This is a working overview of HPLC, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-01-26 and is reviewed periodically as new material appears.
Commercial creatine monohydrate is produced mainly by chemical synthesis rather than extraction from animal tissue. Suppliers provide a certificate of analysis listing assay, water content, and impurity limits, and some products undergo third-party testing. Verification of identity can use infrared or Raman spectroscopy alongside chromatographic methods. Storage recommendations generally call for a cool, dry place and a tightly closed container to limit moisture uptake. Open questions include how packaging, flavoring agents, and long-term storage affect the stability of finished products.
Dry creatine monohydrate is generally stable when kept sealed and protected from heat and moisture. In solution, however, creatine undergoes a slow cyclization to creatinine, a related compound with no role in phosphocreatine storage. The rate of this conversion increases with temperature and is influenced by pH. Because creatinine is a common impurity in liquid or poorly stored products, analytical testing often measures both compounds. The crystalline monohydrate is less prone to degradation than aqueous preparations, though caking can occur if moisture enters the container.
Laboratory analysis of creatine monohydrate typically uses high-performance liquid chromatography to separate creatine from creatinine and other impurities. Detection may be ultraviolet, refractive index, or mass spectrometric, depending on the laboratory's equipment and the required sensitivity. Nuclear magnetic resonance spectroscopy can quantify the main component and identify related substances. Water content is measured by Karl Fischer titration, which is important because the monohydrate has a defined theoretical hydration level. Heavy metals, residual solvents, and microbial limits are also checked in quality control programs.
Analytical laboratories commonly identify creatine monohydrate by high-performance liquid chromatography with ultraviolet detection, often after dissolving the sample in water or dilute acid. Ion-exchange or reversed-phase columns separate creatine from creatinine and related guanidino compounds. Nitrogen content can be checked by Kjeldahl or combustion methods, while moisture is measured by Karl Fischer titration or loss on drying. These techniques give complementary views: chromatographic purity addresses related substances, whereas moisture and elemental data confirm hydrate stoichiometry. No single test defines quality by itself; a combination is used in specifications.
Storage recommendations generally emphasize a cool, dry place away from direct sunlight and strong oxidizers. Sealed containers limit humidity exchange, which helps prevent clumping and gradual conversion to creatinine. Long-term stability studies usually monitor appearance, moisture, and purity at intervals under defined temperature and humidity conditions. Accelerated tests at elevated temperature can reveal degradation pathways, but they do not perfectly predict room-temperature shelf life. Questions remain about how much creatinine formation is acceptable in different product categories and how packaging choices affect that rate over time.
| Property | Value | Notes |
|---|---|---|
| Typical storage temperature | 15–25 °C | Protect from moisture, heat, and direct sunlight |
| Analytical method | HPLC with UV or RI detection | Separates creatine from creatinine and related impurities |
| Water content | About 12.1% w/w | Theoretical value for the monohydrate crystal |
| Degradation product | Creatinine | Formed by cyclization, especially in aqueous solution |
| Common assay specification | 98.0–102.0% | Range depends on the testing method and monograph |
Creatine was first identified in skeletal muscle extracts in the nineteenth century, and its role in phosphagen energy buffering was clarified in the twentieth century. The monohydrate salt became widely studied after methods for inexpensive synthesis and crystallization were developed. Modern research examines its effects on muscle energetics, recovery, and cognitive performance under specific conditions. Findings vary with population, exercise protocol, baseline creatine status, and measurement method. Studies often compare supplementation with placebo during controlled training or testing schedules.
Creatine monohydrate is a hydrated form of creatine, a nitrogen-containing compound involved in cellular energy metabolism. Its molecular formula is C4H9N3O2·H2O, with a molar mass around 149.15 g/mol. The monohydrate is the most common solid form used in research and commercial settings because it crystallizes readily and remains stable under ordinary conditions. The term monohydrate indicates one water molecule per creatine molecule in the crystal lattice. It appears as a white crystalline powder with low odor.
Sourcing and verification of creatine monohydrate involve both manufacturing origin and third-party testing. Industrial production commonly starts with sarcosine and cyanamide, followed by crystallization to obtain the monohydrate. Some products are derived from animal sources, while others are synthesized from non-animal precursors. Certificates of analysis report assay, heavy metals, and microbial limits. Regulations differ by country: in the United States it is sold as a dietary supplement, whereas in the European Union it falls under food supplement rules.
