold temperatures to prevent melting and to maintain the structural integrity of the sea ice sample. Water-soluble resin is then injected to fill the brine pockets and channels and subsequently polymerized under ultraviolet light at around −12 °C (10 °F). The ice is sublimated by freeze drying, freeing the hardened casts, which can be examined using scanning electron microscopes to determine the structure of the brine pockets and channels and the volume of habitable space available to microbes.
== Properties == Supercritical fluids generally have properties between those of a gas and of a liquid. In Table 1, the critical properties are shown for some substances that are commonly used as supercritical fluids.
On 13 December 1904, Hungarian Sándor Just and Croatian Franjo Hanaman were granted a Hungarian patent (No. 34541) for a tungsten filament lamp that lasted longer and gave brighter light than the carbon filament. Tungsten filament lamps were first marketed by the Hungarian company Tungsram in 1904. This type is often called Tungsram-bulbs in many European countries. Filling a bulb with an inert gas such as argon or nitrogen slows the evaporation of the tungsten filament compared to operating it in a vacuum. This allows for greater temperatures and therefore greater efficacy with less reduction in filament life. In 1906, William D. Coolidge developed a method of making "ductile tungsten" from sintered tungsten which could be made into filaments while working for General Electric Company. By 1911 General Electric had begun selling incandescent light bulbs with ductile tungsten wire. In 1913, Irving Langmuir found that filling a lamp with inert gas (nitrogen at first, and later argon) instead of a vacuum resulted in twice the luminous efficacy and reduced bulb blackening. He patented his device on April 18, 1916.
Sources: en.wikipedia.org
Human and mouse protein kinases in UniProt: classification and index Kinase.Com: Genomics, evolution and large-scale analysis of protein kinases (non-commercial). KinMutBase: A registry of disease-causing mutations in protein kinase domains Archived 2022-06-15 at the Wayback Machine KLIFS (Kinase-Ligand Interaction Fingerprints and Structures) Database -- analysis of kinase structures and kinase-inhibitor interactions KinCore: the Kinase Conformation Resource: A web resource for protein kinase sequence, structure and phylogeny Kinomer: A multilevel HMM library for the classification and functional annotation of eukaryotic protein kinases.
== Awards and honours == 2016 United States Department of Energy Early Career Award 2017 American Society for Mass Spectrometry Research Award 2017 Eli Lilly Young Investigator Award in Analytical Chemistry 2017 American Chemical Society Arthur F. Findeis Award 2018 American Society for Mass Spectrometry Faces of Mass Spectrometry 2020 Sloan Research Fellowship
=== Alternative concepts === During their research, Eigen and Schuster also considered types of protein and nucleotide coupling other than hypercycles. One such alternative was a model with one replicase that performed polymerase functionality and that was a translational product of one of the RNA matrices existing among the quasispecies. This RNA-dependent RNA polymerase catalysed the replication of sequences that had specific motifs recognized by this replicase. The other RNA matrices, or just one of their strands, provided translational products which had specific anticodons and were responsible for unique assignment and transportation of amino acids. Another concept devised by Eigen and Schuster was a model in which each RNA template's replication was catalysed by its own translational product; at the same time, this RNA template performed a transport function for one amino acid type. Existence of more than one such RNA template could make translation possible. Nevertheless, in both alternative concepts, the system will not survive due to the internal competition among its constituents. Even if none of the constituents of such a system is selectively favoured, which potentially allows coexistence of all of the coupled molecules, they are not able to coevolve and optimize their properties. In consequence, the system loses its internal stability and cannot live on. The reason for inability to survive is the lack of mutual control of constituent abundances.
Sources: en.wikipedia.org
Cardarine targets PPARδ, a nuclear receptor involved in lipid and energy metabolism. It does not bind the androgen receptor in the way SARMs do.
Most methods use liquid chromatography with tandem mass spectrometry. Urine is common in anti-doping testing, and blood or plasma may be used in research.
Typical guidance is cool, dry, dark storage, often at low temperature and with desiccant. Stability data are limited, so storage conditions should be verified for each batch or supplier.
Legal status varies by country. It is not approved as a medicine, and it is prohibited in sport. Some jurisdictions restrict import, sale, or possession.