In solid form, creatine monohydrate is relatively stable when kept dry and away from heat. Moisture and elevated temperatures promote cyclization into creatinine, a related compound with no role in the phosphagen system. Degradation accelerates in aqueous solution, where the conversion can occur within hours to days depending on pH and temperature. Manufacturers typically recommend storage in sealed containers at room temperature, with relative humidity below 50 percent. Long-term stability data for opened containers are limited.
The above descriptions ignore the effects of Gβγ–signalling, which can also be important, in particular in the case of activated Gαi/o-coupled GPCRs. The primary effectors of Gβγ are various ion channels, such as G-protein-regulated inwardly rectifying K+ channels (GIRKs), P/Q- and N-type voltage-gated Ca2+ channels, as well as some isoforms of AC and PLC, along with some phosphoinositide-3-kinase (PI3K) isoforms.
This technology entails the joining of DNA from different species and the subsequent insertion of the hybrid DNA into a host cell. One of the first individuals to develop recombinant DNA technology was a biochemist at Stanford by the name of Paul Berg. In his experimental design in 1974, he cleaved (cut into fragments) the monkey virus SV40. He then cleaved the double helix of another virus, an antibacterial agent known as bacteriophage lambda. In the third step, he fastened DNA from the SV40 to DNA from the bacteriophage lambda. The final step involved placing the mutant genetic material into a laboratory strain of the E. coli bacterium. This last step, however, was not completed in the original experiment.
Seven genes encode seven distinct 14-3-3 proteins in most mammals (See Human genes below) and 13–15 genes in many higher plants, though typically in fungi they are present only in pairs. Protists have at least one. Eukaryotes can tolerate the loss of a single 14-3-3 gene if multiple genes are expressed, but deletion of all 14-3-3s (as experimentally determined in yeast) results in death. 14-3-3 proteins are structurally similar to the Tetratrico Peptide Repeat (TPR) superfamily, which generally have 9 or 10 alpha helices, and usually form homo- and/or hetero-dimer interactions along their amino-termini helices. These proteins contain a number of known common modification domains, including regions for divalent cation interaction, phosphorylation & acetylation, and proteolytic cleavage, among others established and predicted. 14-3-3 binds to peptides. There are common recognition motifs for 14-3-3 proteins that contain a phosphorylated serine or threonine residue, although binding to non-phosphorylated ligands has also been reported. This interaction occurs along a so-called binding groove or cleft that is amphipathic in nature. To date, the crystal structures of six classes of these proteins have been resolved and deposited in the public domain.
An anticancer drug is coupled to an antibody that targets a specific tumor antigen (or protein) that, ideally, is only found in or on tumor cells. The biochemical reaction that occurs upon attaching triggers a signal in the tumor cell, which then absorbs, or internalizes, the antibody together with the linked cytotoxin. After the ADC is internalized, the cytotoxin kills the cancer. Their targeting ability was believed to limit side effects for cancer patients and to give a wider therapeutic window than other chemotherapeutic agents, although this promise hasn't yet been realized in the clinic. ADC technologies have been featured in many publications, including scientific journals.
Sources: en.wikipedia.org
When measured by fatalities per person transported, however, buses are the safest form of transportation. The number of air travel fatalities per person are surpassed only by bicycles and motorcycles. This statistic is used by the insurance industry when calculating insurance rates for air travel. For every billion kilometers traveled, trains have a fatality rate that is 12 times higher than that of air travel, and the fatality rate for automobiles is 62 times greater than for air travel. By contrast, for every billion journeys taken, buses are the safest form of transportation; using this measure, air travel is three times more dangerous than car transportation, and almost 30 times more dangerous than travelling by bus. A 2007 study by Popular Mechanics magazine found that passengers sitting at the back of an aeroplane are 40% more likely to survive a crash than those sitting at the front. The article quotes Boeing, the FAA, and a website on aircraft safety, all of which claim that there is no "safest" seat. The study examined 20 crashes, not taking into account the developments in safety after those accidents. However, a flight data recorder is usually mounted in the aircraft's empennage (tail section) where it is more likely to survive a severe crash. Between 1983 and 2000, the survival rate for people in U.S. plane crashes was greater than 95 percent.
The first automated insulin delivery system was known as the Biostator. Currently available AID systems fall into three broad classes based on their capabilities. The first systems released can only halt insulin delivery (predictive low glucose suspend) in response to already low or predicted low glucose. Hybrid Closed Loop systems can modulate delivery both up and down, although users still initiate insulin doses (boluses) for meals and typically "announce" or enter meal information. Fully Closed Loops require no manual insulin delivery actions or announcement for meals. A step forward from threshold suspend systems, predictive low glucose suspend (PLGS) systems use a mathematical model to extrapolate predicted future blood sugar levels based on recent past readings from a CGM. This allows the system to reduce or halt insulin delivery prior to a predicted hypoglycemic event.
AlphaFold has been used to predict structures of proteins of SARS-CoV-2, the causative agent of COVID-19. The structures of these proteins were pending experimental detection in early 2020. Results were reviewed by scientists at the Francis Crick Institute in the United Kingdom before being released to the broader research community. The team also confirmed accurate prediction against the experimentally determined SARS-CoV-2 spike protein that was shared in the Protein Data Bank, an international open-access database, before releasing the computationally determined structures of the under-studied protein molecules. The team acknowledged that although these protein structures might not be the subject of ongoing therapeutical research efforts, they will add to the community's understanding of the SARS-CoV-2 virus. Specifically, AlphaFold 2's prediction of the structure of the ORF3a protein was very similar to the structure determined by researchers at University of California, Berkeley using cryo-electron microscopy. This specific protein is believed to assist the virus in breaking out of the host cell once it replicates. This protein is also believed to play a role in triggering the inflammatory response to the infection.
The enzyme converts adenosine to adenosine monophosphate by transferring a phosphate group. Adenosine diphosphate is produced as a byproduct: The AdK gene/protein is mainly found in eukaryotic organisms and its primary sequence shows a high degree of conservation (>55% aa similarity). However, AdK sequences exhibit low (~ 20-25%), but significant similarity to other PfkB family of proteins such as RK and phosphofructokinases, which are also found in prokaryotic organisms. Although a protein exhibiting AdK activity has been reported in Mycobacterium tuberculosis, sequence and biochemical characteristics of this enzyme reveal it to be an atypical enzyme that is more closely related to ribokinase and fructokinase (35%) than to other ADKs (less than 24%).
The predecessor to the CAD, termed an evaporative electrical detector, was first described by Kaufman in 2002 at TSI Inc in US patent 6,568,245 and was based on the coupling of liquid chromatographic approaches to TSI's electrical aerosol measurement (EAM) technology. At around the same time Dixon and Peterson at California State University were investigating the coupling of liquid chromatography to an earlier version of TSI's EAM technology, which they called an aerosol charge detector. Subsequent collaboration between TSI and ESA Biosciences Inc. (now part of Thermo Fisher Scientific), led to the first commercial instrument, the Corona CAD, which received both the Pittsburgh Conference Silver Pittcon Editor's Award (2005) and R&D 100 award (2005). Continued research and engineering improvements in product design resulted in CADs with ever increasing capabilities. The newest iterations of the CAD are the Thermo Scientific Corona Veo Charged Aerosol Detector, Corona Veo RS Charged Aerosol Detector and Thermo Scientific Vanquish Charged Aerosol Detectors.
Sources: en.wikipedia.org
Amino acids are the building blocks of protein and together they form the protein requirements in formula needed for growth and development. The amino acids are in the simplest form, making it easy for the body to process and digest. Amino acid-based formula may be considered hypoallergenic since it does not contain peptides that may trigger an immune response. Because infants and children have different nutritional needs, amino acid-based formulas are typically formulated either for infants 0–1 years of age or for children 1–10 years of age. Amino acid-based formulas may be used for those with cow's milk or soy protein allergy. However, most infants who suffer from food allergy respond well to extensively hydrolysed formulas, and only few of those with the most severe form of the illness require the use of amino acid-based formulas. It may also be used for other medical conditions requiring an amino acid-based diet, such as short bowel syndrome, and for transition from parenteral to enteral nutrition. Milk allergy Food allergy
The cellular response in signal transduction cascades involves alteration of the expression of effector genes or activation/inhibition of targeted proteins. Regulation of protein activity mainly involves phosphorylation/dephosphorylation events, leading to its activation or inhibition. It is the case for the vast majority of responses as a consequence of the binding of the primary messengers to membrane receptors. This response is quick, as it involves regulation of molecules that are already present in the cell. On the other hand, the induction or repression of the expression of genes requires the binding of transcriptional factors to the regulatory sequences of these genes. The transcriptional factors are activated by the primary messengers, in most cases, due to their function as nuclear receptors for these messengers. The secondary messengers like DAG or Ca2+ could also induce or repress gene expression, via transcriptional factors. This response is slower than the first because it involves more steps, like transcription of genes and then the effect of newly formed proteins in a specific target. The target could be a protein or another gene.
Observant Muslims and Jews consider it sinful to eat certain types of meat, pork for both groups, and also horse and many other animals for Jews, due to religious prohibitions. Professor Reilly stated "for some religious groups or people who abstain from eating pig meat, the presence of traces of pig DNA is unacceptable". On 15 March 2013, a Westminster health and safety survey confirmed that pig DNA had been found in halal chicken sausages produced for schools.
In addition to cell signaling, the mTOR pathway also plays a role in beta cell growth leading to insulin secretion. High glucose in the blood begins the process of the mTOR signaling pathway, in which leucine plays an indirect role. The combination of glucose, leucine, and other activators cause mTOR to start signaling for the proliferation of beta cells and the secretion of insulin. Higher concentrations of leucine cause hyperactivity in the mTOR pathway, and S6 kinase is activated leading to inhibition of insulin receptor substrate through serine phosphorylation. In the cell the increased activity of mTOR complex causes eventual inability of beta cells to release insulin and the inhibitory effect of S6 kinase leads to insulin resistance in the cells, contributing to development of type 2 diabetes. Metformin is able to activate AMP kinase which phosphorylates proteins involved in the mTOR pathway, as well as leads to the progression of mTOR complex from its inactive state to its active state. It is suggested that metformin acts as a competitive inhibitor to the amino acid leucine in the mTOR pathway.
Amyloid proteins deposit most commonly inside the knee, followed by hands, wrists, elbow, hip, and ankle, causing joint pain. In males with advanced age (>80 years), there is significant risk of wild-type transthyretin amyloid deposition in synovial tissue of knee joint, but predominantly in old age deposition of wild type transthyretin is seen in cardiac ventricles. ATTR deposits have been found in ligamentum flavum of patients that underwent surgery for lumbar spinal stenosis. In beta 2-microglobulin amyloidosis, males have high risk of getting carpal tunnel syndrome. Aβ2MG amyloidosis (Hemodialysis associated amyloidosis) tends to deposit in synovial tissue, causing chronic inflammation of the synovial tissue in knee, hip, shoulder and interphalangeal joints. Amyloid light chains deposition in shoulder joint causes enlarged shoulders, also known as "shoulder pad sign". Amyloid light chain depositions can also cause bilateral symmetric polyarthritis. The deposition of amyloid proteins in the bone marrow without causing plasma cell dyscrasias is called amyloidoma. It is commonly found in cervical, lumbar, and sacral vertebrae. Those affected may be presented with bone pain due to bone lysis, lumbar paraparesis, and a variety of neurological symptoms. Vertebral fractures are also common.
Sources: en.wikipedia.org
Purity testing often uses high-performance liquid chromatography to measure creatine and creatinine. Water content can be checked by Karl Fischer titration. Additional tests may cover heavy metals, residual solvents, and microbial contamination.
In solution, creatine can cyclize spontaneously to creatinine. Heat and certain pH conditions increase the rate of this conversion. Dry crystalline material is more stable because the reaction requires water.
Typical storage is in a sealed container at room temperature, away from moisture and direct heat. These conditions reduce caking and slow degradation. Liquid products require more careful handling because creatine is less stable in water.
Laboratories typically combine chromatographic separation with moisture and elemental analysis. High-performance liquid chromatography can quantify creatine and related substances such as creatinine. Moisture methods confirm the hydrate form and help detect excess water.